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The U.S. Chemical Safety Board (CSB) issued a safety bulletin and new safety recommendations on October 15 based on the investigation of the July 28, 2005, hydrogen fire in the resid hydrotreater unit (RHU) at the BP refinery in Texas City, Texas.
(The Safety Bulletin PDF file is also available by clicking on http://www.csb.gov/safety_publications/docs/RHU.pdf)
The fire occurred four months after the explosion in the refinery's isomerization (ISOM) unit that killed 15 workers and injured 180. The July 28 fire caused $30 million in property damage. Weeks later, this accident was also cited in the CSB's urgent recommendation for BP to examine its safety culture at all its North American refineries.
The fire occurred at about 6 p.m. on the evening of July 28 when a piping elbow failed catastrophically and without warning, releasing highly flammable hydrogen gas at high temperature and pressure which immediately ignited. A huge fireball erupted and a fire burned for approximately two hours.
The safety bulletin notes that the piping system for an RHU heat exchanger contained three elbows of identical dimensions and appearance. Two elbows were constructed of alloy steel and were resistant to the effects of high-temperature hydrogen, but the third elbow was made of carbon steel, which is not resistant.
In February 2005, five months prior to the fire, the unit was shut down for routine scheduled maintenance. During the maintenance shut down, the contractor JV Industrial Companies inadvertently switched the positions of the carbon steel elbow with one of the alloy steel elbows, placing a carbon steel elbow on the outlet side of the heat exchanger, where it would be exposed continuously to high-temperature hydrogen. The investigation found that BP had not informed the maintenance contractor that the elbows were not interchangeable.
Lead investigator John B. Vorderbrueggen, PE, said "Merely disassembling and reassembling piping components during maintenance resulted in an unacceptable hazardous system modification. BP should have required positive materials verification of these pipe elbows using an X-ray fluorescence test device. This would have identified the mistake in the reassembly of the identically appearing elbows before the unit was returned to service. The accident would not have occurred."
The fire resulted in a Level 3 community shelter-in-place alert in Texas City. Level 3 is the second highest emergency classification that applies to an incident where the situation is not under control and protective action may be necessary for the surrounding or offsite area. The Board issued several formal safety recommendations. The BP Texas City Refinery was urged to revise its maintenance program to include materials testing or verification of all alloy steel piping components and to inform work crews of material handling precautions. The Board also recommended that JV Industrial Companies update its piping component installation procedures to require material identification for components removed during maintenance to ensure they are reinstalled in the correct locations.
"There are important safety lessons for oil and chemical companies from this incident," said CSB chairman Carolyn W. Merritt. "Positive materials verification of the components in piping systems can avoid simple mix-ups that can have devastating consequences." The bulletin also emphasized what is termed "human factors based design" - that is, designing components so that foreseeable human errors are less likely to occur.
The safety bulletin and recommendations were issued at a news conference in Houston on Sunday, October 15, at 11 a.m. The CSB's investigation of the ISOM unit accident remains ongoing with a final report expected in the first part of 2007. CSB lead investigator Don Holmstrom and his team have been continuing to conduct interviews of top BP executives and gathering additional documentary evidence.
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 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. For more information, visit www.CSB.gov.