Which Lightning Protection System Will Protect Your Site?

Lightning in a purple sky
4 Oil & Gas Takeaways From The 2018 Lightning Report
January 22, 2019

If you drive through the Permian, Oklahoma, or South Texas long enough you’re bound to see your fair share of central tank batteries or saltwater disposal sites. Look a little closer and you’ll hopefully see a structural lightning protection system installed on the site that uses air termination devices. Not every type of lightning protection system is created equal, though. There are four main types of air termination systems you’ll see in the oilfield, but only one that gives you a low risk of vapor ignition. Below, we walk you through the differences of each system.


FARADAY SHIELD 

RISK OF VAPOR IGNITION: HIGH 

A Faraday Shield or Faraday Cage, named after 19th-century scientist Michael Faraday, is a metallic structure that shields internal contents from static electric fields by distributing the electromagnetic charge or radiation around the cage’s exterior. When properly bonded and grounded, it can provide direct-strike lightning protection for tank batteries and tanks, however there is a high risk of igniting the vapor space over the tank battery. Additionally, the installation of these systems can be very expensive, so they are usually reserved for extremely sensitive operations. 


CATENARY (OVERHEAD WIRE SYSTEM) 

RISK OF VAPOR IGNITION: HIGH 

A catenary lightning protection system consists of horizontal metallic wires stretched between masts above and around a protected structure, connected at each end to ground rods. For tank batteries, a catenary system and mast must be at least 6 feet away on each side, as well as 6 feet above the highest structure. If the separation distance isn’t adequate, or the structures are not appropriately bonded and grounded, a lightning strike on the wire will likely flashover to the tank battery, risking ignition of vapors.


MAST SYSTEM 

RISK OF VAPOR IGNITION: HIGH 

A mast-type lightning protection system uses metallic, concrete, or wooden masts installed on top or remote from a structure to provide a primary attachment point for lightning discharge. Mast systems can provide a large area of protection and reduce the cost of installation on a tank battery, however the height of the masts must be adequate to ensure the entire structure is enclosed within the protection zone. This increases the risk of direct strikes that terminate to the structure and send electrical current down the mast through the vapor space. Even with a common bonding and grounding system, the vapor space could still ignite. 


INTEGRAL SYSTEM WITH FRANKLIN AIR TERMINALS 

RISK OF VAPOR IGNITION: HIGH 

An integral system with Frankiln Air Terminals uses grounded rods (air terminals) and conductors mounted directly on a protected structure to provide a preferred point for a lightning strike to terminate. As a developing lightning storm impresses an electrical field on the ground, the ground charge rises and accumulates building charge at the tip of the air terminals. When the charge reaches a certain threshold, upward streamers are generated from the air terminals luring a downward leader and sending the lightning charge through a channel to the ground. However, for tank batteries, just like the catenary or mast system, an integral system with franklin air terminals will result in high risk of igniting vapor space.


PETRO GUARDIAN’S INTEGRAL SYSTEM WITH STREAMER DELAYING AIR TERMINALS 

RISK OF VAPOR IGNITION: LOW 

Petro Guardian’s recommended integral system with streamer delaying air terminals mitigates the risk of a direct lightning strike by ionizing the air surrounding the protected structure. As a developing lightning storm impresses an electrical field on the ground, the ground charge dissipates through these air terminals into the surrounding air creating a charged cloud that continually neutralizes the charge build up around the protected structure. This inhibits or delays the formation of streamers, greatly lowering the risk of a direct strike igniting vapor space. Additionally, this system uses a properly bonded and grounded conductor network so all of the structures related to the tank battery are at the same resistance during atmospheric changes.