History has shown that within the fleet of reciprocating compressors numerous catastrophic failures result in significant losses. Although adequate machinery protection systems are available, they are not always in place or applied correctly to mitigate catastrophic failures.

API 670 5th Edition Machinery Protection includes an informative annex aimed to define the key components of reciprocating compressor protection and condition monitoring systems. A crucial aspect was to include crosshead guide acceleration in addition to the frame vibration shutdown recommend by API 618 5th edition.  While these industry standards recommend monitoring and protection points they do not fully explain how the transducers should be monitored.

Numerous case studies with several different failure modes identify that appropriate frequency filter setting has major impact on the machinery protection systems ability to function as needed when critical conditions arise.  Additionally, the application of RMS based analysis instead of peak analysis is also discussed.

This article discusses the most important aspects to consider when implementing machinery protection systems using crosshead acceleration and frame velocity on reciprocating compressors – specifically:

  • API670 5th edition – Requirements and the Frequency Filter Setting Challenge
  • Signal analysis consideration – Filter Setting / RMS / Peak
  • Crosshead acceleration – Why – Where applied – Effective analysis approach
  • Frame velocity – Why – Where applied – Effective analysis approach
  • Conclusion

Knowledge surrounding proper low pass filter settings for acquisition systems performing critical shutdown function is very limited and often misapplied. This paper illustrates why the common practice of setting low pass signal filters at 2 kHz introduces risk that serious failure modes go undetected compromising plant safety, health and the environment.

This whitepaper was published in the Hydrocarbon Engineering magazine (edition August 2017) and is available for download.