Hi Jeff,
"Energetically problematic" is certainly a good way to describe these vessels if they are not handled correctly.
As has been noted, Parr Instrument Company (https://www.parrinst.com?) seems to be the leading company regarding these types of "autoclaves" or "bombs" (I too have heard both) or reaction vessels or whatever researchers want to call them. Parr seems quite
committed to safe use of their products and they have a wealth of information on their webpages related to these vessels. Frankly, if I ever were to run across one that was *not* a Parr vessel I would be somewhat suspicious from the get-go. I know researchers
are super intelligent and like home-built solutions and all that, but I'm not sure I'd trust a lab-built reaction vessel that can build serious pressure like these can.
I will also put in a plug for the Northwestern University Office of Research Safety's Vimeo channel, which has many excellent short videos including one about these types of devices at https://vimeo.com/118520958.
I learned of this from a presentation that Markus Schaufele made at CSHEMA (or maybe at a DCHAS event?, I can't remember) so thanks much Markus.
To answer your specific questions:
Does your institution have specific guidance on using these such as limiting the size of reaction chambers?
=Not that I am aware of, however in my travels around MIT MechE I've only seen small ones, I suppose the 100 or 125 mL size?
Do you have minimum engineering controls for containment (blast shielding, etc.)?
=No, but we carefully and I mean carefully review proposed usage of these. In one case, I think we had a total of less than 10 mL of material in one of the 100 mL vessels, due to as you note the necessity for headspace. We make researchers calculate all of
these kinds of things using information from Parr.
Does your institution explicitly prohibit using them?
=No, but as I say we carefully review.
I'll just add one more thing: If one of these vessels were to be put in an oven which is programmed to ramp up to a certain temperature, hold for a certain amount of time, and then ramp down...someone should stay around for a little while after the temperature
ramp starts to make sure the oven operates as programmed. Otherwise the oven might, potentially, just continue ramping up in temperature to, oh, let's say, a temperature above the melting point of Teflon (327 C) which is what some components of these vessels
are made of. If that were to happen there might possibly be a really weird smell in the lab and both a vessel and an oven that are rendered unusable. Not that such a thing would ever happen, of course...just speaking theoretically. "I heard it from a friend."
We were damn lucky in this case that there wasn't an over-pressurization event or a fire, "just" a softening and/or melting of Teflon and the loss of several thousand dollars of research equipment. Actually let's not call it lucky, let's say that because we
had carefully reviewed the operation and performed a hazard assessment with the researcher, the risks of use of the vessel were understood and there was a sufficient "safety factor" built in to the amount of material in the vessel such that an over-pressurization
event didn't occur even though a temperature excursion did. We didn't consider the possibility of a temperature excursion when performing the hazard assessment though...oops. Not unusually, we were so focused on what we all perceived as the "major" hazard
(over pressurization) that we missed another obvious and probably more likely source of an issue (an ancient oven didn't work as anticipated).
Please let me know if you have comments, questions, or concerns about this.
Thanks
Dan
-----------------------------------------------
Daniel C. Herrick, CIH
Senior EHS Coordinator
Department of Mechanical Engineering (MechE)
--including Sloan Auto Lab, MIT SeaGrant, Lab for Manufacturing Productivity
Massachusetts Institute of Technology (MIT)
77 Massachusetts Avenue, room 3-449g
Cambridge, MA 02139
email herrickd**At_Symbol_Here**mit.edu
phone 617-253-2338
web
http://ehs.mit.edu
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> on behalf of Jeffrey Lewin <jclewin**At_Symbol_Here**MTU.EDU>
Sent: Tuesday, August 27, 2019 12:01 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] Hydrothermal and solvothermal reactor safety
I'm looking for any information on the safe operation of hydrothermal and solvothermal reaction chambers. They are sometimes also referred to as "autoclaves" (different than what this biologist thinks of) and "bombs." which might be the best
description having recently viewed pictures of one that catastrophically failed (no injuries, plenty of damage).
From what I can find Googling - they've been around commercially for some time (10 or more years?); I found very little in written SOP's, but the discussion on researc- gate I've seen several comments that if not handled correctly, the results can be energetically
problematic.
So questions for the group:
Does your institution have specific guidance on using these such as limiting the size of reaction chambers?
Do you have minimum engineering controls for containment (blast shielding, etc.)?
Does your institution explicitly prohibit using them?
Two critical administrative controls I've seen are:
1) not overfilling the reaction chamber, allowing headspace for gas formation. For hydrothermal reactions, this seems pretty well established since water expands about 25% at the temperatures these are operating at (190-220C). For solvents, it doesn't
seem to be as straight forward. For example, I've not been able to find an expansion factor for dimethylformamide (DMF).
2) not heating and cooling too fast. The instructions I've seen with reactors say things like don't heat or cool faster than 5C/min. But I've seen instructions that go outside those guidelines (8C/min) and several that say "cool naturally" i.e. not at
5C/min (I've also seen discussions that specifically advise against quenching them).
Any insight would be appreciated.
Jeff
--
Jeff Lewin
Chemical Safety Officer
Research Integrity Office
Laboratory Operations
207 Advanced Technology Development Complex (ATDC)
Michigan Technological University
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