1、Designation: F 312 97 (Reapproved 2003)Standard Test Methods forMicroscopical Sizing and Counting Particles fromAerospace Fluids on Membrane Filters1This standard is issued under the fixed designation F 312; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, 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 These test methods cover the determination of the sizedistribution and quantity
3、of particulate 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
4、measured 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, sur-faces, and en
5、vironments.1.3 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 of these methods as a standard for initiallyestablishing limits should be avoided unless ample tolerances are permi
6、s-sible.1.4 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. Refe
7、renced Documents2.1 ASTM Standards:F 302 Practice for Field Sampling of Aerospace Fluids inContainers2F 303 Practices for Sampling Aerospace Fluids from Com-ponents2F311 Practice for ProcessingAerospace Liquid Samples forParticulate Contamination Analysis Using Membrane Fil-ters3F 314 Test Method fo
8、r Identification of Metallic and Fi-brous Contaminants in Aerospace Fluids3F 318 Practice for Sampling Airborne Particulate Contami-nation in Clean Rooms for Handling Aerospace Fluids23. Terminology3.1 Definitions:3.1.1 unit areathe area selected for counting particles.This may be the area of a reti
9、cle grid or some subdivisionthereof, the area of one imprinted membrane grid, or any otheraccurately calibrated area.3.1.2 effective filter areathe 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 d
10、imension.4. Summary of Test Methods4.1 The membrane is examined through a microscope andthe particles counted according to size or size categories usinga calibrated reticle. The total number of particles present isestimated by statistical methods from the actual number ofparticles counted. Either si
11、zing Test Method A or B may beselected according to the preference and results expected.5. Significance and Use5.1 Reported particle size measurement is a function of boththe actual particle dimension and shape factor as well as theparticular physical or chemical properties of the particle beingmeas
12、ured. Caution is required when comparing data frominstruments operating on different physical or chemical param-eters or with different particle size measurement ranges.Sample acquisition, handling and preparation can also affectthe reported particle size results.6. Apparatus6.1 Microscope, capable
13、of resolving the smallest particlesto be counted and producing a flat field of view.1These test methods are under the jurisdiction of ASTM Committee E21 onSpace Simulation and Application of Space Technologies are the direct responsi-bility of Subcommittee E21.05 on Contamination.Current edition app
14、roved April 10, 1997. Published November 1997. Originallypublished as F 312 69. Last previous edition F 312 96.2Annual Book of ASTM Standards, Vol 10.05.3Annual Book of ASTM Standards, Vol 14.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit
15、ed States.6.1.1 The following optic combinations are recommended:Magnification Ocular ObjectiveMinimumNumericalAperture503 103 53 0.151003 103 103 0.252003 103 203 0.50Similar ocular-objective combinations resulting in magnifi-cations of 50 6 103, 100 6 103, and 200 6 203 may beused. The optimum equ
16、ipment is a compound binocularmicroscope. Conventional stereo microscopes will not meetthese requirements.6.2 Mechanical Stage, capable of traversing the entireeffective filter area.6.3 Stage Micrometer, with 0.1 and 0.01-mm subdivisions.6.4 Provisions for variable high-intensity external obliqueinc
17、ident 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 following dimensions:Magnification Size, m Tolerance, m200 6 203 5 60.815 61.2100 6 103 15 61.525 62.050 6 103 50 62.550 62.51
18、00 65.06.5.1 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 uses the diameter of a circlefor its comparison of a particle, and automatic counter methodsuse either a par
19、ticle 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 dimension technique.NOTE 2Some reticles combine both patterns in one reticle.6.6 Tally Counter, hand operated, for
20、recording particlecounts.7. Sampling7.1 Collect and process the sample in accordance with theapplicable methods of the American Society for Testing andMaterials, as follows: Practice F 302, Practice F311, PracticeF 318, and Practices F 303.8. Calibration8.1 The sizing reticle shall be calibrated at
21、each magnifica-tion by comparing the reference divisions noted in 6.3 with therulings on 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
22、counted to the totaleffective area of the membrane filter.8.2.1 Unit AreaMeasure the size 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, ca
23、liper, or calibratedmechanical stage and calculate the total area. Area = pr2,where r is the 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 F
24、311.8.2.3 Area Extrapolation FactorThe total particle countfor a given size range is determined 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 detai
25、ls of the counting procedure dependpartly on the specific equipment chosen, all procedures 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
26、.1 Blank analysis counts, which are part of the normalprocessing procedure, must be used 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. Par
27、ticles smallerthan 5 m shall not be counted by this method. Fibers (particleswith length-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 F 314.9.1.3 Place the membrane filter (in a suitabl
28、e holder) on themechanical stage; adjust the lamp and microscope to achievemaximum particle definition.9.1.4 Using 503 or lower magnification, scan the mem-brane surface to assure random particle distribution and toselect the proper unit area to be used.9.1.5 Select a unit area containing less than
29、20 particles inthe size range counted at 503. In most cases this will representthe entire effective filtration area. Record all particles in theunit area exceeding 100 m.9.1.6 Move to a new unit area preselected as part of auniform pattern designed to provide a representative samplingof the entire a
30、rea and record all particles in the new unit areaexceeding 100 m.9.1.7 Continue 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 procedu
31、re described in 9.1.5-9.1.7 forparticles in the 50 to 100-m size range at 503, for the 25 to50-m size range at 1003, for the 15 to 25-m size range at1003, and for the 5 to 15-m size range at 2003, using theappropriate reticle reference. For the purpose of sizing, aparticle shall be counted in a give
32、n size range if its apparentsize is equal to or greater than the reference. Particles whoseapparent size is exactly that of the reference shall be assignedF 312 97 (2003)2to the next highest range. Particles on the upper and left borderof the unit area shall be counted. Particles on the lower andrig
33、ht hand border shall be omitted to avoid duplicate count.NOTE 4All size ranges counted at a given 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, a
34、nd speed: start a pass overthe membrane from the top left corner until the edge of theeffective filtering 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
35、 calculation.10. Calculation10.1 Total particle counts are obtained by multiplying theparticle count 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 b
36、e made in accordance with 8.2.11. Report11.1 Total extrapolated particle counts in each particle 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. Pre
37、cision and Bias12.1 Precision and reproducibility are intended to be ad-equate for use as a monitoring 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 medi
38、um.12.2 RepeatabilityDuplicate results by the same operatorshould be considered suspect if they differ by more than thefollowing amounts:Mean Particle Countper SlideRepeatabilityCounts2500 650280 9433 136313. Keywords13.1 aerospace environments; aerospace fluids; aerospacegases; aerospace surfaces;
39、membrane filter; microscopicalcounting particles; microscopical sizing particles; particulatematter contaminationAPPENDIX(Nonmandatory Information)X1. CALIBRATIONNOTE X1.1The procedures outlined in this appendix have provensatisfactory for calibration within the tolerances required by the method.The
40、y should not be considered mandatory. Alternative procedures areequally acceptable provided the 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
41、 available stage micrometers(smallest division 10 m). It is necessary, therefore, to calibratean 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
42、be counted, is dependent upon thearea of the filter funnel, but is not identical, since a smallquantity of particles will generally be deposited underneath thefunnel walls.X1.2.2 On very dirty samples it will be possible to measurethe area directly. On most samples from aerospace systems,however, a
43、simulated sample will be necessary.X1.2.3 Disperse a small quantity of pigment such 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
44、determine the effective filterarea (EFA) exactly when using the method for referee pur-poses, certain shortcuts may be made when it is to be used forquality control purposes. If the EFA of all of the funnels to beused is known, it will be found that all funnels deviate 6 to 7 %from the average.NOTE
45、X1.2 ExampleTwenty funnels selected at random from stockhad a measured EFA averaging 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 necess
46、ary to calibrate several unitareas to conform to the requirement of the method that 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 h
47、ighly desirable. There is lessF 312 97 (2003)3chance of an operator overlooking a particle or counting a particle 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
48、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 r
49、eviewed 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 theresponsible 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 I
