After about two years in operation

non-regular intermittent vibration had occurred on axialflow primary air fan with double-stage moving blades regulation equipped for boiler of supercritical 600 MW unit in one power plant.Through test

it is believed that the main cause resulting in vibration is serious abrasion on the actuator of said fan.For this

the copper bushes of first-and secondary-stage actuators have been replaced

and the vibration being eliminated.The parts of fan's actuator are easily to be abraded and failed

resulting in non-synchronizing fault in opening degree of the double-stage moving blades

thereby leading to vibration of the air fans.