The movements which are to be absorbed by an expansion joint must be specified. There may be more than one movement condition (i.e. installation misalignment, wind motion, seismic motion, etc…). Each condition must be specified to properly design the bellows element.

Bellows elements are typically required to absorb one or more of the following motions:

Axial motion is motion that occurs parallel to the centerline of the bellows element. This type of motion is generally expressed as compression, a shortening of the bellows element, or extension, elongation of the bellows element.

Lateral motion is motion which occurs perpindicular to the centerline of the bellows element. It is possible for the bellows to absorb lateral deflection that occurs along two axes simulataneously, for example, if the bellows element centerline is along the "X" axis, the bellows can absorb displacement occurring in both the Y and Z displacements.

Angular motion is the rotation, or bending, of a bellows element along its centerline. Like lateral motion, bellows elements can absorb angular rotation about the two axes perpindicular to the bellows centerline. Click on the link below to see a visual depiction of angular movement.