MSS SP-97 Standard Practice covers essential dimensions, finish, tolerances, testing, marking, material, and minimum strength requirements for 90 degree integrally reinforced forged branch outlet fittings of buttwelding, socket welding, and threaded types.

Integrally Reinforced Forged Branch Outlet Fittings – Socket Welding, Threaded, and Buttwelding Ends.

mss sp 97

Fittings manufactured to this Standard Practice are designed to make a fully reinforced branch connection in accordance with applicable piping code requirements, when attached, at an opening in a run pipe by means of a full penetration weld.

Fittings may be made to special dimensions, size, shape, tolerances, or of other wrought material by agreement between the manufacturer and the purchaser.


MSS(Manufacturers Standardization Society) is the only organization in the world dedicated exclusively to the technical needs of the valve and fittings industry.

Standards and codes are written and revised by 25 technical committees and address topics such as valves, valve actuators, pipe fittings, flanges, and pipe hangers.

Chemical Composition Requirements of MSS SP 75

ElementsValue, %
Carbon (C)≤0.30
Manganese (Mn)≤1.60
Phosphorus (P)≤0.035
Sulfur (S)≤0.035
Copper (Cu)≤0.50
Nickel (Ni)≤0.50
Silicon (Si)≤0.50
Chromium (Cr)≤0.25
Molybdenum (Mo)≤0.13
Vanadium (V)≤0.13
Columbium (Cb)≤0.10
*1. The sum of Cu, Ni, Cr and Mo shall not exceed 1%.
*2. Carbon equivalent C.E.=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 shall not exceed 0.45%.

Mechanical properties of MSS SP 75 Pipe Fittings

MSS SP 75 ClassYield StrengthTensile StrengthElongationCharpy Test
Min. psiMin. psimin. %Ave. Energy absorbed @ 20°F

Material, Welding & Manufacture

The raw material of MSS SP 75 pipe fittings shall be fully killed steels made by either open hearth, basic oxygen, or electric furnace process. It consists of blooms, billets, slabs, forging quality bar, plate, seamless or fusion-welded pipes. The welding processes shall be conducted in accordance with Section IX of ASME Boiler and Pressure Vessel Code, or related ASTM & API specifications. Post-weld heat treatment shall be taken in accordance with the requirements of Section VIII, Division 1 of ASME Boiler and Pressure Vessel Code. The welding ends (bevels) of the fitting shall be furnished differently in terms of wall thickness.The MSS SP 75 WPHY pipe fittings may be readily manufactured by forging, hammering, pressing, piercing, rolling, extruding, upsetting, welding, or by a combination of these processes. Finished products shall be free of injurious defect or welding-repair. Machining and grinding of surface defects may be required by some clients.

Heat Treatment

Pipe fittings manufactured to MSS SP 75 shall be furnished in the heat treated condition. Hot formed fittings shall be cooled below the lower critical temperature prior to heat treatment. Fittings shall be heat treated by one or more of the following procedures: annealing (stress relieving), normalizing, normalizing and tempering, quenching and tempering.

Tests and Examinations

The tests and examinations available for WPHY fittings includes hydrostatic test(proof test), tensile tests, PMI(spectrum), Charpy test, radiographic examination(X-Rays, RT), magnetic particles inspection(MPI), ultrasonic examination(UT), Liquid Penetration Examination(LPE), etc.

Dimensions and Tolerances

MSS SP 75 only specifies the dimensions and tolerances for pipe fittings sized from NPS 16 (DN 400) through NPS 60 (DN 1500). Dimensional requirements for NPS 14 and smaller are provided by reference to ASME B 16.9.