Definition
Coupling — A coupling is a short internally threaded sleeve used to join two lengths of externally threaded casing or tubing (a threaded-and-coupled connection), providing the box-box link between two pin ends of pipe.
Also known as: coupling, collar, threaded coupling, T&C
What a coupling is
A coupling is the threaded sleeve that connects two joints of casing or tubing. In a threaded-and-coupled (T&C) system each pipe joint has external (pin) threads on both ends, and a short coupling — internally threaded on both ends (box-box) — is screwed onto one end at the mill. On the rig, the exposed pin of the next joint threads into the open end of the coupling, joining the two.
This differs from drill pipe, which uses integral welded tool joints. Couplings are standard on API 5CT casing and tubing and may be API round or buttress thread, or a proprietary premium thread for gas-tight service.
Key points
- Box-box sleeve — connects two pin ends of pipe.
- Thread forms — API 8-round, buttress, or premium; premium adds a metal-to-metal seal.
- Make-up — power tongs make up the coupling to the recommended torque or position.
Renting coupled tubulars
Coupled tubing and casing accessories are common intervention and completion rentals. Explore workstring tubing and casing accessories, or contact us to match coupling and thread type to your string.