Classification of ventilation systems. Selection of ventilation system. Design features of the local ventilation system. Moscow State University of Printing Basic requirements for ventilation systems
Ventilation is an organized air exchange, during which dusty, gas-polluted or highly heated air is removed from the room and fresh, clean air is supplied in its place.
The ventilation system is a complex of architectural, structural and special engineering solutions, which, when correct operation provides the necessary air exchange in the room.
The ventilation system is engineering design, which has a certain functional purpose(inflow, exhaust, local suction, etc.) and is an element of the ventilation system.
Ventilation systems create conditions for ensuring the technological process or maintaining specified values in the room climatic conditions for highly productive human work. In the first case, the ventilation system will be called technological, and in the second - comfortable.
Technological ventilation provides a given air composition, temperature, humidity, and mobility in a room in accordance with the requirements of the technological process. These requirements are especially high in the workshops of such industries as radio engineering, electric vacuum, textile, chemical and pharmaceutical industries, storage facilities for agricultural products, archives, and premises where historical values are stored.
Comfortable ventilation should provide favorable sanitary hygienic conditions for people working in these premises.
The required meteorological conditions indoors must be ensured in the working area of the premises or at workplaces. Behind work area premises take a space 2m high from the level of the floor or platform on which it is located workplace. Design parameters air - temperature, relative humidity and air mobility - for various workshops and production premises, depending on the category of human work and the conditions of the technological process.
The purpose of room ventilation is to maintain a favorable condition for humans. air environment in accordance with its standardized characteristics.
The chemical composition of indoor air depends on the length of time people stay in them and the operation of technological gas-emitting equipment. The maximum permissible content (concentration) of various harmful gases and vapors (MPC) established by research is given in GOST 12.1 005 76.
Depending on the chosen method, which determines the principle of operation of the systems and their design, ventilation is distinguished: general exchange, local and localizing.
At general ventilation the dilution of harmful substances occurs throughout the entire volume of the room due to the influx of fresh air, which, passing through the room, assimilates the released harmful substances and is then thrown out.
Quantity supplied ventilation air(air exchange) is calculated to dilute the released harmful substances to concentrations acceptable in the workplace.
The main indicator for choosing this method is the location of people and possible sources of hazardous emissions throughout the entire or large area of the premises. The disadvantage of this method is the uneven sanitary and hygienic conditions of the air environment in different places premises, as well as the possibility of their unacceptable deterioration near sources of hazardous emissions or places where air is exhausted from premises.
The latter must be taken into account and, if possible, eliminated by the appropriate location and purpose of the required number of devices for distribution and exhaust of ventilation air.
General ventilation is installed in residential and public buildings. In rooms where the release of heat and moisture causes the natural rise of air, exhaust is usually carried out from the upper zone. ventilation fire hazard material radiation
It is advisable to supply the supply air so that it reaches people as clean and fresh as possible, without disturbing comfortable conditions.
Classification of ventilation systems by purpose
Ventilation systems can be divided according to their purpose into supply and exhaust. Supply systems serve to supply clean air to ventilated rooms to replace polluted air. Moreover, in necessary cases supply air may be subject to processing such as cleaning, heating and humidification.
The supply ventilation system consists of an air intake device, a supply chamber, a network of air ducts and devices for supplying air to the room.
Rice.
- 1. Fence installation.
- 2. Cleaning device.
- 3. Air duct system.
- 4. Fan.
- 5. Feeding device for work. place.
Local supply ventilation devices include air showers, air curtains and air heating.
An air shower is a device in a local supply ventilation system that provides a concentrated air flow. The supplied air creates air conditions in the zone of direct influence of this flow on a person that meet hygienic requirements.
Air and air-thermal curtains are installed in order to cold air V winter time did not penetrate through open doors V public buildings through open doors to public buildings and through gates to production areas of industrial buildings. Air curtain- this is a flat stream of air that is supplied from the sides of the gate or doors at a certain angle towards the outside cold air. For an air-thermal curtain, the air supplied by the fan is additionally heated.
In systems air heating the air is heated in air heaters to certain temperature, and then served into the room. In air heaters, the air is heated by hot or superheated water, steam or hot gases.
Exhaust ventilation serves to remove contaminated or heated exhaust air from the room. To exhaust ventilation systems industrial ventilation include aspiration or pneumatic conveying systems bulk materials, as well as production waste - dust, shavings, sawdust, etc. These materials are moved through pipes and channels by air flow.
Rice.
- 1. Air removal device.
- 2. Fan.
- 3. Air duct system.
- 4. Dust and gas collection devices.
- 5. Filters.
- 6. Air release device.
Aspiration systems use special fans, cleaning devices, dust collectors and other equipment. Aspiration systems are widely used at woodworking enterprises to remove shavings and sawdust from machines, at elevators for loading grain into vehicles, at cement factories when loading cement, in foundries for transporting sand and burnt earth.
In general, both supply and exhaust systems are provided in the room. Their performance must be balanced taking into account the possibility of air flow into or from adjacent rooms. The premises may also have only an exhaust or only a supply system. In this case, air enters this room from the outside or from adjacent rooms through special openings, or is removed from this room to the outside, or flows into adjacent rooms.
The purpose of ventilation is to ensure clean air and specified meteorological conditions in production premises.
Ventilation is achieved by removing polluted or heated air from a room and introducing fresh air into it.
Depending on the method of air movement, ventilation can be natural or mechanical. It is also possible to combine natural and mechanical ventilation(mixed ventilation) in various options.
Depending on what the ventilation system is used for - to supply (supply) or remove (exhaust) air from the room or both at the same time, it is called supply, exhaust or supply and exhaust.
Depending on the location of action, ventilation can be general and local.
The action of general ventilation is based on the dilution of excreted harmful substances fresh air up to maximum permissible concentrations or temperatures. This ventilation system is most often used in cases where harmful substances are released evenly throughout the room. With such ventilation, the necessary parameters of the air environment are maintained throughout its entire volume (Fig. 2, a).
Rice. 2. Ventilation systems:
a, b, c - general exchange; g - general exchange and local; d — organization of air exchange: 1 — control panel room; 2 - local suctions
If the room is very large, and the number of people in it is small, and their location is fixed, it does not make sense (for economic reasons) to improve the health of the entire room completely, you can limit yourself to improving the air environment only in the places where people are. An example of such an organization of ventilation can be observation and control cabins in rolling shops, in which local supply and exhaust ventilation is installed (Fig. 2, d), workplaces in hot shops equipped with air showering units, etc.
Air exchange in a room can be significantly reduced if harmful substances are captured at the points of their release, preventing them from spreading throughout the room. For this purpose, technological equipment that 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 or localization (Fig. 2, d).
Local ventilation, compared to general ventilation, requires significantly lower costs for installation and operation.
In industrial premises in which large quantities of harmful vapors and gases may suddenly enter the air of the working area, emergency ventilation is provided.
In production they often arrange combined systems ventilation (general exchange with local, general exchange with emergency, etc.).
For successful work ventilation system, it is important that the following technical and sanitary-hygienic requirements are met even at the design stage.
1. The volume of air flow into the room Lnp must correspond to the exhaust volume Lext; the difference between these volumes should not exceed 10-15%.
In some cases, it is necessary to organize air exchange in such a way that one of the volumes is necessarily larger than the other. For example, when designing the ventilation of two adjacent rooms (Fig. 2, d), in one of which harmful substances are released (room I), the volume of exhaust from this room is greater than the volume of inflow, i.e. Lout > LnpI, resulting in This room creates a slight vacuum and harmless air from room II with slight overpressure LBblTII There are also possible cases of organizing air exchange when excess pressure relative to atmospheric pressure is maintained throughout the room. For example, in electric vacuum production workshops, for which the absence of dust penetrating through various leaks in enclosures is especially important, the volume of air inflow is greater than the volume of exhaust, due to which a certain excess pressure is created (RPom > Patm). 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 emissions is minimal (or none at all), and removed where the emissions are maximum (Fig. 2, b, c). An effective means of ensuring proper cleanliness and acceptable parameters The indoor air microclimate is controlled by ventilation. Ventilation
called organized and regulated air exchange, ensuring the removal of polluted air from the room and the supply of fresh air in its place. Based on the method of air movement, natural and mechanical ventilation systems are distinguished. A ventilation system in which the movement of air masses is carried out due to the resulting pressure difference outside and inside the building is called natural ventilation.
Unorganized natural ventilation - infiltration,
or natural ventilation,
carried out by changing the air in the premises through leaks in fences and elements building structures due to the difference in pressure outside and inside the room. Such air exchange depends on random factors: wind strength and direction, air temperature inside and outside the building, type of fencing and quality construction work. Infiltration can be significant for residential buildings and reach 0.5-0.75 room volume per hour, and for industrial enterprises- up to 1-1.5 hours. For constant air exchange required by the conditions for maintaining clean air in the room, organized ventilation (aeration) is necessary. Aeration
called organized natural general ventilation of premises as a result of the entry and removal of air through opening transoms of windows and lanterns. Air exchange in the room is regulated by varying degrees of opening of the transoms depending on the outside temperature, wind speed and direction. As a method of ventilation, aeration has found wide application in industrial buildings, characterized technological processes with large heat releases (rolling, foundry, forging shops). The main advantage of aeration is the ability to carry out large air exchanges at no cost mechanical energy. The disadvantages of aeration include the fact that during the warm period of the year, the efficiency of aeration can drop significantly due to an increase in the temperature of the outside air and the fact that the air entering the room is not cleaned or cooled. Ventilation, by which air moves through duct systems using stimulants, is called mechanical ventilation.
Mechanical ventilation has a number of advantages over natural ventilation: a large radius of action due to the significant pressure created by the fan; the ability to change or maintain the required air exchange regardless of the outside temperature and wind speed; the ability to subject the air introduced into the room to pre-cleaning or humidification, heating or cooling; the ability to organize optimal air distribution with air supply directly to workplaces; the ability to capture harmful emissions directly at the places of their formation and prevent their spread throughout the entire volume of the room, as well as the ability to purify polluted air before releasing it into the atmosphere. The disadvantages of mechanical ventilation include the significant cost of construction and its operation and the need to take measures to combat noise. Mechanical ventilation systems are divided into public, local, mixed, emergency and air conditioning systems. General ventilation
designed to assimilate excess heat, moisture and harmful substances throughout the entire working area of the premises. It is used if harmful emissions enter directly into the air of the room; workplaces are not fixed, but are located throughout the room. Typically, the volume of air £pr supplied to the room during general ventilation is equal to the volume of air £b removed from the room. However, in a number of cases it becomes necessary to violate this equality (Fig. 4.1). So, in especially clean industries, for which great importance has no dust, the volume of air inflow is greater than the volume of the exhaust, due to which some excess pressure is created R
in the production area, which prevents dust from entering from adjacent rooms. In general, the difference between the volumes of supply and exhaust air should not exceed 10-15%. Rice. 4.1.
Air circulation in the room and, accordingly, the concentration of impurities and the distribution of microclimate parameters depend not only on the presence of supply and exhaust jets, but also on their relative position. There are four main schemes for organizing air exchange during general ventilation: from top to bottom (Fig. 4.2, i), from top to top (Fig. 4.2, b);
from bottom to top (Fig. 4.2, V);
from bottom to bottom (Fig. 4.2, G).
In addition to these schemes, combined ones are used. The most uniform air distribution is achieved when the inflow is uniform across the width of the room and the exhaust is concentrated. When organizing air exchange in rooms, it is necessary to take into account physical properties harmful vapors and gases, and primarily their density. If the gas density is lower than the air density, then the contaminated air is removed in the upper zone, and fresh air is supplied directly to the working area. When gases with a density greater than the density of air are released, 60-70% of contaminated air is removed from the lower part of the room and 30-40% from the upper part. In rooms with significant emissions Rice. 4.2.
moisture extractor humid air is carried out in the upper zone, and fresh food is supplied in an amount of 60% to the working zone and 40% to the upper zone. Based on the method of supplying and removing air, there are four general ventilation schemes (Fig. 4.3): supply, exhaust, supply and exhaust, and with a recirculation system. By supply system
air is supplied to the room after it has been prepared in the supply chamber. This creates excess pressure in the room, due to which the air escapes outside through windows, doors or into other rooms. The supply system is used to ventilate rooms into which it is undesirable for polluted air from neighboring rooms or cold air from outside to enter. Supply ventilation units (Fig. 4.3, A)
usually made up of the following elements: air intake device / for intake of clean air; 2 air ducts through which air is supplied to the room, filters 3
for cleaning air from dust, air heaters 4,
in which the cold is heated outside air; motion stimulator 5, humidifier-dryer 6, supply openings or nozzles 7 through which air is distributed throughout the room. Rice. 4.3.
A
- forced ventilation(PV); b
- exhaust ventilation (VV); V -
supply and exhaust ventilation with recirculation Air is removed from the room through leaks in the enclosing structures. Exhaust system
designed to remove air from the room. At the same time, a reduced pressure is created in it and the air from neighboring rooms or outside air enters this room. It is advisable to use an exhaust system if the harmful emissions of a given room should not spread to neighboring ones, for example, for hazardous workshops or chemical laboratories. Settings exhaust ventilation(Fig. 4.3, b)
consist of exhaust openings or nozzles 8,
through which air is removed from the room; motion stimulator 5, air ducts 2; devices for air purification from dust or gases 9,
installed to protect the atmosphere, and air release devices 10,
which is located 1 - 1.5 m above the roof ridge. Fresh air enters the production premises through leaks in the enclosing structures, which is a disadvantage of this ventilation system, since an unorganized influx of cold air (drafts) can cause colds. Supply and exhaust ventilation -
the most common system in which air is supplied to the room by a supply system and removed by an exhaust system; systems operate simultaneously. In some cases, to reduce air heating costs, they use ventilation systems with partial recirculation
(Fig. 4.3, V).
In them, air drawn from the room is mixed with the air coming from outside. II exhaust system. The amount of fresh and secondary air is controlled by valves 11 n 12.
Fresh air in such systems usually accounts for 20-10% of the total amount of supplied air. A ventilation system with recirculation is allowed to be used only for those rooms in which there are no emissions of harmful substances or the emitted substances belong to the 4th hazard class (see paragraph 3.2 of Table 3.4) and their concentration in the air supplied to the room does not exceed 30% maximum permissible concentration (MPC) - The use of recirculation is not allowed if the air in the premises contains pathogenic bacteria, viruses or there are pronounced unpleasant odors. Individual installations of general mechanical ventilation may not include all of the above elements. For example, supply systems are not always equipped with filters and devices for changing air humidity, and sometimes supply and exhaust units may not have a network of air ducts. The calculation of the required air exchange during general ventilation is made based on production conditions and the presence of excess heat, moisture and harmful substances. To qualitatively assess the efficiency of air exchange, the concept of air exchange rate is used Ka
- the ratio of the amount of air entering the room per unit time b
(m3/h), to the volume of the ventilated room V, (m3). When correct organized ventilation the air exchange rate should be significantly greater than unity. In a normal microclimate and the absence of harmful emissions, the amount of air for general ventilation is used depending on the volume of the room per worker. The absence of harmful secretions is the amount of them in technological equipment, with the simultaneous release of which in the air of the room the concentration of harmful substances will not exceed the maximum permissible. In industrial premises with a volume of air for each worker Un1< 20 м3 расход воздуха на одного работающего bx
must be at least 30 m3/h. In a room with Ki1 = 20-40 m3I, > 20 m2/h. In rooms with UpH
> 40 m3 and if available natural ventilation air exchange is not calculated. In the absence of natural ventilation (sealed cabins), the air flow per worker must be at least 60 m3/h. Necessary air exchange for everything production premises generally equal Where P
- the number of workers in this room. When determining the required air exchange to combat excess heat, a balance of sensible heat of the room is drawn up, based on which the volume of air for excess heat is calculated D<2из6: where rdr is the density of the supply air, kg/m; £ух, £р - temperature of outgoing and supply air, °С; ср - specific heat capacity, kJ/kg-m3; where bvr is the intensity of formation of harmful substances, mg/h; StsdK, S"r
- concentrations of harmful substances within the maximum permissible concentration and in the supply air. The concentration of harmful substances in the supply air should be as minimal as possible and not exceed 30% of the maximum permissible concentration. The necessary air exchange to remove excess moisture is determined based on the material moisture balance and in the absence of local suction in the production area according to the formula where (gvp is the amount of water vapor released into the room, g/h; p"p is the density of the air entering the room, kg/m; yuh is the permissible content of water vapor in the air of the room at standard temperature and relative humidity, g/ kg; s!pr
- moisture content of supply air, g/kg. When harmful substances that do not have a unidirectional effect on the human body, for example, heat and moisture, are simultaneously released into the work area, the necessary air exchange is assessed by the largest amount of air obtained in calculations for each type of emissions produced. When several harmful substances of unidirectional action are simultaneously released into the air of the working area (sulfur and sulfur dioxide; nitrogen oxides together with carbon monoxide, etc., see CH 245-71), the calculation of general ventilation should be made by summing the volumes of air required to dilute each substance separately up to its conditional maximum permissible concentrations (C), taking into account air pollution by other substances. These concentrations are less than the standard SPdK and are determined from the equation U "" <
1. By using local ventilation
the necessary meteorological parameters are created at individual workplaces. For example, capturing harmful substances directly at the source, ventilation of observation booths, etc. Local exhaust ventilation is the most widely used. The main method of combating harmful secretions is to design and organize suction from shelters. The designs of local suction can be completely closed, semi-open or open (Fig. 4.4). Closed suctions are the most effective. These include casings and chambers that hermetically or tightly cover technological equipment (Fig. 4.4, A).
If it is impossible to arrange such shelters, then exhaust systems with partial shelter or open ones are used: exhaust zones, suction panels, fume hoods, side exhausts, etc. One of the simplest types of local suction is an exhaust hood (Fig. 4.4, and).
It serves to trap harmful substances that have a lower density than the surrounding air. Umbrellas are installed above baths for various purposes, electric and induction furnaces, and above openings for releasing metal and slag from cupola furnaces. Umbrellas are made open on all sides and partially open on one, two and three sides. The efficiency of an exhaust hood depends on the size, height of the suspension and its opening angle. The larger the size and the lower the umbrella is installed above the place where substances are released, the more effective it is. The most uniform suction is ensured when the umbrella opening angle is at least 60°. Suction panels (Fig. 4.4, V)
used to remove secretions carried away by convective currents during manual operations such as electric welding, soldering, gas welding, metal cutting, etc. Fume hoods (Fig. 4.4, e) -
the most effective device compared to other suction systems, since it almost completely covers the source of the release of harmful substances. Only the service openings remain uncovered in the cabinets, through which air from the room enters the cabinet. The shape of the opening is chosen depending on the nature of the technological operations. The required air exchange in local exhaust ventilation devices is calculated based on the localization conditions of impurities released from the source of formation. The required hourly volume of sucked air is determined as the product of the area of the suction intake openings P (m2) and the air speed in them. Air speed in the suction opening Rice. 4.4.
A
- shelter box; b -
onboard suctions (1 -
single-sided, 2 -
double-sided); V -
side blowjobs (1 -
unilateral, 2 -
angular); G -
suction from work tables; d -
stained glass type suction; e
- fume hoods (1st
upper suction, 2nd
bottom suction, 3 -
with combined suction); and -
exhaust hoods (1 -
straight, 2 -
inclined) V
(m/s) depends on the hazard class of the substance and the type of local ventilation air intake (g) =
0.5^-5 m/s). Mixed ventilation system
is a combination of elements of local and general ventilation. The local system removes harmful substances from machine covers and covers. However, some harmful substances penetrate into the room through leaks in shelters. This part is removed by general ventilation. Emergency ventilation
is provided in those production premises in which a sudden release of a large amount of harmful or explosive substances into the air is possible. The performance of emergency ventilation is determined in accordance with the requirements of regulatory documents in the technological part of the project. If such documents are missing, then the performance of emergency ventilation is accepted such that it, together with the main ventilation, is turned on automatically when the maximum permissible concentration of harmful emissions is reached or when one of the general or local ventilation systems is stopped. The release of air from emergency systems must be carried out taking into account the possibility of maximum dispersion of harmful and explosive substances in the atmosphere. To create optimal meteorological conditions in industrial premises, the most advanced type of industrial ventilation is used - air conditioning. Air conditioning is its automatic processing in order to maintain predetermined meteorological conditions in industrial premises, regardless of changes in external conditions and indoor conditions. When air conditioning, the air temperature, its relative humidity and the rate of supply to the room are automatically adjusted depending on the time of year, external meteorological conditions and the nature of the technological process in the room. Such strictly defined air parameters are created in special installations called air conditioners. In some cases, in addition to ensuring sanitary standards for the air microclimate, air conditioners undergo special treatment: ionization, deodorization, ozonation, etc. Air conditioners can be local (to serve individual rooms) and central (to serve several separate rooms). The circuit diagram of the air conditioner is shown in Fig. 4.5. The outside air is cleaned of dust in the filter 2
and enters chamber I, where it is mixed with air from the room (during recirculation). Having passed through the stage of preliminary temperature treatment 4,
the air enters chamber II, where it undergoes special treatment (air washing with water, ensuring the specified parameters of relative humidity, and air purification), and into chamber III (temperature treatment). During temperature treatment in winter, the air is heated partly due to the temperature of the water entering the nozzles 5,
and partially, passing through heaters 4
And 7.
In summer, the air is cooled partially by the supply of chilled (artesian) water to chamber II and, mainly, as a result of the operation of special refrigeration machines. Air conditioning plays a significant role not only from the point of view of life safety, but is also necessary in many high-tech industries, so in recent years it has been increasingly used in industrial enterprises. The adverse effects of excess or lack of heat can be significantly reduced or eliminated by improving technical processes, using automation and mechanization, as well as using a number of sanitary, technical and organizational measures: localization of heat generation, thermal insulation of heating surfaces, shielding, air and water-air showering, air oases, air curtains, rational work and rest regime. In any case, measures must ensure irradiation in workplaces of no more than 350 W/m2 and equipment surface temperature of no higher than 308 K (35 °C) at a temperature inside the source of up to 373 K (100 °C) and not higher than 318 K (45 °C ) at temperatures inside the source above 373 K (100 °C). Rice. 4.5.
1 -
intake duct; 2 - filter; 3 -
connecting duct; 4 -
heater; 5 - air humidifier nozzles; 6 -
drip eliminator; 7 - second stage heater; 8 -
fan; 9 -
exhaust duct For non-fixed workplaces and outdoor work in cold climates, special rooms for heating are organized. Under unfavorable meteorological conditions (air temperature -10 °C and below), heating breaks of 10-15 minutes every hour are required. At outdoor temperatures (-30) - (-45) °C, 15-minute rest breaks are organized every 60 minutes from the start of the work shift and after lunch, and then every 45 minutes of work. It is necessary to provide the possibility of drinking hot tea in heating rooms. The optimal tool for ensuring standard cleanliness and the necessary required parameters of the air microclimate in the workplace is considered to be an industrial ventilation network, i.e. artificial and controlled, which aims to remove waste air mass from the working space and bring in fresh air. Industrial ventilation and air conditioning, BZD - the parameters of which are met in accordance with all standards, SNiP and occupational safety and health standards, creates conditions for the normal work of people, as well as the operation of equipment and tools. Depending on the method of movement and movement of air masses, ventilation networks in production can be grouped into two main classes: Organization of natural ventilation Provided that the movement of air flows will be carried out through door and window openings due to the pressure difference from outside and inside the operating room, we are talking about natural ventilation. This pressure difference is associated with different air densities, air temperatures, and the wind pressure that acts on the building. Natural, or as engineers say, unorganized ventilation is often determined by random, uncontrollable factors, such as: At the same time, unorganized ventilation, according to BZD standards, should reach 1-1.5 room volumes per hour. Such indicators are quite difficult to achieve using only natural air exchange channels. According to labor safety and safety standards, the speed of air flows with this type of ventilation should be 0.5-0.8 meters per second for the upper floor, and 1-1.5 meters per second for the lower level and exhaust shafts. Air movement For permanent (constant) exchange of air flow, which is necessary in accordance with the requirements and conditional parameters of the level of atmospheric cleanliness, it is necessary to install a mechanical ventilation network that has a number of advantages in comparison with the previous type, namely: Schematic diagram of mechanical ventilation Any equipment, engineering device or communications system, which may also include an air exchange system, is subject to certain requirements regarding life safety, occupational safety and health of personnel, and environmental protection. Accordingly, mechanical ventilation also has a number of requirements and standards, compliance with which is a critical condition for its organization. In an operating room where equipment is operating, it is natural for excess heat to develop. From this perspective, provided there are workplaces located non-fixed throughout the room, the volume of supplied air should be equal to the volume of exhausted air. The maximum permissible deviation from this norm is 10-15% of the total mass. To achieve such parameters, the flow speed must be quite high. This can be achieved by increasing the diameter of the duct and the spread between the inlet and outlet openings. Industrial ventilation wiring An important indicator of the air environment in a working or production space is also the presence of impurities in the atmosphere, both solid and gaseous. This can be either dust generated during production or harmful fumes - carbon dioxide or hydrogen sulfide.
It must be remembered that 60-70% of substances with a density higher than atmospheric are removed from the lower layers of the atmosphere of the room (i.e. such gases fall down) and only 30-40% - from the upper section. Conversely, humid air accumulates in the upper part of the room, while dry air falls down. The designer must take into account the specifics of production and arrange ventilation equipment and air ducts accordingly. Ventilation duct layout The optimal solution for such enterprises or buildings would be air supply network installations, which, as a rule, are equipped as follows: To calculate the required ventilation power in the presence of harmful factors, the maximum permissible concentrations of such substances must be determined, as well as the amount of air required for their dilution. An effective means of combating harmful fumes is the installation of local suction systems, such as casings, chambers, fume hoods, exhaust hoods and others. The power of such devices is determined by multiplying the area of the exhaust opening by the speed of movement (accepted according to reference tables, depending on the substance being removed). Exhaust hood To calculate the multiplicity required for a particular room, it is necessary to know the volume of the room, the number of people working in it, and the air exchange rate per person. As a rule, when organizing industrial ventilation in production, the air exchange rate per person is 60 m3/hour. If there is excess thermal radiation in the room, a more complex calculation formula is used, which also takes into account excess heat in kW, heat capacity in kg/0C, and input/output air temperature. In this case, the temperatures of external and internal air taken for such calculations are given in SNiP. At some enterprises, particularly hazardous and hazardous production facilities, emergency ventilation must also be installed in case of sudden emissions and for the purpose of their rapid removal. Such a system must provide at least 8 complete air changes in 1 hour. Emergency system fan An industrial air exchange system is often combined with an air conditioning system. The purpose of this is to create optimal climatic conditions required in accordance with the norms and regulations of the Belarusian Railways in the workplace, in an administrative building or production premises. The air conditioning system will, of course, regulate not only the temperature, but also the humidity of the air, ionize it, remove odors, saturate it with ozone, etc. It all depends on the needs and wishes of the client. When organizing industrial ventilation, local or central air conditioners, heaters (for heating air in winter), filters and other equipment are usually used, selected depending on the required network functions. Industrial air conditioning system Climate control and air ventilation are an important component not only in relation to life safety, but also in many production processes that require stable temperature conditions, humidity or dryness, and air saturation.
Ventilation called - organized air exchange, which involves removing polluted air from the working area and supplying fresh air into it. The classification of types of ventilation systems is based on the following main characteristics: By the method of air movement: natural or artificial ventilation system By purpose: supply or exhaust ventilation system By service area: local or general ventilation system By design: stacked or monoblock ventilation system Natural ventilation is created without the use of electrical equipment (fans, electric motors) and occurs due to natural factors - air temperature differences, pressure changes depending on height, wind pressure. The advantages of natural ventilation systems are low cost, ease of installation and reliability due to the absence of electrical equipment and moving parts The downside of the low cost of natural ventilation systems is the strong dependence of their effectiveness on external factors - air temperature, wind direction and speed, etc. Artificial or mechanical ventilation used where natural is not enough. Mechanical systems use equipment and devices (fans, filters, air heaters, etc.) to move, purify and heat air. Supply system ventilation serves to supply fresh air to the premises. If necessary, the supplied air is heated and cleaned of dust. Exhaust ventilation, on the contrary, removes polluted or heated air from the room. Typically, both supply and exhaust ventilation are installed in the room. Local ventilation designed to supply fresh air to certain places (local supply ventilation) or to remove contaminated air from places where harmful emissions are formed (local exhaust ventilation). General ventilation, unlike local, is designed to provide ventilation throughout the entire room. Stacked ventilation system assembled from individual components - fan, muffler, filter, automation system, etc. Such a system is usually located in a separate one. The advantage of typesetting systems is the ability to ventilate any premises - from small apartments and offices to supermarket sales areas and entire buildings. The disadvantage is the need for professional calculations and design, as well as large dimensions. In a monoblock system ventilation, all components are housed in a single sound-insulated housing. Monoblock systems come in supply and supply and exhaust systems. Supply and exhaust monoblock units can have a built-in recuperator to save energy. Design features of the local ventilation system Ventilation systems have an extensive network of air ducts to move air ( duct systems), or channels (air ducts) may be absent, for example, during aeration - natural ventilation, saturation with air, oxygen (organized natural air exchange), when installing fans in the wall, in the ceiling, etc. ( ductless systems).
Natural ventilation
Mechanical ventilation
BZD parameters of mechanical ventilation
Excess heat
Concentration of harmful impurities
MPC of pollutants
Air exchange rate
Emergency ventilation
Air conditioning
Basics of operation of the supply and exhaust system
(1 ratings, on average: 5,00 out of 5) 
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