Machinery Lubrication

Machinery Lubrication May - June 2018

Machinery Lubrication magazine published by Noria Corporation

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36 | May - June 2018 | www . oils in the presence of contaminating water." e second part of the proce- dure is intended to "investigate the filterability of an oil which is used in applications where the presence of water in the oil is unlikely." e steps of this procedure can be summarized as follows: 1. e oil sample is deliberately contaminated by a controlled volume of water and mixed. 2. e mixture is placed in an oven for two hours, stirred and then returned to the oven, which is set to approximately 70 degrees C, for 70 hours. 3. e mixture is then kept at room temperature and away from light for 24 hours. 4. Using a filter with a 3-micron pore size and a cellulose and nitrate composite membrane on a special filtration apparatus outfitted with a pressure vessel, the treated water/oil mixture is vigorously mixed following a strict procedure and then poured into a filtration funnel. 5. After reaching 25 pounds per square inch differential (psid), the elapsed time and sample mixture volume are measured in a collection cylinder. 6. e resulting filterability can be analyzed from this data. T he f i lterabi lit y factor is reported a s a ratio of the volume of oil passing through the membrane filter divided by the area of the membrane filter. Since the test results are dependent on the amount of water added to the sample, the filterability can be reported in reference to this volume. This procedure is primarily intended for new hydraulic fluids with a viscosity of up to 100 ISO VG. A modification of the procedure can also be performed to establish the filterability of other lubricating oil types. If you are concerned that water contamination is influencing your lubricant's ability to be filtered, consult the lubricant manufactur- er's technical support to determine whether this test has been reported for your lubricant type. Additionally, you may wish to contact your oil analysis laboratory to have this test performed if filterability is a concern. e filterability of some oils may also be influenced by particular addi- tive byproducts or other insoluble contaminants, which are often found as a result of oil oxidation, thermal degradation and varnish. Even some organo-metallic additives can lead to a clogged filter. When certain additives are allowed to react with water in the oil, the formation of precipitates will cause even worse filtration issues. How to Manage Water As mentioned previously, water ingression is difficult to prevent entirely, and avoiding it may not even be necessary. In fact, for some types of equipment, a very small percentage of water is better than being completely dry in order to keep specific materials from drying out. Nevertheless, any water ingestion or moisture that is introduced by a process should always be understood, monitored and controlled. On smaller and simpler wet-sump systems, visual inspection devices should at least be used to recognize the signs of water contamination. These devices would include a bottom sediment and water (BS&W) bowl, 3-D bull's-eye sight glass and/ or columnar sight glass. Other in-line sight glasses or clear-access panels can offer evidence of moisture as well. Water will be revealed by a cloudy or milky appearance, or will drop to the BS&W bowl where it is collected. Equipment with easy access for inspecting the headspace can help provide a quick indication of any moisture ingression. When tempera- tures change, the thermal cycles may cause the oil to sweat out the water, which can collect on headspace machine surfaces. Over time, corro- sion may occur. Evidence of this or any water present can be detected through visual inspections. Headspace moisture-control devices such as a dry-instrument air purge or desiccant breathers can drastically help to avoid airborne moisture conta mination from entering the oil. A desiccant breather can also indicate the likelihood of water being present in the machine. Larger, more complex and crit- ical equipment should follow the same recommendations mentioned previously in addition to oil analysis and possibly even online moisture content analysis. Most industrial equipment should maintain a mois- ture target level between 50-300 parts per million, depending on the component sensitivity, metallurgy, criticality and other factors. LESSONS IN LUBRICATION 61% of lubrication professionals say surface or membrane filters are the most common types of oil filters used at their plant, according to a recent survey at START YOUR FREE SUBSCRIPTION

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