Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/957021
18 | March - April 2018 | www . machinerylubrication.com OIL ANALYSIS bubbles release and rise through the oil. Look for surface foam. Oil containing particles, water and varnish will hold entrained air longer and may create foam. If the air rises slowly, have a lab test the air-release properties. Clean oil will release air faster and reduce the foaming tendency. Cool the Oil Warm oil will dissolve varnish and water easily, while the same oil will be hazy and less clear when cold. Place the oil sample in the refrigerator overnight. A powerful light and a white paper with black lines will make it easy to see any difference. Varnish and water will fall out of solution in cold machine areas and result in jerky valve movements, corrosion, etc. Use a Magnet Break off a piece of a used filter element. Iron wear particles are usually magnetic, so if a strong neodymium magnet can lift the material, you have problems with machine wear. You can also hold the magnet to an oil sample bottle to attract iron. Note that iron particles can be black like soot, shiny as silver or amber/brown like varnish/rust. If you can see iron in the oil or on the used filter, have a lab perform a particle quantifier/wear particle concentration test. Inspect the Filter Element Inspect a used filter for shiny particles from metal wear, such as iron or brass. Break up the used filter element to see multi-layer buildup, which should be clean on the back. If not, the filter has not performed as intended. A USB microscope (magnifying 200-400 times) can reveal the color, size and shape of captured particles. Photos of magni- fied particles can tell more than a thousand words and help predict a wear situation. A ferrogram can show even more. Blotter Spot Test A drop of used engine oil on chromato- graphic paper will reveal soot, glycol and fuel dilution. Excessive soot contamination causes the dispersant additives to deplete, which will form a black spot on the paper. Oil with good additives will lift soot particles easily and show a dark gray color across the paper. Glycol forms a black, sticky paste with sharp edges, which is unable to travel on the paper. Fuel dilution can be seen under ultraviolet (UV) light, as a fluorescent ring will appear after 24 hours. Multi-pass Test and Depth Oil Filters While the methods described previously can verify oil filter efficiencies, so can filter tests like the multi-pass test (ISO 16889). is test is designed for pleated pressure filters to establish a measure for manufacturers to illustrate the performance of oil filters. It can also be used by end users to compare the properties and performance of various filters. e beta value expresses an efficiency quota at a given particle size. For example, Beta3=75 means for each 3-micron particle that has escaped through the filter, 75 pieces of 3-micron particles have been retained. is can be calculated into an efficiency percentage as: (1 – (1/75)) x 100 = 98.67 percent. Unfortunately, multi-pass tests cannot be used for depth filters. Most of these tests utilize medium test dust (ISO 12103-A3), which consists of large, lightweight ceramic particles. ese particles are easy to capture in a pleated filter element, but at a constantly high ingress, they will block the surface of a dense cellulose depth filter. erefore, the results will show only a fraction of the true efficiency and dirt-holding capacity of the depth media. In real-world applications, wear particles, such as iron, are heavy and will slowly press their way through the thin sheets in pleated filter elements, with any pressure pulses or shocks making it worse. Consequently, in most applications, an in-line pressure filter will not perform as well as its multi-pass test result. Adding an off-line depth filter is recommended to ensure performance. Multi-pass test