Hydroturbine manufacture

A method of assembling a runner for a hydraulic machine, comprising the steps of:

• forming a runner segment comprising a band portion, a crown portion, and a blade as an integral component, such that the band portion comprises a curved first joining edge and a curved second joining edge, the crown portion comprises a curved first joining edge and a curved second joining edge, the crown portion and band portion first and second joining edges spaced apart along a length thereof from the blade of the segment;
• the curved joining edges formed with an integral extension, wherein the extensions meet and define a closed-end of a gap between the curved band and crown joining edges of adjacent runner segments, the gap having an open-end facing outward from the runner and chamfered sides that angle towards the closed-end of the gap;
• wherein the curved joining edges have a continuous varying radius curve towards a same direction along a complete length thereof;
• joining a plurality of the runner segments together at the curved joining edges to form the runner, the joining process comprising:
• with a robotic welding tool operating from outside of the runner, forming a weld within the gaps between the adjacent runner segments with a narrow gap welding torch;
• wherein, for each of the crown portion and the band portion, the robotic welding tool follows a predetermined trajectory during the welding step that corresponds to the continuous varying radius curve of the crown portion and the band portion.

A runner for a hydraulic machine, comprising:

• a band;
• a crown;
• a plurality of blades extending between the crown and the band,
• a plurality of runner segments, wherein each runner segment comprises a band portion, a crown portion, and a blade of the plurality of blades;
• wherein the band portion, the crown portion, and the blade of each runner segment are integrally formed with one another;
• each runner segment attachable to another runner segment at a band joining edge and a crown joining edge;
• wherein the band joining edge and the crown joining edge are each spaced apart along a length thereof from the blade of the respective runner segment;
• each of the runner segments comprising an integral extension at the band joining edge and the crown joining edge;
• the extensions meeting and defining a closed-end of a gap between the band or crown joining edges of adjacent runner segments, the gaps comprising an open-end facing outward from the runner and chamfered sides that angle towards the closed-end of the gap, the gap comprising a width to accommodate a narrow gap torch for subsequent welding together of the adjacent runner segments with a weld joint within the gap;
• and
• wherein both of the band joining edges and the crown joining edges are continuously curved in a same direction along a complete length thereof, wherein the continuous curve comprises a profile corresponding to an arc of an ellipse or a portion of an elliptical curve.