Let’s face it, a filter’s primary role is to hold onto dirt. Look for synthetic filter media for the most efficient filtration. Filters with absolute ratings will generally trap all or most of the particles of the expressed size. You can expect this from paper or cellulose filter media. When manufacturers express nominal efficiency, it often describes the percentage of particles the filter may trap. It should be clear that it’s often misleading when you play around with efficiency numbers. The finer filter actually removes two hundred times more particles and is exponentially more efficient. However, with the 99.9% efficient element (1000 Beta Ratio), only 10 of those 100,000 particles can make it through. ![]() So if we have 100,000 particles upstream of the filter, 2000 particles are passing straight through. The 98% efficient filter is trapping particles at a 50:1 clip (Beta Ratio of 50). Although it seems like the 99.9% filter is only 1.9% better than the 98% efficient filter, let me put it another way. Anything less is not worth putting on your machine. For example, a decent filter is anything above 98% efficiency. Using this formula, we can see that a Beta Ratio of 1000 equates to 99.9% efficiency, which is very efficient. I’ll use the example using a Beta Ratio of 1000: To calculate filter efficiency, simply subtract one from the Beta Ratio and then divide that by the Beta Ratio. Really just an expansion of the Beta Ratio, filter efficiency is another way of expressing how well a filter removes particles of a given size. A t-shirt could remove some number of 5-micron particles, albeit not very efficiently. Filter ratings are sometimes arbitrarily based upon the manufacturer’s whim, and any filter could be given any rating without expressing how efficiently it removes those particles. Our 5µ example only becomes valid should the manufacturer express it alongside the Beta Ratio. I should mention that the Beta Ratio must be expressed alongside the micron rating of the filter. For example, if the manufacturer presents their 5 micron (5µ) filter for testing and the lab measures 200,000 particles before the filter and then only 1000 particles after the filter, the Beta Ratio is 200. The lab calculates the Beta Ratio by dividing the number of particles before the filter by the number of particles after. Then, using sophisticated particle counting equipment, they measure the number of particles before and then again after the filter. The lab runs the contaminated hydraulic fluid through the tested filter assembly. For example, using the ISO 16889 multi-pass test standard, labs artificially contaminate a given volume of hydraulic fluid with a given volume of certified test dust until the fluid is saturated. To master hydraulics, you need to master the following terms.īeta Ratio describes the ratio between contamination particles measured upstream of the test filter to downstream of the test filter. Filtration, of course, protects equipment spanning dozens of other industries, but much of the conversation regarding hydraulic oil filtration is unique. ![]() ![]() The subset of filtration is arguably the most universally required, applied by everyone between the engineer and mechanic to ensure pumps, valves, and actuators operate reliably and efficiently. At the same time, nobody is expecting your construction equipment mechanic to learn about the frequency response of servovalves, but other subjects are universal to the industry. Moreover, technicians and mechanics perform their jobs well when familiar with fluid power best practices, especially from a maintenance perspective. Engineers and designers absolutely must consider how to make it easier for the mechanic who will eventually maintain the machine, offering various access points for test gauges, ball valves to isolate sub-circuits and filters located where the technician has easy access. Any fluid power professional worth their weight in hydraulic oil approaches their education holistically, even if this education occurs after your last exam in college. It’s not enough for you to learn how to design or install hydraulic systems.
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