Concrete Encasement Design for Spiral Casing Under Refurbishment

Apoorva, M. S. Ramesh, Ravindra S Kashyap, S. N. Subramaniam

Abstract: Renovation, Modernization and Uprating (RMU) of old power stations are cost effective, environment friendly and require less time for implementation instead of creating new stations. The economy in cost and time essentially results from the fact that, apart from the availability of the existing infrastructure, only selective replacement of critical components is necessary. The turbine is a component which very often needs replacement owing to change in operating head and discharges. The choice is however constrained by the spiral casing which is embedded in concrete. Turbine designs must consider alternatives of designing a new turbine for the existing spiral casing (with its stay vanes) or replace the spiral casing. For the proposed RMU of an undergoing project , which has been implemented about 55 years back, it is proposed to install a new spiral casing over existing foundation by removing the second stage concrete and providing new second stage concrete after the installation. This has called for the design of second stage concrete encasement and this paper gives the methodology adopted in the design of second stage Concrete around the spiral casing.

Keywords: Spiral Casing Encasement, RMU, Total Stresses, Principal Stresses, Tensile Stresses, Compressive Stresses and concrete