Figure 13-36.-Determination of bridle hitch sling capacity.Spreaders Barsspreaders end connection should be the same as thethickness of the shackle pin.In hoisting with slings, spreader bars are used toprevent crushing and damaging the load. Spreader barsare short bars, or pipes, with eyes fastened to each end.By setting spreader bars in the sling legs above the topof the load (fig. 13-34), you change the angle of the slingleg and avoid crushing the load particularly in the upperportion.Spreader bars are also used in lifting long oroversized objects to control the sling angle, as shown infigure 13-35. When spreader bars are used, make sureyou do not overload the end connection. A spreader barhas a rated capacity that is the same as hooks andshackles. A good rule of thumb is the thickness of theSling Safe Working LoadsFormulas for estimating the loads for most slingconfigurations have been developed. These formulasare based on the safe working load of the single-verticalhitch of a particular sling. The efficiencies of the endfittings used also have to be considered whendetermining 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. 13-36) is SWL (of single-vertical hitch) times H(Height) divided by L (Length) times 2 = SWL. When13-19
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