Hazard analysis of main problems existing in lightning protection of out floating roof tanks
(1) Analysis of the hazard of the
combustible gas concentration exceeding the standard in the secondary sealed
cavity
The oil tank with combustible gas
concentration in the secondary sealed cavity reaches the explosion limit range.
Once the tank is struck by lightning, it will cause the secondary sealed space
of the oil tank floating plate to flash and ignite. If the initial fire is not
controlled, the fire will be enlarged.
An oil tank with a combustible gas
concentration of more than 25% lel in the secondary sealed cavity indicates
that the primary seal is not good. If the gas continues to accumulate, it can
reach the explosion limit range. If it is struck by lightning, it may catch
fire.
(2) "Wrapped" conductive sheet
analysis
One side of the coated conductive sheet is
in the secondary sealing rubber plate. When there is lightning current, if
there is a small gap here, discharge will occur. If the combustible gas
concentration in the internal cavity of the secondary seal reaches the
explosive limit concentration, a flash explosion and fire accident will occur.
(3) The number of conductive sheets on the
upper part of the secondary seal is not enough
The conductive sheet is actually a shunting
measure of the lightning current. If the number is not enough, the larger the
lightning current passes through each conductive sheet, and the phenomenon of
ignition has already occurred.
(4) The resistance value between the
conductive sheet and the tank wall
The resistance value between the static
conductive sheet and the tank wall is far beyond the high standard requirement
of no more than 0.032, the maximum value is 0, and the failure rate is 100%.
The greater the contact resistance between the conductive sheet and the tank
wall, the greater the potential difference formed, the greater the discharge
current, and the greater the harm.
