(a) Process of manufacture.- The steel used for the parts shall be made by the open hearth or electric or basic oxygen process or by any other process which gives steel having equivalent properties.

(b) Chemical Analysis.- The steel shall not contain more than 0.05 per cent of sulphur or of phosphorus.

(c) Freedom from and rectification of defects.- Where not machined, the pipes, shall have workman like surfaces as normally obtained by rolling, forging or drawing. Provided that the minimum required thickness is maintained, minor surface defects may be admitted and other defects removed by mechanical means so as to achieve, a smooth surface. Surface defects may also be repaired, by welding only, with the approval of the Inspecting Authority provided that the parts are stress relieved after welding, wherever necessary.

(d) Heat treatment.- Each forging shall be efficiently heat-treated unless during the last stage of manufacture it has been finished at such a temperature as to ensure that the material of the forging will have satisfactory mechanical properties.