Page 8 - Wire Rope News & Sling Technology - February 2019
P. 8

3D Printed Crane Hooks:


                            Are They The Future?


                                                  by Dennis O’Rourke

         In January 2018, using a “3D” printing technique, The Huisman company,
         Netherlands, accomplished the manufacturing and load testing of an 88-ton Duplex
         Port Crane hook. Termed “Wire & Arc Additive Manufacturing,” the process utilizes
         a wire feed and plasma arc to produce the midsize hook.



                n the right is a CAD drawing
                cut-a-way  of the newest 3D
         Ohook  from  Huismann  LLC  us-
         ing Wire & Arc Additive Manufacturing
         (WAAM). This  is a four-pronged  hook
         for heavy lifts offshore. Next to it shows
         the cross-section of one prong. (fig. 1) Is
         this the future? Some think so!
           From  a  user’s  viewpoint,  in  over
         fifty  years  I  have  witnessed  about
         three unplanned hook failures - what
         I mean is, broken in two pieces - when
         working.  And  those  were  in  the  ’70s
         and ’80s. Usually hooks “open” slow-  Fig. 1. CAD cut-a-way of 4-pronged hook and 3D printed cross-section.
         ly. It’s when they are subjected to ex-  Photo courtesy of The Huisman Company, Netherlands.
         treme impacts that they break. Fail-  It’s my opinion that in  the last 50
         ure during certification has different   years we’ve achieved a good safety re-
         criteria depending on the material:   cord for crane hooks in this country. It
         this means not breaking in two, but   was due to the monitoring by employ-
         instead the opening-up of a hook’s   ers of timely inspections that were per-
         throat (the part that the slings enter),   formed by trained people. The improve-
         to a published tolerance, when over-  ment in  the  material manufacturing
         loaded to 200% of capacity.        processes, quality control upgrades,
           The  three  hooks  I mentioned above   and more Non Destructive Evaluation
         were  in  terrible condition  working  at   (NDE) in the field have given us confi-
         low temperatures and should have   dence in our hooks.
         been removed from service before fail-
         ing  (fig.  2).  The  US  Navy  and  OSHA   A new way to manufacture hooks
         from 1971 to 2018 (47 years,  having   Up to 2018, crane  hooks  had  been
         fun  yet?) have drilled into our heads   made by one of two processes: casting
         the importance of proper hook inspec-  and then machining the finished hook,
         tion,  and it’s sunk  in.  Most  everyone   or forging. Casting is how two-prong
         in our industry now is well-aware of   or duplex hooks are produced - due to
         the critical part hooks play in material   their shape, duplex, or “sister” hooks,
         handling. Hooks support all that is be-  cannot be forged. (fig. 4)
         low them! (fig. 3)                   The second process  is hot forging
                                            of steel into a bowl-shaped hook.  (see
                                            fig. 5) The mild steel (about 30 on the
                                            Brinell hardness scale) is heated to its
                                            plastic state and at that elevated tem-
                                            perature is “hammered” or sometimes
                                            rolled into its desired shape and then
                                            given a timed cool-down to relieve any
                                            internal stresses that may  have been
                                            induced during  the procedure.  This
                                            process has taken place for thousands
                                            of years and today with modern equip-
                                            ment monitoring the process,  quality
                                            assurance and testing procedures, forg-
                                            ing is near perfection.            Fig. 3. A cast and machined duplex hook
                                              In 2018, I learned of the new “third”   during a load test.
         Fig. 2. One of the hooks damaged after failure.     continued on page 10  Photos courtesy of Dennis O’Rourke unless otherwise noted.

         8      Wire Rope News & Sling Technology   February 2019
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