A treatise on retrofitting of hydro-turbine materials

Abstract

Hydro-turbine materials endure frequently the detrimental losses on account of slurry or silt erosion, cavitation erosion, corrosion or the collaborative effects of any of their combinations. Rivers emanating from Himalayan region or other hilly areas generally flow with enormous quantity of silt of different sizes and shapes. The shape of slurry particles possesses its wide ranges from sharp angular having very high erosion potential to spherical ones of relatively less erosion capacity. These particles sometimes create very severe damage in the form of huge mass loss and development of cracks within the short span of time in the components or parts of turbines in hydropower plants, situated in these regions for electricity generation. To avoid the extensive monetary loss in replacing the harshly eroded or cracked turbine parts, retrofitting (repair & maintenance) of hydro-turbine materials is mostly preferred for enhancing the service life and the smooth and efficient functioning of the concerned industries, responsible for power genesis. Common practice of retrofitting has been elaborated and discussed on the basis of a local cum private industry visit and subsequently, apt and proper optimized parameters related to different retrofitting operations; preheating, welding and post weld heat treatment (PWHT) have been suggested to meet the intended outcomes. Challenges found in execution of retrofitting the turbine parts also have been discussed. Retrofitting of eroded turbine parts has been advised rather to exhaust unnecessary monetary investment in their substitutions. In this brief study and in view of paucity of research availability as being an unorganized sector, retrofitting of hydro-turbine parts are focused, reviewed and discussed alongwith its underlying process. Some reviews in retrofitting prospect of components or parts of turbines other than hydro-turbines also have been considered for representing its approach for repair & maintenance. Additionally, smart retrofitting in accordance to the Industry 4.0 line has been suggested for further reduction in cost to money and time.