Results of the GT Prime Program Improvements to General Electric MS7001B Gas Turbines at the Houston Light and Power T.H. Wharton Site

Abstract

At the time of the start of the GT PRIME upgrade project, the eight General Electric MS7001 gas turbines in combined cycle service at the Wharton Station of Houston lighting and Power each had 85,000 hours of operation with 2000 starts. The units were ready for their second major overhaul. A number of hot gas path components required replacement at that time. Rather than replacing components one by one, the user devised a Program for Reliability, Improved Maintenance, and Efficiency (GT PRIME). We will discuss turbine condition, design changes, reduced emissions, and increased output in the paper. Actual user experience on maintenance and operating costs resulted in some special requirements to be satisfied in addition to the expected parts replacement. General Electric had developed many improved parts for newer units, all of which could be easily applied to older machines. The use of these newer production MS7001EA parts increase component life, parts availability, inspection intervals, system reliability and performance. These will be described in the paper. These 1972 vintage turbines achieved a 50PPM NOx level by injecting water at a high rate of flow which resulted in the need for more frequent combustion inspection intervals. The development of a dry low NOx system for the unit allowed the combustion inspection interval to double while reducing NOx to 25PPM. The improvement in component efficiencies in the gas path resulted in increased output and improved the heat rate. These changes had a significant impact on customer operating costs which resulted in a very attractive payback period. We will discuss expected versus actual output, heat rate and emissions results for all eight units. The upgrade of the first unit started in 1992 and the last unit was completed in 1996. A detailed listing of uprate program schedule by unit is listed in Figure #1.