[ RadSafe ] potentially combustible helium (Article Explained)
Brennan, Mike (DOH)
Mike.Brennan at DOH.WA.GOV
Tue Jan 3 17:34:21 CST 2012
I accept the idea that if liquid He was heated to the point where pressure cause it to blow out the container, that would be bad.
I am HIGHLY dubious of the idea that liquid He escaping into a room would liquefy the O2 in the room in a way that makes it more available for combustion than it is as a gas. In fact, I suspect that the cooling of liquid He would break the combustion triangle (fuel, oxidizer, heat) much more effectively than water would, and the displacement of O2 by He would also interfere with combustion (depending on a number of interesting factors about the location of the fire in comparison to the flasks).
While I agree that fighting a fire in the presence of liquefied inert gas would present exciting challenges and the opportunity for things to go horribly, horribly wrong in new and unexpected ways, and I don't fault the actions of the technician while if not under fire, at least near it, helium still isn't combustible.
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Roger Helbig
Sent: Tuesday, January 03, 2012 3:22 PM
Subject: Re: [ RadSafe ] potentially combustible helium (Article Explained)
The article explained it very well - and it was about the potential
problems of fighting a fire in an MRI unit which were averted by quick
thinking hospital technician
MRI fire underscores need for education and oversight
December 30, 2011
By Tim Darragh, Of The Morning Call
...kept in operation by super-cooled liquid helium and use enormous
amounts of energy. The liquid helium ? cooled to 450 degrees below
Fahrenheit...thermos" casing, he said, the liquid helium could have
escaped, and immediately chilled...
Nancy Run Fire Company Chief Jamie Hauze said the cause of the fire
still is under investigation. He also said that while the response to
the fire ended up being routine, the threat posed by the fire was
anything but that.
"It just happened to be in the worst place possible," he said.
MRIs employ strong magnets kept in operation by super-cooled liquid
helium and use enormous amounts of energy. The liquid helium - cooled
to 450 degrees below Fahrenheit - essentially keeps the electric
current continuously alive, said Tobias Gilk, president and safety
director for Mednovus, an MRI safety company. If a fire were to have
pierced the "thermos" casing, he said, the liquid helium could have
escaped, and immediately chilled the oxygen in the environment to
liquid, creating a highly explosive scene.
"Any spark or flame in the presence of liquid oxygen becomes virtually
inextinguishable until the oxygen burns out," he said.
Even without a puncture, fire could warm the liquid helium to a
gaseous state, causing the helium to expand and result in a
potentially disastrous buildup in pressure.
Those scenarios did not occur because a St. Luke's MRI technologist
activated a system that "quenched" the unit, according to Hauze and
St. Luke's spokeswoman Dorrit Trate. Essentially, the process
demagnetizes the unit by allowing the gaseous helium to escape safely
through a chimney-like vent into the outside atmosphere.
It was only then that firefighters, who were made aware of the
potential hazards of the MRI during inspections of the hospital before
it opened, could put out the fire.
The MRI had to be quenched because much of the equipment that fire
fighters carry - axes, picks, oxygen tanks and more - contains ferrous
material and would have been sucked into the unit by its magnetic
force. Their equipment, and anything metal, could have become
MRI-seeking missiles, as other firefighters have learned. According to
Gilk, a firefighter in Stockton, Calif., last year lost his ax to the
pull of an the MRI while he was ventilating the roof a building.
On Tue, Jan 3, 2012 at 11:48 AM, Brennan, Mike (DOH)
<Mike.Brennan at doh.wa.gov> wrote:
> The chemistry education of everyone involved in the press release and
> article should also be under investigation. I'd have spotted the
> problem with this article in junior high school, or possibly grade
> -----Original Message-----
> From: radsafe-bounces at health.phys.iit.edu
> [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of FISHER Spencer
> Sent: Tuesday, January 03, 2012 11:42 AM
> To: 'radsafe at agni.phys.iit.edu'
> Subject: [ RadSafe ] potentially combustible helium??????
> MRI safety training pays off in Pa.
> By AuntMinnie.com staff writers
> January 3, 2012
> Officials at St. Luke's Hospital - Anderson Campus in Easton, PA, are
> crediting MRI safety training as the reason injuries and extensive
> damage were avoided following a fire in an MRI suite at the facility.
> A December 30
> 0,7840341.story> in the Morning Call newspaper noted that no one was
> injured at St. Luke's, and damage was limited to smoke in the hallways.
> An MRI technologist activated a system that demagnetized the unit and
> allowed potentially combustible helium to exit the building through a
> vent, according to the report. At that point, firefighters were able to
> extinguish the fire.
> The cause of the incident is under investigation.
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