Yesterday, the Chemical Safety Board announced that it was “opening an investigation into the fatal chemical tank implosion at the Nippon Dynawave Packaging paper mill facility in Longview, Washington, that occurred during the early morning hours of May 26.” According to news reports (here and here) a 900,000-gal tank of ‘white liquor’ imploded on Tuesday and released over 500,000-gal of the mixture of sodium hydroxide and sodium sulfide that is used in the kraft paper making process. There have been two confirmed deaths from the release, and nine employees are missing and expected to be dead.
News reports have been using the word ‘implosion’ to describe the incident. If correct, and that is not inherently necessary, that would imply some sort of vacuum in the tank leading to its collapse. From photographs (see here for example) this would appear to be an atmospheric tank (as opposed to a pressurized tank), so relatively weak levels of negative pressure would certainly compromise the integrity of the tank. Still, no vacuum lines would installed on such a tank, and atmospheric venting should prevent vacuum formation during unloading operations.
This incident has not been added to the list of current investigations (would not expect it to be added for a couple of weeks at a minimum). The Board currently lists eight active investigations.
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