A bellow expansion joint contains one or more metallic bellows with connectors on either ends and tie rods whose design depends on the purpose for which the joint in being used. These metallic expansion joints are broadly classified into three types on the basis of their movement:
1. Axial Expansion Joint: This bellow joint is used in pipelines and places where the expansion due to intense temperature takes place in a straight line. The distance between the two fixed points is measured and this is used to define the axial movement that the joint needs to gain to absorb the heat and temperature. The rules for using an axial bellow joint are as follows:
– When a pipeline has been divided into many straight sections with fixed points.
– When the fixed points have been designed in such a way that they can withstand the pressure and vibrations that are caused by these bellow joints.
– When pipe guides have been used in between the fixed pipes in long pipes to make sure that they do not kink.
– An axial bellow joint should always be installed near the fixed point and the pipe guide.
2. Angular Expansion Joints: Piping systems which are two or three hinged systems are the ones which use angular expansion joints. In case of a three hinged single plane piping system, only one angular expansion joint is required but in case of a three hinged multi plane piping system, two angular expansion joints might be required. Here are the rules on the basis of which angular bellow joints can be used in a piping system:
– When there is more than one 90 degree redirection in the pipeline.
– Since angular bellow joints are capable of absorbing the pressure and force released by the bellows, the fixed points should be designed in such a way that they can compensate the resultant force and torque which is caused by the friction of the pipe guides.
– When the piping system covers more than one plane.
3. Lateral Bellow Joints: Lateral bellow joints are mainly used in pipelines which have 90 degree redirections in single and multiple plane piping system. These are generally put up at the points where the pipe line is redirected at right angles. These joints are far more effective in absorbing heat and pressure than the axial bellow joints. The rules that should be followed when using lateral bellow expansion joints are:
– These joints should always be arranged at right angle to the pipeline.
– Fixed points get relieved of handling any kind of undue stress as these joints are capable of absorbing all the pressure and heat.