Posted 23 May 2016 Hi, Please I am new to PLCs & SCADA. I will appreciate if someone can explain what it means by The inlet valve will be actuated by the SCADA system via two 24V DC digital outputs. Why is it using two 24V DC digital output. Is this because it is a solenoid two way valve? Thanks Share this post Link to post Share on other sites
Posted 23 May 2016 Would guess that you have one signal to "increase" the opening of the valve position, and the other one to "decrease" the opening position. Share this post Link to post Share on other sites
Posted 23 May 2016 1 hour ago, Bryll said: Would guess that you have one signal to "increase" the opening of the valve position, and the other one to "decrease" the opening position. Thank you. I am guessing with a three-way valve there will be three 24v DC digital output for position 1, position 2 and close Share this post Link to post Share on other sites
Posted 23 May 2016 What is the purpose of the valve? I use a lot of three way valves, but it's for temperature or flow control. One of the ports is then used as a by-pass port. Share this post Link to post Share on other sites
Posted 23 May 2016 It is a normal flow control valve. Share this post Link to post Share on other sites
Posted 24 May 2016 Brand and model number ? Might be a good valve to use in the future Share this post Link to post Share on other sites
Posted 24 May 2016 Sounds like a normal bi-stable valve. One output opens the valve, the other closes it. Once an output has been turned on the position of the valve is maintained even if the output is turned off. This is oposite to a "spring return" valve which only uses a single output (generally to open the valve) and when the output is turned off the valve closes using a spring inside the valve. Share this post Link to post Share on other sites
Posted 24 May 2016 1 hour ago, Nightfly said: Sounds like a normal bi-stable valve. One output opens the valve, the other closes it. Once an output has been turned on the position of the valve is maintained even if the output is turned off. This is oposite to a "spring return" valve which only uses a single output (generally to open the valve) and when the output is turned off the valve closes using a spring inside the valve. Thank you. Makes sense Share this post Link to post Share on other sites
Posted 24 May 2016 2 hours ago, Bryll said: Brand and model number ? Might be a good valve to use in the future We haven't yet picked a brand yet. When we do will tell you about it. Thanks Share this post Link to post Share on other sites
Posted 4 Jul 2017 There are many different valve types, we cant help you unless you give us the manufacture and part number. Mike Share this post Link to post Share on other sites
Posted 4 Jul 2017 (edited) The valve is the chunk of metal or plastic in the line that regulates the flow. The actuator is what drives the valve open or closed. An actuator driven by two 24Vdc discrete outputs is likely an electric actuator. Here's an example of an actuator driven by two AC discrete outputs. https://postimg.org/image/vg2qoudr7/ (the forum's "insert other media" doesn't work for some reason) The actuator functions like Bryll describes: powering one output "increases" the valve position (opens); powering the other output "decreases" the valve position (closes). When neither output is ON, the valve position is stationary, it remains at its last position. The diagram shows a slidewire feedback so that the control system knows what current valve position is. The absence of valve position information is 'open loop control'. The control logic has to be written so that there is no circumstance where both outputs can be ON at the same time. One has to consider what happens on Start-up when the valve position is unknown. Edited 4 Jul 2017 by DanW Share this post Link to post Share on other sites
