Construction technology of Jianyuan composite air duct

（1） Production of Jianyuan air duct:

1.1. Production principle

1.1.1 the composite air duct can be prefabricated or made at the construction site. The manufacture specification of air duct shall be determined according to the design data and GB 50243-2002, and the size of air duct shall be subject to the inner dimension to ensure the effective sectional area of air duct.

1.1.2 during construction, reasonable cutting and blanking must be carried out according to the specifications of air duct on the design drawings. Because the size of composite air duct plate is 1300 × 2320 mm (width × length), and the design of duct size is different, so the marking process should be accurate and reasonable, cutting and blanking is the key to reduce the loss of sheet.

1.2 plate cutting

1.2.1 the cutting line must be straight, the length error of diagonal line should be less than 5mm, and the cutting line should be at right angle to the plate surface. The cutting line depth of step plate (side panel) is 20 ± 1.5mm (Fig. 4-1).

1.3 fabrication of Jianyuan rectangular air duct

1.3.1 schematic diagram of air duct assembly (Fig. 4-2). Note: during the assembly of air duct, the step plate must be used as the left and right plates, and shall not be interchanged with the top and bottom panels.

1.3.2 use a scraper to remove the excess part along the cutting line of the side panel to ensure that the step position of the side panel is flat

1.3.3 apply proper amount of special adhesive on the left and right side board steps

1.3.4 first place the bottom panel on the assembly frame and keep it level. Secondly, the left and right panel steps are bonded with the bottom panel, and then the top panel is placed in the middle of the side panel. In order to realize the non flange connection between pipe sections, the side panel and the top and bottom panels should be staggered by 100 mm longitudinally. Finally, tie the assembled air duct tightly with the strapping belt, with a spacing of 600mm, and a 90o angle guard is set at the joint between the air duct and the four corners (Fig. 4-2).

1.3.5 when the perimeter of air duct is less than 2000mm, the error of diagonal length shall not be greater than 3mm. When the perimeter of air duct is greater than 2000mm, the error of diagonal length shall not be greater than 5mm.

1.3.6 remove the residual glue from the joint and fill the gap at the same time. Residual glue shall not be left on the inner and outer walls of the air duct and at the 100 mm staggered steps between the side panel and the top and bottom panels.

1.4 fabrication of reducing air duct

1.4.1 elbow fabrication

According to Fig. 3-4, the plate is cut into pieces.

1.5 production of tee and cross

See 4.3 elbow fabrication

1.6 reinforcement of large air duct

When the side length of air duct is more than 1500mm, reinforcement measures must be taken (Fig. 4-4).

1.6.1 plate splicing. Use wire brush to scrape 1.5mm insulation layer at the joint to form groove. Filled with special adhesive splicing. After curing, sandpaper shall be used to roughen the joints on both sides of the joint, and three layers of glass fiber cloth with width of 200 mm and thickness of 0.2 mm shall be pasted on both sides with special glue.

1.6.2 the supporting rod shall be set in the air duct. The supporting rod is made of Φ 10 mm full thread galvanized round steel, and the inner and outer nuts on both sides are fixed. The inner and outer sides of the air duct are made of metal pad (for ventilation duct) or high strength plastic pad (for air duct). When the air duct of air conditioner is used, the round steel and inner nut shall be wrapped with rubber insulation sleeve (thickness of 40mm). See table 4-1 for the number of supporting rods.

Table 4-1

Side length of air duct mm

1500~2400

2400~3400

3400~4400

4400~5400

Number of support rods

One

Two

Three

Four

1.6.3 the four inner corners of the air duct are bonded with reinforcing strips with the size of 25 × 40mm, which are cut from plates.

1.6.4 when the long side of the air duct is more than 1500 mm and the short side is more than 500 mm, two layers of glass fiber cloth with the width of 50 mm and the thickness of 0.2 mm shall be pasted on the inner wall of the air duct joint with special adhesive.

1.6.5 when the side length of air duct is more than 3000mm, in addition to reinforcement according to the above requirements, it is also necessary to set 50 × 50 angle steel every 1300mm on the outer wall of the air duct, and connect it with the support rod.

（2） Air duct connection

1.1 connection of main air duct and main air duct (Fig. 5-1)

1.1.1 use wire brush to scrape 1.5mm insulation layer at the joint of top and bottom panels of two air ducts to form grooves. Then fill the groove with special glue, and evenly apply the special glue on the left and right side board steps.

1.1.2 connect the two air ducts tightly. Remove the residual glue extruded from the joint and fill the gap at the same time.

1.1.3 in order to ensure the quality of air duct splicing, it is not suitable to splice both ends of a section of air duct at the same time.

1.2 connection of main air duct and branch air duct

1.2.1 open on the wall of main air duct, and the opening size is the inner diameter of main air duct plus 6mm.

1.2.2 the branch air duct shall be made according to the design specifications, and the connection between the branch air duct and the main air duct shall be cut into a ladder shape.

1.2.3 apply proper amount of special adhesive on the ladder step, and connect it tightly. Remove the residual glue extruded from the joint and fill the gap at the same time.

1.3 connection of air duct and valve

The air duct is connected with valve by special flange. Insert the special flange into the air duct wall and fix it with self tapping screw. Then connect the other side of the flange with the flange of the valve (Fig. 5-2).

1.4 connection of air duct and round flexible joint

A section of special-shaped pipe is made according to the size of the circular flexible joint and the connected air duct, and a round opening is cut on the side connected with the flexible joint and connected with the flange of the flexible joint (Fig. 5-3).

1.4 connection of air duct and air outlet

1.4.1 connection of plane tuyere

According to the size of the designed air outlet, the air duct wall is opened, and the "[" shaped component made of 0.5mm thick galvanized steel plate is inserted into the insulation layer on both sides of the opening. Insert the air outlet into the opening of pipe wall and fix it with self tapping screw