What Are ASME B16.11 Threaded Fittings?
ASME B16.11 covers forged, threaded-end fittings from NPS 1/8 through NPS 4, in pressure classes Class 2000, Class 3000 and Class 6000. The threads are taper pipe threads NPT per ASME B1.20.1. Threaded fittings are chosen where easy assembly and disassembly without welding is required — small-bore utility, instrumentation and low-pressure piping.
Fitting Types Covered
- 90° / 45° threaded elbows — center-to-end dimensions per ASME B16.11 Table 3
- Threaded tees & crosses — equal and reducing, Table 3
- Full couplings, half-couplings & reducing couplings — Table 5
- Threaded unions — Table 5
- Caps, plugs & bushings — end-to-end caps Table 5; square/round/hex plugs and bushings Table 6
Pressure Classes
| End Type | Pressure Classes | Size Range | Thread |
|---|---|---|---|
| Threaded fittings | Class 2000 / 3000 / 6000 | NPS 1/8 – 4 | NPT per ASME B1.20.1 |
Available combinations by class and NPS are listed in ASME B16.11 Table 7. Class-to-schedule correlation is given in Table 8.
Materials
Forged construction: A105 carbon steel (-29°C to 425°C), A182 F304 / F316 / F321 stainless steel (up to 538°C), A350 LF2 low-temperature forged carbon steel. Chemistry and mechanical properties per the applicable ASTM forging standard.
Related Standards
- ASME B16.11 — Forged Fittings (parent standard)
- ASME B16.11 Socket-Weld Fittings — Classes 3000/6000/9000
- ASME B16.9 — Buttwelding Fittings (NPS 1/2–48)
- ASME B16.5 — Threaded Flanges
- Our Fittings Range
FAQ
What thread standard do B16.11 threaded fittings use?
Taper pipe threads (NPT) per ASME B1.20.1, the standard American taper pipe thread.
What sizes do threaded fittings cover?
NPS 1/8 through NPS 4, in Class 2000, 3000 and 6000. Available size-by-class combinations are in B16.11 Table 7.
Threaded or socket weld — which is better?
Socket weld gives a more leak-tight, higher-pressure joint. Threaded is easier to install and dismantle without welding, and suits lower-pressure service.
What is Class 2000 used for?
Class 2000 is the lower-pressure threaded rating, used in utility, air and water service. Class 3000 and 6000 suit higher pressure.
Can you supply threaded fittings in stainless steel?
Yes — F304, F316 and F321 forged stainless are standard, for corrosive and sanitary-adjacent small-bore lines.
Which tables give the dimensions?
Threaded elbows, tees and crosses: Table 3. Couplings, unions and caps: Table 5. Plugs and bushings: Table 6.
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