Precautions for correctly installing centrifugal fans

Centrifugal fan is the most commonly used mechanical ventilation equipment, and its working principle is almost the same as that of turbo compressor. However, due to the low gas flow rate and small pressure change, the change in gas specific volume usually does not need to be considered, which means that gas is treated as an incompressible fluid. During the installation process, there are several steps that need to be noted. Let's take a look with the air model fan below:

1. The cutting surface on the base of the centrifugal fan assembled on site should be properly protected and should not be corroded or operated. When the base is placed on a horizontal foundation, paired diagonal shims should be used for leveling.

2. The bearing seat and base should be tightly connected, and the longitudinal non levelness should not exceed 0.2/1000. The horizontal non levelness should not exceed 0.3/1000 when measured on the main shaft with a spirit level. The horizontal non levelness should not exceed 0.3/1000 when measured on the horizontal split of the bearing seat with a spirit level.

3. Before grinding and scraping the bearing shell, the rotor axis line and the casing axis line should be calibrated, and the gap between the impeller and the air inlet, as well as the gap between the main shaft and the rear plate shaft hole of the casing, should be adjusted to comply with the technical specifications of the equipment.

4. When assembling the main shaft and bearing, inspection should be carried out according to the technical specifications of the equipment. The interference fit between the bearing cover and the bearing shell should be maintained at 0.03-0.04 millimeters (measure the outer diameter of the bearing shell and the inner diameter of the bearing seat).

5. When assembling the centrifugal fan casing, the position of the casing should be aligned with the rotor axis line as the reference, and the axial and radial clearances between the impeller inlet and the casing inlet should be adjusted to the range specified in the equipment technical documents at high speed. At the same time, check whether the anchor bolts are tightened. When the clearance value is not specified in the equipment technical documents, the axial clearance should generally be 1/100 of the outer diameter of the impeller, and the radial clearance should be evenly distributed, with a value of 1.5/1000 to 3/1000 of the outer diameter of the impeller (whichever is smaller, take the larger value). When adjusting, strive for a smaller gap value to improve the efficiency of the fan.