General electrostatic discharge phenomenon is divided into corona discharge, brush discharge, spark discharge, spreading brush discharge. Experiments show that the spark discharge fire danger is the largest diameter of 1cm ~ 2cm on the surface of the sphere of the discharge, the tip of < 1cm, the diameter of the spark is small, spark energy is small, not enough to detonate the surrounding combustible mixture, so the tip of the corona discharge is far more dangerous than the tip of the general radius of curvature of the charged body discharge danger of a small general spark discharge is dangerous in the process of chemical production of fire.
In recent years, the world's lightweight flammable liquids and rubber, plastic products in the process of processing and handling of electrostatic fires, explosions increased significantly, resulting in significant economic losses, should attract sufficient attention. The generation of electrostatic hazards have a specific process. In the work environment, all the fire and explosion caused by static electricity follow the same procedure, as described below: the first occurrence of charge separation, and then the accumulation of charge, if the charge can not be dissipated, then the electrostatic discharge will occur, at the same time, may lead to ignition of flammable substances around the fire and explosion hazards occur.
Many industrial processes often use very poor conductivity of the material, and often surface contact, separation and movement of the operation, resulting in the phenomenon of charge separation. Examples include the flow or filtration of highly resistive liquids, the grinding, mixing or screening of powders, the pneumatic transfer of powders, the movement of people or vehicles on insulated floors, the movement of conveyor belts or sheet materials on rollers. The problem of static electricity occurs in these or similar processes. When an electric charge accumulates on an object to the point where the electric field reaches a dielectric strength of 3 MV/m in air, a discharge occurs, releasing all or part of the stored energy, creating a path of light and heat, and potentially igniting flammable substances. Based on the minimum ignition energy data of a flammable substance, it can be deduced whether the energy of the electrostatic discharge is sufficient to ignite the flammable substance. Electrostatic generation can be categorized into friction, static build-up and migration types according to the process mechanism.
Static electricity accumulation and migration type : two charged charged body for the cycle of movement, the accumulation of positive and negative charges are always very close to the constant in the two charged positive and negative charged body formed within the action of the electric field. Such as belt and pulley charge accumulation. With the accumulation of charge, the two positive and negative charged body between the electric field strength increases, and finally reached the breakdown field strength.
Only through the spark discharge between the two positive and negative charged body to disappear energy, this case, the pulley grounding and no effect. Because there is no electric field between the pulley and the earth, pulley grounding and can not eliminate the charge. Can take two ways to prevent the belt and the pulley between the occurrence of electrostatic sparks: one is to make the air humidity increases to accelerate the two charged bodies between the non-spark slow discharge; the second is coated with belt oil on the belt and other easily conductive liquids, so that the ability to start the weakening of the two charged solids between the direct conductive charge removal ability to enhance.