Tyco Valves & Controls has developed a range of enhanced steam conditioning turbine bypass valves that offer greater flexibility and resistance to the severed operating conditions in combined cycle power applications. The Sempell turbine bypass valves play a pivotal role in the protection of the turbine and condensor in the event of a system defect and emergency shut-down. Operating in severe conditions incorporating start-up ingredients of up to 65 degrees C per minute and reaching steam temperatures of over 550 degrees C, the valves incorporate a radial nozzle system which enables efficient pressure reduction and precise temperature control. In contrast to other bypass valves, the Sempell valve enables the gradual reduction of steam pressure in various stages, serving not only maximum load applications but also low-pressure steam applications or those in which the steam is close to saturation point. Assisted steam is supplied through a cage plug at the top of the valve, eliminating the need for a separate assisted steam control valve. The steam is passed through a diffuser/diffusion plate to create an even outflow and eliminate vortex formation. Water droplets are then injected by jets in the nozzle, which is positioned centrally in the steam flow. The steam flow is of a much higher velocity then the droplets, facilitating a quick energy transfer and, consequently, the evaporation of the water droplets at an optimal rate. More rapid evaporation also allows the valves to be positioned in applications with pipe bends situated close to the valve outlet, which previously presented a problem because of minimal building space at some CCP plants.
