Unit 2 Pipe Fittings

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UNITS IN THIS COURSE   g   n    i    t    t    i    f   e   p    i    P     g    2   n  .    i    t    i   o    N    f    t    i   e   n   p    i    U    P      2  .   o    N    t    i   n    U

UNIT 1

PIPING SYSTEMS

UNIT 2

PIPE FITTINGS

UNIT 3

VALVES

TABLE OF CONTENTS Para

Page

2.0

COURSE OBJECTIVE

3

2.1

PIPE FITTINGS

4

2.2

FLANGES

8

2.3

GASKETS

10

2.4 2.5

BLINDS FILTERS

14 18

2.6

STRAINERS

25

2.7

STEAM TRAPS

29

2.8

TYPES OF STEAM TRAPS

31

  g 2.0 COURSE OBJECTIVE   n    i    t    t    i    f This course introduces the students to all major items of static equipment relating to   e a pl plan antt si site te.. Upon Upon comp comple leti tion on of the the cour course se th the e train trainee ees s wi will ll have have a gene genera rall   p    i    P understanding of the following.      2  . • Equipment Terminology T erminology..   o    N    t    i   s Theory of operation. •   n   m    U   e    t • Equipment construction.   s   y   s   g Hands on operation. •   n    i   p   s    i • safety features.   m    P   e   :    t   s    7 Equipment interaction with the overall process. •   y  .   s   o    N   g PIPE FITTINGS   n   e 2.1    i    l   p   u    i Pipe fittings are classed according to the way they are joined to section of pipe. The    d    P   g   o   n   :    i    t    M three main types of pipe fittings are:    t    7    i    f  .   o   e    N   p    i   e    P    l     u Page 1/37    d    2   o  .   o    M

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* Screwed.



Flanged.



Welded.

Screwed or flanged fittings must be used if  the pipe has to be opened up or taken apart for cleaning, inspection or maintenance. The advantages and disadvantages of each are as follows: Screwed Fittings (Advantages) •

Simple design.



Quick to install or remove.



Easy to open for cleaning or maintenance.



Cheaper to install.



Easy to repair / or replace.

Screwed Fittings (Disadvantages) (Disadvantages) •

More leak problems.



More chance of corrosion at the threads.



Threads make pipework weaker.

Flanged Fittings (Advantages) •

Strong.



Quick to open for cleaning and for repair.



Low corrosion possibility.

Flanged Fittings (Disadvantages) (Disadvantages)

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More possibility of leaks occurring.



Prone to leaks if gaskets are not installed correctly.



Expensive to buy and install.



Heavy.



Difficult to insulate.

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Figure 2-1 Pipe Fittings

Figure 2-1 shows the most commonly used pipe fittings in a plant piping system. Table 1 explains what these fittings are used for.

NAME

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DESCRIPTION DESCRIPTI ON AND USE

Coupling

This is a female fitting. Joins piping in a straight line.

Union.

This is a female fitting which can be taken apart

El Elbo bow w (45 (45ºº or or 900 900ºº ang angle le). ).

Chan ange ges s the the direct rectiion of th the e pip pipin ing g by by 4 45º 5º or 90º 90º

Bushing.

Different size Internal and external thread. Joins a large pipe to a smaller pipe

Tee (T) joint. Joins two or more branches together  Y joint .

Joins two or more branches together  

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Cross ( +) joint.

Joins three or Four branches together  

Plug

A solid threaded male fitting. It screws into another   fitting to plug an opening.

Cap

An internally threaded female fitting. It screws onto the pipe to seal the end.

Nipple

This is a male fitting. A short section of threaded pipe. It often Joins two fittings

Reducers.

Female fitting which reduce the size of the pipe. Most of the above fittings can be used as reducers

Table 1 Types of Fittings and Their Uses

Welded Joints

Figure 2-2 Welded Pipe Joints

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Figure 2-3 Screw, Flange and Welded Fittings

 All fittings fit tings can be screwed, flanged or welded (See Figure 2-2 and 2-3). A properly welded joint is as strong as the pipe itself. A welded system does not leak and needs no maintenance. This is important on high pressure systems. The joints are much smoother on a welded system so insulating this type of system is easier.

For all permanent installations welding is used to join the sections of pipe and / or  the pipe fittings. Welded joints may be Butt-welded, Fillet welded or Sleeve-welded. Butt welding is the most common type of welded joint. Figure 2-2 shows some ty typi pica call weld welded ed pipe pipe join joints ts.. ButtButt-we weld lded ed join joints ts prev preven entt leak leaks s and and give give fewer  fewer  corrosion problems. The advantages of welded joints are:

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Very Strong.



Leakproof.



Maintenance free.



Smooth / small joints



Easy to insulate.

The disadvantage of welded joints is that they cannot be taken apart easily.

FLANGES

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Flanges are connecting devices on vesse Flanges vessels, ls, tank equipment equipment and piping piping which which give quick and easy connections and leakproof seals.  A flange has a contact surface which can be joined to another flange. Flanges have holes around the edge so they can be bolted together.   g   n    i    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

Flanges are attached to piping in different ways. They can be screwed or welded. Welding is the strongest and most permanent. Figure 2-4 Shows different flange surfaces Flat Face (Plain)

For low pressures and temperatures.

Raised Faced (Serrated)

For high pressures and temperatures.

Ring Joint (Grooved)

For high pressures and temperatures.

Tongue and Groove

For high pressures and higher temperatures.

Flanges Flange s can be over over 48" in diame diameter. ter. They are made of dif differe ferent nt materi material als s for  different purposes. They are rated according to the pressure they must hold. They are stamped with this rating.

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Figure 2-4 Different Types of Flange Faces

Rating 150 300 600

Low Pressure Intermediate Pressure High Pressure

to to to

Rating 260 PSIG up to 200° C 300 675 PSIG up to 200° C 700 1350 PSIG up to 200° C 1300 Page 6/37

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900 1500 2500

Very High Pressure Very Very High Pressure Maximum Pressure

to to to

2000 PSIG up to 200° C 2000 3375 PSIG up to 200° C 3000 5625 PSIG up to 200° C 5600

 As the operating temperature increases, the allowed operating pressure of the flange decreases. For example a 150 flange at 200 °  C operating temperature is rated for 260 psig.   g   n    i    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

Higher flange ratings use more connecting bolts. The higher the flange rating the more connecting bolts / studs are used. The whole area of a flat face flange is joined to the opposite flange. Only a small inner part of a raised face flange is joined to the opposite opposite flange face. The outer flange edges do not come in contact with each other.  A ring joint has a ring on one face that fits into a circular groove machined on the opposite flange face.

Figure 2-5 Blind Flange Bl Blin ind d fl flan ange ges s are are used used to cl clos ose e off the the ends ends of pipi piping ng,, valv valves es and and equi equipm pmen entt openings. open ings. (See Figure 2-5) The flange bolts pass through the blind blind flange and the mounted flange. After a gasket has been installed the bolts are tightened to the normal operating specification to make a leakproof seal.

2.3 GASKETS Gaskets are a thin plates which fit between the faces of two flanges. They are especially important when joining two flat metal faces. It is hard to machine two metal met al faces faces so that that the they y fit togethe togetherr withou withoutt leakin leaking. g. Therma Thermall expans expansion ion and pressure causes the metal to lose its shape. The gaskets prevent leaks by filling in the small gaps between the metal surfaces.    s   m   e    t   s   y   s   g   n    i   p    i    P   :    7  .   o    N   e    l   u    d   o

Many different types of gaskets are used in the plants. Gaskets are made from dif differe ferent nt materi material als. s. The materi material al that that is used used must must resist resist the temper temperatu ature re and chemic che mical al action action of the fluid in the pipe. pipe. Gasket Gasket materi material als s may be metall metallic ic or  non-metallic.. Some non-metallic gasket material is bought in sheet form and cut to size. Many gaskets for special applications are already cut to size. Table 2 shows some different gasket materials and the different fluids they are used with.

FLUID

GASKET MATERIAL Page 7/37

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Water

Rubber. Asbestos.

Cold Oil

Cor, Neoprene

Hot Oil.

Asbestos. Ingot Iron

Gas (Low Temperature).

Rubber  

Gas (High Temperature)

Asbestos.

 Acids.

Sheet Lead / Steel.  Table 2 Gasket Materials and Applications

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Metallic Gaskets Flat metallic gaskets are made of lead, copper, iron, steel, aluminium and monel. Flat metallic gaskets are a simple and cheaper method of sealing . They are strong en enou ough gh for high high temp temper eratu ature re and and pres pressu sure re cond condit itio ions ns.. They They can can be used used for  pressures up to approximately 500 psig. Tightening the bolts around the flanges forces the gasket material into the small spaces in the flange faces to form a leakproof seal. Gaskets are made in different shapes and different materials to suit any process. The following are examples of non-metallic gasket materials and applications:

 Asbestos Rubber / Neoprene Cork Viton Teflon

High temperature / pressures. Low temperature / pressures. Low temperature / pressures. High / low temperatures / high pressures High temperatures / pressures

The following are examples of metallic gasket materials and their applications: Stainless steel. colonel  Aluminium Lead Tin

High temperature / pressures. High temperature / pressures. High temperature / pressures Low temperature / pressures. Low temperature / pressures.

Figure 2-6 shows the most common types of metallic gaskets available for use in the process plant.

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Figure 2-6 Metallic Gaskets

Spiral Wound Gaskets Spiral wound gaskets are made of metallic strips in a special V shape. They are put together with an asbestos material between the Vs. The V's are compressed between the two metal rings. The asbestos filled V's form a good compressible seal for the flange face.

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They ar They are e us used ed whe here re ex expa pans nsion ion an and d co cont ntrac ractio tion n of th the e me meta tall pa part rts s is common. Most spiral wound gaskets can be used for pressures up to 1200 psig

Ring Joint Gaskets Ring joint gaskets are made of stainless steel, iron, nickel, monel and copper. Ring joint gaskets give a seal like a welded joint. However, they are, better  than a welded joint because they can be taken apart easily. The ring joint Page 9/37

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gasket gask et fits fits int into o a-s a-spe peci cial al groo groove ve ma mach chin ined ed int into o th the e fla flang nge e fa face ce.. .. Th Thes ese e gasket gas kets s are ver very y goo good d for ver very y high press pressures ures and tem temper peratu atures res.. The These se gaskets can be used for pressures up to approximately 5000 psig.

Corrugated Gaskets   g   n    i    t    f   e   p    i    P      2  .   o    N    t    i   n    U

Corrugated gaskets are made of aluminium, copper, steel and monel. These gaskets require very low bolt tightening force for a leakproof seal. These gaskets are limited to approximately 300 psig.

Jacketed Gaskets Jacketed gasket Jacketed gaskets s are made of a soft non-metal non-metallic lic filler mate material rial covered by a meta me talli llic c ca case se.. Th The e filler filler ma mate teria riall is us usua ually lly as asbe best stos os or ru rubb bber. er. Th Thes ese e gask ga sket ets s are are us used ed wh wher ere e me meta tall llic ic pa part rts s ex expa pand nd an and d co cont ntra ract ct du due e to temperature changes. They can be used for pressures up to approximately 1200 psig.

Flat Metallic Gaskets Flat metallic gaskets are made of lead, copper, iron, steel aluminium and monel. Flat metallic gaskets are a simple and cheaper method of sealing . They have a good mechanical strength for high temperature and pressure conditions. They can-be used for pressures up to approximately 500 psig. Gaskets are used when joining the following: Flanges. Manways Manway s to vessels. inspection ports / hand holes to vessels. Heat exchanger parts. e.g., tube bundles , bell ends and end plates. Pump /turbine cases.  Any metal to metal face joint that requires a leakproof seal. Gaskets must be able to handle the following:

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Various fluids. High and low temperatures. High and low pressures. Thermal expansion. Vibration / compression forces.  Always be sure to use the correct gasket for the process application. The gasket must be the correct: Right Size. Right Shape. Right Material. Right Thickness. Installed correctly.

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Metallic gaskets are used for high temperature and high pressure applications. The fol follo lowi wing ng tabl table e li list sts s some some of the the metal metals s used used in gask gaskets ets and and th thei eirr maxi maximu mum m operating temperatures.

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Material Tin Lead Bronze  Aluminium

º c 93 100 260 427

Material Stainless Steel Titanium Silver Monel

ºC 538 538 649 816

Special metallic gaskets are available for temperatures up to 1100 °C. 2.4

BLINDS  A blind is a circular metal plate which is placed between two flanges. It stops the flow of liquids. It is used to isolate a section of piping, usually for maintenance.  After the blind and gaskets have been installed, the flange bolts are tightened to make ma ke a leak leakpr proo ooff se seal al.. The The bolt bolts s are are ti tigh ghte tene ned d to th the e norm normal al oper operat atin ing g specification. The blind fits inside the circle of flange bolts as shown in Figure 2-7

Figure 2-8 Blank Blind Installed Between Flanges   s   m   e    t   s   y   s   g   n    i   p    i    P   :    7  .   o    N   e    l   u    d   o

Sometimes vessels and pipework need to be opened for inspection, cleaning and repair. Before a piece of equipment can be opened it must be totally isolated from the process. Blinds are used to isolate the equipment. Blinds are circular metal plates installed between two flanges or at the end of a pipe to stop any fluid from passing a certain point. They are installed with a gasket on each side to ensure no fluids can leak past and cause a safety hazard for the maintenance workers.

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 As an operator you must be able to isolate correctly any piece of equipment or unit in your section of the plant to ensure the safety of all workers. When isolating a piece of equipment or pipework the following must be performed. Depressurise and purge all lines with an inert gas (usually nitrogen) before opening any line or piece of equipment.   g   n    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

Blind all lines-to and from the equipment. Make a blind list to ensure that all blinds are installed correctly and removed when the work is complete. Use the correct type and size of blind. Purge all the air from the lines using an inert gas (usually nitrogen) before starting the equipment or process.

Blinds are made in three different types: See Figure 2-9

Figure 2-9 Blinds. Blinds.

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Blank Blind two flanges.

Temporary installation only. Installed between

Spectacle Blind It is easier to open and close.

Permanent installation between two flanges.

Blind Flange vessel nozzle to stop fluid flow.

Permanently installed at the end of a pipe or  

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Figure 2-10 Typical Blinding of a Vessel Process Line

Blind in Oper. Initials

Blind Out Oper Initials

Feed Inlet (1) Feed Inlet (2) Reboiler Outlet Reboiler Inlet   s   m   e    t   s   s   y   s   m   e   g    t   n   s    i   y   p   s    i    P   g   :   n    i    7   p    i    P   o  .   :    N    7   e    l  .   u   o    d    N   o   e    l    M   u    d   o

Vapour Inlet Product Inlet Table 3 Blind List for the Vessel in Figure 2-10.

Table 3 is a blind list for the vessel in Figure 2-10 Before you sign the blinds in, as an operator you must: Check to make sure the blind is in the correct position. Page 13/37

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Check that there is a gasket installed on each side of the b Check to make sure the nuts and bolts on the flange are tight

Before you sign the blinds out, as an operator you must:   g   n    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

Ensure all the work on the equipment is complete. Check that the inside of the vessel is clean and free from t Check that all the blinds have been removed. 1.

Check that new gaskets have been installed between the

.

Check that all flanges are aligned. Check that all nuts and bolts have been tightened to the cc specification.

 YOU MUST ALWAYS ALWAYS REMEMBER REMEMBER THAT BLINDS ENSURE THE SAFETY OF EVERY PERSON WORKING IN OR ON A PIECE 0F EQUIPMENT. YOU MUST ENSURE THAT THEY ARE INSTALL CORRECTLY AND HAVE BEEN REMOVED WHEN THE WORK COMPLETE. 2.5

FILTERS The most common types of filter are: Edge Type Filter. Sock Type Filter. Cartridge Type Filter. Mixed Bed Filters.  A filter is a device used to remove unwanted substances from the process fluids and from a system within the process e.g., amine, glycol, air. To do this the fluid is passed through a material which allows the fluid to pass but catches any solid contaminant. The filter material is usually cloth, paper or wire mesh. The thickness and porosity of the surface of the material is very important. It determines both the amount of fluid which can be handled by the filter and the size of the contaminant which will be filtered out.

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Filters do the following: They prevent abrasive material entering pumps and turbines. They reduce pipe wear due to erosion. They keep valves clean so they can operate freely. They keep process fluids pure so that treating chemicals operate properly. They keep towers and vessels clean.

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They keep heat exchangers and reboilers free of dirt. They keep contaminants out of the sales products.

Filters also maintain good / correct instrumentation operation   g   n    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

They keep contaminants from blocking air lines to and from control valves. They keep contaminants from blocking or damaging small instrument orifices. They keep contaminants from blocking gauge glasses or level control column legs.

 All filters are made up of two main parts: The housing (the outside case) which contains the fluid and the filter internals. The filter element or elements. through which the fluids pass. This is the part that traps the contaminants.

Some filters can be removed and cleaned when they become contaminated. Most filters have replaceable elements. These elements are specially designed to fit the particular parti cular filter. When the element becomes contaminated contaminated it is changed. The used element is thrown away. Most filters cause the fluid flowing through them to make a sharp turn. The larger  particles to be removed are too heavy to make the sharp turn. These drop to the bottom of the filter. Other particles are trapped in the filter element.

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Figure 2-11 Edge Type Filter 

 A filter in which the element is not changed is shown in Figure 6-24.

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This is called an edge type filter. It is used to remove impurities from an oil line. This filter is also called a full flow filter. That means all the oil flows through the filter. The filter has a metal case with a large number of thin metal plates inside. The plates are arranged on top of each other. The plates have small bumps on the surface. Every second plate is connected to a shaft which can be rotated. The fluid flows down, across and between the plates.. Any particles or contaminants are trapped between the plates and the small bumps.

To clean the filter the shaft is turned manually. This turns 50% of the plates so the contaminants drop to the bottom of the case. These contaminants collect in the bottom of the filter (the sump). These contaminants can be drained off by removing the drain plug when necessary.

Figure 2-12 Paper Filter / Cartridge Filter 

In cartridge type filters either the filter element or the whole filter are replaceable. The can be int place or sit contaminated is threaded d soit itiscan benscrewed screw onto the filter housing body. When body. thebolted element elemen becomes become contaminate thrown throw awayed and a new element is installed.

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The cartri cartridge dge type type filter filter has a lar large ge metal metal housin housing. g. The cartri cartridge dge elemen elements ts are ridged ridg ed cardboard cardboard or metal. metal. They have cloth or paper type material material inside. They are strong and will not break under high differential pressure. These filters are used in process fluid systems.

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Sock Type Filter 

Figure 2-13 Sock Type Filter  These fil These filter ters s have have a large large metal metal housin housing. g. They They have have sock sock type type filt filter er ele elemen ments. ts. These are long circular tubes of cotton or cloth material through which the fluid passes. The particles / contaminants are trapped in the fibres of the materials. These filters are very good for handling large quantities of particles / contaminants. They are used for low differential pressures. This type of filter will break under high pressure. When the filter elements become blocked they are thrown away and replaced. This type of filter is used in Amine systems.   s   m   e    t   s   y   s   g   n    i   p    i    P   :    7  .   o    N   e    l   u    d   o

Mixed Bed Filters

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Figure 2-14 Example of a Mixed Bed Filter 

These fil These filter ters s have have a large large ci circu rcular lar metal housin housing. g. They They are filled filled with with layer layers s of  different materials. e.g., gravel, sand and anthracite. The particles / contaminants are trapped between the grains of gravel, sand and anthracite. The filter is cleaned when hen th the e fl flui uid d fl flow ow is re reve vers rsed ed,, The The reve revers rsed ed fl flow ow fo forc rces es th the e part partic icle les s / contaminants out to drain. This type of filter is used for water purification. Filters must be cleaned and replaced regularly.  A blocked / plugged filter restricts the fluid flow in a line and this must not be allowed to happen.  A defectiv defective e filter  sy system stem may allow contami contaminan nants ts to rem remain ain in the line. line. You You must must not forget to maintain filters.

Precoat Filters

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Figure 2-15 Principle Operation of a Precoat Filter 

Precoat filtration is used to remove very small solid particles, oil particles, and even bacteria from water. This method is only used for small quantities of water which contain small quantities of contaminants. Precoat filtration may be used after the normal clarification processes. It produces water wa ter which which contain contains s very very small small amount amounts s of suspen suspended ded solids solids.. It is used for  specific purposes. For example, precoat filters are often used to remove oil from contaminated steam condensate.   s   m   e    t   s   y   s   g   n    i   p    i    P   :    7  .   o    N   e    l   u    d   o

In precoat filtration, the precoat material can be organic, (contains living cells). This acts as a membrane between the two the fluids. base must prevent the precoat material without restricting flowThe of filtered water. It mustpassage be able of  to operate under high pressure differentials. Filter cloths, porous stone tubes, and wire wound tubes are used as base materials. Page 19/37

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The supporting base material is first precoated with a slurry of precoat material. More slurry (body feed) is usually added during the filter run. When the material removed by the filter has built up there will be a big pressure drop across the filter. Then the filter coating coating is removed removed by backwashing. backwashing. The filter bed is then precoated precoated and returned to service. Chemical coagulants are not usually -needed. However, if  an extra pure effluent is needed, they may be used.   g   n    i    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

MICRON RATING There are a number of different types of filters for different fluids and contaminant problems. All filters are marked with a micron rating. The micron rating tells you the size of the holes in the filter or the size of the particles the filter will trap. A low micron rating means the filter element has small holes. A higher rating means larger holes. The holes in ratings below 40 micron cannot be seen with the naked eye.

2.6

STRAINERS  A strainer is a wire mesh screen. It is used to remove solid particles from a fluid. The fluid may be water, oil, gas, steam or any other fluid carried by a piping system. Strainers are usually installed in front of valves, pumps or regulators for  protection. Particles allowed to flow through a piping system will cause pipe walls and piping piping system system to bec become ome worn. They may also cause cause valves valves,, pumps pumps and regulators to block so they cannot operate properly. The size of the wire mesh used in a strainer will determine the size of the particles which will be removed or blocked by the strainer. The strainers used in piping systems are usually designed to allow free fluid flow through the system with very little pressure loss. Most strainers contain a blow-out or clean-out plug. This allows the strainer to be cleaned. There are various types of strainer:

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Figure 2-16 Circular Strainer  Page 20/37

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Circular Strainers are made of two circular screens separated by a small space. The inner screen has larger holes than the outer screen. The fluid flows from the inside out. These are used upstream of steam traps.

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Figure 2-17 Disc Strainer 

 A Disc Strainers is a round plate or disc with holes in it. It is installed between two flanges. It will hold small volumes of large particles. It is cheap to make and easy to install and remove. It is installed before pumps.

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Figure 2-18 Cone Strainers Cone Strainers are made in the shape of a cone. It can handle a large volume of  particles parti cles / contaminants contaminants.. This type of strainer strainer is difficult to install install and remove. remove. It is mainly' used to protect equipment during the start-up phase of a process.

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Figure 2-19 Cone Strainer Installed between a Flange

Figure 2-20Y-Type Strainer 

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 Y-Type Strainers are usually used in pipelines of three inches or less. The fluid flows through the screen located in the leg. Any sediment is trapped there.

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The screen can be removed and cleaned by opening the leg cover. The leg cover is either threaded or flanged for this particular purpose. These Y-type strainers can be installed in the horizontal or vertical position. However, the leg must always point Downwards.

Figure 2-21 Simplex Basket Strainer  Basket Strainers are generally used in larger piping systems but can sometimes be used in smaller piping systems. This type of filter allows a basket type screen to be inserted or removed through the top of the strainer. It is usually flanged or has a yoke type cover which can be removed quickly. Basket strainers are installed either  as a simplex or duplex. The simplex is used where the line can be shut down long enough eno ugh to all allow ow time time for cleani cleaning ng the basket basket.. The duplex duplex permit permits s contin continuou uous s operation and does not require the system to be shut down for cleaning.   s   m 2.7 STEAM TRAPS   e    t   s   y   s  A steam piping system may contain a small amount of water along with the t he steam.   g This water must be removed from the steam line. Steam is used to operate high   n    i speed turbines and other equipment. Water in a steam line can damage high speed   p Turbines.    i    P   :    7  . Water may also erode valve faces and seals. Impurities in the water can also cause   o    N   e    l   u Page 23/37    d

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erosion and damage. The steam traps main function is to remove condensate (water) from the steam line and to prevent steam from entering the condensate lines.

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 A steam trap is an automatic valve. It is installed in a piping system. It all allows ows the release of water (condensate) and air without releasing steam. There is no drop in line pressure when a steam trap operates. Steam traps are installed in lines if the condensate must be drained off as quickly as it collects. They allow the condensate to be recovered for heating, for hot water or for return to the boilers. They are used in steam piping, separators and all steam heated or steam operated equipment. Water Hammer  If water is allowed to remain in a steam line it can cause problems such as water hammer, erosion, corrosion and loss of efficiency. Water hammer is a series of  shocks produced by a sudden change in the speed of the water flowing flowing in a pipeline. This sudden change in the speed of  the water may be caused by a valve opening or closing very quickly. It can also be caused by very fast condensation of  a pocket of steam within the pipe. If a pump stops suddenly because of a power failure this can cause water  hammer. This happens because the water in the pump discharge line will stop and reverse its directio direction n of flow. The rapid closing of the check valve at the pump will cause water hammer. Water ham hammer mer will also happen if steam goes into a pipe that contains some water or condensate. As the steam passes over the water it condenses. This-rapid condensation causes a vacuum to form in the pocket. the water  rushing into this vacuum will produce water hammer. This can cause damage to the pipework and fittings. Erosion can occur when water enters high speed turbine blades. This causes erosion damage (rapid wear) to the turbine blades. Corrosion can occur when water lays in low sections of pipework and turbine casings.

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Loss of efficiency will occur when water enters reboilers and heat exchangers because it lowers the heat energy that is available. Loss of efficiency will also occu oc curr whe hen n wat ater er en ente ters rs st stea eam m ejec ejecto tors rs as it re redu duce ces s th thei eirr pu pump mpin ing g efficiency. TYPES OF STEAM TRAPS THERMOSTATIC TRAP

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Figure 2-22 Thermostatic Trap

The thermostatic thermostatic steam trap responds -to The Temperature Temperature difference between the steam and the condensate. Both steam and condensate may enter the trap. When steam enters -.he trap the fluid inside the bellows expands and evaporates. This expands the bellows and closes the valve. (See Figure 2-22) When the fluid in the trap cools and condenses to water the fluid in the bellows condenses This makes the bellows contract. This opens the outlet valve and the condensate escapes into the condensate line. When hot steam re-enters the trap it again expands the bellows and closes the valve.

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Figure 2-23 Float Thermostatic Trap

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FLOAT THERMOSTATIC TRAP When hot steam enters the trap inlet it cannot move the float. So, the trap remains closed. When the steam condenses to water, the water will cause the float to rise. This will open the outlet and allow the condensate to leave the trap and enter the condensate line.   g   n    i    t    i    f   e   p    i    P      2  .   o    N    t    i   n    U

INVERTED BUCKET TRAP

Figure 2-24 Inverted Bucket Trap

When there is only steam in the trap, the steam pressure will hold the bucket up and keep the outlet valve closed. When the bucket fills with condensate the bucket will sink to the bottom of the trap and open the outlet valve. This allows the condensate to leave the trap.

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Figure 2-25 Open Bucket Trap

THERMODYNAMIC TRAP

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Figure 2-26 Thermodynamic Trap

Thermodynamic traps use the heat energy in steam or in hot condensate to open and close the trap. When cool condensate or air enter the trap they flow upward through the inlet orifice. They tilt the disc upward to pass through a hole in the seat plate. They then flow through the discharge ports to the trap outlet. If steam enters the trap it flows at high speed under the disc. This causes pressure to build up in the chamber above the disc. The bu The buil ild-u d-up p of pres pressu sure re for force ces s the disc disc down down whic which h cl clos oses es the trap trap.. If hot hot condensate enters the trap it will flash into steam as it leaves the inlet orifice. This flash steam will also flow at high speed under the disc. This causes a reduction in pressure press ure and flash steam above the disc will again again force the trap to close. close. The trap stays closed until the steam above the disc condenses.

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Figure 2-27 Trap operation Method of checking steam trap operation Listen to it:  A properly working steam trap will be silent except when it opens to allow the condensate to pass out. Check upstream and downstream drains: Upstream should be straight steam. Downstream only hot water.

Check upstream and downstream pressure gauges: Upstream should have steam header pressure (250 psig). Downstream should have condensate pressure only (35 psig).

Check temperature before and after the steam trap (Wearing gloves) Upstream side should be hotter  Where are steam traps installed: Bottom of large steam headers.   s   m   e    t   s   y   s   g   n    i   p    i    P   :    7  .   o    N   e    l   u    d

End of steam headers. Before steam turbines. Bottom of steam turbine cases. Outlet of steam turbines.

Before reboilers.

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On all steam lines.

 

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Figure 2-28 Typical Steam Syste System m

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Steam Separators   g   n    i    t    t    i    f   e   p    i    P      2   o  .    N    t    i   n    U

Figure 2-29 Typical Steam Separators

Steam separa Steam separators tors,, (somet (sometim imes es called called steam steam purifi purifiers ers)) are device devices s which which purify purify steam. When they are installed in the steam line they will remove moisture droplets and other suspended impurities in the steam. To do this, the separator causes the steam to suddenly change its direction of flow it causes the steam to start circulating quickly. Both of these actions cause the moisture and other particles to be thrown out of the flow of steam. The moisture particles collect at the bottom and pass out through a drain.

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