External floating roof oil tank refers to a steel storage tube with a top cover floating on the oil surface. It is mainly used to store volatile petroleum products such as crude oil, gasoline and kerosene. It is more common in petroleum and petrochemical companies. There are usually 20,000 cubic meters, 30,000 cubic meters, 50,000 cubic meters, and 100,000 cubic meters. The outer floating roof oil tanks are all set in an open environment and are prone to lightning strikes. In countries around the world, there are not a few cases of lightning strikes on external floating roof tanks. In recent years, my country's petroleum and petrochemical enterprises have paid special attention to the lightning protection of external floating roof tanks. Today, Qingdao ALPTEC will analyze the lightning protection solutions for external floating roof oil tanks from a professional point of view, and understand what kind of lightning protection devices are used for external floating roof oil tanks. 

1.Analysis on the Current Situation of Lightning Protection for External Floating Roof Oil Tanks 

The external floating roof oil tank is equipped with some lightning protection measures when it is installed. However, with the long-term frequent movement of the floating roof, the external floating roof oil tank lightning protection device will be damaged due to the deformation of the tank and the displacement of the floating plate. Claim. Based on the on-site survey of multiple external floating roof oil tanks, we summarized the findings:

1.1 Wrapped conductive sheet

At present, most of the external floating roof oil tanks use "coated" conductive sheets for lightning protection. One side of this kind of conductive sheet is in the secondary sealing rubber sheet. When there is thunder current, discharge will occur if there is a tiny gap here. If the combustible gas concentration in the internal cavity of the secondary seal reaches the explosive limit concentration, a flash explosion fire accident will occur. The site survey found:

1.1.1 The concentration of combustible gas in the secondary sealed space of many oil tanks is within the explosive limit range (the highest concentration reaches 4%v/v);

1.1.2 The secondary sealing plate is damaged and separated from the tank wall, and the resistance between the conductive sheet and the floating plate is much greater than 0.03Ω, which does not meet the requirements;

1.2 Floating escalator

Floating escalators require four-point bridges at both ends, but most do not use four-point bridges. The transition resistance between the two rollers of the floating plate escalator and the floating plate is much greater than 0.03Ω, which does not meet the safety requirements.

Once the outer floating roof oil tank with these problems is struck by lightning, it may cause fire and explosion and cause major safety accidents.