Electric Wire Rope Hoists are many small and medium enterprises , workshop production lines use more lifting machinery , often resulting in loss of control due to the lifting rope is Jiaoduan , was hanging items 7.5 ton Electric Chain Hoist off situation. The main cause of runaway elevator wire rope hoist has the following three points: ( 1 ) AC contactor main contacts sintering link. Due to the quality of the contactor or contactors improper selection , the main contact is often sintering adhesions, which can not be disconnected when disconnected , causing the hoist can not be stopped rising . Therefore, the quality of the exchanges must be reliable appliances , choose the regular manufacturers of qualified products, due to the frequent Electric Hoist operation, the contactor must 5 ton electric chain hoist choose the appropriate model . ( 2 ) failure of the control button . Mainly for insulation breakdown short circuit button , the button as long as insulation breakdown due to frequent short-circuit operation , make it effective insulation damaged. Poor working conditions caused by leakage current, maintenance is not timely, but also a common electric wire rope hoist cause of substandard quality control button failure. Therefore, to ensure safe operation, in addition to select products of acceptable quality , but also to strengthen the routine maintenance and timely solutions to accidents. ( 3 ) limit switch control failure . Travel hoist control switch is rising to the limit position of power failure timely security measures , due to the long , frequent use , stroke control switch prone to loosening displacement phenomenon , even worse when you replace the rope to remove it , thus losing emergency protection devices, resulting in a total hit problems. So should strengthen the operation , maintenance personnel safety education !