Industrial bellows are either used as seals or connectors. When used as seals, bellows are required to protect reciprocating mechanisms, keeping them free from contamination by their environment. When used as a connector, a bellows function is to contain substances passing between fixing points it connects. In this mode, the bellow can also be designed to take up vibration, thermal expansion, and some misalignment in the system.
An expansion joint bellows is designed with a variable number of convolutions. These convolutions are dependent upon the amount of dimensional change and movement that the bellows must accommodate. These convolutions function to make sure that the system has adequate strength to endure the pressures and temperatures that will be characteristic of it. Bellows can be supplied in various materials including Neoprene, Rubber, Polyurethane, and Silicone. Bellows are sometimes called compensators, flexible connectors, seals, protective covers, etc.