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Reg. 190, Reg. 191, Reg. 192
DISHES END PLATES


Dished ends subject to external pressure

In the case of unstayed dished ends, for the co-efficient 15 in equation (24) the cofficient 12 shall be substituted and R shall be the outer radius of curvature of plate which shall not exceed the external diameter of the shell to which it is attached. For plates exposed to furnace flame the co-efficient shall be 10.5.

In no case shall R exceed 2.75
T



Reg. 191
DISHES END PLATES


Dished ends of Lancashire and Cornish Type Boilers

a) For dished ends of Lancashire and Cornish boilers formed in one piece without stays and subject to internal pressure the maximum working pressure shall be determined by the following formula :-
W.P. = (T - 8) x 30 x S Eqn.(26)
R

where
W.P. is the working pressure in the lbs. per square inch.

T is the thickness of the end plate in 32nds of an inch.

R is the inner radius of curvature of the end in inches which shall not exceed one and a half times the external diameter of the shell to which it is attached.

S is the minimum tensile breaking strength of the plate in tons per square inch or whatever is allowed for it.
b) The inside radius of curvature at the flange shall be not less than 4 times the thickness of the plate and in no case less than 3-1/2 inches



Reg. 192
DISHES END PLATES


Dished shell and firebox crowns

a) In determining the working pressure in accordance with Regulations 189 and 190 no accounts shall be taken of the influence of the up-take tube in vertical boilers. If dished crown plates having uptakes are fit for higher pressures, when considered as flat plates, under Reg.197 such higher pressure shall be allowed.

 

b) The radius Rs of the dished part may be found as follows : -

 

R = C2 + H2 Eqn.(27)
2H

C and H are the lengths in inches of half the base line or chord on which H measured and the height of the dish or camber at the middle of the chord respectively.
 
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