Latest News From ISO TC/131

Mike Day, Pall Corporation
Tags: oil analysis

The ISO committee that deals with the measurement of particulate contamination in fluid samples from Fluid Power Systems is “ISO TC/131/SC6,” that is: “Technical Committee (TC)/131-Hydraulic Fluid Power and Sub-Committee (SC) 6 - Contamination Control,” and is divided into three working groups (WG):

  • WG1 - Sampling, contamination analysis and reporting,
  • WG2 - Filters and Separator Evaluation and
  • WG3 - Component Cleanliness.

The Working Groups are responsible for the development of new ISO Standards, as well as ensuring that existing standards reflect current practice and technology. All current standards are reviewed every five years and a new project introduced if it is considered necessary to update them.

All of the Working Groups of Subcommittee 6 meet in March to discuss the status of their projects and of direct relevance to oil analysis and contaminant measurement. The current projects of WG1 are:

ISO 3938 Hydraulic Fluid Power - Contamination Analysis - Method for Reporting Analysis Data
This standard deals with reporting contamination data and often conflicts with other specific standards which define reporting requirements. The committee decided to withdraw this standard in 2004 when the only remaining document referring to it is fully updated.

ISO (Working Draft) 4405 Hydraulic Fluid Power - Fluid Contamination Determination of Particulate Contamination by the Gravimetric Method
This standard provides the procedure to measure the weight concentration (in mg/Liter) of solid particulate contaminant in a fluid sample, which can be the system fluid, a wash fluid used in a component cleanliness test or the test fluid from an ISO 16889 Multi-pass test stand. The method determines the weight of contamination by separating it from the sample liquid using vacuum filtration and depositing it on a preweighed membrane filter disc. The weight of contaminant in the sample is obtained by subtracting the initial weight of the membrane filter. This is the first revision and it will provide more accurate and repeatable results in what is recognized as a test with limited accuracy, and one that is more relevant to dirty samples.

ISO (Final Draft International Standard) 4407 Hydraulic Fluid Power - Fluid Contamination - Measurement of Particulate Contamination by the Counting Method Using a Microscope
In this test the particles are separated from the sample liquid by vacuum filtration, deposited on a membrane filter for counting using an optical microscope. Counting may be completed directly using incident (reflected) light or by using transmitted light with a membrane filter that has been transparentized. This standard has been updated to allow flexibility in both the pore size of the membrane filter used in the process, (membranes having a larger pore size than the usual 1 µm can be used), the use of both variable membrane filter filtration diameters and the volume of sample filtered. This is to enable data to be obtained from problematic samples. The standard also includes analysis by computer-based image analysis techniques.

ISO (Committee Draft) 11500 Hydraulic Fluid Power - Measurement of Particulate Contamination by Automatic Counting Using the Light Extinction Principle
This standard deals with the counting and sizing of particles in fluid samples using laboratory-based Automatic Particle Counting (APC) instruments working on the light interaction (blockage) principle. The revision details a procedure for treating oil samples that contain free water by diluting it with a compound, which causes the water to form into very small droplets (<0.5 µm), which should not be detected by the APC. There is some disagreement between USA and Europe on the effects of this compound on both the additives within oil and on the sensitivity of the APC. A series of ‘Round Robin’ tests will confirm its suitability. Other changes include a method of quickly detecting whether water is present in sample oil and improved procedures to speed up sample analysis.

ISO (Technical Report) 16144 Hydraulic Fluid Power - Calibration of Liquid Automatic Particle Counters - Procedures Used to Certify The Standard Reference Material SRM 2806
This standard defines the process and methods that were used in the preparation and certification of the Standard Reference Material (SRM) 3806 by the National Institute for Science and Technology (NIST) for ISO 11171 - the method for calibrating APCs. The Technical Report has been approved and is available from ISO and national bodies.

ISO (New Work Item) 21018 Hydraulic Fluid Power - Monitoring the Level of Solid Contaminant
This suite of standards grew out of ISO (Working Draft) 16863 which dealt with solid particulate contaminant monitors that work on the filter blockage principle. This new project was conceived to provide consistent and uniform methods for techniques or instruments that monitor the general levels of particles in hydraulic fluids. The standard is currently in three parts, with a fourth identified:

  • Part 1 - General principles. An explanation of the techniques that can be used and an explanation of how to select a measuring or monitoring instrument.
  • Part 2 - Using the filter blockage technique.
  • Part 3 - Using the comparative membrane technique (sometimes referred to as the Patch test or Conpar method).
  • Part 4 - Using online light extinction methods (projected).

Although the documents have been discussed in some depth, it still has to be proposed as a New Work Item and must go to the full membership for acceptance.

New Work Proposals
Only one item has been received in the last year: that of cleaning so called “hardware” or specifically, containers used in the collection and analysis of fluid samples. It has yet to be approved as a New Work Item, and could either be a standard in its own right or added to ISO 3722 - Fluid Sample Containers - Qualifying And Controlling Cleaning Methods.

You Can Help
If you or your industry has any ideas or requirements, contact Practicing Oil Analysis magazine. Remember, the committee is responsible only for the development of Fluid Power Standards so the ideas must have application in this industry.

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