What is Coupling in Piping?
What is Coupling in Piping?
It is a fitting used to make branch connections, known as a coupling. They are primarily for connecting small-bore screwed and socket-weld pipe to large-bore pipe headers.
Besides, the coupling is also used extensively where instrument connections are required.
About Coupling in Piping?
Couplings may be threaded, socket welded, or, for larger bore piping, of the Mechanical joint variety.
There are two common methods used to make branch connections with couplings
- The coupling rests on the external surface of the pipe header and is welded from the outside.
- A hole is bored into the pipe header large enough to accept the OD of the coupling. The coupling is inserted into the hole and is then welded.
Features of Coupling
- Ends: Both ends are female, threaded or socket-type
- Standards: ASME B16.11 (for forged fittings), ISO, DIN
- Materials: Carbon Steel, Stainless Steel, Alloy Steel, PVC, etc.
- Pressure Ratings: Available in different classes such as 3000#, 6000#, and 9000#
Different Types of Coupling
There are two main types of Coupling
- Full Coupling
- Half Coupling
Full Coupling
- A full coupling is a small pipe fitting that connects two pipes of the same diameter.
- It has threaded ends or socket weld ends.
- It ensures a tight, leak-proof junction when connecting pipes or to a nipple.
Half Coupling
- Half-couplings are used to provide a female threaded branch connection by welding the unthreaded end to the adjoining pipe.
- This may be done in-line (coaxially) with a socket weld half-coupling, or it may be done by fillet welding the half-coupling to the OD of the header pipe.
- For critical applications, a reinforced branch connection fitting is preferred.