ASME-Landmark:Philo 6 Steam-Electric Generating Unit

Philo Unit 6 (1957) was the world's first supercritical-pressure steam-electric generating unit to operate commercially. The mechanical engineering innovations represented by Philo 6 significantly advanced the thermal efficiency of power generation, thereby greatly reducing its production cost. Its performance proved that introduction of higher steam pressure and higher steam temperature to power generation—combined with use of a double-reheat cycle—could produce new levels of thermal efficiency, approaching 40 percent. At that time, the national average thermal efficiency of all fossil-fueled power plants was 29.9 percent. Experience gained from the engineering, design, construction, and operation of Philo 6 provided a firm engineering basis for many larger, efficient generating units that were to follow.

Major innovations included new "highs" in feedwater inlet pressure and turbine throttle pressure, as well as the use of a double-reheat cycle. The cyclone furnace design, integrated unit controls, feedwater chemical control, steam generator startup system, and feed-pump design were all uniquely developed for this pioneering unit. The unit's steam generator, designed and built by Babcock & Wilcox, was rated at 675,000 pounds per hour (8 5 Kg per second) at 4,500 psi (31 MPa) and 1,150 F (621 C), with a feedwater temperature of 525 F (274 C). The unit's turbine-generator, designed and built by the General Electric Co., was a 3600-rpm, tandem-compound, double-flow turbine driving a 156,250 kva hydrogen-cooled generator.

The next supercritical-pressure unit to enter commercial service in the United States, after Philo 6, was Philadelphia Electric Company's Eddystone Unit 1 in February 1960 (ASME landmark #226). See ASME website for more information