1、 W 7 6 w w 9 7 7 7 * $ ! ISO 5293:2004(E) ISO 2004 All rights reserved iiiContents Page Forewordiv 1 Scope1 2 Normative references.1 3 Calculation of minimum transition distance1 4 Application of the formula for transition distance2 4.1 General.2 4.2 Values of elastic modulus, M, of belt2 4.3 Values
2、 of vertical distance, h, which the belt edge raises or lowers.2 4.4 Values of T .4 Annex A (normative) Derivation of the formula for transition distance6 Annex B (normative) Derivation of values of T .8 Bibliography.11 ISO 5293:2004(E) iv ISO 2004 All rights reservedForeword ISO (the International
3、Organization for Standardization) is a worldwide federation of national 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 esta
4、blished has the right to be represented on that committee. International 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 standardiza
5、tion. International Standards are drafted in accordance with the rules 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 votin
6、g. Publication as an International Standard requires approval by at 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
7、patent rights. ISO 5293 was prepared by Technical Committee ISO/TC 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. INTERNATIONAL STANDARD ISO 5293:2004(E)
8、 ISO 2004 All rights reserved 1Conveyor belts Determination 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 no
9、t suitable or valid for light conveyor belts as described in ISO 21183-11. 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 referen
10、ced document (including any amendments) applies. ISO 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
11、Calculation of minimum transition distance The formula for calculating the transition distance, the derivation of which is given in Annex A, is as follows: 0,51 1cossinhMLT where L1 is the transition distance, expressed in metres; h is the vertical distance, expressed in metres, the belt edge raises
12、 or lowers in the transition (see Figure 1); is the idler trough angle; M is the elastic modulus, expressed in newtons per millimetre, measured under tension TR; TR is the maximum recommended belt-to-belt joint tension (RMBT), expressed in newtons per millimetre, for a steady-state condition of the
13、conveyor; T is the induced belt edge stress, expressed in newtons per millimetre, in the transition. ISO 5293:2004(E) 2 ISO 2004 All rights reservedFigure 1 Transition distance 4 Application of the formula for transition distance 4.1 General Calculate the transition distance by using appropriate val
14、ues of M, h and T as 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 Figur
15、e 1) and the position 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). sin3bh where h is the vertical distance, exp
16、ressed in metres, 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. ISO 5293:2004(E) ISO 2004 All rights reserved 3Figure 2 Pulley on line with top centre idler roller 4.3.2.2 The pulley is elevated by 1
17、/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. 2sinsin334,5bbh 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 in metres, of
18、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 sinhb where h is the vertical distance, expressed in metres, the belt edg
19、e raises or lowers in the transition (see Figure 1); b1 is the amount of belt width, expressed in metres, on one of the outer rollers, i.e. 12(2);bbb is the idler trough angle. ISO 5293:2004(E) 4 ISO 2004 All rights reservedFigure 4 Pulley on line with top centre idler roller 4.3.3.2 The pulley is e
20、levated 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. 12 sin3hb where h is the vertical distance, expressed in metres, the belt edge raises or lowers in the transition (see Figure 1); b1 is the amount of belt width, ex
21、pressed 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 express it as a fraction of the maximum recommend
22、ed belt tension for a steady operating condition, TR, taking the strength of the belt joints into account. Values of belt tension at transition higher than 1 TR take into account peak belt loadings which can occur in short-time non-steady operating conditions, for example when starting and stopping
23、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 1537. ISO 5293:2004(E) ISO 2004 All rights reserved 54
24、.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 tension of the belt or the belt joints in the steady conditions by F %
25、; 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 troughing transition will normally also be equalized beyond the transitio
26、n 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 by the belt manufacturer, the values below can be allowed for belt
27、edge tensions in short-time non-steady operating conditions: F u 1,8TR or 180 % max. for textile belts; and F u 2,0TR or 200 % max. for steel cord belts. ISO 5293:2004(E) 6 ISO 2004 All rights reservedAnnex A (normative) Derivation of the formula for transition distance A.1 The following two assumpt
28、ions are made to simplify the mathematics and because they only have a minor effect on the calculated transition distance, the effect of the first partially compensated by the effect of the second. The portion of belt on the inclined troughing roll is assumed to be equal to b/3 whereas it is normall
29、y slightly less than this. The belt edge is assumed to make a straight vertical drop through the transition whereas there is actually a slight lateral displacement as well. A.2 From the stress-strain-modulus relationship 11aLM TL (A.1) or 1 1TaLM (A.2) where a is the length of belt edge in transitio
30、n distance; L1, M, h and T are defined in Clause 3. A.3 Furthermore, by the Pythagorean theorem: 0,522 21 1cossinhaLh (A.3) A.4 Let Equation (A.2) equal Equation (A.3). Square both sides and simplify to the following: 2 22 21111cossinThLLhM 2221221cossinTThLMM (A.4) ISO 5293:2004(E) ISO 2004 All rig
31、hts reserved 7A.5 2TM in Equation (A.4) is very close to zero. 221 1cossinhMLT Therefore 0,51 1cossinhMLT (A.5) ISO 5293:2004(E) 8 ISO 2004 All rights reservedAnnex B (normative) Derivation of values of T B.1 Normal and maximum tensions For normal (steady) operating conditions a maximum recommended
32、belt or belt joint tension TR is assumed. For this condition the belt edge tension is taken as the 100 % 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 tensio
33、ns are taken as F %. NOTE If calculations are based on assumptions of safety factors the following equation applies: staSFS where Ssta is the safety factor in the steady operating condition (in the case of the belt joint strength, Ssta 8); S is the safety factor corresponding to the maximum permissi
34、ble edge tension in short-time non-steady operating conditions (e.g. S 4 for textile belts, S = 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
35、 be mistaken for the geometrical relationship shown in Figure 3.) ISO 5293:2004(E) ISO 2004 All rights reserved 9where b is the belt width 12(2);bbb T is the average belt tension at the transition; Te is the maximum edge tension at the transition; T is the tension in the trough centre; T is the indu
36、ced belt edge stress at the transition. Figure B.1 Belt tension relationship in troughing transition From Figure B.1, it follows that 1122bTTTbb (B.1) B.3 Maximum edge tensions These are given by: RTCT where C is the ratio of the average belt tension at the transition to the maximum recommended belt
37、 tension (RMBT); eTTT (see Clause B.2) eRTFT (see Clause B.1) From Equation (B.1), it follows that the tension in the belt edges can be calculated from Equation (B.2): R12bTFCTbb (B.2) ISO 5293:2004(E) 10 ISO 2004 All rights reservedB.4 No belt centre buckling The tension in the centre of the belt a
38、lways has to be positive in order to prevent buckling. This means that 0T or 1122bTTbb see Equation (B.1) Taking RTCT (see Clause B.3) it is possible to derive Equation (B.3) for the criterion no buckling in the belt centre: R1bTTb (B.3) B.5 Minimum transition distance The transition distance has to
39、 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 (L1) is calculated from Equation (A.5) derived in Clause A.5, i.e. 0,51 1cossinhMLT Perform the calculation twice using values for T calculated from Equation (B.2) in Clause B.3 and Equation (B.3) in Clause B.4. The larger of the tw
