Fluid Analysis Saves Time and Money

My first encounter with fluid analysis was as a young sea cadet. One summer I was fortunate enough to spend a few weeks aboard a U.S. Navy destroyer.
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My first encounter with fluid analysis was as a young sea cadet. One summer I was fortunate enough to spend a few weeks aboard a U.S. Navy destroyer.
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My first encounter with fluid analysis was as a young sea cadet. One summer I was fortunate enough to spend a few weeks aboard a U.S. Navy destroyer. It was a sign of the times I suppose. As a 14-year-old, I was given virtual free reign of the nearly 600-foot fighting vessel, from the “nixie” torpedo decoy gear aft to the anti-submarine rocket launchers forward. The ship was new and undergoing sea trials, which included speed runs, hard-over turns, and even firing of the 5-inch guns. It was great fun and educational, too.

One day, while walking down a passageway I poked my head into a small cubby of a compartment. Inside, neatly stacked on shelf after shelf, were scores of clear glass vials that contained liquids of different hues, from brown and black to red and purple. As I was scanning this strange scene I was startled by a voice from behind me. “Those are samples of all the fluids from the ship’s gear,” said a young petty officer.

Over the course of the next half hour or so he explained the science of fluid analysis, called tribology, and how it helped the ship remain ready to fight and ply the oceans, and how it saved the Navy money by identifying when machinery needed to be serviced or repaired before it actually failed. Despite my being a budding gearhead even then, I’m sure much of what he said went over my head. Many years later my interest in tribology would be rekindled.


As it turns out, my introduction to the world of fluid analysis aboard a Navy vessel was fitting. Fluid analysis has been effectively used for more than a half century, ushered in with the jet age, and specifically, with carrier-born aircraft whose first-generation turbines’ lubrication systems were especially sensitive to water, salt, and metallic debris.


Today, the science of tribology, or the analysis of friction of machinery components and their fluids, which include crankcase oil, transmission fluid, and coolant and hydraulic fluid, is well established in the mechanical world.

During my tenure as a boatyard manager I instituted a comprehensive fluid analysis program. Instead of relying on a mechanic’s or my own intuition or anecdotal experience, I wanted something that was more scientific. I wanted something my customers and I could use to evaluate the condition of equipment when it malfunctioned, and just as importantly, when it appeared to be working well. I wanted to be able to carry out condition-based maintenance, and I wanted to predict failures and prevent them rather than react to them after they occurred. Tribology is the means by which this goal is achieved, providing hard data that could be used to make important maintenance, repair, and replacement decisions.


The return on investment where fluid analysis is concerned can be substantial indeed. Analyzing a few ounces of crankcase oil, for instance, can yield reams of information about the current health of an engine and how it’s been maintained throughout its life. For instance, sodium, when found in an engine’s lubricating oil, may be indicative of ingestion of salt-laden mist (this can happen if spray is ingested into an engine room air intake) while glycol contamination often spells trouble in the area of the cylinder head gasket. Wear metals such as iron, chrome, nickel, copper, lead, tin, and aluminum each tell a different story about a component within the engine, from pistons and rings to bearings and valves.

Contaminant metals such as silicon, sodium, and potassium tell a different story as they are introduced from outside sources such as dust, seawater, and coolant. The quantity of metal in a sample, measured in parts per million, when compared to the number of hours accrued by the sample oil, determine whether there is cause for concern. Still other contaminants, such as fuel and soot, and imbalances such as acidity and viscosity, can indicate malfunctioning fuel injection systems, use of the incorrect stock oil, or simply oil that is old and worn out.

Fluid detective work doesn’t end with crankcase oil. Transmission fluid and coolant are also fertile ground for this sort of testing. Transmission fluid analysis can often detect issues with bearings, clutches, shift mechanism adjustment, damaged gears, or overheating. Many transmissions include some type of cooler; however, if it’s not working properly, oil can overheat and lose some of its lubricating properties. An improperly adjusted shift cable can cause the same problem. Coolant includes additives that inhibit rust and corrosion as well as control pH; however, over time these become depleted. Common wisdom dictates that cooling systems be flushed and coolant replaced every two years, however, that’s likely very conservative. An analysis of the coolant can stave off this service if it’s unnecessary, often paying for itself.


As valuable as fluid analysis is, it isn’t perfect, and in the hands of an inexperienced or tribologist wannabe, misinterpretation is all too easy. For example, a client recently contacted me, distraught over the results of a transmission-fluid analysis. The report showed very high levels of copper—so high that the analysis lab had flagged them in red. After exchanging a few emails with the transmission manufacturer, however, I determined that the clutches are sintered copper alloy and therefore these high copper readings were not abnormal. The lesson here is the value of the amount of data a lab has accumulated on an engine, transmission, or other type of equipment is important when it comes to alerting the user to potential trouble.

Yet another area where analysis often goes awry involves a sample-taking technique. If, for example, a vacuum pump and hose are used to draw a sample and the latter’s intake is dragged across the bottom of an oil pan in the process, it is likely to show elevated wear metal, material that has accumulated over the course of hundreds or thousands of hours. It is for this reason that many commercial users rely on valves rather than vacuum pumps and tubes when drawing crankcase oil samples. The valve delivers oil as it’s circulating through the engine, offering the most accurate representation of its condition.

Practicing fluid analysis isn’t a cure all for your machinery’s ailments; it doesn’t take the place of proper maintenance. One thing, however, is certain: You can’t benefit from its attributes if you don’t take samples and have them analyzed. The average cost of analysis is approximately $25 per sample, a small price to pay for having yet another preventive maintenance arrow in your quiver.