Methods of protection against electricity. Static electricity

Static electricity occurs due to the retention of charges in an electrostatic field on dielectric materials. It negatively affects human life and the operation of electrical devices. The formation of sparks from static electricity contributes to fires and explosions. The energy power is quite enough to ignite gas-air mixtures and dust.

A charge of static electricity can accumulate on a person's body if he is wearing clothing made of wool or chemical fibers. A potential value of about 7 Joules is not dangerous to humans, but can cause cramps and muscle contractions. And this, in turn, can create conditions for injury at work, falling from a height, etc.

Static electricity negatively affects the functioning of precision instruments, radio communications, and causes malfunctions. Workers who are constantly exposed to static electricity are more likely to suffer from cardiovascular diseases and diseases of the nervous system.

Only protection against static electricity can reduce to zero or completely prevent the occurrence of this negative phenomenon.

Sources of static electricity

Action of various radiations.
Sudden change in temperature.
The interaction of bodies with each other during movement.

This phenomenon has a negative impact and poses a danger. Protection against static electricity allows you to completely prevent or significantly reduce its effect.

In everyday conditions, a static field often occurs on animal fur, when removing synthetic clothing, combing hair, wearing rubber shoes, walking on a carpet in wool socks, or using plastic products.

The electrostatic field does not threaten human life; the discharge produces a weak current that is not capable of causing too much harm to the human body. It can only create some discomfort. To prevent this effect, you only need to follow a few simple rules: in frosty and dry weather, do not pet animals, take off woolen clothes more slowly, or treat them with a special compound, and use a wooden or metal comb when combing hair.

The accumulation of electrostatic energy is facilitated by:

Reinforced concrete walls of the building.
The air is too dry.

For electronic devices, electrostatic charge is the worst enemy. Some elements of electronic devices are not able to withstand the high voltages that occur during discharge. Sensitive elements may fail or degrade their performance.

If flammable liquids are exposed to an electric field, this will create conditions for their ignition. These liquids may accumulate a static charge when transported in tanks. Also, a charge arises from a mechanism or a person who comes close to it. Therefore, in industrial production, where there are flammable liquids, much attention is paid to the grounding of movable structures and mechanisms. For sewing shoes and special clothing, production also uses special fabrics that are not capable of accumulating an electric charge.

Operating principle

Let's figure out how a static charge is formed. In a normal state, physical bodies have the same number negative and positive particles. Due to this balance, a neutral state of the body is created. When the neutral state is violated, the body receives an electric charge of one pole.

Statics is the state of a body at rest, when it is without movement. In the substance of the body, polarization can occur, which is expressed in the movement of charges between parts of the body, or from a nearby object.

Substances become electrified due to the separation of bodies, changes in charges during friction, sudden changes in temperature, and irradiation. The electric field charges are located on the surface of the body or are removed from the surface at a distance equal to the interatomic distance. If the bodies are not grounded, then the charges are concentrated on the contact area, and if there is grounding, the charge goes into the ground loop.

The processes of charge accumulation and their drainage occur at the same time. The body becomes electrified if it receives a greater charge of energy compared to the charge consumed. As a result, it becomes clear that protection against static electricity must discharge accumulated charges to the ground loop.

Amount of static electricity

All physical substances have their own characteristic on the triboelectric scale, depending on their ability to create electrical charges of different poles during friction. The main such substances are shown in the figure.

To have an idea of the size of the resulting static charges, consider several examples:

The rotating pulley with the drive belt can charge up to 25,000 volts.
The body of a car moving on a dry road can receive a charge of up to 10,000 volts.
A person wearing wool socks walking on a dry carpet can accumulate a charge on the body of up to 6000 volts.

As a result, it becomes clear that the voltage of the electrostatic field can reach significant levels even in everyday life. This charge does not cause significant harm to a person due to its low power. The discharge flows through a large resistance and is calculated in several fractions of a milliampere.

Air humidity also reduces electrostatic charge. It affects the value of the body's potential during contact with different materials. Therefore, protection against static electricity may consist of using.

IN natural environment There is static electricity, reaching enormous values. For example, when clouds move between them, large energy potentials arise, which are expressed in lightning discharges. The power of these discharges is quite enough to burn wooden house or split the trunk of a perennial tree.

In everyday conditions, during discharges of an electrostatic field, a person feels small tingling sensations in his fingers, sparks are visible from the friction of woolen clothing, and a person’s performance decreases. The electrostatic field negatively affects the human condition, but does not cause obvious damage.

There are measuring instruments that can accurately measure the value of the static potential of the accumulated charge on the human body and on the body of any device.

Anti-static electricity

There are various methods of protection against electrostatic field discharges, both in everyday life and in industrial conditions. They have their differences. Let's take a closer look at each of them.

Protection at home

Every person must present the danger that static discharges pose to the body. You need to know them and be able to limit them. To solve this problem, various events are organized to train people in protection methods, including television programs.

At these events, people are explained where and how the static field appears, methods for measuring it and techniques for performing it preventive work. For example, to avoid the unpleasant sensations of a static field, it is advisable to use wooden combs instead of plastic ones to comb your hair. Wood has neutral characteristics and does not create electrostatic field charges during friction. In stores you can easily purchase a wooden comb of any shape and type.

To prevent the formation of static potential on the car body when driving on a dry road surface, special antistatic tapes are used, which are fixed at the rear of the car on the bottom of the body. In the retail chain you can easily choose any version of such a tape.

If the car is not protected in any way from a possible discharge of the accumulated potential charge, then the voltage can be removed by temporarily grounding the car body by connecting it to the ground through a metal part. To do this, you can use the ignition key. It is imperative to relieve tension before refueling the car with gasoline.

When a static charge forms on clothing made from chemical fibers, it is recommended to use Antistatic. This is a special aerosol can that is sold in stores. It removes static electricity from clothing, fabrics, and synthetic car seat covers, especially in winter when the air is dry. But, in order not to use various spray cans and chemicals, it is recommended to wear clothes made from natural materials: cotton and linen.

If shoes have rubberized soles, this creates conditions for the accumulation of stress potential. To prevent this from happening, it is enough to put special antistatic insoles in your shoes, which are made from natural materials. As a result, the negative impact on a person will decrease.

Too dry air in city apartments in winter contributes to the accumulation of electrostatic charge. There are special devices for this – air humidifiers. If there is no such device, then a large wet wipe that needs to be placed on the battery will do. As a result, the charge accumulation process will decrease and the situation in the apartment will improve. It is also recommended to carry out wet cleaning regularly. This will allow you to remove dust and electrified areas in a timely manner. This method is the best.

Electrical devices in everyday life also accumulate a static charge on the housing during operation. To reduce the effect of static charge, a potential equalization system is installed. It is connected to the ground loop of the entire house. An acrylic bathtub is susceptible to the accumulation of static charge on it, and it must be protected by a potential equalization system. Even a cast iron bathtub with an acrylic liner is also susceptible to this negative phenomenon.

Protection against static electricity in production

In industrial production, several methods are used to maintain the functionality of equipment:

Increasing the resistance of devices and equipment to electrostatic discharge.
Blocking the penetration of charge into the workplace.
Preventing the occurrence of electrostatic charges.

The last two methods make it possible to protect many devices, while the first method is used only for individual species equipment.

Provides high protection against static field discharges and maintains the functionality of the device. This is a metal cage in the form of a mesh with a fine mesh. The cage encloses the equipment on all sides. It is connected to the ground loop. Cells do not go inside electric fields, at the same time, the Faraday cage does not interfere with the magnetic static field. Cables are protected using the same principle by equipping them with a metal shield.

Protection against static electricity is divided according to implementation methods:

Structural and technological.
Chemical.
Physico-mechanical.

The last two methods make it possible to reduce the formation of charges and increase the speed of their sinking into the ground. The first method protects devices from charges, but does not divert them to ground.

You can optimize electrostatic charge reduction as follows:

Increasing the conductivity of materials.
Creation of coronation.

Such problems are solved using:

Selecting materials with good volumetric conductivity.
Increasing working surfaces.
Ionization of airspace.

To implement these tasks, highways are created for the flow of static charges to the ground, bypassing the working components of the devices. If materials have high resistance, then other methods are used.

15.1. Measures to protect against static electricity must be carried out in accordance with current regulations.

15.2. The development of technological processes and equipment must be carried out taking into account the prevention of dangerous electrification of substances during their production and use. The main measures to prevent dangerous manifestations of static electricity must be specified in the directive technological process.

When starting a new or reconstructed production, you should check the presence and sufficiency of existing static electricity protection devices and, if necessary, provide additional protection.

15.3. The technological regulations must contain parameters of substances processed in production, characterizing their electrical properties (electrical resistivity) and sensitivity to electrostatic discharges (minimum ignition energy), and a description of means of protection against static electricity, and in technological instructions and safety instructions it must be described the order of their application.

15.4. The most likely occurrence and accumulation of electrostatic charges is during operations such as sifting, grinding, mixing, loading and unloading from devices, pneumatic and vacuum transportation. Acceptable process parameters that ensure electrostatic safety of processing of each type of product are established by the developer of the directive technological process and technological process regulations.

15.5. To prevent the possibility of dangerous electrostatic discharges, it is necessary to provide the following protective measures, taking into account the specifics of production:

Grounding of electrically conductive equipment and communications;

Use of neutralizers;

Selection of pairs of contacting materials electrified by charges of different signs;

Humidification of the surrounding atmosphere;

Application of electrically conductive materials for equipment;

Use of protective clothing.

15.6. To reduce the intensity of static electricity charges, you should:

Wherever it is technologically possible, steam and dust-air mixtures should be cleaned from suspended liquid and solid particles, and liquids from contamination by solid and liquid impurities;

Maintain the concentration of flammable media outside the explosive limits;

Wherever production technology does not require it, eliminate splashing, crushing, and atomization of substances;

Technological processes are carried out in accordance with established parameters;

Reduce the speed of transportation and processing, turbulence of flows of dust-steam-gas mixtures and liquids;

Avoid condensation and crystallization of vapors and gases when escaping from pipelines, hoses, nozzles, and nozzles.

15.7. All technological equipment (devices, containers, communications, coverings of work tables and shelving, equipment, etc.), where the formation and accumulation of static electricity charges is possible, must be made of metal or electrically conductive materials and grounded (electrically conductive materials are such as specific volumetric electrical whose resistance does not exceed 1E5 Ohm.m).

Apparatuses, containers, units, pipelines in which the movement, crushing, spraying, spraying of products occurs, free-standing machines, units, devices connected by pipelines to common system devices and containers must be connected to the internal grounding loop using a separate branch, regardless of the grounding of the communications connected to them.

The sequential connection of several grounding devices, units or pipelines into the grounding bus (wire) is not allowed.

It is allowed to combine grounding devices for protection against static electricity with protective grounding of electrical equipment.

Grounding of the mixing and charging machine before loading must be carried out in accordance with clause 9.6 of these Rules.

15.8. The design documentation for process equipment must indicate the places for connecting grounding conductors and the method of their fastening.

In each industrial building, a grounding diagram (map) must be drawn up, which must list all equipment, equipment, inventory, etc. that must be grounded.

15.9. The grounding resistance of any most remote point of the internal surface of equipment made of electrically conductive (non-metallic) materials relative to the internal grounding loop should not exceed 1E6 Ohm.

The resistance of a grounding device intended only for protection against static electricity must be no more than 100 ohms.

15.10. Grounding conductors and the grounding loop must be laid openly to allow inspection. At the same time, their resistance to mechanical and chemical influences must be ensured.

Grounding conductors, external and internal grounding loops must be made in accordance with the requirements of the rules for the construction of electrical installations and the rules and regulations for the installation of lightning protection of buildings and structures.

Grounding conductors, intended for protection against static electricity, are painted black with one red transverse strip 15 mm wide applied at the points of connection to process equipment and the internal grounding loop. It is allowed, in accordance with the design of the room, to paint the grounding conductors in colors other than red and marked with a red stripe, as indicated above.

15.11. The connection of the elements of the grounding loop, the connection of grounding conductors and grounded structures must be performed by welding. If welding is not possible, it is allowed to connect grounding conductors using a reliable threaded connection. In this case, the grounding conductors must have an uncut ring at the ends, electrically connected to the main core. Threaded connections must be protected from corrosion.

15.12. Pipelines located in parallel at a distance of up to 0.1 m from each other must be connected to each other by jumpers every 20 m. When pipelines cross each other, with metal stairs and structures at a distance of less than 0.1 m, they must also be connected by jumpers.

Protective grounding of pipelines located on external overpasses must meet the requirements of the norms and regulations for the installation of lightning protection of buildings and structures.

Metal ventilation air ducts must be grounded every 20 m using conductors made of aluminum alloys with a diameter of at least 5 mm, tape with a cross-section of at least 24 mm2.

15.13. Moving parts of machines and devices capable of being electrified, the contact of which with the grounded body may be disrupted, must have special devices (current collectors) to ensure grounding.

Devices in which intensive electrification of substances takes place, as well as moving units of vibrating equipment (vibrating trays, mechanically driven sieves, etc.) must be grounded at at least two points.

15.14. To reduce the specific surface electrical resistance of substances, compositions and structural materials, where this is allowed by the process conditions, it is recommended to maintain a relative air humidity of at least 65%.

15.15. Sprinkling of substances should be done from as low a height as possible. Everywhere, you should systematically, within the time limits established by the instructions, clean equipment, ventilation ducts and other structures in the room from settled dust using a wet method.

It is prohibited to load bulk products directly from paper, polyethylene, polyvinyl chloride and other electrified bags into the hatches of devices containing vapors of flammable liquids. In this case, loading devices made of conductive materials should be used, ensuring the least dusting of substances.

Sampling of bulk matter and measurement of process parameters using inserted samplers and instruments should be carried out after dust has settled.

15.16. Measurement of electrification parameters under production conditions is carried out periodically in accordance with the approved measurement schedule, but at least twice a year. To carry out measurements, intrinsically safe and explosion-proof instruments must be used, approved for use in these industries, ensuring electrostatic safety of measurements and having passed state or departmental tests.

15.17. Acceptance into operation of static electricity protection devices must be carried out simultaneously with the acceptance of process and power equipment.

When using static electricity protection devices, you must:

Before starting work, check the reliability of the electrical contact of the grounding conductors at the connection points and the continuity of the electrical circuit along the entire length;

Avoid contamination, mechanical damage, and prolonged exposure to alkalis, acids, and organic solvents on electrically conductive coatings. technological equipment, work places.

15.18. Inspection and measurement of electrical resistance of grounding devices of process equipment, pipelines, etc. It is recommended to carry out simultaneously with checking the grounding of electrical equipment. The results of verification tests, as well as inspections and repairs of the grounding device must be entered in the passport. The results of measuring the grounding resistance of technological devices, equipment, mobile equipment, transport devices, and equipment must be recorded in a special journal.

Static electricity is a set of phenomena associated with the emergence, conservation and relaxation of a free electric charge on the surface and in the volume of dielectric and semiconductor substances, product materials or on insulated conductors. Charges accumulate on equipment and materials, and accompanying electrical discharges can cause fires and explosions, disruption of technological processes, and the accuracy of readings of electrical devices and automation equipment.
A particular danger due to the accumulation of static electricity is posed by food production enterprises in which technological processes are associated with crushing, grinding and sifting of the product (baking, confectionery, starch, sugar, etc.), with cleaning and processing of grain, transportation of solid and liquid products with using conveyors and pipes (bulk flour storage warehouses, breweries, distilleries, etc.).
When bodies that differ in temperature, concentration of charged particles, energy state of atoms, surface roughness and other parameters come into contact, a redistribution of electrical charges occurs between them. In this case, at the interface between the bodies, positive charges are concentrated on one of them, and negative charges on the other. An electrical double layer is formed. In the process of separating the contacting surfaces, some of the charges are neutralized, and some are retained on the bodies.
In production conditions, the electrification of various substances depends on many factors, and primarily on the physicochemical properties of the processed substances, the type and nature of the technological process. The magnitude of the electrostatic charge depends on the electrical conductivity of the materials, their relative dielectric constant, speed of movement, the nature of the contact between contacting materials, electrical properties environment, relative humidity and air temperature. The electrification of dielectric materials increases especially sharply at a specific electrical resistance of 109 Ohm-m, as well as at a relative air humidity of less than 50%. With a resistivity of 108 Ohm-m or less, electrification is practically undetectable. The degree of electrification of liquids mainly depends on its dielectric properties and kinematic viscosity, flow velocity, diameter and length of the pipeline, pipeline material, condition of its internal walls, liquid temperature. The intensity of charge formation is observed during filtration due to the large area of contact of the liquid with the filter elements. Splashing of liquids when filling tanks with a free-falling stream of flammable liquid, for example in distilleries, is accompanied by electrification of the droplets, resulting in a danger electric charge and ignition of vapors of these liquids. Therefore, pouring liquid into containers using a free-falling stream is not allowed. The distance from the end of the loading pipe to the bottom of the vessel should not exceed 200 mm, and if this is not possible, the jet is directed along the wall.
Heli, the electrostatic field strength above the surface of the dielectric reaches a critical (breakdown) value, and an electric discharge occurs. For air, the breakdown voltage is approximately 30 kV/cm.
Electrostatic spark safety is a condition in which the possibility of an explosion or fire from static electricity is excluded. Safe spark energy (in J) is determined by the formula:

Wi=kb*Wmin

Where kb is the safety factor used equal to 0.4-0.5; Wmin is the minimum energy that can cause ignition of the combustible mixture in question.
The maximum permissible charge value is taken to be such a value at which the maximum possible discharge energy W from the surface of a given substance does not exceed 0.4-0.5 of the minimum ignition energy of the environment Wmin.
The discharge (spark) energy of a dielectric (in J) can be determined by the formula:

W=0.5*C*V 2

Where C is the electrical capacitance discharged by the spark, F; V is the potential difference relative to the ground, V.
The minimum ignition energy of gas and steam-air mixtures is fractions of a millijoule.
The potential difference on the equipment can reach several thousand volts, and, as follows from the formula, even with an insignificant electrical capacitance carrying an electrostatic charge, the spark discharge energy can exceed the minimum ignition energy of an explosive atmosphere. For example, when transporting bulk materials on a conveyor with a rubber belt, the potential relative to ground can reach 45,000 V, and a leather drive belt with a speed of 15 m/s can reach up to 80,000 V.
Electrostatic charges, sufficient to ignite almost all explosive mixtures of air with gases, vapors and some dusts, can accumulate on a person (clothing made of synthetic fabrics, walking on dielectrics, using electrically non-conducting shoes, etc.), and also transfer to him from an electrified equipment and materials.
The potential of an electrostatic charge on a person can reach 15,000-20,000 V. Discharges of such potential do not pose a danger to humans, since the current strength is negligible and is felt like a prick, jolt, or cramp. However, under their influence, reflex movements are possible, which can lead to a fall from a height, falling into danger zone cars, etc.
The discharge energy at a potential of 10,000 V and a human capacitance varying from 100 to 350 pF is 5–17.5 mJ. i.e. exceeds the minimum ignition energy values ethyl alcohol, benzene and carbon disulfide (0.95; 0.2; 0.0009 mJ, respectively).
Measures to protect against static electricity are divided into three main groups:

preventing the possibility of electrostatic charge;
reducing the electrostatic charge potential to a safe level;
neutralizing charges of static electricity.

The main way to prevent the occurrence of electrostatic charge is to constantly remove static electricity from process equipment using grounding. Each system of apparatus and pipelines is grounded in at least two places. Rubber hoses are wrapped around grounded copper wire with a pitch of 10 cm. It should be borne in mind that, unlike electrical engineering, where materials with a resistivity measured in fractions of an Ohm are considered good conductors, in electrostatics the boundary between a conductor and a non-conductor is considered to be a resistivity value of 10 kOhm*m. Therefore, the maximum permissible resistance of a grounding device used only to remove electrostatic charge should not exceed 100 Ohms.
To prevent the formation of static electricity on elements of metal structures, pipelines for various purposes, located at a distance of less than 10 cm parallel to each other, closed circuits are used, created using metal grounded jumpers installed between them every 20 m or less.
To reduce the potential of electrostatic charge formed on equipment and processed materials to a safe level, technological methods are used (safe speeds of movement of transported liquid and dusty substances, selection of friction surfaces, materials for mutually compensating emerging charges, etc.), as well as methods of removal by increasing the relative humidity of the air and material, chemical surface treatment, applying antistatic substances and electrically conductive films. General or local air humidification of more than 70% ensures constant removal of electrostatic charges. The surface conductivity of materials is increased by treatment with surfactants, the use of coatings made of electrically conductive enamels, and lubricants. Charges of static electricity are neutralized using air ionization, in which the number of ion pairs formed per unit volume corresponds to the rate of occurrence of neutralized electrostatic charges. For this purpose, induction, radioisotope and combined ionizers are used.
To continuously remove electrostatic charges from a person, electrically conductive floors, grounded areas or work platforms, equipment, ladders, as well as personal protective equipment in the form of anti-electrostatic gowns and shoes with leather soles or conductive rubber soles are used.

This term is commonly understood to mean the conservation of electrical charges on dielectric surfaces. Static electricity is a negative phenomenon for human life and the operation of electrical devices, because Sparks that occur subsequently can lead to fires and explosions. Their energy is enough to ignite dust and gas-air mixtures.

Discharge of static electricity accumulated on the human body

The charge also accumulates on the human body when wearing synthetics and woolen clothing. In itself, a potential value of no more than 7 kJ is not dangerous to human health, but can cause strong muscle contractions and even cramps, and as a result, falls from heights and injuries in the workplace.

The fact of the beneficial effects of walking barefoot on the ground has been scientifically confirmed, which is the removal of static charge from the human body.

The presence of discharges near high-precision devices can cause malfunctions (radio communication devices, etc.).

Personnel who are constantly exposed to electrical charges are more likely to suffer from chronic diseases of the nervous and cardiovascular systems.

Those who work in close proximity to the electric field often have complaints of excessive irritability, headaches, and sleep disturbances.

Causes

This arises physical phenomenon due to friction of dielectrics against each other or against metals. Charges begin to accumulate on surfaces, which can be retained for long periods of time. The intensity of charge generation increases in proportion to the friction speed, contact area, applied force and resistivity of the materials.

The second reason is considered to be electrical induction, due to which surfaces isolated from the ground accumulate charged particles. For example, static electricity can accumulate on metal objects located near high-voltage power lines during dry weather.

In the chemical industry, the phenomenon is observed during the melting of plastic materials. In radio electronics, discharges occur during the production of equipment where dielectrics are used. The same picture is observed when winding paper and plastic film into rolls, pouring and pneumatic transportation of dielectrics (crushed glass, hard rubber), and transportation of liquids (gasoline and similar compositions). At home, this manifests itself on the monitor screens on which it is collected. a large number of protons caused by electric beams from the ray tube.

Situations where there is a high probability of receiving an electric shock

A number of technologies and means of protection have been developed aimed at minimizing and preventing this phenomenon.

Reducing the intensity of charges

The measures are aimed at ensuring the safety of technological processes:

in accordance with current GOSTs, production ensures control of the speed of raw materials transported through pipes;
Before processing, working gases and liquids must be cleaned of impurities and foreign matter;
splashing of liquids and gases is unacceptable during processing and transportation processes;
in production, where it is impossible to organize the natural drainage of static charges, closed transport systems are used (for pneumatic transportation of liquids, purging of equipment).

Grounding of electrical appliances and live parts:

according to the PUE, current GOSTs and SNiPs, electrical installations can be combined with grounding devices against static charges;
The resistance of the charger for protection against static electricity should not be more than 100 Ohms;
all electrically conductive surfaces and current-carrying parts of equipment must have high-quality grounding;
pneumatic pipelines, ventilation shafts must form a single circuit connected to grounding conductors every 40 m, the minimum number of points is 2 pcs;
It is mandatory to connect separate chargers to the common circuit to devices on the surfaces (inside) of which a charge can form: crushers, sprayers, etc.;
large containers must be grounded at two opposite points according to GOST;
During loading (unloading) of gases, tanks must be connected to chargers, which, in turn, must be located outside explosive zones; depressurization of tank hatches is carried out after connecting the housing to the ground loop;

Grounding of devices to protect people from electric shock

hoses through which liquefied gases and liquids are poured must be entwined with copper wires or cables with a diameter of at least 4 mm. The conductor should be connected on one side to the edge of the hose, and the other to the grounded part of the existing circuit.

Removing Charges from Hard Surfaces

The process consists of neutralizing charges by ionizing air near the technological process. According to current GOSTs, neutralizers are used for this:

radioisotope neutralizers are installed in explosive workshops;
for the production of hygienic products, the use of radioisotope neutralizers is prohibited; in such cases, it is advisable to use induction or high-voltage neutralizers;
if it is impossible to use induction neutralizers, it is advisable to use sliding discharge neutralization devices;
if the equipment has complex geometric shapes and it is impossible to ensure charge removal standard methods, use aerodynamic neutralizers, through which ions are forcibly injected into the required space.

Charges in gas mixtures

to ensure safe conditions, according to current GOST standards for technological processes, it is necessary to use gases pre-cleaned from solid particles;
the equipment must have high-quality sealing;
presence in gas mixtures metal particles and small parts.

Removing Charge from Bulk Materials

According to current GOSTs, it is necessary to process bulk materials in metal containers or conductive non-metallic ones.
Powdered raw materials can be transported in pipelines of similar composition (if these are polymers, then the pipes must be made of polyethylene).
In production premises, air humidity should be at least 65%. If it is impossible to organize this condition, resort to air ionization.
To improve the drainage process, working surfaces are impregnated with surfactant lubricants.
It is prohibited to unload bulk raw materials from cellulose, PVC and plastic bags into containers in which the liquid temperature is higher than their ignition temperature. In such cases, screw installations are used.

To avoid explosions (due to spark formation), the formation of explosive mixtures should be prevented, dust should not accumulate, and equipment should be regularly cleaned of dust-air mixtures.

Protection rules

Rules for protection against static electricity in chemical production industry:

Static discharge devices must be installed at the entrance to the loading pipes of the tanks.
To ensure the safety of the technological process, in accordance with current GOSTs, the following are used: induction neutralizers, submersible type neutralizers, special nozzles for directing the flow, relaxation tanks.
Liquids should not splash during loading (unloading).

Removal of charges from the surfaces of vehicles, devices and people:

According to current GOSTs, mobile trains must be made of electrically conductive materials. Moving around the territory is carried out using metal forklifts.
In rooms where mobile tanks are filled, the floor is made of electrically conductive materials.
Workers must wear anti-electrostatic shoes indoors.
It is not allowed to carry out work in containers in which explosive mixtures may occur, wearing work clothes made of synthetic fibers.

Charge removal from belt drives:

According to current GOSTs, the use of bearings made of non-conducting elements in production is unacceptable.
To increase the reliability of electrical devices, electrically conductive lubricants are used.
In workshops where it is not possible to apply other protective measures, neutralizers are used.
The use of lubricants such as wax and rosin is unacceptable. These substances help increase the surface resistance of electrical installations.
Do not allow belts to become contaminated with oil or flammable substances.
In workshops it is necessary to maintain atmospheric humidity of at least 70%, according to standards.

Antennas installed on the roof are considered to be potentially dangerous equipment: charges accumulate on them from the action of wind and cloud friction. Therefore, in high-rise buildings where there are no appropriate protections nearby, it is necessary to construct a high-quality lightning rod.

Manifestation in everyday life

Carpets (wool or synthetics) accumulate charges that can cause a spark and then a fire.

Sources of static electricity accumulation at home

The accumulation of dust on surfaces can cause household fires. A frequent occurrence in regions with a difficult environmental situation, near metallurgical and machine-building enterprises.

To prevent the harmful effects of static electricity, you must:

provide lightning rods in houses;
provide for neutralization and grounding of electrical wiring in apartments and houses;
regularly test electrical wiring and electrical appliances;
regularly clean the premises;
prevent dust accumulation on carpets and shelves;
During construction, installation and repair work, comply with electrical, fire and fire safety rules.

Presence of static electricity in hair

Video about electricity

How static electricity is formed and why it is dangerous is explained in the video below.

Protection against static electricity is provided modern technologies on high level. Knowledge about the phenomenon and measures to combat it will help to avoid negative influence on human health and emergency situations.

Lecture 11. Protection from occupational radiation exposure

The widespread use of dielectric materials and organic compounds (polymers, paper, solid and liquid hydrocarbons, petroleum products, etc.) in all areas of economic activity is inevitably accompanied by the formation of static electricity charges, which not only complicate technological processes, but also often cause fires and explosions causing great material damage. This often leads to death.

Static electricity- this is a set of phenomena associated with the emergence, conservation and relaxation of a free electric charge on the surface, or in the bulk of dielectrics, or on insulated conductors (GOST 12.1.018). The formation and accumulation of charges on the processed material is associated with two the following conditions:

♦ the presence of surface contact, as a result of which a double electrical layer is created, the appearance

which is associated with the transition of electrons in elementary donor-acceptor acts on the contact surface. The sign of the charge determines the unequal affinity of the surface material for electrons;

♦ at least one of the contacting surfaces must be made of dielectric material.

Charges will remain on surfaces after termination of contact only if the contact destruction time is less than the charge relaxation time. The latter largely determines the magnitude of the charges on separated surfaces.

Mixed charging is observed when electrified material enters any containers isolated from ground. This type of charging is most often found when pouring flammable liquids into containers, when feeding rubber adhesives, fabrics, films into mobile containers, carts, etc. The formation of static electricity charges upon contact of a liquid body with a solid or one solid body with another largely depends on the density of contact of the rubbing surfaces; their physical state, speed and coefficient of friction, pressure in the contact zone, environmental microclimate, the presence of external electric fields, etc.

Charges of static electricity can also accumulate on the human body (when working or coming into contact with electrified materials and products). The high surface resistance of human tissue makes it difficult for charges to flow out, and a person can remain under high potential for a long time.

The main danger when electrifying various materials is the possibility of a spark discharge occurring both from a dielectric electrified surface and from an insulated conductive object.

Along with a fire hazard, static electricity also poses a danger to workers.

Light “pricks” when working with highly electrified materials have a harmful effect on the psyche of workers and in certain situations can contribute to injuries on technological equipment. Strong spark discharges, which occur, for example, when packaging granular materials, can lead to pain. Unpleasant sensations caused by static electricity can cause the development of neurasthenia, headaches, poor sleep, irritability, tingling in the heart, etc. In addition, with the constant passage of small electrification currents through the human body, unfavorable physiological changes in the body are possible, leading to occupational diseases. Systematic exposure to an electrostatic field of increased intensity can cause functional changes in the central nervous, cardiovascular and other systems of the body.

The use of artificial or synthetic fabrics for clothing also leads to the accumulation of static electricity charges on a person. GOST 29191 (IEC 801-2-91) provides information that synthetic fabrics can be charged to a potential of 15 kV. Therefore, the current flowing through the body of a person dressed in a suit or robe made of synthetic fabric can reach 3 μA. Touching grounded areas of the workplace or an uncharged body causes a spark discharge with a current of up to 30 A.

Static electricity also greatly affects the course of technological processes for obtaining and processing materials and the quality of products. At high charge densities, electrical breakdown of thin polymer films for electrical and radio engineering purposes may occur, which leads to defective products. Particularly damaging is caused by the adhesion of dust to polymer films caused by electrostatic attraction.

Electrification complicates processes such as sifting, drying, pneumatic transport, printing, transporting polymers, dielectric liquids, molding synthetic fibers, films, etc., automatic dosing of fine materials, since they stick to the walls of technological equipment and stick together.

Permissible levels of electrostatic field strength are established by GOST 12.1.045 and SanPiN 11-16-94.

Means of protection against static electricity must be used in all explosion- and fire-hazardous rooms and areas of open installations classified according to the PUE classification as classes B-I, B-Ia, B-I6, V-1g, V-P, V-Tsa, P-I, P-P.

When organizing production, processes accompanied by intensive generation of static electricity charges should be avoided. To do this, it is necessary to correctly select the friction surfaces and the speed of movement of substances, materials, devices, avoid the processes of splashing, crushing, atomization, purify flammable gases and liquids from impurities, etc.

Effective method reducing the intensity of static electricity generation is contact pair method. Most construction materials dielectric constant located in triboelectric series in such a sequence that any of them acquires a negative charge upon contact with the material that follows in the series and a positive charge with the previous one. Moreover, with increasing distance in the row between two materials, the absolute value of the charge arising between them increases.

To prevent the possibility of accumulation of static electricity on the surfaces of equipment, processed materials, as well as on the body of workers working above the minimum ignition energy of flammable mixtures, it is necessary, taking into account the specifics of production, to ensure that the resulting charges drain from charged objects.

In accordance with GOST 12.4.124 this is achieved using collective and personal protection.

Collective protection against static electricity according to the principle of action is divided into the following types: grounding devices, neutralizers, humidifying devices, anti-electrostatic substances, shielding devices.

Grounding refers to the basic methods of protection against static electricity and is the intentional electrical connection to ground or its equivalent of metallic non-current-carrying parts that may become energized. It is the simplest but necessary means of protection due to the fact that the energy of a spark discharge from conductive ungrounded elements of technological equipment is many times higher than the energy of a discharge from dielectrics.

The resistance value of a grounding device intended solely for protection against static electricity should not exceed 100 Ohms.

Special attention It is necessary to pay attention to the grounding of mobile objects or rotating elements of equipment that do not have constant contact with the ground. For example, mobile containers into which electrifying materials are poured or poured must be installed on grounded bases before filling or connected to the ground electrode with a special conductor before the hatch is opened.

Neutralization of charges static electricity is produced in cases where it is not possible to reduce the intensity of its formation by technological and other means.

In some cases it is effective to use radiation neutralizers static electricity, which provide ionization of a material or environment under the influence of ultraviolet, laser, thermal, electromagnetic and other types of radiation.

Removal of static electricity charges by reducing specific and surface electrical resistance is used in cases where equipment grounding does not prevent the accumulation of charges to a safe value.

To reduce the specific surface electrical resistance of dielectrics, the relative air humidity can be increased to 65-70%, if this is permissible under production conditions. For this purpose, general or local humidification of the air in the room is used with constant monitoring of its relative humidity. In this case, an electrically conductive film of water is formed on the surface of solid materials, through which charges of static electricity are discharged to grounded technological equipment.

To reduce the specific volumetric electrical resistance, various soluble substances are introduced into dielectric liquids and solutions of polymers (adhesives). anti-electrostatic additives (antistatics), in particular, metal salts of variable valence, higher carboxylic acids, naphthenic and synthetic fatty acids. Such additives include Sigbol, ASP-1, ASP-2, as well as additives based on chromium, cobalt, copper oleates, naphthenates of these metals, chromium salts, etc. Abroad, additives developed by Ecco and Shell (ASA-3 additive) have found the greatest use.

For this purpose, electrically conductive floors are used from materials whose specific volumetric electrical resistance should not be higher than 10 6 Ohm×m. Non-conductive coatings include asphalt, rubber, linoleum, etc. Conductive coatings include concrete, foam concrete, xylolite, etc. Grounded platforms and working platforms, door handles, handrails of stairs, handles of devices, machines, mechanisms, devices are additional means of removing charges from the human body.

Personal protective equipment against static electricity includes special electrostatic shoes and clothing. For the manufacture of such clothing, materials with a specific surface electrical resistance of no more than 10 7 Ohm×m should be used, and the electrical resistance between the conductive element of anti-electrostatic clothing and the ground should be from 10 6 to 10 8 Ohm. The electrical resistance between the heel pad and the running side of the shoe sole should be from 10 6 to 10 8 ohms.

In some cases, continuous removal of static electricity charges from a person’s hands can be carried out using special grounded bracelets and rings. At the same time, they must provide electrical resistance in the human-earth circuit from 10 6 to 10 7 Ohms and freedom of movement of the hands.

Protection against electromagnetic fields (EMF)

Widely used in production electromagnetic fields radio frequencies and industrial frequencies, permanent magnetic and electrostatic fields, the danger of exposure to which is aggravated by the fact that they are not detected by the senses. They are used to heat metal during melting and forging, obtaining a plasma state of the substance, during heat treatment of various materials, in radio engineering and electronic devices. The degree and nature of the impact of EMF on the human body is determined by the energy flux density, radiation frequency, duration of exposure, irradiation modes (continuous, long-term), the size of the irradiated body surface, individual characteristics organism, combined action together with other harmful factors of the working environment (increased ambient temperature, the presence x-ray radiation, noise, etc.).

In the area of EMF action, a person is exposed to thermal and biological effects: overheating, eye irradiation, functional changes in the central nervous and cardiovascular systems (headaches, fatigue, deterioration of health, neuropsychic disorder, etc.) trophic disorders can be observed: weight loss, hair loss hair, brittle nails, changes in blood.

Means and methods of protection: reducing radiation parameters directly in the radiation source itself, shielding radiation sources, shielding the workplace, limiting the time personnel stay in the EMF area, increasing the distance between the radiation source and the workplace, using warning alarms, using personal protective equipment, etc. .