Author Options:

Valve that shuts off once a set pressure is reached? Answered

For something I am in the process of designing, I need a valve that can be connected to a high pressure source and will allow the gas from the high pressure side to to flow into a sealed container on the other side until a pre-set pressure is reached. It should then shut off.

The system used to do this should also be able to handle a very high pressure spike (possibly even the type of compressed pressure wave generated during a super-sonic combustion / detonation) on the sealed container side.

If you can provide a diagram or the name of a type of valve or even just a description of how this could be done it would be appreciated. No computer controlled stuff please.

##################### The answer I have discovered is to use a regular diaphragm-type pressure regulator. ######################


another "try to guess what I'm doing, then tell me how to do it question". if you use a gas regulator you will achieve until a pre-set pressure is reached.
but a detonation is going to break something.
what are you making?


A gun powered by a gasseous fuel mixture.

Be sure and film the operation once you build it. It'll look great on youtube and it'll be good evidence in the trial.

Sure. When this thing blows up and the survivors ask for damages from the estate.

Haha yeah that would be a problem. But for future reference, there are no survivors. I think you underestimate the strength of steel. I have built and tested 4 prototypes of the gun this will be going on already and there has not yet been any injuries or serious property damage associated with them.

I'm not sure I find "there are no survivors" reassuring. [grin]

However, "it hasn't blown up yet" is not, by itself, sufficient evidence that it won't blow up next time -- there may be a flaw in the material, or a bad connection, or a backfire to your fuel source, or something else that takes it over the edge. And after repeated firings, metal fatigue may make that more likely. High-velocity explosions can put one heck of a lot of pressure into a small area; any flaw is likely to become progressively worse.

If you aren't absolutely sure you know what you're doing, I would recommend being a safe distance away and behind a stone wall when you trigger this thing. It may work perfectly ten times and take your arm off the eleventh.

Thanks for the advice. I am sure I know what I'm doing though. And I'm don't just jump to pumping pressurized HHO gas mix into the combustion chamber and pulling the trigger either. A new gun is tried with butane and/or propane and air mix, then hydrogen / air, then HHO (I've only tried HHO once and it was on my newest gun, version 4). The next gun (version 5) will be the first with a pressurized combustion chamber though. There is an element of danger in a lot of things we do. You risk you life on every car ride. Personally I have the balls to test these things. The wall is a good idea though. I will probably just take advantage of curvature of the ground instead of building a stone wall.

. If you don't need a lot of flow, use a long length of small-diameter piping/tubing between the impulse point and the regulator (you may want to add a pulsation damper near the regulator).

The small pipe idea could help protect the regulator, but the entire flow of gas needs to happen in a fraction of a second. What is a pulsation dampener?

I can't see any regulator accepting an overspike like you describe without rupturing. You need to isolate the regulator once you have pressurised the chamber.

Well yeah I could just put a specially built check valve between the main valve and the container.

From your description, I wasn't convinced that a check valve would close quickly enough.

The explosion won't happen immediately after the pressure is reached, there are a few more mechanical things that happen first. Also, I can use switches that won't let the electric igniter cicuit fire until the entire mechanical cycle is completed.

This sounds like a question to take to an expert. There are people who know, but the odds of getting correct advice free on a random website for so specific (and safety-related) a question are pretty low.

I can design something myself if I have to, I just figured that I might as well ask if something already exists that I can copy. That's easier than designing a new thing sometimes.