HOUSTON—The BP blowout happened miles offshore, but it may have something in common with deadly explosions on land in the Houston area. The connection is being revealed in hearings held by the U.S. Coast Guard and the U.S. Minerals Management Service in Kenner, Louisiana.
Judging from a line of questioning repeated over and over as crew members of the doomed Deepwater Horizon rig testified, federal investigators want to know what role diesel engines may have played in igniting the methane gas that blew up the rig and engulfed it in a deadly inferno.
In a hearing held May 27, an investigator asked, "If you have a runaway scenario what is likely to occur?"
"It’ll just run till it blows up," responded Chad Murray, Transocean’s chief electrician.
Transocean is the company that owned the Deepwater Horizon and rented it to BP.
The testimony was about a phenomenon known as a runaway diesel engine, or diesel overspeed.
On the BP rig the night of April 20, crews said they heard the diesel-powered generators start running at higher and higher speeds.
"I just come out of my shop, I heard a bunch of high pressure noise, and when I come out of my shop I went to go through that door and that’s when it exploded," said Murray.
What might have been happening?
"There was a large gas cloud released from there and part of that gas cloud got sucked up into the air intake," Sam Mannan said when asked to speculate about the explosion. Mannan is the director of Texas A&M’s Mary Kay O’Connor Process Safety Center in College Station.
It’s a danger long recognized in the oil exploration and petrochemical industries.
On rigs, diesel engines are used to generate electric power. At refineries and tank farms, diesel engines can be found powering trucks that routinely go in and out of the plants .
If there’s a leak of an explosive vapor, like the methane gas that came up in the BP well, it can get sucked into the diesel engine’s air intake. That can cause the engine to rev out of control and backfire. The engines themselves may even explode.
11 News reported on this danger in April 2009, showing how the design of a diesel engine isn’t like your gasoline-powered car. Experts explained how turning the key to "off" won’t shut down a diesel engine that’s sucking in an explosive vapor. It just keeps on running because, unlike gasoline engines, diesels use compression—not spark plugs—to ignite the fuel.
11 News showed how a runaway diesel engine in a pickup truck is thought to have been what ignited the explosion at BP’s Texas City refinery in 2005. That explosion killed 15 workers.
In a video animation of the explosion prepared by the U.S. Chemical Safety Board, an announcer explains how "two workers fled, unable to shut off the engine. Moments later, witnesses saw the truck backfire and ignite the vapor cloud."
Runaway diesel engines on tanker trucks were also linked to an explosion in Brazoria County in 2003 that killed three workers.
Sam Mannan at Texas A&M said while even cell phones can ignite gas clouds, a diesel engine is worse.
"All ignition sources are not alike. (A diesel engine) creates what’s known in the science as a bang-box type of explosion which has more probability to lead to a high-intensity explosion," said Mannan.
That risk led to government mandates that diesel engines used on offshore rigs must be equipped with emergency shut-off valves that are supposed to cut off the air intake, killing the engine.
At those hearings in Louisiana, an investigator asked, "Were there any safety devices to prevent engine overspeed on those pieces of equipment?"
"Yes, there were," replied Douglas Brown, Transocean’s chief rig mechanic.
The investigator asked Brown, "In your opinion, did those function properly?
"No," replied Brown.
Experts said if the valves had worked, the Deepwater Horizon might never have had the catastrophic explosion that sunk it.
"If (valves are) installed properly and maintained properly, these things can be prevented," said Eric Schellenberger, president of a Houston-based company called AMOT, which makes safety valves that function automatically.
Their valves were not on the Deepwater Horizon. But in recent days, the company said there has been a lot more interest in them as the energy industry looks for ways to reduce risks.
"We have seen an increase in order activity and inquires," said Schellenberger.
He said AMOT has been asking Federal regulators to extend the requirement for safety valves to diesel engines used not only on offshore rigs, but also on engines used onshore at facilities where explosive vapors might present a danger. But so far, no such requirements have been mandated by the government.
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