Application and brief principle of solenoid valve in air separation field

Solenoid valves are widely used in our production. We must have encountered many problems related to solenoid valves during production maintenance, and have also dealt with various faults. We must also have accumulated a lot of problems related to solenoid valves. I have relatively less experience in handling solenoid valve failures during maintenance than other instrumentation and control failures. Now I am discussing this issue with you, hoping to learn more experience from everyone and improve together.
Let’s first have a preliminary understanding of the solenoid valve. The solenoid valve is composed of an electromagnetic coil and a magnetic core. It is a valve body containing one or several holes. When the coil is energized or de-energized, the operation of the magnetic core will cause the fluid to pass through the valve body or be cut off to achieve the purpose of changing the direction of the fluid. The electromagnetic components of the solenoid valve are composed of fixed iron core, moving iron core, coil and other components;the valve body part is composed of slide valve core, slide valve sleeve, spring base, etc. The solenoid coil is installed directly on the valve body, which is enclosed in a sealed tube, forming a simple and compact combination. The solenoid valves we commonly use in production include two-position three-way, two-position four-way, two-position five-way, etc. Let’s first talk about the meaning of the two bits: for the solenoid valve, it means electrification and de-energization, and for the controlled valve, it means on and off.
In our oxygen generator instrumentation and control system, the two-position three-way solenoid valve is most commonly used. It can be used to connect or cut off the gas source during production, thereby switching the gas path of the pneumatic control membrane head.
It consists of a valve body, a valve cover, an electromagnetic component, a spring and a sealing structure. The sealing block at the bottom of the moving iron core closes the air inlet of the valve body with the help of the pressure of the spring. After power is supplied, the electromagnet is attracted, and the sealing block with a spring on the upper part of the moving iron core closes the exhaust port, and the airflow enters the membrane head from the air inlet, which plays a controlling role. When power is lost, the electromagnetic force disappears, and the movable iron core leaves the fixed iron core under the action of spring force, moves downward, opens the exhaust port, blocks the air inlet, and the airflow of the membrane head is discharged through the exhaust port, and the diaphragm recovers. Original location. In our oxygen production equipment, it is used in emergency shut-off of the inlet diaphragm regulating valve of the turbine expander.
Four-way solenoid valves are also widely used in our production. Their working principle is as follows:
When current passes through the coil, excitation is generated, the fixed iron core attracts the moving iron core, and the moving iron core drives the slide valve. The valve core compresses the spring, changing the position of the spool and thereby changing the direction of the fluid. When the coil loses power, the elastic force of the spring pushes the slide valve core and pushes back the iron core, causing the fluid to flow in the original direction. In our oxygen production, the switching of the forced valve of the molecular sieve switching system is controlled by a two-position four-way solenoid valve, and the air flow is supplied to both ends of the piston of the forced valve. To control the opening and closing of the forced valve.
The failure of the solenoid valve will directly affect the action of the switching valve and the regulating valve. A common failure is that the solenoid valve does not operate. It should be checked from the following aspects:
(1) The solenoid valve terminal is loose or the thread is falling off. The valve must not be powered, but the thread can be tightened.
(2) If the solenoid valve coil is burned out, you can remove the wiring of the solenoid valve and measure it with a multimeter. If it is open circuit, the solenoid valve coil is burned out. The reason is that the coil is damp, causing poor insulation and magnetic leakage, causing excessive current in the coil and burning. Therefore, rainwater must be prevented from entering the solenoid valve. In addition, if the spring is too hard, the reaction force is too large, the number of coil turns is too few, and the suction force is not enough, the coil may be burned. During emergency treatment, the manual button on the coil can be moved from the "0" position during normal operation to the "1" position to open the valve.
(3) The solenoid valve is stuck. The matching gap between the slide sleeve and the valve core of the solenoid valve is very small (less than 0.008mm), and it is usually assembled in 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 insert a steel wire through the small hole in the head to make it bounce back. The fundamental solution is to disassemble the solenoid valve, take out the valve core and valve core sleeve, and clean it with CCI4 to make the valve core move flexibly in the valve sleeve. When disassembling, attention should be paid to the assembly sequence of each component and the position of external wiring so that reassembly and wiring are correct. Also check whether the oil spray hole of the lubricator is blocked and whether the lubricating oil is sufficient.
(4) Air leakage. Air leakage will 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 air leakage in several cavities.
When dealing with the solenoid valve failure of the switching system, you should choose the appropriate time to deal with it when the solenoid valve is out of power. If the solution cannot be completed within a switching gap, the switching system can be paused and dealt with calmly.