Bellows joint is also called bellows compensator/expansion joint, which proves a kind of elastic compensation device, mainly used to compensate for the thermal expansion and cold contraction displacement caused by the temperature of the pipeline or equipment (sometimes also called thermal displacement).

In the process of operation, there are bellows producing displacement (deformation), in addition to bear a certain working pressure. Therefore, bellow joint is regarded as a kind of pressure elastic compensation device.

Being used as thermal displacement compensation device, expansion joint is often used for vibration isolation and noise reduction.