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Process Safety Management Investigations

Investigations with findings related to modernization of process safety management



Accident Description

Chevron Refinery Fire

Accident Description:On August 6, 2012, the Chevron U.S.A. Inc. Refinery in Richmond, California, experienced a catastrophic pipe failure in the #4 Crude Unit. The incident occurred from the piping referred to as the “4-sidecut” stream, which was a carbon steel pipe with low silicon concentrations. The pipe ruptured, releasing flammable, hydrocarbon process fluid which partially vaporized into a large vapor cloud. Testing determined that the pipe failed due to thinning caused by sulfidation corrosion, a common damage mechanism in refineries.  Inspection of sufidation corrosion for carbon steel components containing low silicon concentrations is challenging. Rather than switching to an alloy with higher chromium content for high temperature areas susceptible to sulfidation corrosion, Chevron management denied recommendations to replace the 4-sidecut line as data gained primarily from high silicon pipe-fitting components, on which they relied, but did not reflect the corrosion rates of the lower-silicon components of the 4-sidecut piping.

Tesoro Refinery Fatal Explosion and Fire

Accident Description:An explosion and fire led to the fatal injury of seven employees when a nearly forty-year-old heat exchanger catastrophically failed during a maintenance operation at the Tesoro refinery in Anacortes, Washington. The CSB’s investigation found an immediate cause of the tragedy to be long-term, undetected High Temperature Hydrogen Attack (HTHA) of the steel equipment, which led to the vessel rupture. Tesoro, like others in the industry, used published data from the American Petroleum Institute (API), called the Nelson Curves, to predict the susceptibility of the heat exchangers to HTHA damage.  The CSB found these curves unreliable because they use historical experience data concerning HTHA that may not sufficiently reflect actual operating conditions. For example, a CSB computer reconstruction of the process conditions in the exchangers determined that the portion of the carbon steel exchanger that failed likely operated below the applicable Nelson curve—indicating it was “safe.”  The CSB found that recommended practices of the API do not require users to verify actual operating conditions in establishing operation limits of the equipment or to confirm that the materials of construction selection will prevent the damage.  An inspection strategy that relied on design operating conditions rather than verifying actual operating parameters contributed to the accident.  The CSB determined that inspections for such damage are unreliable because the microscopic cracks can be localized and difficult to identify.  The CSB noted that while API has identified high- chromium steels that are highly resistant; these were not installed by Tesoro.

Motiva Enterprises Sulfuric Acid Tank Explosion

Accident Description:On July 17, 2001, an explosion occurred at the Motiva Enterprises refinery in Delaware City, Delaware. A work crew had been repairing a catwalk above a sulfuric acid storage tank farm when a spark from their hot work ignited flammable vapors in one of the tanks. This tank had holes in its roof and shell due to corrosion. The tank collapsed, and one of the contract workers was killed; eight others were injured. The refinery's sulfuric acid tanks had a history of leaks but Motiva took no effective action, even when its own tank inspectors recommended full internal inspections "as soon as possible" in three successive annual reports prior to the explosion. Three weeks before the explosion, an operator submitted a formal Unsafe Condition Report noting holes in two tanks and pointing out that the hose used to blanket the tank with nonflammable carbon dioxide was improperly installed. The CSB found Motiva investigated the Unsafe Condition Report but took no action to correct the deficiencies.

BP Texas City

Accident Description:At approximately 1:20 p.m. on March 23, 2005, a series of explosions occurred at the BP Texas City refinery during the restarting of a hydrocarbon isomerization unit. Fifteen workers were killed and 180 others were injured. The explosions occurred when a distillation tower flooded with hydrocarbons and was overpressurized, causing a geyser-like release from the vent stack.  The investigative team found a number of problems with the facility's preventative maintenance program that were causally related to the March 23 accident. The CSB concluded that BP supervisory personnel were aware of the equipment problems with the level transmitter before the March 23 startup but still had signed off on equipment checks as if they had been done, which the report said reflected the prevalence of production pressures at the refinery.  The day of the incident, a blowdown drum vented highly flammable material directly to the atmosphere. The drum was never connected to a flare since its construction in the 1950s. The previous owner of the refinery, Amoco Corporation, replaced the ISOM unit blowdown drum in 1997 with identical equipment; Amoco refinery safety standards recommended connecting the drum to a flare when such major modifications were undertaken, but this was not done.

Improving Reactive Hazard Management

Accident Description

In August 2000, following its investigation of a serious reactive incident at Morton International, the Board initiated a comprehensive review of reactive hazards nationwide. The purpose of the investigation was to develop recommendations to reduce the number and severity of such incidents.

Donaldson Enterprises, Inc. Fatal Fireworks Disassembly Explosion and Fire

Accident Description

On April 8, an explosion occurred in a fireworks storage facility near Honolulu, Hawaii. According to media reports, the incident occurred in a bunker used to store confiscated fireworks at Donaldson Enterprises, Inc.


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