• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Slings
Figure  13-34.Using  spreader  bars

Equipment Operator Basic - Beginning construction equipment operators manual
Page Navigation
  346    347    348    349    350  351  352    353    354    355    356  
determined  to  ensure  that  the  individual  legs  are  not overloaded. Figure  13-32.—Multi-legged  bridle  slings. The single-leg sling may be used as a choker hitch (fig.  13-31,  view  A)  in  hoisting  by  passing  one  eye through the other eye and over the hoisting hook. The single-leg sling is also useful as a double-anchor hitch (fig. 13-31, view B). The double-anchor hitch works well  for  hoisting  drums  or  other  cylindrical  objects where a sling must tighten itself under strain and lift by friction against the sides of the object. Single-leg slings can be used to make various types of bridles. Three common uses of bridles are shown in figure  13-32.  Either  two  or  more  single  slings  may  be used for a given combination. The bridle hitch provides excellent load stability when the load ia distributed equally among each sling leg. The load hook is directly over the center of gravity of the load, and the load is raised level. The use of bridle slings  requires  that  the  sling  angles  be  carefully NOTE:  It is wrong to conclude that a three- or four-leg bridle will safely lift a load equal to the safe load on one leg multiplied by the number of legs. This is because there is no way of knowing that each leg is carrying its share of the load. With a four-legged bridle sling lifting a rigid load, it  is  possible  for  two  of  the  legs  to  support  practically the full load while the other two legs only balance it. COMSECOND/COMTHIRDNCB  strongly  recom- mend  that  the  rated  capacity  for  two-leg  bridle  slings listed  in  the  COMSECOND/COMTHIRDNCBINST 11200.11 be used also as the safe working load for three- or four-leg bridle hitches. When  lifting  heavy  loads,  you  should  ensure  that the bottom of the sling legs is fastened to the load to prevent damage to the load. Many pieces of equipment have  eyes  fastened  to  them  during  the  process  of manufacture to aid in lifting. With some loads, though, fastening a hook to the eye on one end of each sling leg suffices to secure the sling to the load. Use a protective pad when a fiber line or wire rope sling is exposed to sharp edges at the corners of a load. Pieces of wood or old rubber tires are fine for padding. Sling Angle When  you  are  using  slings,  remember  that  the greater the angle from vertical, the greater the stress on the sling legs. This point is shown in figure 13-33. The rated capacity of any sling depends on the size, the configuration, and the angles formed by the legs of the sling and the horizontal. A sling with two legs used to lift a 1,000-pound object will have 500 pounds of the load on each leg when the sling angle is 90 degrees. The load stress on each leg increases as the angle decreases; for example, if the sling angle is 30 degrees when lifting the same 1,000-pound object, the load is 1,000 pounds on each leg. Try to keep all sling angles greater than 45 degrees;  sling  angles  approaching  30  degrees  are considered  extremely  hazardous  and  must  be  avoided. Figure 13-33.-Stress on slings at various vertical angles. 13-17







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.