NATIONAL FOREWORD

This Indian Standard (Second Revision) which is identical with ISO 16889 : 2008 ‘Hydraulic fluid power - Filters - Filter multi-pass method for evaluating filtration performance of filter element’ issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Fluid Power Systems Sectional Committee and approval of the Production and General Engineering Division Council.

This standard was first published in 1994 and subsequently revised in 2005. This second revision has been harmonized with ISO 16889 : 2008 by adoption to make pace with the latest developments that have taken place at international level.

In hydraulic fluid power systems, one of the functions of the hydraulic fluid is to separate and lubricate the moving parts of components. The presence of solid particulate contamination produces wear, resulting in loss of efficiency, reduced component life and subsequent unreliability. A hydraulic filter is provided to control the number of particles circulating within the system to a level that is commensurate with the degree of sensitivity of the components to contaminant and the level of reliability required by the users.

To enable the relative performance of filters to be compared so that the most appropriate filter can be selected, test procedures should be available. The performance characteristics of a filter are a function of filter element (its medium and geometry) and the housing (its general configuration and seal design). In practice, a filter is subjected to a continuous flow of contaminant entrained in the hydraulic fluid until some specified terminal differential pressure (relief valve cracking pressure or differential pressure indicator setting) is reached.

Both the length of operating time (prior to reaching terminal pressure) and the contaminant level at any point in the system are functions of the rate of contaminant addition (ingression plus generation rates) and the performance characteristics of the filter.

Therefore, a realistic laboratory test that establishes the relative performance of a filter should provide the test filter with a continuous supply of ingressed contaminant and allow the periodic monitoring of the filtration performance characteristics of the filter.

The filtration performance of the filter is determined by measurement of the upstream and downstream particle size distributions using automatic particle counters validated according to ISO Standards. Since it is difficult to specify, achieve and verify a cyclic flow requirement that is both realistic and consistent with the flow variations occurring in actual systems, the compromise of steady-state condition has been used for this test to enhance the repeatability and reproducibility of results.

The text of ISO Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain terminology and conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker.