Re: Contemplating Coldth

On Fri, 09 Dec 2005 12:45:44 +0000 (GMT), "David G. Bell" <dbell@xxxxxxxxxxxxxxx> wrote:
> On Friday, in article <pTHVpJIbbXmDFwSb@xxxxxxxxxxxxxxxxxx>
> nojay@xxxxxxxxxxxxxxxxxx "Robert Sneddon" wrote:
>
>> In message <slrndphtf0.r8j.dmsilev@xxxxxxxxxxxxx>, Daniel Silevitch
>> <dmsilev@xxxxxxxxxxxx> writes
>>
>> >[1] Quenching a superconducting magnet. Not something that one does
>> >delibrately, but it is a hazard of dealing with big magnets.
>>
>> A building company I worked for which specialised in medical
>> installations occasionally got contracts to install after-market ducting
>> for MRI rooms which had been built without thought being given to the
>> (remote) possibility of a magnet quench. Big ducts.
>
> I infer that bad things happen. Is this about vast quantitities of very
> cold liquid suddenly turning to seriously huge volumes of gas?

Seriously huge volumes of a gas which, though it is not poisonous, is
also not metabolically useful. In other words, the helium pushes out
enough of the oxygen to become a safety risk. It's never happened to me,
but I know people who have handled liquid helium in confined spaces,
and, not knowing what they were doing, evaporated off enough liquid that
they started to get dizzy and lightheaded. They did the sensible thing,
which is leave until the helium dispersed.

The MRI magnets that Robert is talking about are a whole other game;
much bigger volumes of liquid and correspondingly greater potential
health hazard than the fairly small research magnets I work with.

-dms
.

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