One of the main causes of damages and failures in industrial plants is the vibrations of related equipment; reciprocating compressors are particularly subject to vibration-related phenomena due to the operating nature of its moving part: alternating forces and pressure pulsations are in fact direct and inevitable consequences of their behaviour.
Particular care must be paid, during the design stage, regarding the interaction between the compressor and the plant as a whole to avoid that vibration problems may also arise after a machine has been installed.
The paper will describe a case that occurred in a polyethylene plant, where high piping vibrations resulted in ruptures, welding failures and hazardous gas leakages.
After a detailed root cause analysis of the failures, new more effective supports were studied and the exact positioning of the supports was decided, based on the results of a dynamic forced-response FEM analysis. The vibration measurements were used to locate the problems but also to tune the model, and subsequently to identify the key points where a stiffer structure could have been more effective. Consequently, many of the existing supports were reinforced and additional supports were added, with high damping fabric pads between the supports and the piping, in order to further reduce the impact of the vibration. Finally, also the cooler structure and foundations were reinforced.