twin-path® slings in action - Hanes Supply, Inc

Wire RopesYOUR SLING AND RIGGING SPECIALISTABRASION AND BENDINGTHE "X CHART": ABRASION RESISTANCE VS. BENDING-FATIGUE RESISTANCEWhile there is a possibility, there is likelihoodthat an application can be foundfor which there is a precisely suitablewire rope – one that can satisfy everyindicated requirement.As with all engineering design problems,feasible solutions demand compromiseto some degree. At times, itbecomes necessary to settle for lessthan optimum resistance to abrasion inorder to obtain maximum flexibility; thelatter being a more important requirementfor the given job. A typical exampleof this kind of trade-off would be inselecting a highly flexible rope on anoverhead crane. Conversely, in ahaulage installation, a rope with greaterresistance to abrasion would be chosendespite the fact that such ropes aremarkedly less flexible.tigue, even though actual wear is slight.The smaller the diameter of the sheave,the sooner these fatigue breaks willoccur and the shorter rope life becomes.Another undesirable effect of smallsheaves is accelerated wear of both ropeand sheave groove. The pressure perunit area of rope on sheave groove for agiven load is inversely proportional to thesize of the sheave. In other words, thesmaller the sheave the greater the ropepressure per unit area on the groove.Both sheaves and rope life can obviouslybe prolonged by using the proper diametersheave for the size and constructionof rope.Sheave diameter can also influence ropestrength. When a wire rope is bent arounda sheave, there is a loss of effectivestrength due to the inability of theindividual strands and wire to adjustthemselves entirely to their changedposition. Tests show that rope strengthefficiency decreases to a markeddegree as the sheave diameter isreduced with respect to the diameter ofthe rope.Therefore, it is evident that a definiterelationship exists between rope serviceand sheave size. As a guide to ropeusers, wire rope manufacturers haveestablished standards for various ropeconstructions. To secure the most economicalservice, it is important that thesuggested size of sheaves given belowbe used.Two compelling factors that governmost decisions as to the selection of awire rope are: abrasion resistance, andresistance to bending fatigue. Strikinga proper balance with respect to thesetwo important characteristics demandsjudgment of a very high order. Agraphic presentation of just such comparisonof qualities between the mostwidely used rope constructions andothers is given by means of X-chart.Referring to this chart when selecting arope, the mid-point (at the X) comesclosest to an even balance betweenabrasion resistance and resistance tobending fatigue. Reading up or downalong either leg of the X, the inverse relationshipbecomes more apparent asone quality increases and the other decreases.effect of sHeaVe sIzeWire ropes are manufactured in a greatvariety of constructions to meet thevarying demands of wire rope usage.Where abrasion is an important factor,the rope must be made of a coarseconstruction containing relatively largewires. In other cases, the greatamount of bending to which the rope issubjected is more important. Here, amore flexible construction, containingmany relatively small wires, is required.In either case, however, if the rope operatesover inadequate size sheaves,the severe bending stresses imposedwill cause the wires to break from fa-The wire rope industry refers to this as the X-chart. It serves to illustrate theinverse relationship between abrasion resistance and resistance to bendingfatigue in a representative number of the most widely used wire ropes.nUMbeR of oUtsIDe WIRes PeR stRanD6910121212141618LEAST×RESISTANCE TO BENDING FATIGUE Ø GREATESTLEAST× RESISTANCE TO ABRASION ØGREATESTPRoPeR sHeaVe anD DRUM sIzes6 X 76 X 19 s6 X 21 fWflattenedstrand6 X 25 fW6 X 31 Ws6 X 36 Ws6 X 49 fWs6 X 64 sfWsconstRUctIonsUGGesteD MInIMUMD/d* RatIo D/d*RatIo6 x 7 72 4219 x 7 or 18 x 7Rotation Resistant 51 346 x 19 Seale 51 346 x 27 H flattened strand 45 306 x 31 V flattened strand 45 306 x 21 filler wire 45 306 x 25 filler wire 39 266 x 31 Warrington Seale 39 266 x 36 Warrington Seale 35 238 x 19 Seale 41 278 x 25 filler wire 32 216 x 41 Warrington Seale 32 216 x 42 filler 21 14HEADQUARTERS: 55 James E. Casey Drive • Buffalo, NY 14206 PHONE: 716.826.2636 FAX: 716.826.4412 www.hanessupply.com141