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.
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