ASME-Landmark:Eddystone Station Unit


Operated by the Philadelphia Electric Company (PECO), now known as Exelon Corp., Eddystone Station Unit #1 is a 325 MW pulverized-coal-fired plant that pushed the technology of steam-electric generating plants. When built in 1960, engineers sought to make a more efficient plant using higher temperatures and pressures and larger machines. Previous experience at Philo 6 (Zanesville, Ohio, 1957, ASME landmark #228) had demonstrated that supercritical steam plants would work, so engineers worked toward even larger machines and efficiencies. By reducing pressure and temperature conditions slightly, the engineers succeeded while discovering a more economically viable generating plant design.

The steam generator and steam turbine were first-time designs, and the ground covered was new: For example, the steam tables had to be extended into the supercriticial pressure region to develop the design information required for equipment design and sizing. During this phase, the supercritical steam vapor behaved more like a liquid than a vapor, in regard to heat transfer properties. The design phase developed a once-through boiler (no mud drum) that required ultra-pure water, which extracted molecules directly from the metals that it contacted. The turbine design feature new high-speed control valves, unique shaft and inlet seals, and many other innovations. The station also required creep rules to be extrapolated from known values, which proved highly accurate.

When designed in 1956-57, this plant consisted of a monotube boiler and cross-compound turbine generator. Philadelphia Electric Company (now Exelon) built a coal-fired 3,600 rpm, tandem compound supercritical-pressure unit of 275 MW capacity (using 25-inch last-row blades) with throttle steam conditions of 5,000 pounds per square inch (psi)/34.5 MPa and 1,200°F/650°C, with two reheats to 1,050°F/565°C. See ASME website for more information