What are Turbine Bypass Systems?
Turbine bypass systems in Combined Cycle Power Plants (CCPPs) are utilized to ramp units online and offline, stably controlling Main Steam pressure and Reheat Pressure in the Heat Recovery Steam Generator. In addition, these systems safely maintain vacuum at the condenser. CCPPs are cycled more frequently, therefore making turbine bypass systems utilized more often – further proving how critical they are to plant operations.
Improperly functioning turbine bypass system valves represent more than just an inconvenience to effective operation of CCPPs. They routinely contribute to unscheduled downtime and trip events. Every unscheduled trip event adds to equivalent plant starts, and greatly reduces the planned maintenance intervals as part of Long Term Service Agreements (LTSAs), causing plants to spend millions of dollars before they should be required to do so.
Through responsive and repeatable performance, our Electraulic™ Actuation enables CCPPs to optimize transitions and eliminate nuisance trips during ramp-up, ramp down and emergency response scenarios. Our actuators provide hydraulic control capable of steps to .05% resolution – completely eliminating the effects of stick-slip inherent of pneumatic actuators. We design our actuators for continuous modulating service and provide stiff, stable control even in the harshest environmental conditions (-40°F to +250°F).
“Performance issues with our pneumatically-operated turbine bypass valves were an ongoing problem at our plant for years. The previous actuators were not stiff enough in ramping/de-ramping and blending scenarios. The resulting valve hysteresis caused unstable operation, degradation to the valve trim and long transitioning periods. Upgrades to REXA actuation have reduced ramp times by as much as 20 minutes, leading to increased generation revenue, and has completely eliminated unwanted trip events. This was the best investment we have made at my plant in my tenure…”