Time relay controls the pneumatic control valve
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There are some ideas regarding gas regulation, using a time relay to control the opening degree of the pneumatic control valve. Imagine: 1. When a signal is sent to the time relay, the relay begins to send instructions to the pneumatic control valve, causing it to open. Open to 10% of full openness, maintain for 10 seconds ； 2. After 10 seconds, the time relay sends another command to the pneumatic control valve, causing it to change its opening degree to 15% of full open, and this state is maintained for 10 seconds ； 3. After 20 seconds, the time relay sends another command to the pneumatic control valve, setting it to 20% of full open position, and this state is maintained for 10 seconds ； 4. After 30 seconds, the time relay sends a command to the pneumatic control valve to close it ； 5. Wait for the next signal to be received to activate the relay. Everyone, please help me figure out whether it’s possible to achieve this operating condition. If there are any issues, please point them out. Thank you very much!
It can’t be done, right? Pneumatic control valves are powered by compressed air – how can a relay control the amount of air?
If you have 4–20 milliampere signals at 10%, 15%, and 20% output, then a time relay can be used to achieve this
I’m simply adjusting the opening degree of the valve; by varying this opening degree, I can regulate the gas pressure. In our operating conditions, the starting pressure isn’t stable, and I want to use the valve to stabilize the pressure somewhat
Could you tell me more in detail? I’m not quite understanding it even though that’s what was said
A relay and three time relays are required to generate the 4-20 milliampere signals corresponding to the three desired valve opening levels. The process works as follows: if an external measuring instrument detects excessive pressure, it outputs a digital signal that causes the relay to engage (the self-sustaining circuit must be controlled by the third time relay). The first time relay then triggers a 10% signal, the second time relay generates a 15% signal, and the third one produces a 20% signal. When the timing specified for each of these three time relays is reached, the self-sustaining circuit of the relay is disconnected (at this point, the signal from the external pressure switch is also disconnected), and the relay releases its hold. Thus, one cycle is completed. The program works fine with no conflicts, but are those three sets of 4-20 milliampere signals easy to obtain?
I have an XMT628 smart PID controller; it uses a pressure transmitter to provide signals, and it adjusts the valve opening based on time – can the controller handle this?
This post was last edited by LongTengJueYin on 2015-7-1 at 17:41. Given my limited capabilities, I think it’s not possible to implement these devices (if connected to a computer, just a pressure transmitter and a valve would be sufficient)
This post was last edited by john1628 on 2015-7-2 08:28. Do you mean to use a PLC to control this process?
Does the pressure transmitter send a signal to the XMT628 intelligent PID controller? Does the controller use a relay to activate the control valve? When the relay is activated at a certain moment, the output of the controller is determined by the pressure setpoint and the measurement deviation. So how can we ensure that the opening degree of the control valve is 10%, 15%, or 20%? If it’s programmed, then it’s open-loop control. What is used to achieve this? A PLC? Where do the signals for 10%, 15%, and 20% come from?
The PLC can send out signals, right? Actually, I’m not too familiar with this either, as we need it for our operational requirements. I just want to ask if this program can be implemented. If it can, what improvements are still needed: lol