1、INTERNATIONAL STANDARD 3870 INTERNATIONAL ORGANlZATlON FOR STANDARDlZATlON .MLY,lYHAP”,HAJ4 OPrAHM3AUMII I70 CTAHLtAPTM3AUMM .ORGANISATION INTERNATIONALE DE NORMALlSATlON Conveyor belts (fabric carcass), with length between pulley centres up to 300 m, for loose bulk materials - Adjustment of take-up
2、 device Courroies transporteuses (ii carcasse textile) de produits en vrac pour transporteurs jusqu3 300 m de longueur den traxe - Course de rdglage du dispositif de tension First edition - 1976-1 l-01 1;: .:1 :, i L ii;/ ! iz UDC 621.867.212.3/.5 Ref. No. IS0 3870-1976 (E) 2 co ; 8 Descriptors : ma
3、terials handling, bulk products, belt conveyors, conveyor belts, take-up devices, adjusting. % 0 22 Price based on 3 pages Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,
4、-FOREWORD IS0 (the International Organization for Standardization) is a worldwide federation of national standards institutes (IS0 Member Bodies). The work of developing International Standards is carried out through IS0 Technical Committees. Every Member Body interested in a subject for which a Tec
5、hnical Committee has been set up 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. Draft International Standards adopted by the Technical Committees are circulated to the Member Bodies f
6、or approval before their acceptance as International Standards by the IS0 Council. International Standard IS0 3870 was drawn up by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts), and was circulated to the Member Bodies in July 1975. It has been approved by the Member Bodies of
7、 the following countries : Australia Germany Austria India Belgium Italy Bulgaria Mexico Canada Netherlands Finland Poland France Romania Spain Turkey United Kingdom U.S.A. Yugoslavia The Member Body of the following country expressed disapproval of the document on technical grounds : Japan 0 Intern
8、ational Organization for Standardization, 1976 l Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTERNATIONAL STANDARD IS0 3870-1976 (E) Conveyor
9、belts (fabric carcass), with length between pulley centres up to 300 m, for loose bulk materials - Adjustment of take-up device 0 INTRODUCTION All belt conveyors must be equipped with a belt take-up device, whose functions are fourfold : - ensuring adequate tension of the belt leaving the drive pull
10、ey so as to avoid any slipping of the belt; - permanently ensuring adequate belt tension at the loading point and at any other point of the conveyor to keep the troughed belt in shape and limit belt sag between carrying idlers; - compensating for operating belt length variations due to physical fact
11、ors (instantaneous tensions, permanent elongation, outside temperature, temperature of conveyed materials, dampness, etc.); - making available, if needed, an adequate extra length of belt to enable rejointing without having to add on extra pieces of belt. 0.1 Take-up devices There are two main types
12、 of take-up device : - fixed take-up devices that are adjusted periodically; - automatic take-up devices (constant load type). 0.1 .I Fixed take-up devices With systems of this type, the take-up pulley remains fixed between successive periodic adjustments. a) The most frequently used type is the scr
13、ew-operated take-up device, where the adjustment is manually effected by means of two screws acting upon the pulley bearings and which are tightened simultaneously or successively. The operator has in general no practical means of measuring the tension; this generally leads to excessive tension of t
14、he belt (when the tension is insufficient, the belt slips and quickly deteriorates). This excessive tension is unavoidable and must be taken into account when determining the size of the belt, designing the mechanical components and calculating the adjustment. For these various reasons, hand-operate
15、d devices are used only in the case of short conveyors (50 to 60 m) and under light duty cycle condition. b) The belt tension can be adjusted by means of a mBzchanical, motorized device (for example, a winch) which does not, however, automatically compensate for belt length variations. A tension ind
16、icator (for example a dynamometer) can be included between winch and pulley. This solution also demands careful checking of the tension and leads to excessive belt tension in order to avoid too frequent take-ups. It may, however, be used for long conveyors and under heavy duty cycle conditions, prov
17、ided that these conveyors are equipped with belts the elongation coefficient of which is very low under the effect of the load and over a long period, i.e. wire belts with high tensile strength steel cords, which are used almost exclusively. 0.1.2 Automatic take-up devices The take-up pulley is moun
18、ted on slides or on a trolley and travels freely while a constant tension is automatically maintained to ensure normal conveyor operation in all cases. The most frequently used type is the gravity weight- operated take-up device. Hydraulic, pneumatic or electrical take-up devices of various types ar
19、e also used. All types must include a system for adjusting belt tension. For a given conveyor, the manufacturer will choose the type which is best adapted. This will be done in agreement with the user and the belt manufacturer. 0.2 Definition adjustment : The total movement of the take-up pulley or
20、pulleys. The percentages are based on the centre-to-centre distance between the end pulleys of the conveyor, excluding the adjustment if it is ensured by one of these pulleys. 1 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproducti
21、on or networking permitted without license from IHS-,-,-IS0 3870-1976 (E) 0.3 Adjustment values The adjustment must be determined for every individual case on consideration of the following factors : - conveyor length; - belt jointing system; - belt carcass, determining elastic and permanent stretch
22、, the values of which are given by the manufacturer; - ratio of the operating tension to the maximum allowed tension; - starting-up system and magnitude of the resulting dynamic force (instantaneous or successive) on the belt; - position of the take-up device; - possibility, when the take-up device
23、has reached the end of its adjustment length, of its being brought back to its former position by cutting and rejointing the belt; - weather conditions in which the installation is operated (wide temperature variations between day and night, for example); - influence on some types of belts of the ph
24、ysical characteristics of the conveyed materials (heat or excessive moisture content, for example), especially if covers are not carefully checked and maintained periodically. 1 SCOPE AND FIELD OF APPLICATION This International Standard recommends the adjustment values which are valid for the most c
25、ommonly used belts and for conveyors with a maximum length not greater than 300 m, fitted solely with fabric carcass belts. Owing to the wide variety of belt types, and to the number of deter- mining factors in choosing the adjustment, it is not possible to propose general numerical values applicabl
26、e to all cases. For belts with a fabric carcass whose length exceeds 300 m and belts with a metal carcass of any length, the manu- facturer should justify the chosen adjustment. 2 NORMAL ADJUSTMENT VALUES These adjustments, shown in the table, are determined on the understanding that during the join
27、ting operation an initial tension, limiting the sag between carrying idlers and between return rollers to 2 %, will be applied to the free ends of the belt. 3 NOTES RELATING TO THE USE OF THE TABLE 3.1 Influence of the jointing methods 3.1 .I “Endless” belts In the case of belts (generally short) or
28、dered “endless” for conveyors, and which are delivered measured tensionless with a tolerance of + 0,5 %, it is recommended that the adjustments given in the table be increased by an amount equal to 1 % of the between-centres conveyor distance, in order to avoid too frequent belt changes. 3.1.2 Belts
29、 with mechanical joints If jointing can be carried out on the conveyor itself, with an initial tension in conformity with the definition given in footnote 1) to the table, adjustment values may be reduced to the minimum compatible with the operating and rejointing conditions of the belt which are sp
30、ecified by the manufacturer. This possibility is, of course, excluded if, subsequently, spliced joints should be used. TABLE - Adjustment values for take-up devices Type of take-up device Conveyor length Otol2m 12to30m 30 to 60 m 60tol50m 150to300m Fixed hand-operated take-up device, without tension
31、 indicator Minimum adjustment Fixed hand-operated or motorized take-up device, with tension indicator Automatic take-up device Minimum adjustment 0.3 m 2.5 % 2,5 % 2,5 to 2 % 2% Automatic take-up device ) Minimum adjustment 3 to 2.5 % 2.5 to 2 % 2% 1) Reduced adjustments are applicable when it is po
32、ssible to applv to the free ends of the conveyor belt, during the jointing operation, an additional tension (pre-tension) which balances the force exerted by the device as allowed for in normal service. This force is calculated to ensure driving of the conveyor belt at all times : empty and loaded,
33、at constant speed, when starting, when braking to a stop. 2 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 3870-1976 (E) 3.1.3 Belts initially with a temporary joint
34、 (mechanical or spliced) and subsequently with a permanent spliced joint after a certain period of use If the belt manufacturer agrees, the normal adjustment values may be reduced by 0,5 to 1 %, the minimum values remaining unchanged. 3.2 Influence of special operating conditions 3.2.1 The adjustmen
35、t may be reduced by approximately 0,5 % : a) when the belt is usually operating at less than 60 % of the recommended maximum belt tension, or b) the conveyor installation and operating conditions are especially favourable, in particular : - if the belt is protected from bad weather conditions, not e
36、xposed to damp; - if the materials transported are at temperatures not exceeding 60 C; - if the starting-up tension is less than 1.5 times the normal operating tension. If conditions a) and b) are met simultaneously, a reduction exceeding 0.5 % may be considered by the conveyor manufacturer, with th
37、e agreement of the belt manufacturer. 3.2.2 The adjustment should be increased by approxi- mately 0,5 % when operating conditions are bad, in particular : - if the belt is exposed to bad weather conditions; - if the materials transported are very damp (either naturally or due to sprinkling); - if th
38、e temperature of the materials exceeds 60 “C; - if the starting up tension is more than I,5 times the normal operating tension. If conditions 3.2.1 a) and 3.2.2 are met simultaneously, the normal values of adjustment should be applied. 3.3 Influence of the type of belt Certain belts used for specifi
39、c applications require adjust- ment values greater than those given in the table. The manufacturers of these belts must draw the attention of the users and conveyor manufacturers to this point. 3.4 Influence of the installation conditions It may happen that, because of local circumstances, the conve
40、yor manufacturer is unable to adhere to the recommended adjustment values. He may in such cases, and with the agreement of the belt manufacturer and the user, adopt shorter adjustments, provided however, that these allow normal operation of the conveyor, subject only to more frequent cutting and rejointing operations. Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
