Construction process of galvanized steel sheet air duct

（1） Duct production

1Organize relevant personnel to familiarize themselves with the drawings and provide safety technical briefing to on-site construction personnel.

2Compare on-site with construction drawings and draw sketches. Organize material procurement in batches according to the project progress, and follow the principle of processing from top to bottom and from large to small.

3Check the quality of galvanized steel plates, angle steels, and auxiliary materials used in the production of air ducts. Those without factory certificates or quality appraisal documents are not allowed to use them. The surface of the galvanized steel plate should be flat, uniform in thickness, without obvious pressure damage, and should not have defects such as cracks, scars, sharp edges, rust, watermarks, etc. The galvanized layer should have crystalline patterns; Angle steel should be of uniform shape, without cracks, distortions, or other defects that affect quality.

4Process flow

5The bite form adopts single bite or corner bite.

6The thickness of steel plates used for making air ducts and accessories is specified in the table below

Long side size or diameter（mm）Low pressure rectangular air duct in circular air duct

80～3200.50.5

340～4500.60.6

480～6300.8

670～10000.8

7The surface of the air duct and fittings should be flat, the longitudinal joints should be staggered, the joints should be tight, the width should be uniform, and there should be no defects such as holes, half joints, or expansion cracks.

8. When making flanges, the same specification should use a unified mold to keep the flange size consistent and the surface flat. The flanges should drill bolt holes in pairs with a spacing of no more than150Millimeters. When connecting flanges and regulating valves, it is necessary to ensure that their dimensions are consistent with the flange dimensions of the components.

9The inner diameter of the flange should be slightly larger than the outer diameter of the air duct2-3Millimeters, when drilling, attention should be paid to placing the hole at the center of the angle steel (minus thickness) or flat steel. The arrangement principle is that when the flange is rotated freely, the screw holes on all four sides can be aligned. For rectangular flanges, the bolt holes on both sides can be aligned. The elevation and plan of the angle steel flange should ensure mutual integration90Degree.

10The connection between the air duct and the angle steel flange, with a wall thickness of less than or equal to1.5Millimeters can be used for flanging riveting, and the riveting part should be on the outside of the flange.

11The connection between the air duct and the flange, if using a flange, the flange size should be6-9Millimeters. The flange should be flat and free of holes.

12If there is an angle error during the processing of elbows and tees, adjust it using methods such as flanging and drawing lines according to the flange.

13To ensure the quality of the project, reinforcement frame reinforcement measures are taken after the production of the air duct to ensure the flatness and rigidity of the air duct. When the side length of the rectangular air duct is greater than or equal to630The side length of millimeters and insulation pipes is greater than or equal to800The length of the pipe segment is in millimeters1.2When the height is above meters, a reinforced frame should be used, and the reinforced frame angle steel should be of the same specification as the air duct flange.

14The air ducts and fittings are made according to the measured dimensions and numbered according to the system parts to prevent errors during transportation and installation. In addition, leave one end of the pipe with a flange that is not fixed, and adjust it according to the actual size on site during installation.

（2） Installation of air ducts

1The materials and semi-finished products on site are arranged in order and in different systems. Self made two wheeled carts are used for horizontal transportation, and elevators are used for vertical transportation. Attention should be paid to the protection of finished products during transportation.

2Check whether the position and size of the reserved holes on site meet the requirements of the drawings, and whether there are any omissions. The reserved holes should be larger than the size of each side of the air duct section100Millimeters.

3Pair the air ducts and components according to their numbers, and after verifying that they are correct, they can be connected and installed.

The connection length depends on factors such as the wall thickness of the air duct, the connection method between the flange and the air duct, the installation structure location, and lifting, but it should be connected on the ground as much as possible. Generally, it can be connected to10-12About meters long, but it is not allowed to install detachable interfaces in floor slabs or walls.

4Process flow

5The installation hanger of the air duct can be fixed on the floor or beam with expansion bolts, but the position should be correct, firm and reliable. The lower bolt of the suspension rod should have a clearance for adjusting the elevation and levelness of the air duct.

6The spacing between hangers is set as3Meter, the diameter of the suspension rod is10Millimeter round steel, angle steel for crossbeam, crossbeam located outside the insulation layer, between the hanger and the air duct, cushioned with anti-corrosion treatment50A millimeter thick wooden square, the same length as the crossbeam, and connected to the suspended beam with wooden bolts.

7The insulation of the air duct adopts glass wool felt with grid line aluminum foil veneer (the surface layer adopts moisture-proof and tensile veneer), and the overlap is sealed with tape. Before insulation, it is necessary to check whether the pipeline components are qualified. The surface of the insulation layer should be smooth and compact, without cracks or gaps. The number of insulation nails is: side20only/㎡, above is10only/㎡.

8For flange gasket material3-5Millimeter thick closed cell latex rubber sheet, with each lifting length controlled within12Within meters, the assembly and insulation are carried out on the erected scaffolding, and the lifting operation is performed standing on the triangular ladder.

9Valves and other components should be assembled and lifted together with the air duct, and regulating valves should be installed in a position that is easy to operate. Fire dampers are system safety devices with horizontal, vertical, left, and right types, and should not be installed incorrectly. To prevent the melting plate from falling off, extra care should be taken during installation. When installing fire dampers in vertical airflow ducts, one end of the melting plate must be tilted towards the closing direction5Degree.

10Allowable deviation of levelness after installation of air ducts3/1000The total deviation is not greater than20Millimeters. Allowable deviation of verticality2/1000.The total deviation is not greater than20Millimeters, when laying along the wall, for ease of operation, the distance between the pipe wall and the wall should be greater than150mm.

11The installation of various air vents should be closely coordinated with the decoration, synchronized with the ceiling, and achieve horizontal and vertical alignment, smooth surface, and parallel to the ceiling. The air vents should be pulled to be in a straight line no matter how they are viewed.