Abstract: This paper introduces the problems of large vibration of No.2 bearing installed in the seat cylinder and the negative differential expansion value of the turbine exceeding the alarm value during the test run of the generator set in a coal chemical company. Through theoretical analysis and field measurement calculation, this paper obtained the impacts of additional blind force on the contact stiffness of the unit and the impacts of thermal imbalance caused by the design defects of shaft seal system on cylinder bearing vibration and steam turbine expansion difference through analysis. Aiming at the causes of the problems, the paper put forward the corresponding countermeasures and carried out technical revamp for the generator set. Thus the problems were solved thoroughly.

Key words: steam turbine, contact stiffness, thermal equilibrium, additional blind force