The present invention generally relates to methods and equipment suitable for use when assembling and disassembling turbomachines. More particularly, this invention relates to a method and system capable of installing and uninstalling inner turbine shells of a turbine engine.
In the hostile operating environments of gas turbine engines, the structural integrity of turbine rotor wheels, buckets, and other components within their turbine sections is of great importance in view of the high mechanical stresses that the components must be able to continuously withstand at high temperatures. For example, the regions of a turbine wheel forming slots into which the buckets are secured, typically in the form of what are known as dovetail slots, are known to eventually form cracks over time, necessitating monitoring of the wheel in these regions. The ability to detect and repair cracks is desirable in order to avoid catastrophic failure of a turbine wheel. While a turbine rotor can be completely disassembled to gain access to its individual components, inspection and maintenance techniques that can be performed with limited disassembly are preferred to minimize downtime, such as to fit within outage schedules of a land-based gas turbine engine employed in the power generating industry.
The construction of turbine sections that utilize multiple shells has become a common approach for facilitating the on-site maintenance of land-based gas turbine engines. A particular example is a dual shell design used for gas turbine engines manufactured by the General Electric Company, a notable example being the 9FB, 9H and 9FB.05 class gas turbines. As known in the art, turbines having this type of construction include casings, shells and frames that are split on the machine horizontal centerline, such that upper halves of the casings, shells and frames may be lifted individually for access to internal parts of the turbine. For example, by lifting the upper half of a turbine shell, the turbine rotor wheels, buckets and nozzle assemblies can be inspected and possibly repaired or replaced without necessitating removal of the entire turbine rotor. Prior to shell removal, proper machine centerline support using mechanical jacks is necessary to assure proper alignment of the rotor, obtain accurate half-shell clearances, etc.
With the use of a dual shell design as described above, the need to remove the turbine rotor from the inner turbine shell for the purpose of inspection and maintenance is often reduced or eliminated, with the result that downtime can be minimized by allowing the rotor and its components to be inspected and maintained at the same time that other internals of the rotor section are inspected and maintained. However, while the removal of the upper half of the turbine shell provides ready access to the exposed portions of the rotor wheels and buckets, access to those portions of the rotor wheels and buckets located in the lower half of the turbine shell is complicated by the presence of the lower half of the turbine shell. The location of the lower turbine shell and the precision of its installation in the turbine section present significant challenges to its removal and reinstallation for the purpose of conducting a complete inspection of the turbine section.
In view of the above, it would be desirable if a method existed that was capable of installing and uninstalling the lower inner turbine shell of a gas turbine engine.
The present invention provides a method and system adapted for installing and removing a shell from an assembly of multiple annular shells, for example, installing and removing an inner turbine shell of a turbine engine.
According to a first aspect of the invention, the method includes removing an upper shell positioned in an upper position relative to a lower shell of the assembly of multiple annular shells, positioning and securing a counterweight in the upper position and securing the counterweight to the lower shell as a replacement for the upper shell in the upper position, rotating the counterweight and the lower shell in unison until the lower shell is in the upper position and the counterweight is in a lower position previously occupied by the lower shell, and then removing the lower shell from the assembly.
According to a second aspect of the invention, the system includes a counterweight adapted to replace an upper shell positioned in an upper position relative to a lower shell of the assembly of multiple annular shells, and also adapted to be secured to the lower shell. The system further includes a device adapted to rotate the counterweight and the lower shell in unison until the lower shell is in the upper position and the counterweight is in the lower position, thereby permitting the lower shell to be readily removed from the assembly.
A technical effect of the invention is the ability of the method and system to install and remove individual shells from an assembly of multiple annular shells, a particularly notable example of which is the removal of the lower inner turbine shell of a turbine engine. In particular, the invention allows for the removal of the lower portion of a turbine shell which, in combination with the conventional removal of the upper portion of the turbine shell, provides easy access to components within the turbine section, for example, the exposed portions of a turbine rotor, including its wheels and buckets, while allowing the rotor to remain in place within the rotor section. The invention is also able to overcome difficulties arising from the location of the lower turbine shell within the turbine section of a gas turbine engine and the precision of its installation within the turbine section.
Other aspects and advantages of this invention will be better appreciated from the following detailed description.
The present invention will be described in terms of a method and system capable of installing and removing a shell from an assembly comprising multiple annular shells. While various applications are foreseeable and possible, applications of particular interest include installing and uninstalling inner turbine shells of gas turbines, including land-based gas turbine engines.
While it is possible to gain access to the rotor 12 and other internal components of the turbine section of the engine 10 by completely disassembling the turbine section, inspections, maintenance, and repairs are preferably completed with the rotor 12 and internal components remaining in-situ. The method herein described involves removing the upper and lower inner shells 18 and 20 in order to provide full access to the rotor 12 and internal components of the turbine section of the engine 10 without the need for a more complicated disassembly of the turbine section. For this purpose, the upper outer shell 14 and the upper inner shell 18 are preferably first removed radially from their respective upper positions within the turbine engine 10, for example, raised with conventional lifting equipment.
The manner in which the counterweight 22 and thrust collar locator 36 are assembled together and interact is evident from a cross-sectional view represented in
Once positioned on the lower inner shell 20 (
A perspective view of the drive system 54 is represented in
The drive system 54 is located on a support plate 52 together with a pressure amplifier 44 and a hydraulic friction braking unit 46. The braking unit 46 comprises a brake slot 50 that, during operation, engages the brake plate 24 of the counterweight 22. The pressure amplifier 44 and braking unit 46 apply friction to the brake plate 24 in order to slow or stop the rotation of counterweight 22 as well as secure its position while stationary. While a disk-type braking system is represented in the figures, other types of braking systems could be used.
The forward and aft roller assemblies 56 and 58 are used in combination to ensure proper alignment of the lower inner shell 20 during its removal and reinstallation. Each roller assembly 56 and 58 is represented in
As also evident from
While the invention has been described in terms of certain embodiments, it is apparent that other forms could be adopted by one skilled in the art. Therefore, the scope of the invention is to be limited only by the following claims.
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