Screw hoist has the advantages of simple structure, convenient installation and low price. It is widely used in culvert gate of irrigation area at all levels and the gate of key water diversion project. However, some screw hoists currently used do not have effective protection measures against the top gate accident, that is, the limit switch is installed on the manual and electric dual-purpose hoist, which can only play a limiting role. Slight carelessness in the operation of the hoist will result in bending the screw, breaking the end cover of the hoist, breaking the upper edge of the reinforced concrete beam by breaking the machine beam, as well as the displacement, rotation and overturning of the hoist platform (beam), even causing casualties. The electric hoist will also lead to overload of the motor and burn the motor, which will seriously affect the safe use of the project and threaten the operation of the staff Personal safety.
1. Accident of screw hoist caused by human factors
The operator was careless and did not check according to the gate opening and closing procedures. The post operator or the original operator asked for leave due to business, and the substitute operator operated blindly when he was not familiar with the opening and closing procedures and methods.
2、 Accidents caused by non human factors
During the operation of the gate, floating objects such as trees or stones are carried to the bottom of the gate by high-speed water flow or blocked in the gate slot. If the gate is closed at this time, the lower edge of the gate will be blocked by obstacles before it touches the bottom of the gate. However, the limit mark or limit switch on the screw is not in place, which can not stop the machine or remind the operator to stop the machine. Therefore, the operator will not stop the machine. The hoist will drive the gate to continue to depress. When the reaction force exceeds the endurance of the hoist or the hoist platform, the top gate accident will also occur.