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I need a quick-opening pressure vessel

  1. Oct 22, 2012 #1
    Hey guys I'm new here.

    I need to find a generic pressure vessel that can take in a gas at up to 6MPa and then have a quick release system that would allow me to very quickly depressurize/open it and remove the contents within ~10 seconds or less.

    Right now we use bolts to hold down the lid on our vessels and it takes too long to remove them even with the pneumatic wrench.

    This should be a tabletop vessel, probably doesn't need to be larger than ~4-5 inches in diameter and ~5-6 inches in length. Not too picky. My google searches weren't successful so I need some guidance on where to look.

    Thanks!
     
  2. jcsd
  3. Oct 23, 2012 #2
    It looks rather easy... Maybe a sphere-in-cone valve, pulled close by a spring, pushed open by an electric motor through a screw? The whole is a standard part for pneumatics. Just watch where you release the pressure to, to prevent damages.
     
  4. Oct 23, 2012 #3
    The problem is the lid-opening mechanism. I need to open the lid quickly so it needs some kind of quick-release latch with a good seal.

    I'm looking to buy one so I'd appreciate any links or companies that make such things.
     
  5. Oct 23, 2012 #4

    Q_Goest

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    I've not heard of any kind of 'off the shelf' type vessel as you describe, but you certainly could make something. Rather than make a vessel with an easily removable cap, you could simply put a length of 4" diameter pipe with a cap on one end and flange it to a 4" ball valve. Once depressurized, you open the ball valve and pull out your specimen. You're probably looking at a ball valve with a 600# flange. Won't be cheap but not particularly expensive either, and as long as it's under 6" ID, you don't need to have it stamped as an ASME coded vessel if you're in the US. Don't know about other countries.
     
  6. Oct 23, 2012 #5
    Okay but if I use a flange with bolts it doesn't solve the quick-opening problem. We have pressure vessels like that and the problem is that it takes too long to unbolt everything even with the pneumatic wrench. I was looking for something like a quick-release latch or something.
     
  7. Oct 23, 2012 #6

    enigma

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    Does it need to be resettable? If not, you could look into pyro valves. Those are used to hold gas and liquids in rocket fuel tanks.
     
  8. Oct 23, 2012 #7
    I believe O Goest was saying that you would reach through the open ball valve's oriface to remove your object.
     
  9. Oct 23, 2012 #8

    Q_Goest

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    Don't worry about the bolts. Just ignore that part. Are you familiar with a ball valve? It's a valve that you turn the handle 90 degrees and it's open. You open the valve as fast as you can turn the handle. The ID of the ball has roughly the same ID as your pipe, so it's like taking the end off your pipe and you can reach inside because it's just an open pipe at that point. I could build one for you, it's not hard.
     
  10. Oct 23, 2012 #9

    Mech_Engineer

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    I agree you need to look into a valve, taking bolts off quickly is a losing proposition and on top of that you're talking about depressurizing the container when opening it, which means you'll be blowing out 870 psi on whatever's holding that pressure back.

    Your best option is a large valve such as Q_Goest's suggestion of a ball valve, or maybe a butterfly valve. Either way, be ready for loud noises (and maybe a blast of condensation) when it opens...
     
  11. Oct 23, 2012 #10
    How are the contents being put in such that the vessel can maintain 870 psi in the first place?

    What sort of contents? Fluid? Solid? Granular? Bulk?

    What's your desired method of retrieval?

    Quickly releasing air stored at 870 psi is no joke.
     
  12. Oct 23, 2012 #11

    Q_Goest

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    I'd agree with the above. To pressurize and depressurize, I'd assume you would want a separate vent/pressurization port so that can be done without the operation of the ball valve. The main issue I see is one of safety. You obviously don't want to operate the ball valve if there's any pressure inside the chamber. Having a pressure gage visible to the operator would be one safety measure.

    Not sure if there could be additional safety measures put in place to prevent that. One thought - I've seen valve handles rigged so that one handle has to be in a given position in order for another handle to be moved. In this case, having a vent valve handle blocking the ball valve handle from opening unless the vent valve were open would be another safety measure.
     
  13. Oct 23, 2012 #12
    I have an inlet which doubles as an outlet which can vent pressure vessels in about 3-4 seconds which is fine. The ball idea sounds good, I'll sketch something up on Solidworks and put it up later tonight.
     
  14. Oct 24, 2012 #13
    Ok I drew up a quick sketch on solidworks. I think this is the idea you were talking about.
    Seems a little inefficient with space, essentially all you would need is just a spherical cap that fits over an O-ring. The pressure from the vessel would keep this shut and you can slide it out of the way after depressurization (throught another outlet).

    Anyone know where I can buy something that will work, or suggest some simple-to-machine designs? I have some machining experience but not a lot of time.
     

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  15. Oct 24, 2012 #14

    Q_Goest

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    I can't quite understand your drawing but that's not important. If I were to have this made, I'd expect to spend a few thousand dollars for the valve, a custom made vessel, engineering and pressure testing. I wouldn't ask for it to be stamped but you could if it's critical. But before anyone can do any engineering on something like this, you need to provide a specification that goes over stuff like what you're putting inside (especially gasses or liquids), what temperature it will be exposed to, what additional ports you need such as for instrumentation or valves, if you need valves or gages that should be defined, if you have a specific material requirement, what dimensions, finishing or painting requirements, cleaning requirements, and a general area you're located in to determine local code requirements and suppliers. Can you give any of that?
     
  16. Oct 24, 2012 #15
    What goes inside is CO2 gas at up to 5MPa and plastic specimens, mostly rolled up films (like a roll of toilet paper except 0.1mm plastic). I need to pull it out fast because thin films desorp very quickly. Everything will happen at room temperature which is about 21C in this lab, and it will have a copper tube inlet/outlet which goes to a controller/gas tank/vent. We have several pressure vessels so maybe it will be sufficient to only work on the valve part, but maybe not.
    I don't have any preference on much else, like I said it should essentially hold a roll of half-used toilet paper (so 3-4 inches in diameter will be enough) and we're in Seattle. Thanks for the help.
     
  17. Oct 24, 2012 #16
    While I'm not that familiar with "sorp-ing?" film, I do know that dropping 49 atmospheres of CO2 in a couple seconds will not stay at room temp... hopefully this is okay for your process.

    An autoclave might be adapted to your purposes...
     
  18. Oct 24, 2012 #17

    Q_Goest

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    Sounds like a length of 4" Sched 40 pipe with an end cap on one end, a ball valve on the other and perhaps a small 1/4" to 1/2" pipe coupling for attaching the pressurization line would work. You'd probably want brackets to mount it as well. The ID of the pipe is 4.026" so the ID of the valve would need to be roughly the same which shouldn't be a problem.

    I'd suggest making up a specification - just jot down the information you presented here in a short format and make up a sketch of the vessel with rough dimensions. Then send it to various ASME vessel manufacturers in your area. I don't see a need for an ASME code stamp in this case but you don't want to use a manufacturer that DOESN'T have a stamp. They should give you the same quality as a stamped vessel without charging you for the stamp.
     
  19. Oct 29, 2012 #18
    If you have the ability to pressurize the vessel to a higher pressure than required for your purposes, why not implement a relief valve set to "pop" at a pressure immediately above your desired pressure?
     
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