The causes leading to stall wind-snatching

resonance

and torsional vibration of shaft etc.occurred easily in energy-saving retrofit of air fans at present in our country have been analysed

and solution measures being put forward as in the following:before retrofit

measures should be taken from aspects of design and opration to prevent the wind-snatching phenominon between two air fans in parallel operation;calculation of natural vibration frequency for various parts

such as impeller

blade

as well as front

rear

and middle disks in centrifugal air fans

to keep away from resonance frequency

if resonance has occurred at one revolution speed

operation at this speed should be avoided

or adopting regulation valve

combined with adjustment of revolution speed

to prevent resonace of air fans;in order to prevent the torsional vibration of shaf in air fans with speed regulation by variable frequency

the inherent frequency of forsional vibration should be calculated before retrofit

preventing the torsional frequency to fall into the speed-regulating range of air fans.