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Reg. 361, Reg. 361 A

STEAM- PIPES FITTINGS AND CONNECTIONS

Wrought Bends

b)

The thickness of the pipes, from which bends are made shall be such that the minimum thickness required by equation 91 is maintained throughout after the bending operation. The deviation from circularity in percentage at any cross-section of a bend shall be calculated by the following formula :-

C = Dmax .- Dmin x 100
D

This deviation shall not exceed 20 D
R


where,
C = The percentage deviation of circularity.
Dmax. = maximum external diameter of the pipe as gauged at the bend.
Dmin = minimum external diameter of the pipe as gauged at the bend.
D = nominal external diameter of the pipe.
R = Radius of the bend on the central line of the bend.
c) Fabricated pipe bends may be made by Welding together bevelled section of straight pipe, provided:-

(i) the angle between the axis of the adjoining sections does not exceed 30° and
(ii) the thickness is at least:

K - 0.5 times the minimum thickness required for the straight pipe to which the bend is joined
K - 1


The thickness at any point of the bend shall not be less than 87.5% of the nominal thickness of the bend. The thickness at any point of the bend shall be such that the minimum thickness required by equation 91 is maintained throughout after finishing operation.

where,

K = ratio of the radius of the bend (from centre of curvature to centre of pipe) to the inside radius of the pipe.

Note: Gusseted Bends shall be used for pressure not exceeding 21 kilogram per square centimetre and temperature not exceeding 260 Degree Centigrade.
d) For the forged bends, the radii shall be not less than those given below:-

Long radii forged bends R = 1.5 x d
Short radii forged bends R = 1.0 x d

Reg. 361 A

Butt-welding fittings

The Butt-welding fittings shall conform to the dimension and tolerances shown in the fig table.

   
   
 
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