question and ans.3.doc
Content
(1) I.
DEFINITIONS, LINES PLAN Aft and fore perpendicular Fore Perpendicular : waterline and stem.
( Answer Sheet)
It is the perpendicular drawn from the intersection of
Aft perpendicular : Perpendicular drawn from the intersection of water line and Rudder post, or perpendicular from the center line of rudder stock if there is no Rudder post. II. Breadth extreme: Breadth moulded + Fenders + Shell plating thickness Breadth moulded: Dist. From the inner side shell of port to the inner shell of starboard. III. Port Side : Left side of ship when looking from aft. Stbd side : Right side of ship when looking from aft IV. Entrance: Forward part of the ship with varying cross section. Run: Aft part of the ship with varying cross section Parallel Middle body: Middle part of the ship with constant cross section. V. Camber: Curve applied to the deck transversely Sheer: Tendency of a deck to rise above the horizontal in profile. VI. Draft: It is the vertical distance from the keel to the designed water line. Denoted as ‘T’ Free board: Difference between the Depth and Draft Depth Moulded: It is the vertical distance from the top of flat keel to the bottom of deck plate 1. 3. Lines Plan: It is a Geometrical representation of 2D form of a 3-D complex shape of the hull of a ship through descriptive Geometry. Different views of lines Plan: Profile, Body plan and Half breadth plan Lines Plan
4.
5.
Offset table: It is a rectilinear tabulation of the following vertical distance - from the keel to the bottom of each section where they are crossed by buttock lines. - half breadth of each stations where they are crossed by waterlines. Lofting: Fairing of lines plan in 1:1 scale Lofting is done mould loft, which are big workshops. Archemedies Principle: The apparent loss in weight of a body when it is fully or partially immersed in liquid is equal to the weight of the water displaced by the body. Law of floatation: A body is said to be floating, then weight of the water displaced is equal to the weight of the body or weight of a floating body is equal to weight of volume of water displaced by immersed prt of body.
6. 7.
8.
Buoyancy: It is the upward force which keep the things afloat, which is equal to weight of water displaced by the body. Center of buoyancy: Is the center of gravity of the vol. of liquid displaced by the body (Hull in case of a ship).
9.
Dead weight: It is the maximum amount of cargo which a ship can carry. Displacement: Weight of the ship in the floating condition.
10.
Reserve buoyancy: It is the difference between the volume under water to the volume below the lowest opening on which it cannot made water tight. Six degree of freedom 1. 2. 3. 4. 5. 6. Pitching Rolling Yawing Swaying Surging Heaving
12.
Trim: Sinkage of ship in the longitudinal direction. Heel: Sinkage of ship in the transverse direction
13.
1.
Rise of floor: Distance from the top of the keel to the tangent drawn at bottom cuts the line of the maximum beam of mid ship.
2. Tumblehome: Tendency of a section to fall towards the middle line plane from vertical while approaching the deck. 3. Rake: Departure from the vertical of any section in profile.
4. Flare: Tendency of a section to fall out from the middle plane as it approaches the deck side. 14. Bernoullis Principle For an incompressible,steady, Ideal fluid flow, the sum of pressure energy, kinetic energy and potential (datum) energy are constant along the flow. P V2 --- + --- + Z = a const. W 2g P = Pressure W = sp. wt. of water V = Velocity g = acceleration due to gravity Z = datum 15. Density: It is the ratio of mass per unit volume at standard temp. and pressure. m ρ = ----v Specific gravity is the ratio of specific weight of liquid to specific weight of water. Sp.gravity = Sp.wt. of liquid -----------------Sp. wt. of water
Sp.weight of water = 1000kg/m3
16.
Viscosity
It is the property of a fluid, which resists the flow of one layer of fluid over the other. It is the measure of friction offered by the fluid particles to the resistance to flow. Its unit is Poise or Stoke 1 stoke = 1 Ns/m2 17. Hydrostatic Pressure: It is the pressure at a point in a liquid which is at equilibrium. Hydrostatic pressure increases with depth upwards will increase due. If h is the depth and ρ is density, then Hydrostatic pressure = ρgh A1 = 100 x 10 A2 = 50 x 10 A3 = 60 x 10 h1 = 5 h2 = 35 h3 = 65 = 1000 = 500 = 600
18.
CG of I section form x axiz A1h1 + A2 h2 + A3 h3 Y= =
---------------------------------------
A1 + A2 + A3 1000 x 5 + 500 x 35 + 600 x 65 ---------------------------------------2100
= 29.29
Section I b1d1 3 MI of (1) at Ix1x1 =
---------
=
12 MI with respect to neutral axis = Ia1 =
100 x 103 -----------12
= 8333.33
Ixx1 + A1h12 = 8333.33 + 1000 x 24.292
= 598337.43 Section 2 MI of (2) at Ixx2 =
2 2 ---------
bd
3
=
12 MI w.r. to neutral axis =
10 x 503 -----------12
= 104166.67
Ia2 =
Ixx2 + A2h22 = 104166.67 + 500 x 5.712
= 104699.27
Section 3 MI of (3) at Ixx3 =
3 3 ---------
Bd 12
3
=
60 x 103 -----------12
= 5000
MI w.r. to neutral axis = Ia3 = Ixx3 + A3h32 = 5000 + 600 x 35.712
= 770122.46 Moment of …….. of whole I section, IG = IG1 + IG2 + IG3 = 598337.43 + 104699.27 + 770122.46 = 60708.564 x 103 Section Modular IG ZTop = --- = Y 60708 – 564 x 103 ---------------------- = 1491244.5 40.71
Ia 60708.564 x 103 Zbottom = --- = ---------------------- = 2072672.03 Y 29.29
(2) 1.
DEFINITIONS, LINES PLAN, SHIP TYPES AND KEEL (Answer Sheet) Difference between cargo liners and tramp ship Cargo lines are cargo ships which have specified ports and regular schedules whereas Tramp ships have no specified routes and schedules Tramp ships can carry cargo which cargo lines can’t handle.
2. 2. 4. 5.
Std. size of container – 30ft x 8 ft x 8ft
8.5 x 8 x30
Flared bow is given in container ship is to prevent shipping green water. Usually Flared bow with high us given. Cofferdam : They are the void spaces given between tanks to prevent the risk of leakage of oil and also to prevent osmosis. Double skin, construction : They are given in ships is to protect the marine environment collision and to prevent Osmosis. If a collision occurs the inner skin protects the oil from leakage to the seawater. Bulk carriers Special requirements of refrigerated cargo vessels: They are used to carry food products. It should contain a refrigerated machinery and should have insulated spaces for carriage of food products like, meat, Daisy products etc. They are fast vessels, and have less stowage rate. LNG are carried in prismatic, spherical or cylindrical tanks. They are to be refrigerated and pressurised. Different types of Barge carrying ships 1. Seabee Type and 2. Lash Type In Seabee type elevators are provided to load the barges. In Lash type crones are provided In sea bee type vends there are no transverse Bulk heads
6. 7.
8. 9.
In lash type the barges are placed on over the other.
(3) BASIC STRUCTURE, HOLD, FRAMINGS, LOCKER, FORCE & AFT END CONSTRUCTION BOTTOM CONSTRUCTION 1. Two methods of Bottom construction are i) ii) Single Bottom Construction Double Bottom Construction
BULKHEADS, CHAIN (Answer Sheet)
2.
Double bottom can contribute longitudinal strength because the cross sectional area increases and due to this the section module increases, providing longitudinal strength. Constructional features of Double bottom Provides extra protection to the vessel Height of the double bottom vary from 1000 to 1500mm height should not be less than 650mm Double bottom extends from forepeak bulkhead to Aft peak bulkhead Contains inner shell (Tank top) and outer shell (Bottem plate) Solid floors are fitted every 3 to 4 mt. apart Used fir carriage of fuel and oil Different types of keel 1. Bar keel 2. Plate keel 3. Duet keel 1. Bar Keel : - For small vessels less than 90 mt in length - Solid floors are fitted in every frame spacing - disadvantage of increased draught for minimum cargo capacity 2. Plate Keel: - commonly used in ship’s
3.
4.
- extends from forward to aft - has a breadth to maximum 1800mm - thickness is equal to the thickness of bottom plate + 2mm 3. Duet Keel: - used in double bottom construction - can be used for piping - provides longitudinal strength - extends from fore peck BHD to Aft peck BHD
Hold framings 5. 6. Frames are used to protect the ship shell plate from collapsing - provides good strength to the vessel Types of framing systems1. longitudinal framing systems 2. Transverse framing system 3. Mixed framing system 7. Primary supporting members 1. 2. 3. 4. 5. 6. 7. 8. 8. Solid floor Bottom CL grinder Bottom side grinder Web frame Side stringers Deep transverse Deck side grider Deck CL girder
Secondary support members 1. Bracket floor 2. Bottom longitudinals 3. Deck longitudinals
4. Side longitudinals 5. Hold frames 6. Deck beams 9. 10. 11. Transverse framing system Longitudinal framing system Mixed framing system
12. BHDsz
Common Profiles 1. Angles - equal - unequal 2. T section 3. Bulb plates - equal - unequal - used in CL Girders and side girders. Also used as side stringers - same use as of Angles - used as stiffeners in shell platings and
4. Flat Bar 5. I Section 6. F Section 7. Solid bar 8. Hollow pipes 9. Half round bar 10. Plates 11. Chequered plates 12. Gratings
- used as face plates in girders are for stiffeners - used as stringers - used as stringers - used for pillars and cline roads - used for pillars and piping - as stiffners - for shell construction, BHD, superstructures etc. - used in engine room - used in passengers and on super structures.
13.
Bale Cargo Capacity:-
- Maximum cargo capacity excluding the stiffners in the cargo area Mixed framing system has better bole cargo capacity - Cargo capacity including the volume inside the stiffeners provided in the cargo area
Grain Cargo Capacity :-
14.
The various framing systems are 1. Tranverse framing system 2. Longitudinal framing system 3. Combined or Mixed framing system
1. Transverse framing system Side frames fitted at every frame spacing Bracket floors are fitted at every frame spacing Frames are bracketed to bracket floors Solid floors are spaced at every 3-4m frame spacing A ring like structure includes solid floor, web frame and deck transverse. Deck transverse are fitted every 3-4m apart Better Bale cargo capacity
2. Longitudinal framing system Provided better longitudinal strength Deck longitudinal are fitted on deck’s bottom Side longitudinal are fitted at sides Bottom longitudinal are fitted to bottom. A ring like structure includes solid floor, web frames, deep transverse are spaced every 3-4mt apart All secondary members are longitudinally spaced Spacing of longitudinal is 750mm
3. Mixed framing system Combination of both Transverse and longitudinal framing system Provides better bole cargo capacity Provides longitudinal strength Mainly used in cargo ships and bulk carriers Top and bottom are spaced 150mm by longitudinal Transverse frames are fitted at the sides
Shell Plating 15. 16. Function of shell plating It acts as a water fight skin Provides longitudinal strength Various platings of Ships
1. 2. 3. 4. 5. 17.
Keel strake Garboard strake Bilge plate Side shell plating includes sheer stroke adjacent to the deck plates Deck shell plating includes stringer plates adjacent to the shear strake
a. Gun whale : It is a portion where the sheer stroke and stringer plates meats b. Seams : longitudinally welded joints c. Butts : Vertically or Transverse welded joints Constructional features of shell plating plates are laid longitudinally Thickness of sheer strake and bottom platting are increased because they are subjected to high stresses In heavy ships deck plates and bottom plates are used of high tensile steel Bottom plate thickness depends on the length, breadth and depth and cargo capacity of the ship Longitudinally welded joints are called seems Transversely welded joints are called butts Thickness of keel plate depends on the bottom plate and carrying capacity Thickness is increased in the slamming and pounding region. Thickness is increased near by the stern frame and bossing.
18.
Bulkheads 19. 20 Functions Divides the ship into different compartments Protects the ship during flooding Prevents free surface effect Restrict the entry of fire from one compartment to other Fore peak collision, BHD arrest the flooding of water to cargo tanker Longitudinal bulkheads provide longitudinal strength. Types of BHDs 1. 2. 3. 4. 5. 6. 7. water tight BHD NON water tight BHD Oil tight BHD Gas tight BHD Collision BHD Longitudinal BHD’s Transverse BHD
21.
Types of BHD Construction 1. Plain type bulk heads 2. Corrugated type bulk heads
22.
Plain Bulkhead
23.
Corrugated BHD
24.
Bulkhead Construction Types of BHD construction are: 1) Plain type and 2) Corrugated type
In Plain types the plates are laid in the horizontal direction In corrugated types the plates are laid vertically. Stiffeners are spaced 750mm vertically for plain BHDS If the height is increasing then stringers are provided vertically and horizontally. Corrugated type BHDs are in the form of corrugations or swedges. They can be subjected to high bending loads or pillar loads than plain BHDs The corrugation angle is 450 Stiffeners can be avoided thereby decreasing the steel weight
Diaphragm plates or stringers are added if the height is increased to provide strength 25. 26. 27. Cofferdam provided in vessels carrying various liquidous cargoes provided between fresh water tanks and oil tanks cofferdoms BHD’s are spaced 760mm apart prevents the risk of leakage of oil from one tank to other through osmosis. in some cases used as pump rooms following tanks are to be separated each other by coffer dam vegetable oil tank mineral oil tank fresh water tank Fuel oil tank prevents contamination of liquids of various densities Minimum spacing of cofferdam – 760mm Typical tanks which needs a cofferdam are Vegitable oil tanks Fuel oil tanks Fresh water tanks Mineral oil tanks
Chain Locker 28. Chain locker - Box type structure - Situated in the fore peak tank - One side of chain locker is fixed to collision BHD - Centerline chain locker BHD divides it into two for post and STBD side - False bottom is provided, to drain mud from anchor chain. - Anchor chain cable supporting assembly is provided - Stiffeners are provided outside - Footsteps are provided in BHDs 29. Chain locker
30.
House pipe - pipe through which anchor chain enters the windlass while taking the anchor on board Spurting pipe - pipe through which anchor chain goes to the chain locker while taking anchor on board Stiffners are provided at the outside of chain lockers to prevent the entackling chains with stiffners. Stiffners are provided on the CL BHD with two sides facing to the CL BHD, to prevent the entackling of chains.
31. of
32.
False bottom in chain lockers are provided because the mud in the chain is collected in the false bottom. The mud can be removed by cleaning the false bottom.
33.
Force end construction
34. 35.
Fore end : Forward quarters of ship length from the forward perpendicular is termed as fore end. Slamming: During slamming the bow suddenly rises and hits the water due to waves. Raking: Lateral movement of frames from side to side. This is due to the forces by waves or wind. Pounding: It is the upward and downward force acted upon the ship by the waves.
36.
Hungry horse effects are produced by panting. Panting is carried by the fluctuating load by waves on the sides of ship. Painting results is the fluctuation of shell plate like the bellows of a hungry horse’s stomach. Panting beam and panting stringers are provided to reduce this effect. Crown deck: It is the upper most deck of the fore peak which is made made water light.
38.
39)
Aft end constructions
40. 41. 42. -
Aft end: It is the portion which is 25% L of the ship from the Aft perpendicular including super structure and aft peak Aft peak tank: It is the aft most tank of the ship for ballasting and fresh water tank carriage consists of centerline BHD to reduce the free surface effect consists of stern frame and bossing stern frames are fabricated forged Brest hooks are provided Solid floors are provided at every frame space Rudder tank is situated Stern tube is situated Consist of painting stringers and swash plates Types of stern construction Cruiser stern Transom stern
Cruiser Stern - provides less resistance - consists of cart frames spaced at a particular angle to center line - reduced slamming effect a) Cant frames:b) They are situated in Cruiser stern Provided to reduce the effect of slamming Cant framed are spaced at angles towards the center line Curved structures Parting beams:provided at fore peak and aft peak tanks to reduce the effect due to panting to distribute the force developed in the transverse directions
-
panting stringers are corrected by panting beams to distribute the load.
c) Wash plates:- also called as non water light BHDs or perforated BHDs or swash BHDs to distribute the load developed in the transverse direction situated in fore peak and Aft peak tanks In some cases they are also used to reduce surface effects Difficult to construct
Transom stern 43. provides greater deck area prevents squatting of high speed small crafts reduces resistance from 3 to 5% at high speed reduced slamming and pounding effects easy to construct Squatting: It is a phenomenon by which a negative pressure is created at the aft end of high speed small crafts, which tends the aft end to touch the bottom in shallow waters.
2) Breast hooks: Panting stringers are held in position together by Brest hooks Brest hooks also provides strength to stem bar and stern frame Brest hooks are equally spaced They supports the plates at the fore end from post and stbd side
Basic Structure 45. Welding imperfections
46.
Different grades of steel IS 2062 MS Allowable stress - 235N/mm2 A Grade B Grade ABS AH Grade- Allowable stress - 400 N/mm2 ABS Grade
47.
Testing methods to identify welding imperfections” 1. Visual inspection 2. NDT (Non Destructive Testing)
48.
Welding techniques
1. 2. 3. 4. 5. 6. 49.
Down hand welding (1G) Horizontal welding (2G) Vertical welding (3G) Over head welding (4G) Cylindrical welding (5G) Spiral welding (6G)
Underwater appendages 1. 2. 3. 4. 5. 6. 7. 8. 9. Speed log Stabilizer Bow thruster Skeg Propeller Rudder Echo sounder Bilge keel Sea chest
50.
a) Bilge keel b) skeg :
- To arrest the movement of ship during rolling - To support the ship in docks - For good directional stability - act as a supporting member at the over changing portion on aft - To control the direction of ship - For directional stability - Situated at aft
c) Rudder
d) Echo sounder - to measure the depth of the sea e) Bow thruster - to turn the ship in a limited space, usually fitted at forward side 52. Doubler plate: Plates are laid one, over the other provided where compressive loads are generated. Mainly provided under the pillars Insert plate: Plates of high thickness are inserted between plates of standard thickess. Provided where compressive and Tensile loads are coming. Outfittings 53. Mooring Fittings 1. Bollards single bollard doublar bollard for tieing the ships in ports for toeing the ship using tugs.
2) Rolling fair leads Situated at Bull warks for the passing and directing the tie ropes 3) Capstan for the ropes to pay through, while mooring It can rotate and move by its own 4) Chokes 54. For the passage of ropes without any obstruction Panama chokes are fitted at the forward side on bull warks
Ventilators are mainly two types - Natural Ventilators & Forced Ventilators Subdivided into
1. Cowl head type 2. Mushroom head type 3. Goose Neck type
Natural Ventilators: functions on the natural draught of air with any mechanical input Forced Ventilators: functions on the forced draught of air by motor driven fans provided inside it. Superstructure: structures having a breadth greater than or equal to 98% of the breadth of ship Deck house: is of lesser breadth than super structure 56. It can also come under cranes It can also come under other access in deck which leads to cargo tanks etc. Sounding: Sounding pipes are provided to measure from the depth of cargo tanks and to find the volume of cargo inside the tanks. Ullage: is to measure from the top of the liquid level and to find the volume of cargo inside it. 57. Striking plates: During sounding plumbs are inserted through sounding pipes to
check the level. At this time the plumb will hit the shell plate. As this procedure is continuous there will be chances of having holes on the shell because of the striking of plumbs. To avoid this striking plates are provided under sounding pipes. 58. a) Forecastle: - To prevent shipping green water - Usually provided in fast vessels like container ship - Ships with well flared bows have a tendency for shipping green water, to avoid this fore castle is provided. - Height depends on the speed and flared bow. - Plates supported by stays b) Funnel:- - vertical structures above deck - Housing of air vents from sea hearts and other lines - Stiffeners are placed vertically - If the height is increased stringers are provided - To fixing owner’s logo - For good appearance - Shape can be according to owner’s style - Shape are cylindrical, rectangle etc. - Sufficient height should to provided to get smoke and grit cleared off the deck Height can be reduced if uses forced draught. d) Engine Casing: - Height of 760mm should be provided above weather deck - Protect various openings from auxiliary engines which comes directly above the engine - Size should be sufficient to take the engine and auxiliary engines out of engine room - Vertical member extending throughout the super structure e) Guard rails For protection of crews and passengers Height should be 1 mtr Consists of shell rods and hallow pipes Shell rods are also called stanchions Hollow pipes are used as rails Supported by stays
f) Sea chest High sea chest : In shallow water, high sea chest is used Sea chest are box type structures Provides the inlet for seawater for engine coiling, deck water etc. High sea section is used in shallow water is to prevent the mud from entering
Low sea chest: - used in deep sea because the high pressure itself cause pumping action. g) Pillar: are used where consentrated loads are acting d) e) Are vertical members They are also used when tension loads are coming They are supported at bottom by doubler or inserted plates Supported at top by header plates Hatch corner pillars are avoided damages during cargo loading and unloading Pillars can be used to avoid deep section beams Insulation is provided to prevent heat and noise FRP and GRP with steal plates are used as insulators Provides supports for various decks Main engine seating: Provides a good platform for the engine Rudder plates are supported by vertical and horizontal members for engine seating Faceplates are drilled in correct line of engine bolts provided Spacing can vary depending on the engine size Shaft tunnel Provided if the engine room is at mid ship Protects the shaft from contact with cargo Can be used for pipelines
-
On the top it is a round like structure Stiffeners are provided inside Stools are provided to support shaft
f) 59. 60.
Can be useful during maintenance Connection of intermediate shaft to tail shaft Bulwark and Guard rail Bulwark For protection of the crew and cargo on deck For fitting radar out fittings and latching of cargo Supported by stays Situated above the force castle Hatch side pillars are corner placed to avoided damages during cargo loading and unloading Insulations is provided in the engine room to prevent excess heat and noise from the engine and auxiliary machines. FRP and GRP with steel plates ones used for insulating engine room. FRP – Fiber reinforced plate are also used. Pillar Header plates are provided at the top and double plates are provided at the bottom. Heavy brackets are provided if the load is tension and simple brackets for compressive loading.
61.
63.
Types of Manholes:
-
Rise with high coming Rise with low coming Flush type
Rise with high comings raised to 100mm above the deck rise with low warming raise to 10mm above the deck flush type are on the level of the deck. 64. 65. Purpose of intermediate shaft is to remove the tail shaft easily during repair or maintenance. Purpose of bulwark: for protection of crew and cargo on deck, for fitting radar out fittings and lashing of cargo, height should be 1m. Purpose of Guard rail: for protection of crew and cargo on board. It should be 1m. Freeing post: openings on the bottom side of bulwark for the drainage of water.
(4) 1.
HYDROSTATICS Hydrostatic Particulars
(Answer Sheet)
- Volume displacement - Mass displacement - Longitudinal center of floatation (LCF) - BMT and BML - Longitudinal center of Buoyancy (LCB) - Vertical center of Buoyancy (VCB) - Form coefficients - Tones per centimeter immersion (TPCI) - Moment to change trim by 1inch (MCTI) - Wetted surface area 2.Law of floatation states that for a floating body, the weight of the body is equal to weight of fluid displaced by the body is which it floats. 3. Different rules of integration 1. 2. 3. 4. 5. 4. a. Simpson’s first rule h Area = -- (1y1 + 4 y2 + 1y3) 3 Where h = dist. Between to full stations or ordinates, y1, y2 are ordinates b. Simpson’s Second rule h Area = -- (1y1 + 3 y2 + 3 y3 +1y4) 8 c.5,8, -1 rule h Area = -- (5y1 + 8 y2 - y3) 12 d. Trapezoidal rule Simpson’s first rule Simpson’s second rule Simpson’s third rule (5,8, -1 rule) Trapezoidal rule Trapezoidal rule
h Area = -- (1y1 + 81y2) 2 5. Tchebycheff’s rule differ from other rules in that the ordinates are not equally spaced There are no internal multipliers Curve is parabolic Is found out by summing up the ordinates and dividing by the no. of full stations and then again multiplying by the length A= 6. (y1 + y2 + y3 +……- yn) L -------------------------------N End ordinates are not taken. Displacement can be calculated by Integrating area along the water planes in longitudinal direction Integrating area along the stations in vertical direction Better way is to calculate by integrating area along the water planes because number of stations are greater than number of water planes 7. Formulas a. TPCI - Tones per centimeter Immersion TPCI = (A*d)/ 1000 A= area of water place d = density of seawater b. MCTI – moment of charge trim by 1inch MCTI = BML x W -----------100 x L BML = longitudinal metacenter from center of Buoyancy W = weight displacement L = length of ship.
c. BML – Dist. From longitudinal meter center from center of Buoyancy
BML = IL
-------
∇ IL = longitudinal moment of inertia with respect to transverse axis ∇ = volume displacement d. BMT = Dist. From Transverse metacenter from center of Bougancy BMT = IT
-------
∇ IT = Transverse moment of Inertia with respect to longitudinal axis ∇ = Vol. displacement e. Cb – Block coefficient Cb = ∇ ------LBT
L = length of ship B = Breadth of ship T = Draft f. CP - Prismatic coefficient CP = ∇ -------------Am x L
Am = area of midship L = length of ship g. Cm = Midship section coefficient Cm Am -----BxT B = Breadth T = Draft
=
h. Cw = water plane area coefficient Cw = A m -----LxB
8. St. 0 0.5 1 2 3 4 5 6 7 8 9 9.5 10
1
/2B 0 5 8 10 12 13 13 12 11 8 3 1 0
SM 0.5 2 1.5 4 2 4 2 4 2 4 1.5 2 1
F(A) 0 10 12 40 24 52 26 48 22 32 4.5 2 0 272.5
Lever 0 0.5 1 2 3 4 5 6 7 8 9 9.5 10
F(M) 0 5 12 80 72 208 130 288 154 256 40.5 19 0 1264. 5
Lever2 0 0.25 1 4 9 16 25 36 44 64 81 90.25 100
f(IL) 0 2.5 12 160 216 832 650 1728 1078 2048 364.5 180.5 0 7271. 5
y3 0 125 512 1000 1728 2197 2197 1728 1331 512 27 1 0
SM 0.5 2 1.5 4 2 4 2 4 2 4 1.5 2 1
f(IT) 0 250 768 4000 3456 8788 4394 6912 2662 2048 40.5 2 0 33320.5
h A = --- x ∑ f (A) x 2 = 2180m2 3 IL = h --- x h2 x ∑ f (IL) x 2 3 h 1 --- x --- x ∑ f (IT) x 2 3 3
IT =
IL - Iaft – Ax2 X = LCF = h. ∑ f (M) -------------∑ f (A) Here we got I(aft) Iaft = 123 ----- x 7271.5 x 2 = 8376768 3 = 12 x 1264.5 --------------272.5 = 55.68m
IL IT
= 8376768 – 2180 x 55.682 = 1618195.968m4 12 = ---- x 33320.5 x 2 = 88854.66 m4 9 BMT = IT ---∇
a)
Cb = 0.75 ∇ ----LBT 88854.6 ---------7200 ∇ = 0.75 x 120 x 10x 8
Cb
=
= 7200 m3
BMT =
= 12.34 m
b)
BML =
IT ---- = ∇
1618195.97 ------------7200
= 224.75 m
c)
TPC
Axρ = ------- = 100
2180 x 1.205 ---------------100
= 26.26 T
d) e)
MCT
BML x W = -----------100 x L
=
224.75 x 7200 x 1025 --------------------------- = 138221.25 kgm 100 x 120
weight of ship in sea water = weight of ship in fresh water ∇sw x ρsw x g = ∇fw x ρfw x g ∇fw = 7200 x 1025 --------------- = 7380 1000 ∇ Cb = ---= 0.75 = 7380 -------
LBT T = 8.2m 50 x 1000 x 90 = ------------------138221.55
120 x 10 x T
f)
Trim
= 32.55cm
9. a) LCF - Longitudinal center of floatation - It is the centeroid of the water plane - It can be referred from aft or midship - for calculation of trim forward and trim aft - point through which the trimmed water line panes LCF = h x ∑ f(MA) -----------∑ f(A) b) LCB - Longitudinal center of Buoyancy - It is the longitudinal position of the center of buoyancy of the volume under the design waterline -longitudinal position of the center of buoyancy through which buoyancy force acts - To calculating the total trim and resistance of ship - can be referred from aft or from midship LCB = h x ∑ f(MV) -----------∑ f(V)
c)
VCB - vertical center of buoyancy - It is the vertical position of center of buoyancy of the volume under the design water line - It is the vertical position of center of buoyancy through which buoyancy fore cuts - For calculating stability of ship
LCB =
h x ∑ f(MV ) -----------∑ f(V)
- Referred from base line or ‘0th’ water line d) IT
-
It is the transverse moment of Interia along the longitudinal axis IT = 2h 1 ---- x --- x ∑ f(IT) 3 3
- can be referred from center line - for calculating BMT e) IL is the longitudinal moment of Inertia along the transverse axis 2h IL = ---- x h2 x ∑ f(IL) 3 10. Can be referred from aft or mid ship For calculating BML a) TPCI is defined as Tonnes per centimeter immersion TPC = A x ρ --------100 A = Area of water plane ρ = density of sea water It is the weight added or reduced to change the mean draft by 1 cm TPI is defined as the Tonnes per inch immersion TPI = A x ρ x 2.54 ---------------100 It is the weight added or deducted to charge the draft by one inch. b) LCF - Longitudinal center of floatation - centroid of water plane - can be referred from aft or midship LCF = h x ∑f(M) --------------
∑f (A) - Calculating trim Aft and trim fore LCB - Longitudinal center of Buoyancy - longitudinal position through which the buoyancy force acts - can be referred from aft or mid ship - calculating total trim and resistance of ships LCF = h . ∑f(M) -------------∑f (V) c) Vertical prismatic coefficient ∇ -----AWL x L
CPV =
∇ = Vol. Displacement AWL = area of water line L = length of ship
(5) 1.
STABILITY
(Answer sheet)
For stability at small angles GM, metacentric height is the stability criteria For stability at large angles Gz, Righting lever is the stability criteria Small angle means upto 5o Large angles means greater than 5o GZ= GM sinφ – for small angles GZ = BOR –BG sin φ - for large angles
M Metacenter is fixed for small angles M charges for large angles 2.
3.
Righting lever: If a ship is inclined at constant displacement, the point B o moves to B1, a new Point. So the buoyancy force and downward fire which is acting upwards will be not in the same line and if a perpendicular drawn to the new waterline intersects the original WL at M called metacenter. Then a restoring couple is generated, GZ x W which tends to bring book the ship to original position, and GZ is called as the Righting lever. Metacenter: It is the point at which a floating body begins to oscillate, when it tilted by a small angle. Metacentric height: If a line drawn through the new buoyancy point B 1 which is perpendicular to the new water line W1L1, the line will meet at the vertical at M called metacentre (M). Metacenteric height: The distance between the metacenter and center of graving is termed metacentric height (GM). GM = metacentric height
4.
5.
Different condition of equilibrium M above G – GZ & GM is +ve - stable equilibrium M is at G - GZ & GM = 0 - Neutral equilibrium M below G - GZ & GM = -ve - unstable equilibrium
6.
7.
Stability of Circular Section Consider a circular section with Radius R, lying in the horizontal axis with section ‘O’. So the buoying force will always acts through the point ‘O’, even if the water level is above or below the section ‘O’. So here the stability is depends on radius ‘R’. If KG < R, stable If R = KG, neutral If R < KG, unstable Stability can also be obtained by adding weight.
8.
Trim – It is the difference between draft forward and draft aft. Center of rotation ‘LCF’ is the centeriod of the water plane area. It is the point through which the trimmed water line passes through. If a weight is placed above this point, the ship sinks with no trim.
9.
Diff. Reasons for trim to occur - Due to movement of weight - Loading and unloading - Ballasting - Fresh water consumption - Fuel consumption etc.
10.
Volume displacement Mass displacement Tones per centimeter immersion. If ship is entering from low density to high density the draft is decreased since buoyant force increases Fully submerged submarines First of all they have no water planes, so there is no metacenter. Care should be taken during fast sub mergence to keep G and B nearby at same point, otherwise it will capsize. As they go to higher depths, its body shrinks due to high hydrostatic forces, thereby reducing the volume displaced. So the buoyant force decreases and submarine begins to sink. So to keep the submarines stable it is to be pump out water from inside or using force provided by hydroplanes etc.
11. 12.
13.
w.h = GG1 ∆ ………………………(i) GG1 = GM tanφ tanφ = t/L GG1 = GM. t/L ………………………(ii) Substitute (ii) in (i) W = GML x t x ∆ -------------Lxh W = t . GML x ∆ ------------ …………………..(iii) Lxh So the moment to cause and charge trim is GML x ∆ --------L The moment to charge trim by 1 cm = ∆ x GML
----------------
100 L So, t = Wh -----MCT from (iii)
14. LCB of a ship can be found out from Hydrostatic curves, if we know the corresponding draft 16. Wall sided formula = sinφ (GM + ½ BM tan2φ) Ship sides in way of water lines all over are assumed to be vertical here. So it is formed as wall sided formula.
17. 18.
Free surface effect is the effect on main tanks carrying liquid cargoes which affects the stability of ship or it is the virtual reduction in GM. Free surface effect = ρf If -----ρ∇ Where ρf is the density of fluid If is the second moment of area of liquid surface ρ is the density of fluid in which strip is float ∇ is the displacement Free surface effects can be reduced by reducing the breadth of cargo tanks by centerline bulkheads and wing bulkheads. Inclining experiment is conducted to find 1. CG of the ship 2. Light ship weight
19. 20.
21. 22.
Condition of inclining experiment is called Asinclined condition. condition of ship with 95% of its structure is completed. Preparation for inclining experiment 1. 2. 3. 4. 5. 6. 7.
It is the
Get approved the agenda of experiment from class and owners Clean the ship Check the whether conditions Find the place to do the experiment – dry dock Loose the mooring rapes Fixing of materials – pendulum, oil tray, scale etc. Tanks are to be completely filled in case of any trim problems to avoid free surface effect.
23.
Inclining experiment is conducted by placing two set of weight each on port and stbd side. At the first stage set 1 is moved to the stbd side and the indination is noted. Then set 2 is moved to stbd side and inclination is noted. Then the two sets are moved back to port and the inclination is noted from the set up provided. The same is done on the port side for set 3 and set 4 and the inclination are noted. density of water is noted for two to three position of ship. Accuracy of inclining experiment is ensured by ploting a graph with deflection Vs weight moved. The accuracy is ensured, when the graph retraces its path during port and stbd movement of weights. w x h = ∆ . GG1 We know GG1 = GM tanφ W x h = ∆ .GM tanφ
24.
25.
x tanφ = --- from inclining experiment L w x h = ∆ . GM . x --L KM = KG +GM - KM from hydrostatics - GM calculated from above eqn. 26. 27. Total Weight required is estimated as the weight which will give an inclination of 1.5 to 2o when it is moved from stbd to port side. Pre survey - Condition survey Tank survey Draft survey Post survey - Draft survey Condition survey. Weight of the block while docking w.x = t.* MCTI w is the weight to be calculated t is the trim MCTI is moment to charge trim by 1cm x is the distance aft from LCF 29. During docking, righting moment = (GM –w .KM)W sinφ -W If the solution inside the brackets becomes –ve the ship will tip over. GZ is the measure of stability of large angles GZ = BoR-BoG sinφ Curve of statical stability GZ curve is the also called curve of statical stability GZ = GM sinφ dGZ ------ - GM cosφ dQ dGZ GM ------- = ----- (cosφ=1) dQ 1
28.
30. 31.
It is a curve with GZ along the y axis and the angle of inclination along the x axis. Positive value of GZ with the angle gives the range of stability. 32.
IMO Criteria Area upto 30o = 0.055 mrad (not less than) Area upto 40o = 0.09 mrad (not less than) Area between 40o and 30o = 0.03 mard (not less than) GM value should be greater than 0.15mts At 30o GZ should not be less than 0.2mts. GZ should be maximum after 30o 33. Angle of loll: When GM is –ve initially, ship is inclined to either part or slbd side and at some point it will reach in equilibrium and remains is that point. This point is now the equilibrium condition of the ship and the angle is called angle of loll. It can happen during weight shift in the ship permanently. Value of GM in the lolled condition is twice as compared to initial GM but negative in sign.
34. 35.
. 36.
37.
GZ = KN -KGSMφ ……………………………(i) GZ = BoR-BoG sinφ In the above equation (i) the value of - KN can be found from knowing the displacement from cross waves - KG can be found from inclining experiment And with there, values GZ can be plotted with respect to φ
38.
Stability information booklet It is a booklet which contain the stability of ship for all condition of loading. Other data’s It contains Hydrostatics datas
It contains a figure showing the profile of ship from which areas and moment can be calculated It contains the GM values. 39. Minimum conditions shown in stability information booklet are stability at 1. 2. 3. 4. 5. 6. 40. 41. Light ship conditions Fully loaded departure condition Fully loaded arrival condition Ballasted departure condition Ballasted arrival condition Other conditions
Additional condition required for a tug is to avoid towing at athwart angle Additional condition required for a ship with crane is the maximum load that can hang and extended on the ship and point at which load acted on the tip of crane is to be noted at same time. GZ curve, when weight is permanently moved
42.
In this condition BC is the new range of stability and C is the new angle of varnishing stability. 43. 44. Angle of Repose: It is the angle at which the bulk cargoes mainly grain cargoes starts repositioning its state, such that it does not come back to its initial state. By adding centerline Bulkheads and shifting boards the prevention of cargo in bulk carriers. Provision of feeders will fill the void spaces after setting down the cargo also helps to avoid shifting of cargoes. Dynamic Stability: It is the measure of energy ship absorbs to resist fore exposed by wind and waves or it is the work done is heeling the ship to an angles δφ and is given by the product of displace, GZ and δφ
45.
46.
When a wind moment is applied, slowly the ship start to heel to an angle represented by A and in theis condition the range of stability will be from A to B. If the moment is applied suddenly like a gust of wind, the amount of energy absorbed by ship as it heels is represented as area DACO. The ship would absorb energy reprented by area OAC and the remaining energy would carry it beyond a starts to some angle F such that area AEF = area DAO. If F is beyond B, the ship will capsize, assuming the wind is still acting.
A severe case for a rolling ship is if it is inclined to its maximum angle to winword and about to return to the vertical when the gust hits it., let it be the position GH.The energy put in to the ship by the wind up to angle L is now represented by area GDKLOH. The ship will continue to heel until this energy is absorbed, perhaps reaching angle Q. 47. Angle of heel due to turning: When ship is turned by self with rudder the rudder holds the ship at an angle of attack with-repositions the path. As a result of this the force developed in the hull which is the hydrodynamic force tends to move the hall towards the center which is turns the ship to new position and then outwards. Additional stability condition taken into consideration while designing passenger ship is the crowding of passengers to one side.
48. 49.
GZ = KN-KG sinφ GZ = BoR-BoG sinφ
50.
Boot Topping area : The area reach to the draft designed which come frequently in contact with air and wakes tends to corrode very fast than other areas. So there areas to be painted with corrosion resistant paints. (6) LAUNCHING - (Answer Sheet) Requirements of end-launching a ship The ship sterns should slides first to water because this part of the ship is more buoyant. Slide ways are to be provided under the ship The gap between the slide ways and ground ways are provided, with grease to avoid friction Usually two to four ways are provided Ground ways are to be cambered to acquire buoyancy faster Waterfront is to be cleared Slide ways are to be cleared Tide is a major factor to be taken into consideration Tugs are to be provided to tow the ship if any frictional resistance arises Drags are to be provided in restricted waterways to decelerate the movement,after ship is become waterborn. Fore poppet is to be provided
1.
2.
Problem associated with launching - The grease is too slippery or not slipping enough - The grease may get squeezed out due to excessive pressure - Tipping and dropping can occurs - local strengthening of the ship is a major factor - Tide which a major factor is taken into consideration Tipping If the moment of weight about Aft end way is greater than moment of buoyancy about aft end way the ship will tip and is termed as tipping.
3.
To avoid tipping the moment of buoyancy about aft end way should lie above the moment of weight about aft end way. The difference (least) between them gives the least moment against tipping. 4. Pivoting When the moment of weight about fore poppet equals the moment of buoyancy about fore poppet the stern lifts and ship pivots on fore poppet and is termed as pivoting. Dropping: If the buoyancy is less compared to the weight after the ship crosses the aft end way the ship drops and is termed as dropping. To avoid dropping, make sure that the buoyancy exceeds weight before ship must pass over the aft end way. Different launching curves Weight Buoyancy Moment of weight about fore poppet Moment of buoyancy about fore poppet Moment of weight about Aft end way Moment of buoyancy about Aft end way Launching Curve
5.
6.
7.
Analysis When the moment of weight about fore poppet equals the moment of buoyancy about fore poppet the stern lifts. Weight – Buoyancy at time of pivoting is the maximum force coming on the fore poppet. Moment of buoyancy about Aft end way should lie above the moment of weight about Aft end way to avoid tipping. The least difference is the least moment against tipping when weight equals buoyancy the ship is fully water bone weight and buoyancy should pass before the aft end way to avoid dropping. Grease pressure can be determined at the tipping point. Height of tide also can be determined. 8. Step by step procedure of calculating the launching curves
First approximate LCG and weight can be calculated from shell expansion drawing. Then Buoyancy and LCB at any position can be found from Bonjeans and Auto ships Upto the stern lift the trim is constant. So LCB and Buoyancy can be found from Bonjeans.
X = Initial slop of K L = LBP h = Initial height of Fore poppet above water e = Distance of fore poppet abaft FP β = Declivity of ground ways α = camber of ground way γ = radius of center Center of arc, F = K2/8R (f-y) = (K-2x)2 ---------8R Y = K2 (K-2x)2 --- - ------8R 8γ = K2 K2 + 4 kx – 4x2 --- - ------------------8R 8γ 4kx – 4x2 ----------= (k – x) ---------
=
8γ
2γ ======
At a dist. ‘x’ the height of FP above water is h-βx + y βx – decrease in height due to slop of ground way y - increase in height due to camper So at any dist. Of abaft the FPP, the height above water = h-βx+y-t(α+x/γ) h--βx + x(kx) ------- - t (α + x/γ) 2γ If there is no camber γ = infinite So, height above water = h - βx - tα If t = -ve gives height of keel at FP above water If t = L-e gives draft of AP After the stern lifts occurs the condition charges because trim changes. calculation can only be done to stern lift. Then the condition to be Is Moment of act about fore poppet = Moment of buoyancy about FP Wxh =∆xa A = approximation value of us Buoyancy and moment is calculated for several trim. Find the trim at which two curves meet 9. Dynamics of launching with diagram So
The force accelerating the ship at any instant can be found by (w-∆)φ - way friction – water resistance – drag force W = weight acting downwards ∆ = buoyancy acting upwards φ = slop of ways (w - ∆)µ = way friction µ = coefficient of friction <0.02 K∆2/3V2 = water resistance V = velocity of travel K = Constant = 0.001 Drag fore = µ w W = weight of chain µ, = 0.4 – 0.8 Curve 1 : This is the net weight of ship (weight – buoyant force) and it becomes zero when the ship becomes water born. Curve 2: curve obtained by reducing way friction from weight component. This also becomes zero when ship floats. Curve 3: Curve obtained by further reducing water resistant component which begins from when stern touching the water to ship comes to rest.
Curve 4: Is drag component, only comes into play when ship floats. The remaining momentum of ship is reduced to zero by drag component and water resistance component after the ship is becomes water borne. 10. Side launching
Side launching is done when the water front is limited. Ship slide down the ways so there is possibility for tipping and dropping. Ships are built on piles which are collapsible. The ship can roll up to 30o, so stability at large angles to be considered. Due to this the waves can change the adjacent shore. Declivity can be from which to 8 inch and grease pressure vary from 2.5 to 3Tforce 10. Docking
Docking is done for any repairing works in ship. The factors considered while docking area.
Ensure the blocks are under primary members Strength of floating docks is to be considered Stability is a major factor Strength of docks to be considered Local distribution between dock and ship Make sure that the openings on the hull are clear Make sure that hull fittings are cleared while docking (like echo sounder, stabilizer, speed loge etc) Ship should have a slight trim by aft. Docking is done based on the docking plan Docking can be in (i) Dry Docks and (ii) Floating docks Blocks can be selected depending on block pressure and crippling pressure Block pressure > 40 Tf/fb2 Crippling pressure = Total load/Total blocks.* Area of blocks 2. Ships weight No. of blocks = --------------------x. block stiffeners x = mean deflection of stacks
(7) 1. 2.
FLOODING (Answer sheet) Flooding is caused due collision, grounding, sprinkling of leak due pitting, welding defects and fatigue After effect of flooding: results in the reduction of stability and loss of buoyancy If the reduction in stability is large the ship will turnover or cap size. If the reduction in stability is not much large the ship will has to an angle, which will be difficult for launching life boats. General consideration is given to ships while flooding but importance is given to passenger ships; get the passengers out off the ship within the limited time. It means not only to get the passengers on board but also to launch the life boats with passengers in them. Emergency illumination stickers showing the way to on board is to be pasted. Limiting the heel, if the heel is large by counter flooding for the easy launching of lifeboats. Time consideration is a major factor so that time allowance from collision to the acceptance damage is considered.
3.
4.
During flooding the ship will sink first and then trims until it acquires loss of buoyancy. So LCB shifts to a new position and the ship trims until the value of B reaches vertically below G. If the reduction in stability is large the ship will turnover or capsize. If the reduction is small the ship will heel to an angle. The hydrostatic behavior can be found by two methods. (1) Lost buoyancy method (2) Added weight method. Lost buoyancy method 1. 2. 3. 4. 5. 6. Displacement remains constant Water plane area changes LCG does not change LCB changes and rechanges back to the position vertically below G BML, IT, MCT changes Sinkage due to lost Buoyancy Added weight method Displacement changes No change is water plane area LCG changes No change in LCB Since no change in water Plane area BML, IT, MCT are constant. Sinkage due to added weight
5.
Permeability: It is the ratio of the floodable volume to the actual volume of the compartment. Floodable volume Permeability = ---------------------Actual volume Spaces Accommodation space Machinery space Cargo holds Stores Permeability % 95 85 60 60
6.
7.
Two methods of flooding calculations are 1) Lost Buoyancy method 2) Added weight method Lost buoyancy method First the volume of the damaged compartment is calculated with respect of original water plane and then area of the damaged water plane is calculated. If A is the area of the intact water plane, the lost volume due to buoyancy is µν1 and the area cost is µa. So parallel sinkage, z occurs, µν1 Z = -------- where µ = permeability
8.
A-µa Second consideration is taken as the draught is changing with respect to water plane, newly formed. So trim and MCT are taken into consideration, where
z/2 is the distance taken for the intermediate water plane area formed. Sinkage will happen till the volume of the lost buoyancy lost is regained from the new water plane. µν ---Am µν x t = -----MCT
Sinkage =
and
Where Am is the area of the inter mediate water plane. This process is repeated until the desired volume are obtained. If the values are greater, the process is to be repeated. The volume can be checked by Bonjeans for allowable floodability and damageability. Here G is constant.
9.
Added weight method Here weight is considered added to the ship to the damaged compartment. Firstly the calculation is same as for the added weight, then as the water is entering to the compartment weight is again added with respect rate of entering and can be stop when the further sinkage becomes negligible.
10.
Damaged stability by lost buoyancy method The buoyancy lost is regained from the intact water plane as a result of which the buoyancy in the original position is shifted above the original water place. This vertical shift of Bo to B1 is the new buoyancy can be given by , νv.bb1 -------∇
bb1 is the distance between centroid of water planes. As B o shifted to B1 there is a reduction in BMd. If Id is the damaged water plane inertia, BMd can be calculated as, Id --∇ So damaged GM, GM damaged = GM intact + µvbb1 Id -------- - --∇ ∇ Here G is assumed as constant 11. Damaged stability by Added cut method In damaged condition the force surface effect is taken into consideration. Here the position of G varies ad weight is changing. So KG varies depending on the draught. GMdamaged = GMintect + µνbb1 Id --------- - --- - free surface effect ∇ ∇ 12. Asymmetric flooding
For ships with longitudinal bulk heads the water may not flood right across the ship. The damaged of penetrations is limited by BHDS to 20% of the breadth of the ship. So the ship will Heel lesser due to BHDS. If µν is the volume lost due to flooding. ∆GM sinφ = µνzρ ρ∇GM sinφ = µνzρ sinφ = µνz -----
GM∇ If heel is large due to flooding the opposite side compartment are flooded which is known as counter flooding. This only sinks the ships by linking the heel there by easyness for bunching life boats. 13. Floodable length : Floodable length at any point along the length is the length of an imaginary comprtment.with that point as center, When allowed to flood, such that no part of the margin line the is immersed, provided no list. Bulkhead deck: It is the uppermost weather tight deck to which water tight transverse BHDS are connected. Margin line: Water line drawn tangent to a line 76mm below the bulkhead deck is termed ad margin line
14.
15.
The significance is that it is the line upto which the ship can be flooded without any list. The ship is considered lost if water line goes above margin line. 16.
Taking water lines WoLo and W1L1 for intact and damaged condition. Loss of buoyancy = V1 - Vo Centeroid of the lost buoyancy is given by V1 x BoB1 X = -----------V1 - Vo It is possible to convert this into length that can be flooded, The calculation can
be repeated for a series of water lines until a reasonable figure, is obtained which gives a curve of floodable length. 17.
18.
Factor of subdivision It is the ratio of permissible length to floodable length. Inverse of factor of safely It is a function of length and criteria numeral Factor of sub division is low for passengers ships compared to cargo ships.
19.
Criterion numeral is defined as the criterion of the service of ship taking into account, number of passengers, machinery volume, Accommodation spaces and total volume of the ship.
(8) 1.
PROPULSION
(Answer Sheet)
The lift and drag forces on a blade section are generally represented by non dimensional terms where are the coefficient of life (C L) and coefficient of Drag (CD) L CL = ---------½ ρAV2 ρ = density of fluid A = Area of plan form of section v = velocity of flow D CD = ---------½ ρAV2
2.
L = lift force D = drag force F = Resultant force V = velocity of flow Lift force is perpendicular to velocity of flow and drag force is parallel to velocity of flow and α is the angle of attack. 3.
4.
Lift generated on an aerofoil section: Consider an aerofoil section with a velocity of flow ‘v’. According to Bernoulli’s equation there will be corresponding decrease in pressure at back and increase in pressure at the face. Due to this a circulation is created around the aerofoil which will results in the lift of aerofoil.
The net pressure on the face and back gives the lift generated in aerofoil. 5. Aspect ratio = span / chord It is the ratio of span to chord of a propeller blade or rudder. 6. Stagnation Point
Considering a fluid flour around a circular section. At points A and B the velocity of fluid is zero and these points are called stagnation point.
At the stagnation point kinetic energy of the fluid is fully converted to potential energy. 6. KT – (thrust coefficient) It is the non-dimensional coefficient of thrust T KT = ---ρN2D4 KQ (Torque coefficient) It is the non-dimensional coefficient of torque produced by propeller KQ = Q ---ρN2D5
J – (Advance Coefficient) It is the ratio of axial velocity (Va) of the propeller to ND Va J = --ND 8. If subscribe ‘S’ represents ‘ship’s propeller and ‘m’ models propeller and are geometrically. Similar operating at same advance coefficient ρs 3 ---- = ---- λ T m ρm Ts Tm = Ts. ρm
--------3 s
a)
where λ =
Ds ---- (ratio of linear dim.) Dm
ρλ b)
ND ---- = ρ is also const. so, Va
Ns Vas Dm ---- = ------- x -----Vm Vam Ds
1 = --λ 0.5
Nm = Nsλ 0.5 c) Thrust power = T.Va Ps ρs --- = ---- λ3.5 Pm ρm Pm = ρs. ρm ------ρs . λ3.5 d) Ratio of torque φs ρs ---- = ---- λ4 φm ρm φs. ρm φm = -------ρs . λ4 PT
9.
Open water efficiency = µo =
----
PD It is the ratio of thrust power developed by the propeller to power delivered when propelling the ship in open water. µo = PT = ---PD T.Va -----2πNÏ• Ï• = torque N = rpm Va = axial velocity T = Trust by propeller
10.
We have Vw = Vs – Va, but Vs the velocity of ship remains same and there only a chance of increase in Vw means Va will have to reduce. Since J = Va / ND, there is chance of reduction in J in actual case. So we take a point slightly forward (4 to 8 % )to maximum propeller efficiency point as the design point
11.
Different series diagram for propeller 1. 2. 3. 4. 5. Frodue’s methodical series Taylor’s methodical series Gawn methodical series Troost methodical series Van Lammersen series
12.
Open water test: are used to determine the work and relative rotative efficiency. It is carried out in towing tank. The propeller is fitted head of the stream lined housing and pushed ahead with the carriage in undisturbed water. Records of thrust and have taken for a range of carriage speeds and rpm. The test provides data of propeller in uniform flew, which eliminates cavitations. The result obtained as series data is used for design purpose, making allowance for actual floor conditions. The different series data are provide, Taylor, Gawn series data etc. Wake: The relative velocity of water to that of ship in propeller location is termed as wake. The three elements of wake are: 1. Velocity of water as it passes round the hull varies being less than average at ends 2. Due to viscous effects, hull drag a volume of water along with it. 3. Due to waves, created by hull, water particles moves in a circular orbit.
13.
The first two components will reduce velocity into propeller. The next component will increase or decrease depending on wave crest or trough. Wakes varies across the disc of propeller so average is taken for design. 14. Froude’s wake fraction = Vw ---Va Taylors wake friction = Vw ---Vs Va = Speed of advance of propeller Vs = Speed of ship In preliminary propeller design before detailed wave pattern is known, an average speed over the whole disc is taken and it is usually expressed in fraction of speed of volume of propeller or ship Wake velocity, Vw = Vs- Va 15. 16. 17. Range of wake fraction : for a single screw ship is from 0.25 to 0.3 Relative Rotative efficiency : ηR is the ratio of efficiency of the propeller working to that of propeller. It is often taken as unity for design calculations. Thrust deduction factor T = (T-R) -----T
T = Thrust reg. R = Resistance of base hull
Thrust of the propeller will always be more than bare hull resistance. 18. Open water efficiency (η0) = PT --PD It is the ratio of thrust power developed by the propeller behind the ship to power delivered in open water. It is the ratio of power delivered by propeller in open water to power delivered by propeller, behind the ship. Hull efficiency (ηH) = PE --PT
It is the ratio of effective horse power of ship with appendages to thrust power developed by propeller. 19. Quasi Propulsive coefficient (QPC) QPC = ηH . η0 . ηR -----------------Appendage coefficient QPC = Propulsive coefficient ----------------------------Transmission efficiency
22.
Propeller theories 1. 2. 3. 4. 5. Momentum theory Blade element theory Lifting line theory Surface vertex theory Vortex lattice theory
23.
Concept of Momentum theory Concept of based on Newton’s second law and Newton’s third law of motion. ie., rate of change of momentum equals force acting and for every force there is an equal and opposite reaction.
Here the propeller in replaced by an actuator disc.
Velocity of water entering the disc Va is increased to Va(1+b) as it leaves the disc means there is a change in momentum. The thrust is produced by the momentum change taking place along the disc. 24. Concept of Blade element theory Propeller thrust is obtained by …… the force acting on the blades, and integrating this over the propeller radius.
Thrust and Torque can be calculated by considering the flow condition on a blade element and then integrating from hub to tip. 25. Need for special propeller The ships are becoming larger and faster, but propeller diameters remains limited by draft and other factors. The aim of propeller design is to achieve high propulsive efficiency at reduced noise and vibration, along with minimum cavitation. In the case of conventional propellers it is difficult to attain this aim. So special propellers are needed to satisfy this aim. 26. Types of special propellers 1. Vertical axis propeller 2. Controllable pitch propellers 3. Contra rotating propellers 4. Ducted propellers 5. Super cavitating propellers 6. Surface propellers 7. Tandem propellers 8. Overlapping propellers 9. Water jet propulsion 10. Paddle wheels
27.
Two types of vertical axis propeller – Kirsten-Boeing Voit-Schneider
28.
CPP are used in Tugs, Trawlers, Fire boats, Ferries, Fire boats, Ice breakers and small warships Advantage of CPP are Full power of main engine can be utilized in also loading conditions (ie. in static, towing, free running, ice breaking, rough weather, shallow water conditions etc.) Can produce a higher astern thrust at maximum efficiency Produces better acceleration, stopping and maneuvering characteristics Reduces weight and space because of non reversing engine Speed of the ship can be varied without changing engine’s speed Speed of ship can be directly controlled from navigational bridge Propulsion can be done at max. efficiency over a range of ship’s speed. Ducted propellers are used in heavily loaded ships and high speeds ships to reduce cavitation.
29.
In the case of accelerating ducts (Kort nozzles) circulation is developed around the duct section. Here the thrust developed is equal to thrust of propeller and duet together. This is usually greater than thrust produced by open propeller, whereas torque is smaller. Therefore the efficiency of propeller is greater than open type. In the case of decelerating ducts (pump jets) it reduced the inflow velocity towards propeller thereby reducing pressure. This type also has a circulation around the duct which produces an outward directed lift with a component directed aft. Here the duct thrust is negative. Therefore, the efficiency is decreased, but the cavitations properties are increased with respect to an open propeller. So they are used in high speed hydrodynamic to minimize cavitations and noise. 30. Principle of super cavitating propeller is sheet cavitations. Here pressure drops below vapor pressure along the whole back of the propeller blade. So they are used in propellers where unacceptable limits of cavitations cannot be avoided. 30. Surface Propeller: is a screw propeller which operates in shallow water. This types of propellers are semi submerged in water so that propeller blades enter and leave the surface of water for every one revolution. They are fitted
behind the hull instead of placing under the hull. Under water appendages, which support the propeller like shaft bracket, A bracket can be avoided thus by reducing the appendage resistance. The main advantage is that it can have large diameters since they are located behind the hull and can operate in shallow water. They are also not affected by cavitations. The main disadvantage is the hydrodynamic forces on blades unsteady are blades enters and leave the water.
31. Contra rotating propellers: Consists of two propellers rotating in opposite directions on co-axial shaft, one being place close behind the other. They impacts directional stability and reduce rotational energy losses in the slip stream. They are generally use din torpedoes.
The main advantage is that the thrust load required is distributed between the two propellers there by increasing efficiency. The propeller diameter and blade area ratio can be reduced. Main disadvantage is greater weight and complicated gearing system and coaxial shafts. 32. Tandem propellers: consists of two propellers mounted on the same shaft and rotating in same direction. The total thrust required is divided between the two propellers provided that propellers are of same diameter and same number of blades. The main disadvantage is that rotational energy loss is higher and greater weight.
33. Overlapping propellers: Consists of two propellers located at longitudinal position of a single conventional propeller, but with a shaft at a transverse separation less that the diameter of either propeller. If the two propellers are in the same transverse plane the two shafts must be interlocked, if they are at a small dist. apart along the length of ship, the shafts must be independent. The main advantage is that load is distributed by the two propellers. They work in a region of high wake, therefore hull effects is higher.
Main disadvantage is increased noise, vibration and cavitation due to mutual interaction. They are usually designed for out board turning. 34. Water jet propulsion: consists of pump with an impeller inside the ship which draws water from outside, imparts an acceleration to it and discharges it in a jet above the water line at the stern. This jet reaction provides the thrust to propel the ship. They are used in high-speed ships.
Advantages
• • • •
Appendage resistance can be reduced since there are no appendages. They can be used in shallow waters Good maneuverability, backing and stopping are obtained No reed of reversing the main engine, because .. is no reversing gear in propulsion plant • Less noise and vibration • Torque of the water jet unit is constant over the complete speed range. Ie., engine is not overloaded because full water is maintained at low speed • Speed of ship can be controlled without altering rpm of engine. Disadvantages Unit occupies large space inside the hull and water passing through caused a decrease in buoyancy Creating provided to prevent ……. Getting into the system decreases the efficiency as it gets clogged. 36. Cavitation It is the phenomenon which occurs on objects having aerofoil blades in a medium at high speeds..
Net force on the face and back side gives the lift force, this is due to the reduction in pressure on back and increased pressure on face. As the pressure in back is reduced, water vapor pressure is reached, then water boils and bubbles are formed. These bubbles get into area outside water vapour pressure area along the flow and implodes. This phenomenon is termed cavitation. This results is erosion and high local force.
37.
Cavitation number:
σ = (P0 – e) --------1/2 ρAV2 e = water vapour pressure P0= pressure at center of hub v = velocity - cavitations number reduces as velocity increases. 38. Different forms of cavitation Depending on nature of cavitation - Bubble cavitation - Sheet cavitation Depending on where it occurs - Tip vortex cavitation - Force cavitation - Hub cavitation - Bock cavitation 39. Cavitation Tunnel :
Cavitation tunnel is a closed channel through which an impeller at the lower section circulates water and model is placed inside the glass viewing ports, at the upper section. Uniform flow is provided to the test model which is tested in open water. Vaccum pump provided before the propeller producer negative pressure. De-aerator is fitted for reducing the amount of dissolved air and gas. In the case of propeller fitted to hull large tunnels are used. Artificial wake is provided by fixing grid ahead of propeller. 40. Cavitation test results.
41.
Bucket diagram They are used to design propeller. The design point should be inside the bucket which is the no-cavitation region. During operation the cavitation number and angle of attack of the designed propeller must be inside the no cavitation region of the diagram
42.
Isotachs:
Isotachs represents the amount of axial flow on a propeller or lines of constant velocity. It we integrate all velocities and taking average we will get wake velocity, Vw. 43. Sample velocity vector is a representation of resultant of tangential and radial velocities at a point along the radial length.
44.
Different views of propeller:
Projected view is a projection on a plane normal to the shaft. Developed view is a projection on a plane normal to the trust of the blade Expended view is a projection on a plane after the blade is mode flat. 44. A surface generated by a line rotated about an axis normal to itself and advance in the axis of rotation in constant speed.
46. 47.
Blade area ratio It is the ratio of blade area to the area of circle circumfrensing the propeller. Skew is the circumferential displacement of the blade tip from normal Rake is the distance in profile from the normal to the axis
48.
Different blade sections: cambered force
are flat face circular back, Aerofoil section and
49.
Right handed propeller: propeller rotation is clockwise and moving ahead when looking from aft. In twin screw stbd propeller is right handed propeller. Left handed propeller: propeller rotation is anticlockwise and moving ahead when looking from aft. In twin screw, port propeller is left handed propeller.
50. 51.
Pitch distribution is given in order to accommodate the change in wake velocity radially. The wake velocity is maximum at hub and minimum at tip so that that the pitch is maximum at hub and minimum at tip. In twin screw ships propellers are out board tuning.
52.
Q is the angle of pitch Pitch is the distance at which a propeller advances for each complete one revolution. When it rotates in a solid medium
`
Pitch angle, Q = tan-1 2πr ----P
53.
54.
Skew is given to propeller to vary the circumferential velocity. Rake is given because there is a good clearance between hull and propeller so that noise and vibration transmission from propeller to hull can be reduced..
(9)
RESISTANCE - (Answer Sheet)
1.
Reynold’s number, Rn = VL ---Ù§ It is connected with viscocity and so with frictional resistance. where, V = velocity L = length Ù§= kinetic viscosity Rn<2000 - Laminar flow Rn >4000 – turbulent flow Froude number, Fn = V2 --gL where g = gravity It is connected with wave making resistance.
2.
If Fn is constant Vm ----√gLm = Vs ----√gLs
If Rn is constant Vm L m = Vs L s Vm = Vs Vs
----------
Lm Vm = Vs
----
Vm = Vs.λ
√Ls/Lm Vm = Vs --√λ Ls --- = λ Lm
Take
So both the laws cannot be achieved simultaneously 3. 4. Rn is connected with frictional resistance. Fn is connected with wave making resistance
5. 6.
Resistance of a ship is the power required to tow the ship at a particular velocity.
For a stream lined body spacing of the stream line changes. Velocity changes because the mass flow is constant. The Bernoulli’s equation for stream line is P V2 -- + --- + gh = a constant. ρ 2 7. Mach number is connected with air resistance Mach Number = V --α Free surface is having constant atmospheric pressure. A pressure variation on the free surface results in waves on the surface. Energy is needed to maintain the waves and this leads to resistance which is the above making resistance and it is controlled by gravity. It decreases as depth from free surface. Fluids are viscous and resistance is produced by that is called frictional resistance. Components of Resistance: Wave making Resistance Frictional Resistance Viscous pressure Resistance or Form resistance Eddy making resistance Appendage resistance Air resistance 11. Kelvin wave pattern:
8.
9. 10.
12.
Interference effects: In the case of ship stem and stern pressure points produce waves of their own. The forward wave start with a crest and aft wave start with a trough. When the stem waves reach the sterm waves and interact the crest coinciding with crest forming high magnitude of the crest coincides with trough which is get neutralized. As a result of this humps and hollows are formed in resistance curves. This effect is formed interference effect.
13.
Viscous pressure drag: Viscocity modifies the flow around the hull which leads to built up of pressure at aft termed as viscous pressure resistance or form resistance, which depends on the hull.
14.
15.
Boundary layer: Volume of water which moves with the body is termed Boundary layer. Boundary layer thickness is the dist. from the hull at which relative water velocity is 99% of ships speed.
16.
Laminar flow: The flow is laminar for Rn < 2000. Velocity of liquid element in laminar flow remains const. in magnitude and direction. Turbulent flow: The flow is turbulent is Rn >4000. Flow is unsteady and non uniform velocity fluctuations and violent.
17. 18.
At critical Reynold’s number the flow changes from laminar to turbulent. Critical Reynold’s number: It is the number at which flow changes from laminar to turbulent flow. Below critical Rn, resistance is proportional to velocity. Above critical Rn resistance is proportional to V1.723 Turbulent stimulators are used in towing tanks which is used to convert flow from laminar to turbulent. Eddy making Resistance Formed as a result of abrupt change in the shape of the hull form. The effect can be minimized by stream lining the body. Appendages such as bilge keel, rudder create eddies. Rudder on activation create eddies. In the case of multi shaft ships shaft brackets creates eddies. Here the flow breakdown on well rounded from due
19. 20.
to viscosity and pressure distribution in boundary layer. Further form the effect is more. 21. Different appendages Bilge keel Rudder Skeg Stabilizer Echo sounder Speed log Propeller Shaft bracket ITTC method Steps for calculation of resistance of ship from model test: 1. RTM is found which is the total resistance of model from the measuring tank. 2. Total resistance coefficient , CTM = RTM ----is found ½ ρsv2 where ρ = density s = wetted surface area v = velocity 3. 4. 5. Frictional resistance coefficient of method can be found from ITTC formula Cfm = 0.075/ (log10Rn-2)2 Viscous resistance coefficient = Cvm = (1 + K) Cfm where K = form factor
22.
Residuary resistance coefficient of model Crm = CTm - Cvm 6. Equating Cr for model and ship Crm = Crs 7. Friction resistance coefficient of ship is found , Cps from ITTC formula 8. Viscous resistance coefficient of ship is found Cvs = (1 + K) Cps + √Cf Where √Cf is the roughness allowance 9. Cfs = Crs + Cvs + Cta Cts = Total resistance coefficient of ship Cta = Air resistance coefficient = 0.01 AT/S (AT = Tr. Projected area)
23.
Froude’s Method: of calculation of resistance of a ship from model test. Steps 1. Total resistance of model from model test at corresponding Froude number (RTM) 2. Calculate the frictional resistance of the model on the basis of a flat plate equivalent surface = Rfm 3. Residuary resistance of model is found out by ………………… frictional resistance of model from total resistance of model Rrm = RTM - Rfm 4. Residuary resistance of ship is found out by Rrs = Rrm ∇s ---∇m 5. Frictional resistance of ship is found out on the basis of a flat plate equivalent surface - Rfs 6. Total resistance of ship is the sum of Residuary resistance of ship and frictional resistance of ship RTS = RFS + RRS 7. Appendage resistance and air resistance we found and added to total resistance of ship 24. Specific Resistance coefficient = R ---½ ρSV2 R = Total resistance ρ = density S = welted surface area V = velocity
25.
Wetted surface area can be found out by plotting girth length of ship at various points along the length to base of ship length and integrating. Wetlted surface area can be calculated by two formula (approx) i) Denny’s formula, S = L (CB.B +ITT) Where L = Length B = Breadth T = Draft CB = Block coefficient Taylor’s formula Where ∆ in tones S = C(∆L)0.5
ii)
L in m. C = 15.2 to 16.5
26.
Methodical series tests starts with a parent form. In this test a number of significant form parameters are varies and results obtained shown as graphs. Resistance varies with the form parameters. This test is very useful in estimating the power requirment for new designs. One of such test is by Admiral Taylor. Two series data of methodical series tests are BSRA - British Ship Research Association DTMB - Dutch Towing Model Basin
27.
28.
Roughness: It is a major factor in determining frictional resistance. Structural roughness depends on design and method of construction and waviness between frames. Roughness also depends on corrosion and pitting. Roughness is also by fouling by weeds and barnacles. Roughness allowance usually given is 0.0004 Ahead Resistance coefficient (ARC) = Fore and Aft component of wind resistance ------------------------------------------------------½ ρVR 2AT Where VR = Relative velocity AT = transverse cross sectional area For tankers ARC = 0.7 wind ahead up to 500 (LS – 0.85m) ARC = 0.6 – 0.7 wind ad tern upto 400
29.
30.
Effects of ship parameters on Resistance 1. Length : increases means frictional resistance increases because welted surface area increases and wave making resistance decreases. C p is the effect of wave making resistance. 2. Form: represents Cb or CP. Fullness increases means resistance increases. Further ships have greater disturbance Cb decreases means dead weight decreases. So both of them should be taken into consideration. 3. Slimness: L3 ----∇ Slimness means high L/B value greater ∇ means steeper angle of entrance and run. For high-speed ship ∇1/3/L is kept low. Increase in volumetric coefficient increases resistance.
4. B/T - Increase in B/T increases resistance. In very high B/T ratio, the flour will go vertical and can reduce resistance. B increases means disturbance increases. 5. LCB : Governs the fullness the end of ship 10% forward of midship for slow ships and 10% aft of midship for fast ships. LCB at aft of midship will create eddies and forward of midship will allow smooth floar. 6. Section shape : For slow and moderate ships U sections at forward and V sections at aft 7. Bulbous bow : bulb reduces the wave making resistance. They are fitted for high speed ships. For slow speed ships bulb changes the four pattern and reduces frictional resistance. 31. Model Experiment Model experiments are done in towing tanks. Towing tanks have greater length but breadth is small. Models are attached to carriage which slides over the tank. Models are made of wood, FRP or paraffin wax. Resistance test are done in smooth water. Tanks are fitted with wave makers or turbulent stimulators. The platform has a dynamometer attached to measure the speed. Here we can measure various motions and resistance. Models attached to the carriage should be free to pitch and heave. Model basins are used to study model performance when maneuvering in waves. 32. Full scale test are conducted to find the scale effect. Scale effect means the predicted value of model and value of actual ship gives a small difference. So to find this full scale tests are done. For doing full scale trials the shape is towed or moved by jets high on ships. Laws of comparison
33.
34. -
Equipments used in towing tanks are Carriage to which model is attached Dynamo meter attached to platform for speed measuring Turbulent stimulators and wave makers for making regular and irregular waves Camera to records the path of model and various motions
(10)
MANEUVERING
- (Answer Sheet)
1. 2.
Maneuvering is the ability of a ship To maintain dynamic and directional stability Response to movement of control surface Ability to turn in a specified space Ability to maintain constant depth for submarine Ability to change depth in submarines Case with which ship can be controlled in a horizontal plane Principle of directional stability
Considering the arrows with large tail area, whose path of travel represented by path of travel of its CG. If a small disturbance deflects the arrow by Ψ, a lateral force F is produced at its tail since lateral surface area is more towards tail. This force can be converted to ‘F’ acting on CG and a moment. ‘F’ will to by to charge direction and ‘M’ will try to decrease Ψ. So arrow will defect to a new path with a direction similar to initial path. If this principle is applied to ship so that if there is a deviation in its path of travel, hydrodynamic force will acts on centroid of wetter surface area on one side which will tend to move the ship to a new path and reduces Ψ. The resultant force must act in centre of lateral resistance which is aft of ‘G’ 3. Center of Lateral Resistance It is the centeroid of lateral surface area which makes the angle of attack during a turning. 4. Ships can be made more directionally stable by using large skegs, using a large area rudder, increasing slenderness of ship (increasing T/L ratio)
5.
Neutral point is the point along the length of the ship, in which an applied force does not cause the ship to steer from its constant heading. This point is 1/6 L of the ship from bow. That is if we place a rudder at neutral point, the rudder movement will not cause to steer the ship. Or Neutral point is ηL forward of CG of ship. Rudder is fitted aft because it is the farthest distance from the neutral point for directional stability and also in propeller stream for directional stability because rudder lateral force increases due to high stream velocity from propeller. Various forces acting on a ship
6.
7.
8.
Factor’s affecting lift are Cross sectional shape Area of Rudder Aspect ratio Square of velocity Density of water Angle of attack Rudder force, Fr = ρArV2 f(α)
9.
Stall angle of rudder If angle of attack increases rudder (lift) force also increases. At a particular angle the lift reaches its maximum value and suddenly reduces and is termed as stalling. This stalling occurs usually at 35-450 and is termed as stalling angle. ie. the rudder angle is usually limited to 350 It is the angle of attack of rudder of which lift fore on rudder suddenly falls.
10.
CP of Rudder: It is the point on the surface of rudder at which the ruddar lateral force acts, which the rudder is put to an angle or it is the centeroid of lateral surface area of rudder through which net resultant hydrodynamic force acts. Geometry of a turning circle
11.
12. 13. 14. 15.
Drift angle is the angle between the center line of ship and tangent to the path. Drift angle is measured at the CG of the ship. Drift angle is zero at pivoting point. Advance is the distance travelled by CG in a direction parallel to the original course after the rudder is put over. Transfer: is the distance travelled by the CG perpendicular to the original course after the rudder is put over. Tactical diameter is the value of transfer when the ships heading changed by 180 degree. It is the dist. Travelled by CG of ship perpendicular to original course after rudder is put over till heading changed by 1800. Pivoting Point is the foot of the perpendicular from the center of the turning circle to the middle line of the ship extended if necessary. This is the point at which the drift angle is zero and is about 1/6 L from bow.
16.
17.
Angle of heel when turning: The ship heels inwards when the rudder is initially applied. The moment is by the athward component of the net rudder force and the hydrodynamic force acting at CG of hull and the centrifugal force. Fh – Fr = ∆V2 ----Rg Fn = Fr + ∆V2 ----Rg
=
R = radious of turn, V = speed of turn Moment which causes heel is (Fh – Fr) KG + Fr KH - Fh KE (Fh – Fr) (KG – KE) + Fr (KH – KE) EH is very small and can be ignored So moment causing heel = (Fh – Fr) (KG – KE) + Fr EH (Fh – Fr) GE Initially Fr vets when rudder is pit over and Fh slowly builds up and ship turns inwards. The effect of Fr is to reduce heel. If Fh builds up and overcomes Fr then ship heels outwards. So if Fr is suddenly taken off or put to opposite side the ship will heel more towards outwards. For small angle of heel ∆GM sinφ = (Fh – Fr) GE = ∆V2 ------- GE Rg GE ---- = Rg sinφ/V2∆ GM ================ 18. ZIG-ZAG maneuvering (Kempf maneuvering) Is used to find out initial response of the ship towards rudder movement.
Ship will go at a steady speed on a straight course Rudder is out to 200 P and held constant When the ship’s heeling charges to 200, the rudder is put to 200 stbd and held constant, till ships heading changes to 200in opposite direction.
Repeat the experiment Time between the successive rudder movements is noted. Overshoot is the amount by which ships heeling exceeds 200 before it reducing after the rudder is reversed. Experiment is repeated for different speeds, different values of rudder angle and heading deviation. Overshoot decreases with increased stability and rudder effectiveness. 19. Spiral maneuvering Indicates directional stability or instability From a steady speed and straight course rudder is out to say 15 0 stbd. Then ship setters to a steady rate of heading and is measured. Then rudder angle is changed to 100 stbd and steady rate of heading is measured. Then successive rudder angles of 50 stbd 00 , 50 P, 150 P etc. and rate of heading is noted.
For a stable ship, there will be unique rate of turn for each rudder angle. For an unstable ship, the graph has two arms for smaller rudder angle, depending on whether rudder is approached from above or below the value. The ship is unstable inside the loop. It is impossible to predict the ship’s way during turning and depends on disturbing faces of ocean. This gives the range of rudder angle over which the movement of ship is indeterminant. 20. Pullout maneuvering: to determine the direction stability of ship. Rudder angle is put to predetermined and held. When the ship is turning at a steady rate, rudder is returned to midship and change of rate of turn is noted. If stable rate of turn reduces to zero and if unstable the ship will take a new path. If the area under the graph is small the ship is more stable. 21. Standards of Maneuvering Large Rudder can increase directional stability and turning moment. Increase of T/L will improve directional stability Increase of B/L improves turning but reducer the directional stability Large skes will improve directional stability, but poor turning ability. Technical diameter/Length : 3.25 – 4.5 at 350 rudder angle Turning rate : 30/sec. for naval ships 0.50-10/sec. for other ships
Speed on turn = 60% of straight course Angle of heel = very important in passenger ships For directional stability there should not be loop in spiral maneuvering For pull out maneuvering, when rudder in centered 15-200 change is good stability 35-400 average 80-900 not good For ZIG ZAG maneuvering 200P - 200 stbd 80-30 sec for t-20 knots for a ship of 150m length Overshoot5.50 for 8knts and 8.50 for 16 knts 22. Selection of Rudder Based on - shape of stern of the ship - size or area of rudder required - capacity of steering gear available 23. Conventional Rudder have stream lined shape. They are double plated structures Conventional rudders are classified, based on degree of balance – Balanced, unbalanced and semi balanced rudders Based on suspension – simplex and spode rudders 24. Different between balanced and unbalanced rudder: For balanced rudder center of pressure is on the rudder axis For unbalanced rudder the center of pressure is at a large dist. From rudder axis Balanced rudder’s require less torque to turn it. Unbalanced rudder regwire large torgue to turn the rudder.
25.
Simplex Rudder Conventional rudder with …….. supports or support from hull. Rudder is fitted to stern frame by rudder post. In most case simplex rudder is unbalanced.
Spade rudder conventional rudder with in a suspended condition from stern frame. Rudder is filled to stern frame by rudder stock.
26. Bow rudder is fitted at the forward point of ….. at the bow. It is fitted to control path and heading independently. In war ships it acts as a stand by to aft rudder. It is less effective compared to aft rudder. 27. Controllable pitch propellers are used for ……………. Thrusters. They are used because they reduce the turn around time and enhances economy of operation. Special Rudder : are used to improve lift to drag ratio conventional rudder are of limited use at low speed i.e. special rudders are used to improve response at low speeds. Flap rudder In this an additional flap is provided at trailing edge of rudder which is capable to move to a greater angle than main portion. One third of total area of rudder is used as flap. Angle of flap is twice that of main rudder. Provides better lift characteristics system is complicated because flap is moved independly.
28.
29.
30.
Flectner Rudder : an example of flap rudder. Flaps of quite small area at trialing edge can be moved .. as to induce hydrodynamics forces on the main rudder assessing the turning it. It reduces torgue required for steering gear. Other types of rudders: Active Rudder Kitchen rudder Balanced reaction rudder Lateral thrust units Voith – Schneider propeller
31.
32.
Simplex Rudder 33. 34. Double plate construction Lift tube to lift rudder for repairing works Vertical and horizontal stiffners ……………… to drain water. Main Basin / Quay Trials : All piping systems and pumps Electrical power plants with all lights and electrical load Main and auxiliary machines and associated alarms Ventilation and air conditioning All main engine control systems Cargo pump capacity trial Navigational and radio equipments Deck machinery Alarms and controls Steering system Bilge and balast system Fuel oil system Fire fighting, CO2 and foam systems a) Speed Trial Trial speed is to be measured at a certified mile course or by GPS Speed trial consist of a double run and speed ………..be obtained by the average of these two consecutive runs.
Two parallel posts each at a distance of 1 knotical mile is placed store. Experiment structs when ship reaches in line with the posts and ends when it pasts the post. Time to travel between these two posts are taken for speed calculation. Experiment is done 2 to 3 times because of disturbances. Two such runs are conducted at 90% MCR condition and one double run at 50%, 75%, and 100% MCR. b) Crash stop astern This is carried out commencing with full ahead when the vessel is running full ahead to MCR and shall be continued till the vessel runs to full astern at normal asbern. c) Turning Test Measurement of tuning circle at MCR out put of main engine, taking 35 0 of …………angle to port. d) Zig – Zag test Test is carried out at 90% MCR of main engine by setting the rudder angle to 20 0 port and 200 stbd and also at 100 P and stbd. e) Endurance test Four hours endurance trial at maximum conditions out put of main engine using HFO, including two hours fuel oil consumption measuring shall be carried out. Bunker consumption to be found is service speed and at max. conditions rating of main engine for full load and ballest conditions. f) Stopping inertia test carried out by stopping the engine when the ship is running full heat at 90% MCR. The ship is continued to run till the speed comes down to five nots. 35. Model experiments in maneuvering A model with geometrical and dynamical similarities are mode Battery ……… electric motors to drive propeller
36. -
Radio control links for rudder and motor controlled A Basin with 122m x 61m is needed Overhead corner as are fitting to photograph the path of model Models are radio controlled and fitted with ……. to sense heel. Lights are provided at bour and stero, so that model moves is a known datum plane Lights are photographed using a multiple exposure technique The print is superimposed on a grid to enable the light positions to be reed off and drift angle deducted Speed and turning path are deducted Heel angle recorded inside the model Rudder forces and movement are recorded Results from model experiment for maneuvering Speed and turning path Heel, rudder force and moments Drift angle Results from model experiment for directional stability
37. 38.
In obluguw tour best, derivatives of forces and moments with respect to your angle measured Viscous effect on forces both with and without propeller are found out Rotating arm facility is used to measure forces at various your angles for a range of speeds and path of ………… These data obtained can be used to study situations of non-linerities RMM to study liner directions of velocity and acceleration ………………………..and ……………. Motions is obtained by force oscillating the ………… Turning circles, Zig-Zag maneuvering are predicted. PMM Test : (Planar ratio mechanisom test) Used to study the linear derivatives of velocity and acceleration Model is force oscillated in towing condition ……………….. swaying and ………… motions are carried out CPMAC The rate of turns or curvature that can be applied in PMM tests are limited and test do not provide good information. I computerized planar motions carriage system have the features to do obligue ………. Test, rotating arm test and PMM
39.
Ship Trials
For model ship ………. Actual ship has not an exact trajectory compared to model test. So there should be sufficient …… between model and ship to believe that model behavior respects ship
(11) 1.
SHIP DESIGN TEST I
(Answer Sheet)
Design is an arrangement of elements that go into human production. It is an activity that integrates the existing bodies of knowledge. In Design field Designer’s create and Engineer’s analyse. Design process is a series of operations leading to an end. Here a step by step description is needed for completing an activity. Design documentation provides Important issues Process is explicit Known to every one A record of decision is mode for future reference Standardised in companies
2.
Safety aspects in Design Plimsol mark to limit the loading of ship IMO requirements to be satisfied for stability of the ship Safety margins or safety factors Faculty free analysis to break down the problems into parts Risk analysis to analyze the risk and to overcome it Use of statistics and probability in design for risk assessment
3. 4.
Risk factors The major risk factors are Not achieving contract speed Not achieving dead weight Structural failure Collision in a crowded sea Mitigation or Risk management It is the use of Risk analysis to identify ways to reduced the identified risks
5.
Fire main categories of world fleet 1. Cargo ships 2. Passenger vessels 3. Naval vessels 4. Other self propeller vessels
6.
5. Barges and other Inland water vessels Types of cargo ships Tankers (liquid cargo carriers) Dry bulk carriers (grain, Coal and ore carriers) General cargo carriers (Containerized, R0-R0, Packaged, Palletized)
7.
Different liquid cargo carriers Oil carriers (Crude oil and refined petroleum products) Chemical carriers (phosphoric acid, Methanol, etc) (Gas carriers (LPG & LNG) Other carriers (water, fruit juice, molasses, vegetable oils, wines, asphalt, motton sulphur etc)
8.
Different general cargo ships They are of four types based on configuration 1. 2. 3. 4. Container ships Roll-on/Roll-off ships Refrigerated ships Packages or bundles type ships
9.
Different passenger ships They are also four types based on service 1. Cruise ships 2. Deep sea ferries 3. Short sea ferries 4. Fast ferries
10. -
Different offshore industry vessels Anchor Handling Tugs Supply boats Crew boats Stand by / Rescue boats Other offshore vessels – a. Offshore drilling equipment b. Offshore construction equipment c. Offshore production equipments
11.
Different offshore drilling equipments Drill ships Jock ups Drilling barges Semi submersibles Submersibles
12.
Different offshore construction equipments Derrick barges Pipe lay barges
13.
Different offshore production equipments Floating production unit (FPU) Floating storage ……………………. Floating production storage and offloading (FPSO)
14.
Main categories of marine industry The main five categories are 1. 2. 3. 4. 5. Ship design firms Ship construction firms Marine manufacturing firms Ship operation firms Ship repair firms
15.
Supporting Industries Supporting industries which comes under marine industries are Marine surveyors Pilots Terminal operations and stevedores Ship brokers Shipping agents Port Authorities Ship breakers Marine Insurance brokers Marine lawyers Bunkering companies and ship chanallers
16.
main manufacturing firms
1. Engine manufactures 2. Propeller manufactories/bour thrusters 3. Steering and mooring systems manufactures 4. Cargo handling system manufactures - This includes communication system Alarms, Systems and Controls Collission avoidance system integrated bridge systems 17. Different ship operations : This includes Govt. owned ship operators Navies and other governmental agencies Major multinationals Independent ship operators Owner operators Ship managers 18. Different Registeries (For registration of ship) Panoma Liberia Honduras 19. Initial cost This includes building costs Spare parts costs Owner furnished materials Plan approval Owners supervision Administrative and legal expenses 20. Operating costs : mainly includes Fuel costs Also Voyage costs Port and canal costs Tug service costs Cargo tendling costs Cargo damage claims Hold celeings Dunnage Pilotoge
21.
Daily costs Includes crews wages Insurance
Benefits Overheads and miscellaneous expenses 22. 23. RFR - Required Fright Rate is the ratio of average annual cost to tons of cargo that carried each year IMO - International Maritime organization Main functions are To provide machinery for cooperation among governments Deals with technical matters of all kinds affecting shipping engaged in international trade To encourage, facilitate and adopt high standards concerning maritime safety, efficiency of navigation and prevention and control of marine pollution from ships It is an international forum not a government body It consists of an assembly, council and four main committees It has a permanent representative from IACS It developes and adopted nearly 40 conventions and 100s of codes and recommendations. 24. Four committees of IMO 1. Marine safety committee (MSC) 2. Marine environmental protection committee (MEPC) 3. Legal committee 4. Technical co-operation committee 5. Marine safety committee (MSC) deals with Maritime safety procedure Maning from a safety stand point Construction and equipment of vessels Matters within the scope of navigation Rules to prevent ship collision Handling of dangerous cargoes Hydrographic information Log book and navigational records Salvage and ……….. Marine causality investigation 26. Marine environmental protection committee (MEPC) deals in considering any matters with prevention and control of pollution
25.
27.
Main conventions :SOLAS - safety of life at sea MARPOL - marine pollution ICLL - International conventional load lone International convention of tonnage measurement of ships
28.
IACS – International Association of classification Society It is not a governmental body IMO develop rules and IACS implements the rules IMO has a permanent representative from IACS This society will have a permanent qualified staff
29.
Functions of classification society To maintain close co-operation with world’s maritime industries To promote improvement of standard of safety at sea To co-operate and consult with relevant international and maritime organization Main classification societies ABS BV CCS DNV GL KRS LRS IRS NKK RINA RCS American Bureau of shipping Bureau veritas Chinese classification society Det Norske veritas Germanisher lloyed Korean Register of shipping Lloyd’s register of shipping Indian register of shipping Nippon Kaijee Kyokai Royale Italino Novale Russian classification society
30.
31.
DG shipping Directorate general of shipping MMD - Mercantile Marine Department
32. -
DG shipping deals with implementation of shipping policy so as to ensure the safety of life and ship at sea Prevention of marine pollution Promotion of maritime edveation and training in international maritime organization
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Examination and clarification of merchant navy officers Development of coastal shipping
MMD deals with registration of ships and all related matters Surveys of cargo and passenger ships coming under conventions like SOLAS, MARPOL, ICLL etc. Survey during construction of ships Inspection and approval of statutory equipments like FFA and LSA, navigational aids etc.
(12) 1.
SHIP DESIGN TEST II
- (Answer Sheet)
Components of dead weight are
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Mass of cargo Mass of stores Mass of crew Mass of water ballast
Dead weight, DW = MCA + Mstores + MCR + MWB 2. Components of cargo mass are Mass of Dry cargo Mass of Refrigerated cargo Mass of fluid cargo Mass of passenger cargo
MCA = MCD + MCR + MCF + MCP 3. Components of stores are 4. Mass of Heavy Fuel Oil Mass of Marine Diesel Oil Mass of Lubricating Oil Mass of boiler Fuel Mass of Fresh water Mass of provisions
MST = MHF + MDF + MLD + MBF + MFW + MPR Fuel store depends on - Power of main engine - Radius of action of ship - Sailing or working hours
5.
Fuel oil tank capacity Capacity of Fuel oil tank mainly depends on the - power of engine - radious of action - working hours Mass of Heavy fuel oil MHF = bHF - PB . DSE bHF = specific fuel consumptions of mane engine (HFO) = gms/kwhr
PB = Power of main engine in KW DSE = No. of days at sea If RA is Radius of action then MHF = bHF . PB . RA ----- + 10% Reserve V.24 V = velocity in knots Capacity of HFO tank = MHF ------ m3 PHF
Capacity of MDO, MDO = (bdf . PBA . RA ------ + bDF . PBA .DPO/24 RH) + 10% reserve V.24 PBA = power of auxiliary engine DPO = Days loyed in posts Capacity of MDO tank = MDO ------ m3 PDO 6. Fresh water tank capacity Fresh water required = Drinking water + wasting water Vol. of FW required = VFW = 20 L x (no. of officers + crews + passengers) + 60L x (no of crews) + 120 L x (no. of officers) + 200 L x (no. of passengers) 10% reserve If the ship has a desalination plant then Fresh water is needed to be stored for 3 to 4 days. 7. Basic owners requirements Type of ship no. of days at sea +
Service speed Cargo carrying capacity Radius of action 8. Dead weight carrier : is the one in which the main dimensions are fixed depending on the weight of cargo that can be carried Eg. Tankers ∆ = Cb x L x B X T X 1.025(HS) = WD + WL S = Shell, stern and appendage ∆ expressed is fraction of modulded ∆ 9. Capacity Carrier : is the one is which main dimensions are fixed depending on the volume of cargo that can be carried. Ef. R0 – R0 ships, Fishing vessels etc. VH = Cbd x L x B x D’ Cbd = moulded depth block coefficient D’ = capacotu depth = depth + mean camber + mean sheer 10. Linear dimension ship: are one in which dimensions are primary fixed other than dead weight and capacity. Here we are considering the internal and external factors. External factors example is, in container ships, the no. of containers to be considered while choosing linear dimension of ship. L/B ratio is related to slimmers and so the resistance on ship If L/B value is small then it is a bulky ship Therefore higher resistance If L/B value is large then slim ship, so lower resistance Ex. Ship with L≥ 130m. , L/B = 6.5 L≤30m., L/B = 4 30<L<130, L/B = 4 + 0.025 (L-30) 12. B/D ratio is primary related to stability of ship For dead weight carriers = B/D ≈ 1.9 (Tankers) For volume carriers = B/D ≈ 1.65 (fishing vessels)
11.
B/D is also related to hull weight, machinery weight and deck cargo. 13. L/D is related to strength of ship Depth is related to deflection and structural strength of hull grider L/D ≈ 10 for General cargo carriers L/D ≈ 12 for bulk carriers L/D ≈ 14 for tankers 14. T/D is related to free board or reserve buoyancy of ship T/D ≈ 0.7 for general cargo T/D ≈ 0.8 for tankers 15. Displacement coefficient : is the ratio of dead weight to displacement CD = Dead weight ------------------------Light ship + Dead weight CD is related to no. of bulk heads no. of decks size of ship Forces on ship Standard range is of 0.3-1 16. Admiralty coefficient : is used to calculate power requirement of a new ship from the parent ship data. Admiralty coefficient, Ac = V3.∆2/3 ------PB V = Velocity in knots ∆ = mass displacement in ones PB = power required in HP 17. Displacement from displacement equation
∆ = ∆LS + DWT = (∆SE + ∆ou +∆EP) + (∆CA + VCR + ∆FU + ∆FR + ∆SO) Where, ∆SE ∆SEO ------ = ------- = ∆SE = MSE ∆ ∆ ∆O (MSE represents the relative mass of parent ship = ∆SEO ------ ) ∆O
∆ou = Mou . ∆ ∆EP = MEP . PB PB can be found from admiralty coefficient AC = V3 . ∆2/3 -----------PB ∆EP = MEP . V3 . ∆2/3 ---------AC Also, ∆FU = MFU . PB . RA ------ ≈ MFU . V2 . ∆2/3 RA V --------- . ----AC 1 ∆ = A∆ + B∆2/s + I I = ∆ (1-A) - B∆2/3 = known value V3 . ∆2/3 PB = ----------AC
So if we draw a curve with ∆ and I on x and y axis We can find the ∆ of newship for required ‘I’ value Further the displacement equation is modified by Harwald and known as Harwly’d equation. He introduces a factor called normand’s factor to find out the increment of new ship for parent ship. 18. Two methods of subdivision of light ship - subdivision of manes according to production - subdivision of groups according to function preferable for design Purpose
Usually the subdivision is done in three groups 1. Steel mass, ∆SE 2. Outfit mass, ∆OU 3. Engine plant mass, ∆EP 19. Two methods of finding the steel mass For this we need to have a parent ship, from which we can assume the steel mass depending on the main dimension of the ship. This is done by the two methods or relations: 1. Cube number 1. 2. Square number
Cube number ; steel mass depends on cube bumber (L.B.D) 0 – represent parent ship 1 – represents new ship
∆SE1 = ∆SEO x L1C --------L0B0D0
If L/D and CB values are different for parent and new ship then correction is to be given. For brg ships, steel mass calculated by Eube number will be very high, so another relation – square number is used. 2. Square number : steel mass depends on square number L (B + D)
∆SE = ∆SE0 . L1(B1D1) ------------L0(B0D0) The calculation according to square number is approximately proportional to shell plating of ship. 20. Factors depending on length - Displacement - Resistance of ship - Building cost Length increases means resistance decreases but building cost increases Length depends on the shape of bour also 21. Factors depending on Breadth
22. 23. 24.
Increase in Breadth increases the stability of ship but building cost increases B is a function of L and depends on L/B ration, which represents the slimness of ship KM should be increased for higher standers of stability Superstructures, Deck cargo, Cargo handling equipments depends on B, since KG value can change affecting stability External factors like Lock gates or canals Breadth influence free board and stowage capacity Factors depending on Depth Is related to strength of ship L/D ratio represents strength of ship Increases the cargo hold capacity Increased stability as ‘G’ moves down due to increased depth For inland vessels – depth of canal, height of bridges is affected Depends of free board regulation D - T + D Freeboard Factors depending on Draft T increases means resistance increases B/T determines initial stability, since T determines VCB Large B/T value is favorable in connections with initial stability Depends on depth of canal, Harbour fecilities Std. size of containers TEU - Twenty Fect equivalent units = 20 x 8 x 8.5 FEU - Fourty Fect equivalent units = 40 x 8 x 8.5
25.
Five loading conditions for stability analysis of IMO light ship condition fully loaded departure fully loaded arrival ballast departure ballast arrival
26.
External conditions of stability analysis Crane loading Towing condition for Tags ……….. of deck Heeling due to turning Heeling due to cargo movement
- Heeling due to crocuding of passengers to one side - wind moment 27. Static loading condition is the critical case of loading analysis done in the preliminary design stage In this case GM is minimum – always 100% cargo and 100% stores ie. fully loading condition is the critical case 28. 29. Approximate method of stability calculation at the initial stage is prohaksas method The CG of a ship can be determined by detailed mass calculation after fixing the settings of the ship. The CG value depends on mass distribution of the ship CG also depends on type of ship, supers ………………….. sheer, engine plant and out fittings CG is also found from inclining experiment First we assume ‘KG’ as a functaion of depth So, KG = C3D3 Where, DE = DE + (Vss + VDH) -------------LB VSS = Vol. of super structure VDH = Vol. of deck house C3 varies according to type of ship. CG of the engine plant is assumed to be at CG of main engine LCG of the ship can be found from AG/LBP ≈ 0.875 (AB/LBP) + 0.049 SHIP DESIGN TEST III - (Answer Sheet)
(13) 1.
Stowage factor is defined as the inverse of density Stowage factor = 1/ρ = m3/t Cargo hold capacity depends on stowage factor
2.
Depth is the dimension parameter affecting capacity. Depth increases means cargo hold capacity increases and also the strength.
3. 4.
Tankers have less freeboard because density of cargo (fluid) carried is less than that of water. So already its having a freeboard. i.e. freeboard is less for tankers Grain capacity is the capacity of cargo hold including the volume between the frames of cargo hold. Grain capacity of cargo hold is 98 to 98.5% of whole volume
5.
Bale capacity is the capacity of cargo hold excluding the volume between the frames of cargo hold. Bale capacity of cargo hold is 88 to 88.5% of whole volume
6.
In capacity plan the location and capacities of various tanks like FO tank, LO tank, FW tank, Ballast tank, Dirty oil tank, etc, are shown. It also show the cargo tanks and its capacity for tankers. LCG and VCG are shown in the capacity plan.
7.
Capacity curve : is a curve showing the capacities of different sections of the ship as a curve. It is drawn using bonjean curves. The area of each sections upto the main deck + vol. of hatch trunk + vol. of cember + vol. of sheer + vol. of cargo hold in superstructure is taken vertically and joined by a smooth curve at top. It is used for trim and stability calculator. Factors influenced by lines are : Decisive influence on - resistance increase in a seaway - course-keeping stability - sea keeping ability - maneurability - roll damping - size of under deck volume During Hill shaping - shape of sectional area curve - midship section area coefficient and midship section form - …. Forms, forward section forms and FWD water lines - special bour forms - stern forms and Aft sections
8.
9. 10.
Factors influenced by LCG and LCB are speed and trim Various methods of lines design:
- Designed freely or form scratch - Derived from existing lines by distortion a. simple affine distortion b. Modified affine distortion (Interpolation method) c. Non-affine distortion - from graph 11. Free design of lines Fine LBP. Cm, CP, Cb, B, T Draw a trapezium as follows Height of trapezium = Am = B x T x Cm Length of base of trapezium = LBP Length of top of trapezium = L of parallel middle body Ratio of trapezium area to rectangle Am x L is CP Ratio of trapezium area to rectangle B x T X L is Cb Fix LCB according to resistance and trim calculations since centroid of trapezium is LCB, distort the trapezium to move the centroid – LCB of ship to fixed position as calculated - Fair the top edges of trapezium - Extent the trapezium to fore of FP and aft of AP to get length overall 12. Lines designs using design curves 13. using Cb and Cw, fix U,V or normal section from Cw, Cb graph using Cb, fix AB/LBP depending on U normal or V shape using Cb and L/B, fix iE half angle of entrance using Cw and iE, fix the load water line using Cb, fix LE, LP and LR using AB/LBP and CP, fix the CPA and CPF from CPAand CPF, fix the area of each station using area of each station, fix the shape of each station by trial and error
Angle of Entrance : It is the twice of angle made by a tangent to load water line with the centerline of ship at FP and generally given as half angle of entrance, iE/2 Angle of Run : It is twice of angle made by a tangent to centerline of ship and load water line at AP and known as half angle of run ir/2
14.
Simple affine distortion method This method is used on existing design of lines of ship Length, Breadth and Depth are multiplied by a standard ratio Dimensions on each coordinate axis changed proportionately Dimension can be L1B1D or all
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Scaling for each dimensions may be same or different Non dimensional values like L/B, B/T, ∇/L3, Cb, LCB ------, Aw, Cm etc remains LBP Unchanged Fore and aft contour can be changed, CBF = C + (0.0211 + a --- - 0.027Cb) 44 CBA = CB – (‘’) Rearrange the lines of design according to calculation Modified affine distortion
15. -
Using interpolation of two ships design liner to generate a new one …………………………… stations of two ships are interpolated Seeking intermediate values in an arbitrary ratio According to interpolation, water planes are also interpolated to get a new displacement New displacement, ∇N = ∇I + (∇II - ∇I) X X = change is breadth as ratio of overall diff. in breadth of two designs. Non-affine distortion
16. 17.
Here distortion of section area curve of existing design using parabolic curve Shift is section areas are plotted as quadratic parabola The addition area of section is distributed to aft horizontally The increase in value due to inverse in section area is distributed uniformly to aft Different types of bow are Normal bow Balbous bow Special bow forms
18.
Adv. Of Raked stem water deflecting effect increase in reverse buoyancy greater protection in collision more attractive
19.
Adv. Of V sections
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Greater vol. at top side Greater B at design WL. More KM Smaller welted surface area Less curved surface Cheep construction Better sea keeping ability greater reserve buoyancy No slamming effect Greater Deck area In ballast condition less CB and less resistance
Disadvantages : Here wave making resistance 20. Adv. Of Flare Defects green area Increase local reserve buoyancy reduces pitching amplitude Increase the height of Righting arm curve
Dis. Adv. of Flare - Produce more water spray - more structural material required - local pitching acceleration and impacts 21. Design parameters of bulbous bow 22. shape of section side view length of projection beyond perpendicular shape of toward region position of axis area ratio transition of hull
Different bulb forms - modern bulb forms - bulbous bow projecting above LWL - parabolic bow
23.
Effects of bulbous bow on ship characteristics are - sea keeping characteristics - effective drag & total resistance - propulsion characteristics
24.
course keeping ability and maeovering bow thruster trim and free beard Anchor handling Sounding devices length ………………… ice operation
Design criteria for stern designs low resistance avoid vibration high propulsive efficiency to minimise focus separation to provide sufficient propeller clearance
25.
Different types of stern Merchant or Elliptical stern ………………….. stern Transom stern
26.
Adv. of transom stern - more deck are - simplified construction - trim can be improved using wedges - reduces squatting
27.
Adv. of bulbous stern - minimised propeller induced vibrations - more uniform wake
28.
Two bulbous stern 1. Hogner’s bulbous stern 2. Nitski’s bulbous stern Hogner’s bulbous stern is concentric to shaft and has a swollen hub\
Nitski’s bulbous stern has a bulbged lower section 29. AsymmFietric aft body is the one which is not symmetric with respect to center line at the aft sections. Advantages: Higher woke froction Low thrust deduction Uniform inflour Pre rotation and reduction in tangential loss 30. 31. Noenmicke stern is an Asymmetric aft body Fin fitted in aft is known as Grothues spiler Purpose is to reduce vibration, power is reduced from 3 to 9%, - Horizontal straightening of boundary layer . They are hydrofoil find before shaft strit barrel. 32. Wake duct is a Ring shaped flow vane of aerofoil type - fitted to hull as two half rings - sets at different angles for both sides and symmetrical - flow creates a circulation around the aerofoil section and accelerates the flow - less than half diameter 33. Forward propellers for breaking the ice by producing a negative pressure due to section in ice breakers - in double ended ferries - in Inland motor driven cargo ships it acts as rudder propeller 34. Minimum propeller clearance is required to reduce the hydrodynamic forces on the hull produced by the propeller power requirement diameter and optimum speed fluctuation in torque vibration excitation of propeller and stern
(14) 1.
SHIP DESIGN TEST IV
-
(Answer Sheet)
Items in Anchor handling system : Anchor Heavy chain cable Hawse pipe Windlass Sparing pipe Chain locker
2.
Hawse pipe: - It is made of mild steel tube with castings at deck and shell or cast is one complete unit for each side of ship - Shell plating is increased is thickness is way of each Hawse pipe and adjacent plate edges are fitted with mouldings to prevent damage
- There must be clearance for anchor stock to prevent damage by jamming and they must be strong enough to withstand the hammering effect when the anchor is received -chaffing piece is to be fitted at the top of each hawse pipe - A sliding cover is tube arranged to guard the opening 3. Function of cable stoppers - is to lock the chain cable in any desired position and thus relieve the load from the windlass, when the anchor is out or stowed. 4. Design aspects of chain locker - fitted between upper and second deck, below the second deck or in the forecastle - It is to be mode of sufficient volume to store chain cable when the anchors are in the stowed position Situated forward of collision bulkhead and use this bulk head as the after locker bulkhead Chain pipes or spaceling pipes are fitted as near as to the center of chain locker for easy of stowage Stiffners are to be fitted outside to prevent the enticing of chain and damage to locker Centerline bulk heads are to be fitted to separate the two chain and it is to carried above the stowed level Centerline divisions are stiffned by angles, facing both srdes to b/H or solid half round bar stiffned, Hinged door is fitted to forward b/H which gives ………… to chain locker from store False bottom is to be provided to drain water and mud Draining is to be provided and hand pump for discharging the drast Cable end is to be connected to deck or b/H is chain locker Windlass For handling and securing the anchor and chain For handling ropes using for towing the ship Parts Capstuns or gypsy heads for mooring and warping operations for keeping the correct line Wildcat is a special type of drum for handling anchor chain, which have a looking head for disengaging and engaging the chain Drive motor for controlling the operations
5.
Hand break for holding the anchor and chain and to control the speed of discent Locking head for engaging and disengaging the chain Control which includes either electric or electro hydraulic Windlass is also located at the aft of ship for stern anchoring. Usually they are located in the bow for handling bower anchors 6. Types of windlass Horizontal shaft type Vertical shaft type In horizontal shaft type the windlass is placed horizontally above the deck. The whole unit is above the deck. In vertical shaft type, its power source is located below deck and have only wild cats and capstans mounted above deck. 7. Power sources for windlass Electro hydraulic drive Electric drive 8. Anchor handling equipment is determined by a parameter equipment number Equipment number depends on profile area, displacement and above deck area Eq. no. - Displacement2/3 + 2(B x H) + 0.1A H = height from summer load line to top of upper most deck A = Area in profile view of hull, super structure and deckhouse above summer local water line 9. Anchor Handling Regulations All windlass shall be capable of being emergency released from the bridge Tugs for ocean towing shall be equipped with ………… Anchor handling ships should have arrangement for controlled release of ……….. forces in wires Anchor handling ships should have a stern roller with greatest possible diameter for with standing max. load Towing hooks shall be designed for maximum towing force of ship and have a factor of safety not less than5
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Cruciform boll cards and other equipments used for towing should be designed in most unfavourable directions form 0-600 to either side in relation to ships center line and 300 upwards in relation to horizontal plane Types of Anchor
10. 11. 12. 13.
Admirality Anchor Stockless bower Anchor Delta Anchor Pool Anchor Plough Anchor Delta twin stank Anchor Hall Anchor AC14 Anchor Minimum requirements for closures are Which are routinely opened and closed while at sea, such as doors, manholes, hatches etc Which are secured normally at sea i.e. remain closed Eg. Should have strength equivalent to surrounding structure Still height and coaming heights should be as of ILLC and in class Minimum requirements of doors: Minimum sill height required depending on space protected, height above assigned …. Water line and distance from the bow Fixed light is to be provided in all door openings to weather deck. Different doors Individually Dogged water light doors Quick acting water light doors Sliding water light doors Quick acting air light doors Frame tight doors Weather light doors Non water light steel doors Non water light joiner doors Doors within doors
14.
Individually dogged water light door Provide access to compartments that are not high usuage spaces and do not require rapid access
eg. are paint rooms, store rooms etc. Quick acting water light door Secured using a single lever or hand wheel which operates all dogs - used in weather decks, main passage ways etc Non water light Joiner doors - used in accommodation areas where regulations prohibit use of joiner wooden doors Doors within doors - used inside of water light envelop where large access is required for movement of cargo, vehicles etc. 16. Different types of scuttles: (Explanation) Raised water tight scuttles: installed in exterior and interior areas and in corners out of high traffic areas. They are placed where rapid access is required. If may also be used as an alternate access is required. It may also be used as an alternate access to manned or unmanned spaces. Flush water tight scuttles: installed in areas with high traffic to eliminate tripping hazards or smooth trucking hazards. i.e. they are included in flight decks, hangar decks, passage ways and cargo decks. 17. Requirements of Manholes - to ensure two means of escape and to facilitate ventilation - Its standard practice to provide two manhole to each tank or void space, located at diagonally opposite corners - International tank association recommends openings suitable for passage of injured personal or stretchers - Min. clearance opening for a manhole should not be less than 460mm for round holes and 1580 x 360mm for oblong holes Sliding water tight doors Used in place of hinged door, when the door sill is less than the prescribed height above the subdivision load line and when the size of opening is two large to make a hinged door practicable.
Quick acting air tight doors Similar to quick acting water tight doors, but installed outside of water tight structure or above main deck where easy access is required. Used in passage ways, officer etc. Prevents fire, toxia vapours etc. Has three dogs on handle side and no dogs on hinge side Fume tight doors Are of lighter construction, but has more tightness than water tightness Installed in boundary bhd’s of a space containing hazardous, toxia fumics etc Weather height doors Fitted where water tight door is not required Made of steel or aluminium Non water tight steel doors Used in entrances to store spaces Made of 5-7mm thick 18. Requirements of freeing ports - provided in bulwarks to rapidly drain the enclosed deck areas of green water - Rectangular openings 150-200mm high by 600-1200mm long to fit frame spacing in the bulwark plating at deck level - ends of freeing ports have a radius shape equal to the height - vertical guard bars are usually fitted 19. Mooring ports: are water tight enclosures in the shell plating for mooring arrangements. They are used when the winches are located below weather deck or when weather deck is too high in relation to mooring bits. Fairleads (Roller) are built within the port opening to lead the mooring lines directly to which. They hinge in bowered and are dogged tighted. Types of windows: a. Rectangular window: cast or bronze or aluminium frames with steal retaining clips, fitted in upper levels of superstructure and wheel house b. Sliding windows : Vertical and horizontal type
20.
Vertical sliding window descend vertically into a metal pocket below the window and pan is drained to exterior c. Large View windows: In passenger vessels Fitted with double pane windows with an air escape to minimise the heat loss Glass is tinted to prevent solar glare in all latations except ……. house d. Wheel house windows Fitted with wire inserted heat treated plate glass at least 6mm thick for protection Two or more windows are fitted with wipers and rotating disc inserts-clear views, for visibility in rain and snow Canted out for protection against sun glare and parallel distortion when looking to the bow 21. Dead weight scale Scale which contains free board measurements, TPC, MCT, Displacement for different drafts in seawater and fresh water. It is a chart kept in wheel house for the easy assessment of above values for captain for different drafts. 22. Requirements of fuel oil day tank: - an over flow pipe - air vent - drain valve - low level and high level alarm - inlet and outlet ports - man hole - slit glass - vel, to hold fuel oil for a day service 23. Onboard discharges 24. sanitary discharge bilge and fire discharge slope tank discharge galley discharge engine cooling water discharge
Noise levels in - engine rook – 110dB - cabin - 60 dB
25.
Navigation equipments
26.
Radar Anemometer Navigation lights and Flags Magnetic compass and Clinometer Autopilot and Gyrocompass GMDSS, EPIRB, SART Echo sounder and speed log
Surface preparation - means before fabrication, all steel and pipings are shot blasted to SA 2.5 and primed - After fabrication, damaged parts, welds, weld burns etc are removed using power tools and finished to ST2 before being painted.
27. 28.
Unit of paint thickness : Dry film thickness (DFT) which is measured in microns Cathodic protection : is provided on ship structures which are subjected to corrosion - Zinc or Al anodes are used for cothodic protection - Number and weight of anodes are calculated based on area to be Protected - Anodes are bolted to hull - Anodes are bolted to Rudder, see chests and ballast tanks
29.
Rules for GA Design SOLAS IMO panama canal rules suez canal rules ILO 92
30.
Main design aspects while making GA - depends on the service of the ship - structural members continuity - high standard of gear comfort - adequate trim - structure to suit GA layout of holds, tanks, machinery space and deck House - to locate cargo gear for efficient loading - smooth movements of crews during work and in case of emergency - adequate support for cargo gear
‘
31.
Design aspects for container GA Large tranes standard size containers TEU and FEU long verticals stagnations throughout Torsion box at end and box girders and center
32.
Design aspects for Tankers Hose handling cranes shore connections P/V valve Cargo manifoild tray Drain plugs and butter worth openings for cargo hold tanks
33.
Design aspects for General Cargo cranes and derricks of different span and range different types of cargo loading
34.
Different types of ladders fixed vertical ladders spar ladder inclined ladder Accommodation badder Embarkation ladder
35.
Fixed vertical loader: - access to all cargo holds, bosun’s stores, tanks etc. - not less than two ladders are provided to each shape - for cargo holds, vertical lodder is installed at each hatch end in way of structural pillar so that it can be protected from damage by cargo and imposes the minimum interference with cargo stowage - container ships lodders are fitted at bulk heads. Spar ladder - installed on masts, king posts, stacks, etc. to provide access for adjustment and servicing of rigging fittings, lines etc. - fitted with stirrups shaped, so that persons foot will not slide off side ways - mode of 76 x 10 mm FB stringers spaced 300mm centers, and are bolted to lug and welded to most
- provided for interior inspection and maintenance of large diameter posts - hoops are installed around most for safely - access is through man hole, where bending stress is minimum Inclined ladder on weather decks for access from one deck level to another used in engine room, store spaces made up of units complete with stringers, treads and hand rails assembly is then welded to top and bottom of stringer to deck non slip deck pod at top & bottom rails made of 32mm galvanised pipe Treads are non slip steel coverings welded or revelted to stringers for safety on weather deck, this lsdders are located to avoid tripping hazards on deck
Accomadation ladder : (Ganoj ways) - designed to reach from weather deck to light operating draft line at an angle of 450 to horizontal and along the hull - length can be adjusted depending on draft conditions - side stringers are made of light weight metal (Al), wood or channel and designed to carry 136 kg/tread - upper end of ladder attached to a portable platform attached to ship side a deck level III’er platform from lower end to facilitate boarding from small ….. Ludders and guard rails are equipped with portable guard rail stanctions Lower end of the ladder is supported by wire ropes while working cleared of from over head discharge openings and cargo loading side ports - equipped on both sides (p and stbd) 36. Different items and Design aspects on a wheel house layout Rudder Indicator Helsman chair Cyrocompass and magnetic compass Instrument panel Battery charger Radar ocemories Engine Telegraph Techometer Steering gear system Fix Alarm panel
Design aspects - All equipments needed for communication and navigation is located together within easy reach - On all ships VHF, radar and AIS should be located together - ECDIS display should be fitted close to radar - confusion between different instrument to be avoided
15. 1. 2.
SHIP DESIGN TEST V - (Anser Sheet) Design aspects of Accommodation layout Combination of std. rooms of Identical size Constructed is one or two blocks More space with adjacent rooms for ranked officers Mass, galley and stores in lower tiers Beds are arranged fore and aft, setter in athwardship Sanitary spaces are vertically aligned Sanitary spaces should not be located on extender BHDs because of condensation problem Berths and not provided near to deck head Stairways and service trunks should be surrounded by fire BHDs and fire doors Wheelhouse windows to be arranged to reduce pardlax distortion. Requirement of closures Closures are doors, hatches, sutter and man holes Sill heights and coaming heights as per ILLC Class I hinged doors are to fitted above bhd deck Class II and III, sliding water tight doors are fitted in subdivision bhds below bhd deck Open/close indicator on the bridge and remote closing control is to be provided
3. 4.
Cargo hatches, side ports and ro/ro bhds are to be gasketed for watertightness and dogged Manholes two in no. for each cargo or other tanks are to be placed diagonally in opposite corners Hatch covers to be provided with counter balance weight Ventilation requirements Wire mesh is to be provided for protection from insects and rats Fire screens are to be fitted for oil tank vents Cowls for natural air supply fitted with weather head dampers Goose neck for natural and mechanical vent system, supply or exhause, watertight covers with dogs Mushroom type natural or mechanical supply or exhaust can be screwed down to make water tight Lowers on weather bhds, with wire mesh screens Air lifts also can be used in place of laivers Bulwarks and rails Bulwarks
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For protection from sea for personal and deck cargo Sufficient strength for attachment of rigging fittings, lashing deck cargo etc Should have freeing ports as per ILLC Steel plates of 6mm thickness and bracket 1.5-1.8m apart Bridge front bulwark 1350mm and others 1000mm ht. Bridge front bulwark of venture type wind shield Break waters on weather deck Rails
5.
In areas other than bulwark Stenchions 1.5m apart Portable in way of hatches to facilitate loading Guard rails in openings on deck Grab rails outside deck house, interiors passengers etc. Ladders 1. 2. 3. 4. 5. Fixed vertical ladder Spar ladder Inclined ladder Accommodation ladder Embarkation ladder
6.
Rigging Fittings
7.
Derricks and cranes Pad eyes in E/R and stern region Miscellaneous rigging fittings for cargo securing, moving stores accommodation and E/R having spare parts Requirements for safe storage of cargo in holds Sparrings or buttons
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Sparring is wood or metal protection of all vertical stiffners Thermal insulated Cargo bottoms is sparring on shell frames in cargo spaces Ceiling
-
To protect Tank tap Dunnage Wooden ………….. plywood sheets for protection of deck cargo Wire rope nettings with quick acting lashings on deck Plastic inflatable dunnage Bulkhead sheeting
-
Sheeting is given in case of bulk heads from boundaries of tanks to prevent condensation is cargo holds Types of Gratings
8. 9.
Wooden gratings for basin stores, dry store to provide walking and working surface Al gratings for refrigerated space GRP gratings Steel diamond plate for M/C space Deck coverings 1. Magnesite - In crew quarters 2. Terrazo - low fire hazards, decorative properties, economical in all wet spaces, swimming pools, passengers etc 3. Ceramic tiles – in wet spaces 4. Rubber tiles and sheets – decorate and resilient 5. Vinyl tile – most widely used and easy to maintain 6. Carpeting – in public rooms, stair ways, passage ways etc.
10.
Electrical load analysis It is used to find the amount of power that is to be generated by the generator on board. It is the summation of maximum power rating of all the sectional appliances on board ship in watts
11.
Items in a Engine room Main Engine Generator (Main) Generator (stand by) Compressor Boiler Sea chest MDo tank HFO tank Oily water separator Day tank Setting tank Engine room ……… pump Lathe Control panel
12. 13.
Requirements of Exhaust system Thermally insulated Sufficient height to be provided for funnel Exhaust water at higher temp and pressure must be delivered under water Heating gas recovery coil must be provided Exhaust must be significant dist. From accommodation Mooring lines
14. -
External forces to be considered while mooring design Wind Current Surge due to passing ships Waves and swell
15. 16. -
Change of free board Mooring equipments Mooring wires or ropes Mooring winch Cap stuns Fair leads Bollards Chocks Windlass Stoppers Mooring wires Wire lines - for limited movement Synthetic lines – for small ships, where case of handling flexibility of mooring and lower line tension are important criteria High modular polyethgiene and synthetic, fiber ropes with strength and low stretch characteristics can be substituted with steel lines Winches classification Control type Drive type No. of drums Types of drums Brake type Automatic and Manual Tensioning steam, hydraulic, electric single, double, triple drum split, undivided Band, Disc, mechanical Screw, Spring applied
17.
18.
Different bollards Vertical bollards Horn Tee Pillar Cruciform
19. -
Types o Fairleads Closed panama type Roller type Pedestal type Universal type Surivel type
20. 21. -
Automated mooring system Vaccum pads on a frame work on the quay which extends out and secures by vaccum to ships side Gaint magnets instead of vaccum is used Elimination of shore mooring gangs and ship line crew Only one operator to moor the ship Minutes are only needed instead of hours for mooring Eliminated mooring winches on board Different cargo handling equipments Derricks and swinging boom arrangement Cranes grantry cranes Grabbing cranes heavy lift cranes forklift truck other ship board lifting and transferring system conveyor belt system pumps for liquideos cargoes elevators – wire and crane operated Burtoning system and winches Different cargo hatches covers Type a. b. c. d. Single pull Folding covers and direct pull covers Roll stowing covers flexible rolling covers Side and end rolling covers lift and roll covers Telescopic covers e. Pontron covers Mode of operation Rolling and tipping Foldable Rolette Rolling Lifting
22.
23. -
Fire fighting equipments Smoke detector Intrared flame detector Alarm Portable extinguishers Automatic water spray or Deluge system Foam systems Carbon dioxide flooding Inert gas Funnel gas inserting system Halon system
24. 25. 26. 27. -
Dry powder extinguisher Life saving equipments Life buoy Life jacket Immersion suit Visual signals Hand flares Buoyant smoke signal Survival craft Rocket parachute flares Life boats Radar transponder Self inflatable raft Different light signals Day shapes, like lights during day Navigational light Mast head light Side light Stern lights Signals that indicate type of vessel Towing lights All round lights Flashing lights Vessels engaged in fishing, not under commend Underway, vessel restricted in her ability to maneuver Sound signals …………… Short blast - 1 sec Prolonged blast - 4-6 sec Maneuvering signals and warning signals Distress signals Signals to attract attention Steering system Telemotor control Electrical control Hydraulic powered - Ram type - Rotary vane type
16.
CLASS TEST II
- ANSWER SHEET
1.
Major stress acting on a ship structure are 1. Built in stresses due to welding and rolling of structural elements 2. Stresses in still water due to uneven distribution of mass and buoyancy 3. Stresses in seaway due to the action of waves causes longitudinal shear stress and bending stresses. Torsion also oceans due to uneven waves 4. Crushing or compressive stress due to pillar loading and stresses due to pending, …….. and panting
2. -
Strength analysis of a ship Analyzing the ships forces in seaway and still water Evaluating the response of ship towards this forces Estimating the ships response towards there forces Make sure that there stresses will not go above the allowable units Strength analysis is done mainly for Long term serviceability unit Ultimate stress limit ………………….. limit Accident limit Strength analysis also include longitudinal strength analysis, Transverse strength analysis and local strength analysis by finite element method Factors affecting strength of a ship Depth of the ship Length of the ship
-
3.
4. 5.
Uneven loading Irregular seaway Corrosion Concentrated load during docking Sectional area Different modes of structural failure Fatigue Welding imperfections Built in stresses Due to corrosion Uneven loading Instability due to large deflection for small increment of loading Major forces acting on a ship in still water As we known weight of ship is equal to buoyances loading pattern …………. …………… in mass/unit length and ship’s shape causes a variation in buoyancy/unit length If mass/unit length = mg Buoyancy/unit length = ρga Net force = mg + ρga Shear force = s= ƒ(mg + ρga) dx Bending movement = ƒ(s) dx
6. 7. A.
Force acting on a ship in seaway Due to woves (logging and sagging) Rudder lateral forces Centfugal force Thrust from propulsion device Wind resistance Wave resistance Weight is buoyancy Simply supported beam subjected to concentrated load RA + R B = W RA x L = W x L/2
RA = W/2 = RB SFD At a dist. ‘x’ from A Fx = +RA FA = +W/2 FC = W/2 SF between ‘C’ and ‘B’ F x = RA – W FC = w/2 – w = -w/2 FB = -w/2 BMD (at a dist x) M x = RA . x MA = RA.O = 0 M C = RA . O = 0 MC = RA . L/2 = wL ---4 BM between ‘C’ and ‘B” Mx = RA.x – w (x-L/2) Mc = wL2 ------ - w (o) 4 = wL ---4 ====
Mb = w L ---- . --- - w (L-L/2) 2 2 = 0 7. B RA + RB = W. x RA x L = w. L. L ----------2 RA = wL ----- = RB 2 SFD At dist. ‘x’ from A Fx = RA – wx FA = wL ---2 FC = = wL ---2 FB = wL ---2 = -0 wL ---2
-
= 0
- wL
- wL ---2 =======
BMD At a dist. ‘x’ from A Mx = RA . x - w.x.x -------2 MA = 0
MC = wL2 wL2 ----- - ----4 8 = wL2 ----8 === MB = wL2
------ - -------
2 7. C
wL2 = 0 2
RA + R B = w RA x L = w x 0.25L RA = 0.25 W RB = 0.75W SFD between A and C SFx = RA . x FA = RA = 0.25W FC = 0.25W Between C and B SFx = RA – W FC = 0.25W – W = -0.75W FB = 0.25W- W = -0.75W BMD between A and C M x = RA . x
MA = 0 MC = RA .0.75L = 0.25W x 0.75 L Between C and B Mx = RA . x – w (x-0.75L) MC = 0.25W x 0.75L – W (o) MB = 0.25WL – W(0.25L) = 0 7. D SFD Fx = w FB = W FA = W BMD Mx = - w. x MB = 0 MA = - W.L 7. E SFD Fx = wx FB = 0 FA = + w.L BMD Mx = -w.x.x -2 MA = 0
MB = - wl2 -----2 8. Welding techniques 1. Rightward techniques 2. Left ward techniques In both the above cases the welding torch is in right hand and filler rod is in the left hand. The main difference in the right ward technique, the welding starts from the left end and move towards the right hand side of the work piece
Are welding techniques include Downhead welding – 1G Horizontal vertical welding – 2G Vertical welding – 3G Uphead welding - 4G Pipe welding - (5G & 6G) 9. Welding Imperfections a. Welding cracks due to lack of root penetration
Ultra sonic testing:- are also used to defect the internal defects. The frequency of waves ranges from 20 KHZ to 20 MHZ, which can be transmitted through object and get reflected by the defects. Aere probes are used to transmit the waves and receiving them after the passage through objects. Since ultra sonic waves are transmitted as a series of …………. …………., the same probe may be used as transmitter and received. In case of any defects between top and bottom surfaces of the objects, the beams striking this defect will get reflected, reach the receiver probe and indicates a echo on the cathode ray oscilloscope screen before the echo given by the waves striking the other end of the job and returning. So time interval is to be noted between transmission and incoming signals. The distance of the defect can be determined by the time distance scale in the form of a square wove, shown in oscilloscope. 11. Welding inspection methods i) Destructive Testing
ii) Non-Destructive testing i) Destructive testing includes a) Impact test b) Bending test c) Hardness test iii) Non-Destructive testing includes a) Visual Inspection a. Liquid penetrate testing b. Magnetic particle testing c. Radiographic testing d. Ultrasonic testing
12. a. Mass and Buoyancy distribution Mass distribution from shell expressions adding structural component and loading pattern Buoyancy distribution from Bonjean curve For a general ship is still water For a general ship in seaway in a ……… wave here also the mass distribution is same
For a general ship in seaway in a sagging wave
b.
Shear force and BM diagram for ships
SR and BM are zero at ends Bendy moment is maximum at deflection for SF = 0 at midship SR is maximum at a quarter length from two ends of ship c. Still water and wave bending moments
a.
Visual inspection: Inspecting the welds visually or by magnifying lens. This method is most popular, simplest and economical for detecting defects on the surface of the welded objects. b. Liquid penetrate test (LPT) : are used for detecting the surface defects. Here the liquid penetrate is applied to the surface of the object after cleaning the surface of the object. After some time the liquid is completely removed and developer is applied. Then the liquid which has penetrated come out of the cracks and developer will helps to detect them easily c. Magnetic ………Inspection (MPI) : Firstly the object is placed in the magnetic field and magnetic liner of flues get intersected by discontinuously such as crack or slag inclusion, magnetic poles are generated on either side of discontinuity. This causes a distribution in the magnetic flare …….. through the job, which can be detected by magnetic particles which are attracted to the region of discontuity. This is applied only for ferrous materials. d. Radiographic test : X-rays, which are produced in a X-ray tube are proceeded towards the objects which is to checked for defects. An X-ray film is placed behind and in contact with the object, perpendicular to the passage of X-rays. As the x-rays …………… through the objects and strikes the film, take the film for developing and film shows light and dark areas, which is easy to determine the defects (like ………….., cracks, slay ………etc.)
17. 1.
MARINE ENGINEERING QUESTIONS (Answer Sheet) In water tube boiler feed water is passed through tubes and hot gases passes over them. It is employed for high pressure, high temperature and high capacity steam applications. It is used for propulsion of main engine, turbine and for cargo pumping. In smoke tube boiler hot gases pass through the tubes and feed water passes around it. It is used for auxiliary engines It is used to produce small quantities of steam which is of the low pressure
2.
Steam to steam Generator: are of vertical and horizontal types. It is used to produce low pressure saturated steam for domestic and other services It is used is conjunction with a high pressure water tube boiler. It is similar to a smoke tubes boiler, but instead of not gases high pressure steam which is passed from the water boiler is used to heat feed water
3. 4.
Advantages of steam to steam generator No fuel burning or furnace burning is required They provide a secondary steam circuit which avoids any possible contamination of primary steam circuit. Can be used in ………….. with a main boiler to produce low pressure steam No separate boiler is required to producing low pressure steam Heat recovery system It uses exhaust gas from diesel main propulsion engines to generate steam Exhaust gas heat exchanger and exhaust boils are the main parts Improved plant efficiency
For slow speed engine, large quantity of steam can be produced if power is increased, by heat recovery system. In some cases this sufficient to provide ships entire electrical power and other heating purpose. 5. Composite boiler: It is a boiler arrangement which permits steam generation either by a furnace when necessary or by using engine exhaust gas (Heat-recovery system) when ship is at sea 6. 7. Separate tube banks for engine exhaust system and oil firing or furnace system It is similar to a Cochran smoke tube boiler Purpose of an Air ejector in a stem plant is to Avoid corrosion problems in boiler due to air entrapment To draws out vapaour particles, dissolved gases and air released from condensing steam from the condenser To increase thermal efficiency of steam plant by leaving the excess steam pressure by book pressure To avoid back pressure in condenser by removing garcons matter Vaccum is maintained in a condenser because for maximum efficiency of the turbine the pressure developed should be maximum. As the condenser is placed after the turbine, if …….. provide a vaccum on the condenser i.e. on the exhaust of the turbine, maximum pressure drop will occur. So we can make use of the maximum useful work from the ………… It also helps in avoiding any backpressure for the turbine outlet. Boiler mountings: 9. Safety valve Main steam stop valve Auxiliary steam stop valve Water level gauges Pressure gauges Air release cock Sampling connection Blow down valve Alarms Purpose of boiler water treatment is to remove salt and imparities To avoid local overheating and failure of tubes due to scale formation To avoid scale formation inside the boiler surface which leads to corrosion To avoid reduction in heat due to dissolved salts To remove dissolved ………………. And carbon dioxide which causes corrosion in boiler
8.
10.
To avoid foaming on surface due to suspended particles, oils etc. Difference between 4-stroke and 2-stroke engines 4 stroke engine 2 stroke engine one power stroke in each revolution, so max. power Engine completes four operations in one revolution values are replaced by ports less maintenance less fuel efficient difficult construction
1. One power stroke in two revolution 2. Engine completes four operation in Two revolution (section, compression, Power exhaust stroke) 3. Valves are used for intake and exhaust 4. Maintenance is maximum 5. Good fuel efficiency 6. Easy construction 11. Parts of marine diesel engines: Cylinder Piston Piston rod Cylinder lining Intake, exhaust valves or ports Cylinder head A frame Cross pin Cross head Crank shaft Valve timing arrng. Lubricating system Cooling system 12.
Difference between Trunk type and cross head type engine Trunk type Cross head type
a. Automobile Engines b. High speed, short stroke
a. b.
Marine Engines low speed, long stroke
c. Small type d. Piston is connected to Connecting rod directly e. No guide shoes or cross Head pin f. Cooling and lubrication is easy 13.
c. d. e. f.
large type piston is connected to piston rod which is then connected to cross head pin guide shoes guide the long stroke on a steady manner cooling and lubrication is difficult
Advantages of oil cooled pistons over water cooled piston is that the small oil can also be used for lubrication of part of engine crank case Piston rings seals the combustion chamber of an IC engine by The outward pressure due to ………… in the compressed ring initially The outward pressure is then increased by the gas pressure which acts on the back of the ring. This pressure will be higher in top rings than the lower ones Symmetrical valve timing If the valve timing is similar for both forward and astern working of a marine engine, it is called as symmetrical valve timing.
14.
15.
16.
Cam shaft is driven in a marine diesel engine by Gear wheel system & Roller chain system
17.
High TBN oil is used in cylinder lubrication because _ TBN (Total base Number) represents the alkalinity of lubricating oil The sulphur content in the fuel mix with water during combustion gives formation to sulphuric acid (H2SO4), which increases the corrosion rate. To nitrides this effect a high alkaling TBN oil is used. Rotocap in an exhaust valve is friction disc or rachet provided on bottom of compression ring in an exhaust valve system which mechanically rotates the exhaust valve during exhaust stroke. This is done to get a uniform heating and wear around the exhaust valve and valve seating.
18.
19.
Under cooling : of charged air means cooling of air to a temperature below its …… point at that pressure. Undercooling causes excessive condensation. It will reduce the intake temperature to a very low value with reduced efficiency. This will also cause thermal shock when it comes into contact with hot siners and piston. Types of Turbo charging system 1. Pulse system 2. Constant pressure system
20.
21. 22.
purpose of Turbo charging : is to increase the power output and efficiency with small increase in size, weight and initial cost. Mass of air per cyde can be increased and so quantity of fuel injected can be raised to give corresponding increase in engine output and increase in thermal efficiency Reduced pollution because of perfect combustion Acts as a recovery system because the turbine receives energy from the exhaust gas Scavenging It is the process of removal of exhaust gas from engine cylinder after combustion and replacing the exhaust gas by fresh gas for further cycles of operation.
23.
Methods of Scavenging In four smoke engines scavenging is carried out mainly by purposing action of piston during its two strokes ie. piston expects exhaust gas on its upward stroke and draws in air on subsequent downward stroke. In two strok engines there are three basic methods of scavenging a. Loop scavenging: in which air passes over the piston crown and rises to form a loop within the cylinder, expelling gas through exhaust ports cut in the same side of liner above scavenging ports. b. Cross scavenging: in which air is directed upwards passing under the cylinder cover and down the opposite side, expelling gas through exhaust ports on that side c. Uniflow or through scavenging: in which air passes straight upwards through the length of cylinder, forcing the exhaust through ports or values at the top of cylinder Purpose of tie bolt or stay bolt is To pre stress the structure Maintain the cylinder block and frames in compression
24.
25.
To transmit main gas loads during combustion from cylinder cover to bed plate For easy dispatch and assembly of engines For fixing of the engine in correct piston Cam shaft is driven from crankshaft using a train of gear arranged in piston known as gear wheel system or driven from crank shaft with a roller chain known as roller chain system. Reversing of marine diesel engine is done by
26. 27.
Cutting off fuel supply to engine …….. the air distributor, such that compressed air to the appropriate cylinders in correct order. This is done by alternating the position of distributor cam Fuel pump timing must be readjusted by using a camshaft in axial direction. Indicated power of a marine diesel engine can be measured from the indicator diagram In the indicator diagram the path of process during a cycle encloses an area which represents the work done Different test of diesel propelling machinery during sea trial
28. 29. -
Guarantee speed test Overload test Astern test Minimum revolution test Starting test Capacity of air bottle Air can be stored at a pressure of 30 bar Capacity should be least sufficient for engine starting without recharging should be 12 starts for revisable 6 starts for non revisable Types of pumps for marine applications
30.
1. Centrifugal pumps single stage multi stage 2. positive displacement pumps screw pumps gear pumps Reciprocating pumps
3. Axial flour pumps 31.
lobe pumps diaphragm pumps
purpose of wear ring in a centrifugal pump Salt and sand in seawater causes high rate of wear in the casing in sea water ……………pump. If casing is provided with a wear ring, then it can be replaced after erosion, barides replacing the whole casing.
32.
Functions of volute casing in a centrifugal pump In volute casing as the cross sectional area is gradually increasing, so as the water passes through the valute casing, the high velocity of water imparted by the impeller reduces and by bernollis theorem, the pressure head is increased.
33.
Printing of a pump: Filling of section line and casing of pump with liquid that have to be pumped is called priming. It is necessary to develop enough section pressure at the eye of impeller.
34.
Centrifugal pump is started with delivery value closed to make the starting torgue minimum, at the time of starting water will be upto impeller. A drain connection is fixed to ensure water inside impeller. Wear rate of bearing and shaft will be high in a centrifugal pump dealing with sea water. Since the shaft is continuously rotating the wear leads to replace of the entire shaft. To avoid this shaft is fitted with a renewable sleeve, so that sleeve only has to replace. Pressure relief valve is fitted in a positive displacement pump because there is no reverse flour in this type of pumps. Here water is displaced from one side to another so if there is any problems with delivery side the pressure inside the pump and pipe system increases which courses damages. To avoid this pressure relief valve is fitted. Different types of positive displacement pumps 1. 2. 3. 4. 5. Screw pump Lobe pump Gear pump Reciprocating pump Diaphragm pump
35.
36.
37.
38.
Reciprocating pumps is used for pumping engine room bilges
-
Engine room bilge contains leaked water and oil It a rotary pump is used, it will cause rotating of the bilge which causes mixing of oil and water to form fine particles This will results difficulting in the separation in an oily water separator, because gravity separation is done in an oily water separator So we …… reciprocating pumps because it displaces the bilge from the engine room without mixing (thoroughly), to the oily water separator and from there it is casting separated by gravity For positive displacement pump slip is the difference between theoretical discharge and actual discharge Fluid flour in a Gear pump
39. 40.
During the flour through a gear pump there will be no movement of flour through the center i.e. through the piston where gear mesh occurs The flour is only through between the tooth spacing and gear casing in one direction. The liquid entrapped between the tooth and casing ensures the flow through the pump. 41. Different types of valves used on board ship Sleeve packed cracks, Globe valve, Butterfly valve, Non return vale, Flap sheck valve, Relief vale, Quick closing valve, Gate vale. 42. We cannot use the gate valve in a partially opened condition because it damages the rubber seal. Here the spindle does not moves up and down only the valve moves up and down, so it is to be fully opened or fully closed. SDNR valve (Screw down non return valve) is used in bilge line as a safety measure to prevent water flowing back and flooding the various compartments. Here the flour is only allowed in one direction only. Purpose of quick closing valve is to cut off the fuel supply by operating from a remote place in case of any fire in the engine room It is used at outlet from Fuel oil storage tank Fuel oil setting tank
43.
44.
Fuel oil service tank Lube oil storage tank Lube oil setting tank Lube oil service tank etc. 45. The steam trap is fitted after steam coil is to prevent steam from escaping and providing the maximum usage, by allowing condensate to pass through Types of Heat exchanger used on board 47. shell and tube type heat exchanger plate type heat exchanger
46.
Advantages of plate type heat exchangers less space is required low maintenance cost highly resistant to corrosion because it is made of titanium plates since there core no tubes, failure due to clogging of tubes can be avoided
48.
Corrosion is prevented in shell type heat exchanges by using sufficient anodes on the body. The anode is sacrificial soft iron. Another method is to introduce iron in the form at Ferrous sulphate fed into the sea water.
49.
Materials of shell and tube heat exchangers Shell – cast iron Tube – aluminum brass Plate - Naval brass
50.
Inert gas system on oil tankers Crude oil is so volatile and it leave hydro carbon vapour while pumping out or unloading the cargo from tankers. These hydro carbon vapors are ……… dangerous. So this is to be removed. For this Inert gas is pumped into the cargo tanks, which prevents the hydrocarbon vapours for catching fire. The main purpose of Inert gas system - to provide an inert atmosphere after oil discharge - to prevent corrosion in tanks - to assist in cargo discharge by applying positive pressure on oil surface
51. 52.
Deck seal prevents the flour back of Hydro carbon vapours from the cargo tanks to the engine room is an Inert gas system. PV valve prevents the pressure inside the tanks to go above a set value and also below a set valve PV breaker also do the same PV valve automatically resets where as PV breaker has to be resetted manually PV valves are provided to prevent bursting and buckling of plates maximum oxygen content permitted in inert gas is between 3-5% of oxygen. Air is supplied to sewage treatment plant because oxygen in the air promotes multiplication of bacteria and satisfactory decomposition of waste. This type of decomposition is called Aerebic-decomposition Maximum oil coatent permitted in water pumped overboard is less than 12PPM Items recorded in oil record book 1. Bunkering 2. Record of pumping out of bilge 3. Sludge/oil disposal and transfer
53. 54.
55. 56.
57.
Application of Ejectors on board ship for complete tank cleaning operations to remove residue and small quantities of water and materials not removed by pumps in fresh water generators air ejectors are used to boil water around 60 0C by creating absolute vaccum in fresh water generator brine is removed by brine ejector.
58.
Purifier removes water and suspended particles from fuel oil and Lube oil Clarifier removes the remaining suspended particles from fuel oil and lube oil coming from the purifier.
59. 60.
Heating is required in fuel oil storage tank for easy pumping of fuel oil to setting tank. For this fuel is storage tank is maintained at 500C Purpose of setting tank Fuel from storage tank is transferred to settling tank where it is heated to about 70-800 C to allow water and sludge to settle down by gravity and can be drained off.
61.
Booster pump or circulating pump draws oil from the primary discharge which is maintained at 4 bar, raising its pressure to about 10-12 bar and delivering it through the heater, viscosity regulator and fine fitter to main engine fuel pumps. MDO line is connected to HFO line to allow flushing with light oil before stopping the engine for long periods or for maintenance. This is because the maintenance is mainly done is boilers and steam trocer tube. At this time we make use of a change over sine the boiler cannot be worked For starting and stopping of engine. Two lube oil system for main engine are One for lubrication of engine cylinder, pistons and piston rings. It is called cylindrical lubrication system Other is a circulating system where oil is used over again and again to lubricate main bearing cross heads bearings, cross heads, stippers, crude and thrust bearing. This is called crank case lube oil system.
62.
63.
64.
Properties of Lube oil correct alkanity and viscocity rust and oxidation intribitiors high viscocity index Detergent and Dispersent propetties water repellants resist foaming an emulsifixation
65.
The main ……………. Of the distributor in a starting air system is to supply the high pressure air to engine cylinders, in which the piston is at TDC (Top dead center) another function is to reverse the sequence of operation during reversing the engine. Flame trap or flame arrester’s function is to prevent the fire entering into the manifold and then to the starting system. Flame trops are fitted to each cylinders connection from the manifold. Starting air valve leaking is found by feeling the temperature of the pipe Fusible plug: It is a non resettable safety valve which is used to ensure safety of boiler. The fusible plug forces at main temp of 1500 0C. If the water level decreases in boiler, the steam will come into direct contact with plug and plug burns out and steam escapes. Inter cooler is to increase the efficiency of the compressor system antis used between ……… pressure and high pressure compressed.
66.
67. 68.
69.
70.
Hydrosphere tank is a pressure tank which is partially filled compressed air above the water surface gives a pressure head to the water causing it to the most remote and highest outlet point of system. The prime movers used for bow thruster are - Auxiliary engine - Electric motor - Hydraulic motor
71.
72.
GPS – Global positioning system It is an US based radio navigation system which proves location and time . It has three parts - satellites orbiting the earth - control and monitoring stations on earth - GPS receivers GPS satellites broad casts the signals from space that are packed up GPS receivers and provides three dimensional locations - latitude - longitude - altitude
DEFINITIONS, LINES PLAN Aft and fore perpendicular Fore Perpendicular : waterline and stem.
( Answer Sheet)
It is the perpendicular drawn from the intersection of
Aft perpendicular : Perpendicular drawn from the intersection of water line and Rudder post, or perpendicular from the center line of rudder stock if there is no Rudder post. II. Breadth extreme: Breadth moulded + Fenders + Shell plating thickness Breadth moulded: Dist. From the inner side shell of port to the inner shell of starboard. III. Port Side : Left side of ship when looking from aft. Stbd side : Right side of ship when looking from aft IV. Entrance: Forward part of the ship with varying cross section. Run: Aft part of the ship with varying cross section Parallel Middle body: Middle part of the ship with constant cross section. V. Camber: Curve applied to the deck transversely Sheer: Tendency of a deck to rise above the horizontal in profile. VI. Draft: It is the vertical distance from the keel to the designed water line. Denoted as ‘T’ Free board: Difference between the Depth and Draft Depth Moulded: It is the vertical distance from the top of flat keel to the bottom of deck plate 1. 3. Lines Plan: It is a Geometrical representation of 2D form of a 3-D complex shape of the hull of a ship through descriptive Geometry. Different views of lines Plan: Profile, Body plan and Half breadth plan Lines Plan
4.
5.
Offset table: It is a rectilinear tabulation of the following vertical distance - from the keel to the bottom of each section where they are crossed by buttock lines. - half breadth of each stations where they are crossed by waterlines. Lofting: Fairing of lines plan in 1:1 scale Lofting is done mould loft, which are big workshops. Archemedies Principle: The apparent loss in weight of a body when it is fully or partially immersed in liquid is equal to the weight of the water displaced by the body. Law of floatation: A body is said to be floating, then weight of the water displaced is equal to the weight of the body or weight of a floating body is equal to weight of volume of water displaced by immersed prt of body.
6. 7.
8.
Buoyancy: It is the upward force which keep the things afloat, which is equal to weight of water displaced by the body. Center of buoyancy: Is the center of gravity of the vol. of liquid displaced by the body (Hull in case of a ship).
9.
Dead weight: It is the maximum amount of cargo which a ship can carry. Displacement: Weight of the ship in the floating condition.
10.
Reserve buoyancy: It is the difference between the volume under water to the volume below the lowest opening on which it cannot made water tight. Six degree of freedom 1. 2. 3. 4. 5. 6. Pitching Rolling Yawing Swaying Surging Heaving
12.
Trim: Sinkage of ship in the longitudinal direction. Heel: Sinkage of ship in the transverse direction
13.
1.
Rise of floor: Distance from the top of the keel to the tangent drawn at bottom cuts the line of the maximum beam of mid ship.
2. Tumblehome: Tendency of a section to fall towards the middle line plane from vertical while approaching the deck. 3. Rake: Departure from the vertical of any section in profile.
4. Flare: Tendency of a section to fall out from the middle plane as it approaches the deck side. 14. Bernoullis Principle For an incompressible,steady, Ideal fluid flow, the sum of pressure energy, kinetic energy and potential (datum) energy are constant along the flow. P V2 --- + --- + Z = a const. W 2g P = Pressure W = sp. wt. of water V = Velocity g = acceleration due to gravity Z = datum 15. Density: It is the ratio of mass per unit volume at standard temp. and pressure. m ρ = ----v Specific gravity is the ratio of specific weight of liquid to specific weight of water. Sp.gravity = Sp.wt. of liquid -----------------Sp. wt. of water
Sp.weight of water = 1000kg/m3
16.
Viscosity
It is the property of a fluid, which resists the flow of one layer of fluid over the other. It is the measure of friction offered by the fluid particles to the resistance to flow. Its unit is Poise or Stoke 1 stoke = 1 Ns/m2 17. Hydrostatic Pressure: It is the pressure at a point in a liquid which is at equilibrium. Hydrostatic pressure increases with depth upwards will increase due. If h is the depth and ρ is density, then Hydrostatic pressure = ρgh A1 = 100 x 10 A2 = 50 x 10 A3 = 60 x 10 h1 = 5 h2 = 35 h3 = 65 = 1000 = 500 = 600
18.
CG of I section form x axiz A1h1 + A2 h2 + A3 h3 Y= =
---------------------------------------
A1 + A2 + A3 1000 x 5 + 500 x 35 + 600 x 65 ---------------------------------------2100
= 29.29
Section I b1d1 3 MI of (1) at Ix1x1 =
---------
=
12 MI with respect to neutral axis = Ia1 =
100 x 103 -----------12
= 8333.33
Ixx1 + A1h12 = 8333.33 + 1000 x 24.292
= 598337.43 Section 2 MI of (2) at Ixx2 =
2 2 ---------
bd
3
=
12 MI w.r. to neutral axis =
10 x 503 -----------12
= 104166.67
Ia2 =
Ixx2 + A2h22 = 104166.67 + 500 x 5.712
= 104699.27
Section 3 MI of (3) at Ixx3 =
3 3 ---------
Bd 12
3
=
60 x 103 -----------12
= 5000
MI w.r. to neutral axis = Ia3 = Ixx3 + A3h32 = 5000 + 600 x 35.712
= 770122.46 Moment of …….. of whole I section, IG = IG1 + IG2 + IG3 = 598337.43 + 104699.27 + 770122.46 = 60708.564 x 103 Section Modular IG ZTop = --- = Y 60708 – 564 x 103 ---------------------- = 1491244.5 40.71
Ia 60708.564 x 103 Zbottom = --- = ---------------------- = 2072672.03 Y 29.29
(2) 1.
DEFINITIONS, LINES PLAN, SHIP TYPES AND KEEL (Answer Sheet) Difference between cargo liners and tramp ship Cargo lines are cargo ships which have specified ports and regular schedules whereas Tramp ships have no specified routes and schedules Tramp ships can carry cargo which cargo lines can’t handle.
2. 2. 4. 5.
Std. size of container – 30ft x 8 ft x 8ft
8.5 x 8 x30
Flared bow is given in container ship is to prevent shipping green water. Usually Flared bow with high us given. Cofferdam : They are the void spaces given between tanks to prevent the risk of leakage of oil and also to prevent osmosis. Double skin, construction : They are given in ships is to protect the marine environment collision and to prevent Osmosis. If a collision occurs the inner skin protects the oil from leakage to the seawater. Bulk carriers Special requirements of refrigerated cargo vessels: They are used to carry food products. It should contain a refrigerated machinery and should have insulated spaces for carriage of food products like, meat, Daisy products etc. They are fast vessels, and have less stowage rate. LNG are carried in prismatic, spherical or cylindrical tanks. They are to be refrigerated and pressurised. Different types of Barge carrying ships 1. Seabee Type and 2. Lash Type In Seabee type elevators are provided to load the barges. In Lash type crones are provided In sea bee type vends there are no transverse Bulk heads
6. 7.
8. 9.
In lash type the barges are placed on over the other.
(3) BASIC STRUCTURE, HOLD, FRAMINGS, LOCKER, FORCE & AFT END CONSTRUCTION BOTTOM CONSTRUCTION 1. Two methods of Bottom construction are i) ii) Single Bottom Construction Double Bottom Construction
BULKHEADS, CHAIN (Answer Sheet)
2.
Double bottom can contribute longitudinal strength because the cross sectional area increases and due to this the section module increases, providing longitudinal strength. Constructional features of Double bottom Provides extra protection to the vessel Height of the double bottom vary from 1000 to 1500mm height should not be less than 650mm Double bottom extends from forepeak bulkhead to Aft peak bulkhead Contains inner shell (Tank top) and outer shell (Bottem plate) Solid floors are fitted every 3 to 4 mt. apart Used fir carriage of fuel and oil Different types of keel 1. Bar keel 2. Plate keel 3. Duet keel 1. Bar Keel : - For small vessels less than 90 mt in length - Solid floors are fitted in every frame spacing - disadvantage of increased draught for minimum cargo capacity 2. Plate Keel: - commonly used in ship’s
3.
4.
- extends from forward to aft - has a breadth to maximum 1800mm - thickness is equal to the thickness of bottom plate + 2mm 3. Duet Keel: - used in double bottom construction - can be used for piping - provides longitudinal strength - extends from fore peck BHD to Aft peck BHD
Hold framings 5. 6. Frames are used to protect the ship shell plate from collapsing - provides good strength to the vessel Types of framing systems1. longitudinal framing systems 2. Transverse framing system 3. Mixed framing system 7. Primary supporting members 1. 2. 3. 4. 5. 6. 7. 8. 8. Solid floor Bottom CL grinder Bottom side grinder Web frame Side stringers Deep transverse Deck side grider Deck CL girder
Secondary support members 1. Bracket floor 2. Bottom longitudinals 3. Deck longitudinals
4. Side longitudinals 5. Hold frames 6. Deck beams 9. 10. 11. Transverse framing system Longitudinal framing system Mixed framing system
12. BHDsz
Common Profiles 1. Angles - equal - unequal 2. T section 3. Bulb plates - equal - unequal - used in CL Girders and side girders. Also used as side stringers - same use as of Angles - used as stiffeners in shell platings and
4. Flat Bar 5. I Section 6. F Section 7. Solid bar 8. Hollow pipes 9. Half round bar 10. Plates 11. Chequered plates 12. Gratings
- used as face plates in girders are for stiffeners - used as stringers - used as stringers - used for pillars and cline roads - used for pillars and piping - as stiffners - for shell construction, BHD, superstructures etc. - used in engine room - used in passengers and on super structures.
13.
Bale Cargo Capacity:-
- Maximum cargo capacity excluding the stiffners in the cargo area Mixed framing system has better bole cargo capacity - Cargo capacity including the volume inside the stiffeners provided in the cargo area
Grain Cargo Capacity :-
14.
The various framing systems are 1. Tranverse framing system 2. Longitudinal framing system 3. Combined or Mixed framing system
1. Transverse framing system Side frames fitted at every frame spacing Bracket floors are fitted at every frame spacing Frames are bracketed to bracket floors Solid floors are spaced at every 3-4m frame spacing A ring like structure includes solid floor, web frame and deck transverse. Deck transverse are fitted every 3-4m apart Better Bale cargo capacity
2. Longitudinal framing system Provided better longitudinal strength Deck longitudinal are fitted on deck’s bottom Side longitudinal are fitted at sides Bottom longitudinal are fitted to bottom. A ring like structure includes solid floor, web frames, deep transverse are spaced every 3-4mt apart All secondary members are longitudinally spaced Spacing of longitudinal is 750mm
3. Mixed framing system Combination of both Transverse and longitudinal framing system Provides better bole cargo capacity Provides longitudinal strength Mainly used in cargo ships and bulk carriers Top and bottom are spaced 150mm by longitudinal Transverse frames are fitted at the sides
Shell Plating 15. 16. Function of shell plating It acts as a water fight skin Provides longitudinal strength Various platings of Ships
1. 2. 3. 4. 5. 17.
Keel strake Garboard strake Bilge plate Side shell plating includes sheer stroke adjacent to the deck plates Deck shell plating includes stringer plates adjacent to the shear strake
a. Gun whale : It is a portion where the sheer stroke and stringer plates meats b. Seams : longitudinally welded joints c. Butts : Vertically or Transverse welded joints Constructional features of shell plating plates are laid longitudinally Thickness of sheer strake and bottom platting are increased because they are subjected to high stresses In heavy ships deck plates and bottom plates are used of high tensile steel Bottom plate thickness depends on the length, breadth and depth and cargo capacity of the ship Longitudinally welded joints are called seems Transversely welded joints are called butts Thickness of keel plate depends on the bottom plate and carrying capacity Thickness is increased in the slamming and pounding region. Thickness is increased near by the stern frame and bossing.
18.
Bulkheads 19. 20 Functions Divides the ship into different compartments Protects the ship during flooding Prevents free surface effect Restrict the entry of fire from one compartment to other Fore peak collision, BHD arrest the flooding of water to cargo tanker Longitudinal bulkheads provide longitudinal strength. Types of BHDs 1. 2. 3. 4. 5. 6. 7. water tight BHD NON water tight BHD Oil tight BHD Gas tight BHD Collision BHD Longitudinal BHD’s Transverse BHD
21.
Types of BHD Construction 1. Plain type bulk heads 2. Corrugated type bulk heads
22.
Plain Bulkhead
23.
Corrugated BHD
24.
Bulkhead Construction Types of BHD construction are: 1) Plain type and 2) Corrugated type
In Plain types the plates are laid in the horizontal direction In corrugated types the plates are laid vertically. Stiffeners are spaced 750mm vertically for plain BHDS If the height is increasing then stringers are provided vertically and horizontally. Corrugated type BHDs are in the form of corrugations or swedges. They can be subjected to high bending loads or pillar loads than plain BHDs The corrugation angle is 450 Stiffeners can be avoided thereby decreasing the steel weight
Diaphragm plates or stringers are added if the height is increased to provide strength 25. 26. 27. Cofferdam provided in vessels carrying various liquidous cargoes provided between fresh water tanks and oil tanks cofferdoms BHD’s are spaced 760mm apart prevents the risk of leakage of oil from one tank to other through osmosis. in some cases used as pump rooms following tanks are to be separated each other by coffer dam vegetable oil tank mineral oil tank fresh water tank Fuel oil tank prevents contamination of liquids of various densities Minimum spacing of cofferdam – 760mm Typical tanks which needs a cofferdam are Vegitable oil tanks Fuel oil tanks Fresh water tanks Mineral oil tanks
Chain Locker 28. Chain locker - Box type structure - Situated in the fore peak tank - One side of chain locker is fixed to collision BHD - Centerline chain locker BHD divides it into two for post and STBD side - False bottom is provided, to drain mud from anchor chain. - Anchor chain cable supporting assembly is provided - Stiffeners are provided outside - Footsteps are provided in BHDs 29. Chain locker
30.
House pipe - pipe through which anchor chain enters the windlass while taking the anchor on board Spurting pipe - pipe through which anchor chain goes to the chain locker while taking anchor on board Stiffners are provided at the outside of chain lockers to prevent the entackling chains with stiffners. Stiffners are provided on the CL BHD with two sides facing to the CL BHD, to prevent the entackling of chains.
31. of
32.
False bottom in chain lockers are provided because the mud in the chain is collected in the false bottom. The mud can be removed by cleaning the false bottom.
33.
Force end construction
34. 35.
Fore end : Forward quarters of ship length from the forward perpendicular is termed as fore end. Slamming: During slamming the bow suddenly rises and hits the water due to waves. Raking: Lateral movement of frames from side to side. This is due to the forces by waves or wind. Pounding: It is the upward and downward force acted upon the ship by the waves.
36.
Hungry horse effects are produced by panting. Panting is carried by the fluctuating load by waves on the sides of ship. Painting results is the fluctuation of shell plate like the bellows of a hungry horse’s stomach. Panting beam and panting stringers are provided to reduce this effect. Crown deck: It is the upper most deck of the fore peak which is made made water light.
38.
39)
Aft end constructions
40. 41. 42. -
Aft end: It is the portion which is 25% L of the ship from the Aft perpendicular including super structure and aft peak Aft peak tank: It is the aft most tank of the ship for ballasting and fresh water tank carriage consists of centerline BHD to reduce the free surface effect consists of stern frame and bossing stern frames are fabricated forged Brest hooks are provided Solid floors are provided at every frame space Rudder tank is situated Stern tube is situated Consist of painting stringers and swash plates Types of stern construction Cruiser stern Transom stern
Cruiser Stern - provides less resistance - consists of cart frames spaced at a particular angle to center line - reduced slamming effect a) Cant frames:b) They are situated in Cruiser stern Provided to reduce the effect of slamming Cant framed are spaced at angles towards the center line Curved structures Parting beams:provided at fore peak and aft peak tanks to reduce the effect due to panting to distribute the force developed in the transverse directions
-
panting stringers are corrected by panting beams to distribute the load.
c) Wash plates:- also called as non water light BHDs or perforated BHDs or swash BHDs to distribute the load developed in the transverse direction situated in fore peak and Aft peak tanks In some cases they are also used to reduce surface effects Difficult to construct
Transom stern 43. provides greater deck area prevents squatting of high speed small crafts reduces resistance from 3 to 5% at high speed reduced slamming and pounding effects easy to construct Squatting: It is a phenomenon by which a negative pressure is created at the aft end of high speed small crafts, which tends the aft end to touch the bottom in shallow waters.
2) Breast hooks: Panting stringers are held in position together by Brest hooks Brest hooks also provides strength to stem bar and stern frame Brest hooks are equally spaced They supports the plates at the fore end from post and stbd side
Basic Structure 45. Welding imperfections
46.
Different grades of steel IS 2062 MS Allowable stress - 235N/mm2 A Grade B Grade ABS AH Grade- Allowable stress - 400 N/mm2 ABS Grade
47.
Testing methods to identify welding imperfections” 1. Visual inspection 2. NDT (Non Destructive Testing)
48.
Welding techniques
1. 2. 3. 4. 5. 6. 49.
Down hand welding (1G) Horizontal welding (2G) Vertical welding (3G) Over head welding (4G) Cylindrical welding (5G) Spiral welding (6G)
Underwater appendages 1. 2. 3. 4. 5. 6. 7. 8. 9. Speed log Stabilizer Bow thruster Skeg Propeller Rudder Echo sounder Bilge keel Sea chest
50.
a) Bilge keel b) skeg :
- To arrest the movement of ship during rolling - To support the ship in docks - For good directional stability - act as a supporting member at the over changing portion on aft - To control the direction of ship - For directional stability - Situated at aft
c) Rudder
d) Echo sounder - to measure the depth of the sea e) Bow thruster - to turn the ship in a limited space, usually fitted at forward side 52. Doubler plate: Plates are laid one, over the other provided where compressive loads are generated. Mainly provided under the pillars Insert plate: Plates of high thickness are inserted between plates of standard thickess. Provided where compressive and Tensile loads are coming. Outfittings 53. Mooring Fittings 1. Bollards single bollard doublar bollard for tieing the ships in ports for toeing the ship using tugs.
2) Rolling fair leads Situated at Bull warks for the passing and directing the tie ropes 3) Capstan for the ropes to pay through, while mooring It can rotate and move by its own 4) Chokes 54. For the passage of ropes without any obstruction Panama chokes are fitted at the forward side on bull warks
Ventilators are mainly two types - Natural Ventilators & Forced Ventilators Subdivided into
1. Cowl head type 2. Mushroom head type 3. Goose Neck type
Natural Ventilators: functions on the natural draught of air with any mechanical input Forced Ventilators: functions on the forced draught of air by motor driven fans provided inside it. Superstructure: structures having a breadth greater than or equal to 98% of the breadth of ship Deck house: is of lesser breadth than super structure 56. It can also come under cranes It can also come under other access in deck which leads to cargo tanks etc. Sounding: Sounding pipes are provided to measure from the depth of cargo tanks and to find the volume of cargo inside the tanks. Ullage: is to measure from the top of the liquid level and to find the volume of cargo inside it. 57. Striking plates: During sounding plumbs are inserted through sounding pipes to
check the level. At this time the plumb will hit the shell plate. As this procedure is continuous there will be chances of having holes on the shell because of the striking of plumbs. To avoid this striking plates are provided under sounding pipes. 58. a) Forecastle: - To prevent shipping green water - Usually provided in fast vessels like container ship - Ships with well flared bows have a tendency for shipping green water, to avoid this fore castle is provided. - Height depends on the speed and flared bow. - Plates supported by stays b) Funnel:- - vertical structures above deck - Housing of air vents from sea hearts and other lines - Stiffeners are placed vertically - If the height is increased stringers are provided - To fixing owner’s logo - For good appearance - Shape can be according to owner’s style - Shape are cylindrical, rectangle etc. - Sufficient height should to provided to get smoke and grit cleared off the deck Height can be reduced if uses forced draught. d) Engine Casing: - Height of 760mm should be provided above weather deck - Protect various openings from auxiliary engines which comes directly above the engine - Size should be sufficient to take the engine and auxiliary engines out of engine room - Vertical member extending throughout the super structure e) Guard rails For protection of crews and passengers Height should be 1 mtr Consists of shell rods and hallow pipes Shell rods are also called stanchions Hollow pipes are used as rails Supported by stays
f) Sea chest High sea chest : In shallow water, high sea chest is used Sea chest are box type structures Provides the inlet for seawater for engine coiling, deck water etc. High sea section is used in shallow water is to prevent the mud from entering
Low sea chest: - used in deep sea because the high pressure itself cause pumping action. g) Pillar: are used where consentrated loads are acting d) e) Are vertical members They are also used when tension loads are coming They are supported at bottom by doubler or inserted plates Supported at top by header plates Hatch corner pillars are avoided damages during cargo loading and unloading Pillars can be used to avoid deep section beams Insulation is provided to prevent heat and noise FRP and GRP with steal plates are used as insulators Provides supports for various decks Main engine seating: Provides a good platform for the engine Rudder plates are supported by vertical and horizontal members for engine seating Faceplates are drilled in correct line of engine bolts provided Spacing can vary depending on the engine size Shaft tunnel Provided if the engine room is at mid ship Protects the shaft from contact with cargo Can be used for pipelines
-
On the top it is a round like structure Stiffeners are provided inside Stools are provided to support shaft
f) 59. 60.
Can be useful during maintenance Connection of intermediate shaft to tail shaft Bulwark and Guard rail Bulwark For protection of the crew and cargo on deck For fitting radar out fittings and latching of cargo Supported by stays Situated above the force castle Hatch side pillars are corner placed to avoided damages during cargo loading and unloading Insulations is provided in the engine room to prevent excess heat and noise from the engine and auxiliary machines. FRP and GRP with steel plates ones used for insulating engine room. FRP – Fiber reinforced plate are also used. Pillar Header plates are provided at the top and double plates are provided at the bottom. Heavy brackets are provided if the load is tension and simple brackets for compressive loading.
61.
63.
Types of Manholes:
-
Rise with high coming Rise with low coming Flush type
Rise with high comings raised to 100mm above the deck rise with low warming raise to 10mm above the deck flush type are on the level of the deck. 64. 65. Purpose of intermediate shaft is to remove the tail shaft easily during repair or maintenance. Purpose of bulwark: for protection of crew and cargo on deck, for fitting radar out fittings and lashing of cargo, height should be 1m. Purpose of Guard rail: for protection of crew and cargo on board. It should be 1m. Freeing post: openings on the bottom side of bulwark for the drainage of water.
(4) 1.
HYDROSTATICS Hydrostatic Particulars
(Answer Sheet)
- Volume displacement - Mass displacement - Longitudinal center of floatation (LCF) - BMT and BML - Longitudinal center of Buoyancy (LCB) - Vertical center of Buoyancy (VCB) - Form coefficients - Tones per centimeter immersion (TPCI) - Moment to change trim by 1inch (MCTI) - Wetted surface area 2.Law of floatation states that for a floating body, the weight of the body is equal to weight of fluid displaced by the body is which it floats. 3. Different rules of integration 1. 2. 3. 4. 5. 4. a. Simpson’s first rule h Area = -- (1y1 + 4 y2 + 1y3) 3 Where h = dist. Between to full stations or ordinates, y1, y2 are ordinates b. Simpson’s Second rule h Area = -- (1y1 + 3 y2 + 3 y3 +1y4) 8 c.5,8, -1 rule h Area = -- (5y1 + 8 y2 - y3) 12 d. Trapezoidal rule Simpson’s first rule Simpson’s second rule Simpson’s third rule (5,8, -1 rule) Trapezoidal rule Trapezoidal rule
h Area = -- (1y1 + 81y2) 2 5. Tchebycheff’s rule differ from other rules in that the ordinates are not equally spaced There are no internal multipliers Curve is parabolic Is found out by summing up the ordinates and dividing by the no. of full stations and then again multiplying by the length A= 6. (y1 + y2 + y3 +……- yn) L -------------------------------N End ordinates are not taken. Displacement can be calculated by Integrating area along the water planes in longitudinal direction Integrating area along the stations in vertical direction Better way is to calculate by integrating area along the water planes because number of stations are greater than number of water planes 7. Formulas a. TPCI - Tones per centimeter Immersion TPCI = (A*d)/ 1000 A= area of water place d = density of seawater b. MCTI – moment of charge trim by 1inch MCTI = BML x W -----------100 x L BML = longitudinal metacenter from center of Buoyancy W = weight displacement L = length of ship.
c. BML – Dist. From longitudinal meter center from center of Buoyancy
BML = IL
-------
∇ IL = longitudinal moment of inertia with respect to transverse axis ∇ = volume displacement d. BMT = Dist. From Transverse metacenter from center of Bougancy BMT = IT
-------
∇ IT = Transverse moment of Inertia with respect to longitudinal axis ∇ = Vol. displacement e. Cb – Block coefficient Cb = ∇ ------LBT
L = length of ship B = Breadth of ship T = Draft f. CP - Prismatic coefficient CP = ∇ -------------Am x L
Am = area of midship L = length of ship g. Cm = Midship section coefficient Cm Am -----BxT B = Breadth T = Draft
=
h. Cw = water plane area coefficient Cw = A m -----LxB
8. St. 0 0.5 1 2 3 4 5 6 7 8 9 9.5 10
1
/2B 0 5 8 10 12 13 13 12 11 8 3 1 0
SM 0.5 2 1.5 4 2 4 2 4 2 4 1.5 2 1
F(A) 0 10 12 40 24 52 26 48 22 32 4.5 2 0 272.5
Lever 0 0.5 1 2 3 4 5 6 7 8 9 9.5 10
F(M) 0 5 12 80 72 208 130 288 154 256 40.5 19 0 1264. 5
Lever2 0 0.25 1 4 9 16 25 36 44 64 81 90.25 100
f(IL) 0 2.5 12 160 216 832 650 1728 1078 2048 364.5 180.5 0 7271. 5
y3 0 125 512 1000 1728 2197 2197 1728 1331 512 27 1 0
SM 0.5 2 1.5 4 2 4 2 4 2 4 1.5 2 1
f(IT) 0 250 768 4000 3456 8788 4394 6912 2662 2048 40.5 2 0 33320.5
h A = --- x ∑ f (A) x 2 = 2180m2 3 IL = h --- x h2 x ∑ f (IL) x 2 3 h 1 --- x --- x ∑ f (IT) x 2 3 3
IT =
IL - Iaft – Ax2 X = LCF = h. ∑ f (M) -------------∑ f (A) Here we got I(aft) Iaft = 123 ----- x 7271.5 x 2 = 8376768 3 = 12 x 1264.5 --------------272.5 = 55.68m
IL IT
= 8376768 – 2180 x 55.682 = 1618195.968m4 12 = ---- x 33320.5 x 2 = 88854.66 m4 9 BMT = IT ---∇
a)
Cb = 0.75 ∇ ----LBT 88854.6 ---------7200 ∇ = 0.75 x 120 x 10x 8
Cb
=
= 7200 m3
BMT =
= 12.34 m
b)
BML =
IT ---- = ∇
1618195.97 ------------7200
= 224.75 m
c)
TPC
Axρ = ------- = 100
2180 x 1.205 ---------------100
= 26.26 T
d) e)
MCT
BML x W = -----------100 x L
=
224.75 x 7200 x 1025 --------------------------- = 138221.25 kgm 100 x 120
weight of ship in sea water = weight of ship in fresh water ∇sw x ρsw x g = ∇fw x ρfw x g ∇fw = 7200 x 1025 --------------- = 7380 1000 ∇ Cb = ---= 0.75 = 7380 -------
LBT T = 8.2m 50 x 1000 x 90 = ------------------138221.55
120 x 10 x T
f)
Trim
= 32.55cm
9. a) LCF - Longitudinal center of floatation - It is the centeroid of the water plane - It can be referred from aft or midship - for calculation of trim forward and trim aft - point through which the trimmed water line panes LCF = h x ∑ f(MA) -----------∑ f(A) b) LCB - Longitudinal center of Buoyancy - It is the longitudinal position of the center of buoyancy of the volume under the design waterline -longitudinal position of the center of buoyancy through which buoyancy force acts - To calculating the total trim and resistance of ship - can be referred from aft or from midship LCB = h x ∑ f(MV) -----------∑ f(V)
c)
VCB - vertical center of buoyancy - It is the vertical position of center of buoyancy of the volume under the design water line - It is the vertical position of center of buoyancy through which buoyancy fore cuts - For calculating stability of ship
LCB =
h x ∑ f(MV ) -----------∑ f(V)
- Referred from base line or ‘0th’ water line d) IT
-
It is the transverse moment of Interia along the longitudinal axis IT = 2h 1 ---- x --- x ∑ f(IT) 3 3
- can be referred from center line - for calculating BMT e) IL is the longitudinal moment of Inertia along the transverse axis 2h IL = ---- x h2 x ∑ f(IL) 3 10. Can be referred from aft or mid ship For calculating BML a) TPCI is defined as Tonnes per centimeter immersion TPC = A x ρ --------100 A = Area of water plane ρ = density of sea water It is the weight added or reduced to change the mean draft by 1 cm TPI is defined as the Tonnes per inch immersion TPI = A x ρ x 2.54 ---------------100 It is the weight added or deducted to charge the draft by one inch. b) LCF - Longitudinal center of floatation - centroid of water plane - can be referred from aft or midship LCF = h x ∑f(M) --------------
∑f (A) - Calculating trim Aft and trim fore LCB - Longitudinal center of Buoyancy - longitudinal position through which the buoyancy force acts - can be referred from aft or mid ship - calculating total trim and resistance of ships LCF = h . ∑f(M) -------------∑f (V) c) Vertical prismatic coefficient ∇ -----AWL x L
CPV =
∇ = Vol. Displacement AWL = area of water line L = length of ship
(5) 1.
STABILITY
(Answer sheet)
For stability at small angles GM, metacentric height is the stability criteria For stability at large angles Gz, Righting lever is the stability criteria Small angle means upto 5o Large angles means greater than 5o GZ= GM sinφ – for small angles GZ = BOR –BG sin φ - for large angles
M Metacenter is fixed for small angles M charges for large angles 2.
3.
Righting lever: If a ship is inclined at constant displacement, the point B o moves to B1, a new Point. So the buoyancy force and downward fire which is acting upwards will be not in the same line and if a perpendicular drawn to the new waterline intersects the original WL at M called metacenter. Then a restoring couple is generated, GZ x W which tends to bring book the ship to original position, and GZ is called as the Righting lever. Metacenter: It is the point at which a floating body begins to oscillate, when it tilted by a small angle. Metacentric height: If a line drawn through the new buoyancy point B 1 which is perpendicular to the new water line W1L1, the line will meet at the vertical at M called metacentre (M). Metacenteric height: The distance between the metacenter and center of graving is termed metacentric height (GM). GM = metacentric height
4.
5.
Different condition of equilibrium M above G – GZ & GM is +ve - stable equilibrium M is at G - GZ & GM = 0 - Neutral equilibrium M below G - GZ & GM = -ve - unstable equilibrium
6.
7.
Stability of Circular Section Consider a circular section with Radius R, lying in the horizontal axis with section ‘O’. So the buoying force will always acts through the point ‘O’, even if the water level is above or below the section ‘O’. So here the stability is depends on radius ‘R’. If KG < R, stable If R = KG, neutral If R < KG, unstable Stability can also be obtained by adding weight.
8.
Trim – It is the difference between draft forward and draft aft. Center of rotation ‘LCF’ is the centeriod of the water plane area. It is the point through which the trimmed water line passes through. If a weight is placed above this point, the ship sinks with no trim.
9.
Diff. Reasons for trim to occur - Due to movement of weight - Loading and unloading - Ballasting - Fresh water consumption - Fuel consumption etc.
10.
Volume displacement Mass displacement Tones per centimeter immersion. If ship is entering from low density to high density the draft is decreased since buoyant force increases Fully submerged submarines First of all they have no water planes, so there is no metacenter. Care should be taken during fast sub mergence to keep G and B nearby at same point, otherwise it will capsize. As they go to higher depths, its body shrinks due to high hydrostatic forces, thereby reducing the volume displaced. So the buoyant force decreases and submarine begins to sink. So to keep the submarines stable it is to be pump out water from inside or using force provided by hydroplanes etc.
11. 12.
13.
w.h = GG1 ∆ ………………………(i) GG1 = GM tanφ tanφ = t/L GG1 = GM. t/L ………………………(ii) Substitute (ii) in (i) W = GML x t x ∆ -------------Lxh W = t . GML x ∆ ------------ …………………..(iii) Lxh So the moment to cause and charge trim is GML x ∆ --------L The moment to charge trim by 1 cm = ∆ x GML
----------------
100 L So, t = Wh -----MCT from (iii)
14. LCB of a ship can be found out from Hydrostatic curves, if we know the corresponding draft 16. Wall sided formula = sinφ (GM + ½ BM tan2φ) Ship sides in way of water lines all over are assumed to be vertical here. So it is formed as wall sided formula.
17. 18.
Free surface effect is the effect on main tanks carrying liquid cargoes which affects the stability of ship or it is the virtual reduction in GM. Free surface effect = ρf If -----ρ∇ Where ρf is the density of fluid If is the second moment of area of liquid surface ρ is the density of fluid in which strip is float ∇ is the displacement Free surface effects can be reduced by reducing the breadth of cargo tanks by centerline bulkheads and wing bulkheads. Inclining experiment is conducted to find 1. CG of the ship 2. Light ship weight
19. 20.
21. 22.
Condition of inclining experiment is called Asinclined condition. condition of ship with 95% of its structure is completed. Preparation for inclining experiment 1. 2. 3. 4. 5. 6. 7.
It is the
Get approved the agenda of experiment from class and owners Clean the ship Check the whether conditions Find the place to do the experiment – dry dock Loose the mooring rapes Fixing of materials – pendulum, oil tray, scale etc. Tanks are to be completely filled in case of any trim problems to avoid free surface effect.
23.
Inclining experiment is conducted by placing two set of weight each on port and stbd side. At the first stage set 1 is moved to the stbd side and the indination is noted. Then set 2 is moved to stbd side and inclination is noted. Then the two sets are moved back to port and the inclination is noted from the set up provided. The same is done on the port side for set 3 and set 4 and the inclination are noted. density of water is noted for two to three position of ship. Accuracy of inclining experiment is ensured by ploting a graph with deflection Vs weight moved. The accuracy is ensured, when the graph retraces its path during port and stbd movement of weights. w x h = ∆ . GG1 We know GG1 = GM tanφ W x h = ∆ .GM tanφ
24.
25.
x tanφ = --- from inclining experiment L w x h = ∆ . GM . x --L KM = KG +GM - KM from hydrostatics - GM calculated from above eqn. 26. 27. Total Weight required is estimated as the weight which will give an inclination of 1.5 to 2o when it is moved from stbd to port side. Pre survey - Condition survey Tank survey Draft survey Post survey - Draft survey Condition survey. Weight of the block while docking w.x = t.* MCTI w is the weight to be calculated t is the trim MCTI is moment to charge trim by 1cm x is the distance aft from LCF 29. During docking, righting moment = (GM –w .KM)W sinφ -W If the solution inside the brackets becomes –ve the ship will tip over. GZ is the measure of stability of large angles GZ = BoR-BoG sinφ Curve of statical stability GZ curve is the also called curve of statical stability GZ = GM sinφ dGZ ------ - GM cosφ dQ dGZ GM ------- = ----- (cosφ=1) dQ 1
28.
30. 31.
It is a curve with GZ along the y axis and the angle of inclination along the x axis. Positive value of GZ with the angle gives the range of stability. 32.
IMO Criteria Area upto 30o = 0.055 mrad (not less than) Area upto 40o = 0.09 mrad (not less than) Area between 40o and 30o = 0.03 mard (not less than) GM value should be greater than 0.15mts At 30o GZ should not be less than 0.2mts. GZ should be maximum after 30o 33. Angle of loll: When GM is –ve initially, ship is inclined to either part or slbd side and at some point it will reach in equilibrium and remains is that point. This point is now the equilibrium condition of the ship and the angle is called angle of loll. It can happen during weight shift in the ship permanently. Value of GM in the lolled condition is twice as compared to initial GM but negative in sign.
34. 35.
. 36.
37.
GZ = KN -KGSMφ ……………………………(i) GZ = BoR-BoG sinφ In the above equation (i) the value of - KN can be found from knowing the displacement from cross waves - KG can be found from inclining experiment And with there, values GZ can be plotted with respect to φ
38.
Stability information booklet It is a booklet which contain the stability of ship for all condition of loading. Other data’s It contains Hydrostatics datas
It contains a figure showing the profile of ship from which areas and moment can be calculated It contains the GM values. 39. Minimum conditions shown in stability information booklet are stability at 1. 2. 3. 4. 5. 6. 40. 41. Light ship conditions Fully loaded departure condition Fully loaded arrival condition Ballasted departure condition Ballasted arrival condition Other conditions
Additional condition required for a tug is to avoid towing at athwart angle Additional condition required for a ship with crane is the maximum load that can hang and extended on the ship and point at which load acted on the tip of crane is to be noted at same time. GZ curve, when weight is permanently moved
42.
In this condition BC is the new range of stability and C is the new angle of varnishing stability. 43. 44. Angle of Repose: It is the angle at which the bulk cargoes mainly grain cargoes starts repositioning its state, such that it does not come back to its initial state. By adding centerline Bulkheads and shifting boards the prevention of cargo in bulk carriers. Provision of feeders will fill the void spaces after setting down the cargo also helps to avoid shifting of cargoes. Dynamic Stability: It is the measure of energy ship absorbs to resist fore exposed by wind and waves or it is the work done is heeling the ship to an angles δφ and is given by the product of displace, GZ and δφ
45.
46.
When a wind moment is applied, slowly the ship start to heel to an angle represented by A and in theis condition the range of stability will be from A to B. If the moment is applied suddenly like a gust of wind, the amount of energy absorbed by ship as it heels is represented as area DACO. The ship would absorb energy reprented by area OAC and the remaining energy would carry it beyond a starts to some angle F such that area AEF = area DAO. If F is beyond B, the ship will capsize, assuming the wind is still acting.
A severe case for a rolling ship is if it is inclined to its maximum angle to winword and about to return to the vertical when the gust hits it., let it be the position GH.The energy put in to the ship by the wind up to angle L is now represented by area GDKLOH. The ship will continue to heel until this energy is absorbed, perhaps reaching angle Q. 47. Angle of heel due to turning: When ship is turned by self with rudder the rudder holds the ship at an angle of attack with-repositions the path. As a result of this the force developed in the hull which is the hydrodynamic force tends to move the hall towards the center which is turns the ship to new position and then outwards. Additional stability condition taken into consideration while designing passenger ship is the crowding of passengers to one side.
48. 49.
GZ = KN-KG sinφ GZ = BoR-BoG sinφ
50.
Boot Topping area : The area reach to the draft designed which come frequently in contact with air and wakes tends to corrode very fast than other areas. So there areas to be painted with corrosion resistant paints. (6) LAUNCHING - (Answer Sheet) Requirements of end-launching a ship The ship sterns should slides first to water because this part of the ship is more buoyant. Slide ways are to be provided under the ship The gap between the slide ways and ground ways are provided, with grease to avoid friction Usually two to four ways are provided Ground ways are to be cambered to acquire buoyancy faster Waterfront is to be cleared Slide ways are to be cleared Tide is a major factor to be taken into consideration Tugs are to be provided to tow the ship if any frictional resistance arises Drags are to be provided in restricted waterways to decelerate the movement,after ship is become waterborn. Fore poppet is to be provided
1.
2.
Problem associated with launching - The grease is too slippery or not slipping enough - The grease may get squeezed out due to excessive pressure - Tipping and dropping can occurs - local strengthening of the ship is a major factor - Tide which a major factor is taken into consideration Tipping If the moment of weight about Aft end way is greater than moment of buoyancy about aft end way the ship will tip and is termed as tipping.
3.
To avoid tipping the moment of buoyancy about aft end way should lie above the moment of weight about aft end way. The difference (least) between them gives the least moment against tipping. 4. Pivoting When the moment of weight about fore poppet equals the moment of buoyancy about fore poppet the stern lifts and ship pivots on fore poppet and is termed as pivoting. Dropping: If the buoyancy is less compared to the weight after the ship crosses the aft end way the ship drops and is termed as dropping. To avoid dropping, make sure that the buoyancy exceeds weight before ship must pass over the aft end way. Different launching curves Weight Buoyancy Moment of weight about fore poppet Moment of buoyancy about fore poppet Moment of weight about Aft end way Moment of buoyancy about Aft end way Launching Curve
5.
6.
7.
Analysis When the moment of weight about fore poppet equals the moment of buoyancy about fore poppet the stern lifts. Weight – Buoyancy at time of pivoting is the maximum force coming on the fore poppet. Moment of buoyancy about Aft end way should lie above the moment of weight about Aft end way to avoid tipping. The least difference is the least moment against tipping when weight equals buoyancy the ship is fully water bone weight and buoyancy should pass before the aft end way to avoid dropping. Grease pressure can be determined at the tipping point. Height of tide also can be determined. 8. Step by step procedure of calculating the launching curves
First approximate LCG and weight can be calculated from shell expansion drawing. Then Buoyancy and LCB at any position can be found from Bonjeans and Auto ships Upto the stern lift the trim is constant. So LCB and Buoyancy can be found from Bonjeans.
X = Initial slop of K L = LBP h = Initial height of Fore poppet above water e = Distance of fore poppet abaft FP β = Declivity of ground ways α = camber of ground way γ = radius of center Center of arc, F = K2/8R (f-y) = (K-2x)2 ---------8R Y = K2 (K-2x)2 --- - ------8R 8γ = K2 K2 + 4 kx – 4x2 --- - ------------------8R 8γ 4kx – 4x2 ----------= (k – x) ---------
=
8γ
2γ ======
At a dist. ‘x’ the height of FP above water is h-βx + y βx – decrease in height due to slop of ground way y - increase in height due to camper So at any dist. Of abaft the FPP, the height above water = h-βx+y-t(α+x/γ) h--βx + x(kx) ------- - t (α + x/γ) 2γ If there is no camber γ = infinite So, height above water = h - βx - tα If t = -ve gives height of keel at FP above water If t = L-e gives draft of AP After the stern lifts occurs the condition charges because trim changes. calculation can only be done to stern lift. Then the condition to be Is Moment of act about fore poppet = Moment of buoyancy about FP Wxh =∆xa A = approximation value of us Buoyancy and moment is calculated for several trim. Find the trim at which two curves meet 9. Dynamics of launching with diagram So
The force accelerating the ship at any instant can be found by (w-∆)φ - way friction – water resistance – drag force W = weight acting downwards ∆ = buoyancy acting upwards φ = slop of ways (w - ∆)µ = way friction µ = coefficient of friction <0.02 K∆2/3V2 = water resistance V = velocity of travel K = Constant = 0.001 Drag fore = µ w W = weight of chain µ, = 0.4 – 0.8 Curve 1 : This is the net weight of ship (weight – buoyant force) and it becomes zero when the ship becomes water born. Curve 2: curve obtained by reducing way friction from weight component. This also becomes zero when ship floats. Curve 3: Curve obtained by further reducing water resistant component which begins from when stern touching the water to ship comes to rest.
Curve 4: Is drag component, only comes into play when ship floats. The remaining momentum of ship is reduced to zero by drag component and water resistance component after the ship is becomes water borne. 10. Side launching
Side launching is done when the water front is limited. Ship slide down the ways so there is possibility for tipping and dropping. Ships are built on piles which are collapsible. The ship can roll up to 30o, so stability at large angles to be considered. Due to this the waves can change the adjacent shore. Declivity can be from which to 8 inch and grease pressure vary from 2.5 to 3Tforce 10. Docking
Docking is done for any repairing works in ship. The factors considered while docking area.
Ensure the blocks are under primary members Strength of floating docks is to be considered Stability is a major factor Strength of docks to be considered Local distribution between dock and ship Make sure that the openings on the hull are clear Make sure that hull fittings are cleared while docking (like echo sounder, stabilizer, speed loge etc) Ship should have a slight trim by aft. Docking is done based on the docking plan Docking can be in (i) Dry Docks and (ii) Floating docks Blocks can be selected depending on block pressure and crippling pressure Block pressure > 40 Tf/fb2 Crippling pressure = Total load/Total blocks.* Area of blocks 2. Ships weight No. of blocks = --------------------x. block stiffeners x = mean deflection of stacks
(7) 1. 2.
FLOODING (Answer sheet) Flooding is caused due collision, grounding, sprinkling of leak due pitting, welding defects and fatigue After effect of flooding: results in the reduction of stability and loss of buoyancy If the reduction in stability is large the ship will turnover or cap size. If the reduction in stability is not much large the ship will has to an angle, which will be difficult for launching life boats. General consideration is given to ships while flooding but importance is given to passenger ships; get the passengers out off the ship within the limited time. It means not only to get the passengers on board but also to launch the life boats with passengers in them. Emergency illumination stickers showing the way to on board is to be pasted. Limiting the heel, if the heel is large by counter flooding for the easy launching of lifeboats. Time consideration is a major factor so that time allowance from collision to the acceptance damage is considered.
3.
4.
During flooding the ship will sink first and then trims until it acquires loss of buoyancy. So LCB shifts to a new position and the ship trims until the value of B reaches vertically below G. If the reduction in stability is large the ship will turnover or capsize. If the reduction is small the ship will heel to an angle. The hydrostatic behavior can be found by two methods. (1) Lost buoyancy method (2) Added weight method. Lost buoyancy method 1. 2. 3. 4. 5. 6. Displacement remains constant Water plane area changes LCG does not change LCB changes and rechanges back to the position vertically below G BML, IT, MCT changes Sinkage due to lost Buoyancy Added weight method Displacement changes No change is water plane area LCG changes No change in LCB Since no change in water Plane area BML, IT, MCT are constant. Sinkage due to added weight
5.
Permeability: It is the ratio of the floodable volume to the actual volume of the compartment. Floodable volume Permeability = ---------------------Actual volume Spaces Accommodation space Machinery space Cargo holds Stores Permeability % 95 85 60 60
6.
7.
Two methods of flooding calculations are 1) Lost Buoyancy method 2) Added weight method Lost buoyancy method First the volume of the damaged compartment is calculated with respect of original water plane and then area of the damaged water plane is calculated. If A is the area of the intact water plane, the lost volume due to buoyancy is µν1 and the area cost is µa. So parallel sinkage, z occurs, µν1 Z = -------- where µ = permeability
8.
A-µa Second consideration is taken as the draught is changing with respect to water plane, newly formed. So trim and MCT are taken into consideration, where
z/2 is the distance taken for the intermediate water plane area formed. Sinkage will happen till the volume of the lost buoyancy lost is regained from the new water plane. µν ---Am µν x t = -----MCT
Sinkage =
and
Where Am is the area of the inter mediate water plane. This process is repeated until the desired volume are obtained. If the values are greater, the process is to be repeated. The volume can be checked by Bonjeans for allowable floodability and damageability. Here G is constant.
9.
Added weight method Here weight is considered added to the ship to the damaged compartment. Firstly the calculation is same as for the added weight, then as the water is entering to the compartment weight is again added with respect rate of entering and can be stop when the further sinkage becomes negligible.
10.
Damaged stability by lost buoyancy method The buoyancy lost is regained from the intact water plane as a result of which the buoyancy in the original position is shifted above the original water place. This vertical shift of Bo to B1 is the new buoyancy can be given by , νv.bb1 -------∇
bb1 is the distance between centroid of water planes. As B o shifted to B1 there is a reduction in BMd. If Id is the damaged water plane inertia, BMd can be calculated as, Id --∇ So damaged GM, GM damaged = GM intact + µvbb1 Id -------- - --∇ ∇ Here G is assumed as constant 11. Damaged stability by Added cut method In damaged condition the force surface effect is taken into consideration. Here the position of G varies ad weight is changing. So KG varies depending on the draught. GMdamaged = GMintect + µνbb1 Id --------- - --- - free surface effect ∇ ∇ 12. Asymmetric flooding
For ships with longitudinal bulk heads the water may not flood right across the ship. The damaged of penetrations is limited by BHDS to 20% of the breadth of the ship. So the ship will Heel lesser due to BHDS. If µν is the volume lost due to flooding. ∆GM sinφ = µνzρ ρ∇GM sinφ = µνzρ sinφ = µνz -----
GM∇ If heel is large due to flooding the opposite side compartment are flooded which is known as counter flooding. This only sinks the ships by linking the heel there by easyness for bunching life boats. 13. Floodable length : Floodable length at any point along the length is the length of an imaginary comprtment.with that point as center, When allowed to flood, such that no part of the margin line the is immersed, provided no list. Bulkhead deck: It is the uppermost weather tight deck to which water tight transverse BHDS are connected. Margin line: Water line drawn tangent to a line 76mm below the bulkhead deck is termed ad margin line
14.
15.
The significance is that it is the line upto which the ship can be flooded without any list. The ship is considered lost if water line goes above margin line. 16.
Taking water lines WoLo and W1L1 for intact and damaged condition. Loss of buoyancy = V1 - Vo Centeroid of the lost buoyancy is given by V1 x BoB1 X = -----------V1 - Vo It is possible to convert this into length that can be flooded, The calculation can
be repeated for a series of water lines until a reasonable figure, is obtained which gives a curve of floodable length. 17.
18.
Factor of subdivision It is the ratio of permissible length to floodable length. Inverse of factor of safely It is a function of length and criteria numeral Factor of sub division is low for passengers ships compared to cargo ships.
19.
Criterion numeral is defined as the criterion of the service of ship taking into account, number of passengers, machinery volume, Accommodation spaces and total volume of the ship.
(8) 1.
PROPULSION
(Answer Sheet)
The lift and drag forces on a blade section are generally represented by non dimensional terms where are the coefficient of life (C L) and coefficient of Drag (CD) L CL = ---------½ ρAV2 ρ = density of fluid A = Area of plan form of section v = velocity of flow D CD = ---------½ ρAV2
2.
L = lift force D = drag force F = Resultant force V = velocity of flow Lift force is perpendicular to velocity of flow and drag force is parallel to velocity of flow and α is the angle of attack. 3.
4.
Lift generated on an aerofoil section: Consider an aerofoil section with a velocity of flow ‘v’. According to Bernoulli’s equation there will be corresponding decrease in pressure at back and increase in pressure at the face. Due to this a circulation is created around the aerofoil which will results in the lift of aerofoil.
The net pressure on the face and back gives the lift generated in aerofoil. 5. Aspect ratio = span / chord It is the ratio of span to chord of a propeller blade or rudder. 6. Stagnation Point
Considering a fluid flour around a circular section. At points A and B the velocity of fluid is zero and these points are called stagnation point.
At the stagnation point kinetic energy of the fluid is fully converted to potential energy. 6. KT – (thrust coefficient) It is the non-dimensional coefficient of thrust T KT = ---ρN2D4 KQ (Torque coefficient) It is the non-dimensional coefficient of torque produced by propeller KQ = Q ---ρN2D5
J – (Advance Coefficient) It is the ratio of axial velocity (Va) of the propeller to ND Va J = --ND 8. If subscribe ‘S’ represents ‘ship’s propeller and ‘m’ models propeller and are geometrically. Similar operating at same advance coefficient ρs 3 ---- = ---- λ T m ρm Ts Tm = Ts. ρm
--------3 s
a)
where λ =
Ds ---- (ratio of linear dim.) Dm
ρλ b)
ND ---- = ρ is also const. so, Va
Ns Vas Dm ---- = ------- x -----Vm Vam Ds
1 = --λ 0.5
Nm = Nsλ 0.5 c) Thrust power = T.Va Ps ρs --- = ---- λ3.5 Pm ρm Pm = ρs. ρm ------ρs . λ3.5 d) Ratio of torque φs ρs ---- = ---- λ4 φm ρm φs. ρm φm = -------ρs . λ4 PT
9.
Open water efficiency = µo =
----
PD It is the ratio of thrust power developed by the propeller to power delivered when propelling the ship in open water. µo = PT = ---PD T.Va -----2πNÏ• Ï• = torque N = rpm Va = axial velocity T = Trust by propeller
10.
We have Vw = Vs – Va, but Vs the velocity of ship remains same and there only a chance of increase in Vw means Va will have to reduce. Since J = Va / ND, there is chance of reduction in J in actual case. So we take a point slightly forward (4 to 8 % )to maximum propeller efficiency point as the design point
11.
Different series diagram for propeller 1. 2. 3. 4. 5. Frodue’s methodical series Taylor’s methodical series Gawn methodical series Troost methodical series Van Lammersen series
12.
Open water test: are used to determine the work and relative rotative efficiency. It is carried out in towing tank. The propeller is fitted head of the stream lined housing and pushed ahead with the carriage in undisturbed water. Records of thrust and have taken for a range of carriage speeds and rpm. The test provides data of propeller in uniform flew, which eliminates cavitations. The result obtained as series data is used for design purpose, making allowance for actual floor conditions. The different series data are provide, Taylor, Gawn series data etc. Wake: The relative velocity of water to that of ship in propeller location is termed as wake. The three elements of wake are: 1. Velocity of water as it passes round the hull varies being less than average at ends 2. Due to viscous effects, hull drag a volume of water along with it. 3. Due to waves, created by hull, water particles moves in a circular orbit.
13.
The first two components will reduce velocity into propeller. The next component will increase or decrease depending on wave crest or trough. Wakes varies across the disc of propeller so average is taken for design. 14. Froude’s wake fraction = Vw ---Va Taylors wake friction = Vw ---Vs Va = Speed of advance of propeller Vs = Speed of ship In preliminary propeller design before detailed wave pattern is known, an average speed over the whole disc is taken and it is usually expressed in fraction of speed of volume of propeller or ship Wake velocity, Vw = Vs- Va 15. 16. 17. Range of wake fraction : for a single screw ship is from 0.25 to 0.3 Relative Rotative efficiency : ηR is the ratio of efficiency of the propeller working to that of propeller. It is often taken as unity for design calculations. Thrust deduction factor T = (T-R) -----T
T = Thrust reg. R = Resistance of base hull
Thrust of the propeller will always be more than bare hull resistance. 18. Open water efficiency (η0) = PT --PD It is the ratio of thrust power developed by the propeller behind the ship to power delivered in open water. It is the ratio of power delivered by propeller in open water to power delivered by propeller, behind the ship. Hull efficiency (ηH) = PE --PT
It is the ratio of effective horse power of ship with appendages to thrust power developed by propeller. 19. Quasi Propulsive coefficient (QPC) QPC = ηH . η0 . ηR -----------------Appendage coefficient QPC = Propulsive coefficient ----------------------------Transmission efficiency
22.
Propeller theories 1. 2. 3. 4. 5. Momentum theory Blade element theory Lifting line theory Surface vertex theory Vortex lattice theory
23.
Concept of Momentum theory Concept of based on Newton’s second law and Newton’s third law of motion. ie., rate of change of momentum equals force acting and for every force there is an equal and opposite reaction.
Here the propeller in replaced by an actuator disc.
Velocity of water entering the disc Va is increased to Va(1+b) as it leaves the disc means there is a change in momentum. The thrust is produced by the momentum change taking place along the disc. 24. Concept of Blade element theory Propeller thrust is obtained by …… the force acting on the blades, and integrating this over the propeller radius.
Thrust and Torque can be calculated by considering the flow condition on a blade element and then integrating from hub to tip. 25. Need for special propeller The ships are becoming larger and faster, but propeller diameters remains limited by draft and other factors. The aim of propeller design is to achieve high propulsive efficiency at reduced noise and vibration, along with minimum cavitation. In the case of conventional propellers it is difficult to attain this aim. So special propellers are needed to satisfy this aim. 26. Types of special propellers 1. Vertical axis propeller 2. Controllable pitch propellers 3. Contra rotating propellers 4. Ducted propellers 5. Super cavitating propellers 6. Surface propellers 7. Tandem propellers 8. Overlapping propellers 9. Water jet propulsion 10. Paddle wheels
27.
Two types of vertical axis propeller – Kirsten-Boeing Voit-Schneider
28.
CPP are used in Tugs, Trawlers, Fire boats, Ferries, Fire boats, Ice breakers and small warships Advantage of CPP are Full power of main engine can be utilized in also loading conditions (ie. in static, towing, free running, ice breaking, rough weather, shallow water conditions etc.) Can produce a higher astern thrust at maximum efficiency Produces better acceleration, stopping and maneuvering characteristics Reduces weight and space because of non reversing engine Speed of the ship can be varied without changing engine’s speed Speed of ship can be directly controlled from navigational bridge Propulsion can be done at max. efficiency over a range of ship’s speed. Ducted propellers are used in heavily loaded ships and high speeds ships to reduce cavitation.
29.
In the case of accelerating ducts (Kort nozzles) circulation is developed around the duct section. Here the thrust developed is equal to thrust of propeller and duet together. This is usually greater than thrust produced by open propeller, whereas torque is smaller. Therefore the efficiency of propeller is greater than open type. In the case of decelerating ducts (pump jets) it reduced the inflow velocity towards propeller thereby reducing pressure. This type also has a circulation around the duct which produces an outward directed lift with a component directed aft. Here the duct thrust is negative. Therefore, the efficiency is decreased, but the cavitations properties are increased with respect to an open propeller. So they are used in high speed hydrodynamic to minimize cavitations and noise. 30. Principle of super cavitating propeller is sheet cavitations. Here pressure drops below vapor pressure along the whole back of the propeller blade. So they are used in propellers where unacceptable limits of cavitations cannot be avoided. 30. Surface Propeller: is a screw propeller which operates in shallow water. This types of propellers are semi submerged in water so that propeller blades enter and leave the surface of water for every one revolution. They are fitted
behind the hull instead of placing under the hull. Under water appendages, which support the propeller like shaft bracket, A bracket can be avoided thus by reducing the appendage resistance. The main advantage is that it can have large diameters since they are located behind the hull and can operate in shallow water. They are also not affected by cavitations. The main disadvantage is the hydrodynamic forces on blades unsteady are blades enters and leave the water.
31. Contra rotating propellers: Consists of two propellers rotating in opposite directions on co-axial shaft, one being place close behind the other. They impacts directional stability and reduce rotational energy losses in the slip stream. They are generally use din torpedoes.
The main advantage is that the thrust load required is distributed between the two propellers there by increasing efficiency. The propeller diameter and blade area ratio can be reduced. Main disadvantage is greater weight and complicated gearing system and coaxial shafts. 32. Tandem propellers: consists of two propellers mounted on the same shaft and rotating in same direction. The total thrust required is divided between the two propellers provided that propellers are of same diameter and same number of blades. The main disadvantage is that rotational energy loss is higher and greater weight.
33. Overlapping propellers: Consists of two propellers located at longitudinal position of a single conventional propeller, but with a shaft at a transverse separation less that the diameter of either propeller. If the two propellers are in the same transverse plane the two shafts must be interlocked, if they are at a small dist. apart along the length of ship, the shafts must be independent. The main advantage is that load is distributed by the two propellers. They work in a region of high wake, therefore hull effects is higher.
Main disadvantage is increased noise, vibration and cavitation due to mutual interaction. They are usually designed for out board turning. 34. Water jet propulsion: consists of pump with an impeller inside the ship which draws water from outside, imparts an acceleration to it and discharges it in a jet above the water line at the stern. This jet reaction provides the thrust to propel the ship. They are used in high-speed ships.
Advantages
• • • •
Appendage resistance can be reduced since there are no appendages. They can be used in shallow waters Good maneuverability, backing and stopping are obtained No reed of reversing the main engine, because .. is no reversing gear in propulsion plant • Less noise and vibration • Torque of the water jet unit is constant over the complete speed range. Ie., engine is not overloaded because full water is maintained at low speed • Speed of ship can be controlled without altering rpm of engine. Disadvantages Unit occupies large space inside the hull and water passing through caused a decrease in buoyancy Creating provided to prevent ……. Getting into the system decreases the efficiency as it gets clogged. 36. Cavitation It is the phenomenon which occurs on objects having aerofoil blades in a medium at high speeds..
Net force on the face and back side gives the lift force, this is due to the reduction in pressure on back and increased pressure on face. As the pressure in back is reduced, water vapor pressure is reached, then water boils and bubbles are formed. These bubbles get into area outside water vapour pressure area along the flow and implodes. This phenomenon is termed cavitation. This results is erosion and high local force.
37.
Cavitation number:
σ = (P0 – e) --------1/2 ρAV2 e = water vapour pressure P0= pressure at center of hub v = velocity - cavitations number reduces as velocity increases. 38. Different forms of cavitation Depending on nature of cavitation - Bubble cavitation - Sheet cavitation Depending on where it occurs - Tip vortex cavitation - Force cavitation - Hub cavitation - Bock cavitation 39. Cavitation Tunnel :
Cavitation tunnel is a closed channel through which an impeller at the lower section circulates water and model is placed inside the glass viewing ports, at the upper section. Uniform flow is provided to the test model which is tested in open water. Vaccum pump provided before the propeller producer negative pressure. De-aerator is fitted for reducing the amount of dissolved air and gas. In the case of propeller fitted to hull large tunnels are used. Artificial wake is provided by fixing grid ahead of propeller. 40. Cavitation test results.
41.
Bucket diagram They are used to design propeller. The design point should be inside the bucket which is the no-cavitation region. During operation the cavitation number and angle of attack of the designed propeller must be inside the no cavitation region of the diagram
42.
Isotachs:
Isotachs represents the amount of axial flow on a propeller or lines of constant velocity. It we integrate all velocities and taking average we will get wake velocity, Vw. 43. Sample velocity vector is a representation of resultant of tangential and radial velocities at a point along the radial length.
44.
Different views of propeller:
Projected view is a projection on a plane normal to the shaft. Developed view is a projection on a plane normal to the trust of the blade Expended view is a projection on a plane after the blade is mode flat. 44. A surface generated by a line rotated about an axis normal to itself and advance in the axis of rotation in constant speed.
46. 47.
Blade area ratio It is the ratio of blade area to the area of circle circumfrensing the propeller. Skew is the circumferential displacement of the blade tip from normal Rake is the distance in profile from the normal to the axis
48.
Different blade sections: cambered force
are flat face circular back, Aerofoil section and
49.
Right handed propeller: propeller rotation is clockwise and moving ahead when looking from aft. In twin screw stbd propeller is right handed propeller. Left handed propeller: propeller rotation is anticlockwise and moving ahead when looking from aft. In twin screw, port propeller is left handed propeller.
50. 51.
Pitch distribution is given in order to accommodate the change in wake velocity radially. The wake velocity is maximum at hub and minimum at tip so that that the pitch is maximum at hub and minimum at tip. In twin screw ships propellers are out board tuning.
52.
Q is the angle of pitch Pitch is the distance at which a propeller advances for each complete one revolution. When it rotates in a solid medium
`
Pitch angle, Q = tan-1 2πr ----P
53.
54.
Skew is given to propeller to vary the circumferential velocity. Rake is given because there is a good clearance between hull and propeller so that noise and vibration transmission from propeller to hull can be reduced..
(9)
RESISTANCE - (Answer Sheet)
1.
Reynold’s number, Rn = VL ---Ù§ It is connected with viscocity and so with frictional resistance. where, V = velocity L = length Ù§= kinetic viscosity Rn<2000 - Laminar flow Rn >4000 – turbulent flow Froude number, Fn = V2 --gL where g = gravity It is connected with wave making resistance.
2.
If Fn is constant Vm ----√gLm = Vs ----√gLs
If Rn is constant Vm L m = Vs L s Vm = Vs Vs
----------
Lm Vm = Vs
----
Vm = Vs.λ
√Ls/Lm Vm = Vs --√λ Ls --- = λ Lm
Take
So both the laws cannot be achieved simultaneously 3. 4. Rn is connected with frictional resistance. Fn is connected with wave making resistance
5. 6.
Resistance of a ship is the power required to tow the ship at a particular velocity.
For a stream lined body spacing of the stream line changes. Velocity changes because the mass flow is constant. The Bernoulli’s equation for stream line is P V2 -- + --- + gh = a constant. ρ 2 7. Mach number is connected with air resistance Mach Number = V --α Free surface is having constant atmospheric pressure. A pressure variation on the free surface results in waves on the surface. Energy is needed to maintain the waves and this leads to resistance which is the above making resistance and it is controlled by gravity. It decreases as depth from free surface. Fluids are viscous and resistance is produced by that is called frictional resistance. Components of Resistance: Wave making Resistance Frictional Resistance Viscous pressure Resistance or Form resistance Eddy making resistance Appendage resistance Air resistance 11. Kelvin wave pattern:
8.
9. 10.
12.
Interference effects: In the case of ship stem and stern pressure points produce waves of their own. The forward wave start with a crest and aft wave start with a trough. When the stem waves reach the sterm waves and interact the crest coinciding with crest forming high magnitude of the crest coincides with trough which is get neutralized. As a result of this humps and hollows are formed in resistance curves. This effect is formed interference effect.
13.
Viscous pressure drag: Viscocity modifies the flow around the hull which leads to built up of pressure at aft termed as viscous pressure resistance or form resistance, which depends on the hull.
14.
15.
Boundary layer: Volume of water which moves with the body is termed Boundary layer. Boundary layer thickness is the dist. from the hull at which relative water velocity is 99% of ships speed.
16.
Laminar flow: The flow is laminar for Rn < 2000. Velocity of liquid element in laminar flow remains const. in magnitude and direction. Turbulent flow: The flow is turbulent is Rn >4000. Flow is unsteady and non uniform velocity fluctuations and violent.
17. 18.
At critical Reynold’s number the flow changes from laminar to turbulent. Critical Reynold’s number: It is the number at which flow changes from laminar to turbulent flow. Below critical Rn, resistance is proportional to velocity. Above critical Rn resistance is proportional to V1.723 Turbulent stimulators are used in towing tanks which is used to convert flow from laminar to turbulent. Eddy making Resistance Formed as a result of abrupt change in the shape of the hull form. The effect can be minimized by stream lining the body. Appendages such as bilge keel, rudder create eddies. Rudder on activation create eddies. In the case of multi shaft ships shaft brackets creates eddies. Here the flow breakdown on well rounded from due
19. 20.
to viscosity and pressure distribution in boundary layer. Further form the effect is more. 21. Different appendages Bilge keel Rudder Skeg Stabilizer Echo sounder Speed log Propeller Shaft bracket ITTC method Steps for calculation of resistance of ship from model test: 1. RTM is found which is the total resistance of model from the measuring tank. 2. Total resistance coefficient , CTM = RTM ----is found ½ ρsv2 where ρ = density s = wetted surface area v = velocity 3. 4. 5. Frictional resistance coefficient of method can be found from ITTC formula Cfm = 0.075/ (log10Rn-2)2 Viscous resistance coefficient = Cvm = (1 + K) Cfm where K = form factor
22.
Residuary resistance coefficient of model Crm = CTm - Cvm 6. Equating Cr for model and ship Crm = Crs 7. Friction resistance coefficient of ship is found , Cps from ITTC formula 8. Viscous resistance coefficient of ship is found Cvs = (1 + K) Cps + √Cf Where √Cf is the roughness allowance 9. Cfs = Crs + Cvs + Cta Cts = Total resistance coefficient of ship Cta = Air resistance coefficient = 0.01 AT/S (AT = Tr. Projected area)
23.
Froude’s Method: of calculation of resistance of a ship from model test. Steps 1. Total resistance of model from model test at corresponding Froude number (RTM) 2. Calculate the frictional resistance of the model on the basis of a flat plate equivalent surface = Rfm 3. Residuary resistance of model is found out by ………………… frictional resistance of model from total resistance of model Rrm = RTM - Rfm 4. Residuary resistance of ship is found out by Rrs = Rrm ∇s ---∇m 5. Frictional resistance of ship is found out on the basis of a flat plate equivalent surface - Rfs 6. Total resistance of ship is the sum of Residuary resistance of ship and frictional resistance of ship RTS = RFS + RRS 7. Appendage resistance and air resistance we found and added to total resistance of ship 24. Specific Resistance coefficient = R ---½ ρSV2 R = Total resistance ρ = density S = welted surface area V = velocity
25.
Wetted surface area can be found out by plotting girth length of ship at various points along the length to base of ship length and integrating. Wetlted surface area can be calculated by two formula (approx) i) Denny’s formula, S = L (CB.B +ITT) Where L = Length B = Breadth T = Draft CB = Block coefficient Taylor’s formula Where ∆ in tones S = C(∆L)0.5
ii)
L in m. C = 15.2 to 16.5
26.
Methodical series tests starts with a parent form. In this test a number of significant form parameters are varies and results obtained shown as graphs. Resistance varies with the form parameters. This test is very useful in estimating the power requirment for new designs. One of such test is by Admiral Taylor. Two series data of methodical series tests are BSRA - British Ship Research Association DTMB - Dutch Towing Model Basin
27.
28.
Roughness: It is a major factor in determining frictional resistance. Structural roughness depends on design and method of construction and waviness between frames. Roughness also depends on corrosion and pitting. Roughness is also by fouling by weeds and barnacles. Roughness allowance usually given is 0.0004 Ahead Resistance coefficient (ARC) = Fore and Aft component of wind resistance ------------------------------------------------------½ ρVR 2AT Where VR = Relative velocity AT = transverse cross sectional area For tankers ARC = 0.7 wind ahead up to 500 (LS – 0.85m) ARC = 0.6 – 0.7 wind ad tern upto 400
29.
30.
Effects of ship parameters on Resistance 1. Length : increases means frictional resistance increases because welted surface area increases and wave making resistance decreases. C p is the effect of wave making resistance. 2. Form: represents Cb or CP. Fullness increases means resistance increases. Further ships have greater disturbance Cb decreases means dead weight decreases. So both of them should be taken into consideration. 3. Slimness: L3 ----∇ Slimness means high L/B value greater ∇ means steeper angle of entrance and run. For high-speed ship ∇1/3/L is kept low. Increase in volumetric coefficient increases resistance.
4. B/T - Increase in B/T increases resistance. In very high B/T ratio, the flour will go vertical and can reduce resistance. B increases means disturbance increases. 5. LCB : Governs the fullness the end of ship 10% forward of midship for slow ships and 10% aft of midship for fast ships. LCB at aft of midship will create eddies and forward of midship will allow smooth floar. 6. Section shape : For slow and moderate ships U sections at forward and V sections at aft 7. Bulbous bow : bulb reduces the wave making resistance. They are fitted for high speed ships. For slow speed ships bulb changes the four pattern and reduces frictional resistance. 31. Model Experiment Model experiments are done in towing tanks. Towing tanks have greater length but breadth is small. Models are attached to carriage which slides over the tank. Models are made of wood, FRP or paraffin wax. Resistance test are done in smooth water. Tanks are fitted with wave makers or turbulent stimulators. The platform has a dynamometer attached to measure the speed. Here we can measure various motions and resistance. Models attached to the carriage should be free to pitch and heave. Model basins are used to study model performance when maneuvering in waves. 32. Full scale test are conducted to find the scale effect. Scale effect means the predicted value of model and value of actual ship gives a small difference. So to find this full scale tests are done. For doing full scale trials the shape is towed or moved by jets high on ships. Laws of comparison
33.
34. -
Equipments used in towing tanks are Carriage to which model is attached Dynamo meter attached to platform for speed measuring Turbulent stimulators and wave makers for making regular and irregular waves Camera to records the path of model and various motions
(10)
MANEUVERING
- (Answer Sheet)
1. 2.
Maneuvering is the ability of a ship To maintain dynamic and directional stability Response to movement of control surface Ability to turn in a specified space Ability to maintain constant depth for submarine Ability to change depth in submarines Case with which ship can be controlled in a horizontal plane Principle of directional stability
Considering the arrows with large tail area, whose path of travel represented by path of travel of its CG. If a small disturbance deflects the arrow by Ψ, a lateral force F is produced at its tail since lateral surface area is more towards tail. This force can be converted to ‘F’ acting on CG and a moment. ‘F’ will to by to charge direction and ‘M’ will try to decrease Ψ. So arrow will defect to a new path with a direction similar to initial path. If this principle is applied to ship so that if there is a deviation in its path of travel, hydrodynamic force will acts on centroid of wetter surface area on one side which will tend to move the ship to a new path and reduces Ψ. The resultant force must act in centre of lateral resistance which is aft of ‘G’ 3. Center of Lateral Resistance It is the centeroid of lateral surface area which makes the angle of attack during a turning. 4. Ships can be made more directionally stable by using large skegs, using a large area rudder, increasing slenderness of ship (increasing T/L ratio)
5.
Neutral point is the point along the length of the ship, in which an applied force does not cause the ship to steer from its constant heading. This point is 1/6 L of the ship from bow. That is if we place a rudder at neutral point, the rudder movement will not cause to steer the ship. Or Neutral point is ηL forward of CG of ship. Rudder is fitted aft because it is the farthest distance from the neutral point for directional stability and also in propeller stream for directional stability because rudder lateral force increases due to high stream velocity from propeller. Various forces acting on a ship
6.
7.
8.
Factor’s affecting lift are Cross sectional shape Area of Rudder Aspect ratio Square of velocity Density of water Angle of attack Rudder force, Fr = ρArV2 f(α)
9.
Stall angle of rudder If angle of attack increases rudder (lift) force also increases. At a particular angle the lift reaches its maximum value and suddenly reduces and is termed as stalling. This stalling occurs usually at 35-450 and is termed as stalling angle. ie. the rudder angle is usually limited to 350 It is the angle of attack of rudder of which lift fore on rudder suddenly falls.
10.
CP of Rudder: It is the point on the surface of rudder at which the ruddar lateral force acts, which the rudder is put to an angle or it is the centeroid of lateral surface area of rudder through which net resultant hydrodynamic force acts. Geometry of a turning circle
11.
12. 13. 14. 15.
Drift angle is the angle between the center line of ship and tangent to the path. Drift angle is measured at the CG of the ship. Drift angle is zero at pivoting point. Advance is the distance travelled by CG in a direction parallel to the original course after the rudder is put over. Transfer: is the distance travelled by the CG perpendicular to the original course after the rudder is put over. Tactical diameter is the value of transfer when the ships heading changed by 180 degree. It is the dist. Travelled by CG of ship perpendicular to original course after rudder is put over till heading changed by 1800. Pivoting Point is the foot of the perpendicular from the center of the turning circle to the middle line of the ship extended if necessary. This is the point at which the drift angle is zero and is about 1/6 L from bow.
16.
17.
Angle of heel when turning: The ship heels inwards when the rudder is initially applied. The moment is by the athward component of the net rudder force and the hydrodynamic force acting at CG of hull and the centrifugal force. Fh – Fr = ∆V2 ----Rg Fn = Fr + ∆V2 ----Rg
=
R = radious of turn, V = speed of turn Moment which causes heel is (Fh – Fr) KG + Fr KH - Fh KE (Fh – Fr) (KG – KE) + Fr (KH – KE) EH is very small and can be ignored So moment causing heel = (Fh – Fr) (KG – KE) + Fr EH (Fh – Fr) GE Initially Fr vets when rudder is pit over and Fh slowly builds up and ship turns inwards. The effect of Fr is to reduce heel. If Fh builds up and overcomes Fr then ship heels outwards. So if Fr is suddenly taken off or put to opposite side the ship will heel more towards outwards. For small angle of heel ∆GM sinφ = (Fh – Fr) GE = ∆V2 ------- GE Rg GE ---- = Rg sinφ/V2∆ GM ================ 18. ZIG-ZAG maneuvering (Kempf maneuvering) Is used to find out initial response of the ship towards rudder movement.
Ship will go at a steady speed on a straight course Rudder is out to 200 P and held constant When the ship’s heeling charges to 200, the rudder is put to 200 stbd and held constant, till ships heading changes to 200in opposite direction.
Repeat the experiment Time between the successive rudder movements is noted. Overshoot is the amount by which ships heeling exceeds 200 before it reducing after the rudder is reversed. Experiment is repeated for different speeds, different values of rudder angle and heading deviation. Overshoot decreases with increased stability and rudder effectiveness. 19. Spiral maneuvering Indicates directional stability or instability From a steady speed and straight course rudder is out to say 15 0 stbd. Then ship setters to a steady rate of heading and is measured. Then rudder angle is changed to 100 stbd and steady rate of heading is measured. Then successive rudder angles of 50 stbd 00 , 50 P, 150 P etc. and rate of heading is noted.
For a stable ship, there will be unique rate of turn for each rudder angle. For an unstable ship, the graph has two arms for smaller rudder angle, depending on whether rudder is approached from above or below the value. The ship is unstable inside the loop. It is impossible to predict the ship’s way during turning and depends on disturbing faces of ocean. This gives the range of rudder angle over which the movement of ship is indeterminant. 20. Pullout maneuvering: to determine the direction stability of ship. Rudder angle is put to predetermined and held. When the ship is turning at a steady rate, rudder is returned to midship and change of rate of turn is noted. If stable rate of turn reduces to zero and if unstable the ship will take a new path. If the area under the graph is small the ship is more stable. 21. Standards of Maneuvering Large Rudder can increase directional stability and turning moment. Increase of T/L will improve directional stability Increase of B/L improves turning but reducer the directional stability Large skes will improve directional stability, but poor turning ability. Technical diameter/Length : 3.25 – 4.5 at 350 rudder angle Turning rate : 30/sec. for naval ships 0.50-10/sec. for other ships
Speed on turn = 60% of straight course Angle of heel = very important in passenger ships For directional stability there should not be loop in spiral maneuvering For pull out maneuvering, when rudder in centered 15-200 change is good stability 35-400 average 80-900 not good For ZIG ZAG maneuvering 200P - 200 stbd 80-30 sec for t-20 knots for a ship of 150m length Overshoot5.50 for 8knts and 8.50 for 16 knts 22. Selection of Rudder Based on - shape of stern of the ship - size or area of rudder required - capacity of steering gear available 23. Conventional Rudder have stream lined shape. They are double plated structures Conventional rudders are classified, based on degree of balance – Balanced, unbalanced and semi balanced rudders Based on suspension – simplex and spode rudders 24. Different between balanced and unbalanced rudder: For balanced rudder center of pressure is on the rudder axis For unbalanced rudder the center of pressure is at a large dist. From rudder axis Balanced rudder’s require less torque to turn it. Unbalanced rudder regwire large torgue to turn the rudder.
25.
Simplex Rudder Conventional rudder with …….. supports or support from hull. Rudder is fitted to stern frame by rudder post. In most case simplex rudder is unbalanced.
Spade rudder conventional rudder with in a suspended condition from stern frame. Rudder is filled to stern frame by rudder stock.
26. Bow rudder is fitted at the forward point of ….. at the bow. It is fitted to control path and heading independently. In war ships it acts as a stand by to aft rudder. It is less effective compared to aft rudder. 27. Controllable pitch propellers are used for ……………. Thrusters. They are used because they reduce the turn around time and enhances economy of operation. Special Rudder : are used to improve lift to drag ratio conventional rudder are of limited use at low speed i.e. special rudders are used to improve response at low speeds. Flap rudder In this an additional flap is provided at trailing edge of rudder which is capable to move to a greater angle than main portion. One third of total area of rudder is used as flap. Angle of flap is twice that of main rudder. Provides better lift characteristics system is complicated because flap is moved independly.
28.
29.
30.
Flectner Rudder : an example of flap rudder. Flaps of quite small area at trialing edge can be moved .. as to induce hydrodynamics forces on the main rudder assessing the turning it. It reduces torgue required for steering gear. Other types of rudders: Active Rudder Kitchen rudder Balanced reaction rudder Lateral thrust units Voith – Schneider propeller
31.
32.
Simplex Rudder 33. 34. Double plate construction Lift tube to lift rudder for repairing works Vertical and horizontal stiffners ……………… to drain water. Main Basin / Quay Trials : All piping systems and pumps Electrical power plants with all lights and electrical load Main and auxiliary machines and associated alarms Ventilation and air conditioning All main engine control systems Cargo pump capacity trial Navigational and radio equipments Deck machinery Alarms and controls Steering system Bilge and balast system Fuel oil system Fire fighting, CO2 and foam systems a) Speed Trial Trial speed is to be measured at a certified mile course or by GPS Speed trial consist of a double run and speed ………..be obtained by the average of these two consecutive runs.
Two parallel posts each at a distance of 1 knotical mile is placed store. Experiment structs when ship reaches in line with the posts and ends when it pasts the post. Time to travel between these two posts are taken for speed calculation. Experiment is done 2 to 3 times because of disturbances. Two such runs are conducted at 90% MCR condition and one double run at 50%, 75%, and 100% MCR. b) Crash stop astern This is carried out commencing with full ahead when the vessel is running full ahead to MCR and shall be continued till the vessel runs to full astern at normal asbern. c) Turning Test Measurement of tuning circle at MCR out put of main engine, taking 35 0 of …………angle to port. d) Zig – Zag test Test is carried out at 90% MCR of main engine by setting the rudder angle to 20 0 port and 200 stbd and also at 100 P and stbd. e) Endurance test Four hours endurance trial at maximum conditions out put of main engine using HFO, including two hours fuel oil consumption measuring shall be carried out. Bunker consumption to be found is service speed and at max. conditions rating of main engine for full load and ballest conditions. f) Stopping inertia test carried out by stopping the engine when the ship is running full heat at 90% MCR. The ship is continued to run till the speed comes down to five nots. 35. Model experiments in maneuvering A model with geometrical and dynamical similarities are mode Battery ……… electric motors to drive propeller
36. -
Radio control links for rudder and motor controlled A Basin with 122m x 61m is needed Overhead corner as are fitting to photograph the path of model Models are radio controlled and fitted with ……. to sense heel. Lights are provided at bour and stero, so that model moves is a known datum plane Lights are photographed using a multiple exposure technique The print is superimposed on a grid to enable the light positions to be reed off and drift angle deducted Speed and turning path are deducted Heel angle recorded inside the model Rudder forces and movement are recorded Results from model experiment for maneuvering Speed and turning path Heel, rudder force and moments Drift angle Results from model experiment for directional stability
37. 38.
In obluguw tour best, derivatives of forces and moments with respect to your angle measured Viscous effect on forces both with and without propeller are found out Rotating arm facility is used to measure forces at various your angles for a range of speeds and path of ………… These data obtained can be used to study situations of non-linerities RMM to study liner directions of velocity and acceleration ………………………..and ……………. Motions is obtained by force oscillating the ………… Turning circles, Zig-Zag maneuvering are predicted. PMM Test : (Planar ratio mechanisom test) Used to study the linear derivatives of velocity and acceleration Model is force oscillated in towing condition ……………….. swaying and ………… motions are carried out CPMAC The rate of turns or curvature that can be applied in PMM tests are limited and test do not provide good information. I computerized planar motions carriage system have the features to do obligue ………. Test, rotating arm test and PMM
39.
Ship Trials
For model ship ………. Actual ship has not an exact trajectory compared to model test. So there should be sufficient …… between model and ship to believe that model behavior respects ship
(11) 1.
SHIP DESIGN TEST I
(Answer Sheet)
Design is an arrangement of elements that go into human production. It is an activity that integrates the existing bodies of knowledge. In Design field Designer’s create and Engineer’s analyse. Design process is a series of operations leading to an end. Here a step by step description is needed for completing an activity. Design documentation provides Important issues Process is explicit Known to every one A record of decision is mode for future reference Standardised in companies
2.
Safety aspects in Design Plimsol mark to limit the loading of ship IMO requirements to be satisfied for stability of the ship Safety margins or safety factors Faculty free analysis to break down the problems into parts Risk analysis to analyze the risk and to overcome it Use of statistics and probability in design for risk assessment
3. 4.
Risk factors The major risk factors are Not achieving contract speed Not achieving dead weight Structural failure Collision in a crowded sea Mitigation or Risk management It is the use of Risk analysis to identify ways to reduced the identified risks
5.
Fire main categories of world fleet 1. Cargo ships 2. Passenger vessels 3. Naval vessels 4. Other self propeller vessels
6.
5. Barges and other Inland water vessels Types of cargo ships Tankers (liquid cargo carriers) Dry bulk carriers (grain, Coal and ore carriers) General cargo carriers (Containerized, R0-R0, Packaged, Palletized)
7.
Different liquid cargo carriers Oil carriers (Crude oil and refined petroleum products) Chemical carriers (phosphoric acid, Methanol, etc) (Gas carriers (LPG & LNG) Other carriers (water, fruit juice, molasses, vegetable oils, wines, asphalt, motton sulphur etc)
8.
Different general cargo ships They are of four types based on configuration 1. 2. 3. 4. Container ships Roll-on/Roll-off ships Refrigerated ships Packages or bundles type ships
9.
Different passenger ships They are also four types based on service 1. Cruise ships 2. Deep sea ferries 3. Short sea ferries 4. Fast ferries
10. -
Different offshore industry vessels Anchor Handling Tugs Supply boats Crew boats Stand by / Rescue boats Other offshore vessels – a. Offshore drilling equipment b. Offshore construction equipment c. Offshore production equipments
11.
Different offshore drilling equipments Drill ships Jock ups Drilling barges Semi submersibles Submersibles
12.
Different offshore construction equipments Derrick barges Pipe lay barges
13.
Different offshore production equipments Floating production unit (FPU) Floating storage ……………………. Floating production storage and offloading (FPSO)
14.
Main categories of marine industry The main five categories are 1. 2. 3. 4. 5. Ship design firms Ship construction firms Marine manufacturing firms Ship operation firms Ship repair firms
15.
Supporting Industries Supporting industries which comes under marine industries are Marine surveyors Pilots Terminal operations and stevedores Ship brokers Shipping agents Port Authorities Ship breakers Marine Insurance brokers Marine lawyers Bunkering companies and ship chanallers
16.
main manufacturing firms
1. Engine manufactures 2. Propeller manufactories/bour thrusters 3. Steering and mooring systems manufactures 4. Cargo handling system manufactures - This includes communication system Alarms, Systems and Controls Collission avoidance system integrated bridge systems 17. Different ship operations : This includes Govt. owned ship operators Navies and other governmental agencies Major multinationals Independent ship operators Owner operators Ship managers 18. Different Registeries (For registration of ship) Panoma Liberia Honduras 19. Initial cost This includes building costs Spare parts costs Owner furnished materials Plan approval Owners supervision Administrative and legal expenses 20. Operating costs : mainly includes Fuel costs Also Voyage costs Port and canal costs Tug service costs Cargo tendling costs Cargo damage claims Hold celeings Dunnage Pilotoge
21.
Daily costs Includes crews wages Insurance
Benefits Overheads and miscellaneous expenses 22. 23. RFR - Required Fright Rate is the ratio of average annual cost to tons of cargo that carried each year IMO - International Maritime organization Main functions are To provide machinery for cooperation among governments Deals with technical matters of all kinds affecting shipping engaged in international trade To encourage, facilitate and adopt high standards concerning maritime safety, efficiency of navigation and prevention and control of marine pollution from ships It is an international forum not a government body It consists of an assembly, council and four main committees It has a permanent representative from IACS It developes and adopted nearly 40 conventions and 100s of codes and recommendations. 24. Four committees of IMO 1. Marine safety committee (MSC) 2. Marine environmental protection committee (MEPC) 3. Legal committee 4. Technical co-operation committee 5. Marine safety committee (MSC) deals with Maritime safety procedure Maning from a safety stand point Construction and equipment of vessels Matters within the scope of navigation Rules to prevent ship collision Handling of dangerous cargoes Hydrographic information Log book and navigational records Salvage and ……….. Marine causality investigation 26. Marine environmental protection committee (MEPC) deals in considering any matters with prevention and control of pollution
25.
27.
Main conventions :SOLAS - safety of life at sea MARPOL - marine pollution ICLL - International conventional load lone International convention of tonnage measurement of ships
28.
IACS – International Association of classification Society It is not a governmental body IMO develop rules and IACS implements the rules IMO has a permanent representative from IACS This society will have a permanent qualified staff
29.
Functions of classification society To maintain close co-operation with world’s maritime industries To promote improvement of standard of safety at sea To co-operate and consult with relevant international and maritime organization Main classification societies ABS BV CCS DNV GL KRS LRS IRS NKK RINA RCS American Bureau of shipping Bureau veritas Chinese classification society Det Norske veritas Germanisher lloyed Korean Register of shipping Lloyd’s register of shipping Indian register of shipping Nippon Kaijee Kyokai Royale Italino Novale Russian classification society
30.
31.
DG shipping Directorate general of shipping MMD - Mercantile Marine Department
32. -
DG shipping deals with implementation of shipping policy so as to ensure the safety of life and ship at sea Prevention of marine pollution Promotion of maritime edveation and training in international maritime organization
-
Examination and clarification of merchant navy officers Development of coastal shipping
MMD deals with registration of ships and all related matters Surveys of cargo and passenger ships coming under conventions like SOLAS, MARPOL, ICLL etc. Survey during construction of ships Inspection and approval of statutory equipments like FFA and LSA, navigational aids etc.
(12) 1.
SHIP DESIGN TEST II
- (Answer Sheet)
Components of dead weight are
-
Mass of cargo Mass of stores Mass of crew Mass of water ballast
Dead weight, DW = MCA + Mstores + MCR + MWB 2. Components of cargo mass are Mass of Dry cargo Mass of Refrigerated cargo Mass of fluid cargo Mass of passenger cargo
MCA = MCD + MCR + MCF + MCP 3. Components of stores are 4. Mass of Heavy Fuel Oil Mass of Marine Diesel Oil Mass of Lubricating Oil Mass of boiler Fuel Mass of Fresh water Mass of provisions
MST = MHF + MDF + MLD + MBF + MFW + MPR Fuel store depends on - Power of main engine - Radius of action of ship - Sailing or working hours
5.
Fuel oil tank capacity Capacity of Fuel oil tank mainly depends on the - power of engine - radious of action - working hours Mass of Heavy fuel oil MHF = bHF - PB . DSE bHF = specific fuel consumptions of mane engine (HFO) = gms/kwhr
PB = Power of main engine in KW DSE = No. of days at sea If RA is Radius of action then MHF = bHF . PB . RA ----- + 10% Reserve V.24 V = velocity in knots Capacity of HFO tank = MHF ------ m3 PHF
Capacity of MDO, MDO = (bdf . PBA . RA ------ + bDF . PBA .DPO/24 RH) + 10% reserve V.24 PBA = power of auxiliary engine DPO = Days loyed in posts Capacity of MDO tank = MDO ------ m3 PDO 6. Fresh water tank capacity Fresh water required = Drinking water + wasting water Vol. of FW required = VFW = 20 L x (no. of officers + crews + passengers) + 60L x (no of crews) + 120 L x (no. of officers) + 200 L x (no. of passengers) 10% reserve If the ship has a desalination plant then Fresh water is needed to be stored for 3 to 4 days. 7. Basic owners requirements Type of ship no. of days at sea +
Service speed Cargo carrying capacity Radius of action 8. Dead weight carrier : is the one in which the main dimensions are fixed depending on the weight of cargo that can be carried Eg. Tankers ∆ = Cb x L x B X T X 1.025(HS) = WD + WL S = Shell, stern and appendage ∆ expressed is fraction of modulded ∆ 9. Capacity Carrier : is the one is which main dimensions are fixed depending on the volume of cargo that can be carried. Ef. R0 – R0 ships, Fishing vessels etc. VH = Cbd x L x B x D’ Cbd = moulded depth block coefficient D’ = capacotu depth = depth + mean camber + mean sheer 10. Linear dimension ship: are one in which dimensions are primary fixed other than dead weight and capacity. Here we are considering the internal and external factors. External factors example is, in container ships, the no. of containers to be considered while choosing linear dimension of ship. L/B ratio is related to slimmers and so the resistance on ship If L/B value is small then it is a bulky ship Therefore higher resistance If L/B value is large then slim ship, so lower resistance Ex. Ship with L≥ 130m. , L/B = 6.5 L≤30m., L/B = 4 30<L<130, L/B = 4 + 0.025 (L-30) 12. B/D ratio is primary related to stability of ship For dead weight carriers = B/D ≈ 1.9 (Tankers) For volume carriers = B/D ≈ 1.65 (fishing vessels)
11.
B/D is also related to hull weight, machinery weight and deck cargo. 13. L/D is related to strength of ship Depth is related to deflection and structural strength of hull grider L/D ≈ 10 for General cargo carriers L/D ≈ 12 for bulk carriers L/D ≈ 14 for tankers 14. T/D is related to free board or reserve buoyancy of ship T/D ≈ 0.7 for general cargo T/D ≈ 0.8 for tankers 15. Displacement coefficient : is the ratio of dead weight to displacement CD = Dead weight ------------------------Light ship + Dead weight CD is related to no. of bulk heads no. of decks size of ship Forces on ship Standard range is of 0.3-1 16. Admiralty coefficient : is used to calculate power requirement of a new ship from the parent ship data. Admiralty coefficient, Ac = V3.∆2/3 ------PB V = Velocity in knots ∆ = mass displacement in ones PB = power required in HP 17. Displacement from displacement equation
∆ = ∆LS + DWT = (∆SE + ∆ou +∆EP) + (∆CA + VCR + ∆FU + ∆FR + ∆SO) Where, ∆SE ∆SEO ------ = ------- = ∆SE = MSE ∆ ∆ ∆O (MSE represents the relative mass of parent ship = ∆SEO ------ ) ∆O
∆ou = Mou . ∆ ∆EP = MEP . PB PB can be found from admiralty coefficient AC = V3 . ∆2/3 -----------PB ∆EP = MEP . V3 . ∆2/3 ---------AC Also, ∆FU = MFU . PB . RA ------ ≈ MFU . V2 . ∆2/3 RA V --------- . ----AC 1 ∆ = A∆ + B∆2/s + I I = ∆ (1-A) - B∆2/3 = known value V3 . ∆2/3 PB = ----------AC
So if we draw a curve with ∆ and I on x and y axis We can find the ∆ of newship for required ‘I’ value Further the displacement equation is modified by Harwald and known as Harwly’d equation. He introduces a factor called normand’s factor to find out the increment of new ship for parent ship. 18. Two methods of subdivision of light ship - subdivision of manes according to production - subdivision of groups according to function preferable for design Purpose
Usually the subdivision is done in three groups 1. Steel mass, ∆SE 2. Outfit mass, ∆OU 3. Engine plant mass, ∆EP 19. Two methods of finding the steel mass For this we need to have a parent ship, from which we can assume the steel mass depending on the main dimension of the ship. This is done by the two methods or relations: 1. Cube number 1. 2. Square number
Cube number ; steel mass depends on cube bumber (L.B.D) 0 – represent parent ship 1 – represents new ship
∆SE1 = ∆SEO x L1C --------L0B0D0
If L/D and CB values are different for parent and new ship then correction is to be given. For brg ships, steel mass calculated by Eube number will be very high, so another relation – square number is used. 2. Square number : steel mass depends on square number L (B + D)
∆SE = ∆SE0 . L1(B1D1) ------------L0(B0D0) The calculation according to square number is approximately proportional to shell plating of ship. 20. Factors depending on length - Displacement - Resistance of ship - Building cost Length increases means resistance decreases but building cost increases Length depends on the shape of bour also 21. Factors depending on Breadth
22. 23. 24.
Increase in Breadth increases the stability of ship but building cost increases B is a function of L and depends on L/B ration, which represents the slimness of ship KM should be increased for higher standers of stability Superstructures, Deck cargo, Cargo handling equipments depends on B, since KG value can change affecting stability External factors like Lock gates or canals Breadth influence free board and stowage capacity Factors depending on Depth Is related to strength of ship L/D ratio represents strength of ship Increases the cargo hold capacity Increased stability as ‘G’ moves down due to increased depth For inland vessels – depth of canal, height of bridges is affected Depends of free board regulation D - T + D Freeboard Factors depending on Draft T increases means resistance increases B/T determines initial stability, since T determines VCB Large B/T value is favorable in connections with initial stability Depends on depth of canal, Harbour fecilities Std. size of containers TEU - Twenty Fect equivalent units = 20 x 8 x 8.5 FEU - Fourty Fect equivalent units = 40 x 8 x 8.5
25.
Five loading conditions for stability analysis of IMO light ship condition fully loaded departure fully loaded arrival ballast departure ballast arrival
26.
External conditions of stability analysis Crane loading Towing condition for Tags ……….. of deck Heeling due to turning Heeling due to cargo movement
- Heeling due to crocuding of passengers to one side - wind moment 27. Static loading condition is the critical case of loading analysis done in the preliminary design stage In this case GM is minimum – always 100% cargo and 100% stores ie. fully loading condition is the critical case 28. 29. Approximate method of stability calculation at the initial stage is prohaksas method The CG of a ship can be determined by detailed mass calculation after fixing the settings of the ship. The CG value depends on mass distribution of the ship CG also depends on type of ship, supers ………………….. sheer, engine plant and out fittings CG is also found from inclining experiment First we assume ‘KG’ as a functaion of depth So, KG = C3D3 Where, DE = DE + (Vss + VDH) -------------LB VSS = Vol. of super structure VDH = Vol. of deck house C3 varies according to type of ship. CG of the engine plant is assumed to be at CG of main engine LCG of the ship can be found from AG/LBP ≈ 0.875 (AB/LBP) + 0.049 SHIP DESIGN TEST III - (Answer Sheet)
(13) 1.
Stowage factor is defined as the inverse of density Stowage factor = 1/ρ = m3/t Cargo hold capacity depends on stowage factor
2.
Depth is the dimension parameter affecting capacity. Depth increases means cargo hold capacity increases and also the strength.
3. 4.
Tankers have less freeboard because density of cargo (fluid) carried is less than that of water. So already its having a freeboard. i.e. freeboard is less for tankers Grain capacity is the capacity of cargo hold including the volume between the frames of cargo hold. Grain capacity of cargo hold is 98 to 98.5% of whole volume
5.
Bale capacity is the capacity of cargo hold excluding the volume between the frames of cargo hold. Bale capacity of cargo hold is 88 to 88.5% of whole volume
6.
In capacity plan the location and capacities of various tanks like FO tank, LO tank, FW tank, Ballast tank, Dirty oil tank, etc, are shown. It also show the cargo tanks and its capacity for tankers. LCG and VCG are shown in the capacity plan.
7.
Capacity curve : is a curve showing the capacities of different sections of the ship as a curve. It is drawn using bonjean curves. The area of each sections upto the main deck + vol. of hatch trunk + vol. of cember + vol. of sheer + vol. of cargo hold in superstructure is taken vertically and joined by a smooth curve at top. It is used for trim and stability calculator. Factors influenced by lines are : Decisive influence on - resistance increase in a seaway - course-keeping stability - sea keeping ability - maneurability - roll damping - size of under deck volume During Hill shaping - shape of sectional area curve - midship section area coefficient and midship section form - …. Forms, forward section forms and FWD water lines - special bour forms - stern forms and Aft sections
8.
9. 10.
Factors influenced by LCG and LCB are speed and trim Various methods of lines design:
- Designed freely or form scratch - Derived from existing lines by distortion a. simple affine distortion b. Modified affine distortion (Interpolation method) c. Non-affine distortion - from graph 11. Free design of lines Fine LBP. Cm, CP, Cb, B, T Draw a trapezium as follows Height of trapezium = Am = B x T x Cm Length of base of trapezium = LBP Length of top of trapezium = L of parallel middle body Ratio of trapezium area to rectangle Am x L is CP Ratio of trapezium area to rectangle B x T X L is Cb Fix LCB according to resistance and trim calculations since centroid of trapezium is LCB, distort the trapezium to move the centroid – LCB of ship to fixed position as calculated - Fair the top edges of trapezium - Extent the trapezium to fore of FP and aft of AP to get length overall 12. Lines designs using design curves 13. using Cb and Cw, fix U,V or normal section from Cw, Cb graph using Cb, fix AB/LBP depending on U normal or V shape using Cb and L/B, fix iE half angle of entrance using Cw and iE, fix the load water line using Cb, fix LE, LP and LR using AB/LBP and CP, fix the CPA and CPF from CPAand CPF, fix the area of each station using area of each station, fix the shape of each station by trial and error
Angle of Entrance : It is the twice of angle made by a tangent to load water line with the centerline of ship at FP and generally given as half angle of entrance, iE/2 Angle of Run : It is twice of angle made by a tangent to centerline of ship and load water line at AP and known as half angle of run ir/2
14.
Simple affine distortion method This method is used on existing design of lines of ship Length, Breadth and Depth are multiplied by a standard ratio Dimensions on each coordinate axis changed proportionately Dimension can be L1B1D or all
-
-
Scaling for each dimensions may be same or different Non dimensional values like L/B, B/T, ∇/L3, Cb, LCB ------, Aw, Cm etc remains LBP Unchanged Fore and aft contour can be changed, CBF = C + (0.0211 + a --- - 0.027Cb) 44 CBA = CB – (‘’) Rearrange the lines of design according to calculation Modified affine distortion
15. -
Using interpolation of two ships design liner to generate a new one …………………………… stations of two ships are interpolated Seeking intermediate values in an arbitrary ratio According to interpolation, water planes are also interpolated to get a new displacement New displacement, ∇N = ∇I + (∇II - ∇I) X X = change is breadth as ratio of overall diff. in breadth of two designs. Non-affine distortion
16. 17.
Here distortion of section area curve of existing design using parabolic curve Shift is section areas are plotted as quadratic parabola The addition area of section is distributed to aft horizontally The increase in value due to inverse in section area is distributed uniformly to aft Different types of bow are Normal bow Balbous bow Special bow forms
18.
Adv. Of Raked stem water deflecting effect increase in reverse buoyancy greater protection in collision more attractive
19.
Adv. Of V sections
-
Greater vol. at top side Greater B at design WL. More KM Smaller welted surface area Less curved surface Cheep construction Better sea keeping ability greater reserve buoyancy No slamming effect Greater Deck area In ballast condition less CB and less resistance
Disadvantages : Here wave making resistance 20. Adv. Of Flare Defects green area Increase local reserve buoyancy reduces pitching amplitude Increase the height of Righting arm curve
Dis. Adv. of Flare - Produce more water spray - more structural material required - local pitching acceleration and impacts 21. Design parameters of bulbous bow 22. shape of section side view length of projection beyond perpendicular shape of toward region position of axis area ratio transition of hull
Different bulb forms - modern bulb forms - bulbous bow projecting above LWL - parabolic bow
23.
Effects of bulbous bow on ship characteristics are - sea keeping characteristics - effective drag & total resistance - propulsion characteristics
24.
course keeping ability and maeovering bow thruster trim and free beard Anchor handling Sounding devices length ………………… ice operation
Design criteria for stern designs low resistance avoid vibration high propulsive efficiency to minimise focus separation to provide sufficient propeller clearance
25.
Different types of stern Merchant or Elliptical stern ………………….. stern Transom stern
26.
Adv. of transom stern - more deck are - simplified construction - trim can be improved using wedges - reduces squatting
27.
Adv. of bulbous stern - minimised propeller induced vibrations - more uniform wake
28.
Two bulbous stern 1. Hogner’s bulbous stern 2. Nitski’s bulbous stern Hogner’s bulbous stern is concentric to shaft and has a swollen hub\
Nitski’s bulbous stern has a bulbged lower section 29. AsymmFietric aft body is the one which is not symmetric with respect to center line at the aft sections. Advantages: Higher woke froction Low thrust deduction Uniform inflour Pre rotation and reduction in tangential loss 30. 31. Noenmicke stern is an Asymmetric aft body Fin fitted in aft is known as Grothues spiler Purpose is to reduce vibration, power is reduced from 3 to 9%, - Horizontal straightening of boundary layer . They are hydrofoil find before shaft strit barrel. 32. Wake duct is a Ring shaped flow vane of aerofoil type - fitted to hull as two half rings - sets at different angles for both sides and symmetrical - flow creates a circulation around the aerofoil section and accelerates the flow - less than half diameter 33. Forward propellers for breaking the ice by producing a negative pressure due to section in ice breakers - in double ended ferries - in Inland motor driven cargo ships it acts as rudder propeller 34. Minimum propeller clearance is required to reduce the hydrodynamic forces on the hull produced by the propeller power requirement diameter and optimum speed fluctuation in torque vibration excitation of propeller and stern
(14) 1.
SHIP DESIGN TEST IV
-
(Answer Sheet)
Items in Anchor handling system : Anchor Heavy chain cable Hawse pipe Windlass Sparing pipe Chain locker
2.
Hawse pipe: - It is made of mild steel tube with castings at deck and shell or cast is one complete unit for each side of ship - Shell plating is increased is thickness is way of each Hawse pipe and adjacent plate edges are fitted with mouldings to prevent damage
- There must be clearance for anchor stock to prevent damage by jamming and they must be strong enough to withstand the hammering effect when the anchor is received -chaffing piece is to be fitted at the top of each hawse pipe - A sliding cover is tube arranged to guard the opening 3. Function of cable stoppers - is to lock the chain cable in any desired position and thus relieve the load from the windlass, when the anchor is out or stowed. 4. Design aspects of chain locker - fitted between upper and second deck, below the second deck or in the forecastle - It is to be mode of sufficient volume to store chain cable when the anchors are in the stowed position Situated forward of collision bulkhead and use this bulk head as the after locker bulkhead Chain pipes or spaceling pipes are fitted as near as to the center of chain locker for easy of stowage Stiffners are to be fitted outside to prevent the enticing of chain and damage to locker Centerline bulk heads are to be fitted to separate the two chain and it is to carried above the stowed level Centerline divisions are stiffned by angles, facing both srdes to b/H or solid half round bar stiffned, Hinged door is fitted to forward b/H which gives ………… to chain locker from store False bottom is to be provided to drain water and mud Draining is to be provided and hand pump for discharging the drast Cable end is to be connected to deck or b/H is chain locker Windlass For handling and securing the anchor and chain For handling ropes using for towing the ship Parts Capstuns or gypsy heads for mooring and warping operations for keeping the correct line Wildcat is a special type of drum for handling anchor chain, which have a looking head for disengaging and engaging the chain Drive motor for controlling the operations
5.
Hand break for holding the anchor and chain and to control the speed of discent Locking head for engaging and disengaging the chain Control which includes either electric or electro hydraulic Windlass is also located at the aft of ship for stern anchoring. Usually they are located in the bow for handling bower anchors 6. Types of windlass Horizontal shaft type Vertical shaft type In horizontal shaft type the windlass is placed horizontally above the deck. The whole unit is above the deck. In vertical shaft type, its power source is located below deck and have only wild cats and capstans mounted above deck. 7. Power sources for windlass Electro hydraulic drive Electric drive 8. Anchor handling equipment is determined by a parameter equipment number Equipment number depends on profile area, displacement and above deck area Eq. no. - Displacement2/3 + 2(B x H) + 0.1A H = height from summer load line to top of upper most deck A = Area in profile view of hull, super structure and deckhouse above summer local water line 9. Anchor Handling Regulations All windlass shall be capable of being emergency released from the bridge Tugs for ocean towing shall be equipped with ………… Anchor handling ships should have arrangement for controlled release of ……….. forces in wires Anchor handling ships should have a stern roller with greatest possible diameter for with standing max. load Towing hooks shall be designed for maximum towing force of ship and have a factor of safety not less than5
-
Cruciform boll cards and other equipments used for towing should be designed in most unfavourable directions form 0-600 to either side in relation to ships center line and 300 upwards in relation to horizontal plane Types of Anchor
10. 11. 12. 13.
Admirality Anchor Stockless bower Anchor Delta Anchor Pool Anchor Plough Anchor Delta twin stank Anchor Hall Anchor AC14 Anchor Minimum requirements for closures are Which are routinely opened and closed while at sea, such as doors, manholes, hatches etc Which are secured normally at sea i.e. remain closed Eg. Should have strength equivalent to surrounding structure Still height and coaming heights should be as of ILLC and in class Minimum requirements of doors: Minimum sill height required depending on space protected, height above assigned …. Water line and distance from the bow Fixed light is to be provided in all door openings to weather deck. Different doors Individually Dogged water light doors Quick acting water light doors Sliding water light doors Quick acting air light doors Frame tight doors Weather light doors Non water light steel doors Non water light joiner doors Doors within doors
14.
Individually dogged water light door Provide access to compartments that are not high usuage spaces and do not require rapid access
eg. are paint rooms, store rooms etc. Quick acting water light door Secured using a single lever or hand wheel which operates all dogs - used in weather decks, main passage ways etc Non water light Joiner doors - used in accommodation areas where regulations prohibit use of joiner wooden doors Doors within doors - used inside of water light envelop where large access is required for movement of cargo, vehicles etc. 16. Different types of scuttles: (Explanation) Raised water tight scuttles: installed in exterior and interior areas and in corners out of high traffic areas. They are placed where rapid access is required. If may also be used as an alternate access is required. It may also be used as an alternate access to manned or unmanned spaces. Flush water tight scuttles: installed in areas with high traffic to eliminate tripping hazards or smooth trucking hazards. i.e. they are included in flight decks, hangar decks, passage ways and cargo decks. 17. Requirements of Manholes - to ensure two means of escape and to facilitate ventilation - Its standard practice to provide two manhole to each tank or void space, located at diagonally opposite corners - International tank association recommends openings suitable for passage of injured personal or stretchers - Min. clearance opening for a manhole should not be less than 460mm for round holes and 1580 x 360mm for oblong holes Sliding water tight doors Used in place of hinged door, when the door sill is less than the prescribed height above the subdivision load line and when the size of opening is two large to make a hinged door practicable.
Quick acting air tight doors Similar to quick acting water tight doors, but installed outside of water tight structure or above main deck where easy access is required. Used in passage ways, officer etc. Prevents fire, toxia vapours etc. Has three dogs on handle side and no dogs on hinge side Fume tight doors Are of lighter construction, but has more tightness than water tightness Installed in boundary bhd’s of a space containing hazardous, toxia fumics etc Weather height doors Fitted where water tight door is not required Made of steel or aluminium Non water tight steel doors Used in entrances to store spaces Made of 5-7mm thick 18. Requirements of freeing ports - provided in bulwarks to rapidly drain the enclosed deck areas of green water - Rectangular openings 150-200mm high by 600-1200mm long to fit frame spacing in the bulwark plating at deck level - ends of freeing ports have a radius shape equal to the height - vertical guard bars are usually fitted 19. Mooring ports: are water tight enclosures in the shell plating for mooring arrangements. They are used when the winches are located below weather deck or when weather deck is too high in relation to mooring bits. Fairleads (Roller) are built within the port opening to lead the mooring lines directly to which. They hinge in bowered and are dogged tighted. Types of windows: a. Rectangular window: cast or bronze or aluminium frames with steal retaining clips, fitted in upper levels of superstructure and wheel house b. Sliding windows : Vertical and horizontal type
20.
Vertical sliding window descend vertically into a metal pocket below the window and pan is drained to exterior c. Large View windows: In passenger vessels Fitted with double pane windows with an air escape to minimise the heat loss Glass is tinted to prevent solar glare in all latations except ……. house d. Wheel house windows Fitted with wire inserted heat treated plate glass at least 6mm thick for protection Two or more windows are fitted with wipers and rotating disc inserts-clear views, for visibility in rain and snow Canted out for protection against sun glare and parallel distortion when looking to the bow 21. Dead weight scale Scale which contains free board measurements, TPC, MCT, Displacement for different drafts in seawater and fresh water. It is a chart kept in wheel house for the easy assessment of above values for captain for different drafts. 22. Requirements of fuel oil day tank: - an over flow pipe - air vent - drain valve - low level and high level alarm - inlet and outlet ports - man hole - slit glass - vel, to hold fuel oil for a day service 23. Onboard discharges 24. sanitary discharge bilge and fire discharge slope tank discharge galley discharge engine cooling water discharge
Noise levels in - engine rook – 110dB - cabin - 60 dB
25.
Navigation equipments
26.
Radar Anemometer Navigation lights and Flags Magnetic compass and Clinometer Autopilot and Gyrocompass GMDSS, EPIRB, SART Echo sounder and speed log
Surface preparation - means before fabrication, all steel and pipings are shot blasted to SA 2.5 and primed - After fabrication, damaged parts, welds, weld burns etc are removed using power tools and finished to ST2 before being painted.
27. 28.
Unit of paint thickness : Dry film thickness (DFT) which is measured in microns Cathodic protection : is provided on ship structures which are subjected to corrosion - Zinc or Al anodes are used for cothodic protection - Number and weight of anodes are calculated based on area to be Protected - Anodes are bolted to hull - Anodes are bolted to Rudder, see chests and ballast tanks
29.
Rules for GA Design SOLAS IMO panama canal rules suez canal rules ILO 92
30.
Main design aspects while making GA - depends on the service of the ship - structural members continuity - high standard of gear comfort - adequate trim - structure to suit GA layout of holds, tanks, machinery space and deck House - to locate cargo gear for efficient loading - smooth movements of crews during work and in case of emergency - adequate support for cargo gear
‘
31.
Design aspects for container GA Large tranes standard size containers TEU and FEU long verticals stagnations throughout Torsion box at end and box girders and center
32.
Design aspects for Tankers Hose handling cranes shore connections P/V valve Cargo manifoild tray Drain plugs and butter worth openings for cargo hold tanks
33.
Design aspects for General Cargo cranes and derricks of different span and range different types of cargo loading
34.
Different types of ladders fixed vertical ladders spar ladder inclined ladder Accommodation badder Embarkation ladder
35.
Fixed vertical loader: - access to all cargo holds, bosun’s stores, tanks etc. - not less than two ladders are provided to each shape - for cargo holds, vertical lodder is installed at each hatch end in way of structural pillar so that it can be protected from damage by cargo and imposes the minimum interference with cargo stowage - container ships lodders are fitted at bulk heads. Spar ladder - installed on masts, king posts, stacks, etc. to provide access for adjustment and servicing of rigging fittings, lines etc. - fitted with stirrups shaped, so that persons foot will not slide off side ways - mode of 76 x 10 mm FB stringers spaced 300mm centers, and are bolted to lug and welded to most
- provided for interior inspection and maintenance of large diameter posts - hoops are installed around most for safely - access is through man hole, where bending stress is minimum Inclined ladder on weather decks for access from one deck level to another used in engine room, store spaces made up of units complete with stringers, treads and hand rails assembly is then welded to top and bottom of stringer to deck non slip deck pod at top & bottom rails made of 32mm galvanised pipe Treads are non slip steel coverings welded or revelted to stringers for safety on weather deck, this lsdders are located to avoid tripping hazards on deck
Accomadation ladder : (Ganoj ways) - designed to reach from weather deck to light operating draft line at an angle of 450 to horizontal and along the hull - length can be adjusted depending on draft conditions - side stringers are made of light weight metal (Al), wood or channel and designed to carry 136 kg/tread - upper end of ladder attached to a portable platform attached to ship side a deck level III’er platform from lower end to facilitate boarding from small ….. Ludders and guard rails are equipped with portable guard rail stanctions Lower end of the ladder is supported by wire ropes while working cleared of from over head discharge openings and cargo loading side ports - equipped on both sides (p and stbd) 36. Different items and Design aspects on a wheel house layout Rudder Indicator Helsman chair Cyrocompass and magnetic compass Instrument panel Battery charger Radar ocemories Engine Telegraph Techometer Steering gear system Fix Alarm panel
Design aspects - All equipments needed for communication and navigation is located together within easy reach - On all ships VHF, radar and AIS should be located together - ECDIS display should be fitted close to radar - confusion between different instrument to be avoided
15. 1. 2.
SHIP DESIGN TEST V - (Anser Sheet) Design aspects of Accommodation layout Combination of std. rooms of Identical size Constructed is one or two blocks More space with adjacent rooms for ranked officers Mass, galley and stores in lower tiers Beds are arranged fore and aft, setter in athwardship Sanitary spaces are vertically aligned Sanitary spaces should not be located on extender BHDs because of condensation problem Berths and not provided near to deck head Stairways and service trunks should be surrounded by fire BHDs and fire doors Wheelhouse windows to be arranged to reduce pardlax distortion. Requirement of closures Closures are doors, hatches, sutter and man holes Sill heights and coaming heights as per ILLC Class I hinged doors are to fitted above bhd deck Class II and III, sliding water tight doors are fitted in subdivision bhds below bhd deck Open/close indicator on the bridge and remote closing control is to be provided
3. 4.
Cargo hatches, side ports and ro/ro bhds are to be gasketed for watertightness and dogged Manholes two in no. for each cargo or other tanks are to be placed diagonally in opposite corners Hatch covers to be provided with counter balance weight Ventilation requirements Wire mesh is to be provided for protection from insects and rats Fire screens are to be fitted for oil tank vents Cowls for natural air supply fitted with weather head dampers Goose neck for natural and mechanical vent system, supply or exhause, watertight covers with dogs Mushroom type natural or mechanical supply or exhaust can be screwed down to make water tight Lowers on weather bhds, with wire mesh screens Air lifts also can be used in place of laivers Bulwarks and rails Bulwarks
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For protection from sea for personal and deck cargo Sufficient strength for attachment of rigging fittings, lashing deck cargo etc Should have freeing ports as per ILLC Steel plates of 6mm thickness and bracket 1.5-1.8m apart Bridge front bulwark 1350mm and others 1000mm ht. Bridge front bulwark of venture type wind shield Break waters on weather deck Rails
5.
In areas other than bulwark Stenchions 1.5m apart Portable in way of hatches to facilitate loading Guard rails in openings on deck Grab rails outside deck house, interiors passengers etc. Ladders 1. 2. 3. 4. 5. Fixed vertical ladder Spar ladder Inclined ladder Accommodation ladder Embarkation ladder
6.
Rigging Fittings
7.
Derricks and cranes Pad eyes in E/R and stern region Miscellaneous rigging fittings for cargo securing, moving stores accommodation and E/R having spare parts Requirements for safe storage of cargo in holds Sparrings or buttons
-
Sparring is wood or metal protection of all vertical stiffners Thermal insulated Cargo bottoms is sparring on shell frames in cargo spaces Ceiling
-
To protect Tank tap Dunnage Wooden ………….. plywood sheets for protection of deck cargo Wire rope nettings with quick acting lashings on deck Plastic inflatable dunnage Bulkhead sheeting
-
Sheeting is given in case of bulk heads from boundaries of tanks to prevent condensation is cargo holds Types of Gratings
8. 9.
Wooden gratings for basin stores, dry store to provide walking and working surface Al gratings for refrigerated space GRP gratings Steel diamond plate for M/C space Deck coverings 1. Magnesite - In crew quarters 2. Terrazo - low fire hazards, decorative properties, economical in all wet spaces, swimming pools, passengers etc 3. Ceramic tiles – in wet spaces 4. Rubber tiles and sheets – decorate and resilient 5. Vinyl tile – most widely used and easy to maintain 6. Carpeting – in public rooms, stair ways, passage ways etc.
10.
Electrical load analysis It is used to find the amount of power that is to be generated by the generator on board. It is the summation of maximum power rating of all the sectional appliances on board ship in watts
11.
Items in a Engine room Main Engine Generator (Main) Generator (stand by) Compressor Boiler Sea chest MDo tank HFO tank Oily water separator Day tank Setting tank Engine room ……… pump Lathe Control panel
12. 13.
Requirements of Exhaust system Thermally insulated Sufficient height to be provided for funnel Exhaust water at higher temp and pressure must be delivered under water Heating gas recovery coil must be provided Exhaust must be significant dist. From accommodation Mooring lines
14. -
External forces to be considered while mooring design Wind Current Surge due to passing ships Waves and swell
15. 16. -
Change of free board Mooring equipments Mooring wires or ropes Mooring winch Cap stuns Fair leads Bollards Chocks Windlass Stoppers Mooring wires Wire lines - for limited movement Synthetic lines – for small ships, where case of handling flexibility of mooring and lower line tension are important criteria High modular polyethgiene and synthetic, fiber ropes with strength and low stretch characteristics can be substituted with steel lines Winches classification Control type Drive type No. of drums Types of drums Brake type Automatic and Manual Tensioning steam, hydraulic, electric single, double, triple drum split, undivided Band, Disc, mechanical Screw, Spring applied
17.
18.
Different bollards Vertical bollards Horn Tee Pillar Cruciform
19. -
Types o Fairleads Closed panama type Roller type Pedestal type Universal type Surivel type
20. 21. -
Automated mooring system Vaccum pads on a frame work on the quay which extends out and secures by vaccum to ships side Gaint magnets instead of vaccum is used Elimination of shore mooring gangs and ship line crew Only one operator to moor the ship Minutes are only needed instead of hours for mooring Eliminated mooring winches on board Different cargo handling equipments Derricks and swinging boom arrangement Cranes grantry cranes Grabbing cranes heavy lift cranes forklift truck other ship board lifting and transferring system conveyor belt system pumps for liquideos cargoes elevators – wire and crane operated Burtoning system and winches Different cargo hatches covers Type a. b. c. d. Single pull Folding covers and direct pull covers Roll stowing covers flexible rolling covers Side and end rolling covers lift and roll covers Telescopic covers e. Pontron covers Mode of operation Rolling and tipping Foldable Rolette Rolling Lifting
22.
23. -
Fire fighting equipments Smoke detector Intrared flame detector Alarm Portable extinguishers Automatic water spray or Deluge system Foam systems Carbon dioxide flooding Inert gas Funnel gas inserting system Halon system
24. 25. 26. 27. -
Dry powder extinguisher Life saving equipments Life buoy Life jacket Immersion suit Visual signals Hand flares Buoyant smoke signal Survival craft Rocket parachute flares Life boats Radar transponder Self inflatable raft Different light signals Day shapes, like lights during day Navigational light Mast head light Side light Stern lights Signals that indicate type of vessel Towing lights All round lights Flashing lights Vessels engaged in fishing, not under commend Underway, vessel restricted in her ability to maneuver Sound signals …………… Short blast - 1 sec Prolonged blast - 4-6 sec Maneuvering signals and warning signals Distress signals Signals to attract attention Steering system Telemotor control Electrical control Hydraulic powered - Ram type - Rotary vane type
16.
CLASS TEST II
- ANSWER SHEET
1.
Major stress acting on a ship structure are 1. Built in stresses due to welding and rolling of structural elements 2. Stresses in still water due to uneven distribution of mass and buoyancy 3. Stresses in seaway due to the action of waves causes longitudinal shear stress and bending stresses. Torsion also oceans due to uneven waves 4. Crushing or compressive stress due to pillar loading and stresses due to pending, …….. and panting
2. -
Strength analysis of a ship Analyzing the ships forces in seaway and still water Evaluating the response of ship towards this forces Estimating the ships response towards there forces Make sure that there stresses will not go above the allowable units Strength analysis is done mainly for Long term serviceability unit Ultimate stress limit ………………….. limit Accident limit Strength analysis also include longitudinal strength analysis, Transverse strength analysis and local strength analysis by finite element method Factors affecting strength of a ship Depth of the ship Length of the ship
-
3.
4. 5.
Uneven loading Irregular seaway Corrosion Concentrated load during docking Sectional area Different modes of structural failure Fatigue Welding imperfections Built in stresses Due to corrosion Uneven loading Instability due to large deflection for small increment of loading Major forces acting on a ship in still water As we known weight of ship is equal to buoyances loading pattern …………. …………… in mass/unit length and ship’s shape causes a variation in buoyancy/unit length If mass/unit length = mg Buoyancy/unit length = ρga Net force = mg + ρga Shear force = s= ƒ(mg + ρga) dx Bending movement = ƒ(s) dx
6. 7. A.
Force acting on a ship in seaway Due to woves (logging and sagging) Rudder lateral forces Centfugal force Thrust from propulsion device Wind resistance Wave resistance Weight is buoyancy Simply supported beam subjected to concentrated load RA + R B = W RA x L = W x L/2
RA = W/2 = RB SFD At a dist. ‘x’ from A Fx = +RA FA = +W/2 FC = W/2 SF between ‘C’ and ‘B’ F x = RA – W FC = w/2 – w = -w/2 FB = -w/2 BMD (at a dist x) M x = RA . x MA = RA.O = 0 M C = RA . O = 0 MC = RA . L/2 = wL ---4 BM between ‘C’ and ‘B” Mx = RA.x – w (x-L/2) Mc = wL2 ------ - w (o) 4 = wL ---4 ====
Mb = w L ---- . --- - w (L-L/2) 2 2 = 0 7. B RA + RB = W. x RA x L = w. L. L ----------2 RA = wL ----- = RB 2 SFD At dist. ‘x’ from A Fx = RA – wx FA = wL ---2 FC = = wL ---2 FB = wL ---2 = -0 wL ---2
-
= 0
- wL
- wL ---2 =======
BMD At a dist. ‘x’ from A Mx = RA . x - w.x.x -------2 MA = 0
MC = wL2 wL2 ----- - ----4 8 = wL2 ----8 === MB = wL2
------ - -------
2 7. C
wL2 = 0 2
RA + R B = w RA x L = w x 0.25L RA = 0.25 W RB = 0.75W SFD between A and C SFx = RA . x FA = RA = 0.25W FC = 0.25W Between C and B SFx = RA – W FC = 0.25W – W = -0.75W FB = 0.25W- W = -0.75W BMD between A and C M x = RA . x
MA = 0 MC = RA .0.75L = 0.25W x 0.75 L Between C and B Mx = RA . x – w (x-0.75L) MC = 0.25W x 0.75L – W (o) MB = 0.25WL – W(0.25L) = 0 7. D SFD Fx = w FB = W FA = W BMD Mx = - w. x MB = 0 MA = - W.L 7. E SFD Fx = wx FB = 0 FA = + w.L BMD Mx = -w.x.x -2 MA = 0
MB = - wl2 -----2 8. Welding techniques 1. Rightward techniques 2. Left ward techniques In both the above cases the welding torch is in right hand and filler rod is in the left hand. The main difference in the right ward technique, the welding starts from the left end and move towards the right hand side of the work piece
Are welding techniques include Downhead welding – 1G Horizontal vertical welding – 2G Vertical welding – 3G Uphead welding - 4G Pipe welding - (5G & 6G) 9. Welding Imperfections a. Welding cracks due to lack of root penetration
Ultra sonic testing:- are also used to defect the internal defects. The frequency of waves ranges from 20 KHZ to 20 MHZ, which can be transmitted through object and get reflected by the defects. Aere probes are used to transmit the waves and receiving them after the passage through objects. Since ultra sonic waves are transmitted as a series of …………. …………., the same probe may be used as transmitter and received. In case of any defects between top and bottom surfaces of the objects, the beams striking this defect will get reflected, reach the receiver probe and indicates a echo on the cathode ray oscilloscope screen before the echo given by the waves striking the other end of the job and returning. So time interval is to be noted between transmission and incoming signals. The distance of the defect can be determined by the time distance scale in the form of a square wove, shown in oscilloscope. 11. Welding inspection methods i) Destructive Testing
ii) Non-Destructive testing i) Destructive testing includes a) Impact test b) Bending test c) Hardness test iii) Non-Destructive testing includes a) Visual Inspection a. Liquid penetrate testing b. Magnetic particle testing c. Radiographic testing d. Ultrasonic testing
12. a. Mass and Buoyancy distribution Mass distribution from shell expressions adding structural component and loading pattern Buoyancy distribution from Bonjean curve For a general ship is still water For a general ship in seaway in a ……… wave here also the mass distribution is same
For a general ship in seaway in a sagging wave
b.
Shear force and BM diagram for ships
SR and BM are zero at ends Bendy moment is maximum at deflection for SF = 0 at midship SR is maximum at a quarter length from two ends of ship c. Still water and wave bending moments
a.
Visual inspection: Inspecting the welds visually or by magnifying lens. This method is most popular, simplest and economical for detecting defects on the surface of the welded objects. b. Liquid penetrate test (LPT) : are used for detecting the surface defects. Here the liquid penetrate is applied to the surface of the object after cleaning the surface of the object. After some time the liquid is completely removed and developer is applied. Then the liquid which has penetrated come out of the cracks and developer will helps to detect them easily c. Magnetic ………Inspection (MPI) : Firstly the object is placed in the magnetic field and magnetic liner of flues get intersected by discontinuously such as crack or slag inclusion, magnetic poles are generated on either side of discontinuity. This causes a distribution in the magnetic flare …….. through the job, which can be detected by magnetic particles which are attracted to the region of discontuity. This is applied only for ferrous materials. d. Radiographic test : X-rays, which are produced in a X-ray tube are proceeded towards the objects which is to checked for defects. An X-ray film is placed behind and in contact with the object, perpendicular to the passage of X-rays. As the x-rays …………… through the objects and strikes the film, take the film for developing and film shows light and dark areas, which is easy to determine the defects (like ………….., cracks, slay ………etc.)
17. 1.
MARINE ENGINEERING QUESTIONS (Answer Sheet) In water tube boiler feed water is passed through tubes and hot gases passes over them. It is employed for high pressure, high temperature and high capacity steam applications. It is used for propulsion of main engine, turbine and for cargo pumping. In smoke tube boiler hot gases pass through the tubes and feed water passes around it. It is used for auxiliary engines It is used to produce small quantities of steam which is of the low pressure
2.
Steam to steam Generator: are of vertical and horizontal types. It is used to produce low pressure saturated steam for domestic and other services It is used is conjunction with a high pressure water tube boiler. It is similar to a smoke tubes boiler, but instead of not gases high pressure steam which is passed from the water boiler is used to heat feed water
3. 4.
Advantages of steam to steam generator No fuel burning or furnace burning is required They provide a secondary steam circuit which avoids any possible contamination of primary steam circuit. Can be used in ………….. with a main boiler to produce low pressure steam No separate boiler is required to producing low pressure steam Heat recovery system It uses exhaust gas from diesel main propulsion engines to generate steam Exhaust gas heat exchanger and exhaust boils are the main parts Improved plant efficiency
For slow speed engine, large quantity of steam can be produced if power is increased, by heat recovery system. In some cases this sufficient to provide ships entire electrical power and other heating purpose. 5. Composite boiler: It is a boiler arrangement which permits steam generation either by a furnace when necessary or by using engine exhaust gas (Heat-recovery system) when ship is at sea 6. 7. Separate tube banks for engine exhaust system and oil firing or furnace system It is similar to a Cochran smoke tube boiler Purpose of an Air ejector in a stem plant is to Avoid corrosion problems in boiler due to air entrapment To draws out vapaour particles, dissolved gases and air released from condensing steam from the condenser To increase thermal efficiency of steam plant by leaving the excess steam pressure by book pressure To avoid back pressure in condenser by removing garcons matter Vaccum is maintained in a condenser because for maximum efficiency of the turbine the pressure developed should be maximum. As the condenser is placed after the turbine, if …….. provide a vaccum on the condenser i.e. on the exhaust of the turbine, maximum pressure drop will occur. So we can make use of the maximum useful work from the ………… It also helps in avoiding any backpressure for the turbine outlet. Boiler mountings: 9. Safety valve Main steam stop valve Auxiliary steam stop valve Water level gauges Pressure gauges Air release cock Sampling connection Blow down valve Alarms Purpose of boiler water treatment is to remove salt and imparities To avoid local overheating and failure of tubes due to scale formation To avoid scale formation inside the boiler surface which leads to corrosion To avoid reduction in heat due to dissolved salts To remove dissolved ………………. And carbon dioxide which causes corrosion in boiler
8.
10.
To avoid foaming on surface due to suspended particles, oils etc. Difference between 4-stroke and 2-stroke engines 4 stroke engine 2 stroke engine one power stroke in each revolution, so max. power Engine completes four operations in one revolution values are replaced by ports less maintenance less fuel efficient difficult construction
1. One power stroke in two revolution 2. Engine completes four operation in Two revolution (section, compression, Power exhaust stroke) 3. Valves are used for intake and exhaust 4. Maintenance is maximum 5. Good fuel efficiency 6. Easy construction 11. Parts of marine diesel engines: Cylinder Piston Piston rod Cylinder lining Intake, exhaust valves or ports Cylinder head A frame Cross pin Cross head Crank shaft Valve timing arrng. Lubricating system Cooling system 12.
Difference between Trunk type and cross head type engine Trunk type Cross head type
a. Automobile Engines b. High speed, short stroke
a. b.
Marine Engines low speed, long stroke
c. Small type d. Piston is connected to Connecting rod directly e. No guide shoes or cross Head pin f. Cooling and lubrication is easy 13.
c. d. e. f.
large type piston is connected to piston rod which is then connected to cross head pin guide shoes guide the long stroke on a steady manner cooling and lubrication is difficult
Advantages of oil cooled pistons over water cooled piston is that the small oil can also be used for lubrication of part of engine crank case Piston rings seals the combustion chamber of an IC engine by The outward pressure due to ………… in the compressed ring initially The outward pressure is then increased by the gas pressure which acts on the back of the ring. This pressure will be higher in top rings than the lower ones Symmetrical valve timing If the valve timing is similar for both forward and astern working of a marine engine, it is called as symmetrical valve timing.
14.
15.
16.
Cam shaft is driven in a marine diesel engine by Gear wheel system & Roller chain system
17.
High TBN oil is used in cylinder lubrication because _ TBN (Total base Number) represents the alkalinity of lubricating oil The sulphur content in the fuel mix with water during combustion gives formation to sulphuric acid (H2SO4), which increases the corrosion rate. To nitrides this effect a high alkaling TBN oil is used. Rotocap in an exhaust valve is friction disc or rachet provided on bottom of compression ring in an exhaust valve system which mechanically rotates the exhaust valve during exhaust stroke. This is done to get a uniform heating and wear around the exhaust valve and valve seating.
18.
19.
Under cooling : of charged air means cooling of air to a temperature below its …… point at that pressure. Undercooling causes excessive condensation. It will reduce the intake temperature to a very low value with reduced efficiency. This will also cause thermal shock when it comes into contact with hot siners and piston. Types of Turbo charging system 1. Pulse system 2. Constant pressure system
20.
21. 22.
purpose of Turbo charging : is to increase the power output and efficiency with small increase in size, weight and initial cost. Mass of air per cyde can be increased and so quantity of fuel injected can be raised to give corresponding increase in engine output and increase in thermal efficiency Reduced pollution because of perfect combustion Acts as a recovery system because the turbine receives energy from the exhaust gas Scavenging It is the process of removal of exhaust gas from engine cylinder after combustion and replacing the exhaust gas by fresh gas for further cycles of operation.
23.
Methods of Scavenging In four smoke engines scavenging is carried out mainly by purposing action of piston during its two strokes ie. piston expects exhaust gas on its upward stroke and draws in air on subsequent downward stroke. In two strok engines there are three basic methods of scavenging a. Loop scavenging: in which air passes over the piston crown and rises to form a loop within the cylinder, expelling gas through exhaust ports cut in the same side of liner above scavenging ports. b. Cross scavenging: in which air is directed upwards passing under the cylinder cover and down the opposite side, expelling gas through exhaust ports on that side c. Uniflow or through scavenging: in which air passes straight upwards through the length of cylinder, forcing the exhaust through ports or values at the top of cylinder Purpose of tie bolt or stay bolt is To pre stress the structure Maintain the cylinder block and frames in compression
24.
25.
To transmit main gas loads during combustion from cylinder cover to bed plate For easy dispatch and assembly of engines For fixing of the engine in correct piston Cam shaft is driven from crankshaft using a train of gear arranged in piston known as gear wheel system or driven from crank shaft with a roller chain known as roller chain system. Reversing of marine diesel engine is done by
26. 27.
Cutting off fuel supply to engine …….. the air distributor, such that compressed air to the appropriate cylinders in correct order. This is done by alternating the position of distributor cam Fuel pump timing must be readjusted by using a camshaft in axial direction. Indicated power of a marine diesel engine can be measured from the indicator diagram In the indicator diagram the path of process during a cycle encloses an area which represents the work done Different test of diesel propelling machinery during sea trial
28. 29. -
Guarantee speed test Overload test Astern test Minimum revolution test Starting test Capacity of air bottle Air can be stored at a pressure of 30 bar Capacity should be least sufficient for engine starting without recharging should be 12 starts for revisable 6 starts for non revisable Types of pumps for marine applications
30.
1. Centrifugal pumps single stage multi stage 2. positive displacement pumps screw pumps gear pumps Reciprocating pumps
3. Axial flour pumps 31.
lobe pumps diaphragm pumps
purpose of wear ring in a centrifugal pump Salt and sand in seawater causes high rate of wear in the casing in sea water ……………pump. If casing is provided with a wear ring, then it can be replaced after erosion, barides replacing the whole casing.
32.
Functions of volute casing in a centrifugal pump In volute casing as the cross sectional area is gradually increasing, so as the water passes through the valute casing, the high velocity of water imparted by the impeller reduces and by bernollis theorem, the pressure head is increased.
33.
Printing of a pump: Filling of section line and casing of pump with liquid that have to be pumped is called priming. It is necessary to develop enough section pressure at the eye of impeller.
34.
Centrifugal pump is started with delivery value closed to make the starting torgue minimum, at the time of starting water will be upto impeller. A drain connection is fixed to ensure water inside impeller. Wear rate of bearing and shaft will be high in a centrifugal pump dealing with sea water. Since the shaft is continuously rotating the wear leads to replace of the entire shaft. To avoid this shaft is fitted with a renewable sleeve, so that sleeve only has to replace. Pressure relief valve is fitted in a positive displacement pump because there is no reverse flour in this type of pumps. Here water is displaced from one side to another so if there is any problems with delivery side the pressure inside the pump and pipe system increases which courses damages. To avoid this pressure relief valve is fitted. Different types of positive displacement pumps 1. 2. 3. 4. 5. Screw pump Lobe pump Gear pump Reciprocating pump Diaphragm pump
35.
36.
37.
38.
Reciprocating pumps is used for pumping engine room bilges
-
Engine room bilge contains leaked water and oil It a rotary pump is used, it will cause rotating of the bilge which causes mixing of oil and water to form fine particles This will results difficulting in the separation in an oily water separator, because gravity separation is done in an oily water separator So we …… reciprocating pumps because it displaces the bilge from the engine room without mixing (thoroughly), to the oily water separator and from there it is casting separated by gravity For positive displacement pump slip is the difference between theoretical discharge and actual discharge Fluid flour in a Gear pump
39. 40.
During the flour through a gear pump there will be no movement of flour through the center i.e. through the piston where gear mesh occurs The flour is only through between the tooth spacing and gear casing in one direction. The liquid entrapped between the tooth and casing ensures the flow through the pump. 41. Different types of valves used on board ship Sleeve packed cracks, Globe valve, Butterfly valve, Non return vale, Flap sheck valve, Relief vale, Quick closing valve, Gate vale. 42. We cannot use the gate valve in a partially opened condition because it damages the rubber seal. Here the spindle does not moves up and down only the valve moves up and down, so it is to be fully opened or fully closed. SDNR valve (Screw down non return valve) is used in bilge line as a safety measure to prevent water flowing back and flooding the various compartments. Here the flour is only allowed in one direction only. Purpose of quick closing valve is to cut off the fuel supply by operating from a remote place in case of any fire in the engine room It is used at outlet from Fuel oil storage tank Fuel oil setting tank
43.
44.
Fuel oil service tank Lube oil storage tank Lube oil setting tank Lube oil service tank etc. 45. The steam trap is fitted after steam coil is to prevent steam from escaping and providing the maximum usage, by allowing condensate to pass through Types of Heat exchanger used on board 47. shell and tube type heat exchanger plate type heat exchanger
46.
Advantages of plate type heat exchangers less space is required low maintenance cost highly resistant to corrosion because it is made of titanium plates since there core no tubes, failure due to clogging of tubes can be avoided
48.
Corrosion is prevented in shell type heat exchanges by using sufficient anodes on the body. The anode is sacrificial soft iron. Another method is to introduce iron in the form at Ferrous sulphate fed into the sea water.
49.
Materials of shell and tube heat exchangers Shell – cast iron Tube – aluminum brass Plate - Naval brass
50.
Inert gas system on oil tankers Crude oil is so volatile and it leave hydro carbon vapour while pumping out or unloading the cargo from tankers. These hydro carbon vapors are ……… dangerous. So this is to be removed. For this Inert gas is pumped into the cargo tanks, which prevents the hydrocarbon vapours for catching fire. The main purpose of Inert gas system - to provide an inert atmosphere after oil discharge - to prevent corrosion in tanks - to assist in cargo discharge by applying positive pressure on oil surface
51. 52.
Deck seal prevents the flour back of Hydro carbon vapours from the cargo tanks to the engine room is an Inert gas system. PV valve prevents the pressure inside the tanks to go above a set value and also below a set valve PV breaker also do the same PV valve automatically resets where as PV breaker has to be resetted manually PV valves are provided to prevent bursting and buckling of plates maximum oxygen content permitted in inert gas is between 3-5% of oxygen. Air is supplied to sewage treatment plant because oxygen in the air promotes multiplication of bacteria and satisfactory decomposition of waste. This type of decomposition is called Aerebic-decomposition Maximum oil coatent permitted in water pumped overboard is less than 12PPM Items recorded in oil record book 1. Bunkering 2. Record of pumping out of bilge 3. Sludge/oil disposal and transfer
53. 54.
55. 56.
57.
Application of Ejectors on board ship for complete tank cleaning operations to remove residue and small quantities of water and materials not removed by pumps in fresh water generators air ejectors are used to boil water around 60 0C by creating absolute vaccum in fresh water generator brine is removed by brine ejector.
58.
Purifier removes water and suspended particles from fuel oil and Lube oil Clarifier removes the remaining suspended particles from fuel oil and lube oil coming from the purifier.
59. 60.
Heating is required in fuel oil storage tank for easy pumping of fuel oil to setting tank. For this fuel is storage tank is maintained at 500C Purpose of setting tank Fuel from storage tank is transferred to settling tank where it is heated to about 70-800 C to allow water and sludge to settle down by gravity and can be drained off.
61.
Booster pump or circulating pump draws oil from the primary discharge which is maintained at 4 bar, raising its pressure to about 10-12 bar and delivering it through the heater, viscosity regulator and fine fitter to main engine fuel pumps. MDO line is connected to HFO line to allow flushing with light oil before stopping the engine for long periods or for maintenance. This is because the maintenance is mainly done is boilers and steam trocer tube. At this time we make use of a change over sine the boiler cannot be worked For starting and stopping of engine. Two lube oil system for main engine are One for lubrication of engine cylinder, pistons and piston rings. It is called cylindrical lubrication system Other is a circulating system where oil is used over again and again to lubricate main bearing cross heads bearings, cross heads, stippers, crude and thrust bearing. This is called crank case lube oil system.
62.
63.
64.
Properties of Lube oil correct alkanity and viscocity rust and oxidation intribitiors high viscocity index Detergent and Dispersent propetties water repellants resist foaming an emulsifixation
65.
The main ……………. Of the distributor in a starting air system is to supply the high pressure air to engine cylinders, in which the piston is at TDC (Top dead center) another function is to reverse the sequence of operation during reversing the engine. Flame trap or flame arrester’s function is to prevent the fire entering into the manifold and then to the starting system. Flame trops are fitted to each cylinders connection from the manifold. Starting air valve leaking is found by feeling the temperature of the pipe Fusible plug: It is a non resettable safety valve which is used to ensure safety of boiler. The fusible plug forces at main temp of 1500 0C. If the water level decreases in boiler, the steam will come into direct contact with plug and plug burns out and steam escapes. Inter cooler is to increase the efficiency of the compressor system antis used between ……… pressure and high pressure compressed.
66.
67. 68.
69.
70.
Hydrosphere tank is a pressure tank which is partially filled compressed air above the water surface gives a pressure head to the water causing it to the most remote and highest outlet point of system. The prime movers used for bow thruster are - Auxiliary engine - Electric motor - Hydraulic motor
71.
72.
GPS – Global positioning system It is an US based radio navigation system which proves location and time . It has three parts - satellites orbiting the earth - control and monitoring stations on earth - GPS receivers GPS satellites broad casts the signals from space that are packed up GPS receivers and provides three dimensional locations - latitude - longitude - altitude
