1、BRITISH STANDARD MARINE SERIES BS MA 47:1977 Incorporating Amendment No.1 Code of practice for Ships cargo blocks UDC 629.12.011.51:621.861.2BSMA47:1977 This BritishStandard, having been prepared under the directionof the Mechanical Engineering Standards Committee, was published underthe authority o
2、f the Executive Board on 30November1977 BSI02-2000 First published as BS408 in February1931 Revised in1949 and1963 This revision published as BSMA47 November 1977 The following BSI references relate to the work on this standard: Committee reference MEE/64 Draft for comment72/34747 DC ISBN 0 580 0991
3、6 4 Amendments issued since publication Amd. No. Date of issue Comments 3721 August1981 Indicated by a sideline in the marginBSMA47:1977 BSI 02-2000 i Contents Page Foreword ii 1 Scope 1 2 References 1 3 Definitions 1 4 Factor of safety 1 5 Permissible working stresses 1 6 Material 5 7 Side and part
4、ition plates 5 8 Fixed head fittings 5 9 Shanked swivel head fittings 6 10 Screw threads 6 11 Heat treatment 6 12 Axle pins 6 13 Lubrication 6 14 Sheaves 6 15 Becket 7 16 Locking nuts 7 17 Proof load 7 18 Examination after proof load 8 19 Marking 8 20 Certificate of test and examination 8 Appendix A
5、 Recommendations relating to contracts 9 Appendix B Proof load in relation to safe working load 9 Appendix C Single sheave blocks: marking of safe workingloadanduseinthederrick rig 10 Appendix D Guidance for the ordering of blocks 12 Appendix E Particulars of screw threads for the shanks of head fit
6、tings 13 Appendix F Care and maintenance of ships cargo blocks 14 Appendix G Formulae for round section eyes 15 Appendix H Head fittings 16 Figure 1 Ships cargo blocks 3 Figure 2 Shear pull-out and tensile stress in straps 4 Figure 3 Position of reactions in crossheads 4 Figure 4 Typical rigs using
7、single sheave blocks 11 Figure 5 Head fittings 16 Table 1 Load transmitted by block sheaves 2 Table 2 Load on supporting straps (equal spans) 2 Table 3 Permissible tensile stress on shanks of head fittings 4 Table 4 Diameter in sheave grooves 7 Table 5 Diameter of sheaves 7 Table 6 Proof load in rel
8、ation to safe working load 9 Table 7 Typical table of information that may be supplied with an enquiry or order 12 Table 8 Particulars of screw threads: ISO metric screw threads, coarse series with graded pitches 13BSMA47:1977 ii BSI 02-2000 Foreword In this revision of BS408 (now BS MA47), this sta
9、ndard has been brought into line with complementary standards and its scope has been extended by the inclusion of snatch blocks. All units are now in metric values and wire ropes are sized by diameter in place of circumference. In the case of sheaves, the diameter is now measured at the bottom of th
10、e rope groove. The relationship between the proof load and safe working load (SWL) has been brought into line with the values in the International Labour Office pamphletNo.188 “Safety and health in dock work” (ILO code), which are being incorporated in the new Docks Regulations now in preparation. A
11、s in the1963 edition of this standard, limitations have been placed on the use of screw threads having a depth of thread less than0.04D, where D is the diameter at the top of the thread. This limitation, which assumes a length of engagement equal to the diameter D, is a precaution against the possib
12、ility of the threads beginning to fail before the tensile failure of the core diameter area. (In the case of internal threads the increased circumferential area in shear will compensate for the reduced depth of thread.) Where hooks are required they should comply with the relevant BritishStandard. U
13、nlike blocks for general engineering purposes, the SWL marked on any multiple sheave block will correspond to the resultant load on the head fitting of that block. Thus the fixed block in a purchase should normally have a greater SWL marked on it than the moving block, to allow for the downhaul pull
14、. This standard applies to ships cargo blocks for use with wire rope. In order to determine the appropriate size of wire rope, and the resultant loads on the head fittings, reference should be made to the design information in BS MA48 “Code of practice for the design and operation of ships derrick r
15、igs”. Where the position of a block in any set of lifting tackle is changed (for example, when the block is used in another combination of blocks), the loading imposed upon a block under a given cargo load may vary with the position in which it is placed. Care and discretion must therefore be exerci
16、sed in the selection of blocks to be used in different sets or combinations, to avoid the possibility of overloading (see BS MA48). Attention is drawn to Appendix A which deals with provisions for testing and inspection in contracts. Cargo blocks should be periodically overhauled and, when not in us
17、e, they should be stowed and protected against undue exposure to weather. Recommendations as to maintenance, overhaul and lubrication are given in Appendix F. Neglect of adequate lubrication seriously increases friction in the block and can also lead to rapid pin wear. While those types of blocks wh
18、ich are known as “malleable blocks” and “wood blocks” are not included in this standard, this should not be interpreted as deprecating such blocks for the purposes for which they are commonly used. A British Standard does not purport to include all the necessary provisions of a contract. Users of Br
19、itish Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to16 and a back cover. This standard has be
20、en updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BSMA47:1977 BSI 02-2000 1 1 Scope This standard covers ships steel cargo blocks for use with wire rope and forming part of the cargo derrick rig, embracin
21、g the body, sheave(s), axle pin, head fittings and becket. Materials, workmanship, design particulars (screw threads, bearings, sheave diameters for given rope sizes, sheave grooves), permissible stresses, proof loading, inspection, marking and certificate of test and examination are specified. 2 Re
22、ferences This standard makes reference to the follow standards publications: BS302, Wire ropes for cranes, excavators and general engineering purposes. BS309, Whiteheart malleable iron castings. BS310, Blackheart malleable iron castings. BS919, Screw gauge limits and tolerances. BS970, Wrought steel
23、s in the form of blooms, billets, bars and forgings Part1: Carbon and carbon manganese steels, including free cutting steels. BS1452, Grey iron castings. BS1486, Lubricating nipples. BS1610, Methods for the load verification of testing machines. BS1700, Memorandum on ships derrick rigs. BS1936, Unde
24、rcuts and runouts for screw threads. BS2772, Iron and steel for colliery haulage and winding equipment Part2: Wrought steel. BS2789, Iron castings with spheroidal or nodular graphite. BS3017, Mild steel forged ramshorn hooks. BS3100, Specification for steel castings for general engineering purposes.
25、 BS3810, Glossary of terms used in materials handling Part6: Terms used in connection with pulley blocks. BS4360, Weldable structural steels. BS MA48, Design and operation of ships derrick rigs. 3 Definitions For the purposes of this BritishStandard the following definitions apply. 3.1 ships cargo b
26、lock (see Figure 1) a block suitable for use with wire rope and forming part of the cargo derrick rig, embracing the body, sheave(s), axle pin, head fittings, becket, and/or other components 3.2 single, double, treble, four-fold, five-fold, etc. block a block with one, two, three, four, five, etc.,
27、sheaves 3.3 mast head span block, lower cargo purchase block, etc. blocks used in particular positions on derricks 3.4 snatch block a single block with a hinged portion through which a rope can be passed to facilitate reeving 3.5 head fittings the means by which the block is attached to its anchorag
28、e or to the load being lifted. Types of head fittings are shown in BS3810-6, and are reproduced as Appendix H of this standard 3.6 safe working load of a single sheave block the maximum load, W, which can safely be lifted in the manner shown in Figure 4, Appendix C 3.7 safe working load of a multipl
29、e sheave block the maximum resultant load which can safely be applied to the head fitting of the block in service NOTEA snatch block is regarded as suitable only when rigged as a lead block, and only when the hinged portion is properly closed and secured. In such condition it is deemed to have a sim
30、ilar function to that of a single sheave block, and the safe working load is similarly defined. 4 Factor of safety For the purpose of this standard, the factor of safety of a block is the ratio between the ultimate strength of the block as a unit, and the maximum permitted load imposed on the block,
31、 neglecting frictional resistance, acceleration of the load and the affect of a ships list, which are taken care of by the factor of safety. The factor of safety, as so defined, should be not less than5. It is further required that the permissible working stresses specified in clause5 should not be
32、exceeded in the design of the block. 5 Permissible working stresses 5.1 Bearing pressure on axle pin. The bearing pressure between any sheave bush and the axle pin should not exceed39N/mm 2for single sheave blocks, or31N/mm 2for multiple sheave blocks.BSMA47:1977 2 BSI 02-2000 For the purpose of cal
33、culation, the load transmitted by any sheave should be taken as not less than that shown in Table 1. The pressure between the axle pin and the stress-bearing members (i.e.straps and supporting partitions) of the block should not exceed154N/mm 2and, for the purpose of calculation, the load sustained
34、by such members when each individual sheave has a support should be taken as not less than that shown in Table 2. For the foregoing requirements, the projected area of the axle pin in contact should be taken, i.e.Area=appropriate length diameter. 5.2 Shearing stress in axle pins and through bolts. I
35、n single shear the shearing stress should not exceed62N/mm 2for mild steel, or77N/mm 2for higher tensile steel (see clause6). Twice these values may be taken in the case of double shear. In the design of snatch blocks, the loading may be assumed to be equally distributed on each side strap. Table 1
36、Load transmitted by block sheaves Table 2 Load on supporting straps (equal spans) Type of block Number of sheaves in block Percentage of resultant load on head fitting transmitted by any sheave, max. Sheaves with bushed plain bearings (Friction allowance6%) Sheaves with ball or roller bearings (Fric
37、tion allowance2%) Without becket With becket Without becket With becket Double Treble Four-fold Five-fold Six-fold Seven-fold Eight-fold 2 3 4 5 6 7 8 % 53 38 30 25 22 20 19 % 44 33 27 24 21 19 18 % 51 35 27 22 19 17 15 % 42 30 24 20 18 16 14 NOTE 1For all blocks covered by this table, the resultant
38、 load on the head fitting is the value of the SWL marked on the block (See definitions, clause3). NOTE 2The percentages in this table are based on the maximum rope tensions on the moving block when hoisting, as calculated from the friction coefficients given in section2 of BS1700:1963. Type of block
39、 Number of sheaves in block Number of supports Percentage of total load on axle pin sustained by supports, max. Inner support Outer support Sheaves with bushed plain bearings (Friction allowance6%) Sheaves with ball or roller bearings (Friction allowance2%) Any inner support Any outer support Any in
40、ner support Any outer support Double Treble Four-fold Five-fold Six-fold Seven-fold Eight-fold 2 3 4 5 6 7 8 1 2 3 4 5 6 7 2 2 2 2 2 2 2 % 63 40 32 27 24 22 20 % 20 15 12 10 9 8 7 % 63 38 30 24 21 18 16 % 19 14 11 9 8 7 6 NOTE 1Provision should be made on the appropriate supports for the load impose
41、d by the becket. NOTE 2The loadings shown in this table have been calculated on the assumption that the axle pin is a continuous beam having free ends and supports equally spaced, and is subjected to a varying load, due to rope/sheave friction and increasing in magnitude along the length of the axle
42、 pin, when hoisting or lowering.BS MA 47:1977 BSI 02-2000 3 Figure 1 Ships cargo blocksBSMA47:1977 4 BSI 02-2000 5.3 Permissible stress on screwed shanks of head fittings. The average tensile stress on the shanks of head fittings should be based on the core area( square of core diameter). For the pu
43、rpose of this calculation, screw thread tolerances may be neglected (see Appendix E). The average tensile stress due to the resultant load on the shank should not exceed the values given in Table 3. Table 3 Permissible tensile stress on shanks of head fittings When calculating the resultant load, W,
44、 on the screwed shank, the effect of acceleration of the load, and of any increased loading due to a ships list, may be neglected. 5.4 Bearing pressure on collars and nuts of shanks. To prevent excessive bearing pressure between the screwed collar or nut and the crosshead of the block, the diameter
45、of the collar should be not less than1.5D+3mm, where D is the diameter of the shank inmm. 5.5 Shear pull-out and tensile stress in straps. The shear pull-out in the cross section at the end of a strap should not exceed54N/mm 2in single shear, on the area2(a t), as shown in Figure 2. The average tens
46、ile stress in the cross section at either side of the hole for the axle pin, and at either side of the hole for the crosshead trunnion, should not exceed77N/mm 2on the area2(b t). In the case of snatch blocks, the loading may be assumed to be equally distributed on each side strap. 5.6 Bending stres
47、s in axle pins. Adequate support should be provided for the axle pins to prevent excessive bending stress, and the design of the axle pins and supports should be such that there is no apparent permanent set after the removal of the proof load. 5.7 Stress in crossheads. The extreme fibre stress at th
48、e centre of the length of the crosshead when housing a swivel head-fitting should not exceed77N/mm 2for mild steel, or93N/mm 2for higher tensile steel. This stress is related to the resultant load on the crosshead when supporting the safe working load, taking into account the stress concentration at
49、 the cross section at the central hole receiving the shank of the head fitting. For the purpose of calculation, the reactions may be assumed to act at the positions shown in Figure 3. Resultant load on head fitting Permissible tensile stress Higher tensile steel hook and mild steel eye Higher tensile steel eye and alloy steel head fittings Up to t 50 55 60 65 70 75 and over N/mm 262 65 68 71 74 77 N/mm 2 85 (all sizes) NOTEWith ramshorn hooks, the stress values in BS3017 should be used. 4 - Figure 2 Shear pull-out and
