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Types of Air Ducts for Ventilation

The ventilation system is an important element of any house, apartment or enterprise, which ensures the removal of unpleasant odors from the premises, the reduction of humidity, and the flow of clean air from the external environment. All rooms of the house need ventilation, especially the bathroom, the bathroom, where there is always high humidity, as well as the kitchen, where there is a lot of steam, fat fumes, and smells of cooking in the air. If a gas boiler is used in the house, then the installation of an air duct is also mandatory for fire safety. Also learn more about air duct cleaners.

The main element of ventilation is the air duct, the quality, design and size of which directly affects the functioning of ventilation systems. It has a number of requirements:

  • provide high tightness;
  • meet the standards for the level of aerodynamic noise;
  • guarantee the necessary air throughput;
  • restrain the estimated pressure of the air mass;
  • provide the required thermal insulation.

Another criterion that ventilation ducts must meet is their compact size. It is important that the air ducts do not reduce the useful area of the premises.

WHAT DOES THE AIR DUCT LOOK LIKE?

Externally, the ventilation duct looks like a pipeline through which air moves. The duct system can usually be formed both by straight pipes and elements of various shapes that determine the desired direction of air flow, as well as the combination or separation of air mass flows. The appearance of the duct depends on many different factors, such as the material from which it is made, the shape of the section, size, purpose, scope, and so on. Let's look at the classification in more detail.

DUCT CLASSIFICATION

There are various types of air ducts, differing in their design, performance characteristics, and scope. To understand what air ducts are, a classification is introduced according to several parameters:

  • section shape and size;
  • design of air ducts;
  • rigidity of the structure;
  • ways and types of connections.

SECTION SHAPE AND SIZE

When designing ventilation systems for residential and industrial premises, air ducts of rectangular and round cross section are most often used. Less often, if necessary, you can use products with an elliptical section. 

Round air ducts are easier to manufacture and require less material to produce. If metal is used for production, its costs for round products are 20 ... 25% less than for rectangular air ducts. Buying air ducts with a circular cross section will be more profitable from a financial point of view.

The advantage of round ducts is:

  • high tightness;
  • high speed of air supply;
  • low noise levels;
  • small weight;
  • ease of installation.

The advantage of models with a rectangular cross section is:

  • optimal location in space (occupies a minimum of usable area);
  • they are easy to adjust to the features of the object;
  • ample opportunities in the planning of premises.

Installation of round air ducts is more often performed in industrial premises, and square - in private houses, apartments, cottages.

According to the norms , air exchange in residential buildings (apartments) should be at least 30 m3 / hour per family member. The required volume of air, subject to natural ventilation, is able to provide an air duct with a diameter of 0.15 m.

For round air ducts, the most common diameters are from 0.1 to 0.2 m. Rectangular air ducts have dimensions from 0.1x0.055 m to 0.2x0.06 m. If necessary, air ducts of large sizes can be manufactured.

AIR DUCTS DESIGN

According to the design, there are three types of air ducts: 

  • folded (with a straight seam);
  • spiral-wound or spiral-lock;
  • spiral welded.

Pipelines with a straight seam are made from steel sheets with a thickness of 0.55 ... 1.25 mm (length about 1.2 ... 1.3 m). For models with a straight section, the seam is located on the fold - this provides additional rigidity to the structure.

Spiral-wound air ducts are made from a special tape with a thickness of 0.55 ... 1 mm (width of about 0.13 m), an anti-corrosion coating is applied to its surface. Two different technologies are used for production: in a tape, in a ring. The cost of air ducts using ring technology is high, but this is offset by higher quality.

Spiral welded ducts for ventilation are made from steel tape with a protective coating. Its thickness can vary within 0.85...2.2 mm, the width is approximately 0.45...0.75 m, and the length is not limited. Using the overlap welding technology, it is possible to obtain a high-strength even seam.

DUCT RIGIDITY

For laying ventilation systems, air ducts of three categories are used:

  • rigid;
  • semi-rigid;
  • flexible.

A rigid air duct has a rectangular or circular cross section, it is produced from sheet metal (galvanized steel, stainless steel, aluminum) or high-strength plastic. The metal pipeline is made on roll forming machines, and the plastic pipeline is made on special extruders. To exclude heat loss through a metal pipeline, it can be insulated with special heat-insulating materials.

The rigid type of pipelines is used in those facilities where high strength and load-bearing capacity are needed for the ventilation system. They are mainly installed at production facilities.

When creating complex branched systems, it must be taken into account that the total weight of the structure can be large. Therefore, it is necessary to take care of the reliable fastening of this type of air ducts in advance.

The advantages of rigid pipelines include good aerodynamic performance (very low noise level), ease of maintenance and installation work.

Flexible air ducts for ventilation are produced in the form of corrugated reinforced sleeves. The frame of flexible air ducts is made of high-strength steel wire, and the shell is made of laminated foil.

The advantage of flexible air ducts is the ease of construction and ease of installation. Elastic corrugated pipe can be bent at any angle, directed in the right direction. The disadvantage of such pipelines is their corrugated surface. Due to such a surface, the throughput of the duct is reduced, the speed of passage of air masses decreases, and aerodynamic noise also increases.

Semi-rigid air ducts occupy an intermediate link between rigid and flexible. They also have high strength, like rigid structures, while possessing high elasticity, like a flexible duct. Their disadvantage is the low speed of the passage of the air flow. Given this fact, they are not used in the structure of complex branched ventilation ducts.

VARIETY OF COMPOUNDS

To connect air ducts to each other, two main types of connections are used: flangeless and flanged.

The flange connection technology provides for the connection of sections of the ventilation duct with flanges that are attached to the ends of the connected air ducts. Flanges are fixed with rivets or self-tapping screws. To ensure the tightness of the connection, rubber seals are installed.

Wafer connections are made using a bandage of thin steel sheets with metal rails.

In the process of installing air ducts, several types of connectors are used:

  • Confusers and diffusers - they are used to connect pipes with different cross sections; confusers narrow the air flow, and ventilation diffusers expand it;
  • Tees - are installed in the places of branching of the ventilation duct;
  • Adapters - needed to connect sections with different sizes and cross-sections of pipelines used;
  • Elbows and Elbows - used to rotate ventilation ducts.

When installing ventilation ducts, it is important to take into account the fact that the working area of the duct must provide normal air inflow / outflow, depending on the number of people living at the facility or the equipment used there.

MATERIALS FOR AIR DUCTS

If earlier only plastic was used for the production of elements of ventilation systems, now the choice is much wider. Ventilation ducts can be made of plastic, metal-plastic, as well as textile material. Consider the advantages and disadvantages of each of these materials.

PLASTIC

Inexpensive air ducts for private construction are made from plastic. Products are strong enough, have high rigidity, can be used for many years without deterioration of their characteristics. They are made from different types of plastic:

  • polyvinyl chloride is an inexpensive material, resistant to ultraviolet radiation, does not deform in a wide temperature range - from 0°С to +80°С;
  • polypropylene - the material can withstand heating up to +100°C, but becomes brittle at low temperatures;
  • fluoroplast - products and it are resistant to vapors with acids and alkalis, do not deform and do not collapse at ambient temperatures from -40°С to +140°С;
  • polyethylene - air ducts made of this material are distinguished by antistatic protection and can be used at temperatures from -40°С to +80°С; if black carbon is added to polyethylene, the material becomes resistant to ultraviolet radiation.

ADVANTAGES OF PLASTIC DUCTS

The advantages of plastic air ducts are as follows:

  • 100% moisture resistant;
  • long service life;
  • low price;
  • ease of maintenance and cleaning of air ducts;
  • a smooth inner surface does not reduce the air speed and throughput of the air duct;
  • ease of installation;
  • environmental friendliness of the material.

DISADVANTAGES OF PLASTIC DUCTS

  • low fire resistance;
  • not suitable for industrial ventilation.

METAL

Metal is a traditional material for the manufacture of air ducts for ventilation systems of both industrial and residential facilities. Most often, steel is used for production (black, galvanized, stainless).

  • black steel is used for the manufacture of air ducts for industrial use - this material is highly fire resistant, it is durable, guarantees high structural rigidity; the tightness of such a pipeline is ensured by welds; 
  • stainless steel - this material is used in cases where aggressive substances (acid, alkali) may appear in the environment and humidity is increased; in addition, stainless steel is durable and resistant to temperature extremes;
  • galvanized steel - products made of this metal can be used in any climatic zone, the surface of pipelines is reliably protected from corrosion by a layer of zinc.

ADVANTAGES OF METAL DUCTS

The advantages of metal air ducts are as follows:

  • high mechanical strength;
  • durability;
  • resistance to ultraviolet, temperature extremes;
  • high fire safety;
  • can be used at home and at work.

DISADVANTAGES OF METAL AIR DUCTS

  • high price;
  • high weight of the elements, which requires additional fasteners when installing the air duct;
  • increased noise during operation of the air duct.

METALLOPLASTIC

Air ducts made of metal-plastic have a sandwich structure, which consists of two layers of metal and one layer of plastic. Often the metal layer is made from corrugated aluminium. It provides products with good rigidity, low weight and durability.

ADVANTAGES OF METAL-PLASTIC AIR DUCTS

The advantages of this category of air ducts are as follows:

  • air passes well through the metal-plastic channel;
  • low noise level during ventilation;
  • ease of installation and maintenance;
  • small weight;
  • environmentally friendly materials are used.

DISADVANTAGES OF METAL-PLASTIC AIR DUCTS

A significant disadvantage of such air ducts is their high cost.

VENTILATION FROM TEXTILE DUCTS

Textile air ducts are a new type of air ducts used in the creation of ventilation systems for premises for various purposes. These products provide optimal air distribution, they are actively used to create supply and exhaust ventilation, climate control systems, and air conditioning.

Air ducts can be of several types, they differ in the material used and performance characteristics.

  1. Breathable - they are made of polyamide, they are designed for transportation and uniform distribution of air masses throughout the premises. They are also called fabric diffusers. The breathable material serves both as a channel for transporting air and for filtering it from mechanical impurities.
  2. With microperforation - the presence of micro-holes in the fabric allows you to evenly distribute the air in the room at a low speed of its movement through the air duct. Thanks to this method of supplying and distributing air, such ventilation ducts are used in places where many people often accumulate.
  3. "Textile nozzle" - this type of air duct is used to supply air point to a specific area of the workspace. They are also installed to create an air curtain.

There is another type of textile diffusers made using membrane technology. An airtight membrane is installed in the fabric air duct along its entire length, the position of which is regulated by a servomotor. The direction of air movement and the ability to dissipate it depend on the position of the membrane. In this way, it is possible to regulate the movement and distribution of air flows directed to different rooms.

In systems for transporting hot air, as well as in rooms with an increased fire hazard, air ducts made of a material that includes fiberglass are used. Air heated up to +300°С can be transferred through such channels.

MAIN CHARACTERISTICS OF THE TEXTILE MATERIAL

  • high strength;
  • resistance to ignition and combustion (combustibility class G1, flammability class B1);
  • can be installed in "clean rooms" (up to class 4);
  • antistatic and antibacterial effect;
  • ease of maintenance;
  • the color of the fabric does not fade for many years.

ADVANTAGES OF THE TEXTILE AIR DUCT

  • uniform distribution of air;
  • high throughput rates;
  • large operating temperature range: from -10°С to +130°С (some models withstand up to +300°С);
  • resistance to chemicals and damp environment;
  • low specific gravity;
  • are not subject to corrosion and accumulation of condensate;
  • good sound insulation;
  • ease of installation, repair and routine maintenance;
  • a large selection of colors;
  • can be combined with air ducts from other materials;
  • affordable price.

Thanks to the unique design of fabric ducts, they are easy to fit into any interior, and in some cases they even help to improve the design of the room. Textile air ducts are installed in concert and exhibition halls, in swimming pools, in catering establishments, in food and chemical industries. In addition to numerous advantages, a feature of textile air ducts is the possibility of their production in non-standard shapes and sizes.


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