The Reisseck II pumped-storage power plant is Austria’s Verbund AG’s biggest project at the moment. Verbund AG has been working on the expansion of the Malta and Reisseck power plant group since 2010.

With the completion of the works in early 2016, Malta/Reisseck will be one of Europe’s most powerful hydropower plant groups. The first test runs were carried out in February 2016. One of the key elements of the plant, situated directly below Lake Mühldorf, is the butterfly valve, consisting of a revision valve and an operation butterfly valve. CKD Blansko Holding has manufactured the gigantic custom unit with an inner diameter of 3.6 m and installed it in an exposed position at 2218 m above sea level. The plant will be commissioned this fall.

Austria’s biggest power plant construction site is located in the high mountain region of Carinthia’s Möll Valley, in Mühldorfer Graben. Hikers might easily miss the construction progress as the works for Verbund’s pumped-storage power plant Reisseck II are carried out deep inside the mountain. When the construction works began in the fall of 2010 a huge rock cavern was cut out of the mountain within just a few months. Once commissioned the power plant in this cavern will house two pump-turbines with an output of 430 MW – in both pump and turbine modes. Reisseck II is an expansion of the already existing Malta/Reisseck power plant group and will increase its output by 40 percent. What is so special about this project is that no additional water resources are used, only the existing potential is being exploited. This shows that the plant is all about efficiency.

THE COMMISSIONING
The project entered the phase of the wet commissioning with the completion of the installation of both machine units in February 2015. The last phase before Reisseck II will finally be connected to the grid will follow a strict procedure. In this phase all power plant components will be examined and adjusted. Key elements of this stage are the inspection of the machine units and the butterfly valves chamber II. The val ves are the “colossal water tap” of the reservoir above the plant and the essential aspect of the operating and safety systems of the Reisseck II pumped-storage power plant.

HIGH QUALITY REQUIREMENTS
For this reason only material of the highest quality was used and there were strict production controls during the construction of this special arrangement. Each production step and each material component was checked twice, by the constructing company itself, but also by external controllers. CKD Blansko Holding, from Blansko, near the city of Brno, was responsible for the production of the butterfly element. The Czech turbine manufacturer and specialist for butterfly valves and armatures employs 450 people and has been in business for 115 years. During the Cold War era the company mainly did business in the German Democratic Republic and in Eastern Europe. Today the company operates globally. In Europe it is establishing a growing presence in the German-speaking regions. “It was important for us to receive the contract for Reisseck II, so we could finally demonstrate our expertise with a project in Austria,” states Filip Hitl, project manager of CKD Blansko Holding. The Czech company won the tender thanks to its thorough know-how and its specific job specialization. Furthermore the company’s office and production hall are only 80 km from the Austrian border, which facilitated a good collaboration and smooth logistics.

DOUBLE JACKET DESIGN
The order for CKD Blansko Holding comprised the manufacture, delivery and installation of two identical, rapidly closing safety valves – operation and revision valves – with a diameter of 3.6 m, a hydraulic power unit as well as two cones for the inlet and the outlet. All parts, except for the hydraulic power unit, were manufactured by CKD Blansko Holding. High-quality sheet steel was used for the entire housing and the two valves. It was welded and tested by the valves specialist at its factory in Blansko and, like all products from CKD Blansko Holding, the two valves meet the high technical standards of the hydropower specialist. CKD Blansko Holding knows from experience that it is best to always produce valve casings in a double jacket design. Another speciality of CKD Blansko Holding is the usage of three seals with the bearing journals: an additional seal is located between the inner and the outer seal. In case of revision the additional seal can be impinged with grease and revision works can be carried out quickly and safely. During operation a nominal pressure of 12 bar is achieved at a flow rate of 80 m³/s directed towards the turbine. In case of emergency the valve structure is able to master up to 200 m³/s.

COMMISSIONING IN EARLY 2016
Dry run tests and impingement tests have already been completed successfully. The leak tests have also produced satisfactory results. “We were very satisfied with the perfect test runs and we are now looking forward to running tests in operating mode,” says Mr Hitl. These tests, however, will not take place until early 2016, as various works in the pressure gallery are currently being completed. The final phase – the commissioning – is scheduled for initiation in early 2016.