How to prevent static fires in the petrochemical industry
Static electricity is one of the major causes of fires in the petrochemical industry and in industries where flammable gases, vapors and dust are often produced. Therefore, it is necessary to take measures to prevent static electricity generation and electrostatic protection.
In general, static and solid surfaces, solid and liquid surfaces contact and impact, or solid fractures, liquid splashes, may generate static electricity. For example, the flow of high resistivity liquids (such as petroleum), the filtration of liquids, the grinding of dust, the movement during mixing and screening, the gas transfer of dust, the movement of people and machines on insulated floors, the relative movement of belts and axles. Static electricity can be generated by similar processes. When the electrostatic potential reaches a certain value, it will break through the surrounding gas and generate a spark. When the energy of the spark reaches a sufficient value, it can ignite certain flammable substances and cause a fire.
According to past experience, there are three main conditions for causing an electrostatic fire. The first is the existence of flammable or explosive materials; the second is the generation of electric charge during the installation, operation and operation of the equipment, the accumulation of electric charge, the electric field strength formed by the electric charge is greater than the surrounding breakdown electric field strength; the third is that the electric spark has more energy than the surrounding The minimum ignition energy. If one of the above three conditions is missing, it will not cause an explosion or fire. Anti-static safety measures are to remove one or more of the above factors for specific situations. There are several ways to do this.
The first is grounding. The static charge on the conductor can be grounded by grounding so that the charge does not accumulate on the conductor.
The second is to avoid the accumulation of static charge in people. The main causes of the static charge on a person are the friction between the clothes, the transfer of charge after contact with other electrostatically charged objects, or the electrostatic induction when the object is close to the charged object. To prevent the accumulation of static charge in people, low-resistance anti-static footwear, floor, etc. can be used.
The third is to ionize the atmosphere. Since ionization increases the conductivity of the surrounding air and facilitates the movement of static charges on the surface of the object, the discharge of the charged object or the use of a dose of an isotope to ionize the air to neutralize static electricity in the object or in the air.
The fourth is humidification. Increasing the humidity of the air can improve the electrical conductivity of the surface of the object and form a conductive path between the object and the ground. Generally, the relative humidity is controlled at 60%-70%, and the anti-static effect is very good.
Finally, do anti-static treatment of non-metallic materials. Many non-metallic materials, such as plastics, rubber and fiberglass, are insulators that are extremely static and can last for a long time. It is common to add some substances to these materials to make them electrical conductors, and then use grounding to eliminate the accumulation of static charges.