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I have a pressure regulator to maintain a specified pressure in a vessel that also contains a liquid. The regulator can pressurize or relieve pressure of the vessel. I want to prevent the liquid from flowing back to the regulator while keeping the gas flowing both ways. I can imagine a device that would do that but can't find a readily available one on the market. Any ideas?

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I thought simplifying my problem was gonna help but now I'm thinking that sharing the exact context of my situation might help you help me. So, this situation is happening on a counter-pressure beer canning machine (cheers!) The pressure regulator maintains a set pressure of CO2 in the machine's can filling tank. The level of beer is this tank is regulated by an actuated globe valve and the beer transfers from the BBT to the machine's tank by a differential pressure between the two tanks. During operation, the regulator has to supply and relieve pressure from the machine's tank (two-way flow). My issue is that if for any reason the beer supply valve doesn't close completely, the beer level rises up to the CO2 supply port, eventually overflows right into the regulator and ruins it...so as a safety, I want to install a check valve that would only close in the presence of liquid (beer) while allowing gas (CO2) to flow both ways the rest of the time.

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  • $\begingroup$ Cryogenic tanks have relief valve on tops of the tank since the gas boiling off the liquid is less dense, so it floats to the top and out of the relief valve while leaving the liquid behind. Could you try something like that? $\endgroup$ – jko Apr 3 '20 at 16:59
  • $\begingroup$ Hi jko, the problem is that if the gas enters by the same port where the liquid might overflow. $\endgroup$ – Paskoual Apr 6 '20 at 13:33
  • $\begingroup$ can you draw a P&ID sketch with the essential components? and give approx. flowrates? $\endgroup$ – mart Apr 7 '20 at 13:41
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If the flow rate is low for the gas then a ball that floats on the liquid will work - similar to how most wet vacs stop liquid getting into the motor...

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  • $\begingroup$ I know, it's exactly what I need but I can't seem to find the name for such a device nor can I find anything on the market... $\endgroup$ – Paskoual Apr 6 '20 at 13:31
  • $\begingroup$ The term you need is "bleeding valve", like this: mankenberg.de/en/20/prgb:6/pr:147/product:eb-1.32/products.html you need one that's food grade and likely far far smaller than what I linked you to. $\endgroup$ – mart Apr 7 '20 at 13:39
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Any form of gravity trap. For examplea piece of vertical pipe with a large enough diamter will work - liquid gathers at the bottom, diameter need to be large enough to let bubbles pass through the fluid, avoiding plug flow.

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  • $\begingroup$ I thought of that but the volume of liquid to handle is too great for it to work. That's why I need a device that simply blocks the flow in the presence of liquid. $\endgroup$ – Paskoual Apr 6 '20 at 14:02
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A "steam trap" should do what you want. There are a few types with different characteristics .

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  • $\begingroup$ A steam trap works only in one direction of flow. $\endgroup$ – Paskoual Apr 6 '20 at 13:59

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