Comprehensive Process Analysis of Ventilation and Air Conditioning Duct Installation: Key Steps and Quality Control Points

 

In the ventilation and air conditioning system, the installation quality of the ducts directly affects the air supply efficiency, energy consumption control, and the service life of the equipment. A standardized construction process and precise quality control are the core elements to ensure the stable operation of the system. The following analyzes the core technical points of duct installation from seven aspects.

 

I. Site Survey and Preparation before Construction

Before construction, it is necessary to confirm that the building's enclosure structure has been completed, and obstacles and debris on the ground in the installation area should be cleared. Special attention should be paid to checking the positioning accuracy and dimensional deviation of the reserved holes, and the allowable error should be controlled within ±5mm. For ducts passing through the concrete structure, steel sleeves should be pre - embedded, and both ends should protrude 20mm from the wall.

 

II. Precise Positioning of the Support and Hanger System

The support and hangers should be made of hot - dipped galvanized profiles, and the elevation error should not exceed ±3mm. When the diameter of the circular duct changes, the installation height of the support should be adjusted at a slope of 1:100 to maintain the horizontal center line. The oil and rust on the embedded parts must be thoroughly removed, and the implantation depth of the expansion bolts should be 1.5 times the length of the sleeve. The spacing setting should follow the rules: for horizontally installed ducts with a diameter ≤400mm, the spacing should not be greater than 4m; for those with a diameter >400mm, the spacing should not be greater than 3m; for vertically installed ducts, the spacing should be uniformly 4m.

 

III. Connection Technology for Ducts of Various Shapes

1. Flange Connection: In the air - conditioning system, the spacing between bolt holes should be strictly controlled at 120mm, and in the smoke prevention and exhaust system, it should be reduced to 80mm. The bolts at the four corners must be tightened in both directions, and the compression rate of the sealing gasket should reach 30% - 40%.

2. Common Plate Flange: The installation method of alternate front and back is adopted. The spacing between adjacent clamps should be maintained at 80mm, and elastic sealant should be used to fill the gaps at the four corners.

3. Flexible Hose Transition Section: The length should not exceed 2m. During installation, a slackness of 3% - 5% should be maintained. It should be fastened with double - layer stainless - steel wire hoops, and the spacing between the hoops should be 150mm.

 

IV. Selection of Modular Installation Techniques

1. Overall Lifting: It is suitable for straight pipe sections with a diameter <800mm. The spacing between lifting points should not exceed 6m, and the lifting angle should be ≤30°.

2. Sectional Installation: For complex pipe fittings, on - ground pre - assembly is preferred. After 70% of the connections are completed, they should be lifted in sections, and the butt joint error should be controlled within 2mm/m.

 

V. Treatment Specifications for Special Parts

When passing through the fire - prevention partition, a fire - prevention wrapping layer with a fire resistance limit of ≥1.5h should be installed, and the installation spacing of the expansion joints should not exceed 20m. For insulated ducts, anti - corrosion - treated hardwood pads should be installed at the supports. The thickness should be the same as that of the insulation layer, and the contact area should be >80% of the cross - section of the support.

 

VI. System Integrity Testing

After the installation is completed, a three - level test should be carried out:

1. Air - tightness test: For the medium - pressure system, the air leakage rate should be ≤2.11m³/(h·㎡), and for the high - pressure system, it should be ≤1.36m³/(h·㎡).

2. Mechanical strength test: Apply 1.5 times the working pressure and maintain it for 10 minutes without permanent deformation.

3. Airflow organization verification: The deviation of the terminal wind speed should be ≤15%, and the noise value should not exceed the design value by 3dB(A).

 

VII. Whole - Process Quality Control System

A double - acceptance system for materials entering the site should be established. Special attention should be paid to detecting the thickness of the galvanized layer (≥100g/㎡) and the thickness deviation of the plates (±0.05mm). During the construction phase, the "three - inspection system" should be implemented: self - inspection by the work team, hand - over inspection between processes, and special quality inspection. Image data should be retained at key nodes, and a traceable quality file should be established.

By strictly implementing the above technical standards, the air leakage rate of the duct system can be effectively controlled within 5%, and the post - maintenance cost can be reduced by 30%. Special attention should be paid to the protection of finished products during the construction process. After lifting, dust - proof covering should be carried out immediately to avoid surface damage caused by cross - operations.