Answer
When the fuel trucks are full the fuel constantly hits the metal container due to movement and there are chances of developing static charges while fuel is pumped. Also, charges may be created due to friction when the vehicle is moving. The metal chains drain this extra charge to the ground to prevent any unwanted circumstances like explosion etc.
Work Step by Step
When the fuel trucks are full the fuel constantly hits the metal container due to movement and there are chances of developing static charges while fuel is pumped. Also, charges may be created due to friction when the vehicle is moving. The metal chains drain this extra charge to the ground to prevent any unwanted circumstances like explosion etc.