Proportional Valve recomendation for low flow rates

[themroc]

I am looking for a proportional control valve. The flow I have to control is quiet low. It has to be controlled in the range from 0 to 10 l/min. From my PID controller I have got a output signal 0 to 10 Volt available. The medium is water like.

I was thinking using a solenoid valve, but I did not really find any company which provides proportional 2 way valves they seam to do only on / off valves. I have to say that at the location there is no pressurised air available.
I also thought of valves with electro motor, can anyone recommend a supplier for this kind of application?
Thanks

 

[itsmoked]

How do you propose to actually measure the flow for the PID to control with?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[themroc]

In the same line of the valve there is an heat exchanger and also a flow meter. Depending what kind of temperature is desired the flow needs to be controlled. Therefore the valve.

 

[JLSeagull]

Within process plants we use globe style valves with pneumatic actuators. The Fisher division of Emerson electric is among the suppliers. They offer electric to pneumatic converters too. For valves with trim smaller than available from Fisher consider Research valves.

http://www.badgermeter.com/rcvrb.htm

 

[danw2]

There are indeed proportional solenoid valves. A continuous analog control signal is internally PWM'd to 'float' the solenoid partially open.

But it takes 24Vdc at 0.5A to drive the coil.

Click on the 8202 at

http://www.ascovalve.com/Applications/Products/ProportionalControl.aspx

The spec sheet has some valves with a Cv =1, a 1 PSI drop at 1gpm and your 10L/m is only 2.5 gpm.

Dan

 

[themroc]

Thanks danw2,
I actually looked at their page before but did not find anything. Sometimes it needs a hint from someone else. The valves seams to be ok for the job. I will get a quote.
Only as a matter of interest, maybe there is someone out there who has experience with samll valves actuated with electro motors. I pressume they are more accurate with respect to repeatability and they probably have a less pronounces hysterese effect. But as a drawback they are probably much more expencive. I did not find so far a manufacturer of these kinds of valves for low flow rates. May be I use the wromg search keywords.
themroc

 

[danw2]

An HVAC valve would work for you.

Try Johnson Controls or Honeywell for electric actuated proportional valves.

http://www.johnsoncontrols.com/publ...hvac/valve_products0/bronze_globe_valves.html

A couple of 1/2" valves with 0-10Vdc proportional actuators:

http://cgproducts.johnsoncontrols.com/CAT_PDF/1900084.pdf

I notice that they are not spring return valves. Do you have to account for input signal failure ?

Dan

 

[moltenmetal]

Burkert sells a product similar to the one offered by Asco. It's a pulse-width modulation driven continuously variable proportioning solenoid valve.

http://www.burkert.com/COM/buerkert_products.php?sk_id=36

The smaller sizes work extremely well for simple control applications such as what you're describing.

 

[themroc]

Thanks moltemetal,
They seam to have just the valves I am looking for!
Did you actually use the. I used valves from Danfoss before, they worked more or less fine but
1. There was quiet a difference between the flow when operating from an open state and operating from a closing state. This is I thing due to the Hysteresis.

2. They operated from 1 to 10 Volt corresponding 0 to max flowrate. But actually up to 1 Volt there was no flow.

In case you have any experience with the burkert valves are they bahaving similar?

 

[itsmoked]

themroc; You are stating the common problems with these valves.

Sometimes you need a valve with a closed loop flow control that is able to provide the setting you need thru constant valve manipulation or depending on your application's resiliency just the closed loop around the system will work.

I once was asked about controlling a valve that was very clever. It cammed the butterfly valve plate straight away from the seat face and then once a certain amount of flow was reached the valve would start to rotate in the conventional manner. This was all to avoid the starting flow anomalies you mention. Maybe someone knows who makes these.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com