On May 20, a 12-inch overhead pipe ruptured in the refinery's hydrotreater, a unit that uses hydrogen to remove sulfur from a hydrocarbon feedstock. The rupture of the pipe caused a loud boom and began releasing flammable gaseous hydrocarbons at a temperature high enough to cause spontaneous ignition.
No one was injured by the explosion or in the subsequent fire.
After completing its 2-day assessment of the incident, CSB said that the fire destroyed two fan-type heat exchangers and an approximately 50-foot section of piping. The electrical conduit also was damaged by radiant heat.
According to the CSB, however, no blast damage was observed.
CSB lead investigator John Vordebrueggen said Valero personnel have cooperated fully with the investigation team.
"Valero has assembled an incident investigation team to identify the proximate causes and more importantly, any management system deficiencies that contributed to the incident," Vordebrueggen said. "Valero management has committed to sharing the recommended corrective actions and program improvement throughout the company's global refining operations."
Although CSB board member Gary Visscher cautioned that the cause of the pipe rupture has not been determined, he did noted that there have been a number of past cases of corrosion-related failures in refinery hydrotreater units.
"While this incident fortunately caused no injuries, it is important to carefully maintain the integrity of piping that contains hazardous substances through rigorous inspection and testing," he said.