A flange coupling is a type of coupling device meant to bring two tube ends together in a flush, sealed manner. This two-piece coupling unit consists of a keyed receiving side for the flanged end to be fastened to, so it may be married to the opposing tube end, which also has a flanged end. Each flange has either a male or female coupler opening so that when the two ends are brought together, they are aligned without causing resistance or drag in the material being passed through them. This male/female coupling method also creates a stable connection that is resistant to shifting, keeping the flange coupling sturdily in place.
Flange couplings are typically used in pressurized piping systems where two pipe or tubing ends have to come together. The connecting methods for flange couplings are usually very strong because of either the pressure of the material or the sometimes hazardous nature of materials passed through many industrial piping systems. High thread count nut-and-bolt connections are used to secure the flange couplings in place. These nuts and bolts are usually made from tempered steel or alloys to provide enduring strength and the ability to be tightened to the utmost level to ensure the piping system doesn’t leak at any flanged junction. Most flange couplings utilize four, six, or up to 12 bolt assemblies.
The flange coupling itself is usually made out of cast iron or manufactured from drop-forged steel. The materials used to make flanged couplings depend directly on the application they may be used in. For smaller scale, low pressure situations, there are composite couplings that provide decent sealing qualities, but lend themselves to chipping or breaking when they are exposed to the elements for an extended period of time.
Even in steel or cast iron flange couplings, the sealing power is created by a rubber or otherwise malleable gasket. This is usually made out of a substance designed for the material being distributed through the piping system. For instance, if the piping system is used to transfer acids from point to point, then the gasket material inside the flange coupling should be acid-resistant.
There are three common types of flange couplings. Unprotected, protected, and marine flange couplings are the most commonly used in industrial or underwater applications. Unprotected means that both the bolts and nuts are exposed for access, while protected flange couplings hide the bolt assemblies inside individual flanges on the coupling. Marine flange couplings look a bit different, with the bolt being of a headless, tapered form.