Steps and Precautions for Replacing High-Speed Axial Flow Fans

Steps and Precautions for Replacing High-Speed Axial Flow Fans

High-speed axial flow fans must be replaced once they reach their design service life. During the replacement process, paying attention to certain details can yield twice the results with half the effort. The high-speed axial flow fan features a concrete foundation, a combined drive system, and a water-cooled drive unit, with a 200 kW motor. 1. When dismantling the old high-speed axial fan, be sure to keep the bearing housing and shims beneath the motor. These will be needed when fine-tuning the installation of the new fan. 2. First, install the bearing housing of the high-speed axial fan. Use a level or a water level to ensure the four corners of the base are level. Tighten the bolts once leveled. 3. Install the housing with the front cover removed. The position of the bushing must be aligned with the head of the drive shaft, centered in the bushing’s shaft bore. 4. After securing the outer cover, install the inner cover. First, sand the shaft end and the inner shaft bore with fine sandpaper, then apply grease to the shaft end. Thread the lifting ring through 3–5 blades, lift the propeller, and align it to the correct position. (There is a horizontal steel pipe inside the housing where the impeller can be placed; use a three-pronged tool to lift the impeller and align it with the shaft head.) 5. Adjust the gas flame to a red-yellow color and evenly heat the impeller’s shaft bore for 10–15 minutes. Then, press the impeller horizontally inward to allow the shaft head to pass through the shaft bore. At the same time, use a steel ball or steel pipe weighing over 200 kg to strike the shaft disc at the center of the impeller (the shaft disc must be fitted with a wooden or steel plate). Once the impeller portion of the shaft end has fully entered the shaft hole, secure it in place with screws. 6. Install the front cover of the cabinet, seal the gaps with asbestos strips, and secure it with bolts. 7. Rotate the impeller to check for friction between the impeller and the side plates on the front and back of the housing. If friction is present, adjust the front-to-back position of the housing relative to the shaft. 8. Install the motor. The clearance between the two couplings should be 3–5 mm. After adjusting and securing the height at the four corners of the motor base, verify that the motor shaft and drive shaft are aligned (at this point, the two couplings should be perfectly aligned with the shaft, and the clearance between the couplings should be consistent across all positions). This step is critical and may require multiple adjustments. Please be patient. 9. Tighten the coupling bolts, verify the overall installation of the high-speed axial fan, and begin the test run. If abnormal vibration occurs in the fan bearing housing or motor, the motor shaft and drive shaft may be misaligned; in this case, repeat steps 8 and 9.