Axial fan for ventilating systems

摘要

An insert ring (12) is fastened on the inside wall of the housing (1) and comprises a material which does not wear in use and which wears during smoke removal. The distance of the tips of the blades (8) from the inside wall of the housing is preferably 0.2-2.0% of the impeller diameter and from the inside of the insert ring is 0-0.5% of the impeller diameter.