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Analysis of causes of excessive vibration of bearing during operation of centrifugal fan

Jun 13, 2018

Centrifugal fan is a kind of machinery that converts mechanical energy into high pressure wind energy. It uses high speed rotating impeller to accelerate gas, then decelerate, change flow direction, and convert mechanical energy into wind energy. We all know that centrifugal fan is made up of housing, spindle, impeller, bearing drive mechanism and motor. Centrifugal fan because of the long time work and wear its bearing will more or less malfunction, the following is to explain the centrifugal fan bearing vibration exceeding the standard reasons.

Bearing vibration of centrifugal fan is a common fault in operation. The vibration of centrifugal fan will cause bearing and blade damage, bolt loosening, casing and air duct damage and so on, which seriously endanger the safe operation of centrifugal fan. There are many reasons for the vibration of centrifugal fan bearings exceeding the standard. If we can take appropriate measures to analyze the causes of different phenomena, we can often achieve twice the result with half the effort.

The defects such as non-working area ash treatment by incessant furnace and the vibration of centrifugal fan are often found in boiler centrifugal fan. The main phenomenon is that the vibration of centrifugal fan rises suddenly in operation. This is because when the gas enters the impeller, there is a certain angle with the rotating blade face. According to the principle of hydrodynamics, there must be vortex of the gas in the non-working face of the blade. Thus the ash particles in the gas will slowly deposit on the non-working face due to the vortex action. Wing blades are the most likely to accumulate ash. When the ash reaches a certain weight, a part of the ash is thrown out of the impeller due to the centrifugal force of impeller rotation. Due to the fact that the ash deposition on each blade can not be completely uniform, the time of agglomeration or ejection of ash block is not always synchronized, the result is that the mass distribution of impeller is not balanced due to the uneven ash deposition on the blade, and the vibration of centrifugal fan increases.

In the practical operation , the general treatment method is to open the manhole door of the centrifugal fan casing after temporarily stopping the furnace , and the overhaul personnel enter into the casing to remove the accumulated ash on the impeller . In this way, not only the environment is bad, there are unsafe factors, but also the unplanned outage of the unit, long overhaul time and heavy labor intensity.

After study, a practical proven effective treatment method is put forward. Add a row of nozzles to the throat and adjust the nozzles at different angles. The nozzle is connected to the ash flushing pump, the ash washing water is used as the power medium for washing ash, the centrifugal fan is stopped on one side after reducing the load, the valve is quickly opened at the moment when the centrifugal fan is stopped, and the non-working face on the blade is sprayed by the inertia action of the impeller. Open the valve added to the bottom of the housing to drain the ash. In this way, the purpose of treating the vibration of centrifugal fan by incessant furnace is realized. Compared with steam and compressed air, it has the advantages of low nozzle structure, wide ash removal range, good effect and less wear on blade.

To sum up, the damage of centrifugal fan bearing vibration is still very large, so we should pay attention to check whether there is ash on the impeller of centrifugal fan at ordinary times. If there are some, we need to clear it immediately to avoid causing the bearing vibration to exceed the standard, so that the whole centrifugal fan is damaged. http://www.jnblower.com/