Experimental Study on Frictional Vibration in Bearing Case of Centrifugal Fan

Abstract

In the operation of a centrifugal fan installed on a steel plate floor reinforced with steel frames, applied to the heated air recirculation for the paint drier plant, abnormal vibration of the fan was observed in the transient condition of the plant operation. In view of the complexity of the vibration on the fan at the site, an experimental study on the vibration characteristics was conducted by using an identical fan and a simulated steel plate floor. As a result, there were three characteristic vibration phenomena during heating-up or cooling-down operation. The instantaneous increase of vibration occurred when the bearing case was new and there was insufficient lubrication even on the concrete slab. The temporary increase of vibration in vertical direction was caused by raising or sinking of the floor and the fan base due to thermal expansion. And, the fluctuation of vibration in axial direction was caused by friction, which yielded when the bearing moved inside the bearing case due to thermal expansion or contraction of the shaft. It seems that this fluctuation was due to self-excited vibration by friction.