Modern Trends in Hydraulic Turbine Design

Large welded plate steel spiral casings with plate thickness up to 2 5/16¿ for operation under heads up to 435 feet have been manufactured in recent years. On some casings both the shop joints and the field joints were welded without stress relieving by annealing. After three to five years operation there has not been a single case of a weld failure. Other intricate turbine parts such as coverplates, discharge rings, speed rings, Francis runners and impulse wheel buckets have also been fabricated out of welded plate steel. There has been an increase in the use of stainless steel to resist pitting, erosion and corrosion, resulting in reduced maintenance costs. Newly designed self-lubricating bearings and carbon ring seal rings have simplified trouble and failure.