Quantcast Sling Safe Working Loads

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terminals must be proof-tested before placing the sling in  initial  service. The     COMSECOND/COMTHIRDNCBINST 11200.11   has   rated   capacity   charts   enclosed   for numerous wire rope classifications. You must know the  diameter,  rope  construction,  type  core,  grade,  and splice on the wire rope sling before referring to the charts.  The  charts  provide  you  the  vertical-rated capacity for the sling. The test weight for single-leg bridle slings and endless slings is the vertical-rated capacity (V. R. C.) multiplied by two or (V.R.C. x 2 = sling  test  weight). The test load for multi-legged bridle slings must be applied to the individual legs and must be two times the vertical-rated capacity of a single-leg sling of the same size, grade, and wire rope construction. When slings and rigging are broken out of the TOA for field use,  they  must  be  proof-tested  and  tagged&fore  being returned  to  CTR  for  storage. Check fiber line slings for signs of deterioration caused by exposure to the weather. Ensure none of the  fibers  have  been  broken  or  cut  by  sharp-edged objects. SLING SAFE WORKING LOADS There  are  formulas  for  estimating  the  loads  in most sling configurations. These formulas are based on  the  safe  working  load  of  the  single-vertical  hitch  of a particular sling. The efficiencies of the end fittings used also have to be considered when determining the capacity of the combination. The  formula  used  to  compute  the  safe  working load (SWL) for a BRIDLE HITCH  with two, three, or  four  legs  (fig.  6-17)  is  SWL  (of  single-vertical hitch)  times  H  (Height)  divided  by  L  (Length) times 2 = SWL. When the sling legs are not of equal length,  use  the  smallest  H/L  measurement.  This formula is for a two-leg bridle hitch, but it is strongly recommended  it  also  be  used  for  the  three-  and four-leg hitches. NOTE: Do NOT forget it is wrong to assume that a three- or four-leg hitch can safely lift a load equal to the safe load on one leg multiplied by the number of legs. Other formulas are as follows: Single-basket hitch (fig. 6-18): For vertical legs: SWL = SWL (of single-vertical hitch) x 2. For inclined legs: SWL = SWL (of single-vertical hitch) x H divided by L x 4. Double-basket hitch (fig. 6-19): For vertical legs: SWL = SWL (of single-vertical hitch) x 4. For  inclined  legs: SWL = SWL (of single-vertical hitch) x H divided by L x 4. Single-choker hitch (fig. 6-20): For sling angles of 45 degrees or more: SWL  =  SWL  (of  single-vertical  hitch)  x  3/4  (or .75). Sling  angles  of  less  than  45  degrees  are  not recommended;  however,  if  they  are  used,  the  formula is as follows: SWL = SWL (of single-vertical hitch) x A/B. Double-choker hitch (fig. 6-21): For sling angle of 45 degrees or more: SWL = SWL (of single-vertical hitch) x 3 divided by 4 x H divided by L x 2. Sling angles of less than 45 degrees: SWL = SWL (of single-vertical hitch) x A divided by B x H divided by L x 2. 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 comers of a load. Pieces of wood or old rubber tires are fine for padding. SLING  ANGLE When using slings, remember that the greater the angle from vertical, the greater the stress on the sling legs. This factor is shown in figure 6-22. 6-9

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