When Lightning Strikes

Aug 3rd 10
By Janine Ketterer

You may recall an incident in 2008 during which a single bolt of lightning destroyed an entire yacht at an Antiguan marina. Sailing yacht Keturah, a 94-foot private vessel, was engulfed in flames after she was struck by lightning and then she sank. If you do a bit of Googling, you will come across several accounts of vessels, large and small, that have been struck by lightning, most of which saw fires, electrical problems, other damage or all of the above.

Lightning, an atmospheric discharge of electricity, generally strikes during thunderstorms, but other forms include {deletion} lightning produced during a volcanic eruption. The powerful natural occurrence is to blame for disasters such as forest fires and has the capacity to kill as it can reach temperatures approaching 30,000°C/54,000°F and can travel 60,000 m/s/130,000 mph. For yachts, it can not only short out all electric equipment, but also can cause a devastating fire, burning the vessel to the waterline.

Ewen Thomson, president of Marine Lightning Protection Inc., says the first thing captains and crew should do if the vessel has been struck by lightning is to stop the vessel and throw the anchor. “The potential for damage is immense [on large vessels] because of the quantity of electronics,” says Thomson. He maintains that regardless of whether the vessel has lightning protection or not, electronics most likely will be affected. “The captain may have to go manual and rely on back-ups. At the very least many systems will have some sort of glitch so it is important to check them all.”

Thomson adds that there is a possibility of a hole in the hull as the lightning is searching out a path to the water – the charges at the top of the water will neutralize the lightning. Generally, the hole will not be large enough to sink a large vessel, but crew should check to see if the vessel is taking on any water.

The biggest concern after a vessel has been struck by lightning is the potential for a fire to break out. Thomson says that steel and aluminum vessels are much safer because the entire structure is a conductor. “A fire may not be immediate,” says Thomson. “Usually, when you hear about the extremely large fires, the cause is a spark in an engine room or somewhere around a combustible substance like fuel, gasoline or diesel.” If there is smoke, there is potential for a fire so captains should first evacuate anyone who is not going to fight the fire. Smoldering wires behind panels are an issue because they are not initially seen by crew checking the vessel. If this is noticed at a later time and the panel is removed, oxygen could immediately ignite the smolder wires so great care must be taken.

Lightning protection systems can help protect a vessel. They consist of a system of conductors designed to carry the lightning through and around the vessel without overheating. Air terminals, or lightning rods, are placed at key points on the vessel decks, at the bow, stern and amidship, to create multiple attachment points for the lightning. These air terminals are connected to down conductors that run throughout the vessel, horizontally and vertically, making a network preferably near the outside of the vessel. All metallic fixtures, like handrails, should be included in this. A grounding system is connected to the down conductors and provides multiple exit terminals to the water, which will neutralize the lightning charge.

Thomson also recommends transient voltage surge suppressors for all electronics. “Even with a perfect lightning protection system, there will be voltage surges,” says Thomson. He maintains that it’s crucial to ensure that anything topside have surge suppressors to protect it.

These systems are the same as those used on buildings to protect them from lightning strikes.

Thomson says sailing yachts are more susceptible to lightning strikes due to the height of the mast. “Typically, the larger the vessel, the more likely it will be struck,” says Thomson. Statistics by Boat U.S., available on Thomson’s website (http://www.marinelightning.com/catamaran/index.html#BoatUSStats) show  that catamarans are twice as likely to be struck due to their width. Thomson's analysis of these stats predicts that vessels in a marina are five times less likely to be stuck because of their proximity to other vessels, therefore spreading the odds.

Thomson says if there is lightning in the area the captain must clear the decks and get everyone inside. He says that unprotected vessels are much more dangerous because if someone is holding onto a metal fixture when the vessel is struck, they will be shocked. “You can’t prevent lightning from striking,” says Thomson, “but you can certainly be protected.”



Ewen Thomson is president of Marine Lightning Protection Inc. For more information on lightning protection systems, go to http://www.marinelightning.com/ or email EwenT@marinelightning.com.  

 

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Drilled into Memory: Safety drills on board






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