MINISTRY OF AGRICULTURE OF THE RF
"ALTAI STATE AGRICULTURAL UNIVERSITY"
DEPARTMENT OF “LIFE SAFETY”
DETERMINATION OF DUST CONTAINMENT IN THE AIR OF PRODUCTION PREMISES AND WORK AREA
Guidelines to perform laboratory work
Barnaul 2004
UDC 613.646: 613.14/15
Determination of air dust content production premises Andworking areas: Methodological manual / Compiled by: A. M. Markova, ; edited by: Barna4. - 12s.
The guidelines contain information about the effect of dust on the human body, methods for determining and assessing the concentration of dust in the air of industrial premises.
Designed for laboratory classes with students of all specialties.
© Altai State Agrarian University
Determination of dust content in industrial premises
GOAL OF THE WORK : Study the methodology for determining and assessing dust concentration in the air working area
ORDER OF WORK:
1. Familiarize yourself with the classification of dust and its effect on the human body
2. Study the methodology for determining dust levels in industrial premises
3. Determine the dust content of the air in the work area according to the task
Equipment : 1. Air sampling aspirator - model 822
2. Analytical balances
3. Filters AFA-V-18, AFA-V-10
4. Filter cartridge (allonge)
5. Rubber tubes
6. Experimental setup
1. GENERAL INFORMATION ABOUT DUST
In many industries, due to the characteristics of the technological process, the production methods used, the nature of raw materials, intermediate and finished products and many other reasons, dust is generated that pollutes the air in rooms and work areas. Consequently, dust in the air becomes one of the factors in the production environment that determines the working conditions of workers.
Dust refers to small particles that are crushed or otherwise produced. solids, soaring (in motion) in the air of the working area. Dust can be in two states: suspended in the air (aerosol) and settled on the surface of walls, equipment, lighting fixtures(aerogel).
The nature and severity of the harmful effects primarily depend on chemical composition dust, which is mainly determined by its origin. Important has a dust classification based on particle size (dispersity). It determines the stability of particles in the air and the depth of penetration into the respiratory system.
Table 1
Classification of industrial dust
By method of education | By origin | By dispersion |
|
Occurs during the destruction of hard rocks (drilling, crushing, grinding), transportation and packaging of bulk materials, machining products (grinding, polishing, etc.) | I. Organic: a) vegetable (cereals, fibers, etc.) b) animal (wool, leather, etc.) c) microorganisms and their breakdown products d) artificial (plastic, dye dust, etc.) | I. Visible Has a size of over 10 microns and quickly falls out of the air II. MicroscopicSkye Has a size of 10 to 0.25 microns and slowly falls out of the air |
II. Aerosol condensation Occurs during the evaporation and subsequent condensation of metal and non-metal vapors in the air (electric welding, evaporation of metals during electric smelting and other technological processes) | II. Inorganic: a) mineral (silicon, silicate, etc.) b) metal (dust of iron, zinc, lead, etc.) III. Mixed: a) mineral-metallic (for example, a mixture of iron and silicon dust) b) organic and inorganic (for example, dust from cereals and soil) | III. Ultramicroscopic Has a size of less than 0.25 microns, floats in the air for a long time, obeying the laws of Brownian motion |
Based on the method of formation, dusts (aerosols) are distinguished between disintegration and condensation. For practical purposes, industrial dust is classified according to the method of formation, origin, particle size - dispersity (Table 1).
2. EFFECT OF DUST ON THE HUMAN BODY
The harmful effects of industrial dust on workers' health depend on many factors.
Different types of dust due to different physical and chemical properties pose various dangers to workers and in all cases have an adverse effect on the body.
Exposure to non-toxic dust on the respiratory system causes a specific disease called pneumoconiosis.
Pneumoconiosis is a collective name that includes dust diseases of the lungs from exposure to all types of dust (silicosis, silicatosis, anthracosis).
The most common and severe form of pneumoconiosis is considered to be silicosis from the release of dust containing silica. Silicates occur in persons working under conditions of exposure to silicate dust, in which silicon dioxide is in a bound state with other compounds, and anthracods - when exhaling coal dust.
Industrial dust can lead to the development of occupational bronchitis, pneumonia, asthmatic rhinitis and bronchial asthma. Under the influence of dust, conjunctivitis and skin lesions develop - roughness, peeling, thickening, hardening, acne, asbestos warts, eczema, dermatitis, etc. Systematic work under conditions of exposure to dust predetermines an increased incidence of workers with temporary disability, which is associated with a decrease in the protective immunobiological functions of the body . The effects of dust can aggravate severe physical work, cooling, certain gases (SO3), which, when combined, lead to a more rapid onset and increased severity of pneumoconiosis. Aerosols of metals (vanadium, molybdenum, manganese, cadmium, etc.), dust of toxic chemicals, if hygienic working conditions are not observed in workers, can cause occupational diseases.
The electrical charge of dust particles affects the stability of the aerosol and its biological activity. Particles carrying electric charge, linger in the respiratory tract 2-8 times longer. The electrical charge of dust particles affects the activity of phagocytosis (Note. Phagocytosis - one of defensive reactions organism, which consists in the active capture and absorption of living cells and non-living particles by unicellular organisms or special cells of multicellular organisms - phagocytes.).
Controlling the presence and content of dust in the air of the work area is the most important task. When analyzing production process the sources and causes of dust formation must be established, a hygienic assessment must be given taking into account quality composition and its quantity in a certain volume of air. Based on this, the value of the dust factor is assessed, if necessary, information about the health status of workers is used, and these data make it possible to justify health-improving measures.
In addition to its hygienic significance, dust emission also has other negative aspects: it causes economic damage, accelerating equipment wear and leading to the loss of valuable materials, deteriorates the general sanitary condition of the production environment, in particular, reduces illumination due to contamination of windows and lighting fixtures. Some types of dust - coal, sugar, etc. can contribute to fires and explosions.
3. METHOD FOR DETERMINING DUST CONTAINMENTAIR WORKING AREA
3.1. General provisions
To carry out activities to create healthy and safe conditions labor and their choice optimal option At every workplace where dust is generated, its concentration should be periodically monitored. In accordance with GOST 12.1.005-88 “General sanitary and hygienic requirements for the air of the working area”, the frequency of control (except for substances with a highly targeted mechanism of action) is established depending on the hazard class of the harmful substance: for class I - at least 1 time in 10 days, II class - at least 1 time per month, III and IV classes - at least 1 time per quarter. If harmful substances with a highly targeted mechanism of action may enter the air of the working area, continuous monitoring must be provided with an alarm when the maximum permissible concentration is exceeded. If the content of hazardous substances of hazard classes III and IV is established in accordance with the MPC level, it is allowed to carry out monitoring at least once a year.
When determining the dust content in the working area, air samples are taken at a height of approximately 1.5 m (which corresponds to the breathing zone) in close proximity to the place of work. To assess the spread of dust throughout the room, air samples are also taken at so-called neutral points, i.e. at a certain distance (1-3-5 m or more) from the places of dust formation, as well as in passages.
Sometimes air dust content needs to be determined to assess the effectiveness of existing or reconstructed dust removal devices. In these cases, air samples are taken before and after installation in the on and off state. During the period of air sampling, the sampling conditions must be recorded: temperature and barometric air pressure at the workplace, the type of operation being performed, factors that can affect the dust content of the air (open or closed transoms, ventilation on or off, etc.), time and duration of sampling , air drawing speed.
To determine the concentration of dust in the air and its composition, use various methods, which can be divided into two groups:
straight, based on the preliminary sedimentation of dust particles (filtration, sedimentation, etc.) with their subsequent weighing;
indirect(mechanical, vibration-frequency, electrical, radiation, etc.). They provide determination of the mass concentration of dust based on measurements of either the pressure drop across the filter material when dusty air is pumped through it, or the frequency (amplitude) of vibration, or the displacement current resulting from the friction of dust particles against the walls of the primary transducer housing, or the intensity of penetrating radiation through a dust filter, etc.
The resulting single or average value of dust concentration is compared with the maximum permissible concentration (Table 2).
table 2
Maximum permissible concentrations (MPC)
dust in the air of the work area
(GOST 12.1.005-88)
MPC value, Mg/m3 | Predominant state of aggregation | Hazard Class | Features of the effect on the body |
|
1. Dust generated duringbot with: | ||||
limestone, clay, silicon carbide (carborundum), cement, cast iron | ||||
2. Dust of plant and animal origin: | ||||
a) grain | ||||
b) flour, wood, etc. (with an admixture of silicon dioxide less than 2%) |
Continuation of table 2
c) bast, cotton, linen, wool, down, etc. (with an admixture of silicon dioxide less than 2% | ||||
d) with an admixture of silicon dioxide from 2-10% | ||||
3. Carbon dust: | ||||
a) cokes: coal, pitch, oil, shale | ||||
b) anthracite containing up to 5% silicon dioxide in dust | ||||
c) other fossil coals containing free silicon dioxide up to 5% | ||||
4. Glass and mineral fiber dust | ||||
5. Tobacco and tea dust | ||||
6. Nitroammophoska | ||||
7. Potassium nitrate | ||||
8. Potassium sulfate |
Note: a - aerosol;
A - substances that can cause allergic diseases in industrial conditions;
F - aerosols of predominantly fibrogenic action.
3.2. Determination of dust content by mass method
The most common mass method for determining dust concentration is based on pumping a given volume of contaminated air through a filter, determining the excess dust on the filter and then calculating the dust concentration in the air. The complete absorption of harmful substances that pollute the air of the working area must comply with the requirements of GOST 12.1.005-88 and be established experimentally.
As a filter material, aerosol filters AFA with disks made of FP fabric (Petryanov filter) and FPP (Petryanov perchlorovinyl filter) with a high degree of filtration (close to 100%) due to their electrostatic properties are most often used. Most often, filters are used in the form of disks with an area of 10 and 18 cm, which are covered with protective substrates and placed in a polyethylene bag (AFA-V-10, AFA-V-18).
To draw dusty air through the filter, an M-822 aspirator is used (Fig. 1), powered by alternating current voltage 220 V.
Rice. 1. M-822M aspirator for air sampling:
1 - aspirator body; 2 - rotameters; 3 - handle for regulating the flow of sucked air; 4 - suction fittings of the rotameter; 5 - connecting hose; 6 - allonge (cartridge); 7 - unloading valve; 8 - toggle switch; 9 - light bulb
The aspirator housing 1 contains: an electric motor with a blower and four rotameters 2, used for sampling air for dust content. The volume of drawn air per unit of time is adjusted using the valve handle 3. The suction fitting 4 of the rotameter is connected using a rubber hose 5 to an allonge (cartridge) 6, which is a hollow cone with a socket and a nut for attaching a filter to it. Unloading valve 7 serves to prevent overloading of the electric motor when taking air samples at low speeds and to facilitate the start-up of the apparatus. The device is turned on by toggle switch 8. At the same time, the light on the 9 rotameter scales lights up and the floats in them rise with the air flow, indicating its flow.
3.3. Practical task
Based on studying the methodology for determining dust content by the mass method, determine the dust concentration using a laboratory installation (Fig. 2).
Rice. 2. Installation diagram for determining air dust content:
1 - dust suction device (pump); 2 - rotameter; 3 - dust chamber; 4 - filter; 5 - allonge (cartridge); 6 - connecting hose; 7 - handle for regulating the flow of sucked air
The sequence of taking air samples for dust content:
Weigh the clean filter;
Set the selected air flow rate on the rotameter;
Install the filter into the cartridge;
Connect the cartridge to the dust chamber;
Turn on the dust suction device and note the time;
After the set time has elapsed, turn off the device;
Record the results in the report protocol and draw conclusions;
Lead workplace in order.
Dust collection to the filter
Insert filter 4 in the protective ring (Fig. 2) into the cartridge and secure it with a clamping nut. Similar operations are carried out for the filter in the cassette. Connect the cartridge with a rubber tube to the dust chamber 3. At the sampling site, attach the allonge 5 (cartridge) to a tripod (or in another way depending on local conditions) and connect rubber tubes 6 in series with the rotameter 2 and the dust suction device 1.
Turn on the aspiration device and set the selected air flow using the rotameter using valve handle 7.
The beginning and end of the selection are marked with a clock or stopwatch.
During the entire sampling period, it is necessary to monitor the speed of air movement through the equipment using a rotameter.
The duration of sampling depends on the degree of dust in the air, the speed of sampling and the required amount of dust on the filter. The air sampling time for toxic dust is 15 minutes, for substances of predominantly fibrogenic action - 30 minutes. During this time, one or several samples are taken at equal intervals and the average value is calculated. The duration of dust collection can also be determined by calculation using the formula:
Humidity" href="/text/category/vlazhnostmz/" rel="bookmark">humidity from 30 to 80% is 1 mg.
After sampling is completed, the cartridge with the filter is disconnected from the aspiration device with a clamp and the filter with the sample taken is removed from the cartridge. The filter is folded in half with the dust inside and placed in the environment in which it was located before taking the sample.
When taking samples for each filter, a protocol is kept, the date, place and conditions of air sampling, filter number, speed and duration of sampling are recorded.
Calculation of dust concentration
The actual dust concentration is calculated using the formula:
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where V is the speed of air suction according to the rotameter, l/min;
R - Atmosphere pressure air at the time of sampling, kPa;
t - air temperature at the time of sampling, oC.
Enter the results obtained and the value of the MPC Sdop into the report report and draw conclusions about the dust content of the air at the sampling site.
Report protocol
Table 1
Dust sampling conditions
table 2
Measurement results
Questionsfor self-control:
1. Dust classification
2. What is the effect of dust on various organisms person?
3. Methods for determining air dust levels
4. What is the operating principle of the aspirator?
5. What is the method for determining air dust content using the mass method?
6. How to prepare the aspirator for use?
7. How to prepare filters for sampling?
8. Types of application of filters and their differences?
10. Requirements for sampling conditions
11. How to determine the time of sampling?
12. What is the purpose of assessing the dust content of the air in a work area?
LITERATURE FOR WORK
1. Kasparov of labor and industrial sanitation. - M.; "Medicine". 1977.-С-106-128.
2. GOST 12.1.016-79 Air in the working area. Requirements for methods for measuring concentrations of harmful substances.
3. GOST 12.1.005-88. SSBT. General sanitary and hygienic requirements for the air in the working area.
4. R 21.2.755-99 2.2 Occupational hygiene. Hygiene criteria assessment and classification of working conditions according to indicators of harmfulness and danger of factors in the working environment, severity and intensity of the labor process. Management. Ministry of Health of Russia. Moscow 1999
Air dust research
Production premises
Guidelines for performing laboratory work
in the discipline "Life Safety"
for students of all specialties
Novokuznetsk
UDC 658.382.3(07)
Reviewer:
Doctor of Technical Sciences, Professor
Department of Technology and Automation of Forging and Stamping Production of SibGIU
Peretyatko V.N.
P24 Study of dust content in the air of industrial premises: Method. decree/comp.: I.G. Shilingovsky: SibGIU, Novokuznetsk 2007. – 19 p.
Methods for determining dust content in the air are considered, diagrams of the design of aspirators, a sampler, radiation devices and rules for using them are given.
Designed for students of all specialties.
Laboratory work
Study of dust levels in industrial premises
Goal of the work: to familiarize students with the basic methods and instruments for measuring dust concentration in a production area, as well as teach them to measure and evaluate the value of dust concentration.
In the process of performing laboratory work, students must:
– become familiar with basic information about industrial dust, its sources and methods for measuring concentrations;
– study the device for measuring dust concentration;
- to conduct an experiment .
Basic information about industrial dust
Industrial dust These are solid particles suspended in the air of the working area ranging in size from several tens to fractions of a micron. Dust is also commonly called an aerosol, meaning that air is a dispersed medium, and solid particles are a dispersed phase. Industrial dust is classified according to the method of formation, origin and particle size.
In accordance with the method of formation, dusts (aerosols) are distinguished between disintegration and condensation. The former are a consequence of production operations associated with the destruction or grinding of solid materials and the transportation of bulk substances. The second way of dust formation is the appearance of solid particles in the air due to cooling or condensation of metal or non-metal vapors released during high-temperature processes.
Based on their origin, dust can be divided into organic, inorganic and mixed. The nature and severity of the harmful effects depend, first of all, on the chemical composition of the dust, which is mainly determined by its origin. Inhalation of dust can cause damage to the respiratory system - bronchitis, pneumoconiosis or the development of general reactions (intoxication, allergies). Some dusts have carcinogenic properties. The effect of dust is manifested in diseases of the upper respiratory tract, mucous membranes of the eyes, skin. Inhalation of dust can contribute to the occurrence of pneumonia, tuberculosis, and lung cancer. Pneumoconiosis is one of the most common occupational diseases. Exclusively high value has a classification of dust according to the size of dust particles (dispersity): visible dust (size over 10 microns) quickly settles from the air; when inhaled, it lingers in the upper respiratory tract and is removed when coughing, sneezing, or with sputum; microscopic dust (0.25 - 10 microns) is more stable in the air, when inhaled it enters the alveoli of the lungs and affects the lung tissue; ultramicroscopic dust (less than 0.25 microns), up to 60–70% of it is retained in the lungs, but its role in the development of dust injuries is not decisive, since its total mass is small.
The harmful effects of dust are also determined by its other properties: solubility, particle shape, their hardness, structure, adsorption properties, and electrical charge. For example, the electrical charge of dust affects the stability of the aerosol; particles carrying an electrical charge are retained in the respiratory tract 2–3 times more.
The main way to combat dust is to prevent its formation and release into the air, where the most effective are technological and organizational nature: introduction of continuous technology, mechanization of work; equipment sealing, pneumatic transportation, remote control; replacement of dust-producing materials with wet, paste-like materials, granulation; aspiration, etc.
Great importance has application systems artificial ventilation, complementing the main technological measures to combat dust. To combat secondary dust formation, i.e. by the entry of already settled dust into the air, wet cleaning methods, air ionization, etc. are used.
In cases where it is not possible to reduce the dust content of the air in the work area by more radical measures of a technological and other nature, personal protective equipment is used various types: respirators, special helmets and spacesuits with supply in them clean air.
Automatic devices for determining dust concentration include the commercially produced IZV-1, IZV-3 (air dust meter), PRIZ-1 (portable radio-isotope dust meter), IKP-1 (dust concentration meter), etc.
The need for strict compliance with maximum permissible concentrations requires systematic monitoring of the actual dust content in the air of the working area of the production premises.
Maximum permissible dust concentrations
Table 1 - Maximum permissible dust concentrations
Maximum permissible concentration (MAC) of a harmful substance is a concentration that, during daily work for 8 hours or another duration, but not more than 40 hours per week, during the entire work experience, cannot cause diseases or health problems. To determine the dust content of air means to measure the dust content per unit volume of air, that is, to measure the dust concentration. To determine the dust content in the air, sampling should be carried out in the breathing zone and working area under typical production conditions, taking into account all influencing factors.
Dust concentration measuring device
The device used is a radioisotope portable dust concentration meter “Priz-01”, designed for express analysis of dust concentration directly at workplaces and industrial sites.
The concentrator operates in a semi-automatic mode: after cocking the sensor mechanism of the dust sampling operation and measuring the sample, it returns to its original position automatically.
The measured dust concentration value is displayed in a digital field on the device display.
Method for measuring dust concentration
Methods for measuring dust concentration are divided into two groups: methods based on preliminary deposition (gravity, radioisotope, optical, piezoelectric, etc.) and methods without preliminary deposition of dust (optical, electrical, acoustic).
The main advantage of the methods of the first group is the ability to measure the mass concentration of nitrate.
IN laboratory work gravimetric and radioisotope methods for measuring dust concentration are used.
Weight method is based on drawing dust-laden air through a filter that traps dust particles. Knowing the mass of the filter before and after sampling, as well as the amount of air drawn in, it is possible to determine the dust content per unit volume of air. Dust concentration is calculated using the formula:
where Δm is the mass of dust on the filter, mg;
V – volumetric speed of air suction through the filter, l/min.;
t – sampling time, min.
The place for sampling dusty air is a mock-up of an industrial premises with sources of dust (aerosol) of various compositions placed in it.
The filters used are AFA filters made from FPP fabric (based on perchlorovinyl fabric). They are resistant to chemically aggressive environments and have high percentage particle retention.
The stimulator of air movement is an electric aspirator model 882, which has a device for measuring the volumetric velocity of air movement (rheometers). The optimal sampling rate is equal to the rate of human breathing (pulmonary ventilation) - 10 - 15 l/min.
Radioisotope method based on the use of property radioactive radiation absorbed by dust particles. The dusty air is pre-filtered, then the mass of settled dust is determined by the attenuation of radioactive radiation as it passes through the dust sediment.
experimental part
Exercise. Measure the dust concentration in a mock-up production facility and select respiratory protection equipment.
1. Familiarize yourself with the installation device.
2. Turn on the installation and necessary devices.
3. Take three dust samples (the composition is set by the teacher).
4. Turn off the installation and devices.
Methods for determining air dust levels
Air dustiness can be determined by gravimetric (weight), counting (microscopic), photometric and some other methods.
Removing dust from the air can be carried out in various ways: aspiration, based on drawing air through a filter; sedimentation, based on the process of natural settling of dust on glass plates or jars with subsequent calculation of the mass of dust deposited on 1 m of surface; using electrodeposition, the principle of which is that it creates electric field high voltage, in which dust particles are electrified and attracted to the electrodes.
In sanitary and hygienic practice, the main method for determining dust content is the gravimetric method, because with a constant chemical composition, the mass of dust retained in the human body is of primary importance. Determining only the mass of dust does not give a complete picture of its harmfulness to humans and the technological process, since with the same mass the chemical and granulometric composition of the dust may be different, which affects its impact on humans, equipment and technology. Full characteristics dust consists of its mass contained in a unit volume of air, chemical and dispersed composition.
The counting (microscopic) method makes it possible to determine the total number of dust particles per unit volume of air and the ratio of their sizes. To do this, dust contained in a certain volume of air is deposited on glass covered with a transparent adhesive film. Under a microscope, the shape, quantity and size of dust particles are determined.
The qualitative characteristics of dust are determined by the photometric method using a current ultraphotometer, which registers individual dust particles using strong side light.
To separate dust from the air, various filters are used that trap dust particles up to 0.1 microns in size or more, depending on the pore size of the filter. Such filters are produced in many countries. The filter material may vary depending on its purpose: cellulose, synthetic materials, asbestos (to determine combustible dust particles). Combination filters are also used. Special filters are produced, impregnated with immersion oil, which makes them transparent - this also allows additional microscopic examination of dust.
In Ukraine, AFA filters (analytical aerosol filter) are most often used. round shape with filtration planes 3; 10, 20 cm2, which have a support ring, a filter element and a protective paper ring with a protrusion. The filter element consists of a uniform layer of ultra-thin polymer fibers with or without a gauze base (Petryanov filter). Filters allow you to work with them without preliminary drying due to the hydrophobic properties of the polymer.
Methods for normalizing the air composition of the working area
There are many in various ways and measures designed to maintain the cleanliness of the air in industrial premises in accordance with the requirements sanitary standards. They all boil down to specific measures:
1. Preventing the penetration of harmful substances into the air of the working area by sealing equipment, sealing connections, hatches and openings, improving the technological process.
2. Removal of harmful substances entering the air of the working area through ventilation, aspiration or air purification and normalization using air conditioners.
3. Application of human protective equipment.
Sealing and compaction are the main measures for improvement technological processes, in which harmful substances are used or formed. The use of automation makes it possible to remove a person from a polluted room to a room with clean air. Improvement of technological processes makes it possible to replace harmful substances with harmless ones, abandon the use of dust-producing processes, and replace solid fuel for liquid or gaseous, install gas, dust collectors in the technological cycle, etc.
When the technology is imperfect, when it is not possible to avoid the penetration of harmful substances into the air, their intensive removal is used using ventilation systems(gas, steam, aerosols) or aspiration systems(solid aerosols). Installing air conditioners in rooms where there are special requirements for air quality creates normal microclimatic conditions for workers.
Special requirements apply to premises where work is carried out with hazardous substances generating dust. So, the floor, walls, ceiling should be smooth and easy to clean. In workshops where dust is generated, wet or vacuum cleaning is regularly done.
In rooms where it is impossible to create normal conditions, meeting microclimate standards, use personal protective equipment (313).
According to GOST 12.4.011-87 "SSBT Protective equipment for workers. Classification", all 313, depending on the purpose, are divided into the following classes: insulating suits, respiratory protection, special protective clothing, leg protection, hand protection, head protection, face protection, eye protection, hearing protection, fall protection and other precautions, dermatological protective equipment, comprehensive protective equipment.
Effective use of 313. depends on their the right choice and operating conditions. When choosing, it is necessary to take into account specific production conditions, the type and duration of exposure to a harmful factor, as well as individual characteristics person. Only correct application 313 can provide maximum protection for the worker. To do this, employees must be familiar with the range and purpose of 313.
To work with toxic and polluting substances, they use special clothing - overalls, gowns, aprons, etc.; for protection against acids and alkalis - rubber shoes and gloves. To protect the skin, hands, face, and neck, protective creams and pastes are used: antitoxic, waterproof, grease-resistant. Protect your eyes from possible burns and aerosols with sealed glasses, masks, and helmets.
Personal respiratory protection equipment (RPP) includes respirators, industrial gas masks and self-contained breathing apparatus used to protect against harmful substances (aerosols, gases, vapors) in the ambient air.
According to the principle of operation, RPEs are divided into filtering (used when there is at least 18% free oxygen in the air and a limited content of harmful substances) and insulating (when the oxygen content in the air is insufficient for breathing and there is an unlimited amount of harmful substances).
According to their purpose, filtering RPEs are divided into:
anti-dust - for protection against aerosols (respirators ShB-1, "Lepestok", "Kama", "Snezhok", U-2K, RP-K, "Astra-2", F-62Sh, RPA, etc.);
gas masks - for protection against gas and vapor-like harmful substances (respirators RPG-67A, RPG-67V, RPG-67KD, gas masks of brands A, B, KD, G, E, SO, M, BKF, etc.);
gas-dust protective - for protection against vapor-gas-like and aerosol harmful substances simultaneously (Respirators Ru 60M, "Snezhok PG", "Lepestok-G");
isolating devices - there are hose and autonomous ones.
Isolating hose devices are designed to operate in atmospheres containing less than 18% oxygen. They have a long hose through which breathing air is supplied from the clean area. Their disadvantages are that the breathing hose interferes with work and does not allow free movement (hose gas mask PSh-I without forced submission air, hose length 10 m; PSh-2 with a blower - ensures the work of two people at the same time, hose length is 20 m; respirator for artists RMP-62; pneumatic helmets LIZ-4, LIZ-5, myotom-49 - operate from a compressor air line).
Self-contained breathing apparatus operates from a self-contained chemical oxygen source or from cylinders with air or a breathing mixture. They are designed to perform rescue work or evacuation of people from a gas-contaminated area.
Small-sized mine self-propelled gun ShSM-1. Has a chemical source of oxygen. Duration of use is 20-100 minutes, depending on the intensity of oxygen consumption (energy consumption), weight 1.45 kg.
Isolating auxiliary respirator RVL-1. It has a compressed oxygen cylinder and a regenerative chemical cartridge for oxygen regeneration. Works 2:00, weight 9 kg.
Respirator "Ural-7". The principle of operation is the same as in the RVL-I respirator, but it is larger in size. Valid for 5:00, weighs 14 kg. Worn over the shoulders, mass shock-absorbing devices for comfortable wearing.
The P-30 respirator has the same life support system as above. Designed for 4:00 action, weighs 11.8 kg.
The ASV-2 breathing apparatus consists of 2 air cylinders, a mask or mouthpiece, a hose, a reducer, and has a pressure gauge for monitoring air pressure, safety valve etc. Designed to protect the respiratory system in a polluted atmosphere.
Industrial dust is defined as solid particles suspended in the air of the working area ranging in size from several tens to fractions of a micron. Dust is also commonly called an aerosol, meaning that air is a dispersed medium, and solid particles are a dispersed phase. Industrial dust is classified according to the method of formation, origin and particle size. .
In accordance with the method of formation, a distinction is made between aerosols, disintegration and quaidence. First; are a consequence
vii production operations associated with the destruction or grinding of solid materials and transportation of bulk substances. The second way of dust formation is the appearance of solid particles in the air due to cooling or condensation of metal or non-metal vapors released during high-temperature processes.
Based on their origin, dust can be divided into organic, inorganic and mixed. The nature and severity of the harmful effects depend, first of all, on the chemical composition of the dust, which is mainly determined by its origin. Inhalation of dust can cause damage to the organs of the duck - bronchitis, pneumoconiosis or the development of general reactions (intoxication, allergies). Some dusts have carcinogenic properties. The effect of Dust manifests itself in diseases of the upper respiratory tract, mucous membranes of the eyes, and skin. Inhalation of dust can contribute to the occurrence of pneumonia, tuberculosis, and lung cancer. Pneumoconiosis is one of the most common occupational diseases. The classification of dust according to the size of dust particles (dispersity) is of exceptionally high importance: visible dust (size over 10 microns) quickly settles from the air; when inhaled, it lingers in the upper respiratory tract and is removed when coughing, sneezing, with sputum; microscopic dust (0.25 -10 microns) is more stable in the air, when inhaled it enters the alveoli of the lungs and affects the lung tissue; ultramicroscopic dust (less than 0.25 microns), up to 60-70% of it is retained in the lungs, but its role in the development of dust injuries is not decisive, since its total mass is small.
The harmful effects of dust are also determined by its other properties: solubility, particle shape, their hardness, structure, adsorption properties, electrical charge. For example, the electrical charge of dust affects the stability of the aerosol; particles carrying an electrical charge are retained in the respiratory tract 2-3 times more. "
The main way to combat dust is to prevent it; formation and release into the air, where the most effective are technological and organizational measures: the introduction of continuous technology, mechanization of work;
equipment sealing, pneumatic transportation, remote control; replacement of dust-producing materials with wet, paste-like materials, granulation; aspiration, etc.
The use of artificial ventilation systems is of great importance, complementing the main technological measures to combat dust. To combat secondary dust formation, i.e. by the entry of already settled dust into the air, wet cleaning methods, air ionization, etc. are used.
In cases where it is not possible to reduce the dust content of the air in the work area by more radical measures of a technological and other nature, personal protective equipment of various types is used: respirators, special helmets and spacesuits with clean air supplied to them. ,
The need for strict compliance with maximum permissible concentrations requires systematic monitoring of the actual dust content in the air of the working area of the production premises.
Automatic devices for determining dust concentration include the commercially produced IZV-1, IZV-3 (air dust meter), PRIZ-1 (portable radioisotope dust meter), IKP-1 (dust concentration meter), etc.
Ventilation of industrial premises
Ventilation is a complex of interrelated processes designed to create organized air exchange, i.e. removal of contaminated or overheated (cooled) air from the production premises and supply instead; it contains clean and cooled (heated) air, which allows you to create favorable air conditions in the working area.
Industrial ventilation systems are divided into mechanical (see Fig. 6.5) and natural. It is possible to combine these two types of ventilation (mixed ventilation) in various options. " " " V
In the first case, air exchange is carried out with the help of special movement stimulants - fans, in the second -
due to the difference specific gravity air outside and inside the production premises, as well as due to wind pressure (pressure from wind loads). Based on the location of action, a distinction is made between a general ventilation system, which carries out air exchange on the scale of the entire production premises, and a local one, in which air exchange is organized on the scale of only the working area. A specific characteristic of general exchange ventilation systems is the air exchange rate:
k=u/u pom,
where V is the volume of ventilation air, m 3 /hour; V n 0 M is the volume of the room, m 3.
General exchange systems can be supply (only supply is organized, and exhaust occurs naturally due to an increase in pressure in the room), exhaust (only exhaust is organized, and supply occurs by sucking air from outside due to its rarefaction in the room) and supply and exhaust (organized as inflow and exhaust). Supply and exhaust natural ventilation is called aeration. Local systems can be exhaust or supply.
Basic requirements for ventilation systems:
correspondence of the amount of supply air to the amount of air removed. It should be borne in mind that if two areas are located nearby, one of which contains harmful emissions, a slight vacuum is created in this area, for which more air is removed than supplied, and in an area where there are no harmful emissions, vice versa . Increasing the pressure in the “clean” area in relation to the adjacent one prevents the penetration of harmful vapors, gases and dust into it;
inlet and exhaust systems ventilation must be properly placed. Air is removed from the area with the most pollution, and air is supplied to areas with the least pollution. The height of the air intake and air distribution devices is determined by the ratio of the air density in the room and the density of the substance polluting it. In case of heavy pollution, air is removed from the lower part of the room, in case of light pollution - from the upper part.
Ventilation systems must ensure the required air purity and microclimate in the work area, be electrical, fire and explosion-proof, simple in design, reliable in operation and efficient, and also should not be a source of noise and vibration. .
Rice. 6.5. Mechanical ventilation: a - supply; b - exhaust; c - supply and exhaust with recirculation
Installations of supply systems! # ventilation (Fig. 6.5a) consist of an air intake device (1), air ducts (2), filters
for cleaning the intake air from impurities, heater
Centrifugal fan (5) and supply devices (6) (holes in air ducts, supply nozzles, etc.).
Installations of the exhaust ventilation system (Fig. 6.56) consist of exhaust devices (7) (holes in the air ducts, exhaust nozzles), a fan (5X air ducts (2), a device for cleaning the air from dust and gases (8) and devices for air emission ( 9).
Supply and exhaust ventilation system installations (Fig. 6.5c) are closed air exchange systems. The air sucked from the room (10) by exhaust ventilation is partially or completely re-supplied to this room through the supply system connected to the exhaust system by an air duct (11). When the qualitative composition of the air in a closed system changes, it is supplied or exhausted using
valves (12).
In the production workshops of industrial enterprises, the most common are general exchange ventilation systems designed to remove
removal of harmful vapors, gases, dust, excess humidity or the concentrations of these harmful substances are brought to pre-; strictly acceptable standards. . ,
Several harmful substances can enter production premises at the same time. In this case, air exchange; calculated for each of them. If the released substances act on the human body unidirectionally, then the calculated volumes of air are summed up. .
" G The calculated volume of air should be supplied heated to the working area of the room, and contaminated air should be removed from places where harmful substances are emitted from upper zone premises.
The volume of air (m 3 / h) required to remove carbon dioxide from the room is determined by the formula:
L=G/(x 2 -x,)y
Where G- the amount of carbon dioxide released in the room, g/h or l/h; Xi- concentration of carbon dioxide in the outside air; X 2 - concentration of carbon dioxide in the air of the working area, g/m3 or l/m3. The volume of air (m^h) required to remove harmful vapors, gases and dust from the room is determined by the formula; :
■ ^1=с/(с^-с^; : ■- 1 " ■" ■ ;
Where G- the amount of gases, vapors and dust released in the room, m 3 / h; With 2 - maximum permissible concentration of gas, vapor or dust in the air of the working area, mg/m 3 ; c t - concentration of these harmful substances in the outside (supply) air, mg/m3. ;
< Объем воздуха (м 3 /ч), который требуется для удаления из? но- Мещения вдагодабытков^ определяют по формуле: : ;
* 1 = S/r.(
Where G- the amount of moisture evaporating in the room, g/h; p - air density in the room, kg/m3; d 2 - moisture content of air removed from the room, g/kg of dry air; d t - moisture content of supply air g/kg dry air.
The volume of air (m 3 / h) required to remove excess heat from the room is determined by the formula:
L ~ Oizb IСp(t ebt m~t n pum) > "
Where Qms - amount of excess heat entering the room, W; WITH - specific heat capacity of air, J/(kgK); R- air density in the room, kg/m3; team - air temperature in the exhaust system, °C;tnpum- supply air temperature, *C. ■■■■ -■ . - ■ ■ ■
We will illustrate the practical application of the calculations given in accordance with SNiP 2-04.05-86 using specific examples.
Example!. N - 50 people gathered in a room for short-term stay of people. The volume of the room is V = 1000 m. Determine how long after the start of the meeting it is necessary to turn on the supply and exhaust ventilation if the amount of CO 2 emitted by one person q = 23 l/h in the outside air X = 0.6 l/m3.
, Y(x 2 -X,)
■■■■- ■■G’ ■ ^
. . .% ....
Where G the amount of CO 2 released by people
G=JVd = 50-23 = 1150l/h,1000 ( 2- 0, 6)
“ T=-- --- = 1.21h=73l<ин
1150 ... . ...... ... . ;.
Example 2. Determine the required air exchange based on*
heating units in the assembly shop for the warm period of the year. The total power of equipment in the workshop N 0 b 0р = 120 kW. Number of employees - 40 people. The volume of the room is 2000 m3. Supply air temperature npHT = +22.3 °C, humidity j = 84%. The heat from solar radiation is 9 kW. (Q cp). Specific heat capacity of dry air "C = 0.237 W/kgK; density of supply air p = 1.13 kg/m 3 ; exhaust air temperature t BKT = 25.3" C. Take the amount of heat generated by one person as 0.11<Г кВТ; от оборудования 0,2 на 1 кВт мощности
^ QuafiJ^P^out- ^ad)
, ,. R„ «<&л^ +&**":+fi^v^(u.-w
Amount of heat from people, kW,
^^“=0.116x40 = 4.64
Amount of heat from equipment, kW,
Qu36 ° 6 ° P= 120x 0.2= 24
Required air exchange, m 3 / h,
£= (4.63+ 24+9)-100 _ 44280
0,237-1,13(25,3-22,3)
Air conditioning
With the help of air conditioning in enclosed spaces and structures, it is possible to maintain the required temperature, humidity, gas and ionic composition, the presence of odors in the air, as well as the speed of air movement. Typically, in public and industrial buildings it is necessary to maintain only part of the specified air parameters. The air conditioning system includes a set of technical means that carry out the required air processing (filtration, heating, cooling, drying and humidification), its transportation and distribution in the serviced premises, devices for muffling the noise caused by the operation of the equipment, sources of heat and cold supply , means of automatic regulation, control and management, as well as auxiliary equipment. The device in which the required heat and humidity treatment of air and its purification is carried out is called an air conditioning unit, or air conditioning.
Air conditioning provides the necessary microclimate in the room for the normal flow of the technological process or the creation of comfortable conditions. ■
Heating
Heating involves maintaining in all industrial buildings and structures (including crane operator cabins, control panels and other isolated rooms, permanent workplaces and work areas during main and repair and auxiliary work) a temperature that meets established standards.
The heating system must compensate for heat loss through building fences, as well as provide heating for the cold air penetrating into the room during the import and export of raw materials, materials and workpieces, as well as these materials themselves.
Heating is arranged in cases where heat loss exceeds heat release in the room. Depending on the coolant, heating systems are divided into water, steam, air and combined.
Water heating systems are the most acceptable from a sanitary and hygienic point of view and are divided into systems with water heating up to 100°C and above iOO°C (superheated water).
Water is supplied to the heating system either from the enterprise’s own boiler house, or from a district or city boiler house or thermal power plant.
A steam heating system is suitable for enterprises where steam is used for the technological process. Steam heating devices have a high temperature, which causes food to burn. Radiators, finned pipes and registers made of smooth pipes are used as heating devices.
In industrial premises with significant heat generation, devices with good surfaces are installed that allow them to be easily cleaned. Finned radiators are not used in such rooms, since the settled dust due to heating will burn* giving off a burning smell. Dust at high temperatures can be dangerous due to the possibility of ignition. The temperature of the coolant when heating the local area and heating devices should not exceed: for hot water - 150 ° C, water steam - 130 0 C. *: » ; . :
An air heating system is characterized by the fact that the air supplied to the room is preheated in heaters (water, steam or electric heaters).
Depending on the location and design, air heating systems can be central or local. In central systems, which are often combined with supply ventilation systems, heated air is supplied through a duct system.
A local air heating system is a device in which an air heater and a fan are combined in one unit installed in a heated room.
The coolant can be obtained from a central water or steam heating system. It is possible to use electric autonomous heating. .
In administrative premises, panel heating is often used, which works as a result of heat transfer from building structures in which pipes with coolant circulating in them are laid.
Dear readers, in this article we will talk about how the category of a room with dust is determined.
Despite the fact that the mathematical apparatus of SP 12.13130.2009, which is intended to determine the fire hazard category of a room with dust, is quite simple, determining a number of parameters causes certain difficulties.
Let's look at everything in order. To begin with, it should be noted that rooms with dust can be classified as category B for explosion and fire hazard or explosion and fire hazard.
Before proceeding to the calculation of whether a room belongs to one of categories B for fire hazard, it is necessary to justify by calculation whether the room where the formation of an air suspension is possible belongs to category B for fire and explosion hazard.
The basic calculation formulas are contained in section A.3 of Appendix A of SP 12.13130.2009.
In accordance with formula A.17 of the set of rules, the estimated mass of dust suspended in the room as a result of an emergency situation should be taken as the minimum of two values:
— the sum of the masses of swirling dust and dust released from the apparatus as a result of the accident;
- a mass of dust contained in a dust-air cloud, capable of burning when an ignition source appears.
It should be noted here that not all dust is capable of burning, i.e. the coefficient of participation of combustible dust in the explosion is ≤0.5, which is confirmed by formula A.16 of the set of rules.
The coefficient of participation of suspended dust in combustion depends on the fractional composition of the dust, namely a parameter called the critical particle size.
For most organic dusts (wood dust, plastics, flour, etc.), the critical size value is about 200-250 microns.
Dust consisting of larger particles will not participate in combustion, except when it is burned in special hearths (furnaces). When the category of a room with dust is determined, as a rule, we are dealing with either completely fine dust, the particle size of which is less than critical (for example, powdered sugar), or with dust, which includes particles of various sizes, both larger and smaller than critical. Such dust includes wood dust, grain dust, etc.
The fractional composition of dust is determined experimentally by sifting through a system of special sieves called “fractionator”. It is hardly possible to find such data, although for a number of industrial dusts (powders), data on the fractional composition can be requested from the manufacturer.
In the absence of data, it is assumed that all dust particles have a size less than critical, i.e. capable of spreading fire. The mass of dust that can come out of the device as a result of an emergency is determined by the characteristics of the technological process.
The mass of swirling dust is that part of the deposited dust that can become suspended as a result of an emergency.
In the absence of experimental data, it is assumed that 90% of the mass of deposited (accumulated) dust can become an air suspension. Dust, which is released in small quantities in the production area during normal operation, settles on the enclosing structures (walls, floor, ceiling), on the surface of the equipment (cases of technological devices, transport lines, etc.), on the floor under the equipment.
At the designed production facility, the frequency of dust collections is determined: routine and general. According to SP 12, it is accepted that all the dust that settles in hard-to-reach places for cleaning accumulates there during the period between general dust collections. Dust that settles in places accessible for cleaning accumulates there during the period between current dust collections. Estimation of the proportion of dust settling on a particular surface (accessible or difficult to access) is possible only experimentally or by modeling methods.
Assessing the dust collection efficiency of designed production facilities, as a rule, is also impossible, therefore it is conventionally accepted that all dust released from the equipment into the room settles inside the room.
The amount of dust settling on different surface areas located in the room also varies. Dust, which is released normally, floats in the air and, due to gravity, gradually settles on various surfaces.
However, it is expected that the greatest amount of dust will settle at lower levels of the room, provided that the source of the dust (equipment) is also located at the lower level. It is obvious that horizontal surfaces can accumulate dust in almost unlimited quantities; a limited amount of dust settles on vertical surfaces, depending on the type of surface.
For, the amount of dust that settles on the walls is as follows: painted metal partitions - 7-10 g/m2, brick walls - 40 g/m2, concrete walls - 30 g/m2. Most likely, the data presented can be used for other industries.
Now let's turn to the formula for calculating the amount of dust depending on the volume of the dust-air cloud. It should be noted that there are no analytical expressions by which the volume of a dust-air cloud can be calculated in the domestic literature.
It has not yet been possible to find such data in foreign fire-technical literature, probably because such an approach is not used in the USA and Europe (meaning the calculation of categories). Therefore, in practice, the volume of the dust cloud has to be estimated in some way.
For example, we can conditionally take as the characteristic shape of a cloud a cone with a height from the floor to the dust source and a base with a radius several times greater than this height. Although, I’m not sure how true this assumption is, since there are no experimental data available.
In addition to the critical size, the stoichiometric dust concentration is also a determining parameter.
Stoichiometric dust concentration is the concentration of dust at which its complete combustion occurs, taking into account the amount of oxygen contained in a unit volume of air.
The stoichiometric dust concentration can be determined by calculation only for substances and materials for which the chemical composition is known. These include most polymer materials (polyethylene, polypropylene, polystyrene, etc.), various medications, metal and alloy powders.
For other materials, for example, for plant (wood and grain dust, tea, etc.) and food materials (flour, milk powder, cocoa, etc.), the stoichiometric concentration must be determined either experimentally, or by looking for the chemical composition of the corresponding material from which it is composed. dust.
Determining the stoichiometric concentration comes down to solving the following sequential problems:
1. The chemical composition of the dust is determined.
2. The chemical equation for the reaction of complete combustion of dust is written.
3. The mass of oxygen required for complete combustion of 1 kg of dust is determined.
4. The mass of oxygen contained in 1 m 3 of air is determined, taking into account the design temperature.
5. The mass of dust that can completely burn in the mass of oxygen contained in 1 m 3 of air is determined. The resulting value is the stoichiometric concentration of dust in the dust-air cloud.
Determining the category of a room with dust does not take into account such an indicator of fire danger as the lower concentration limit of flame propagation (LCFL). As a rule, the concentration of dust in a dust-air cloud during emergency situations exceeds the LEL.
And finally, a couple of very interesting videos about dust explosions in industries. Even without knowledge of English, everything is shown clearly and interestingly. I recommend watching!
I look forward to seeing you again on fire safety!