Hoist lifting height H refers to the top of the crane running track, or the vertical distance from the ground to the limit position on the pickup device. Some hoist lifting device allows the device to be placed below the top of the ground or the track, and its downward distance is called the depth of descent. At this time, lifting range of the electric hoist is the sum of the lifting height and the descending depth, that is, the vertical distance between the highest and lowest working position of the spreader. Hoisting in the lifting of the actual operation, the lifting height shall not exceed the allowable value. Failure to do so due to an overrun can overload the wire rope slinging mechanism wound on the winding drum of the hoisting mechanism and cause a heavy object crash.