This specification covers wrought carbon steel and alloy steel pipe fittings of seamless and welded construction for use in pressure piping and pressure vessel service at low temperatures. Materials shall consist of forgings, bars, plates, seamless or fusion welded tubular products with filler metal added, and shall be produced by open-hearth, basic-oxygen, or electric-furnace process. Forging or forming operations shall be performed by one or a combination of two or more of the following procedures: hammering, pressing, piercing, extruding, upsetting, working, bending, fusion-welding, or machining. All welding shall be completed prior to the austenitizing heat treatment, which shall be executed in the normalized, normalized and tempered, annealed, or quenched and tempered conditions. Steel specimens shall conform to required values of chemical composition, tensile strength, yield strength, elongation, wall thickness, and Charpy V-notch impact value. All fusion-welded butt joints shall undergo radiographic examination, while hydrostatic testing of fittings is not required in this specification. Repair welding shall be permissible for parts made to dimensional standards.

1.1 This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction, covered by the latest revision of ASME B16.9, ASME B16.11, MSS-SP-79, MSS-SP-83, and MSS-SP-95. Fittings differing from these ASME and MSS standards shall be furnished in accordance with Supplementary Requirement S58 of Specification A 960/A 960M. These fittings are for use in pressure piping and pressure vessel service at low temperatures.

1.2 Optional supplementary requirements are provided for fittings where a greater degree of examination is desired. When desired, one or more of these supplementary requirements shall be specified in the order.

1.3 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable "M" specification designation (SI units), the material shall be furnished to inch-pound units.

1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other.