Washington, DC, April 18, 2013 – A new metallurgical evaluation of crude unit pipe samples from the Chevron refineries in El Segundo, California, and Richmond, California, shows the same sulfidation corrosion process occurred in both, causing up to 60% wall loss in a pipe sample from the El Segundo Refinery, according to a report issued today by the U.S. Chemical Safety Board (CSB) and the California Division of Occupational Safety and Health (Cal/OSHA).
The piping sample from the Chevron El Segundo Refinery, immediately west of Los Angeles, had lost up to 60% of its wall thickness, from 0.322 inches to 0.12 inches in the thinnest part.
The Richmond Refinery experienced a major process fire on August 6, 2012, after crude unit distillation tower piping failed catastrophically due to sulfidation corrosion and severe pipe thinning. Following its investigation, Cal/OSHA issued 25 citations to Chevron alleging serious and willful violations of the process safety standard. The CSB released a draft interim report on that fire earlier this week, establishing the history of corrosion in the piping and proposing new standards. A public meeting to discuss and consider the report is scheduled for Friday, April 19, at 6:30 p.m. at the Richmond Memorial Auditorium.
The new report was completed this week by Anamet, Inc., an independent materials engineering and laboratory testing company. After the August 6, 2012, fire in Richmond, Chevron voluntarily inspected and upgraded corresponding sections of piping from El Segundo, which has a nearly identical crude unit. The tests compared sections of pipe from the #4-sidecuts in the two crude units. It was the #4-sidecut pipe in Richmond that released a massive quantity of combustible gas-oil and other hydrocarbons in August 2012. No release or incident occurred in El Segundo, and Chevron has since replaced the corroded piping with an upgraded metallurgy that is more resistant to sulfidation corrosion.
The removed pipe from El Segundo was secured and preserved for testing under an order from Cal/OSHA process safety inspectors, who recognized the similarity between the two crude units and sought to determine whether similar corrosion had occurred in El Segundo to what was observed in Richmond. The pipe was later transferred to the Anamet lab in Hayward, California, under a joint testing protocol. Chevron cooperated with the CSB in the testing.
The report’s main conclusion: “Sulfidation corrosion had affected the [Chevron] El Segundo samples to a similar extent as the [Chevron] Richmond samples had been affected.”
The report notes that both refineries processed similar crude oil, leading to sulfidation corrosion in the carbon steel piping used in both facilities, and that silicon content – which aids in corrosion resistance – was low in both cases. Older carbon steel piping, which is common in refineries, can have widely varying levels of protective silicon, a trace constituent that is hard to measure under field conditions.
“Consequently,” the report authors stated, “it is not surprising that the presence of thick sulfide scale on the inside surfaces of the pipe, and generally uniform wall thinning indicate that sulfidation corrosion was active during service of the El Segundo 4-sidecut, and that the general extent of sulfidation corrosion was similar in both systems. The obvious difference between the two 4-sidecut lines was that Richmond suffered more extensive corrosion in one component that resulted in rupture.”
CSB Chairperson Rafael Moure-Eraso said, “This latest metallurgical report confirms the consequences of running high-sulfur crude through low-silicon carbon steel piping over a period of years without using inherently safer materials of construction. The tests underscore the importance of new actions to eliminate this hazard through requiring inherently safer designs and materials, rather than relying on inspections alone to find developing safety problems.”
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov.
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