Valve Balancing with Electric Actuators

[aarotech]

I have a problem comming up with the best solution for after switching from manual mode to auto to balance valve posistion.

1. Valves have posistion resistors monitored with converters, 0-10v into PLC

2. Manual mode two valves opened and closed thru switches on
panel.

3. When returning to Auto mode combined % open added together for a % value needs to be balanced between the two valves.

example-

% open among both valves added together is 40%

valve 1 = 25%
valve 2 = 15%

need both to balance at 20% each maintaining the 40% total.

Using RSLOGIX 5000

 

[Roy Matson]

I take it that the valves are set via open/close pulses
Add the 2 feedback signals, divide by 2 and use that value to set the output for bump-less transfer. When you go to Auto one valve will open to 20% the other will close to 20%.
I may have miss-interpreted your question.
Just because the signals still add to 40%doesn't mean the flow will be the same as before. The flow to valve position is not a linear relationship.
Tell us a little more about yor process.
Regards
Roy

 

[nonuke]

My 2 cents,
After the switch goes from Man to Aut just force the 2 analog outputs to 2V (20%)for a certain time, before you go to full Auto mode.

 

[Roy Matson]

Nonuke,
The poster said the valves are driven by switches, I assume one for Open one for Close, your idea is good though. Perhaps compare the voltage feedback to 20% (Total/2) and drive valve until the two match.
I can't help thinking it's a bit strange what he is doing. If you set the valves up in Manual why would you want to upset everything when you switch back to Auto. It's normal to start where you were (Bumpless Transfer)
Roy

 

[aarotech]

Thank you for your replys much help! When in auto I don't control the valves independently. so i would like them to be as close as possible to each other.