1、Designation: F 312 08Standard 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, in the case of rev
2、ision, the 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 These test methods cover the determination of the sizedistribution and quantity of particulate matt
3、er 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 measured as thediam
4、eter 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 environments.1.3 The
5、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 of these m
6、ethods 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-priate sa
7、fety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F 302 Practice for Field Sampling of Aerospace Fluids inContainersF 303 Practices for Sampling for Particles in AerospaceFluids and ComponentsF311 Practice for
8、 ProcessingAerospace Liquid Samples forParticulate Contamination Analysis Using Membrane Fil-tersF 314 Method of Test for Identification of Metallic andFibrous Contaminants in Aerospace Fluids3F 318 Practice for Sampling Airborne Particulate Contami-nation in Cleanrooms for Handling Aerospace Fluids
9、3. 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 areathe area of the membrane whichentraps th
10、e 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 categories usinga calibrated reticle. The total
11、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 measurement is a function of boththe actual pa
12、rticle dimension and shape factor as well as theparticular physical or chemical properties of the particle beingmeasured. Caution is required when comparing data frominstruments operating on different physical or chemical param-eters or with different particle size measurement ranges.1These test met
13、hods are under the jurisdiction of ASTM CommitteeE21 onSpace Simulation andApplications of Space Technology are the direct responsibilityof Subcommittee E21.05 on ContaminationCurrent edition approved Nov. 1, 2008. Published December 2008. Originallyapproved in 1969. Last previous edition approved i
14、n 2003 as F 312 97(2003).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 website.3Withdrawn. The last approved versio
15、n of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Sample acquisition, handling and preparation can also affectthe reported particle size results.6. Apparatus6.1 Microscope, cap
16、able 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 ObjectiveMinimumNumericalAperture503 103 53 0.151003 103 103 0.252003 103 203 0.50Similar ocular-objective combinations resulting in ma
17、gnifi-cations of 50 6 103, 100 6 103, and 200 6 203 may beused. The optimum equipment 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
18、-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 following dimensions:Magnification Size, m Tole
19、rance, m200 6 203 5 60.815 61.2100 6 103 15 61.525 62.050 6 103 50 62.550 62.5100 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 circle
20、for 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 dimension technique.NOTE 2Some retic
21、les 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 with theapplicable methods of
22、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 each magnifica-tion by comparing the reference divisions noted in 6.3 with therulings on the stage micrometer. Deta
23、iled 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 of the appropriate unitar
24、ea 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 = pr2,where r is the radius of the effectiv
25、e 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 determined as follows:Ct5 C 3
26、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 mustconform to the requi
27、rements 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 to determine the adequacyo
28、f 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-to-width ratio exceeding 1
29、0 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 suitable holder) on themechanical stage; adjust the lamp and microscope to achievemaximum particle definition.9.1.4 Using
30、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 20 particles inthe size range counted at 503. In most cases this will representthe entire effective filtration area
31、. 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 area and record all particles in the new unit areaexceeding 100 m.9.1.7 Continue until either the entire effective f
32、ilter 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.F3120829.1.8 Repeat the procedure 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
33、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 given size range if its apparentsize is equal to or greater than the reference. Particles whoseapparent size is
34、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 magnification may becounte
35、d 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 filtering area is reached on
36、 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 count times the area extrapol
37、ation 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 sizecategory shall be repor
38、ted 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 monitoring method, but the color
39、 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 differ by more than thefollo
40、wing amounts:Mean Particle Countper SlideRepeatabilityCounts2500 650280 9433 136313. Keywords13.1 aerospace environments; aerospace fluids; aerospacegases; aerospace surfaces; membrane filter; microscopicalcounting particles; microscopical sizing particles; particulatematter contaminationAPPENDIX(No
41、nmandatory 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 end result is equivalent.X1.
42、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 even multiple of 10 m and c
43、alculate 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 smallquantity of particles will ge
44、nerally 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 simulated sample will be necessary.X1.2.3 Disperse a small quantity of pigment such as ironoxide in a sample of the fluid to
45、 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 referee pur-poses, certain shortcuts may be made
46、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 X1.2 ExampleTwenty funnels selected at random from stockhad a measured EFA averaging 1018 mm2and ranging from 984 to 1081mm2
47、. 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 notmore than 20 particles in a given siz
48、e range be counted per unitarea. It should be emphasized that the 20-particle limit is aF312083maximum and that to avoid operation confusion a unit areacontaining fewer particles is highly desirable. There is lesschance of an operator overlooking a particle or counting aparticle twice if a smaller n
49、umber 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 reviewed every five years andif not revised, either reapproved or withdrawn. Your
