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What happens when a pressurized gas cylinder falls over?

  1. Mar 6, 2015 #1

    f95toli

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    This is health&safety related question that came out of a discussion I had with a friend.

    I sometimes keep a large (L sized) helium cylinder in my lab. It is pressurized to 200 Bar and equipped with a standard regulator.

    Now, the question is what would happen if it fell over and the regulator was damaged?
    I am fully aware of what would happen if it was actually knocked off and the gas could escape (we have all heard stories about cylinders flying through walls), but presumably the regulator/cylinder is designed to minimize the risk of that happening?
    Is the regulator designed in such a way that it should break in a way that blocks the gas flow?

    I haven't been able to find anything about this online (except the usual "don't let it happen" warnings)

    I should mention that both the cylinder and regulator are approved etc.
     
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  3. Mar 6, 2015 #2

    Bystander

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    There do exist excess flow shut-off valves (essentially a stopper that gets blown into a seat under free/high flow rates). I'm unaware that any such devices are available in ordinary gas cylinders (might be a precaution for some of the super-toxic and expensive semiconductor materials). Plain old brass regulators? You bend screws, rupture diaphragms, and distort the fittings to where they're useless.
     
  4. Mar 6, 2015 #3

    f95toli

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    I thought perhaps the regulators were designed to bend/break in such a way that it at least would limit the flow?
    Gas cylinders are so common that accident must happen quite frequently, but you rarely hear of any serious consequences (not that serious accidents do not occur).
     
  5. Mar 6, 2015 #4

    Bystander

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    None that I've ever seen. Stands and chains for safety. Regulator design? Outlet gauges (at least from thirty years ago) had ranges three to four times what the regulator screws and diaphragms could safely handle, and invariably some nimrod would try cranking up outlet pressure to what the gauge would show, and the screw and bushing would go flying across the lab --- never got hit with one, but had a couple close calls. Screw loss/failure does shut the regulator off, so that much is failsafe (unless you need uninterrupted gas flow).
     
  6. Mar 6, 2015 #5

    f95toli

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    That is the problem: I do. We need to leave the gas on for several days so we can't shut the valve on the cylinder. This is not entirely uncommon for lab use.

    Of course we are using a stand/chain so we are not doing anything dangerous. This was more of a general question.
     
  7. Mar 6, 2015 #6

    Q_Goest

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    Cylinders have a valve screwed into them and the regulator is always attached to the valve using a short nipple. At least, I've never seen a regulator that is screwed into a cylinder. When they fall over, the danger is in breaking off the valve at the base where it screws into the cylinder. Breaking the regulator off at the nipple could also happen and with similar results. If your tubing broke downstream of the regulator, and assuming the regulator isn't damaged which should be reasonable, then the regulator will still try to maintain downstream pressure which may or may not be tremenously dangerous.

    That you're using a stand and a chain is fine. I think that's actually an OSHA requirement. Sounds like you're doing things safely.

    Just a side note, you should also have a relief valve on the outlet of your regulator if there's anything downstream of the reg that can't handle full bottle pressure. We would typically install a relief valve on the outlet with a set point no higher than the pressure rating of lowest rated part downstream and capable of handling the full flow through the regulator at the maximum source pressure.
     
  8. Mar 6, 2015 #7

    nsaspook

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    Who can resist some experiments with different types of bottles and what happens when the valve is sheared off without safety restrictors. o0)
     
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