Patent Application
20100104431
This invention relates generally to rotary machines and, more particularly, to a method and a system for aligning a shell of the rotary machine with a standard, or pedestal, of the rotary machine.
The high pressure section of a turbine may require maintenance, including replacement of certain parts. For example, a shell may require replacement and be required to interface with the existing standards, or pedestals, of the turbine. The existing standards may have different provisions for axial and transverse constraint of the turbine shell and they may be undersized and not capable of carrying the operating loads of the unit when the turbine shell is replaced.
Current designs for replacing the turbine shell have worked for decades, and provide axial and transverse constraint on the turbine. One known design uses a fabricated I-beam. The flanges of the fabricated I-beam are bolted to both the standard and the shell to provide the axial and transverse support. However, the I-beams are hard to assemble, service, and are prone to failures of the weld between the flange and web on the I-beam.
According to one embodiment of the invention, a system for aligning a shell of a rotary machine with a standard along an axial centerline and a transverse centerline of the rotary machine comprises a pair of generally L-shaped hooks on the shell; a generally T-shaped member comprising a base, a post, and a cross member; a pair of axial gib keys provided on opposing sides of the cross member, at least one of the axial gib keys configured to engage at least one of the L-shaped hooks and the other being configured to engage the shell; and a pair of transverse gib keys provided on opposing sides of the post, each transverse gib key configured to engage a respective L-shaped hook.
According to another embodiment of the invention, a method of constraining and aligning a shell of a rotary machine with a standard along an axial centerline and a transverse centerline of the rotary machine comprises fastening at least one axial gib key to a generally T-shaped member provided to the standard so that the at least one axial gib key is in contact with at least one L-shaped hook of a pair of generally L-shaped hooks of the shell; fastening a second axial gib key to the T-shaped member so that the second axial gib key is in contact with the shell; and fastening a pair of transverse gib keys to opposing sides of the T-shaped member so that each transverse gib key is in contact with a respective L-shaped hook.
Referring to
The shell 4 comprises a pair of generally L-shaped hooks 12 that are configured to interface with a cross member 42 of the T-shaped member 6. Although the L-shaped hooks 12 are shown as integrally formed with the shell 4, it should be appreciated that the L-shaped hooks 12 may be formed separately and fastened to the shell 4. The cross member 42 of the T-shaped member 6 is connected to the base 40 by a post 44. A groove 24 may be provided at the junction of the cross member 42 and the post 44 of the T-shaped member 6. It should also be appreciated that the T-shaped member may be formed integrally, e.g. as a one-piece construction, with the standard.
A pair of first axial gib keys 14 and a second axial gib key 18 are configured to constrain the shell 4 with respect to an axial centerline 20. The first axial gib keys 14 may also be referred to as pull gib keys and the second axial gib key 18 may be referred to as a push gib key. A pair of transverse gib keys 16 are configured to constrain the shell 4 with respect to a transverse centerline 22 of the turbine 8. Each gib key 14, 16, 18 may be a gib key as disclosed, for example, in U.S. Pat. No. 7,273,348.
Referring to
The push gib key 18 comprises a first plate 36 and a second plate 38. The first plate 36 is secured to the cross member 42 by fasteners 26. The second plate 38 of the second axial gib key 18 comprises a contact face 48 that is configured to contact the shell 4. The contact face 48 may also comprise a coating as discussed with respect to the contact faces 50 of the pull gib keys 14. The axial keys 14, 18 may be fastened to either the T-shaped member 6, or the shell 4.
The shell 4 is axially constrained and aligned with the standard 2 along the axial centerline 20 between the first axial gib keys 14 and the second axial gib key 18.
Referring again to
The shell 4 is transversely constrained and aligned with the standard 2 along the transverse centerline 22 between the transverse keys 16.
The combined axial and transverse constraint and alignment system described herein can handle the operating loads of rotary machine, for example a steam or gas turbine, while conforming to current design limits and best practices. The combined axial and transverse constraint and alignment system also provide a design option if design space limits use of current fixation methods. It may be used on retrofits to turbines.
The combined axial and transverse constraint system is also capable of supporting the high loads caused by piping, steam torque, and seismic events. The system is configured to reside in an environment with thermal gradients and little maintenance room. The system is easily adjustable for alignment of the unit, accessible for maintenance, and is capable of long operation without repair.
The gib keys and the T-shaped member may be produced from high grade material, which will handle the forces from both operation and seismic events while maintaining acceptable material stresses. The gib keys and T-shaped member do not contain any welds, which are more prone to failure due to the thermal gradients from the shell to the standard. The gib keys allow easy alignment/adjustment of the unit without the need to take apart the whole assembly.
The combined axial and transverse constraint and alignment system disclosed herein provides a more robust design compared to existing I-beam designs currently in use.
The system may also be used on inner shells if design space required deviation from current standard practices.
Unlike some current designs, which only provided one degree of fixation( i.e. vertical, transverse, or axial), the system disclosed herein provides two degrees of fixation, transverse and axial, from a single component.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
