Design Considerations for Piping Systems with Expansion Joints

Expansion joints or Expansion bellows are mechanical devices. They are used in the piping systems to absorb thermal expansion or terminal mobility. Expansion joints are used where the use of expansion loops is undesirable or impractical. They are available in different shapes and a variety of materials.

Different types of Metal Expansion Joints include,

  • Simple expansion joints
  • Universal expansion joints
  • Inline pressure balanced expansion joints
  • Hinged expansion joints
  • Gimbal expansion joints
  • Elbow pressure balanced metal expansion joints
  • Axial expansion joints
  • Lateral expansion joints
  • Pressure switch metal bellows



Let's have a look at the expansion joints applications in different situations:

  • When the space limitations do not permit adequate flexibility by traditional methods such as expansion loops to maintain the system stresses within standard limits.
  • When expansion loops create undesirable process conditions like excessive pressure drop.
  • When it is impractical to limit the piping induced loads on the terminal nozzles of the connected equipment within acceptable limits by conventional methods.
  • When the equipment such as Compressors, Turbines, Pumps and more necessitate separating the mechanical vibrations from being transmitted to the connected piping system.

Some Considerations for Designing Piping Systems with Expansion Bellow

  • Consider recommendations made by the Expansion Joint Manufacturer Association (EJMA) Standard. These Standards combine the expertise and experience of the association's Technical Committee. It assists users, designers, and others in selecting and applying expansion joints for safe and reliable piping and vessel installation.
  • Choose the type of expansion below depending on the magnitude of the connected piping's thermal movement. Consider the configuration of the piping profile concerning the joints' location.
  • Practice caution for piping systems operating under cyclic loading conditions due to the temperature cycle. Consider mentioning the total number of processes predicted during the system's design life in the Bellow specification for the vendor to confirm fatigue life expectancy.
  • The expansion bellow is not subject to torsional rotation.
  • The expansion joint's hydraulic test pressure shall be 1.5 times the design pressure and 1.1 times pneumatic test pressure.
  • Specify the minimum, maximum & installation temperature precisely. Consider an appropriate pre-compression of the bellow and define accordingly if ambient temperatures vary significantly during pipeline construction.
  • Consider specifying Insulation Guard Sleeve in case of insulated bellows.

Conclusion

The good practice is to provide a sketch of the piping system with all supports and other design data as part of the expansion Bellow specification. It establishes a clear understanding of the bellow manufacturer. A complete solution that enables quick and accurate analysis of the piping system is using the CAESAR II Pipe Stress Analysis software.