The universal pipe expansion joint consists of two bellows separated by a pipe section or spool. The primary purpose of this arrangement is to have a unit which will accept large amounts of lateral deflection. The amount of lateral deflection they can accept is a function of the amount of angulation each bellows can absorb and the distance between the bellows. For a given bellows element, the amount of lateral deflection capability can be increased or decreased by simply changing the length of the center spool.
Since deflections are usually the result of piping thermal expansion, and universal expansion joints are usually long, the thermal expansion of the entire unit's length is accepted as compression by the two bellows elements. In this way, the overall length of the unit does not change when the piping is heated.

The universal pipe expansion joint consists of two bellows separated by a pipe section or spool. The primary purpose of this arrangement is to have a unit which will accept large amounts of lateral deflection. The amount of lateral deflection they can accept is a function of the amount of angulation each bellows can absorb and the distance between the bellows. For a given bellows element, the amount of lateral deflection capability can be increased or decreased by simply changing the length of the center spool.
Since deflections are usually the result of piping thermal expansion, and universal expansion joints are usually long, the thermal expansion of the entire unit's length is accepted as compression by the two bellows elements. In this way, the overall length of the unit does not change when the piping is heated.