Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/778560
important since the delivery person will not be willing to wait around for a long time while you sample and test the oil. Although it would be obvious if you received an ISO 220 gear oil instead of an ISO 32 hydraulic fluid, can your eyes tell the difference between an ISO 32 and an ISO 46 or 68? Granted, moving up a grade may not have much of an impact on the equipment's operation, but going down a grade or two most certainly will. While you may not be able to distinguish between the two different viscosities, I can assure you that your equipment will. The chart at the bottom of this page shows how a lubricant's film thickness increases by 62 percent when the viscosity is doubled. The reverse also applies. If you cut the viscosity in half, you reduce the film thickness by a comparable amount. Particle Counting A particle count is another easy test to conduct prior to the acceptance of a lubricant. Again, there are many simple-to-use, quick and fairly accurate particle counters available on the market. This test can give you a good idea of how much filtration will be needed prior to adding the new oils to your equipment. Offsite Testing The viscosity comparison and particle count tests can and should be performed onsite prior to accepting a lubricant delivery, as they can quickly reveal if something is wrong. However, neither of these tests provides a true indication that the product in the container matches what is on the label. To accurately determine this, a series of tests must be conducted. In most cases, this level of testing will require the sample be sent offsite to a laboratory. Trust But Verify Some lubricant suppliers offer oil analysis as part of their services. However, I warn you to not allow the fox in the henhouse. Although many who provide testing are honorable and do a good job, unfortunately some do not. If you send a sample from a new drum of oil to your supplier, it is in their best interest to "confirm" that drum is good. Likewise, if you send a sample of in-service oil, it is in the supplier's best interest to "determine" that it is bad and in need of changing out. While serving in the U.S. Navy, I learned a tenet that Ronald Reagan was famous for saying: "Trust but verify." This expression applies here as well. I would suggest having a third-party lab on standby to help keep your supplier honest. Again, most are decent and honest, but how will you know unless you follow Reagan's advice? You don't have to send every sample to an independent lab for verification, just enough to feel confident that the supplier is providing trustworthy analysis. I would also recommend visiting the supplier's warehouse and laboratory if possible. How to Draw a Proper Oil Sample Proper oil sampling will be essential for your oil analysis program to be effective. The question then becomes how can you draw a representative sample. The procedure below outlines the best practice for drawing a sample on a static container. PERSPECTIVE 38 | January - February 2017 | www.machinerylubrication.com 62% 62% 35% 45% -9% 70 60 50 40 30 20 10 0 -10 *Increase in viscosity under load What happens to film thickness when you double these factors? Double Oil's Viscosity Double Shaft Speed (rpm) Double Bearing Diameter Double Oil's Pressure/Viscosity Coefficient Percent Change in Oil Film Thickness Double the Applied Load (psi) Incoming Oil Test Slate The following is a recommended slate of tests for incoming oil: • Viscosity at 40 degrees C (ASTM D445) • Viscosity at 100 degrees C (ASTM D445) • ISO particle count (ASTM D7647) • Acid number (ASTM D664, D2896, D974, D3339) • Karl Fischer moisture (ASTM D1744 or D6304) • Elemental spectroscopy (ASTM D5185, D6595) • Fourier transform infrared (FTIR) spectroscopy (ASTM E2412) Additional Tests by Fluid Type Compressor, Gear, R&O and Turbine Oils • Color (ASTM D1500) • Foam stability/tendency (ASTM D892) • Demulsibility (ASTM D1401, D2711) • Linear sweep voltammetry (ASTM D6810, D6971) Hydraulic and Motor Oils • Varnish potential (ASTM D7843) • RPVOT (ASTM D2272)