PR: RUD Trash rack

The Danzermühl hydro power plant has been working in the River Traun in Laakirchen, Upper Austria, since 1880. As the decades passed, it has been constantly modernised, modified and extended, until it was finally decided to replace it with a new one in 2014. We wanted to generate more power, maximise protection against floods and also improve the habitat for fish and other organisms in the Traun", explained Christian Hufnagel, Project Leader at the power station company, Kraftwerk Laakirchen GmbH. "Renovating the old power station made no commercial or ecological sense. For this reason, we decided to go for complete reconstruction."

New weir system with 240 m² grille

A new completely automatically regulated weir system, that holds back the Traun's water for the power station, was also created during the course of the project. It consists of two dams with two wide sluice gates that are 16 m and 4.5 m high, and a bottom outlet. This is equipped with a radial gate with flap gate. A fine horizontal grille with rungs spaced at 30 or 45 mm and a surface area of 240 m² catches the floating debris.

Horizontal mechanical grille cleaning system saves disposal costs

For the weir system and the power station to operate efficiently, floating debris must cleaned off the grille when required. This is the job of a mechanical grille cleaning system. Here too, Heinzel Energy took a new approach: instead of a vertical mechanical grille cleaning system, the company installed a horizontal system which cleaned down to a depth of 8.1 meters. The horizontal system has two benefits: it has the minimum possible impact on the natural environment and the operating firm has fewer disposal costs. That is because, unlike a vertical grille cleaning system which collects floating debris out of the water, the biomass in a horizontal system is transported downstream, over the weir system, remaining in the river.

The mechanical grille cleaning system has been supplied by the company Braun Maschinenfabrik GmbH, whose headquarters are in Vöcklabruck, also in Upper Austria. It is scarcely 25 kilometres from the hydro power plant at Danzermühl. The company also supplied all the steel construction for the hydraulic engineering reconstruction. The grille cleaner in Laakirchen is the largest of this type that we have ever built: it was a real design innovation. For example, we completely redesigned the running gear", stated Robert Konrad, Head of Hydraulic Engineering Steel Construction Design at Braun Maschinenfabrik GmbH. That was because existing drive types, such as control rack and cable, were unsuitable, due to the weather conditions and the length of the grille. "It was clear that we needed a different solution", Konrad then explained.

Innovative drive system: Tecdos Omega Drive

This was supplied by RUD Ketten Rieger & Dietz GmbH and. Co. KG with headquarters in Aalen, Baden-Württemberg (Germany). Working as a development partner for Braun's new mechanical grille cleaning system, the company supplied its innovative Tecdos Omega Drive drive system to handle rotary and linear movements. The drive installed in this project has a maximum tractive force of 6.5 tonnes or 65 kN and it weighs 297 kg. The system now in place at the Danzermühl power station weir system can run at two different speeds: 14 m per minute under full load, and 28 m per minute load-free.

The Tecdos Omega Drive system is based on a high-performance round steel chain, also developed by RUD. This makes the drive system especially robust and resistant to dirt, sand, water and ice. That's a major advantage when compared to alternative systems, such as cable drives or rack and pinion drives. "Our Tecdos Omega Drive can be used anywhere in particularly challenging conditions: in dirty environments and in extreme weather conditions. No matter whether the Tecdos Omega Drive is used frequently or at irregular intervals, it always starts up and runs perfectly. This is where the benefits of the exceptionally wear-resistant case-hardened Tecdos round steel chain can clearly be seen", explained Heribert Herzog, Applications Engineer at RUD.

Rapid installation and lower maintenance

The drive is also designed to be extremely compact. In the "Omega 65" drive that is currently in use in Laakirchen, the drive is 468 mm high, 649 mm long and 296 mm wide. Its compact size, in comparison to other types of drive, also makes it much easier to install. "For example, in rack and pinion drives, the racks must be screwed to a robust base at close intervals to ensure that no deformation occurs as a result of operation. The mechanical grille cleaning system at the Danzermühl power station travels almost 50 meters, which would pose quite a challenge. A rack and pinion drive is not only more expensive, and slower, to install but also requires more maintenance and is more prone to breakdowns", explained Emanuele Frisi, Business Development Manager in the Conveyor & Drive Division at RUD. And Heribert Herzog added: "We can be completely flexible when it comes to travel paths: theoretically, we can build drives to handle any distance, from two metres to a couple of hundred metres."

Even thread algae are no problem

The mechanical grille cleaning system in Laakirchen is in daily use and can't afford stoppages. "Even in autumn, when the River Traun has very little floating debris, the grille cleaner is used once a day on average. In contrast, in spring, when the river is full of floating debris, the system cleans the grille every two hours", explained Christian Hufnagel from Kraftwerk Laakirchen GmbH. One of the special challenges we face is how to handle the thread algae that occurs in the Traun in the spring and summer months, and wraps itself around the bars of the grille. To combat this problem, Braun has developed special ripper teeth that can be mounted on the 9 m long rake when needed. 

From bespoke manufacturing to series production

This was Braun Maschinenfabrik GmbH's first joint project with RUD. "Everything went very smoothly, and we hope to be involved with RUD on other projects again in future. We've even added the newly developed horizontal mechanical grille cleaning system, with its Tecdos Omega Drive chain drive, to our product range as a standard item. You could describe it as "from bespoke manufacturing to series production"", said Konrad cheerfully about the results of this joint project.

RUD also has the right solution for water treatment plants

Weir systems are not the only places that need efficient and reliable mechanical grille cleaning systems. Water treatment plants with rectangular tanks do too. RUD can also provide innovative solutions here, with its Omega Drive and Pi-Gamma Tecdos drives. When installed as a complete 2-in-1 system, the Tecdos Pi-Gamma drive is ideally suited for horizontal and vertical applications, with a fixed chain deflection of 180 degrees or a flexible deflection from 90 to 180 degrees. Both of these RUD Tecdos drive systems are convincing alternatives to more standard friction wheel drives. Friction wheel drives quickly reach the limit of their abilities when the travel path is covered in ice, snow or dirt. As Tecdos drive systems work together with Tecdos round steel chain, they ensure forces are transferred safely and reliably, no matter what the weather.

About the new Danzermühl power station:

Since coming into operation in summer 2019, the new Danzermühl hydro power plant has generated 2.5 times more electricity than its predecessor, i.e. 44.8 GWh, per year. In comparison: the old hydro power plant generated 16.5 GWh per annum. This huge increase is thanks to two particular factors: the drop was increased from 7 to 9.2 meters by combining the Danzermühl barrage with the Kohlwehr barrage which lies further downstream. the discharge flow volume was also raised from 60.1 m³ to 120 m³ per second. This is the maximum volume of water that the two new turbines can use to generate electricity. 100 % of the power goes directly to the neighbouring Laakirchen Papier AG which, like the hydro power plant, is part of the Heinzel Group.

About Heinzel Energy:

Heinzel EMACS Energie GmbH, operating as Heinzel Energy, develops projects in the renewable energy sector. These include hydro power plants on the River Pöls in Styria, Southern Austria, and on the River Traun in Upper Austria. Both plants supply electricity directly to their sister companies Zellstoff Pöls AG and Laakirchen Papierfabrik AG. The company also runs a wind farm at the Domaine Albrechtsfeld GmbH site in the Burgenland, in Lower Austria, where it is building a photovoltaic solar array with more than 1,000 solar panels. Heinzel Energy has already installed over 5 MWp of PV generating capacity. In Laakirchen, the company is currently setting up a PV system that will generate 2.6 MWp and has already installed more than 23,000 PV modules. More projects are already in planning for the next few years.

Info:

RUD Ketten Rieger & Dietz GmbH u. Co. KG

Bereich Fördern & Antreiben
Friedensinsel
73432 Aalen
Telefon +49 7361 504-1457
salesfa@rud.com
www.rud.com

Ansprechpartner für die Presse:

Kai Eder
Marketing Manager Fördern & Antreiben
RUD Ketten Rieger & Dietz GmbH u. Co. KG
Telefon 0049 7361 504-1303
kai.eder@rud.com