Wire Rope when bent over Sheaves or Shackles
When a wire rope is bent around any sheave, shackle or other object there is a loss of strength due to this bending action. As the D/d ratio becomes smaller this loss of strength becomes greater and the wire rope becomes less efficient.
Small diameter shackles reduce the wire rope sling strength. Regardless of whether it is a shackle, hook or other lifting lug, all hook up points must at least ensure a D/d ratio of 5:1 to ensure optimum service life of the wire rope sling.
To combat this, when planning lifts you should:
- Use large enough hooks and large diameter shackles to avoid crushing and kinking of the wire rope sling
- If possible use wide body shackles. They increase the D/d ratio
Wire Rope Slings with deformation or kinking at point of pickup is a sign that D/d ratios being used may not be correct.
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