Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1289708
6 | September - October 2020 | www . machinerylubrication.com locations of all four states of water and oil. At the top you see dissolved water (but not really). Just as water in humid air is invisible to the eye, the same is the case with dissolved water in oil. It is worth noting that all lubricants have dissolved water to some degree. Oil is hygroscopic and as such will draw water directly from humid air above. For instance, if the air has a rela- tive humidity of 80% then a hygroscopic oil in contact with the air will absorb water from it until it is also at 80% rela- tive humidity. At which point the air and the oil are in equilibrium. The Most Destructive State Emulsif ied water-in-oil is the greatest offender in terms of damage to the oil and the machine. Its enormous oil-water interfacial puts it at high risk to incite considerable harm, both phys- ically and chemically. Most serious is the fact that it is mobilized, meaning that it travels unrestricted to the far reaches of the machine including those critically sensitive frictional surfaces. Wherever the oil goes, so goes this aggressive contaminant. As we've said many times in this publication and throughout Noria training courses… get water under control! Recognize it quickly, remove it quickly. Inspection is your first line of defense. Any visual form of water should be of serious concern. Oil analysis is even more revealing. Figure out where it's coming from and stop its ingression into the oil. Different Oils; Different States Know your oils from the standpoint of how water behaves and co-exists with them. Engine oils for instance are loaded with polar additives such as detergents, dispersants, antiwear additives, etc. e free water state is unlikely with engine oil, even if there is 90 percent water. Conversely, emul- sions quickly and tightly form between water and engine oil. Healthy, clean turbine oil is at the other extreme. It rapidly sheds water as there are no polar handles for the water to latch onto to form emulsions. erefore, only free water and dissolved water may exist. As turbine oil ages, you will see water hang in the oil in a direct microemulsion state and/or as an invert-emulsion at the interface. Because of this we are using water as an inspec- tion aid to help us learn more about the health of the oil. When oil-water mixtures are at rest, stratification occurs based on oil density, polarity and Stoke's Law. is is seen hypothetically in the illustration of Figure 2 and the photo images of the oil samples in Figure 3. Violently agitating an oil contaminated with water in a sample bottle and then letting it rest helps us understand more about both the oil and the water (also air release and foaming tendency). Very similar to the blender test for field inspection of oil condition (use our search engine for more information on this method). 35 Things that Aren't Going Wrong Have a good sight glass center-line with your machine's target oil level. Have another one at the sump bottom (BS&W bowl). Let's say that you visually inspect your machine with good light at both locations. All you see is clear and bright oil of the right color. What can you conclude? Well, there are about 35 things that could be going wrong with your oil and machine but you know are not going wrong (see sidebar) due to this simple visual inspection, including the harmful presence of water. Do it! ML About the Author Jim Fitch has a wealth of "in the trenches" experience in lubrication, oil analysis, tribology and machinery failure investigations. Over the past two decades, he has presented hundreds of courses on these subjects. Jim has also published more than 200 technical articles, papers and books. He serves as a U.S. delegate to the ISO tribology and oil analysis working group. Since 2000, he has been the director and a board member of the International Council for Machinery Lubrication. He is the CEO and a co-founder of Noria Corporation. Contact Jim at jfitch@noria.com. Figure 3. Two different samples exhibiting all four states of water and oil. Note the milky white appear- ance of the free water phase in both samples. Many oil impurities transfer to free water including some dead additives. Seeing what's in the water phase can provide supplemental information about other contaminants and the condition of the oil. Pay attention! e band in the middle of both samples is the oil-in-water emulsion. How thick is this band? Does it diffuse or does it have good definition? AS I SEE IT START YOUR FREE SUBSCRIPTION www.machinerylubrication.com