Electric actuator ball valve Control. No 4-20 mA Control.

What platform?
Here is what I have done in the past. Assumed two solenoids, Ladder Logic:
Network1: Create a 2.0 second self resetting timer.
Network2: If flow < setpoint, and Timer.Q energize Open Output.
Network2: If flow > setpoint, and Timer.Q energize Close Output.

You may have to change the timer to fit your situation.
Every time the timer "done" bit is true, the output will be energized for 1 scan.
You may have to add a deadband to you setpoint. So that when is "close" you do nothing.

I think the deadband could be achieved using two LIM instructions, essentially if flow is between your lower deadband and say -1000 (essentially negative infinity depending on the scaling, I’m imagining controlling the flow between 0-10 GPM or something), then open the valve, and vice versa for the upper deadband and +1000. I’ve done this for high and low level detection, you may have to reverse the direction of the LIM instruction, I cant’t remember the normal operation. I think normally it operates such that if your “Test” value is between your Upper Limit and Lower Limit values, it evaluates as True but if you have your Upper and Lower Limit values swapped (eg. upper limit of 0 and lower limit of 100) then it will be false until it goes outside of the range between the two. Two LIM instructions are needed to cover both situations of the low or high flow compared to the setpoint.
 
I am not sure how accurate this control needs to be, but getting a decent linear flow out of a ball valve is "up hill" this was never a part of the ball valve design.

In my experience, the type of valve matters, but the resolution of the actuator is more important. In other words, being able to move the valve in small steps determines control accuracy. I have found that being able to achieve less than 1% increments in position will enable pretty good accuracy, even with a ball or butterfly valve.
 
In my experience, the type of valve matters, but the resolution of the actuator is more important. In other words, being able to move the valve in small steps determines control accuracy. I have found that being able to achieve less than 1% increments in position will enable pretty good accuracy, even with a ball or butterfly valve.

Hi Tom

You are right, In my mind I was thinking standard ball valve with an on/off actuator that he would have to start stop.
 
Another thing - most motorized valves I have seen had a moving handle or pointer to indicate the position.


Shouldn't be too hard to replace that with a small rotary encoder and know the exact position through a high-speed counter card.
 
In my experience, the type of valve matters, but the resolution of the actuator is more important. In other words, being able to move the valve in small steps determines control accuracy. I have found that being able to achieve less than 1% increments in position will enable pretty good accuracy, even with a ball or butterfly valve.


Yeah, but I can lead also to rapidly wearing on relays and gearbox (and brakes) if not designed for that.
 
Another thing - most motorized valves I have seen had a moving handle or pointer to indicate the position.


Shouldn't be too hard to replace that with a small rotary encoder and know the exact position through a high-speed counter card.


If actuator is desinged from factory to control then there can be also designed potentiometer from manufacturer for measuring.
 

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