January 29, 2016

Understanding the basics of oil analysis

by fluidlife in Fluid Insights, Oil Analysis


Just like a person, industrial equipment tends to perform better the better shape it is in, and as such tends to last longer. As individuals we go to see a doctor regularly for checkups, and sometimes doctors will request blood tests as a diagnostic tool to determine the health of your body.

Reliability personnel are essentially “Component Doctors”, as they are charged with maintaining equipment health using any available tools they may have. As lubricating oil is essentially the blood of industrial equipment, oil analysis can be used as a diagnostic tool to determine the health of the component and/or system.


There are many different condition monitoring techniques, each with their own benefits and areas of specialty.

  • Thermography is useful when looking for hot spots
  • Ultrasonic detection can be used to inspect bearings and gearboxes, detect leaks in vacuums/chillers/pipes, and identify arcing in electrical systems
  • Vibration analysis can be used to detect misalignment in rotating equipment
  • Oil Analysis can be used to determine the condition of the lubricating oil, as well as provide insight into the equipment condition

No one form of condition monitoring is enough to accurately predict all failure modes.


Oil Analysis can provide valuable information about the component/system being tested, such as the viscosity of the oil in use, the cleanliness of the oil in use, the presence of internal or external contamination (water/ fuel/ coolant).

With proper sampling techniques, reliability personnel analyzing the sample results should be able to answer the following questions:

  1. Is the correct oil being used in this system?
  2. Is the oil in use meeting specified cleanliness levels?
  3. Is the oil in use providing sufficient lubrication to the component?

As is the case in most testing regimes, a single sample’s test results are not usually sufficient to diagnose the health of a component. Multiple samples are required in order to establish a trend of test results.

Trending based on the test results of multiple oil analysis samples can provide the following information:

  1. Increasing or decreasing trends in viscosity may indicate oil oxidation or breakdown, as well as cross-contamination between connected systems.
  2. Increasing or decreasing trends in additive levels may indicate additive depletion, or cross-contamination between connected systems.
  3. Increasing trends of particle counts may indicate external contamination ingress due to failed seals and/or breathers.
  4. Increasing trends of wear metal concentrations may indicate imminent component failure.
  5. The presence of fuel or glycol may indicate a fuel or coolant leak.
  6. The presence of water may indicate external ingress due to failed seals/breathers, internal generation due to condensation, or failure to reach proper operating temperatures.

Knowing the condition of the lubricating oil in a system can allow reliability personnel to adequately schedule maintenance in order to manage and extend component life.