1、BRITISH STANDARD BS 1752:1983 ISO 4793:1980 Specification for Laboratory sintered or fritted filters including porosity grading ISO title: Laboratory sintered (fritted) filters Porosity grading, classification and designation UDC 542.67.07BS1752:1983 This British Standard, having been prepared under
2、 the directionof the Laboratory Apparatus Standards Committee,was published underthe authority of the BoardofBSI and comes intoeffecton 30 December 1983 BSI 11-1999 BS 1752 First published February1952 BS 1969 First published July 1953 First combined revision as BS1752 February 1963 Second revision
3、December 1983 The following BSI references relate to the work on this standard: Committee reference LBC/13 Draft for comment 78/53345 DC ISBN 0 580 13629 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Laboratory Apparatus Standards Co
4、mmittee (LBC/-) to Technical Committee LBC/13 upon which the following bodies were represented: British Laboratory Ware Association British Plastics Federation Confederation of British Industry Glass Manufacturers Federation Institution of Chemical Engineers Royal Society of Chemistry Coopted member
5、s Amendments issued since publication Amd. No. Date of issue CommentsBS1752:1983 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 Definitions 1 3 Quality 1 4 Grading of filters 1 5 Limits for pore size index 1 6 Uniformit
6、y test 1 7 Permeability 1 Annex A Method for determination of pore size index 2 Annex B Procedure for assessing uniformity of filters 3 Annex C Method for determination of air permeability 3 National appendix Differences between the 1963 and 1983 editions of BS 1752 Inside back cover Figure 1 Appara
7、tus for determination of pore size index 4 Figure 2 Apparatus for determination of air permeability 5 Table 1 Grading of filters 1 Table 2 Permeability of filters 1 Table 3 Suitable test liquids 2BS1752:1983 ii BSI 11-1999 National foreword This British Standard has been prepared under the direction
8、 of the Laboratory Apparatus Standards Committee and is identical with ISO4793 “Laboratory sintered (fritted) filters Porosity grading, classification and designation” published in 1980 by the International Organization for Standardization (ISO). It is a revision of BS1752:1963 which is withdrawn. T
9、he principal differences between this edition of BS1752 and the 1963 edition concern the porosity grading and designation. Whilst all the designations have changed, only some of the limits of pore size have changed. To assist purchasers of laboratory sintered filters, the changes are shown graphical
10、ly in a National appendix. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn es
11、pecially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Ad
12、ditional information. The unit of pressure used in this standard is the bar. For conversion to SI units, the equation 1bar = 100kPa should be used. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct
13、application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright
14、date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS1752:1983 BSI 11-1999 1 1 Scope and field of application This International Standard specifies a system of porosity grading, classifying and designating laboratory sintered (frit
15、ted) filters by the determination of pore size index. It is applicable to laboratory filters made of glass, vitreous silica, ceramics, metals and plastic materials. Test methods are included in Annex B and Annex C for the determination of air permeability and uniformity of pore size, but these chara
16、cteristics do not form part of the requirements of this International Standard. 2 Definitions 2.1 sintered (fritted) filter a filter produced from porous material formed by the thermal bonding of particles 2.2 pore size index a characteristic of a filter related to pore diameter 2.3 permeability a c
17、haracteristic of a filter related to the rate of flow through it under specified conditions 3 Quality Filters shall not shed particles under conditions of normal use and shall withstand a working pressure differential of 1,013 bar applied in the normal direction of use. When tested for pore size ind
18、ex by the method specified inAnnex A, there shall be no evidence of faults in the filter material, or the sealing into the holder. 4 Grading of filters Filters shall be graded according to their pore size index in one of the eight grades specified inTable 1. The designation allotted to each grade co
19、nsists of the upper limit of its pore size index range, expressed in micrometres preceded by the letter “P”. Filters may be provided in certain materials or for special purposes with pore size indexes falling within narrower ranges than those given inTable 1; if so, this should be indicated by stati
20、ng both the minimum and maximum limits of the range. Table 1 Grading of filters 5 Limits for pore size index When the filter is tested in accordance with the method specified inAnnex A, the pore size index shall be within the limits specified inTable 1 for its grade. NOTEIt is recommended that filte
21、rs be manufactured with pore size indexes near the centre of the range of the appropriate grade. 6 Uniformity test If it is required to assess the uniformity of the filter over its working area, the method of test described in Annex B should be used. 7 Permeability If it is required to measure the p
22、ermeability of the filter, it should be tested in accordance with the method described inAnnex C, and should not havea permeability less than the value specified inTable 2 for its grade. Table 2 Permeability of filters Designation of grade Pore size index, 4m u P 1,6 P 4 P 10 P 16 P 40 P 100 P 160 P
23、 250 1,6 4 10 16 40 100 160 1,6 4 10 16 40 100 160 250 NOTEThe figures given relate to filter discs up to 6mm thick. Designation of grade Minimum permeability (airflow at 1 mbar) m 3 /m 2 ks cm 3 /cm 2 min P 1,6 P 4 P 10 P 16 P 40 P 100 P 160 P 250 0,12 0,33 0,83 1,7 5,0 33 67 83 0,72 1,98 4,98 10,2
24、 30 198 402 498BS1752:1983 2 BSI 11-1999 Annex A Method for determination of pore size index A.0 This method of test measures the pressure at which the first air bubble breaks away from the filter under specified conditions. This pressure is then used to calculate the equivalent capillary diameter.
25、Thus, the test does not constitute a measurement of pore size but provides an indication of pore diameter, which is related to the maximum size of particle that the filter will pass. The retentivity of a filter is also affected by other factors. A.1 Ensure that the filter is thoroughly clean, especi
26、ally that it is free from detergents, and wettable by the test liquid. Table 3 lists some of the test liquids that have been found suitable for various filter materials, and that have the desirable properties of low or zero flammability and low toxicity. In the case of filters made of materials such
27、 as glass, vitreous silica, ceramics, platinum, bronze or stainless steel, the choice of the test liquid is wide, in relation to both wettability and non-reactivity with the filter material. In the case of plastic materials, reactivity is an important consideration, and certain liquids may cause par
28、tial dissolution or swelling. In order to give an adequate reading on a mercury manometer, it is generally preferable to use water as the test liquid on the coarse filters. There may, however, be important reasons for using one of the liquids of low surface tension on some filters, and in such cases
29、 it is more appropriate to employ a water manometer and make the necessary correction. Examples are 1) polytetrafluoroethylene filters, which are not wetted by water; 2) domed filters, for which excessive pressure on the concave side could cause fracture; 3) fine grade filters, because the pressure
30、necessary when using water may be greater than that the filter can withstand. Table 3 Suitable test liquids A.2 Assemble the filters in a suitable apparatus, for example that illustrated inFigure 1. NOTEIf the filters comprise a fine grade material supported on a coarser grade, the filter characteri
31、stics stated should be those of the finer grade and the filter should be tested in such a way that the bubbles appear at the surface of the finer grade material. Connect an adequate source of clean, dry air, that is supplied at an accurately and finely controlled pressure, for example using a needle
32、 valve (the equations inA.5 are based on the assumption of static conditions in the system). Situate the manometer so as to indicate the actual pressure at the filter. A.3 Cover the filter with a layer of the test liquid, as shallow as is convenient, and ensure that all the pores are impregnated. As
33、suming the usual flat form of filter is used, there should be no excessive variation of hydrostatic head over its working area. If this hydrostatic head is significant, convert its value to the appropriate pressure units, and deduct this pressure from the manometer reading to give the effective pres
34、sure. When a domed filter is being tested, bubbles tend to appear first at the uppermost region of the dome, owing to the varying hydrostatic head. It may be desirable in this case to tilt the filter to bring different regions into the uppermost position, to ascertain a) the point of maximum pore si
35、ze index; b) the general uniformity of the filter (see Annex B). Hollow filters (for example cylindrical) should be supported with the axis horizontal and suitably rotated. Test liquid Nominal surface tension at 20 C Filter material N/m dyn/cm Ethanol, 95% (V/V) 0,022 22 All Propan-2-ol (iso-propano
36、l) 0,022 22 All 1,1,1-trichoroethane 0,025 25 All except plastic materials Water 0,073 73 See A.1 NOTEThe surface tension values quoted are sufficiently accurate for the purposes of the test, but they are liable to be affected by contamination of the test liquid (for example by the air supply) and t
37、his should be avoided.BS1752:1983 BSI 11-1999 3 A.4 Gradually increase the air pressure until the first air bubble breaks away from the surface of the filter. (For hollow filters it is necessary to allow sufficient time to ensure that all free liquid is driven out of the central cavity of the filter
38、.) Read the pressure at the filter from the manometer. Repeat the test, taking the precautions stated above, with the pressure being increased more slowly. If concordant results are obtained the test has been performed satisfactorily. A.5 Calculate the pore size index, d, in micrometres(4m), using e
39、ither of the following formulae a) where 1 is the surface tension, in newtons per metre, of the test liquid; P 1 is the effective pressure, in bars; b) where 2 is the surface tension, in dynes per centimetre, of the test liquid; P 2 is the effective pressure, in millimetres of mercury. NOTE 11bar =
40、10 5N/m 2= 750,24mmHg NOTE 2If a manometer liquid other than mercury is used, the actual reading of the manometer should be converted to bars or millimetres of mercury, as required. NOTE 3The manometer may be calibrated or a graph constructed for a particular test liquid, so that the pore size index
41、 can be read directly. A.6 When the pore size index has been determined, the filter may be left connected to the apparatus and its uniformity checked as described inAnnex B. Annex B Procedure for assessing uniformity of filters B.1 Use the procedure specified inAnnex A for determination of pore size
42、 index. B.2 Following the appearance of the first air bubble, as described inA.4, increase the air pressure until bubbles emerge uniformly over the upper surface and note the new pressure readings. This should correspond to a pore size index not less than the minimum for the grade (seeTable 1). Anne
43、x C Method for determination of air permeability C.0 This method measures the rate of flow of air through a filter under specified conditions. It is related (but not necessarily by simple proportionality) to the rate of liquid flow through the filter, and hence to the speed of filtration. C.1 Ensure
44、 that the filter is thoroughly clean and dry. Assemble the filter in a suitable apparatus, for example that illustrated inFigure 2. Establish a suitable pressure difference P 3(for example1 mbar) across the filter and maintain this during the test. Measure the air flow rate Q by means of a suitable
45、air flow meter, and convert the rate to cubic metres per kilosecond or cubic centimetres per minute, as required. C.2 Determine the effective surface area A of the filter in square metres or square centimetres, as required, making allowance for the part of the filter near the edge which is rendered
46、ineffective by the fixing process. C.3 Calculate the air permeability per millibar pressure difference, expressed in cubic metres persquare metre kilosecond m 3 /(m 2 ks) or cubiccentimetres per square centimetre minutecm 3 /(cm 2 min), as required, from the formula NOTEThe test assumes viscous flow
47、 of air through the filter, and is adequate for the general requirements of laboratory sintered filters. For particular purposes, for example filters required for accurate work in fluid flow, more detailed tests may be required and should be agreed upon by the interested parties. 40 1 P 1 - 30 2 P 2
48、 - Q A P 3 -BS1752:1983 4 BSI 11-1999 WARNING For safety reasons, this apparatus must be suitably shielded when in use. Figure 1 Apparatus for determination of pore size indexBS1752:1983 BSI 11-1999 5 Figure 2 Apparatus for determination of air permeability6 blankBS1752:1983 BSI 11-1999 National app
49、endix Differences between the 1963 and 1983 editions of BS 1752BS 1752:1983 ISO4793:1980 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest
