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Reg. 565, Reg. 566

Horizontal shelves of tube plates forming part of the shell.-

 

The number of gussets required to support the horizontal shelves of tube plates to withstand the vertical load due to the pressure on the boiler ends shall be determined in the following manner:-

For combustion chamber tube plates the minimum number of the gussets shall be:-
Where C exceeds 4560 1 gusset.
Where C exceeds 6240 2 gussets.
Where C exceeds 7440

3 gussets.

For the smoke fox tube plate the minimum number of gussets shall be:-
Where C exceeds 4560 1 gusset.
Where C exceeds 8400

2 gussets.



C =   PAD
Equation XII/4
t

where,

A is maximum horizontal dimension of the shell from the inside of the shell plate is to the outside of the tube plate in inches  (see Fig.XII/61) .

D is inside diameter of the boiler in inches.
P is working pressure in pounds per square inch
t is thickness of tube plate in thirty seconds of an inch.

The shell plates to which the sides of the tube plates are connected shall be not less than 1/16 inch thicker than is required by the formula applicable to shell plates with continuous circularity; and where gussets or other stays are not fitted to the shelves, the strength of the parts of the circumferential seams at the top and bottom of these plates from the outside of one tube plate to the outside of the other, shall be sufficient to withstand the whole load on the boiler end, with a factor of safety of not less than 4.5.




Reg. 566

Dished end plates for Lancashire and Cornish boilers

For the dished ends of Lancashire and Cornish boilers without stays and subject to internal pressure the maximum working pressure shall be determined by the following formula:-

WP = (t-8)30 x S Equation XII/5
R

Where,

t is minimum thickness of the end plate in thirty-seconds of an inch
WP is working pressure in pounds per square inch.
R is inner radius of curvature of the end plate in inches
S is minimum tensile strength of the plate in tons per square inch.

The inner radius of curvature of the end plate shall not exceed 1 ½ times the external diameter of the shell to which it is attached.

The inner radius of flanging of the end plate shall be not less than 4 times the thickness of the plate but in no case less than 2 ½ inches.

Where the end plate has a manhole, compensation shall be obtained by flanging the edge of the opening or by providing a fabricated ring (see Fig. XII/52).

In either case the depth of the flanging or ring measured at the minor axis shall not be less than that determined by the following formula:-

D = TW Equation XII/6

Where,

D is depth of flange or ring in inches, measured from the outside of the plate to the joint face.

T is thickness of the plate in inches.
W is width of the opening in inches, measured on the minor axis.

 
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