Limit switch for pneumatic ball valve
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Hello, teacher. May I ask how the limit switch of the pneumatic ball valve is connected to the DCS, and how the solenoid valve on the pneumatic ball valve functions?
Hello, the limit switch of a pneumatic ball valve is commonly referred to as the \"feedback sensor,\" and it is connected to the DCS via a DI channel. The operating mode of the solenoid valve on the cylinder is determined by whether 24V power is supplied or not. Typically, the power goes from the circuit board to the relay, and from there to the solenoid valve. There are various operating modes; the three-position two-way type is relatively easy to understand: one port is used for air intake, and out of the two other ports, one is used for air output
Thank you for your guidance. I also have a question: the wire connected to the limiter serves only to provide a feedback signal. Is it the solenoid valve that controls the operation of the pneumatic ball valve?
Yes, the solenoid valve controls the movement of the piston inside the cylinder, thereby causing the valve core to rotate; the feedback mechanism merely provides feedback signals and does not participate in the control process. However, a logical comparison can be performed on the feedback signal and the control signal in the DCS, primarily to determine whether the current state of the valve matches the desired control state.
Thank you very much, teacher. I now basically understand it. The limiter is just a feedback component for detecting the card
If the limit switch is a DI, then some valves have two DI feedback signals in addition to a limit switch – how should this be understood?
In my definition, a limit switch is a feedback signal, also known as a position switch. There are two sets of feedback signals, one for the on signal and one for the off signal. All signals are digital signals, which are connected to the DI cards of the DCS system. In your definition, what is a limit switch...?
When I was working on projects at Yokogawa, I encountered a situation where the feedback signals were ‘O’ for open and ‘C’ for closed; there were also separate limit switches. Now that I think about it, those two limit switches were used in interlocks – my understanding is that they served to prevent the valve from opening or closing once certain conditions were met
It can be understood that the limit switch does not function when it is not connected to the air pipe, right?
You’re not talking about a limit switch, right? That’s a SIS – it’s a separate signal with a higher priority than DCS