Pipe Coupling & Union

Pipe couplings are highly demanded in the pipe fitting market. Pipe couplings are fittings that help to extend or terminate pipe runs. These fittings are also used to change pipe size. Couplings extend a run by joining two lengths of pipe. They are known as reduced coupling if they are used to connect pipes of different size.

Material Types

Normally there are carbon steel coupling and stainless steel coupling.

Carbon Steel Pipe Coupling

For carbon steel pipe coupling the material standard is ASTM A105, manufacturing standard ASME B16.11. (There are also casing and tubing coupling material in carbon steel, referred API 5CT J55/K55, N80, P110 etc).

​Stainless Steel Pipe Coupling

For stainless steel coupling material standard is ASTM A182, grades in F304/L or 316/L.

Application types

Reducing Coupling

Joint different diameter of pipes.

Half Coupling

Joint one end anther end will be welded directly to the run pipe.

Full Coupling

Joint two pipe or joint pipe to a nipple. (Threaded full coupling is same shape but just ends in threaded)

Differences between Half Coupling vs Full Coupling

A half coupling is only threaded or socket-welded at one end, and the other end can be welded directly into the service pipe to form a branch joint. It is a joint that helps to extend or terminate a pipe.

A full coupling, on the other hand, has a threaded or socket weld at both ends.

Design of threaded coupling ends (NPT or BSP)

In the case of a threaded coupling, the coupling ends are normally female NPT (National Pipe Threads) or male and female BSP (British Standard Pipe Threads). In North American terms, a coupler is a double female while a nipple is a double male.

So there are several variations:
Coupling has one end threaded in NPT, the other end threaded in BSP, then an adapter must be used during installation.
Coupling has one end in socket weld, the other end in threaded socket.
One end in larger NPT, the other in smaller diameter NPT. (Also known as reducing coupling or reducer coupling)

Manufacturing methods for couplings and half-couplings

There are two methods of manufacture: Forging and casting

Forging process: Raw material as steel ingot or round bar, heating and forging. Then threading or not as required. (Applied to carbon, alloy and stainless steel material)

Casing process: Melting the steel ingot and casting it in a fixed mode and cooling. (Applied to cast iron material)

C&N’s product range:

Material in carbon steel according to ASTM A105 standard or stainless steel ASTM A182 grade F304/L and F316/L:
Dimensional range (ASME B16.11): 1/4″, 1/2″, 3/4″, 1″, 1 1/2″, 2″, 3″ and up to 4″.
Coupling types: Full port, half port
Pressure ratings: 3000#, 6000#, 9000#
Connection Types: Socket weld, Threaded (NPT & BSP

Carbon steel material under standard API 5CT body and tube coupling:
Sizes: Up to 20 inches.
Connection Threads: BTC, EUE, NUE, Premium