Solenoid valve application and a brief theory in the air separation field
Solenoid valve are widely used in our production, in our production maintenence we meet many problems on electromagnetic valve, and also dealt with a variety of failures, we must also have accumulated a lot of the solenoid valve failure treatment experience, while I am relatively less to deal with solenoid valve maintenance failure as compared to other instrumentation failuresl, and now I discuss this issue with you together and we are eager to learn more from the experience, and improve together.
We have a preliminary understanding to solenoid valves firstly, the solenoid valve is formed by the electromagnetic coil and core, is a body contains one or more holes. When the coil power on or power off, the core operation will lead to flow through the valve body or cut off, in order to achieve the purpose of changing the direction of fluid. The solenoid valve electromagnetic components consist of the stationary iron core, moving core, coil and other components; body is composed by the sliding spool valve, slide valve sleeve, spring base and so on. Electromagnetic coil is directly installed on the body, the body is sealed in a sealed tube to form a concise, compact combination. the solenoid valves in the production we commonly use are two-position three-way, two-position four-way, two-position five-way and so on. Here to talk about the two-position meanings: for the solenoid valve it means with power and power loss, to the valve controlled, it indicates opene and close.
In our oxygen instrument control system, two-position three-way solenoid valves are most widely used, which can be used to connect or cut off the gas source in production, thus switch the pneumatic control membrane gas circuit.
It consists of body, valve cover, electro-magnetic components, springs and sealing structure and other components, sealing part in the bottom of dynamic iron core using spring pressure to close the body air intake. Power on, the solenoid pull-in, the upper moving iron core sealing part closes the vent, air from the air intake enters into the diaphragm head, played the role of control. When losing electricity, the electromagnetic force disappeared, moving iron core leaves from the fixed iron core under the action of the spring force, downward movement to open the exhaust port, blocked air intake, the diaphragm head air discharged through the exhaust port, to restore the original position. In our oxygen equipment, it is used in the turbo-expander inlet diaphragm emergency cut off.
Four-way solenoid valve in our production applications are a lot, and its working principles are as follows:
When there is current through the coil, it produces excitation effect, fixed-iron core pull-moving core, moving iron core drives sliding spool and compress spring, changing the sliding spool position, thus changing the flow direction. When the coil loses power, depending on * elastic spring to promote sliding spool, back moving core, so that fluid flows the original direction. In our oxygen production, molecular sieve switching system forced valve switches are controlled through two-position four-way solenoid valve, the airflow is respectively supplied to the two piston ends of the forced valve. In order to control the force valve open and close. Solenoid valve failure will directly affect the switching valve and control valve movements, common faults are solenoid valves without action, we should start to troubleshoot the following areas:
（1） Solenoid valve wiring loose or end off, solenoid valve fasten end without gaining electricity.
（2） Solenoid valve coil is burn out, removing the solenoid valve wiring, using multimeter to measure, if open, then the solenoid valve coil is burn out. The reasons are coils have been damp, magnetic flux leakage caused by bad insulation, resulting in the winding currents are too large to burn, so need to prevent flood water entering solenoid valve. In addition, the spring is too hard, reaction is too large, the coil turns too few, not enough suction makes the coil can also be burned. Emergency management, can turn the normal working "0" bit to "1" bit of manual button on the coil, making valve opened.
（3）Solenoid valve locks. Solenoid valve slide sleeve and spool gap is too small (less than 0.008mm), are generally one-piece assembly, when there are mechanical impurities or too little lubricant, it is easy to get stuck. Dealing method is using holes hold into the wire from the head to make it bounce. The fundamental solution is to remove the solenoid valve, remove the spool and spool cover, cleaned with CCI4, making the valve spool comprising a flexible movement. Demolition should pay attention to the various components of the assembly sequence and location of the external wiring for re-assembly and wiring is correct, and also check the lubricator oil spray holes whether are blocked, and whether lubricating oil is adequate.
（4）Leakage. Lack of air pressure can cause leakage, making forced valve difficult to open and close, the reason is sealing gasket is damaged or sliding valve is weared to cause a few cavities channeling gas.
in dealing with switched systems electromagnetic valve failures, should choose an appropriate time, and dealing when the solenoid valve is in a loss of power, if can not finished within a switch gap, you can stop the switch system and handle calm.
