Upgrade and Life Extension of 4 × 110 MW Units: A Case Study

Achieving rated capacity and economical operation of existing thermal power plants are vital issues for utilities. Plants nearing their design life are likely to show declining trend in availability as well as increasing trend in operation and maintenance costs due to ageing. Constraints in system adequacy, decreasing trend in efficiency and poor reliability are key issues to be addressed while planning life extension. 4×110 MW power plant located in southern part of India has been taken up for renovation and modernization. Pressure parts failures mainly accounted for the reduced availability of the units. The exit gas temperature in boiler was on the higher side leading to operation of the units with reduced efficiency. Change in fuel quality over the years as compared to what has been considered during design was a constraint in achieving rated capacity. The poor heat rate of turbine necessitated incorporation of the state-of-art design to achieve better heat rate. Improvements required in control and instrumentation system were also addressed in the renovation and modernization. Improvements in plant load factor, availability and unit heat rate could be achieved in the two units where renovation and modernization has been completed. The details of the renovation and modernization of these units are discussed in this paper.