Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/655822
www.machinerylubrication.com | March - April 2016 | 17 enter the machine during manufacturing or routine service, as well as through faulty seals, poor breathers or open hatches. No matter how the contaminants enter the oil, they can cause significant damage. Elemental spectroscopy is a test used to determine the concen- tration of wear metals, contaminant metals and additive metals in a lubricant. A concentration of wear metals can be indicative of abnormal wear. However, spectroscopy cannot measure particles larger than roughly 7 microns, which leaves this test blind to larger solid particles. As with any type of testing, spectroscopy is subject to inherent variance. When oil additives containing metallic elements are present, signif- icant differences between the concentrations of the additive elements and their respective specifications can indicate that either incorrect oil is being used or a change in the formulation has occurred. Also, keep in mind that sump sizes can vary in custom applications. Understanding Wear Limits When reviewing the wear levels in your test results, look at the trend history of each machine, not just the recommendations from the original equipment manufacturer (OEM). OEMs offer good benchmarks, but it is not wise to just follow their recommendations because most machines are used differently. For example, two identical pieces of equipment may have vastly different elemental spectroscopy results due to variations in load, duty cycle and maintenance practices. Their results might even show a variety of particle count levels. Both machines could still be considered healthy based on the trending of the analysis. Trending is extremely important in determining a machine's health. A good rule of thumb is to use your best judgment and review the trend data. Has anything changed with the operating conditions? Have you been running the machine longer? Have you been putting more load on the machine? You should also discuss the test results with the lab analyst before making any decisions. Watch for Contaminants Contamination causes a number of oil system failures. It often takes the form of insoluble materials such as water, metals, dust particles, sand and rubber. The smallest particles (less than 2 microns) can produce significant damage. These typically are silt, resin or oxidation deposits. The objective with contaminants is to detect the presence of foreign materials, identify where they came from and determine how to prevent further entry or generation. Contaminants act as a cata - lyst for component wear. If the cycle is not broken, wear accelerates and downgraded serviceability results. Typical elements that suggest contamination include silicon (airborne dust and dirt or defoamant additives), boron (corrosion inhibitors in coolants), potassium (coolant additives) and sodium (detergent and coolant additives). Quantifying the Amount of Water When free water is present in oil, it poses a serious threat to the equipment. Water is a very poor lubricant and promotes rust and corrosion of metal surfaces. Dissolved water in oil produces oxida- tion and reduces the oil's load-handling ability. Water contamination can also cause the oil's additive package to precipitate. Water in any ISO VG MID POINT LIMITS (KV 40° C) ISO VG MID POINT LIMITS (KV 40° C) KV 40° C mm 2 s-1 Min. Max. KV 40° C mm 2 s-1 Min. Max. ISO VG 10 10 9 11 ISO VG 460 460 414 506 ISO VG 15 15 13.5 16.5 ISO VG 680 680 612 748 ISO VG 22 22 19.8 24.2 ISO VG 1000 1000 900 1100 ISO VG 32 32 28.8 35.2 ISO VG 1500 1500 1350 1650 ISO VG 46 46 41.4 50.6 ISO VG 2200 2200 1980 2420 Kinematic Oil Viscosity in Centistokes