1、Designation: D 6786 08Standard Test Method forParticle Count in Mineral Insulating Oil Using AutomaticOptical Particle Counters1This standard is issued under the fixed designation D 6786; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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
3、 mineral insulat-ing oil. It is suitable for testing oils having a viscosity of 6 to20 cSt at 40C. The test method is specific to liquid automaticparticle analyzers that use the light extinction principle.1.2 This standard does not purport to address all of thesafety concerns, if any, associated wit
4、h 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. Referenced Documents2.1 ASTM Standards:2D 923 Practices for Sampling Electrical Insulating Liquids2.2 ISO S
5、tandards:4406:1999 Hydraulic Fluid PowerFluidsMethod forCoding the Level of Contamination by Solid Particles311171:1999 Hydraulic Fluid PowerCalibration of Auto-matic Particle Counters for Liquids33. Terminology3.1 Definitions:3.1.1 coincidencethe presence of more than one particlein the sensing zon
6、e 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 particles in the sensingzone and is supplied by the instrument manufacturer.3.1.2 concentration limita di
7、rect 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 the instrumentmanufacturer.3.1.3 electronic saturation levelparticle concentration atwhich the electron
8、ic 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 analyzer,caused by the absorption and/or scattering of the light byparticles. Synonyms: light obscura
9、tion, 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 particles in the oil, then the oil is placed in anautomatic particle counter, where the number of part
10、icles 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 signal is translated to an equivalent projectedarea diameter based on calibration with a NIST
11、-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,concentration, and nature of the particles. The source of theseparticles can be external contaminants
12、, 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 ofspecific types of electrical equipment. Particle counts can alsobe used to determine fil
13、tering 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 Test.Current edition approved Jan. 1, 2008. Published February 2008. Originallyappr
14、oved in 2002. Last previous edition approved in 2007 as D 678607.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM webs
15、ite.3Available from American National Standards Institute, 11 West 42nd Street,New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 If more specific knowledge of the nature of the particlesis needed, other tests suc
16、h 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
17、 bubbles in the oil may be counted as particles givingfalse positive readings. Mixing or agitating the sample intro-duces bubbles into the oil, but these readily dissipate andgenerally do not interfere with insulating oil particle counts.6.3 Suspended or free water in the oil will generally becounte
18、d as particles. Normally, free water concentrationsbelow 10 ppm will not interfere.6.4 Excessive concentrations of particles in the oil willcause coincidence and/or electronic saturation errors. Limitsare determined by ISO 11171 and are generally supplied by theinstrument manufacturer. These errors
19、may be avoided bydiluting the sample with particle-clean dilution oil or particle-clean solvent.6.5 Odd-shaped particles and fibers may be improperlyanalyzed, depending on their orientation as they pass throughthe sensing zone of the instrument.7. Apparatus7.1 Automatic Particle Counter, liquid opti
20、cal particlecounter based on the light extinction principle. The instrumentshall be capable of recording the size and number of particlesas they pass across the detector. The particle counter shallinclude a bottle sampling apparatus that automatically deliversa predetermined volume of specimen at a
21、controlled flow rateto the sensing zone of the analyzer.7.2 Mechanical Shaker, paint shaker, table shaker, or othermechanical device to vigorously agitate sample bottles.8. Materials8.1 Particle-clean Bottles, recommended sample containersare cylindrical bottles made of polypropylene, polystyrene,PE
22、T, or glass with flat bottoms, fitted with a suitable non-shedding threaded cap. Bottles should be at least 100-mLcapacity. The bottles shall meet the cleanliness criteria ofcontributing less than 1 % of the total particles expected in thecleanest sample.8.2 Particle-clean Solvent, petroleum spirits
23、, hexane, kero-sene, or other suitable solvent, filtered through a 0.45 mmembrane filter.8.3 Calibration Fluid, suspension of ISO Medium Test Dustin oil or hydraulic fluid, either a primary sample obtaineddirectly from NIST4(SRM 2806) or a secondary sampleprepared in accordance to ISO 11171 and trac
24、eable to NIST.8.4 Dilution Oil, insulating oil that has been filtered tocontain fewer than 1 % of the total particles expected in thecleanest sample.9. Sampling9.1 Refer to Practice D 923 for precautions for samplingfrom energized electrical equipment.9.2 Proper sampling is crucial to particulate an
25、alysis. Thefollowing guidelines are offered to ensure representative sam-pling and to preserve sample integrity:9.2.1 Wipe the sample port outlet with a clean lint-freetowel. Open the sample valve and flush about 3 times the flowpath volume of oil into a container.9.2.2 While flushing, uncap the sam
26、ple bottle and retain thecap in one hand and the bottle in the other. Without adjustingthe valve or disturbing sample flow, fill the bottle to about80-95 % capacity. Do not completely fill the bottle since theheadspace will be needed for sample agitation.9.2.3 Cap the sample bottle, then close the s
27、ample valve.10. Calibration10.1 Calibration of the instrument shall be with a NIST-traceable calibration fluid in accordance with ISO 11171.10.2 Calibrate the instrument annually, unless experiencejustifies longer or shorter intervals.10.3 Interim calibration checks should be made regularly byusing
28、a particle count standard fluid prepared using theprocedures of ISO 11171. The check values should be within10 % of the standard values.11. Procedure11.1 If necessary, wipe the outside of the sample bottle witha clean lint-free towel.11.2 If other tests are to be run on the same sample, shakethe sam
29、ple bottle as described in 11.3 and transfer a specimenfor particle count to another particle-clean bottle. Do thisbefore running any other tests in order to avoid contamination.11.3 Agitate the sample bottle vigorously for 30-60 s toredistribute particles, the length of time depending on theeffecti
30、veness of the method of agitation. Use hand shaking ora mechanical shaker. Do not use a magnetic stir bar or anyother device that comes in contact with the oil. Do not use anultrasonic bath as this may break up the large particles.11.4 Allow a few seconds for gas bubbles to escape or applyvacuum to
31、the bottle until bubbles dissipate.11.5 Immediately analyze the sample with the automaticparticle counter according to the manufacturers operatinginstructions. Usually the analyzer is flushed with a specimen ofthe oil prior to testing. After the initial flush, 2-3 runs on eachsample are recommended.
32、11.6 When particle count runs are finished, flush the instru-ment with particle-clean solvent or particle-clean oil in accor-dance with the instrument manufacturers recommendations.12. Report12.1 Report the average of the particle count runs as thecumulative number of particles per mL 4, 6, 10, 14,
33、21,38, and 70 m (c). The “(c)” after the size indicates that theparticle counter was calibrated using ISO 11170. These particlesizes correspond approximately to 2, 5, 10, 15, 25, 50,and 100 m for particle counters that were calibrated with theold ISO 4402 calibration standard. If only one particle c
34、ountrun is analyzed, report the results of the single run.4Available from National Institute of Standards and Technology, 100 BureauDrive, Gaithersburg, MD 20899.D678608212.2 Optionally, also report the ISO solid contaminant codecorresponding to the number of particles per mL 4, 6, and 14m (c), as p
35、rescribed in ISO 4406:1999.13. Precision and Bias13.1 The precision of this test method is based on anInterlaboratory Study of D 6786 Particle Count in MineralInsulating Oil Using Automatic Optical Particle Counters conducted in 20062007. Each of eleven laboratories testedfour materials (in triplica
36、te); covering seven particle sizeranges to determine the intralaboratory and interlaboratoryprecision of D 6786.513.1.1 RepeatabilityTwo test results obtained within onelaboratory shall be judged not equivalent if they differ by morethan the “r” value for that material; “r” is the intervalrepresenti
37、ng the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.13.1.2 ReproducibilityTwo test results should be judgednot equivalent if they differ by more than the “R” value for thatmaterial; “R”
38、 is the interval representing the difference be-tween two test results for the same material, obtained bydifferent operators using different equipment in different labo-ratories.13.1.3 Any judgment in accordance with statements 13.1.1or 13.1.2 would have an approximate 95 % probability of beingcorre
39、ct.13.1.4 Results from the Interlaboratory Study are summa-rized in Tables 1-4. Data for the larger particle sizes wereomitted because the small number of particles present did notproduce good statistical results.13.2 BiasAt the time of the study, no certified referencematerial suitable for determin
40、ing bias was analyzed; thereforeno statement on bias can be made from this data.14. Keywords14.1 optical particle counter; particle count; particulatecontaminationASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this s
41、tandard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be re
42、viewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of therespons
43、ible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West
44、Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).5Supporting data a
45、re available from ASTM International Headquarters. RequestRR:D271018.TABLE 1 New OilParticle SizeRangeAverage,XRepeat-abilityStandardDeviation,srReproduci-bilityStandardDeviation,sRRepeat-ability Limit,rReproduci-bility Limit,R4 m(c) 147 18 95 50 2656 m(c) 56 8 50 23 13910 m(c) 25 5 35 14 9914 m(c)
46、16 5 18 14 5121 m(c) 6 2 8 7 22TABLE 2 Reclaimed Oil Spiked with ISO Medium Test DustParticle SizeRangeAverage,XRepeat-abilityStandardDeviation,srReproduci-bilityStandardDeviation,sRRepeat-ability Limit,rReproduci-bility Limit,R4 m(c) 3039 202 1787 566 50056 m(c) 1264 86 668 242 187110 m(c) 424 9 70
47、 24 19514 m(c) 137 12 59 35 16421 m(c) 42 5 22 13 61TABLE 3 Transformer OilParticle SizeRangeAverage,XRepeat-abilityStandardDeviation,srReproduci-bilityStandardDeviation,sRRepeat-ability Limit,rReproduci-bility Limit,R4 m(c) 117 45 59 126 1676 m(c) 45 17 24 49 6810 m(c) 22 6 17 18 4814 m(c) 13 6 9 1
48、7 2621 m(c) 6 3 5 9 14TABLE 4 Breaker OilParticle SizeRangeAverage,XRepeat-abilityStandardDeviation,srReproduci-bilityStandardDeviation,sRRepeat-ability Limit,rReproduci-bility Limit,R4 m(c) 15529 794 10283 2223 287926 m(c) 2650 232 1545 649 432510 m(c) 338 57 247 160 69114 m(c) 104 24 88 66 24721 m(c) 34 12 40 34 111D6786083
