Hydraulic Transient Investigation of Power Plant Condensate Systems

In thermal power plants, the function of a condensate system is to remove and recycle condensed steam from the steam turbine and to deliver condensate to the feedwater system and/or to other equipment depending on the configuration of the power plant. Hydraulic transients are created when sudden changes in flow rates occur due to operations of pumps and valves in the pumping systems. The pressures generated due to these transient events may be high enough to damage or even cause catastrophic failure of pipelines. Therefore, it is very important to perform the hydraulic transient analysis to identify problem areas and provide mitigation measures to avoid potential piping over-pressure or damage to pipes. The current study simulates numerically the transient events and calculate transient pressures and dynamic loads associated with condensate pump operations (startup, trip, switch-over) and valve operations (opening, closing) under normal (pump startup, shutdown) and accidental operating conditions (power failure, accidental valve closure, etc.) of a condensate system. Different operating conditions are analyzed and transient mitigations are evaluated and recommended to avoid extreme transient pressures and associated high dynamic loads to the piping segments. Furthermore, in order to minimize check valve slamming during a pump trip or switch-over, different kinds of check valves (ball, swing, resilient hinge, tilted disc, dual plate, and center guided silent) with different dynamic characteristics are evaluated, and the resulting dynamic loads are estimated. The magnitude of the dynamic loadings for different kinds of check valves are compared and a recommendation for the correct selection of check valves is proposed.