It is absolutely true that inspections of Gas Turbines are strictly carried out as per OEM’s guidelines. Accordingly mainly three types of inspection are carried out and termed as ‘A”, “B” and “C” type of inspection. The scope of works and equivalent operating hours, after which these inspections are to be carried out, are well defined.

There is no dispute regarding the scope of works for various inspections. Since, OEM recommends an expected life of each and every Hot Gas Path Critical Components after which these Components are supposed to either be refurbished or to be replaced.

While specifying the expected life of Hot Gas Path Critical Components, OEM assumes that the Gas Turbine will be operated at base load mode (Temp. control) throughout the day 24X7. But this is not the case. We also know that Gas Turbine Hot Gas Path Components undergo metallurgical degradation due to prolong exposure to very high temperature. Therefore, metallurgical degradation is a function of “Exposed Time” and “Temperature exposed of”.

This indicates that the metallurgical degradation will be less if the Gas Turbine is operated at part load (in load control mode) with respect to base load mode of operation. There are innovative ways of increasing the time interval between inspections by assessing the metallurgical condition of Gas Turbine Hot Gas Path Critical Components. To take such decision, a few in-situ tests are to be carried out which is Gas Turbine specific and component specific. There are instances that one complete Major Overhauling has been skipped during its life cycle of operation resulting in both increase in Generation and reduction in inspection cost resulting in increase in profit.