Analysis and experimental investigation of direct lightning protection for floating roof oil tanks

To improve the lightning protection of large floating roof oil tanks, the process of floating roof tanks stroked by lightning is analyzed, and relevant tests have been developed according to standards. Test results indicate that the major role of conductive film is to release lightning current rapidly, but the presence of conductive films has counter-effects. As long as conductive film is present, it will generate electric sparks when the floating roof tanks stroked by lightning. This paper proposes to eliminate the conductive film on the second seal floating roof top edge and instead use a scalable grounding device (SGD) as the lightning protection measure. An empirical formula has been used to calculate the transient voltage drop when the 100,000 m3 tank is stroked by lightning. The results show that the floating tank is safe when there are 20 SGDs uniformly connecting the floating roof and tank wall.

► 90% lightning current would be released using single conductive film and single SGD.
► To avoid spark discharge of conductive film is to use SGD as lightning protection measure instead of conductive film.
► The safety of floating roof tank can be ensured with 20 SGDs connecting floating top and tank wall.
► Calculated the union protection range of tank wall to floating roof at different height.