Cyclic or Fatigue Life of Metal Bellows Expansion Joints

The bellows cycle life or Bellows Fatigue Life is defined as the total number of complete cycles which can be expected from the expansion joint based on data tabulated from tests performed at room temperature. A bellows cycles can be defined as one complete movement of an expansion joint from initial position to the extreme position and return to initial position. The bellows fatigue life or bellows cycle life is affected by the following design factors.

  • Operating Pressure.
  • Operating Temperature.
  • Bellows Material.
  • Thickness of bellows and number of piles/layers.
  • The movement per convolution.
  • Pitch depth and shape of convolutions.
  • Heat Treatment of Bellows.


Cyclic Life Testing Under Pressurized Condition as per EJMA Guidelines.

The chart shown below gives the relation between bellows design variables and the performance parameters for the same bellow material. On prototype bellows we can carry out bellows cycle life test to verify the results as per the E.J.M.A Standard design.