Application and principle of solenoid valve in air separation field
Production Line With Clapboard Clapboard,equipment,line ChangZhou FENGJU Machinery Equipment CO., LTD , https://www.fengjumachinery.com
Solenoid valves are widely used in our production processes, and during maintenance, we've encountered numerous issues related to them. We've dealt with various failures and have accumulated a significant amount of experience in troubleshooting solenoid valve problems. Compared to other instrument control faults, addressing solenoid valve issues is generally less complex. I would like to share my insights on this topic and look forward to learning from everyone else's experiences, so we can all improve together.
To begin, let me give you a basic understanding of what a solenoid valve is. A solenoid valve consists of a solenoid coil and a core, along with one or more holes in the valve body. When the coil is energized or de-energized, the magnetic core moves, allowing or blocking the flow of fluid through the valve body, thus changing the direction of the fluid flow. The electromagnetic components include a fixed iron core, a movable iron core, and a coil. The valve body typically includes a spool valve, a sliding sleeve, and a spring base. The solenoid coil is mounted directly on the valve body, and the entire assembly is enclosed in a sealed housing, making it compact and efficient.
In our production, we use various types of solenoid valves, such as 2/2, 2/4, and 2/5-way valves. Let me explain the meaning of the first two: a 2/2-way solenoid valve controls the opening and closing of the valve when powered or de-energized. In our oxygen meter instrument control system, the 2/3-way solenoid valve is the most commonly used. It is used to connect or cut off the gas source, enabling the switching of the pneumatic control diaphragm’s air path.
The structure of the 2/3-way solenoid valve includes a valve body, cover, electromagnetic component, spring, and sealing mechanism. At the bottom of the moving iron core, there is a sealing block that closes the air inlet under the pressure of a spring. When the valve is energized, the electromagnet pulls the moving core, lifting the sealing block and closing the exhaust port, allowing airflow to enter the diaphragm and perform control functions. When power is lost, the electromagnetic force disappears, and the spring pushes the moving core back, opening the exhaust port and blocking the intake, which allows the diaphragm to return to its original position.
In our oxygen plant, 2/3-way solenoid valves are used for emergency shutdowns of turbo-expander inlet regulating valves, among other applications.
A 2/4-way solenoid valve has many applications in our production. Its working principle is as follows: when current flows through the coil, it generates a magnetic field, pulling the fixed core and moving core, which drives the spool and compresses the spring, changing the spool's position and thus the direction of the fluid flow. When the coil is de-energized, the spring pushes the spool back to its original position, restoring the fluid flow to its initial direction.
In our oxygen production, the molecular sieve switching system uses a 2/4-way solenoid valve to control the forced valve switch. Air is supplied to both ends of the piston of the forced valve, allowing precise control over the opening and closing of the valve.
Solenoid valve failures can directly affect the operation of switching and regulating valves. Common issues include failure to actuate, which should be checked from the following aspects:
1. Loose connections or missing threads — ensure the solenoid valve is tightly secured.
2. Burned-out coil — use a multimeter to check for continuity. If open, the coil is damaged. This can happen due to moisture, poor insulation, or excessive current caused by insufficient coil turns or strong springs.
3. Stuck valve — the small gap between the valve sleeve and spool (less than 0.008mm) can cause jamming if impurities enter or if lubrication is insufficient. You can try using a thin wire to dislodge it, but the best solution is to disassemble the valve, clean the spool and sleeve, and ensure smooth movement.
4. Leaks — damaged seals or worn sliding valves can cause leakage, leading to low air pressure and difficulty in operating the forced valve. Regular inspection and maintenance are essential.
When dealing with solenoid valve failures in the switching system, it's important to choose the right time. During power loss, if it's not within a switching window, the system can be temporarily suspended to handle the issue safely. Always remain calm and follow proper procedures to avoid further complications.