1、BRITISH STANDARD BS 6620-2: 1991 ISO 7805-2: 1987 Industrial plate screens Part 2: Guide for screens of thickness below 3 mmBS6620-2:1991 This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Policy Committee, waspublished under the authorityo
2、f the Standards Boardand comes intoeffecton 31January1992 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference GME/29 Draft for comment 86/76076 DC ISBN 0 580 20390 5 Committees responsible for this British Standard The preparation of this British Standar
3、d was entrusted by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee GME/29, upon which the following bodies were represented: BCIRA British Cement Association British Laboratory Ware Association Coated Abrasives Manufacturers Association Guild of Metal Per
4、forators Incorporated National Association of British and Irish Millers Institution of Chemical Engineers Institution of Mining and Metallurgy Mechanical Handling Engineers Association Ministry of Defence National Coal Board Society of Chemical Industry Society of Cosmetic Scientists Woven Wire Asso
5、ciation The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Aggregate Construction Materials Industries Minerals Engineering Society Coopted members Amendments issued since publication Amd. No. Date CommentsBS6620-2:1991 BSI 09-1999 i
6、 Contents Page Committees responsible Inside front cover National foreword ii 0 Introduction 1 1 Scope and field of application 1 2 References 1 3 Definitions 1 4 Material and design 1 5 Tolerances 2 6 Testing 3 7 Designation and ordering 3 Annex Examples 4 Figure 1 Round holes : 60 staggered arrang
7、ement 1 Figure 2 Square holes : in-line arrangement 1 Figure 3 Square holes : half-pitch staggered arrangement 2 Table 1 Pitch/hole ratios and related open areas 2 Table 2 Examples of round hole perforations 4 Table 3 Examples of square hole perforations 4 Table 4 Examples of tolerances on pitch 5 P
8、ublication(s) referred to Inside back coverBS6620-2:1991 ii BSI 09-1999 National foreword This Part of BS6620 has been prepared under the direction of the General Mechanical Engineering Standards Policy Committee and is identical with ISO7805-2:1987 “Industrial plate screens Part2: Thickness below3m
9、m” published by the International Organization for Standardization (ISO). ISO7805-2 was prepared by ISO/TC24 in which the UK took an active part The Technical Committee has reviewed the provisions of ISO2184 and ISO2395, to which reference is made in the text, and has decided that they are suitable
10、for use in conjunction with this standard. ISO 2194 is related to both BS410 “Specification for test sieves” and to BS481 “Specification for industrial wire mesh” Part2 “High tensile steel wire mesh with square apertures from125mmto2mm”. There is no corresponding British Standard for ISO2395. A Brit
11、ish Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresp
12、onding British Standard ISO 3-1973 BS 2045:1965 Preferred numbers (Technically equivalent) ISO 7806:1983 BS 6511:1984 Specification for designation of perforations in industrial plate screens (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, p
13、ages1to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6620-2:1991 BSI 09-1999 1 0 Introduction The purpose of ISO7805 is to provide guid
14、ance for the development of national standards for industrial plate screens. As both parts of ISO7805 provide a diversity of choice, it is unlikely that every one of the many possible combinations of size of hole, pitch and plate thickness will be manufactured. The selection for national standards f
15、or industrial plate screens should be made from those combinations which suit the products and screening methods in the country concerned. 1 Scope and field of application This part of ISO7805 describes three patterns using round (circular) and square perforations in plate of less than3mm thickness;
16、 the sizes of holes range down to2mm for square holes and to0,5mm for round holes. Five ratios of pitch to hole are specified which result in nominal open areas ranging from about60% to23%. Tolerances for both hole and pitch are given. NOTEIndustrial plate screens of thicknesses of3mm and above are
17、dealt with in ISO7805-1, Industrial plate screens Part1: Thickness of 3mm and above. 2 References ISO 3, Preferred numbers Series of preferred numbers. ISO 2194, Wire screens and plate screens for industrial purposes Nominal sizes of apertures. ISO 2395, Test sieves and test sieving Vocabulary. ISO
18、7806, Industrial plate screens Codification for designating perforations. 3 Definitions For the purposes of this part of ISO7805, the definitions given inISO2395 and the following definition apply. open area ratio of the total area occupied by the holes to the overall area of the perforated part of
19、the plate 4 Material and design 4.1 Material The material of perforated plates less than3mm thick shall be agreed by manufacturer and purchaser. 4.2 Design 4.2.1 Arrangement of holes Three permissible arrangements of holes are illustrated in Figure 1 toFigure 3: Figure 1 for round holes in a 60 stag
20、gered arrangement (T-arrangement), andFigure 2 andFigure 3 for square holes in line (U-arrangement) or at half-pitch stagger (Z-arrangement). Figure 1 Round holes : 60 staggeredarrangement (T-arrangement) Open area . 0,9(w/p) 2 Figure 2 Square holes : in-line arrangement(U-arrangement) Openarea=(w/p
21、) 2 BS6620-2:1991 2 BSI 09-1999 4.2.2 Size of holes, w The nominal sizes of round or square holes in industrial plate screens are tabulated inISO2194. First choice shall be made from theR10series of preferred numbers (seeISO3) and the second choice from theR20 series; if necessary, sizes may be chos
22、en from theR40 series. NOTEThe R 10 series of sizes is shown, by way of example, inTable 2 andTable 3 in the Annex. 4.2.3 Pitch, p Values for pitch shall be calculated from the five options of pitch/hole ratio given inTable 1 in which the approximate open area is also given, as a percentage, for rou
23、nd and square hole perforations based on these ratios. The calculated values shall be rounded to the nearestR40 number in accordance with ISO3. Table 1 Pitch/hole ratios and related openareas 4.2.4 Plate thickness Plate thickness before perforation shall be agreed by purchaser and supplier. A chosen
24、 thickness shall be less than the size of holes and also less than the bridge width (bar). 5 Tolerances The tolerances given in5.1 to5.3 apply to unused plate screens. 5.1 Tolerance on average size of hole, %w The average measured size of hole shall not deviate from the nominal size, w, by more than
25、 the value %w given by equation(1) or(2), where w and %w are given in millimetres: a) For sizes of holes above 6,3 mm: b) For sizes of holes of 6,3 mm and below: with a minimum value of 0,1 mm. NOTEExamples of %w rounded to the nearest0,05mm are shown inTable 2 andTable 3 in the Annex. 5.2 Tolerance
26、 on individual size of hole The measured value of any individual size of hole shall not deviate from the nominal size, w, by more than2%w. 5.3 Tolerance on average pitch, %p The average measured pitch shall not deviate from the nominal pitch, p, by more than the value%p given by equation(3) or(4), w
27、here p and%p are given in millimetres: a) For pitches of 6,3 mm and above: b) For pitches below 6,3 mm: NOTEExamples of tolerance on average pitch are shown in Table 4 in the Annex. 5.4 Tolerance on individual pitch The measured width of any bridge (bar) shall be not less than0,5times the nominal si
28、ze of hole. Figure 3 Square holes : half-pitch staggeredarrangement (Z-arrangement) Openarea=(w/p) 2 Pitch/hole ratio Approximate open area p/w Round holes % Square holes % 1,25 1,4 1,6 1,8 2 58 46 35 28 23 64 51 39 31 25 NOTEExamples in Table 2 andTable 3 in the Annex include pitch selections. . .
29、. (1) . . . (2) . . . (3) . . . (4)BS6620-2:1991 BSI 09-1999 3 6 Testing 6.1 General A survey of the screen to be tested shall be made to note positions, if any, where there appear to be variations in hole size and/or bridge widths. At the same time, irregular holes, broken bars and deformed plate c
30、an be detected. The measurements described in6.2 and6.3 shall be made on the punch side of the plate at positions noted in the general survey. Additional sample measurements shall be made. 6.2 Size of holes The size of holes shall be tested with a limit plain plug gauge. The average size should be d
31、etermined by measuring consecutive holes, preferably20, ifavailable. 6.3 Pitch The average pitch shall be measured, preferably over at least20 pitches, e.g.by using a transparent rule marked with20 consecutive nominal pitches. Individual pitch shall be measured at positions described in6.1. 7 Design
32、ation and ordering Industrial plate screens shall be designated by shape of holes; size of holes; arrangement and orientation of holes; pitch of holes. The above items of designation shall be described by use of the code specified inISO7806. In addition to the designation, the purchasers choice of p
33、late thickness, shape and size of plate, and the required material shall be clearly stated when an industrial plate screen is ordered.BS6620-2:1991 4 BSI 09-1999 Annex Examples (This Annex forms an integral part of the standard.) Examples which list sizes of holes in theR10 series and include hole/p
34、itch combinations which have been manufactured or suggested are given inTable 2 andTable 3. The criteria for selection made for national standards is described inclause0. Table 2 Examples of round hole perforations Table 3 Examples of square hole perforations Dimensions in millimetres Hole Nominal p
35、itch, p, for an approximate open area of Nominal size Tolerance on average size w %w 58 % 46 % 35 % 28 % 23 % 10 0,35 12,5 14 16 18 8 0,3 10 11,2 12,5 14 16 6,3 0,25 8 9 10 11,2 12,5 5 0,25 6,3 7,1 8 9 10 4 0,25 5 5,6 6,3 7,1 8 3,15 0,25 4 4,5 5 5,6 6,3 2,5 0,25 3,55 4 4,5 5 2 0,2 3,15 3,55 4 1,6 0,
36、2 2,5 2,8 3,15 1,25 0,15 2 2,24 2,5 1 0,15 1,6 1,8 2 0,8 0,1 1,25 1,4 1,6 0,63 0,1 1,25 0,5 0,1 1 NOTEThe tolerances %w are rounded to the nearest0,05mm. Dimensions in millimetres Hole Nominal pitch, p, for an approximate open area of Nominal size Tolerance on average size w %w 64 % 51 % 39 % 31 % 2
37、5 % 10 0,35 12,5 14 16 18 8 0,3 10 11,2 12,5 14 6,3 0,25 8 9 10 11,2 12,5 5 0,25 7,1 8 9 10 4 0,25 6,3 7,1 8 3,15 0,25 5 6,3 2,5 0,25 4 5 2 0,2 4 NOTEThe tolerances %w are rounded to the nearest 0,05 min.BS6620-2:1991 BSI 09-1999 5 Table 4 Examples of tolerances on pitch Dimensions in millimetres No
38、minal pitch Tolerance on average pitch p %p 18 0,5 16 0,45 14 0,4 12,5 0,35 11,2 0,35 10 0,3 9 0,25 8 0,25 7,1 0,2 6,3 0,26 blankBS6620-2:1991 BSI 09-1999 Publication(s) referred to See national foreword.BS 6620-2: 1991 ISO 7805-2: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsIns
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