Flexible Couplings BE, EE, BB, BF, FF: How to Tell Them Apart

Flexible couplings are divided into 5 main types: BE, EE, BB, FF and BF. They are used to join pipe to pipe, pipe to valves (usually resilient-seated gate valves), water flow meters or other fittings in water supply and drainage networks.

Key points

• The pipe may be steel, HDPE plastic, cast iron, stainless steel and so on.
• Advantages: easy to remove and refit for replacement, warranty work and maintenance; they also avoid pressure from thermal expansion.
• Made of ductile iron or grey cast iron with an epoxy coating.
• Working pressure of cast iron couplings: 0-16 bar; working temperature: 0~80ºC.

1. BE flexible coupling

The BE coupling (also called the BE flexible joint) is known in English as the Universal Flange Adaptor. One end is a standard BS, JIS or DIN flange and the other end is a cylinder with a gasket having tapered serrations. It is used to connect valves and meters to pipe. The gasket covers a range of sizes, so it can be fitted to HDPE, galvanized, stainless steel and cast iron pipe, among others.

• Body and cover are made of ductile iron or grey cast iron.
• EPDM rubber gasket with tapered serrations.
• Bolts connecting the flange and cover are stainless steel or galvanized steel.
• Epoxy paint coating on both faces with a thickness of >=250µm, so it is safe for clean water.

2. EE flexible coupling

The EE flexible coupling (EE flexible joint) is used to connect pipe to pipe. The pipe may be HDPE, cast iron, steel, stainless steel, uPVC and so on. Its English name is Universal Flexible Coupling Adaptor. It can be used to connect different types of pipe.

• Cylindrical body made of ductile iron or grey cast iron.
• Cover made of ductile iron or grey cast iron.
• Gasket with tapered serrations at both ends.
• Galvanized or stainless steel bolts connect the two covers together.
• Epoxy coating both inside and outside, so it is safe for clean water.

3. BB flexible coupling

The BB flexible coupling (dismantling joint BB) is used to connect two flanged ends and to compensate for the gap between two pipelines.

4. BF flexible coupling

The BF flexible coupling has the same function as the cast iron BE coupling, but differs in that the bolts are not connected directly from the flange to the part that connects to the pipe; they are connected at the end of the pipe section instead, which gives more strength and makes it easier to tighten the pipe and coupling.

5. FF flexible coupling

The FF flexible coupling is similar to the EE coupling, but the bolts only connect the ends to each other, so it is stronger than the cast iron EE coupling. However, it costs more because of the additional bolts and the flanges at both ends.