Tie rods Expansion joints

Features of Tied Design:

  • Simple design, Relatively low cost
  • The universal configuration can be designed with a very low lateral spring rate and high lateral movement capacity
  • Versatile and common throughout all industries
  • Two degrees of movement capability for tied single or universal design
  • Three degrees of movement for two tie rod design
  • Tie rods contain pressure thrust

Benefits of tied design:

  • Pressure thrust is accommodated by hardware, external anchorage is only required for spring forces
  • Can be designed with very low lateral spring rate

The function of tie rods on an Expansion Joints is to continuously restrain the full pressure thrust during normal operation while permitting only lateral deflection. Angular rotation can be accommodated only if two tie rods are used and located 90 degrees opposed to the direction of rotation.

The tied expansion joint (EJ) consists of a bellows element attached to end fittings with threaded rod or bar hardware traversing the bellows element. The tie rods are attached to lugs or rings that limit the length of the EJ. The tie rods and the attachment hardware are designed to contain pressure thrust.

Tied expansion joints are designed to have a fixed overall length. The tie rods are attached in a way that eliminates axial movement and forces the ends of the EJ to remain parallel at all times. This configuration allows for only two degrees of freedom, lateral in two axes.