Machinery Lubrication

Machinery Lubrication March April 2018

Machinery Lubrication magazine published by Noria Corporation

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Page 21 of 86

ML Cellulose Depth Filters vs. Pleated Filters You may have heard that an oil filter made of cellulose is not as good as a filter made of glass fiber. If you are referring to pleated filter elements, then it is correct that a thin filter material of cellulose is not optimal. Water and particles will wear on the thin sheets, which will break over time. Caterpillar recommends an in-line pressure filter made of cellulose be used for a maximum of 500 hours with diesel engine lube oil. However, do not be misled into thinking that all cellulose depth filters are the same. Some depth filters incorporate a completely different design and do not wear over time. ese filters use strong, specialized cellulose fibers for strength and improved filter effi- ciency, especially for the retention of very small particles. en again, are extremely small particles (0.2 to 4 microns) important when particle counting most often looks at particles that are 4 microns and larger, e.g., 4, 6 and 14 microns? Consider the dynamic oil film thickness in gears, roller bearings and servo valves. ey are all less than 3 microns. is is why off-line depth filters have been chosen for more than 80,000 heavily loaded wind turbine gearboxes running dynamic oil film thicknesses below 1 micron. When it comes to the retention of particles smaller than 6 microns, cellulose depth filters have excellent performance. ey also have a high dirt-holding capacity for submicron particles and can maintain their capture effi- ciency even when loaded with particles. us, cellulose depth filters release few small particles under stress and pressure bursts. In addition, many of these filters can absorb water from oil, and some types can even remove varnish. High base number values and a lower acid number can be maintained if special cellulose blends are used to reduce acidity, oxidation byprod- ucts and submicron particles. Installing an off-line cellulose depth filter can often result in longer oil service life, some- times by as much as three to five times. For example, Volvo engines on mobile mining equipment are now running 1,500 hours instead of requiring 250-hour oil change intervals. e oil analysis results have also never looked better. In conclusion, used oil and filters carry a lot of information about your oil and machine components. Although it may not seem easy to interpret this information at first, there are a number of tools available to do so. Remember, all oil filters are not created equal and cannot be tested using the same standards. Keeping your oil clean, cool and dry is the most efficient way to reduce the operating and maintenance costs associated with downtime, component wear and oil replacement. ML Submicron particles adhere to the surfaces and crevices on special cellulose fibers. The graph above shows the particle distribution sizes in medium test dust (blue) vs. real wear particles in oil (orange).

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