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Precautions against static electricity in oil depots: During storage, transportation, loading, unloading, filling, and blending, oils come into contact with tanks, pipelines, tank trucks, fueling vehicles, filters, piston-type electro-hydraulic valves, pumps, and other components, which leads to the generation of static electricity through movement and friction. When static electricity accumulates to a certain level, the electric field strength generated around it may exceed the breakdown strength of the surrounding medium, leading to discharge. If the discharge energy is greater than the minimum ignition energy of the fuel, and the fuel-air mixture reaches a certain concentration, static electricity can cause ignition, leading to fire and explosion accidents. This not only leads to massive waste and loss of fuel, but also results in casualties and damage to weapons and equipment; it may even cause the entire fuel depot to be destroyed. Of course, electrostatic accidents mostly occur during loading or oil reception into tanks. To prevent static electricity accidents in oil depots, the safety measures mainly include: reducing the generation of static electricity ； Accelerate the discharge of static electricity to prevent its accumulation ； Prevent the formation of explosive gases ； To prevent the human body from becoming charged, etc. I. Reducing the generation of static electricity To reduce the generation of static electricity in oils, measures such as controlling the flow rate of the oil, improving the method of filling the oil, preventing mixing of oils with different flash points, avoiding impurities, ensuring that the oil passing through filters has sufficient time to discharge static electricity, preventing water from entering the oil, reducing the number of bends and valves in the pipelines, and selecting appropriate transfer pipes should be considered. (1) Controlling the oil flow rate: Since the flow charge and the saturation value of charge density generated by the flow of oil in pipes are proportional to the square of the oil flow rate, controlling this flow rate – especially during the intake of oil into tanks, filling processes, and refueling – is an effective way to reduce static electricity generation in oil. According to the \"Code for Design of Oil Storage Tanks\" (GBJ74—84), the outlet of the loading arm can increase the tank filling speed only when it is submerged in oil; therefore, submerging the flow while filling with oil is recommended. Meanwhile, the tank filling speed for light oils such as gasoline, kerosene, and light diesel should not exceed 4.5 m/s, and the initial filling speed should be less than 1 m/s. (II) Improving the oil filling method The oil filling methods include two types: one is filling from the bottom through undercurrent ； The second is to fill the oil by spraying from the top. Generally speaking, oil filling from the top by splashing generates twice as much static electricity as filling from the bottom by underflow, so filling from the bottom is a better method. If a tank filling method with oil inlet from the top is used, the dip pipe should be inserted into the bottom of the tank. During spraying and filling, the rapid expulsion of oil from the dip pipe causes the liquid to separate quickly, resulting in the generation of a large amount of static electricity ； At the same time, when oil hits the tank walls, it can also cause splashing droplets that generate static electricity. Of course, the amount of charge generated is closely related to factors such as the diameter of the oil loading hose, the flow rate of the oil, the shape of the pipe opening, and the height of the pipe end above the oil surface. Filling oil from the top not only generates static electricity due to splashing but also produces oil mist, allowing the mixture of oil vapor and air to easily reach an explosive concentration. Furthermore, top filling can also cause local charge accumulation on the oil surface, thereby facilitating spark discharge. Filling from the bottom undercurrent can reduce oil splashing, thereby lowering volatility and losses ； And to prevent oil flow from passing through the middle of the tank car with a smaller capacity, thereby avoiding a high oil surface potential. However, oil intake at the bottom can also generate new charges. If there is settled water at the bottom of the tank, oil entering from the bottom will stir up this settled water, resulting in a very high static electric potential. (III) Preventing the mixing of oils with different flash points and avoiding impurities There are many cases both domestically and internationally of serious accidents resulting from the mixing of oils with different flash points. Oil blending generally occurs during blending, switching, or when two pipelines feed different types of oil into a tank simultaneously ； And when pouring heavy oil into containers filled with gasoline or other light oils. In addition to the increased chargeability that can result from mixing oils, another reason oil mixing leads to accidents is that diesel, kerosene, fuel oil, and similar substances are all oils with low vapor pressures, whose flash points are all above 38°C. Under normal circumstances, no accidents occur when transporting oil at temperatures below its flash point. However, if this type of oil is poured into a container containing oil with a low flash point, the heavier oil will absorb the vapors of the lighter oil, thereby reducing the pressure inside the container and allowing air to enter. As a result, the space that was previously filled with gases from the lighter oil turns into an explosive mixture of oil vapor and air. Once a fire source appears, it can trigger fire and explosion accidents. The presence of impurities is also one of the causes of static electricity accidents. If a facility uses one pipeline to transport aviation fuel to a tank while simultaneously using another pipeline to supply oil, the residues remaining in the latter pipeline are also sent into the tank. Although the flow rate is not high, at only 2 m/s, an explosion occurred due to static electricity. Therefore, preventing impurities from mixing into the oil is also one of the methods to reduce static electricity. (IV) The oil flowing through the filter must have sufficient time for leakage to occur. To reduce the generation of static electricity, it is necessary to ensure that the oil passing through the filter has enough time for leakage to take place. As the oil flows through the filter, it comes into intense friction with the filter, causing the charge level to increase by 10 to 100 times; moreover, filters made of different materials generate different amounts of static electricity. The static electricity generated by filters made of different materials. Therefore, to prevent large amounts of charged oil from entering tanks and tank trucks, the leakage time of the oil flowing through the filter should be at least 30 seconds. (V) Other methods to reduce static electricity generation The amount of static electricity generated during the filling of oil tanks depends not only on the flow rate of the oil being poured in, but also on factors such as the height of the filler nozzle, the shape of the nozzle, and the material from which the nozzle is made. When a large hose is used, an electrostatic potential of tens of thousands of volts is generated when the oil flow rate exceeds 5 m/s. Therefore, selecting the appropriate flexible hose and positioning its outlet properly is also an effective way to reduce static electricity generation; usually, the outlet of the flexible hose is placed 100–200 mm from the bottom of the tank. When oil flows through pipelines, static electric charges are generated due to contact and separation with the elbows and valves present in the pipeline; therefore, the number of elbows and valves in the pipeline should be reduced as much as possible. Additionally, it is also necessary to prevent moisture and other substances from mixing into the oil in order to reduce the generation of static electricity. II. Preventing the accumulation of static electricity Measures to prevent the accumulation of static electricity include: adding antistatic additives to oils, grounding and bonding equipment and facilities, and installing static eliminators and static relaxers on pipelines. (1) Adding antistatic additives Any type of oil has a certain level of electrical conductivity. Experiments have shown that when the conductivity of the oil is too high or too low, the static electric charge generated is not significant; generally, when the conductivity is in the range of 1–20 mS/cm, the generation of static electricity in the oil is dangerous. The conductivity of oils such as gasoline, kerosene, diesel, and jet fuel is around 5–10 mS·cm, which poses a high risk of causing static electricity accidents. By adding trace amounts of antistatic additives to the oil, its conductivity can be increased by ten or even a hundred times, thereby accelerating the discharge of static electricity from the oil, reducing the accumulation of static charge, and lowering the electric potential of the oil, without affecting its quality. The additives currently in use are mainly the domestically produced T1501 antistatic agent and the ASA-3 antistatic agent developed by Shell Oil Company in the Netherlands. The T1501 antistatic agent consists of three components: chromium alkyl salicylate, calcium diisostearate sulfonate, and a copolymer of “603”. The first two components are the key elements that modify the electrical conductivity of the oil, while “603” serves as a stabilizing and performance-enhancing agent. Different oil types exhibit varying effects of antistatic agents on reducing resistivity, but the general trend is that the resistivity of the oil decreases as the content of the antistatic agent increases, in a roughly linear manner. The relationship between the antistatic agent content and the electrical conductivity of the oil is shown in Table 4–6. Relationship between additive content and oil conductivity: The amount of this additive used is generally one part per million by weight (i.e., 1 ppm). For domestic aviation fuels of various grades, adding just 1 ppm of T1501 is sufficient to keep the conductivity within the range of 140–210 conductance units, which is safe enough for loading onto trains. Since antistatic agents are flammable in nature, they should be stored in iron drums, kept away from strong oxidizers and acids, and areas around them must be free of open flames. (II) Grounding and bonding of facilities and equipment Oil products are non-static conductors (resistivity of 106 Ω·m) or sub-static conductors (resistivity > 106 Ω·m),