The microclimate of the working environment. Microclimatic conditions of the production environment
Sources of adverse factors and their impact
per person
In the human body, heat exchange processes constantly occur, the intensity of which depends mainly on the parameters of the microclimate. working area(temperature, humidity, air velocity and thermal radiation), as well as the severity and intensity of labor. The assessment of the microclimate is carried out on the basis of measurements of its parameters at all places of stay of the employee during the shift and their comparison with the standards. The basis for assessing working conditions for this factor and protecting workers from the consequences of exceeding the permissible levels of microclimate parameters, as well as assigning working conditions to one or another class of hazard in terms of the level of impact of the factor on the employee, are the documents “Guidelines for the hygienic assessment of factors of the working environment and the labor process. Criteria and classification of working conditions "R 2.2.2006-05 and" Hygienic requirements for the microclimate industrial premises» SanPiN 2.2.4.548-96.
If the measured parameters meet the requirements of these documents, then the working conditions in terms of microclimate indicators are characterized as optimal (1st class) or acceptable (2nd class). In case of non-compliance of the measured parameters with the requirements of the specified documents, the working conditions are classified as harmful. At the same time, the degree of harmfulness is established, which characterizes the level of overheating or cooling of the human body.
Temperature. The heating and cooling microclimate is considered, as well as the microclimate of non-standard situations with transitions from a heating to a cooling environment and vice versa (work in an open area and indoors for various durations and physical activity).
Heating microclimate - a combination of microclimate parameters (air temperature, humidity, air velocity, relative humidity, thermal radiation), in which there is a violation of the normal heat exchange of a person with the environment. It is expressed in the accumulation of heat in the body above the upper limit of the optimal value and (or) an increase in the proportion of heat loss due to the release and evaporation of sweat (more than 30%). At the same time, discomfort of heat sensations appears (slightly warm, warm, hot). The heating microclimate is considered as a negative factor. High air temperature contributes to rapid fatigue of the worker, can lead to overheating of the body, heat stroke or occupational disease. In those who work for a long time at elevated temperatures, there is a violation of water-salt metabolism associated with a deficiency of potassium ions in the body. Overheating of the body possible reason accident at work (heat stroke).
At railway transport facilities, heating microclimate areas include greenhouses, where defrosting of bulk cargo frozen during transportation is carried out, locomotive cabs in summer time, thermal, galvanic, welding and hot shops at rolling stock repair enterprises.
Cooling microclimate - a combination of microclimate parameters, in which a violation of heat transfer leads to the formation of a heat deficit in the body as a result of a decrease in the temperature of the deep and surface layers of body tissues.
One of the early signs of cooling, characterizing the vascular response to cold irritation, is a change in the temperature of the skin of open areas of the body. Cooling causes a weakening and even complete disappearance of reflexes, a decrease in skin sensitivity. The consequence of this is a decrease in working capacity, and with a systematic impact - the emergence of occupational diseases. Low air temperatures can cause colds or frostbite. The highest frequency of manifestation of temporary disability in railway transport is associated with the cooling microclimate of the working environment. The cooling microclimate causes occupational diseases such as chronic pneumonia, chronic colds, etc. The general cooling of the body is a possible cause of an accident at work (frostbite).
At an air temperature of minus 40 ° C and below, respiratory and face protection is necessary.
At railway transport facilities, areas with a cooling microclimate include areas of work on the tracks during the cold periods of the year, work in refrigerated warehouses and refrigerated cars.
For example, for the climatic region (zone) III, with the corresponding average air temperature in the winter months (-9.7 ° C), and the average wind speed in the winter months (5.6 m/s), for works of category II a and II b the working conditions of workers in an open area are assessed by class 3.3 in the absence of regulated breaks and class 3.2 if there are any (see Table 9 of the Guidelines).
Climatic region III includes the regions: Astrakhan, Belgorod, Bryansk, Vladimir, Volgograd, Voronezh, Ivanovo, Kaluga, Kursk, Leningrad, Lipetsk, Moscow, Nizhny Novgorod, Novgorod, Oryol, Rostov; republics: Mari El, Mordovia, Kalmykia.
The microclimate in the room, in which the air temperature at the workplace is below the lower limit, admissible norms SanPiN 2.2.4.548-96 is harmful. The hazard class is determined by the average shift values of air temperature and their comparison with those indicated in the "Manual".
Assessment of the microclimate during operation during work shift both in an open area and indoors or in other non-standard situations, with different duration and physical activity, it requires a separate assessment. The class of working conditions is determined in relation to each level of the microclimate and is evaluated by the largest value, provided that the length of stay at this (worst) workplace is greater than or equal to 50% of the work shift.
With sudden changes in ambient temperature, the human body needs a certain time to adapt to new conditions, which leads to an additional load on the mechanisms of thermoregulation.
At railway transport facilities, zones with a dynamic microclimate include areas for loading and unloading operations into refrigerated cars from refrigerated warehouses through open spaces in the summer.
For workers at trackside machine stations, the meteorological conditions at outdoor work sites are determined by seasonal weather conditions and are often associated with sudden changes in temperature. In the cabs of drivers in the summer, the temperature reaches plus 40 ° C with a sharp decrease in relative humidity and low air mobility (0.2-0.5 m / s), despite the fact that in the air at this time the temperature averages plus 20 ° WITH. In winter, the air temperature on the SM-2 track machines at outdoor temperature minus 20 °С is only plus 4 °С, while significant temperature drops are observed at their negative values at the floor level.
The heating or cooling effect increases or decreases depending on the humidity of the air.
Humidity. Humidity has a significant effect on thermoregulation. Depending on the relationship between temperature and humidity, a person feels differently, receives different thermal sensations.
At low temperatures, the presence of water vapor in the air enhances heat transfer from the surface of the skin and contributes to hypothermia of the body, at high temperatures it makes it difficult, which can lead to overheating of the body.
High humidity at railway transport enterprises is typical for rolling stock washing areas, workshops where washing baths are installed or irrigation devices operate. High humidity is also present in tunnels and when working on railway tracks during bad weather.
Air mobility. Air movement, like humidity, affects the thermal sensations of a person. With the entry into the air flow, the heat transfer of the human body increases significantly. Air mobility is positive at high temperatures and negative at low temperatures.
Air mobility in industrial premises occurs during ventilation (natural and / or artificial), with uneven heating of various volumes of air in the room and the occurrence of air flows on this basis, as well as due to the movement of air masses in the room by moving parts of equipment and vehicles. At high temperature air, its mobility has a positive effect on the well-being of workers, as it increases heat transfer. However, during the cold season, the movement of air leads to drafts and causes colds.
At railway transport facilities, drafts are present in vehicles, driver's cabs, repair shops, and when working on tracks in windy weather.
Insufficient air exchange in the premises of enterprises (stuffiness) weakens attention, causes nervousness, irritability and, as a result, reduces productivity and quality of work. At the same time, high air mobility (drafts) causes colds.
Thermal radiation. Thermal (infrared) radiation is a part of electromagnetic radiation, the energy of which, when absorbed by tissues human body causes them to heat up. Intense and prolonged thermal exposure can lead to burns, overheating of the body, depletion of metabolic processes, disruption of the cardiovascular and nervous systems, excitation, and eye disease. After the organs of vision, the most affected in humans is skin covering. With chronic irradiation, persistent changes in pigmentation may appear, red complexion in workers (glass blowers, steel workers, etc.).
Sources of infrared radiation are melting furnaces heated to a high temperature, molten metal, gas lamps, mercury rectifiers and other production equipment.
Prolonged exposure of a person to unfavorable meteorological conditions sharply worsens his state of health, reduces labor productivity and leads to diseases. Therefore, in the workplace quite often there are problems associated with the need to normalize the air environment.
department "Safety life"
Essay
Subject : Microclimate
By discipline "Safety life"
Ekaterinburg
Introduction
1 Classification of industrial microclimate
2 Influence of climatic conditions on human performance and health
Today's problems such as drought, wildfires and floods will only get worse due to climate change. In Nepal, changes in monsoon patterns will greatly exacerbate the unacceptable presence of poverty and inequality of opportunity in the country. While many Nepalese people cope with the current stresses on their own, the government must develop and implement effective strategies to adapt to the impacts of climate change in order to achieve economic and social progress. Adapting to long-term and short-term climate challenges requires creative collaboration between government, market participants and civil society.
3 Creation of the required microclimate parameters in production premises
4 Air environment of the working area
4.1 Causes and nature of air pollution in the working area
4.2 Weather conditions and their regulation in industrial premises
5 Measures to improve the air environment
5.1 Ventilation as a means of protecting the air environment of industrial premises
Climate change has been labeled as an "evil problem" characterized by many major layers of nested, intractable and unforeseen predicaments. Because the relationships between these many complexities are non-linear and complex, solving this problem goes beyond the comfort zone of our traditional knowledge systems. We need an interdisciplinary understanding of the problems we face and the search for solutions mediated by multiple institutional approaches.
Nowhere is the challenge of responding to the various impacts of climate change more complex than in the Hindu Kush-Himalaya region. This article discusses the physical, climatic and social variability of Nepal. It summarizes the results of a climate change scenario from recent modeling. While temperatures are likely to rise in the region, future precipitation will be more erratic, implying increased uncertainty. The paper states that increasing uncertainty does not imply any vulnerability and adaptation.
5.2 Natural ventilation
5.3 Mechanical ventilation
5.4 Aeration
5.5 Local ventilation
5.6 Equipment for ventilation systems
6 Air purification devices
Conclusion
Bibliographic list
Introduction
Most of the active life of a person is occupied by purposeful professional work carried out in a specific production environment, which, if the accepted regulatory requirements may adversely affect his performance and his health. Labor activity human and work environment are constantly changing due to the development of scientific - technical progress. All this imposes on a person the responsibility for observing safety precautions and creating optimal conditions for work. At the same time, labor remains the first, basic and indispensable condition for the existence of a person, the social, economic and spiritual development of society, and the comprehensive improvement of the individual. Ensuring the safety of work and rest contributes to the preservation of life and health of people by reducing injuries and diseases.
He then discusses two types of disasters - fast onset and slow onset. Floods and landslides are considered rapid natural disasters, while drought, wildfires, snowmelt and regional sedimentation are in the latter category. The risks associated with climate change, which are imposed on both types, are highlighted when determining the implications for decision-making for adaptation. In conclusion, it is suggested that responses to the impacts of climate change require multiple institutions and that approaches need to take complementary decisions at local, regional and national scales.
In this paper, we will talk about the microclimate at work, about its impact on a person, about creating optimal conditions for him. This topic will always be relevant as long as humanity lives and works.
1 Classification of industrial microclimate
In the process of working in a room, a person is under the influence of certain meteorological conditions or microclimate. Industrial microclimate- the climate of the internal environment of industrial premises is determined by the combination of temperature, humidity and air velocity acting on the human body, as well as the temperature of the surrounding surfaces.
Adaptation: a strategic switch for well-being. Recent research has helped improve understanding of adaptation. It is increasingly seen as adjustments in environmental, social and economic systems in response to actual or expected climate stimuli and their consequences or consequences. The adaptation that is now recognized is much more than coping. In well-adapted systems, people actually "thrive" despite changing conditions, including those associated with climate change.
They thrive either because they change strategies or because the underlying systems on which their livelihoods are based are resilient and resilient enough to absorb the impact of these changes. Field studies in South Asia documenting factors that increase people's vulnerability to floods and drought have identified factors that help people achieve well-being by building their resilience or adaptive capacity. Drawing on a series of shared learning dialogues with affected communities, non-governmental organizations, and local government officials, the researchers came up with a range of soft and hard resiliency measures that reduce vulnerability to natural disasters.
The industrial microclimate depends on the climatic zone and season of the year, the nature of the technological process and the type of equipment used, the size of the premises and the number of workers, the conditions of heating and ventilation. However, with all the variety of microclimatic conditions, they can be divided into four groups.
1) The microclimate of industrial premises in which the production technology is not associated with significant heat release. The microclimate of these rooms mainly depends on the local climate, heating and ventilation. Here, only a slight overheating in summer on hot days and cooling in winter with insufficient heating is possible.
The ability to reduce vulnerability to disasters is related to the reliability of the systems summarized in the table. Table 1: Factors contributing to adaptation. The role of such systems serves as the necessary physical-institutional infrastructure, which, in turn, allows for the provision of health, education, finance, social media and markets. Both are the basis for implementing adaptive strategies. Climate “adapted” systems will help build social resilience. Where such systems are weak or fail, they limit adaptive behavior such as livelihood diversification, disaster response and recovery.
2) The microclimate of industrial premises with significant heat emissions. These include boiler houses, forges, open-hearth and blast furnaces, bakeries, sugar factories, etc. In hot shops, the thermal radiation of heated and hot surfaces has a great influence on the microclimate.
3) The microclimate of industrial premises with artificial air cooling. These include various refrigerators.
Nepal: Land of climate. Despite its relatively small area, Nepal has a very diverse climate, ranging from tropical in the south to alpine in the north. In three different geographic regions countries - snow-capped mountains, medium hills and tarai - correspond to this diversity. Its hydrology is fed primarily by the South Asian monsoon system, but the relationship between timing, monsoon rainfall, and mountainous terrain is poorly understood. The abrupt change in altitude over a short distance has resulted in pronounced orographic effects that severely limit our ability to explain Nepal's precipitation dynamics.
4) The microclimate of the open atmosphere, depending on climatic conditions (for example, agricultural, road and construction work).
2 Influence of climatic conditions on human performance and health
Human life is accompanied by continuous energy consumption. Only a part of this energy is expended by a person to perform work, the rest of the energy is spent on the main exchange and heat release with the environment. There are three ways of heat propagation: conduction, convection and thermal radiation.
Another complication is that the data set needed to explain the processes is limited. such a lack of information, it is impossible to adequately record the temporal and spatial dynamics of precipitation. As a result, simulation exercises face fundamental limitations.
The diversity of Nepal's climate is linked to the diversity of its many ecosystems and flora and fauna. Mountainous, hilly and flat landscapes also support diverse cultures and livelihoods. Each of these many socio-economic systems is commonplace - an opportunity to take advantage of the opportunities that specific micro-climates and localized ecosystems can offer and respond to the constraints they place on livelihoods. Over three-quarters of all Nepalese livelihoods are based on agriculture and forest resources and nearly 65 percent Agriculture rains, but only 21% of Nepal's area is cultivated, and irrigated agriculture depends on the types of local surface sources that are most likely to be affected by rainfall.
Thermal conductivity is the transfer of heat due to the random (thermal) movement of microparticles - atoms, molecules or electrons - in direct contact with each other.
Convection is the transfer of heat due to the movement and mixing of macroscopic volumes of gas or liquid.
Thermal radiation is the process of propagation of electromagnetic oscillations with different radiating wavelengths, due to the thermal motion of atoms or a radiating body. In real conditions, heat is transferred not by any one of the above methods, but by a combined one. In industrial premises with high heat release, approximately 2/3 of the heat comes from radiation, and almost all the rest comes from convection. The amount of heat transferred to the surrounding air by convection Q k (W) during a continuous heat transfer process can be calculated using Newton's heat transfer law
It is clear, therefore, that climate change has serious implications for Nepal's ability to produce food for its people. Global climate scenario modeling results suggest that the impacts of climate change can be intense at high altitudes and in regions with complex topography, as occurs in the middle hills of Nepal. More than a decade ago, preliminary analysis by Mirza and Dixit that climate change in the Ganges and Brahmaputra basins is likely to change river flows, which in turn will affect low flows, drought, flood and sedimentation processes, and suggest that precipitation, are likely to be more uncertain and that the intensity of the storm will increase.
Q K = a∙S∙(t – t in),
where a is the convection coefficient, W / (m 2 ∙ deg);
S - heat transfer area, m 2;
t is the source temperature, °C;
t is the ambient air temperature, °С.
A significant source of thermal radiation in working conditions is molten or heated metal, open flame, heated surfaces.
The following key messages were included in the exercise report. On the ground, farmers' perceptions suggest that precipitation is becoming more erratic, days are getting hotter, patterns of winds, fogs and hail have changed, and farmers are becoming more vulnerable. A review of adaptation research supports their view that Nepal tends to experience climate fluctuations.
Slow and fast natural disasters. Climate-related disasters can generally be triggered by fast-onset events and slow-onset events. Unexpected climate hazards that appear suddenly or whose origin cannot be predicted far in advance cause sudden natural disasters. They include cyclones and other storms, landslides, avalanches and floods. The warning time before these dangerous attacks hit is anywhere from a few seconds or minutes to several days.
The best thermal well-being of a person will be when the heat release (Q tv) of the human body is completely given to the environment (Q then), i.e. there is a heat balance (Q tv \u003d Q then). The excess of body heat release over heat transfer in environment(Q tv > Q then) leads to heating of the body and to an increase in its temperature, the person becomes hot. On the contrary, the excess of heat transfer over heat release (Q tv< Q то) приводит к охлаждению организма и к снижению его температуры, человеку становится холодно. average temperature human body - 36.5 ° C. Even slight deviations of this temperature in one direction or another lead to a deterioration in a person's well-being.
Most discussions about slow disasters focus on drought, the results of which in terms of water and food shortages and loss of livelihoods can take months or sometimes years to become apparent. Rising temperatures, wildfires, regional sedimentation, and accelerated melting of snow and glaciers can also lead to slow natural disasters, the cumulative impact of which may not be felt for decades, although they can increase rapid events such as flash floods.
Ability human body maintaining a constant temperature is called thermoregulation. Thermoregulation is achieved by the removal of excess heat in the process of life from the body into the surrounding space. This value depends on the degree of physical activity and the parameters of the microclimate in the room (at rest - 85 W, increasing with heavy physical work up to 500 W).
However, the distinction between these two types of disasters is, in a sense, artificial. A disaster cannot occur if there are hazards with little or no vulnerability, or if the vulnerability is high but there is no hazard in the area. Disasters occur only when danger intersects with the vulnerability of societies and individuals.
Vulnerability is also deeply rooted in a given social context and is a symptom of the marginalization of various groups, the fragility of systems and the exposure of populations, activities and systems to specific hazards. For these reasons, for most disasters, long-term trends are likely to be more influential than short-term ones, and the distinction between slow and fast onset becomes irrelevant. However, the distinction may support a long-term holistic perspective in minimizing the risks associated with both.
The ways of such heat transfer are: heat conduction through clothing (Q t), body convection (Q k), radiation to surrounding surfaces (Q and), evaporation of moisture from the skin surface (Q exp), as well as due to heating of exhaled air (Q in) , which is represented by the heat balance equation
Q total \u003d Q t + Q to + Q and + Q isp + Q in
The contribution of the listed components of heat transfer is not constant and depends on the parameters of the microclimate in the room, on the temperature of the walls, ceiling, and equipment. Heat transfer by convection depends on the air temperature in the room and the speed of its movement in the workplace. The effect of ambient temperature on the human body is primarily associated with the narrowing or expansion of blood vessels in the skin. Under the influence of low air temperatures, the blood vessels of the skin narrow, as a result of which the blood flow to the body surface slows down and the heat transfer from the body surface due to convection and radiation decreases. At high ambient temperatures, the reverse picture is observed: due to the expansion of the blood vessels of the skin and an increase in blood flow, heat transfer to the environment increases significantly.
It is clear that climate change has become a key factor that exacerbates the risks. In the following paragraphs, we will discuss the implications of climate change for these two types of disasters. The flood is considered a quick disaster, while drought and wildfire are considered a slow start.
Floods during the monsoons are a natural occurrence in Nepal. Flooding damages crops and property and often leads to epidemics. The poor are the most vulnerable to its effects. The magnitude of the impact of any given flood depends on both environmental conditions and the characteristics of the population. Of course, climate change affects floods, but there is no scientific explanation for floods for climate change.
Prolonged overheating of the body leads to profuse sweating, increased heart rate and respiration, severe weakness, dizziness, seizures, and in severe cases, heat stroke.
Hypothermia leads to the occurrence of colds, chronic inflammation joints, muscles. To avoid all this, you need to create optimal microclimatic conditions in the workplace, which undoubtedly creates the prerequisites for high performance.
Along with the regular monsoon floods, the country also has two special types of floods: the glacial lake flood and the bishyara flood. In the Himalayan region, glacial lakes form between the end of a glacier and its moraine. The glaciers retreated rapidly in the second half of the 20th century, forming in many cases icy moraine lacustrine lakes of molten water.
Bishyari is a flood that occurs when a landslide that impounds a river is disturbed by a body of water that forms in front of it. They are usually found in the middle of the hills after a cloud burst. Bishyari happens randomly and cannot be predicted exactly.
3 Creation of the required microclimate parameters in production premises
The required parameters of the microclimate are regulated by " Sanitary regulations on the organization of technological processes and hygiene requirements to production equipment” and are carried out by a complex of technological, sanitary-technical, organizational and medical-preventive measures.
The leading role in the prevention of the harmful effects of high temperatures, infrared belongs to technological measures (for example, the use of stamping instead of forging works). The introduction of automation and mechanization makes it possible for workers to stay away from sources of radiation and convection radiation.
The group of sanitary and technical measures includes the use of collective means of protection: localization of heat releases, thermal insulation of hot surfaces, shielding of sources or workplaces; high quality air environment - air showering, radiation cooling, fine water spraying, general ventilation or air conditioning.
Measures to ensure the tightness of the equipment contribute to reducing the flow of heat into the workshop. Tightly fitted doors, shutters, blocking the closing of technological openings significantly reduce the release of heat from sources. The choice of heat protection means in each case should be carried out according to the maximum values of efficiency, taking into account the requirements of organic, technical aesthetics, safety for the process or type of work and feasibility study. Thermal protective equipment installed in the workshop should be easy to manufacture and install, convenient for maintenance, not complicate inspection, cleaning, lubrication of units, have the necessary strength, and have minimal operating costs.
4 Air environment of the working area
One of necessary conditions healthy and highly productive work is to ensure clean air and normal meteorological conditions in the working area of the premises, that is, a space up to 2 m above the floor or platform where the workplaces are located.
4.1 Causes and nature of air pollution in the working area
Atmospheric air in its composition contains (% by volume): nitrogen - 78.08; oxygen -20.95; argon, neon and other inert gases - 0.93; carbon dioxide- 0.03; other gases -0.01. The air of this composition is the most favorable for breathing. Work area air rarely has the above chemical composition, since many technological processes are accompanied by the release of harmful substances into the air of industrial premises - vapors, gases, solid and liquid particles. Vapors and gases form mixtures with air, and solid and liquid particles of a substance - dispersed systems - aerosols, which are divided into dust (solid particle size more than 1 micron), smoke (less than 1 micron) and fog (liquid particle size less than 10 microns). Dust is coarse - (particle size more than 50 microns), medium - (50 - 10 microns) and fine (less than 10 microns).
The entry into the air of the working area of one or another harmful substance depends on the technological process, the raw materials used, as well as on intermediate and final products. So, vapors are released as a result of the use of various liquid substances, for example, solvents, a number of acids, gasoline, mercury, etc., and gases - most often during the technological process, for example, during welding, casting, heat treatment of metals.
The reasons for the release of dust in mechanical engineering enterprises can be very diverse. Dust is generated during crushing and grinding, transportation of crushed material, machining brittle materials, surface finishing (grinding, glossing), packaging and packaging, etc. These causes of dust formation are the main or primary ones. Under production conditions, secondary dust formation may also occur, for example, during cleaning of premises, people moving, etc. Such dust emission is sometimes very undesirable (in the electrovacuum industry, instrument making).
Smoke arises from the combustion of fuel in furnaces and power plants, and fog - from the use of cutting fluids, in electroplating and pickling shops in the processing of metals. For example, in the charging compartments of batteries, an aerosol of sulfuric acid is formed.
Harmful substances enter the human body mainly through the respiratory tract, as well as through the skin and with food. Most of these substances are classified as dangerous and harmful production factors, since they have a toxic effect on the human body. These substances, being well soluble in biological media, are able to interact with them, causing disruption of normal life. As a result of their action, a person develops a painful condition - poisoning, the danger of which depends on the duration of exposure, concentration q (mg / m3) and the type of substance. According to the nature of the impact on the human body, harmful substances are divided into:
General toxic - causing poisoning of the whole organism (carbon monoxide, cyanide compounds, lead, mercury, benzene, arsenic and its compounds, etc.).
Irritant - causing irritation of the respiratory tract and mucous membranes (chlorine, ammonia, sulfur dioxide, hydrogen fluoride, nitrogen oxides, ozone, acetone, etc.).
Sensitizing - acting as allergens (formaldehyde, various solvents and varnishes based on nitro - and nitroso compounds, etc.).
carcinogenic - causing cancer diseases(nickel and its compounds, amines, chromium oxides, asbestos, etc.).
Mutagenic - leading to a change in hereditary information (lead, manganese, radioactive substances, etc.).
Influencing reproductive (childbearing) function (mercury, lead, manganese, styrene, radioactive substances, etc.).
Regulation of the content of harmful substances in the air of the working area
According to GOST 12.1.005 - 76, maximum permissible concentrations of harmful substances q MPC (mg / m 3) in the air of the working area of industrial premises are established. Harmful substances according to the degree of impact on the human body are divided into the following classes: 1st - extremely dangerous, 2nd - highly dangerous, 3rd - moderately dangerous, 4th - low-dangerous. As an example, in Table. 1 shows the normative data for a number of substances (in total, more than 700 substances are standardized).
Table 1. - Values of permissible concentrations of substances
| Substance | MPC value, mg / m 3 | Hazard Class | State of aggregation |
| Beryllium and its compounds | 0,001 | 1 | aerosol |
| Lead | 0,001 | 1 | aerosol |
| Manganese | 0,05 | 1 | aerosol |
| Ozone | 0,1 | 1 | Vapors or gases |
| Chlorine | 1 | 1 | Vapors or gases |
| Hydrochloric acid | 5 | 2 | Vapors or gases |
| Silica-containing dust | 1 | 3 | Vapors or gases |
| iron oxide | 4 – 6 | 4 | aerosol |
| Carbon monoxide, ammonia | 20 | 4 | Vapors or gases |
| Fuel gasoline | 100 | 4 | Vapors or gases |
| Acetone | 200 | 4 | Vapors or gases |
4.2 Meteorological conditions and their regulation in industrial premises
Meteorological conditions, or microclimate, in production conditions are determined by the following parameters: air temperature (°C), relative humidity (%), air velocity at the workplace V (m / c).
In addition to these parameters, which are the main ones, one should not forget about atmospheric pressure R. which affects the partial pressure of the main components of air (oxygen and nitrogen), a. hence the process of respiration.
Human life can take place in a fairly wide range of pressures 734 - 1267 hPa (550 950 mm Hg). However, here it is necessary to take into account that a rapid change in pressure is dangerous for human health, and not the value of this pressure itself. For example, a rapid decrease in pressure of just a few hectopascals in relation to the normal value of 1013 hPa (760 mmHg) causes a painful sensation.
The need to take into account the main parameters of the microclimate can be explained based on the consideration of the heat balance between the human body and the environment of industrial premises.
At high air temperature in the room, the blood vessels of the skin expand, while there is an increased flow of blood to the surface of the body, and heat transfer to the environment increases significantly. However, at ambient air temperatures and surfaces of equipment and premises of 30 - 35 ° C, heat transfer by convection and radiation basically stops. At higher air temperatures, most of the heat is given off by evaporation from the surface of the skin. Under these conditions, the body loses a certain amount of moisture, and with it salts, which play an important role in the life of the body. Therefore, in hot shops, workers are given salted water. When the ambient temperature drops, the reaction of the human body is different: the blood vessels of the skin narrow, the blood flow to the surface of the body slows down, and the release of heat by convection * and radiation decreases. Thus, for the thermal well-being of a person, a certain combination of temperature, relative humidity and air velocity in the working area is important.
Air humidity has a great influence on the thermoregulation of the body. High humidity (av>85%) makes it difficult to thermoregulate due to a decrease in sweat evaporation, and too low humidity (f<20%) вызывает пересыхание слизистых оболочек дыхательных путей. Оптимальные величины относительной влажности составляют 40 -60%.
The movement of air in rooms is an important factor influencing the thermal well-being of a person. In a hot room, air movement increases the body's heat transfer and improves its condition, but it has an adverse effect at low air temperatures during the cold season. The minimum air velocity felt by a person is 0.2 m/s. In winter, the air velocity should not exceed 0.2 - 0.5 m/s, and in summer - 0.2 - 1.0 m/s. In hot shops, it is allowed to increase the blowing speed of workers (air showering) up to 3.5 m/s.
In accordance with GOST 12.1.005 - 76, optimal and permissible meteorological conditions are established for the working area of the premises, the choice of which takes into account:
1) season - cold and transitional periods with an average daily outdoor temperature below + 10 ° * С; warm period with a temperature of +10°C and above;
a) light physical work with energy consumption up to 172 J / s (150 kcal / h), which include, for example, the main processes of precision instrumentation and mechanical engineering;
b) physical work of moderate severity with energy consumption of 172 - 293 J / s (150 - 250 kcal / h). for example, in mechanical assembly, mechanized foundries, rolling, thermal shops, etc.;
c) heavy physical work with energy consumption of more than 293 J / s, which includes work associated with systematic physical stress and the transfer of significant (more than 10 kg) weights; these are blacksmith shops with hand forging, foundries with hand stuffing and filling of flasks, etc.;
3) characteristics of the premises in terms of sensible heat excesses: all production premises are divided into premises with insignificant excesses of sensible heat per 1 m3 of the volume of the premises. 23.2 J/(mSs) and less, and with significant excesses - more than 23.2 J/(mSs).
Sensible heat is the heat that enters the working room from equipment, heating devices, heated materials, people and other sources, as a result of insolation and affects the air temperature in this room.
5 Measures to improve the air environment
The required state of the air in the working area can be ensured by the implementation of certain measures, the main of which include:
1. Mechanization and automation of production processes, their remote control. These measures are of great importance for protection against the effects of harmful substances, thermal radiation, especially when performing heavy work. Automation of processes accompanied by the release of harmful substances, not only
increases productivity, but also improves working conditions as workers are moved out of the danger zone. For example, the introduction of automatic welding with remote control instead of manual welding makes it possible to dramatically improve the working conditions of the welder, the use of robotic manipulators makes it possible to eliminate heavy manual labor.
2. The use of technological processes and equipment that exclude the formation of harmful substances or their entry into the working area. When designing new technological processes and equipment, it is necessary to achieve the exclusion or sharp reduction in the release of harmful substances into the air of industrial premises. This can be achieved, for example, by replacing toxic substances with non-toxic ones, by switching from solid and liquid fuels to gaseous ones, by electric high-frequency heating; application of dust suppression with water (humidification, wet grinding) when grinding and transporting materials, etc.
Reliable sealing of equipment containing harmful substances, in particular, heating furnaces, gas pipelines, pumps, compressors, conveyors, etc., is of great importance for the improvement of the air environment. gas pressure. The amount of escaping gas depends on its physical properties, the area of leaks and the pressure difference outside and inside the equipment.
3. Protection from sources of thermal radiation. This is important to reduce the air temperature in the room and the thermal exposure of workers.
4. The device of ventilation and heating, which is of great importance for the improvement of the air environment in industrial premises.
5. Use of personal protective equipment.
5.1 Ventilation as a means of protecting the air environment of industrial premises
The task of ventilation is to ensure the purity of the air and the specified meteorological conditions in industrial premises. Ventilation is achieved by removing polluted or heated air from a room and supplying fresh air to it.
According to the method of moving air, ventilation can be with natural motivation (natural) and with mechanical (mechanical). A combination of natural and mechanical ventilation (mixed ventilation) is also possible.
Ventilation can be supply, exhaust or supply and exhaust, depending on what the ventilation system is used for - to supply (inflow) or remove air from the room, or (and) for both at the same time.
At the place of action, ventilation can be general and local.
The action of general ventilation is based on the dilution of polluted, heated, humid room air with fresh air to the maximum allowable standards. This ventilation system is most often used in cases where harmful substances, heat, moisture are released evenly throughout the room. With such ventilation, the necessary parameters of the air environment are maintained throughout the entire volume of the room.
Air exchange in the room can be significantly reduced if harmful substances are trapped at the places of their release. For this purpose, technological equipment, which is a source of emission of harmful substances, is equipped with special devices from which polluted air is sucked out. Such ventilation is called local exhaust. Local ventilation in comparison with general exchange requires significantly lower costs for installation and operation. In industrial premises, in which a large amount of harmful vapors and gases may suddenly enter the air of the working zone, along with the working one, an emergency ventilation device is provided.
For the effective operation of the ventilation system, it is important that the following technical and sanitary and hygienic requirements are met at the design stage.
1. The amount of supply air must match the amount of air removed (exhaust); the difference between them should be minimal.
In some cases, it is necessary to organize air exchange in such a way that one amount of air is necessarily greater than another. For example, when designing ventilation of two adjacent rooms, one of which emits harmful substances. The amount of air removed from this room must be greater than the amount of supply air, as a result of which a slight vacuum is created in the room. Such air exchange schemes are possible when the pressure in the entire room is maintained in excess of atmospheric pressure. For example, in the workshops of electrovacuum production, for which the absence of dust is especially important.
2. Supply and exhaust systems in the room must be correctly placed. Fresh air must be supplied to those parts of the room where the amount of harmful substances is minimal, and removed where the emissions are maximum. The air supply should be carried out, as a rule, in the working area, and the exhaust - from the upper area of the room.
3. The ventilation system should not cause hypothermia or overheating of workers.
4. The ventilation system should not create noise in the workplace that exceeds the maximum permissible levels.
5. The ventilation system must be electrically, fire and explosion-proof, simple in design, reliable in operation and efficient.
5.2 Natural ventilation
Air exchange during natural ventilation occurs due to the temperature difference between the air in the room and the outside air, as well as as a result of the action of the wind. Natural ventilation can be unorganized and organized. With unorganized ventilation, air enters and leaves through leaks and pores of external fences (infiltration), through windows, vents, special openings (ventilation).
Organized natural ventilation is carried out by aeration and deflectors, and can be adjusted.
5.3 Mechanical ventilation
In mechanical ventilation systems, air movement is carried out by fans and, in some cases, ejectors, supply and exhaust ventilation.
Forced ventilation. Supply ventilation installations usually consist of the following elements: an air intake device for intake of clean air; air ducts through which air is supplied to the room: filters for cleaning the air from dust; air heaters; fan; supply nozzles; control devices that are installed in the air intake and on the branches of the air ducts.
Exhaust ventilation. Exhaust ventilation installations include: exhaust openings or nozzles; fan; air ducts; device for air purification from dust and gases; air ejection device, which should be located 1-1.5 m above the roof ridge.
During the operation of the exhaust system, clean air enters the room through leaks in the building envelope. In some cases, this circumstance is a serious drawback of this ventilation system, since an unorganized influx of cold air (drafts) can cause colds.
Supply and exhaust ventilation. In this system, air is supplied to the room by supply ventilation, and removed by exhaust ventilation, operating simultaneously.
For recirculation, it is allowed to use the air of rooms in which there are no emissions of harmful substances or the emitted substances belong to the 4th hazard class, and the concentration of these substances in the air supplied to the room does not exceed 0.3 concentrations of MPC.
5.4 Aeration
It is carried out in cold shops due to wind pressure, and in hot shops due to the joint and separate action of gravitational and wind pressures. In summer, fresh air enters the room through the lower openings located at a small height from the iol (1 - 1.5 m), and is removed through openings in the building's skylight.
The intake of outside air in winter is carried out through openings located at a height of 4 - 7 m from the floor. The height is taken in such a way that the cold outside air, descending to the working area, has time to warm up sufficiently due to mixing with the warm air of the room. By changing the position of the flaps, you can adjust the air exchange.
When buildings are blown with wind from the windward side, an increased air pressure is created, and on the leeward side, a rarefaction is created.
Under the pressure of air from the windward side, the outside air will flow through the lower openings and. propagating in the lower part of the building, to displace the more heated and polluted air through the openings in the lantern of the building to the outside. Thus, the action of the wind enhances air exchange, which occurs due to gravitational pressure. The advantage of aeration is that large volumes of air are brought in and removed without the use of fans or ducts. An aeration system is much cheaper than mechanical ventilation systems.
Disadvantages: in the summer, the efficiency of aeration is reduced due to an increase in the outdoor temperature; the air entering the room is not processed (not cleaned, not cooled).
Ventilation with deflectors. Deflectors are special nozzles installed on exhaust ducts and using wind energy. Deflectors are used to remove polluted or overheated air from rooms of a relatively small volume, as well as for local ventilation, for example, for extracting hot gases from forges, furnaces, etc.
5.5 Local ventilation
Local ventilation is supply and exhaust.
Local supply ventilation is used to create the required air conditions in a limited area of the production facility. Local supply ventilation installations include: air showers and oases, air and air-thermal curtains.
Air showering is used in hot shops at workplaces under the influence of a radiant heat flux with an intensity of 350 W/m2 or more. The air shower represents the air stream directed on a working. The blowing speed is 1 - 3.5 m/s depending on the irradiation intensity. The effectiveness of showering units is increased by spraying water in an air stream.
Air oases are part of the production area, which is separated from all sides by light movable partitions and filled with air that is colder and cleaner than the air in the room.
Air and air-thermal curtains are arranged to protect people from being chilled by cold air entering through the gate. Curtains are of two types: air curtains with air supply without heating and air-thermal curtains with heating of the supplied air in heaters. The operation of curtains is based on that the air supplied to the gate exits through a special air duct with a slot at a certain angle at a high speed (up to 10 - 15 m / s) towards the incoming cold stream and mixes with it. The resulting mixture of warmer air enters the workplaces or (in case of insufficient heating) deviates away from them. During operation of the curtains, additional resistance is created to the passage of cold air through the gate.
Local exhaust ventilation. Its application is based on the capture and removal of harmful substances directly at the source of their formation.
Local exhaust ventilation devices are made in the form of shelters or local suctions.
Shelters with suction are characteristic of those. that the source of harmful secretions is inside them. They can be made as shelters-casings, completely or partially enclosing equipment (fume hoods, display shelters, cabins and chambers). A vacuum is created inside the shelters, as a result of which harmful substances cannot enter the indoor air. This method of preventing the release of harmful substances in the room is called aspiration.
It is important even at the design stage to develop technological equipment in such a way that such ventilation devices would be organically included in the overall design, without interfering with the technological process and at the same time completely solving sanitary and hygienic problems.
Protective and dedusting covers are installed on machines where the processing of materials is accompanied by dust emission and flying off of large particles that can cause injury. These are grinding, peeling, polishing, grinding machines for metal, woodworking machines, etc.
Fume hoods are widely used in thermal and galvanic treatment of metals, painting. * weighing and packaging of bulk materials, during various operations associated with the release of harmful gases and vapors.
Cabins and chambers are containers of a certain volume, inside which work is carried out related to the release of harmful substances (sandblasting and shot blasting, painting, etc.).
Exhaust hoods are used to localize harmful substances rising up, namely, during heat and moisture release. Suction panels are used in cases where the use of exhaust hoods is unacceptable due to the condition of the ingress of harmful substances into the respiratory organs of workers.
An effective local suction is the Chernoberezhsky panel used in such operations as gas welding, soldering, etc.
Dust and gas receivers. funnels are used for soldering and welding.
They are located in close proximity to the place of soldering or welding.
Side suctions. When pickling metals and applying electroplating, acid and alkali vapors are emitted from the open surface of the baths; during zinc plating, copper plating, silver plating - extremely harmful hydrogen cyanide, during chromium plating - chromium oxide, etc. To localize these harmful substances, onboard suctions are used, which are slot-like air ducts 40–100 mm wide, installed along the periphery of the baths.
The principle of operation of the onboard suction is that. that the air drawn into the slot, moving above the surface of the liquid, carries with it harmful substances, preventing them from spreading up the room.
5.6 Equipment for ventilation systems
Fans are blowers that create a certain pressure and serve to move air with pressure losses in the ventilation network of not more than 12 kPa. The most common are axial and radial (centrifugal) fans.
Depending on the composition of the transported air, fans are made of certain materials and of various designs:
1) normal design for moving clean air, made of ordinary steel grades:
2) anti-corrosion design - for moving aggressive environments, chromium and chromium-nickel steels, vinyl plastic, etc.:
3) fireproof design - for moving explosive mixtures (containing hydrogen, acetylene, etc.). the main parts are made of aluminum and duralumin, a stuffing box seal is installed in bulk;
4) dust - to move dusty air, impellers are made of high strength materials, they have few (4 - 8) blades.
Ejectors are used in exhaust systems in cases where it is necessary to remove a very aggressive environment, dust that can explode not only from impact, but also from friction, or flammable explosive gases (acetylene, ether, etc.). The disadvantage of the ejector is the low efficiency. not exceeding 0.25.
6 Air purification devices
Air purification from dust can be coarse, medium and fine.
For coarse and medium cleaning, dust collectors are used, the action of which is based on the use of gravity or inertial forces: dust settling chambers, cyclones, vortex, louvre. chamber and rotary dust collectors.
Dust settling chambers are used for settling coarse and heavy dust with a particle size of more than 100 microns. The air speed in the cross section of the housing 2 is not more than 0.5 m/s. Therefore, the dimensions of the chambers are quite large, which limits their application.
Cyclones are used to clean the air from dry non-fibrous and non-sloughing dust.
Electrostatic precipitators are used to clean the supply air from dust and fog. The operation of electrostatic precipitators is based on the creation of a strong electric field using a rectified high voltage current (up to 35 kV). supplied to the corona and collecting electrodes. When dusty air passes through the gap between the electrodes, air molecules are ionized with the formation of positive and negative ions. Ions, being adsorbed on dust particles, charge them positively or negatively. Dust that has received a negative charge tends to settle on the positive electrode, and positively charged dust settles on the negative electrodes. These electrodes are shaken periodically by means of a special mechanism, the dust is collected in a hopper and periodically removed. For medium and fine air purification, filters are widely used, in which dusty air is passed through porous filter materials. If the size of the dust particles is larger than the pore size of the filter material, then the surface (mesh) effect of dust collection operates. If the dust particle size is smaller than the pore size, then the dust penetrates the filter material and settles on the particles or fibers that form this material. This filtering process is called depth filtering. As filter materials, fabrics, felts, paper, nets, fiber packings, metal chips, porcelain or metal hollow rings, porous ceramics or porous metals are used.
Conclusion
With the development of scientific and technological progress, the number of dangers in the technosphere is constantly growing, and unfortunately, methods and means of protection against them are created and improved with a delay, especially in Russia.
Many factories and enterprises are barely alive. What kind of innovation or normal microclimate can we talk about. As a result of accidents and disasters, many people suffer and die.
The problem of achieving an optimal microclimate is the main one at enterprises and the development of our industry largely depends on this, because only healthy people can produce high-quality products.
Bibliographic list
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