Study of Charging Nitrogen to External Floating Roof Tank to Prevent Rim-seal Fires from Lightning

摘要

It is estimated that 95% of rim seal fires are caused by lightning strikes. To avoid rim-seal fires caused by lightning, the existing methods mainly focus on the use of secondary sealing to reduce volatilization of oil and the electrical connections measures such as air terminals, deflectors, grounding device, discharge shunts and scalable grounding device to avoid sparks caused by lightning current. But these devices can't eliminate the spark generation thoroughly. A new method charging nitrogen to external floating roof tank seal ring is proposed to prevent rim-seal fires from lightning. In this paper, the safe oxygen content is set as the goal to charge nitrogen. An annular nitrogen charging pipe network is designed and its reliability is verified by experiment. The time of filling nitrogen to the seal ring of an external floating roof tank with the capacity of 10 x 10~4 m~3 at the rate of 63.38 m~3/h to reach the nitrogen charging goal is proved within the time of lightning warning through experiment. And this experiment can provide some reference to the application of nitrogen charging.