Common use of Modes of Operation Clause in Contracts

Modes of Operation. During normal operation, steam flows from the exit of the HP steam turbine, through the reheat section of the HRSG, and through the hot reheat line to the IP turbine inlet valves. Steam from the HRSG IP superheater outlet flows to the CT steam cooling system with excess steam flowing to the cold reheat system. IP steam that is heated in the CT steam cooling system mixes with the hot reheat steam from the HRSG. Cold reheat steam is supplied to the condenser air ejectors and the gland steam system. During startup, steam is directed through the full-flow bypass to the condenser until the lines have been warmed and drained of condensate and the steam turbine has been warmed using main steam and rolled up to operating speed. In the event of a turbine trip, the condenser bypass valves will open to maintain the required pressures throughout the system and prevent opening of the Safety Relief Valves. -------------------------------------------------------------------------------- Proprietary Information Page 11 AES IRONWOOD CONTRACT FINAL ISSUE - OCTOBER 30, 1998 --------------------------------------------------------------------------------