ASTM F312-08(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F312 − 08 (Reapproved 2023)
Standard Test Methods for
Microscopical Sizing and Counting Particles from
Aerospace Fluids on Membrane Filters
This standard is issued under the fixed designation F312; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 These test methods cover the determination of the size 2.1 ASTM Standards:
distribution and quantity of particulate matter contamination F302 Practice for Field Sampling of Aerospace Fluids in
from aerospace fluids isolated on a membrane filter. The Containers
microscopical techniques described may also be applied to F303 Practices for Sampling for Particles in Aerospace
other properly prepared samples of small particles. Two test Fluids and Components
methods are described for sizing particles as follows: F311 Practice for Processing Aerospace Liquid Samples for
1.1.1 Test Method A—Particle sizes are measured as the Particulate Contamination Analysis Using Membrane Fil-
diameter of a circle whose area is equal to the projected area of ters
the particle. F314 Methods of Test for Identification of Metallic and
1.1.2 Test Method B—Particle sizes are measured by their Fibrous Contaminants in Aerospace Fluids (Withdrawn
longest dimension. 1990)
F318 Practice for Sampling Airborne Particulate Contami-
1.2 The test methods are intended for application to particle
nation in Cleanrooms for Handling Aerospace Fluids
contamination determination of aerospace fluids, gases,
(Withdrawn 2013)
surfaces, and environments.
1.3 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 unit area, n—the area selected for counting particles.
1.4 These test methods do not provide for sizing particles
This may be the area of a reticle grid or some subdivision
smaller than 5 μm.
thereof, the area of one imprinted membrane grid, or any other
accurately calibrated area.
NOTE 1—Results of these methods are subject to variables inherent in
any statistical method. The use of these methods as a standard for initially
3.1.2 effective filter area, n—the area of the membrane
establishing limits should be avoided unless ample tolerances are permis-
which entraps the particles to be counted.
sible.
3.1.3 particle size, n—the size of a particle as defined by
1.5 This standard does not purport to address all of the
area comparison or by its longest dimension.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Methods
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4.1 The membrane is examined through a microscope and
1.6 This international standard was developed in accor-
the particles counted according to size or size categories using
dance with internationally recognized principles on standard-
a calibrated reticle. The total number of particles present is
ization established in the Decision on Principles for the
estimated by statistical methods from the actual number of
Development of International Standards, Guides and Recom-
particles counted. Either sizing Test Method A or B may be
mendations issued by the World Trade Organization Technical
selected according to the preference and results expected.
Barriers to Trade (TBT) Committee.
1 2
These test methods are under the jurisdiction of ASTM Committee E21 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Space Simulation and Applications of Space Technology and are the direct contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
responsibility of Subcommittee E21.05 on Contamination. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Sept. 1, 2023. Published September 2023. Originally the ASTM website.
approved in 1969. Last previous edition approved in 2016 as F312 – 08 (2016). The last approved version of this historical standard is referenced on
DOI: 10.1520/F0312-08R23. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F312 − 08 (2023)
5. Significance and Use 7. Sampling
5.1 Reported particle size measurement is a function of both 7.1 Collect and process the sample in accordance with the
the actual particle dimension and shape factor, as well as the applicable methods of the American Society for Testing and
particular physical or chemical properties of the particle being Materials, as follows: Practice F302, Practice F311, Practice
measured. Caution is required when comparing data from F318, and Practices F303.
instruments operating on different physical or chemical param-
eters or with different particle size measurement ranges. 8. Calibration
Sample acquisition, handling, and preparation can also affect
8.1 The sizing reticle shall be calibrated at each magnifica-
the reported particle size results.
tion by comparing the reference divisions noted in 6.3 with the
rulings on the stage micrometer. Detailed calibration proce-
6. Apparatus
dures and a discussion of errors are given in Appendix X1.
6.1 Microscope, capable of resolving the smallest particles
8.2 The area extrapolation factor used for statistical count-
to be counted and producing a flat field of view.
ing is determined by the ratio of the area counted to the total
6.1.1 The following optic combinations are recommended:
effective area of the membrane filter.
Minimum
8.2.1 Unit Area—Measure the size of the appropriate unit
Magnification Ocular Objective Numerical
area with the stage micrometer or previously calibrated reticle
Aperture
50× 10× 5× 0.15 and calculate its area.
100× 10× 10× 0.25
8.2.2 Effective Filter Area (Note 3)—Measure the diameter
200× 10× 20× 0.50
of the effective filter area with a scale, caliper, or calibrated
Similar ocular-objective combinations resulting in magnifi-
mechanical stage and calculate the total area. Area = π r ,
cations of 50 6 10×, 100 6 10×, and 200 6 20× may be used.
where r is the radius of the effective circle.
The optimum equipment is a compound binocular microscope.
NOTE 3—Where accurate effective filtering area measurements are
Conventional stereo microscopes will not meet these require-
required, a colored pigment solution should be filtered through the
ments.
filtration apparatus as described in Practice F311.
6.2 Mechanical Stage, capable of traversing the entire
8.2.3 Area Extrapolation Factor—The total particle count
effective filter area.
for a given size range is determined as follows:
6.3 Stage Micrometer, with 0.1-mm and 0.01-mm subdivi-
C 5 ~C × A !/~A × N! (1)
t e u
sions.
where:
6.4 Provisions for variable high-intensity external oblique
C = total extrapolated count,
t
incident illumination and for a focusing condenser. A flexible
C = actual particle count,
or jointed arm is desirable.
A = effective filter area,
e
A = unit area, and
u
6.5 Reticles, inscribed with reference markings that can be
N = number of unit areas counted.
calibrated to represent the following dimensions:
Magnification Size, μm Tolerance, μm
9. Procedure
200 ± 20× 5 ±0.8
15 ±1.2
9.1 While exact details of the counting procedure depend
100 ± 10× 15 ±1.5
25 ±2.0 partly on the specific equipment chosen, all procedures must
50 ± 10× 50 ±2.5
conform to the requirements given in 9.1.1 – 9.1.9 to achieve
50 ±2.5
reproducibility. Methods A and B differ only in the sizing of
100 ±5.0
particles, and the detailed procedure given shall be used for
6.5.1 The reticles shall be as follows:
either Reticle A or B.
6.5.1.1 Reticle A, Globe and Circle Pattern, provides a
9.1.1 Blank analysis counts, which are part of the normal
means for correlation of the microscopic method with auto-
processing procedure, must be used to determine the adequacy
matic counter methods. Reticle A uses the diameter of a circle
of environmental control.
for its comparison of a particle, and automatic counter
...