Most overhead cranes are required to have limit switches governing their hoisting operation. This means a switch(es) capable of stopping the up or down motion when the hook has traveled past the design limits. If the hook travels past those design limits, very expensive damage may occur, or injury and death of the operator.
This is a topic directly addressed in OSHA regs for overhead cranes and hoists: “The trip setting of hoist limit switches shall be determined by tests with an empty hook traveling in increasing speeds up to the maximum speed. The actuating mechanism of the limit switch shall be located so that it will trip the switch, under all conditions, in sufficient time to prevent contact of the hook or hook block with any part of the trolley.”OSHA 29 CFR 1910.179(k)(1)(ii).
Manufacturers are required to provide cranes with a limit switch and owners are required to properly inspect and maintain those switches. Traditionally a limit switch was operated by a lever or weight that hangs by gravity below the hoist and is actuated by physical contact with the hook block as it rises past the designed height. When the limit switch is contacted, it releases an electric switch which should stop up motion.
Today many wire rope hoists have a geared limit switch that can be pre-set my the manufacturer or owner to stop over-lifting or lowering. This may or man not take the place of a weighted limit switch. It is important to understand your specific application and local regulations before accepting one type of limit switch over the other.