REXA installed a series of high performance units in a New York based combined cycle power plant. For years, REXA has been known as a problem solver for critical service applications for many power companies. REXA tackles difficult applications from Gas Turbine IGV upgrades, to supercritical start-up valves, to problematic drum level control, to boiler feedpump turbine actuation upgrades. The plant is a 3 x 3 x 1 combined cycle plant ((3) GE Frame 7 GTs; (3) Nooter Eriksen HRSGs; (1) GE D11 steam turbine) with cascading bypass system.
The plant is required to cycle frequently as it is a load following plant. These plants are required to operate with a high level of flexibility and respond to grid demands to produce power during day light hours while demand is high, and cycle down at night when demand is low. The turbine bypass system is responsible for controlling superheat and reheat pressures during ramp up and cooling scenarios. The turbine bypass system can greatly affect the ramp up and ramp down rates of these plants.
The existing HP bypass and hot reheat were originally pneumatically operated; they were giving them a great deal of difficulty in accurately controlling in these scenarios. Thermal expansion in these critical control valves can be a cause of great instability for pneumatic actuation. The plant turned to REXA to optimize with stiff and repeatable hydraulic control. Each unit required a 5 second stroking speed for 4.6" and 14" strokes. Three X2L15000-6-D,P9-P and three X2L30000-16-D,P50-P booster pump units were installed.