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Oil, Coolant and Fuel Contamination


It doesn’t matter if it came from outside the equipment, was generated inside the equipment or if it worked its way into the oil from another system in the machine, contamination is any substance that isn’t supposed to be in the fluid being tested.

Most people think of contamination as something working its way into the equipment from the outside. Water and many types of particles, like dirt, sneak in through cracks, broken seals or unprotected ports, but in equipment with physical and chemical reaction occurring inside of it, foreign substances are only part of what we consider “contamination”.

Some contaminates are created during equipment operations. Soot is a natural byproduct of diesel combustion and commonly works its way into the engine oil, which is why the oil is formulated with additives to deal with soot. Lubricant additives are designed to protect components and prolong oil life; however they can become contaminants when heat, pressure or a chemical reaction causes them to fall out of suspension.

Fluids from other systems can be contaminants, such as coolant and fuel mixing with engine oil. All three systems need to operate in conjunction with the others, and leaks happen. Small holes and cracks between the oil and cooling systems could leak fluid one-way, so testing both fluids is recommended to catch leaks early. Over-fueling or worn cylinder rings can lead to fuel entering crankcase oil. Either way, cross-contamination from other systems is a sign of a mechanical problem that needs to be fixed before it escalates into a breakdown.

The type of equipment and application will determine what contamination could affect it and what tests to perform. The Contamination Flagging Limits technical bulletin has more information on how POLARIS Laboratories® determines the severity of contamination.

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How We Set Flagging Limits


In the Data Analysis department, one of our key responsibilities is to answer any questions customers have about fluid analysis. A lot of our calls are about what results mean. Does the fluid need to be changed? What could be causing that strange noise? We also get questions asking for testing recommendations for a specific application or issue being seen. However, the hardest questions to answer are about our flagging limits. The only easy answer for these questions is: “It’s complicated…”

Our process for defining flagging limits is actually something that we are quite proud of. It can be difficult to provide our limits because they are very dynamic and specific to the information provided about the equipment, fluid, and application. For example, one engine in your fleet may have different flagging limits than another because our limits are customized based on the specific equipment manufacturers and models. Limits are also affected by the rate of change from prior samples. Individual severities may change based on other results that are flagged. These are just a few scenarios that affect limits, but I think you can begin to understand some of the complexities surrounding our limits.

We’d like to clear up some of the confusion by publishing a series of articles to address the more common questions surrounding flagging and alarm limits. What aspects of your report flagging have you been curious about? Post your questions in the comments section of this blog so we have an opportunity to reply and use your questions to guide the topics of our articles.

Proven Impact. Proven Uptime. Proven Savings.
Let us prove it to you.