WELDING CHALLENGE

Building a pumped-storage power plant poses a huge challenge, as the majority of the construction work takes place inside the mountain. To join the reservoir to the cavern located lower down, a five-kilometre underground steel pipe system was installed in a power plant in Carinthia. This consists of a headrace tunnel and a pressure shaft with an incline of 42 degrees. The cramped and difficult underground conditions place particularly high demands on the technology.

“The TPS/i in combination with LSC Root is perfectly suited to one-sided root pass welding in a downward position and is easy to work with.” Peter Krenmayr, head of the Welding and Testing Engineering business division at Bilfinger VAM Anlagentechnik GmbH.

SOLUTION

To complete the shaft, VAM Anlagentechnik used 3,963 tonnes of steel in the construction of the pressure shaft lining and the associated system components. For the first time in Europe, thermomechanical steel was used – this is inexpensive and easy to weld. To produce the best welding results, VAM deployed the latest TPS/i MIG/MAG power source from Fronius and the stable LSC Root dip transfer arc. Thanks to the high arc pressure and optimal deposition rate, welding can be performed in a downward direction and more quickly. The LSC Root ensures excellent root formation and gap-bridging ability, reduces incomplete fusion to a minimum and produces perfect weld seams. VAM was also able to use the TPS/i as a universal MIG/MAG power source for filling and final runs. This not only reduced the number of devices required, but also simplified the welding operations in the cramped pressure shaft.