Ventilation of industrial premises: the types of air

The main work, which performs ventilation of industrial premises - removal of used air and injecting fresh. Using it in the shops and offices of the enterprise create a comfortable air environment, the relevant regulatory requirements.

To overestimate the role of an effective ventilation system is difficult. You must agree, only in clean air, normal temperature and humidity conditions can achieve greater productivity.

To understand how to arrange sufficient ventilation of the building, it is necessary to understand the types and the features of the different ventilation systems.

We will explain how the natural and mechanical ventilation, we describe how the local ventilation arrangement of the work area, as well as explain the principles of calculation of ventilation.

Classification of ventilation systems

All existing ventilation systems grouped according to 4 criteria:

1. By way of moving air called ventilation: natural, artificial or mechanical, combined, when simultaneously present both options.
2. In the direction of air flow ventilation systems are divided into supply, exhaust and air handling.
3. According to the site of action Ventilation systems are combined in 3 groups: general exchange, local, and combined.
4. by appointment allocate operating and emergency systems.

The basis for the design of ventilation for manufacturing jobs are norms prescribed in the SNIP 41-01-2003. Natural and mechanical ventilation work under different schemes.

While the processes occurring during natural ventilation depends on the thermal and wind pressure and almost are beyond man, then forced ventilation is possible only when it is active participation.

Scheme action of natural ventilation

Venting Improvement performing the first method, no other than the simple ventilation. It takes place without human intervention and possible when dense enough fences and passed into the air space from both outside and inside.

It exerts pressure on the direction of impact. If his figures have a higher value on the outside, it opens the way for the penetration of the clean air space from the street. Otherwise the warm air from the room is a way out to the outside. Often, these processes take place in parallel.

Active natural ventilation occurs disorganized due to accidental circumstances. It is observed in conditions where the temperature of the air outside and inside the building are very different.

It facilitates this process and the appearance of individual sections with high and too low indices pressure from the body rapidly and windy, with its more sheltered side respectively. In this scenario, there is infiltration - air into the room on the windward side, and goes out to leeward.

air coefficient characterizing the intensity of the process, with a natural ventilation method, does not exceed 0.5.

Comfortable conditions for people in the workplace and working equipment, unorganized ventilation can not provide. There must be present specially designed system.

Natural ventilation is organized by the type sold by aeration or by using deflectors. As the supply and removal of air from the room or going through openings in the building envelopes, or venting through. The ventilation channel is necessarily present deflector.

Natural ventilation using aeration

In the workshops, which provides heat generation technology in large quantities, aeration involves breathability, carried out through the skylights and window openings under the influence of temperature and wind pressure. The cold air shops assimilation occurs only under the pressure of the wind.

When the device requires aeration compulsory registration wind rose, or a production area may fall pipe emissions from neighboring enterprises. Nothing should not interfere with the vapor outlet and harmful gases through skylights.

The best conditions for ventilation creates a layout structure on the windward side with respect to the harmful production. Opening and closing the transoms should be automated, so that you can manage from the bottom.

Miscellaneous their location allows you to adjust the supply of fresh air. Aeration - a more suitable option for high-volume shops that do not have the possibility to apply mechanical ventilation due to its high cost.

The recommended height of the feed air into the room with this type of ventilation - at least 0.3 and at most 1.8 m in the warm season and at least 4 m in the cold. Optimal - special design of the vents on 3 levels. When warm, fresh air passes through the transom, which are at the bottom and dirty - goes through the top.

The average number of vent allows air flow at a negative temperature. For a time, until the air mass reaches the floor, it is time to warm up.

In industrial buildings of small volumes on the channels or tubes intended for drawing, install deflectors. They are removed via the exhaust air of the shops where there is a general exchange extractor.

As well as their use for removal of heated gases from the ovens, presses, horns. When installing them originate from the dominant airflow path.

Artificial or mechanical ventilation

Being more perfect than the natural, this type of ventilation requires considerable financial and operational investments. In such a system may be present device not only cleaning, but also ionizing, wetting, heats the air.

Mechanical ventilation is, that is, as the supply and exhaust plenum and exhaust or combined.

Its advantages are obvious:

• providing clean air intake and processing it - heating, drying, moistening;
• moving air mass significant distances;
• delivery of clean air directly to the workplace;
• removal of dirty air and its treatment;
• working independently - effectiveness of the system does not depend on the environmental conditions.

Basically, exhaust and supply systems work together, but sometimes it is recommended to use only one of these two species.

A task ventilation - ensure the supply of air of the working premises, has beneficial effects on human health.

Apply it where production processes are accompanied by large heat generation, containing a slight amount of harmful substances. Clean air entering the duct, by workplaces partitioned by use of distribution nozzles.

System, removing from the room air containing various polluting substances, called exhaust. This type of ventilation is used in industrial premises where there are no harmful emissions and it is possible minimum value of such a parameter as the ventilation rate.

This can be storage, auxiliary, amenity rooms. air flow is provided by infiltration. The task of efficient removal of polluted air and its purification cope well aspiration systems.

In the case of the need for an active and reliable air exchange used purge ventilation. In order to somehow protect malozagryaznennye premises from adjoining shops with elevated levels of contaminants in the system, create little pressure.

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

Lots = 3600FWowhere

F - the total area of ​​openings in m², Wo - the average value of the speed at which the air intake. This parameter depends on the toxicity of emissions and type of operations performed.

Adoptive suction devices may be at different heights. The main thing that contaminated air streams do not change their natural trajectory. Emissions that are larger than the specific gravity of the air, are always in the lower zone, so there it is necessary to place the device for their collection.

In autumn and winter the air supplied to the room should be heated. To reduce the cost of using recyclingProviding for display portion of the purified air and returns it into a room.

For SSP works with recovery must be respected 2 rules:

1. Outside enters at least 10% fresh air, and back to the air supply of contaminated impurities content does not exceed 30% relative to the maximum allowable capacity.
2. Recirculation is prohibited to use in manufacturing, where the air mass is present explosive dust, microorganisms which can cause various diseases, emissions related to the classes 1-3 danger.

The choice of the air at the place of action depends on the weight of emissions, their concentration, temperature. Generalized ventilation allows allocate the entire volume of dirty air no matter from what point he enters.

The most widely used version of the channel. Here, for the promotion of special air ducts provides for a ejector unit or involve fan - axial or centrifugal.

If the ducts are not available, then the system is called a channel-free. Ventilation equipment in this case is mounted directly to the wall or ceiling. The main condition - the presence of natural ventilation.

The possibility of emissions in a room with a high degree of explosion is not possible to mount on the air ducts for ventilation equipment, so in these cases the use of ejectors.

Ventilation general exchange artificial ventilation system is often connected to a central heating. Outside the building is organized air inlets for fresh air supply.

A mine on the roof and on the ground. The main thing that was not near the receiver manufactures with harmful emissions.

Sami air inlets must be at a distance from the ground at least 2 m, and if the production placed in the green zone - the minimum allowed distance from ground level to the bottom of the opening point should equal to 1 m.

The operating principle of dilution ventilation simple:

• fan sucks air mass through a heater;
• the air is heated and humidified;
• air flows into the interior of the building by a special air ducts.

The volume of incoming air to coordinate, provided for this purpose, valves or dampers.

General exchange forced ventilation supply and exhaust of the form is open and closed. In the first case two independent systems, one of which pumps air, and the second - parallel removes the spent pre-neutralized.

Suitable those systems for all facilities where the substance hazard classes 1-2, and the production itself are allocated refers to categories A, B, C.

Besides working ventilation in potentially hazardous production areas, should be present and alert her option. They do it mainly exhaust. For the facilities belonging to categories A, B, E, the system is provided with a mechanical drive.

All elements of the system must comply with the SAE requirements. In the shops of category B, C, D allowed the presence of a natural impulse ventilation, if performance is provided under the most adverse weather conditions.

Grating emergency ventilation tubes disposed in the field of the highest concentration of hazardous substances.

On pipes and shafts emergency ventilation, do not need to install umbrellas. Sami holes unacceptable place where people reside. This will worsen the local microclimate.

Ventilation emergency ventilation installed in shops, where in the case of an emergency, will release of vapors or gases, which are lighter than air. Switching to the emergency ventilation should take place automatically as soon as the system comes out with a conventional system.

Local ventilation of premises

Local exhaust removes stale air in places where it is pollution. The complete production of extracts consists of exhaust fans, piping, ventilation grilles.

Local ventilation intended for the removal of substances from the equipment belonging to the classes 1 and 2 danger, arrange so that when turned off the ventilation system equipment start getting impossible.

In some cases, provide redundant fans and provide local pumps automation. Divide adequate ventilation into 2 types - the supply and exhaust. Supply form venting operate as curtains, air showers.

Heat from the air curtain

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 people in the room. The negative consequences of job leads and dryers that emit pollution.

In these cases, arrange air curtains. They act as a barrier to cold or very superheated air.

Air and air-heat screen is designed so that in a cold temperature when opening the apertures in shops did not drop below:

• 14 ° C - during a job that does not require great physical effort;
• 12 ° C - when the operation is classified as moderate;
• 8 ° C - when performing heavy work.

If jobs are not far from the gate, and technological openings set screens or partitions. Air curtains near the door, facing outwards, must consist of air at a maximum temperature of 50 ° C, and the gate - not more than 70 ° C.

Local exhaust, using special suction

Local system using special stretching suctions first captures and then removes harmful impurities in the form of gases, fumes and dust.

This kind of air shower, whose task is to fresh air injection at a fixed location and the temperature in the intake area. It is used in manufacturing where workers exposed to high temperatures and the intensity of radiant energy 300 kcal / hour m²v emitted by the heating and melting furnaces.

There are such setup from both stationary and mobile. They should provide airflow rate of 1 to 3.5 m / s.

There is such a thing as an oasis of air, it is a same device included in the system of local ventilation. It creates a certain part of the production area a microclimate with the specified parameters.

The purified air is supplied to the predetermined exclusion zone typically subjected to special heat and humidity treatment.

If a local suction device directly to the approximate allocation pollutants space will be able to remove the air containing a higher percentage of them than in the general dilution ventilation type. Local ventilation can significantly reduce air exchange.

calculation of ventilation

If as a result of industrial activity produces no harmful substance, the amount of air required for ventilation is calculated by the formula:

L = N x Ldwhere

N - a number of people, usually in the room, Ld - the amount of air required for 1, measured in mᶾ / h. It is the norm of 20 to 60 mᶾ / h.

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

L = n x S x Hwhere

n - ventilation rate in the room (n = 2 for the production area) S - floor space in m² and H - the height in meters.

Conclusions and useful videos on the topic

Here, all of the intricacies of various ventilation systems:

For details on installing the system:

Whatever the ventilation system is chosen, it must have two main characteristics: a competent structural performance and functionality. Only when these conditions are met in the production will be supported by an optimal healthy microclimate.

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