Application 30 years experience with Sulzer-Bypass-Systems, including controls and safety functions, show that the bypass- controller is neither an integrated part of the boiler controls nor the turbine controls. The Sulzer-Bypass-System is an independent system which serves to coordinate the boiler and turbine operation during startup, shutdown and load disturbances. The necessary signal exchange between the bypass-controller and other systems is small. Much more important is a bypass-controller which exactly fullls the requirements of the bypass operation in the plant and allows the easy implementation of required safety functions. The life conserving operation of the heavily stressed valves and pipework, especially by accurate steam desuperheating in all operating modes and transients, poses a special challenge for the bypass- controller. Features Standardisedn Proven solutions from more than 30 years ofexperience with HP & LP-bypass automation n System responsibility in one hand Flexible n State Controller with Observer (SCO) reduces temperature transients for valves and pipes n For any type of boiler plant n With or without safety function n Degree of automation selectable Open n Clear and simple interface to boiler and turbine controls n Hundreds of bypass controllers installed n Satises highest automation requirements Bypass Controller Type AV6+ Fig.1 HP Bypass with ControllerFunction HP Bypass ControllerThe HP-bypass controller consists of a pressure controller, controlling superheaterpressure through the position of the steam valve, a temperature controller, controlling downstream temperature through the position ofthe spray control valve and a Op/Cl- Controller for the spraywater isolation valve. The key part of the pressure controller is the setpoint generator. It has to produce the correct setpoint for all the different operating modes during start-up, load operation, load rejection and shutdown. The heart of the setpoint generator is a rate limiter, which limits the gradient of any pressure increase during all operating modes, therefore protecting components from pressure/tem perature transients.
