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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.

 

 

REGULATIONS FOR DETERMINING THE WORKING PRESSURE OF WATER TUBE BOILERS WITH FUSION WELDED AND SEAMLESS FORGED DRUMS


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.
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
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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