Roots blower impeller damage can be caused by the following:

1. Wear and Fatigue: Prolonged operation can lead to wear on the impeller surface, especially if particulate matter or solid contaminants are present. Repeated stress and vibration may also lead to the development and expansion of fatigue cracks in the impeller.
2. Corrosion: If the Roots Blower is operated in a corrosive environment, the impeller may corrode. Corrosion can cause the impeller surface to thin and lose strength, ultimately resulting in damage to the impeller.
3. Overload: If a Roots blower is subjected to operating conditions that exceed its design load, such as excessive flow or pressure, the impeller may not be able to withstand this overload and damage may occur.
4. Improper Operation: Improper operation, faulty maintenance or improper installation can cause damage to the impeller of the Roots Blower. This includes excessive start/stop frequency, excessive temperatures, poor lubrication, etc.
5. Material clogging: In the process of handling granular materials, the impeller may be clogged with granular materials, which may prevent the impeller from rotating properly and may cause damage to the impeller.

To avoid impeller damage, it is recommended that the Roots Blower be regularly inspected and maintained to clean particulate matter from the impeller surface, ensure proper lubrication and operating parameters, and proper operation and maintenance procedures. If the impeller is found to be damaged or in an abnormal condition, it should be repaired or replaced in a timely manner to ensure the normal operation of the Roots Blower.