A typical expansion joint is comprised of one or more metal bellows (most commonly stainless steel) or from materials such as rubber, fabric or plastic such as PTFE. Expansion joints are considered as very important components of a complete pipe system and are widely used particularly in industries where thermal expansion in pipe systems occur. Expansion joints also offer the advantage of reducing stresses in pipe systems generated by thermal expansion and reduce pipe loads at connections to sensitive equipment such as pumps and steam turbines. Taken together this acts to prolong the service life of pipe systems and reduces the risk of their downtime for additional maintenance and repair. Expansion joints are routinely incorporated into piping systems, as expansion joints add flexibility into the design and reduce costs through removing the complexity of fixpoints, guides and reduce the overall space requirements for the pipe system. Expansion joints are more effective than alternatives such as pipe bends and pipe loops due to their greater ability to conserve space, their economic efficiency and better performance in absorbing larger movements.
Expansion joints are employed in piping systems to absorb different thermal expansion while containing the system pressure. They are successfully utilized in refineries, chemical plants, fossil, and nuclear systems, heating and cooling systems, and cryogenic plants. Any pipe connecting two points is subject to numerous types of action which result in stresses on the pipe.
Some of the causes of these stresses are:
Internal or external pressure at working temperature
Weight of the pipe itself and the parts supported
Movement imposed on the pipe sections by external restraints
The stress on the wall of piping is related to the force or movement exerted on it by external resistance and the flexibility of the pipe itself. When either the value of the stresses or the value of the external forces on movements exceeds the maximum allowable value, the flexibility of the pipe must be increased artificially. This can be done either by altering the layout of the pipe by inserting high flexibility sections. This is precisely the function of expansion joints.
Expansion Joints are mainly used in Pipelines to Offset Vibrations or Movements from Equipment, Thermal Movements or any other movements in the line. Basic movements could be Axial, Angular or Lateral and Joints are available in Rubber and Metal based on the medium.