Repower AG is carrying out a comprehensive modernisation of the Robbia hydropower plant in the canton of Graubünden, Switzerland. As part of this modernisation, the buildings are being renovated and replaced, and valves, turbines and pipelines are also being replaced. KLINGER Gysi was authorised to supply valves for the first section of the project.
The VAG EKN DN 1300 PN10 butterfly valve with emergency shut-off function forms the interface to the next section of the Robbia HPP up to the Asciali apparatus chamber. A 3 km long pressure pipe with a diameter of 1.3 m runs from the Braita apparatus building to the Asciali apparatus chamber. If this pipeline breaks, the VAG EKN DN1300 PN10 butterfly valve with emergency shut-off function closes within 120 seconds to prevent the water from flowing out.
Three turbines for power generation
KLINGER Gysi supplied two VAG RIKO DN 800 PN10 for the Asciali apparatus chamber. The installation was carried out by Josef Muff AG. Both VAG RIKOs are used to regulate the volume flow of the water flowing through the pressure pipe from the Braita apparatus building. A maximum volume flow of 3.4 m3/s is possible. From the Asciali apparatus chamber, the water flows through a tunnel to the Robbia power plant, where three turbines are used to generate electricity. However, this construction phase has not yet been completed.
The Asciali chamber is not accessible in winter, so Repower AG has to operate the valves installed there from an operations centre. The two VAG RIKO DN 800 PN10 valves with AUMA actuators are located in the Asciali chamber. One of the two VAG RIKO valves is equipped with a frost protection bypass to ensure a minimum flow rate in winter, which prevents the water in the pressure pipe from freezing.
Extensive tests
During wet commissioning, those responsible first tested the correct setting and function of the drives. In the second step, they opened each VAG RIKO individually in predefined steps. During this test, the signal comparison between the position transmitter of the drive and the signal arriving at the operating centre was carried out. This is necessary in order to be able to specify a setpoint for the valve position using the external controls. The AUMA actuator then moves the valve to the selected position. At the same time, the volume flow is measured when the setpoint position is reached and compared with the design data.
This commissioning test is necessary in order to be able to regulate the required volume flows as required during subsequent operation of the system. Following the individual tests of the VAG RIKO, the persons responsible carried out the same test with parallel opening VAG RIKO. There is a backwater basin behind the two VAG RIKOs. The back pressure basin can be used to generate back pressure in order to prevent possible cavitation behind the VAG RIKOs. Both VAG RIKOs and the VAG EKN DN 1,300 PN10 butterfly valve with emergency shut-off function are now successfully in operation.
