ASME B16.11
Forged fittings, socket-welding and threaded
Covers forged socket-welding and threaded fittings — elbows, tees, couplings, caps, unions and plugs — in Class 2000, 3000, 6000 and 9000.
- Dimensional standards
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is ASME B16.11?
ASME B16.11 is the standard for forged socket-welding and threaded fittings, NPS ⅛ to NPS 4. Socket-weld fittings are rated Class 3000, 6000 and 9000; threaded fittings Class 2000, 3000 and 6000. The class is matched to the pipe schedule — for example socket-weld Class 3000 with Schedule 80 pipe. Material is ordered separately, usually ASTM A182 for stainless and ASTM A105 for carbon steel.
ASME B16.11 at a glance
| Sizes | NPS ⅛ – 4 |
|---|---|
| Socket weld classes | 3000 · 6000 · 9000 |
| Threaded classes | 2000 · 3000 · 6000 |
| Fittings | Elbows, tees, crosses, couplings, half couplings, caps, plugs, bushings, unions (per MSS SP-83) |
| Material | Not set by B16.11 — e.g. A182, A105, B564 |
ASME B16.11 class vs pipe schedule
Use this to match the fitting class to the pipe wall.
| Pipe schedule | Socket-weld class | Threaded class |
|---|---|---|
| Sch 80 / XS | 3000 | 2000 |
| Sch 160 | 6000 | 3000 |
| XXS | 9000 | 6000 |
How to write ASME B16.11 on a purchase order
Name the product, size, material specification and grade, the dimensional standard and the certificate. An example line:
Illustrative only — sizes, tests, inspection level and any project values come from your purchase specification.
ASME B16.11 edition and verification status
Which edition we have confirmed, and what is still being checked before any numerical requirement is published here.
| Current edition | Not yet confirmed against the publisher listing |
|---|---|
| Full-text verification | In progress — numerical requirements are not published on this page |
| Edition on your order | The edition named in your purchase order or design code governs — confirm it with your enquiry |
What to know before ordering to ASME B16.11
The points that decide whether material to ASME B16.11 is accepted at inspection.
- Socket-weld classes are 3000, 6000 and 9000; threaded classes are 2000, 3000 and 6000.
- Threads are NPT to ASME B1.20.1.
- Used mainly for NPS 2 and smaller.
Products made to ASME B16.11
How ASME B16.11 fits into an order
A purchase order line is only complete when it names the material standard, the dimensional standard and the inspection document. Miss one and the mill, the inspector and the buyer can each read the order differently.
Standards used with ASME B16.11
Same family
ASME B16.11 — questions buyers ask
What is ASME B16.11?
ASME B16.11 is the standard for forged socket-welding and threaded fittings, NPS ⅛ to NPS 4. Socket-weld fittings are rated Class 3000, 6000 and 9000; threaded fittings Class 2000, 3000 and 6000. The class is matched to the pipe schedule — for example socket-weld Class 3000 with Schedule 80 pipe. Material is ordered separately, usually ASTM A182 for stainless and ASTM A105 for carbon steel.
Which class of socket-weld fitting goes with Schedule 80 pipe?
Class 3000. Class 6000 matches Schedule 160 and Class 9000 matches XXS.
Why leave a gap in a socket weld?
About 1.6 mm (1/16") is left between the pipe end and the socket bottom before welding so the weld does not crack as the joint expands.
Is there a Class 2000 socket-weld fitting?
No. Class 2000 exists only for threaded fittings; socket-weld classes are 3000, 6000 and 9000.
Does ASME B16.11 specify the material?
No. ASME B16.11 sets dimensions; the material comes from a separate specification such as ASTM A182, A105 or B564 for flanges, or A403 and B366 for fittings. A complete order names both.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026