1、BRITISH STANDARD BS 6521:1984 ISO 7592:1983 Guide for Proper use and maintenance of calibrated round steel link lifting chains ISO title: Calibrated round steel link lifting chains Guidelines to proper use and maintenance UDC 621.86.065.4:672.6BS6521:1984 This British Standard, having been prepared
2、under the direction of the Mechanical Engineering Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 August 1984 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference MEE/12 Draft for comment 82/76817 DC
3、ISBN 0 580 13959 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Mechanical Engineering Standards Committee (MEE/-) to Technical Committee MEE/12 upon which the following bodies were represented: Associated Offices Technical Committee
4、British Chain Manufacturers Association British Ports Association and the National Association of Ports Employers British Railways Board Chain Testers Association of Great Britain Corporation of Trinity House Department of Trade and Industry (National Physical Laboratory) Federation of Civil Enginee
5、ring Contractors Federation of Manufacturers of Construction Equipment and Cranes Federation of Wire Rope Manufacturers of Great Britain Health and Safety Executive Ministry of Defence National Association of Drop Forgers and Stampers National Coal Board Coopted members The following body was also r
6、epresented in the drafting of the standard, through subcommittees and panels: British Steel Industry Amendments issued since publication Amd. No. Date of issue CommentsBS6521:1984 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of applicat
7、ion 1 2 References 1 3 Chain usage 1 4 Inspection 2 5 Chain replacement 4 6 In-service testing of chain 4 7 Repair of chain 4 8 Record keeping 4 Publications referred to Inside back coverBS6521:1984 ii BSI 07-1999 National foreword This British Standard, prepared under the direction of the Mechanica
8、l Engineering Standards Committee, is identical with ISO7592 “Calibrated round steel link lifting chains Guidelines to proper use and maintenance” published in1983 by the International Organization for Standardization (ISO). The UnitedKingdom has taken part in the preparation of the international st
9、andard through Sub-Committee 1 of ISO/TC111, Round steel link chains, lifting hooks and accessories, and considers that these guidelines give useful advice to users of calibrated chains. The guidance given is in the form of recommendations concerning the main principles involved. Terminology and con
10、ventions. The text of the international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been
11、used as a decimal marker. In British Standards, it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. There is no corresponding British Standard for
12、ISO4301 (which is referred to in the note to 4.1). As this standard is referred to for information only, the validity of this British Standard is not affected. Additional information. In the note to clause 1 the international standard draws attention to national and local laws and regulations applyi
13、ng to lifting chain. For industrial use in Great Britain, these are the Factories Act1961, (particularly Sections26 and27) and Regulations made under the Act, e.g. the Construction, (Lifting Operations) Regulations1961, the Ship-building and Ship-repairing Regulations1960, etc. NOTETypographical err
14、or. In 5.1, paragraph 3, for “worm” read “worn”. A British 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 oblig
15、ations. Cross-references International standards Corresponding British Standards BS 4942 Short link chain for lifting purposes ISO 1836:1980 Part 3:1981 Specification for grade M (4) calibrated chain (Identical) ISO 3077:1980 Part 6:1981 Specification for grade T (8) calibrated chain (Identical) Sum
16、mary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to4, 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 theinside front
17、 cover.BS6521:1984 BSI 07-1999 1 1 Scope and field of application This International Standard specifies the main principles for the use, inspection, in-service testing and maintenance of calibrated round steel link chains operating over chain wheels. The principal applications include manual and pow
18、er driven hoists. NOTELifting chains may be governed by national and local laws and regulations. 2 References ISO 1836, Short link chain for lifting purposes Grade M(4) calibrated, for chain hoists and other lifting appliances. ISO 3077, Short link chain for lifting purposes Grade T(8) calibrated, f
19、or chain hoists and other lifting appliances. ISO 4301, Lifting appliances Classification. 3 Chain usage 3.1 In the interests of safety, reliable operation and satisfactory life, proper usage of chain is very important. Some of the responsibility rests with the equipment manufacturer, being dependen
20、t upon choice of relative dimensions of chain and pocket wheel, as well as the means provided for guiding, where necessary, the chain on and off the pocket wheel, and in and out of the equipment. There are also important factors under the direct control of the user. One essential requirement is that
21、 the chain be aligned correctly with the chain wheel. If the chain forms a closed loop, aligned with the wheel and always under tension, no external guide is needed. In any installation where the chain may become slack or twisted or where it may approach the wheel at an angle to the plane of rotatio
22、n, a suitable chain guide must be provided. Usage should be avoided that prevents direct entry of the chain into a hoist or lower hook block or that twists the chain upon entry. 3.2 In order to maintain the gauge length dimensions, it is necessary that the chain be under tension. Very little tension
23、 (for example the weight of a few links) is sufficient to maintain the gauge length, provided that the chain is otherwise free and not subjected to restraining side forces. The chain should not be allowed to pick up dirt, etc. which would impair its free movement and which if carried into the equipm
24、ent and deposited in the pockets, of the pocket wheel could affect the proper seating of the chain in the pockets. 3.3 There are two types of pocket wheels over which chain may be required to run: a) idler wheels, which change the direction of the chain but do not substantially affect its tension; b
25、) driving wheels, which change both tension in the chain and its direction. This type also includes driven wheels, such as the wheel driven by the hand chain of a manually operated hoist. 3.3.1 Idler wheels of relatively large diameter (not less than6X pitch of chain recommended) used with lightly l
26、oaded chain may be plain sheaves with circular grooves. Smaller wheels, or a higher chain tension, require flats or pockets to accommodate the link as chords to the wheel circumference to avoid bending and to provide sufficient bearing area. In most installations guides are required to remove twist
27、from the approaching chain and to align it correctly in the rotational plane of the wheel. Such guides should also prevent the chain disengaging the wheel should it become slack. 3.3.2 Driving wheels are more demanding and generally pocketed wheels are essential. In addition to the guiding requireme
28、nts as for idler wheels, there are two conditions which require additional restraints, both involving the chain at the slack side. One is stripping, or forcible removal from the wheel, of chain whose pitch appears to be too short. When the wheel is rotated to draw in chain under tension, the links a
29、t the slack side tend to remain in the wheel and must be mechanically disengaged. The condition may occur with new chain of too short pitch for the wheel or with chain of correct pitch operating over a worn wheel. The stripper usually takes the form of a finger installed between the chain strands an
30、d extending well into the centre groove of the wheel. It engages links in the plane of rotation and forces them to leave the wheel. The other condition occurs with chain, either new or worn, whose pitch is too long for the wheel. In this case it is necessary to guide the slack chain approaching the
31、wheel into engagement by advancing the links which are transverse to the plane of rotation. This is a difficult task at best, and in extreme conditions, may cause high rubbing forces and severe external wear.BS6521:1984 2 BSI 07-1999 3.4 The design of end connections to develop full chain tension be
32、comes more difficult as chain strength increases. For example, a circular transverse pin may be used, but is limited to a diameter very little larger than that of the chain material, whereas a pin of oval cross-section may provide greater strength in bending. Two mating blocks, contoured to fit the
33、end link, also will develop full chain strength. Strength requirements are therefore sufficiently important and demanding that only the equipment manufacturers recommended replacement parts should be used. 3.5 Chain is a mechanism in which high bearing pressures are developed. In order to attain max
34、imum life it is therefore necessary to ensure that lubrication is maintained, particularly in the interlink contact areas where pressures are highest. Suitable lubricants are those that cling and are capable of withstanding high pressures, but in all cases where equipment manufacturers recommendatio
35、ns are available they should be strictly followed. In those special applications where chain lubricant cannot be used because of possible contamination of the material being handled or the lubricant itself, the life of the chain and pocket wheel may be drastically reduced. 3.6 A protective coating f
36、or steel chain will reduce corrosion. Whatever process is chosen, the following points should be taken into consideration: a) the possibilites of reduction in pitch due to thickness of the coating applied, for example hot galvanizing is generally unsuitable; b) the possible effects on the mechanical
37、 properties of the chain. Users shall not apply any coating unless approved by the chain manufacturer. 3.7 If the slack chain descending from an overhead hoist is undesirable, a chain container may be installed. It is essential that the container be of adequate size, properly aligned and provided wi
38、th a means of drainage. If a few links of chain overflow the edge of the container (whether caused by improper alignment or inadequate capacity) all of the chain may be caused to run out of the container. The top of the chain pile is a cone, which must not build up so high as to remove all tension f
39、rom the slack side chain, as otherwise the chain may not re-enter the wheel properly. 3.8 Chains fitted to lifting appliances are usually provided with free swivelling hooks to ensure that any twists in the chain will be removed automatically before the load is moved. Such chains used in choke hitch
40、 (i.e. by back hooking after passing the chain round the object to be moved) renders the safety swivelling ineffective and is therefore an unsafe procedure. Also using the load chain and hook in a choking hitch configuration may damage the load chain and shorten the driving wheel life. Slinging shou
41、ld always be carried out using separate equipment attached to the hook. In the case of hooks supported on two or more falls of chain, care should be taken that the chain does not become twisted by the operator inadvertently passing the hook through the loop of the chain and turning the hook block ov
42、er. If such twisting has occurred, it should be rectified by passing the hook through the loops of chain in the reverse direction. 4 Inspection 4.1 Classification of service Proper maintenance depends on an evaluation of the severity of usage to which the chain and the appliance, in which it is inst
43、alled, are subjected. The duty should be evaluated to conform to one of the following classes so that inspection can then be performed as described in 4.2: 4.1.1 light service: Chains and appliances subjected very rarely to the maximum load and, normally, to light loads; 4.1.2 moderate service: Chai
44、ns and appliances subjected fairly frequently to the maximum load and, normally, to moderate loads; 4.1.3 heavy service: Chains and appliances subjected frequently to the maximum load and, normally, to loads of heavy magnitude; 4.1.4 very heavy service: Chains and appliances subjected regularly to t
45、he maximum load. NOTEFurther information on the classification of lifting appliances is given in ISO4301, from which the above duties are extracted. 4.2 Inspection classification Inspection procedure is divided into two general classifications based upon the intervals at which inspection should be p
46、erformed for chains in regular service. The general classifications are herein designated as “frequent” and “periodic” with respective intervals between inspection as defined below. (In addition, visual observations shall be conducted during regular service for any damage or evidence of malfunction
47、which might occur between regular inspections.)BS6521:1984 BSI 07-1999 3 4.2.1 Frequent inspection This is a visual examination by the operator or other designated personnel, without requiring records to be made. Inspection should be carried out at the following intervals: a) light service every mon
48、th; b) moderate service every two weeks; c) heavy service every week; d) very heavy service every day. 4.2.2 Periodic inspection This is a thorough examination by an appointed person, making records of external conditions to provide the basis for a continuing evaluation. Inspection should be carried
49、 out at least at the following intervals: a) light service yearly (equipment in place); b) moderate service half yearly (equipment in place unless external conditions indicate that disassembly should be done to permit detailed inspection); c) heavy service quarterly (equipment in place unless external conditions indicate the disassembly should be done to permit detailed inspection); d) very heavy service six weekly (equipment in place unless external conditions indicate that disassembly should be done to permit detailed inspection). 4.3 Inspection pr
