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Reg. 208
STAYS

Bolts and Studs

a) Bolts and studs connecting parts by boilers such as shell, end plates, tube plates, furnaces, up takes, externally fitted manhole covers, mountings, etc. may be made either of steel or good quality wrought iron.
b) The maximum working pressure for the bolts or studs shall be calculated by the following formula: -

 

W. P. =

N x C

( D - 1.28 )2 Eqn.(45)
A n

where
D is the diameter of bolt or stud over threads in inches

N is the number of bolts or studs securing the part,

n is the number of threads of screws per inch,

C = 4,700 for steel bolts or studs of 28 tons/sq. in. minimum ultimate tensile stress where the diameter over thread is less than 3/4 inch,

C = 5,100 for steel bolts or studs of 30 tons/sq. in. minimum ultimate tensile stress where the diameter over thread is less than 3/4 inch

C = 5,600 for steel bolts or studs of 35 tons/sq. in minimum ultimate tensile stress where the diameter over thread is less than 3/4 inch.

C = 5,600 for steel bolts or studs of 28 tons/sq. in minimum ultimate tensile stress where the diameter over thread is not less than 3/4 inch and not greater than 7/8 inch.

C = 7,000 for steel bolts for studs of 28 tons/sq. in minimum ultimate tensile stress where the diameter over thread is greater than 7/8 inch.

When the material is iron, a reduction, of 15 per cent shall be made in the working pressure as calculated by the formula.

A is the area in square inches of the surface supported by the bolts or studs. For jointed flanges the area shall be taken to extend to midway between the pitch line of the bolts and the inner edge of the flange by which the part is secured.
 
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