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To those who are beginning the quest for knowledge in oil analysis and machinery lubrication, learning and comprehending terms, concepts and facts that seem like a foreign language can be a major obstacle. As an instructor, I'm always looking for new ways to introduce real-world analogies to help people understand these underlying concepts.
How to properly set and use particle count limits to effectively meet reliability objectives is a concept often misunderstood. Oil analysis users submit samples for particle count analysis each month; unfortunately, many have little idea what targets they should be aiming toward, and how to effectively use them. For a better understanding, consider fluid cleanliness in terms of driving a vehicle.
From the first lesson, drivers are taught that each road, be it a highway or suburban road, has a posted speed limit. Typically that limit is set by either the state or municipality to achieve a reliability objective: ensure drivers can get from point A to point B without compromising the safety of the themselves, passengers, fellow motorists, cyclists and pedestrians. Factored in to these decisions are critical issues such as vision and sight lines, road curvature and the presence of pedestrians (particularly around schools).
In this analogy, the posted speed limit is equivalent to a target cleanliness level: a limit that will not be exceeded if reliability objectives are being met. Often, particularly when it involves hydraulic components, OEMs provide guidelines on the optimum target levels in the same way the appropriate municipal or state authorities provide the maximum safe (and legal) speed. But is this enough?
Proceed with Caution
Consider the posted speed limit for a highway. While on a bright sunny day, it may be safe to drive at (or slightly above) the posted limit. But consider driving the same highway at night, in a snow storm. Under these conditions, a careful driver will adjust to an acceptable speed to match the prevailing conditions. The same holds true for lubricant cleanliness: whenever an adverse condition is present such as high load, high speed, dirty working environment, etc., limits should be stricter to reflect the challenging condition. When faced with the inability to meet a target goal, oil analysis users are tempted to increase the limit, stating "I know the oil should be cleaner but that target cannot be achieved because of X." This is analogous to stating the speed limit should be increased on a steep downward hill; after all, it's hard to stay within the posted limited without extreme braking. Limits - whether they are speed limits or target cleanliness levels, are there for a reason - to ensure reliability objectives are met.
Now consider the role of oil analysis. While most drivers see speed limits as a necessary evil, deep down, they realize they are set for a reason. But on a day-to-day basis, the goal is to stay within the limit - or a "safe" margin slightly over - to avoid a costly speeding ticket. So here's how it works.
Motorists drive along observing the posted limit. Upon seeing a speed limit sign, the immediate reaction is to check the speedometer to make sure the speed is within the limit to avoid a speeding ticket! Particle counting is similar to checking the speedometer. It is a sanity check against the posted limit. Just like the brakes should be applied if the car is going too fast for the posted limit, any deviation above the posted target cleanliness level should invoke a reaction; whether it be to check the condition of the breather, filter, seals, etc., or to consider changes to the machine to help achieve the objective.
Fluid cleanliness is really no different than driving: they both require a clear understanding of the target, an ability to validate the target is being met, and a mechanism to take correct action when a deviation is observed.
So drive safe, always obey the posted signs and make sure the oil analysis date counts!
As always, this is my opinion. I'm interested in hearing yours.