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CSB investigations involving delayed or deferred preventive maintenance



ExxonMobil Refinery Explosion (Torrance)

Incident Description:On February 18, 2015, an explosion occurred in the ExxonMobil Torrance, California refinery’s Electrostatic Precipitator (ESP), a pollution control device in the fluid catalytic cracking (FCC) unit that removes catalyst particles using charged plates that produce sparks—potential ignition sources—during normal operation. The incident occurred when ExxonMobil was attempting to isolate equipment for maintenance while the unit was in an idled mode of operation; preparations for the maintenance activity caused a pressure deviation that allowed hydrocarbons to backflow through the process and ignite in the ESP. The CSB found that this incident occurred due to weaknesses in the ExxonMobil Torrance refinery’s process safety management system. These weaknesses led to operation of the FCC unit without pre-established safe operating limits and criteria for unit shutdown, reliance on safeguards that could not be verified, the degradation of a safety-critical safeguard, and the re-use of a previous procedure deviation without a sufficient hazard analysis that confirmed that the assumed process conditions were still valid.

Carbide Industries Fire and Explosion

Incident Description:Two workers were killed and two others injured as a result of a fire and explosion that occurred at the Carbide Industries facility located in Louisville, Kentucky, which produces calcium carbide products. Post-incident examination revealed recurring water leaks in multiple zones of the furnace cover. Rather than replacing the furnace cover, the company directed workers to attempt repairs. The investigation found that the company would inject a mixture of oats and commercially available “boiler solder” into the cooling water, in an effort to plug the leaks and keep the aging cover in operation. Water leaks into the furnace interfere with the steady introduction of lime and coke raw materials, through an effect known as “bridging” or “arching”. In a carbide-producing electric arc furnace, this can result in an undesirable and hazardous side reaction between calcium carbide and lime, which produces gas much more rapidly that the normal reaction to produce calcium carbide itself. Industry literature described the phenomenon as early as 1965, and an independent CSB analysis confirmed that operating conditions at Carbide on the day of the incident could have resulted in this effect, causing hot materials to be expelled from the furnace. The company continued operating the furnace despite the hazard from ongoing water leaks.  The accident was a case study into the tragic, predictable consequences of running equipment to failure when repeated safety incidents over many years warn of impending failure. When control room windows blew out during previous furnace incidents, the company reinforced them, rather than moving the control room farther from the furnace and investigating why the smaller furnace overpressure events were happening in the first place.

DuPont Corporation Toxic Chemical Releases (Belle)

Incident Description:On January 23, 2008, there was a release of highly toxic phosgene, exposing a veteran operator at the DuPont facility in Belle, West Virginia and resulting in his death one day later. A braided steel hose connected to a one-ton capacity phosgene tank suddenly ruptured, releasing phosgene into the air. The phosgene hose that burst in front of a worker was supposed to be changed out at least once a month, but the hose that failed had been in service for seven months. The CSB found the type of hose involved in the accident was susceptible to corrosion from phosgene.

BP America Refinery Explosion

Incident 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.

Motiva Enterprises Sulfuric Acid Tank Explosion

Incident 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.


 Last updated July 27, 2017

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