I need a fast switch/valve between two fluid sources

[deanC4]

I'm working on an idea. I have two fluid sources (very thin liquid) each with it's own hose (around 1/2" ID), each with 35-80psi. They are going to come together in a "Y". 98% of the time, only one of the fluid sources will be used, but occasionally it needs to switch to the other with no gap in the liquid pressure or supply.

What I am thinking is that I need some type of a fast valve that goes in each of the two supply lines before the "Y". The primary source will be open most of the time, but when needed, the other source's valve will open and after it's open the primary source's valve will close so that the only thing being delivered is this secondary source. Then I need to be able to reverse this process and transition back to the primary source. It needs to be some type of valve that is opened and closed by an electrical switch or signal.

Any suggestions?

If this is the wrong forum/area for this question, please point me in the right direction. Thanks!

 

[Latexman]

An actuated 3-way valve may be less expensive and more reliable. At 1/2" you may be able to get a 3-way solenoid valve, but I do not prefer this method if the fluids are pressurized. Solenoids have been known to lift when under pressure.

Good luck,
Latexman

 

[EmmanuelTop]

Go to

http://www.metso.com/Automation/valve_prod.nsf/WebWID/WTB-090526-2256F-792E6?OpenDocument

I guess the best thing is to discuss the subject directly with the vendor. Provide a sketch of your system and the exact operating/safeguarding requirements.

Best regards,

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[moltenmetal]

Regulate the pressure of both supplies to the SAME pressure, then use a diverter valve such as a 3-way solenoid valve or diaphragm-actuated 3-way valve to switch between them. You should then get a bumpless switch-over between the two fluids. But if the two supplies are at pressures which differ significantly under flowing and non-flowing conditions, you will get some pressure fluctuation.

A three-way ball valve would be a poor choice, as it will stop flow from one source before starting flow from the other.

If you use a solenoid valve, make sure it's of a type which will permit pressure to be used on all three ports, i.e. one that does not require that one of the ports be vented to a lower pressure. Some designs require this differential pressure in order to operate a pilot which actually does the switching, while others (direct-acting type units) rely only on the force generated by the solenoid.

How well this will work adequately, and what other things might go wrong with whatever approach is chosen, depends greatly on other things that you're not mentioning in your initial post.

 

[deanC4]

What I was thinking was to have one of these valves/switch/solenoid in each of the supply lines, that way I could open the secondary first allow it to start it's flow (it would already be pressurized), then shut off the primary. Then just reverse the process when needed. I think that is the only way I can ensure that there is always liquid flow with no gaps in pressure or volume.

There is a pressure regulator just upstream from this "Y" junction, but there may be a pressure difference if one is flowing and the other is capped off.

 

[unclesyd]

If you have low viscosity non-reactive fluids you should look at something like the valves used in hydraulics, like a shuttle valve or an open center control valve.

We used a slightly modified shuttle valve to spare some coatings where we had to spray a primer and quickly spray the top coat.

 

[moltenmetal]

unclesyd, that's exactly the kind of thing I was thinking about- a "spool valve" style solenoid- the only concern is where/how to vent the pilot fluid used to drive the spool back and forth. I assumed actuation, but dean could certainly use a handle-actuated hydraulic valve if he could get one compatible with his fluids.

 

[deanC4]

Someone offline recommended a 2 into 1 shuttle type valve, electronically actuated. But he didn't know who made them. Thanks for all the information so far! I really appreciate it. I think I am a lot closer to finding what I'm looking for now. If I can just find some manufacturer's with products in the size that I need...

 

[unclesyd]

You need to find someone well versed in the art and science of hydraulic valves to help you. I'm pretty sure we did modifications on the valves we used, like change the spool from Al to SS.
There are some water mixing valves that might be made to work so check around.

Look at these people's valves as they have good cross section of what available.

http://www.lexairinc.com/valves/index.html

 

[Compositepro]

A three-way ball valve could work well. There are several different ball designs available. One works very much like a spool valve where one port starts to open as the other port starts to close.

 

[EricWales]

What about a 3-way ball valve with a pressure damping device downstream? This would provide a smoother switch over because as the 3-way valve turns and cuts the supply, the stored pressure/volume in the damper would continue to feed forwards for the split second it would take for the 3-way valve to swing and start feeding from the other source.

Another option is to have the secondary source regulated to a higher supply pressure than the primary. Then use a non-return valve in the primary supply and a simple ball valve in the secondary supply. As soon as the ball valve is opened, the higher pressure will close the NRV on the primary supply and only the secondary will feed forwards. (Caution - beware of passing NRV).