1、Designation: F778 88 (Reapproved 2014)Standard Methods forGas Flow Resistance Testing of Filtration Media1This standard is issued under the fixed designation F778; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () 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 off
3、ers 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 outli
4、ned in ASME“Fluid Meters.” The test fluid is air.1.4 This standard may involve hazardous materials,operations, 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 safe
5、ty and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D461 Test Methods for Felt (Withdrawn 2003)3D585 Practice for Sampling and Accepting a Single Lot ofPaper, Paperboard, Fiberboard, and Related Product(Withdrawn 20
6、10)3D645/D645M Test Method for Thickness of Paper andPaperboard (Withdrawn 2010)3D685 Practice for Conditioning Paper and Paper Productsfor TestingD737 Test Method for Air Permeability of Textile FabricsD1776 Practice for Conditioning and Testing TextilesD1777 Test Method for Thickness of Textile Ma
7、terialsD2905 Practice for Statements on Number of Specimens forTextiles (Withdrawn 2008)3D3574 Test Methods for Flexible Cellular MaterialsSlab,Bonded, and Molded Urethane FoamsE105 Practice for Probability Sampling of MaterialsE122 Practice for Calculating Sample Size to Estimate, WithSpecified Pre
8、cision, the Average for a Characteristic of aLot or Process2.2 ASME Document:“Fluid Meters,” Sixth Edition, 197143. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 air density, mass per unit volume.3.1.2 air flow resistance, Ppressure drop or pressuredifferential across a test sp
9、ecimen of filter medium at aspecified air face 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 bypasses thetest specimen in geometric planes other than those int
10、ended forresistance measurement.3.1.5 face area, A cross-sectional area perpendicular to airflow 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 p
11、er unit facearea.NOTE 2If specimen inlet and 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
12、 air flow.NOTE 3Medium area may be greater than face area due to pleating,folding, etc.3.1.9 medium velocity, Vmvolumetric flow rate per unitmedium area.3.1.10 normalized resistance, Pproduct of sigma andmeasured air flow resistance.1These methods are under the jurisdiction of ASTM Committee D22 on
13、AirQuality and are the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved April 1, 2014. Published May 2014. Originallyapproved in 1982. Last previous edition approved in 2007 as F778 88 (2007).DOI: 10.1520/F0778-88R14.2For referenced AST
14、M 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.3The last approved version of this historical standard is referenced onwww.astm.
15、org.4Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Two Park Ave., New York, NY 10016-5990, http:/www.asme.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.11 sigma, ratio of air
16、 density existing at test condi-tions to standard air density. Density at standard conditions istaken to be 0.075 lb/ft3(1.201 kg/m3).3.1.12 unconstituted bulk mediathose types of filter mediaformed from unbonded aggregates or discrete solid materials.3.1.13 volumetric rate of flow, Qair volume tran
17、sport perunit time through the test specimen.4. Summary of Methods4.1 The testing outlined in this standard consists of measur-ing 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 o
18、fair-flow resistance across the specimen. In either case, testresults are reported as single or multiple data point orderedpairs of (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 sp
19、ecimen may not be ignored, or the airflowresistance is not linear with face velocity. In these cases,ordered pairs of (normalized resistance, mass flow) are re-ported rather than ordered pairs of (resistance, face velocity).4.3 To provide for quality control application, statisticalprocedures are ou
20、tlined to guide in the selection of a multiplenumber of specimens.4.4 Two test methods involving substantially different testtechniques 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
21、cartridge-type specimens. Thetest technique consists simply of mounting a specimen in aholder and applying air flow.4.4.2 Method BA limited method applying particularly tonondestructive testing of sheets of material that either edgeleak or substantially deform when using the simple clampingapproache
22、s of Method A. The technique for Method B is basedon the “guarded cylinder” principle and requires a concentriccylinder specimen holder, plus provision for two individuallyadjustable air flows. (See Section 15 and Fig. 1.) In theimplementation of Method B, a parallel, evenly distributed airFIG. 1 Sy
23、stem for Measuring Air-flow Resistance of Specimens with Moderate Pressure DropsF778 88 (2014)2flow is perpendicularly directed through a specimen subdividedinto concentric guard and measuring area sections. The twoareas have separate downstream air chambers. To obtain a(resistance, face velocity) d
24、ata 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 the downstream side of the specimen. Pressuredrop is then read for
25、 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 make-up as well as the utility of a filter.5.2 Therefore, flow c
26、haracteristics 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 consumer as a criterion for media selection.5.3 These methods may
27、 also be used for acceptance testing.5.4 For purposes of quality control, meeting productspecification, or acceptance testing, a single-point flow regimeon multiple samples is adequate. However, for design,development, and research, a multiple-point flow regime maybe necessary.6. General Requirement
28、s6.1 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, instrumentation such as manom-eters shall be selected so as to measure pr
29、essure 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 flowmeter air density. In other cases, flow rate maybe obtained from some ki
30、nd of direct-reading instrument suchas a turbine-type flow meter. Whether read directly orcomputed, flow rate shall be determined to within 63%,unless stated otherwise in the data report. This value shall bechecked using a flow prover with traceable accuracy.6.2 Test Apparatus EnvironmentEffects of
31、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.Seasonal changes could reflect a temperature differential of30C and result in
32、 the apparent flow resistance error of 4.5 %.Temperature control must be provided.6.2.2 PressureThe American Institute of PhysicsHandbook, 2nd Edition, gives the pressure increment of airviscosity at 20C and 1 atm as 0.1224 p or a possible 0.67 %error per atmosphere. No precaution is necessary.6.2.3
33、 HumidityThe ASHRAE 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 isnecessary. However, humidity control is required in specimenpreparation. Se
34、e 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 between the purchaser and seller.8. Number of Specimens8.1 Practice D2905
35、 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 depend on the purpose of the test and the availableinformation.8.2 The recom
36、mendations in Practice D2905 describe twoconditions:8.2.1 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 have a reliable estimate of thevariability of the method in his own laboratory.8.3 If the lab
37、oratory 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 t23s2!/E2n 5 t23v2!/A2where:n = number of test specimens required, rounded to the nexthigher whole numb
38、er,s = standard deviation of individual observations expressedin the appropriate units, = coefficient of variation of individual observations ex-pressed as percent of the average, = 100 s/x, andx = average of all the observations for a specific materialt = a constant depending upon the desired proba
39、bility 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 5.410 2.576 6.636E = the allowable variation of the test results expressed inthe same units as s, a
40、ndA = the allowable variation of the test results expressed as apercent of the average.8.4 Criterion for the selection of the appropriate procedurehinges on: (1) choosing between s or as the measure ofvariability; (2) choosing a one-sided or two-sided limit for theF778 88 (2014)3property being measu
41、red; 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 D2905.9. Conditioning of Test Specimens9.1 Because many of the materials used in filter mediaundergo physi
42、cal changes with changes in temperature andmoisture, it is usually desirable to expose the test specimen toa standard 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; fi
43、ber batts ormats; or coated fabrics) should be conditioned as specified byPractice D1776. The standard atmosphere 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
44、6 2C may beused.9.3 Those materials which are considered to be paper orpaper-like should be conditioned as specified by Method D685.The standard atmosphere for this Practice is a relative humidityof 50 6 2 % and a temperature of 23 6 1C (73.4 6 1.8F).9.4 The time duration required for conditioning s
45、hould bethat necessary for the test specimen to attain equilibrium withthe conditioning atmosphere. This is considered 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 ti
46、mes, it may be judged inappropriate to condition thespecimen prior to testing. When conditioning is not used itshould 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 s
47、uch as Methods D461(Section 10), D645/D645M, D1777, and D3574 (Section 7).10.2 Cut media specimens to be used in 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 a
48、rea (and medium area ifdifferent) subsequent to specimen mounting according toSection 6.NOTE 4For flat media to 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 p
49、acking procedures forbulk media are required prior to test. Note any settling of these media asa result of air-flow 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 desi
