Contamination Control Standards Group Continues Interlaboratory Testing

Salt Lake City

The U.S. Technical Advisory Group (TAG) on contamination control continued development of several fluid power filter-related ISO standards and interlaboratory tests at its recent meetings in Salt Lake City. Three projects in particular came to the forefront:

  1. Work continues in the revision of ISO 11171, Calibration of automatic particle counters for liquids. A round robin is going on in parallel with the revision to define the consensus standard. Results will be included in the final draft. Updates of note are:
    • Major revisions are being made to include threshold settings for calibration specified with an equation in the current version.
    • Use of the Bezier cubic spline method was decided at the last TC 131/SC6 meeting, but the appropriate name has been updated to the “constrained cubic spline” method.
    • The current version of ISO 11171 specifies a minimum of 16 sizes to interpolate sizes/thresholds for primary and secondary calibrations. Three different samples must be taken, resulting in average error of 14% down to <1%, max error of 52% down to ~1%. Minimum count 1.5x noise, 30-micron max, and calculate a constant K which determines the offset of sizes between these extremes.
  2. ISO 23369, Hydraulic fluid power — Multi-pass method of evaluating filtration performance of a filter element under cyclic flow conditions. The purpose of this study is to measure the intra-company repeatability and inter-company reproducibility of data obtained using the procedures of ISO/DIS 23369:2013 along with particle counters calibrated with the ISO/DIS 11943:2013 with traceability to ISO 11171: evaluating fine and coarse filters with ISOMTD and ISOFTD.
  3. An interlaboratory study is also underway for ISO 4405, Determination of particulate contamination level by the gravimetric method. This standard has not been updated since 1991. The objective of the study was to demonstrate a U.S. best practice to ISO-counterparts for inclusion in a possible ISO 4405 update. The TAG is in the process of drafting new technical procedures that can be incorporated into the ISO 4405 standard. The findings will be circulated during the October ISO meetings to the broader ISO fluid power community.

The U.S. TAG on contamination control meets three times per year. If you would like to get involved in the U.S. ISO Standards development process, please contact Denise Husenica at