Date: Mon, 12 May 2025 09:43:13 -0500
Brian,
What you have the arrow pointing to are not burst caps. They are the 10 and 15 PSI pressure
release spring loaded valves. They don't burst. They reseal after the pressure drops.
You can read the pressure rating on the side as you can the 0.5 PSI one ..
Quinn
On Mon, May 12, 2025 at 9:25 AM Brian Myers via groups.io wrote:
>
> Thank you all for the helpful replies. Several people reported receiving
> dewars with the safety off. One time, I accidentally left all three valves
> closed on a dewar after a fill, and I had one of the burst caps activate.
> That was an exciting event and one I would like to avoid in the future.
>
> When receiving a tank, I really like to see shrink wrap or a cable-type
> tie on the safety valve when receiving dewars. I appreciate David Jones ’
> very helpful comment: “Venting these quickly causes a rapid helium boil-off
> as the temperature of the helium drops and more of it starts to boil” .
> Quinn Kleerekoper reiterated this.
>
> Regarding Quinn’s comment on the tank needing another 10/15 PSI valve, I
> haven’t seen such on a liquid helium tank in the 23 years I’ve been
> maintaining our magnet. I attached a picture of the tank after I finished
> venting it, which I believe is a standard configuration. I didn’t look at
> the gauge because I immediately pushed it open when I saw the safety was
> shut.
>
> I am unsure how much helium we lost with me venting quickly, but we did
> have enough to fill our 400 MHz magnet with some to spare.
>
> Brian
> --------
> Brian Myers, Ph.D.
> Professor of Chemistry
> Meyer Hall of Science (rm 256)
> Ohio Northern University
>
>
> *From: *"Jones, David (Pharm) via groups.io" <david.jones=
> cuanschutz.edu_at_groups.io>
> *Subject: **Re: [AMMRL] Helium Delivery-Safety Valve in off position*
> *Date: *May 10, 2025 at 11:05:32 AM EDT
> *To: *"main_at_ammrl.groups.io" <main_at_ammrl.groups.io>
> *Cc: *"main_at_ammrl.groups.io" <main_at_ammrl.groups.io>
> *Resent-From: *david.jones_at_cuanschutz.edu
> *Reply-To: *main_at_ammrl.groups.io
>
> We have had many deliveries by FedEX over the years. Some of it delivered
> overnight by air.
>
> Technically they have to have the correct shipping label “un1963” on their
> truck.
> They should open and vent the truck before going in to get the dewar.
> Helium is more dangerous than N2 in this regard. As it is at the top and n2
> is at the bottom of the air space.
>
> We have also received the occasional dewars with the relief valve
> closed. After 30 years of doing this this adds up to a lot of dewars. My
> experience is that these get to about 3 PSI, rarely higher. Venting these
> quickly causes a rapid helium boil off as the temperate of the helium drops
> and more of it starts to boil. Often when you open the valve there is a
> short period with no plume and then the plume builds quickly aniindication
> of the increased boil off and it is dramatic. Venting slowly is as an and
> less dramatic. But it does take a while.
>
> This boil off is related to the recent discussion on fills with helium
> recovery systems. Sudden drops in pressure lead to rapid increase in helium
> boil off.
>
>
> David
>
> Associate Professor
> Dept. Of Pharmacology
> University of Colorado
> School of Medicine
> Tel (303)-724-3600
>
>
> On May 10, 2025, at 10:42 AM, Quinn Kleerekoper via groups.io wrote:
>
> 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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