Electrostatic fire hazard analysis —electrostatic discharge

Static electricity can generate high voltages and electrostatic fields. If the electric field strength exceeds the dielectric breakdown electric field of the nearby dielectric, discharge will begin. Generally speaking, the dielectric constant of gas is smaller than that of liquid or solid, so it is easier to discharge. Preventing gas discharge, especially the discharge in the air, is the focus of electrostatic fire prevention.

Electrostatic discharge can be divided into air discharge and surface discharge. The air discharge includes corona discharge, brush discharge and spark discharge. There is no essential difference between the various discharge forms, and the difference in the discharge form depends on the amount of charge. Distribution and leakage rate.

Corona discharge generally occurs between different electrodes that are far apart and have sharp protrusions on the surface. Partial air ionizes during discharge, the discharge energy is small, and the risk is small.

Brush-shaped discharges mostly occur on insulators. During discharge, the air between the electrodes is broken down, forming many bifurcated discharge paths. The discharge energy is slightly larger than that of corona discharge, which is more dangerous.

Spark discharge mostly occurs between metal objects. The air between the electrodes is broken down during discharge, forming a very concentrated discharge path, and the risk of ignition is the greatest. Preventing spark discharge is a static hazard that needs special control in the chemical production process.

The main reason for the damage caused by static electricity is that the electrostatic discharge spark has enough energy. The calculation formula is as follows:

E=1/2QU—1/2CU2