Applies to the general and detail construction of the pipework connecting a land steam boiler to engine, turbine or industrial plant and all auxiliary pipework in connection therewith, together with the individual pipes and pipe fittings forming parts of such installations for - pipes or any bore where the pressure exceeds 50 lb. per square inch; and pipes over 10 in. bore for steam at pressures of 50 lb. per square inch and below. Steam recievers, separators and other unfired pressure vessels are excluded.