Written By: Joshua Kovac, Siemens Energy, Inc., 4400 Alafaya Trail, Orlando, FL 32826-2399

The SGT6-5000F engine has demonstrated an exceptional operational record over a 15-year, 4.7+ million fleet hour history. Since its introduction in 1993, this F-Class gas turbine has undergone continuous development to improve performance, reliability and operational flexibility and to reduce emissions and life cycle costs. The result is a gas turbine with an excellent operational record and customer value. In 2008, Siemens Energy started production of the latest upgraded version of the SGT6-5000F. The capabilities of this newest offering include a dual-fuel gas turbine which can deliver 150MW of power to the grid within 10 minutes, Ultra Low NOx combustion system (9ppm) and hot gas path components designed for extended maintenance intervals. This paper describes the technological advances now available in the SGT6-5000F gas turbine which will further improve performance, reliability, operational flexibility and customer value.

The hallmark of the SGT6-5000F gas turbine, first introduced in 1993, has been its steadily increasing capabilities as market requirements have evolved over time. The SGT6-5000F kept pace with the need for rapid expansion in the 1990’s with increasing power output and improved thermal efficiency as deregulation and low natural gas prices opened new market opportunities for base loaded gas turbines. Then with the dramatic downturn in the market in the early 2000’s, the industry saw changing operating modes. The new challenge required transitioning plants from expected base load operations to nightly and weekend shut downs to remain economically viable. Now, the recent upturn in requirements for gas turbines and expected robust market in the future comes along with the need for a fully flexible gas turbine solution.

The latest evolution of the Siemens SGT6-5000F version or simply the F(4), will excel within these market requirements with increased power output, improved thermal efficiency, extended maintenance intervals and greatly enhanced operating flexibility. The SGT6-5000F gas turbines leaving the Siemens factory in North America includes options for improved economic viability and success of our customers. These capabilities include fast start (10 minutes to 150 MW), improved starting reliability, single digit NOx capability, low turndown ratios for reduced CO emissions at part loads and extended operating hours and starts between maintenance intervals.

Figure 1. SGT6-5000F
Figure 1. SGT6-5000F

SGT6-5000F Engine Development Background

The SGT6-5000F introduction represented a technology step change made possible by advancements in manufacturing, materials, analytical techniques and airfoil cooling. The improvement in thermal performance was achieved simultaneously with emissions reduction through dry low NOx technology. This gas turbine, which was designed for both simple cycle and combined cycle (CC) power generation in utility and industrial applications, represented the evolutionary improvement in the successful W501 family. Its design was based on fundamental, time-proven design concepts used in previous models, as well as new concepts and technologies incorporated to increase efficiency, reduce emissions and enhance reliability. It was designed to operate on all conventional fuels, as well as coal-derived low BTU gas. New technologies were validated for engine application by extensive rig and two full load engine shop tests, as well as field tests in the initial installation. Figure 1 shows a cross-section of the SGT6-5000F layout. The 13-stage compressor is connected to the 4-stage turbine by a single tie bolt, and the ultra low NOx combustion system employs 16 can annular baskets.

SGT6-5000F Operating Fleet Overview
The 205 SGT6-5000F engines currently in service are employed in peaking, intermediate and continuous duty operation. The fleet has amassed more than 4.7 million operating hours and has demonstrated excellent reliability, availability and starting reliability. These units, plus an additional 27 committed, represent the highest number of any one model of 60 Hz Siemens gas turbines sold. Due to design enhancements, development efforts, and technology cross flow from other Siemens’ advanced gas turbines, the simple cycle output has increased from 150 MW to 208 MW and its efficiency from 35% to 38+%. In 1×1 Combined Cycle applications, the net plant output and efficiency are now more than 300 MW and 57.5%, respectively.


Figure 2. SGT6-5000F Performance Evolution
Figure 2. SGT6-5000F Performance Evolution

The criterion by which a gas turbine is judged to be successful is its operating experience. The specific criteria for success include performance, emissions, mechanical integrity (as defined by RAM and starting reliability), life cycle costs and operational flexibility. All of the above are important, but in the current competitive and changing market environment, operational flexibility and adaptability to this environment have assumed a much greater significance. To be economically viable, the electricity generating plant must respond quickly, efficiently and reliably to any required changes in operating conditions such as load demand, start-stop operation, different fuels, etc., while operating within emissions regulations. The SGT6-5000F has demonstrated over the last 15 years its success in this environment, providing its operators with exceptional service.

The demonstrated median measured fleet values for availability and reliability (as of August ’08) are 95.6% and 99.7% respectively as shown in Figure 3. The values presented represent a statistical view of the service fleet as opposed to simple averages of these parameters. This provides a more accurate view of the fleet performace. The lead SGT6-5000F engine has accumulated more than 120,000 operating hours. The SGT6-5000F engine has demonstrated its mechanical integrity, operational flexibility and excellent performance through a continuous improvement and dedicated product development effort carried out since its introduction. This includes not only the gas turbine, but also the generator, mechanical auxiliaries (lube oil, fuel, etc.), electrical components and control system.

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