How to improve the sealing performance of air duct?

To improve the sealing performance of air duct, it is necessary to start with many links such as material selection, manufacturing, installation process and post-inspection and maintenance. The following is a detailed introduction for you:

Material selection

High-quality plate: the quality of air duct plate directly affects the sealing performance. For example, galvanized steel plates should be made of plates with uniform coating, no zinc layer falling off and smooth surface, which can reduce the hidden danger of air leakage caused by surface defects of plates. For places with special requirements, such as food factories and pharmaceutical factories, which require high sanitary conditions, stainless steel plates can be used to make air ducts, which not only has good sealing performance, but also has the advantages of corrosion resistance and easy cleaning.

Sealing material: It is very important to choose a suitable sealing material. At the joint of air duct, such as flange connection, the corresponding sealing material should be selected according to the working pressure, temperature and conveying medium of air duct. For example, rubber sheet, asbestos rubber sheet and other sealing materials can be used to seal the air duct flange of general ventilation and air conditioning system, which has good elasticity and sealing performance and can effectively prevent air leakage. For air duct system in high temperature environment, such as smoke exhaust duct of boiler, high temperature resistant sealing materials, such as ceramic fiber gasket and graphite composite gasket, should be selected. These sealing materials can still maintain good sealing performance and mechanical strength at high temperature to ensure the normal operation of air duct system.

Processing and manufacturing

Accurate bite: bite connection is a common connection method in duct processing, and the quality of bite directly affects the sealing performance of duct. During the bite processing, the parameters of the bite machine should be adjusted reasonably according to the thickness of the air duct plate and the bite form to ensure that the width, depth and shape of the bite meet the design requirements. For example, the width of a single bite is generally 6-8mm, and the width of a double bite is generally 8-10 mm. The depth of the bite should be moderate. Too deep will cause the plate to break, and too shallow will affect the connection strength and sealing performance of the bite. At the same time, in the process of bite processing, it is necessary to ensure that the surface of the plate is flat, so as to avoid cracks at the bite caused by uneven surface of the plate and affect the sealing performance of the air duct.

Flange fabrication and connection: Flange is an important part of air duct connection, and its fabrication quality and connection mode have a key impact on the sealing performance of air duct. In the process of flange manufacture, the dimensional accuracy of flange should be strictly controlled according to the design requirements, including outer diameter, inner diameter and thickness, as well as the position and spacing of bolt holes. For example, the deviation of outside diameter of circular flange should be controlled within 1 mm, the deviation of diagonal length of rectangular flange should be controlled within 3 mm, and the deviation of bolt hole position should be controlled within 1 mm, so as to ensure that the flanges can fit closely in the connection process, and avoid cracks at the connection parts due to excessive flange size deviation, which will affect the sealing performance of the air duct. In the process of connecting the flange with the air duct, the connection should be made by welding or riveting, and the connection should be firm and reliable. For welding connection, appropriate welding technology and welding materials should be selected to ensure the quality of weld and avoid defects such as virtual welding and missing welding. For riveted connection, the appropriate rivet specification and riveting method should be selected according to the thickness of the plate of the air duct and the material of the flange to ensure the strength and sealing of riveting. At the same time, after the connection between the flange and the air duct is completed, the connection parts should be sealed, such as applying sealant to the joint between the flange and the air duct to further improve the sealing performance of the air duct.

Installation process

Tight connection: during the installation of air ducts, it is the key to improve the sealing performance to ensure the tight connection between air ducts and between air ducts and components. For air duct systems that cannot be connected by flange, such as hoop connection and plug connection, the operation should be carried out according to the requirements of the product manual to ensure that the installation position of the connecting parts is correct and the tightness is moderate. For example, the hoop of hoop connection should be close to the outer wall of the air duct, and the bolt of hoop should be tightened to form a good seal between hoop and air duct; The insertion depth of the plug-in air duct should meet the design requirements, and the plug-in parts should be sealed with sealant or other sealing materials after insertion to prevent air leakage. For the air duct system with flange connection, attention should be paid to ensure the flatness and verticality of the flange during the installation process to avoid the loose connection caused by flange deformation. At the same time, when the flanges are connected, the bolts should be tightened according to the specified sequence and torque to ensure that the gasket between the flanges is uniformly compressed to form a good seal. For example, for the flange connection of rectangular air duct, the bolts at four corners should be tightened first, and then the other bolts should be tightened in turn. The tightening torque of bolts should be reasonably selected according to the specifications of the flange and the material of the gasket. In general, the tightening torque of bolts should be controlled between 40-60N・m, so as to ensure the tightness and sealing performance of flange connection.

Sealing treatment: in addition to ensuring the tightness of the connection parts of the air duct, some special parts of the air duct should be sealed to further improve the sealing performance of the air duct. For example, when the air duct passes through building structures such as floors and walls, fireproof, moisture-proof and sound-proof sealing materials, such as fireproof mud, rock wool board and polyurethane foam, should be filled in the gap between the air duct and the building structure to ensure that the gap is completely sealed and prevent air, smoke and fire from spreading through the gap. At the same time, in order to ensure the sealing effect, before filling the sealing material, the gap between the air duct and the building structure should be cleaned to remove impurities, dust and oil stains, so that the surface of the gap is clean and dry. In addition, some holes in the air duct, such as inspection holes, measuring holes, vents, etc., should also be sealed after installation to prevent air leakage. In general, sealing strips, sealants or other sealing materials can be used to seal holes to ensure good sealing performance. For example, for the inspection hole on the air duct, the sealing strip should be installed at the edge of the inspection hole, and then the cover of the inspection hole should be covered. By tightening bolts or other fixing methods, the cover of the inspection hole should be closely attached to the surface of the air duct, and the sealing strip should be compressed to form a good seal.