Within the station building, each turbine has a fully embedded spiral casing and water flow is controlled by a spherical rotary main inlet valve and a turbine relief valve designed to prevent spiral casing overpressure.
The description details how turbines within a station are equipped with a spiral casing that's completely embedded, along with a system for controlling water flow using a spherical rotary valve and a pressure relief valve to prevent excessive pressure buildup inside the casing.