ISO HYDRAULIC FLUID POWER – FILTERS – MULTI-PASS METHOD FOR EVALUATINGFILTRATION PERFORMANCE OF A FILTER ELEMENT. Introduction. The obsolescence of AC Fine test dust (ACFTD) has led to the adoption of a new test dust, ISO Medium Test. Dust (ISO MTD), and the impending. ISO Multi-Pass Test. The multi-pass test is a means of determining a filter’s performance; it measures the ability of the filter to remove particles of test dust.
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The current data requirement is a substantial improvement. However, the multi-pass test is carried out in a laboratory under steady-state conditions and does not represent strenuous operational conditions. Most manufacturers published ratings at other sizes but there was no consistency. The Beta ratio is defined as:. This gives a series of Beta ratios ieo the filter as opposed to a percentage efficiency.
It also enables the user to discriminate between elements that achieve the desired control and those that do not. The Best Gets Better: A filter must control the levels of all contaminant ieo at and above the size critical to its operating system. It is a preselection requirement that provides the user and specifier of filter standards with more consistent information.
Clarifying the New ISO Contamination Filtration Standards
Therefore, the highest Beta ratio that can be reliably measured should be selected. When the contaminated hydraulic fluid passes through the filtration medium, it takes the line of least resistance. Current Issue Archive Advertise. If the filter fails to provide the necessary control of damaging-sized particles, then their presence in the system will lead to a substantial increase in the number of particles generated within the system through a chain reaction of wear.
The need to remove particles consistently across a wide size range was recognized by the ISO Working Group responsible for updating the multi-pass filter test. The more critical the system, the stronger the filter element and the more frequent the monitoring required.
To appreciate the importance of the filter 1689 the management of the system, consider the primary function of the filter: Consequently, the number of different Beta ratings used has proliferated. What value is most appropriate?
In the s and s, a compromise was reached between what is desirable and what can be consistently achieved for the range of filters assessed by this test. The effectiveness of the hydraulic filter to control clearance-sized particles is essential if the desired level of reliability is to be realized in the hydraulic system concerned.
Particles entering component working clearances will become work hardened and produce more wear particles. The changes in the ISO multi-pass test method and associated standards provide greater precision in measurement. The group also stipulated that detailing comprehensive performance data was necessary so users can make informed selections.
Users were often confused when comparing performance data of seemingly identical filters. The slope of the curve effectively defines the pore size distribution PSD of the filtration medium; the wider the PSD the less able the filter is to control those critically sized damaging particles.
About the Author Mike Day. This will be through the larger pores in the medium and any holes created by poor manufacturing techniques. However because of particle count statistics in the multi-pass test, the absolute rating cannot be measured with any degree of confidence.
The 168889 of the Filter To appreciate the importance of the filter in the management of the system, consider the primary function of the filter: The data that can be made available is as follows:.
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Create your own user feedback survey. Therefore, the desired level of control will not be achieved. Now, users can quickly see how the filter performs over a specified range of isso sizes and can compare the performance of candidate elements.
The filter should control the fluid cleanliness to a level that is equal to the performance, life and reliability of the system required by the user. This demands care in the selection of the most appropriate filter for the system. It is able to control the critically sized iwo better than Element B. While primarily developed for fluid power, the new standards are equally applicable to the lubricating oil sector.
The data that can be made available is as follows: These standards have been developed to increase the precision in the measurement of contamination and filtration performance, and to extend the amount of information from the tests. Users of filters have 168889 liked the simplicity of a single point rating the size where a specified Beta ratio is attained. Figure 2 shows the advantages of this approach. This is essential to achieve the required system reliability and life.