Page 56 - Wire Rope News & Sling Technology - February 2019
P. 56

Denny’s                                  Rigging in Construction,
         crane and                            Changing Times, for Some!

         rigging notes

                                                                     by Dennis O’Rourke



                                            employee  training needs and supervi-  moving of the load; which I have mea-
            hinking   about   “Construction”  sory controls for safety. The Rigging   sured at 100% in some abnormal load
         Tbrings to mind many images. These   skills  and cranes  needed in  residen-  movements (shock loading.)
         visions are of buildings, bridges, hous-  tial construction as contrasted to the   Now,  at the “bite” (contact area be-
         es, tunnels, roads, and so much more.   building of a Nuclear power plant is so   tween the top and lower slings) is what
         And, the types of objects moved to com-  dramatically different as to be almost   could be mistaken as a basket hitch,
         plete these  projects  are  as diverse  as   unrecognizable, yet, it is all generically   but it’s missing the required PD to RD
         their locations. Now adding to this, the   called “Rigging.”          diameter. And you must never  con-
         need  for  longer  crane  radius  and  the   On a typical building site, what are the   nect  two  fiber  slings  without  using  a
         loads getting heavier, taller, more com-  rigger’s basic duties? (1) Selecting the   shackle, this reduces the D/d ( diame-
         plexed, modular,  pre-assembled and   gear of the proper capacity, they (2) In-  ter of the support to the diameter of the
         just harder to set in place using “our”   spects the gear to make sure of its satis-  sling)  ratio  and  significantly  reduces
         dad’s tools and knowhow! (fig. 1)  factory condition and (3) determines the   the sling’s strength.
                                            attaching methods to control the load   The  most horrifying  in  this  photo
                                            throughout  its  movements.  And  finally   is  the  unpadded  area  where  the  fiber
                                            (4) determine acceptable weather condi-  slings contact the concrete and the lack
                                            tions at the “moment” of the lift. The em-  of shackles connecting the lower slings.
                                            ployer can assign other duties, but these   These mistakes are elementary topics
                                            are their “core” responsibilities.  in  rigging  training.  So  why  are these
                                              Now your guy “Denny” has been    well-dressed works so negligent?
                                            promoted  to  a  foreman  on  this  job   The  configuration  of  a  basket  hitch
                                            (white hat, far side.) The job is to   is with both Eyes on the hook and the
                                            place  a  pre-cast  concrete  floor  panel   body of the sling in  contact with 180
                                            with a mobile crane. Pictured below   degrees of the object’s surface. The sur-
                                            is one of the “best” examples of “how-  face area support is what provides the
                                            not-to-do-it!” (fig. 3)            “grip” to double the capacity of a basket
                                                                               over an eye to eye sling. Sharp corners
                                                                               can cut the fiber sling. Am I getting too
                                                                               elementary here? Well if so, these guys
                                                                               need elementary training. There are
                                                                               six basic problems with  this lift, can
                                                                               you spot them?
         Fig. 1 A simpler day!
                                                                                  How should the floor panels be set in
           In the past material came in by truck                               place? The job above looks like they all
         and were off-loaded  with wire rope                                   showed up and started looking around
         slings and a mobile crane. The “formed                                for  some  rigging  gear  and started to
         and poured in place” concrete structure                               “get it done!” How, if it were planned, it
         and “setting steel” was the standard                                  would look like this. (fig. 4) n
         practices.  Now  being  substituted by
         methods calling for elaborate  rigging
         methods and off-site planning. (fig. 2)
           The  point being  is;  what  are  your
         worker’s  duties  and  specific  responsi-  Fig. 3 How-not-to-do-it!
         bilities on these new construction sites?
         An analysis is a must to determine the   He is using two fiber slings over the
                                            crane  hook  in  a basket  hitch.  These                            Photos courtesy of Dennis O’Rourke
                                            slings pass through two other sling
                                            eyes that are in a basket hitch around
                                            the concrete floor panel. The angles are
                                            severe, increasing tension in the slings.
                                              Let’s assume  the  capacity of  the   Fig. 4.
                                            slings are greater than the load plus   DENNIS J. O’ROURKE, CSP, dennis@natlcrane.com,
                                            the 45 degrees angle (to the horizontal)   is the Director of National Crane Services, Inc. He has over
                                            which adds about 41.7% stress  to the   fifty years’ experience in the industrial, maritime, and con-
                                                                               struction fields working with heavy equipment and material
                                            slings.  Also,  adding to sling  stress  is   handling devices. As a safety engineer, Mr. O’Rourke has de-
                                                                               veloped and/or presented over 300 safety-training programs
         Fig. 2 Formal Lift Plan Needed!    inertial loading caused by the normal   for all representative elements of government and industry.
         56     Wire Rope News & Sling Technology   February 2019
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