Steel pipe coupling is a very short length of tube used in piping or plumbing, it usually refers to the socket weld or a threaded on one or both ends that allows two tubes connected together.
Socket Weld Full Coupling
Threaded Full Coupling
Normally there are carbon steel coupling and stainless steel 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).
For stainless steel coupling material standard is ASTM A182, grades in 304/L or 316/L
As we mentioned above there are:
Socket weld coupling
One end in socket weld another end in threaded
And for all of these types for different applications, the are ranges:
Full Coupling: Joint two pipe or joint pipe to a nipple. (Threaded full coupling is same shape but just ends in threaded)
Half Coupling: Joint one end anther end will be welded directly to the run pipe.
Reducing Coupling:Joint different diameter of pipes.
In case of the threaded coupling, the coupling ends normally in female of NPT (National Pipe Threads) or in male and female BSP (British Standard Pipe Threads). Where in North American term, a coupler is a double female while a nipple is double male.
So there are several variation types:
Coupling has one end threads in NPT another end in BSP, then an adapter shall be used during installation.
Coupling has one end in socket weld, another end in threaded socket.
One end in bigger NPT another in smaller dia NPT. (Also called reducing coupling or reducer coupling)
There are two manufacturing methods: Forging and Casting
Forging process: Raw material as steel ingot or a round bar, heating and forging. After that do threading or not as required. (Applied for carbon, alloy and stainless steel material)
Casing process: Melting the steel ingot and pouring it into a fixed mode and cooling it. (Applied for cast iron material)
Material in carbon steel under standard ASTM A105 or Stainless steel ASTM A182:
Dimensions Range (ASME B16.11): Up to 4 inch.
Pressure Ratings: 3000#, 6000#, 9000#
Connection Types: Socket Weld, Threaded
Material in carbon steel under standard API 5CT Casing and Tubing Coupling:
Sizes: Up to 20 inch.
Connection Threads: BTC, EUE, NUE, Premium