233. An electric hoist shall be installed such that the power supply to the engine of the hoist is cut off, and the braking force necessary to immobilize the hoist is automatically applied:(1) when the emergency switch is in the open position;
(2) when the conveyance or the counterweight travels beyond an overwind or upper and lower limit travel switch before the conveyance, the counterweight or the cable attachments can reach the headsheave or any other obstacle in the shaft or the headframe; however, during shaft sinking, the lower limit of travel shall be regulated to enable the hoist to reach the bottom of the shaft, but the length of rope that can be unwound after the hoist has reached the bottom of the shaft shall be less than twice the circumference of the hoist drum;
(3) when there is an interruption in electrical power supply to the hoist;
(4) when the automatic overspeed protective device is activated;
(5) when there is a preset drop in voltage;
(6) when there is a power overload exceeding by a preset percentage the power required for normal hoisting operations;
(7) when there is a short circuit in the electrical system of the hoist;
(8) before any part of the control mechanism of a brake reaches its limit of travel while the brake is being applied.