Large-scale project

High-tech under the toughest conditions

In Austria, hydropower has a long tradition of being an environmentally friendly alternative to produce energy. In the Alps, this type of energy generation is a genuine alternative for the reliable provision of electricity, especially due to geographical conditions. A recent example is the Kühtai project in the Stubai Alps where Tiroler Wasserkraft AG (TIWAG) has been operating two storage reservoirs at the Sellrain-Silz power plant for many years. During a comprehensive refurbishment and modernization project, the power plant group will, among other things, expand with a third reservoir in the nearby Längental valley. Under the leadership of the regional utility, ARGE SKW Kühtai has been entrusted with the implementation for the main construction lot of the project.


For projects of this magnitude, the best and most experienced engineers require the best and most experienced execution personnel, which in turn must be based on the best and most sophisticated plant technology. For this process chain, the SKW Kühtai consortium relies on rock processing solutions from Sandvik. As a fullline, manufacturer and supplier, Sandvik can provide a complete processing plant which can operate and deliver the meet the tough requirements. The optimally coordinated technology ranges from the feed hopper to the finished products.


The material is fed to the plant from the 30 m3 bunker via a fully automated feeder. A Sandvik SH1361 Mining pusher feeder is used here. An individually definable setting of stroke length and stroke frequency allows even difficult feed material to be fed to the pre-screen, depending on its specific properties. Here, a first separation cut is provided at 150 mm. The oversize material reaches the primary stage of the Sandvik CJ613 jaw crusher. The proven single-swing jaw crusher with its exceptional robustness enables a continuously adjustable gap width (CSS) of 125 to 300 mm. The possible feed size ranges up to more than 1000 mm, i.e., a full meter edge length – an important parameter, because almost anything that comes from the push feeder must be processed. According to the preliminary reports, this is heterogeneous loose rock in the existing boulder dumps from the area of the future storage ground in the reservoir of the new basin. Because large blocks are to be expected here again and again, Sandvik has adapted the plant technology accordingly: To complete the system, a Sandvik Rammer C450 hydraulic hammer boom system has been installed in the inlet area. This means that even oversized boulders can be split into manageable pieces before entering the jaw crusher.


The as-needed processing of the pre-crushed rock as well as the undersize of the prescreening is carried out by Sandvik CH840i. This technology is proven to be the most reliable and robust secondary crushing system. Sandvik’s latest i-series covers the required features for the tough Kühtai project application. A robustly designed one-piece main shaft supported a both ends, with a unibody, reinforced top & bottom shells form the basis of the crusher. The one-piece spherical spider bushing has been further developed and offers at least five times longer wear life than previous crushers from Sandvik. Many different crushing chambers as well as various eccentric bushings allow the machine to be set up for the specific crushing application. An essential unique selling point is the hydraulic crushing gap adjustment via the hydroset system. The automatic crusher setting regulation control system not only optimizes production, but also monitors the wear of the crushing chamber.


The material is classified on a SANDVIK SL2473 linear screen. Among other things, the moisture content is also decisive for the overall process, which is why the preparation also has a dryer. The result is fractions ranging from 0/16 mm to 16/32 mm or mixtures such as 0/63 mm. These compositions largely make up the products, with the special fractions required for the dam fill standing out. The 100-m-high fill dam is to be the centerpiece of the storage basin; it will hold back the enormous masses of water and release it in a controlled manner to the turbines in the valley. The lack of space in the construction area of the rear longitudinal valley and the production of the dam core material, also make the rock processing work even more complex. The main product, mixed with bentonite, is installed in the dam core as the innermost dense layer. Because these products have a limited shelf life due to the plastic consistency with which they are processed, the aggregate processing plant must be reliably able to provide material on a continuous just-in-time basis. The requirements for operational reliability therefore took on a special focus. Even under the adverse conditions, such as the weather conditions in the high altitudes of the Tyrolean Stubai Alps with large temperature fluctuations, wind, and precipitation, to which the construction project is permanently exposed, a required plant capacity of around 550 t/h must be reliably guaranteed. Sandvik has successfully met this challenge and additionally secured the robust technology The entire plant is connected to the SAM by SANDVIK digitalization tool – an essential part of the competent service organization for plant operation – and a guarantor for an efficient supply of spare and wear parts, for professional observation of machine-operating data, for efficient maintenance.


With this impressive rock processing technology, the SKW Kühtai consortium is tackling a gigantic task profile in the remote Längental valley at an altitude of 2000 m: A usable capacity of 31 million m³ is projected for the new storage basin. No less than 6.9 million m³ of rock will have to be moved and, for the most part, processed. The raw material is suitable for demanding everything from the plant technology – and Sandvik has provided the necessary technology for this. The loose rock, which mainly comes from block dumps, as well as the resulting blasting debris consist of heterogeneous materials with a cross-section of the most diverse metamorphic rocks. The range extends from soft mica schists to hard quartzites, different gneiss varieties and other rock variants with a wide variety of technical properties. The rocks to be processed are primarily taken from the area of the future storage ground in the reservoir.


One of the tasks in the specifications for the tender was to process as completely usable aggregates as possible from these different materials. This requirement also follows the perspective of sustainability, because on remote construction sites such as the Kühtai project, it is more important than elsewhere to make optimum use of the available resources. Both the removal of superfluous overburden and the hauling of usable mineral raw materials would require an immense logistical effort and would be associated with considerable environmental pollution.


In the total investment volume – TIWAG speaks of around 1 billion € – the plant technology of Sandvik’s rock processing represents only a comparatively small part, which is nevertheless of eminent importance as the basis for a permanently successful project implementation. The equipment is a central factor, and reliability and performance must go hand in hand. In order to ensure the smooth provision of the processed intermediate products in the required quality and quantity, Sandvik and the Austrian engineers of ARGE SKW Kühtai worked closely together to define the requirements and translate them into practical plant technology. A segmental combination of the plants allowed transport to the back of Längental as well as assembly on site.


Autor/Author: Bodo Wistinghausen


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