An expansion joint (also known as a compensator) is a device used to absorb thermal expansion and contraction, vibration, or other motion in a piping system. Expansion joint tie rod (or limit rod, guide rod) is mainly used for the following two purposes:
Protection during shipping and installation：
During transportation and installation, the tie rod is used to prevent excessive displacement of the expansion joint without restraint, avoiding damage to the bellows.
They are typically designed to be adjustable in order to adjust the preload or length of the expansion joint as needed.
Positioning after installation：
In some cases, the tie rod remains in place after installation and is used to limit the range of displacement of the expansion joint, ensuring that the expansion joint only moves in the direction and range the design allows.
These tie rods typically do not completely prevent the displacement of the expansion joint, but rather limit it beyond safety limits.
Conditioning method：
For pre-installation adjustments, the tie rod is usually pre-set at an appropriate length that allows the expansion joint to remain stable during transport and initial installation. When the expansion joint is in place and ready for final connection, the tie rod may require further adjustment to ensure that the expansion joint is in the correct position.
If the expansion joint requires axial compensation, then the tie rod may need to be adjusted according to field conditions and temperature change predictions to provide proper pre-compression or pre-tension.
For laterally or angularly compensated expansion joints, the tie rod may be set at a specific tension to control the lateral or angular displacement of the expansion joint.
Notes：
The manufacturer's instructions should be followed when adjusting the tie rod, as different expansion joint types and applications may have different requirements.
After final adjustment of the tie rod, if the tie rod is intended for transportation and installation only, it should be removed or loosened as directed by the manufacturer to allow the expansion joint to expand or contract freely.
If the tie rods are functioning in operation, ensure that they do not hinder the normal displacement of the expansion joint.
When adjusting the tie rod, it may be necessary to use a wrench or other tool to twist the nut or bolt on the tie rod to achieve the correct tension or length. In any case, ensure that all operations comply with safety specifications and manufacturer's recommendations. If you are not sure how to adjust it correctly, it is best to consult a professional or the manufacturer of the expansion joint.