No Contamination, No Wear, No Kidding

Tags: contamination control

I realize that this statement - No Contamination, No Wear, No Kidding -  may not sit well with some readers, such as a few purists within the tribology community. But before anyone gets too excited, let me start by listing my assumptions:

  1. The machine is well designed, manufactured and installed.
  2. It is used in the target application within rated operating parameters (loads, speeds, etc.).
  3. The lubricant is properly selected and produces an oil film (EHL or HDL).
  4. Lubricant levels and change intervals are properly maintained.
  5. Oil analysis and other condition monitoring practices are performed to best practice.

We all know contamination comes in many chemical, physical and radiological states. These forms include invasions such as solids, water, heat, antifreeze, soot, fuel and air. Some contaminants may be electrical while others are microbial. Some may be chemically inert while others are catalytic. Some are dissolved while others are free or colloidal. And some may be benign while others aggressive and destructive.

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Evil Lurks… As Does Opportunity
Many lubricants seem to be continuously "possessed" by evil-seeking contaminants. Perhaps they need an exorcism. When contaminants invade a lubricant they either alter the good qualities of the lubricant, or they become a hazardous agent by transporting the contaminants into sensitive zones deep within the machine. Keeping a lubricant in a pristine, uninfected state is typically not a real-world possibility. Instead, best practice tends to address the degree of cleanliness or dryness and the rate of ingression.

One reason for this is the often disproportionate relationship between contaminant level and destruction (wear). For instance, if a lubricant's clearance-size particle concentration doubles, there's a good chance that the resulting machine wear rate will not double. Instead, the wear rate may increase three to six times, depending on the circumstances. From a maintenance perspective, we need to think in reverse. Reducing the concentration of dirt by 50 percent may increase the expected machine service life manyfold.

Lower the Volume, Please
Contaminant levels in machines are like wear-rate control knobs. Imagine the volume control on a stereo console. You rotate the knob clockwise and the wear rate runs up fast. Turn it in the opposite direction, and the wear fades. However, unlike the volume-control knob that gives you immediate audio feedback, the contaminant wear-rate knob is almost stealth-like, similar to an inaudible high-pitched whistle. Our senses cannot immediately detect the damage that is occurring. Instead, feedback is found in one of two forms: changing wear debris concentration (predictive maintenance) or machine failure (breakdown maintenance).

Many of us are familiar with another tactic known as proactive maintenance. This tactic is not about monitoring symptoms (wear debris) or reacting to failure, but rather the vigilant eradication of root causes. The operative word here is "control", like the control knob. Maintenance and reliability activities should focus on factors that are controllable, ignoring all else.

For instance, many of the conditions on my list of assumptions are not within the practical realm of control of machine maintainers. What is not controllable by maintenance activities may instead be controllable by machine designers, manufacturers or purchasing agents. Asset owners exercise control by being selective when purchasing machines and accessorizing those machines for contamination control and lubrication excellence. Buying cheap machines that are stripped to the bones (no filters, breathers, sampling ports, instrumentation, sight glasses, etc.) is equivalent to being party to the very hazards caused by contamination.

As a practical matter, it is nearly impossible to test my premise stated in the title of my column. There are always exceptions, few absolutes and we know rules are made to be broken. Therefore, we can allow ourselves to be distracted by dogma and debate, or we can get busy and get lubricant contamination in check.