Lubricant Water Contamination
by David Doyle, CLS, OMA I, OMA II
Vice President, Americas

Water contamination exists in several forms:

Dissolved Water – All oil has some amount of dissolved water within normal levels. The oil appears bright and clear and is difficult to separate without special processes.

Free Water – Large drops that readily settle out and collects at the bottom of the fluid level.

Suspended – Water droplets that are held in suspension, giving the product a hazy appearance. The water is not chemically bonded to the oil and may drop out in time or can be removed by filtration.

Emulsified Water – Very small droplets dispersed in oil. The water held in suspense will give the oil a milky appearance and is difficult to drop out due to either additives or contaminants, which are attracted to both the oil and water. This allows the two liquids to attach to each other and become chemically bonded.

The amount of water a system can tolerate before problems arise depends on system design and application, environment and lubricant formulation. In general, the best practice is to maintain the lowest level practical within maximum permissible levels. Various sources can contribute to water or moisture contamination. When excessive water contamination is noted the source and entry point should be determined to prevent the need for future corrective action. Water contamination sources can be System Internal (In-Operation) or External (Ingressed or Induced).

Internal water contamination sources can be the result of leaking heat exchangers and coolers or poor reservoir maintenance.

External water contamination sources can result from several influences:

  • Wet work environments
  • Normal condensation
  • Poorly functioning seals
  • Poorly operating breathers
  • Poorly sealed fill caps
  • Insufficient flushing after maintenance
  • Poor new oil storage practices

Excessive water contamination is a very destructive contaminant. Some product formulations are engineered to shed water readily, such as paper machine oils, hydraulic and turbine oils, either due to wet environments or because they are required for clean/dry applications. Research indicates that a very small amount of water reduces bearing life. Bearings, especially in clean systems such as turbine systems, are recommended a maximum of 0.02% (200ppm) water contamination. A bearing lubricated with oil that has 1000 ppm water has one quarter the life of a bearing where the oil only has 100 ppm water

If the water is emulsified the oil viscosity may go up (like mayonnaise). Tiny amounts of detergent from oil additives, due to product mixing, can contaminate industrial oils, causing water to emulsify and chemically bond in the oil. Free water with oil can become suspended when passing through a pump. The action of the pump will shear the water into smaller droplets which will be carried within the oil throughout the system. These droplets can eventually drop out and settle on internal components, causing corrosion.

Serious equipment life and reliability problems will arise if excessive water contamination is not addressed.

  • Premature failure or excessive wear due to reduced lubricating ability (lubricity)
  • Rusting of ferrous components and corrosion of bearings or other machine elements
  • Premature filter plugging
  • Premature oxidation of lubricant
  • Depletion of oil additives
  • Viscosity increase

Removal of excess water contamination can be approached by:

  • Filtration; coalescesing or water absorbent filters
  • Vacuum dehydration with heat
  • Reservoir cleanup and maintenance
  • Centrifuge
  • Gravity Settling

The best approach to managing water contamination is to set maximum contamination levels for equipment health and reliability and monitor through routine oil analysis. When water content increases, internal and external sources should be determined; including maintenance and new lubricant storage practices.