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Reg. 565, Reg. 566
Horizontal shelves of tube plates forming
part of the shell.-
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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.
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| 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.
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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.
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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:-
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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