A LDPE company from the US avoided costs of 250 Million for line cleanings, labor and lost production. They made use of deep diagnostics by the PROGNOST®-NT online condition monitoring system. Both monitored machines a Hyper and secondary compressor (commissioned 1976) are equipped with a online condition monitoring system. In 2005, the customer decided to replace the existing monitoring system by PROGNOST®-NT online condition monitoring technology.

Old monitoring system

The old system monitored process pressures and temperatures, lube oil pressures and temperatures, main bearing temperature, plunger proximity (x/y). In 2002, the customer added impact monitors to the system.

Both machines have a failure history which begins with main and connecting rod bearing failures (resulted in crankshaft damage). Also there where main crosshead and auxiliary drive yoke slipper failures, and last but not least discharge valve spring failures.

Some of these failures resulted in very expensive line cleaning procedures.

Change of condition monitoring strategy

In 2005, the PROGNOST®-NT was installed. Existing measuring loops have been integrated and additional loops where added. This resulted in the following configuration: Crosshead vibration, Cylinder vibration, Plunger temperatures (sliding contact TC’s), Integration of plunger proximity probes, Integration of main bearing temperatures, and Integration of relevant DCS process values.

First results with new online condition monitoring system

Vibration signature
Vibration signature comparison: Normal (Blue) vs Abnormal (Red): The defective discharge valve (red) opens too early and the intact valve (blue) opens accurately

Within the first months, several damages occurred and where precisely detected by the early failure module of the system.

  • April 4, Discharge Valve Failure, machine 2
  • June 1, Discharge Valve Failure, machine 2
  • July 5, Discharge Valve Failure, machine 1
  • July 7, Discharge Valve Failure, machine 2
  • Aug 22, Discharge Valve Failure, machine 2
  • Sep 4, Packing Failure, machine 1
  • Sep 5, Discharge Valve Failure, machine 2
Default Thresholds
Default factory thresholds (yellow, orange) detected the failing valve
3D Valve Spring broken
Discharge Valve Failure on Sep 5 – clearly visible change in 3D waterfall plot indicating the changing signal

Benefits and Conclusion

PROGNOST Systems supported the customer in the early detection of various valve failures within the first six weeks of online condition monitoring system run time. This allowed early intervention before more serious valve damages run into catastrophic failures and send valve pieces downstream. All in all 250 M dollars comparable to two line cleanings (plus labor and lost production) have been saved in this startup phase of the monitoring system.

The cylinder vibration data collected and analyzed by and with the online condition monitoring system PROGNOST®-NT stopped the guesswork in diagnosing, and is illustrated by the collected data.