EVOLUTIONARY DEVELOPMENT AND VALIDATION OF SIEMENS
INDUSTRIAL SGT-800 GAS TURBINE
Mats Björkman
Siemens Industrial Turbomachinery AB SE-612 83 Finspong, Sweden
mats.bjorkman@siemens.com
ABSTRACT
Siemens industrial 50 MW class gas turbine SGT-800 has dominated the Small Power Producer (SPP) program in
Thailand for the last six years with 70 units sold, all in 2x1 Combined Cycle configuration with two SGT-800 and
one steam turbine. The SGT-800 is continuously being improved for higher plant efficiency and the 53 MW rating
capable of > 56% net plant efficiency at ISO-condition is now entering the Thai market. In total, 18 units with this
gas turbine rating will be delivered to customers in Thailand before the end of 2018. With only minor additional
design improvements, the rating of the SGT-800 was recently further enhanced to 54 MW. This paper describes the
evolutionary development strategy of the SGT-800 and Siemens facilities at the Finspong works in Sweden for full
load Mechanical Running Test used for performance validation of design improvements.
KEYWORDS SGT-800, combined cycle, evolution, validation, fuel flexibility
INTRODUCTION
The SGT-800 is the largest industrial gas turbine manufactured by Siemens Industrial Turbomachinery AB and it
was launched in 1997 as a 43 MW gas turbine named GTX100 [1]. The SGT-800 was shortly after rated to 45 MW
and in 2007 the engine was enhanced to 47.5 MW with 37.7% simple cycle efficiency [2], 53.8% combined cycle
operation efficiency and including cogeneration (district heating) the efficiency further increased up to > 90%. The
47.5 MW rating was the last evolutionary step of the ‘A-platform’, ranging from the introductory 43 MW to the
mature rating of 47.5 MW.
In 2010 Siemens launched [3] the next generation (‘B-platform’) introducing more significant enhancements, e.g.
 new enhanced blade profiles for all 15 stages to improve the compressor aerodynamic performance
 modifications for improved combustion performance, reduction of emissions, improved fuel flexibility
capabilities, reduced pressure drop over the combustion system and improved cooling of liners
 new design of turbine stage #1 and 3# for better aerodynamic and cooling efficiencies
The introductory performance of the ‘B-platform’ was 50.5MW with a 38.3% simple cycle electrical efficiency
(ISO) and at that time the best in class combined-cycle performance of 55.4%. Siemens has since then continued the
stepwise evolutionary development based on engine testing, extensive field experience and proven design solutions
in order to always assure high reliability. Today the ‘B-platform’ delivers up to 54 MW with 39.1% electrical
efficiency and 154 MW with a plant net efficiency of 56.7% in a 2x1 CC configuration.
Up to June 2016 more than 300 SGT-800 units have been sold worldwide, of which only the ‘B-platform’ has 115
units sold. The SGT-800 fleet has accumulated more than 4 million hours and the fleet leader of the ‘B-platform’
has passed 40,000 hours. The excellent proven average fleet availability, reliability and mean time between forced
outages, have also made the SGT-800 an attractive choice for the Oil & Gas industry and about 15% of the total
SGT-800 sales is in that field of application.
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EVOLUTIONARY PERFORMANCE ENHANCEMENTS
Siemens strategy for the continuous development of the SGT-800 is based on small step evolutionary enhancements,
rather than doing large leaps not being able to claim a proven and reliable design base for the gas turbine type. This
has shown to be a successful way of working appreciated by new and existing customers as well as the insurance
community. Since first introduction to the market in 1997, the SGT-800 basic design has been kept the same: a
single shaft engine that consists of inlet housing, 15-stage axial compressor, an annular serial cooled combustor, a 3stage axial turbine and an outlet diffuser. In order to meet the engine operation requirements the first 3 stages of the
compressor are made of variable guide vanes (VGV). The combustor is equipped with 30 Dry Low Emissions
(DLE) dual-fuel burners with a capability of NOx ≤ 15ppmv (≤ 9ppmv with certain conditions) on natural gas and
25-74 ppmv on diesel oil (depending on e.g. burner options). For both fuels, CO is ≤ 5ppmv. The first two turbine
stages are air-cooled and in addition to its high efficiency in simple cycle, the gas turbine is especially suitable for
combined cycle operation and cogeneration due to its high exhaust energy after the exhaust diffuser.
Figure 1: The SGT-800 core engine
The launch of the ‘B-platform’ in 2010 with its introductory rating of 50.5 MW was a perfect timing and power
matching for the SPP program in Thailand. Its high plant efficiency and the requirement for delivering about 110 to
135 MW power in a 2x1 CC configuration normally in combination with certain steam production for the local
industries, together with Siemens large experience of industrial gas turbine plants, made the SGT-800 the obvious
choice in many cases. The Thailand fleet leader units of the ‘B-platform’ successfully passed the first Hot Section
Inspection at 30 000 EOH last year. Typical appearance of hot section components are shown in Figure 2.
Figure 2: Typical appearance of hot section components after 30 000 EOH. Components found to be in excellent condition.
During the development of the ‘B-platform’, a thermo-crystal test was performed, in addition to the more traditional
measuring techniques, with instrumented components assembled into the machine. For the turbine section, a total
number of 1710 thermo-crystals were used, with 1528 for metal temperature, 176 for gas inlet temperature for both
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stationary vanes and rotating blades, and 6 for cooling air inlet temperature of rotating blades. In addition, a limited
number of thermocouples and pressure taps were used, with a few thermocouples installed on typical positions to
record the transient for estimating the equivalent hold time for the thermo-crystals. Thermal paint was also used in
certain locations as complement to the thermo-crystals.
It is of great value to measure the gas inlet temperature profile by thermo-crystals, so that the CFD aerodynamic
model can be calibrated by the measurement results. The boundary conditions provided by the calibrated CFD
aerodynamic model were then used for the cooling model, and the final metal temperature of the cooling model was
calibrated against the thermo-crystal test results. As an example, the temperature distribution of vane #1 and blade
#1, which was calibrated by the thermo-crystal results, is shown in Figure 3. The dot points in the figure are the
measurement points of the thermo-crystals. With the dense usage of thermo-crystals, the distribution of thermal
gradients can be assured. This work was done for all the components along the hot gas path in the turbine section.
The results did not only confirm the expected temperature levels of turbine hot components, they also gave a strong
basis for future upgrade, e.g. identifying potential for cooling air and clearance optimization. A general description
of the thermo-crystal technique used by Siemens for more than ten years can be found in [4].
Figure 3: Vane #1 and blade #1 metal temperature distribution calibrated by thermo-crystals (crystal positions are shown)
Extensive operational feedback and detailed engine measurements exemplified above, served as an excellent basis
for evolutionary improvement steps used for enhancement of the introductory rating of the ‘B-platform’. In a first
step and without any change of hot section castings, the cooling schemes of guide vane #1 and #2 were improved.
Together with optimized clearances in turbine stage #1 and #2 and improved front stages in the compressor section
for increased mass flow and efficiency, the nominal rating at ISO conditions within the ‘B-platform’ was achieved at
53 MW and 39% electrical efficiency. Once again this was a perfect match for several plants within the SPP
program and 18 units with this rating have been sold so far to customers in Thailand.
A second evolutionary step was recently taken, further improving the ‘B-platform’ performance to 54 MW and
39.1% electrical efficiency. More over the performance in a 2x1 CC configuration is now 154 MW and 56.7% net
plant efficiency at ISO conditions. Compared to the previous 53 MW rating, only three components in the turbine
section have been improved, again without introducing any new castings. The stage #1 blade has received improved
cooling of the tip and platform sections, on the stator #1 heat shield an oxidation protective coating has been
introduced and the turbine guide vane #2 has an improved coating and platform seal layout. Furthermore the built in
capacity of increased firing temperature in the ‘B-platform’ has only partly been utilized in combination with
optimized setting of the VGV’s. Up to June 2016, eight units of the 54 MW rating have been sold.
All components within the ‘B-platform’ are interchangeable and thus it is possible to upgrade an existing
introductory rated 50.5 MW core engine to 53 or 54 MW with just the replacement of a few components in the
compressor inlet section and in the turbine section. Any other limitations in the overall plant equipment must of
course also be considered for an existing plant before upgrading.
The introductory 50.5 MW rating of the ‘B-platform’ is kept in parallel to the 53/54 MW rating, intended especially
for new sales projects where the customer requires extensive operational experience without even minor changes.
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WORKSHOP FACILITIES FOR VALIDATION
At Siemens Industrial Turbomachinery AB Siemens located in Finspong, Sweden, validation testing of the SGT-800
can be performed at 100% load. A permanent Mechanical Running Test (MRT) rig for core engine testing is located
within the workshop area, see Figure 4. Both the 53 and 54 MW ratings have been successfully validated in this rig.
Figure 4: Mechanical Running Test facility for the SGT-800
The present capacity is limited to 60 MW and the power absorption is via load banks and to the national grid. An
electrical anti-icing system is used not only for anti-icing purposes, but also for easy variation of inlet air conditions.
When running only against the load banks, off-nominal rotor speeds can also be tested. This enables e.g. operation
of the compressor at different normalized speeds to simulate its working conditions in hot or cold ambient
conditions. The capacity of the test rig can easily be increased by adding more load banks and adjusting a few
systems, if required in the future.
The MRT rig is not only used for validation of improvements, but also for performance and functional verification
before shipment to customer site if specifically required in a customer contract. Such test requirement is not
uncommon within the Oil & Gas industry.
Besides an MRT of the core engine only, a string test of the complete package can also be performed before
shipment to the customer site. Figure 5 shows such string test set up performed for an Oil & Gas customer.
Figure 5: String Test area for the SGT-800
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GAS TURBINE PACKAGE EVOLUTION
The original package developed for the SGT-800 (today called the ‘Classic package’) has evolved over the years to a
mature cost effective package solution optimized for easy transport and on-site maintenance. The enclosure has a
built in overhead crane for lifting of modules and components during maintenance. The core engine is placed on a
steel base frame and the speed reduction gear box can be placed either directly on the concrete foundation together
with the generator, or on a common base frame with the core engine. The current Classic package is shown in Figure
6.
Figure 6: SGT-800 Classic package
As an alternative, the SGT-800 is also available with a Single lift package, Figure 7. This package incorporates
additional features and benefits, such as:





only 60 days installation and commissioning time on site
reduced customer site manpower requirements
48 hours core engine swap with customer spare to maximize uptime
reduced footprint with only 4.7m enclosure width (compared to 7.1m for the Classic package)
available also as a Single Lift Driver with the generator on foundation for reduced transport weight
Depending on customer and site requirements, the optimum package solution can be selected within the broad
flexibility of options available.
Figure 7: SGT-800 Single Lift package
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FUEL FLEXIBILTY EVOLUTION
Siemens is continuously improving the fuel flexibility of the SGT-800 to meet increasing market requirements. The
key ‘working tool’ here is the robust and simple DLE-system. The SGT-800 uses thirty 3rd generation DLE burners
in an annular combustor. The burner, shown in Figure 8, uses totally five fuel lines for dual fuel capability: main gas,
pilot gas, central gas, main liquid and pilot liquid, where the respective injection locations are shown in the figure.
(1) (4)
(2) (5)
(3)
Figure 8: SGT-800 DLE burner. The fuel injection locations are shown for (1) pilot gas,
(2) central gas, (3) main gas, (4) pilot liquid and (5) main liquid
The corresponding fuel line system is shown in Figure 9, indicating the uncomplicated fuel system using small
amount of fuel lines. Few fuel lines and continuous flow in all fuel pipes in the entire load range due to the absence
of fuel staging are important features for stable DLE systems, allowing for example for rapid load changes.
Fuel manifolds
around the gas
turbine core
Central gas valve
Main gas valve
Pilot gas valve
Figure 9: SGT-800 fuel line system showing the central, main and pilot gas valve locations
The growing requirements on the gas turbine market for using not only normal natural gases has been the driving
force for Siemens fuel flexibility evolution. This involves gas fuels such as Propane and Ethane, as well as gases
containing Hydrogen or substantial amount of inert components (Nitrogen or CO2). As one example, two of the units
in Thailand has successfully operated more than 15,000 hours each on the “West gas” containing high content of
inert gases (16% Nitrogen + 6% CO2).
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Another area attending high focus is firing Hydrogen rich fuels. In many industrial areas, Hydrogen can be seen as a
waste product that if fired in a gas turbine will not only reduce cost of fuel but also contribute to a more
environmentally-friendly production of electricity. Burning Hydrogen emits water rather than harmful carbon
dioxide. However, when compared to natural gas, Hydrogen is a more reactive fuel. The flame is more intense and
will be closer to the burner outlet and this increases material temperatures. Development of increasing capabilities
for handling of Hydrogen rich fuels involves then making adjustments of the standard burner with more advanced
cooling design. This is one interesting application for Siemens Additive Manufacturing (“3D printing”) workshop in
Finspong. Design solutions that are not feasible using traditional machining and welding techniques, can be applied.
The Figure 10 shows a 3D printed burner front to the left and a traditionally welded design to the right.
Figure 10: An SGT-800 burner front, the 3D printed unit is on the left
Advanced measurement and visualization techniques, such as high temperature borescope, are used for validation
tests of burner capabilities. Figure 11 shows borescope probe photos of the flame during single burner combustion
tests in an annular high pressure test rig [5], for 0-32% by volume content of Hydrogen mixed into natural gas (NG).
During natural gas operation of the test burner, yellow flames are seen and there are no clear pilot flames at the pilot
exits. As Hydrogen is fed into the test burner, the pilot flames appear and the fuel burns closer to the fuel exit ports.
Increasing hydrogen content from 12% by volume up to the 32% does not significantly change the flame position
but the light intensity increases and the flames appear whiter. Further reading of Siemens work on co-firing
Hydrogen can be found in [6].
Figure 11: Flame appearance during test with 0%, 12%, 20% and 32% by volume H2 in the natural gas
The present gas fuel capability of the SGT-800 is summarized in Figure 12. Note that auxiliary systems and turbine
governor will always be adapted for the specific site gases and requirements, and may then not apply to all gases
within this specification without further adaptions. The levels of certain constituents or properties may influence the
design of the fuel system, enclosure ventilation, gas detection, area classification, materials selection, etc.
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Figure 12: SGT-800 gas fuel capabilities
CONCLUSION
Siemens continuous evolutionary development strategy of the SGT-800 gas turbine has been outlined in this paper.
The strategy is based on platform generations with an introductory rating followed by step-wise fine tunings to
enhance performance built on extensive commercial operation feedback and engine testing. This strategy will secure
reliability since proven experience is valid for the engine type platform generation. At the same time both new and
existing customers can utilize the results of the improvements thanks to compatibility within the same generation.
This paper has also highlighted Siemens continuous improvements to meet market demands for flexible package
solutions and fuel flexibility. The latter requires a robust DLE system without complicated staging or water systems
and innovative manufacturing processes like 3D printing.
Siemens will continue to gently improve performance, reliability and availability, flexibility in solutions, fuels and
operations, and this will be done platform by platform and small step enhancements in-between the generations.
ACKNOWLEDGMENTS
The author would like to acknowledge Siemens Industrial Turbomachinery AB, Finspong, Sweden for the
permission to publish this paper. Additionally the author acknowledges all Siemens employees involved in the
continuous evolutionary development that has made the SGT-800 the clear market leader for combined cycle
application in its power range during the last four years.
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REFERENCES
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design modifications and operation experience”, ASME GT2008-50087, 2008.
[3] Lörstad, D., Wang, L., Axelsson, S. and Björkman, M.; “Siemens gas turbine SGT-800 enhanced to 50MW:
design modifications, validation and operation experience”, PowerGen Europe, Vienna, Austria, 2013.
[4] Annerfeldt M., Shukin S., Bjorkman M., Karlsson A., Jonsson A., Svistounova E., “GTX100 turbine section
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analysis”, PowerGen Europe, Barcelona, Spain, 2004.
[5] Andersson, M., Larsson, A., Lindholm, A., Larfeldt, J., “Extended fuel flexibility testing of Siemens industrial
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[6] Larfeldt J., Larsson A., Andersson M., “Co-firing hydrogen in Siemens industrial gas turbines”, SGC report,
Sweden, 2013. http://www.sgc.se/
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