ASTM E3278-21

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: E3278 − 21
Standard Test Method for
Bubble Point Pressure of Woven Wire Filter Cloth
This standard is issued under the fixed designation E3278; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E1638Terminology Relating to Sieves, Sieving Methods,
and Screening Media
1.1 This test method is based on a capillary flow test that
E2814Specification for Industrial Woven Wire Filter Cloth
measures the pressure required to force an air bubble through
a flat specimen of industrial woven wire filter cloth wetted 2.2 SAE Standards:
under a test liquid of known surface tension. An established ARP901Bubble-Point Test Method
physical phenomenon, the pressure is inversely proportional to
the pore size. This test method details the methodology to 3. Terminology
determine the bubble point pressure, and the applicable vari-
3.1 Definitions:
ables to calculate a standardized pressure. The test is recom-
3.1.1 For definitions of related terms, refer to Terminology
mended for filter cloth with a minimum test pressure of 1.0
E1638.
inches of water.
3.2 Definitions of Terms Specific to This Standard:
1.2 A means for determining a pore size calculation factor
3.2.1 absolute filtration rating, n—largestporesizefoundin
(CF)isprovidedtoallowthecalculationofaporesizefromthe
the test specimen.
resultant pressure (see 15.2).
3.2.2 hydraulic diameter, n—the diameter equal to four
1.3 This test method uses mixed unit of measures. The
times the pore throat area divided by the pore throat perimeter.
values stated in inch-pound units shall be considered standard
3.2.2.1 Discussion—This diameter can be generated using
with regard to the bubble point pressure, test fixture, and
4,5
procedures. The values stated in SI units shall be considered the PoroDict module in the software GeoDict (see 4.2.2).
standard for the test fluid properties and pore size.
3.2.3 hydraulic diameter bubble point pressure, n—a pres-
1.4 This standard does not purport to address all of the
sure calculated using the hydraulic diameter.
safety concerns, if any, associated with its use. It is the
3.2.3.1 Discussion—This pressure can be generated using
responsibility of the user of this standard to establish appro-
the PoroDict module in the software GeoDict (see 4.2.2), and
priate safety, health, and environmental practices and deter-
is based on a statistically fitted bubble contact angle of 40
mine the applicability of regulatory limitations prior to use.
degrees and the hydraulic diameter.
1.5 This international standard was developed in accor-
3.2.4 percolationpathfittingparticlediameter,n—themaxi-
dance with internationally recognized principles on standard-
mum pore diameter based on the percolation path geometric
ization established in the Decision on Principles for the
pore size analysis.
Development of International Standards, Guides and Recom-
3.2.4.1 Discussion—This diameter can be generated using
mendations issued by the World Trade Organization Technical
the PoroDict module in the software GeoDict (see 4.2.2), and
Barriers to Trade (TBT) Committee.
which results have been shown to correspond to the results of
glass bead testing (see Specification E2814, Table 1).
2. Referenced Documents
3.2.5 pore size, n—themaximumequivalentsphericaldiam-
2.1 ASTM Standards:
eter of an opening in the filter cloth.
This test method is under the jurisdiction ofASTM Committee E29 on Particle
and Spray Characterization and is the direct responsibility of Subcommittee E29.01 AvailablefromSAEInternational(SAE),400CommonwealthDr.,Warrendale,
on Sieves, Sieving Methods, and Screening Media. PA 15096, http://www.sae.org.
Current edition approved May 1, 2021. Published September 2021. DOI: GeoDict is a trademark of Math2Market GmbH, Kaiserslautern, Germany.
10.1520/E3278-21. The sole source of supply of this simulation program known to the committee
For referenced ASTM standards, visit the ASTM website, www.astm.org, or atthistimeisGeoDictbyMath2MarketGmbH,Kaiserslautern,Germany.Ifyouare
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM aware of alternative suppliers, please provide this information to ASTM Interna-
Standards volume information, refer to the standard’s Document Summary page on tional Headquarters.Your comments will receive careful consideration at a meeting
the ASTM website. of the responsible technical committee, which you may attend.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3278 − 21
3.2.6 pore size calculation factor (CF), n— a factor calcu-
p = measured pressure (inches of water).
lated using the hydraulic diameter bubble point pressure and
This measured pressure will be corrected for other test
the percolation path fitting particle diameter.
6 conditions (that is, surface tension as a function of tempera-
FILTECH 2016
ture) to a standardized pressure P as in accordance with 15.1:
3.2.6.1 Discussion—This factor can be generated using the
PoroDict module in the software GeoDict (see 4.2.2), and is D 5340⁄P (3)
used to calculate the pore size from the bubble point pressure.
4.2.1 However, this equation is only for this perfect model,
3.2.7 tortuosity factor, n—the ratio of the length of the path
and must be corrected based on either the actual contact angle
aparticlemustfollowthroughthefilterclothtotheactualfilter
oratortuosityfactorforthefiltercloth.Forthecaseofabubble
cloth thickness.
passingthroughtheirregular,obtusetriangularopeningformed
3.2.7.1 Discussion—The fluid flow path through filter cloth
by the round wires of woven filter cloth, the bubble does not
is a distance somewhat longer than the mere thickness of the
stay circular and the contact angle can only be hypothesized.
cloth due to its complex geometry; the tortuosity factor of the
Based on glass bead testing data (see Specification E2814,
filterclothspecificationisusedtocorrecttheporesizeequation
Table1),reversecalculationindicatesacontactangleof40–50
(see 4.2.1), and in general the greater the porosity of the filter
degrees is most likely for woven wire filter cloth (see the
cloth the lower the tortuosity factor.
Discussion for 3.2.3, hydraulic diameter bubble point pres-
sure).Alternatively, a tortuosity factor (TF) may be applied to
4. Summary of Test Method
correct for the path of the bubble:
4.1 A bubble point test, a type of liquid-gas capillary flow
D 5340⁄ P · TF (4)
porometry, is conducted by mounting the filter cloth specimen ~ !
in a special test fixture, immersed in a test liquid, and gas
The same empirical data indicates a tortuosity factor in the
pressure is slowly applied to the wetted specimen. A manom-
rangeof1.3–1.5ismostappropriate,andwhileSAEARP901
eter is used to determine the pressure when the first gas bubble
suggests a value of 1.65 be used, it recognizes that significant
stream is observed on the surface of the specimen. This
variation is actually likely (see Specification E2814, 6.3.1). So
pressureindicatestheabsolutefiltrationratingofthespecimen.
for example, if TF = 1.45 is applied, D = 235 / P.
The procedure to correct for specific test conditions is pre-
4.2.2 A new type of software-based conversion factor, the
sented in order to standardize the test result pressure.
pore size CF, is suggested by this test method. The PoroDict
4.2 As background information, the bubble point test
module of the commercially available software GeoDict cal-
characterization technique is based on displacing a wetting
culates the CF based on the non-circular cross-section of the
liquidfromaporebyapplyingagaspressure,withthephysical
bottle neck of the through-path of the filter cloth. The CF is
phenomena that smaller pores are emptied at higher pressures.
different than the geometric tortuosity factor. In addition to
The pore diameter is calculated using the measured pressure
improved correlation, the ability to generate a specific factor
basedontheYoung-Laplaceequationfortheequilibriumofthe
for each different filter cloth specification is achieved (see
gas pressure and surface tension forces:
Appendix X1).
D 54γ cosθ⁄p (1)
5. Significance and Use
where:
D = pore size diameter (µm),
5.1 Usersofindustrialwovenwirefilterclothascoveredby
p = measured pressure (kPa),
Specification E2814 commonly desire to specify the largest
γ = surface tension of the wetting liquid (dynes/cm), and
pore size as determined by converting the pressure result of a
θ = contact angle of the wetting liquid with the sample
bubble point test to an absolute filtration rating in micrometres
(degrees).
(also known as microns). This test method requires a compre-
Then simplifying for the case of a straight, cylindrical pore
hensive bubble point test method as well as a valid tortuosity
through a thin film where the contact angle is 0, and for
or conversion factor for the calculation. This pore size result
isopropanol wetting liquid (see 8.1) with a surface tension of
may be used as a standard rating of a material specification, a
21.2dynes/cmat77°F(25°C),converting pinkPatoinchesof
performance evaluation or acceptance criteria for material
st
water using 0.24909 yields:
supplied, or a 1 article inspection requirement during the
D 5340⁄p (2) weaving of the cloth. The test is conducted using sample
material cut from a woven roll of cloth, and hence should be
where:
indicative of the manufactured lot, given the application of
D = pore size diameter (µm), and
appropriate tolerances.
5.2 While some users may desire a bubble point test
conducted on some finished, fabricated filter unit, the test
FILTECH2016–L11FilterMedia–PoreSizeAnalysis,“The‘True’PoreSize
of Textile Filter Media and its Relevance for the Filtration Process with Respect to
conditions for this type of test are outside the scope of this test
the Interaction withApparatus and Suspension,” HaraldAnlauf, Karlsruhe Institute
method. The geometric test parameters for this type of speci-
of Technology (KIT), Karlsruhe, Germany.
7 menmustbeexplicitlyagreedtobytheuserandproducer,and
Drioli,E.,andGiorno,L., Comprehensive Membrane Science and Engineering,
Elsevier, UK, 2010, p. 318. is to be considered a custom test method.
E3278 − 21
6. Interferences 7.2.1 Reservoir depth shall be 0.5 in. minimum/2.0 in.
maximum.
6.1 Cleanliness of Test Specimen—The specimen should be
7.2.2 Gas inlet diameter shall be 0.12 in. diameter mini-
cleaned to be free of foreign contamination.
mum.
6.2 Temperature of the Test Liquid—Thesurfacetensionand
7.2.3 Gas Inlet Depth—the center of the inlet shall be no
densityofthetestliquidisafunctionoftemperature(see12.1).
less than 3× the inlet diameter below the bottom of the test
specimen (which results in 0.36 in. minimum depth for a
6.3 Rate of Gas Pressure Increase—The bubble point test
result is a function of gas pressure ramp rate, and excessive minimum inlet diameter, and effectively limits the inlet diam-
eter to ~0.57 in. maximum at a 2.0 in. reservoir depth).
ramp rate will cause false readings (see 14.6).
6.4 Test Specimen Immersion Depth—While bubble point 7.3 Manometer—accuracy within 60.1 % (full scale), read-
ability 0.01 inches of water if ability to record maximum
theoryisbasedonsurfacetensionbeingthedominantforce,for
larger pore size specifications where the test pressure is below pressure (recommended), readability 0.1 inches of water if
visual only.
~2in.ofwater,anexcessiveimmersiondepthmayresultinthe
fluid column head pressure force becoming significant, which
7.4 Compressed air (or nitrogen) with dual pressure regu-
will cause erroneous results (see 12.2 and Appendix X2).
lators
6.5 Depth of Test Fixture Gas Outlet—There is the potential
7.5 Liquid temperature measurement, accuracy 60.5°F
for bubble turbulence due to the gas outlet too close to the
7.6 Scale—to measure specimen immersion depth within
bottom surface of the test specimen (see 7.2.3).
0.1 in. (use of gauge strip recommended).
6.6 Cleanliness of Gas—The gas should be sufficiently
clean and dry to prevent variability of results.
8. Reagents and Materials
6.7 Specific Gravity of the Test Liquid—For isopropyl alco-
8.1 The standard test liquid shall be reagent grade isopro-
hol within the range of typical room temperature, the effec
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