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  Reg. 365 F

Shell Joints

1)

Riveted Shells. Preparation of plates, butt straps, rivet holes and riveting shall comply with the relevant Regulations of Chapter III.

Longitudinal joints of riveted shells may be lap jointed or fitted with double butt straps, but in cases where the design pressure exceeds 130 lbs/sq. in. or the product of the design pressure in lbs/sq. in. and maximum internal diameter in inches exceeds 9,500, the longitudinal joints shall be butt jointed with double cover strap. The design of riveted joints shall be in accordance with Regulation 177 to 184.

2) Fusion Welded Shells.- These shall be classified as follows:-

Class I-No limit to scantlings.

Class II- When none of the following limits is exceeded:-

(i) Working pressure – 35 kg/sq. cm. (500 lbs/sq. in.)
(ii) Product of Working Pressure and internal diameter-3750 (21,000)
(iii) Design temperature - 343°C (650°F).


Class III-When none of the following limits is exceeded:-

(i) Working Pressure –7.4 kg/sq. cm. (105 p si).
(ii) Product of Working Pressure and internal diameter-940 (5250)
(iii) Design temperature-171°C (340°F).


Fusion welds, preparation of seams, the method of formation of cylindrical shells including heat treatment after bending, method of making welded seams, types of welded joints, test plates and circularity of shells shall all conform to the requirements of Chapter V, except for the following namely-

Whenever practicable, seams shall be welded from both sides of the plate. Additional runs of metal shall be deposited at both surfaces of the welded seams to build up to a thickness 10 per cent greater than thickness of the plate. The surfaces of welds wherever carried out on both sides shall be ground smooth and flush with the respective surfaces of the plates. Where the seam is welded from one side only, these provisions shall apply to the exposed of the surface weld.

Tests for Class I fusion welded seams shall comply with the requirements of the relevant Regulations of Chapter V.

Tests for Class II fusion welded seams shall comply with the requirements of those of Chapter XII, except that an additional provision for one micro and macro examination shall be made.

Tests for Class III fusion welded seams shall comply with the requirements of those of Chapter XII.

Class I and Class II shells shall be effectively stress relieved by heat treatment when the wall thickness exceeds 20mm or the carbon content exceeds 0.25% or the pipes are made of alloy steel.
(3) Seamless Forged Shells.- These shall comply with the requirements of Regulation 235 to 243.
 
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