Evaluating the technologies available to protect against direct lightning strikes
Lightning poses a very real hazard for oil and gas operators. Here, Nicola Brittain explores a range of technologies that either diffuse the charge itself or eliminate the impact of a strike
Oil and gas facilities are extremely vulnerable to direct lightning strikes and their secondary effects such as fires and explosions. Their vulnerability lies in the fact that they are often open or elevated (such as flat plains or offshore). The presence of flammable gases and liquids compounds the risk. A lightning strike in such conditions can easily trigger fires or explosions leading to damage, injury and more.
As a result, many oil and gas facilities have adopted lightning defence strategies. Broadly speaking these comprise two key approaches: lightning protection and lightning avoidance.
Mike McMahon, CEO at Lightning Eliminators & Consultants (LEC) talks about the company’s work with its clients. “Lightning protection and mitigation should be tailored to a facility’s unique vulnerabilities, whether that involves bonding solutions for storage tanks, direct strike avoidance, secondary damage caused by a nearby strike or grounding improvements,” he says.
LEC helps facilities identify vulnerabilities by first conducting a thorough site assessment and implementing mitigation strategies.
PREVENTING LIGHTNING
According to McMahon, the most effective defence is to prevent a lightning strike from occurring. He explains that lightning comes from a difference in potential between storm clouds and the earth that triggers an electrical discharge. For lightning to strike, a connection between a downward leader from the cloud and an upward streamer from the ground is required.
The Dissipation Array System (DAS) from LEC is designed to prevent direct lightning strikes by lowering the electric field or charge differential. DAS uses point discharge technology that facilitates the exchange of ions between the air and the ground, disrupting the conditions necessary for a lightning strike, thereby neutralising the charge differential. LEC even offers a ‘no-strike’ warranty for all supervised installations, ensuring protection when the system is properly maintained and inspected.
The effectiveness of DAS is enhanced when combined with a comprehensive lightning protection system that includes a low-impedance grounding system, transient voltage surge suppression, and modular strike prevention devices. Together, these components ensure optimal protection and can prevent oil storage tank fires, one of the most significant and well documented risks at oil and gas plants.
OIL STORAGE TANK FIRES
The most common tank fire is a seal fire, resulting from a lightning-induced spark or a buildup of static charge igniting vapours near the tank’s rim seal.
Floating roof tanks are particularly susceptible to fires resulting from lightning strikes. Electrical currents from such strikes can traverse the tank’s shell and roof, potentially arcing across the roof-shell interface. This arcing can ignite flammable vapours present near the floating roof seal, leading to catastrophic fires.
Proper bonding and grounding solutions are critical to preventing these. As an example, LEC’s Retractable Grounding Assembly (RGA) is a patented and ATEX-approved solution that ensures a permanent, low-impedance bond between the tank’s floating roof and shell, preventing dangerous arcing and subsequent ignition of flammable vapours.
Even non-metallic and internally lined storage tanks can accumulate static electricity during regular operations. This accumulation poses another risk, as static discharge or external factors like nearby lightning strikes can ignite flammable vapours within the tank, leading to catastrophic events.
Another product from LEC called the In-Tank Potential Equalizer (IPE) can be submerged into the liquid in the tank to provide a conductive path for the charge accumulated on the fluid to safely dissipate to the ground.
EXPERTISE IN INSTALLATION
Having a single source oversight of the installation of these systems can also be a key aspect of effective implementation as piecemeal lightning protection strategies might lead to problems. As operations become more complex and the consequences of downtime more severe, the company argues that the need for a site-specific lightning protection strategy is imperative.
