ASTM D6786 - 08

    Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters

    Active Standard ASTM D6786 | Developed by Subcommittee: D27.07

    Book of Standards Volume: 10.03


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    Significance and Use

    Particles in insulating oil can have a detrimental effect on the dielectric properties of the fluid, depending on the size, concentration, and nature of the particles. The source of these particles can be external contaminants, oil degradation by-products, or internal materials such as metals, carbon, or cellulose fibers.

    Particle counts provide a general degree of contamination level and may be useful in accessing the condition of specific types of electrical equipment. Particle counts can also be used to determine filtering effectiveness when processing oil.

    If more specific knowledge of the nature of the particles is needed, other tests such as metals analysis or fiber identification and counting must be performed.

    1. Scope

    1.1 This test method covers the determination of particle concentration and particle size distribution in mineral insulating oil. It is suitable for testing oils having a viscosity of 6 to 20 cSt at 40°C. The test method is specific to liquid automatic particle analyzers that use the light extinction principle.

    1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ISO Standards

    11171:1999 Hydraulic Fluid Power--Calibration of Automatic Particle Counters for Liquids

    ASTM Standards

    D923 Practices for Sampling Electrical Insulating Liquids


    ICS Code

    ICS Number Code 91.100.15 (Mineral materials and products)

    UNSPSC Code

    UNSPSC Code 15121505(Transformer oil or insulating oil)


    DOI: 10.1520/D6786-08

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