The correct capacity of the screw pin anchor shackle when side-loaded at a 43-degree angle can be calculated by understanding how the Working Load Limit (WLL) of rigging equipment is affected by angles. The WLL of the shackle in normal, direct pull conditions is 6 tons. However, when side-loaded, the effective load capacity is reduced due to the angle at which the load is applied.
For a side load, you can determine the new capacity using trigonometric principles. The formula typically used is:
New Capacity = WLL × Cosine(θ)
Where θ is the angle of the side load. In this case, the angle is 43 degrees.
Calculating the cosine of 43 degrees gives approximately 0.731. Thus,
New Capacity = 6 t × 0.731 = 4.386 t
When comparing this value to the provided choices, it rounds to approximately 4.2 tons. This reflects the maximum effective capacity of the shackle when subjected to the side load at that angle, which is consistent with good rigging practices to ensure safety and equipment integrity.
Understanding how angles affect loads in rigging is crucial, as it helps riggers to make informed decisions about equipment safety