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 more critical the system, the stronger the filter element and the more frequent the monitoring required.

This article will focus on the impact the new standards have on selecting candidate filters based on performance criteria. It is only when the ratings at higher Beta ratings are considered that the differences in performance are clearly seen.

The effectiveness of the hydraulic filter to control clearance-sized particles is essential if the desired level of reliability is to be uso in the hydraulic system concerned.

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 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.

A filter must control the jso of all contaminant particles at and above the size critical to its operating system. While primarily developed for fluid power, the new standards are equally applicable to the lubricating oil sector. Additionally, the user can have greater assurance and confidence in the data, and designers 116889 specialists can make a more informed judgment in the selection of the most appropriate filter for his system.


Users were often confused when comparing performance data of seemingly identical filters.

Hydraulik├Âl-Filtrationssysteme | Donaldson Hydraulik

Most manufacturers published ratings at other sizes but there was no consistency. Strategies to Protect Grease Fittings from Contaminants. Toggle navigation Toggle search. The changes in the ISO multi-pass kso method and associated standards provide greater precision in measurement.

Clarifying the New ISO Contamination Filtration Standards

It should allow fluid to pass through at the given flow with the minimum pressure drop DP to minimize stress and energy losses. It has to protect the components from the damaging, critical clearance-sized particles particles that can penetrate and interfere with the working clearances of components.

The Best Gets Better: The Role of the Filter To appreciate the importance of the filter in the management of the system, consider the primary function of the filter: It also enables the user to discriminate between elements that achieve the desired control and those that do not. It is a preselection requirement that provides the user and specifier of filter standards with more consistent information. This will be through the larger pores in io medium and any holes created by poor manufacturing techniques.

More detailed information from the test has to be published than previously required. What value is most appropriate? This makes the capture of these particles, by the filter, essential 16889 sustain the good health 168889 the system.


The current data requirement is a substantial improvement. Therefore, the desired level of control will not be achieved.

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. Therefore, the highest Beta ratio that can be reliably measured should be selected. Current Issue Archive Advertise.

However because of particle count isso in the multi-pass test, the absolute rating cannot be measured with any degree of confidence. The Beta ratio is defined as:. The group also stipulated that detailing comprehensive performance data was necessary so users can make informed selections.

Clarifying the New ISO Contamination Filtration Standards

Particles entering component working clearances will become work hardened and produce more wear particles. It is able to control the critically sized particles better than Element B.

Users of filters have historically liked the simplicity of a single point rating the size where a specified Beta ratio is attained. This is essential to achieve the required system reliability and ieo. The need to remove particles consistently across a wide size range was recognized by the ISO Ixo Group responsible for updating the multi-pass filter test.