General Major Incident # 2: Chevron Refinery Fire
On 08/06/2012, an explosion occurred in the Chevron Refinery Fire, located in Richmond, CA.
The incident happened when a small leak was detected by refinery workers. Engineers decided to remove the insulation around the pipe but shortly thereafter, a vapor cloud formed.
The rupture resulted from being extremely thin due to a damage mechanism known as sulfidation corrosion.
Root Cause of Failure:
- 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 caused pipe walls to gradually lose thickness over time.
- Sulfidation corrosion is common in crude oil distillation where naturally occurring sulfur and sulfur compounds found in crude oil feed, such as hydrogen sulfide, react with steel piping and equipment. Process variables that affect corrosion rates include the total sulfur content of the oil, the sulfur species present, the flow conditions, and the system temperature. Virtually all crude oil feeds contain sulfur compounds. Sulfidation corrosion can cause thinning to the point that pipe failure happens when it is not properly monitored and controlled.
- The Chevron Richmond Refinery 4-sidecut piping was constructed of carbon steel, which corrodes at a much faster rate from sulfidation than other typical alternative materials of construction, such as higher chromium-containing steels.
Total loss was of $15 million.
Approximately ± 15,000 people were affected, 20 people were hospitalized, but no serious injuries or deaths was reported. An estimated 600 nearby residents were taken to area hospitals with symptoms of nausea and a metallic taste in their mouths or a burning sensation in their throats.
Black smoke was visible across the bay in San Francisco and Marin County. It took firefighters approximately 5-1/2 hours to contain the blaze.
Was there any missing inspection or reliability practice that has led to incident?
Yes, the below timeline shows that:
2011-Jan: Recommended upgrade and 100% inspection DENIED as did not meet “Framing Document” work request requirements Previous inspection data for the 4-sidecut piping* indicated the piping could safely operate through 2016 (*measurements historically taken on 4-sidecut piping with high silicon fittings, not older pipes)
2011-Oct: Refinery lowered pipe “Alert Thickness” without multi-person review, allowing 4-sidecut line to continue operating
Poor Inspection-Pipes were not properly inspected and measured. Did not account for pipe thinning. Human factor was also key.
How this incident could have been avoided?
Chevron inspectors knew over the years, the wall to the #4-sidecut line had thinned due to sulfidation corrosion and if it was repaired the incident could have been avoided.
What were the main recommendations of the CSB to solve the problem?
- Revise API RP 939-C: Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries to establish minimum requirements for preventing catastrophic rupture of low-silicon carbon steel piping.
- Revise API RP 574: Inspection Practices for Piping System Components (3rd edition) to incorporate as a normative reference API RP 939-C: Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries and to follow the leak response protocol requirements established in API RP 2001: Fire Protection in Refineries.