Thursday, December 11, 2014

Bonus Process Wednesday: CSB speculation as to DuPont methanethiol deaths

From CSB chairman Rafael Moure-Eraso's written testimony in front of Congress today, the relevant portion on the November DuPont deaths due to methanethiol exposure: 
...DuPont is certainly no “outlier.” In fact, DuPont has long been regarded as one of industry’s leading lights in safety, and it markets its safety programs to other companies. What happened last month, however, was the fifth release incident at a DuPont facility that the CSB has investigated since 2010, and three of these had associated fatalities. While the CSB investigation remains underway in La Porte, some preliminary facts are already emerging. 
The incident occurred following an unplanned shutdown of the methomyl unit due to inadvertent water dilution of a chemical storage tank several days earlier. Efforts were underway to restart the process, but problems occurred including plugged supply piping leading from the methyl mercaptan storage tank.  
As efforts were underway to troubleshoot these problems, it is likely that methyl mercaptan (and possibly other toxic chemicals) inadvertently entered the interconnected process vent system inside the building. The release occurred through a valve that was opened as part of a routine effort to drain liquid from the vent system in order to relieve pressure inside. We found that this vent system had a history of periodic issues with unwanted liquid build-up, and the valve in question was typically drained directly into the work area inside the building, rather than into a closed system.  
In addition, our investigators have found that the building’s ventilation fans were not in service, and that the company did not effectively implement good safety practices requiring personnel to wear appropriate personal protective equipment (PPE) that was present at the facility. Appropriate PPE would include equipment, such as supplied air respirators, for workers performing potentially hazardous tasks inside the building....
Not enough time to do a detailed analysis here, but the fact that MeSH inadvertently entered the vent system seems relevant, as well as the fact that the valve drained into the building. (How can a valve drain? That wording seems odd.) I suspect that the vent system and where it drained was poorly understood and that the amount of MeSH they were dealing with was not understood well, either. 

1 comment:

  1. I think that instead of "...and the valve in question was typically drained directly into the work area inside the building, rather than into a closed system.", the following was intended. "... and the vent system was typically drained through the valve in question directly into the work area inside the building, rather than into a closed system."

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