Corning hot plates are generally work very well. These fires may be associated with improper use or could be due to solvent/chemical exposures (vapors). Any volatile solvents with high vapor density will descend during heating, when solvent vapors are not condensed using a reflux condenser. Also, in case the hot plate thermostat is corroded that can also create a spark inside the plate. Hot plates should be removed from electrical receptacles once experiment is over, at least for the weekend. Just my thoughts!
Tilak Chandra, Ph.D.
Chemical Safety Specialist
“--our job in safety is to make the task happen, SAFELY; not to interfere with the work…” Neal Langerman
In the past 2 years on our campus we’ve had 1 suspected and 2 confirmed “runaway” hotplate events in chemistry labs (2 resulting in fires). In our case, each device was a model manufactured by Corning (PC320 or PC420-D). (We have not seen the same behavior with hotplates manufactured by other companies, but it’s worth noting that the Corning models are popular on our campus, so that could be the reason that the issue was isolated to this manufacturer.)
I am familiar with the April 2015 DCHAS-L thread [subject: Runaway Hot Plates] and the various warnings and studies that are frequently cited on this topic (see bottom of this message for more on that). For those who aren’t familiar with these, quick recap: We’re not the only ones who have noticed this problem.
My question is this: Isn’t it surprising that there was never a safety recall issued (or a law suit for that matter)? Does anyone know if that was ever explored?
We recently did a presentation to our chemistry department about these malfunctions, and I’m starting to get questions from the researchers about recall or class-action suits. The best I can figure is that it’s hard to prove that manufacturer recommendations for care and use of the equipment have been followed to the letter. For instance, a used-and-abused piece of equipment that malfunctions in this manner would probably be considered compromised, right(?) Similarly, if the hotplates are not unplugged when not in use, even though the user manual may recommend that they should be(?), is there really a case that can be made against the manufacturer?
On a related topic, we aren’t asking labs to replace all of their devices, but we do want to recommend a preferred product for higher-risk operations or environments. In reviewing the 2007 UC Santa Cruz study on hotplates (excerpt below) I see that the question of “processor watchdogs” was raised. Does anyone have any additional information about the current state of the design in the popular models (visa vi processor watchdogs)? I know that IKA boasts “redundant processors” and “over-temperature safety controls”, but I haven’t been able to figure out whether this exactly controls for the inherent design flaw described in the report (see excerpt below).
Thanks for any additional information you can lend to this conversation.
Lab Safety Specialist
Environmental Health and Radiation Safety
University of Pennsylvania
3160 Chestnut St., Suite 400
Philadelphia, PA 19104-6287
Hotplate study, April 2007 UC Santa Cruz Excerpt
The current industry standard for hotplate design seems to put all functions under firmware control, and exclude any type of hard power cutoff that would be independent of the processor. The units listed above all have the “power-off” hot-top indicator feature that requires the control circuitry to be powered up at all times. Every one of them is capable of a processor failure leading to thermal runaway. It should be noted that the manuals are currently worded to suggest that the units remained plugged for the user to benefit from the hot-top indicator feature. Corning is currently working on modifying their manual.
It has not yet been determined for all units to what extent processor watchdogs are being utilized, and whether they would be hardware, software, internal, or external in these various units. It is safe to say that none of the Corning units have adequate watchdog protection.
University of California Santa Cruz: Hot Plate [Failure] Study
University of Illinois Division of Research Safety: Warning about Malfunctioning Hot Plates
Lawrence Berkeley National laboratory: Hot Plate Switch Failure
Northwestern University: Safety Issues of Hotplate Heating Controls
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