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Reg. 227, Reg. 228, Reg. 229

FURNACES

Cross Tubes

The working pressure of the tubes shall be determined by the following formula :-
W. P. = 200 (t - 7)
Eqn.(64)
D

where
W. P. = working pressure in lbs. per sq. inch.

t = minimum thickness in 32nds of an inch.

D = the internal diameter in inches of the cross tube.



Reg. 228

FURNACES

Uptakes of Vertical Boilers

The working pressure for uptake tube of vertical boilers shall be determined by Eqns. 57 and 58 but only half the least pressure so found is to be allowed for uptake tubes.



Reg. 229

SUPPORTS FOR COMBUSTION CHAMBER AND FIREBOX CROWN

Girder stay for firebox crowns

a) For girders supporting crown plates of rectangular fireboxes, where the ends of the girders are supported by the vertical end or side plates, their proportions shall be calculated from the following formula : -
W. P. = CSTD2 Eqn.(65)
L2Y

where
W. P. = working pressure in lb. per sq. inch,

S = Minimum tensile stress of the material in tons per sq. inch,

T = Total thickness of the stay in thirty seconds of an inch,

D = Depth of the girder stay in inches,

L = Length of girder stay in inches measured between the inside of the tube plate and the firehole plate, or between the inside of the side plates, according to the method of support

Y = Pitch of girder stays in inches,

C = 22 for steel plates or steel forgings, 19 for steel castings.
b) Where girders are supported in any other way than by the end or side plates of the firebox or combustion chamber the calculations for determining the working pressure shall be made in accordance with the actual conditions of support.

In such cases the length of the strip of firebox or combustion chamber top plate to be supported by the girder shall, subject to the limit imposed on the distance of the nearest stay, be taken as equal to the product of the number of bolts carried by the girder into the pitch of the bolts. A maximum nominal stress of 14,000 lbs. per square inch on girder section shall be allowed for steel.

c) Slings, links pins, rivets and connections to shell of slung girders shall be sufficient to carry the whole load that would otherwise be carried by the girder, and each girder must be equally slug or supported. For stresses allowed on the sections, see Regulation 203.
d) In the case of girders supported at the ends only by angle bars riveted to casing crown, the length L may, when the girder extends over the full breadth of the angle face, be taken as the distance between the centres of the angle faces. When this distance does not exceed that of L in the formula, the pressure shall be determined in the ordinary way. The supporting angles and rivets shall be of sufficient section for the intended purpose. For stresses allowed on the sections, see Regulation 203.
 
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