Freudenau: Lock chamber requires extensive repair work

During regular inspections and tests, VERBUND technicians discovered complex damage to one of the two lock chambers of the Danube power plant in Freudenau. The right lock chamber had to be taken out of operation for safety reasons. The damage turned out to be a complicated fracture in the mechanism. In order to repair the damage, a special part designed to withstand the enormous physical strain of operation needs to be produced. The production of replacement parts, installation, and load testing are expected to last until Easter 2026. In the meantime, the left lock chamber will be available as usual. VERBUND and viadonau regret any delays in passage and kindly ask for your understanding.

Every year, around 14,000 vessels pass through the lock at the Vienna-Freudenau power plant. viadonau is responsible for overseeing shipping traffic. Lockage is free of charge for shipping. As the power plant operator, VERBUND is responsible for the upkeep and maintenance of the structure. The quarterly inspections at the end of July 2025 revealed damage to an important element of the upstream lock. Upon closer examination, the damage turned out to be a fracture of the bearing bolt. 

The bearing bolts form the pivot points for a lock's main tilting elements, allowing the water level to be lowered or raised again. A special replacement bolt now needs to be produced, which is a complex task. First, a blank weighing around 13 tonnes has to be produced. This blank is then machined to the required dimensions to achieve a diameter of 78 cm and a length of 3.6 metres. For the new bolt to be inserted, the 500-tonne lock, which has shifted several centimetres due to the pressure of the water, needs to be returned to its original position. As with all structures at Danube power plants, the parts involved are huge and need to be able to withstand recurring loads. The requirements in terms of materials and construction quality are correspondingly high, which is also one of the reasons for the long completion time.

Shipping on the Danube remains guaranteed at all times. However, the restriction to just one lock chamber in Freudenau means that, unfortunately, there will be unavoidable waiting times for passenger and freight traffic on this section of the Danube.

Danube power plant—a multi-functional facility

Since 1998, the Freudenau Danube power plant has generated electricity for 300,000 Viennese homes each year, making it an important part of the backbone of the electricity supply. As a bridge structure, the power plant connects the city with Danube Island. Each year, 8,000 people visit the power plant as part of guided tours. As the last link in the Danube traffic chain, Freudenau guarantees a reliable level of water between the power plants. The lock is 275 metres long and 24 metres wide. Ships are lowered by 6.8 metres when they pass through the lock. 

Importance of the Danube River for freight

The Danube is an important transport corridor in Europe and also a provides lifeline for people, nature, and the economy. A total of 55 million tonnes of goods were transported on the entire Danube River in 2023. In Austria, the figure was 6.6 million tonnes in 2024. The Danube flows through Austria for around 350 km, negotiating a height difference of more than 150 metres as it does so. The nine Danube power plants exploit this energy potential to generate energy from hydropower. To overcome the height difference, ships need to pass through a lock at each of these power plants. Service-oriented operation of the locks is therefore an essential part of a functioning waterway infrastructure.