ASTM_E_128_-_99_2011.pdf

Designation:E12899(Reapproved 2011)Standard Test Method forMaximum Pore Diameter and Permeability of Rigid PorousFilters for Laboratory Use1This standard is issued under the fixed designation E128;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of maximumpore diameter and permeability of rigid porous filters used inthe laboratory for filtration or diffusion.They are applicable tofilters made of sintered glass,ceramic,metal,or plastic.Thistest method establishes a uniform designation for maximumpore diameter and also provides a means of detecting andmeasuring changes which occur through continued use.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety problems,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D845 Specification for Five-Degree Xylene(Withdrawn1980)33.Terminology3.1 Definitions:3.1.1 maximum pore diameterthe diameter in micrometresof a capillary of circular cross section that is equivalent(withrespect to characteristics related to surface-tension effects)tothe largest pore in the filter under consideration.NOTE1It is recognized that the maximum pore diameter as definedherein does not necessarily indicate the physical dimensions of the largestpore in the filter,and furthermore,that the pores are highly irregular inshape.Because of this irregularity in shape and other phenomenacharacteristic of filtration,a filter may be expected to retain all particleslarger than the maximum pore diameter as defined and determined by thistest method,and will generally retain particles which are much smallerthan the determined diameter.3.1.2 permeabilitythe flow of air,in millimetres per min-ute per square centimetre of filter area per 1 cm of waterpressure differential.4.Summary of Test Method4.1 Maximum Pore Diameter,is determined by immersingthe filter in a suitable test liquid and applying air pressure untilthe first bubble of air passes through the filter.The maximumpore diameter is calculated from the surface tension of the testliquid and the applied pressure.4.2 Permeability is determined by measuring the flow of airthrough the filter when subjected to a pressure differential.5.Apparatus5.1 Because of the variety of shapes of apparatus in whichporous filters are incorporated,the apparatus for this testmethod is not specified in detail.Apparatus that has been foundsatisfactory is illustrated in Fig.1 and Fig.2.6.Procedure6.1 Maximum Pore DiameterThoroughly wet the cleanfilter to be tested by soaking it in the prescribed test liquid(seeTable 1).Connect the filter to a controllable source of clean,dry compressed air,and a manometer(Fig.1).Immerse thefilter just below the surface of the test liquid(Note 2)andgradually increase the air pressure at a rate of about 5 mm/minin the area of the test until the first dynamic bubble passesthrough the filter and rises through the liquid.The appearanceof the first true dynamic bubble is readily recognized since it isfollowed by a succession of additional bubbles.Read thepressure from the manometer.If the test is to be repeated,thoroughly re-wet the filter by soaking it in the test liquid,before proceeding with the retest.Calculate the maximum porediameter from the following equation(see Appendix X1 forderivation):D 5 30/p(1)1This test method is under the jurisdiction of ASTM Committee E41 onLaboratory Apparatus and is the direct responsibility of SubcommitteeE41.01Apparatus Materials.Current edition approved Oct.1,2011.Published November 2011.Originallyapproved in 1957.Last previous edition approved in 2005 as E128 99(2005).DOI:10.1520/E0128-99R11.2For 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 onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 where:D=maximum pore diameter as defined in 3.1.1,=surface tension of test liquid in dynes/cm at the tem-perature of the test,andp=pressure,mm Hg(Note 3).The uniformity of distribution of pores approaching themaximum pore size may be observed by gradually increasingthe air pressure and noting the uniformity with which streamsNOTE1For tests on filter-type crucibles,use a standard rubbe