Ventilation and air conditioning system in the workshop. Industrial premises ventilation systems: exhaust, local, natural

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, in the workshops and offices of the enterprise, they create a comfortable air environment that meets regulatory requirements.

It is difficult to overestimate the role of an effective ventilation system. After all, you must admit that only in conditions of clean air, normal temperature and humidity conditions, it is possible to achieve an increase in labor productivity.

To understand how to organize sufficient air exchange in a building, it is necessary to understand the types and features of the operation of different ventilation systems.

We will describe how natural and mechanical ventilation functions, describe how to arrange local ventilation of the working area, and also explain the principles for calculating air exchange.

In case of need for active and reliable air exchange, they are used. In order to somehow protect slightly polluted premises from neighboring workshops with a high level of pollution, a slight pressure is created in the system.

The air exchange scheme at the enterprise is mounted on the basis of calculations. Their accuracy is the key to the competent and efficient functioning of the system.

At the stage of design work on the creation of a supply and exhaust ventilation system, the air flow is calculated, for which the following formula is used:

Lots = 3600FWо, 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 at different heights. The main thing is that polluted air flows do not change their natural trajectory. Emissions, which have a specific gravity greater than that of air, are always in the lower zone, so it is also necessary to place devices for their intake there.

In the autumn-winter period, the air supplied to the room must be heated. To reduce costs, they use, which provides for heating a part of the purified air and returning it to the room.

If there are no air ducts, then the system is called ductless. In this case, ventilation equipment is mounted directly in the wall or in the ceiling. The main condition is the presence of natural ventilation.

The possibility of emissions with a high degree of explosiveness in the room does not allow mounting ventilation equipment on air ducts, therefore, in these cases, ejectors are used.

Supply general exchange artificial ventilation system is often connected to central heating. Outside the building, air inlets are organized for the supply of fresh air.

Mines 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 located at a distance of at least 2 m from the ground, and if the production is located in a green zone, the minimum allowable distance from ground level to the lowest point of the opening should be 1 m.

The principle of operation of general exchange ventilation is simple:

• the fan sucks in air masses through the heater;
• the air is heated and humidified;
• air flows into the building through special ventilation ducts.

The volume of incoming air is coordinated by valves or dampers designed for this purpose.

Concentrated vapors, 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 exchange artificial ventilation of the supply and exhaust type is open and closed. In the first case, these are 2 independent systems, one of which pumps air, and the second simultaneously removes the previously neutralized waste.

These systems are suitable for workshops where substances of 1-2 hazard classes are emitted, 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 of it. They make it basically exhaust. For rooms 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 EMP. In the workshops of category C, D, D, the presence of a natural induction of ventilation is permissible if the productivity is ensured under the most adverse weather conditions.

Grilles and branch pipes of the emergency ventilation system are located in places with the highest concentration of hazardous substances.

Umbrellas should not be installed on emergency ventilation pipes and shafts. The holes themselves are unacceptable to be placed where people are constantly located. 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 working in production, the longer the evacuation process takes.

Forced emergency ventilation is installed in workshops where, in the event of an emergency, vapors or gases that are lighter than air will be released. Switching to emergency ventilation should occur automatically as soon as the normal system fails.

Local ventilation of premises

Local exhaust eliminates the exhaust air in places where it is polluted. The set of industrial hoods includes exhaust fans, pipelines, ventilation grilles.

Local ventilation designed to remove substances belonging to hazard classes 1 and 2 from 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 exhausts are equipped with automatic equipment. Such ventilation is divided into 2 types - supply and exhaust. The supply type of ventilation is performed in the form of thermal curtains, air showers.

Air curtains

Apertures 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, arrange air curtains. They act as a barrier to cold or very hot 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 fall below the mark:

• 14°C- during the performance of work that does not require great physical effort;
• 12°C- when the work is classified as moderate;
• 8°С- when doing hard work.

If workplaces are located near gates and technological openings, screens or partitions are installed. The air-thermal curtain near the doors facing the outside must consist of air with a maximum temperature of 50°C, and at the gate - no more than 70°C.

Local extraction using special suction

The local exhaust system, using special suction, first captures and then removes impurities harmful to health in the form of gases, smoke and dust.

This is a kind of air shower, the task of which is to pump fresh air at a fixed place and lower the temperature in the inflow zone. 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 melting furnaces.

There are such installations both stationary and mobile. They must provide a blowing speed of 1 to 3.5 m/s.

There is 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 facility.

The 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 jet of air is directed to the workplaces

If the local suction device is brought closer to the place of release of substances that pollute 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 emitted as a result of production activities, then the amount of air required for ventilation is calculated by the formula:

L \u003d N x Ln, where

N is the number of people usually in the room, Ln- the volume of air required for 1 person, measured in mᶾ / h. Normally, this is from 20 to 60 mᶾ / h.

Using such a parameter as the air exchange rate, the calculation is performed according to the formula:

L = n x S x H, where

n- the frequency of air exchange in the room (for the production room n=2), S- floor area in m², and H- its height in m.

Conclusions and useful video on the topic

Here is everything 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, an optimal microclimate for health will be maintained at the production site.

Do you have something to add, or do you have any questions about the organization of ventilation of industrial buildings? Please leave comments on the post. The contact form is in the bottom block.

Ventilation in the production shop is a complex set of interrelated processes and devices, aimed at creating high-quality air exchange inside the production room.

The shop floor ventilation system plays a much more important role than a similar system in any other room. The main emphasis is that this is a whole system of engineering developments, which is designed to ensure uninterrupted air filtration from harmful and toxic impurities and its functional circulation, without disturbing the course of technological processes, but contributing to favorable conditions for their successful implementation.

Types of ventilation of industrial shops

Depending on the method of air movement, ventilation of production workshops can be:

• natural;
• mechanical.
  

In the first case, air exchange occurs due to the temperature difference and the difference in pressure of the air flows. This type of ventilation can be unorganized (based on elementary physical phenomena - for example, a draft) and organized (aeration). To do this, special structures are used (for example, boxes with barriers), which allow you to adjust the size and strength of the air flow.

Mechanical ventilation allows pre-treatment of supply air (cooling, heating, humidification) and filtration of polluted air before being released into the atmosphere.

* When creating a project for the ventilation of a workshop and determining the norms of air exchange for natural and mechanical ventilation, they are guided by SNiP 41-01-2003.

As an engineering and technological object, the ventilation of industrial workshops can be divided into 2 types, according to the method of organizing air exchange:

• local type;
• general type.

In the first case, the main task of local ventilation is the localization and subsequent removal of harmful and toxic substances and emissions, directly at the place of their occurrence. In practice, the source of pollution is covered from all sides by the so-called. shields, forming a kind of cap. Inside such a shelter, a vacuum occurs during the suction of air masses because the pressure inside is below atmospheric. This measure prevents the entry of harmful impurities into the room. The local ventilation system of the workshop is quite effective in purifying the air, and its organization is quite budgetary.

In cases where local ventilation cannot localize pollution sources in full, the general exchange type of ventilation is used. Its purpose is to comprehensively purify the air in all industrial premises (or a significant part of them), by diluting the concentration of harmful impurities, dust and dirt, thermal radiation, etc.

General exchange ventilation copes well with heat absorption and is mainly used in cases where there is no emission of harmful impurities into the atmosphere of industrial premises. If the specifics of production involve the release of gases, harmful vapors, carcinogens and dust, mixed ventilation is used: general exchange + local suction.

In some cases, enterprises whose production is associated with significant dust emission or the release of toxic impurities completely abandon general ventilation. This is explained by the fact that a powerful general exchange system can simply spread these hazards and dust throughout the workshop.

The key concept of building ventilation systems is to remove the maximum amount of harmful substances with the help of local suction (and this is the main basis on which industrial exhaust ventilation is built), and dilute the remaining impurities with fresh air, reducing their concentration to the maximum permissible level.

Classification of ventilation of industrial workshops according to the mode of action:

• forced ventilation of the workshop;
• exhaust ventilation of the workshop;
• supply and exhaust ventilation of the workshop.
  

Supply ventilation in the workshop Exhaust ventilation in the workshop

The supply ventilation system of the workshop is aimed at ensuring a free flow of fresh air in volumes that will be sufficient for the full functioning of the production. In supply-type systems, duct fans are mainly used, which take in air from the outside and then pass it through the heaters, where heating and humidification (if required) take place.

Such systems are able to fully ensure the forced flow of air masses into the workshop. At the same time, the air pressure increases in comparison with atmospheric pressure, which contributes to the natural (unorganized) extrusion of exhaust air into the street through slots, outlets or holes.

Local supply ventilation can be of several types and include equipment such as:

• air shower (clean air flow directed to the workplace: stationary and mobile)
• air and air-thermal curtains (with and without heating)
• oases (serve entire sections of the workshop, where air moves at a calculated speed and temperature)

The exhaust system removes polluted/humid/hot/toxic air, and its replacement with clean air occurs in an unorganized way - through window and door openings, etc. Such ventilation of the workshop is very relevant in technological processes that involve a large release of heat, moisture, harmful with a significant staff involved in the production of employees.

All types of exhaust ventilation units of production workshops consist of several components:

• suction (open type - consisting of a protective casing, exhaust hood, hinged telescopic / side suction, air inlets; or closed type - which include fume hoods (for industries with increased emission of toxic gases and toxic fumes), chambers, shelter boxes (for work with especially toxic and radioactive substances), cabins)
• fan (centrifugal or axial);
• exhaust channel;
• filter;
• duct

Supply and exhaust ventilation of the workshop removes dirty air while simultaneously supplying fresh air masses. Thread allocation can happen in 2 ways:

• by stirring;
• by displacement.

For the first option, high-speed diffusers are installed in the ceiling or wall space, through which outdoor air is forced into the room. Inside, it naturally mixes with waste and is removed through a diffuse valve.

In the second option, air distributors are installed at the floor level, through which a forced influx of fresh air occurs. Cool air is distributed at the bottom of the room, while warm air rises and is naturally forced out through the ventilation grilles.

Features of calculations and ventilation devices in workshops for various purposes

Designing the ventilation of a workshop is a complex engineering task, which requires careful calculations, which largely depend on its purpose.Industrial ventilation must remove all hazards, including hot air, explosive impurities and toxic emissions, water vapor - everything that is released during the production process by products, equipment and personnel.

The calculation of the ventilation system of the workshop is carried out separately for each type of pollution:

For excess heat:

Q \u003d Q u + (3.6V - cQu * (Tz - Tp) / c * (T 1 - T p), where

Q u(m 3) - the volume that is removed by local suction,

V(Watts) - the amount of heat that products or equipment emit,

With(kJ) - heat capacity indicator = 1.2 kJ (reference data),

Tz(°C) - t of polluted air discharged from the workplace,

T p(°C) - t supply air masses,

T 1- t of air removed by general-exchange ventilation.

For explosive or toxic production:

With such calculations, the key task is to dilute toxic emissions and fumes to the maximum permissible level.

Q = Qu + (M - Qu(Km - Kp)/(Ku - Kp), where

M(mg * hour) - the mass of toxic substances released in one hour,

Km(mg / m 3) - the content of toxic substances in the air, removed by local systems,

K r(mg / m 3) - the number of toxic substances in the supply air masses,

K u(mg / m 3) - the content of toxic substances in the air, removed by general exchange systems.

Excess moisture:

Q \u003d Q u + (W - 1.2 (O m -O p) / (O1-Op)), where

W(mg * hour) - the amount of moisture that enters the workshop premises in 1 hour,

O m (gram * kg) - the volume of steam removed by local systems,

About r(gram * kg) - indicator of supply air humidity.,

About 1(gram * kg) - the amount of steam removed by the general exchange system.

From staff releases:

Q=N*m, where

N- number of employees,

m- air consumption based on 1 person * hour (according to SNiP it is 30 m 3 per person in a ventilated room, 60 m 3 - in an unventilated one).

Calculation of the exhaust ventilation of the workshop

The amount of exhaust air can be determined using the following formula:

L=3600*V*S, where

L (m 3)- air flow,

V- air flow rate in the exhaust device,

S- the area of ​​​​the opening of the exhaust type installation.

Features of ventilation of shops of various directions

Machine shop ventilation

Hazards: thermal emissions from electric motors, personnel, vapors of aerosols and coolants, oils, emulsions, dust - emery and mechanical.

Local suction: over grinding/grinding machines, machines without cooling, emulsion tanks, baths for washing parts.

General exchange: air flow from above; calculation of air by excess moisture and heat - at least 30 m 3 per 1 person.

Hazards: heat from presses, solvent vapors, glue, woodworking waste - dust, shavings, sawdust

Heating: air, combined with a ventilation system

Local suctions: floor and underground for wood waste, suction from machine tools; air purification occurs in bag filters, cyclones

General exchange: dispersed air inflow to the upper zone, through perforated type air ducts (mainly)

Hazards: evaporation of alkalis, acids, electrolytes, excess heat and moisture, dust, hydrogen cyanide

Heating: air, combined with a ventilation system

Local suctions: onboard for baths, independent exhaust systems above baths with cyanide and acid solutions, explosion-proof fans, mandatory equipment of suctions for acid baths of various types with standby fans. Mandatory filtration of exhausted air masses

General exchange: air ducts made of anti-corrosion materials or mandatory anti-corrosion coating of all air ducts; supply of 5% of the inflow to all adjacent premises; 3-fold air exchange in the compartments for the preparation of solutions and cyanide salts. Mandatory filtration of the extracted air masses.

Hazards: fluorine compounds, oxides of nitrogen, carbon, ozone

Heating: air, combined with a ventilation system

Local suctions: desirable (if possible)

General exchange: extract: 2/3 from the lower zone, 1/3 from the upper zone. Calculation of air for dilution of harmful emissions from welding to the maximum permissible level.

The calculation is based on the weight of the welding electrodes, which are consumed in 1 hour: for manual welding - 1500-4500 m 3 * h per 1 kg. electrodes, 1700-2000 m 3 * h for semi-automatic carbon dioxide, 2500-5400 m 3 * h - for welding using flux-cored wire.

Painting shop ventilation

Hazards : solvent/thinner fumes, paint particles

Heating: central or air, which is combined with ventilation

Local suction: at degreasing units, painting booths, jet dousing plants, drying booths, tables, stands, dipping baths.

General exchange: inflow to compensate for local exhaust + 1 fold, general exchange exhaust ventilation at least 1 fold from the upper zone.

Ventilation in foundries

The main task of ventilation of the foundry is to cope with the huge amount of heat that is released into the production rooms.

Hazards: radiant heat, a huge amount of heat, ammonia, sulfur dioxide, carbon monoxide

Heating: together with the ventilation system

Local suction : for almost all types of hot shop equipment

General exchange exhaust with mechanical stimulation in the upper area of ​​the workshop + aeration + dusting of workplaces + general exchange supply ventilation.

The creation and design of ventilation in production workshops for any purpose is entrusted exclusively to professionals who will ensure compliance with all necessary standards and perform calculations, taking into account the characteristics of your production.

Ventilation plays an important role in production. The system is a set of measures, technical means and organization of its optimal installation and operation.

Purpose of the system:

• Creation and support of air exchange
• Movement of air currents
• Removal of dust, excess heat, harmful gases
• Formation of a suitable microclimate

The appropriate working conditions of workers and the serviceability of mechanisms and equipment depend on the proper ventilation of industrial places.

Types of industrial ventilation

Air exchange in industrial places can be carried out in different ways. Depending on the organization of the device, there are three types of industrial ventilation:

1. Natural
2. Mechanical (artificial)
3. mixed

Each type has its own characteristics and disadvantages, which should be taken into account when organizing the system in production.

Natural ventilation in production

The natural system operates due to the physical properties of fluctuations in pressure and temperature of the air in the room and outside.

It differs in turn:

• Organized
• unorganized

Disorganized is considered when the air enters the room through leaky gaps in the building structure, if there are no equipped devices for ventilation.

Organized ventilation system for industrial premises carried out by means of exhaust shafts, channels, vents, etc., with which you can control the amount and strength of the incoming air flow. Above the shafts of ventilation systems, an umbrella or a special device, a deflector, is often installed to increase traction.

Ventilation created artificially (mechanical) in production

This type provides the intake and removal of air flows with the help of fans. The organization of a mechanical system requires the investment of large energy resources and economic costs. Despite this, it has several advantages:

• Allows air to be taken from the desired location
• It is possible to influence the physical properties: cool or heat the air flow, increase or decrease the humidity level
• It is possible to supply air directly to the workplace or exhaust with subsequent filtration

Purification of polluted air from the premises, a prerequisite for production. This factor is under strict control of environmental organizations.

The mechanical system, depending on the design, goals, and tasks assigned to it, differs:

1. Supply
2. exhaust
3. Supply and exhaust

In production places, the air system is selected based on the needs and specifics of the place of operation.

Supply ventilation in production

Designed to supply the production area with clean air. Installed mainly in places with elevated operating temperatures and low concentrations of harmful substances. Unclean air is removed through the natural ventilation outlets (transoms, ventilation shafts) supported additionally by the air flow of the supply ventilation.

According to the type of device, the following air handling units are distinguished:

• Monoblock. These devices are easy to operate and maintain, but are expensive. During installation, the main unit is fixed, to which air ducts are connected and electrical power is connected.
• Typesetting. Devices require special skills to install, are relatively inexpensive in price.

With forced ventilation can influence the environment and subjected to the necessary processing: heat, dry, moisten, depending on the type of production.

Exhaust ventilation in production

It performs the functions opposite to supply ventilation. Exhaust ventilation system for industrial premises provides ventilation. In production, it is independently used for small movements of the air flow. Depending on the prevalence, exhaust ventilation is distinguished:

• General exchange. Air movement covers the volume of the entire room
• Local. Designed to remove air from a specific workplace

It is mainly installed in warehouses, utility rooms, in places where there is no high concentration of harmful gases and impurities. The inflow in this case comes by infiltration through the frame of the building, windows, transoms.

Supply and exhaust ventilation in industrial premises

The main task of the supply and exhaust system is providing production premises with fresh air flow and removal of treated, polluted air. This type of system is the most common in industries with increased requirements for air exchange. It is necessary to correctly calculate when installing flow-exhaust ventilation in production, so that air flows do not fall, unnecessarily, into adjacent rooms and are not removed from there.

Fresh air supply devices are located on the maintenance side of the equipment, so that harmful substances or warm vapors do not fall on personnel. Precise calculations are required for this type of installation.

How to calculate supply and exhaust ventilation

The first step in the design of supply and exhaust ventilation in industrial areas is to determine the source of harmful or hazardous substances. Next, it is calculated how much air needs to be removed from the room and the air inflow for the safe work of workers. Ideally, if there is no environmental pollution in the enterprise, then the required air flow is calculated:

Where:
L is the amount of air used;
N is the number of people working in the room;
M is the air consumed per person per hour.

The amount of air flow per person is regulated by sanitary standards and is: 60 m3 / h per person - not ventilated room, 30 m3 / h - ventilated room.

Individual substances have their own concentration standards in production. To ensure that the amount of harmful substances does not exceed the permissible values, a clean air flow is supplied to the production sites, which is calculated by the formula:

L \u003d Mv / (yom - yp),

Where:
L is the required amount of fresh air to supply m3/h;
Mv - harmful substances entering the room, mg/h;
ypom – specific contamination of the entire production area, mg/m3;
yp is the amount of this substance in the incoming air flow, mg/m3.

To create the correct air balance, it is necessary to take into account the amount of harmful substances and local suctions in order to accurately calculate how much fresh air should be supplied.

Requirements for the ventilation system in the workplace

The systems are regulated by special sanitary standards, which are disclosed in the SNiP "Ventilation of special and industrial buildings". Key points to highlight:

1. Installation in industrial places should be carried out in any production, regardless of the number of employees and pollution. This is necessary for safety reasons in the event of an accident or fire in order to be able to clean the required place
2. The system itself must not cause contamination. In new technologies, this is excluded. Requirements apply to older devices requiring replacement
3. The noise of the ventilation unit must comply with the norms and not increase the noise from the production
4. With the predominance of air pollution, the amount of exhaust air must be greater than the supply air. If the place is clean, then the situation should be the opposite, the inflow is larger, and the exhaust is smaller. This is necessary to avoid the ingress of polluted air flow into those adjacent to these places. In most other cases, it is necessary to maintain a balance between the inflow and removal of air.
5. According to the norms, not less than 30 m3 / h per person of fresh air, with increased areas of production sites, the amount of clean air supplied should be increased
6. The amount of incoming clean air per person must be sufficient. Calculations set the air flow rate and its mass. The following factors are taken into account: humidity, excess heat and environmental pollution. If several or all of the above factors are observed, then the amount of inflow is calculated by the superior value.
7. The device and type of system in each production are regulated by SNiP. Any system can be installed if the design is done in compliance with laws and regulations

Emergency ventilation in production

It is an independent installation, which is necessary to ensure safe working conditions in the workplace with the likelihood of the release of harmful and hazardous substances.

The emergency system device works only on the hood. This is necessary to avoid the entry of polluted air into different places.

Ventilation of industrial premises is a labor-intensive and energy-consuming process that requires specialized knowledge and skills. Regardless of the type and type of ventilation device in production, two main factors must be observed: correct design and functionality. Under these conditions, a correct and healthy microclimate is ensured.

Industrial ventilation is a set of measures aimed at organizing and maintaining stable air exchange in industrial premises. Operating equipment and production processes are often a source of airborne particles and toxic fumes, which can adversely affect human health. In addition, the lack of fresh air reduces productivity and the ability to endure physical activity.

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Solution

Ventilation of industrial facilities is essentially the supply of fresh air and the removal of exhaust air. And it includes a number of solutions.

The first stage is planning. And for this it is necessary to take into account several important conditions: the presence of harmful fumes in the premises, gas contamination and temperature conditions.

To solve the tasks set, it is necessary to take into account the necessary working conditions, as well as build on the parameters of the room and its technical characteristics.

Most often, in large rooms, supply and exhaust ventilation with air cooling or heating is used.

Currently, there are many ventilation systems that differ in functionality and cost. Often this is a specific solution for each individual room. It is thanks to this that we get an efficient, economical, and ideally coping with the tasks set. It should be understood that the ventilation system is a very complex mechanism that not only provides clean and fresh air in the room, and therefore high performance of not only equipment, but also employees, as well as their well-being, and also allows you to control many parameters to create optimal climatic conditions depending on the time or part of the room. The ventilation system can be controlled mechanically or electronically, but mixed types are also possible.

The task of industrial ventilation

The main task of industrial ventilation is to ensure the constant presence of clean air in the premises (without impurities, odor and harmful components). This is ensured in 2 ways: by removing polluted air masses from the workshops and by providing an influx of fresh air. The second task is to maintain a certain microclimate. This includes temperature and humidity requirements. These requirements are especially relevant for industries accompanied by a large release of heat, moisture and harmful fumes.

A professionally designed ventilation system contributes to the following benefits:

• staff get sick less
• labor productivity increases
• a favorable microclimate is maintained
• moisture does not accumulate on the equipment, the metal does not oxidize or corrode
• compliance with the requirements for production processes.

Exhaust aeration in production

Air ducts are mainly used for ventilation of local spaces inaccessible to infiltration flows. The movement and distribution of air occurs without external coercion, only under the influence of temperature differences and atmospheric pressure outside and inside the room. To increase the efficiency of aeration, deflectors are installed at the outlet, special expansion nozzles that draw the exhaust air out of the room. This is also facilitated by window transoms and ajar skylights.

In the summer, the role of supply air channels is performed by open gates, openings in the outer walls and doors. In the cold season, in warehouses up to 6 meters high, only openings are opened at a height of at least 3 meters from the zero mark. With a height of more than 6 meters, the bottom of the ventilation openings is designed at a distance of 4 meters from the floor level. All openings are equipped with water-repellent visors, which, moreover, deflect the supply air jets upwards.

Supply and exhaust aeration

Extraction of polluted air occurs due to transoms and ventilation shafts. Transoms act as a kind of thermal damper, the opening and closing of which regulates the air pressure in the ventilation streams. As an additional pressure regulator, special holes are designed, equipped with louvered doors:

• slightly above floor level - stimulating air flow,
• just below the ceiling level - optimizing its outflow.

The volume of circulating air is proportional to the area of ​​open transoms, openings and vents.

Note

1. If the concentration of harmful substances in the outdoor air exceeds the maximum allowable limits by 30%, natural ventilation is not used.
2. The elements of the upper hood are installed approximately 10-15 degrees below the ridge on the roof. This reduces the risk of their destruction.

Design and installation

To ensure the highest quality ventilation, it is necessary to carry out its design and installation already at the construction stage. This is the only way to take into account all safety measures, to properly design exhaust zones.

But it also happens that it is necessary to install a ventilation system in an already built building. In this case, all the conditions in which the system will be operated, as well as the purpose of the room itself, should be taken into account. The choice of equipment always depends on the explosion and fire hazard of the room.

As is known, general exchange and local ventilation is used for industrial premises. The first is responsible for air exchange and air purification of the entire room. But with the help of local suctions, it is possible to solve only local problems at the place of formation of those very harmful substances. But it is not possible to keep and neutralize such air flows completely, preventing their spread throughout the room. Here additional elements are needed, such as umbrellas.

The choice of equipment for the installation of ventilation of industrial premises is influenced by the type of production and the amount of harmful substances emitted, the parameters of the premises itself, and the design temperature for the cold and warm seasons.

Summing up, I would like to say that such a difficult task as the calculation, design and subsequent installation of ventilation should be performed by qualified specialists who have a wealth of knowledge and years of experience behind them.

Classification of industrial ventilation by type of action

There are different types industrial ventilation. They are classified according to the following parameters:

• the method of organizing the inflow and outflow of air masses (natural, forced);
• by functionality (supply, exhaust, supply and exhaust);
• method of organization (local, general exchange);
• design features (channelless, channel).

The simplest and most cost-effective is natural ventilation. It is based on the laws of physics, when the warmer layers of air, rising up, displace the cold ones. The main disadvantage of such systems is the dependence of the time of year, weather conditions and a limited scope (suitable for a limited range of industries). To organize natural ventilation in production shops, 3 levels of adjustable openings (windows) are arranged. The first 2 are arranged at a height of 1-4 m from the floor, the 3rd level is under a stream or in a light-aeration lamp. Fresh air enters through the lower openings, and dirty air is forced out through the upper ones. The intensity of air exchange is regulated by opening/closing the vents. Natural ventilation can only be used for one-story buildings.

Forced ventilation- a more efficient system, including a set of equipment and engineering networks. However, you have to pay for efficiency, as it is associated with the purchase of expensive equipment and the consumption of a large amount of electricity.

Only supply or only exhaust ventilation is used extremely rarely (mainly in industries where air pollution is low). Much more common supply and exhaust systems providing more uniform air exchange.

General ventilation organized in large industries. Depending on production processes and air composition, it can be used in combination with other systems. local ventilation, unlike the general exchange, monitors the purity of the air in certain areas - for example, above the welding or painting area. This type is selected if the general exchange cannot cope with ventilation in all rooms.

What gives a combination of local exhaust and supply general exchange systems? Taking in polluted air, the exhaust system does not allow it to spread throughout the room, and the supply system provides an influx of fresh air (it can be equipped with filters and a heating system).

duct ventilation involves the organization of boxes or pipes of large cross-section, designed to transport air. Channelless systems - a set of fans and air conditioners built into the openings of walls or ceilings.

Design of ventilation of production shops

Design industrial ventilation systems has its own specifics. There is no universal equipment that can meet the needs of all types of industries. When designing, a lot of data is taken into account. The algorithm for solving the problem is as follows:

1. Calculation of the required air exchange.
2. Selection of equipment that supports the calculated parameters.
3. Calculation of air ducts.

At the first stage of design, a technical task (TOR) is developed. It is compiled by the customer and includes requirements for air parameters, features of technological processes, and system tasks.

• architectural plan of the object with reference to the area;
• construction drawings of the building, including a general view and sections;
• the number of employees in one shift;
• facility operation mode (one-shift, two-shift, round-the-clock);
• features of technological processes;
• potentially dangerous zones with reference to the plan;
• required air parameters (temperature, humidity) in winter and summer.

The calculation of the required air exchange is carried out in the following areas:

• supply of fresh air according to sanitary standards (according to the norms per person 20-60 m³ / h);
• heat assimilation;
• moisture assimilation;
• dilution of air to the maximum permissible concentrations of harmful substances.

The largest air exchange obtained as a result of the calculations described above is taken as the basis.

Using the emergency ventilation system

According to SNiP ("Ventilation of special and industrial buildings") in hazardous industries, it is necessary to provide emergency ventilation system. An emergency situation may arise in the event of an emergency release of explosive or toxic gases, a fire. It is a completely independent exhaust type installation and is calculated in such a way that when working with a conventional system, 8 air changes are provided in 1 hour.

Ventilation systems management

Automation control of ventilation systems allows you to optimize the process and reduce operating costs. This approach allows minimizing human participation in management and reducing the risk of the "human factor". Automatic control involves the installation of sensors that record the temperature / humidity of the air, the concentration of harmful substances, the degree of smoke or gas contamination. All sensors are connected to the control unit, which, thanks to the specified settings, turns the equipment on or off. Thus, automation helps to comply with the requirements of sanitary standards, quickly respond to emergencies and save significant money.

Ventilation systems are one of the main consumers of electrical and thermal energy, so the introduction of energy saving measures allows to reduce the cost of products. The most effective measures include the use air recovery systems, air recirculation and electric / motors with no "dead zones".

The principle of recuperation is based on the transfer of heat from the displaced air to a heat exchanger, which reduces heating costs. The most widespread recuperators are plate and rotary type, as well as installations with an intermediate coolant. The efficiency of this equipment reaches 60-85%.

The principle of recirculation is based on the reuse of air after it has been filtered. At the same time, part of the air from the outside is mixed in with it. This technology is used during the cold season in order to save heating costs. It is not used in hazardous industries, in the air environment of which there may be harmful substances of hazard classes 1, 2 and 3, pathogens, unpleasant odors, and where there is a high probability of emergency situations associated with a sharp increase in the concentration of flammable and explosive substances in the air. .

Given that most electric motors have a so-called "dead zone", their correct selection allows you to save energy. As a rule, "dead zones" appear during start-up, when the fan is running in idle mode, or when the mains resistance is much less than what is required for its correct operation. In order to avoid this phenomenon, motors with the possibility of smooth speed control and with no starting currents are used, which saves energy at start-up and during operation.

Optimal air parameters for some industrial premises according to the conditions of work or storage of materials

Type of production and premises	Temperature	Relative Humidity
Libraries, book depositories
Museum premises with exhibits made of wood, paper, parchment, leather
Studios of artists with paintings on easels
Warehouses of paintings in museums
Fur storage rooms
Leather storage rooms
Engineering enterprises
Metal Laboratories
Thermal constant rooms for precision work of various groups
Extra clean rooms for precision work:
Shop of precision engineering
Workshop for winding transformers and coils, assembling radio tubes
Workshop for the manufacture of electrical measuring instruments
Selenium and Copper Oxide Plate Processing Workshop
Optical glass melting shop
Lens grinding shop
Computer rooms with built-in fans:
Parameters of the air supplied inside the machines
Air parameters at the outlet of machines
Room air parameters
Hospitals
Surgical
Operating
Woodworking industry
Wood machining shop
Carpentry and Procurement Department
Workshop for making wooden models
Match production
Drying matches
Printing production
Sheet-fed offset printing workshop
Roll Paper Rotary Printing Workshop
Offset paper warehouse
Warehouse of coated paper in sheets
Rotary Roll Paper Warehouse
Workshops: bookbinding, drying, cutting, gluing paper
photographic production
Photographic film processing rooms
Film cutting department

The air environment inside industrial buildings is polluted much more intensively than in apartments and private houses. The types and amount of harmful emissions depend on many factors - the industry, 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 in an accessible language to state 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:

1. Collection of initial data - the characteristics of the structure, the number of workers and the severity of labor, the variety and amount of harmful substances formed, the localization of places of release. It is very useful to understand the essence of the technological process.
2. Choosing a ventilation system for a workshop or office, developing schemes. There are 3 main requirements for design solutions - efficiency, compliance with SNiP (SanPin) standards and economic feasibility.
3. Calculation of air exchange - determination of the volume of supply and exhaust air for each room.
4. Aerodynamic calculation of air ducts (if any), selection and placement of ventilation equipment. Refinement of schemes for supplying inflow and removal of polluted air.
5. 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 surveys are required. The design engineer constantly works in conjunction with the technologists of the enterprise.

We are interested in points No. 2 and 3 - the choice of the optimal air exchange scheme and the determination of air flow rates. Aerodynamics, installation of ventilation ducts and equipment are extensive topics of other publications.

Types of ventilation systems

To properly organize the renewal of the indoor air environment, you need to choose the best ventilation method or a combination of several options. The block diagram below shows a simplified classification of existing ventilation systems installed in production.

Let's explain each type of air exchange in more detail:

1. Unorganized natural ventilation includes ventilation and infiltration - the penetration of air through door porches and other gaps. Organized supply - aeration - is carried out from the windows by means of exhaust vents and skylights.
2. Auxiliary roof and ceiling fans increase the intensity of exchange during the natural movement of air masses.
3. The mechanical system implies the forced distribution and extraction of air by fans through air ducts. This also includes emergency ventilation and various local exhausts - umbrellas, panels, shelters, laboratory fume hoods.
4. Air conditioning - bringing the air environment of a workshop or office to the required condition. Before entering the working area, the air is cleaned by filters, / dried, heated or.

Heating / cooling of air with the help of heat exchangers - heaters

Reference. According to the regulatory documentation, the serviced (working) area includes the lower part of the workshop volume 2 meters high from the floor, where people are constantly located.

Often, mechanical supply ventilation is combined with air ventilation - in winter, the street flow is heated to the optimum temperature, water radiators are not installed. Polluted hot air is sent to the heat exchanger, where it gives off 50-70% of the heat to the inflow.

To achieve maximum efficiency at a moderate price of equipment allows a combination of these options. Example: in a welding shop, it is allowed to design natural aeration, provided that each post is equipped with a forced local exhaust.

Scheme of flow movement under 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. Documents have been developed separately for public buildings and various industries - metallurgical, chemical, catering and so on.

Example. When developing the ventilation of a hot welding shop, we find the document “Sanitary rules for 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 of industrial premises is selected depending on the purpose, economic feasibility and in accordance with applicable standards:

1. In office buildings, it is customary to do natural air exchange - aeration, ventilation. With an increased crowding of people, it is planned to install auxiliary fans or organize air exchange with mechanical stimulation.
2. In machine-building, repair and rolling shops of large sizes, it will 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, the upper windows (height - 4 m) swing open in winter, and the lower ones in summer.
3. When toxic, dangerous and unhealthy vapors are released, aeration and ventilation are not allowed.
4. At workplaces next to heated equipment, it is easier and more correct to organize the showering of people with fresh air than to constantly renew the entire volume of the workshop.
5. In small industries with a small number of sources of pollution, it is better to install local exhausts in the form of umbrellas or panels, and provide general ventilation with natural ventilation.
6. In industrial buildings with a large number of jobs and sources of harmful emissions, powerful forced air exchange should be done. It is not advisable to fence 50 or more local hoods, unless such events are dictated by the norms.
7. In laboratories and working rooms of chemical plants, all ventilation is mechanical, and recirculation is prohibited.

The project of general exchange forced ventilation of a three-story building with the use of a central air conditioner (longitudinal section)

Note. Recirculation - the return of part of the selected air back to the workshop in order to save heat (in summer - cold) spent on heating. After filtering, this part is mixed with the fresh street stream in various proportions.

Since it is unrealistic to consider all types of industries within the framework of one publication, we have outlined the general principles of air exchange planning. A more detailed description is presented in the relevant technical literature, for example, the textbook by O. D. Volkov “Designing the ventilation of 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 spot hoods are used in production, then the amount of air mixture removed by umbrellas is added to the resulting inflow volume.

For reference. Exhaust devices have very little effect on the movement of flows inside the building. Supply jets help to tell them the right direction.

According to SNiP, the calculation of the ventilation of the industrial premises is done according to the following indicators:

• excess heat emanating from heated equipment and products;
• water vapor saturating the shop air;
• harmful (toxic) emissions in the form of gases, dust and aerosols;
• the number of employees of the enterprise.

An important point. In utility and various household rooms, the regulatory framework also provides for the calculation of 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 a single fan. Dust collection with scrubber and additional filter

Ideally, the inflow rate is considered for all indicators. The largest of the obtained results is accepted for the subsequent development of the system. One caveat: if 2 types of dangerous gases are released that interact with each other, the inflow is calculated for each of them, and the results are summed up.

We calculate the consumption by heat release

Before undertaking calculations, it is necessary to carry out preparatory work to collect the initial data:

• find out the areas of all hot surfaces;
• find out the heating temperature;
• calculate the amount of heat released;
• determine the temperature of the air in the working area and beyond (above 2 m above the floors).

In practice, the task is solved together with the process engineer of the enterprise, who provides information about the production equipment, product characteristics and the intricacies of the manufacturing process. Knowing the specified parameters, perform the calculation according to the formula:

Explanation of designations:

· L - the desired volume of air supplied by supply units or penetrating through the transoms, m³ / h;

• Lwz is the amount of air taken from the serviced area by point suctions, m³/h;
• Q is the amount of heat release, W;
• c is the heat capacity of the air mixture, taken equal to 1.006 kJ/(kg °C);
• Tin is the temperature of the mixture supplied to the workshop;
• Tl, Twz - air temperatures above the working area and within it.

The calculation seems cumbersome, but if the data is available, it is performed without problems. Example: indoor heat flow Q is 20000 W, exhaust panels remove 2000 m³/h (Lwz) outdoor temperature + 20 °C, inside - plus 30 and 25 respectively. We consider: L \u003d 2000 + \u003d 8157 m³ / h.

Excess water vapor

The following formula practically repeats the previous one, only the heat parameters are replaced by humidity notation:

• W is the amount of water vapor coming from sources per unit of time, gram/hour;
• Din is the 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 rest of the designations are the same as in the previous formula.

The complexity of the technique lies in obtaining the initial data. When the facility is built and the production is running, it is not difficult to determine the humidity indicators. Another issue is to calculate the vapor emissions inside the workshop at the design stage. Development should be carried out by 2 specialists - a process engineer and a designer of ventilation systems.

Emissions of dust and harmful substances

In this case, it is important to study the subtleties of the technological process well. The task is to compile a list of hazards, determine their concentration and calculate the flow rate of supplied clean air. Calculation formula:

• Mpo is the mass of a harmful substance or dust emitted per unit of time, mg/hour;
• Qin is the content of this substance in the outdoor air, mg/m³;
• Qwz is the 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 rest of the workshop;
• the interpretation of the designations L and Lwz is given in the first formula.

The ventilation algorithm is as follows. A calculated amount of inflow is sent to the room, diluting the indoor air and lowering 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 applied to calculate the inflow to 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 to 1 workplace. In ventilated offices, the value of m is assumed to be 30 m³/h, in fully closed offices - 60 m³/h.

Comment. Only permanent jobs are taken into account, where employees stay at least 2 hours a day. The number of visitors does not matter.

Calculation of the local exhaust hood

The task of local suction is to remove harmful gas and dust at the stage of isolation, directly from the source. To achieve maximum efficiency, you need to choose the right size of the umbrella, depending on the dimensions of the source and the height of the suspension. It is more convenient to consider the calculation method with reference to the suction drawing.

Let's decipher the lettering in the diagram:

• A, B - the desired dimensions of the umbrella in terms of;
• h is the distance from the lower edge of the retractor to the surface of the ejection center;
• a, b - the dimensions of the overlapped equipment;
• D is the diameter of the ventilation duct;
• H - suspension height, taken 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 terms of simple formulas:

• F - the area of ​​​​the wide part of the umbrella, calculated as A x B;
• ʋ - air flow velocity in the duct section, for non-toxic gases and dust we take 0.15 ... 0.25 m / s.

Note. If it is necessary to suck out toxic hazards, the standards require an increase in the exhaust flow rate to 0.75 ... 1.05 m / s.

Knowing the amount of bleed air, it is not difficult to choose a duct fan of the required performance. The cross section and diameter of the exhaust duct is determined by the inverse formula:

Conclusion

Designing ventilation networks is the task of experienced engineers. Therefore, our publication is for informational purposes, 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 - a method for calculating air heating in the framework of the video.