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I'm in the design process for a cooling system. There is the need for some valves to control the flow of cooling fluid. In most machine states there's a constant fluid flow through either of two branches of the circuitry.

Initially I was working with 2/2 directional control valves with direct acting solenoid. Having low system pressure I'm forced to use direct acting valves. A power consumption of 4 W seems to be the lower boundary for a valve with ND 2mm. This is a waste of energy, since most of the time the valves stay in a constant state.

I then changed to 3/2 valves, so that only one state will consume energy. But 3/2 direct acting valves are exceptionally expensive and are available with small diameters only. I thought about ball valves, but those in turn are manufactured with diameters starting from 1/2" and have big gearboxes making them expensive as well.

So finally: Is there a possiblilty to switch a liquid between two brances of a circuit which I didn't think/know of? Tubing has mostly 8mm inner diameter, fluid is water/glycol mixture with temperatures between 10 and 90 degrees. Voltage available for controlling valves is 12V. Perhaps I'm just missing the affordable ball valve manufacturer or some tricky workaround?

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  • $\begingroup$ What about Fluidics (wikipedia)? You may have to roll your own with a milling machine, and I've no idea of the back pressures a fluidic flip flop will tolerate, that is, how well your two switchable branches must be matched, hence comment rather than answer. If it works, then you only need two off/on valves, energise one briefly to switch the flow. $\endgroup$ – Neil_UK Sep 19 '16 at 6:38
  • $\begingroup$ Depending on the size and flow - about all industrial servo valves only take energy when moving. But they are usually big, heavy things. You might really want to look into thermostat based valves; entirely passive and easy to obtain through automotive parts suppliers - regulating water flow to the radiator. $\endgroup$ – SF. Nov 18 '16 at 12:04
  • $\begingroup$ Do a search for bistable solenoid valves. These are exactly what you are looking for. $\endgroup$ – Eric Shain May 18 '17 at 2:04
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A stepper controlled proportional valve has the characteristics you're looking for. This one, for example, only consumes 4J to open or close. Then, they consume no power to stay in position.

The drawbacks are:

  1. The valves are much slower than a solenoid (1s to open or close for the linked one)
  2. They'll cost more because they're giving you functionality you don't apparently need (its a proportional control valve, not just on/off)
  3. They're typically harder to control. You either need to supply a chopper drive or you have to pay for them to supply one.
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Have you thought about an electromagnetic valve? Needs power only when moving. What I am envisioning would be a piston type 90° to the flow and watertight when closed. The other possibility would be a thermostat.

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  • $\begingroup$ The bistable solenoid valves you mean are difficult to obtain. I never got hold of one despite trying. If you know a reliable source, I'm glad to hear. Do you know of thermostates with G1/4" vor G1/8" bore? $\endgroup$ – Ariser Sep 18 '16 at 4:15
  • $\begingroup$ Do you have any machining capability? Could make the valve out of brass and the cylinder out of steel. The biggest issue would be control. Temp from a sensor sent to a controller to the valve switch. Oh, another possibility would be a microservo from the radio control world. $\endgroup$ – Tobin S Sep 18 '16 at 6:44
  • $\begingroup$ Where are you located? Seems the U.K. has more than a few results that I have found. $\endgroup$ – Tobin S Sep 18 '16 at 6:55
  • $\begingroup$ Do you habe an idea what a valve machined in demand nicht cost? I think 300€ may not be enough if one works really fast. Servo sounds interesting. Could it be capable if turning a 1/4" ball valve? $\endgroup$ – Ariser Sep 18 '16 at 10:50
  • $\begingroup$ If you mind sharing a link for bistable solenoid valves? $\endgroup$ – Ariser Sep 18 '16 at 10:51

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