This has been an issue long recognized in industry. The real problem is that almost all modern solid state equipment can fail in any (energized, de-energized, partially energized) position. This is why industry always requires separate high temperature alarms and automatic shut offs on heated equipment. You may want to read this article on the subject:

https://www.linkedin.com/pulse/high-over-temperature-protection-research-environment-richard-palluzi/

NFPA 45 Fire Protection for Laboratories Using Chemicals in the 2019 edition requires this type of shutdown:

11.3.3.4 All heating operations whether attended or unattended shall be provided with an independent high-temperature alarm and an automatic shutdown with manual reset to prevent system failure that can result in fire or explosion.

And lest you think it can't happen to you, look at this public data:

Year Fire
2019 YTD 9
2018 21
2017 35
2016 25

Richard Palluzi
PE, CSP

Pilot plant and laboratory consulting, safety, design,reviews, and training
www.linkedin.com/in/richardppalluzillc/

Richard P Palluzi LLC
72 Summit Drive
Basking Ridge, NJ 07920
rpalluzi**At_Symbol_Here**verizon.net
908-285-3782

-----Original Message-----
From: ACS Division of Chemical Health and Safety On Behalf Of DCHAS Membership Chair
Sent: Monday, March 18, 2019 3:29 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] JCHAS Editor‰??s Spotlight: Catching Up With Runaway Hot Plates

https://dchas.org/2019/03/15/jchas-editors-spotlight-catching-up-with-runaway-hot-plates/

JCHAS Editor‰??s Spotlight: Catching Up With Runaway Hot Plates

The JCHAS Editor‰??s Spotlight for the March / April 2019 issue of the Journal of Chemical Health and Safety is shining on:

Catching up with Runaway Hot Plates, by Joseph M. Pickel, Mark Mathews, and Kimberly Brown

In recent years, there have been numerous reports of ‰??runaway hot plates‰??. This is to say, hot plates that heat uncontrollably regardless of the temperature setting or whether the controls are in the off position. Some of these events have resulted in injuries to laboratory personnel and damage to research facilities. Investigations into the cause of several of these events have determined that failure of a non-mechanical switch, a ‰??triac‰??, in the hot plate can result in the circuit failing open, causing uncontrolled heating. The number of events in recent years has led to greater awareness of the issue; however, in spite of this, devices utilizing this technology continue to be sold and used in research laboratories without additional controls to ensure their safety.

The article can be downloaded from the URL above.

Let me know if you have any questions about this.

- Ralph

Ralph Stuart, CIH, CCHO
membership**At_Symbol_Here**dchas.org

Membership chair
American Chemical Society
Division of Chemical Health and Safety

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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**acsdchas

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