Valve jumping problem in pneumatic control valves
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On the return pipeline of the chlorine compressor, when manual adjustment of the control valve is performed and a value is set for the valve opening, the valve’s feedback keeps changing, resulting in fluctuations in the compressor’s inlet pressure. When a value of 0.6% is manually entered, the feedback shows 0.1%, and it remains unchanged thereafter.
A large pressure difference across the control valve can lead to cavitation at low opening degrees, causing the valve to vibrate and resulting in pressure fluctuations. This phenomenon disappears once the opening degree increases to a certain level; as described by the original poster, this is mainly due to an inappropriate selection of the control valve.
Is there any good alternative if this valve isn’t replaced? Ensure stable production. How to select a valve if it needs to be replaced.
Have the technician check the valve positioner, relays, and clean air filter to see if there are any problems!
When the usage amount is very low, the shut-off valve in front of the control valve can be closed to reduce the pressure at the front end of the control valve. To replace the valve, it is best to inform the manufacturer of the operating conditions and usage details; the manufacturer will then propose a suitable solution.
If the opening degree is low, as mentioned above, it is due to an excessive pressure difference between the front and back. This issue can be addressed by increasing the stiffness of the actuator; however, this will affect its service life at low opening degrees, so it’s important to take this into account when selecting a model next time
The impact is significant when the opening degree is low; there are also fluctuations when the opening degree is increased, but the situation is relatively better in that case. Moreover, when the opening is small, the fluctuations are regular, occurring roughly every 6 or 7 minutes.
The fluctuations are relatively less severe when the opening is large. Is there any good way to address this?
This might be due to the thrust of the actuator being set too low; it’s also best to first rule out issues such as problems with the air supply pressure or the positioner
The air source pressure regulator and other components have been checked, but the pressure still fluctuates.