Date: Wed, 20 Jan 2010 12:24:17 -0800
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: Rebecca R Lally <rrlally**At_Symbol_Here**UCI.EDU>
Subject: Re: Flammable gas in a quartz tube/electric furnace assembly
In-Reply-To: <8EDCBF65F98F1C40BCC235C034B3ED3704D7A1BA7C**At_Symbol_Here**capsm01.CAPSD.USC.EDU>


Alfred, We have a couple of researchers performing similar operations. I required the researchers to perform a hazop analysis of the entire operation including piping and instrumentation diagrams, emergency shut down procedures, required the use of non- combustible tubing and the use of process flow controllers. The researcher needs to calculate the purging time to evacuate the quartz tube of ambient air at the beginning of the experiment and at the end of the testing using inert gas to ensure you never reach the LEL at the exhaust. The researcher also needs to set up a cooling coil or jacket at the end of the tube to lower the temperature below the auto-ignition temperature. I also required the researcher to perform a dry run of the experiment to verify his mass flow calculations. Our cleanroom staff also installed a lexan shield. These are just the highlights of what we went through. Our failure hazard analysis was several pages long and the SOP re-written several times. Hope this helps. Rebecca Lally, CIH Chemical Hygiene Officer UC Irvine EH&S > 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 (~18"h x 24"d 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 lab's 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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