How should manufacturing enterprises prevent static electricity

Thread Content

Static electricity is a natural phenomenon that is commonly present in production and daily life. It’s winter now; the weather is dry, making it easier for static electricity to occur. The generation of static electricity is inevitable in safe production activities, and it poses a serious threat to enterprises engaged in safe production. This is because, in various safety production processes, flammable and explosive materials are inevitably used, and factors such as processes, equipment, or personnel can generate static electricity; if not properly controlled, this can lead to fire and explosion accidents. Avoiding the hazards of static electricity is one of the issues that all types of enterprises should pay attention to, and it is necessary to strictly implement various preventive measures. Cause of static electricity: Static electricity is a form of charge that is at rest. It is primarily caused by charge transfer that occurs due to close contact, separation, or friction between objects, which disrupts the balance of positive and negative charges within the atoms of those objects, resulting in a potential difference being created at the point of contact between the two materials. 1. Close contact and rapid separation. This is the most common way in which static electricity is generated. When two objects come into contact, charge transfer occurs; if they are separated fast enough, the objects will acquire static electricity. 2. The attachment surface is charged. The attachment of certain polar ions or charged dust to a solid that is insulated from the ground can endow that solid with static electricity or change its charge status. The amount of charge an object acquires depends on its capacitance to the ground and the surrounding conditions. When people are in environments with charged particles, their bodies too accumulate static electricity. 3. Induced electricity. In industrial production, there is a phenomenon in which objects with static electricity charge nearby unconnected conductors. 4. Electrolytic generation of electricity. When a metal is immersed in an electrolyte solution, metal ions diffuse into the solution, and a double layer forms at the interface, creating a potential difference. Under certain conditions, the potential difference is sufficient to prevent further dissolution of metal ions, achieving an equilibrium state. When the equilibrium state is disrupted, metal ions continue to diffuse, thereby generating an electric current. 5. Generation of electricity via the piezoelectric effect. Certain solid materials generate charge under mechanical force. Although the charge density generated by the piezoelectric effect is low, it still possesses enough energy to cause an explosion. 6. Polarization charging. In an electrostatic field, charges appear inside and on the surface of an insulator; this is the result of polarization. Based on different molecular structures, it can be divided into non-polar molecule polarization and polar molecule polarization. 7. Ejected charge. When powders, liquids, and gases are ejected from openings with very small cross-sections, these flowing substances experience intense friction with the nozzle, and at the same time their molecules collide with each other, generating a large amount of static electricity. 8. Droplets are charged. The liquid sprayed into space forms new liquid surfaces due to diffusion and separation, generating static electricity. Additionally, other ways to generate static electricity include floating and freezing. It should be noted that the ways in which static electricity is generated are usually not singular, but rather the result of several factors working together. Three common hazards: causing fires and explosions. Triggering explosions and fires is the greatest hazard of static electricity. Although the energy of static electricity is not high, it can generate static sparks due to its tendency to discharge. In flammable and explosive areas, fires and explosions can be caused by static electricity sparks. Electric shocks caused by static electricity can occur when a person comes close to a charged object, or when a person carrying static electricity comes close to a grounded object. Under normal circumstances, the energy of static electricity is low; therefore, electric shocks caused by static electricity during the production process do not lead to death directly. However, static electric shocks can cause injuries such as falls and trips, and they can also lead to psychological stress among workers, affecting their normal work. Impact on production: In certain manufacturing processes, failing to eliminate static electricity can affect production or reduce product quality. In addition, static electricity can cause electronic components to malfunction, leading to secondary accidents. Measures to eliminate static electricity: There are two main ways to eliminate static electricity: creating conditions to accelerate its dissipation or neutralization; and controlling the manufacturing process, that is, limiting the generation of static electricity. The first approach includes two methods: the leakage method and the neutralization method. The second approach includes measures such as material selection and process design. The leakage diversion method, also known as static grounding, is the most fundamental measure for eliminating static electricity. Companies can use technical methods to humidify the air and add antistatic agents; they can also employ methods such as static bonding, direct grounding, and indirect grounding to connect various components of the equipment to the ground through grounding electrodes. ☆Some fixed equipment, such as towers, containers, pumps, heat exchangers, and the enclosures of centrifuges, should be subjected to electrostatic grounding. For equipment with a diameter of 2.5 meters or more and a volume of 50 cubic meters or more, there should be no fewer than two grounding points, which should be arranged evenly along the perimeter of the equipment, with a distance between them not exceeding 30 meters. For fixed equipment that experiences vibration, its vibrating components should be grounded using copper-core flexible stranded wire; single-strand wire shall not be used. Between several devices that are connected via flexible connections, copper core flexible stranded wire should be used for bridging. The belt-driven units, as well as their anti-static grounding brushes and protective covers for the belts, must all be grounded. Fixed equipment and grounding wires or connection wires should preferably be connected using bolts. Metal components insulated from the ground, such as flanges and hose couplings, shall be cross-connected to a grounding conductor using flexible copper stranded wire. ☆The pipes in the piping system should be grounded at the points where they enter and exit the equipment area (including the production workshop buildings) as well as at the branching points. Long-distance unbranched pipelines should be grounded every 100 meters. When the clear distance between parallel pipes is less than 100 millimeters, jumper wires should be installed every 20 meters; when the pipes intersect and the clear distance is less than 100 millimeters, jumper wires should also be installed. When a metal flange is fastened with metal bolts or clamps, it is generally not necessary to install additional electrostatic connection wires, but it must be ensured that there is good electrical contact between at least two of the bolts or clamps. For the non-conductive sections in the metal piping, in addition to requiring special anti-static treatment, the metal pipes at both ends should be connected to the grounding main line respectively, or bridged with copper-core flexible wire and then grounded. All metal components on non-conductive pipe sections shall be grounded. ☆In work areas where human body grounding is required, metal grounding rods should be installed for static electricity discharge from the human body. The operators can touch the metal grounding rod at any time to discharge the static electricity on their bodies. At the location where work is done while sitting, the workers can wear grounding wristbands. At the entrance of anti-static areas, there should be metal grounding devices. In areas where there is a risk of static electricity, workers should pay attention to their attire: they must wear anti-static clothing, conductive shoes, and anti-static gloves. Wearing clothes made of synthetic fibers is prohibited. The electrostatic neutralization method primarily involves ionizing molecules to generate the ions necessary for eliminating static electricity. The ions with a polarity opposite to that of the charged object move toward that object and neutralize its charge, thereby achieving the elimination of static electricity. The main types of static eliminators made using this principle include self-inductive type, externally powered type, radiation type, ion flow type, and combined type, allowing enterprises to make a choice based on their production needs. The process control method involves taking appropriate measures in terms of the process flow, equipment design, material selection, and operational management, in order to limit the generation of electric current or control the accumulation of static electricity, keeping it within safe limits. The amount of static electricity generated by the flow of hazardous chemicals in pipes is proportional to the square of the flow velocity. Reducing the flow rate lowers friction, thereby reducing the generation of static electricity. Therefore, the conveying speed of the material can be restricted; the larger the pipe diameter, the slower the speed should be. When filling liquid materials, it is possible to enter from the bottom or insert the injection tube into the bottom of the container. The stirring speed of the flammable liquids in the reactor must be controlled in accordance with the operating procedures. During the filling process, on-site operations such as sampling and temperature measurement are prohibited; it is necessary to wait for a period of time before carrying out such actions. Appropriate materials should be selected for equipment and pipes; metal materials should be used as much as possible, while plastic pipes should be used sparingly or not at all. Inert gas protection can be employed. In liquid transportation, 1. The flow velocity of the liquid within the pipeline must be stable. The number of bends and reductions in the pipes should be as few as possible; the inner walls of the pipes must be smooth, and the diameter of all pipes should be uniform. 2. Air, water, dust, oxides, etc., should not be mixed into the liquid; in particular, colloidal substances such as rubber and asphalt should not be included. 3. Buffers should be installed at the ends of pipes and hoses; their function is to widen the pipe, allowing most of the charge to be discharged as the flammable liquid flows through the buffer zone. 4. Bulk tank trucks transporting flammable liquids should be equipped with partitions to prevent the liquid from sloshing or splashing. The filling level should be at least 85%. Additionally, iron chains should be used for grounding, and the truck must be driven at a constant speed. 5. For pipes made of insulating materials, a copper wire mesh should be lined on the inner wall of the pipe, and steel wire should be wrapped around the outside of the pipe to form a unified structure; thereafter, it should be grounded. A wire should also be used to connect the material discharge trough to the grounding trough, after which that connection should be grounded as well. 6. The interior of the tank should be cleaned regularly. In the warehousing stage, 1. efforts should be made to prevent static electricity from being generated in materials; this includes limiting the flow rate of flammable liquids in pipelines, controlling the methods used for their loading and unloading, and preventing mixing of different types of oils as well as the presence of water or air in the liquids. 2. A proper grounding system can be installed on the equipment, relative humidity can be increased, conductive flooring can be laid, and conductive coatings can be applied to tools, etc. 3. Apply a certain amount of countercharge to the charged object in order to prevent an increase in static voltage, such as by using an inductive electrostatic neutralizer. 4. Fill flammable storage tanks with inert gases such as nitrogen, install control and alarm devices, and use efficient exhaust systems to ensure that flammable gases or dusts in the air do not reach their explosive limits. 5. Workers should wear conductive shoes and anti-static work clothes to promptly eliminate static electricity on their bodies.