Development, experience and qualification of steel grades for hydropower conduits

In this contribution the historical development of materials and applied welding procedures in the field of hydropower plant shafts and penstocks is summarized. Based on the experiences and failure cases observed in the past in combination with modern methods, a best practice solution for the qualification of materials and processes is proposed. Additionally to weldability based on strength and toughness, fracture mechanics, fatigue behaviour and stress corrosion sensitivity have to be considered. All these measures have to be validated by application of related advanced NDT processes.