Valve bellows expansion joints (bellows, compensators, expansion joints, expansion joints) is mainly used to connect the valve shaft bellows expansion joints to shape the course of deformation and displacement due to thermal expansion and contraction caused by other reasons, leaving the valve inadequate missing features, performance and other aspects of weakening. Compensation to all aspects of the model, such as how to understand in the course: 1, before installation first check their models, specifications and piping configuration, must meet two originals of all activities related to compensator design requirements, external member can not be stuck or limit its scope of activities, we must ensure the normal operation of the various moving parts, so that it can operate normally work