Fans generally rely on the main shaft to drive the blades to run. Most of the spindles of centrifugal fans are directly connected to the transmission, so they require a high level of performance. If a fault occurs, the operating efficiency of centrifugal fans will be reduced or even unable to run.


I. Causes of Main Shaft Faults of Common Centrifugal Fans


1. Reasons for surface damage of spindle


The spindle of centrifugal fan has a certain bare part. If impact or scratch occurs on the bare part, there will be scar defects. In addition, if proper maintenance is not carried out, surface damage will also occur due to rust. In the past, cracks or surface cracks will easily occur on the stepped end of the spindle after catalysis of fan vibration.

2. Reasons for wear of spindle Journal


Most of journal wear is caused by poor lubrication. If lubrication is not in place, or if impurities in lubricating oil, such as metal chips, lead to journal scratches and wear. In addition, if the bearings are not properly installed or the bolts are loose, the main shaft is not bent correctly, the rotor dynamic imbalance is too large, etc., the journal will be subject to uneven wear, resulting in ovality and conicity.

3. Reasons for Bending of Main Shaft


There are four main reasons for the bending of the main shaft of centrifugal fan: 1. When installing the centrifugal fan, the coupling is not aligned, which causes the clearance between the shaft and the sealing ring to be too small, and the bending is caused by the excessive heat of friction; Second, the foundation sinks unevenly, resulting in bending of shaft and bushing due to friction overheating; Third, vibration during operation of fan causes metal relaxation and bending at impact of shaft; Fourth, the bending is caused by local heat during repair welding.


II. Solutions to Main Shaft Fault of Centrifugal Fan


1. Treatment of spindle surface damage: Remove surface scratches with a file and polish with an oil-soaked abrasive cloth. If the wound is serious or the depth is greater than 1~2mm and the area is greater than 10mm. ² When doing so, replace the new shaft.

2. Treatment of Journal wear: No more than 1mm wear ² The metal repair material can be used to coat the compensation and then the dimension can be adjusted by turning or scraping. If greater than 1 mm ² When repairing, it should be welded and then cut.


3. Treatment of bending of main shaft: After wearing of impeller and bearing, repair or replace in time to avoid violent vibration of fan; During installation and overhaul, control the parallelism and concentricity between centrifugal fan and motor axes to 0.05~0.1mm according to technical requirements, and leave 5~6mm clearance between the two couplings. If the bending of the main shaft exceeds 0.5~1mm, the new shaft should be corrected or replaced.