Fabrication

APPLICATION OF ERROR ON CALIBRATED TAPES
TYPES OF ERROR
+VE ERROR TAPE

STD TAPE
- VE ERROR TAPE

25005

WITH USER

25000

WITH QA

24995

WITH USER

ERROR CORRECTION

TYPE OF
ERROR

OPERATION
MARKING

MEASURING

(ADD ERROR)

(SUBTRACT ERROR)

+ VE

X + (+Y)

X -- (+Y)

-- VE

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

4 UNITS

K2

TS
NI

ROLLING DIR.

5U

W

SA 516 GR
70 24357
9262 /
3

K1

3 UNITS

L
TOLERANCE
• L - + 1 mm / M, Max. 3 mm., &
• K1 - K2 = + 1 mm / M,

W - + 1 mm / M, Max. 3 mm

Max. + 5 mm

• IDENTIFICATION MARKING
TO ROLLING DIRECTION.
• L - NOMINAL CIRCUMFERENCE = MEAN DIA. X





=

3.1415926535897932384626433832792………...

CHECKING AXIAL ALIGNMENT OF SHELLS
PROCEDURE

• LEVEL THE

SHELL ORIENTATIONS VERTICALLY / HORIZONTALLY

• ARRANGE SHELL ASSEMBLY AS SHOWN IN SKETCH BELOW
X

F
90

E
D

C
B

180

0

Z2

Z1

270

A
X
PLAN

PLUMB BOBS
FRONT VIEW

CHECKING AXIAL ALIGNMENT OF SHELLS
MEASURE PERPENDICULAR DISTANCE BETWEEN PLUMB LINE AND
HORIZONTAL TWINE & TABULATE READINGS AS SHOWN BELOW.
LOCATIONS

TWINE TO PLUMB DIST.

HALF DIFF ( Z1- Z2 / 2 ) MM
Z1 AT 0
Z2 AT 180

OF READING
A
B
C
D
E
F
• SIMILARLY REPEAT THIS EXERCISE FOR 90 / 270
ROTATING THE SHELL ASSEMBLY.
LOCATIONS
270
ABCDE & F

ORIENTATIONS BY

TWINE TO PLUMB DIST. HALF DIFF ( Z1-Z2 / 2 ) MM
ENTER DIM.
Z1 AT 90
Z2 AT
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

+3

+2

+2

+1

+1

00

00

-1

A

B

C

D

E

-2
-3

F

-1

A

B

C

-2
0 - 180 DEG.

-3

90 - 270
DEG.

D

E

F

CHECKING SURFACE ALIGNMENT OF SHELLS
Y0
Y1

A(END)
B

Y2
Y3

X0
X1

X2
C

Y4

X3

X4

Y5

X5
D

Y6
Y0

1.

X6
E
(END)

X0

LEVEL THE SHELL ORIENTATIONS ( 0 - 180 , 90-270 ) VERTICALLY /
HORIZONTALLY

2.

DROP THE PLUMBS NEAR EACH CIRC.SEAM AND PUT TWINES

HORIZONTALLY ON BOTH SIDE OF SHELLS.

CHECKING SURFACE ALIGNMENT OF SHELLS
3.

MAINTAIN SAME DIMENSIONS AT BOTH ENDS OF THE SECTIONS
BETWEEN HORIZONTAL TWINES & PLUMB.

4.

MEASURE PERPENDICULAR DISTANCE BETWEEN OTHER PLUMBS
AND HORIZONTAL TWINES AND RECORD THE READINGS IN THE
TABLE BELOW.

5.

SIMILARLY ROTATE THE JOB 90 DEGREES AND TAKE DIMENSIONS
FOR OTHER TWO ORIENTATIONS AND RECORD THEM.

6.

SURFACE ALIGNMENT IS
READING.
SEAM NO

=

MAXIMUM READING
ORIENTATION

0

90

180

A ( END )

X0

Y0

B

X1
X2

Y1
Y2

C

X3
X4
X5
X6

Y3
Y4
Y5
Y6

X0

Y0

D
E ( END )

270

MINIMUM

CHECKING SURFACE ALIGNMENT OF SHELLS
SECTION WITH DIFFERENT THICKNESS OF SHELLS
Y1

THK T1
Y2

A(END)

X2
B

Y3
Y4

X1

X3

C

X4

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

Y5

X5

Y6

X6

D

Y7

THK T2

X7

X1 = X8 + ( T2-T1 )

E(END)
Y8

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

REMARKS

UP TO 8

9 TO 18

19 TO 50

ABOVE 50

ROLLED SHELLS AT
L/S SET-UP STAGE

(+) 5
(-) 2

(+) 7
(-) 4

(+) 10
(-) 7

(+) 12
(-) 9

CIRCUM. TO BE CHECKED AT
3 LOCATIONS, 2 ENDS AND AT
CENTRE

PRESSED / FORMED
D’END, CONE &
EXPANSION BELLOW
AFTER COMPLETING
WELD JOINT IF ANY

(+ / - ) 5

(+ / - ) 8

(+ / - ) 10

(+ / - )15

(-0 / +10)**

(-0 / +15)**

(-0 / + 18)**

(-0 / + 25)**

IF COMPONENT IS IN SET-UP
STAGE WITHOUT WELDING
PER JOINT 3MM SHRINKAGE
SHALL BE ADDED TO BASIC
CIRCUMFERENCE.

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

2 PIN 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
SHELL DIA
**TOLERANCE ON

UP TO 3500
<,= 3

>3

3500-4500

>4500

>3

<, = 3

>, <, = 3

TSR LEVEL WITHIN
THICKNESS <, = 25

O

P

O

O

O

O

THICKNESS > 25

O

P

P

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

GROUND LEVEL

PARAGON
LEVEL

PROCEDURE FOR REFERENCE LINE MARKING BY PIN METHOD

4

4

SPIDER
3

SPIDER

2

3

2

REF.LINE
1

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

SWING ARM

GRAPH
PAPER

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)

MEAN R

(II)

MEAN R+ TOLERANCE

(III)

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
CLOSING SEAM
4. TACK FRAMES # SHELL

FRAME MANUFACTURE
APPLICABLE TOLERANCES
1.

FRAME HEIGHT = + 4MM
- 3

2.

ID/OD ( MACHINED ) = D +/- 0.3

3.

FLANGE WIDTH. +/- 2 MM

4.

UNBALANCE +/- 1 MM

3

4

4
1

5
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.

JOIN ALL WEB SEGMENT AND FROM A CIRCLE

2.

WELD & CLEAR NDT OF WEB L/S.

3.

MARK OD/ID ( AS APPLICABLE ) FOR MACHINING & MACHINE

4.

S/U FLANGE # WEB & WELD

5.

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

A = 2/3 t Tan(X- )
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.

MARK THE CENTRE POINT OF PENETRATION ON SHELL.

02.

MAKE THE CUT OUT USING THE DEVELOPMENT.

03. C LEAR MARKING FROM INSPECTION.
04.

MAKE CUT OUT TO THE ABOVE SIZE.

05.

MARK THE ROOT FACE BY JOINING TWO POINTS
USING SCALE ( -90 ).

PROCEDURE FOR WELD EDGE PREPARATION ON
CUTOUT OF PENETRATION

SINE-1

OFFSET
0- 
DISTANC
90
E

OFF SET DIST.
O/S RADIUS

 = 1400/4027.5
 =20.3410



OU
RA T S
DI IDE
US

 = 900- 
 = 900 - 20.3410
 =69.6590

PROCEDURE FOR WELD EDGE PREPARATION ON
CUTOUT OF PENETRATION

SHELL
500

50 - ( 90 -  )
X2

900



X1

X1 = H tan(90 - )
X2 = H tan [ 50 - ( 90 -  )]

500

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.
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

Thk 17.5
Thk 20.5

20 mm
76.50
‘v’ = 24.91 mm

 = 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
X2 = H tan [ 50 - ( 900 -  )]

EXP :- X1 = H tan ( 900 -  )
= 26.5 tan ( 900 - 69.6590 )

= 26.5 tan [ 500 - ( 900 - 69.6590 )]

= 26.5 tan ( 20.3410 )

= 26.5 tan [ 500 - ( 20.3410 ) ]

= 26.5  0.37072

= 26.5 tan ( 29.6590 )
X2 = 26.5 9.82 mm  0.56944

X1 = 9.82 mm

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.

RECORD ALL DIMENSIONS IN GIVEN FORMAT.

8.

CHECK ALL 72 VALUES OF TOTAL ( S )AFTER ADDING 2 MM
ROOT GAP.

9.

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.