1、Designation: F 778 88 (Reapproved 2007)Standard Methods forGas Flow Resistance Testing of Filtration Media1This standard is issued under the fixed designation F 778; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 The flow resistance of any fabricated filter device willdepend on the flow resistance of the media used.1.2 This standard
3、offers procedures sufficient to determinethe gas flow characteristics of flat specimens of media used inthe filtration process. The methods are extended to includepleated specimens and bulk media as well.1.3 In all cases, flow rates through the specimen aredetermined in accordance with procedures ou
4、tlined in ASME“Fluid Meters.” The test fluid is air.1.4 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety problems associated with its use. It isthe responsibility of the user of this standard to establishappropriate
5、 safety and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 461 Test Methods for Felt3D 585 Practice for Sampling and Accepting a Single Lot ofPaper, Paperboard, Fiberboard, and Related ProductD 645/D 645M Test Metho
6、d for Thickness of Paper andPaperboardD 685 Practice for Conditioning Paper and Paper Productsfor TestingD 737 Test Method for Air Permeability of Textile FabricsD 1776 Practice for Conditioning and Testing TextilesD 1777 Test Method for Thickness of Textile MaterialsD 2905 Practice for Statements o
7、n Number of Specimensfor TextilesD 3574 Test Methods for Flexible Cellular MaterialsSlab,Bonded, and Molded Urethane FoamsE 105 Practice for Probability Sampling Of MaterialsE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic of a
8、Lot or Process2.2 ASME Document:“Fluid Meters,” Sixth Edition, 197143. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 air density, rmass per unit volume.3.1.2 air flow resistance, DPpressure drop or pressuredifferential across a test specimen of filter medium at aspecified air f
9、ace velocity or mass flow rate.3.1.3 constituted bulk mediathose types of filter mediaformed from bonded aggregates or discrete solid materials.3.1.4 edge leakageair flow that passes into or bypassesthe test specimen in geometric planes other than those intendedfor resistance measurement.3.1.5 face
10、area, A cross-sectional area perpendicular toair flow at the specimen test boundary.NOTE 1If specimen inlet and exit face areas are different, “Inlet” or“Exit” shall be used to describe the face area in question.3.1.6 face velocity, V volumetric flow rate per unit facearea.NOTE 2If specimen inlet an
11、d exit face areas are different, “Inlet” or“Exit” shall be used to describe the face velocity in question.3.1.7 mass rate of flow, m mass transport of air per unittime through the test specimen.3.1.8 medium area, Amtotal area of filtration media ex-posed to air flow.NOTE 3Medium area may be greater
12、than face area due to pleating,folding, etc.3.1.9 medium velocity, Vmvolumetric flow rate per unitmedium area.3.1.10 normalized resistance, sDPproduct of sigma andmeasured air flow resistance.3.1.11 sigma, sratio of air density existing at test condi-tions to standard air density. Density at standar
13、d conditions istaken to be 0.075 lb/ft3(1.201 kg/m3).1These methods are under the jurisdiction of ASTM Committee D22 on AirQuality and are the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved April 1, 2007. Published June 2007. Original
14、lyapproved in 1982. Last previous edition approved in 2001 as F 778 - 88(2001).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 o
15、nthe ASTM website.3Withdrawn.4Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States
16、.3.1.12 unconstituted bulk mediathose types of filter me-dia formed from unbonded aggregates or discrete solid mate-rials.3.1.13 volumetric rate of flow, Qair volume transport perunit time through the test specimen.4. Summary of Methods4.1 The testing outlined in this standard consists of measur-ing
17、 air-flow resistance (pressure drop) across a specimen ofknown geometry at one or more air-flow rates. Alternatively,the flow rate may be measured at one or more values ofair-flow resistance across the specimen. In either case, testresults are reported as single or multiple data point orderedpairs o
18、f (resistance, face velocity).4.2 For many specimens, the air-flow resistance at flow ratesof interest is of sufficient magnitude that changes in air densityacross the specimen may not be ignored, or the airflowresistance is not linear with face velocity. In these cases,ordered pairs of (normalized
19、resistance, mass flow) are re-ported rather than ordered pairs of (resistance, face velocity).4.3 To provide for quality control application, statisticalprocedures are outlined to guide in the selection of a multiplenumber of specimens.4.4 Two test methods involving substantially different testtechn
20、iques are presented.4.4.1 Method AA general method applicable to all filtra-tion media and forms of media: flat, pleated, constituted, andunconstituted bulk media; small cartridge-type specimens. Thetest technique consists simply of mounting a specimen in aholder and applying air flow.4.4.2 Method B
21、A limited method applying particularly tonondestructive testing of sheets of material that either edgeleak or substantially deform when using the simple clampingapproaches of Method A. The technique for Method B is basedon the “guarded cylinder” principle and requires a concentriccylinder specimen h
22、older, plus provision for two individuallyadjustable air flows (See Section 15 and Fig. 1.) In theimplementation of Method B, a parallel, evenly distributed airflow is perpendicularly directed through a specimen subdividedinto concentric guard and measuring area sections. The twoareas have separate
23、downstream air chambers. To obtain a(resistance, face velocity) data point, the appropriate volumet-ric flow rate is established through the measuring area. Theguard area volumetric flow rate is then established so that thedifferential pressure between guard and measuring area cham-bers is zero on t
24、he downstream side of the specimen. Pressuredrop is then read for flow through the specimen measuringarea. Guard area flow rate need not be determined.5. Significance and Use5.1 The air-flow resistance (pressure drop) of a filter is animportant parameter that can assist in characterizing thephysical
25、 make-up as well as the utility of a filter.5.2 Therefore, flow characteristics of clean filter media canbe used for quality control, product development, and basicresearch. It may be used by the producer of filter media toillustrate media type or to meet product specification and canbe used by the
26、consumer as a criterion for media selection.5.3 These methods may also be used for acceptance testing.5.4 For purposes of quality control, meeting product speci-fication, or acceptance testing, a single-point flow regime onmultiple samples is adequate. However, for design, develop-ment, and research
27、, a multiple-point flow regime may benecessary.6. General Requirements6.1 Instrument Accuracy:6.1.1 The procedures of these methods require measurementof pressure drop and either volumetric or mass flow rate.6.1.2 Pressure drop is a direct measurement. Unless statedotherwise in the data report, inst
28、rumentation such as manom-eters shall be selected so as to measure pressure within 63%of the indicated value. Instruments shall be checked against atraceable standard.6.1.3 Flow rate is generally a derived quantity obtainedfrom computations involving a differential pressure type ele-ment and flowmet
29、er air density. In other cases, flow rate maybe obtained from some kind of direct-reading instrument suchas a turbine-type flow meter. Whether read directly or com-puted, flow rate shall be determined to within 63 %, unlessstated otherwise in the data report. This value shall be checkedusing a flow
30、prover with traceable accuracy.6.2 Test Apparatus EnvironmentEffects of environmentalconditions on the test air viscosity need to be examined toensure duplication of test results.6.2.1 TemperatureAir viscosity increases as temperatureincreases at a rate which, at 20C, is approximately 0.15 %/C.Seaso
31、nal changes could reflect a temperature differential of30C and result in the apparent flow resistance error of 4.5 %.Temperature control must be provided.6.2.2 PressureThe American Institute of Physics Hand-book, 2nd Edition, gives the pressure increment of air viscosityat 20C and 1 atm as 0.1224 p
32、or a possible 0.67 % error peratmosphere. No precaution is necessary.6.2.3 HumidityTheASHRAE Handbook of Fundamentalsin the chapter on Psychrometrics reveals that even for theextreme case of saturated air at 100F there is not a significantviscosity difference from that of dry air. No precaution isne
33、cessary. However, humidity control is required in specimenpreparation. See Section 10.7. Sampling7.1 The sample to be tested as a flat media, pleated media,or bulk media should be obtained under the guidance of theparticular standard or specification covering the generic mate-rial or as agreed upon
34、between the purchaser and seller.8. Number of Specimens8.1 Practice D 2905 covers six recommendations for deter-mining the number of specimens necessary to elucidate theaverage quality of a material under various conditions. Thechoice of the six recommendations to be used in a specificmethod will de
35、pend on the purpose of the test and the availableinformation.8.2 The recommendations in Practice D 2905 describe twoconditions:F 778 88 (2007)28.2.1 The procedure to follow when the user has a reliableestimate of the variability of the method in his own laboratory;and,8.2.2 When the user does not ha
36、ve a reliable estimate of thevariability of the method in his own laboratory.8.3 If the laboratory has a reliable estimate of variationexpressed either as a standard deviation or as a coefficient ofvariation, then the number of specimens could be determinedby the following equations:n 5 t23 s2!/E2n
37、5 t23 v2!/A2where:n = number of test specimens required, rounded to the nexthigher whole number,s = standard deviation of individual observations expressedin the appropriate units,n = coefficient of variation of individual observations ex-pressed as percent of the average,n = 100 s/ x, andx = averag
38、e of all the observations for a specific materialt = a constant depending upon the desired probability leveland equal to Students t for infinite degrees of freedom,for example:Probability Level, % One-sided Limits Two-Sided Limitstt2tt290 1.282 1.644 1.645 2.70695 1.645 2.706 1.960 3.84299 2.326 5.4
39、10 2.576 6.636E = the allowable variation of the test results expressed inthe same units as s, andA = the allowable variation of the test results expressed asa percent of the average.8.4 Criterion for the selection of the appropriate procedurehinges on: (1) choosing between s or n as the measure ofv
40、ariability; (2) choosing a one-sided or two-sided limit for theproperty being measured; and, (3) if no variation data areavailable, arbitrarily decide on the number of specimensdictated by the type and character of the material. For moredetails, refer to Section 5 of Practice D 2905.FIG. 1 System fo
41、r Measuring Air-flow Resistance of Specimens with Moderate Pressure DropsF 778 88 (2007)39. Conditioning of Test Specimens9.1 Because many of the materials used in filter mediaundergo physical changes with changes in temperature andmoisture, it is usually desirable to expose the test specimen toa st
42、andard conditioned atmosphere for a period of time beforetesting is initiated.9.2 Those materials which are considered to be textiles ortextile-like (woven, knitted, or nonwoven fabrics; fiber batts ormats; or coated fabrics) should be conditioned as specified byPractice D 1776. The standard atmosph
43、ere for this Practice is arelative humidity of 65 6 2 % and a temperature of 21 6 1C(70 6 2F). When international testing is involved, a relativehumidity of 65 6 2 % and a temperature of 20 6 2C may beused.9.3 Those materials which are considered to be paper orpaper-like should be conditioned as spe
44、cified by MethodD 685. The standard atmosphere for this Practice is a relativehumidity of 50 6 2 % and a temperature of 23 6 1C (73.4 61.8F).9.4 The time duration required for conditioning should bethat necessary for the test specimen to attain equilibrium withthe conditioning atmosphere. This is co
45、nsidered to haveoccurred when the change in the mass of the specimen insuccessive weighings made at intervals of not less than 2 h,does not exceed 0.2 % of the mass of the specimen.9.5 At times, it may be judged inappropriate to condition thespecimen prior to testing. When conditioning is not used i
46、tshould be so reported in the results. See Section 18.10. Dimensional Measurement of Test Specimens10.1 Determine media thickness prior to mounting for testand in accordance with standards such as Methods D 461(Section 10), D 645, D 1777, and D 3574 (Section 7).10.2 Cut media specimens to be used in
47、 other than simplemounting techniques and install in holders without altering thephysical character of the matrix (for example, fused edges, tornedges, etc.).10.3 Determine specimen face area (and medium area ifdifferent) subsequent to specimen mounting according toSection 6.NOTE 4For flat media to
48、be tested using the simple clampingprocedures of MethodA, or to be tested using Method B, the test specimenholder will dictate specimen face area.NOTE 5Dimensions of specimen holders and packing procedures forbulk media are required prior to test. Note any settling of these media asa result of air-f
49、low testing (see Section 18).METHOD A11. Requirements for Method A11.1 Specimen Mounting:11.1.1 GeneralSpecimen mounting is a critical consider-ation in the application of this test method. It is a requirementthat mounting techniques be selected which eliminate edgeleakage, yet do not deform the medium to the extent thatair-flow resistance is affected.11.1.2 Flat MediaFor flat filtration media in particular, itis desirable to use simple clamping techniques such as sug-gested in Annex A1 instead of more elaborate specimenpreparation. Absenc
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