Compressor Varnish Case Study

Varnished compressor journal bearing before and after-ESP

An operational co-compressor with 1600 litre capacity reported varnish on the titled-pad bearing and the gear system during maintenance.

Prior to ESP Installation

  • High bearing temperatures were recorded between 120 and 140°C
  • Initially using the OEM’s oil, the oil was degrading very quickly (RPVOT drop, A.N. increase)
  • Average oil life-time between 4-6 months (prior to ESP)

The chart below shows MPC (varnish potential) test results over a period of 500 days following ESP installation.

Compressor MPC varnish potential case study


  • Oil MPC varnish potential reduced from “critical” to “normal” quickly in just 15 days
  • After consecutive increases in MPC test results, the ESP filter element was changed on day 215
  • By day 234, MPC varnish potential result of 9.81 achieved = “Normal”
  • After consecutive increasing MPC test results, ESP filter element was changed on day 460
  • By day 492, MPC varnish potential result of 11.2 achieved = “Normal”

ESP filtration and oil additives

Over the same 500 day period following ESP installation, antioxidant oil additive (Amine) oil analysis was conducted by RULER to determine the oils remaining useful life. It can be seen that while ESP filters out the varnish causing contaminants (rapid drop in MPC value), oil additives are not removed. Amine additives deplete at a steady rate as would be expected under normal operation as they are consumed when combating oxidation. After 354 days, two drums of new oil were added to the compressor which increased the remaining useful life of the oil (RULER %).

Antioxidant Additive (Amine) RULER results case study

Results of ESP136 installation

  • High bearing temperature issues eliminated
  • Oil has lasted 16+ months and counting
  • Images (top of page) of journal bearing varnish removal evidence before and after ESP installation