Page 32 - Wire Rope News & Sling Technology
P. 32

continued from page 30
         the limits, listen to it for unusual noise
         and “feel” for roughness.  It  is good
         practice  to perform  two  full  cycles  of
         each function.
         Common Mechanical and
         Structural Failures
           Crane accident statistics can be mis-
         leading and could have a negative effect
         on a safety program. The leading cause
         of fatality is electrocution and occurs
         mostly with boom trucks. If you oper-
         ate boom trucks, your program should
         concentrate on “site power line recogni-
         tion.” If you don’t own boom trucks you
         have reduced electrical hazard!
           Wire rope failures are the number
         one cause of crane structural accidents.
         All cranes wear out their wire rope, but
         at different rates and locations. To re-                                 Figure 8. Cracks around the turntable.
         duce these types of accidents, the own-
         er must a) properly install the correct   ure 8) are being found. The area must   read and evaluate it for accuracy. Af-
         rope,  with  certification  documents;  b)   be clean and good lighting is needed to   ter reviewing the historical equipment
         properly lubricate the rope; c) inspect   detect them.                files, the crane owner can compare per-
         the rope at wear  points;  d) maintain   Pictured in Figure 9 is a rusted out   formance between cranes, identify prob-
         the complete reeving system; e) keep a   “back hitch” on an older Lima crane.   lems areas, appraise the working life
         log of operating hours and f) after re-  This was caused by the drain holes   of  components,  and  note  trends.  Most
         placing the rope, analyze why it failed   being  plugged.  The  accumulation  of   importantly,  this  process  can  lead  to
         and act (Figures 4 and 5, page 28).  moisture rusted the tubing from in-  greater assurance that the cranes will
           Making sure the crane is configured   side. Inspect all weep holes to ensure   reliably hold a load against the gravita-
         correctly is critical for heavy lift cranes.   that they are clean and clear to allow   tional pull of the earth, the hazard we
         This  is  not always straightforward.   moisture to drain.            can’t eliminate!  WRN
         The point is, know your crane and that
         it is properly assembled.          A final word about Inspection        DENNIS J.  O’ROURKE, CSP,  dennis@natlcrane.com,
           Boom  luffing  ropes  failure  is  also  a   In summary, to perform a good in-  is the Director of National Crane Services, Inc. He has over
                                                                               fifty years’ experience in the industrial, maritime, and con-
         common cause of conventional crane   spection you must use a motivated and   struction fields working with heavy equipment and mate-
                                                                               rial handling devices. As a safety engineer, Mr. O’Rourke
         accidents  (Figure  6,  page 28).  Boom   knowledgeable person, the correct loca-  has  developed  and/or  presented  over  300 safety-training
         rope  inspection  can  be  difficult.  The   tion, and a proper length of time to do   programs for all representative elements of government and
                                                                               industry.  He has personally performed hundreds of load
         ropes  must  be  relaxed to check  the   the job well. Inspectors will produce a   tests, physical examinations, heavy lift consulting and acci-
                                                                               dent investigations on nearly all types of material handling
         sheaves by laying the outer bail on the   report  and  a  Qualified  Person  should   and personnel lifting devices.
         boom and the boom on the ground (Fig-
         ure 7, page 30). The one failure mode
         for boom ropes is fatigue and this can-
         not be seen, so the length of time the
         rope is in service must be recorded.
           Brakes are another common cause
         of  failure.  When  boom brakes  have
         been replaced the adjustments need
         to be checked.  For example,  a hoist
         brake  with  a  lining  7/16"  thick  must
         be checked to ensure it meets specifica-
         tions. The anchor structure is checked
         for cracks and brake adjustment.
           Make sure the drum surface is dry
         and smooth; some streaking from the
         new shoes may be noted but deemed
         okay. Although brakes are inspected
         and adjusted, it’s their operation
         that counts. The security that comes
         when lifting a heavy load is only as-
         sured after the brakes have been
         load tested.
         Uncommon Mechanical and
         Structural Failures
           Although uncommon, cracks (like
                                                                                          Figure 9. Rusted back hitch.
         these seen around a turntable in Fig-                                            Figure 9. Rusted back hitch.
         32     Wire Rope News & Sling Technology   June 2018
   27   28   29   30   31   32   33   34   35   36   37