Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2000-12-07
2002-01-29
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S029000
Reexamination Certificate
active
06343251
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of the operation and maintenance of industrial turbomachinery. In particular, the invention relates to monitoring and tracking the operation of turbomachinery, predicting the operational life of the turbomachinery and its parts, and scheduling maintenance for the turbomachinery.
BACKGROUND
Gas turbines generally include a compressor and turbine arranged on a rotating shaft(s), and a combustion section between the compressor and turbine. The combustion section burns a mixture of compressed air and liquid and/or gaseous fuel to generate a high energy combustion gas stream that drives the rotating turbine. The turbine rotationally drives the compressor and provides output power. Industrial gas turbines are often used to provide output power to drive an electrical generator or motor. Other types of gas turbines may be used as aircraft engines, on-site and supplemental power generators, and for other applications.
Gas turbines have many parts and components that are exposed to corrosive combustion gases, extreme temperatures, centrifugal stresses and other adverse conditions. These conditions impose stresses and corrosive elements on the gas turbine that cause wear, strain, fatigue, corrosion and other harmful effects. Moreover, the major rotating components, e.g., shaft, turbine and compressor, sustain stresses and are critical to the operation of the gas turbine.
In addition, the compressor, combustion section and turbine form a gas-path for the air and combustion gases that flow through the gas turbine. These gas-path components withstand extremely high energy loads, temperatures and corrosive gases. The elevated temperatures, high stresses and aggressive environmental conditions create time-dependent and cyclic failure mechanisms that act on the gas turbine, and especially the gas path components of the gas turbine. These conditions can lead to failure of components of the gas turbine and, possibly, failure of the gas turbine itself.
The gas turbine components that generally require much attention to maintenance are those associated with the combustion process, e.g., combustion chambers (cans), combustion liners, end caps, crossfire tubes, turbine nozzles, turbine buckets, etc. These “hot-gas-path” components tend to be those that require regular replacement, and are the subject of regular preventive maintenance and replacement programs. In addition, other basic gas turbine components, such as control devices, fuel metering equipment, gas turbine auxiliaries, load packages, and other station auxiliaries require periodic servicing.
Preventive maintenance safeguards industrial gas turbines from failure and undue wear of components. Preventative maintenance requires a maintenance schedule to be established for each gas turbine. The schedule is created based on the operating history of the gas turbine. The technicians who operate the gas turbines maintain detailed and comprehensive logs of their operation, including the start-stop times, operating conditions, fuel, load and other conditions. Using these logs, the technicians and supervising engineers monitor the operation of the gas turbine and schedule preventive maintenance and parts replacements.
In recent years, control systems for gas turbines have been developed that collect data from sensors on the turbine. This data reflects the operating condition of the gas turbine, in a manner similar to the data manually logged by earlier technicians. Accordingly, some of the manual logging of operating conditions have been replaced by automatic data collecting control systems.
Manufacturers of gas turbines generally provide instructional manuals as to how to monitor the gas turbine and schedule maintenance and repairs. For example, the Power System Division of the General Electric Company provides a manual entitled “Heavy-Duty Gas Turbine Operating and Maintenance Considerations” (GER-3620G) that explains how to create maintenance schedules for gas turbines and how to conduct preventive maintenance. By following the instructions described in the manual, a technician evaluates the logged operating history of a gas turbine and determines when and what preventive maintenance should be performed.
Prior techniques for scheduling maintenance for industrial gas turbines relied on algorithms that predicted the expected operating life of various components of the turbine. These algorithms for predicting component life are typically based on a defined “design duty cycle”, which is a standardized operational cycle for the gas turbine or one of its components. The design duty cycle is used to predict the deterioration of parts in a gas turbine during a standard cycle of starting, a power production (which may be constant or variable) period and shut-down. The design duty cycle simulates the actual deterioration of parts in a gas turbine operating under conditions for the turbine was designed. However, the design duty cycle does not truly reflect the actual operating conditions of a gas turbine, actual operating conditions are often substantially different than those for which the gas turbine was designed.
The actual maintenance requirements of a gas turbine depend on its actual operational history, which includes the actual operating conditions. The actual life of a gas turbine is a strong function of actual usage of that turbine. Off-design operating conditions and off-design modes (e.g., operating conditions substantially different than duty cycle conditions) affect metal temperatures and stresses, and result in more (or less) than predicted damage to the gas turbine. To reflect off-design conditions, prior techniques have used “maintenance factors” to supplement the duty cycle analysis. “Maintenance factors” quantify the severity of off-design operation. Maintenance factors have been manually determined by gas turbine technicians and engineers.
Conventional methods of predicting part failure for gas turbines and scheduling maintenance have not been entirely accurate in predicting part failures or optimally scheduling maintenance. The traditional “duty cycle” used for predictive maintenance does not reflect real operational conditions, especially off-design operations. The actual life of a component of a gas turbine depends strongly on the actual usage of that gas turbine and the part within the turbine. For example, elevated temperatures and stresses within the turbine, and aggressive environmental conditions may cause excessive wear on components in the turbine beyond that predicted with the standard design duty cycle. Off-design operating conditions, which are often experienced by industrial gas turbines, are not reflected by the standard duty cycles. The actual part life of components in the gas turbine may be substantially less than that predicted by the design duty cycle. Alternatively, if more favorable conditions are experienced by an actual gas turbine (than are reflected in the design duty cycle), the actual part life may last substantially longer than that predicted by maintenance schedules based on the design duty cycle. In either event, the standard “design duty cycle” model for predicting preventive maintenance in industrial gas turbines does not reliably indicate the actual wear and tear experience by a gas turbine. Accordingly, there is a long-felt need for a technique to more accurately predict the life of a gas turbine and its components.
Prior techniques for predicting maintenance and part replacement relied on skilled technicians to acquire or interpret data regarding the operation of a gas turbine. Such techniques were subject to the varying interpretations of that data by technicians. The operational logs and/or data collected from gas turbines were manually evaluated by technicians. Technicians, for example, would evaluate start and stop times, and power settings to determine how many duty cycles had been experienced by the gas turbine, their frequency, period and other factors. In addition, if the log data of the gas turbine indicated that extraordinary condition
Germain David R.
Herron William L.
Schick Louis Andrew
Camby Richard M.
General Electric Company
Nixon & Vanderhye P.C.
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