When designing a piping system that undergoes significant thermal movement, choosing the right type of flexible support is a critical decision. The debate often centers on variable spring hangers versus constant force hangers. While both serve to support the weight of the pipe, they operate on very different mechanical principles.
What are Variable Spring Hangers? A variable spring hanger uses a helical coil spring to support the pipe load. As the pipe moves vertically due to thermal expansion, the spring compresses or extends. This change in length causes the supporting force to "vary." According to industry standards (like MSS SP-58), the load variation should generally not exceed 25%.
What are Constant Force Hangers? A constant force hanger is designed to provide a uniform supporting force throughout its entire travel range. Through a sophisticated counterbalancing mechanism involving springs and lever arms, the load remains "constant" regardless of the pipe's vertical position.
5 Key Differences to Consider:
Load Consistency: Constant hangers offer 0% load variation, whereas variable hangers change force based on movement.
Travel Range: Constant hangers are preferred for large vertical movements (typically over 50mm) where load variation in a variable spring would be too high.
Mechanical Complexity: Constant hangers are more complex and larger in size compared to the relatively simple design of variable springs.
Criticality of Application: Constant supports are used for high-temperature, high-pressure systems near sensitive equipment like turbines or boilers to prevent stress transfer.
Cost and Maintenance: Variable springs are generally more cost-effective for systems with minimal vertical travel.
When to Choose Constant Force Hangers? If your piping system is connected to sensitive strain-limited equipment or if the calculated load variation of a variable spring exceeds 25%, a constant force hanger is mandatory. This ensures that the weight of the pipe does not shift onto the equipment nozzles, which could cause mechanical failure or leaks.
Conclusion: Selecting between these two supports depends on your specific piping stress analysis. CN-Pipesupport provides a wide range of both variable and constant supports tailored to meet your project's technical specifications.
References:
CN-Pipesupport Technical Manual: Spring Hanger Selection Guide.
Pipe Support Engineering Standards.
