Jan 22, Washington, D.C.- The US Chemical Safety Board has published a draft investigation report, inviting comments from the public, regarding the August 2012 Chevron’s Richmond, California refinery pipeline rupture and resultant vapor cloud fire.
Incident Summary:
On August 6, 2012, the Chevron U.S.A. Inc. Refinery in Richmond, California (“the Chevron Richmond Refinery”) experienced a catastrophic pipe rupture in the #4 Crude Unit. The incident occurred from piping referred to as the “4-sidecut” stream, one of several process streams exiting the refinery’s C-1100 Crude Unit Atmospheric Column.The pipe rupture occurred on a 52-inch long component of the 4-sidecut 8-inch line (the 52-inch component). At the time of the incident, light gas oil was flowing through the 8-inch line at a rate of approximately 10,800 barrels per day (bpd).
The ruptured pipe released flammable, high temperature light gas oil, which then partially vaporized into a large, opaque vapor cloud that engulfed 19 Chevron U.S.A. Inc. (Chevron) employees. At 6:33 p.m.,approximately two minutes following the release, the released process fluid ignited.
Eighteen of the employees safely escaped from the vapor cloud just before ignition; one employee, a Chevron refinery
firefighter, was inside a fire engine that was caught within the fireball when the process fluid ignited. Because he was wearing full-body fire-fighting protective equipment, he was able to make his way through the flames to safety. Six Chevron employees suffered minor injuries during the incident and subsequent emergency response efforts.The release, ignition, and subsequent burning of the hydrocarbon process fluid resulted in a large plume of vapor, particulates, and black smoke, which traveled across the surrounding area. This chain of events resulted in a Community Warning System (CWS) Level 3 alert, and a shelter-in-place advisory (SIP) was issued at 6:38 p.m.for the cities of Richmond, San Pablo, and North Richmond. It was lifted later that night, at 11:12 p.m., after the fire was fully under control. In the weeks following the incident, approximately 15,000 people from the surrounding communities sought medical treatment at nearby medical facilities for ailments including breathing problems, chest pain, shortness of breath, sore throat, and headaches. Approximately 20 of these people were admitted to local hospitals as inpatients for treatment.
CSB’s interim report
After extensive investigations, the US Chemical Safety Board (CSB) released an interim investigative and recommendation report in April 2013.The report issued recommendations to Chevron; the city of Richmond, California; Contra Costa County, California; the State of California; the California Air Quality Management Divisions; the California Environmental Protection Agency; and the U.S. Environmental Protection Agency.
The main thrust of the recommendation was to carry out an extensive Process Hazard Analysis (PHA) that identifies potential process damage mechanisms and consequences of failure and ensures safeguards are in place to control hazards presented by those damage mechanisms. The end goal is to drive the risk of major accidents to As Low As Eeasonably Practicable (ALARP).
Note: For an excellent understanding of PHA, ALARP and other concepts, please refer to Abhisam’s excellent e-learning courses on HAZOP and SIS.
Key Findings on the report
1. The rupture of the 4-sidecut piping resulted from the 52-inch component being extremely thin due to a damage mechanism known as sulfidation corrosion. Sulfidation corrosion, also known as sulfidic corrosion,is a damage mechanism that causes thinning in iron-containing materials, such as steel, due to the reaction between sulfur compounds and iron at temperatures ranging from 450°F to 1,000°F. This damage mechanism causes pipe walls to gradually thin over time. Crude oil contains varying amount of Sulfur and this results in the sulfidation corrosion. This may be common to many refineries across the US as many of these were built prior to 1985 when Carbon Steel piping used was of a specification that does not take into account this risk of corrosion by sulfidation.
The damage due to such corrosion can only be ascertained by proper inspection.
2. Chevron did not effectively implement internal recommendations to help prevent pipe failures due to sulfidation corrosion. In the 10 years prior to the incident, a small number of Chevron personnel with knowledge and understanding of sulfidation corrosion recommended on several occasions either a one-time inspection of every component within the 4-sidecut piping circuit—known as 100 percent component inspection—or an upgrade of the material of construction of the 4-sidecut piping. The recommendations were not implemented effectively, and the 52-inch component remained in service until it failed on August 6, 2012. An independent corporate entity within Chevron, the Chevron Energy Technology Company (ETC), provides technology solutions and technical expertise for Chevron operations worldwide. Chevron ETC metallurgists released within Chevron a formal report dated September 30, 2009 (nearly 3 years before the incident), titled Updated Inspection Strategies for Preventing Sulfidation Corrosion Failures in Chevron Refineries (ETC Sulfidation Failure Prevention Initiative). The initiative specifically recommends that inspectors perform 100 percent component inspection on high-temperature carbon steel piping susceptible to sulfidation corrosion. However Chevron’s team in charge at the refinery for turnarounds did not implement their recommendation.
3. On the day of the incident, Chevron had no leak response guidance or formal protocol for operations personnel, refinery management, emergency responders, or the Incident Commander to refer to when determining how to handle a process leak. Without a protocol, Chevron had no formal system to ensure the right people were gathering all important information before deciding on leak mitigation strategies. Such an evaluation could have led to the conclusion that the cause of the leak was general thinning due to sulfidation corrosion, and clamping the pipe—a mitigation strategy being considered—was not a viable solution because the pipe likely did not have the
structural integrity to support a clamp. This realization likely would have resulted in deciding to immediately shut down the unit. Following this incident, Chevron improved its internal policies by developing and implementing a leak response protocol for determining how to assess and mitigate leaks within the refinery.
The entire report can be downloaded here.