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Reg. 269, Reg. 270
INSPECTION AND TESTING
Inspection during Construction |
Inspections
during construction and fees therefore shall be governed
by the rules in Appendix ‘J’ and regulation
395A.
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REGULATIONS FOR DETERMINING THE WORKING PRESSURE OF WATER
TUBE BOILERS WITH FUSION WELDED AND SEAMLESS FORGED DRUMS
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Reg. 270
SHELLS
Shell of steam and water drums
| a) |
The
working pressure shall be determined by the following
formula:-
| W.
P. = |
2 f E
(t - .03) |
Equation (72) |
| D + T
- .03 |
where,
T = Thickness in inches.
D = Maximum internal diameter in inches.
W. P .= Working pressure in lb. per sq.inch.
f = Permissible working stress in lbs. per sq. inch at
working metal temperature (see Reg.
271).
E
= The efficiency of ligaments between the tube holes or
other uncompensated openings in shell, or the weld
factor of the longitudinal joints.
For
Class I boilers, the weld factor shall be taken as 1
In the particular case of an unpierced wrapper plate of
a fusion welded drum.
E
= 1 |
| b) |
Irrespective
of the thickness obtained by the use of the foregoing
formula “T” shall not be less than:-
| i) |
For tube plates (where
the tubes are expanded therein) the thickness shall
be at least such as to allow a minimum parallel
belt width of tube seat of 3/8 inch, this seating
to be measured as explained below. |
| ii) |
All tubes shall be carefully
expanded into the holes in the tube plates. The
tubes shall be belled or beaded to resist withdrawal
and if belled they shall project through the parallel
tube seat at least ¼ inch. |
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| c) |
The
Belling shall be as shown in table below:-
| TABLE |
| Outside diameter of
tube |
Amount of diameter
of belling over diameter of the tube holes |
| |
In. |
| Upto and including 1 ½ in. |
3/32 |
| Over 1½ in. up to and including
2 in. |
4/32 |
| Over 2 in. up to and including 3¼
in. |
5/32 |
| Over 3¼ in. up to and including
4 |
6/32 |
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| d) |
The
tube holes in the tube plates of drums, pockets of headers
shall be formed in such a way that the tubes can be effectively
tightened in them. Where the tube ends are not normal
to the tube plate, there shall be a neck or belt of parallel
seating at right angles to the axis of the tube at least
½ in. in depth measured in a plane containing the
axis of the tube at the hole. |
| e) |
Where
the tubes are practically normal to the tube plate or
the header this parallel seating shall, wherever practicable,
be not less than 3/8 in. in depth. |
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