Federal investigators are looking at corrosion of an old pipe as the possible cause of a near-catastrophic fire at the Chevron Refinery last week in California.
Toni Hanna / richmondconfidential.org
|About a dozen workers were engulfed in a large vapor cloud that ignited just after they escaped at the Chevron Refinery.|
“A large number of workers were engulfed” in a vapor cloud just before it ignited Aug. 6, causing a series of explosions and a massive blaze that forced tens of thousands of area residents to shelter in their homes with the windows and doors closed.
No plant workers were killed, but more than 900 community residents sought emergency medical treatment for various effects of the fire. Plumes of smoke were visible for miles around the refinery in Richmond, CA, 10 miles northeast of San Francisco.
The blasts followed the leak of a combustible hydrocarbon liquid known as “gas oil” from an eight-inch pipe connected to a crude-oil distillation tower in the refinery’s crude unit.
Workers noticed the leak and were attempting repairs on piping connected to the still-operating tower when the leak suddenly intensified, reported the U.S. Chemical Safety Board, which is investigating the accident.
“Due to the high temperature of the material in the tower, in excess of 600 degrees Fahrenheit, the gas oil immediately formed a large flammable vapor cloud” that ignited shortly after the dozen or so workers fled.
|Tens of thousands of area residents were ordered to stay in their homes with the windows and doors closed after the series of blasts northeast of San Francisco.|
“Witness testimony collected by CSB investigators indicates that a large number of workers were engulfed in the vapor cloud,” said CSB Team Lead Dan Tillema, P.E. “These workers might have been killed or severely injured, had they not escaped the cloud as the release rate escalated and the cloud ignited.”
Seven CSB investigators arrived at the refinery Aug. 8 and have been interviewing witnesses and reviewing documents at the site. CSB structural and industrial safety experts were to arrive Monday (Aug. 13) to prepare the site for safe entry by investigators.
“Monday’s fire was a near-disaster for refinery personnel,” said Dr. Rafael Moure-Eraso, CSB Chairperson. “The circumstances warrant a full and independent federal investigation to determine the root causes.
“Although fortunately no workers were killed, the overall impact of the incident ranks it as among the most serious U.S. refinery incidents in recent years.”
Focus on Pipe Failure
Tillema said important issues in the investigation included understanding why the pipe that later failed was kept in service during a late 2011 maintenance turnaround.
CSB inspectors told the Associated Press that an old pipe connected to the one that failed was replaced after the November 2011 inspection. However, the decades-old pipe that failed was not replaced.
CSB inspectors said they have not yet seen testing records for the pipe that failed but believe corrosion is a strong possible cause of its failure, given its age and the condition of pipes connected to it, the AP reported.
Tillema said the Safety Board anticipated executing a site preservation and evidence testing agreement with Chevron and other investigative groups and arranging for independent testing of the leaking section of pipe to determine the failure mechanism.
The board also wants to examine what procedures and industry practices exist for responding to a leak of combustible material from a running unit.
Chevron will not comment on the leaking pipe but says it is cooperating in the investigation, which also includes Cal/OSHA, Contra Costa County, the U.S. Environmental Protection Agency, and other investigative groups are fully cooperating.
The refinery is still operating at a reduced capacity. Only the equipment that had been involved in the fire remains shut down.