CUTTING

&

EDGE PLANNING

PROCEDURE FOR MARKING, CUTTING AND CHECKING OF SHELL PLATES

TOLERANCE

• L - + 1 mm / M, Max. 3 mm., & W - + 1 mm / M, Max. 3 mm

• K1 - K2 = + 1 mm / M, Max. + 5 mm

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

SHELL PLATE

SA

516

GR

7 0

24 3

5 7

926

2 /

3

K1

K2

L

W

ROLLING DIR.

3 UNITS

4 U

NIT

S

5 UN

ITS

= 3.1415926535897932384626433832792………...

GENERAL WEP

WHEN JOINING PLATES OF DIFFERENT THICKNESS

X

T1 T2

FORMING

Provide necessary allowance ( 1.5 to 2 times the thickness)

• Gas cut

• Wastage of the material

• increased cycle time

Edge breaking to remove out peak out

Not feasible for all the thickness

Pressure required is more

ROLLING DEPENDS

THE PROCESS OF STRETCHING BEYOND THE YIELD POINT OF THE METAL

METHODS

PINCH ROLLING

PYRAMID ROLLING

COLD ROLLING

WARM ROLLING

HOT ROLLING

NORMAL ROLLING

ROLLING

PINCH ROLLING

BENDING AT THE PLATE ENDS

BOTTOM ROLLER SHIFTED FROM CENTRE TO EITHER LEFT OR RIGHT

PRESSURE APPLIED > NORMAL ROLLING PRESSURE

PYRAMID ROLLING

TOP ROLLER

BOTTOM ROLLER

BOTTOM ROLLER

NORMAL ROLLING

COLD ROLLING

ROLLING AT NORMAL ROOM TEMPERATURE

WARM ROLLING

PLATE HEATED BELOW ITS CRITICAL TEMPERATURE BEFORE ROLLING .

WHY? PLATE THICKER THAN THE CAPACITY OF THE ROLLING M/C

PLATE MATERIAL HAS HIGHER YIELD POINT

HOT ROLLING

PLATE HEATED BEYOND UPPER CRITICAL TEMP. BEFORE ROLLING .

WHY?

PLATE THICKER THAN THE CAPACITY OF THE ROLLING M/C

PLATE MATERIAL HAS HIGHER YIELD POINT

NORMAL ROLLING

PLATE PLACED BETWEEN TOP AND BOTTOM

ROLLERS AND PRESSURE APPLIED SLOWLY ON

TOP ROLLER TO ROLL THE REQUIRED DIAMETER.

CHECKING SHELL OVALITY AND CIRCUMFERENCE

ACTUAL THK.OVALITY = ID max - ID min

= 0.5 % of Nominal ID

I/D CHECK IN HP PLANE

D/4 T

EMP

D/4 TEM

PPEAK INPEAK OUT

TEMPLATES

TO CHECK THE INSIDE DIAMETER

MADE OUT OF 3-4MM THICKNESS PLATES

D/4 TO D/8 TEMPLATES

R

D/4

PEAK IN / PEAK OUT

WHY?

OVER / UNDER BENDING DURING EDGE BREAKING OPERATION

PRECAUTIONS

PROPER CARE

RE ROLLING

ID Allowed gap Pick in /

out

< 152 0.8 MM < 305 1.2 MM < 457 1.6 MM

< 610 2.4 MM <

914 3.2 MM < 1219 4.0 MM

< 1524 4.8 MM <

1905 5.6 MM < 2133 6.4 MM < 2438 6.4 MM < 2743 7.1 MM

< 3048 7.9 MM

>3048 0.2% OF ID

SKEW

Rollers not aligned

Plate edges not kept parallel to roller axis plate

diagonals not checked

SKEW

15 TO 20MM AND LOW THICKNESS

SKEW HIGH THICKNESS

SKEW

TURN BUCKLES

PROPER DEVELOPMENT & MARKING OF CONE

CHECK THE DIAGONALS

EDGE BREAKING WITH CARE ( D/4 LENGTH )

KEEP SUITABLE RADIUS GAUGE (HANDY)

ENSURE THE GENERATOR LINE OF THE CONE IS

PARALLEL TO THE TOP ROLLER

TO AVOID FLARE, INCREASE PREISURE SLOWLY

PRECAUTIONS

Check diagonals of the plates to be rolled.

Stamp identification mark on the outer surface of

the width so that, when the plate is rolled in to a

shell the identification mark can be seen from

outside.

Identification mark should be stamped parallel to

the width of the plate

GOOD ENGINEERING PRACTICES ( FOR ROLLING )

Always pain rolling direction with an arrow on the plate to be rolled

Remove burrs, dust, dirt from the edges of the

plate before it is fed in to rolling machine

While edge breaking a very long plate, hold one

end of such plate with crane while other end is

being edge broken

While edge breaking a very long plate, hold one end of such plate with crane while other end is being

edge broken.

GOOD ENGINEERING PRACTICES ( FOR ROLLING )

Always refer capacity chart of a particular rolling machine before attempting any bending/rolling

on that machine

Check alignment of the rollers, before rolling is attempted.

Ensure that required templates are available before rolling is taken up.

Before taking up s.s plate for rolling, the rollers must be thoroughly cleaned with wire brush.

GOOD ENGINEERING PRACTICES ( FOR ROLLING )

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.