http://pubs.acs.org/cen/news/84/i43/8443plantsafety.htmlA piping mix-up during reassembly following routine maintenance was the cause of a $30 million explosion last year at the BP refinery in Texas City, Texas, concludes the U.S. Chemical Safety & Hazard Investigation Board in a safety bulletin released on Oct. 15.
The bulletin was based on an accident that occurred on July 28, 2005. The board found that a carbon-steel, 8-inch-diameter elbow had inadvertently been installed in a high-pressure, high-temperature hydrogen line during a repair. In all, three similarly appearing elbows had been removed during maintenance. Three months after the repair was completed, the carbon-steel elbow blew, and the released hydrogen ignited in a fireball that burned for two hours.
The maintenance contractor had accidentally installed the carbon-steel elbow instead of one made from a more resistant alloy steel during scheduled maintenance at the plant's "resid hydrotreater unit," the board says. The board notes that contractor JV Industrial Cos. conducted the repairs and adds that BP had not informed the contractor that the pipe elbows were not interchangeable....
...The July accident resulted in no fatalities and one minor injury. However, it occurred only four months after a fire and explosion killed 15 workers and injured 180 at the same refinery, which is the U.S.'s third largest. Consequently, the board urges BP to examine the "safety culture" at all its North American refineries.
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Steel metallurgists will tell you that high-pressure hydrogen cause embrittlement in carbon steels.