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MSS SP-75

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Specification for High-Test Wrought Butt-Welding Fittings

MSS SP-75 specifies requirements for wrought (seamless or welded) steel butt-welding fittings for high-pressure gas and oil pipelines — elbows, tees, reducers, caps, and similar components.

Overview — MSS SP-75

MSS SP-75 specifies requirements for wrought (seamless or welded) steel butt-welding fittings for high-pressure gas and oil pipelines — elbows, tees, reducers, caps, and similar components. While it is a fittings standard rather than a valve standard, MSS SP-75 is directly relevant to valve procurement because pipeline valves with butt-weld ends must have end dimensions and wall thicknesses compatible with SP-75 pipeline fittings. API 6D and ASME B16.25 govern the butt-weld end geometry for valves; MSS SP-75 governs the adjacent fittings.

Scope

Applies to wrought steel butt-welding fittings for gas transmission and distribution, petroleum refinery, and high-pressure service. Covers NPS ½" to NPS 60" (DN 15 to DN 1500). Materials: ASTM A234 WPB/WPC (carbon steel), ASTM A420 WPL6 (low temperature), ASTM A860 WPHY (high yield pipeline steel).

Applicable Valve Types

Butt-weld end (BW) ball valves — API 6D pipeline valves with BW ends must match MSS SP-75 fitting bores

Butt-weld end gate valves — flanged or BW end pipeline gate valves

Applicable Pressure Classes

Class 150Class 300Class 600Class 900Class 1500Class 2500

Key Requirements — MSS SP-75

01.

Yield strength: WPHY grades — WPHY 42, WPHY 46, WPHY 52, WPHY 56, WPHY 60, WPHY 65, WPHY 70 — matched to pipeline steel grades

02.

Wall thickness: compatible with API 5L pipe schedule (Schedule Std, XS, XXS and specific pipeline wall thicknesses)

03.

Impact testing: mandatory for low-temperature service per ASTM A420 requirements

04.

NDE: all butt welds in fittings radiographically examined per ASME Section V

05.

Dimensional tolerances: fittings must mate with pipe to API 5L or ASME B36.10M dimensions

06.

Weld bevel: 37.5° included angle per ASME B16.25 for compatibility with pipeline butt-weld joints

Testing Requirements — MSS SP-75

Hydrostatic test of fitting body per ASME B16.9 (for shaped fittings) or per manufacturer's procedure

Radiographic examination of girth welds in fittings

Impact testing per ASTM A420 for low-temperature fittings (Charpy V-notch at -46°C for WPL6)

Hardness testing for sour-service NACE MR0175 compliance where applicable

Documentation Required for MSS SP-75 Compliance

Material Test Reports (MTRs) per EN 10204 3.1 or ASTM

NDE (radiography) reports for welded fittings

Impact test results for low-temperature grades (WPL6)

Dimensional inspection certification

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