Precise PLC control of a ball valve?

[NetNathan]

You may not want an electric actuator if response needs to be fairly fast.

In that case you would want a pneumatic actuator and positioner.

I use a lot of the ABB TZ1DC Electro-Pneumatic psoitioners. Nice unit...

 

[OkiePC]

Dude, you need an $80 2 way solenoid valve wired to a thermostat, but, if you want to get fancy, use PID time proportional control. The vortec type cooler will use the volume of air it is designed to use. When your temp control logic (sold separately) decides to turn it on or off. Do not try to adjust the temperature by limiting flow with any expectation of anything more than a mad science project. I suspect you will find a sharp drop off in performance at some level, and no part of the system will be linear.

EDIT: Having reread the first post, it seems you need a steady stream of controlled temperature air, for that, I would suggest still running the cooler at a fixed flow rate but maybe limit how much of its output goes to the part, and how much gets diverted elsewhere. Mac Valves PPC "proportional pressure controllers" are very fast and accurate, reliable, easy to set up and can be used as pilots for larger valves.

So maybe you need a three way servo valve instead of a two way with time proportional control, but if the air can go on and off without fouling your process, it is certain proven and simple to do it that way.

 

[Andybr]

You can always open your flow control valve to a preset position (for example, leave it in the last operating position or move it to 45 degrees) and use a separate solenoid valve in series with the control valve to control off/on operation of the air.

I would definitely do it this way. Aside from the problem of repeatedly having to achieve set point from 0% valve opening you will probably find that a "control" valve will not work reliably as an isolation valve and you will have problems with the valve passing when set at 0% open. If your design is already based on a ball valve you may be able to get a "V-Port" version from the valve supplier which will give you much better control.

 

[mnevans93]

I think TConnolly has a pretty good idea there. It will be reasonably fast and uses standard digital outputs.

Here is another valve option that is a better design match to what you are trying to do:
http://www.ascovalve.com/Common/PDFFiles/Product/PosiflowR3.pdf

I have no idea on cost on this thing but would guess in the $500-$1000 area.

Keith

This one is very promising. The price is great and from the looks of it, it seems to meet all of our requirements. Even with the controller, it's less than 1000$. The only thing I forgot to ask was how quickly this valve moves from fully closed to fully open, but I can always ask that.

You can always open your flow control valve to a preset position (for example, leave it in the last operating position or move it to 45 degrees) and use a separate solenoid valve in series with the control valve to control off/on operation of the air.

This is my plan if the ASCO valve takes too long to open up, and it would be relatively simple to program.

...I'm going to suggest something else, that though more physically complex will be easier to control: A bank of multiple small on/off solenoid type valves feeding a single nozzle. How many valves are on is determined by dividing the PID output range into zones. Three full flow valves plus a half flow valve with an orfice can give you control of the process in 16% increments. That is likely to already be better than you have with a manually opened ball valve, however by time proportioning the half flow valve you can get even finer control. A box of solenoid valves will cost quite a bit less than just a single ball valve actuator.

This is another promising option. I'm considering this as well and looking at ASCO 2-way solenoid valves.

Having reread the first post, it seems you need a steady stream of controlled temperature air, for that, I would suggest still running the cooler at a fixed flow rate but maybe limit how much of its output goes to the part, and how much gets diverted elsewhere. Mac Valves PPC "proportional pressure controllers" are very fast and accurate, reliable, easy to set up and can be used as pilots for larger valves.

So maybe you need a three way servo valve instead of a two way with time proportional control, but if the air can go on and off without fouling your process, it is certain proven and simple to do it that way.

I checked out the Mac Valves units, and they're a bit pricy for what we need to do. Like I said before, we don't need incredible precision, and as long as we're relatively close to our target temperature, we should be fine.

In that case you would want a pneumatic actuator and positioner.

I use a lot of the ABB TZ1DC Electro-Pneumatic psoitioners.

This is the right type of unit I'm going for, but it's got quite a bit more than we need. The response time issue (if there is one with the ASCO units) can be resolved with an in-series open-close valve like Tom Jenkins suggested.

Thanks so much for everyone's responses! I don't know what I would have done without all of your input. I've definitely got a solid idea of what I'm looking for now, and now it's just down to figuring out what is the best fit for the price.