Expansion joint tie rods play several key roles in the pipeline system. Their roles mainly include:
Shipping Protection： The tie rod acts as a support during transportation and storage of the expansion joint, preventing the bellows from being squeezed or bumped, protecting the shape and structural integrity of the bellows.
Preloading and positioning： When installed, the tie rod can help adjust the position of the expansion joint, ensuring that the expansion joint is in the correct pre-tension state in the piping system to achieve the proper amount of compensation. This usually involves adjusting the degree of tightening of the tie rod according to the amount of compensation designed.
Limit action： The tie rod can limit the displacement range of the expansion joint, prevent overextension or compression, and avoid damage to the bellows. In some designs, the tie rod acts as a limiting device, ensuring that the expansion joint can only work within a safe displacement range.
Withstand internal pressure thrust： Especially in the transverse expansion joint of large tie rod, the tie rod not only limits the position, but also helps to offset the thrust generated by the internal pressure of the pipeline and reduce the load on the pipeline support and fixed point.
Adjustment and calibration： During installation, the tie rod can calibrate the expansion joint by elasticity adjustment to ensure its correct position in the system, and at the same time, the preload state of the expansion joint can be fine-tuned during commissioning and early operation.
Prevent blind plate force： In some cases, tie rods can prevent blind plate forces (i.e., unintended lateral forces) in the piping system from acting on the expansion joint, avoiding twisting or damage to the bellows.
Security measures： In special cases, such as when the main fixation bracket fails, the tie rod can act as a safety mechanism to prevent excessive displacement of the expansion joint, thus avoiding larger system failures.
The way the tie rod is used and handled varies depending on the type of expansion joint. For example, in general-purpose expansion joints, the transport tie rods can be removed or loosened after installation, whereas in large-tie transverse expansion joints, the tie rods are non-removable and must remain fixed throughout the entire system operating cycle. Therefore, it is important to properly understand and follow the manufacturer's guidance regarding tie rods when installing and maintaining expansion joints.