Abstract: The abnormal problems occurred frequently in starting and shutting process of S109FA tandem combined cycle unit manufactured by CE Corporation. These problems were as follow: the vacuity dropped when by-pass put in operation during cold starting, the control valve of high pressure by-pass closed no tightly and leaked when high by-pass quitted, the drain pressure of desuperheator can not achieved auto-close set point in operation with low load, the level in the drain tank of steam turbine proper lowered and vacuity dropped, the circulating water temperature deviation on the second outlet of condenser increased. The relevant handling methods for solving the problems mentioned above were put forward.

Key words: gas turbine, combined cycle, starting and shutting process, abnormality handling