Role of the Limit Switch in Promoting Overhead Crane Safety

Limit switches have practically limitless applications in regulating crane operation to prevent potential incidents. For instance, when ropes come out of groove or in preventing two trolleys from impacting on the same bridge structure.

In addition, a limit switch keeps a crane from lifting loads above rated capacity. Another kind of limit switch prevents a hoist from reaching the upper block and rope drum. Yet another type protects motors from overheating.

Without overhead crane limit switches, the potential for harm is quite high. For this reason, each limit switch should be inspected and maintained regularly.

Check limit switches daily.

• As they open or close electrical circuits, limit switches wear out over time. To monitor wear and replace switches before they fail, limit switches should be checked daily before a crane is used.

Know how a limit switch works.

• Knowing how a limit switch works is important for understanding how the crane works and how these established set points keep the crane operating safely and efficiently.

In some cases, there may be multiple limit switches associated with a crane operation such as crane travel or hoist motion. The first switch will signal that the end of the safe travel limit is approaching and slows the crane motion. A subsequent switch will indicate that the end of the safe travel distance has been reached and stops the motion.

• Hoisting motions may be served by several limit switches, which provide set points for safety and reliability. An initial limit switch will slow the hoist before it reaches the stop limitation. Slowing the hoist prior to reaching the limit decreases mechanical wear, as the hoist is traveling below maximum speed when the brakes set.

Limit switches can also be used for travel motions, providing consistent and predictable motion limitations without impact at end stops.