Testing Method for Rotor Imbalance in the No. 5 High-Pressure Centrifugal Fan

Testing Method for Rotor Imbalance in the No. 5 High-Pressure Centrifugal Fan

When the No. 5 high-pressure centrifugal fan is rotating, it generates centrifugal force. This centrifugal force periodically impacts the bearings, causing vibration. Prolonged vibration of the No. 5 high-pressure centrifugal fan’s bearings can damage them, potentially causing the fan blades to collide with the housing. Today, I have found some testing and adjustment methods online to share with you. The No. 5 high-pressure centrifugal fan must undergo vibration testing before leaving the factory. Firstly, use a vibration meter to measure the vibration values of the bearings to assess the rotor’s imbalance under operating conditions. 1. Select an area near the impeller on the No. 5 high-pressure centrifugal fan shaft where rotation has ceased, wipe the surface clean, and confirm that its true roundness meets the standard. 2. Start the No. 5 high-pressure centrifugal fan at operating speed. Using a sharp pencil, slowly extend the centre line of that section of the shaft. If the pencil comes into contact with the shaft surface, stop extending it forward, but move it along the shaft for a short distance, then retreat while the line drawn by the pencil remains on the shaft section. Repeat this several times. Complete this procedure on multiple shaft sections before making a selection. The movement must be light and steady. Take care not to extend the pencil line too far. Otherwise, a full arc will be drawn on the shaft. If the extension is insufficient, contact between the pencil and the shaft will be inadequate. It will be impossible to mark the line segments, the lines will be unclear, and it will be difficult to make a judgement. When drawing the lines, a vibration meter may be used to measure the bearing vibration value A. 3. After the No. 5 high-pressure centrifugal fan has stopped, locate the centre line A-A of the line drawn on the shaft. Mark its position F on the other part of the shaft, and rotate line A-A to a horizontal position. At this point, the horizontal position A on the same side of the impeller is the point of imbalance, and the opposite side is point B. After prolonged practice, the impeller’s diameter is as follows: 1600 mm, speed 1480 rpm. 4. Restart the No. 5 high-pressure centrifugal fan, redraw the lines on the shaft using the method described above, and measure the bearing vibration value B. Compare this with the original vibration value A to confirm the change in the rotor’s vibration value. After maintenance, once the No. 5 high-pressure centrifugal fan has stopped again, verify whether the position mark F of the centre line of the newly drawn line segment aligns with the centre line A-A of the originally drawn line segment. If they align, verify that value B meets the standard requirements. Otherwise, if point B is present (i.e. B > A), the centre line of the new segment is 180° relative to F, indicating excessive weight, which can be reduced accordingly. If the centre lines of the two lines do not overlap or are 180° apart, this indicates an error between the two marked lines, and they can be revised again.