The main work that the ventilation of industrial premises performs is the removal of used air and the injection of fresh air. With its help, in the shops and offices of the enterprise create a comfortable air environment that meets regulatory requirements.
It is difficult to overestimate the role of an effective ventilation system. Indeed, you must agree that only in conditions of clean air, normal temperature and humidity conditions can you increase labor productivity.
To understand how to organize sufficient air exchange in a building, it is necessary to understand the types and features of various ventilation systems.
We will tell you how natural and mechanical ventilation works, describe the methods for arranging local ventilation of the working area, and also explain the principles of calculating air exchange.
Classification of ventilation systems
All existing ventilation systems are grouped by 4 signs:
- By the method of moving air ventilation is called: natural, mechanical or artificial, combined when both options are present at the same time.
- In the direction of air flow ventilation systems are divided into supply, exhaust or supply and exhaust.
- At the scene ventilation systems are combined into 3 groups: general exchange, local, combined.
- By appointment emit a working and emergency systems.
The basis for the design of ventilation for workplaces in production are the norms prescribed in SNiP 41-01-2003. Natural and mechanical air exchange operate according to different schemes.
While the processes that occur during natural ventilation depend on the heat and wind pressure and are practically not subject to man, forced air exchange is possible only with his active participation.
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Ventilation of industrial premises is a mandatory component of the equipment of workshops, focused on the specifics of production and its category for fire and explosion hazard
Production facilities are equipped with a mechanical or combined system. Air movement in them is stimulated by fans.
Fresh air is supplied to industrial plants through air ducts, which, in addition to fans, are equipped with heating and filtering devices
According to the prepared air supply schemes, the systems are divided into local and general. Local varieties are designed for a specific workplace.
Ventilation systems can work in tandem with air conditioning. When selecting equipment for power and functionality, this must be taken into account
In systems designed for processing industrial premises, fans are installed both in the supply and exhaust part, but they are involved only on one side: either to supply air or to exhaust
For the organization of ventilation, a wide range of steel elements is produced, from which the system is assembled as a children's designer
Elements for assembling air ducts, exhaust domes and umbrellas are made of plastic. The plastic variety is easier to install and operate, cheaper, more convenient to replace parts and upgrade
Production room ventilation
The mechanical version of the system
Ventilation ducts
Local production ventilation option
Ventilation operation paired with air conditioners
Supply and exhaust ventilation system
Galvanized steel system
Plastic type of ventilation
Scheme of natural air exchange
The ventilation of the premises, carried out in the first way, is nothing more than simple ventilation. It occurs without human intervention and is possible when the fences are not dense enough and allow air to enter the room both from the outside and from the inside.
The direction is influenced by pressure. If its indicators have a higher value from the outside, it opens the way for clean air to enter the room from the street. Otherwise, warm air from the room finds its way out. Often these processes occur in parallel.
A big plus of natural ventilation is that its installation does not require significant costs for either equipment or power supply. Of all the existing schemes, this is the simplest
Active natural ventilation occurs unorganized due to accidental circumstances. It is observed in conditions when the air temperature outside and inside the building are very different.
Contributes to this process and the emergence of individual sections with high and low pressure indicators from the side of the body, intensively blown by the wind and from its more protected side, respectively. In this situation, infiltration is observed - air enters the room from the windward side, and goes outside with the leeward.
The air exchange coefficient characterizing the intensity of the process, with a natural method of ventilation does not exceed 0.5.
Unorganized ventilation can not provide comfortable conditions for people in the production room and working equipment. Specially designed systems must be present here.
Natural ventilation of an organized form is realized by aeration or using deflectors. Both the supply and the removal of air from the room take place either through openings in the building envelope or through air vents. In channel ventilation, a deflector is necessarily present.
When they talk about ventilation in production, they mean not only equipment, but also its maintenance, and a whole range of measures related to creating a healthy microclimate
Natural ventilation using aeration
In workshops where the technology provides for the formation of heat in large quantities, aeration involves air exchange through light lamps and window openings under the influence of temperature and wind pressure. In cold shops, air assimilation occurs only under wind pressure.
When an aeration device is required, wind rose compulsory metering, otherwise harmful emissions from pipes of neighboring enterprises may get into the production room. Nothing should interfere with the release of vapors or harmful gases through the light lamps.
The best conditions for ventilation are created by the location of the structure on the windward side with respect to harmful production. Opening and closing transoms must be automated so that they can be controlled from below.
Their different location allows you to adjust the supply of fresh air. Aeration is a more suitable option for large-scale workshops in which it is not possible to use mechanical ventilation due to its high cost.
Using aeration in some cases, it turns out to organize, based on natural draft, efficient air exchange. For this purpose, light aeration lamps are installed.
The recommended height of the air supply to the room with this type of ventilation is a minimum of 0.3 and a maximum of 1.8 m in the warm period and at least 4 m in the cold. The best option is the air vents of a special design on 3 levels. When warm, fresh air passes through transoms located below, and dirty air leaves through the top.
The middle row of vents provides airflow at subzero temperatures. While the air mass reaches the floor level, it manages to warm up.
When it is necessary to remove a large volume of air, a significant deflector is required or several smaller ones equal to a larger one
In industrial buildings of small volumes, deflectors are installed on channels or pipes intended for drawing. With their help, exhaust air is removed from the workshops where there is a general exchange hood.
And also they are used for the removal of heated gases from furnaces, presses, and furnaces. When installed, they proceed from the trajectory of the prevailing air flow.
Artificial or mechanical ventilation
Being more perfect than natural, this type of ventilation requires significant financial and operational investments. In such a system, there may be devices not only purifying, but also ionizing, moisturizing, warming the air.
The mechanical ventilation scheme includes: air intake shaft (1), air heater (2), air supply (3), exhaust fan (4), exhaust duct air ducts (5), ventilation ducts (6), cyclone (7)
Mechanical ventilation can be either supply or exhaust or combined, that is, supply and exhaust.
Its advantages are obvious:
- clean air intake and its processing - heating, drying, moisturizing;
- air mass movement over significant distances;
- clean air delivery directly to the workplace;
- dirty air removal and its cleaning;
- work independence - the effectiveness of the system does not depend on environmental conditions.
Basically, exhaust and intake systems work together, but sometimes they recommend using only one of these two types.
The purpose of the supply ventilation is to provide the working room with air that has a beneficial effect on human health.
It is used where production processes are accompanied by large heat releases containing a small amount of harmful substances. Clean air coming in through the air ducts is distributed to workplaces through the use of distribution nozzles.
Systems that remove air from a room containing various pollutants are called exhaust systems. This type of air exchange is used in industrial premises where there are no harmful emissions and the minimum value of such a parameter as the rate of air exchange is not ruled out.
It can be warehouse, auxiliary, household premises. Air supply is provided by infiltration. The task of efficiently removing contaminated air and cleaning it is well managed by suction systems.
In case of need for an active and reliable air exchange, supply and exhaust ventilation is used. In order to somehow protect the slightly contaminated premises from the adjacent workshops with a high level of pollution in the system, a little pressure is created.
The air exchange scheme at the enterprise is mounted on the basis of calculations. Their accuracy is the key to the competent and effective functioning of the system
At the stage of design work on the creation of a supply and exhaust ventilation system, the air flow rate is calculated, for which the formula is used:
Lots = 3600FWwhere
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.
The exhaust hoods may be at different heights. The main thing is that polluted air currents do not change their natural trajectory. Emissions with a specific gravity higher than that of air are always in the lower zone, therefore, devices for their intake must be placed there.
In the autumn-winter period, the air supplied to the room must be heated. To reduce costs, recirculation is used, which involves heating part of the purified air and returning it to the room.
For the operation of the PVU with recovery, 2 rules must be observed:
- At least 10% of fresh air is supplied from the outside, and the content of contaminated impurities in the return air does not exceed 30% relative to the maximum permissible capacity.
- It is forbidden to use recirculation in production where explosive dust is present in the air mass, microorganisms that can cause various diseases, emissions related to hazard classes 1-3.
The choice of type of ventilation at the scene depends on the weight of the emissions, their concentration, temperature. Generalized ventilation allows you to divert the entire volume of dirty air, regardless of where it comes from.
Mechanical ventilation can be either general or local. The first one is channel and non-channel
The most widely used channel option. Here, for the advancement of air through special air ducts, an ejector installation is provided or a fan is used - axial or centrifugal type.
If there are no air ducts, then the system is called channelless. Ventilation equipment in this case is mounted directly in the wall or in the ceiling. The main condition is the presence of natural ventilation.
The possibility of the appearance of emissions with a high degree of explosion hazard in the room does not allow the installation of ventilation equipment on the air ducts, therefore, in these cases, ejectors are used.
The supply general ventilation artificial ventilation system is often connected to central heating. Outside the building, air intakes are organized for fresh air.
The mines are located above the roof and above the ground. The main thing is that there should be no production facilities with harmful emissions near the receivers.
The air sampling openings themselves should be at least 2 m from the ground, and if the production is located in the green zone, the minimum allowable distance from the ground level to the bottom of the opening should be 1 m.
The principle of operation of general exchange ventilation is simple:
- the fan draws in air masses through the air heater;
- the air heats and moistens;
- 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 the exhaust ventilation, general and local, were not able to remove, are diluted by the supply air general exchange system. It also assimilates excess moisture and heat.
General exchange artificial ventilation of 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 in parallel removes the 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 production facilities, an emergency version must also be present. They make it mainly 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 B, D, D, the presence of a natural ventilation motive is permissible if the performance is provided under the most adverse weather conditions.
The grilles and pipes of the emergency ventilation system are located in places of the highest concentration of hazardous substances.
There is no need to install umbrellas on pipes and shafts of emergency ventilation. The holes themselves should not 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 who work in production, the longer the evacuation process takes.
Supply emergency ventilation is installed in workshops where, in 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
Local exhaust eliminates the exhaust air in places where it is polluted. The set of production hoods includes exhaust fans, pipelines, ventilation grilles.
Local ventilation, designed to remove substances belonging to hazard classes 1 and 2 from the equipment, is arranged in such a way that when the ventilation system is turned off, equipment start-up becomes impossible.
In some cases, provide for redundant fans and supply local suction 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, air showers.
Thermal curtains from the air
Apertures that remain open for a long time (more than 40 m per shift) or open quite often (more than 5 times) contribute to the hypothermia of people in the room. The operation of drying plants emitting pollution leads to negative consequences.
In these cases, air curtains are arranged. They act as a barrier to cold or very superheated air.
Air and air-thermal screens are designed so that in cold weather when opening the openings, the temperature in the shops does not fall below the mark:
- 14 ° C - during the execution of work that does not require great physical effort;
- 12 ° C - when the work is classified as moderate;
- 8 ° C - when doing hard work.
If workplaces are close to gates and technological openings, screens or partitions are installed. The air-thermal curtain near the doors facing the 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 a kind of air shower, the task of which is to inject fresh air in 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, radiated by heating and melting furnaces.
There are such installations, both stationary and mobile. They must provide a blow rate of 1 to 3.5 m / s.
The use of an air shower is one of the ways to establish a thermal balance between a person and the environment in which he is forced to be
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 predetermined parameters in a certain part of the production room.
Purified air supplied to a given alienated zone is usually subjected to special heat and humidity treatment.
An air oasis creates improved conditions at the workplace and neutralizes the effects of harmful substances. Often these are separate cabins, but when their installation is not possible, a stream of air is sent to workplaces
If the local suction device is brought closer 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 ventilation of a general exchange type. Local ventilation can significantly reduce air exchange.
Air exchange calculation
If harmful substances are not released as a result of production activities, the amount of air required for ventilation is calculated by the formula:
L = N x Lnwhere
N Is the number of people who are usually indoors, Lн - the amount of air required for 1 person, measured in mᶾ / h. Normally, it is from 20 to 60 mᶾ / h.
Using a parameter such as air exchange rate, the calculation is performed according to the formula:
L = n x S x Hwhere
n - the rate of air exchange in the room (for the production room n = 2),S - area of the premises in m², and H - its height in m.
Here is all about the intricacies of all kinds of ventilation systems:
System Installation Details:
Whatever ventilation system is chosen, it must have two main properties: competent design and functionality. Only when these conditions are met at the factory will the microclimate optimal for health be maintained.
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