Plug — ASME B16.11
Plug — a threaded fitting that closes a female connection. Hex-head, square-head and round-head plugs close threaded outlets, drains and vents. Made to ASME B16.11.
- ASME B16.11
- 22 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is a plug?
A plug is a threaded fitting that closes a female connection. Hex-head, square-head and round-head plugs close threaded outlets, drains and vents. Made to ASME B16.11.
Plug: What to Know Before Ordering
- Hex, square and round head
- NPT threads
- Forged from bar
Plug Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 plug | ASTM B564 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L plug | ASTM A182 F904L | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 plug | ASTM A182 F304 | General corrosion resistance, food, water and architectural work |
| SS 304L plug | ASTM A182 F304L | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S plug | ASTM A182 F310 | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L plug | ASTM A182 F316L | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 plug | ASTM A182 F321 | High-temperature service between 425 and 815 °C |
| SS 347 plug | ASTM A182 F347 | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 plug | ASTM A182 F51 / F60 | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 plug | ASTM A182 F53 | Seawater and high-chloride service where strength also matters |
| Inconel 600 plug | ASTM B564 | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 plug | ASTM B564 | Seawater, high strength and high temperature in one alloy |
| Inconel 718 plug | a specification not yet established | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT plug | ASTM B564 | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 plug | ASTM B462 / B564 | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 plug | ASTM B462 / B564 | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 plug | ASTM B564 | Seawater, hydrofluoric acid and marine service |
| Super Duplex S32760 plug | ASTM A182 F55 | Seawater firewater, injection and offshore piping |
| ASTM A106 Gr B plug | ASTM A105 | High-temperature process and steam piping in refineries and power plants |
| ASTM A333 Gr 6 plug | ASTM A350 LF2 | Cold-climate and refrigerated piping down to −45 °C |
| ASTM A335 P11 plug | ASTM A182 F11 | Steam and hot-oil piping up to about 550 °C |
| ASTM A335 P22 plug | ASTM A182 F22 | High-pressure steam and hydrogen service up to about 580 °C |
Other pipe fittings
Plug — questions buyers ask
What is a plug?
A plug is a threaded fitting that closes a female connection. Hex-head, square-head and round-head plugs close threaded outlets, drains and vents. Made to ASME B16.11.
Which plug head type should I use?
Hex-head plugs are easiest to tighten with a spanner; square-head suits older equipment; round-head is used where the plug should not be removed.
Which grades are plugs 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 plug dimensions?
ASME B16.11. The material standard depends on the grade.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026