APPLICATION OF ERROR ON CALIBRATED TAPES
TYPES OF ERROR
+VE ERROR TAPE 25005 25000 24995
WITH USER WITH QA WITH USER
STD TAPE
- VE ERROR TAPE
ERROR CORRECTION
TYPE OF ERROR
+ VE -- VE
OPERATION
MARKING
(ADD ERROR)
MEASURING
(SUBTRACT ERROR)
X + (+Y) X + (--Y)
X -- (+Y) X -- (--Y)
NOTE :1. USE CALIBRATED TAPES ONLY
2. DO NOT USE TAPE HAVING ERROR MORE THEN +1 mm FOR CRITICAL JOBS.
PROCEDURE FOR MARKING, CUTTING AND CHECKING OF SHELL PLATES
SHELL PLATE
W
ROLLING DIR.
L TOLERANCE
• L - + 1 mm / M, Max. 3 mm., & • K1 - K2 = + 1 mm / M, • IDENTIFICATION MARKING
3 UNITS
W - + 1 mm / M, Max. 3 mm
Max. + 5 mm TO ROLLING DIRECTION.
• L - NOMINAL CIRCUMFERENCE = MEAN DIA. X
=
3.1415926535897932384626433832792………...
CHECKING AXIAL ALIGNMENT OF SHELLS
PROCEDURE
• LEVEL THE
F
SHELL ORIENTATIONS VERTICALLY / HORIZONTALLY • ARRANGE SHELL ASSEMBLY AS SHOWN IN SKETCH BELOW X 90
E D
180 0
Z1
C B
Z2
270
A
PLUMB BOBS
X PLAN FRONT VIEW
CHECKING AXIAL ALIGNMENT OF SHELLS
MEASURE PERPENDICULAR DISTANCE BETWEEN PLUMB LINE AND HORIZONTAL TWINE & TABULATE READINGS AS SHOWN BELOW. LOCATIONS A B C TWINE TO PLUMB DIST. HALF DIFF ( Z1- Z2 / 2 ) MM Z1 AT 0 Z2 AT 180 OF READING
D
E F • SIMILARLY REPEAT THIS EXERCISE FOR 90 / 270 ROTATING THE SHELL ASSEMBLY. LOCATIONS ENTER DIM. ABCDE & F TWINE TO PLUMB DIST. Z1 AT 90 Z2 AT 270 ORIENTATIONS BY
HALF DIFF ( Z1-Z2 / 2 ) MM OF READING
CHECKING AXIAL ALIGNMENT OF SHELLS •
PLOT THE POINTS ON A GRAPH PAPER WITH SUITABLE SCALE AND FIND OUT THE BEST POSSIBLE CENTRE. THE RADIAL DISTANCE FROM THIS LINE IS “OUT OF ALIGNMENT”
• FIND OUT MAX. OUT OF ALIGNMENT IN BOTH THE PLANES & NOTE AS ( A ) 0 - 180 DEG. = ____________ ( B ) 90 - 270 DEG. = ____________
• SUPERIMPOSE BOTH THE GRAPHS IN ORDER TO FIND OUT THE TOTAL “OUT OF ALIGNMENT” OF THE ASSEMBLY.
+3 +2 +1 00 -1 A B C D E F
+3 +2 +1 00 -1 -2 0 - 180 DEG. -3 90 - 270 DEG. A B C D E F
-2
-3
CHECKING SURFACE ALIGNMENT OF SHELLS
Y0 Y1 A(END) B X0 X1
DROP THE PLUMBS NEAR EACH CIRC.SEAM AND PUT TWINES HORIZONTALLY ON BOTH SIDE OF SHELLS.
CHECKING SURFACE ALIGNMENT OF SHELLS
3. 4. MAINTAIN SAME DIMENSIONS AT BOTH ENDS OF THE SECTIONS BETWEEN HORIZONTAL TWINES & PLUMB. MEASURE PERPENDICULAR DISTANCE BETWEEN OTHER PLUMBS AND HORIZONTAL TWINES AND RECORD THE READINGS IN THE TABLE BELOW. SIMILARLY ROTATE THE JOB 90 DEGREES AND TAKE DIMENSIONS FOR OTHER TWO ORIENTATIONS AND RECORD THEM. SURFACE ALIGNMENT IS READING.
SEAM NO
0 A ( END ) B C D E ( END ) X0 X1 X2 X3 X4 X5 X6 X0
CHECKING SURFACE ALIGNMENT OF SHELLS SECTION WITH DIFFERENT THICKNESS OF SHELLS
Y1 X1 A(END) Y2 X2
THK T1
B
IN CASES OF X2,X3,X4, ALIGNMENT IS DIFFERENCE OF THAT W.R.T X1 IN CASES OF X5,X6,X7, ALIGNMENT IS DIFFERENCE OF THAT W.R.T X8 PLUMB BOBS
Y3
X3
Y4
C
X4
Y5 Y6
X5 X6
THK T2
D
Y7 E(END) Y8
X7
X1 = X8 + ( T2-T1 )
X8
SKETCH - 2
CHECKING SURFACE ALIGNMENT OF SHELLS
SECTION WITH DIFFERENT THICKNESS OF SHELLS
1. THE DIMENSION SETTING AT ENDS ( X0 ) ARE DECIDED TAKING IN TO CONSIDERATION OF SHELL COURSE THICKNESSES ( REFER SKETCH 2 )
FOR REST SAME PROCEDURE IS TO BE ADOPTED.
NOTE: THE SHELL OVALITY / SHAPE SHALL BE CONTROLLED WITHIN THE LIMIT IN ORDER TO GET BETTER ALIGNMENT.
TOLERANCES ON CIRC. OF SHELLS, D‟ENDS , CONES & BELLOWS
• THE REQUIRED CIRCUMFERENCE SHALL BE COMPUTED
BY THE FOLLOWING METHOD.
REQUIRED CIRCUMFERENCE = ( ID + 2T ) * PIE
WHERE,I.D = INSIDE DIA. AS SPECIFIED IN DRAWINGS T = ACTUAL THICKNESS MEASURED AT ENDS
PIE = VALUE OBTAINED FROM CALCULATOR • MEASURE THE ACTUAL CIRCUMFERENCE ON THE JOB. • ONLY CALIBRATED TAPES SHOULD BE USED FOR MEASUREMENT. • COMPARE THESE TWO VALUES OF CIRCUMFERENCE AND CHECK THE ACCEPTABILITY BASED ON BELOW GIVEN TOLERANCE CHART.
TOLERANCE ON CIRCUMFERENCE
TOLERANCE ON CIRCUMFERENCE
COMPONENTS
THICKNESS OF COMPONENTS IN MM
UP TO 8 9 TO 18 (+) 7 (-) 4 19 TO 50 (+) 10 (-) 7 ABOVE 50 (+) 12 (-) 9
REMARKS
ROLLED SHELLS AT L/S SET-UP STAGE
(+) 5 (-) 2
CIRCUM. TO BE CHECKED AT 3 LOCATIONS, 2 ENDS AND AT CENTRE IF COMPONENT IS IN SET-UP STAGE WITHOUT WELDING PER JOINT 3MM SHRINKAGE SHALL BE ADDED TO BASIC CIRCUMFERENCE.
PRESSED / FORMED D’END, CONE & EXPANSION BELLOW AFTER COMPLETING WELD JOINT IF ANY
(+ / - ) 5 (-0 / +10)**
(+ / - ) 8 (-0 / +15)**
(+ / - ) 10 (-0 / + 18)**
(+ / - )15 (-0 / + 25)**
NOTES: • THE ABOVE LIMITS ARE APPLICABLE ONLY IF NO OTHERS STRINGENT TOLERANCE IS SPECIFIED. • ** THIS TOLERANCE IS APPLICABLE ONLY WHEN ABUTTING SHELLS HAS HIGHER THICKNESS WITH OUTSIDE TAPER AND INSIDE FLUSH.
REFERENCE LINE MARKING PROCEDURE
1 OPTICAL METHOD
DECIDING FACTORS
1 DIAMETER OF SHELL 2. THICKNESS OF SHELL 3. TOLERANCE ON TSR. THE CHART BELOW RECOMMENDS THE METHOD (PIN OR OPTICS ) TO BE FOLLOWED FOR MARKING THE REFERENCE LINE ON TOWERS WITH INTERNALS AS TSR
2 PIN METHOD
SHELL DIA **TOLERANCE ON
UP TO 3500 <,= 3 >3
3500-4500 >3 <, = 3
>4500 >, <, = 3
TSR LEVEL WITHIN
THICKNESS <, = 25 THICKNESS > 25 O O P P O P O O O O O O
- P DENOTES PIN METHOD OF MARKING
- O DENOTE S OPTICAL METHOD OF MARKING / MARKING ON MACHINE BED WITH SHELL
AXIS VERTICAL. - ** TOLERANCE ON TSR WITHIN 3 mm MEANS THAT THE SPECIFIED TOLERANCE IS + 1.5 mm - ALL DIMENSIONS ARE IN mm
REFERENCE LINE MARKING / CHECKING WITH OPTICAL INSTRUMENTS.
• PLACE THE SHELL WITH THE AXIS VERTICAL. • THE BOTTOM EDGE OF THE SHELL SHALL BE AT LEAST 1 MT ABOVE THE GROUND LEVEL. • SHELL OVALITY TO BE CORRECTED WITHIN 0.25 % OF I/D AT BOTH THE ENDS USING SPIDERS. • THE ALIGNMENT OF THE SHELL SHALL BE WITHIN 2 MM. THIS IS TO BE ASCERTAINED BY DROPPING PLUMBS AT FOUR ORIENTATIONS 90 DEG. APART. • THE MARKING / CHECKING SHALL BE DONE ON SHELL O/D AS WELL AS I/D BY KEEPING THE PARAGON LEVEL OUTSIDE THE SHELL AS SHOWN BELOW
REF.LINE
LINE OF SIGHT
PARAGON LEVEL
GROUND LEVEL
PROCEDURE FOR REFERENCE LINE MARKING BY PIN METHOD
4 SPIDER
4
SPIDER
3 3
2 REF.LINE 1
2
1
POINTS (e.g 1,2,3,4) 250 mm APART CONST.DIST APPROX.1000 MM TANK ROTATERS OIL BATH
PROCEDURE FOR REFERENCE LINE MARKING BY PIN METHOD
• KEEP THE SHELL HORIZONTAL ON A PAIR OF TANK ROTATERS. • CORRECT THE OVALITY TO 0. 25 % BOTH ENDS. • SPIDERS SHALL BE RIGID ENOUGH TO PREVENT BUCKLING. • TACK WELD A PIN OF 10 DIA AT THE CENTRE OF THE SPIDER. ( the pin shall be parallel to shell axis) • THE PIN SHALL HAVE A MACHINED „V‟ GROOVE FOR THE PLUMB. • DROP A PLUMB ALONG THE GROOVE OF THE PIN. • THE PLUMB IS TO BE SUSPENDED IN AN OIL BATH.
( PROC. CONTD…..)
• • • DIVIDE THE CIRCUMFERENCE OF SHALL APPROX. 250 mm APART ON I/D AND O/D AS SHOWN IN SKETCH. CHECK SQUARENESS OF THE SHELL PUNCH MARK A CONSTANT DISTANCE FROM THE PLUMB ON
I/D AND ON O/D • • JOIN THE PUNCH MARKS BY A FLEXIBLE STEEL RULE. MINIMUM 3 POINTS ARE TO BE COVERED IN ONE SETTING OF SCALE • ROTATE THE SHELL IN BOTH DIRECTIONS AND CONFIRM THE REFERENCE LINE MARKED ON I/D & O/D. • WRITE THE REFERENCE LINE ELEVATION FROM I/S & O/S WITH PAINT.
P-1402 GENERAL REQUIREMENTS
CIRCULARITY (0.20 % OF RADIUS )
+/- 8 FOR 8 M DIA SECTION +/-10 FOR 10 M DIA SECTION
“CIRCULARITY IS DEVIATION FROM IDEAL CIRCLE” METHODS OF MEASURING CIRCULARITY
1. SWING ARM METHOD 2. MESUREMENT BY TAPE OR TELESCOPIC GAUGE
1. SWING ARM METHOD
PENCIL
SECTION
SPIDER
GRAPH PAPER
SWING ARM ROLLER
METHOD OF FINDING OOC
1. MEASURE THE AREA OF CURVE
2. CALCULATE MEAN RADIUS R= A/
3. MARK THREE CIRCLE ON A PAPER (I) (II) (III) MEAN R MEAN R+ TOLERANCE MEAN R- TOLERANCE
4. ADJUST THE CURVE ON THE CIRCLES & DEMONSTRATE THAT THE CURVE IS WITHIN THE OUTER & INNER CIRCLES.
MESUREMENT BY TAPE OR TELESCOPIC GAUGE
1. FIND THE GEOMETRIC CENTRE OF THE SHELL-COURSE BY CROSSING 4 TWINES, MARK THE CENTRE OF POLYGONE POLYGONE TWINES SHELL
2. MEASURE THE RADIUS AT 48 LOCATIONS (R1 TO R48) 3. CALCULATE AVERAGE RADIUS = R1+R2+……+R48 / 48
MESUREMENT BY TAPE OR TELESCOPIC GAUGE
4. PLOT THE DEVIATIONS R(av.) - Rn ON A CIRCLE
5.1
SUPER- IMPOSE THE CURVE DRAWN THOUGHT ALL 48 POINTS ON TWO CIRCLES MARKED SHOWING MAXIMUM & MINIMUM ALLOWABLE DEVIATIONS
5.2 ENTER THE DATA IN CIRCLE PROGRAM & OBTAIN THE CIRCULARITY
PROCEDURE FOR MAINTAINING CIRCULARITY
HAZIRA METHOD
1. MAKE THE FRAMES & M/C OD/ID 2. WRAP THE SHELL AROUND THE FRAMES WITHOUT TACKING FRAME & SHELL 3. ENSURE GAP 1, S/U, WELD & CLEAR NDT OF
ID/OD ( MACHINED ) = D +/- 0.3
FLANGE WIDTH. +/- 2 MM UNBALANCE +/- 1 MM
5
FLANGE TILT 3 MM
T FRAME MANUFACTURE
CURRENT METHOD
1. MAKE COMPLETE FLANGE WITH REQUIRED CIRCUMFERENCE ** 2. MAKE WEB SEGMENTS COMPLETE WITH ID/OD MACHINED & WEP COMPLETED AS APPLICABLE
3.
USE THE FIXTURE WITH APPROPRIATE BRACKETS FOR
WEB # FLANGE S/U
4.
WELD ROOT RUN ON WEB SEGMENT L/S ,TACK THE WEB
# FLANGE JOINTS
5. REMOVE THE FRAME FROM THE FIXTURE & COMPLETE WELDING OF WEB L/S & CLEAR RT.
T FRAME MANUFACTURE
OLD METHOD
1. 2. 3. 4. 5. JOIN ALL WEB SEGMENT AND FROM A CIRCLE WELD & CLEAR NDT OF WEB L/S. MARK OD/ID ( AS APPLICABLE ) FOR MACHINING & MACHINE S/U FLANGE # WEB & WELD FLANGE WIDTH MACHINING WAS DONE AS THE FINAL OPERATION
SHRINKAGE ALLOWANCE
FOLLOWING SHRINKAGE ALLOWANCE IS TO BE ADDED ON THE CIRC. OF FRAMES WHILE S/U. • • INTERNAL FRAMES = 0.6 mm/M OF CIRC. EXTERNAL FRAMES = 0.9 mm/M OF CIRC.
HENCE THE S/U STAGE DIMENSIONS OF T FRAMES ARE NOT AS PER DRAWING & THE DIMENSIONS ARE GIVEN BY PLANNING IN A DATA SHEET.
GENERAL WEP
WHEN THE JOINING COMPONENTS ARE NOT AT 900
MARKING AT...
A B X
A = 2/3 t Tan(X- ) B = 1/3 t Tan(X + )
X
GENERAL WEP
WHEN JOINING PLATES OF DIFFERENT THICKNESS
X
T1
T2
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
01.
02.
MARK THE CENTRE POINT OF PENETRATION ON SHELL.
MAKE THE CUT OUT USING THE DEVELOPMENT.
03. C LEAR MARKING FROM INSPECTION. 04. 05. MAKE CUT OUT TO THE ABOVE SIZE. MARK THE ROOT FACE BY JOINING TWO POINTS USING SCALE ( -90 ).
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
OFF SET DIST.
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
SHELL
50 - ( 90 - )
900
500
500
X1 = H tan(90 - ) X2 = H tan [ 50 - ( 90 - )]
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
90
90 + Y
+ 2Y
+Y Y= 90- 3
9.
WE WILL CALCULATE THE DISTANCE OF “V” FROM CUT OUT BY DIVIDING EACH QUADRANT AS ABOVE. THE ANGLE OF PENETRATION WITH THE SHELL VARIES FROM TO 90 DEG & THEN FROM 90 DEG TO 180 - .
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION 06. CALCULATE ANGLE AS INDICATED IN THE SKETCH.
USING OUT SIDE RADIUS & OFFSET.
OFF SET DISTANCE FROM CENTRE OF PEN. = INV. SIN OUT SIDE RADIUS
07.
CALCULATE ANGLE A OF PENETRATION WITH THE SHELL = 90 -
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
09.
DIST. OF MARK FROM CUTOUT = X1 + X2 X1 =H * TAN ( 90- ), X2 = H * TAN ( 50 - ( 90 - ))
10.
JOIN ALL THE POINTS FREE HAND AND PUNCH THE LINE
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
14.76 mm 970 8.77 mm 1040 Thk -Q Thk -5 900 14 mm 18.5 mm 83.50 20 mm 76.50 „v‟ = 24.91 mm
Thk 17.5 Thk 20.5
= 69.6590
Thk-1 Thk 26.5
X1 = „V‟ Dist = H ( thk ) tan ( 90 - ) X2 = H ( thk ) tan [ 50 - ( 90- ) ]
PROCEDURE FOR WELD EDGE PREPARATION ON CUTOUT OF PENETRATION
EXP :- X1 = H tan ( 900 - ) = 26.5 tan ( 900 - 69.6590 ) = 26.5 tan ( 20.3410 ) = 26.5 0.37072 X1 = 9.82 mm X2 = H tan [ 50 - ( 900 - )] = 26.5 tan [ 500 - ( 900 - 69.6590 )] = 26.5 tan [ 500 - ( 20.3410 ) ] = 26.5 tan ( 29.6590 ) X2 = 26.5 9.82 mm 0.56944 X2 = 15.090 mm „V‟ Dist = X1 + X2
9.82 + 15.090
24.91 mm
PROCEDURE FOR TRIMMING LINE MAKING ON SUB-SECTION FWD end Y2
Y1
FWD end
X1
X2
AFT end
PROCEDURE FOR TRIMMING LINE MAKING ON SUB-SECTION
1. LEVEL SECTION FWD SIDE REF. LINE WITHIN +/- 1 MM. 2. CORRECT THE SAME TO +/- 1 MM IF REQUIRED.
3. ENSURE THAT FOLLOWING DIMENSIONS ARE ACHIEVED
WITHIN TOLERANCE. • ACTUAL POSITION OF FRAME
•
FRAME REF. LINE
4. MARK REF. LINE AT (SECTION LENGTH - 200 MM) ON AFT SIDE MEASURED FROM FWD SIDE. 5. COMPLETE ABOVE ACTIVITY FOR BOTH SECTIONS. 6. CHECK THE DIMENSIONS X1,X2,Y1,Y2 AT EVERY 5 DEGREE AS SHOWN IN SKETCH.
PROCEDURE FOR TRIMMING LINE MAKING ON SUB-SECTION
7. 8. 9. RECORD ALL DIMENSIONS IN GIVEN FORMAT. CHECK ALL 72 VALUES OF TOTAL ( S )AFTER ADDING 2 MM ROOT GAP. IN CASE, IT IS NOT WITHIN +/- 6 MM, X2 & Y2 SHOULD BE ADJUSTED TO GET THE DESIRED SPACING. 10. INVOLVE SUPERVISOR & IN CHARGE IN ABOVE TRIMMING LINE MARKING. 11. MARK TRIMMING LINE & COMPLETE TRIMMING / SQUARENESS.
12. COMPLETE WEP MARKING IN FULL CIRC. USING.
13. CLEAR INSPECTION.
Orientation Marking
Shell With Weld Seam
90 Orientation line 90 90
Long Seam Weld
Weld Center line 155°
Orientation Marking
Shell With Long Seam 0°
90°
270° 155°
180°
Orientation Marking
Shell Horizontal, Without Weld Seam
Manometer
0
Line Marked by Optical Level Water Tube
0
270
180
D
0
Orientation Marking Shell Vertical Without Seam
90 &270 180