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S&WB turbine explosion likely caused by human error, analysis finds

S&WB told the City Council's public works committee in 2020 that the explosion was caused by a mechanical failure and they were not at fault.

NEW ORLEANS — The December 2019 explosion that knocked out a major source of electricity for the city’s drainage pumps was likely caused by operator error, according to a consultant’s incident report, contradicting the explanation given by the Sewerage & Water Board last year as it sought insurance money for turbine repairs.

A causal analysis by consultant ABS Group says the exhaust stack exploded on Turbine 5, a large gas-fired generator at the Sewerage & Water Board’s Carrollton Power Plant, because the operator likely opened the primary valve to feed gas into the turbine “late,” after already starting the machine.

“Opening the ¼ turn valve late results in an even larger opening position of the gas pressure ratio valve at the onset of firing,” the report says.

The report says the turbine operator denied opening the valve late. But the report also says the operator’s word was the only thing contradicting its conclusion that the valve was opened later than it should have been.

HJ Bosworth, an engineer with the watchdog group Levees.org, said opening that valve late would have created a rush of gas into the system that likely caused the explosion, which broke windows in nearby homes and could be felt miles away.

“The first valve that they have in the sequence of valves that power the turbine, from what I have read from that report, wasn't open until all of the other valves were busy opening and closing for no good reason,” Bosworth said. “You didn't have any gas in through those other little valves until someone decided, ‘Oh, wait, the main valve may not be open.’”

Bosworth said the ABS report strongly suggests operator error was a cause of the explosion. But that conclusion would appear to contradict a Sewerage & Water Board report to the City Council’s Public Works Committee in August 2020. The S&WB told the council it had been briefed by ABS on its investigation and “we understand that the cause of the explosion was due to a mechanical failure, and SWBNO was not at fault.”

The same S&WB report to the council suggests a no-fault finding would help the agency collect insurance to cover the cost of repairs to Turbine 5, which are currently under way and scheduled for completion in mid-June.

Right after saying the ABS report would show S&WB was not at fault, the agency’s statement to the City Council continued: “Accordingly, we expect to receive insurance proceeds over and above our $1 million deductible to be used in the repair of the turbine.”

WWL-TV asked the S&WB about the apparent contradiction between the ABS report and what the S&WB told the council, but an agency spokeswoman did not respond to that question Tuesday.

On Thursday, City Councilman Joe Giarrusso, head of the council's Public Works Committee that oversees the S&WB and received the ABS report in February, said he asked the council's utility engineer to review the ABS report in response to WWL-TV's investigation.

"According to the (S&WB) operator, all manual operations were conducted properly. However, (S&WB) does not have records on the valve operation prior to or during the event," Giarrusso said. "Without these records, we cannot say that mechanical issues were the only cause. Mechanical issues could have been exacerbated by improper manual operations of the fuel gas supply valve, especially if the valve was opened too late in the sequence."

Crews from the turbine's manufacturer, GE, and S&WB engineers had fully tested and repaired key parts of Turbine 5's ignition system shortly before the explosion, another factor that engineers believe points to human error.

But the S&WB has stood by the operator, whom it hasn’t named, and praised its crew for how it handled the incident. The crew was hurrying to start the gas-fired Turbine 5 on Dec. 14, 2019, because the workhorse steam turbine, Turbine 4, had just tripped off. Two workers, including the operator, were rushed to the hospital after the explosion, although the operator returned to work that same day.

“We are proud of the quick work of our operators in minimizing the potential for more severe injuries when Turbine 5 exploded,” she said. “Given the magnitude of the event, it is clear things could have been much worse.”

The S&WB had not publicly discussed the findings of the ABS report until WWL-TV asked about it Tuesday, just two days before President Joe Biden is scheduled to visit the power plant and see the infrastructure that has so often failed during heavy rains in recent years.

S&WB leaders repeatedly promised to talk about the explosion’s cause while ABS was working on the report last summer. In a letter to the City Council in August, the agency said it was expecting the final ABS report soon and would send it over right away.

The final ABS report is dated in November 2020, but it doesn’t appear to have been transmitted to the City Council until February 2021, when it was sent as an attachment to the agency’s required quarterly report.

Also Tuesday, WWL-TV learned the S&WB did not have a checklist of what operators needed to do to start up Turbine 5, but one was created after the explosion. Agency spokeswoman Courtney Barnes appeared to acknowledge the lack of a checklist for Turbine 5 in response to the station’s questions Tuesday.

“As part of bringing it back online, we are adding a completely new control system to Turbine 5,” Barnes said. “We also have an external team on the ground as we speak, training our employees on how to operate that new system. That training includes the establishment of a standard operating procedure and operational checklist.”

Bosworth said the lack of an operational checklist, especially for a major piece of equipment with manual valves, is inexcusable. But he said the current upgrades to Turbine 5’s control system will make it safer to operate when it comes back online this summer.

“Everybody should have a checklist. We're all human. We all make mistakes,” he said. “And going forward, it's always it's nice to have a computer that checks us as we're doing what we're doing, making sure that we don't make a big bang out of making a mistake.”

UPDATE May 7, 2021: This story was updated with the results of a review of the ABS findings by the City Council's utility engineer, in response WWL-TV's initial story.

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