A lightning strike caused a major fire in an oil storage tank on Butcher Island (Jawahar Dweep), off the Mumbai shore. It took four days to extinguish the fire on the island, which houses a marine oil terminal of the Mumbai Port Trust, where oil tankers discharge crude oil, thereafter transported to refineries through submerged pipelines. Following an investigation, India’s Oil Industry Safety Directorate (OISD) found serious lapses in procedure and protocol. One point mentioned was that the roof plate thickness of the tank was less than 4.8 mm and thus able to be punctured by the lightning strike, allowing the fire to be ignited.

This kind of disaster attests to the critical necessity of making sure that flammable substances, which may present potentially explosive atmospheres, are protected from the possibility of lightning currents and surges.

According to Julienne Puttkammer, part of the technical team at DEHN AFRICA, this is a very illustrative example of how badly things can go wrong when lighting strikes a potential explosive zone that is not adequately protected. “The strike at Butcher Island - Jawahar Dweep - followed the usual expected scenario when the tank’s contents burned rather than exploding, incurring huge costs. Fortunately, there was no loss of life.

“It’s not surprising that anywhere flammable substances such as fuel, alcohol, liquid gas and explosive dusts are produced, processed, stored and transported, could potentially be an explosive atmosphere.

Essentially, temperature differences where flammable liquids are stored can create fumes within the storage facility, and then if this area becomes too warm, it can be ignited, or even explode. Similarly, when it comes to flammable powders, static can cause friction in the fine particles of the powder, which could then catch fire. Part of the reason that the Jawahar Dweep fire burned for so long is because reignition of the fuel – due to the extreme heat – kept the blaze going.

To ensure the safety and availability of a chemical or petrochemical plant, procedures are required to protect the tanks from a direct lightning strike, as well as electrical and electronic installations from lightning currents and surges that could be the cause of an explosion. As Puttkammer explains, “The point is therefore to prevent sparking and ignition of these explosive atmospheres, particularly at oil depots, fuel stations and biogas tanks, where biological waste and fermentation processes create the gas that is used for energy sources. The simplified science is that if something is used for energy, it is often explosive or flammable.”

Puttkammer says petrol stations and storage depots are governed by stringent regulations around protection from static sparking and lightning strikes. “The electrical systems in these zones must be housed in special explosive proof piping and enclosures to isolate any potential sparking and must be designed to prevent any heating of the conductors, known as intrinsic safety, so that even in a worst case scenario, the stored fuel in the area will still be safe from ignition. This is a big part of managing the lightning risk. Furthermore, if fuel tanks are exposed to direct lightning strikes or not made of adequate housing to be safe in the event of a direct strike, the threat, as illustrated by the Jawahar Dweep fire, would be virtually unmanageable. Therefore, the earthing, lightning protection and equipotential bonding precautions are critically important.”