Why does static electricity occur in hazardous chemical storage tank areas?

Thread Content

Why does static electricity occur in hazardous chemical storage tank areas? The production processes in hazardous chemical storage tank areas typically include various tasks such as the loading and unloading, transportation, blending, sampling, measuring volume, taking temperature readings, and cleaning of equipment. But why does static electricity arise in hazardous chemical storage tank areas? Security experts point out the following aspects: 1. The resistivity of hazardous chemicals affects the generation of static electricity. When the resistivity of a liquid is between 1010–1015 Ω·m, dangerous levels of static electricity can be generated, with the highest levels of static electricity occurring at a resistivity of 1013 Ω·m. At values above 1015 Ω·m and below 1010 Ω·m, the generation and accumulation of static electricity are minimal. For example, the resistivity of crude oil and heavy oil is 109–1010 Ω·m, so the risk of static electricity generation is low, whereas the resistivity of gasoline, kerosene, light oils, and jet fuel is 1012–1013 Ω·m, making these substances the most prone to generating static electricity. 2. Static electricity generated by the methods of loading and unloading hazardous chemicals. The methods of loading and unloading hazardous chemicals can be divided into two types: one is bottom-loading, and the other is top-loading. Compared to the two methods, the latter generates more static electricity. The top-loading method generates static electricity not only due to the charge created by liquid separation, but also because of the splashing droplets resulting from hazardous chemicals hitting the tank walls; the amount of static electricity produced by top-loading is much greater than that generated by bottom-loading. 3. Mixing different hazardous chemicals increases static electricity generation. When different hazardous chemicals are mixed together, their densities and particle properties vary; friction between these particles during transportation or mixing can easily lead to the generation of static electricity. 4. Water deposits at the bottom of the tank increase static electricity charge. If there is water deposited at the bottom, loading hazardous chemicals there will stir up this water, thereby generating a high static electric potential. Water is a good conductor of static electricity; however, when a small amount of water is mixed with hazardous chemicals, the movement of water droplets relative to these chemicals generates static electricity, thereby increasing the amount of static electricity present in the hazardous chemicals. 5. Static electricity dissipation time factor: When hazardous chemicals are poured into storage tanks, it often takes some time from the moment pouring stops until the maximum static electric potential is reached at the liquid surface; this time is commonly referred to as the delay time. When it is necessary to directly measure the liquid level or the temperature of hazardous chemicals, the discharge time of static electricity within the tank should be avoided. The greater the filling volume, the longer the static electricity dissipation time. It is generally safer to conduct measurements after 3 to 5 minutes.