Pipe Fittings · MSS SP-83
Union — MSS SP-83
Union — a three-piece forged fitting that joins pipes and can be taken apart. Unions let a small-bore line be disconnected for maintenance without cutting. Made to MSS SP-83 in threaded or socket-weld ends.
- MSS SP-83
- 22 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
Union: What to Know Before Ordering
- Three pieces: nut, male and female ends
- Threaded or socket weld
- Class 3000 / 6000
Union Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 union | ASTM B564 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L union | ASTM A182 F904L | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 union | ASTM A182 F304 | General corrosion resistance, food, water and architectural work |
| SS 304L union | ASTM A182 F304L | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S union | ASTM A182 F310 | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L union | ASTM A182 F316L | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 union | ASTM A182 F321 | High-temperature service between 425 and 815 °C |
| SS 347 union | ASTM A182 F347 | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 union | ASTM A182 F51 / F60 | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 union | ASTM A182 F53 | Seawater and high-chloride service where strength also matters |
| Inconel 600 union | ASTM B564 | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 union | ASTM B564 | Seawater, high strength and high temperature in one alloy |
| Inconel 718 union | ASTM B637 | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT union | ASTM B564 | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 union | ASTM B564 | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 union | ASTM B564 | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 union | ASTM B564 | Seawater, hydrofluoric acid and marine service |
| Super Duplex S32760 union | ASTM A182 F55 | Seawater firewater, injection and offshore piping |
| ASTM A106 Gr B union | ASTM A105 | High-temperature process and steam piping in refineries and power plants |
| ASTM A333 Gr 6 union | ASTM A350 LF2 | Cold-climate and refrigerated piping down to −45 °C |
| ASTM A335 P11 union | ASTM A182 F11 | Steam and hot-oil piping up to about 550 °C |
| ASTM A335 P22 union | ASTM A182 F22 | High-pressure steam and hydrogen service up to about 580 °C |
Other pipe fittings
ElbowA fitting that changes the direction of a pipe run.TeeA fitting with a 90° branch that splits or combines flow.ReducerA fitting that joins two pipes of different sizes.CapA fitting that closes the end of a pipe.Stub endA short pipe length with a flared lap that works with a lap joint flange.CrossA four-way fitting with branches at 90°.BendA pipe bend with a larger radius than a standard elbow.LateralA fitting with a 45° branch.CouplingA short forged fitting that joins two pipes.NippleA short length of pipe, threaded or plain, used to connect fittings.PlugA threaded fitting that closes a female connection.
Union — questions buyers ask
Can unions be used in high-pressure lines?
Class 3000 and 6000 unions are rated for high pressure on small bores, but many codes limit their use in hazardous service.
Which grades are unions available in?
Inconel 825, SS 904L, SS 304, SS 304L, SS 310 / 310S, SS 316 / 316L, SS 321, SS 347, Duplex 2205, Super Duplex 2507, Inconel 600, Inconel 625, Inconel 718, Incoloy 800 / 800H / 800HT, Hastelloy C276, Hastelloy C22, Monel 400, Super Duplex S32760, ASTM A106 Gr B, ASTM A333 Gr 6, ASTM A335 P11, ASTM A335 P22.
Which standard covers union dimensions?
MSS SP-83. The material standard depends on the grade.
India · Gulf · South-East Asia · South America · Europe · USA · UKSend your union requirement today.
Start RFQ