The US Chemical Safety Board has determined the cause of an April 2010 explosion and fire at Tesoro’s 120,000-b/d Anacortes, Wash., refinery could have been prevented by the US independent refiner (OGJ Online, Apr. 5, 2010).
The explosion and ensuing fire was caused by damage to the heat exchanger, a mechanism known as “high temperature hydrogen attack” (HTHA), which severely cracked and weakened carbon steel tubing leading to a rupture, according to a CSB draft investigation report released on Jan. 29.
Using sophisticated computer models, the investigation found the industry-wide method used to predict the risk of HTHA damage to be inaccurate, with equipment failures occurring under conditions the deemed to be safe from HTHA.
The report also cites deficiencies in the company’s safety culture that led to a “complacent” attitude toward flammable leaks and occasional fires.
“The accident at Tesoro could have been prevented had the company applied inherent safety principles and used HTHA-resistant construction materials to prevent the heat exchanger cracking,” CSB Chairman Rafael Moure-Eraso said, adding that this accident is very similar to the one that occurred at the Chevron Corp.’s 257,000-b/d Richmond, Calif., refinery in August 2012, where corrosion of piping went undetected for decades until it ruptured (OGJ Online, Dec. 17, 2013; Aug. 13, 2012; Aug. 7, 2012).
“The report is a clarion call for refinery safety reform,” Moure-Eraso said.
The draft report, which makes far-reaching recommendations to the US Environmental Protection Agency and the state of Washington to heighten regulatory standards for refinery safety, will be available for public comment until Mar. 16.
The draft report, following the public comment period, will be subject to a vote of approval by the CSB later in the year.