Both GE & MHI manufacture Gas Turbines with can annular design. But Alstom make Gas Turbines are of Sylo type design. Most popular frame of MHI make Gas Turbine in 50Hz series are 701D and 701F and its equivalent Frame in 60 Hz are 501D and 501F. Similarly most popular frame of GE make Gas Turbines are 9E, 9F,9FA in 50Hz series and 7E, 7F,7FA in  60Hz  series. GE make most popular Gas Turbine is Frame-6.  Alstom Make most popular models are 13D, 13E2 .All the three Original Equipment Manufacturer (OEM) have uprated their models. How the existing Models can be uprated so that the capacity is improved beyond site rating or if not beyond Site rating, at least the loss occurred due to aging gets compensated.

We invite all to discuss possible measures for enhancing the capacity of existing Gas Turbine and the Heat Rate.

Renounce Gas Turbine manufacturers normally uprate their model time to time.  For uprating the existing model by a few notches, normally all the reputed OEMs follow the flowing Techniques:-

1. Changing original material with improved material.
2. Applying advance Coating.
3. Increasing the IGV angle by few Degrees.

By adopting Technique at Sl no (i) & (ii), i.e. with improved material and advance coating, Gas Turbine output is increased by increasing the Turbine Inlet Temp (TIT) by 15 Deg-C  to 50 Deg-C. By increasing the TIT, not only the output of Gas Turbine is increased but the output of Steam Turbine is also increased due to increase in Gas Turbine exhaust temp.  By this technique, Gas Turbine output as well as efficiency, both are improved.

By adopting Technique at Sl No-(iii), Gas Turbine output is increased due to increase in mass flow. In this methodology, Gas Turbine output is increased but not the efficiency. Even by adopting all three techniques, mentioned above, Gas Turbine output is increased by 10 to 30 MW only.

Since market demands more and more output and efficiency, then OEM developed advance version in which there is ample jump in Gas Turbine output as well as efficiency.

Accordingly, Gas Turbines are mainly classified in to Two categories which are:-

1. Conventional Class Gas Turbines: -   GE make Gas Turbine Feame-9E &7E, MHI make Gas Turbine 701D, 501D, Alstom make Gas Turbine 13D &13E  and Siemens make V94.2 model comes  under this category.
2. Advance Class Gas Turbines: - GE make Gas Turbine Feame-9F &7F, MHI make Gas Turbine 701F, 501F, Alstom make Gas Turbine GT26 & GT24 and Siemens make model V94.3 comes under this category.

Whatever be the version, existing Gas Turbine output can always be increased. However, advance version always comes from OEM with cost. But It has been found, in so many cases, that the enhanced output from Gas Turbine could not be utilised due to limitation of various aux. drives and equipment.

A thorough study is required to assess the capabilities of various Equipment and Drives, before finalising the scope of work for uprating of Gas Turbine.

Since a substantial amount of money has to be spent for uprating the Gas Turbines, it is always advisable to replace the all Hot Gas path Components at a time preferably during major Inspection of respective Gas Turbines. A suitable Clause has to be incorporated in the LOA for proving performance in terms of Gas Turbine output and Efficiency at least in Open Cycle Mode where possible or in Closed Cycle mode where open Cycle Mode of operation is not possible.