Methods and means of protection against static electricity. ESD Protection Measures

Permissible levels of electrostatic fields are set in GOST 12.1.045-84. “Electrostatic fields. Permissible levels in the workplace and requirements for monitoring. Permissible levels of field strength depend on the time spent at the workplace. The maximum permissible level of electrostatic fields is 60 kV / m per 1 hour.

The use of protective equipment for workers is mandatory in cases where the actual levels of electrostatic fields in the workplace exceed 60 kV / m.

When choosing means of protection against static electricity, the features of technological processes, the physical and chemical properties of the processed material, the microclimate of the premises, etc., should be taken into account, which determines a differentiated approach in the development of protective measures.

Protection against static electricity is carried out in two ways:

• * a decrease in the intensity of the formation of electric charges;
• * elimination of the formed charges of static electricity.

Reducing the intensity of the formation of electric charges is achieved by reducing the speed and friction force, differences in the dielectric properties of materials and increasing their electrical conductivity. Reducing the friction force is achieved by lubrication, reducing the roughness and contact area of ​​the interacting surfaces. Friction speeds are limited by reducing the processing and transportation speeds of materials.

Since static electricity charges are generated by splashing, spraying and splashing dielectric liquids, it is desirable to eliminate these processes or at least limit them. For example, “filling tanks with dielectric liquids by a free-falling jet is not allowed. The drain hose must be lowered below the liquid level or, in extreme cases, the jet should be directed along the wall so that there is no splashing.

Since the intensity of the formation of charges is higher, the lower the electrical conductivity of the material, it is desirable to use, if possible, materials with higher electrical conductivity or to increase their electrical conductivity by introducing electrically conductive (antistatic) additives. So, for flooring it is necessary to use antistatic linoleum, it is desirable to periodically carry out antistatic treatment of carpets, carpet materials, synthetic fabrics and materials using household chemicals.

It is preferable to make contacting objects and substances from the same material, since contact electrolysis will not occur in this case. For example, it is desirable to store polyethylene powder in polyethylene barrels, and pour it and transport it through polyethylene hoses and pipelines. If this is not possible, then materials similar in their dielectric properties are used. For example, the electrification in a pair of fluoroplast-polyethylene is less than in a pair of fluoroplast-ebonite.

Thus, to protect against static electricity, it is necessary to use low-electrifying or non-electrifying materials, to eliminate or limit friction, spraying, splashing, splashing of dielectric liquids.

“The elimination of static electricity charges is achieved primarily by grounding the equipment cases. Grounding for the removal of static electricity can be combined with the protective earthing of electrical equipment. If grounding is used only to remove static electricity, then its electrical resistance can be significantly higher than for the protective resistance of electrical equipment (up to 100 ohms). Even a thin wire is enough for electric charges to constantly flow into the ground.

To remove static electricity from the car body, an electrically conductive strip is used - an "antistatic" attached to the bottom of the car. If you notice that the body is “sparkling” when exiting the vehicle, discharge the body by touching it with a metal object, such as the ignition key. It is not dangerous for a person. Be sure to do this if you are going to fill up the car with gasoline.

Aircraft are equipped with metal cables attached to the landing gear and fuselage bottoms, which makes it possible to remove static charges from the body during landing.

To remove electrical charges, protective screens of computer monitors are grounded. Gasoline trucks are supplied with grounding conductors in the form of chains that are constantly in contact with the ground when the car is moving. When draining gasoline into tanks at a gas station, the tanker car and the gasoline drain system must be additionally grounded.

Humid air has sufficient electrical conductivity to allow the resulting electrical charges to flow through it. Therefore, in a humid air environment, electrostatic charges are practically not formed, and air humidification is one of the simplest and most common methods of dealing with static electricity.

Another common method of eliminating electrostatic charges is air ionization. The ions formed during the operation of the ionizer neutralize the charges of static electricity. Thus, household air ionizers not only improve the aeroionic composition of the indoor air, but also eliminate electrostatic charges that form in dry air on carpets, synthetic carpets, and clothing. In production, special powerful air ionizers of various designs are used, but electric ionizers are the most common.

Personal protective equipment may include antistatic shoes, antistatic gowns, grounding wrist straps, and other equipment that provides electrostatic grounding to the human body.

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, materials, products or on insulated conductors.

The occurrence of static electricity charges occurs during deformation, crushing of substances, relative movement of two bodies in contact, layers of liquid and bulk materials, with intensive mixing, crystallization, and also due to induction.

The nervous, cardiovascular, neurohumoral and other body systems are most sensitive to electrostatic fields. This necessitates hygienic regulation of the maximum permissible intensity of the electrostatic field.

An electrostatic field is characterized by a strength determined by the ratio of the force acting in the field on a point electric charge to the magnitude of this charge. The unit of measure for tension is volts per meter. Permissible level of intensity of electrostatic fields - 60 kV/m. if the field strength exceeds this value, appropriate protective measures must be applied.

Static electricity seems like a joke to people not familiar with the Robert Van de Graaff generator. Today we will look at measures to protect against static electricity and tell you why lightning appears. Then we will apply part of the knowledge in practice in the field of the oil industry. You will learn how the antenna is protected, why lightning always strikes in one place. Thanks to static electricity, the discharge selects exceptionally tall trees on the plain. You can not hide at the foot of a tree during a thunderstorm. The topic of today's conversation is protection against static electricity.

Static electricity in nature

Everything flows - everything remains the same. Previously, it was required to protect the vacuum cleaner from static, today they simply use improved materials. There is always the possibility of accumulating charges. In this light, the protection of microcircuits from static electricity disturbs the minds. Electrostatic voltage was formerly quite suitable for entertaining the public and profiting from professors' lectures. For example, learned minds had fun like this:

1. The homeless child was charged with static electricity by friction with a charge of a certain sign.
2. The experimenter then touched the subject's nose.
3. There was a click of an electric discharge, part of the money migrated to the homeless child.
4. As a result, everyone was satisfied: the audience, who saw static electricity in action, the homeless child, who earned a piece of bread, and the professor, who raised his own popularity.

Static electricity has been observed in Ancient Greece, but the first reliable description, as well as a mathematical model, was invented by Coulomb after centuries. Coulomb came up with the concept of electric charge, explained the mechanics of the interaction of bodies with an excess of electrons or a deficiency.

It turned out that dielectric materials, like an ebonite stick, concentrate an excess of positive or negative charges in a limited area. An explanation was given later. It turns out that in order to distribute charges evenly over the surface, the material must have electrical conductivity. Similarly, metals were singled out into a single class. Then followed a series of discoveries on static electricity:

• It turns out that if you bring a charge closer to a metal object, the charges of the same name flow to the opposite side. On the first one, there is an excess of carriers of the opposite sign.

Magicians demonstrated an entertaining phenomenon to ignorant people. A metal rod, isolated (for example, with varnish) from static electricity, concentrated on a thin gold plate, reinforced at the bottom. When the maestro brought the "magic wand", rubbed on the rabbit, to the opposite end of the axis, the petal rose. The audience did not see - but before the experiment, the plate of gold was charged by the carriers of the desired sign (by friction). When the magic wand approached the rod, a potential difference was created at the ends. As a result, the plate, being suitably charged with static electricity, repelled.

• The charge is able to transfer between bodies.

On the example of the previous layout, the magician acted as follows: the wand approached the rod, then they touched. The surface density of static electricity charges was equalized (with proportion). When the wand was removed, the plate still remained hanging in the air. Can you imagine the effect that static electricity had on the audience? But the need for a protection device is explained by an undescribed trick.

• Robert Van de Graaff (American physicist, 1901 - 1967) was able to amaze the audience with the third effect. He came up with an original device for injecting the potential of static electricity onto the surface of a steel ball.

Meaning: the conveyor belt rubbed against the glass and followed a circular path to the metal sphere. The moving material is a dielectric, the charge of static electricity was not lost anywhere. But the ball had a large surface, in addition, it conducted current. Due to what is happening, a small section of a highly charged tape began to give up carriers. And the sphere was charged with static electricity. Comedians and pranksters are not recommended to touch such a little thing, standard protection methods may not work: the potential of the curiosity exceeded 1 MV (megavolt, million volts). As a result, the Van de Graaff generator was created, which reached 7 MV.

• Protection of pipelines in the oil business was not required because of the ability of bodies (pipes) to transfer or receive a charge. At a certain field strength (potential difference), static electricity poured into a thunderstorm.

As you know, lightning is caused by the ionization of air molecules at points between charged parts. A plasma path appears. Like an air electrolyte. It carries charges, so an arc (of a welder) occurs.

Lightning protection is installed on each aircraft: at the rear of the wing there are devices ending in a heap of the thinnest steel wires, landing, the car does not hit the strip with lightning (which easily leads to an explosion). Instead, the excess carriers form a spark and flow back during the movement of the aircraft in the form of plasma. Such measures are actively used by motorists, but the excess is given to the Earth. Our planet is electrically conductive, willingly accepts static charges in order to spread them over the surface, then the process fades away, compensated by winds, water, losses in the soil and other effects.

Measures to combat static electricity

Actually, the protection of equipment from static electricity has already been partially considered. These are vehicle stackers. A piece of rubber was often used, but only works in wet weather. When the car is driving on the road, the friction of dust and air molecules causes a static charge to build up. Dry rubber is an insulator, dripping is inefficient. In wet weather, the problem is solved completely. At the same time, the risk of human injury is low in a dry environment, rubber is often enough.

When organizing protection against static electricity in production, they are guided by standards. For example, oilmen refer to the resolution of Gosgortekhnadzor dated May 20, 2003. Documents state that any equipment with a metal case and any type of paint is considered protected by being grounded. In this case, the resistance to the input to the local circuit bus is not more than 10 ohms. Check your computer with a tester and a properly equipped outlet.

Make sure that the resistance from the far point of each plate of the system unit to the side petals does not exceed 10 ohms. By the way, according to the specified standards, the circuit must fit within the framework of up to 5 ohms relative to the globe. Grounding is carried out with a residential section of 6 square millimeters for copper or 10 for aluminum. Take note if you want to protect yourself from lightning and static electricity at the same time. According to the norms of the standards of the TN-С-S group, it is allowed to connect the grounding in the house (under the foundation) to the lightning protection circuit.

What is often done in practice. An ESD cable is known. For employees of workshops and laboratories associated with computer technology, protection measures are not limited to the described. It is allowed to buy special slabs for the floor, but at home it is easier to limit yourself to a set:

1. Protective measures against static electricity begin with the presence of a ground terminal at the workplace. This is a branch in the form of a bolt with a nut, an eyelet for connecting a number of devices.
2. People working with microcircuits usually wear special antistatic wristbands on both hands. Woolen sweaters are forbidden, but the additional charge is designed to drain immediately.
3. Special footwear (primarily sole material) prevents the accumulation of static charge. If you work with expensive microcircuits, spend a couple of thousand rubles to save (protect from loss) millions.
4. For large enterprises, industrial ESD regulations often require advanced steps. On sale there are trousers, jackets and suits made of special fabrics. Such an employee is no longer a thunderstorm for sensitive electronic equipment. Such a set is often cheaper than the daily clothes of an employee (sometimes it does not reach a pair of decent sneakers). There are insulated options for the cold conditions of the North (do not forget about the oilmen).

Antennas are often located on the roof, protection is required first. Due to the friction of clouds and winds, static electricity accumulates in the atmosphere. The charge density is the same from the constant movement of air masses. Ionization occurs where the distance to the sky is less. These are tree peaks. When it comes to the city, the targets are the roofs of high-rise buildings. For this purpose, lightning rods are made. The peak of the device must exceed all objects located on the roof.

Features of the organization of lightning protection are discussed in RD 34.21.122C. The potential drift to the floors along the path of pipes, metal braiding of cables is discussed. To exclude the phenomenon, these objects at the basement level are combined with the grounded reinforcement of the foundation. If this is not possible, additional steps are taken:

• According to paragraph 2.2 g of RD 34.21.122C, a circuit is equipped.
• It consists of three vertical rods not shorter than 3 m with a distance between them of 5 m.
• The section of the contour elements is determined by Table 3 of the section under discussion: gradation is carried out depending on the location and shape. The underground part is assembled from round electrodes with a diameter of at least 10 mm. Rectangular are selected according to the cross section in square millimeters (40 external, 100 underground), and the thickness of the reinforcement is not less than 4 mm. Finally, round current leads above the soil surface are not thinner than 6 mm.

The information given is enough to understand: the ground loop does not go on YouTube in comparison with the recommendations of gardeners. In reality, everything is much more complicated. Methods for protecting integrated circuits are carried out in accordance with GOST, and not according to the recommendations of neighbors. By the way, a hat is put on the head so that the hair does not fall, and bracelets are worn on both hands.

Instead of a conclusion on protection against static electricity

It happened that the graphics adapter burned out from touching the monitor. The VGA adapter burned out, as expected, during the test. A potential was applied to the kinescope, a charge was also present outside. Guess the ESD rules are now bouncing off readers' teeth.

Static electricity is the appearance of a free charge on the surfaces of dielectrics. The occurrence of an electrostatic field carries a great danger for production cycles associated with combustible substances, dust, flammable vapors. These charges can cause malfunctions in the operation of electronic devices and devices. Protection against static electricity is also necessary for the prevention of many diseases.

The nature of static electricity

In an equilibrium state, the molecules and atoms of any substance have the same number of positively and negatively charged particles. Negatively charged particles, electrons, can move from one atom to another, thus creating different charges of atoms.

Where an extra electron appears, the charge is negative. Where an electron is missing, it is positive. These charges that are stationary in space create an electrostatic field. It occurs in such cases:

It is very dangerous to transport gasoline in plastic cans. Fluid rubbing against walls generates static electricity that can spark and ignite gasoline vapors.

Sparks generated during the discharge of electrostatic fields can cause a fire in dusty and gassed rooms.

Human danger

The need to eliminate the dangers associated with the appearance of an electrostatic field exists both in production and in everyday life. Protection against static electricity in production is mandatory when explosive and flammable production processes. In accordance with safety regulations, it is necessary to protect workers in enterprises from electric shock.

The intensity of the electrostatic field is low and, with rare exposure, does not harm health, but at the same time, muscle reactions and convulsions may occur, which will lead to an accident. Prolonged exposure to electrostatic fields may affect performance of cardio-vascular system . The electrostatic field also has a negative effect on electronic devices. As a result of the discharge, they often fail.

Enterprise protection

Static electricity and protection against it are issues that are being seriously considered when creating safety regulations in enterprises. Compliance with them must protect personnel from electric shock and prevent violations technological process.

The measures applied in production are to reduce the intensity of the generation of fields and to remove the charge. To reduce the intensity is used:

• Purification of combustible gases and liquids from contamination by solid and liquid impurities.
• Refusal, if possible, from crushing and spraying substances in the technological cycle.
• Compliance with the design speed of movement of materials in highways and apparatuses.

To remove the charge, grounding of all metal and electrically conductive parts of the equipment, metal casings and pipelines is required. Both moving devices and rotating elements that do not have constant contact with the ground should be grounded. An increase in the conductivity of dielectric materials also contributes to the removal of charge. This is achieved by using surfactants that increase the conductivity of dielectrics. Maintaining air humidity of at least 60-70% is a successful method of dealing with static electricity.

Neutralizers are used if technological measures are not enough. These devices are used to neutralize surface electric charges by ions of different signs. Induction and high-voltage neutralizers are used to ionize air with a high-voltage electric field.

In order to neutralize charges in explosive rooms, radioisotope neutralizers are successfully used. Ionization occurs due to active α or β radiation.

Individual methods of protection are special footwear and clothing.

Ensuring the safety of the house and apartment

Free electric charge accumulate: rubber shoes, synthetic clothing, linoleum and plastic, carpets, reinforced concrete walls. To protect residential premises, first of all, it is necessary to ensure that the humidity of the air is not less than 60%.

There is a large selection of humidifiers that can solve this problem. Air ionizers are used to neutralize electrostatic charges. Rules for protection against static electricity:

• Use in residential premises grounding and grounding of electrical wiring.
• Get rid of dust, prevent its accumulation on carpets.
• Comply with electrical safety rules.
• Treat synthetic clothing with an antistatic agent.

Protection against free electric charges will help preserve health, avoid explosions and fires, improve the operation of technological devices and electronic devices. These measures are very important both for the protection of every home, and for the safety and improvement of conditions for workers in the workplace.

Every person on earth has encountered a natural phenomenon when, when leaving a car, he receives an electric shock. Or when petting a cat, crackling is heard and tingling of the fingertips is felt. And in the dark, glowing paths behind the hands are visible. This phenomenon is called static electricity.

It occurs when a charge accumulates on the surface of an object. This occurs when intraatomic or molecular equilibrium is disturbed.

As a result, the loss or acquisition of an electron occurs. The electronic balance is disturbed and the ions acquire a positive or negative charge.

Experiments with static electricity are known to every schoolchild when they showed an experiment with an ebonite stick and pieces of paper.

Causes

The conditions for the emergence of potential on objects is the dryness of the air. At 80% humidity, this natural phenomenon does not occur.

• When one object touches another. Potential arises after their separation. Friction, winding / unwinding of artificial materials, friction of the car body against the air, etc.;
• As a result of rapid temperature change. So, static electricity arises on objects when they are placed in a heated oven;
• Radiation and ultraviolet radiation, X-rays X-rays, strong electromagnetic and electric field;
• Guidance - there is an electric field caused by a charge. The potential arises when processing sheet or roll materials. The phenomenon occurs at the moment of separation of the material and surface. This effect can occur when moving one layer relative to another. This process is not yet fully understood. It can be compared to the separation of the plates of a capacitor. In this case, mechanical energy is converted into electrical energy.

The ability of items to accumulate charges has a negative effect on vehicles. If you do not take any measures, then damage and failure may occur.

The danger of the phenomenon

Particularly at risk of failure are electronics and all mechanisms that use electronic control units. In fire and explosion hazardous industries, sparks occur as a result of the discharge.

They may cause a fire or explosion. Protection against static electricity can completely eliminate or significantly reduce the risk of an emergency. The main danger is the occurrence of an electrical discharge.

The accumulation of charge is facilitated by dry air and reinforced concrete walls of buildings and structures. The charge polarity can be either positive or negative.

With working devices that have a rotating pulley with drive belts, the charge can reach 25,000 volts. In dry weather, electrostatic electricity of 10,000 volts can accumulate on the body of a car.

And a person who walks on a carpet in woolen socks is able to accumulate up to 6,000 volts. Even in domestic conditions, the voltage of static electricity can reach significant values.

However, it is not capable of causing significant harm to a person, due to insufficient power. The current flowing through a person is only a fraction of a milliamp.

In nature, such a phenomenon can accumulate huge values ​​and manifests itself in lightning discharges. With the release of large capacities that are capable of producing significant destruction.

Means of protection in the domestic environment

To reduce the impact on humans, a system of protection against the harmful effects of static voltage is used.

In domestic conditions, the most effective means is to increase the humidity of the air with the help of a humidifier. That not only eliminates the occurrence of stress on objects.

But it also reduces dust formation in the room. Reducing static electricity and reducing dust in the room is a log for children with allergies.

Protection methods at manufacturing enterprises

To ensure protection against static electricity in production, the following methods are used:

• Development of special methods of the technological process, excluding the accumulation of charge in the workplace;
• AT industrial premises create a microclimate;
• When processing overalls and floors in the room, substances with certain physical and chemical properties are used that can relieve stress from materials.
• This is done to ensure security measures. The harm of static electricity to process equipment is reduced with the help of a "Faraday cage".

It is a casing made of fine mesh, which is connected to ground. In the same way, cables are shielded, protecting them from harmful effects.

Types of discharges

There are several types of discharge:

• Spark discharge. The occurrence of a spark between two objects. For example, a body of equipment and a person. If the discharge power is high, then there is a high probability of ignition in the presence of solvent or gasoline vapors in the air;
• Brush discharge. Occurs when charges are concentrated at sharp corners of equipment with dielectric properties. It has less energy and does not pose such a danger as a spark discharge;
• Sliding discharge. Occurs on sheet or roll materials with high resistivity. This phenomenon occurs at the moment of friction or spraying of the powder coating. It can be compared to the discharge of an ordinary capacitor. And compare with a spark discharge with the same consequences.

Additional Precautions

Considering the negative consequences, enterprises apply special measures that exclude sources of static electricity. Workers' overalls are processed to remove static electricity, which eliminates the occurrence of sparks from clothing.

In addition to creating conditions under which the accumulation of charges is reduced, powerful air ionizers are used to protect against static electricity.

Such devices have undeniable advantages. Improving the aeroionic composition of the indoor air. This helps to reduce the accumulation of charges on the clothing of service personnel, synthetic carpets and equipment.

Application in industry

The use of static electricity in industry has not found wide application. Most often, things did not go beyond laboratory installations. Therefore, all instruments were used solely to demonstrate examples of static electricity in nature.

AT industrial plants found the use of corona discharges. With their help, air mixtures are purified from impurities. Paint installations have also been created that use static electricity. This makes it possible to paint complex surfaces with the least loss of paint.

Human impact

We encounter this natural phenomenon not only in enterprises. Most often, static electricity is observed in everyday life.

When removing clothes, a crackling sound is heard and sparks from the discharge are visible, and the hair on the head cannot be combed. These charges adversely affect the condition of people. The effect of such fields on human health and the immune system has not been fully elucidated.

However, it can be said that being in an apartment where there is static electricity has a negative effect on a person. The main violations can be noted:

• There are disorders in the central nervous system, which are accompanied by vasospasm and high blood pressure;
• Persistent headaches;
• Irritability and emotional excitability;
• Sleep disturbances appear, and appetite disappears;
• A phobia appears - the fear of receiving a discharge, which is accompanied by painful sensations.

Therefore, it is very important to know the methods of protection against static electricity in everyday life. For this, techniques such as grounding of all electrical appliances are used.

Use of household air humidifiers. Regularly carry out wet cleaning of the apartment, preferably in the morning and evening.

In order to ensure the removal of static electricity from synthetic fabrics, they are treated with antistatic liquids. Everyone should be aware of the dangers of being in the field for a long time and use ESD protective equipment.

If electric charges move freely through a conductor, it is called an electric current. If they stop without moving, start to accumulate on something, we should talk about static electricity. In accordance with GOST, statics is the totality of the occurrence, preservation and free accumulation of an electric charge on the outer surface of dielectric materials or on insulators.

The occurrence of static electricity

When a physical body is in its usual neutral state, the balance of negatively and positively charged particles in it is observed. If it is violated, an electric charge with one sign or another is formed in the body, polarization occurs - the charges begin to move.

Additional Information. Each physical object is capable of producing charges of either a positive or negative direction, which is what they are characterized by on the triboelectric scale.

For example:

• positive: air, skin, asbestos, glass, leather, mica, wool, fur, lead;
• negative: ebonite, teflon, selenium, polyethylene, polyester, brass, copper, nickel, latex, amber;
• neutral: paper, cotton, wood, steel.

Static electrification of objects can occur due to various reasons. The main ones are the following:

• direct contact between bodies with subsequent separation: friction (between dielectrics or dielectric and metal), winding, unwinding, moving layers of material relative to each other and other similar manipulations;
• instantaneous change in ambient temperature: sudden cooling, placing in the oven, etc.;
• radiation exposure, exposure to ultraviolet or X-rays, induction of strong electric fields;
• cutting processes - on machines for cutting or cutting paper sheets;
• special directional guidance by a statistical discharge.

At the molecular level, the occurrence of static electricity occurs as a result of complex processes, when electrons and ions from colliding inhomogeneous surfaces with different atomic bonds of surface attraction begin to redistribute. The faster the materials or liquids move relative to each other, the lower their resistivity, the larger the area that comes into contact and the interaction forces, the higher the degree of electrization and electric potential.

Sources of electrostatics, both in domestic and industrial conditions, are computer and office equipment, televisions and other units and devices powered by electric current. For example, the simplest computer has a pair of fans to cool the system unit. When the air is accelerated, the dust particles contained in it become electrified and, retaining a charge, settle on surrounding objects, people's skin and hair, and even penetrate into the lungs.

Also, static accumulates in large quantities on monitor screens. In homes and industrial premises, electrostatic charges are formed on floors covered with linoleum or PVC tiles, on people (in hair and on synthetic clothing).

In nature, static electricity is very powerful, which occurs when cloud masses move: huge potentials of electricity arise between them, which manifests itself in lightning discharges.

In industry, the formation of static charges is common in the following cases:

• friction of conveyor belts on shafts, wire belts on pulleys (especially in cases of slippage and jamming);
• during the passage of flammable liquids through pipelines;
• filling tanks with gasoline and other liquid petroleum fractions;
• ingress and movement of dust particles in the air ducts at high speed;
• during grinding, mixing and screening of solids;
• during the mutual compression of dielectric materials of various kinds and consistency;
• mechanical processing of plastics;
• the passage of liquefied gas (especially containing suspensions or dust) through pipelines;
• moving trolleys with rubber tires on insulating flooring.

The danger of static electricity

The greatest danger of accumulated static electricity is in industrial production. Unexpected ignition of combustible material by sparks from the operator's contact with the equipment on earth and subsequent explosion can occur. The energy of an electrostatic discharge is sometimes about 1.4 joules - this is more than enough to bring the mixtures of dust, steam, gas and air present in any combustible substances into a state of combustion. According to GOST, the highest energy of accumulated charges on the surface of an industrial facility should not be more than 40 percent of the lowest energy for material ignition.

During certain technological operations, for example:

• pouring and transporting sand in trucks;
• pumping fuel through pipelines;
• pouring alcohol, benzene, ether into ungrounded tanks at high speed;
• during conveyor work, etc., electrical potentials from 3 to 80 kilovolts are generated.

Note! In order to explode gasoline vapors, 300 volts are enough, combustible gases - 3 kilovolts, and combustible dusts - about 5 kilovolts.

Static also negatively affects the operation of all precision and ultra-precise instruments, radio communication equipment, and creates big problems in the functioning of automation and television mechanics. Many parts of complex electronic devices are simply not designed for such high voltages generated by static discharge. It disables these parts, as a result of which the devices lose their accuracy.

People can also accumulate charged particles if they wear shoes with non-conductive soles, woolen, silk or synthetic clothing. Electrification occurs when moving (if the flooring does not conduct electricity) and interacting with dielectric objects.

The effect of static on the human body is carried out in the form of a long-flowing electric current of low voltage or a momentary discharge, which causes slight and not always pleasant tingling on the skin (sometimes they are rated as moderate or even strong injections). In general, such exposure with a potential of no more than 7 joules is considered harmless to health, however, even a weak discharge of current can lead to reflex muscle contraction, which is fraught with various industrial injuries (getting into the working areas of mechanisms, catching parts of the body or clothing by unprotected moving parts of machines, falling from height).

If we consider the effect of static electricity on the human body at the cellular level, then as a result of the activation of the neuroreflex mechanism, skin neurons and the smallest capillaries are irritated. This leads to changes in the ionic composition of the tissues of our body, which manifests itself in increased fatigue during the day, a constant irritable mental state, sleep disturbances and other problems in the functioning of the central nervous system. Overall performance is reduced. Spasms provoked by constant exposure to static electricity blood vessels can cause bradycardia - a decrease in the frequency of contractions of the heart muscle and high blood pressure.

Ways to protect against static in production

A complex of protective measures is developed and applied against the harmful and dangerous manifestation of the accumulated static electric current in production conditions. They are based on the following methods:

• increasing the conductive properties of materials and the surrounding working environment, which leads to the dispersion in space of periodically appearing static electric charges;
• reduction in the speed of processing and movement of materials, which significantly reduces the possibility of generating static electric charges;
• full-scale use of well-arranged grounding, which helps to eliminate the accumulation of dangerous potentials;
• increasing the stability of the machines and mechanisms themselves to the action of statistical discharges;
• preventing the penetration of electric current into the working area.

All methods used to prevent static electrical discharges are divided into structural, technological, chemical, physical and mechanical. The last three are aimed mainly at reducing the activity of generating electric charges and their fastest disappearance into the soil. At the same time, the first of the listed methods are not connected with grounding.

The so-called Faraday cage acts as a highly reliable means of protection against static electricity. It is made in the form of a fine mesh that encloses the machine over the entire area, it has a connection to the ground loop.

Thanks to this design, the fields of electricity do not penetrate inside the Faraday cage, and it does not affect the magnetic field in any way. Electric cables pre-coated with a sheet metal shield are protected according to the same principles.

The electrostatic charge can be optimally reduced by increasing the electrical conductivity of industrial materials and performing corona (i.e., creating an air plasma on the surface of materials with a corona discharge at room temperature). This is achieved with the help of a special selection of materials with increased volumetric conductivity, increasing the working area and increasing the ionization of the air around the protected mechanisms. Special units - ionizers, generate positively and negatively charged ions, which are attracted to oppositely charged dielectrics and neutralize their charges.

Important! For substances with high electrical resistance, such methods of protection against static are not suitable.

Mandatory in the list of measures to protect against static electricity is grounding. The grounding device includes a grounding conductor (conductive element) and a grounding conductor between the grounding point on the soil and the grounding conductor. Sufficient grounding against electrostatics is considered when the resistance at any point of the equipment is not higher than 1 megaohm. For equipment, conductive films are often used to cover the work surface.

Antistatic floors are laid in the workrooms, operators must work in antistatic clothing and footwear (the resistance of the sole material is not higher than 100 ohms).

Protection against static electricity in the home

In domestic conditions, there is a set of measures and measures to help prevent the formation of electrostatic discharges:

• wet cleaning every day reduces the amount of dust circulating in the air;
• prevention of drying out of the air, daily airing of the premises;
• use of antistatic brushes in cleaning;

• use of antistatic pieces of furniture;
• finishing the house with materials that remove static well: wood, antistatic linoleum and others;
• as for clothing, remove woolen clothing with slow movements, and to remove the sticking effect of silk items, use antistatic sprays;
• do not iron animal hair in cold and dry air;
• comb hair with combs made of wood or metal instead of plastic combs.

Do not forget about the protection of personal vehicles from the formation of static on the car body, especially before refueling it with gasoline. This is done with a simple antistatic strip under the bottom of the body.

Static electricity is free electric charges collected on various dielectrics. Both in industry and in everyday life, completely useless static electricity accumulates, and protection against it is necessary, since such charges can harm both machines, mechanisms, and industrial facilities and human health. Only reliable methods can nullify or completely prevent this negative phenomenon.

Video