There is no doubt about how important industrial ventilation is, since it is a mandatory factor for the safety and health of workers at work. Quite often on industrial enterprises people work with compounds, metals, and impurities that are harmful to health, and the ventilation system for such premises must be at a high level.
Types of ventilation systems in production
Of course, production facilities place not only high demands on ventilation. Given the large area and often difficult working conditions, ventilation of industrial premises is carried out in slightly different ways than for a residential building, for example.
You can select the following types industrial ventilation:
- Natural.
- Mechanical.
Depending on which circulation method is chosen for a given room, ventilation is divided into local and general exchange.
And the systems themselves for air ventilation in industrial premises are divided into:
- exhaust units - which forcefully remove large volumes of air from a workshop or any other room.
- air supply units - they, in turn, ensure uninterrupted supply fresh air into a ventilated room.
Production premises with natural ventilation
At the core natural ventilation air exchange is based on temperature differences. This indicator affects, first of all, the different specific gravity of the air, inside the production workshop and outside. The efficiency of such a system depends on the difference between these parameters. That is, the greater the difference in specific gravity and temperature, the greater the operating efficiency of this system.
This ventilation system can be organized or unorganized. In the first option, air volumes enter through gaps between windows or doors, as well as when opening vents or doors. The flow of fresh air is improved by installing special ventilation shafts, and the shafts or channels themselves are additionally equipped with special nozzles, they are also called deflectors.
This system, even of an organized type, can only be used in industrial buildings with a small area. It is most often used in agricultural workshops or farms.
In small workshops, natural ventilation is carried out by aeration. Calculation of the ventilation system for industrial premises when using this method consists of placing windows at a certain height, as well as special openings, the size of which depends on the size of the room itself.
For example, a small workshop in which ventilation will be carried out by aeration should be equipped with openings with special transoms. The openings themselves must be mounted in two levels. In this case, the height of the first level should vary from 1 to 1.5 meters from the floor, and the second level from 4 to 6 meters from the same floor.
The ceilings in the workshop should be equipped with transoms in the upper part, with so-called aeration lanterns with transoms that open to the required value.
This method is not applicable for production areas that contain harmful substances or exhaust gas vapors that pollute the atmosphere. Natural circulation does not provide for air purification, therefore, for such premises more complex ventilation systems must be installed with mandatory filters for air purification, both in the room and when leaving it.
Industrial premises with mechanical ventilation
Industrial ventilation carried out by this method has greater productivity compared to the natural method. In addition, special equipment is used here that cleans the air coming from outside from dust and dirt, and the exhaust air released into the atmosphere also necessarily passes through special system cleaning.
These systems are installed in such a way that they do not simply purify the air, but also prevent the release of harmful dust or vapors directly into the workroom itself.
Elements of installations with mechanical ventilation include air intakes. fans, ventilation ducts, filters for purifying the air from harmful impurities and, of course, a device for exhaust air outflow.
The systems are calculated in such a way that air from outside is supplied to the place highest concentration harmful substances. Most often, supply channels are made of ordinary steel. But if there are aggressive reagents in the work shop, for example, alkali vapor, then the installation of supply air ventilation ducts should only be made of stainless steel, ceramics or plastic.
During the cold season, large volumes of air entering workshops are usually heated using air heaters. At the same time, to prevent the air from becoming too dry due to heating, it is passed through special irrigation chambers. Passing through these devices, it is moistened with water or steam.
Recycling of industrial premises
Ventilation of industrial premises using this method is carried out through air circulation. When using this method, energy is saved, which is used to heat the air in the cold season. In this case, there is a continuous air circulation. The purified street air entering the room exits through a special installation, is cleaned and again enters the working room.
But the use of such a system also has its limitations. For example, using the recirculation method is prohibited in those workshops where the air may have unpleasant odors or a variety of microscopic fungi. If the work shop contains substances belonging to the 1st, 2nd or 3rd hazard class, the recirculation method is also prohibited.
Air conditioning of industrial premises
In this case, powerful systems are installed in production, which are configured specifically to create a favorable microclimate. The settings set the appropriate parameters for air temperature, humidity and indoor circulation. IN difficult conditions When working with materials of increased contamination or danger, additional requirements are put forward for installations, since they must provide additional ionization of the air and purification from bacteria.
In production, air conditioning is used mainly either to maintain the required humidity (when, for example, work is carried out on precision equipment) or to ensure certain sanitary conditions. As a rule, such capabilities are available only to air conditioning systems.
Ventilation systems for industrial premises based on air conditioning are divided into general and local. In general type systems, the installation is installed in a room specially allocated for it, and the inflow and outflow of air flows is carried out through air ducts. With the local type, the air conditioning unit is installed directly in the workshop, and ventilation is carried out without air ducts.
This method is the most expensive today, both in installation and maintenance. But this one best option when creating a climate in production premises required by hygienic standards.
It is worth noting that practice has shown that these installations pay for themselves over time, since the production environment creates exactly the right microclimate that helps improve staff performance. Improving working conditions affects not only well-being, but also productivity, which quite naturally becomes higher.
As statistics show today, in industries where premises have high level heat and gas emissions, more and more enterprises began to install these installations. Only powerful equipment can provide those comfortable working conditions in a difficult working environment.
Currently, special requirements are imposed on the ventilation of industrial premises: this includes ventilation equipment, ventilation ducts and shafts, and the efficiency of systems.
In relation to industry, ventilation of industrial premises is a set of measures, equipment and organization of its maintenance, pursuing the goals of maintaining stable air exchange and movement of air flows in the premises.
Ventilation systems are installed to maintain standard meteorological parameters in rooms of different functionality. The types of ventilation of industrial premises can be classified according to the following criteria:
- The method of organizing air exchange is natural and forced (mechanical) ventilation.
- Purpose: supply or exhaust ventilation.
- Service area: general exchange or local system.
- Structurally: ducted or ductless ventilation system.
Types of industrial ventilation
Such natural ventilation of industrial premises is based on natural air draft, the appearance of which is influenced by the following factors:
- The difference between outdoor air temperatures and indoor temperatures (aeration).
- The difference in atmospheric pressure between the lower level in the room and the hood, which is mounted on the roof.
- Wind speed and pressure.
Organizing the operation of natural ventilation of premises will not require significant investments in equipment. Installation of natural ventilation is the simplest of existing systems and does not require an electricity supply. Disadvantages: dependence on temperature, pressure, wind direction and speed. Accurate calculation of natural ventilation of industrial premises is made using the formulas:
Air flow exchange options
The current standards for ventilation of industrial premises are reflected in SNiP 41-01-2003 dated June 26, 2003. According to these requirements, general ventilation must ensure air exchange throughout the entire room. Properly installed general ventilation of industrial premises removes waste materials throughout the entire volume of the premises, and supply equipment supplies clean air back.
- Supply exchange of air masses
Assimilation of excess moisture, heat and dilution of harmful secretions and impurities are the tasks of forced-air general ventilation. All this allows you to comply with sanitary and hygienic regulations and standards for a comfortable stay at the work site.
If the room is cold, then general supply ventilation also solves the problems of mechanical stimulation, purification and heating of the supply air masses.
- General exchange hood
The simplest device for organizing general exchange exhaust system ventilation - a fan with air exhaust into the windows or into the exhaust duct. When the air duct length is more than 30-40 m and the pressure drop is more than 30-40 kg/m2 axial fan should be replaced with the central one. General ventilation systems for industrial premises often work in tandem with other ventilation systems (usually natural or mechanical ventilation), because due to the heterogeneity of harmful impurities and different conditions their education, the use of any one system is ineffective.
- Air ducts for ventilation of premises
The use of ventilation systems in some cases requires the presence of a network of air ducts, that is, duct systems, to effectively move air. If there are no ventilation ducts, such a system is called ductless. For example, a fan is installed in a ceiling or in a wall, if there is a natural ventilation system, etc. Any ventilation system has 4 main properties: functionality, volume of serviced areas, method of moving air masses and design.
The air inside industrial buildings is polluted much more intensively than in apartments and private houses. The types and amounts of harmful emissions depend on many factors - the industry of production, the type of raw materials, the technological equipment used, and so on. It is quite difficult to calculate and design ventilation of industrial premises that removes all harmful substances. We will try to present in accessible language the calculation methods prescribed in the regulatory documents.
Design algorithm
The organization of air exchange inside a public building or in production is carried out in several stages:
- Collection of initial data - characteristics of the structure, number of workers and severity of labor, types and quantities of hazardous substances generated, localization of release points. Very useful to get to the bottom of this technological process.
- Selecting a ventilation system for a workshop or office, developing diagrams. There are 3 main requirements for design solutions - efficiency, compliance with SNiP (SanPin) standards and economic feasibility.
- Calculation of air exchange – determination of the volume of supply and exhaust air for each room.
- Aerodynamic calculation of air ducts (if any), selection and placement of ventilation equipment. Clarification of supply and removal schemes for contaminated air.
- Installation of ventilation according to the project, start-up, further operation and maintenance.
Note. For a better understanding of the process, the list of works is greatly simplified. At all stages of documentation development, various approvals, clarifications and additional examinations are required. The design engineer constantly works in conjunction with the enterprise's technologists.
We are interested in points No. 2 and 3 - choosing the optimal air exchange scheme and determining air flow rates. Aerodynamics, installation of ventilation ducts and equipment are extensive topics in other publications.
Types of ventilation systems
To properly organize the renewal of the indoor air environment, you need to choose the optimal ventilation method or a combination of several options. The block diagram below shows a simplified classification of existing ventilation systems installed in production.
Let us explain each type of air exchange in more detail:
- Unorganized natural ventilation includes airing and infiltration - the penetration of air through doorways and other cracks. Organized supply - aeration - is carried out from windows using exhaust deflectors and skylights.
- Auxiliary roof and ceiling fans increase the intensity of exchange during the natural movement of air masses.
- The mechanical system involves the forced distribution and extraction of air by fans through air ducts. This also includes emergency ventilation and various local suction systems - umbrellas, panels, shelters, laboratory fume hoods.
- Air conditioning – bringing the air environment of a workshop or office to the required condition. Before being supplied to the work area, the air is purified by filters, / dehumidified, heated or.
Air heating/cooling using heat exchangers - air heaters Reference. According to regulatory documentation, the serviced (working) area includes bottom part the workshop volume is 2 meters high from the floor, where people are constantly present.
Often, mechanical supply ventilation is combined with air ventilation - in winter, the street flow is heated to the optimal temperature, water radiators are not installed. Contaminated hot air is sent to the recuperator, where it transfers 50-70% of the heat to the influent.
A combination of the above options allows you to achieve maximum operating efficiency at a reasonable price of equipment. Example: in a welding shop it is allowed to design natural aeration, provided that each station is equipped with forced local exhaust.
Scheme of flow movement during natural aeration Direct instructions for the development of air exchange schemes are given by sanitary and industry standards; there is no need to invent or invent anything. The documents were developed separately for public buildings and various industries - metallurgical, chemical, catering establishments and so on.
Example. When developing ventilation for a hot welding shop, we find the document “ Sanitary rules when welding, surfacing and cutting metals,” read section 3, paragraphs 41-60. It sets out all the requirements for local and general ventilation, depending on the number of workers and the consumption of materials.
Supply and exhaust ventilation industrial premises are selected depending on the purpose, economic feasibility and according to current regulations:
- In office buildings, it is customary to provide natural air exchange - aeration, ventilation. In case of increased crowding of people, it is planned to install auxiliary fans or organize air exchange with mechanical stimulation.
- In machine-building, repair and rolling shops large sizes it would be too expensive to arrange forced ventilation. The generally accepted scheme: natural exhaust through skylights or deflectors, the inflow is organized from openable transoms. Moreover, in winter the upper windows open (height - 4 m), in summer – the lower ones.
- If toxic, hazardous and harmful vapors are released, aeration and ventilation are not allowed.
- In workplaces near heated equipment, it is easier and more correct to organize the showering of people with fresh air than to constantly update the entire volume of the workshop.
- In small industries with a small number of sources of pollution, it is better to install local suction in the form of umbrellas or panels, and provide general ventilation with natural ventilation.
- In production buildings with a large number of workplaces and sources of harmful emissions, it is necessary to use powerful forced air exchange. It is not advisable to fence 50 or more local hoods, unless such measures are dictated by regulations.
- In laboratories and work areas of chemical plants, all ventilation is mechanical, and recirculation is prohibited.
General exchange project forced ventilation three-story building with central air conditioning (longitudinal section) Note. Recirculation is the return of part of the selected air back to the workshop in order to save heat (cold in summer) spent on heating. After filtering, this part is mixed with fresh street flow in various proportions.
Since it is unrealistic to consider all types of production within the framework of one publication, we have outlined general principles air exchange planning. More detailed description presented in the relevant technical literature, e.g. training manual O. D. Volkova “Design of ventilation for an industrial building.” The second reliable source is the ABOK engineers forum (http://forum.abok.ru).
Methods for calculating air exchange
The purpose of the calculations is to determine the flow rate of the supplied supply air. If point hoods are used in production, then the amount of air mixture removed by the umbrellas is added to the resulting volume of inflow.
For reference. Exhaust devices have very little effect on the movement of flows inside the building. Inflow jets help inform them in the right direction.
According to SNiP, calculation of ventilation of production premises is done according to the following indicators:
- excess heat emanating from heated equipment and products;
- water vapor saturating the workshop air;
- harmful (toxic) emissions in the form of gases, dust and aerosols;
- number of employees of the enterprise.
Important point. In utility rooms and various household rooms, the regulatory framework also provides for calculations based on the frequency of exchange. You can familiarize yourself with the methodology and use the online calculator.
An example of a local suction system operating from one fan. Dust collection is provided with a scrubber and an additional filter Ideally, the inflow flow rate is calculated according to all indicators. The largest of the obtained results is accepted for subsequent development of the system. One caveat: if 2 types of dangerous gases are released that interact with each other, the influx is calculated for each of them, and the results are summed up.
We calculate the consumption by heat releases
Before you take on the calculations, you need to carry out preparatory work for collecting initial data:
- find out the areas of all hot surfaces;
- find out the heating temperature;
- calculate the amount of heat released;
- determine the air temperature in the work area and outside it (above 2 m above the floors).
In practice, the problem is solved jointly with the enterprise’s process engineer, who provides information about production equipment, product characteristics and subtleties of the manufacturing process. Knowing the specified parameters, perform the calculation using the formula:
Explanation of symbols:
· L – the required volume of air supplied by air supply units or penetrating through transoms, m³/h;
- Lwz – amount of air taken from the serviced area by point suction, m³/h;
- Q – amount of heat release, W;
- c – heat capacity of the air mixture, taken equal to 1.006 kJ/(kg °C);
- Tin – temperature of the mixture supplied to the workshop;
- Tl, Twz – air temperatures are higher working area and within its limits.
The calculation seems cumbersome, but if you have the data, it can be done without problems. Example: the heat flow indoors Q is 20,000 W, the exhaust panels remove 2,000 m³/h (Lwz), the temperature outside is + 20 °C, inside – plus 30 and 25, respectively. We consider: L = 2000 + = 8157 m³/h.
Excess water vapor
The following formula practically repeats the previous one, only the heat parameters are replaced by humidity symbols:
- W – the amount of water vapor coming from sources per unit of time, grams/hour;
- Din – moisture content in the inflow, g/kg;
- Dwz, Dl – moisture content of the air in the working area and the upper part of the room, respectively;
- the remaining designations are as in the previous formula.
The complexity of the technique lies in obtaining the initial data. When the facility is built and production is running, humidity indicators are not difficult to determine. Another question is to calculate the vapor emissions inside the workshop at the design stage. The development should be carried out by 2 specialists - a process engineer and a ventilation system designer.
Emissions of dust and harmful substances
In this case, it is important to thoroughly study the intricacies of the technological process. The task is to compile a list of harmful substances, determine their concentration and calculate the flow rate of supplied clean air. Calculation formula:
- Mpo – mass of harmful substance or dust released per unit of time, mg/hour;
- Qin – content of this substance in street air, mg/m³;
- Qwz – maximum permissible concentration (MPC) of harmfulness in the volume of the serviced area, mg/m³;
- Ql is the concentration of aerosol or dust in the remaining part of the workshop;
- the decoding of the designations L and Lwz is given in the first formula.
The ventilation operation algorithm is as follows. A calculated amount of inflow is directed into the room, diluting the internal air and reducing the concentration of pollutants. The lion's share of harmful and volatile substances is drawn in by local umbrellas located above the sources; the mixture of gases is removed by mechanical exhaust.
Number of working people
The methodology is used to calculate the inflow into office and other public buildings where there are no industrial pollutants. You need to find out the number of permanent jobs (denoted by the Latin letter N) and use the formula:
Parameter m shows the volume of clean air mixture allocated per 1 workplace. In ventilated offices, the value of m is taken to be 30 m³/h, completely closed - 60 m³/h.
Comment. Only permanent workplaces where employees stay for at least 2 hours a day are taken into account. The number of visitors does not matter.
Calculation of local exhaust hood
The purpose of local suction is to remove harmful gas and dust at the extraction stage, directly from the source. To achieve maximum efficiency, you need to choose the right umbrella size depending on the dimensions of the source and the height of the suspension. It is more convenient to consider the calculation method in relation to the suction drawing.
Let's decipher letter designations on the diagram:
- A, B – the required dimensions of the umbrella in plan;
- h – distance from the lower edge of the retractor to the surface of the ejection source;
- a, b – dimensions of the equipment to be covered;
- D – diameter of the ventilation duct;
- H – suspension height, assumed to be no more than 1.8…2 m;
- α (alpha) – the opening angle of the umbrella, ideally does not exceed 60°.
First of all, we calculate the dimensions of the suction in plan using simple formulas:
- F – area of the wide part of the umbrella, calculated as A x B;
- ʋ — air flow speed in the duct, for non-toxic gases and dust we take 0.15...0.25 m/s.
Note. If it is necessary to suck out toxic pollutants, standards require increasing the exhaust flow speed to 0.75...1.05 m/s.
Knowing the amount of air taken out, it is not difficult to select a duct fan of the required performance. The cross-section and diameter of the exhaust air duct is determined by the inverse formula:
Conclusion
Designing ventilation networks is the task of experienced engineers. Therefore, our publication is for informational purposes only; the explanations and calculation algorithms are somewhat simplified. If you want to thoroughly understand the issues of ventilation of premises in production, we recommend that you study the relevant technical literature; there is no other way. Finally, the calculation method air heating as part of the video.
When installing ventilation systems in industrial buildings, it is necessary to take into account not only their features, but also their types. Ventilation in production has the following classification:
Supply;
- exhaust;
- local;
- general exchange;
- supply and exhaust;
- natural;
- mechanical.
Each type has its own distinctive features, advantages and disadvantages compared to others.
Supply ventilation
The system supplies clean air from outside in an organized manner. The mass escapes outward using pressure through cracks and openings in windows and doors. Supply ventilation can have a ducted air outlet, as well as a special valve. It prevents the spread unpleasant odor from other rooms and does not allow the contaminated composition to pass between neighboring rooms. The capacity can be 500 m3/h, which ensures fast air supply and replacement of the entire composition in a set time unit. Depending on the area of the room, you can select the required power of the device.Exhaust ventilation
Installing such a system allows you to thin the air even over a large area. It pulls out the contaminated composition, and instead it enters clean through the cracks, holes and window openings. The device helps remove exhaust air and all combustion products that arise during the operation of the enterprise. The performance of such a hood must be perfectly balanced to the volume of air in the room. Its main advantage is its widespread installation in industrial premises due to the simplicity of design and installation. One of the leaders in the production of fans is the VENTS plant.Supply and exhaust ventilation
The most popular type in enterprises. Combines everything best properties both systems, which allows you to achieve better results, quickly and effectively purify the air. This does not require additional installations and equipment, the purchase of which may affect costs. The peculiarity of the combined system is its functionality. It naturally attracts clean air and returns the contaminated air outside the building in the same organized manner.Local ventilation
The main purpose of the installation is local air supply. It also removes contaminated compounds from specific places of formation. the largest number harmful substances. The system is used in cases where it is possible to determine the location of contamination and prevent the spread of bacteria throughout the room. This type is used only in industrial enterprises.General ventilation
The use of this type involves uniform creation of air flow under the same environmental conditions. The air temperature, its humidity and the mobility of air masses must be the same throughout the entire volume of the room. The system is provided in case bacteria spread in space and there is no way to connect them all together. Usually installed when there is little air pollution, which allows you to quickly clean it.All types of ventilation have their advantages. They are quite simply mounted on the surface and are not difficult to maintain. The choice of system depends on its capacity, as this affects the level of performance and ensures clean air. Installing a ventilation system in production is an important stage in ensuring occupational safety and maintaining a comfortable and clean climate.
The main work performed by the ventilation of industrial premises is the removal of used air and the injection of fresh air. With its help, enterprises create a comfortable air environment in workshops and offices that meets regulatory requirements.
It is difficult to overestimate the role of an effective ventilation system. After all, you must agree that only in conditions of clean air, normal temperature and humidity conditions can an increase in labor productivity be achieved.
To understand how to organize sufficient air exchange in a building, it is necessary to understand the types and operating features of different ventilation systems.
We will tell you how natural and mechanical ventilation functions, describe methods for arranging local ventilation of the work area, and also explain the principles of calculating air exchange.
If there is a need for active and reliable air exchange, use. In order to somehow protect lightly contaminated premises from adjacent workshops with increased level contaminants in the system create a slight pressure.
The air exchange scheme at the enterprise is installed on the basis of calculations. Their accuracy is the key to competent and efficient functioning of the system.
At the stage design work To create a supply and exhaust ventilation system, air flow is calculated using the formula:
Lots = 3600FWo, Where
F– total area of openings in m², Wo- the average value of the speed at which air is drawn in. This parameter depends on the toxicity of the emissions and the type of operations performed.
Receiving exhaust devices can be located on different heights. The main thing is that polluted air flows do not change their natural trajectory. Emissions greater than air specific gravity, are always located in the lower zone, so devices for collecting them must be placed there.
In the autumn-winter period, the air supplied to the room must be heated. To reduce costs, it is used that involves heating part of the purified air and returning it to the room.
If there are no air ducts, the system is called ductless. In this case, ventilation equipment is mounted directly in the wall or ceiling. The main condition is the presence of natural ventilation.
The possibility of emissions with a high degree of explosion hazard appearing in the room does not allow the installation of ventilation equipment on air ducts, so in these cases ejectors are used.
The supply general exchange artificial ventilation system is often connected to central heating. Outside the building, air intakes are installed to supply fresh air.
The shafts are located above the roof and above the ground. The main thing is that there are no industries with harmful emissions near the receivers.
The air intake openings themselves must be at least 2 m away from the ground, and if the production is located in a green zone, the minimum permissible distance from the ground level to the bottom point of the opening should be 1 m.
The principle of operation of the general exchange supply ventilation simple:
- the fan sucks air masses through the heater;
- the air is heated and humidified;
- air flows enter the building through special ventilation ducts.
The volume of incoming air is coordinated by valves or dampers designed for this purpose.
Concentrated vapors and gases that general and local exhaust ventilation could not remove are diluted by the supply general exchange system. It also assimilates excess moisture and heat
General supply and exhaust artificial ventilation can be open or closed. In the first case, these are 2 independent systems, one of which pumps air, and the second, in parallel, removes previously neutralized waste.
These systems are suitable for workshops where substances of 1-2 hazard classes are released, and the production itself belongs to categories A, B, C.
In addition to working ventilation in potentially hazardous industrial premises, there must also be an emergency version. They make it mostly exhaust. For premises belonging to categories A, B, E, the system is equipped with a mechanical drive.
All elements of the system must comply with the requirements of the PUE. In workshops of categories B, D, D, the presence of natural ventilation is acceptable if productivity is ensured under the most unfavorable weather conditions.
Grilles and pipes of the emergency ventilation system are located in areas of the highest concentration of hazardous substances.
There is no need to install umbrellas on emergency ventilation pipes and shafts. The holes themselves should not be placed where people are constantly present. This will worsen the local microclimate.
The role of emergency ventilation is to reduce the saturation of emissions with harmful substances during the evacuation of workers from the workshop. The more people work in production, the longer the evacuation process takes
Supply emergency ventilation is installed in workshops where, in the event emergency, there will be a release of vapors or gases that are lighter than air. Switching to emergency ventilation should occur automatically as soon as the normal system fails.
Local ventilation of premises
Local exhaust eliminates exhaust air in places where it is polluted. The set of industrial hoods includes exhaust fans, pipelines, and ventilation grilles.
Local ventilation, designed to remove substances belonging to hazard classes 1 and 2 from the equipment, is arranged so that when the ventilation system is turned off, starting the equipment becomes impossible.
In some cases, backup fans are provided and local exhaust systems are equipped with automation. Such ventilation is divided into 2 types - supply and exhaust. The supply type of ventilation is performed in the form of thermal curtains and air showers.
Thermal curtains from the air
Openings that remain open for a long time (more than 40 m per shift) or open quite often (more than 5 times) contribute to hypothermia of people in the room. The operation of drying plants that emit pollution also leads to negative consequences.
In these cases, air curtains are installed. They act as a barrier against cold or very overheated air.
Air and air-thermal screens are designed so that in cold weather, when the openings are opened, the temperature in the workshops does not drop below the mark:
- 14°С- while performing work that does not require much physical effort;
- 12°С- when the work is classified as moderate;
- 8°С- when doing heavy work.
If workplaces are located close to gates and technological openings, screens or partitions are installed. The air-thermal curtain near doors facing outside should consist of air with a maximum temperature of 50°C, and at the gate - no more than 70°C.
Local exhaust using special suction
The local exhaust system, using special suction, first captures and then removes harmful impurities in the form of gases, smoke and dust.
This is peculiar air shower, whose task is to pump fresh air at a fixed location and lower the temperature in the inflow area. It is used in production, where workers are exposed to high temperatures and radiant energy with an intensity of more than 300 kcal/m² per hour emitted by heating and smelting furnaces.
There are such installations both stationary and mobile. They must provide a blowing speed from 1 to 3.5 m/s.
There is also such a thing as an air oasis, which is the same device included in the local ventilation system. It creates a microclimate with specified parameters in a certain part of the production room.
An air oasis creates improved conditions in the workplace and neutralizes exposure to harmful substances. Often these are separate cabins, but when their installation is not possible, a stream of air is directed to the workplaces
If the local suction device is brought directly to the place of release of substances polluting the space, it will be possible to remove air containing a higher percentage of them than with general-exchange ventilation. Local ventilation can significantly reduce air exchange.
Air exchange calculation
If no harmful substances are released as a result of production activities, then the amount of air required for ventilation is calculated using the formula:
L = N x Lн, Where
N is the number of people usually present in the room, Lн- the volume of air required for 1 person, measured in mᶾ/h. According to the norm, this is from 20 to 60 mᶾ/h.
Using a parameter such as air exchange rate, the calculation is performed using the formula:
L = n x S x H, Where
n- air exchange rate in the room (for production premises n=2), S- room area in m², and H- its height in m.
Conclusions and useful video on the topic
Here is all about the intricacies of various ventilation systems:
System installation details:
Whatever ventilation system is chosen, it must have two main properties: competent design and functionality. Only if these conditions are met will an optimal microclimate for health be maintained in production.
Do you have anything to add, or do you have any questions about organizing the ventilation of industrial buildings? Please leave comments on the post. The contact form is located in the lower block.