EVENT: OIL REFINERY EXPLOSION
DATE: MARCH 23, 2005
For safety inspector Charles Ramirez, March 23 got off to a good start. His team of specialized contractors from Houston-based JE Merit had just polished off a celebratory lunch held on the grounds of BP's massive Texas City, Texas, refinery. The 1200-acre facility processes up to 460,000 barrels of raw crude oil a day, and the contractors had just wrapped up their part in its complicated, nine-week "turnaround," or scheduled maintenance cycle, accident-free. When the lunch hour ended, Ramirez's colleagues returned to their offices in temporary trailers while he left to run a final safety check.
What he didn't realize as he hustled across the yard was that, just 100 ft. behind him, the huge steel isomerization unit was being restarted after two weeks spent offline. The "isom" unit, which boosts the octane level of gasoline, was about to cause the deadliest U.S. refinery disaster in a decade.
The most dangerous time for an oil refinery isn't when it is running, but when it's in transition. During a refinery turnaround, some 30,000 separate procedures are performed. Dozens are required to move volatile contents safely out of and into position when the isom unit is coming back on line.
As workers restarted a component of the unit, abnormal pressure built up in the production tower, and so three relief valves opened to allow highly volatile gasoline components to escape to the 10 x 20-ft. "blowdown" drum. But so much fuel flooded into the drum that its capacity was rapidly exceeded. Liquid and vapor shot straight up the 113-ft. vent stack, into the open air.
Witnesses saw a cloud of vaporizing fuel geyser out of the stack and cascade to the ground. One person reported hearing a desperate call crackle over a handheld radio. "What is this? Stop all hot work! Stop all hot work!"
But too much equipment was running to shut it all down. As vapors were sucked into its engine, an idling pickup at the base of the tower began to rev up, according to witnesses. A worker raced to turn it off, but he was too late. Somewhere in the cloud of fumes, perhaps in the truck's engine, a spark touched off the gas and ignited a firestorm.
HOW A REFINERY WORKS
Refineries separate raw crude oil into its various components, called fractions, by taking advantage of the distinct boiling point of each. The process begins with fractional distillation, when crude oil is heated to about 720 F. Hot liquid and vapors enter a distillation column where the vapors cool as they rise, condensing on collection trays at different heights. These liquids, such as naphtha and kerosene, may then be diverted to other units for further processing. Each fuel is made of a distinct chain of hydrocarbons, and manipulating these molecules produces different petroleum products. Cracking units and cokers break large chains into smaller ones to create medium-weight and heavy fuels. Alkylation units combine short chains, forming mainly aviation gasoline. Isomerization units rearrange the structure of molecules to turn naphtha into high-octane gasoline.
Spring is typically when refineries buzz with maintenance work to prepare for summer's heavy fuel demand, and that morning workers from a variety of contractors were in the vicinity of the isom unit. Across the street, a contractor overhauling a turbine at a cogeneration plant heard a pair of distinct explosions--one quiet, one loud. He instinctively checked for shrapnel. "I looked up, and the sky was clear, so then I looked over at the guys on the scaffolding," he says, referring to men working near the isom unit. "They were just gone."
When a cloud of highly flammable material is ignited, two events occur almost instantaneously, producing two audible blasts. First, an initial flash consumes all available oxygen, creating a giant vacuum. Once the suction brings in fresh oxygen, the combustibles explode into a well-fueled inferno that flings a shock wave in front of it.
At close range, this supercompressed wall of air is actually visible as it rockets outward at more than 1000 ft. per second. Ramirez says he saw it just before it blew him to the ground. But his colleagues would have had no warning before it slammed into the flimsy frames of their trailer offices. Eleven of Ramirez's teammates were killed instantly by the blunt force of the shock wave. A fireball then rolled over the shattered trailers and melted nearby porta-potties.
Investigators now suspect there may have been as many as five separate explosions, in rapid succession--including one directly beneath the trailer Ramirez had just left.
Almost a mile from the explosion, BP retiree Shera Shurley was watching TV in her mobile home when its windows blew in. She ran outside to escape. Standing in her driveway, she looked at the swirling black cloud climbing into the sky. There was no sound, she remembered later, not even a siren.
Texas City's emergency services crews began rolling moments after the isom unit shattered. BP maintains its own fire brigade, and has a mutual response plan with the brigades of the other two Texas City oil refineries, owned by Marathon Ashland Petroleum and Valero. They get plenty of practice: According to Texas City Fire Department chief Gerald Grimm, BP had 30 fire alarms in 2003 and 27 in 2004, although he says this was no more than other plants of a similar size.
Soon 75 local, regional and industrial emergency response units surrounded the site, where walls of water erupted from "monitors"--strategically located water cannons, each capable of hurling up to 1500 gal. per minute. The thwack of rotors could be heard pounding through the thick smoke overhead. First on scene were news choppers, followed by a Life Flight helicopter from Memorial Hermann Hospital in Houston. Just 20 minutes after the accident, the airspace had become so crowded that the Federal Aviation Administration declared a no-fly zone 3000 ft. high and 3 miles wide.
At the end of 1 hour, the fire had been contained, and within 2 it was nearly out. Only then did the tally sink in: 15 dead, over 100 injured. Of the fatalities, more than two-thirds worked for Ramirez's team, and had nothing to do with the unit that exploded.
HOW THE ACCIDENT HAPPENED
According to the Chemical Safety Board, computerized records from the control system equipment indicate pressure inside the production tower (1) rose rapidly from 20 psi to 60 psi. This triggered three pressure-relief valves (2) to open for 6 minutes, discharging enough fuel into the blowdown drum (3) to overwhelm the system. Petroleum could not be recycled back through the refinery (4) quickly enough, forcing liquid and vapors up the 120-ft. stack (5). As fuel settled to the ground, it ignited in a blast strong enough to rip the roof off a benzene storage tank 300 yards away. Investigators discovered that a 6-in. drain leading to the plant sewer (6) had been chained open. Fumes traveling under the refinery may have fueled one of what is believed to have been five explosions.
Texas City knows industrial facilities and their dangers. Often referred to as "Toxic City," it is home to four chemical plants and three refineries. The sprawling BP complex, built in 1934, is the third largest of 149 petroleum refineries nationwide. At night it glows like a forested landscape of steel Christmas trees, strung with flickering safety lights. Since records were kept in 1971, there have been at least nine other accidents at the refinery that injured or killed workers, but the explosion on March 23 was by far the most destructive.
In the weeks following the accident, BP's operations came under intense scrutiny. Blowdown drums are a common feature at refineries, as are towers used to release evaporating gases. Most tower vents, however, include a flare system--a sort of pilot light that ignites potentially hazardous vapors as they funnel out. In 1992, the Occupational Safety and Health Administration (OSHA) mandated that the Texas refinery switch to a flare system. Amoco, which merged with BP in 1998, appealed and OSHA withdrew the request. The refinery continued to use stacks that allowed gases to escape.
Former BP employee Wydell Dixon says she has seen lightning ignite vapors wafting out of the isom stack. Whether a flare would have ultimately prevented the explosion is questionable given the quantity of liquid as well as vapor involved, says Don Holmstrom, an investigator with the U.S. Chemical Safety and Hazard Investigation Board (CSB), but "a flare does provide an extra layer of safety."
The location of the temporary trailers also has been questioned. BP rules allowed trailers within 350 ft. of refining units--at least two were within 150 ft.--provided they receive site-specific analysis. (BP has since mandated trailers be located at least 500 ft. away.) Some other refiners take the additional precaution of requiring nonessential personnel to be evacuated when units like the isom are being brought on line. According to BP spokesman Hugh Depland, BP has no such requirement.
OSHA and CSB are both conducting investigations. According to Holmstrom, the CSB is looking into such factors as whether the fuel was heated too quickly, which may have led to the pressure spike in the tower, and whether all outflow valves had been working properly. An official report isn't expected for up to a year. BP is also conducting an investigation. Says Depland, "It would be inappropriate to comment on an investigation that's ongoing."
Ramirez, who survived the explosion, was left wondering if an evacuation order that might have saved his colleagues was ever passed along. His boss, Eugene White, might have known, but he died when his trailer office was demolished by the shock wave.
A week after the accident, workers wearing a who's who of petro industry caps gathered between shifts in the Texas Tavern. One said a buddy had quit; he'd been having lunch with his wife in a minivan when the plant blew right in front of them. Someone else noted the date: exactly a year since an explosion in another unit at the plant. Soon the bar grew crowded with men drinking longneck Buds and shooting pool. Down the street at the refinery, skeletal cranes, shrouded in fog, continued to pick over the rubble.
Tom Price is a freelance writer.
T.J. Aulds is an editor for the Galveston County Daily News.