Date: Tue, 19 Jan 2010 20:11:33 -0500
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Dan Crowl <crowl**At_Symbol_Here**MTU.EDU>
Subject: Re: Flammable gas in a quartz tube/electric furnace assembly
Comments: cc: Alfred Bouziane
In-Reply-To: <8EDCBF65F98F1C40BCC235C034B3ED3704D7A1BA7C**At_Symbol_Here**capsm01.CAPSD.USC.EDU>

I assume that there is no air or oxygen in the gas streams?  Otherwise 
the gases will self-ignite.

You will need to have a system to insure that no air or oxygen is 
present in the streams under all conditions.  On-line gas analysis might 
be necessary.  What procedure will you use to remove the air initially 
from the tubes?  How will you know it is gone?

Also, if the gas leaks out it will mix with air and spontaneously ignite 
since it is above the ait.

Where do the gases come from, how are the gases mixed and where do they go?

I would recommend a complete hazards analysis of the entire system, 
including the location, in order to do this properly.  The operational 
details are just as important as the design.   The hazards analysis 
would need to be reviewed by a team of safety experts. This would 
require a lot of documentation and complete flow diagrams of the process 
and specifications for all equipment.

The days of going into a lab and incrementally building a lab experiment 
are gone.

Dan Crowl
Michigan Tech University

On 1/19/2010 6:16 PM, Alfred Bouziane wrote:
> Hello everyone:
> A 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 (~18h x 24d x 60 w) in the lab; at least
> two units will be active throughout the day.
> The 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 labs 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).
> Here are my questions:
> 1. Has anyone tackled a problem like this in the past? How was it resolved?
> 2. What other safeguards do you recommend?
> I welcome your collective input. Thank you in advance for your help.
> Best regards,
> Alfred M. Bouziane
> Project Manager
> Environmental Health and Safety
> University of Southern California

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