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  System for restoring turbine vane attachment systems in a turbine engineThe Patent Description & Claims data below is from USPTO Patent Application 20070077148. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention is directed generally to turbine engines, and more particularly to turbine vane attachment systems in turbine engines. BACKGROUND [0002] Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. The turbine blade assembly typically includes a rotor assembly rotatable positioned in a turbine combustion case and having a plurality of turbine blades extending radially outward from the rotor assembly. The turbine engine also includes a plurality of stationary turbine vanes, which are also referred to as diaphragm airfoils, extending radially inward from the turbine combustor case. The turbine blades and turbine vanes are aligned into rows, or stages, and are positioned in alternating rows of vanes and blades. The turbine vanes are typically attached to a turbine combustion case via a hook fit, as shown in cross-section in FIG. 1. The hook fit releasably and securely attaches the turbine vanes within a turbine engine. During operation, the hooks fits are susceptible to wear due to vibration, heat, and other factors. For instance, a hook fit is typically worn in the areas shown in FIG. 1. Such wear negatively affects the safety and efficiency of a turbine engine in which the wear occurs. [0003] Typically, such wear regions are repaired on turbine engines during outages in which other aspects of the turbine engine are repaired. The hook fits of a turbine engine are repaired by first removing the cover half of a turbine of the combustion turbine case to provide access to the internal aspects of the turbine engine. Once the cover half has been removed exposing the rotor assembly, the rotor assembly may be removed from the turbine engine. Removing the rotor assembly from the turbine engine typically takes about two weeks of time and costs about $500,000 per turbine engine. Once the rotor assembly is removed, the cover half is reassembled and the hook fits are repaired using a boring bar. [0004] Conventionally, hooks fits of a turbine engine have been restored manually. For instance, personnel typically use handheld grinders to prepare the worn regions before material is welded to the regions. Once the worn region is prepared, personnel weld material to the worn regions and then manually work the added material into shape using manually controlled grinders. Thus, the quality and precision of the restoration process is limited by the skill, experience, and ability of the personnel operating the grinding equipment. Because the majority of the process is manually controlled, the restoration process lacks the necessary precision to restore the hook fits to their original shape consistently and in a cost efficient and time efficient manner. Thus, a need exists for a more precise, time efficient method of repairing a hook fit of a turbine engine. SUMMARY OF THE INVENTION [0005] This invention is directed to a system and method for repairing turbine vane attachment systems in a turbine engine. In at least one embodiment, the invention may be directed to a system and method for repairing wear on diaphragm hook fits configured to attach diaphragm airfoils, which are also referred to as stationary turbine vanes, to a combustion turbine case. The restoration system may be formed from a carriage assembly having an assortment of material processing implements usable to build up material in the worn locations of the turbine vane attachment system in a manner to reestablish a diaphragm hook fit within the specified tolerances. The restoration system may be configured so that the carriage assembly can be positioned within a turbine engine without removing a rotor assembly, thereby resulting in significant time and cost savings. In large scale applications of power generation turbine engines, use of the restoration system can reduce the restoration process by about two weeks. [0006] The restoration system may include a movable carriage assembly formed from a housing configured to support a plurality of material processing implements usable to restore worn regions of a diaphragm hook fit. The material processing implements may include, but are not limited to, a milling cutter, such as a dovetail cutter, a welding head, and other appropriate devices. The carriage assembly may include a transport system for moving the carriage assembly in a turbine engine automatically without requiring service personnel to physically move the carriage assembly. In at least one embodiment, the transport system may be formed from a plurality of wheels configured to be attached to a generally curved track. The generally curved track may be configured to support the carriage assembly and to enable the carriage assembly to be movably attached to the combustion turbine case. The track may be configured to be removably attached to the combustion turbine case during the restoration process. [0007] The carriage assembly may also include a component drive system configured to drive the material processing implements. The material processing implements may include, but are not limited to, a milling cutter, a weld head, and other appropriate devices. The component drive system may also include a spindle in communication with a spindle drive device for driving the material processing implements. The spindle may be configured to receive the material processing implements. [0008] The restoration system may be used to repair a turbine vane attachment system, such as a diaphragm hook fit. In at least one embodiment, the restoration system may be used to restore wear regions in conventional diaphragm hook fits that, without restoration, negatively effect performance of the turbine engine. Access to a diaphragm hook fit may first occur by removing a cover half of the combustion turbine case. Once the cover half has been removed, the turbine vanes may be removed using conventional procedures. Removal of the turbine vanes and turbine blades provides sufficient room for the restoration system to be installed in the turbine engine without having to remove the rotor assembly and incur costs of about $500,000. Thus, use of the restoration system to repair a worn region of a turbine vane attachment system results in a tremendous cost and time savings. [0009] A first generally curved track may be attached to the combustion turbine case proximate to a diaphragm hook fit corresponding to a second row of turbine vanes. A carriage assembly may be movably coupled to the track so that the carriage assembly may travel along the length of the track. Movement of the carriage assembly may be controlled by personnel or by a program on a microcontroller or other appropriate device. The carriage assembly may be placed adjacent to a worn region. A milling cutter may be extended to contact an adjacent worn region, if necessary, to prepare the worn region for repair. The amount of material to be removed may be determined using conventional procedures. A welding head may then be placed in close proximity with the worn region to add material to the worn region to restore the worn region within the specified tolerances of the diaphragm hook fit. The welding head may be passed over a worn region a sufficient number of times to build up the material to a predetermined amount within the specified tolerances of the diaphragm hook fit. The carriage assembly may be moved along the track to facilitate building up material along a length of a worn region. Use of the carriage assembly to add material along the length of a worn region results in a tremendous time savings compared with conventional, manual repair methods. [0010] After material has been added to the worn regions, the carriage assembly may be moved along the track adjacent to the worn region to which material has been added. A milling cutter may be placed into contact with the material added to the worn region to remove excess material that was added. The milling cutter may be rotated with the spindle and spindle drive device. Once the material added to the worn regions has been shaped to fit within the specified dimensional tolerances for the diaphragm hook fit, the material removal procedure may be ceased. The carriage assembly may then be used to work on worn regions on another adjacent diaphragm hook fit using the same process. The process may be preformed on adjacent diaphragm hook fits by attaching a corresponding curved track to the combustion turbine case proximate to another diaphragm hook fit. [0011] An advantage of this invention is that the restoration system and method may be used restore worn regions of a turbine vane attachment system without requiring removal of a rotor assembly. Leaving the rotor assembly in place during the restoration process eliminates about two weeks of work typically required to remove a rotor assembly, thereby saving approximately $500,000 in repair costs per turbine engine. [0012] Another advantage of this invention is that the restoration system reduces the time necessary to restore a worn region. Many worn regions on turbine vane attachment systems extend along a length of the turbine vane attachment system. The restoration system enables material processing implements to be mechanically controlled and precisely positioned to restore the worn regions in less time than conventional restoration procedures conducted manually. [0013] Yet another advantage of this invention is that the restoration system enables diaphragm hook fits to be restored more precisely than is capable with conventional, manual restoration procedures. [0014] These and other embodiments are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS [0015] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention. [0016] FIG. 1 is cross-section of a conventional turbine vane attachment system. [0017] FIG. 2 is a partially exploded perspective view of a turbine engine. [0018] FIG. 3 is a perspective view of the restoration system of this invention. [0019] FIG. 4 is a perspective view of the carriage assembly coupled to a track. [0020] FIG. 5 is detailed perspective view of the carriage assembly. Continue reading... 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