Early Failure Detection
Automatic early failure detection and shutdown of a critical compressor caused by crosshead fracture
A Prognost customer in Germany operates four, fourcylinder reciprocating compressors at a natural gas production facility in Northern Germany. This case study describes the detection of critical damage in the crosshead with a subsequent safety shutdown to avoid consequential damage. Different parameters such as crosshead slide vibration and piston rod position are monitored for the detection of the failure and shutdown of the compressor. This article describes the development of the failure and its detection, as well as the root cause of the failure in the demanding H2S environment.
Introduction
Over the last few years, more and more operators of piston compressors use specific monitoring systems particular for their reciprocating machines that implement an automatic machine shutdown function to prevent catastrophic machine failures. The current trend is moving away from simply placing a velocity vibration sensor on the frame of critical machines. In fact, having safety shutdown criteria on the basis of measured acceleration values directly at the crosshead slide is much more effective to me a sure the dynamic piston rod motion continuously. Specifically, this kind of safety monitoring is possible, since modern and fast data acquisition systems are available. Furthermore, the method of automatic data interpretation plays an essential role.
Developing such an analysis to calculate an average value over a specific period and compare it with the appropriate alarm limits is simply not enough. With piston compressors, recognizing and analyzing the individual events over one revolution is important. This, however, carries the responsibility to manage more system limit values. In doing so, the experience on which actual limit-values one adjusts with this modern monitoring system plays a very large and important role.
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