The central component of each expansion joint is the metal bellows that, due to its shape and thin wall, acts like a spring.
According to their physical properties, most metals expand with increasing temperatures and contract with decreasing temperatures.
In pipeline systems, this phenomena causes a variation in the length of the individual sections of the pipeline.
As pipelines are normally anchored at least on two connection points, any variation in length will result in thermal strain in the material and enhanced forces and moments at these terminal points.
As far as possible, one will utilize the inherent flexibility of a pipeline to compensate the pipe expansion (natural compensation).
Should the expansion, however, exceed the inherent flexibility of the pipe, expansion joints are necessary to compensate these movements.
Additionally, mechanical vibrations of pumps, compressors, turbines and motors should be dampened to avoid any damage to adjoining pipelines, their supports or any installed instruments.
Forces and moments on nozzles of compressors, turbines, vessels and other plant components are limited and must not be exceeded.
In all these cases, expansion joints can be utilized.