(1) the hook over hoisting limiter failure, breaking through, steel wire rope, the hook landing.
(2) the counterweight of the heavy hammer type hoist limiter or the wire rope button is inclined, so that the hoisting structure can not reach the weight when the crane is hoisted, and the power cable can not be cut off.
(3) the steel wire rope of crane is seriously worn, corroded or broken. When the load is too large, the wire rope is broken so that the hook falls to the ground.
(4) there is too little rope left in the drum or the press plate is not fastened properly. The steel rope is pulled out so that the hook falls down with the wire rope.