AIR-PREHEATER MOTOR TRIPS/ AIR MOTOR DOES NOT START

AIR-PREHEATER MOTOR TRIPS/ AIR MOTOR DOES NOT START:

LIKELY CAUSES
·         Motor may trip on overload.
·         Power supply to the motor failed.
·         Air motor failure or solenoid failure
·         No compressed air available.
·         Lube oil system fail.
·         Some foreign material fallen on the APH & got stuck.
·         Seal of the APH has got disturbed.

PLANT RESPONSE

·         Rapid fall of hot air temperature on one side.
·         Rapid rise of gas temperature of stopped APH.
·         Possibility of deformation of APH.
·         Alarm at ECP/ DCS electrical motor stop- appears.
·         Furnace draft will fluctuate due to ingress of cold FD air.
·         Mill temp will drop as a result of drop in hot PA temperature.

OPERATOR ACTIONS

·         Reduce boiler/generator load to 60% MCR gradually.
·         Attempt for starting the electric motor, if the power has resumed or after resetting the over load.
·         If the air motor has not started because of air solenoid problem open the bypass valve of the solenoid.
·         Isolate affected air heater on the gas side first if all the attempts of starting the air motor or electric motor has failed. (Keep watch on draft)
·         Isolate the affected APH at airside (keep watch on total airflow)
·         Try to rotate air heater manually.
·         Maintain generator load depending upon the parameters of the running AH.
·         Watch hot air temperatures to mills
·         Cut in oil burners, when load is reduced.
·         Reduce corex to minimum.
·         Checks lube oil system & restore lubrication.

PARAMETERS OF CONCERN

·         Flue gas temp at APH I/L & O/L.
·         Furnace draft.
·         Mill o/l temp / hot PA temperature
       Secondary air temperature.