Wire-Rope Sling D/d Bend Efficiency
Bend efficiency factor and reduced working load limit of a wire-rope sling from the D/d ratio, per the WRTB curve. Inspect every sling before the lift.
Formula and source
ratio = bend_dia / sling_dia; efficiency interpolated from the WRTB 6x19 / 6x37 D/d curve (1->0.50 ... 25+ ->1.00); reduced_wll = rated_wll x efficiency.
Wire Rope Technical Board Wire Rope Users Manual (D/d bend efficiency) and ASME B30.9 by name; the curve ships as editable breakpoints.
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