Forged socket weld and threaded fittings are ordered by pressure class, not by pipe schedule alone – and the two are easy to mix up. A quotation that lists “3000# elbow” without the end connection, size range or matching pipe wall can come back with the wrong fitting. This guide sets out what belongs in a forged fitting enquiry.
Classes in ASME B16.11
| End connection | Pressure classes | Typical pipe wall match |
|---|---|---|
| Socket weld | Class 3000, 6000, 9000 | Class 3000 – Sch 80; Class 6000 – Sch 160; Class 9000 – XXS |
| Threaded | Class 2000, 3000, 6000 | Class 2000 – Sch 80; Class 3000 – Sch 160; Class 6000 – XXS |
The pipe-wall correlation above is the general guide used in ASME B16.11 for selecting a class; the actual pressure rating of the joint depends on the pipe, the material and the design code. Note that the same class number means a different wall match for socket weld and threaded fittings.
What a Forged Fitting Line Item Needs
- Fitting type: 90° or 45° elbow, tee, cross, full or half coupling, union, cap, plug, bushing, boss or swage nipple.
- End connection: socket weld or threaded; for threads, the thread form (for example NPT to ASME B1.20.1).
- Nominal size – B16.11 covers 1/8" to 4" NPS.
- Pressure class from the table above, matched to the line class.
- Material: for example ASTM A105, A350 LF2, A182 F316L or A182 F11.
- Documents: EN 10204 3.1 or 3.2 certificates.
Common Mistakes
- Quoting a threaded fitting in Class 9000 – B16.11 threaded fittings stop at Class 6000.
- Matching a Class 3000 threaded fitting to Sch 80 pipe, when the general correlation is Sch 160.
- Leaving out the thread type, so NPT and BSP fittings are confused.
- Ordering sizes above 4" as forged fittings when the line class calls for buttweld fittings.
Related: carbon steel forged fittings, butt weld vs socket weld vs threaded and the fitting RFQ guide.
Frequently Asked Questions
What is the difference between Class 3000 and Class 6000 forged fittings?
They are pressure classes in ASME B16.11 with different wall thicknesses. For socket weld fittings, Class 3000 is generally matched to Sch 80 pipe and Class 6000 to Sch 160 pipe.
Are threaded fittings available in Class 9000?
No. Under ASME B16.11, threaded fittings are made in Class 2000, 3000 and 6000; Class 9000 applies to socket weld fittings.
What sizes do forged fittings cover?
ASME B16.11 covers nominal sizes from 1/8" to 4" NPS. Larger lines normally use buttweld fittings.
