Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1475671
www.machinerylubrication.com | July - August 2022 | 27 ML ML ML tial catastrophic equipment failure by means of implementing timely corrective action. ere are different test methods used in industry to measure contaminants in lube oil. Currently, two test methods are utilized for measuring insoluble contaminants, and these tests are part of the regular test slate for specific types of lube oil testing. e insoluble contaminants in hydraulic, transmission, refrigeration and synthetic turbine oils are measured by the gravimetric method (filter test), whereas the remaining oils are measured through high-speed centrifuge (ultra-centrifuge) analysis. As the objective for both tests is identical, it was decided to evaluate both test methods by correlating their results, with the goal of keeping only one test to measure the insoluble contaminants in lube oil, irrespective of the lube oil type. e study was conducted for the replacement of filter analysis by ultra-centrifuge (UC) test to determine insoluble contaminants by performing simultaneous analysis, i.e., gravimetric and centrifugal methods on various lube oil samples. Methodology e popular test methodologies being followed in the laboratory for measuring insoluble contaminants in lube oils are: Gravimetric Analysis is test method covers the determination of insoluble contamination in lube oils by gravimetric analysis. e contamination determined includes both particulate and gel-like matter, organic and inorganic, which is retained on a membrane filter disk. Insolubles in lube oil are determined by a known volume of the sample filtered through pre-weighed 1.2 ยต filters, and then the increase in weight is determined after washing and drying the filter. e total contaminant content of the partic- ular sample is determined by the increase in the weight of the filter. is is a manual method, and the technician is exposed to two solvents: kerosene for dissolving oil and petroleum ether to remove oil from the filter. is is a time-consuming process. Centrifugal Method A small amount of lube oil sample in a test tube is run for 30 minutes at 17,000 RPM in a refrigerated ultra-centrifuge. By subjecting the sample to G-forces, the insoluble contaminants can be extracted with different sizes or densities at controlled temperatures. e density of the agglomerated material at the bottom of the test tube is visually compared to a reference chart. e shapes in the reference chart reading range from 0 (the cleanest) to 8 (the most contami- nated). When the UC value exceeds 2, a marginal condition is noted. A UC value exceeding 5 is considered to be a critical result. In this method, no solvent is used, and sample processing is not required to determine the contamination level. Figure 2: Ultra-Centrifuge Test Cover Cylinder M e m b r a n e Filter Vacuum Pump Flask S a m p l e Oil Figure 1: Filtering Test 1 2