The compressor was monitored online using vibration and SPM LR/HR HD shock pulse measurement. Interestingly, the LR/HR readings did not show increasing shock pulse levels while this machine fault was developing, nor did the Vel Rms values reach the configured alert levels. A different approach was needed to capture this particular failure mode. A closer look at the vibration readings revealed a significant increase in the Kurtosis levels, indicating that this was a more suitable parameter to monitor in this case. Thus, an alert on the Kurtosis level was added to the system to help prevent future compressor breakdowns. Furthermore, the case study also demonstrates how viewing the time signal in a circular plot is useful to determine the running condition of reciprocating compressors.

During maintenance of the failed compressor, carbon residue was found on the piston rod, confirming the theory that high Kurtosis levels can indicate the rubbing of residues.