Fault Diagnosis of Centrifugal Fan--Part 1 Fan Bearing Over-standard Vibration

Fault Diagnosis of Centrifugal Fan--Part 1 Fan Bearing Over-standard Vibration 

 ---by Xianrun Blower 

The fan bearing vibration is the most common problem during the working, because it causes bearing and blade damage, bolts looseness, casing and duct system breakdown. 

centrifugal fan main shaft

1.1 Dust deposition 

When air enters the impeller, and rotating blades surface have angle. According to the fluid mechanics principle, the non-working face of blade leaves a vortex, so dust will deposit
slowly under the effect of vortex. The rotating impeller will throw out a part of dust when the dust reaches a certain weight. 
As a result, uneven dust in impeller blade causes impeller unbalanced, then make the fan over-standard vibration.


1.2  Duct system vibration

Smoke or air duct system vibration lead to centrifugal fan forced vibration. And the vibration usually cause fan outlet enlarge; the air volume increas; the vibration changes.
On the other hand, uneven incoming air area of fan inlet, such as not unified baffle opening and closing, can also cause impeller vibration.

centrifugal blower in cement plant

1.3 Collision of dynamic and static parts

(1) the fan impeller and air inlet are not on the same axis. 
(2) air inlet  has damage and deformation. 
(3) impeller looseness increases impeller waggle. 
(4) bearing failure. 
(5) the connection between shaft and bearing become loose. 
(6) main shaft distortion. 

centrifugal fan in cement plant