What Is a Coupling?
A coupling is a pipe connection fitting used to join two pipe ends, or to connect a pipe to a valve, pump or other equipment, quickly and securely. A coupling with a flanged end, known as a flange adapter, allows equipment with flanged connections, such as pumps and hydrophore units, to be connected to a grooved or plain-end pipeline.
Luna Flow Control supplies couplings made of ductile iron (GGG40) with EPDM or NBR sealing gaskets, in nominal sizes DN 40 – 600 and nominal pressures PN 10 – 16, with flanged and threaded connection options.
Working Principle
The coupling housing clamps around the two pipe ends and compresses an elastomer gasket onto the pipe surface, creating a leak-tight joint. The gasket material is selected according to the medium: EPDM is typically used for water and fire protection systems, while NBR is preferred where oil or hydrocarbon resistance is required. Because the joint is mechanical, it can be assembled and disassembled without welding, which simplifies installation and maintenance.
Coupling Types
- Rigid coupling: creates a fixed, rigid joint between well-aligned pipes, providing maximum stability of the connection.
- Flexible coupling: allows limited movement, deflection and misalignment of the pipes, and helps absorb vibration and pressure fluctuations in the system.
- Flange adapter: connects flanged valves, pumps and equipment to the pipeline.
Where Are Couplings Used?
Couplings are practical alternatives to welded joints wherever branches and transitions are required on a pipeline, where flanged equipment has to be connected to grooved pipes, or where a pipeline must be terminated. Typical applications include:
- Fire protection installations
- Liquid lines
- Gas installations
- Oil-free compressed air lines
- Food industry
- Pharmaceutical facilities
- General industrial piping
Advantages
- Fast installation without welding
- Easy disassembly for maintenance and system modifications
- Flexible types tolerate misalignment and reduce stress on the system
- Durable ductile iron (GGG40) body
- A choice of EPDM or NBR seals to suit the medium
- Cost-effective compared with welded connections
Selection Tips
To choose the right coupling, define the pipe diameter and outside dimensions, the operating pressure, the medium and its temperature, and whether a rigid or flexible joint is required. Select EPDM seals for water-based systems and NBR seals for oily media. Informing Luna Flow Control about the intended application before ordering ensures that the most suitable coupling or flange adapter is supplied for your system.
