Effect of welding pattern during repair and maintenance of Francis runner on sediment erosion: An experimental investigation using RDA

Abstract

In Nepal, sediment erosion is a major cause of hydro-turbine failure. Every year turbine parts expose to water got eroded and failed ultimately resulting in loss of efficiency as well as increase in the repair cost. For repair of these eroded surfaces welding is quit famous in Nepal due to low cost to build up the eroded surface however specific welding pattern on the eroded surfaces has not been used which results low strength in repaired equipment. In this paper, the study of the relation of the welding pattern on the erosion rate had carried out taking the Francis turbine blade of Dhamile Khola (14 kW) as reference. Experimental analysis was adopted for studying the effect of welding pattern on erosion rate through laboratory tests. Four different welding patterns on four different specimens were developed and accelerated tests were carried out in the Rotating Disc Apparatus (RDA) at Turbine Testing Lab (TTL), Kathmandu University. Furthermore, erosion pattern on forged blades were compared with the CFD analysis carried out on same blade which is similar. After an operation time of 1050 minutes, the extent of wear was found significantly less in the test specimen with right inclined welding pattern taking material loss as a basis for comparison. The aim of this paper is to provide a specific welding pattern with relatively less erosion rate during the repair and maintenance of the sediment eroded surface of the runners.