ASTM D6786-15(2023)
(Test Method)Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
SIGNIFICANCE AND USE
5.1 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.
5.2 Particle counts provide a general degree of contamination level and may be useful in assessing the condition of specific types of electrical equipment. Particle counts can also be used to determine filtering effectiveness when processing oil.
5.3 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.
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 mm2/s to 20 mm2/s at 40 °C. The test method is specific to liquid automatic particle analyzers that use the light extinction principle.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6786 − 15 (Reapproved 2023)
Standard Test Method for
Particle Count in Mineral Insulating Oil Using Automatic
Optical Particle Counters
This standard is issued under the fixed designation D6786; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method covers the determination of particle 3.1 Definitions:
concentration and particle size distribution in mineral insulat- 3.1.1 coincidence, n—the presence of more than one particle
ing oil. It is suitable for testing oils having a viscosity of in the sensing zone of a particle analyzer at the same time,
2 2
6 mm /s to 20 mm /s at 40 °C. The test method is specific to causing mis-sizing and mis-counting of the particle present; the
liquid automatic particle analyzers that use the light extinction coincidence limit of the counter is determined by the maximum
principle. acceptable concentration of particles in the sensing zone and is
supplied by the instrument manufacturer.
1.2 The values stated in SI units are to be regarded as
3.1.2 concentration limit, n—a direct function of coinci-
standard. No other units of measurement are included in this
dence and electronic saturation; the concentration limit of the
standard.
system is determined by the maximum acceptable concentra-
1.3 This standard does not purport to address all of the
tion of particles in the given sample and is supplied by the
safety concerns, if any, associated with its use. It is the
instrument manufacturer.
responsibility of the user of this standard to establish appro-
3.1.3 electronic saturation level, n—particle concentration
priate safety, health, and environmental practices and deter-
at which the electronic circuitry of the analyzer ceases to
mine the applicability of regulatory limitations prior to use.
function properly due to excessive counting rates.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard- 3.1.4 light extinction, n—the reduction in intensity of a light
ization established in the Decision on Principles for the
beam passing through the sensing zone of a particle analyzer,
Development of International Standards, Guides and Recom- caused by the absorption and/or scattering of the light by
mendations issued by the World Trade Organization Technical
particles; synonyms: light obscuration, light interruption, light
Barriers to Trade (TBT) Committee.
blockage.
4. Summary of Test Method
2. Referenced Documents
4.1 Samples are taken in particle-clean bottles that are
2.1 ASTM Standards:
suitable for particle analysis. The sample bottle is agitated to
D923 Practices for Sampling Electrical Insulating Liquids
redistribute particles in the oil, then the oil is placed in an
2.2 ISO Standards:
automatic particle counter, where the number of particles and
4406:1999 Hydraulic Fluid Power—Fluids—Method for
their size distribution are determined by the light extinction
Coding the Level of Contamination by Solid Particles
principle.
11171:2010 Hydraulic Fluid Power—Calibration of Auto-
4.2 As particles pass through the sensing zone of the
matic Particle Counters for Liquids
instrument, the quantity of light reaching the detector is
obscured. This signal is translated to an equivalent projected
1 area diameter based on calibration with a NIST-traceable fluid
This test method is under the jurisdiction of ASTM Committee D27 on
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
(ISO Medium Test Dust suspension).
mittee D27.07 on Physical Test.
Current edition approved Dec. 1, 2023. Published January 2024. Originally 5. Significance and Use
approved in 2002. Last previous edition approved in 2015 as D6786 – 15. DOI:
5.1 Particles in insulating oil can have a detrimental effect
10.1520/D6786-15R23.
on the dielectric properties of the fluid, depending on the size,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
concentration, and nature of the particles. The source of these
Standards volume information, refer to the standard’s Document Summary page on
particles can be external contaminants, oil degradation by-
the ASTM website.
products, or internal materials such as metals, carbon, or
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. cellulose fibers.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6786 − 15 (2023)
5.2 Particle counts provide a general degree of contamina- directly from NIST (SRM 2806) or a secondary sample
tion level and may be useful in assessing the condition of prepared in accordance to ISO 11171 and traceable to NIST.
specific types of electrical equipment. Particle counts can also
8.4 Dilution Oil, insulating oil that has been filtered to
be used to determine filtering effectiveness when processing
contain fewer than 1 % of the total particles expected in the
oil.
cleanest sample.
5.3 If more specific knowledge of the nature of the particles
9. Sampling
is needed, other tests such as metals analysis or fiber identifi-
cation and counting must be performed.
9.1 Proper sampling is crucial to particulate analysis. Obtain
a sample of the liquid to be tested in accordance with Practice
6. Interferences
D923.
6.1 Dirty environmental conditions and poor handling tech-
niques can easily contaminate the sample and/or test specimen. 10. Calibration
Care must be taken to ensure test results are not biased by
10.1 Calibration of the instrument shall be with a NIST-
introduced particle
...
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