Static electricity hazards and prevention in chemical enterprises

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In recent years, electrostatic disaster accidents in the chemical industry have occurred frequently, drawing widespread attention within the sector. Electrostatic hazards exist at every stage of chemical production, transportation, storage, and handling, especially in the petrochemical industry, where approximately 80% to 90% of substances pose fire and explosion risks. Accidents caused by static electricity have occurred on multiple occasions in fine chemical companies ； The stable operation of the equipment is a fundamental condition for a company to achieve economic benefits; on the contrary, an accident-induced shutdown can result in financial losses for the company. Some chemical companies do not fully recognize the severity of the hazards posed by static electricity. While each company has safety procedures in place, most lack specific anti-static safety measures, which gives static electricity an opportunity to cause problems. Therefore, avoiding accidents caused by static electricity is an issue that companies should pay close attention to. Only by carefully analyzing the causes of static electricity in production, predicting its potential hazards, and giving sufficient emphasis to static electricity prevention measures in order to prevent problems before they occur, can such measures be effectively implemented. Static electricity is not far from you. In terms of processing methods, friction between large areas of solid materials, contact between solid materials under pressure followed by separation, friction between solid materials and the walls of pipes or filters during extrusion or filtration, as well as processes such as crushing, grinding, and mixing of solid materials, can all lead to the accumulation of dangerous static electricity. Processes such as filtration, screening, pneumatic conveying, mixing, spraying, and transfer of powder materials can also lead to dangerous static electricity accumulation. Dangerous static electricity buildup can occur in liquid materials during processes such as high-speed flow, filtration, mixing, spraying, jetting, flushing, splashing, pouring, and even sedimentation. Flammable liquid vapors and flammable gases can also experience dangerous static electricity buildup when they are ejected at high speed from gaps or valves, or when flowing rapidly within pipes, due to impurities present in the solids or liquids. Furthermore, dangerous static electricity buildup can also occur during activities involving people wearing clothing made of synthetic fibers, as well as while airplanes are in flight. Therefore, many fires and explosions are caused by static electricity buildup. The hazards of static electricity cannot be ignored. 01 Static electricity can cause fires or explosions; most of the media used in petrochemical production facilities are flammable and explosive. According to available data, in petrochemical plants, approximately 80% to 90% of the substances pose a fire and explosion hazard. Experiments have shown that materials with a resistivity of around 10 m can generate static electricity. Petrochemical gases such as gasoline, benzene, and ether have a resistivity ranging from 1010 m to 1012 m, allowing them to generate and store static electricity. A large amount of static electricity can be generated during material leaks and spills, frictional mixing, gas-liquid flow, gluing operations in chemical and adhesive products, injection molding processes, as well as during transportation. The voltage generated can reach tens of thousands of volts. If this electricity is discharged in an environment prone to static fires or explosions, it can ignite explosive mixtures formed by flammable benzene, hydrogen, liquid vapors, flammable particles, and air, as well as other chemically flammable substances, thereby causing fires or explosions. If static sparks accompany a person as they move around and pose a threat to the production area, they become a dangerous ignition source that is highly mobile, easy to conceal, and difficult to control. The energy of human body electrostatic discharge can reach several dozen millijoules, which can easily ignite flammable substances such as benzene, hydrogen, and combustible particles, leading to fire and explosion accidents. 02 Impact on normal production: Static electricity can cause significant harm to safe operations, as well as to the quantity and quality of products, to equipment, and to the production environment. Static electricity can cause the powder in production to descend continuously, blocking pipes and sieve pores and resulting in poor flow and pressure buildup within the system; excessive pressure can damage the equipment. During the storage and transportation of products such as plastics, static discharge can cause the products to melt, stick together, change color, and even decompose and become damaged or unusable. The energy of electrostatic discharge can, on occasion, cause silicon components in computers, production control instruments, and safety control systems to be damaged, leading to misoperations that result in accidents. 03 Delivering an electric shock: An electric shock is damage caused by electric current passing through the body, affecting its central nervous system and nerves. An electrostatic shock is not a shock caused by a continuous flow of electricity through the body; it refers specifically to the instantaneous, sudden injury resulting from an electrostatic discharge. This electric shock is not caused by the human body coming into direct contact with the live parts of electrical equipment, nor is it due to a malfunction in such equipment. Instead, it occurs because, during physical activities, the contact and separation of solid materials such as clothing generate static electricity in the body, leading to electrostatic discharge. In the case of electrostatic shocks, since the amount of static electricity energy accumulated during production is very limited, such shocks cannot directly cause death. However, the possibility of serious consequences resulting from electrostatic shocks cannot be ruled out. For example, a person might fall or stumble due to an electrostatic shock, leading to secondary accidents. Static electricity protection is not difficult. The most dangerous aspects of static electricity are explosions and fires. Therefore, the focus of static electricity hazard prevention is on avoiding explosions and fires; meanwhile, certain protective measures are also very effective in preventing static electric shocks and avoiding disruptions to production. The following are the 5 key protective measures to eliminate the hazards of static electricity. 01 Protective measures for the surrounding environment: In environments where static electricity generated by synthetic fibers and powders is a concern, the humidity must be kept within specified limits. Reduce the concentration of explosive mixtures to keep it outside the explosive range. When the concentration of an explosive mixture is within the lower or upper explosive limit, it will not cause an explosion; therefore, in areas with explosion and fire hazards, ventilation or exhaust systems should be used to remove such mixtures promptly, keeping their concentration below the lower explosive limit and thus preventing explosions and fires caused by static electricity sparks. In most chemical processing operations, flammable media are replaced with non-flammable ones. Organic solvents and volatile liquids are commonly used, which can lead to human-caused disasters such as explosions and fires. Under conditions that do not interfere with the normal operation of the processes or the quality of the products, and that are also economically feasible, replacing flammable media with non-flammable ones is one of the key measures to prevent explosions and fires caused by static electricity. Liquids such as trichloroethylene and carbon tetrachloride can be used instead of gasoline and kerosene to remove grease and similar substances from equipment components. This is because although gasoline and kerosene have good solvency, they pose a relatively high risk of ignition. By reducing the content of oxidizers, this method essentially involves replenishing nitrogen or other inert elements such as benzene and hydrogen, thereby lowering the proportion of oxygen in explosive mixtures of benzene, hydrogen, steam, or particles; this eliminates the factors that lead to combustion and prevents explosions and fires. 02 Strengthen anti-static safety management. Since static electricity hazards can occur unexpectedly, improving the management of the anti-static environment can help prevent such hazards. By utilizing anti-static surveys, accident studies, environmental monitoring, and the maintenance of anti-static devices, the monitoring of anti-static parameters is improved. Computers are used for remote control to measure static charge density, the currents and voltages generated by gas and liquid flow as well as the electric potential at the liquid surface, along with surrounding temperature and humidity, as well as the concentrations of flammable benzene, hydrogen, and particles. This enables timely adjustment of parameters to prevent the occurrence of static electricity accidents. Formulate safety operation procedures suited to the actual conditions and enforce them strictly. Any chemical company has safety codes, but some of these codes lack specific anti-static safety measures. Deepening the formulation and implementation of anti-static safety guidelines can effectively prevent the occurrence of static electricity hazards. Monitor the concentrations of flammable benzene and hydrogen. In flammable and explosive environments, when the concentration of combustion and explosion impurities lies outside the lower and upper explosive limits, no static electricity-induced fire or explosion hazards will occur. Therefore, measures such as improving ventilation, using inert gases for dilution and conversion, and enhancing the integrity of the system can be adopted to keep the mixture concentration below the lower explosive limit. Selecting its combustible gas concentration monitoring and alarm device also enables the monitoring of the concentration of combustible substances. Training in the design of fine chemical plants, the layout planning of multi-functional workshops, and the design of process systems and utility systems. 03 Anti-static measures for humans: It is strictly prohibited to wear clothing that generates static electricity in flammable and explosive areas; in particular, one should not put on or take off clothes in such areas, nor use synthetic fiber fabrics to wipe equipment. Provide enhanced training on static electricity safety in chemical production for operators and relevant personnel working in flammable and explosive environments, in order to raise their awareness of complying with relevant safety regulations. At the entrance to flammable and explosive environments, add static discharge grounding handles or handrails to reduce human body static electricity through touch. During production, gloves that are conductive or that make it difficult for static electricity to accumulate should be worn to avoid or reduce the hazards of static electricity. In environments prone to fire and explosion or where static electricity is likely to occur, it is required to wear anti-static clothing; clothing and footwear that can generate static electricity are prohibited. Dressing and undressing, as well as putting on and taking off shoes and footwear, are forbidden. During inspections, the carrying of any metal materials that are not related to the work is prohibited. At the same time, production workers in flammable and explosive environments require anti-static clothing with excellent flame-retardant properties. The safety management department plays a positive role in preventing static electricity. In areas with explosion hazards, it is prohibited to use mops and rags made of synthetic fibers to clean objects and floors. Prevent other personnel from coming into contact with the workers handling explosive materials, in order to reduce unnecessary static discharge. The floors in areas with explosion hazards should be replaced with anti-static floors, so that the static electricity carried by them can be safely discharged into the ground. When manually cleaning oil tanks and tank trucks, it is required to wear anti-static work clothes, anti-static raincoats, and conductive rubber boots. 04 Static Grounding: In areas prone to fire and explosion, as well as in devices where static electricity can be generated due to synthetic fibers and powders, it is essential to ensure proper anti-static grounding of the equipment ； The conductivity of concrete floors, rubber flooring, etc. shall meet the specified requirements. Static grounding is the most widespread and effective method for preventing static electricity in petrochemical operations. For objects in areas prone to fire and explosion that may generate static electricity, as well as for processes during production, storage, and transportation where pipelines, valves, equipment, etc. may also generate static electricity, electrostatic grounding must be selected in strict accordance with process requirements during design and construction. Fixed equipment (1) The enclosures of fixed equipment such as towers, vessels, pumps, heat exchangers, centrifuges, etc., should be electrically grounded. For covering devices, static grounding is generally not required. (2) For equipment with a diameter of 2.5 m or more and vessels with a volume of 50 m³ or more, there shall be no fewer than two grounding points. These grounding points shall be evenly distributed along the perimeter of the equipment, with a maximum spacing of 30 m between them. (3) For fixed equipment that vibrates, its vibrating components shall be grounded using copper core flexible stranded wire with a cross-sectional area of not less than 6 mm2; single-strand wire shall not be used. Between several devices with flexible connections, copper-core flexible stranded wires should be used for interconnection. (4) The belt-driven units, as well as their anti-static grounding brushes and protective covers for the belts, must all be grounded. (5) Bolted connections are preferred for fixing equipment to grounding wires or connecting wires. (6) Metal components insulated from the ground (such as flanges, hose fittings, etc.) should be grounded by using copper-core flexible stranded wire for bonding. Piping system: (1) The pipes shall 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. (2) When the clear distance between parallel pipes is less than 100 mm, a jumper should be installed every 20 m ； When pipes intersect with a clear distance of less than 100 mm, a jumper should be added. (3) When a metal flange is fastened using metal bolts or clamps, it is generally not necessary to install an additional electrostatic connection wire, but it must be ensured that there is good electrical contact between at least two of the bolts or clamps. (4) 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 stranded wire having a cross-sectional area of not less than 6 mm2 and then grounded. (5) All metal components on non-conductive pipe sections shall be grounded. Human body static grounding (1) Operators must use various anti-static protective equipment properly in areas where static electricity poses a risk, and shall not wear clothing made of synthetic fibers or silk. (2) It is prohibited to put on or take off clothes, hats, or similar items in areas prone to explosions. For objects not located in environments at risk of fire or explosion, anti-static measures are even more necessary when static electricity can affect production, reduce product quality, or pose a risk of electric shock. 05 Adopt the small dip pipe sealing loading technology; splash-type unloading of oil is strictly prohibited, and tank trucks should use dip pipes for under-water loading. The liquid storage tank area is characterized not only by relatively large tank capacities but also by a large number of pipelines, pumps, and transfer pipes, as well as frequent operations at various stages. Therefore, the use of small transfer pipe sealing technology for loading can effectively control and limit the generation of static electricity. The small flexible hose sealed loading technology is a new type of loading technique that features the ability to reduce the static electricity hazards associated with oils, prevent environmental pollution, and improve operating conditions. According to actual measurements, when the spray method is used, the upper limit of the static electric potential on the oil surface can reach 5 kV, whereas the small flexible hose sealing technique is employed. The hazards of static electricity in storage in the chemical industry and their prevention. The dangers caused by static electricity have received considerable attention in the production units of the chemical industry, but research on the hazards resulting from static electricity as well as measures to prevent them remains a weak area in the storage units of these industries. As the functions and scale of warehousing continue to expand, how to control and prevent the hazards caused by static electricity has gradually attracted attention. I. Generation of static electricity in the warehousing process. The generation of static electricity has its internal and external causes. Internal factors depend on the electrical conductivity of a material, while the most common external factor is the generation of electricity due to friction between materials. Such as friction, rolling, impact, etc., between substances during storage and transportation. Next are adsorbed charging, induced charging, etc. In terms of the warehousing department, many goods and packaging materials possess the internal conditions for static electricity to be generated. Moreover, warehousing operations involve tasks such as handling, stacking, covering, and shielding, which inevitably lead to friction, rolling, and collisions between the goods. For example, during transfer in warehouses containing oil or organic solvents and when pouring them into tanks, friction occurs between these materials and the pipe walls as well as the equipment, which leads to a high accumulation of static electricity. Plastic packaging for ordinary goods also generates static electricity due to friction between them during stacking. Summary: The chemical industry plays an extremely important role in the development of our country. II. The hazards of static electricity in warehousing The harm caused by static electricity in warehousing activities is mainly due to its ability to accumulate on object surfaces, resulting in high static voltages and the potential for static discharge sparks. The hazards are primarily of two types: 1. It can easily lead to fire and explosion accidents. For example, flammable liquids stored in warehouses such as gasoline, kerosene, and diesel, as well as organic solvents like benzene derivatives and ethers; when the vapors they emit mix with air in a certain proportion, or when solid dust reaches a certain concentration – that is, the explosive limit – any static discharge spark can serve as a ignition source that triggers a fire or explosion. 2. Electric shock is likely to occur. If high-voltage static electricity discharge occurs during handling, it can cause discomfort in the form of electric shocks to the operators; this happens frequently among workers who handle plastic-packed items in warehouses. Intense friction during handling and stacking processes leads to high-voltage static electricity discharge, and in some cases, operators have even been knocked down by such discharges. III. Prevention and control of static electricity hazards in warehouses In warehousing, the following steps are generally taken to prevent and control the hazards caused by static electricity. 1. It is necessary to control the materials so as to minimize the generation of static electricity; for example, for flammable liquids, the flow rate within the pipes should be restricted, the methods of loading and unloading should be controlled, and mixing of different types of oils or solvents should be prevented, as well as the presence of water or air in the liquid. 2. Take measures to dissipate the generated static electricity as quickly as possible to prevent accumulation. For example, installing proper grounding devices on equipment, increasing the relative humidity in the workplace, laying conductive floors on the ground, and applying conductive coatings to certain tools all help to discharge static electricity. 3. Apply a certain amount of countercharge to the charged body to neutralize the charge on it, thereby preventing an increase in static voltage. The use of inductive electrostatic neutralizers falls under this category of methods. 4. In some cases, static electricity accumulation is inevitable; the static voltage can rise rapidly, leading to static discharge sparks. Measures must therefore be taken to ensure that such discharges do not result in fires or explosions. For example, inert gases such as nitrogen can be introduced into the space of flammable liquid storage tanks, control and alarm devices can be installed, and efficient ventilation systems can be used to ensure that the concentration of flammable gases or dust in the air does not reach the explosive limit. 5. In areas where there is a risk of fire and explosion, such as chemical hazard storage sites, it is also an effective measure to prevent the hazards caused by static electricity that staff wear conductive shoes and anti-static work clothing in order to discharge the static electricity accumulated on their bodies promptly. In summary, static electricity poses a serious threat to the safe production in the chemical industry; we must pay close attention to it, be aware of the hazards associated with static electricity during production as well as the measures to eliminate it, in order to prevent fires and explosions caused by static charge accumulation and achieve safe production. To carry out thorough optimization during the production process in order to reduce static electricity generation, selecting effective control measures that allow static charges to be dissipated and discharged promptly is the only way to reduce and eliminate static electricity-related fires or explosions. By using selective optimization for material matching, adjusting the logistics speed, and adding antistatic agents, it is possible to effectively reduce the formation and accumulation of static electricity during production and storage and transportation ； By utilizing effective static electricity elimination devices, exploring new types of non-conductive static shielding materials and putting them into production, static charges can be dissipated and removed promptly.