Piping stress analysis for compressor systems must consider two fundamentally different load types: static thermal and weight loads, and dynamic vibration-induced loads. These are often analyzed separately but they interact in ways that matter for the final design.
Static Loads: Thermal and Weight
Static piping stress analysis per ASME B31.3 evaluates whether the piping system can accommodate thermal expansion from startup to operating temperature without exceeding code allowable stresses. It also checks sustained loads — primarily weight and pressure — against a separate set of allowables.
The output of static analysis is typically a set of support locations and expansion loop requirements that keep static stresses within limits. This analysis is well understood and routinely performed for compressor installations.
Dynamic Loads: Vibration-Induced
Dynamic analysis evaluates the vibration response of the piping system to the forces generated by the compressor. The output is vibration amplitude and dynamic stress range at critical locations, compared to fatigue endurance limits.
The support configuration that optimizes static stress performance is not necessarily the same configuration that optimizes dynamic behavior. A long flexible span that accommodates thermal expansion efficiently may have a natural frequency that coincides with compressor excitation, creating a dynamic problem.
The Interaction
The interaction between static and dynamic design requirements means that both analyses must be performed together, not sequentially. Changes made to satisfy static requirements must be re-evaluated for dynamic impact, and vice versa.
Tech Transfer performs integrated static and dynamic piping analysis, ensuring that the final support and routing configuration satisfies both sets of requirements simultaneously. This is the only approach that reliably produces a piping system that performs correctly in service.
