September 9, 2020

What is contamination?

by fluidlife in Fluid Insights, Oil Analysis

According to Merriam-Webster, to contaminate is “to make unfit for use by the introduction of unwholesome or undesirable elements”. If left undetected, contamination of lubricating oils and fluids can lead to damage, machinery failure, and unplanned downtime of important equipment and machine assets.

How is contamination created?

For equipment oils, lubricants and other fluids, contamination can be introduced in any of the following ways:

  • External Contamination or Ingestion:
    • Airborne contaminants
    • Contamination caused by adding oil
    • Contamination by adding grease
    • Water ingress
    • Air entrapment
  • Self-Generated Contamination:
    • Metallic wear caused by abrasion, adhesion, fatigue, and erosion
    • Seal abrasion
    • Chemical corrosion
    • Oxidation residue
  • Chemical Contamination or Chemically Generated:
    • Mixing of lubricants
    • Additives
    • Oil-insoluble substance caused by mixing oil or greases.
  •  Built-in / Break-in Contamination:
    • Foundry sand, dust.
      • Manufacturing residue:
      • Welding residue
      • Metals swarf (turnings, filings, shavings, etc…)
      • Blasting material, lacquer/paint particles
      • Preservation material
      • New parts install
    • Residue from cleaning agents (rag fibers).
    • New part installation or equipment repair/overhauls.

Note that new equipment or new oils are not necessarily clean.  Before first operation, new equipment can have contaminants introduced from the assembly process (e.g. metal shavings or sand from castings). New oil can be 8 to 16 times more contaminated than OEM recommended cleanliness levels for an operating fluid.  Because of this, doing routine oil sampling and analysis can detect if contamination levels are improving or becoming more serious over time.

Filtering & Contamination Control

It’s important to remember that it’s not only is the amount of contamination, but also the size of the contaminants that can impact on wear. For example, bearing life can be extended up to 4x with simply filtering particles 10 micron or greater out. Similarly, by reducing water contamination in bearings down to 100ppm, bearing life will increase by 55%.

We can feel particles down to about 40 micron in size, but depending on the dynamic clearances of your equipment this may not be enough. Controlling the abrasive contaminants in the range of 2 to 22 microns in lube oil is generally accepted for controlling engine wear. Inexpensive oil filters can filter down to around 40 microns, while more expensive down to around 20 microns.  

Maximizing Equipment Life

Most failures can be attributed to some form of contamination leading to corrosion; surface deterioration; surface, adhesive, or abrasive wear; or surface fatigue.  Cleanliness and contamination control are the most important aspects of proper lubrication for long equipment life. This is provided we have the right lubricant in place.  Furthermore, the right viscosity and additive package will help maximize oil and equipment life by keeping the right oil clean, cool, and dry.   

Interested in learning more? Contact our team of reliability specialists and find out how we can help you with your lubrication program.