1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 254:2011Belt drives Pulleys Quality, finish and balanceBS ISO 254:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 254:2011. Its
2、upersedes BS ISO 254:1998 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee MCE/10, Belts it does not apply to those pulleys for variable speed drives that have one or more moving flanges.The other characteristics of transmission pulleys can be found in t
3、he relevant International Standards.2 Normative referencesThe 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)
4、applies.ISO 1940-1, Mechanical vibration Balance quality requirements for rotors in a constant (rigid) state Part 1: Specification and verification of balance tolerancesISO 4287, Geometrical Product Specifications (GPS) Surface texture: Profile method Terms, definitions and surface texture parameter
5、s 3 Choice and quality of materialsThe pulleys shall be made of any material that can be shaped to the standardized dimensions and tolerances, and is capable of withstanding the conditions of service (heating, mechanical stresses, abrasion, environment, etc.) without damage. Moreover, it is desirabl
6、e that the pulley material be capable of dissipating any significant heat which can be generated by the belts.4 Surface roughness4.1 Transmission pulleysThe surface roughness of the working surfaces shall not be coarser than the value given in Table 1.Table 1 Transmission pulleysWorking surface Surf
7、ace roughness, RaamV-pulley and V-ribbed pulley grooves and all pulley bores 3,2Flat pulley rims and all pulley rim edges 6,3Synchronous pulley tooth flanks and tips: industrial type drives 3,2 high-performance type drives (for example for automotive applications)1,6aAs defined in ISO 4287. ISO 2011
8、 All rights reserved 1BS ISO 254:20114.2 Test pulleysThe surface roughness of the working surfaces shall not be coarser than the value given in Table 2.Table 2 Test pulleysWorking surface Surface roughness, RaamV-pulley and V-ribbed pulley grooves (dynamic test) 1,6Synchronous pulley grooves 1,6Idle
9、r pulleys 1,6aAs defined in ISO 4287.4.3 EdgesThe edges of flat pulley rims, V-pulley grooves and V-ribbed pulley grooves shall be chamfered or radiused.5 Balance5.1 The purpose of balancing a pulley is to improve its mass distribution so as to diminish the out-of-balance forces exerted as it revolv
10、es; these forces cannot be completely eliminated, but the remaining imbalance shall not be greater than the allowable limit.5.2 As balancing is an expensive operation, the specified limit of the residual imbalance should be given a value as large as the envisioned applications allow.5.3 Two classes
11、of balancing may be considered: balancing in one plane, called static balancing; balancing in two planes, called dynamic balancing.5.4 Static balancing is usually sufficient; dynamic balancing may be necessary for pulleys with a wide-faced rim or those revolving at relatively high speeds.5.5 Pulleys
12、 manufactured for stock shall be statically balanced since their future conditions of use are not known at the time of manufacture.5.6 Static balancing shall be done so as to leave an eccentric residual mass on the working diameter (datum or effective, according to the type of pulley) which does not
13、 exceed the larger of the two following values:a) 0,005 kg;NOTE This value applies only to pulleys where there is adequate material to remove for balancing. Many light-duty pulleys have inadequate space to drill balancing holes or to add appropriate masses by permanent means.b) 0,2 % of the equivale
14、nt mass of the pulley, eventually including any companion bushing.The equivalent mass is taken as the mass of a geometrically identical pulley made of cast iron.5.7 When the rotational frequency, n, in minutes to the power minus one (min-1), of a pulley becomes known, it is advisable to ascertain wh
15、ether dynamic balancing may be necessary, as follows.NOTE The term “rotations per minute (r/min)” is usually used for rotating machines.ISO 254:2011(E)2 ISO 2011 All rights reservedBS ISO 254:2011Determine the limiting speed n1(min-1) by reference to Figure 1 or by calculation using the formula:nld1
16、=1,58 1011(1)wherel is the pulley rim face width, in millimetres;d is the diameter (datum or effective) of the pulley, in millimetres.Then:if n n1: dynamic balancing may be necessary.5.8 For dynamic balancing, the operation shall be implemented in accordance with ISO 1940-1. The balance quality grad
17、e G is determined by the largest of the following two numbers:G1= 6,3 mm/s (2)GvM25= mm/s (3)The expression for G2is derived from the definition in ISO 1940-1.In Formula (3):5 is the practical limit of the residual eccentric mass, in grams, specified in 5.6 a);v is the circumferential pulley speed,
18、in metres per second;M is the equivalent mass of the pulley, in kilograms, as given in 5.6 b).The G quality grade may be less than G1or G2if the user specifies a particular requirement.ISO 254:2011(E) ISO 2011 All rights reserved 3BS ISO 254:2011Figure 1 Limit n1(min-1) for static or dynamic balanci
19、ngISO 254:2011(E)4 ISO 2011 All rights reservedBS ISO 254:2011BS ISO 254:2011ISO 254:2011(E) ISO 2011 All rights reservedICS 21.220.10Price based on 4 pagesThis page deliberately left blankBSI is the independent national body responsible for preparing British Standardsand other standards-related pub
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