The working principle and common faults of solenoid valves

Electromagnetic valve is an industrial equipment controlled by electromagnetism, which is an automation basic component used to control fluids and belongs to the actuator; Not limited to hydraulic, pneumatic. It is widely used in our daily lives. Firstly, we have a preliminary understanding of electromagnetic valves. Electromagnetic valves are composed of electromagnetic coils and magnetic cores, and are valve bodies that contain one or several holes. When the coil is energized or powered off, the operation of the magnetic core will cause the fluid to pass through the valve body or be cut off, in order to change the direction of the fluid.

Working principle of solenoid valve: There is a sealed chamber in the solenoid valve, with through holes at different positions. Each hole leads to a different oil pipe. In the middle of the chamber is the valve, and there are two electromagnets on both sides. The magnetic coil on which side is energized will be attracted to which side of the valve body. By controlling the movement of the valve body, different oil discharge holes can be blocked or leaked. The oil inlet hole is usually open, and hydraulic oil will enter different oil discharge pipes, Then, the pressure of the oil pushes the piston of the oil cylinder, which in turn drives the piston rod, which drives the mechanical device to move. In this way, mechanical motion is controlled by controlling the current of the electromagnet.

Electromagnetic valves are divided into three categories based on their principles: direct acting, distributed direct acting, and pilot operated; According to structure, it is divided into two types: diaphragm type solenoid valves and piston type solenoid valves.

The failure of the solenoid valve will directly affect the operation of the switching valve and regulating valve. Common faults include the solenoid valve not acting, and should be investigated from the following four aspects:

(1) Air leakage: Air leakage can cause insufficient air pressure, making it difficult to open and close the forced valve. The reason is that the sealing gasket is damaged or the slide valve is worn, causing several cavities to blow air. When dealing with electromagnetic valve faults in the switching system, appropriate timing should be chosen to handle them when the electromagnetic valve is in a state of power loss. If the process cannot be completed within a switching gap, the switching system can be suspended and handled calmly.

(2) Electromagnetic valve stuck: The fit gap between the spool sleeve and the valve core of the electromagnetic valve is very small (less than 0.008mm), usually assembled as a single piece. When mechanical impurities are brought in or there is too little lubricating oil, it is easy to get stuck. The treatment method can be to poke a steel wire through a small hole in the head to make it rebound. The fundamental solution is to remove the solenoid valve, take out the valve core and valve core sleeve, clean them with CCI4, and make the valve core move flexibly inside the valve sleeve. When disassembling, attention should be paid to the assembly sequence of each component and the position of external wiring, in order to reassemble and wire correctly. It is also necessary to check whether the oil mist injector injection hole is blocked and whether the lubricating oil is sufficient.

(3) If the solenoid valve wiring head is loose or the wire head falls off, the solenoid valve should not be electrified and the wire head can be tightened.

(4) If the solenoid valve coil is burnt out, the wiring of the solenoid valve can be removed and measured with a multimeter. If there is an open circuit, the solenoid valve coil will be burnt out. The reason is that the coil is damp, causing poor insulation and magnetic leakage, resulting in excessive current inside the coil and burning. Therefore, it is necessary to prevent rainwater from entering the solenoid valve. In addition, if the spring is too hard, the reaction force is too large, the coil turns are too few, and the suction force is not enough, it can also cause the coil to burn out. During emergency handling, the manual button on the coil can be turned from the "0" position during normal operation to the "1" position to open the valve.