Applies to shop and site arc-welding using manual, automatic or semi-automatic fusion welding processes for Class 1 and Class 2 piping installations. Tables list parent metal, electrodes, preheating and post heat-treatment requirements. Preparation, assembly and welding of butt joints, branches and bosses, gusseted bends, flanges, sockets and structural attachments are covered. Acceptance, non-destructive and qualification testing are detailed; requirements for preparation of macro-etch specimens and inspection of etched sections are given in appendices.