An oil rig module weighing 20,000 kg needs to be lifted. Due to site constraints, the crane's boom must be positioned such that the load line is not perfectly vertical, introducing an angle of 10 degrees from vertical. How does this 'side pulling' affect the crane's rated capacity and boom stresses?

Question: An oil rig module weighing 20,000 kg needs to be lifted. Due to site constraints, the crane's boom must be positioned such that the load line is not perfectly vertical, introducing an angle of 10 degrees from vertical. How does this 'side pulling' affect the crane's rated capacity and boom stresses?

Answer options:

• It increases the effective rated capacity slightly due to the angle.
• It has no significant effect on rated capacity or boom stresses. ✅ It reduces the crane's effective rated capacity and significantly increases boom side stresses.
• It only affects the load's swing radius, not the crane's stability.

Correct answer: It reduces the crane's effective rated capacity and significantly increases boom side stresses.

Explanation: Any deviation from a vertical hoist line introduces side loading on the boom. This reduces the crane's effective rated capacity and places adverse, unintended bending and torsional stresses on the boom structure, which it is not designed to withstand.