Implementation of optimal oil flushing methodology for nuclear steam turbo generator oil circuits

The first turning gear operation is regarded as a significant milestone in the overall activities of Turbine Generator system commissioning. To accomplish this critical goal, the lube oil circuit must be clean and free of all type of contaminants. The purpose of this paper is to elaborate on the various flushing tactics used in the Prototype Fast Breeder Reactor 500 MW Turbo Generator (TG) oil systems, to understand the factors that influence oil circuit flushing, the difficulties encountered during flushing, and to optimise the flushing process of TG oil circuits. Also A simple method was used in this paper to determine the minimum amount of oil required to begin flushing and the make-up requirements of lube oil at various stages of flushing. The percentage of oil passing through the cooler and cooler bypass line during the thermal shocking process was also determined using an energy balance approach. Based on TG oil circuit commissioning experience, an optimised methodology for completing the TG oil circuits flushing exercise is also proposed. This study demonstrates that the cooling and heating times of lube oil can be controlled during oil flushing, resulting in an increase in the number of thermal shocks per day and a significant reduction in flushing time. Article Highlights This paper is the result of flushing experiences with oil circuits of a 500 MW Nuclear power plant. This can be used to minimize oil quantity and the time flushing thereby lot of man hours and cost of flushing could be saved during flushing of turbine oil circuits. The minimum oil required for turbine oil circuit flushing is not readily available. The method outlined here can be used to determine the minimum amount of oil required for each stage of oil circuit flushing. This paper describes an energy balance methodology that can be used to increase the number of thermal shocks per day during flushing, thereby significantly reducing flushing time.