The four tie rod screws (or bolted tie rods) on the expansion joint (also known as the compensator) serve two main functions:
Shipping Protection：
During the transportation and installation of the expansion joint, tie rod screws are used to maintain the shape of the expansion joint, preventing the bellows from mechanical damage during transportation or cracking of the weld due to shock. They can limit excessive expansion or compression of the bellows, ensuring that the expansion joint remains in good condition when it arrives at the installation site.
Installation and adjustment：
When installed, these tie rods can be used to adjust the length of the expansion joint, ensuring that it is properly aligned and connected into the ductwork. Once the expansion joint is installed in place, some or all of the tie rods may be loosened or removed depending on the specific design requirements so that the expansion joint is free to perform a compensating action.
However, some tie rods on expansion joints are permanent, such as large tie rods of transverse type expansion joints, these tie rods are load-bearing pieces and cannot be removed, they are used to support the stability of the expansion joint in lateral displacement, providing additional support.
During installation, the method of adjusting the tie rod screw is usually carried out according to the designed compensation amount of the expansion joint. If the expansion joint has an adjustable tie rod, then after installation, the tension degree of the tie rod should be appropriately adjusted according to the working conditions of the pipeline system and the specification manual of the expansion joint, so as to ensure that the expansion energy saving can expand and contract freely within a predetermined range, while avoiding excessive stretching or compression.
It is important to note that some types of tie rods need to be completely removed after installation, while others need to be adjusted to a preset tension state. Specific operation should follow the manufacturer's guidance and relevant industry standards. In some cases, tie rods will be painted with a specific color (such as yellow) indicating that these tie rods should be removed after installation is complete.