During the use of the impeller of AC & DC cooling fans, the causes of imbalance can be briefly divided into two types: wear of the impeller and fouling of the impeller.

These two situations are related to the dust removal device connected in front of the induced draft fan. The dry dust removal device causes the impeller imbalance mainly due to wear; while the wet dust removal device affects the impeller imbalance due to fouling. Now they are described as follows.

1. Wear of the impeller

Although the dry dust removal device can remove most of the large particles of dust in the flue gas, a small amount of large particles and many tiny dust particles pass through the induced draft fan along with the high temperature and high speed flue gas, so that the blades are continuously washed. If things go on like this, a blade-like abrasion will be formed at the blade exit. Because this wear is irregular, it causes an imbalance of the impeller. In addition, the surface of the impeller is easily oxidized at high temperatures, resulting in thick oxide scale. The bonding force between these scales and the surface of the impeller is not uniform, and some scales will fall off automatically under the action of vibration or centrifugal force, which is also a reason for the imbalance of the impeller.

2. Fouling of the impeller

The flue gas purified by the wet dust removal device (Venturi water film dust collector) has a high humidity, and the uncleaned dust particles are small, but the viscosity is high. When they pass the induced draft fan, they will be adsorbed on the non-working surface of the blade under the action of the gas vortex, especially at the inlet and outlet of the non-working surface, serious dust fouling will be formed, and the thickness will gradually increase. When part of the dust falls off under the combined action of centrifugal force and vibration, the balance of the impeller is destroyed, and the entire induced draft fan will vibrate.

In summary, the stable operation of the high temperature cooling fan and the high speed cooling fan has a great relationship with the balance of the impeller.