Main characteristics and ranges of application of ventilation pipes in exhaust air duct systems

From the middle of the last century, a new stage began in the production of ventilation pipes: in addition to ordinary rectangular ones, they began to produce round ones. A little later, scientists became interested in air exchange in the premises, and after 10 years they began to apply certain standards. Today, the selection of these products is extremely diverse.

Requirements for ventilation pipes

Supply and exhaust duct pipes must meet the following requirements:

1. Tightness.
2. The level of the aerodynamic angle should not exceed the noise standards.
3. Ensuring the free passage of air masses at a speed set for the project.
4. Maintaining the air pressure calculated in the project.
5. Compliance with thermal insulation standards.
6. Should fit into the interior of the building without taking up extra space.

To determine which ventilation structures

more suitable for living quarters, we will first consider their main characteristics and types.

Rectangular and circular section

In modern ventilation equipment with forced or natural draft, circular or rectangular air ducts are used. There are 22 standard cross-sections of round pipe from 100 to 2 thous. mm. The diameter of the chimney over 500 mm is considered to be large. Gasket allowed straight sections no more than six meters.

Rectangular structures are produced with the same standard dimensions, but the length of the straight the plot is no more than 2.5 m. The sections are connected by shaped elements of the corresponding shapes and diameters.

It is customary to select the configuration and dimensions of air ducts based on the area, purpose and design of the room. For example, for a small room with a low ceiling, a rectangular ventilation pipe will be more acceptable. But such constructions have some deficiencies in aerodynamics compared to round. The angular shape creates additional resistance to air masses and reduces the speed of their movement, as well as enhances the noise effect. Considering this, rectangular ventilation pipes in living quarters are placed in soundproofing cases.

Types of exhaust pipes

The main materials for the manufacture of ventilation structures are metal and plastic. Which pipes are preferable depends on the characteristics of the room, the air environment in it and the requirements of the project.

Plastic constructions

Plastic chimneys, whether rigid or flexible, are made from polymers such as:

• polyvinyl chloride (PVC);
• polypropylene;
• fluoroplastic (PVDF);
• polyurethane (PPU).

PVC ventilation systems are often installed in apartments and cottages. They are inexpensive, easy to use and easy to install. In addition, they are resistant to destruction by ultraviolet light and remain operational at temperatures from 0 to 80 degrees Celsius. There are some more advantages:

• Perfect tightness.
• Noise indicators do not exceed the permissible values.
• PVC products are cheaper than similar ones made of polyethylene and metal.
• They do not distort the interior when carefully installed.
• A huge number of shapes and sizes that allow you to assemble a system of any complexity.
• Not harmful to health.

Polyethylene ventilation ducts are made with antistatic protection. They differ in wider temperature range, they can be used from minus 40 to plus 80 degrees.

Polypropylene are resistant to aggressive environments and moisture, keep temperatures from 1 to 98 degrees. Non-flammable and antistatic models are available in a special version. At low temperatures, polypropylene hardens and breaks easily, which limits its use only in warm rooms.

PTFE ventilation systems are the most durable of all plastic categories. The material adequately withstands temperatures from minus 40 to plus 140 degrees in very aggressive environments.

Metal ventilation ducts are made of the following materials:

• Cink Steel;
• stainless steel;
• aluminum;
• thin sheet black steel.

Ventilation tubes are practically not made of sheet aluminum; foil is used for these purposes. The thickness of the sheet metal depends on the diameter and shape of the product.

Positive qualities of metal ventilation structures:

• Strength and durability.
• Excellent aerodynamics provided by a perfect inner surface.
• They perfectly hold high pressure and temperature.
• They have increased hygienic properties, as a result of which they are often used in premises with high sanitary requirements.
• Resistant to aggressive environments.

Galvanized ventilation products, most used in industrial, administrative and residential premises, have the following advantages:

1. Temperature range up to plus 80 degrees with a humidity of 60 percent.
2. Light weight, so you don't need to create additional load-bearing structures.
3. Good resistance to pressure and mechanical stress.
4. Strong resistance to corrosion, even in constantly humid environment. Ideally fits under the exhaust pipe with an outlet to the outside.
5. When the temperature rises, it retains its shape and size. Refractoriness limits are about 90 minutes.
6. The safety margin of operation is within 25 years.

Stainless steel air ducts are characterized by full range of advantages steel, the main of which are reliability and durability. And when added to the alloy, chromium provides the product with resistance to corrosion for many years. In addition, such products have additional qualities:

1. corrosion resistance in many working environments;
2. excellent manufacturability;
3. strength and ductility;
4. heat resistance up to 500 degrees;
5. inertness to toxic and radioactive substances.

Products made of stainless and galvanized steel are very visually similar. But you can still distinguish - the galvanized steel has characteristic crystal patterns.

Ventilation systems made of ferrous metal are used for smoke removal, ventilation and aspiration. An excellent option for a chimney with an external outlet. Such products are distinguished by increased indicators of rigidity, heat resistance and fire resistance.

Parameters of black steel air duct structures:

• Walls of products with a thickness of 1.2 to 1.5 mm.
• The length of the sections is from 1.25 to 2.5 m.
• Flange connection.
• They are made in round and rectangular sections.

The price category of such products is lower than stainless steel, but higher than galvanized ones of the same sizes and shapes.

Aluminum for the manufacture of such equipment is used, as a rule, in the form of foil. Such air ducts are of two types: flexible and rigid. In a rigid system, the turns of the line are performed using connecting corner elements, in a flexible system, aluminum corrugation is used, and there are also mixed options. In such cases, the composition of the pipe determines its technical properties:

• Aluminum corrugation has corrosion resistance, good air tightness, temperature resistance from 30 degrees below zero to 270 degrees above zero, fire resistance and chemical inertness.
• The properties of polyester with a reinforced steel frame are reduced to excellent moisture resistance, low flammability, retention of performance at temperatures from minus 20 to plus 65 degrees, low weight. The cost of this product is low, and of the obvious disadvantages is the accumulation of static electricity.
• Distinctive features of polyester film with aluminum foil are increased pressure resistance (withstands up to 2400 Pa) and excellent aerodynamic properties.

However, all corrugated air ducts, regardless of the material of manufacture, have common disadvantages: the ribs of the corrugation resist the flow of air masses, they significantly reduce the speed of their passage. For the same reason, and also due to the lack of rigidity, the level of noise effect is much higher than we would like.

New technologies - technical textiles

At the end of the last century, Danish developers proposed a fabric duct system. The innovation immediately found application and partially replaced metal ventilation sections in the food, electronic, chemical industry, catering, swimming pools, concert and exhibition halls.

Textile pipes are classified into two types: breathable and airtight.

Breathable ventilation ducts, also called textile diffusers, are designed to evenly distribute the flowing air in rooms through perforated holes and outlet adapters. The material for their manufacture is polyester.

Airtight systems are used to transport and evacuate air. They are made from polyamide.

These designs do not have the disadvantages of their metal counterparts. And the significant advantages of textile air ducts are as follows:

1. Drafts are often observed in metal and plastic structures in the air supply area. Air is supplied to the textile ducts in diffused jets, and no draft arises.
2. Excellent noise reduction properties. The fabric dampens aerodynamic noise of air masses and the fan very well.
3. The fabric acts as a kind of filter and accumulates filtration products, but is easily washed and disinfected. Ease of cleaning is one of the advantages of textile ventilation ducts.
4. Due to the impermeability, condensation does not settle on the surfaces of textile pipes and a moist environment does not form, which means that there is no possibility of development for microorganisms. Condensation protection is another advantage of such systems.

The air flow rate in the textile pipe is from 5 to 8 meters per second, if the pressure drops, the shape will be maintained with the help of sewn-in rings. The service life is determined by ten years. In rooms with an increased risk of fire, textile air ducts are mounted with additional fiberglass, which increases the heat resistance up to 300 degrees.