L+M Industrial Steel Construction: Repair Welding of a Pelton Turbine Runner

Our client is looking for a solution to repair a Pelton turbine runner whose blades have sustained significant surface damage due to cavitation and corrosion.

The leading edges of the cups are particularly affected, showing the typical “corroded” damage pattern. In addition, a crack has formed at the root of one blade; it has already been ground down deeply and must now be repaired by welding.

It was clear from the very start of the project that, after repair, the component would have to undergo a precisely defined heat treatment—even locally, if necessary.

The challenge

The Pelton turbine runner has a diameter of nearly 3 meters and weighs over 8 metric tons. The areas to be repaired consist of complex free-form surfaces whose original geometry must be strictly preserved. After welding, these contours can only be restored to their exact original shape through careful, manual grinding. The welding process requires a high degree of precision, particularly along the edges of the blades, and is critical both in terms of preventing cracks and ensuring that the exact geometry is maintained in the area of the damaged blade.

The solution – unique and clever

L+M Industriestahlbau conducted and evaluated specific process tests and test specimens for the welding process and used the results to determine the optimal welding parameters.

The results obtained showed that both the cup edges and the crack at the blade root can be successfully welded and repaired. A specialized partner company was brought in for the subsequent heat treatment. Over the course of several days, this company followed a precisely specified heat curve using ceramic mats and thermal insulation.

The customer was extremely satisfied, as the repair method we used is technically sound and has proven to be significantly more cost-effective than alternative repair solutions.

Specification