Operating Experience With Compressors of Large Heavy-Duty Gas Turbines

The shaft power of compressors in industrial-type gas turbines exceeds that which is attained by any other axial compressors. Their operating efficiency and availability are thus of prime importance expecially since gas turbines are being increasingly utilized for medium-range and base-load electric power generation. In addition to good aerodynamic design of the blading, correct dimensioning of the compressor blades to withstand the static and dynamic stresses that occur under various service conditions is a decisively important prerequisite for reliable operating performance. Measurement of the dynamic stresses is important for design verification and reliability confirmation. Within the period between scheduled maintenance of a Model V 94 gas turbine, approx. 3,000 kg of solid particles flow through the compressor blading if the intake ambient air has a dust content of 0.1 mg/m3. The possible resulting erosion, corrosion and fowling negatively affect the long-term operating performance. The paper describes how these harmful effects can be effectively combatted by intake-air filtering, machine washing and blade coatings. The operating experience based on over one million service hours, of which more than one-third is with protected blades, demonstrates the success of the recommended compressor protection methods in achieving remarkably high operating availability.

Root Cause Analysis of Outages in Combined-Cycle Power Plants

A data base system has been developed to analyze root causes of failures and unplanned outages in combined-cycle power plants and related equipments. Raw data in the form of plant work orders and outage reports are provided by thirteen utilities. Data encompasses both scheduled and unscheduled maintenance activities involving all plant equipments of mostly combined cycle installations. Primary objectives are to evaluate combined-cycle plant maintenance records to determine root causes of equipment failures, to analyze maintenance data to identify key areas for reliability, availability, and maintainability (RAM) improvement, and to develop an automated data processing system for feedback to project participants. ERAS (EPRI Reliability Assessment System) data were analyzed to determine failure rates and mean downtimes of critical equipment used in combined-cycle plants and integrated gasification combined-cycle plants of the future. A primary ERAS data requirement is to document plant equipment failures involving planned outages, unplanned outages, and noncurtailing maintenance. Maintenance data are mailed directly from the plant on a monthly or weekly basis. In order to maintain significant coordination and feedback, documentation is also mailed by ARINC Research to manufacturers and EPRI project personnel. ERAS is foremost a repository, based on dBASE II software, of raw data records which address combined-cycle plant equipment scheduled and unscheduled maintenance activity. By using dBASE II commands, data contained in “DAILY”, “MONTHLY”, “PROBLEMS”, and “FIREHRS” data base files (DBFs) are analyzed in many ways. Data may be separated by manufacturer or utility. RAM statistics may be analyzed according to six data hierarchies, grouping data by common plant design, system, subsystem, or components. Special report forms can be developed depending on specific data processing needs. During 1982 a total of 1744 maintenance records for the thirteen participating plants were processed. Seventy percent of the events were noncurtailing, of which 612 events involved component failures. The data base included 968 failure events to over 200 different combined-cycle plant components each described by a three digit code. Component repairs accounted for over 50 percent of these failures. Detailed descriptions of these failures identifying causes and failed piece parts can be listed by the computer from the “PROBLEMS” DBF using “FRM’s SYSCOMP” (failures grouped by components) or “SYSPLANT” (failures grouped by plant). It is concluded that work orders do provide insight into possible root cause and can assist engineering in followup failure investigations, although discussions with power plant personnel are often required for additional insight into root cause. The extent of successful root cause determination in the ERAS data base is difficult to quantify due to different root cause interpretations. However, project efforts have successfully identified the failed piece part in 86 percent of equipment failures. An analysis of plant reliability problems showed that failures of combustion turbine and heat recovery boiler panel controls and remote sensing equipment are the most frequent cause of combined-cycle plant unavailability. Each plant appears to have specific problem areas generic to these control system failures. Generic problems were observed in drum level set points, control valves, panel cards and timers, computers and data links, flame scanners, and thermo-couples. Many of the control related problems documented in ERAS records identify the failed part number of the control circuit affected. It is expected that these documented control system failures will begin to yield better insight into root cause as the number of records increase, and cause and effect relationships are established.

The Effect of Water Injection for Emissions Control on Industrial Gas Turbine Combustors

One common method of reducing the NOx emissions from industrial gas turbines is to inject water into the combustion process. The amount of water injected depends on the emissions rules that apply to a particular unit. Westinghouse W501B industrial gas turbines have been operated at water injection levels required to meet EPA NOx emissions regulations. They also have been operated at higher injection levels required to meet stricter California regulations. Operation at the lower rates of water did not affect combustor inspection and/or repair intervals. Operation on liquid fuels with high rates of water also did not result in premature distress. However, operation on gas fuel at high rates of water did cause premature distress in the combustors. To evaluate this phenomenon, a comprehensive test program was conducted; it demonstrated that the distress is the result of the temperature patterns in the combustor caused by the high rates of water. The test also indicated that there is no significant change in dynamic response levels in the combustor. This paper presents the test results, and the design features selected to substantially improve combustor wall temperature when operating on gas fuels, with the high rates of water injection required to meet California applications. Mechanical design features that improve combustor resistance to water injection-induced thermal gradients also are presented.

The MIT Blowdown Turbine Facility

A short duration (0.4 sec) test facility, capable of testing 0.5-meter diameter, film-cooled, high work aircraft turbine stages at rigorously simulated engine conditions has been designed, constructed, and tested. The simulation capability of the facility extends up to 40 atm inlet pressure at 2500°K (4000°F) turbine inlet temperatures. The facility is intended primarily for the exploration of unsteady, three-dimensional fluid mechanics and heat transfer in modern turbine stages.

Turbomachinery Engineering and Optimization for 25 MW and 50 MW Compressed Air Energy Storage Systems

Results of engineering and optimization of 25 MW and 50 MW turbomachinery trains for compressed air energy storage (CAES) power plant application are presented. Submitted by equipment suppliers, proposals are based on the commercially available equipment. Performance data and budget prices indicate that the CAES power plant is one of the most cost effective sources of providing peaking power and load management.

Current Status of Advanced Reheat Gas Turbine AGTJ-100A: Part 3 — Experimental Results of Shop Tests

The outline of plans for the research and development of an advanced reheat gas turbine under the Moonlight Project (Agency of Industrial Science and Technology, Ministry of International Trade and Industry) has already been announced in 1981 at Houston (81-GT-28), while technical problems related to the pilot plant (Paper No. 83-TOKYO-IGTC-117) as well as performance and characteristics (Paper No. 83-TOKYO-IGTC-40) have been announced at the 1983 Tokyo International Gas Turbine Congress. No-load shop tests conducted on the pilot reheat gas turbine during the period of May to July, 1983, were consummated with highly satisfactory results, so this paper is dedicated primarily to giving a description of the shop tests.

Seven Years of Putnam Plant Operation: Part 1–2

Florida Power and Light Company’s Putnam Station, one of the most efficient power plants in the FP&L system, is in a unique and enviable position from an operational viewpoint. Its operation, in the last seven years, has evolved through a triple phase fuel utilization from distillate to residual oil and finally to natural gas. This paper compares the availability/reliability of the Putnam combined cycle station and the starting reliability of the combustion turbines in each of the operating periods. A review of the data shows that high availability/reliability is not fuel selective when appropriate actions are developed and implemented to counteract the detractors. This paper also includes experience with heat rate and power degradation of various power plant components and programs implemented to restore performance.

Evaluation of the Compression-Intercooled Reheat-Gas-Turbine-Combined Cycle

Interest in the reheat-gas turbine (RHGT) as a way to improve combined-cycle efficiency is gaining momentum. Compression intercooling makes it possible to readily increase the reheat-gas-turbine cycle-pressure ratio and at the same time increase gas-turbine output; but at the expense of some combined-cycle efficiency and mechanical complexity. This paper presents a thermodynamic analysis of the intercooled cycle and pinpoints the proper intercooling pressure range for minimum combined-cycle-efficiency loss. At the end of the paper two-intercooled reheat-gas-turbine configurations are presented.

Taipower Tunghsiao Stag Combined Cycle Power Plant

Units 1 and 2 in the Tiawan Electric Power Co. (Taipower) are General Electric STAG 307E combined cycle systems with rated output of 570 MW. These combined cycle generation systems include high technology gas turbines, an unfired steam system with steam generation at two pressures and computer based control systems. The net plant thermal efficiency at the rating point is 45.3% on distillate oil and 44.8% on residual oil. Currently one of the six gas turbines is operating on residual oil and five are operating on distillate. When the residual oil conversion is complete, these will be the World’s most efficient residual oil fired power generation units. A description of the distinguishing features, construction and early operating history are presented.

Experience in the Operation of Air Filters in Gas Turbine Installations

Industrial gas turbines swallow air at a rate of approximately 14 to 16 kg/kWh. Even in clean environments the amount of solid particle ingestion is significant. A 70.000 kW gas turbine operating in a typical residential area could ingest 1.3 to 1.5 kg of solid contaminants in a 24 hour period. The same gas turbine operating in a typical mining or oil field region could ingest 33 to 39 kg of solid contaminants in a 24 hour period. Depending on the composition, size, quantity and condition (wet, dry, sticky) of the ingested particles, performance loss, due to the fouling of the compressor and/or turbine and hardware deterioration, due to erosion, corrosion and/or foreign object damage, can be experienced. To protect against performance loss and hardware deterioration, industrial gas turbines are normally equipped with air inlet filtration systems. However, the effectiveness of the filtration system depends on how well it is matched to the contaminants and site conditions. Matching the filtration system to the contaminants and site conditions is usually a judgement decision based on experience and available information. This paper was written in an effort to enhance the equipment selection process by reviewing BBC’s experience with air inlet filtration systems.