What is the problem when a pneumatic valve stops in one position for a while?
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There is a pneumatic plunger valve in the factory. There is no problem with the on feedback, off feedback, or mid-stop feedback. The valve is manually turned on and off. There is no problem with the valve switch. However, the valve stops alone and stops in one position for a while. I asked the master in the bar what is going on. The picture is the pneumatic control box of the valve.
Do you have any pictures of pneumatic plunger valves? What are your three feedbacks?
I don’t quite understand what you mean. Why don’t you take a picture of the valve? What do you mean by trembling? Hand wheel operation? Let me not talk about your manual operation first. I haven’t seen the structure, so it’s hard to say. When it comes to pneumatic operation, the equipment circled in red in the picture should play the role of intermediate stop.
There are three feedbacks: on, off, and stop.
When the automatic mode is turned on, the program switches the valve on and off by itself. The dcs program is Yokogawa Cs3000. When the manual mode is turned on, the valve can be opened, closed, or stopped by itself.
I want to know what this mid-stop means. Is it moving or opening to 50 degrees? If it is to 50 degrees, why not turn on the positioner?
Oh, no pictures of the pneumatic plunger valve?
It's probably a fault with the guard valve. Try replacing it with a new one.
Check the interlock valve or the relevant options in the program or operation screen.
Judgment ideas: Your pneumatic plunger valve should be a double-acting rack and pinion pneumatic actuator. The valve position feedback has nothing to do with it. It should be a limit switch or proximity switch. This does not affect the action of your valve. Now you say it stops, but it cannot stop. The valve moves for a while, and then moves for a while. Move it, the reason may be the shuttle valve, which is the valve I drew before. When the valve stops in the middle, it should be in the closed position, blocking all the two air inlet holes on the upper side, and all the two air outlet holes on the lower side. At this time, the cylinder piston is still moving. , the explanation is not strict, but if the position of the shuttle valve is wrong, the air intake and exhaust are connected or blocked at the same time. For example, when you open the valve, the air intake on the right side is open, and the exhaust on the left side is also open. When the valve is closed, the left side becomes air intake and the right side becomes exhaust. This is not the case. It is difficult to accurately judge on site, but the principle is this. For example, when the valve is opened, the left coil of the dual-electric solenoid valve is energized, and the single solenoid valve on the left is also energized. The same is true when the valve is closed. The coil on the right side of the dual-electric solenoid valve is energized, and the single solenoid valve is also energized. Only during a stop, the single solenoid valve loses power. Of course it could also have the opposite effect. This is an air leakage problem. One is a cylinder leakage, and the other is a shuttle valve leakage. But for this kind of air leakage problem, if you remove the load, it may not leak, but if you connect the load, you can't see where the problem is. Is the problem solved? Looking forward to your reply.