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Previous by Date: Subject: Re: Flammable gas in a quartz tube/electric furnace assembly Date: Wed, 20 Jan 2010 10:34:25 -0500 Author: Pierre Chantal

Next by Date: Subject: Re: Flammable gas in a quartz tube/electric furnace assembly Date: Wed, 20 Jan 2010 12:24:17 -0800 Author: Rebecca R Lally

I'm curious as to the LEL and UEL of the gas. (Lower & upper explosive limi
t, usu. expressed as % in air). If the gas has a low LEL then purging and/o
r any leaks could be very hazardous. If the UEL is low, then within the fur
nace, the only consideration would be expansion of the gass due to heat and
 degradation/combustion into less complex hydrocarbons. The furnace vent wo
uld have to allow free flow of the gas to potentially keep the furnace from
 overpressurizing, but also have backflow prevention to keep air from comin
g back into the furnace.  Lastly, are there any concerns about the vent: wh
ere the vent is located and where the exhaust goes, is any monitoring requi
red of the gas composition, gas temperature, or personnel exposure, and doe
s the vented gas require regulatory reporting.

I've heard of exhaust vents that essentially created enclosed spaces with h
azardous atmospheres because there was no oversight of where the exhaust we
nt, airflow, etc. - both inside labs, and outside in areas with limited air
flow.

Todd Perkins
Safety Director 
Airgas Mid America
p3wt3r**At_Symbol_Here**charter.net

--- On Wed, 1/20/10, Joseph Passante  wrote:

> From: Joseph Passante 
> Subject: Re: [DCHAS-L] Flammable gas in a quartz tube/electric furnace as
sembly
> To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
> Date: Wednesday, January 20, 2010, 8:18 AM
> What the original poster describes
> is very common. =C2=A0Nanotube are made this way (lab scale)
> =C2=A0and furnaces used to pacify surfaces (such as silicon
> wafers) in fabrication labs. =C2=A0The only difference is
> the flow volumes. =C2=A0Is it CFM or scfm? =C2=A0I've
> never seen flow rates in excess of a 100
> cc/min.
> Hello
> everyone:=C2=A0A
> researcher here plans to continuously flow 100 % flammable
> gas (methane, ethylene, hydrogen, or mixture) at 1 cfm
> through a quartz tube/electric furnace assembly that is
> heated to 800 degrees C (exceeds the auto-ignition
> temperature of the gases). The researcher intends to have
> four (4) of these units (~18="h x 24="d x 60=" w) in
 the
> lab;=C2=A0 at least two units will be active throughout the
> day.=C2=A0The
> discussion centers on where to safely set up and operate
> them. The researcher proposed mounting the units on open
> benchtops (two per benchtop) to accommodate their size and
> facilitate use (the gases would be piped to the units via
> stainless steel tubing from an adjacent gas room). Though
> seemingly practical, I feel this would require considerable
> $$ investment in engineering controls (canopy hood, blast
> shields, etc.) to adequately protect the research staff from
> potential mishaps (gas leaks, explosions). My thought is to
> mount the assembly in the lab=E2=80=99s wet process hood (vertical
> laminar flow) and lower the sash during operation. Though
> not ideal, it would reduce the potential of these mishaps.
> NOTE: There are only two available process hoods in the lab,
> hence, only two assemblies would be up and running (not a
> bad thing in my opinion).=C2=A0 Joseph R. Passante, CIH,
> CHOAssociate DirectorChemical Hygiene
> OfficerEnvironmental Health & Radiation
> SafetyUniversity of
> Pennsylvania215.746.6550
> 
> 
>  
> 

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