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Reg. 267 a, Reg. 267 b, Reg. 267 c, Reg. 267 D
(a) Heat Treatment |
After the completion
of the welding of the seams and the welding on of the
stand pipes and including welding repairs but before the
hydraulic test, each drum shall be heat treated for stress
relieving; during this heat treatment the official test
plates shall be lying inside the drum.
Heat treatment of Alloy Steel plates shall be carried
out on the basis of composition of the alloy as shown
in the table below:-
Table
Type of
Steel
|
Range
of Temperature in degree centigrade
|
Time
at temperature per mm of thickness of plate
|
|
½Mo
½Cr
½Mo
|
620-660
|
2.5
minutes (30 minutes min.)
|
|
1Cr
½Mo
1½Cr
½Mo
|
630-670
|
2.5
minutes (30 minutes min.
|
|
2¼Cr
1Mo
|
650-750
|
2.5
minutes (1 hour min.)
|
Note.- For pipes of 2¼Cr 1Mo specification upto
and including 127 mm outside diameter and upto 13 mm
wall thickness, the time may be 30 minutes minimum.
The
heat treatment of steels having Cr Mo V shall be carried
out as per the requirements of the code of manufacture
of plates, pipes.
|
| aa) |
The heat treatment
referred to in clause (a) shall not be necessary in case
of Carbon Steel.
Provided that the thickness of the part/weld/recess does
not exceed 20 mm, and the carbon content does not exceed
0.25%. |
| ab) |
Where the welded
joint connects parts that are of different thickness,
the thickness, the thickness to be considered in applying
the limiting thickness of 20 mm for carbon steel shall
be the following nominal thickness including corrosion
allowance:
| i) |
The thinner of two adjacent
butt welded component including shell to end connections; |
| ii) |
the thickness of the
shell in connections to flat ends; |
| iii) |
the thickness of the
shell or end in nozzle attachment welds; |
| iv) |
the thickness of the
nozzle at the joint in nozzle to flange connections; |
| v) |
the thickness of the
pressure parts at the point of attachment where
a non-pressure part is welded to a pressure part,
in case of butt welds; |
| v) |
the thickness of the
fillet weld at the point of attachment where a non-pressure
part is welded to a pressure part, in case of fillet
welds.” |
|
Reg. 267 b
|
Where the shell is subjected to a primary stress relieving
treatment identical to the final heat treatment to be
given to the drum, the test plates may be placed inside
the shell during the primary treatment and thereafter
cut up and tested without waiting for the final treatment
of the drum.
|
Reg. 267 c
|
Where the shell is not subjected to primary stress
relieving treatment or is subject to a primary stress
relieving treatment which is not identical with the
final heat treatment, the test plates may be placed
inside any other drum of comparable dimensions which
is to be heat treated in accordance with this Chapter.
The heat treatment is to take place in the furnace in
which the drum relating to the test plates will eventually
be given its final heat treatment.
|
Reg. 267 d
|
Temperature charts shall be submitted to indicate that
the test plates and the drums they represent have been
subjected to identical heating, soaking and cooling
treatment.
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