Need of Protection for Tanks against Direct Lightning Strikes

01/04/2023

Introduction:

Lightning strike is a natural phenomenon of sudden discharge of charges from highly concentrated cloud or any objects. Lightning cannot be avoided but the damages can be reduced by proper preventive measures. Tank farms consists of metal tanks of different sizes and the inflammable materials are stored in this tank of different quantity.

Lightning strikes on metal tanks

Even the sudden increase in temperature due to the flow of lightning impulse current may result in the explosion at these site conditions Hence Lightning Protection System is very much essential for these kinds of very sensitive areas. Fugitive emissions are unintended leakage of gases or vapors from pressurized container due to faults or improper maintenance activities. The fugitive emissions may also occur due to the evaporation of inflammable materials in storage tanks. The leakage of highly inflammable vapors from the storage tanks increases the risk of fire and explosion at the tank farms.

When lightning strikes directly hits the metal storage tanks, the following effects may occur,

Explosion of tanks may occur along with the outbreak of fire.
Lightning current flowing through the metal part of the tank may damage the tank
While lightning strike, the temperature reaches very high level around the environment which will turn it into the major risk of ignition or fire.
The high temperature due to lightning may cause puncture in the metal sheet and result in fire or explosion.
Hotspot on the metal sheet can ignite the fuel kept inside the container.

Steps to be followed

OISD-GDN-180, an exclusive standard for Oil industry explains about the preventive measures for the storage tanks. The measures provided by the standard are as follows.

Flammable liquid shall be stored in the gastight structure.
Periodical maintenance should be carried out and the proper operating conditions of all the accessories shall be ensured.
All the openings to atmosphere should be properly closed at the same time entrance of flame should be arrested.
Accumulation of the mixture of air and highly inflammable vapour outside the tanks should be prevented.
The spark gaps between metallic conductors in places where the flammable vapour escapes accumulates shall be avoided.