Prevent, don't attract, lightning, says one US company.
Lightning is a problem in the petroleum industry, as elsewhere. Consider one example: independent studies show that in 1995, 16 out of 20 accidents involving petroleum product storage tanks were due to direct or nearby lightning strikes.
But a technology to prevent lightning exists, and during the past 30 years or so, oil companies have applied it widely at storage, refining and petrochemical facilities.
There's also a growing trend toward using this technology to protect offshore petroleum facilities. With an ever-growing offshore infrastructure, the industry hopes to raise the odds against lightning's effects.
Of course, thunderstorms are more prevalent nearer the Equator, so the Gulf of Mexico, Southeast Asia, South America and West Africa - all major offshore petroleum centers - are all too familiar with them. But lightning can strike almost anywhere, so even operators in less likely regions like the North Sea are said to be using the technology.
Thunderstorms contain electrically charged clouds. The air serves as an insulator, separating the cloud's charge from the ground or other clouds. This charge builds during the storm, inducing a similar charge of opposite polarity onto the earth beneath it, creating a strong electrical field between. The charges remain apart until the air no longer can insulate them. That's when the electrons flow and lightning occurs.
When a structure like a fixed platform sits between the sea bottom and the storm cloud, it is likewise charged, and since its above-water structure shorts out a portion of the separating air space, it, too, can trigger a strike. The higher the structure, the greater the chance of a lightning strike - or strikes.
For some 250 years, the conventional way to tackle lightning has been the lightning rod - attributed to Benjamin Franklin - which attracts the electrical energy produced by lightning, channeling it, via a "safe" wire route, to ground. There are variations, but none has worked more safely.
However, since the Franklin rod actually attracts current, allowing it to flow very near the equipment it's meant to protect, problems can arise when the equipment contains flammable materials or gases that can catch fire or explode. And a less-than-adequate ground can allow current to jump or arc to unprotected surfaces.
Back in the 1960s, the Manned Spacecraft Program spawned a new process to handle lightning called Charge Transfer Technology (CTT). It's based on the "point discharge" principle, which says a sharp point in a strong electrostatic field will leak off electrons by ionizing the adjacent air molecules, provided that the sharp point's potential is raised 10,000 volts above that of its surroundings. CTT worked successfully to prevent lightning around rocket launch areas.
By 1971, CTT became available to the public, and a Boulder, Colo.-based company, Lightning Eliminators & Consultants (LEC), expanded on it, creating what it calls the Dissipation Array System (DAS). Since then, LEC has engineered and installed thousands of its DAS systems around the world
Jerry Kerr, LEC marketing director, said the DAS employs the point discharge principle by offering thousands of separate points that simultaneously produce ions over a large area, thus preventing formation of "streamers," the precursors of lightning. This ionization process creates current flow from the points into the surrounding air.
"The ionization current increases exponentially with the storm's electrostatic field, which during a mature storm, can reach up to 30,000 volts per meter (v/m) of elevation above the earth (or, in the case of tethered or fixed offshore structures, the ocean bottom)," said Kerr. "The storm's charge is removed from the DAS-protected area and transferred to the air molecules, which are always moving during the storm."
Thus, he said, DAS prevents strikes by continually reducing the voltage differential between the ground and the charged cloud to well below lightning potential, even in a worst-case storm. Voltage reductions of up to 7,000% have been measured. That lowers a mature storm's 30,000 v/m to just 500 v/m, not enough to cause lightning.
Kerr said the DAS has repeatedly prevented lightning from striking facilities it protects, including plant areas as large as 1.2 sq miles (3 sq km) and structures as high as 1,700 ft (519 m). Combined, installed DAS systems have exhibited 99.7% reliability for more than 30,000 system years, he said.
Storm energy activates the DAS, said Kerr. It uses no generated power. Systems are custom-engineered for size, height, area storm patterns and other factors. The hardware array is proprietary.
But there's a guarantee, he said. If lightning penetrates a DAS-protected area, LEC will upgrade the system's capability at no extra charge for a year from date of installation or recertification.
A quick search by Kerr indicated Chevron is using a DAS on a platform off Papua New Guinea. Texaco is using one in Nigeria, and three Transocean Sedco Forex mobile rigs have DAS protection.
To find out more, contact Kerr at 303-447-2828, ext. 111, or marketng@ lightningeliminators.com.

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