Page 44 - Wire Rope News & Sling Technology - December 2019
P. 44

         Denny’s                                  Synthetic Ropes, “to be or
         crane and
         crane and                            not to be” Installed on Mobile
         rigging notes
         rigging notes Cranes – that is the Question

                                                                by Dennis J. O’Rourke, CSP

            here is a long-established belief that “if it ain’t broke,   there reduced because the overhaul weight requirement will
          Tdon’t fix it.” Steel wire rope has been used successfully   be approximately 65% of its original weight. The new total
          on cranes since the 1800s. Now some are replacing steel   weight in the hypothetical situation is approximately 1,352
          ropes with synthetic ropes. At the last two conferences   pounds, a 3584 pound reduction. This weight decrease really
          that I attended, held by the Crane Certification Associa-  gets crane manufacturers excited, especially the ability to
          tion of America (CCAA), synthetic rope manufacturers   reduce weight at the boom point. Also, note the nylon point
          (Samson and Yale respectively) gave presentations as to   sheaves a further weight reduction over steel. Fig. 2
          why replacing steel ropes with synthetic ropes on cranes
          makes sense.                                                                                    Fig.2
           What the crane industry has experienced in the past is
          fiber roped being easily cut when they are used as slings,
          blocks, and tag lines. Fig. 1 There is an established “belief”
          this material is too soft to be used on multipart reeving. It’s
          said that facts and words do little to alter a belief, experi-
          ences are what one trusts. Crane owners have required the
          installed synthetic rope be removed from their crane based
          on this weakness belief. Yet, no evidence of damage was
          evident. Fig. 1

                                                      Fig.1                                                     Photo courtesy of Dennis O’Rourke

                                                               Synthetic  ropes  have  been  installed  on  utility  truck
                                                              winches used in the power industry for decades. Synthetic
                                                              ropes are less conductive than steel wire ropes, an advan-
                                                              tage  when  working  around  powerlines.  For  most  opera-
                                                              tions, the synthetic rope on utility truck winches is used in
                                                              a one-part configuration. Now we are looking at synthetic
                                                              ropes being used as multi-part configuration on a mobile
                                                              crane, greater wear.
                                                               At various locations the Navy, Grove, and others have con-
                                                              ducted trial tests of synthetic ropes on cranes, and the per-
                                                              formance of the rope was reported satisfactory. I question
           The popularity of synthetic ropes on cranes is growing just   how safe it is to trust a synthetic rope that can be cut with a
          by the number of companies offering the product. They call   knife, to lift 80-ton loads? Especially since I have witnessed
          it in  sales  terms,  “market push” The  Heavy Lift off-shore   synthetic ropes damaged when used for rigging slings and
          Oil industry is a major user of these products due to their   tag lines. How will the rope last in “real” job activities?
          reduced weight.                                      When  a crane  is  operated and used  conservatively,  the
           The benefits of synthetic rope over steel are lighter weight,   synthetic rope should be as reliable as steel ropes. That is
          more flexibility, anti-spin, and no need for lubrication to pre-  the rub. When we factor humans into the equation, things
          vent corrosion. Some synthetic rope manufacturers claim a   get complicated, job pressures increase. What “predictable
          fourfold  increase  in  rope  life,  thereby  reducing  operating   misuse” should be expected. I think of the ABBA song “Take
          costs – a true advantage if proven. The benefit of reduced   a Chance on Me.” Do I take a change when not knowing if
          weight has caught the attention of the crane industry.  the crane  will  be properly operated and maintained some
           Let’s do a little arithmetic. Let’s assume the weight of   months down the line? I believe that synthetic rope needs
          eight parts of 7/8” steel wire rope at 1.42 pounds per foot at a   the “test of time” to show the crane community how it sur-
          100’ hook height (1.42 x 8 x 100 = 1,136 pounds) add a 3,800   vises in the real-world struggles of a modern job site. WRNWRN
          pounds load block. Now have 4,936 pounds suspended over
                                                               DENNIS J. O’ROURKE, CSP, is the Director of National Crane Services, Inc. He has over
          the crane’s boom point. Replace the steel rope with synthetic   fifty years’ experience in the industrial, maritime, and construction fields working with heavy
          rope, as pictured in Fig. 2, will see a reduction of the weight   equipment and material handling devices. As a safety engineer, Mr. O’Rourke has developed
                                                              and/or presented over 300 safety-training programs for all representative elements of govern-
          of the rope by 80%. The weight of the block will also be fur-  ment and industry. (
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