Lessons Learned and Testing Philosophy for the Piping System of a sCO2 Facility

Abstract The team leading the testing of the STEP facility in San Antonio, TX, has taken several steps to monitor the health of the piping systems used on the plant during and leading up to the facility’s commissioning. The STEP facility is a 10 MWe pilot plant that consists of an indirect fired Supercritical CO2 (sCO2) cycle with pressures up to 265 bar and a turbine inlet temperature up to 715°C. The first phase of the project, a simplified cycle configuration producing less power, has recently been completed, and modifications for the RCBC (Recompression Closed Brayton Cycle) cycle are underway. This manuscript will discuss the philosophy and lessons learned from piping vibrations. It also discusses changes in fluid conditions on the loop while undergoing the startup and shutdown transients, operating at and in between steady-state conditions. Special considerations are given to the loop reaction to changes in density, mass flows, stub creation while closing valves, and quick transients in the event of a facility trip. Loop monitoring has been performed using various accelerometers and dynamic pressure probes placed strategically in the testing facility with care to select probes appropriate to the testing environment or modify them accordingly. As the team underwent longer testing phases, expansions to the monitoring capabilities had to be performed, and the priority locations for monitoring were modified as needed. Between operating and commissioning activities, the data collected on the system was used to perform facility modifications to mitigate any high vibrations. The data was collected using in-house software called fieldDAS, which uses NI hardware to collect and process data. The software was chosen based on its customizability and high-speed data collection capabilities.