With the demands of today’s society, some storage places for dangerous goods, flammable and explosive goods have been further expanded and increased. Due to the special nature of these items, once a fire or explosion occurs, it will cause great harm to the society. Lightning, as an unforeseen weather phenomenon in nature, has a fatal hazard to the safety of flammable and explosive places. So, how to detect hidden dangers more directly and quickly in the lightning protection safety inspection of flammable and explosive places, so as to avoid disasters caused by lightning?
1. Lightning protection safety testing of oil depots
According to the “Code for Design of Petroleum Depots” (GB50074-2002), the oil depots we usually refer to are receiving and storing crude oil, gasoline, kerosene, diesel, solvent oil and heavy oil and other bulk and bulk oils. Independent or company-affiliated warehouses or facilities.
1. Metal storage tanks with a volume of more than 50,000 cubic meters require a grounding resistance of less than 5Ω, and metal storage tanks with a volume of less than 50,000 cubic meters require a grounding resistance of less than 10Ω. When the thickness of the tank top plate is greater than 4mm, the tank body can be used as an air-termination device. The metal storage tank must be provided with a ring-shaped lightning protection ground, with no less than 2 grounding points, its lightning protection grounding resistance not greater than 10Ω, and its lightning protection induction grounding resistance not greater than 30Ω. Metal fittings such as flame arrestor, breathing valve, oil metering hole, light transmission hole, and inlet hole of metal oil tank must be equipotentially connected.
2. Non-metallic oil tank.
Non-metal oil tanks generally adopt independent lightning rod (net) protection measures. First of all, it should be noted that the horizontal distance between the independent lightning protection device and the protected object should not be less than 3m. If the lightning protection net is adopted, its grid should be no more than 6m×6m, and there should be no less than 2 down conductors, and they should be arranged evenly or symmetrically. The non-metal lightning protection grounding resistance should be less than 10Ω, and the metal fittings such as flame arrestor, breathing valve, oil metering hole, light penetration hole, and inlet hole must be equipotentially connected and within the protection range of the lightning protection device.
3. Oil depot power supply system.
The power, lighting and communication lines of the oil depot should be buried in the ground with armored shielded cables. Overvoltage protection (surge protection) devices should be installed at the connection with dangerous overhead lines. Voltage protectors, cable sheaths and insulator iron feet should be made. Electrical connection and grounding, the impulse resistance is not more than 10Ω.
4. Oil depot transportation system.
The oil unloading station of the oil depot should have an anti-induction lightning grounding test point, and the oil delivery pipeline should be connected to an electrical path, and be anti-induction grounding.
2. Lightning protection safety inspection of automobile gas stations.
According to the “Code for Design and Construction of Automobile Gas Stations” (GB50156-2002), automobile gas stations are mainly composed of underground oil storage tanks, gas islands, automobile unloading yards and station buildings. .
Lightning protection detection for car gas stations. The steel body oil tank must be grounded for lightning protection, and its grounding points shall not be less than two. Gas station buildings, refueling islands, tank farms, and canopies in lightning-struck and mine-ridden areas should adopt anti-lightning protection devices; metal fittings such as the tank body, oil gauge, and flame arrestor of buried oil tanks should be electrically connected and grounded. The contact resistance of its connection is not more than 0.03Ω; the impact ground resistance of the lightning protection grounding device is not more than 10.00Ω; the oil delivery pipeline of the automobile gas station should be equipped with an induction lightning protection grounding device, and its grounding resistance is less than 30.00Ω.
3. Lightning protection safety inspection
for explosives warehouses When conducting lightning protection inspections for gunpowder, explosives and chemical reagent warehouses, the following should be paid attention to:
1. Facilities for preventing direct lightning strikes and lightning protection wave intrusion must be installed around explosives warehouses. There must be anti-lightning devices around the warehouse, such as lightning arresters or lightning rods, overhead lightning protection nets, etc., and the cross-sectional area of the down conductor is greater than 50mm2.
2. The electrical wiring of the warehouse should be laid in the ground with armored shielded cables, and the metal sheath of the cable at the lead-in end should have a lightning protection induction grounding test point.
3. The grounding resistance of the explosives warehouse against direct lightning should be less than 10Ω, and the grounding resistance against lightning induction and lightning wave intrusion should be less than 5Ω.
4. The distance between the grounding device of the explosives warehouse and the warehouse should be more than 3m.
4. Lightning protection safety detection
of gas storage tanks Gas storage tanks are equipment used for city gas, natural gas supply regulation and various gas storage in industrial production.
1. When the thickness of the bell top cover of the gas storage tank is greater than 4mm, the top plate of the bell top cover can be used as the air-termination device; on the contrary, a lightning arrester or lightning protection line should be provided on the bell top plate. The grounding resistance value of its anti-direct lightning strike should not be greater than 5Ω.
2. There should be a grounding device at the difference of the gas storage pipe of the storage tank. For directly buried pipelines, grounding test devices should be made at the buried and ground ends.
3. All electrical circuits in the tank area should be directly buried with armored shielded cables. The metal sheath of the cable should be grounded for lightning protection at the lead-in end, and corresponding overvoltage protectors should be provided.
4. The grounding device of electrical equipment and the grounding device for preventing direct lightning should be installed separately, and the grounding resistance of electrical equipment should be less than 4Ω.
V. Lightning protection safety detection in high-risk locations
According to the “Building Lightning Protection Design Plan” (GB50057-1994 2000), high-risk locations refer to buildings and locations that cause explosions or fires when sparks are generated by lightning or other methods.
High-risk places should have independent direct lightning protection devices (lightning rods, lightning conductors or overhead lightning protection nets) to protect the roof of the entire building and its protruding parts. The space below the pipes and nozzles where explosive gases, vapors, dusts are discharged should be within the protection range of the anti-lightning device. The lines leading into high-risk places should be directly laid with armored shielded cables, and should be connected to a lightning-proof grounding device at the entrance of the house. Its impulse grounding resistance should not be greater than 10Ω. An over-voltage protector should be installed at the main power distribution cabinet where the power supply is introduced. When buildings in high-risk locations are higher than 30m, a side lightning protection device should be added.