The concept of static electricity is familiar to all of the school courses of physics. Static electricity occurs during the appearance of charges on the conductors, surfaces of various items. They appear as a result of friction arising from the contact of objects.
All substances consist of atoms. In the atom there is a kernel around which electrons and protons are located in the same amount. They are capable of moving from one atom to another. When driving, negative and positive ions are formed. Their imbalance leads to the fact that the static arises. The static charge of protons and electrons in the atmosphere is the same, but has different polarity.
Status appears in everyday life. Static discharge can occur at low currents, but high voltages. There is no danger to people in this case, but the discharge is dangerous for electrical appliances. During the discharge, microprocessors, transistors and other elements of the scheme suffer.
Statistics occur in the following states:
Status often occurs during a thunderstorm or in front of it. Thunderstorm clouds when moving through the air, saturated moisture, form static electricity. The discharge occurs between the cloud and the earth, between the individual clouds. The lightning device helps to hold the charge in the ground. Thunderstorm clouds create electric potential on metal objects that cause light shocks when touched. For a person, the blow is not dangerous, but the powerful spark is capable of changing some objects.
Each resident repeatedly heard a crackling, which is heard when removing the clothes, hit from touching the car. This is a consequence of statics. Electric discharge is felt when cutting paper, combing hair, when overflowing gasoline. Free charges accompany a person everywhere. The use of various electrical devices increases their appearance. They occur when speckling and grinding solid products, pumping or overflowing combustible liquids, when transporting them in tanks, when brushing paper, tissues and films.
The charge appears as a result of electrical induction. On metal corps of cars, large electrical charges are created on the dry season. The TV screen or computer monitor can be charged from the exposure to the beam created in the electron beam tube.
Static charge tried to use many scientists and inventors. Claimed bulky units, the benefits of which were low. It was useful to discovery by scientists of the corona discharge. It is widely used in industry. With the help of electrostatic charge, complex surfaces are painted, the gases from impurities are cleaned. All this is good, but there are numerous problems. Electric equipment are high power. They are sometimes affected by a person. It happens at home and in the workplace.
The harm of static electricity is manifested in the blows of different power when removing the synthetic sweater, when leaving the car, turn on and off the kitchen combine and vacuum cleaner, laptop and microwave oven. These strikes may be harmful.
Static electricity occurs, which affects the work of cardiovascular and nervous systems. It should be defended from it. The person himself is also often the carrier of charges. In contact with the surfaces of electrical appliances, their electrification occurs. If this is a measurement device, the case can end it with a breakdown.
The current of the discharge brought by man, its warmth destroys the compounds, breaks the tracks with chips, destroys the film of field transistors. As a result, the scheme comes into disrepair. Most often it does not happen immediately, but at any stage during the operation of the instrument.
In enterprises, manufacturing paper, plastic, textiles, materials often behave incorrectly. They glued together with each other, stick to various types of equipment, repel, collect a lot of dust on themselves, wound incorrectly on coils or bobbins. The fault of this is the occurrence of static electricity. Two the same charges of charge pushed apart from each other. Other, one of which is charged positively, and the other is negative, attract. Charged materials also behave.
At printing enterprises and in other places where flammable solvents are used in the work, a fire may occur. This happens in cases where the shoes with a toxconded sole, and the equipment does not have the right grounding. The ability of fire depends on the following factors:
Discharges are spark, wet, sliding wedges. From man comes spark discharge. Bruschet occurs on pointed parts of the equipment. Its energy is so small that it practically does not cause a fire threat. A brush digit sliding occurs on leaf synthetic, as well as on rolled materials with different charges on each side of the canvas. Danger He represents the same as a spark discharge.
The striking ability is the main question for safety professionals. If a person holds for a bottle and himself is in the voltage zone, his body will also charge. To remove the charge, you must necessarily touch the ground or to grounded equipment. Only then will go to the ground. But the person will get a strong or weak electric blow. As a result, reflex movements occur, which sometimes lead to injury.
Prolonged stay in the charged zone leads to the irritability of a person, to a decrease in appetite, worsening sleep.
Dust from industrial premises is removed by ventilation. It accumulates in the pipes and can ignite from the statistical spark discharge.
The simplest means of protection against it is grounding equipment. In terms of production, screens and other devices are used for this purpose. Special solvents and additives are used in liquid substances. Antistatic solutions are actively used. These are substances with low molecular weight. Molecules in antistatic panel are easily moved and react with moisture contained in the air. Due to this characterization, the static is removed from the person.
If the operator's shoes on a toxconducting sole, it must necessarily touch the ground. Then the departure of the static current in the ground can not be stopped, but the person will get a strong or weak blow. The action of static current we feel after walking through the carpets and pales. Shock beats get drivers leaving the car. From this problem to get rid of easy: just touch the door with the hand, sitting on the spot. Shoulder stroke into the ground.
Ionization helps well. This is done using an antistatic strip. It has a lot of needles from special alloys. Under the action of current in 4-7kv, the air is decomposed on the ions. Aerial knives are used. They represent an antistatic bar through which air blows and cleans the surface. The static charges are actively formed when spraying liquids with dielectric properties. Therefore, to reduce the effect of electrons, an incident jet cannot be allowed.
It is advisable to use an antistatic linoleum on the floor and more often clean up with the help of household chemicals. In enterprises related to the processing of tissues or paper, the problem of getting rid of static is solved by wetting materials. Improving humidity does not allow to accumulate harmful electricity.
To relieve statics, you need:
Well moisturizes the atmosphere of indoor flowers, a boiling kettle, special devices. Antistatic compositions are sold in household chemicals. They are sprayed over the carpet surface. You can make an antistatic yourself. For this, tissue softener (1 cap) is poured into a bottle. Then the container is filled with clean water, which is sprayed above the carpet surface. Napkins, moistened with antistatic, neutralize charges on the upholstery of the seats.
Moisturizing the skin is made by lotion after the shower. Hands are wiping several times a day. It should be swapped clothes on natural. If it is charging, to handle antistaste. It is recommended to wear shoes with a leather sole or walk through the house barefoot. Before washing, it is desirable to pour on the clothes ¼ glass of soda (food). She removes the discharge of electricity and softens the fabric. When ringed linen, you can add vinegar to the car (¼ cup). Lingerie drying better in the fresh air.
All listed measures help neutralize static problems.
Elektrostatic charges occur on the surfaces of some rubbing materials - both liquid and solid, as a result of a complex process of contact electrification. Electrification occurs by friction of two dielectric or dielectric and conductive material, if the latter is isolated.
The intensity of the formation of electrical charges is determined by the difference in the electrical properties of materials, as well as the strength and speed of friction. The larger the strength and speed of friction and more differences in electrical properties, the more intense the formation of electrical charges. For example, electrostatic charges are formed on the body of a car moving into dry weather, if the wheel rubber has good insulating properties. As a result, an electrical voltage occurs between the body and the ground, which can reach 10 kV and lead to the appearance of a spark when the person's output from the car is a discharge through a person to Earth.
In production in various technological processes, large electrical charges are also formed, the potentials of which can reach tens of kilovolt, for example, when grinding, crossing and pneumatic transportation of solid materials, when overflowing, pumping through pipelines, transportation in tanks of dielectric liquids (gasoline, kerosene, etc.). When singing the rubber tape of the conveyor relative to the rollers or belt of the belt transmission relative to the pulley, electrical charges can occur with the potential of up to 45 square meters.
In addition to friction, the cause of static charges is an electric induction, as a result of which the electrical charge is acquired from the body in the external electric field. Especially high induction electrical connection of electrically conductive objects. For example, on metal objects (vehicles, etc.), isolated from the ground, in dry weather under the action of the electric field of high-voltage power lines or thunder-clouds, significant electrical charges can be formed.
When touched a person to the subject carrying an electrical charge, the discharge of the latter through the human body occurs. The values \u200b\u200bof the currents arising from the discharge are not large, and they are very short-lived. Therefore, the electrician does not occur. However, the discharge, as a rule, causes the reflex movement of a person, which in some cases can lead to a sharp movement of the arm, falling from a height or its getting into a dangerous production area.
The greatest danger of electrostatic charges is that a spark discharge can have energy sufficient to ignite a combustible or explosive mixture. Spark, arising from the discharge of electrostatic charges, is a frequent cause of fires and explosions. At a voltage of 3 kV spark discharge may cause the ignition of almost all pair and gas-air mixtures; At 5 kV - ignition most of the combustible dust.
The greatest danger of static electricity is in production and in transport, especially in the presence of fire-hazardous mixes, dust and vapors of flammable liquids.
In domestic conditions (for example, when walking through the carpet), small charges are accumulated, and the energy of the arising spark discharges is not enough to initiate a fire under normal conditions of life.
To protect against static electricity, use:
First method The most effective and is carried out due to the selection of pairs of materials of the elements of machines that interact with the friction. Another way to neutralize the charges of static electricity is the mixing of materials, which, when interacting with elements of equipment, charge varies varies. For example, with a friction of a material consisting of 40% nylon and 60% Dacron, the chrome-plated surface of electrolysis is not observed.
A decrease in the intensity of the formation of electrostatic charges contributes to a decrease in the strength and speed of friction, roughness of interacting surfaces. For this purpose, during transportation on pipelines of flammable liquids with high specific electrical resistance (for example, gasoline, kerosene, etc.), regulate the limit rates of pumping. Equipping such liquids into the tanks fluidly falling on the surface of the liquid, the jet is not allowed: the drain hose is plugged under the surface of the fluid being drained.
The main technique of implementation second method It is grounding of electrically conductive parts of technological equipment for removal in the ground of the charges of the charges of the static electricity. For this purpose, you can use the usual protective grounding, designed to protect against electric shock. If it is impossible to ground the elements of machines and equipment on their surface, electrically conductive coatings (antistatics) are applied, and tissue materials (for example, filters) are subjected to a special impregnation that increases their electrical conductivity. Essentially important is the grounding of gas ducts of ventilation systems, according to which the stuffed air is transported.
To increase the intensity of static charges with elements of the air in the room, where they are installed, moisturize.
People constantly face static electricity, more precisely with its manifestations (in their apartment, in the car, in production, etc.). However, not many of us seriously thought about the nature of its occurrence, physical properties, characteristics, means of protection against static electricity. This article is devoted to finding answers to listed questions.
For a molecule or atom of any substance, an equilibrium state is normal, i.e. The number of positive (protons) and negative (electrons) particles in the atom is the same. But electrons of the substance can easily (in different materials in different) move from one atom to another, thereby forming a positive (missing electron) or negative (excess electron) atom charge. It is such an imbalance in atoms and molecules forms a static electroopol. Such fields are unstable and at the first time discharged.
GOST 17.1.018-79 "Static electricity. Introbalissacity "interprets the term" static electricity "as the ability of free electrical charges to occur, persist and relax in the volume and on the surface of semiconductors and dielectrics.
A mandatory "satellite" of the static field is dry air. With humidity above 80%, such fields almost never form because Water is an excellent conductor and does not allow excessive electricity to accumulate on the surface of the materials.
We all remember from the school course of physics experience with an ebonite rod, or plastic comb and a piece of wool fabric. After rubbing the rod with a cloth, he was able to attract finely chopped pieces of paper.
The friction of the two surfaces is the most common sources of the occurrence of the static field. You do not need to rub two materials about each other. The static field may occur during single contact, for example, in the case of winding / unwinding the tape tape.
Also, the sources of the static field generation can be:
The static field can be "delused" and "induced", i.e. obtained from another highly electrical object without direct contact with it. This method of "forced electrification" is called induction.
We all know well a well-known electric crackling when removing the outerwear or "electric blow" from the body of the car. We observe and often experiencing the action of static discharges when combing hair, cutting paper, transfusion of gasoline, etc.
A prerequisite for generating a static electro-tube is the presence of magnetic fields. Thus, it should be stated that free charges surround us constantly. But the person of this is not enough and he actively uses in his daily life and work a huge number of different electrical devices, thereby only increasing the overall "electrical tension" of the habitat.
Electrostatic devices and devices whose principle was based on friction, and could not leave laboratory shelves and training, where they are mainly used as a demonstration material.
Attempts to use static fields to generate an electric current also did not bring special success. Generators Van De Grafa and Felici, which were created in the 30th and 40th year of the last century, also did not find a wide application, because This equipment was quite cumbersome.
In addition, their functioning and maintenance was very expensive.
Very useful in terms of industrial use, there was a discovery of a corona discharge, which is widely used in various fields of industry. In particular, with its help, you can purify gases from various impurities and apply paint to the surface of any configuration.
Much more attention is paid today to issues that are direct consequence of the accumulated electrostatic voltage. Electric equipment of different capacities may affect a person, both at home and at work.
For example, a synthetic tissue sweater, as a result of friction with a back of the chair or with the material of the outerwear, is able to accumulate a discharge, which "will give yourself to know" when removing it. It is much more powerful when touched by a car, which has electrified from friction about the air.
Any electrical device, whether it is a food processor, a laptop, a computer monitor or a vacuum cleaner, necessarily carries an electrostatic charge that "willingly" goes into a person when contacting. Such a "transition" can cause, and may not cause painful sensations, but it is definitely harmful to the human body.
Scientists have long proved that the effect of static electricity energy is a danger to human health, in particular for the cardiovascular and central nervous system.
In the previously mentioned, the GUT is considered in detail the ways to protect against the influence of static fields, the most simple of which is a reliable earth grounding.
What can be made from static fields of the premises of the private house and industrial premises?
Video: How to get rid of static electricity.
http://www.youtube.com/watch?v\u003dls-hblqju9y
To protect people and high-precision equipment from exposure to static electricity, special screens and other electromechanical devices are used. Special additives and solvents are used to suppress electrification in liquid polymers. Widely used as to protect against static electricity in everyday life, various anti-static production.
These are chemicals having a low molecular weight, which allows their molecules to easily move and, in addition to this, enter the reaction with atmospheric moisture. The combination of these characteristics allows them to dispel the foci of the occurrence of static fields and remove statistical stress per person.
5.1. General provisions
5.1.1. To prevent the possibility of dangerous discharges from the surface of the equipment, substances, processed, and also from the body of a person must be provided, taking into account the peculiarities of production and measures that the charge can ensure:
Reducing the intensity of the charge of static electricity;
Charge removal by grounding equipment and communications, as well as providing permanent electrical contact with human grounding;
Charge discharge by reducing the specific volume and surface electrical resistance;
Neutralization of charge by using various means of protection against static electricity according to GOST 12.4.124-83.
5.1.2. To reduce the intensity of the charge:
Wherever it is technologically possible, combustible gases should be purified from suspended liquid and solid particles, liquids - with contamination with insoluble solid and liquid impurities;
Wherever the production technology does not require this, splashing, crushing, spraying of substances should be excluded;
The speed of movement of materials in the devices and highways should not exceed the values \u200b\u200bprovided for by the project.
5.1.3. Reducing the sensitivity of objects surrounding and penetrating them in them to ignite the effects of static electricity discharges should be ensured by the regulation of the parameters of production processes (moisture content and dispersion of the aero-dependent, pressure and temperature of the medium, etc.) affectingW,and phlegmation combustible media.
5.1.4. In the case when it is impossible to secure emerging charges, to prevent sparkling discharges of static electricity medium inside the devices when transferring flammable liquids, pneumatic transportation of combustible fine and bulk materials, blowing equipment at start-up, etc., it is necessary to eliminate the occurrence of explosive mixtures by using closed Systems with excess pressure or inert gases to fill the devices, containers, closed transport systems or other methods.
5.1.5. In the case of the use of equipment that is made of materials with a specific voluminous electrical resistance of more than 105 Om · m, you must be guided by the requirements of section 5.8 of these Rules.
5.1.6. In the case of processing and transporting in electrically conductor equipment (see p.5.8.1) without spraying and spraying substances that have a specific voluminous electrical resistance of less than 105 Om · m, the use of protection against static electricity in accordance with these rules is not necessary.
5.2. Distraction of charge by grounding
5.2.1. Grounding devices for static electricity protection are allowed to combine with grounding devices for electrical equipment. Such grounding devices must be performed in accordance with the requirements of the rules of electrical installations (PUE, section 1), and GOST 12.1.030-81, GOST 21130-75, SNiP 3.5.06-85 "Electrical devices".
Resistance to grounding devices that are intended exclusively for protection against static electricity is allowed not above 100 ohms.
5.2.2. All metal and electrically conductive non-metallic parts of technological equipment must be grounded regardless of whether other protection measures are taken from static electricity.
5.2.3. Non-metallic equipment is considered electrostatically grounded if the resistance of any point of its inner surface relative to the ground circuit does not exceed 107 ohm.
Measurements of this resistance should be carried out at the relative humidity of the ambient air 50 ± 5% and the temperature of 23 ± 2 ° C, and the area of \u200b\u200bcontact of the measuring electrode with the surface of the equipment should not exceed 20 cm 2, and the electrode must be located at the measurement of the equipment, the most remote From the point of contact of this surface with grounded metal elements, parts, reinforcement.
5.2.4. Metallic and electrically conductive equipment, pipelines, ventilation boxes and housings of thermal insulation of pipelines and devices located in the workshop, as well as on external installations, overpass and channels, must be along the entire length of the continuous chain, which within the workshop (separation, installation) must be It is attached to the ground circuit every 40-50 m, but not less than two points.
5.2.5. Accession to the ground contour with the help of a separate branch (regardless of the presence of grounding of communications connected to them and structures) are subject to objects on the surface and inside which the charge can be formed: devices, containers, aggregates in which crushing, spraying, spraying products can be formed; Lounged and enameled devices (containers); Machines that are worth separately, aggregates, devices, not connected by pipelines with a common system of apparatus and containers. These branches must be performed in accordance with SNiP 3.05.06-85 "Electrical Devices".
5.2.6. Tanks and capacity of more than 50 m3, with the exception of the vertical tanks with a diameter of up to 2.5 m, should be attached to the earthing machine with at least two ground conductors in diametrically opposite points.
5.2.7. Flange compounds of pipelines, apparatuses, enclosures with a lid and compound on bulbvyvini, not painted with non-electrically conductive paints, are sufficient to drain the charge of static electricity (no more than 10 ohms), do not require additional measures to create a continuous electrical circuit, for example, the installation of special jumpers.
In these compounds, the use of washers made from dielectric materials and painted with non-electrically conductive paints are prohibited.
5.2.8. Grounding pipelines located on external overpass must be performed in accordance with the current "instructions on the lightning protection device of buildings and structures" RD 34.21.122-87.
5.2.9. Bulk risers The overpass to fill the railway tanks must be grounded. Rail track rails within the drain-filling front should be electrically connected together and attached to a grounding device, not related to grounding electrical network.
5.2.10. Tank trucks, as well as tanks of bulk vessels under bulk and plums of liquefied gases and fire-hazardous liquids, throughout the entire filling and emptying time must be attached to a grounding device.
Contact devices for connecting grounding conductors from tank trucks and bulk vessels must be installed outside the explosive zone.
Flexible ground conductors cross-section for at least 6 mm2 must be constantly attached to the metal housings of tank trucks and tanks of bulk vessels and have at the end of a clamp or a tip for a M10 bolt to connect to a grounding device. In the absence of constantly attached grounding conductors of tank trucks and bulk vessels should be carried out in inventory conductions in the following order: the grounding conductor first joins To the cistern or tank case), then to the grounding device.
It is possible to use in an explosive zone of grounding devices with the appropriate level of explosion protection.
5.2.11. The opening of the hatches of tank trucks and tanks of bulk vessels and the immersion of the hoses should be made only after connecting grounding conductors to the grounding device.
5.2.12. Rubber or other hoses made of non-electrically conductive materials with metal tips used for fluids in railway tanks, tank trucks, bulk vessels and other mobile vessels and devices must be wrapped with a wire with a diameter of at least 2 mm (or a copper cable cross section of at least 4 mm2) With a pitch of a turn of 100-150 mm. One end of the wire (or cable) is connected by soldering (or under the bolt) with metal grounded parts of the product pipeline, and the other with the hose tip.
When using reinforced hoses or anti-selectrottatrical sleeves, their charge is required under the condition of the mandatory compound of the reinforcement or electrically conductive rubber layer with a grounded product pipeline and the metal tip of the hose.
Hose tips should be made of copper or other metals that do not give a mechanical spark.
5.3. Dispersion of charge by reducing the specific volume and surface electrical resistance
5.3.1. In cases where equipment grounding does not prevent the accumulation of a dangerous amount of static electricity, it is necessary to take measures to reduce the specific volume or surface electrical resistance of the materials, are processed by using moisturizing devices or anti-selectrotatrical substances.
5.3.2. To reduce the specific surface electrical resistance of dielectrics, it is recommended to increase the relative humidity of the air to 55-80% (if it is allowed by the terms of production). To do this, it is necessary to apply a general or local humidification of air in the room with constant control of its relative humidity.
Note.
A method for reducing specific surface electrical resistance by increasing the relative humidity of air and creating the adsorbed moisture layer on the surface of the material is not effective in cases when:
When the material is electrified, hydrophobic;
When the temperature of the material is electrified, above the ambient temperature;
When the time movement of the material in the zone of the effect of moisturizing air is less than the time of the formation of adsorbed wet film;
When the air temperature in the working area is higher than the temperature at which the moisture film can be resistant on the material.
5.3.3. For a local increase in the relative humidity in the area where the electrification of materials occurs, it is recommended:
Feeding to the water vapor zone (with electrically conductive items that are in the zone must be grounded;
The cooling of the surfaces were ocked, to a temperature of 10 ° C below the ambient temperature;
Spraying water;
Free evaporation of water from large surfaces.
For a general increase in humidity in the room, a system of air ventilation ventilation in an irrigation chamber can be used.
5.3.4. To reduce the specific surface electrical resistance, in cases where the increase in the relative humidity of the environment is ineffective, it is possible to further recommend the use of anti-selectrottatrical substances (applications 5, 6, 7).
Application of them on the surface of materials, electrified, can be carried out by immersion, impregnation or spraying, followed by drying, wipe the surface of the product with a cloth, which is impregnated with anti-selectrottatic solution.
Note.
The effect of anti-selectrottatical substances with surface application of their short-term (up to one month) for nonstability to washing with solvents, long-term storage and friction.
The duration of the anti-selectrotrtic action can be increased by the introduction into materials, processed, of various polymeric binders (for example, polyvinyl acetate) or the use of high molecular weight anti-selectrottatical means with film-forming properties.
The introduction of anti-selectrottatical substances to the composition of materials is processed, less efficiently, but these substances are contained for several years.
The introduction of anti-selectrottatical substances can be carried out in various ways:
Adding to the monomers before their polymerization;
Administration directly at the moment of polymerization itself;
Introduction when rolling, extrusion or mixing in the mixer.
5.3.5. To reduce the specific volume resistance of dielectric liquids and solutions of polymers (adhesives), the introduction of various anti-selectrottrottatrical additives, in particular, salts of metals of variable valence, higher carboxylic, naphthenic and synthetic fatty acids (see Appendices 8, 9) can be used.
5.3.6. The introduction of surfactants and other anti-selectrottatrical additives and additives is permissible only in cases where there is a resolution of sanitary supervision organs and the application does not entail violations of the technical requirements for manufactured products.
5.4. Neutralization of charge on the surface of solid dielectric materials
5.4.1. In cases where the dangerous impact of electrification is limited to any place or small number of places in the process, or when it is impossible to achieve a charge of static electricity charge with simpler means (div. 5.2, 5.3), it is recommended to neutralize by ionization of air in Immediately proximity to the surface of the charged material. For this purpose, static electricity neutralizers (GOST 12.4.124-83), types and basic technical characteristics of which are given in Appendix 10 can be used.
5.4.2. To neutralize the charges of static electricity in the explosive premises of all classes, radioisotope neutralizers should be used if they are not prohibited by other regulatory documents. Their installation and operation is carried out in accordance with the requirements of the instructions, they are attached to them.
The choice of the necessary type of radioisotope neutralizers is carried out according to sectoral methods and recommendations.
Note.
In the manufacture of sanitary and sanitary and domestic products (napkins, tampons, cigarette and mouthpiece, fabrics, etc.), as well as the airtal products of the use of radioisotope neutralizers are prohibited.
5.4.3. In cases where the material (film, tissue, tape, sheet) is electrified so much that the use of radioisotope neutralizers does not ensure the neutralization of the charge of static electricity, the installation of combined (induction-radioisotope) or explosion-proof induction and high-voltage (constant and voltage variable) of neutralizers is allowed.
5.4.4. In all cases, when the nature of the technological process and the design of the machines, induction neutralizers should be applied.
They should be installed in such a way that the distance between their coronating electrodes (needles, strings, ribbons) and the charged surface is minimal and did not exceed 20-50 mm (depending on the construct of the neutralizer). In the explosive premises, it is necessary to take measures to exclude the possibility of a spark discharge between the charged surface and coronating electrodes.
5.4.5. In case of the impossibility of using induction neutralizers or insufficient efficiency in a room, which is not explosive, it is necessary to use high-voltage neutralizers and al-slump sliding discharge.
Note.
In the case of the use of needle induction and high-voltage neutralizers, it is necessary to provide measures to prevent the possibility of injury to the service personnel with neutralized needles.
5.4.6. To neutralize the charge of static electricity in hard-to-reach places, on the surface of objects having a complex configuration, the geometrical dimensions change continuously, i.e. Where the installation of neutralizers in the immediate vicinity of the charged surface is impossible, aerodynamic neutralizers with forced fluid flow of air jet should be used.
In the case when this neutralization method is used in an explosive room, ionizers (except radioisotope) should be explosion-proof or located in neighboring premises that are not explosive.
Note.
In the case when on charged material, there are both positive and negatively charged areas, or when the charge sign is unknown, it is necessary to use ionizers that ensure the formation of both positive and negative ions in the air flow.
When the material is charged mainly by the charge of one mark, it is desirable to provide unipolar ionization of the air flow (opposite sign ions). In this case, the degree of ionization of the air flow decreases more slowly than with bipolar ionization, which allows you to install an ionizer at a greater distance.
5.5. Prevent dangerous discharges from liquids
5.5.1. When in pipelines and technological equipment, in which liquid products are contained, the possibility of the formation of explosive concentrations of steam-air mixtures (fluid temperature below the lower temperature limit of explosive, the environment does not contain oxidizers and is under excess pressure; devices and communications are filled with inert gases), fluid transportation speeds On pipelines and their expirations are not limited to the devices.
In other cases, the speed of movement of liquids over pipelines and their expirations in the devices (tanks) must be limited in such a way that the charge density, potential, field strength in the tank (apparatus), which is filled, did not exceed the values \u200b\u200bat which the spark discharge occurs with the energy does not exceed 0.4 minimum energy ignition energy.
The most secure speeds of the movement of liquids through pipelines and their expirations in the devices (tanks) are determined in each individual case, depending on the properties of the liquid and the content of insoluble impurities, the size, the properties of the material of the pipeline walls (apparatus), pressure and temperature in the machine that is filled in . In this case, it is clearly safe to transportation on grounded metal pipelines of liquids with a specific voluminous electrical resistance up to 105 Om · m with speeds up to 10 m / s, and liquids with specific voluminous electrical resistance up to 109 Om · M - with speeds up to 5m / s.
For liquids with a specific voluminous electrical resistance of more than 109 Om · m The permissible transportation speeds and expirations are set for each liquid separately, safe speed of such fluids from grounded metal pipelines into grounded metal tanks (devices) is 1.0 m / s.
5.5.2. To reduce the safe value of the charge density in a fluid flow having a specific voluminous electrical resistance of more than 109 Om · m, if necessary, transporting it through pipelines with speeds exceeding safely, it is necessary to apply special charge removal devices.
Devices for removing the charge from a liquid product must be installed on the loading pipeline directly at the entrance to the device (tank), which is filled in so that at maximum transportation speed of the product through the loading pipeline after exiting the device until it has expired in the device, 10% permanent Charge relaxation time in liquid. When this condition can not be done constructively, the removal of the charge arising in the loading nozzle must be provided in the middle of the device, filled (tank) until the charged flow is released on the surface of the fluid that is in the device.
5.5.3. As a device for draining a charge from a liquid product can be used:
Induction neutralizers with strings or needles;
Relaxation containers, which are a horizontal portion of the increased diameter pipeline.
In this case, the diameter of this section of the pipeline must be at least:
where D R. - diameter of relaxation capacity, m;
D T. - diameter of the pipeline, m;
V.t. - fluid speed in the pipeline, m / s.
The length of it (m) must be at least
where E. - dielectric constant liquid;
r. v is a specific voluminous electrical resistance of the liquid, Ohm · m.
5.5.4. As a device for removing charge inside the device (tank), which is filled, it is possible to apply:
Cells with a grounded metal mesh covering some volume near the end of the loading nozzle so that the charged flow from the nozzle flows inside the cell.
In this case, the cell volume must be at least
where V.- cell volume, m 3;
Q.- Productivity of liquid pumping (expenses), m3 / h;
t \u003d EE 0 R v - constant time relaxation charge in liquid, C;
e. - dielectric permeability of fluid, dimensionless;
e. 0 - electrical constant, equal to 8,854 · 10-12 f / m;
r. v is a specific voluminous electrical resistance of the liquid, Ohm · m;
Special nozzles at the end of the loading nozzle, which so form and direct the charged jet, resulting in to ensure maximum distribution time it on the surface of the bottom and walls of the device (tank), which is filled;
Submersible type neutralizers, which are a thick-walled dielectric tube with extended string electrodes installed in it.
5.5.5. To ensure a charge of charge from a fluid flow, in a wide range of changes in specific voluminous electrical resistance from 109 to 13 October Om · m can use an autonomous system of static electricity protection devices, which consist of an induction string neutralizer and a relaxation device.
5.5.6. To prevent dangerous spark discharges, it is necessary to prevent the presence on the surface of combustible and flammable liquids in the devices and reservoirs of ungrounded electrically conductive floating objects.
Pontoons from electrically conductive materials designed to reduce the loss of fluid from evaporation must be grounded using at least two flexible grounding conductors attached to the pontoon in diametrically opposite points.
Notes:
1. When using float or buoying levels of their floats should be made of electrically conductive material and to have reliable contact with grounding.
2. In the case when, with the existing production technology, it is impossible to prevent ungrounded floating objects on the surface of the liquid, it is necessary to take measures to exclude the possibility of creating an explosive medium over it.
3. The use of non-electrop-wire floating devices and items (pontoons, plastic balls, etc.), which are intended to reduce fluid losses from evaporation, is allowed only by coordination with a specialized organization.
5.5.7. The fluids must be supplied to the devices, tanks, the container to the full pipe cross section in such a way as to prevent them from spraying, spraying.
5.5.8. The fluid pouring fluid is not allowed. The distance from the end of the loading tube to the bottom of the receiving vessel should not exceed 200 mm, and when it is impossible, the jet should be directed along the wall. In this case, the shape of the pipe and the flow rate of the fluid must be selected in such a way as to prevent its spray.
With the upper body of the device, tank, tanks, etc. With the help of the rubber hose, it is necessary to provide its vertical location.
The exceptions are only cases when it is guaranteed that the impossibility of explosive concentrations of volatile mixtures in the receiving vessel is guaranteed.
5.5.9. The fluids should flow into the tanks below the level of the liquid residue in them.
At the beginning of the filling of the empty reservoir of the liquid, having a specific volume electrical resistance of more than 105 Om · m must be supplied to it at a speed of not more than 0.5 m / s until the end of the loading pipe is immersed.
With further filling, the speed should be selected taking into account the requirements of P.5.5.1.
5.5.10. Manual selection of fluid from tanks and tanks, as well as a level measurement with a different kind of dimensional line, and meter rods through hatches is allowed only after a time exceeding 3 (see paragraph 5.5.4) after the cessation of fluid movement when it is in State of rest. At the same time, measurement devices must be made of material with a specific voluminous electrical resistance of less than 105 Ohm · m and grounded.
In the case of the manufacture of these devices from dielectric materials, the conditions of electrostatic intrinsic safety must comply with the conditions according to GOST 12.1.018-93.
5.6. Prevent dangerous discharges in gas streams
5.6.1. To prevent hazardous spark discharges when moving gases and vapors on pipelines and devices, it is necessary wherever technologically possible to take measures to exclude the presence of solid and liquid particles in gas streams.
5.6.2. Condensation of vapors and gases with a large pressure drop causes a strong electrification of gas jets when leakage through looseness. This requires increased attention to the sealing of equipment, which holds the pairs and gases under high pressure.
5.6.3. The presence in the gas stream uncoated metal parts and equipment parts are not allowed.
5.7. Discretion of charge in the processing of bulk and finely dispersed materials
5.7.1. Recycling of bulk (especially finely dispersed) materials will be carried out in a metal or electrically conductive (see paragraph 5.8.1) of non-metallic equipment.
It is especially important to comply with this requirement in the installations for transportation, drying and grinding of materials in gas streams (jets.
5.7.2. In cases of application for the processing of bulk materials of anti-selectrottic or dielectric equipment and pipelines (see PP.5.8.2, 5.8.3) to improve the conditions of charge flow from the reprocessable material, special attention should be paid to the careful fulfillment of the requirements set forth in PP. 5.8.5, 5.8.6, 5.8.8, 5.8.10, 5.8.11.
To reduce electrification during pneumatic transportation of granular, crushed and powdered polymeric materials on non-metallic pipelines, it belongs to apply pipes from the same or close in the composition of the polymer material (for example, the transportation of powdered or granulated polyethylene is better to conduct polyethylene pipes).
5.7.3. In the installations for transporting and grinding materials in air flow (jets) of air supplied to be moistened to such an extent that the relative humidity of air at the outlet of the pneumatic transport, as well as at the site of grinding materials in mills, was at least 65%.
When the technological conditions, the increase in relative air humidity is not allowed, it is recommended to use its ionization (see Ridge.5.4). At the same time, the most suitable for use in bunkers, cyclones, on the final sections of pneumatic transport pipelines, there are special devices with rod, needle or string grounded electrodes (induction neutralizers).
5.7.4. In the case where the measures specified in paragraph 5.7.3 for which reasons cannot be applied, the listed processes should be carried out in the stream of inert gas.
Note.
Air use is allowed only when the results of direct measurements of the degree of electrification of materials in the current equipment confirm the security of the process.
5.7.5. In order to improve the conditions of the charge flow from the tissue sleeves used to raise granular and other bulk materials and the combination of movable elements of equipment with fixed, as well as with the sleeve filters, belongs to heave them with the corresponding solutions of surfactants (see Appendix 5) followed by drying By securing reliable contact with grounded metal elements.
For hosted filters, impregnation should be chosen, which does not reduce after drying the filter properties of the tissue.
It is allowed to use metallized tissue.
5.7.6. It is prohibited to load bulk products directly from paper, polyethylene, polychlorvinyl and other bags in the hatches of the devices, in which the fluids are contained at temperatures above their flash temperature.
In this case, metal screw, sectoral and other feeders should be applied.
5.7.7. To prevent dust explosions from spark discharges:
Avoid the formation of explosive dusty mixtures;
Do not allow falling and discharge of dust, the formation of dust clubs and its swirls;
Cleaning systematically equipment and building structures in rooms from dust, settled in the deadlines established by the current standards and rules.
5.8. Protection of lined and non-metallic equipment
5.8.1. Electrically conductive equipment in which surfaces that have contact with substances (raw materials, semi-products, finished products) are processed, which are processed, made of materials with a specific voluminous electrical resistance of not more than 105 Ohm · m.
5.8.2. The anti-selectrottachic is considered to be equipment in which surfaces that have contact with substances are processed, made of materials with a specific voluminous electrical resistance of not more than 108 Ohm · m.
5.8.3. The dielectric is the equipment in which the surfaces having contact with substances are processed, made of materials with a specific voltage electrical resistance of more than 108 Ohm · m.
5.8.4. Protection against static electricity of electrically conductive non-metallic equipment and equipment with electrically conductive lining should be carried out by methods provided by these Rules for Metal Equipment (see Section 5.2).
5.8.5. In the case of using anti-selectrottic and dielectric non-metallic equipment, there are no metallic parts and parts in them having resistance relative to the Earth more than 100 ohms.
5.8.6. The outer surface of the dielectric pipelines for which substances and materials with specific voluminous electrical resistance are transported to more than 105 Ohm · m should be metalizing or painted with electrically conductive enamels and varnishes (see section 11). At the same time, electrical contact between the electrically conductive layer and grounded metal reinforcement should be provided.
Instead of electrically conductive coatings, the specified pipelines with metal wire with a cross section of at least 4 mm are allowed2 winding step 100-150 mm, which must be attached to grounded metal reinforcement.
The electrically conductive coating (or wrapping) of the outer surfaces, the solid electrically conductive bases, separate electrically conductive elements and the armature of dielectric pipelines should be a solid electrical circuit along the entire length, which within the workshop (separation, installation) must be connected to the ground contour every 20-30 m But not less than two points.
5.8.7. To ensure the necessary contact with the grounding of anti-selectrottatical non-metallic pipelines, there are enough challenges to their metal wire according to p.5.8.6 or styling them on a solid electrically conductive basis.
5.8.8. Polymer piping supports should be made of electrically conductive materials and grounded, or have grounded gaskets from electrically conductive materials in places where pipelines are based on them.
5.8.9. Liquid with specific volume resistance no more than 109 Om · m is practically not electrified when moving at speeds before:
2 m / s - in pipelines and devices with dielectric materials and with dielectric lining;
5 m / s - in pipelines and apparatus with anti-selectrotruster material and with anti-selectrottatic lining.
5.8.10. Non-metallic anteelectrical and dielectric containers and apparatuses should be covered outside (and when it allows an existing medium in the apparatus, then inside) electrically conductive lacquers and enamels, provided that they are reliable contact with grounded metal reinforcement.
The reliable contact of the electrically conductive coating with the ground can be provided by coloring the solid layer of the electrically conductive enamel of all internal and external surfaces of the devices (containers) with the installation under its support grounded metal (or electrically conductive non-metallic) gaskets.
With the impossibility of coating with a solid layer of the inner and outer surfaces of the grounding apparatus of the internal electrically conductive layer, it is allowed by using additional electrodes or conductors.
5.8.11. To remove static electricity from substances that are in the middle of dielectric equipment and are capable of accumulating charges with contact or inductive effects from the electrical surface of this equipment, at least two grounded electrodes resistant to this medium are allowed.
It should not be disturbed by the tightness of the equipment and the electrodes, which are entered, should not appear on the inner surface. These measures are sufficient when the specific voluminous electrical resistance of the medium in the device does not exceed 109 Ohm · m for liquid media and 108 Om · m - for bulk.
5.9. Discretion of charge arising in humans, mobile tanks and devices
5.9.1. Mobile devices and vessels, especially for the transportation of dielectric combustible and flammable liquids, should be carried out from electrically conductive materials (see paragraphs. 5.8.1, 5.8.2). It should be transported on the workshops of the enterprise, they should on metal trolleys with an outer of electrically conductive materials, and the contact of the vessel or apparatus with the trolley body should be ensured.
When transporting explosive substances, it is electrified on trolleys or electrocaras with non-electrop-wire tires of wheels allowed to contact the trolley or electrocarios with the ground and electrically conductive flooring (see paragraph 5.9.7) using the chain connected to the body from copper or other metal that does not give Mechanical spark, has such a length so that several rings during transportation are constantly on Earth or on the floor.
Note.
To reduce noise when moving metal carts, their wheels can be coated with electrically conductive rubber (see Appendix 12).
5.9.2. In places of filling of mobile vessels, the floor must be electrically conductive (see p.5.9.7) or there should be grounded metal sheets on which vessels are installed during filling; It is allowed to ground the mobile vessels by attaching them to the grounding device with a copper cable with a clamp.
5.9.3. When filling out mobile vessels, the hose tip must be omitted to the bottom of the vessel at a distance of no more than 200 mm.
When the diameter of the neck of the vessel with a capacity of more than 10 liters does not allow to lower the hose inside, it is necessary to use a grounded funnel from copper or other electrically conductive material that does not give a mechanical spark, the end of which should be at a distance of no more than 200 mm from the bottom of the vessel.
In the case of using a short funnel, a chain of electrically conductive material should be attached to the end, does not give a mechanical spark that is resistant to fluid transfusions which when lowering the funnels in the vessel should go to the bottom.
5.9.4. To prevent dangerous spark discharges that arise from the accumulation of static electricity charge on the human body with contact or inductive influential electrical material or clothing elements, are electrified by friction, in hazardous industries, it is necessary to drain this charge to the Earth.
The main method of implementing this requirement is to ensure the electrostatic conductivity of the floor and the use of anti-selectrottic shoes.
Note.
Due to the large distribution of clothing from synthetic materials, which is strongly electrified when driving and leads to a rapid accumulation of charge on a person's body, a device of grounded handles, railings, dismisses should be considered as an additional charge tool from the body of a person.
5.9.5. Anti-selectrotatchic properties of shoes are determined by domestic and international standards and specifications on this shoes.
In some cases, to provide shoes of anti-selectrottatic properties, it is allowed to flash or pierce the sole with electrically conductive materials that do not give a mechanical spark, and the insole is obtained.
The use of wool and synthetic yarn socks is not allowed, as they hinder the flow of charge from the human body.
5.9.6. In the case when the employee performs work in non-electrically conductive shoes sitting, the charge of static electricity, which has accumulated on its body, is recommended to be removed using an anti-selectrotruster bathrobe in combination with the electrically conductive pillow of the chair or with the help of electrically conductive bracelets that are easily removed connected to the ground through the resistance 105 - 10 7 ohms.
5.9.7. To ensure continuous charge of charge from the body of a person, with mobile vessels and apparatuses in explosive rooms, the floors should be electrostatically leading.
Notes:
1. The floor covering is considered electrostatically leading when the electrical resistance between the metal plate of 20 cm2, laid on the floor and pressed to it in 5 kgf, and the ground loop does not exceed 106 ohms.
2. The scattering floor is the floor that is characterized by electrical resistance from 106 ohm to 10 9 ohms.
3. Astricted floor is the floor, which is characterized by electrical resistance of more than 109 OM and in what is minimized by the occurrence of charges when separating the contact of the surfaces or with friction with another material, namely the soles of shoes or wheels.
4. The specific voluminous electrical resistance of some floor coatings is given in Appendix 13.
5.9.8. It is forbidden to carry out work within tanks and devices, where it is possible to form explosive steam, gas and dusty mixtures, in overalls, jackets and other top clothing from materials, electrified.
Note.
To provide the upper clothes of anti-selectrottatrical properties, it is recommended to impregnate with the solutions of surfactants with the subsequent drying, the use of which is coordinated with the states of the State Session of Ukraine.
5.9.9. In the case when the service personnel is constantly in the electrostatic field created by charge on the material, electrostatically, or dielectric equipment, including display terminals, the electrostatic field strength in the workplace should not exceed the maximum permissible values \u200b\u200bset by GOST 12.1. 045-84.
5.10. Distraction of charge from rotating and belt gears
5.10.1. Can electrify or charge from the electrically conductive parts of the machines and devices that rotate and the contact of which with a grounded body can be impaired due to the presence of a lubricant layer in the bearings or the use of dielectric antifriction materials, must have special devices to ensure reliable grounding. Applications should be avoided in explosive premises of bearings or inserts to them from non-electrically conductive materials.
The best tool to ensure contact in electrically conductive bearings is the use of electrically conductive lubricants.
In the case when there is no possibility to ensure a charge of charge from rotating, simpler methods, permissible to use neutralizers (see Section 5.4).
5.10.2. In explosion and fire hazardous shops, it is recommended to directly connect the electric motor with the actuator or use gearboxes and other types of gears made of metal and provide electrical contact of the axis of the engine and the actuator.
5.10.3. If necessary, the use of belt gears, they and all parts of the installation must be made from materials having a specific voluminous electrical resistance of no more than 105 Om · m, in particular, anteelectrottatical Wedge belts, and all installation (fence and other metal objects near the pass) should be grounded.
5.10.4. In the case of using belts made of materials with a specific voluminous electrical resistance of more than 105 Om · m should be used one of the means of preventing dangerous electrification:
An increase in the relative humidity of air in the location of the belt transmission is not less than 70%;
Electrically conductive coatings (lubricants) of passes;
In special conditions - air ionization with the help of neutralizers installed from the inside of the belt, as close as possible to the point of its removal of the pulley.
Notes:
1. As an electrically conductive coating for leather and rubber belts, oil of this composition is recommended: per 100 wag.ch. Glycerin 40 wag.ch. Say. This lubricant has to be applied to the outer surface with the help of a brush when stopping the mechanism within the deadlines that establishes the administration of the enterprise, but at least once a week.
2. It is necessary to take measures to prevent contamination with belts of oil and other liquid and solid substances that have a specific volume resistance of more than 105 Ohm · m.
5.10.5. It is forbidden to lubricating belts in the rosin, wax and other substances that increase the surface resistance in the explosive rooms of all classes.
Widespread use in all areas of economic activity of dielectric materials and organic compounds (polymers, paper, solid and liquid hydrocarbons, petroleum products, etc.) is inevitably accompanied by the formation of static electricity charges, which not only complicate carrying out technological processes, but often become the cause of fires and explosions bringing large material damage. Often this leads to the death of people.
Static electricity- This is a combination of phenomena associated with the occurrence, preservation and relaxation of a free electric charge on the surface, or a conversation of dielectrics, or on insulated conductors (GOST 12.1.018). Education and accumulation of charges on the processed material is associated with two following conditions:
♦ The presence of contact of the surfaces, resulting in a double electric layer, the occurrence of which is associated with the transition of electrons in elementary donor-acceptor acts on the contact surface. The charge sign determines the unequal affinity of the surface of the surfaces to the electron;
♦ At least one of the inactive surfaces should be made of dielectric material.
The main factors affecting the electrification of substances are their electrophysical properties and the surface separation rate. It is experimentally established that the intensive process is carried out, i.e. The higher the speed of the separation, the greater the charge remains on the surface.
The following ways of charging objects are known: direct contact with electrified materials, inductive and mixed charge.
To pure contact charges of surfaces refers, for example, electrification when pumping hydrocarbon fuels, solvents on pipelines. It is known that pipelines from transparent dielectric material when pumping liquids will even glow.
Along with the contact, there is often inductive charge of conducting objects and attendants in an electric field of a moving flat electrical material.
Mixed charge is observed when the electrified material enters any containers, isolated from the ground. This type of charge is most common when pouring flammable liquids in the container, when feeding rubber adhesives, tissues, films in mobile tanks, trolleys, etc. The formation of static electricity charges when contacting liquid body with solid or one hard
the body with another largely depends on the density of contacting the rubbing surfaces, their physical condition, the speed and coefficient of friction, pressure in the contact zone, environmental microclimate, the presence of external electric fields, etc.
Static electricity charges can accumulate on human body (when working or contact with electrified materials and products). High surface resistance of human fabrics makes it difficult for charges, and a person can be under great potential for a long time.
The main danger in the electrification of various materials is the possibility of spark discharge, both with a dielectric electroded surface and with an isolated conductive object.
The ignition of combustible mixtures by spark discharges of static electricity can occur if the energy released in discharge will be higher than the minimum energy of the fuel mixture.
Along with the fire hazard, static electricity is danger and for working.
Light "injections" when working with strongly electrified materials, harmful effect on the psyche of working and in certain situations can contribute to injuries on technological equipment. Strong spark discharges arising, for example, when rearing granular materials, can lead to painful sensations. The unpleasant sensations caused by static electricity can be caused by the causes of neurasthenia, headache, poor sleep, irritability, tingling in the heart region, etc. In addition, with constant passage through the human body of small currents of electrification, adverse physiological changes in the body, leading to professional diseases, are possible. The systematic effects of the electrostatic field of increased tension can cause functional changes in the central nervous, cardiovascular and other organism systems.
The use of artificial or synthetic tissue clothing also leads to the accumulation of static electricity charges on a person.
Static electricity also strongly affects the course of technological processes for obtaining and processing materials and product quality. With large charge densities, an electric breakfast of thin polymer films of electrical and radio engineering can occur, which leads to marriage of products. Especially large damage is caused by an electrostatic attraction of sticking of dust on polymer films.
Electrification makes it difficult for such processes as sifting, drying, pneumatic transport, printing, transportation of polymers, dielectric fluids, molding synthetic fibers, films, etc., automatic dosing of fine materials, since they adhere to the walls of the process equipment and stick together.
When organizing production, processes accompanied by intensive generation of static electricity charges should be avoided. To do this, it is necessary to properly select the surfaces of the friction and the speed of the substances, materials, devices, avoid the processes of splashing, crushing, spraying, clean the combustible gases and fluids from impurities, etc.
The effective method of reducing the intensity of the generation of static electricity is method of contact pairs.Most design materials on dielectric constant are located in triboelectric rowsin such a sequence, that any of them acquires a negative charge when contacting with the subsequent material and positive - with the previous one. At the same time, with an increase in distance in a row between two materials, the absolute value of the charge arising between them increases.
In accordance with GOST 12.4.124, collective and individual protection means are used.
The means of collective protection against static electricity on the principle of action are divided into the following types: grounding devices, neutralizers, moisturizers, anti-electrostatic substances, shielding devices.
Groundit refers to the basic methods of protection against static electricity and is a deliberate electrical connection with the Earth or its equivalent of metal inadequate parts, which may be under voltage. It is the most simple, but necessary tool for protection due to the fact that the energy of the spark discharge with the imminent elements of the technological equipment is many times higher than the discharge energy from dielectrics.
GOST 12.4.124 prescribes that grounding should be applied on all electrically conductive elements of technological equipment and other objects on which the occurrence or accumulation of electrostatic charges may occur independently of the use of other means of protection against static electricity. It is also necessary to ground metal ventilation boxes and housings of thermal insulation of devices and pipelines located in the shops, exterior installations, overpass, channels. Moreover, these technological lines should be throughout the continuous electrical circuit, which is attached to the ground contour of at least two points.
Special attention should be paid to grounding of mobile objects or rotating elements of equipment that do not have permanent contact with the Earth. For example, mobile containers in which the electrified materials pour or pour, must be installed on the grounded bases or are attached to the ground with a special conductor before the hatch is open.
Neutralization chargesstatic electricity is made in cases where it is not possible to reduce the intensity of its formation by technological and other ways. For this purpose, neutralizers of various types are used:
· Crown discharge (induction and high-voltage);
· Radioisotope with α- and β-emitting sources;
· Combined, unifying in one construct corona and radioisotope
neutralizers;
· Creating a flow of ionized air.
The most simple on execution are induction neutralizers.In most cases, they are a hull or rod with grounded arresters attached to them, representing needles, strings, brushes. In these neutralizers, an electric field created by the electroded material itself is used.
To reduce the intensity of electrification of liquids use stringor needle neutralizers,which by increasing the conductivity of the medium contribute to the flow of the generated charges on the grounded walls of pipelines (equipment) or the neutralized body.
IN high voltage neutralizerscrown and sliding discharges, in contrast to induction, high voltage up to 5 kV, supplied to the arrester from an external power source. However, the need to use high voltage does not allow them to be used in explosive rooms and industries.
In the explosive premises of all classes it is recommended to use radioisotope neutralizersbased on α-emitting (plutonium-238, -239) type HP and β-emitting (tritium) type of NTSE sources. These neutralizers are small, simple on the device and maintenance, have a long service life and radiation safe. The use of them in industry does not require coordination with sanitary supervisory authorities.
In cases where the material (film, fabric, ribbon, sheet, etc.) is electrified with high intensity or moves at high speed and the use of radioisotope neutralizers does not provide static electricity neutralization, set combined induction radioisotope neutralizerstype NRI. They are a combination of radioisotope and induction (needle) neutralizers or explosion-proof induction, high-voltage (direct and alternating current), high-frequency neutralizers.
Very promising are pneumoelectric neutralizersvEN-0.5 and VEN-1.0 brands and pneumatic radiosotropicprinting grades in which ionized air or any gas is sent towards the electrical material. Such neutralizers not only have an increased radius of action (up to 1 m), but also provide the neutralization of volume charges in pneumatic transport systems, boiling layer devices, in bunkers, as well as the neutralization of static electricity on the surfaces of complex shape products. Devices for supplying ionized air in this case, explosive rooms must have a grounded metal screen over all of its mass.
In some cases, effectively use radiation neutralizersstatic electricity, which ensure the ionization of material or medium under the influence of ultraviolet, laser, thermal, electromagnetic and other types of radiation.
To reduce the specific voluminous electrical resistance into dielectric fluids and solutions of polymers (adhesives), various soluble in them are introduced antiolectrostatic additives (antistics),in particular, the salts of metals of variable valence of higher carboxylices, naphthenic and synthetic fatty acids. Such additives include "Sigball", ASP-1, ASP-2, as well as additives based on chromium oleats, cobalt, copper, naphthettes of these metals, chromium salts and SZhK, etc. Abroad, the greatest application found additives developed by ECCO and Shell firms (ASA-3 additive).
The electrical resistance of solid polymer materials (plastics, rubber, plastics, etc.) can be reduced by introducing various electrically conductive materials in their composition (technical carbon, powders, etc.).
In explosive industries to prevent the dangerous spark discharges of static electricity, arising from the body of a person with contact or inductive charge with electrified materials with elements of clothing, it is necessary to ensure the moaning of these charges to the ground. The non-conductive coatings include asphalt, rubber, linoleum, etc. conductive coatings are concrete, foam concrete, xylolite, etc. Grounded dilutes and work platforms, door handles, handrails of stairs, instrument handles, machinery, mechanisms, devices are additional charges of charge charges from human body.
Individual means of protection against static electricity include special electrostatic shoes and clothing.
In some cases, the continuous discharge of static electricity charges from the hands of a person can be carried out with the help of special grounded bracelets and rings. At the same time, they should provide electrical resistance in the chain. Man - Earth and freedom of movement of hands.
