In every shaft exceeding 100 meters in depth, adequate provision shall be made whereby the hoistman is warned of the arrival of the cage, skip or other means of conveyance at a point in the shaft, the distance of which from the top landing place is less than the equivalent of ______ revolutions of the drum or sheave of the winding engine

• A. Three revolutions
• B. Two revolutions
• C. Four revolutions
• D. Five revolutions

Answer: (A)

When a shaft is very deep, safe operation needs the hoistman to be alerted well before the cage or skip reaches the top landing. The distance is measured in revolutions of the winding drum because each drum turn corresponds to a fixed amount of rope unreeling and vertical movement of the conveyance. Giving the hoistman warning within three revolutions provides enough time to observe the approaching load, communicate if needed, and bring the cage to a controlled stop or slow descent before it reaches the top landing. Two revolutions would leave less time to react, while four or five revolutions would be more conservative than required by the rule. So, the required warning distance is within three revolutions of the drum.