237. A friction hoist shall have a device causing application of the braking devices and stopping the hoist when:(1) slipping produces a difference in speed of 2 m (6.6 ft) per second or more between the pulley and a rope;
(2) the loop of a tail rope rises 1 m (3.3 ft) or more;
(3) a hoist or a counterweight traverses 25% of the upper retarding zone at its full rated speed.