ASME B16.11 is the standard for forged fittings, socket-welding and threaded, in sizes from NPS ⅛" to NPS 4". It covers pressure-temperature ratings, dimensions, tolerances, marking and material requirements for elbows, tees, crosses, couplings, caps, plugs, bushings and similar fittings forged from carbon, alloy and stainless steel and nickel alloys, and it is the standard named for small-bore fittings in almost every process piping specification.
Raaj Fittings forges and machines ASME B16.11 fittings in-house at our two plants in India in all classes, from Class 2000 threaded to Class 9000 socket weld, and supplies them to refineries, petrochemical and power plants, fabricators and stockists across the Middle East, Europe and the Americas.
Related small-bore items have their own MSS standards: reducer inserts (MSS SP-79), unions (MSS SP-83), swage nipples and bull plugs (MSS SP-95) and branch outlet fittings such as weldolets and sockolets (MSS SP-97). We supply all of these alongside B16.11 fittings.
ASME B16.11 does not tabulate pressures. Each class is matched to a pipe wall thickness, and the fitting is rated the same as straight seamless pipe of equivalent material in that wall:
| Class designation | End connection | Matching pipe |
|---|---|---|
| 2000 | Threaded | SCH 80 / XS |
| 3000 | Threaded | SCH 160 |
| 3000 | Socket weld | SCH 80 / XS |
| 6000 | Threaded | XXS |
| 6000 | Socket weld | SCH 160 |
| 9000 | Socket weld | XXS |
Because threads remove metal, a threaded fitting needs a heavier body than a socket weld fitting for the same pipe, which is why the threaded class is one step lower for the same schedule.
B16.11 fittings are made from forgings, bars, seamless tubular products or rolled shapes to the ASTM / ASME forging and bar specifications, such as A105, A350, A182 and the nickel alloy B-specifications. Each fitting is marked with the manufacturer's name or trademark, the material identification, the class designation and the size. B16.11 does not require hydrostatic testing of each fitting; designs are proven by calculation or proof test. Our fittings also carry the heat number and are supplied with EN 10204 3.1 certificates.
Use socket weld fittings for permanent, leak-tight process lines, and threaded fittings where welding is not possible or joints must be broken for maintenance, within the limits of your piping code. Above about 2", buttweld fittings to ASME B16.9 are normally used.
ASME B16.11 covers forged socket weld and threaded fittings from NPS ⅛" to 4". Class 9000 socket weld fittings are covered from ½" to 2".
They are class designations linked to pipe wall thickness, not pressures. For example, Class 3000 socket weld fittings match SCH 80 pipe and Class 3000 threaded fittings match SCH 160 pipe; the fitting is rated the same as that pipe.
No. Unions are covered by MSS SP-83, swage nipples and bull plugs by MSS SP-95, reducer inserts by MSS SP-79 and branch outlets by MSS SP-97. We supply all of them.
ASME B16.11 specifies NPT taper pipe threads to ASME B1.20.1. BSPT or BSPP threads to BS 21 / ISO 7-1 can be supplied on request for equipment that uses British threads.
B16.11 does not require each fitting to be hydrostatically tested; the design is proven by calculation or proof testing. Testing of individual fittings can be added to an order where a project specification requires it.