Rigging Masterclass

A: Governing principle: sling tension varies inversely with the sine of the sling angle. At 45°, tension jumps ~22% compared to 60°, pushing slings and shackles closer to WLL even though gross weight is unchanged. Distractor B catches engineers who remember load stays constant but forget geometry drives internal forces.

A: Governing principle: WLL already embeds a design factor addressing unknowns during service. ASME B30 keeps operational loading below tested strength to account for fatigue, D/d losses, and shock that proof tests don’t simulate. Distractor B traps those who confuse proof load with allowable service load.

A: Governing principle: tag lines control orientation, not load path. Failure allows uncontrolled rotation, increasing side loading and shock on rigging, but vertical load remains carried by hoist lines. Distractor D appeals to those who treat tag lines as load-sharing elements.

A: Governing principle: unit clarity matters in legacy drawings. Metric tonne-force vs mass ton can hide small but real discrepancies that matter when margins are thin. Distractor B traps those who assume terminology is interchangeable across eras.