Quantcast Field-Erected Hoisting Devices

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should  be  1  7/8  inches  (51.2  mm)  in  circumference. Lifelines  and  safety  belts  must  be  used  when  working on unguarded scaffolds at heights of 10 feet (3 m) and above (as well as on boatswain’s chairs, as explained earlier). If working over water, life jackets must be worn. All  scaffolds  and  scaffold  equipment  should  be maintained  in  safe  condition.  Avoid  making  repairs  or alterations to a scaffold or scaffold equipment while in  use.  Rather  than  take  a  chance,  NEVER  permit personnel to use damaged or weakened scaffolds! FIELD-ERECTED HOISTING DEVICES Because  of  the  nature  of  heavy  construction, Steel workers must at times erect heavy structural members   when   constructing   pre-engineered buildings,  piers,  bridges,  and  many  other  components related  to  Advanced  Base  Functional  Components (ABFC).  These  members  are  usually  hoisted  into position using cranes, forklifts, or other construction equipment.   In   contingency/   combat   operations, however,  because  of  operational  commitments  this equipment   may   not   be   available   and   structural members must be hoisted without the use of heavy equipment. We will now discuss some of the methods which can be used for the erection process when heavy equipment  is  not  available. The term field-erected hoisting device  refers to a device that is constructed in the field, using material available  locally,  for  the  purpose  of  hoisting  and moving  heavy  loads.  Basically,  it  consists  of  a block-and-tackle  system  arranged  on  a  skeleton structure consisting of wooden poles or steel beams. The  tackle  system  requires  some  form  of  machine power  or  work  force  to  do  the  actual  hoisting.  The three types of field-erected hoisting devices used are gin poles, tripods, and shears. The skeleton structure of  these  devices  are  anchored  to  holdfasts. HOLDFASTS Gin poles, shear legs, and other rigging devices are held in place by means of guy lines anchored to holdfasts.  In  fieldwork,  the  most  desirable  and economical types of holdfasts are natural objects, such as trees, stumps, and rocks. When natural holdfasts of suffient  strength  are  not  available,  proper  anchorage can  be  provided  through  the  use  of  man-made holdfasts.   These   include   single   picket   holdfasts, combination picket holdfasts, combination log picket holdfasts,  log  deadmen,  and  steel  picket  holdfasts. Natural Types of Holdfasts When   using   trees,   stumps,   or   boulders   as holdfasts,  you  should  always  attach  the  guys  near ground  level.  The  strength  of  the  tree,  stump,  or boulder size is also an important factor in determining its suit ability as a holdfast. With this thought in mind, NEVER use a dead tree or a rotten stump or loose boulders and rocks. Such holdfasts are unsafe because they are likely to snap or slip suddenly when a strain is placed on the guy, Make it a practice to lash the first tree  or  stump  to  a  second  one  (fig.  6-43).  This  will provide  added  support  for  the  guy. Rock   holdfasts   are   made   by   inserting   pipes, crowbars, or steel pickets in holes drilled in solid rock. Using a star drill, drill holes in the rock 1 1/2 to 3 feet apart, keeping them in line with the guy. Remember to drill the holes at a slight angle so the pickets lean away Figure 6-43.—Using trees as a holdfast. 6-23

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