Research on lightning sparks discharge and protection measures of large floating roof tank

In order to avoid and greatly reduce floating roof tank fire accidents caused by lightning, theoretical analysis is carried out on shunts, mechanical seal structure and guide pole spark discharge in the oil and gas space. To study the problem of shunts spark discharge, a 2m diameter tank model was made to carry out simulation lightning experiment of shunts spark discharge. Experimental results show that shunts attached to the tank shell by its own flexibility can generate sparks when the lightning current flow reaches a peak value of about 400 Amperes. If there are gaps between shunts and the tank shell during lightning high voltage stock, potential difference between the roof and shell may breakdown the gaps and cause sparks. Lightning spark discharge on large floating roof tanks is inevitable if shunts are set as an interval of 3m according to the standard. Finally, according to the actual operation of the floating roof tank, some protective measures were put forward, such as removing the shunts, making mechanical seal structure insulating from the tank shell or using soft seal structure, connecting the floating roof and the tank shell by using more equipotential bonding wires, ensure a safe distance for the metal parts in the oil gas space, bonding scraping wax with floating roof, making the guide pole insulating from the floating roof, etc.