How to prevent static electricity hazards in oil tankers

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1. The amount of fuel in the tank of a fuel truck should be appropriate. If too little fuel is in the tank, there is more movement during transportation, which increases the risk of static electricity generation； If too much is loaded, it can easily cause leakage in tank trucks with poorly sealed tank openings; therefore, a filling level of around 85% is appropriate. Additionally, a moderate speed should be maintained during transportation to ensure stability of the fuel in the tank of the fuel truck, and emergency braking should be minimized as much as possible. 2 When changing the type of fuel, the existing fuel must be completely drained. Changing the type of fuel refers to situations such as a tank that was originally filled with gasoline now being filled with kerosene or diesel, or vice versa. Changing the type of fuel can easily lead to the formation of explosive mixtures inside the tank, especially when a tank truck’s tank originally contained gasoline and is now filled with kerosene or diesel. The reason is that both kerosene and diesel have the property of absorbing gasoline vapor, which dilutes oil tanks that are already filled with gasoline vapor and in a fuel-rich state to a level where explosion can occur. This is especially true in winter; if static electricity causes a spark, it can lead to serious accidents such as fires and explosions. According to an accident investigation report by the American Petroleum Institute, out of 620 static electricity-related accidents involving tank trucks, 440 were caused by changes in the process of loading oil. Therefore, when a tank truck changes its cargo, it is necessary to drain as much of the sedimented oil from the tank as possible, open the tank’s opening, and allow any remaining oil in the tank to evaporate. Additionally, when filling the tank with oil, it is also necessary to inform the person responsible for pouring the oil about the type of oil that was originally in the tank, so that they can carry out their tasks in accordance with the regulations, such as by limiting the flow rate of the oil. 3. Keep the fuel tank of the fuel tanker clean. The tank must not contain any water or impurities, as water in the fuel can significantly alter its electrical properties, causing the voltage inside the tank to increase by dozens or even hundreds of times; it may also lead to discharge in the form of sparks. A tank truck is equipped with two fire extinguishers; the manufacturer installs two extinguisher cylinders at the time of production, one on the left side of the tank truck’s tank and the other on the right side. Impurities in oils also have a significant impact on static electricity; in particular, certain floating substances such as wood chips, rubber, and isolated metal balls (e.g., floats that fall off the level gauges in some oil tankers) are extremely dangerous. Primarily, this type of conductivity possesses capacitive properties that enable it to collect and store a large amount of static electric charge. Moreover, since there is no fixed path of movement within the oil tank of the tank truck, it can easily come into contact with the tank walls or other components inside the tank, thereby creating an appropriate discharge gap. Tests have shown that once this phenomenon occurs, a spark discharge can take place as long as there is a potential difference of 1-2 KV with respect to the liquid surface (the normal value for a liquid surface is 28-30 KV). The discharge energy is high, allowing all the stored energy to be released at once. 4. Ensure that all other accessories of the fuel tank truck are in good condition. Valves, vent valves, and the sealing rings on the tank cover of the fuel tank truck should always be in proper working order to prevent fuel leakage or spillage, as well as fires caused by static electricity sparks. 5. Connect the static electricity wires properly: Before loading or unloading oil, it is necessary to connect the oil tank truck and the oil loading/unloading equipment using static electricity wires (static electricity wires for connecting to the oil tank truck are installed in all oil depots). Its function is: ① To conduct away the static electricity generated in the oil tank, preventing sparks from being generated in contact with external substances ； ②Keep the oil tank trucks and the entire oil loading/unloading equipment at the same potential to prevent potential differences ； ③It accelerates the leakage of charge in oils. When connecting the electrostatic wires, it is essential to choose rust-free and exposed metal parts on the tank truck; they must not be connected to areas that are severely rusted or covered with paint. Data shows that good electrostatic conductivity can only be achieved when the resistance of the entire static grounding system is less than 10 ohms. A more ideal approach is to install a special copper plate at a certain part of the tank truck, dedicated to connecting the static electricity wires. Furthermore, the static grounding wire on a tank truck cannot be used as a static conductor for loading and unloading oil, because when loading and unloading oil, the tank truck is usually parked on concrete or relatively hard surfaces, and the resistance of its static grounding wire is unlikely to be lower than 10 ohms; as a result, it is difficult to keep the equipment used for loading and unloading oil at the same potential. 6 It is necessary to ensure that the anti-static equipment on oil tankers is in good condition. The main components of such anti-static equipment include static grounding wires and oil separation plates inside the oil tanks. Electrostatic grounding wires come in two types: chain-type and conductive rubber strap-type. The former has disadvantages such as the tendency to generate sparks due to friction from mopping, intermittent electrical connection when grounded, and increased leakage resistance due to susceptibility to rust; therefore, newly manufactured tank trucks now all use rubber grounding straps. Therefore, the static grounding wire should be adjusted regularly to ensure good contact with the ground, and a multimeter should be used frequently to check for continuity and any breaks; if issues are detected, the wire should be replaced promptly. The function of the oil separation plate is to reduce the shaking and splashing of the oil inside the tank during transportation by tank trucks, thereby minimizing the generation of static electricity. If the oil separation plate is removed from the maintenance tank, it must be reinstalled promptly; it should not be considered a dispensable component.