HBZhan Content Introduction:Screw type opening and closing machineDue to its advantages of simple structure, easy installation, and low price, it is widely used in the opening and closing of culverts and gates in various levels of irrigation channels and water diversion hub projects.
　　
However, some screw hoists currently in use do not have effective measures to protect against top gate accidents. Even if limit switches are installed on hand electric dual-purpose hoists, they can only play a limiting role. A slight mistake during the operation of the hoist may cause the screw to bend, the end cover of the hoist to break, and the upper edge of the reinforced concrete beam to crack and damage. In severe cases, the hoist (beam) may shift, rotate, tilt, and even cause casualties. Electric hoists can also cause motor overload and burn out the motor, seriously affecting the safe use of the project and threatening the personal safety of operators.
　　
1. The cause of the top gate accident
　　
1.1 Top gate accidents caused by human factors
　　
The operators were careless in their work, failing to follow the gate opening and closing procedures for inspection before operation, or the original operators took leave due to personal reasons. The substitute personnel blindly operated without being familiar with the opening and closing procedures and methods. If the opening and closing direction is reversed, the gate will open when it is in the closed state. If the wrong button is pressed during electric opening or manual opening and closing, the direction of closing will be mistakenly operated as opening the gate; Some of them are due to the operator's lack of concentration when closing the gate, and the gate cannot be stopped immediately when it reaches the lower limit position. Some are due to the displacement of the limit nut and limit mark of the screw, which does not have a limiting effect.
　　
The electric hoist may also encounter changes in the phase sequence of the power supply when the power supply department is repairing electrical equipment or power supply lines, causing the motor on the hoist to change its original direction of operation, resulting in a change in the direction of the hoist's opening and closing. At this time, if the gate is opened when it is in the closed state, a top gate accident will inevitably occur. Such top gate accidents have occurred in the Wei Jia Bao channel flushing gate of Baoji Gorge.
　　
1.2 Top gate accidents caused by non-human factors
　　
During the operation of the gate, floating objects such as trees or obstacles such as rocks are carried to the bottom of the gate or washed into the gate groove by high-speed water flow. If the gate is closed at this time, when the lower edge of the gate has been blocked by the obstacle before contacting the bottom of the gate, a reaction force will be generated. However, the limit sign or limit switch on the screw is not in place, and it will not stop the gate or remind the operator to stop. Therefore, the operator will not stop the gate, and the hoist will continue to press the gate downwards. When the reaction force exceeds the bearing capacity of the hoist or the hoist platform, a top gate accident will also occur.
　　
2. Preventive measures for top gate accidents
　　
In addition to strengthening the education and skill training of operators' sense of responsibility and requiring them to operate according to the opening and closing procedures, the key is to improve technical measures to prevent the occurrence of top gate accidents.
　　
To solve this problem, the following conditions must be met technically: firstly, it must be able to issue a misoperation alarm to the opening and closing personnel, reminding them to stop the misoperation, and the electric opening and closing should be able to automatically stop the machine, terminating the occurrence of misoperation accidents; The second requirement is for the gate to encounter obstacles during the descent process
　　
When the gate descends, it can automatically sound an alarm to remind the operator to stop the machine. Electric opening and closing should be able to automatically stop the machine; Thirdly, regardless of the type of operational accident, automatic shutdown can only be resumed after the operator has eliminated the shutdown fault, which can avoid accidents caused by repeated operations before the fault is eliminated.