On Wednesday December 18, 2019, the US Chemical Safety Board (CSB) released a factual update into the May 3, 2019, explosion and fire at AB Specialty Silicones facility in Waukegan, Illinois. The factual update provided a comprehensive incident timeline, detailing the events that led up to the massive explosion and fire that fatally injured four workers and seriously injured another.
“This incident didn’t need to happen. Like so many other incidents we have investigated, it was preventable. Safety management systems could have avoided the incident.”
— U.S. Chemical Safety Board Interim Executive Kristen Kulinowski at a press conference Wednesday, December 19, 2019
Interim Executive Dr. Kristen Kulinowski said, “The CSB’s ongoing investigation will establish how a similar incident can be prevented. To date, the agency has determined important details about this tragic explosion that destroyed the facility and took the lives of four workers. Ultimately, we will find the root cause and issue safety recommendations to prevent a similar incident.”
While the CSB’s investigation is ongoing, the 22-page factual update provides details of the incident collected through witness interviews and examination of physical evidence:
At the time of the incident, the facility was manufacturing a product referred to as EM 652, which is AB Specialty Silicone’s trade name for a silicon hydride emulsion that is used as a water repellent. Under certain conditions, both EM 652 and one of the raw materials used to make EM 652, a compound called XL10, have the capability to produce hydrogen gas. Under certain conditions, hydrogen gas is flammable, and can react violently with other chemicals.
On May 3, 2019, AB Specialty Silicones operators were making back-to-back batches of EM 652. AB Specialty Silicones had started the first batch earlier in the week. During the second shift on May 3, the first batch was packaged into storage containers and an operator began production of the second batch.
Around 9:30 p.m., a few minutes before the incident, workers told the CSB that the operator making EM 652 began yelling, apparently concerned and frustrated by a problem developing in the EM 652 process.
This unusual activity captured the attention of a second operator and the Shift Supervisor, who ran over to where the EM 652 was being produced. Our interviews determined that by the time the second operator and the shift supervisor made it to the emulsions area a tank making EM 652 was overflowing with foam. There, the operator told them that he had just added the first two raw materials of the process into the tank, including XL 10.
While the operators and the shift supervisor were talking, the tank made a “very strange sound” and “erupted.” Witnesses described a hot and smoky scene as material overflowed from the tank and spilled onto the floor.
The CSB learned that the Shift Supervisor directed workers to take actions to ventilate the hazy vapor from the building by turning on exhaust fans and opening the garage doors. But before an operator was able to turn on the fans, the building exploded, fatally injuring four people. The force from the explosion was felt up to 20 miles away in neighboring communities and damaged surrounding businesses.
To date, these are the events that the CSB has determined led up to the incident. The investigation team has also documented the scene, finding a number of details which are key to the ongoing analysis:
The instructions to make EM 652 warn of the dangers of the production of hydrogen gas when XL 10 is in contact with acids or bases.
The EM 652 was made in a set of two atmospheric tanks that were loosely sealed. Workers would open the top of these tanks during the production process to, among other things, perform visual observations. These tanks had no engineered system to direct flammable gas, including hydrogen, to a safe location.
The building ventilation system likely caused the flammable gas cloud to mix with air and disperse throughout the building.
Finally, the CSB determined that there were no flammable gas detectors or hydrogen gas detectors with alarms to warn workers of the significant hazard. The generation of gas in the emulsions tank could produce foaming; however, foaming does not normally occur during this portion of the EM 652 process. The placement of the main air mover near the EM 652 process further increased the potential explosion danger from flammable gases generated in the emulsions area.
The CSB is an independent, non-regulatory federal agency whose mission is to drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the president and confirmed by the Senate. CSB investigations looks into all aspects of chemical incidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.
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