MSS SP 75: 2019 [paper]

This Standard Practice covers factory-made, seamless and electric welded carbon and low-alloy steel, butt-welding fittings for use in high pressure gas and oil transmission and distribution systems; including pipelines, compressor stations, metering and regulating stations, and mains.

This Standard Practice governs dimensions, tolerances, ratings, testing, materials, chemical and tensile properties, heat treatment, notch toughness properties, manufacture, inspection, certification, and marking for high-strength, butt-welding fittings NPS 60 and smaller. Dimensional requirements for NPS 14 and smaller are provided by reference to ASME B16.9.

The term “welding fittings” applies to butt-welding fittings such as elbows, segments of elbows, reducing elbows, caps, tees, single or multiple-outlet extruded headers, reducers, and extensions and transition sections(1). Hot induction bends are outside the scope of this Standard Practice. Girth weld requirements are outside the scope of this Standard Practice and are covered by the applicable ASME B31 Code for Pressure Piping and/or customer specifications.

Fittings may be made to special dimensions, sizes, shapes, and tolerances, or of wrought materials other than those covered by this Standard Practice by agreement between the manufacturer and the purchaser. When such fittings meet all other stipulations of this Standard Practice they shall be considered as being in partial compliance therewith, providing they are appropriately marked.

Fittings manufactured in partial compliance, as provided in Section 1.4, shall be identified with “Part” following the respective grade designation.

Fittings specified as “PSL2” will automatically invoke the additional requirements of SR-24 which are intended to be complementary to PSL2 line pipe in the API 5L Specification.