1、BRITISH STANDARD BS ISO 5293:2004 Incorporating corrigendum July 2008 Conveyor belts Determination of minimum transition distance on three idler rollers ICS 53.040.20 BS ISO 5293:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 Septemb
2、er 2004 BSI 2009 ISBN 978 0 580 63650 9 National foreword This British Standard is the UK implementation of ISO 5293:2004, incorporating corrigendum July 2008. The start and finish of text introduced or altered by corrigendum is indicated in the text by tags. Text altered by ISO corrigendum July 200
3、8 is indicated in the text by . The UK participation in its preparation was entrusted to Technical Committee PRI/67, Conveyor belts. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provi
4、sions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publication Date Comments 28 February 2009 Implementation of ISO corrigendum July 2008 Reference number ISO 529
5、3:2004(E) OSI 4002INTERNATIONAL STANDARD ISO 5293 Second edition 2004-09-15 Conveyor belts Determination of minimum transition distance on three idler rollers Courroies transporteuses Dtermination de la distance minimale de transition dauge trois rouleaux gaux BSISO5293:2004IS:3925 O4002(E) DPlcsid
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10、ttseuqer ehe.r ISO cirypothg fofice saCe tsopale 65 eneG 1121-HC 02 av leT. 4 + 10 947 22 1 11 xaF0 947 22 14 + 9 74 E-mail coirypthgiso.o gr We bwww.is.o gro Pulbisdehi n Switlrez dnaii ISO 4002 Allr ithgsr esedevrBSISO5293:2004IS:3925 O4002(E) I SO 4002 All irthgs ersedevr iiiContents Page Forewor
11、d iv 1 Scope 1 2 Normative references . 1 3 Calculation of minimum transition distance 1 4 Application of the formula for transition distance 2 4.1 General. 2 4.2 Values of elastic modulus, M, of belt 2 4.3 Values of vertical distance, h, which the belt edge raises or lowers. 2 4.4 Values of T . 4 A
12、nnex A (normative) Derivation of the formula for transition distance 6 Annex B (normative) Derivation of values of T . 8 Bibliography . 11 BSISO5293:2004IS:3925 O4002(E) iv I SO 4002 All irthgs ersedevrForeword ISO (the International Organization for Standardization) is a worldwide federation of nat
13、ional standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. Interna
14、tional organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the r
15、ules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by a
16、t least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 5293 was prepared by Technical Committee ISO/TC
17、 41, Pulleys and belts (including veebelts), Subcommittee SC 3, Conveyor belts. This second edition cancels and replaces ISO 5293:1981 and ISO/TR 10357:1989, which have been technically revised. BSISO5293:2004INTENRATIONAL TSANDADR IS:3925 O4002(E)I SO 4002 All irthgs ersedevr 1Conveyor belts Determ
18、ination of minimum transition distance on three idler rollers 1 Scope This International Standard specifies the formula for calculating conveyor belt transition distances and details its application and derivation. This International Standard is not suitable or valid for light conveyor belts as desc
19、ribed in ISO 21183-1 1 . 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. I
20、SO 1537, Continuous mechanical handling equipment for loose bulk materials Troughed belt conveyors (other than portable conveyors) Idlers ISO 9856, Conveyor belts Determination of elastic and permanent elongation and calculation of elastic modulus 3 Calculation of minimum transition distance The for
21、mula for calculating the transition distance, the derivation of which is given in Annex A, is as follows: () 0,5 1 1c o s sin hM L T = where L 1is the transition distance, expressed in metres; h is the vertical distance, expressed in metres, the belt edge raises or lowers in the transition (see Figu
22、re 1); is the idler trough angle; M is the elastic modulus, expressed in newtons per millimetre, measured under tension T R ; T Ris the maximum recommended belt-to-belt joint tension (RMBT), expressed in newtons per millimetre, for a steady-state condition of the conveyor; T is the induced belt edge
23、 stress, expressed in newtons per millimetre, in the transition. BSISO5293:2004IS:3925 O4002(E) 2 I SO 4002 All irthgs ersedevrFigure 1 Transition distance 4 Application of the formula for transition distance 4.1 General Calculate the transition distance by using appropriate values of M, h and T as
24、described in 4.2 to 4.4, as appropriate. 4.2 Values of elastic modulus, M, of belt Determine the values in accordance with ISO 9856. 4.3 Values of vertical distance, h, which the belt edge raises or lowers 4.3.1 General Calculate the values from the idler trough angle (see Figure 1) and the position
25、 of the terminal pulley with respect to the centre idler roller. Four common situations are described in 4.3.2 and 4.3.3. 4.3.2 Three equal length roller 4.3.2.1 The pulley is on a line with the top centre idler roller (see Figure 2). sin 3 b h = where h is the vertical distance, expressed in metres
26、, that the belt edge raises or lowers in the transition (see Figure 1); b is the width, expressed in metres, of the belt; is the idler trough angle. BSISO5293:2004IS:3925 O4002(E) I SO 4002 All irthgs ersedevr 3Figure 2 Pulley on line with top centre idler roller 4.3.2.2 The pulley is elevated by 1/
27、3 of the trough depth above the line of centre idler roller (see Figure 3). h is then equal to 2/3 full trough depth, i.e. 2s i n s i n 334 , 5 bb h = = where h is the vertical distance, expressed in metres, the belt edge raises or lowers in the transition (see Figure 1); b is the width, expressed i
28、n metres, of the belt; is the idler trough angle. Figure 3 Pulley elevated by 1/3 of trough depth above line of centre idler roller 4.3.3 Long centre roller 4.3.3.1 The pulley is on a line with the top centre idler roller (see Figure 4). 1 sin hb = where h is the vertical distance, expressed in metr
29、es, the belt edge raises or lowers in the transition (see Figure 1); b 1is the amount of belt width, expressed in metres, on one of the outer rollers, i.e. 12 (2 ) ; bbb =+ is the idler trough angle. BSISO5293:2004IS:3925 O4002(E) 4 I SO 4002 All irthgs ersedevrFigure 4 Pulley on line with top centr
30、e idler roller 4.3.3.2 The pulley is elevated by 1/3 of the trough depth above the line of centre idler roller (see Figure 5). h is then equal to 2/3 full trough depth, i.e. 1 2 sin 3 hb = where h is the vertical distance, expressed in metres, the belt edge raises or lowers in the transition (see Fi
31、gure 1); b 1is the amount of belt width, expressed in metres, on one of the outer rollers, i.e. 12 (2 ) ; bbb =+ is the idler trough angle. Figure 5 Pulley elevated by 1/3 of trough depth above line of centre idler roller 4.4 Values of T 4.4.1 Calculate the average belt tension at the transition and
32、 express it as a fraction of the maximum recommended belt tension for a steady operating condition, T R , taking the strength of the belt joints into account. Values of belt tension at transition higher than 1 T Rtake into account peak belt loadings which can occur in short-time non-steady operating
33、 conditions, for example when starting and stopping the conveyor belt. In agreement with the belt manufacturer, select a maximum belt edge tension of F % related to the steady operating condition (100 %), provided that the gap (or overlap) between the rollers complies with the requirements of ISO 15
34、37. BSISO5293:2004IS:3925 O4002(E) I SO 4002 All irthgs ersedevr 54.4.2 The values of T selected (calculated in accordance with Annex B) will a) prevent edge tension not only in the steady operating conditions but also in the temporary non-steady conditions from exceeding the maximum recommended ten
35、sion of the belt or the belt joints in the steady conditions by F %; b) keep the tension in the belt centre adequate and always positive to prevent the centre of the belt from buckling. NOTE Further information regarding F % is given in Clause B.1. 4.4.3 The additional tensions induced at the trough
36、ing transition will normally also be equalized beyond the transition distance. For this reason the actual existing edge stress will be lower. For determining the maximum transition distances a higher value of T can be agreed with the belt manufacturer, if necessary. 4.4.4 Unless otherwise specified
37、by the belt manufacturer, the values below can be allowed for belt edge tensions in short-time non-steady operating conditions: F u 1,8T Ror 180 % max. for textile belts; and F u 2,0T Ror 200 % max. for steel cord belts. BSISO5293:20046 Annex A (normative) Derivation of the formula for transition di
38、stance A.1 A.2 From the stress-strain-modulus relationship 1 1aL M T L = (A.1) or 11 T aL M =+ (A.2) where a is the length of belt edge in transition distance; L 1 , M, h and T are defined in Clause 3. A.3 Furthermore, by the Pythagorean theorem: () 0,5 2 2 2 1 1c o s sin h aLh =+ (A.3) A.4 Let Equa
39、tion (A.2) equal Equation (A.3). Square both sides and simplify to the following: () 2 2 2 2 11 11 c o s sin Th LL h M +=+ () 22 2 1 2 21 c o s sin TTh L MM += (A.4) BSISO5293:2004 To simplify the mathematics, and because it only has a minor effect on the calculated transition distance, it is assume
40、d that the portion of belt on the inclined troughing roll is equal to b/3 whereas it is normally slightly less than this. IS:3925 O4002(E) I SO 4002 All irthgs ersedevr 7A.5 2 T M in Equation (A.4) is very close to zero. () 2 2 1 1c o s sin hM L T = Therefore () 0,5 1 1c o s sin hM L T = (A.5) BSISO
41、5293:2004IS:3925 O4002(E) 8 I SO 4002 All irthgs ersedevrAnnex B (normative) Derivation of values of T B.1 Normal and maximum tensions For normal (steady) operating conditions a maximum recommended belt or belt joint tension T Ris assumed. For this condition the belt edge tension is taken as the 100
42、 % basis. In the troughing transition, the edge tension will be twice as high during each revolution and higher still during the non-steady conditions (starting and stopping). These belt edge tensions are taken as F %. NOTE If calculations are based on assumptions of safety factors the following equ
43、ation applies: sta S F S = where S stais the safety factor in the steady operating condition (in the case of the belt joint strength, S sta= 8); S is the safety factor corresponding to the maximum permissible edge tension in short-time non-steady operating conditions (e.g. S 4 for textile belts, S =
44、 3 for steel cord belts). B.2 Belt tension distribution Figure B.1 shows the tension relationship in the troughing transition. The two assumptions made in Clause A.1 apply likewise. (The diagram should not be mistaken for the geometrical relationship shown in Figure 3.) BSISO5293:2004IS:3925 O4002(E
45、) I SO 4002 All irthgs ersedevr 9where b is the belt width 12 (2 ) ; bbb =+ T is the average belt tension at the transition; T eis the maximum edge tension at the transition; T is the tension in the trough centre; T is the induced belt edge stress at the transition. Figure B.1 Belt tension relations
46、hip in troughing transition From Figure B.1, it follows that 1 12 2 bT TT bb =+ +(B.1) B.3 Maximum edge tensions These are given by: R TCT = where C is the ratio of the average belt tension at the transition to the maximum recommended belt tension (RMBT); e TTT = (see Clause B.2) eR TFT = (see Claus
47、e B.1) From Equation (B.1), it follows that the tension in the belt edges can be calculated from Equation (B.2): () R 12 b TF C T bb = +(B.2) BSISO5293:2004IS:3925 O4002(E) 10 I SO 4002 All irthgs ersedevrB.4 No belt centre buckling The tension in the centre of the belt always has to be positive in
48、order to prevent buckling. This means that 0 T or 1 12 2 bT T bb +see Equation (B.1) Taking R TCT = (see Clause B.3) it is possible to derive Equation (B.3) for the criterion “no buckling in the belt centre”: (B.3) B.5 Minimum transition distance The transition distance has to be sufficient to avoid excessive edge tension as described in Clause B.3 and belt centre buckling as described in Clause B.4. The minimum transition distance (L 1 ) is cal
