1、Designation:D678615Standard Test Method forParticle Count in Mineral Insulating Oil Using AutomaticOptical Particle Counters1This standard is issued under the fixed designation D6786;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,th
2、e year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of particleconcentration and particle size distribution in mineral insu
3、lat-ing oil.It is suitable for testing oils having a viscosity of 6 to20 mm2/s at 40C.The test method is specific to liquidautomatic particle analyzers that use the light extinctionprinciple.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in
4、 thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Re
5、ferenced Documents2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating Liquids2.2 ISO Standards:4406:1999Hydraulic Fluid PowerFluidsMethod forCoding the Level of Contamination by Solid Particles311171:2010 Hydraulic Fluid PowerCalibration of Auto-matic Particle Counters for Liquids3
6、3.Terminology3.1 Definitions:3.1.1 coincidencethe presence of more than one particlein the sensing zone of a particle analyzer at the same time,causing mis-sizing and mis-counting of the particle present.The coincidence limit of the counter is determined by themaximum acceptable concentration of par
7、ticles in the sensingzone and is supplied by the instrument manufacturer.3.1.2 concentration limita direct function of coincidenceand electronic saturation.The concentration limit of the systemis determined by the maximum acceptable concentration ofparticles in the given sample and is supplied by th
8、e instrumentmanufacturer.3.1.3 electronic saturation levelparticle concentration atwhich the electronic circuitry of the analyzer ceases to functionproperly due to excessive counting rates.3.1.4 light extinctionthe reduction in intensity of a lightbeam passing through the sensing zone of a particle
9、analyzer,caused by the absorption and/or scattering of the light byparticles.Synonyms:light obscuration,light interruption,lightblockage.4.Summary of Test Method4.1 Samples are taken in particle-clean bottles that aresuitable for particle analysis.The sample bottle is agitated toredistribute particl
10、es in the oil,then the oil is placed in anautomatic particle counter,where the number of particles andtheir size distribution are determined by the light extinctionprinciple.4.2 As particles pass through the sensing zone of theinstrument,the quantity of light reaching the detector isobscured.This si
11、gnal is translated to an equivalent projectedarea diameter based on calibration with a NIST-traceable fluid(ISO Medium Test Dust suspension).5.Significance and Use5.1 Particles in insulating oil can have a detrimental effecton the dielectric properties of the fluid,depending on the size,concentratio
12、n,and nature of the particles.The source of theseparticles can be external contaminants,oil degradation by-products,or internal materials such as metals,carbon,orcellulose fibers.5.2 Particle counts provide a general degree of contamina-tion level and may be useful in assessing the condition ofspeci
13、fic types of electrical equipment.Particle counts can alsobe used to determine filtering effectiveness when processingoil.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.07 on Physical T
14、est.Current edition approved Oct.1,2015.Published October 2015.Originallyapproved in 2002.Last previous edition approved in 2008 as D678608.DOI:10.1520/D6786-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of AS
15、TMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA
16、19428-2959.United States1 5.3 If more specific knowledge of the nature of the particlesis needed,other tests such as metals analysis or fiber identifi-cation and counting must be performed.6.Interferences6.1 Dirty environmental conditions and poor handling tech-niques can easily contaminate the sample and/or test specimen.Care must be taken to ensure test results are not biased byintroduced particles.6.2 Air bubbles in the oil may be counted as particles givingfalse positive readings.Mixing or a
