Expansion Joints With Tie Rods

How Tied Expansion Joints are properly used to Reduce Main Anchor Loads

A single bellows type expansion joint will exert a pressure thrust force on the main anchors of a pipe system equal to the internal pressure times the effective area of the bellows. The spring force to compress the bellows is additive to the-pressure thrust force.

A tied expansion joint has tie rods that cross the bellows. The tie rods are designed to take the full pressure thrust of the bellows.

Tied expansion joints can be used to reduce main anchor loads by eliminating pressure thrust forces for applications in which there is NO AXIAL COMPRESSION.

If a tied expansion joint is compressed axially, the tie rod nuts no longer contact the lugs. Therefore, all of the pressure thrust force is imposed upon the main anchors.

Tied expansion joints can be designed to move axially. However, in this case, tie rods only serve the purpose of limiting the movement of the bellows in the event of a failure of a main anchor.