
Reg. 189
DISHES END PLATES
Dished ends subject to internal pressure
a) 
For unstayed ends of steam
and water drums, tops of vertical boilers, etc., when
dished to partial spherical form the maximum working pressure
shall be determined by the following formula : 
W.P. = 
15 x S
x (t  1) 
Eqn.(24) 
R 
Where
W.P. is the working pressure in lbs. per square inch,
t is the thickness of end plates in 32nds of an inch.
R is the inner radius of curvature of the end in inches,
which shall not exceed the external diameter of the shell
to which it is attached,
S is the minimum tensile breaking strength of plate in
tons per square inch, or whatever is allowed for it. 
b) 
The inside radius of curvature
of the flange shall be not less than 4 times the thickness
of the end plate, and in no case less that 21/2 inches. 
c) 
When the end has a manhole
in it (t  5), shall be substituted for (t  1) in the
formula. 
d) 
The total depth of flange of
manhole from the outer surface in inches measured on the
minor axis shall be at least equal to 
(T x W) ^{1/2}
= depth of flange
in inches. 
Eqn.(25) 
where
T is the thickness of the plate in inches,, and
W is the minor axis of the hole in inches.
NOTE  The foregoing provisions shall not preclude the
use of dished ends in compliance with Regs.275 to
278,
where not fitted with an uptake. 

