Tuesday, November 21, 2023

Do you know how ships are protected from lightning?

Lightning over the West Pier on Tuesday 23 July 2019 
Picture by Helen Pearce from the Brighton Skies Facebook group

While the chances of being struck by lightning in a given year are less than one in a million, lightning remains one of the most significant dangers for outdoor workers, including maritime and offshore workers.
Have you ever wondered what protects ships from lightning?

Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground, often resulting from the collision between cool and warm air masses.
When this process starts, the air takes the role of an insulator between the positive and negative charges in the cloud, as well as between the cloud and the ground.

When the opposite charges build up enough, this insulating capacity of the air breaks down and there is a rapid discharge of electricity -what we perceive as lightning.
The risk of a ship encountering lightning is higher offshore rather than at port.

Did you know ?
Lightning is one of the oldest observed natural phenomena on earth.
Lightning is considered one of the top three weather-related causes of death in the United States: It kills more than 100 people per year in the country, which is equivalent to more deaths than the ones caused by hurricanes, floods or tornadoes.
Not everyone struck by lightning dies: researchers estimate that two-thirds of those struck by lightning survive, and often people apparently “killed” by a lightning strike can be revived by cardiopulmonary resuscitation.
Lightning is what causes thunder.
According to US NOAA, energy from a lightning channel heats the air briefly to around 50,000 degrees Fahrenheit, (hotter than the surface of the sun), which causes the air to explode outward.
The huge pressure in the initial outward shock wave decreases rapidly with increasing distance and within ten yards or so has become small enough to be perceived as the sound we call thunder.

While onshore the focus is on human safety, on ships the focus is also on machinery because any disruption in the equipment function can seriously compromise safety onboard.
Lightning damage affects all electrical equipment, such as electrical or electronic equipment if it happens to directly strike lighting, power equipment, or radar antennas.

For example, if the steering gear is isolated, the safety of navigation is at serious risk.
Meanwhile, navigation and communication systems onboard vessels are pretty sensitive to any disruption in the power supply, which can lead to groundings, collisions, etc.

The lack of a protection system against lightning can affect not only machinery and equipment, but also the people onboard.
If a lightning strike causes a fire and critical fire safety systems are out of service due to power disruption, the impact of fire may turn uncontrollable.
Frequent lightning damage to vessels includes:Electrical failures, such as damage to the battery, refrigeration controls, air conditioning, and sensors;
Mast damage – particularly on sailboats with non-metallic masts;
Hull problems – especially those made of fiberglass; and
More destructive events, such as fires onboard.
A lightning bolt strikes the sea near Fort St Elmo during a storm in Valletta, Malta, on February 27, 2019.
The highest concentration of superbolts have been observed in the Mediterranean Sea, the North Atlantic, and the Altiplano in Peru and Bolivia—regions where storms' charging zones are closer to the Earth's surface.
Photograph by Darrin Zammit Lupi, Reuters/Redux

How are ships protected from lightning?

Unpredictable weather, including lightning, is among the most common external factors that can affect the safety of a ship.
However, ships today are typically equipped with lightning protection installation systems to protect them from lightning.
The system is put at the top of the monkey island reaching towards the hull.
Generally, a comprehensive Lighting Protection System includes, but is not limited to, the following arrangements:Air terminal system, which aims to protect the vessel from the effects of any direct strike.
Bonding and Earthing system, which is achieved by connecting two electrical conductors.
Such systems usually depend on the type and size of each vessel.
Surge protection system, which includes individual breakers and fuses, as well as power supply protection kits.

Of course, modern ships are made of steel, which is a good conductor for power.
This means that in case lightning strikes the mast, it is possible that power will run through the mast to the hull and then, end up at sea, achieving earthing.
For instance, cruise ships are basically designed in a way that any lightning strike would hit the highest point on the ship and then be conducted through the hull to the water.

However, in case the highest part of a ship is not the mast, but a radio antenna, which is connected to radio receiver equipment, it is not uncommon that it will cause an explosion and damage to equipment.
Unlike shore arrangements, any vessel on the water is a possible strike point during a thunderstorm due to its electric field enhancements.

In most ships, the antenna is isolated from the radio equipment, but if someone forgets the radio connected to the antenna, the equipment may be damaged with consequent costs or even more severe outcomes.
Some more modern antenna models have special gas tubes that ground the equipment automatically in case of a lightning strike.

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