| About This Archive | | DCHAS-L 2022 Index | | DCHAS-L Yearly Index | |
Check out Safety Emporium for your N95, N99, and face shield needs.
|
Previous by Date: Subject: [DCHAS-L] Chemical Safety headlines (8 articles) Date: Wednesday, March 30, 2022 at 6:46:47 AM Author: Ralph Stuart <membership**At_Symbol_Here**DCHAS.ORG> |
Next by Date: Subject: [DCHAS-L] CHAS Journal Club report now available Date: Wed, 30 Mar 2022 18:09:02 -0400 Author: Ralph Stuart |
Rare, yes. The closest I have seen (after the fact) was a deflagration of a Teflon stir bar in NaK - Teflon was gone, leaving a bit of soot and a bare ALNICO rod (the flask seemed OK). Next closest was when a janitor rolled a wheeled stool onto the right side of a glove-box foot switch - both gloves inflated until they were each bigger than the glove-box (a VAC single). [like an inflatable parade balloon]. I also saw the aftermath of a glove-box implosion (I was told the gloves pushed in until they completely filled the interior, blacking out the windows, and then popped).
So many questions here:
The injuries suggest the researcher was hit in the left side of the head/neck by a chunk of something moving fast - piece of glove-box window, glove, or glove port, or something blown off of an intervening bench? Would love to see pictures of the aftermath.
How big was the e-chem cell?
Was it made of glass?
Were the gases mixed in the cell?
Were the gases vented into the glove-box?
What were the gas flows?
Were the H2 and O2 saturated with water before entering the cell?
What was the catalyst? (Many carbon supported metals will ignite H2/O2 mixtures if allowed to dry - platinum, palladium, iridium, rhodium, etc.)
Were the electrical appliances used in the glove-box explosion proof (very unlikely, in my experience - stir plates, overhead stirrers, freezer controls etc., are all possible ignition sources).
Did the glove box have an atmospheric recirculator and oxygen scrubber (typically copper on alumina - another possible ignition source for H2/O2)?
What was the N2 flow through the glove-box?
How were the H2 and O2 flows regulated?
Were the H2 and O2 tank valves checked afterwards?
Were the H2 and O2 regulators set to zero pressure during the shut-down?
Were the regulators equipped with exit valves? If so, were they shut?
Were the H2, O2 and N2 tank pressures checked after (i.e. did the H2 and O2 tanks run empty, even though they were "closed")?
Was the glove-box distorted by the explosion (i.e. did the explosion occur in the e-chem cell, or the glove-box itself)?
Had to be at least a few screw-ups to get the final result. A guess would be that the cell was vented into the glove-box, the flow of H2 and O2 exceeded that of the nitrogen flush (maybe the nitrogen source ran dry), the tanks were not fully closed (cylinder valves are often very stiff), the regulators were not set to zero pressure (or leaked through the regulating valve seat), the regulator outlets were not closed (if there were any to begin with) and the gases were not pre-saturated with water. This would allow explosive levels of H2 and O2 to build up in the box and let the liquid level in the cell drop until the catalyst was exposed to the head space causing ignition.
For working with very hazardous (explosive and/or toxic) gases in industry, the standard is "double block and bleed" - when you want to positively prevent the gas from flowing to the process, you shut two valves and vent the space in between the valves. I have used this for hydrogen and ethylene oxide feeds.
Any idea where this occurred? I googled "glove-box explosion 2022-02-17" and came up empty. Kind of reminds me of the explosion a few years ago (in Hawaii?) where a H2/O2 mix tank (with non-explosion proof instruments) feeding an experiment detonated and took the researcher's arm off: https://cen.acs.org/articles/94/web/2016/04/Spark-pressure-gauge-caused-University.html .
On Mar 28, 2022, at 4:17 PM, James Kaufman <jkaufman**At_Symbol_Here**LABSAFETYINSTITUTE.ORG> wrote:--- For more information about the DCHAS-L e-mail list, contact the Divisional membership chair at membership**At_Symbol_Here**dchas.org Follow us on Twitter **At_Symbol_Here**acsdchasLSI has no additional information at this time.Can anyone add to the account? ... Jim
Accident Date: 2022-02-17
Injuries? A researcher (with ca. 8 years of research experience) was injured. She was not working on the experiment at the moment of the explosion but she was standing close to the glove box where the explosion occurred. Injuries include: some wounds on her face/neck, a tooth avulsion and the mobility of other 7 teeth, the fracture of the left lamina of the 6th cervical vertebra, maxillary sinus fracture. The researcher was taken to the ER and hospitalized for one week. Surgical intervention was provided the night of the accident to close the wounds and clean them (several tiny glass pieces were all over her face and hair and clothes). Luckily the wound on the neck did not impact the blood vessels, vocal cords and trachea. Also the researcher was wearing her personal eyeglasses, which probably protected her eyes. She is fine now, still wearing a neck brace (the prognosis was 45 days). Provisional splinting was applied to mobile teeth, while an implant will be necessary to replace the avulsed tooth.
The injured researcher is also the author of this report.
Accident Description: The researcher was conducting an experiment to test the activity of a catalyst for the oxygen reduction reaction (for application in fuel cells). The catalyst is composed mainly of carbon and some metal traces and it is deposited as a thin film on the tip of a rotating ring disk electrode. The electrode is immersed in an electrochemical cell together with other two electrodes. The cell contained an aqueous solution 0.1 M KOH. Since the goal of the exp was to evaluate the durability of the catalyst, the test was supposed to last for a few days, therefore the exp was conducted inside a glove box (called in the lab "wet box" because the use of solvents and water was permitted inside it, differently from traditional dry boxes). The electrodes were connected through cables to a potentiostat located outside the box. Inside the box there was also a magnetic stirrer that was on all the time, mixing some closed vials containing (non flammable) solutions of another student in the group. The glove box is under constant N2 flow. The researcher started the experiment in the morning. The first step implies the use of hydrogen gas that was delivered from a cylinder in the room to the electrochemical cell. The solution in the electrochemical cell is saturated with H2 to measure the potential of the reference electrode. The second step implies the use of O2 gas: the solution in the cell is saturated with O2 and the activity of the catalyst is measured. The researcher completed these steps in the morning, noticing though a noisy electrochemical signal in O2 and a measured potential of the reference electrode that was 40-50 mV off her expectations. She shared what she noticed with other people in the group. Since she had also to help a student with another experiment, she stopped her experiment at around 11 am (H2 and O2 cylinders were both closed and only N2 was flowing in the box) with the intention of restarting in the early afternoon. After lunch at around 1.30 pm she was close to the wet box trying to decide how to proceed, when an explosion occurred inside the box. The researcher has no memories of the moment of the explosion and she was alone in the room at that moment. The first memory is immediately after the explosion: she was a bit farther from the box, but still standing, she realized that there was blood running on her face and that she was alone, but in that moment a student of the group entered so she asked to call the ambulance and walked to the nearby small office to sit down on a chair where she remained until doctors arrived. She always remained conscious. Her colleagues didn't call immediately the ambulance because they first try to reach by phone the professor and older group members. A technician of the department called the ambulance.
An investigation is still open, so the precise causes are not yet officially defined. However, such an explosion is likely caused by the presence of hydrogen and oxygen inside the box. It is unclear why the gases remained inside the box for hours and what was the ignition source.PS. LSI now has virtual lab inspections, safety program evaluations, document reviews, plus courses and seminars ... all virtual
James A. Kaufman, PhDFounder/President EmeritusThe Laboratory Safety Institute (LSI)A Nonprofit Educational Organization for Safety in Science, Industry, and Education192 Worcester Street, Natick, MA 01760-2252(O) 508-647-1900 (F) 508-647-0062 (C) 508-574-6264 Skype: labsafe; 508-401-7406jkaufman**At_Symbol_Here**labsafety.org www.labsafety.org Teach, Learn, and Practice Science Safely
Previous post | Top of Page | Next post