I'm afraid you all missed the boat.  Any liquefied gas is subject to 
suckback of  of liquid when its discharge piping is immersed in liquid.  
This will happen as the pressure drops, unless prevented against backflow. 
Water was obviously sucked back into the cylinder which generates 
hydrofluoric acid, which will react with any metal to form hydrogen gas.  
With the valve closed, the reaction will continue to eat the wall of the 
cylinder and increase the pressure until the cylinder bursts. 
 
This can happen with any acidic liquified gas, such as HBr, HCl, hydrogen 
sulfide, sulfur dioxide, even carbon dioxide.
 
I suggest you contact your gas supplier to investigate the failure and to 
teach your chemists how to prevent suckback.
 
Dave Siegel
Wyeth
 

>>> Joseph Passante  7/11/2005 6:39:40 AM >>>

This is documented issue and the pressures have been verified

http://www.airproducts.com/Responsibility/EHS/ProductSafety/
ProductSafetyInformation/safety_bulletins_PotentialPressurization.htm

Quoting Jay Young :

> I fail to see how gaseous HF can react with steel to produce an 
excessive
> hydrogen pressure and burst a cylinder:
>                                             6HF + 2Fe yields 2FeF3 + 3H2
> The product would be FeF3, not FeF2, because fluorine is an excellent
> oxidizing agent.  Consequently, if anything, the gas pressure inside the
> cylinder would necessarily be reduced as the HF attacks the iron of the
> cylinder.
>
> It's obvious that the cause of the explosion was the thinning of the
> cylinder wall at one or more locations, NOT the pressure of the 
hydrogen.
>
> Jay Young
>
> PS: Alas, in these modern times, these young folks just don't know their
> descriptive chemistry like us old guys do.  I predict disaster and
> catastrophe--as we old guys die off, the world will be left with 
chemists
> who don't know descriptive chemistry.  Alas and Alak! (or whatever)
>
> *************************************************************************

> **********************************
>
> On Fri, 8 Jul 2005 15:42:58 -0700 Debbie Decker 
> writes:
> > Hi gang:
> >
> >  From our intranet for your information.  If you want copies of the
> > photos,
> > lemme know.
> >
> > BTW, I did have a potentially scary situation with HBr in lecture
> > bottles -
> > quite ancient stuff.  It has a similar nasty habit of
> > over-pressurizing
> > over time.  It was managed without incident, several $10K later.
> >
> > Ya'll be safe,
> > Debbie
> >
> >
> > >Priority: NORMAL
> > >X-Mailer: Execmail for Win32 5.1.1 Build (10)
> > >X-Scanned-By: MIMEDefang 2.49 on 169.237.104.156
> > >X-Scanned-By: MIMEDefang 2.51 on 128.111.125.200
> > >Date:         Fri, 8 Jul 2005 13:55:39 -0700
> > >Reply-To: UCIH Program Management Group
> > 
> > >Sender: UCIH Program Management Group 
> > >From: Kevin Kaboli 
> > >Subject:      recent lab explosion 
> > >To: SBUCIH-L**At_Symbol_Here**LISTSERV.UCSB.EDU
> > >
> > >Hi Folks,
> > >FYI-Here is the report of the explosion by Dave Vandenberg:
> > >
> > >Best
> > >Kevin
> > >
> > >
> > >
> > >UC EH&Sers:  Below is a note describing an accident that occurred
> > recently
> > >on our campus.  You may already be aware of this potential safety
> > issue
> > >with hydrogen fluroride cylinders.  If not, would recommend that
> > you
> > >identify and dispose of old cylinders of this material.  We were
> > fortunate
> > >that no one was injured in this accident.  Feel free to contact me
> > with any
> > >questions about this incident, but I will be away next week.
> > >
> > >- Dave Vandenberg, UCSB Laboratory Safety Manager
> > >
> > >
> > >
> > >This past Sunday evening (7/3/05) an old gas lecture bottle
> > cylinder of
> > >anhydrous hydrogen fluoride spontaneously exploded within a gas
> > cabinet on
> > >the first floor of the Chemistry building.  Thankfully, no one was
> > injured
> > >because no one was in the room, or adjoining spaces.  However,
> > given the
> > >extensive damage to the lab, it is likely that anyone present would
> > have
> > en seriously injured from flying debris and/or HF exposure.  The
> > >explosion also resulted in the building being locked down for about
> > 12
> > >hours by the Fire Department.
> > >
> > >Attached are pictures showing the remains of the lecture bottle and
> > a shelf
> > >about 10 feet away where the heavy-duty window from the gas cabinet
> > can be
> > >seen after it was hurled.
> > >
> > >Anhydrous hydrogen fluoride in carbon steel cylinders may react
> > slowly over
> > >years with the iron in the steel to form iron fluoride and
> > hydrogen.  The
> > >hydrogen pressure can ultimately build to the point where it
> > ruptures the
> > >cylinder.  This is discussed more fully on the bottom of pg. 5 of
> > this MSDS
> > >from Air Products:
> > >
> > >http://www.airproducts.com/MSDS/searchresults.asp
> > >
> > >Given this potentially serious hazard, WE ASK THAT EACH RESEARCH
> > GROUP
> > >VERIFY WHETHER THEY HAVE ANY GASEOUS HYDROGEN FLUORIDE IN STOCK.
> > If some
> > >is  on hand, please do not move it, but inform EH&S at x-4899
> > (after Friday
> > >call x-3293). Each cylinder will be evaluated individually as to
> > it's
> > >condition and ultimate fate.
> > >
> > >Thanks for your cooperation.
> > >
> > >
> > >
> > >----------------------
> > >David Vandenberg
> > >Laboratory Safety Specialist
> > >UCSB Env. Health & Safety
> > >(805) 893-4899
> > >David.Vandenberg**At_Symbol_Here**ehs.ucsb.edu
> > >--- End Forwarded Message ---
> > >
> > >
> > >----------------------
> > >Kevin Kaboli, MA, MS, CIH
> > >Industrial Hygiene Program Manager
> > >University of California
> > >Santa Barbara, CA 93106
> > >Kevin.Kaboli**At_Symbol_Here**ehs.ucsb.edu
> > >(805)893-8787
> > >(805)893-8659 FAX
> > >
> > >
> > >
> >
> >
>

--
Joseph R Passante, CIH, CHO
Industrial Hygiene Manager
Environmental Health & Radiation Safety
University of Pennsylvania
215.746-6550
215-898-0140 (F)
215-651-0554 (M)

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