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The Baton Rouge Fire Department, hazmat and EMS are on scene of a fire at the ExxonMobil refinery on Scenic Highway, Tuesday, November 22, 2016, in Baton Rouge, La.

Two former contract workers severely burned in a November 2016 explosion at ExxonMobil's Baton Rouge refinery reached a financial settlement Monday with the company and others.

Lawyer Darrel Papillion, who represents one of the men, said the terms of the settlement hammered out in state District Judge Trudy White's courtroom are confidential.

"I'm happy that we were able to secure a recovery for our client, who sustained horrible injuries, and to hold Exxon accountable for the role they played," Papillion said before leaving the 19th Judicial District Courthouse.

Papillion said his client was burned over 38% of his body. He has not returned to work.

Jury selection had been scheduled to begin Monday in a lawsuit filed by the two men, but the settlement with Exxon entities and a scaffolding company made a trial in their case moot.

Papillion said the cases of two other men badly burned in the blast on Nov. 22, 2016, are pending in the courts.

The afternoon explosion in an alkylation unit of the 2,100-acre refinery came after a worker disassembled a malfunctioning valve, according to a 2017 report by the state Department of Environmental Quality. The worker was trying to open a pipe but was unable to use a hand wheel.

When the worker disassembled the valve, it released isobutane, which was ignited by welding equipment about 70 feet away, the report stated. The explosion left four workers with critical burns and two other workers with minor injuries that required first aid treatment.

A federal agency that investigates industrial chemical accidents ruled that the worker was following "accepted practice" in stripping down the malfunctioning valve, the Chemical Safety Board said Wednesday.

But the particular malfunctioning valve the workers were trying to open — unlike roughly 97 percent of pipe valves in the sprawling plant — was a "30-plus-year-old design," which meant pulling it apart "can have catastrophic consequences," the Chemical Safety Board said in a video detailing the fire.

When the operator tried to open the disassembled valve, it "immediately failed and came apart," releasing a cloud of pressurized isobutane, a highly flammable liquefied petroleum gas created during oil refining, according to the video. The cloud ignited when it reached the welding equipment and erupted into a large fireball that severely burned four people — one ExxonMobil employee and three contractors — working in the area.

After the agency's release of the video, ExxonMobil said an internal investigation by the company identified the cause of the incident and the company took "appropriate corrective action."

In the moments before the explosion, workers were trying to open a plug valve in order to put a spare isobutane pump into service, but found the hand wheel and gear box used to open it were not working, the Chemical Safety Board said.

Taking off the gear box to open the valve with a pipe wrench was "an accepted practice in the akylation unit," the board said, and one of the workers unscrewed four bolts that connected the gearbox and its support bracket to the valve body.

"Unknown to the operators, these bolts also secured a critical pressure-containing component of the valve," the board said, something true of only some 3% of valves at the refinery. The other, newer valves are designed in ways that make it "less likely to remove the incorrect bolts."

Once the valve failed and isobutane began rushing out, the two workers warned other employees in the area to flee.

The ExxonMobil refinery was also the scene of a fatal explosion in December 1989 in which two people were killed and several others injured.

Email Joe Gyan Jr. at jgyan@theadvocate.com.