Static electricity prevention measures should be taken for belt conveyor lines

In most industrial processes, the accumulation of electrostatic charges can cause discomfort and harm to the human body. Even during the loading, unloading, and transportation of flammable gases, liquids, and dust, fires and explosions can occur. Belt conveyor lines are no exception, therefore, it is necessary to take measures to prevent static electricity. Below, we will talk about how to do a good job of static electricity protection for belt conveyor lines.

There is no single method for preventing electrostatic hazards that can be applied to all industrial processes or situations, and sometimes two or more methods for preventing electrostatic hazards in belt assembly lines are used simultaneously.

（1） Grounding is an effective and economical method for preventing electrostatic hazards in grounding. During the manufacturing process, static electricity is generated through friction, induction, or conduction. If charges accumulate on metal equipment, conductive products, or personnel that are insulated from the ground, the accumulated charges will release energy in a single discharge. Electrostatic discharge from conveyor line manufacturers is the main cause of electrostatic hazard accidents. The prevention method is to ground all conductive objects and maintain a low grounding resistance, quickly dispersing the charges accumulated on metal equipment, conductive products, or personnel's bodies towards the ground to avoid electrostatic hazards.

According to relevant research, in general workplaces with flammable vapors, the potential of insulated metal equipment/components, conductive products, or personnel themselves must reach over 100V in order to ignite the surrounding flammable substances due to discharge. Therefore, grounding insulated metal equipment/components, conductive products, etc. in the factory, maintaining a grounding resistance of less than 106 Ω, is sufficient to quickly dissipate accumulated charges towards the ground and reduce the electrostatic potential to below 100V, in order to avoid electrostatic hazards.

（2） Increasing humidity to increase the relative humidity of the air in the working environment is also a common method for preventing static hazards in traditional industrial processes. In high humidity (R.H.>65%) environments, if the surface of a substance is hydrophilic, it is easy to adsorb water from the air, thereby reducing the surface resistance value of the substance, increasing the rate of charge dissipation, and reducing the degree of charge accumulation to Z. These substances include cotton, paper, and cellulose acetate. In the production process of conveyor line factories, methods such as humidifiers, ground watering, or steam spraying are usually used to increase the relative humidity of the air in the working environment. If the surface of a substance is non hydrophilic, it is not easy to adsorb water in the air, resulting in the inability to reduce the surface resistance value of the substance, and therefore cannot increase the rate of charge dissipation. This type of substance includes some artificial polymers such as ABS (Acrylonitrile Butadiene Styrene), Teflon (Teflon, fluorocarbon polymer), etc. This type of high water repellent substance requires a relative humidity increase of 80%, or even more than 90%, in order to effectively reduce the surface resistance value of the substance and reduce the degree of charge accumulation to Z low.

（3） The static electricity accumulated in the process of producing anti-static materials on the conveyor line will dissipate towards the ground through the conduction path. If the conduction path is made of insulating materials (with low conductivity), the electrostatic escape rate is low; if the conduction path is made of conductive materials (with high conductivity), the electrostatic escape rate is high. The surface resistance coefficient of a substance is less than 1011 Ω/m2 or the volume resistance coefficient is less than 1010 Ω/m2, which can avoid excessive accumulation of static electricity in the substance. This type of substance is called an anti-static material. However, in workplaces containing flammable substances, the surface resistance coefficient of anti-static materials should be less than 108 Ω/m2 or the volume resistance coefficient should be less than 106 Ω/m2. For various materials used in the industrial process, they can be made into anti-static materials by the following methods: the material itself has anti-static capacity (such as cotton, wood, paper and soil), the surface of insulating materials is coated with anti-static materials (such as carbon powder, antistatic agent, etc.), and conductive or anti-static materials (such as carbon powder, metal, antistatic agent, conductive fiber, etc.) are added in the manufacturing process of insulating materials.

（4） Electrostatic eliminators use high-voltage electricity to generate charged ions in the air. Due to the mutual attraction and neutralization of opposite charges, ions can neutralize the charges of objects with static electricity, reducing their charge accumulation to a low level, thus avoiding electrostatic discharge. Electrostatic eliminators can be roughly divided into three types: passive, active, and radiation source. When choosing an electrostatic eliminator, it is necessary to consider the working environment factors in order to achieve the maximum electrostatic elimination effect. Generally speaking, the installation position of electrostatic eliminators should be close to objects with static electricity and away from grounded metal objects, in order to achieve the maximum static electricity elimination effect. In addition, attention should be paid to the industrial hygiene issues of ozone generated by ionization, as well as the industrial safety issues caused by short circuits and discharges between high-voltage power sources and charged bodies.

（5） In industrial processes, two types of objects may generate static electricity due to friction and gradually accumulate, resulting in static electricity hazards. Therefore, reducing the friction speed can slow down the generation of static electricity and achieve the goal of preventing static electricity hazards from occurring. In industrial processes, electrostatic hazard prevention methods that limit speed due to material characteristics and production requirements are usually applied to the transportation of flammable liquids. When transporting liquid raw materials to storage tanks or containers, if the flammable liquid has a low conductivity (less than 50 pS/m) and contains incompatible substances such as suspended solids and water, the flow rate of the flammable liquid should be limited to less than 1m/s during on-site operations. If the flammable liquid does not contain incompatible substances, the liquid flow rate should be limited to less than 7m/s. General industrial processes can follow this principle for process design and production operations. The splashing caused by the feeding operation of flammable liquids with low conductivity is also one of the potential sources of electrostatic hazards in the manufacturing process. The liquid feeding pipeline can be placed as close as possible to the bottom of the storage tank/container, or the liquid raw material can be transported by the feeding pipeline at the bottom of the storage tank/container, or the flow rate of flammable liquid can be reduced. The main purpose is to reduce the friction and disturbance of the liquid when passing through the liquid surface, in order to avoid generating a large amount of static electricity due to excessive friction.