A report from the U.S. Chemical Safety Board (CSB) says a large explosion at Carbide Industries (CI) in Louisville, KY, that killed two workers and injured two others resulted from a failure by the company to investigate similar but smaller explosions over many years.
The CSB investigation also says the company deferred crucial maintenance of the large electric arc furnace that blew up.
“This accident is literally a case study into the tragic, predictable consequences of running equipment to failure even when repeated safety incidents over many years warn of impending failure,” said CSB chairperson Rafael Moure-Eraso. “When control room windows blew out during previous furnace incidents, the company merely reinforced them rather than … investigating why the smaller furnace overpressure events were happening in the first place.”
The CSB called this incident an example of “normalization of deviance,” in which abnormal events become acceptable in everyday operations. Investigators found furnace incidents were so common that workers took them as normal.
The report said hot liquid from the furnace eroded its cover, eventually melting holes in it. Instead of replacing the furnace cover, CI directed workers to attempt repairs. The company issued 26 work orders to repair the cover in the five months before the explosion. CI continued operating the furnace even though it planned to replace the cover in May 2011 — two months after the explosion occurred.
The particular problems experience by CI’s furnace weren’t unique. The CSB report says industry literature described similar situations as early as 1965.
The CSB lead investigator said something else that would have prevented this incident and the deaths was the application of elements of a process safety management program, such as hazard analysis, incident investigation and mechanical integrity.
In a statement, Carbide said it has addressed all the recommendations made by the CSB and additional safeguards and policies have been implemented.