A Comprehensive Guide to the Entire Construction Process of Ventilation Ducts: Key Steps and Precautions

 

The construction of ventilation ducts is a crucial part of building engineering, and its quality directly affects the operating efficiency and safety of the ventilation system. This article will systematically sort out the construction process and provide practical technical points to help practitioners efficiently complete engineering tasks.

 

I. Pre - construction Preparation

Before construction, it is necessary to confirm that the building envelope has been completed, the on - site obstacles have been cleared, and the positions of the reserved holes are consistent with the design drawings. It is recommended to prepare a list of construction tools in advance, including professional tools such as electric double - blade shears, angle grinders, and electric welders, and verify the quality certification documents of the materials. The main materials such as plates and pipes should be free of defects such as deformation and cracking, and the thickness of the galvanized steel sheets should meet the requirements of the GB50243 specification. For example, it is recommended to use 0.6mm galvanized sheets for circular air ducts with a diameter ≤ 300mm.

 

II. Duct Fabrication

1. Plate Cutting: Use mechanical cutting to ensure that the cut is flat, and the curved parts should have a smooth transition.

2. Connection Process: The combination lock seam (suitable for plates with a thickness ≤ 1.2mm) is preferred. The corner lock seam is suitable for reinforcing the four corners of rectangular air ducts. It should be noted that the width of the lock seam should match the thickness of the plate. For example, it is recommended to use an 8mm single lock seam for 0.7mm galvanized sheets.

3. Flange Fabrication: The distance between the bolt holes of the angle steel flange should be ≤ 150mm, and anti - rust treatment should be carried out after welding.

 

III. Installation Specifications of Supports and Hangers

1. Positioning and Measurement: Use a laser locator to determine the position of the hanging rods. The single hanging rod should coincide with the center line of the air duct, and the double hanging rods should be symmetrically distributed according to the tray screw holes.

2. Spacing Control: During horizontal installation, for air ducts with a long side ≤ 400mm, the spacing between the brackets should be ≤ 4m; when the long side is > 400mm, the spacing should be ≤ 3m. During vertical installation, the spacing between the brackets should be ≤ 4m, and each straight pipe should be provided with 2 fixing points.

3. Installation Skills: When using expansion bolts for fixing, the mechanical load - bearing requirements should be met. The threads of the hanging rods should be complete, and gas cutting for hole - making is strictly prohibited.

 

IV. Installation of Duct Assembly and Fittings

1. Connection Method: Flange connection is preferred. The bolts should be uniformly tightened, and the nuts should face in the same direction. The soft connection part should use a titanium - silica non - combustible hose, and the length is recommended to be 100 - 150mm.

2. Valve Positioning: The fire damper should be installed at a position ≤ 200mm from the wall, and the valve actuator should be exposed for easy operation. After installation, an opening and closing test should be carried out to ensure flexible operation.

3. Elevation Adjustment: Use a hydraulic lifting platform to assist in installation. For exposed air ducts, the horizontal deviation should be ≤ 3mm/m, and the vertical deviation should be ≤ 2mm/m.

 

V. Quality Inspection and Protection

1. Leakage Test: The medium - pressure system needs to undergo a light leakage test, with ≤ 2 light - leakage points per 10m of the joint. The high - pressure system should use an air leakage test, and the qualified value should be ≤ 1.5% of the system air volume.

2. Finished Product Protection: After installation, a dust - proof film should be wrapped in time. A rain cap should be installed on the outdoor air ducts. A steel protective sleeve with a thickness ≥ 1mm should be installed at the wall - penetrating part, protruding 50 - 100mm from the wall.

3. Anti - vibration Measures: Rubber shock - absorbing pads (with a thickness ≥ 5mm) should be configured for the fan installation, and a fire - proof soft connection should be set at the connection between the equipment and the air duct.

 

VI. Solutions for Special Environments

1. Corrosive Gases: It is recommended to use air ducts made of PP/PVC materials, and the flange connection should be sealed and strengthened.

2. High - temperature Environment: Stainless - steel air ducts (preferably made of 304 material) should be selected, and heat - resistant insulating gaskets should be configured for the brackets.

3. Clean Workshop: The inner wall of the air duct should be coated with epoxy resin, and the oil stains should be removed before installation.

 

By strictly implementing the above construction standards, common problems such as air leakage and vibration noise of the air ducts can be effectively avoided. It is recommended to establish a quality traceability card during the construction process and conduct tri - party acceptance for each process to ensure that the overall performance of the system meets the design requirements.