The dual-flow-ring seal oil system used for 600MW unit in Suzhou Power Plant and the structure features of the sytem have been analysed

it is believed that the causes of water entering into seal oil at the air side of unit no.1 are as follows:the worn-out of shaft at sealing shoe of the turbine end and the exicitor end makes the seal oil of air side and hydrogen side to be crossed.For this

in order to prevent the occurrence of said crossed phenomenon

when the offset of balanced valve between air side and hydrogen side at turbine end and excitor end being discovered

it is necessary to carry out minute adjustment of the seal oil recirculation at the hydrogen side;during the time of major and temporary repairs

the defect of shaft worn-out at sealing shoe on turbine end of the unit should be welded;the clearance of sealing shoe has to be inspected during repair to satisfy the requirement;the inspection of blowdown water from rotary screen of seal oil

and the monitoring of seal oil quality should be strengthened.