1、Designation: F312 08 (Reapproved 2016)Standard Test Methods forMicroscopical Sizing and Counting Particles fromAerospace Fluids on Membrane Filters1This standard is issued under the fixed designation F312; the number immediately following the designation indicates the year of originaladoption or, in
2、 the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the determination of the sizedistribution and quantity of part
3、iculate matter contaminationfrom aerospace fluids isolated on a membrane filter. Themicroscopical techniques described may also be applied toother properly prepared samples of small particles. Two testmethods are described for sizing particles as follows:1.1.1 Test Method AParticle sizes are measure
4、d as thediameter of a circle whose area is equal to the projected area ofthe particle.1.1.2 Test Method BParticle sizes are measured by theirlongest dimension.1.2 The test methods are intended for application to particlecontamination determination of aerospace fluids, gases,surfaces, and environment
5、s.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 These test methods do not provide for sizing particlessmaller than 5 m.NOTE 1Results of these methods are subject to variables inherent inany statistical method. The use
6、of these methods as a standard for initiallyestablishing limits should be avoided unless ample tolerances are permis-sible.1.5 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
7、-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F302 Practice for Field Sampling of Aerospace Fluids inContainersF303 Practices for Sampling for Particles in AerospaceFluids and ComponentsF311 Prac
8、tice for Processing Aerospace Liquid Samples forParticulate Contamination Analysis Using Membrane Fil-tersF314 Methods of Test for Identification of Metallic andFibrous Contaminants in Aerospace Fluids (Withdrawn1990)3F318 Practice for Sampling Airborne Particulate Contami-nation in Cleanrooms for H
9、andling Aerospace Fluids(Withdrawn 2013)33. Terminology3.1 Definitions:3.1.1 unit areathe area selected for counting particles.This may be the area of a reticle grid or some subdivisionthereof, the area of one imprinted membrane grid, or any otheraccurately calibrated area.3.1.2 effective filter are
10、athe area of the membrane whichentraps the particles to be counted.3.1.3 particle sizethe size of a particle as defined by areacomparison or by its longest dimension.4. Summary of Test Methods4.1 The membrane is examined through a microscope andthe particles counted according to size or size categor
11、ies usinga calibrated reticle. The total number of particles present isestimated by statistical methods from the actual number ofparticles counted. Either sizing Test Method A or B may beselected according to the preference and results expected.5. Significance and Use5.1 Reported particle size measu
12、rement is a function of boththe actual particle dimension and shape factor, as well as theparticular physical or chemical properties of the particle beingmeasured. Caution is required when comparing data from1These test methods are under the jurisdiction of ASTM Committee E21 onSpace Simulation and
13、Applications of Space Technology and are the directresponsibility of Subcommittee E21.05 on Contamination.Current edition approved Oct. 1, 2016. Published October 2016. Originallyapproved in 1969. Last previous edition approved in 2008 as F312 08. DOI:10.1520/F0312-08R16.2For referenced ASTM standar
14、ds, 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 website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyr
15、ight ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1instruments operating on different physical or chemical param-eters or with different particle size measurement ranges.Sample acquisition, handling, and preparation can also affectthe reporte
16、d particle size results.6. Apparatus6.1 Microscope, capable of resolving the smallest particlesto be counted and producing a flat field of view.6.1.1 The following optic combinations are recommended:Magnification Ocular ObjectiveMinimumNumericalAperture50 10 5 0.15100 10 10 0.25200 10 20 0.50Similar
17、 ocular-objective combinations resulting in magnifi-cations of 50 6 10, 100 6 10, and 200 6 20 may be used.The optimum equipment is a compound binocular microscope.Conventional stereo microscopes will not meet these require-ments.6.2 Mechanical Stage, capable of traversing the entireeffective filter
18、 area.6.3 Stage Micrometer, with 0.1 and 0.01-mm subdivisions.6.4 Provisions for variable high-intensity external obliqueincident illumination and for a focusing condenser. A flexibleor jointed arm is desirable.6.5 Reticles, inscribed with reference markings that can becalibrated to represent the fo
19、llowing dimensions:Magnification Size, m Tolerance, m200 20 5 0.815 1.2100 10 15 1.525 2.050 10 50 2.550 2.5100 5.06.5.1 The reticles shall be as follows:6.5.1.1 Reticle A, Globe and Circle Pattern, provides ameans for correlation of the microscopic method with auto-matic counter methods. Reticle A
20、uses the diameter of a circlefor its comparison of a particle, and automatic counter methodsuse either a particle volume, projected area, or particle areameasurements which are all directly related to the diameter.6.5.1.2 Reticle B, Linear Scale, provides for measurementof the longest linear dimensi
21、on technique.NOTE 2Some reticles combine both patterns in one reticle.6.6 Tally Counter, hand operated, for recording particlecounts.6.7 Video imaging and software packages are allowedprovided they meet the calibration requirements of 6.5.7. Sampling7.1 Collect and process the sample in accordance w
22、ith theapplicable methods of the American Society for Testing andMaterials, as follows: Practice F302, Practice F311, PracticeF318, and Practices F303.8. Calibration8.1 The sizing reticle shall be calibrated at each magnifica-tion by comparing the reference divisions noted in 6.3 with therulings on
23、the stage micrometer. Detailed calibration proce-dures and a discussion of errors are given in Appendix X1.8.2 The area extrapolation factor used for statistical count-ing is determined by the ratio of the area counted to the totaleffective area of the membrane filter.8.2.1 Unit AreaMeasure the size
24、 of the appropriate unitarea with the stage micrometer or previously calibrated reticleand calculate its area.8.2.2 Effective Filter Area (Note 3)Measure the diameterof the effective filter area with a scale, caliper, or calibratedmechanical stage and calculate the total area. Area = r2,where r is t
25、he radius of the effective circle.NOTE 3Where accurate effective filtering area measurements arerequired, a colored pigment solution should be filtered through thefiltration apparatus as described in Practice F311.8.2.3 Area Extrapolation FactorThe total particle countfor a given size range is deter
26、mined as follows:Ct5 C 3 Ae!/Au3 N! (1)where:Ct= total extrapolated count,C = actual particle count,Ae= effective filter area,Au= unit area, andN = number of unit areas counted.9. Procedure9.1 While exact details of the counting procedure dependpartly on the specific equipment chosen, all procedures
27、 mustconform to the requirements given in 9.1.1 9.1.9 to achievereproducibility. Methods A and B differ only in the sizing ofparticles, and the detailed procedure given shall be used foreither Reticle A or B.9.1.1 Blank analysis counts, which are part of the normalprocessing procedure, must be used
28、to determine the adequacyof environmental control.9.1.2 Size and count the particles in the following order:particles greater than 100 m (including fibers), 50 to 100 m,25 to 50 m, 15 to 25 m, and 5 to 15 m. Particles smallerthan 5 m shall not be counted by this method. Fibers (particleswith length-
29、to-width ratio exceeding 10 to 1 and over 100 min length) may be identified additionally if desired. Identifica-tion may be made in accordance with Test Method F314.9.1.3 Place the membrane filter (in a suitable holder) on themechanical stage; adjust the lamp and microscope to achievemaximum particl
30、e definition.9.1.4 Using 50 or lower magnification, scan the membranesurface to assure random particle distribution and to select theproper unit area to be used.9.1.5 Select a unit area containing less than 20 particles inthe size range counted at 50. In most cases, this will representthe entire eff
31、ective filtration area. Record all particles in theunit area exceeding 100 m.F312 08 (2016)29.1.6 Move to a new unit area preselected as part of auniform pattern designed to provide a representative samplingof the entire area and record all particles in the new unit areaexceeding 100 m.9.1.7 Continu
32、e until either the entire effective filter area hasbeen counted or until the complete count for the last unit areabrings the total count above 100 particles. Record the numberof unit areas utilized.9.1.8 Repeat the procedure described in 9.1.5 9.1.7 forparticles in the 50 to 100-m size range at 50,
33、for the 25 to50-m size range at 100, for the 15 to 25-m size range at100, and for the 5 to 15-m size range at 200, using theappropriate reticle reference. For the purpose of sizing, aparticle shall be counted in a given size range if its apparentsize is equal to or greater than the reference. Partic
34、les whoseapparent size is exactly that of the reference shall be assignedto the next highest range. Particles on the upper and left borderof the unit area shall be counted. Particles on the lower andright hand border shall be omitted to avoid duplicate count.NOTE 4All size ranges counted at a given
35、magnification may becounted simultaneously and recorded.9.1.9 In counting particles on the membrane surface, ascheme of programmed randomness such as the following issuggested for uniformity, clarity, and speed: start a pass overthe membrane from the top left corner until the edge of theeffective fi
36、ltering area is reached on the cross scan, thentransverse downward in the same manner as above. Stop thescan point as 100 or more particles have been counted, makingnote of the area covered for the final calculation.10. Calculation10.1 Total particle counts are obtained by multiplying theparticle co
37、unt times the area extrapolation factor. Since thefactor will usually vary according to the size range considered,this calculation must be repeated for each size range. Thenecessary extrapolation shall be made in accordance with 8.2.11. Report11.1 Total extrapolated particle counts in each particle
38、sizecategory shall be reported as follows:Over100 m50 to100 m25 to50 m15 to25 m5to15 mC+1C+2C+3C+4C+511.2 Fibers or the identification of particles may be reportedin addition to particle counting.12. Precision and Bias12.1 Precision and reproducibility are intended to be ad-equate for use as a monit
39、oring method, but the color of themembrane filter (white, black, green) has to be specifiedbecause the number of translucent and contrasting particlesdetected will vary depending upon the background medium.12.2 RepeatabilityDuplicate results by the same operatorshould be considered suspect if they d
40、iffer by more than thefollowing amounts:Mean Particle Countper SlideRepeatabilityCounts2500 650280 9433 136313. Keywords13.1 aerospace environments; aerospace fluids; aerospacegases; aerospace surfaces; membrane filter; microscopicalcounting particles; microscopical sizing particles; particulatematt
41、er contaminationAPPENDIX(Nonmandatory Information)X1. CALIBRATIONNOTE X1.1The procedures outlined in this appendix have provensatisfactory for calibration within the tolerances required by the method.They should not be considered mandatory. Alternative procedures areequally acceptable, provided the
42、end result is equivalent.X1.1 Calibration of ReticlesX1.1.1 Usually it will not be possible to calibrate directlythe references to be used within the required tolerances of themethod due to limitations of available stage micrometers(smallest division 10 m). It is necessary, therefore, to calibratean
43、 even multiple of 10 m and calculate the smaller unmea-surable size references.X1.2 Calibration of Effective Filter AreaX1.2.1 Effective filter area, the area of the membranecovered with the particles to be counted, is dependent upon thearea of the filter funnel, but is not identical, since a smallq
44、uantity of particles will generally be deposited underneath thefunnel walls.F312 08 (2016)3X1.2.2 On very dirty samples it will be possible to measurethe area directly. On most samples from aerospace systems,however, a simulated sample will be necessary.X1.2.3 Disperse a small quantity of pigment su
45、ch as ironoxide in a sample of the fluid to be tested. Approximately14 gof one of the MIL-G-25013 greases also is satisfactory.X1.2.4 Average the measured diameters and calculate thearea.X1.2.5 While it is necessary to determine the effective filterarea (EFA) exactly when using the method for refere
46、epurposes, certain shortcuts may be made when it is to be usedfor quality control purposes. If the EFA of all of the funnels tobe used is known, it will be found that all funnels deviate 6 to7 % from the average.NOTE X1.2ExampleTwenty funnels selected at random from stockhad a measured EFA averaging
47、 1018 mm2and ranging from 984 to 1081mm2. However, by eliminating the five extreme examples, 15 funnelsaveraged 1018 mm2with a range from 1012 to 1035 mm2.X1.3 Calibration of Unit AreaX1.3.1 It will usually be necessary to calibrate several unitareas to conform to the requirement of the method that
48、notmore than 20 particles in a given size range be counted per unitarea. It should be emphasized that the 20-particle limit is amaximum and that to avoid operation confusion a unit areacontaining fewer particles is highly desirable. There is lesschance of an operator overlooking a particle or counti
49、ng aparticle twice if a smaller number of particles is present.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. 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 reviewe
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