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Which is the best choice for central air-conditioning ventilation ducts?
1. Thin steel plate
Sheet steel is the main material for the manufacture of ventilation ducts and components. Plain sheet and galvanized steel are commonly used. Its specifications are expressed as short side, long side and thickness. The thickness of commonly used thin plates is 0.5×4mm, and the specifications are 900mm×1800mm and 1000mm×2000mm.
The thin steel plates used to manufacture air ducts and pipe fittings require a smooth surface, uniform thickness, no cracks and scars, and should be properly preserved to prevent rust.
(1) Ordinary sheet
There are two types of ordinary thin steel plates: sheet and coil. This kind of steel plate belongs to the B-type steel plate, which is a cold-rolled and hot-rolled steel plate of Q235B steel, which has good processing performance and high mechanical strength, and is cheap.
(2) Galvanized steel sheet
The thickness of galvanized steel sheet is generally 0.5×1MM. The length and width of galvanized steel sheets are the same as ordinary thin steel sheets, 5mm. There is a protective layer on the surface of galvanized steel sheets to prevent corrosion, and generally do not need to be painted. The requirement for this kind of steel plate is that the surface is smooth and clean, and the thickness of the galvanized layer should not be less than 0.02 mm. It is mainly used for acid-proof and moisture-proof air duct systems, and the effect is better.
2. Stainless steel and aluminum plate
(1) stainless steel plate
A. With high plasticity, toughness, mechanical strength and corrosion resistance, it is a stainless steel commonly used in chemical corrosion-resistant air duct systems.
B. The main element of stainless steel is chromium, which has high chemical stability. A passivation film is formed on its surface to protect the steel plate from oxidation and improve its corrosion resistance.
C. Stainless steel is easy to bend during cold working, and it will cause internal stress and uneven deformation when hammered, thereby reducing the toughness of the stainless steel plate, increasing its strength, and making it brittle and hard.
D. When stainless steel is heated to 450 ° C ~ 850 ° C, the steel will undergo deterioration, hardening and cracks after slow cooling.
(2) Aluminum plate
A. Aluminum plates include pure aluminum plates and alloy aluminum plates, which are mainly used in chemical ventilation projects.
B. The aluminum plate has the advantages of beautiful color, low density, good plasticity, and strong acid resistance, but it is easily corroded by hydrochloric acid and alkali, and has good chemical corrosion performance.
C. Aluminum alloy aluminum plate has high mechanical strength and poor corrosion resistance. Most of the aluminum plates used in ventilation projects are pure aluminum plates and annealed aluminum alloy plates.
Because the aluminum plate is soft and there is no spark in the collision, it is mainly used as a ventilation duct with explosion-proof requirements.
(3) Plastic composite board
If you paste or spray a layer of plastic film on the ordinary steel plate, you will become a plastic composite steel plate. It is characterized by corrosion resistance, bending, biting, drilling and other processing properties.
Plastic clad steel plates are often used in air cleaning systems and ventilation and air conditioning systems with temperatures ranging from -10°C to 70°C.
Plastic composite steel plate specifications are: 450mm×1800 mm, 500 mm×2000 mm, thickness 0.35≤, 0.7mm≤1000 mm×2000 mm, thickness 0.8~2.0mm, etc.
3. PVC plastic board
The main results are as follows: (1) It has good corrosion resistance and generally does not react with acids, alkalis and salts, but it shows instability under the action of concentrated nitric acid, fumigation sulfuric acid and aromatic hydrocarbons.
(2) High strength, good elasticity, poor thermal stability, strength decreases at high temperature, becomes brittle, easy to crack at low temperature, it is in a soft state when heated to 100°C~150°C, and can be used under small pressure at 190°C~200°C combine with each other.
(3) Due to the different longitudinal and transverse properties of the plate, there is residual stress inside. When manufacturing air ducts and components, it needs to be heated and cooled to produce shrinkage. The total longitudinal shrinkage and transverse shrinkage are respectively 3%≤4 % and 1.5%≤2%.
(4) The density of PVC plastic board is 1350~1450 kg/m3. In ventilation and air conditioning engineering, this plate is mainly used to transport corrosive gases such as acids, alkalis, and salts, and can also be used to clean air conditioning systems.
(5) For the requirements of plastic sheets, the surface should be smooth, thin and uniform, without defects such as bubbles, cracks and delamination.
4. Glass steel plate
The main research results are as follows: (1) In ventilation engineering, the commonly used glass tubes are not made of FRP, but are hand-made with plates or thin steel plates as molds.
(2) During operation, firstly apply the adjusted resin on the mold bread layer of transparent cellophane, and then apply a layer of glass cloth, each layer of resin is coated with a layer of glass cloth, the cloth should be staggered, and finally The surface of the outer glass cloth is also coated with a thin layer of resin.
(3) The air duct and the flange are integrated. The flange should be prepared in advance, added during the resin coating process, and bonded with the air duct. After curing for a period of time, the entire air duct can come out and reach a certain strength.
(4) The synthetic resin used in the manufacture of glass tubes and pipe fittings should be selected according to the design requirements of acid resistance, alkali resistance, self-extinguishing and other properties, and the content of fillers in the synthetic resin should meet the requirements of the technical documents.
(5) The contents and specifications of the glass cloth should meet the design requirements, and the glass cloth should be kept dry and clean without wax. The laying and stitching of glass cloth should be staggered and should not overlap.
(6) The insulating glass tube can make the tube wall form an interlayer. The interlayer material can be made of rock wool, polystyrene, polyurethane foam, honeycomb paper and other insulating materials. The thickness and material of the interlayer should be selected according to the needs of the project.
(7) The inner surface of the fiberglass air duct and accessories should be neat and smooth, the surface should be flat and beautiful, the thickness should be uniform, the edges should be free from burrs, there should be no bubbles and delamination, and the curing degree of the resin should reach more than 90%.
(8) The flange must be integrated with the air duct or fittings, and must be perpendicular to the air duct, and the allowable deviation of the flange plane shall not be greater than 2mm.
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