What caused the massive El Segundo explosion? Refinery experts have some theories

The investigation focuses on what caused a massive explosion and fire at Chevron’s El Segundo plant last week, turning into a jet fuel processing unit in the southeast corner of the sprawling refinery.

Chevron officials have said little about what caused the explosion but confirmed that the Isomax unit, which converts oil into high-value products such as jet fuel, remained shut down because of Inferno even as other refinery operations continued.

“Until we can figure out what happened here and make sure it doesn’t happen again, we will not restart,” Chevron spokesman Ross Allen said, adding that the refinery continues to produce jet fuel, gasoline and diesel from other units.

While refinery fires are not yet unheard of – and Chevron has dedicated on-site firefighting teams to prepare for them – industry experts say the sheer scale of last week’s El Segundo Fire raises concerns that something went wrong and requires a thorough investigation. The explosion blasted the night sky bright orange across the South Bay, sending a roar that echoed for miles. No one died in the incident and damage was limited to the refinery’s footprint. Only a handful of workers reported minor injuries.

“I think Chevron is very, very lucky… [given] “The size of the explosion,” said USC engineering professor Najmedin Meshkati.

Meshkati and several other experts who spoke to The Times said that few details had been shared that night by locals or Chevron investigators, but it was still difficult to know exactly what caused the El Segundo fire, but there were likely some culprits.

Andrew Lipow, president of Houston-based consulting firm Lipow Oil Associates, said that in his experience, refinery fires can often be traced to equipment failures, especially those that lead to “a situation that allows hot oil and natural gas to reach the atmosphere.”

“It found an ignition source and created a fire,” Lipow said.

Faisal Khan, director of the Mary Kay O’Connor Process Safety Center in Texas, said errors in the refinery’s oil sensors could lead to a larger system failure that could end in a fire.

Oil sensors (which monitor good conditions and measure pressure, temperature and flow rates) have been used for a long time. However, over the past decade, the technology has evolved to the point where it may become overly reliant on data. That can cause problems when refineries don’t have backup mechanisms to track information or people who can double-check updates, he said.

El Segundo Fire Chief Casey Snow said once a fire like this breaks out, it’s difficult to fight because of how readily available fuel is available from refineries.

Fire departments isolate and extinguish such fires by “controlling valves that can restrict the flow of fuel,” Snow said. It will also use water to limit where active fires can spread.

Neither Chevron nor state investigators have provided details about how the fires became widespread in El Segundo on Thursday and Friday.

Although the destruction was not apparent from outside the refinery, Lipow said significant damage could still have been caused. He said that as long as a fire is large enough to melt high-temperature equipment, it can cause direct fire damage, even if it is unclear to people looking at the refinery from the outside.

“You can start a fire in one part of the refinery … and it spreads because there’s so much heat that it causes the failure of other equipment nearby,” Lipow said.

But even for the size of a fire, huge damage to infrastructure is usually reduced because these refineries are mostly burning fuel.

“Typically, the combustion you see is fuel inside the equipment, not the structure itself,” said Chevron spokesman Allen. “In many cases, firefighters use water to lay out and cool nearby structures to prevent the fire from spreading further. This minimizes additional damage to the facility.”

But downplaying the scope of the fire doesn’t help, said Meshkati, an engineering professor at the University of Southern California.

He said he wanted officials investigating the fire to look for a “convergence of three sets of contributing factors” divided into human-related, organizational and technical factors.

The human factor can be operator error. Organizational factors are problems stemming from company decisions, such as not providing adequate training or staffing; technical factors are equipment failures, such as corrosion, he said. In a 2015 explosion at what was then Model X Mobil Corp.’s Torrance refinery, federal investigators found a combination of organizational and technical problems caused the major explosion.

“We need to look at each of these three sets of factors and then see how those factors interact,” Meshkati said.

Meshkati’s main concern is that the investigation into the fire may not be as thorough and rigorous as it could be, especially if the US Chemical Safety and Hazard Investigation Board is not fully funded or staffed, which is the case – a situation that worries some locals and environmental groups.

“We haven’t heard or seen anything from the Chemical Safety Board, which is the lead accident investigator at U.S. refineries,” Meshkati said. “I think it’s kind of weird.”

The federal government is shut down, and The New York Times’ inquiries to the Federal Chemistry Council received automatic and thorough responses. The Trump administration has also proposed budget cuts to give back to the board.

But a number of other investigations into the blaze are already underway. Chevron officials said the company is looking into its own investigation and the South Coast Air Quality Management District will look into potential violations of air quality rules and permit conditions.

The California Department of Industrial Relations, which includes the CAL/OSHA Process Safety Management Division, also investigated the refinery fire and conducted a thorough investigation to determine the cause of the incident and whether any state safety standards were violated.

It’s unclear when the findings will be ready, but Chevron must submit a report to the air quality district within 30 days analyzing potential causes and equipment failures.

Allen, the Chevron spokesman, did not respond to questions about the role of the Federal Chemistry Council or a timeline for the outcome of Chevron’s investigation.

Local authorities reported no injuries following the explosion. But as of Tuesday, four workers claimed they were harmed in the incident, according to a lawsuit filed in Texas. One of their lawyers, Victoria Alford, said they were injured while fleeing the massive explosion, describing the plant workers’ physical injuries as “orthopedic in nature” and saying they also suffered from anxiety.