Lube oil in compression chamber

NEA horizontal reciprocating compressor

Machine data

  • NEA (Neumann Esser) horizontal reciprocating compressor
  • 4 throws, 1 stage in Natural gas service
  • Inlet pressure: 33 bar (479 psi) / Outlet pressure: 75 bar (1088 psi)
NEA horizontal reciprocating compressor

Installed monitoring software modules

  • Machine Protection
  • Early Failure Detection
  • Wear Monitoring
  • Performance Optimization
  • Process Data Integration

Sequence of events

PROGNOST Systems received a call from the customer with the information that the compressor, shortly after start up, was shut down by the PROGNOST system due to protection limit violations on two measuring points. The shutdown was triggered by increased vibrations at the crosshead guides 3 and 4. Affected were segment 20 of crosshead slide (CHS) 3 and segment 19 of the CHS 4.

Vibration plots of two the affected crosshead slides three seconds prior shutdown

Root cause analyses

  • Since there were only high vibrations in the area of the Bottom Dead Center (BDC), the possible cause for the shutdown was lube oil from the packing in the crankend compression chamber.
  • A second attempt to start up the compressor again resulted in a emergency stop. Again, the shutdown was due to two limit violations.
  • It was decided to open the compressor.

Findings

After consultation with the customer it turned out that a lube oil accumulation in the compression chamber on the crank side was the cause for the shutdowns. The reason for this accumulation was very a too long lead time of the lubricating oil pump before compressor start up.

Lessons learnt

  • Liquids in the compression chamber are detectable with PROGNOST
  • This real life case underlines the necessity to properly monitor vibrations at the dead centern (TDC and BDC).
  • It´s an undeniable fact that larger amiunts of uncompressable liquids cause massive and costly damages.