ASTM E128-99(2019)

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: E128 − 99 (Reapproved 2019)
Standard Test Method for
Maximum Pore Diameter and Permeability of Rigid Porous
Filters for Laboratory Use
This standard is issued under the fixed designation E128; 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 3.1.1 maximum pore diameter—thediameterinmicrometres
of a capillary of circular cross section that is equivalent (with
1.1 This test method covers the determination of maximum
respect to characteristics related to surface-tension effects) to
pore diameter and permeability of rigid porous filters used in
the largest pore in the filter under consideration.
the laboratory for filtration or diffusion. They are applicable to
filters made of sintered glass, ceramic, metal, or plastic. This
NOTE 1—It is recognized that the maximum pore diameter as defined
herein does not necessarily indicate the physical dimensions of the largest
test method establishes a uniform designation for maximum
pore in the filter, and furthermore, that the pores are highly irregular in
pore diameter and also provides a means of detecting and
shape. Because of this irregularity in shape and other phenomena
measuring changes which occur through continued use.
characteristic of filtration, a filter may be expected to retain all particles
larger than the maximum pore diameter as defined and determined by this
1.2 The values stated in SI units are to be regarded as
test method, and will generally retain particles which are much smaller
standard. No other units of measurement are included in this
than the determined diameter.
standard.
3.1.2 permeability—the flow of air, in millimetres per min-
1.3 This standard does not purport to address all of the
ute per square centimetre of filter area per 1 cm of water
safety concerns, if any, associated with its use. It is the
pressure differential.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 Maximum Pore Diameter, is determined by immersing
1.4 This international standard was developed in accor-
the filter in a suitable test liquid and applying air pressure until
dance with internationally recognized principles on standard-
the first bubble of air passes through the filter. The maximum
ization established in the Decision on Principles for the
pore diameter is calculated from the surface tension of the test
Development of International Standards, Guides and Recom-
liquid and the applied pressure.
mendations issued by the World Trade Organization Technical
4.2 Permeability is determined by measuring the flow of air
Barriers to Trade (TBT) Committee.
through the filter when subjected to a pressure differential.
2. Referenced Documents
5. Apparatus
2.1 ASTM Standards:
5.1 Because of the variety of shapes of apparatus in which
D845 Specification for Five-Degree Xylene (Withdrawn
3 porous filters are incorporated, the apparatus for this test
1980)
method is not specified in detail.Apparatus that has been found
satisfactory is illustrated in Fig. 1 and Fig. 2.
3. Terminology
3.1 Definitions:
6. Procedure
6.1 Maximum Pore Diameter—Thoroughly wet the clean
filter to be tested by soaking it in the prescribed test liquid (see
This test method is under the jurisdiction of ASTM Committee E41 on
Table 1). Connect the filter to a controllable source of clean,
Laboratory Apparatus and is the direct responsibility of Subcommittee E41.01 on
Laboratory Ware and Supplies.
dry compressed air, and a manometer (Fig. 1). Immerse the
Current edition approved Nov. 1, 2019. Published November 2019. Originally
filter just below the surface of the test liquid (Note 2) and
approvedin1957.Lastpreviouseditionapprovedin2011asE128 – 99(2011).DOI:
gradually increase the air pressure at a rate of about 5 mm/min
10.1520/E0128-99R19.
in the area of the test until the first dynamic bubble passes
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
through the filter and rises through the liquid. The appearance
Standards volume information, refer to the standard’s Document Summary page on
of the first true dynamic bubble is readily recognized since it is
the ASTM website.
followed by a succession of additional bubbles. Read the
The last approved version of this historical standard is referenced on
www.astm.org. pressure from the manometer. If the test is to be repeated,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E128 − 99 (2019)
NOTE 1—For tests on filter-type crucibles, use a standard rubber crucible adapter. For test sticks and candles a rubber stopper with a rubber tubing
attached is suitable. Clean dry compressed air shall be used.
FIG. 1 Apparatus for Determining Maximum Pore Diameter of Rigid Porous Filters
NOTE 1—For tests on filter-type crucibles, use a standard rubber crucible adapter. For test sticks and candles a rubber stopper with a rubber tubing
attached is suitable. Clean dry compressed air shall be used.
FIG. 2 Apparatus for Determination of Permeability
TABLE 1 Test Liquids Suitable for Use with Various Types of Filters
A
Filter Suitable Test Liquids
Approximate Surface
Max Pore Diameter, Tension, dynes/cm at
Material of Construction µm Liquid 20°C
Glass >4 water 72
B
<4 alcohol 22
Porcelain >3 water 72
<3 alcohol 22
Stainless steel all alcohol 22
C
xylene 29
Tetrafluoro-polyethylene all alcohol 22
Trifluoromonochloropolyethylene all alcohol 22
A
The specified liquids wet the respective
...