Galvanized air duct

Galvanized air ducts are widely used in hotels, shopping malls, textiles, chemical fibers, petrochemicals, machinery manufacturing, instrumentation, electronics, pharmaceuticals, tobacco, food, medical, warehousing, office buildings, as well as in the supply, exhaust, and smoke exhaust ducts of subways, civil air defense, basements, and other engineering projects. The thickness and specifications of galvanized spiral ducts can vary according to requirements. Usually, when connecting, both ends of galvanized spiral ducts are always externally connected to fittings (such as elbows and reducers). Generally, there are no grooves at both ends and a sealing ring is provided.

Galvanized air ducts are piping systems used for air transportation and distribution. Galvanized air ducts can be classified according to their cross-sectional shape and material. According to the cross-sectional shape, galvanized air ducts can be divided into various types such as circular air ducts, rectangular air ducts, flat circular air ducts, etc. Among them, circular air ducts have the lowest resistance and the highest height dimension, making them complex to manufacture. So the application is mainly based on rectangular ducts.

Galvanized air duct with common flange

3.2.1 The production of galvanized air ducts with common flanges shall meet the following requirements:

The thickness of the sheet metal for rectangular ducts and their accessories should not be less than the specifications in Table 3.2.1-1.

Table 3.2.1-1 Thickness of Ordinary Steel Plate or Galvanized Steel Plate Duct Sheet (mm)

2. The splicing of galvanized steel plates or color coated steel plates should be done by biting or riveting, and there should be no cross shaped splicing joints. The coated surface of the color coated steel plate should be located on the inside of the air duct, and damage to the coated layer should be avoided during processing. Damaged parts should be repaired.

3. Welding air ducts can be done in three forms: lap joint, corner joint, and butt joint. The position of the weld seam is shown in Figure 3.2.1. Before welding the air duct, rust and oil should be removed. The weld seam should be well fused and flat, with no defects such as cracks, weld beads, penetrating slag inclusions, or pores on the surface. The deformation of the welded plate should be corrected, and welding slag and spatter should be removed completely.

Ducts with a wall thickness greater than 1.2mm can be connected to flanges using continuous welding or flanged intermittent welding. The pipe wall and flange inner port should be tightly attached, and the weld seam should not protrude from the flange end face. The length of the intermittent weld seam should be between 30-50mm, and the spacing should not exceed 50mm. Figure 3 2.1 Welding position of air duct welds

The connection between the dust removal system duct and the flange should use full welding on the inside and intermittent welding on the outside, and the end face of the duct should be no less than 5mm from the flange interface plane.

5. The reinforcement of air ducts shall comply with the following regulations:

1) Thin steel plate flange air ducts should be rolled with reinforcing ribs, and the protruding part of the reinforcing ribs should be located on the outer surface of the air duct, with uniform spacing and no obvious deformation on the plate surface.

2) When the flange strength of the air duct is lower than the specified strength, external fixing frames and internal supports can be used for reinforcement. The distance between the reinforcement piece and one end of the air duct connecting flange should not exceed 250mm

3) The height of the externally fixed profile should be equal to or less than the height of the air duct flange, and the spacing should be uniform and symmetrical. The connection with the air duct should be firm, and the spacing between bolts or rivet points should not exceed 220mm. The four corners of the externally fixed frame should be connected as a whole.

4) The arrangement of support reinforcement inside the air duct should be neat, with even and symmetrical spacing. Special gaskets should be installed at the stress (pressure) surfaces of the air duct at both ends of the support. When using pipe sleeve internal support, the length should be equal to the length of the air duct connection.

5) The stiffness level and reinforcement spacing of rectangular ducts should be selected and determined according to Tables 3.2.1-2, 3.2.1-3, 3.2.1-4, 3.2.1-5, and 3.2.1-6.

Galvanized angle iron flange air duct

3.2.1 The production of galvanized air ducts with angle iron flanges shall meet the following requirements:

The thickness of the sheet metal for rectangular ducts and their accessories should not be less than the specifications in Table 3.2.1-1.

Table 3.2.1-1 Thickness of Ordinary Steel Plate or Galvanized Steel Plate Duct Sheet (mm)

2. The splicing of galvanized steel plates or color coated steel plates should be done by biting or riveting, and there should be no cross shaped splicing joints. The coated surface of the color coated steel plate should be located on the inside of the air duct, and damage to the coated layer should be avoided during processing. Damaged parts should be repaired.

3. Welding air ducts can be done in three forms: lap joint, corner joint, and butt joint. The position of the weld seam is shown in Figure 3.2.1. Before welding the air duct, rust and oil should be removed. The weld seam should be well fused and flat, with no defects such as cracks, weld beads, penetrating slag inclusions, or pores on the surface. The deformation of the welded plate should be corrected, and welding slag and spatter should be removed completely.

Ducts with a wall thickness greater than 1.2mm can be connected to flanges using continuous welding or flanged intermittent welding. The pipe wall and flange inner port should be tightly attached, and the weld seam should not protrude from the flange end face. The length of the intermittent weld seam should be between 30-50mm, and the spacing should not exceed 50mm. Figure 3 2.1 Welding position of air duct welds

The connection between the dust removal system duct and the flange should use full welding on the inside and intermittent welding on the outside, and the end face of the duct should be no less than 5mm from the flange interface plane.

5. The reinforcement of air ducts shall comply with the following regulations:

1) Thin steel plate flange air ducts should be rolled with reinforcing ribs, and the protruding part of the reinforcing ribs should be located on the outer surface of the air duct, with uniform spacing and no obvious deformation on the plate surface.

2) When the flange strength of the air duct is lower than the specified strength, external fixing frames and internal supports can be used for reinforcement. The distance between the reinforcement piece and one end of the air duct connecting flange should not exceed 250mm

3) The height of the externally fixed profile should be equal to or less than the height of the air duct flange, and the spacing should be uniform and symmetrical. The connection with the air duct should be firm, and the spacing between bolts or rivet points should not exceed 220mm. The four corners of the externally fixed frame should be connected as a whole.

4) The arrangement of support reinforcement inside the air duct should be neat, with even and symmetrical spacing. Special gaskets should be installed at the stress (pressure) surfaces of the air duct at both ends of the support. When using pipe sleeve internal support, the length should be equal to the length of the air duct connection.

5) The stiffness level and reinforcement spacing of rectangular ducts should be selected and determined according to Tables 3.2.1-2, 3.2.1-3, 3.2.1-4, 3.2.1-5, and 3.2.1-6.