Centrifugal fans are used in both industrial production and ventilation in public places. In addition to the performance of the fan itself, which can meet the ventilation requirements, the correct selection and layout of the air duct is also a prerequisite to ensure the normal operation of the centrifugal fan, especially the material of the air duct. , If it is applied to the wrong occasion, it is easy to cause damage and air leakage, and maintenance and replacement are also very troublesome. What materials are used for the air duct of the centrifugal fan?
1. Air duct material of centrifugal fan
Generally, the air duct of centrifugal fan is required to have the characteristics of sturdiness and durability, smooth surface, good corrosion resistance, easy manufacture and installation, and no surface shedding, so there are usually two types of materials that can be made into centrifugal fan air duct:
1. Sheet metal
(1) Ordinary thin steel plate: It has good processing performance and structural strength, and its surface is easy to rust, so it should be painted for anti-corrosion.
(2) Galvanized steel plate: It is made of galvanized ordinary steel plate. Because the surface is galvanized, it can prevent rust. It is generally used to make air ducts in humid environments that are not affected by acid mist.
(3) Aluminum and aluminum alloy plates: Good processing performance and corrosion resistance. It is not easy to generate sparks during friction, and is often used in explosion-proof systems of centrifugal fans for ventilation.
(4) Stainless steel plate: It has rust and acid resistance, and is often used in centrifugal fan systems that require acid and corrosion resistance in chemical environments.
2. Non-metallic materials
(1) Rigid PVC plastic board: It is suitable for the ventilation system with acid corrosion effect, and has the advantages of smooth surface and convenient production. However, it is not resistant to high temperature and cold, and is only suitable for the air environment of 0~60 ° C. Under the action of solar radiation, it is easy to be brittle.
(2) FRP: Inorganic FRP is made of medium-alkali glass fiber as reinforcing material, scientifically formulated with more than ten kinds of inorganic materials into binder as matrix, and made by certain molding process. It has the characteristics of light weight, high strength, non-combustibility, corrosion resistance, high temperature resistance and cold melting resistance.
In addition to the above metal and non-metal materials, there is also a plastic composite steel plate that can also be used for the production of centrifugal fan air ducts. It is sprayed with a 0.2~0.4mm thick plastic layer on the surface of ordinary thin steel plates. Centrifugal fan ventilation system with high dust-proof requirements, and corrosion-resistant centrifugal fan air duct at -10℃~60℃.
2. centrifugal fan air duct layout requirements
The duct arrangement of the centrifugal fan directly affects the overall arrangement of the ventilation system, and is closely related to technology, civil engineering, electrical, water supply and drainage, fire protection, etc., and should be coordinated and coordinated with each other. The specific requirements are as follows:
1. In the layout, the air duct should occupy less building space and not hinder the production operation. It is often laid along the wall, column, floor beam or roof truss, and installed on the bracket or hanger.
2. The air duct of the centrifugal fan for dust removal should be laid as vertically or inclined as possible. When inclined, the angle with the horizontal plane should be greater than 45°. If it must be laid horizontally or the inclination angle is less than 30°, corresponding measures should be taken, such as increasing the flow rate, setting Clean mouth etc.
3. When transporting gas containing steam and mist droplets, the air duct of the centrifugal fan should have a slope of not less than 0.005, and a water seal drain pipe should be installed at the bottom of the air duct and the bottom of the fan. operating conditions.
4. Centrifugal fan ducts of workshops with explosion hazard and air ducts for excluding explosive hazard substances should not pass through fire walls. Other air ducts should not pass through fire walls such as firewalls and non-combustible floors. If they must pass through, they should be Fire dampers are installed across. The air ducts and thermal insulation materials within 2m on both sides of the fire damper shall be made of non-combustible materials. The gap where the air duct passes through shall be sealed with fireproof material.
5. Combustible gas pipelines, combustible liquid pipelines, electric wires, drainage pipelines, etc. shall not pass through the inner cavity of the air duct of the centrifugal fan, nor shall they be laid along the outer wall of the air duct. Combustible gas pipes and flammable gas pipes should not pass through the fan room.
6. When there is an electric heater in the air duct of the centrifugal fan, the air ducts within the range of 800mm before and after the electric heater and the air ducts and insulation materials that pass through the rooms with fire sources that are prone to fire should be made of non-combustible materials.
7. Necessary adjustment and measurement devices (such as valves, pressure gauges, thermometers, measuring holes and sampling holes, etc.) should be installed on the air duct or the interface for installing the measurement device should be reserved, and it should be located at a place that is convenient for operation and observation.
8. The layout of the centrifugal fan air ducts should be straight and avoid complicated local pipe fittings. Pipe fittings such as elbows and tees should be arranged properly, and the connection with the air duct should be reasonable to reduce resistance and noise.
9. For the ventilation system that excludes harmful gases and dust, the exhaust port of the air duct should adopt a conical hood or a rain-proof hood.