Brian,
When you speak of the helium safety valve are you referring to the 1/4 PSI
pressure release valve that has a manual shutoff valve? There should be
another pressure release valve (10 PSI) without a manual valve. If the dewar
doesn't have this I would be shocked, Is it a Cryofab dewar? As long as
you have the 10/15 PSI pressure relief valve there is no danger outside of
the annoyance of having to release the excess pressure by cracking the
valve that controls the 1/4 PSI valve. If you just crack it you can
prevent the massive loss of
helium both gas and liquid.
Quinn
On Sat, May 10, 2025 at 8:55 AM b-myers via groups.io wrote:
> Two days ago, while off campus, colleagues helped receive a 100 L dewar of
> liquid helium. Today, I checked the dewar and found the safety valve off.
> Opening it released a lot of pressure, so I opened the side vent, and a 2
> meter jet of helium shot out for a few minutes. Thankfully, no one was near
> the vent. None of the valves were shrink-wrapped, and my colleagues said
> they didn’t touch them. I know the tank has blast safety burst caps, so
> it’s unlikely it would explode, but it was disturbing. I am guessing that
> if the burst cap had ruptured after we took the dewar, we’d have had to
> replace the helium. It’s also strange that FedEx could transport liquid
> helium.
>
> In any event, I am curious to know if others in this group have received a
> liquid helium dewar with the safety valve off? And is it common to get
> deliveries of liquid helium by FEDEX (box truck)?
>
> Brian
> --------
> Brian Myers, Ph.D.
> Professor of Chemistry
> Meyer Hall of Science (rm 256)
> Ohio Northern University
>
>
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Received on Sat May 10 2025 - 08:26:13 MST