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Reg. 567, Reg. 567A

Dished ends subject to internal pressure

 

a)

For unstayed ends of shells and tops of vertical boilers and the like boiler parts, when dished to partial spherical form the maximum working pressure shall be determined by the following formula:-

WP = 15 x S X (t-1)
Equation XII/7
R

WP is the working pressure in pounds per square inch.

t is thickness of the end plate in thirty seconds of an inch but in no case this shall be less than the thickness of the shell to which it is attached.

R is the inner radius of curvture 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 to which a crown plate is dished shall be not greater than the external diameter of the cylinder to which it is attached.
c) The inside radius of curvature of the flanges to the shell shall be not less than 4 times the thickness of the crown plate and in no case less than 2 ½ inches.
d) The inside radius of curvature of flanges to uptakes shall be not less than twice the thickness of the crown plate and in no case less than 1 inch.
e) When the end has a manhole in it (t-5), shall be substituted for (t -1) in the formula.
f) 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 depth of flange in inches Equation XII/8

where T is the thickness of the plate in inches and W is the minor axis of the hole in inches.
g) The depth of the crown plate opening from the commencement of the curvature of the flanging radius shall be not less than twice the plate thickness with a minimum of one inch.



Reg. 567A

Nothing in Regulation 567 shall preclude the use of dished ends in compliance with Regulations 275 to 278, where not fitted with an uptake.
 
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