Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/793941
22 | March - April 2017 | www.machinerylubrication.com tionally, the initial oil analysis results will provide you with direction in terms of the solutions that should be implemented and on which machinery. What to Look for When you receive your first oil sample results, you most likely will see a number of abnormal or critical sample reports. The main issues to watch for are water contami- nation, high levels of oil particulate, improper oil top-ups and poor oil condition. It is also possible that you will have results showing abnormal or severe wear in some machines. The purpose of establishing a lube program is to maintain proper lubrication and avoid unnecessary wear, so let's assume your reliability team is assessing these reports and has the situation in hand. Instead, we will focus on the oil-related problems, beginning with dirt and water contamination. Water will show up on your sample report as "water" or "H 2 O." Are these results abnormal or severe? At this point, you have not set any alarm levels for water contamina- tion, so it is acceptable to use the laboratory defaults for your industry and type of machine. With most rotating equipment, the contamination limit for water will be 0.1 percent. Limits will range as low as 0.03 percent for turbines and as high as 0.2 percent for gearboxes. Some compressors using synthetic oils may go as high as several percent water. Dirt will appear on a sample report under silicon (Si), along with the other elemental data for wear and additives. If you are sampling machines with oil filtration, the laboratory should perform particle count testing. Ensure that you are purchasing the correct test kits for this type of machinery. Pay attention to the ISO cleanliness code as well as the particle counts by micron size. Abnormal or severe silicon levels and/or particle count results indicate a problem with contamination. Again, the laboratory will be using typical industry limits for silicon and oil cleanliness, which is fine when you are starting your oil analysis program. Standard silicon alarm levels for most equipment are approxi- mately 25 parts per million (ppm). ISO cleanliness codes for filtered systems are generally around 19/17/14. Improper oil top-ups are a bit more diffi- cult to detect, but look for comments about changes in the elemental additive levels (phosphorus, zinc, magnesium, boron, barium, sulfur, etc.) and monitor any changes in oil viscosity that are plus or minus 10 percent from the oil specification. Elemental additive levels can fluctuate as much as 25 percent, so a laboratory will look for other elements that shouldn't be present or the lack of an element that should be present in the oil. Some labs have very sophisticated algorithms that not only compare the used oil to the new baseline but can also deter - mine the fluid type and compare it to the generic fluid type for the oil you have speci- fied. They can then alert you when a different type of fluid is being used. You may want to inquire whether your laboratory has the ability to perform this level of comparison. The most blatant types of improper oil top-ups or incorrect oil usage are when the viscosity varies drastically from the specifica - tion. This would include when you believe you are using an ISO 320 gear oil, but the viscosity is actually 100 centistokes (cSt), indicating a possible top-up with hydraulic, compressor or circulating oil. For most lubricated plant machinery, the oil condition is monitored using the oil's acid number (AN). When oil oxidizes, it forms acidic degradation products. An increasing AN signi - fies oil degradation. Once the AN is over the limit for the oil, it is time to schedule an oil change. Large systems like turbines require more advanced testing, such as rotating pres - sure vessel oxidation testing (RPVOT), water WATER CONTAMINATION HIGH LEVELS OF OIL PARTICULATE IMPROPER OIL TOP-UP POOR OIL CONDITION 1 2 3 4 Water (H20): >0.1% Free Water: >0.5% Ferrography: Ferrous Red Oxides (FRo) Silicon (Si): > 25 ppm ISO Code +2 above target cleanliness code Viscosity: +/- 10% One or more of boron (B), barium (Ba), molybdenum (Mo), magnesium (Mg), phosphorus (P), zinc (Zn): +/- 25% AN: +1.0 mg/KOH from base RPVOT: <25% of New Oxidation: >0.20 Abs/0.1 mm The most common oil-related issues uncovered by oil analysis and their associated general warning limits Organiza- tions must be proactive so the solution to an oil-related problem is not always an oil change. OIL ANALYSIS