The Effects of Water Contamination on Oil Filters

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The Effects of Water Contamination on Oil Filters von Mind Map: The Effects of Water Contamination on Oil Filters

1. Lubricant Filterability

1.1. Just as contaminants and operating conditions can disrupt or damage a filter, certain oil properties can also cause challenges in the oil’s ability to be filtered.

1.2. Filterability is the term used to describe the ease at which oil can be filtered, even in the presence of external contaminants such as water. Many oils are tested for their filterability using the procedure specified by ISO 13357-1:2017.

1.3. The second part of the procedure is intended to “investigate the filterability of an oil which is used in applications where the presence of water in the oil is unlikely.” The steps of this procedure can be summarized as follows:

1.3.1. °The oil sample is deliberately contaminated by a controlled volume of water and mixed. °The 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. °The mixture is then kept at room temperature and away from light for 24 hours. °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. °After reaching 25 pounds per square inch differential (psid), the elapsed time and sample mixture volume are measured in a collection cylinder. °The resulting filterability can be analyzed from this data. The filterability factor is reported as 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.

2. Water-induced Filter Failures

2.1. The differential pressure gauge should change gradually as the filter element becomes saturated. After several cycles of normal filter changes, the maintenance schedule will become predictable. However, when unexpected water is exposed to the system, it can clog the filter and cause a drastic change in the differential pressure, putting sudden strain on the filter element. If this continues for days or weeks, the element can form a bypass gap in the damaged media, enabling oil to flow through unfiltered.

2.2. Another way water can damage filters is through oxidation. Small amounts of water in oil, typically in the dissolved state, are not unusual and in some cases unavoidable.

2.3. In addition, water encourages the growth of microbial organisms. For example, bacterial growth can cause the formation of sulfuric acid, which can become corrosive in the oil and to machine surfaces. When this type of growth goes unnoticed and uncontrolled, it can result in premature lubricant degradation, corrosive wear and shorter filter life.

3. How to Manage Water

3.1. 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.

3.2. 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.

3.2.1. Equipment with easy access for inspecting the headspace can help provide a quick indication of any moisture ingression.

3.3. Headspace moisture-control devices such as a dry-instrument air purge or desiccant breathers can drastically help to avoid airborne moisture contamination from entering the oil. A desiccant breather can also indicate the likelihood of water being present in the machine.

4. How to Manage the Filter

4.1. Filter management should include a combination of activities, beginning with the selection of filters for the system’s needs.

4.2. Secondly, being aware of and controlling the ingression points for all types of contaminants will increase not only the filter life but also the life of the oil and machine.

4.3. Also, solid contaminants aren’t the only types of contamination that should be considered. Moisture is the second most destructive contaminant and is often ignored.