The selection of clearance for self-aligning roller bearings in fans should be based on matching the operating temperature, fitting method, and load characteristics of the fan, to avoid overheating and jamming caused by too small clearance, and severe vibration and abnormal noise caused by too large clearance.
Standard clearance selection for different working conditions
Table
Fan working condition typesRecommended clearance levelTypical radial clearance rangeApplicable scenarios
Normal temperature ventilation fanC3 level 0.10~0.20mm Conventional civil ventilation, small workshop fans, operating at temperatures below 80 ℃
Industrial dust removal/induced draft fansC3 level 0.15~0.25mm Steel plant dust removal, boiler induced draft fan, operating temperature 80~120 ℃
High temperature kiln/circulating fanC4 level 0.20~0.35mm High temperature circulating fan for kilns, operating at temperatures exceeding 120 ℃ for a long time
Heavy duty impact fanC4 level 0.25~0.40mm Mining fans, high flow centrifugal fans, with a load exceeding the fixed dynamic load by 30%
Selection core calculation logic
Final working clearance=original clearance - interference fit reduction+thermal expansion compensation.
Hot fit interference fit will consume 15% -20% of the initial clearance. When selecting, a margin must be reserved to avoid the clearance returning to zero directly after installation.
.For every 10 ℃ increase in temperature of steel bearings, the components expand by about 0.01mm. High temperature fans must use larger clearances to counteract thermal expansion and prevent bearing locking during operation.
.The axial clearance should be controlled at 1.5~2 times the radial clearance to ensure that the shaft does not experience axial buckling after thermal elongation.
.Key Points for Avoiding Pits
Ordinary room temperature fans must not choose CN standard clearance. After hot installation, the clearance will be completely consumed, and bearings will overheat and burn out after running for a few hours.
. The larger the clearance, the better. Excessive clearance beyond C4 level can cause severe vibration of the fan rotor during operation, leading to early pitting corrosion of the bearings and significantly reducing their service life. After installation, the actual clearance must be retested with a dial gauge to confirm that the value falls within the recommended range before starting up for trial operation.