On July 29, 2022, at 7:45 a.m., an explosion and fire occurred at a facility in Mississippi. The explosion and subsequent fire fatally injured one employee and seriously injured five other employees
The facility separates crude oil condensate (flammable liquid hydrocarbon) from salt water through a series of four tanks. After the crude oil condensate is recovered, the saltwater waste is pumped into a saltwater disposal well. Two of the tanks used in the disposal process were replaced with new tanks shortly before the incident occurred, but two tanks were not replaced.
The company's investigation found that although most of the liquid was removed from the two tanks that were not replaced, some salt water, residual hydrocarbon material, and air remained inside these tanks. At the time of the incident, seven employees were completing the tank replacement work, which included installing an elevated walkway between the tanks and finishing piping and structural connections. While welding piping between the two middle tanks, one of the employees opened a valve to the older tank that contained residual crude condensate material, likely releasing some hydrocarbon vapors into the new piping being welded. The flammable vapor ignited, and flames traveled back into the tank, resulting in an explosion and fire that ejected the top of the tank. In addition, the blast launched and forcefully propelled an adjacent tank approximately 80 feet into the woods
As a result of the explosion and fire, six of the employees were transported and admitted to the hospital, where they received treatment for their burn injuries. One of these employees died at the hospital six days later.
The company's investigation found that no work permits were written for the welding work associated with the tank replacement task. An investigation by the federal Occupational Safety and Health Administration (OSHA) found that the tanks involved in the explosion had not been thoroughly cleaned, which allowed flammable material to remain near the welding activity at the time of the incident.
Probable Cause
Based on the company's and OSHA’s investigations, the CSB determined that the probable cause of the incident was the presence of flammable vapors near a welding activity being performed. Not thoroughly draining, cleaning, and purging the tanks to remove the flammable material before starting construction contributed to the incident. Had the tanks been thoroughly drained, cleaned, and purged prior to the commencement of construction, this incident likely could have been prevented.
Source:csb.gov
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