The vacuum system consists of evacuation piping, isolation valves, and vacuum extraction equipment for the condenser. Internationally, steam-jet ejectors are commonly used for this system. An auxiliary ejector is employed during steam turbine startup to meet the requirement of establishing the necessary vacuum within a specified timeframe (e.g., 30 minutes).
During normal operation, a main ejector with lower capacity is used to maintain the vacuum in the exhaust system. In China, direct air-cooled units predominantly utilize water-ring vacuum pumps; typically, three pumps-each with 100% capacity-are installed per unit, with all three operating during startup. During normal operation, one or two pumps remain in service. The vacuum system is also equipped with vacuum-breaking valves, which can be opened when it is necessary to break the system vacuum.
