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I want to keep the pressure inside a balloon (effectively - a rubber vessel) constant, as the balloon is compressed. I'm wondering if a regulator like this (wiki page here showing mechanism - I believe) can do it? They're designed to regulate a higher relatively constant pressure (eg large volume at 30bar) down to <1bar in a smaller vessel to keep that constant. I think these are one way tho - if the pressure starts increasing in the outlet the inlet will close off, rather than dissipate that increase back to the source, whereas I want to effectively use it to do exactly that. Would this work? Or is there a better way to do this?

Thanks for all help given!

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  • $\begingroup$ Have an second separate balloon that expands as the first is compressed... $\endgroup$ – Solar Mike Feb 29 at 6:44
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Have a second separate balloon that expands as the first is compressed.

This will also keep the pressure constant as the volume is increased if that is part of your requirement.

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  • $\begingroup$ Awesome idea cheers, like it. Will have a go! $\endgroup$ – Oliver Walters Feb 29 at 23:00
  • $\begingroup$ As a development of this idea, since I'm not sure if two different balloons will necessarily expand/contract the same (I can't double this balloon) I will try using a syringe with a weight on top rather than the balloon. Cheers $\endgroup$ – Oliver Walters Feb 29 at 23:04
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The only way to keep pressure constant as volume is reduced is by let out the same amount of liquid/gas as the volume contracts. That is exactly what a pressure reducing valve does. As long as it has the capacity to vent at the rate you need you should be fine.

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  • $\begingroup$ Could you give me a link to such a valve pls? If I look it up, the same valve as I have in my question comes up - and the wiki definition is that it 'reduces the input pressure of a fluid or gases to a desired value at its output' whereas I effectively want to control the input. I'm still not sure if such a valve will work in my situation $\endgroup$ – Oliver Walters Feb 29 at 22:53
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    $\begingroup$ try an adjustable pressure relief valve. $\endgroup$ – Tiger Guy Mar 1 at 6:58
  • $\begingroup$ thought of that, but pretty sure they will vent more than is necessary to return the pressure to the level set, so it won't remain constant, it'll go up, then when it gets high enough will come far down, hence giving a wavy pressure graph rather than a straight line. But will keep in mind $\endgroup$ – Oliver Walters Mar 1 at 8:50

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