What is the minimum D/d ratio allowed for a wire rope sling?

The minimum D/d ratio for a wire rope sling, defined as the ratio of the diameter of the sheave (D) to the diameter of the rope (d), indicates how tightly the wire rope can bend without risking damage or reducing its load-carrying capacity. A D/d ratio of 1:1 means that the diameter of the sheave is equal to the diameter of the wire rope, which is acceptable for minimizing bending stress on the rope during lifting operations.

Having a minimum ratio of 1:1 allows the wire rope to function adequately in various lifting applications, as it ensures that the rope can negotiate sheaves without excessive bending that could induce wear, kinking, or potential failure. When the D/d ratio is maintained at or above this minimum, it promotes safety and longevity of the wire rope sling, which is crucial in lifting operations.

Higher ratios, such as 2:1 or even 4:1, would provide further assurance against bending stress and are typically advisable for more stringent applications, but they are not the minimum required for safe operation. Therefore, the minimum D/d ratio allowed is appropriately set at 1:1.