Safe electrical design of mine elevator control systems

A mine elevator recently experienced an ascending car overspeed accident resulting in serious injuries to four passengers. Although the four miners laid down on the floor prior to impact, the miners struck the ceiling of the elevator car as it collided into the overhead structure at an estimated speed four times faster than normal. Several electrical design precautions can be implemented to prevent elevator control system failures. This paper examines safe electrical design of elevator control systems. Supplemental circuits and devices which improve the safety integrity and maintenance of the elevator control system are presented. These circuits and devices provide protection that eliminates the potential hazard and significantly reduces the possibility of a mine elevator accident.