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The trouble with the varnish



A “peaking station” at a large power plant with a 3,700-gallon capacity GE frame size 6 gas-powered turbine had problems with varnish caused by moisture contamination building up in the turbine lubricants while running at sump temperatures reaching 140°F.

The moisture and varnish that accumulate in the lubricating fluid causes the following problems: reduced heat transfer; sticking valves, and equipment failure.

In order to keep the varnish under control, this power plant would perform regular testing of oil samples and change the oil often. The initial sample showed the varnish potential rating was at 66 per the Quantitative Spetrophotometric Analysis, used by Analysts, Inc. The level of varnish is found to be high due to oil degradation with the .45 micron filter patch visually showing some darkening.


In order to see if the Harvard Filtration System® could help, the power plant conducted a 30-day test. A Harvard system was added to the turbine oil sump which ran continuously for four weeks without interrupting operation of the turbine.

After four weeks a new sample of oil was taken to evaluate the effectiveness of the filter. The sample was measured at the same lab with the same process as the “before” sample. This sample measured 24 on the varnish potential rating, in the normal range. The .45 micron filter patch showed very little visually.


Varnish was removed quickly and efficiently using one filter set in 30 days, restoring the existing oil to the normal range. The Harvard Filtration System was installed without any downtime to the turbine operation. Removal of varnish contamination will extend the service life of the oil and keep the equipment operating at high levels of cleanliness while increasing efficiency and reducing downtime. The cost to clean and maintain the oil was less than 20% of the cost of changing the oil in the system.


  • Without Harvard Filters
    • Oil change every 8 years
    • 3,700
    • gallons x $6 per gallon = $22,200
    • Clean-up of varnish build-up requires 2 days of downtime, cleaning chemicals and flushing. The cost of this clean-up is $60,000 to $80,000
  • With Harvard Filters
    • Oil change every 12 to 18 years
    • Initial cost of Harvard Filtration System = $12,890
    • Annual cost of replacement filters and electricity = $2,000 / year
    • Cleaning and flushing not required
    • Total Savings over 8 years = ($22,200 +
    • $60,000) – ($12,890 + $2,000 x 8 years) = $49,310
    • Total Savings over 16 years = ($44,400 +
    • $120,000) – ($12,890 + $2,000 x 16 years) = $119,510
    • Downtime cost was not even factored in!


Varnish caused by moisture contamination can be costly in terms of maintenance and downtime. Maintaining oil cleanliness with a Harvard Filtration System is far more efficient than changing oil and cleaning/flushing. Keeping the oil clean keeps the machinery operating at peak performance and eliminates downtime. Costly cleaning is not required. The cost to clean and maintain the oil was less than 20% of the cost of changing the oil in the system