Washington, DC, February 13, 2013 - The U.S. Chemical Safety and Hazard Investigation Board (CSB) and the California Division of Occupational Safety and Health (Cal/OSHA) today released a technical evaluation report on piping samples taken from the Chevron Refinery in Richmond, California, where a hydrocarbon release and massive fire occurred on August 6, 2012. Cal/OSHA participated in this technical evaluation as part of its enforcement investigation.
The report, prepared by Anamet, Inc., a metallurgical laboratory in Hayward, California, concludes that the 8-inch steel pipe, from a section designated as 4-sidecut which was installed in 1976, ruptured due to severe sulfidation corrosion, and that tested pipe samples showed a very low concentration of corrosion-inhibiting silicon.
CSB Chairperson Rafael Moure-Eraso said, “The report, resulting from a cooperative effort between the CSB, Cal/OSHA, the United Steelworkers (USW), and Chevron provides a solid, technical basis for the firm conclusion that the pipe corroded over time from sulfidation corrosion. We hope this report receives widespread attention throughout the petrochemical industry as a precaution to all refiners to carefully examine potential corrosion mechanisms and use the safest possible materials of construction to avoid failures. Refineries and other plants must incorporate strong mechanical integrity and inherently safer strategies in their process safety management programs.”
The Anamet report provides the following conclusions:
1. Rupture of the 8-inch 4-sidecut resulted from wall thinning caused by sulfidation corrosion.
2. Post rupture corrosion destroyed fracture morphology that could have indicated the rupture initiation site. However, rupture likely originated in the thinnest region and initially followed a longitudinal path driven by the hoop stress. Consequently, an area of likely rupture initiation was identified.
3. The wall thickness of the ruptured section was less than all the other sections of the 8-inch 4-sidecut that were evaluated.
4. Chemical analysis showed the silicon concentration of the ruptured section was 0.01-wt%.
5. Six of twelve specimens (50%) from unique sections of the 8-inch 4-sidecut, 12-inch 4-sidecut, and 2011 12-inch samples were found by chemical analysis to have a silicon concentration of less than 0.1-wt%.
6. Deformation of a small region of the 8-inch 4-sidecut rupture edge was consistent with mechanical force applied from the outside surface of the pipe, possibly from a fire pike, such as samples E-099 and E-082-2, or other pointed object. This deformed region was located within the area of likely rupture initiation.
Cal/OSHA has already issued 25 citations and civil penalties of $963,000. Chevron has announced it will appeal these citations.
Article Source: http://www.csb.gov/newsroom/detail.aspx?nid=457
Publication Date: 13 Feb 2013