The metal tank body shall be grounded against direct lightning strikes. The grounding point shall not be less than 2, and shall be evenly arranged along the circumference of the tank. The spacing of the down conductor shall not exceed 18m. The impact grounding resistance of each down conductor should not exceed 10Ω.
1. The thickness of the tank wall of the steel storage tank is ≥ 4mm. When the breathing valve with the flame arrester is installed on the top of the tank, the tank itself is used as the lightning receptor (lightning rod).
2. The thickness of the tank wall of the steel storage tank is ≥ 4mm. When the top of the tank is equipped with a breathing valve without a flame arrester, the tank top device should be connected to the flasher (lightning rod).
3. The thickness of the tank wall of the steel storage tank is <4mm, which should be connected to the lightning device at the tank top device (lightning rod).
4. Non-metallic storage tanks should be equipped with lightning receptors, so that the protected storage tanks and the breathing valves on the top of the protruding tanks are all within the protection range of the lightning receptor.
5. When the buried layer is ≥0.5m, the partial lightning protection should be adopted.
1. Each metal pipe should be equipotentially connected to the grounded pipe rack. The connection should be grounded. When multiple metal pipes can be connected to each other, they should be connected to the grounded pipe rack.
2. For metal pipes laid in parallel, when the net spacing is <100mm, they should be connected by metal wires every 30m. When the pipeline intersection is less than 100mm, the intersection is bridged by metal wires.
3. The metal pipe conveying the flammable medium shall be laid on the pipe rack. At the beginning, the end and the branch, the grounding device for lightning protection shall be installed. The power frequency grounding resistance shall not be ≥30Ω.
4. The metal pipe entering and leaving the production device should be grounded on the outside of the device and connected to the protective grounding device of the electrical equipment and the grounding device for lightning protection.
Note: The protection scope of the lightning receptor in this paper should meet the GB50650-2011 "Lightning Protection Specification for Petrochemical Plants".
1. Use Balic electric thickened zinc steel material (referred to as zinc clad steel) as the grounding body. The horizontal grounding body should be round zinc-clad steel (zinc-clad steel grounding wire), and its diameter should not be less than 10mm. The vertical grounding body should be made of cylindrical zinc-clad steel with a diameter of not less than 16mm. The zinc layer should be high-purity zinc (Zn≥99.9%), and the contact resistance between the steel core and the zinc layer should be <0.5mΩ.
2. The relationship between soil resistivity and zinc layer thickness is in accordance with the following table:
|Soil resistivity（Ω·m）||Horizontal grounding zinc layer thickness (mm)||Vertical grounding zinc layer thickness (mm)|
3. When using copper materials, the cathodic protection uses the impressed current method.
The connection between metal conductors should be based on the exothermic welding method of Balic; if the traditional welding method is used, it needs to be treated with anti-corrosion treatment.