Proportional Control of a Fill Water Tank Valve

I'm trying to do proportional control of a valve on a water tank without the use of a PLC. Does any one has any experience using a PID control like Watlow to control a proportional valve on a water tank.

What variables do I need to know and what kind of calculations do I need to do to figure out how to set up the controller.

Any help will be greatly appreciated....

Level control (I ASSUME this is what you want) has been done for decades without PLCs, so it can be done.

You need to first define your objective. Do you want to maintain constant level in the tank? Do you want to maintain constant flow out of the tank as the level varies? Do you need tight control, or just maintain above a minimum for fire fighting or such? what kind of control do you have on the supply?

Until you define the questions, you can't get good answers.

Thank you so much for your reply. I'm trying to control the supply of water going to this tank to maintain a very precise level under high and low demand. I do need to also maintain constant flow coming out of the tank because this system is supplying water to a pump skid that is used on a humidity control system.

You won't get tight control with proportional only control.

I don't think the OP intended to mean proportional only PID control. I think he intended to say that he is using a proportional flow valve as opposed to a discrete open/closed valve so he has proportional control over the flow rate. But only he really knows that.

Keith

This is exactly my situation. I have a water tank that holds 1000 gallons. Currently it has a Radius pneumatic valve-slow closing. There is a Watlow small controllers with a Maximum and a minimum level setting that controls the opening and closing of the valve.

I want to use a Radius pneumatic valve that uses a 4-20 mA to control its opening and replace the existing one, so I can have control of the flow of water going to this tank to maintain level.

I thinking of using a Watlow controller to control the opening of the valve using a 4-20 mA signal. All this is done to prevent water hammering which is causing some of our pipes to burst open.

water hammering can be controlled with a few smaller pipes running from the valve back to the tank.
and yes you can use a prop valve, control can be done very easy depending on the type of activation. with a simple potmeter you can have a proportional control over the band of the potmeter.
something like the valve on the toilet is very good, and is pure mechanical, it can withstand 6 bar. opens slow and closes slow to prevent this waterhammer.

I'm going to use a proportional flow valve that I already purchase and all the other aspects that go along this kind of project are already in place.

The only thing I need some help understanding is how to set up the control of this flow using a controller like a Watlow.

You would use a level transmitter as the input to the controller. You would use the output of the controller as the position signal to the valve.

If your discharge restriction to the skid is constant you won't need a separate flow control loop - the constant level will provide a constant flow out.