Which type of personnel hoist must have an anti-piling switch installed?

The correct choice is the traction drum hoist, which requires an anti-piling switch for safety reasons. The anti-piling switch is a critical safety device designed to prevent the piling of personnel or materials within the hoist, which can occur if the hoisting mechanism engages improperly or if there is an overload condition.

Traction drum hoists operate by wrapping a wire rope around a drum, and if the load is not managed properly, it can lead to an accumulation of materials or individuals at the top or bottom of the hoist, creating a hazardous situation. The anti-piling switch acts as a preventive measure, ensuring the hoist adheres to strict safety protocols and operates within safe limits, minimizing the risk of accidents.

In contrast, other hoist types may not have similar operational dynamics or loading conditions that necessitate such a safety feature. Counterweight hoists, traction hoists, and other configurations are designed differently and may incorporate various safety mechanisms, but they do not specifically require an anti-piling switch like the traction drum hoist does.