HEALTH, SAFETY & WELLBEING
LIGHTNING PROTECTION: A LIFE STORY
Marc Pilkington, Lightning Protection Committee at Association of Technical Lightning & Access Specialists (ATLAS), provides a historical overview of lightning protection systems, and explains why they’re so crucial for businesses.
Historically it was well observed that certain objects and structures were more prone to lightning strikes. The two most common man-made structures that were hit were places of worship and tall ships. Church strikes would often be seen as an act of God, but strikes to tall ships were of far more critical concern. The term ‘St. Elmo’s Fire’ (St. Elmo being the patron saint of sailors) was coined to describe the coronal discharges seen from the points of masts during occasions of high electromagnetic activity and atmospheric charge build up.
The observation of the ‘fire’ at the tips of the masts would often forewarn of a lightning strike. As the ship was usually the only isolated object above the sea surface, there was little that could be done to alleviate the risk of a strike in storm conditions. The grave concern here being that cargo could include gunpowder, giving a significant probability of explosion and loss of life.
Between 1810 and 1818, a total of 58 ships were struck or sunk with around 600 sailors losing their lives as a result. Due to this, rudimentary conductor systems were applied to ships in an effort to prevent, or at least lessen, the damage caused by lightning strikes. However, these systems were often installed by the sailors themselves and many would simply drape chains from the tops of
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masts down into the sea - a cumbersome, heavy and expensive system.
Sir William Snow Harris (also known as Thunder-and- Lightning Harris), a British physician and electrical researcher, was eventually tasked with providing an updated and more effective lightning protection solution. He had presented an initial solution to the Admiralty in 1821, but had been dismissed without interest. He continued to campaign for Naval and public recognition of his system, and in 1839 the Admiralty eventually conceded that their current system was woefully inadequate.
Harris’ system used a series of bonded copper plates, rivetted to the masts, from their tips down to sea level, with all metallic parts of the ship also connected to these plates to avoid risks from secondary flashes, a principle still used today. Secondary flashing has long been known to be one of the most serious consequences from lightning strikes, as these will often occur between parts that are more sensitive and critical to the continued safety and operation of the structure. With ships, secondary flashing was a prime concern due to the practice of lining the powder rooms with copper sheet - a side flash could therefore be devastating.
One of the first test ships that Harris would apply his protection system to was HMS Beagle, the ship that
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