System and method for heating a stator segment

A system for heating a stator segment includes a first frame member, a plurality of arms extending radially from the first frame member, and a heater releasably connected to each arm. The system further includes a biasing element for biasing each heater away from the first frame member.

FIELD OF THE INVENTION

The present invention generally involves a system and method for heating a stator segment. In particular, embodiments of the present invention may facilitate heating and removal of the stator segment from a compressor without requiring removal of the rotor.

BACKGROUND OF THE INVENTION

Compressors are widely used in industrial and commercial operations. For example, a typical commercial gas turbine used to generate electrical power includes a compressor at the front, one or more combustors around the middle, and a turbine at the rear. A casing generally surrounds the compressor to contain a working fluid flowing through the compressor, and alternating stages of rotating blades and stationary vanes inside the casing progressively impart kinetic energy to the working fluid to produce a compressed working fluid at a highly energized state. Each rotating blade may be releasably connected to a rotor located along an axial centerline of the compressor, and each stator vane may be attached to a stator segment. For example, six stator segments may circumferentially surround the rotor, with three stator segments in each half of the casing. The casing may include a hook fit slot that extends circumferentially around the casing for each stage of stator vanes, and the stator segments may releasably slide into the hook fit slots.

Periodically, the stator vanes and stator segments in the compressor must be removed and/or replaced. Doing so typically requires at least partial removal of the casing surrounding the compressor to provide access to the stator vanes and stator segments. With the rotor still in place, however, access is somewhat restricted, and particular care must be taken to ensure that removal of the stator vanes and stator segments does not result in collateral damage to the rotor, casing, or adjacent rows of rotating blades. For example, a cutting tool may be manually inserted around the rotor to individually cut each stator vane, and once all stator vanes have been cut from a particular stator segment, the stator segment may be removed from the hook fit slots in the casing.

Occasionally, however, corrosion, creep, and/or other plastic deformation of the hook fit slots and/or stator segments prevent the stator segments from readily sliding out of the casing. For example, the stator segments may be constructed from carbon steel, and moisture from condensation, water washes, and other environmental factors may product corrosion that makes it extremely difficult to remove the stator segments from the hook fit slots. Rapid heating and cold water quenching of the stator segments is a very effective method to loosen the corrosion and remove the stator segments. However, the current method to heat the stator segments uses a torch or other open flame that may inadvertently damage the adjacent components and presents a fire hazard if exposed to rotor dams temporarily installed to protect the rotating blades. In addition, a single torch has a limited surface area for heating the stator segments, requiring several hours to heat a single stator segment. Therefore, an improved system and method for heating a stator segment would be useful.

BRIEF DESCRIPTION OF THE INVENTION

One embodiment of the present invention is a system for heating a stator segment. The system includes a first frame member, a plurality of arms extending radially from the first frame member, and a heater releasably connected to each arm. The system further includes means for biasing each heater away from the first frame member.

Another embodiment of the present invention is a system for heating a stator segment that includes a first frame member, a second frame member separated from the first frame member, and a plurality of heaters connected to the second frame member. The system further includes means for biasing each heater away from the first frame member.

The present invention may also include a system for heating a stator segment that includes a first frame member and a plurality of arms extending radially from the first frame member. A heater is releasably connected to each arm, and a biasing element is operably connected to the first frame member and each heater to bias each heater away from the first frame member.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention include a system and method for heating a compressor stator segment. In particular embodiments, the system may include a collapsible frame that conforms to the various diameters of the various stages inside the compressor and allows the system to be quickly inserted between a rotor and a casing. A series of heaters attached to the collapsible frame rapidly heat each stator segment, and the collapsible frame allows the system to be quickly removed for a subsequent quenching sequence. The system and method are thus designed to quickly heat stator segments while also reducing any danger of collateral damages to adjacent components. As a result, the system and method aid in the removal of stator segments from the compressor without requiring removal of the adjacent components. Although exemplary embodiments of the present invention will be described generally in the context of a compressor stator segment for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present invention are not limited to heating compressor stator segments unless specifically recited in the claims.

FIG. 1provides a side view of an exemplary compressor10, andFIG. 2provides an axial cross-section view of the exemplary compressor10shown inFIG. 1taken along line A-A. A casing12that generally surrounds the compressor10has been partially removed fromFIG. 1to reveal that the compressor10includes alternating stages of rotating blades14and stator vanes16inside the casing12. Each rotating blade14may be releasably connected to a rotor18located along an axial centerline20of the compressor10, and each stator vane16may be fixedly or releasably attached to a stator segment22. As shown most clearly inFIG. 1, the casing12may include a hook fit slot24for each stage of stator vanes16, and the stator segments22may releasably slide into the hook fit slots24. Referring toFIG. 2, the compressor10may include, for example, six stator segments22that circumferentially surround the rotor18, with each half of the casing12holding two side stator segments26and one center stator segment28. Each stator vane16may in turn include a dovetail extension30that axially slides into a complementary dovetail slot32in the stator segments22to securely hold the stator vanes16in place with respect to the rotor18. In this manner, the rotor18may turn each stage of rotating blades14while the casing12and stator segments22hold each stage of stator vanes16in place.

FIG. 3provides a perspective view of a system40for heating stator segments22according to a first embodiment of the present invention. As shown, the system40generally includes a collapsible frame42, one or more heaters44, and means for biasing each heater44toward and/or away from the stator segment22.

The collapsible frame42enables the system40to be easily manipulated in the confined space between the casing12and the rotor18. In the particular embodiment shown inFIG. 3, the collapsible frame42includes first and second frame members46,48separated by a plurality of arms50that extend radially between the first and second frame members46,48. The first frame member46may have an arcuate shape that generally conforms to an outer surface of the rotor18, and the second frame member48may have an arcuate shape that generally conforms to the casing12and/or stator segment22. Inasmuch as the radius or shape of the outer surface of the rotor18, casing12, and/or stator segment22may change slightly, depending on the particular stage inside the compressor10, the system40may utilize different first and second frame members46,48for each stage of the compressor10, with each first and second frame member46,48sized and shaped to complement a particular stage of the compressor10.

The arms50generally extend between the first and second frame members46,48to allow relative or reciprocal movement between the first and second frame members46,48. For example, in the particular embodiment shown inFIG. 3, each arm50includes an upper arm segment52connected by an articulated portion54to a lower arm segment56. The articulated portion54may include, for example, multiple braces57pivotally connected to one another and to the upper and lower arm segments52,56. In this manner, the articulated portion54of each arm50may alternately expand or retract to move the first frame member46radially with respect to the second frame member48.

The heaters44are generally connected to the arms50and may include any suitable device known to one of ordinary skill in the art for transferring heat to another object. For example, as shown inFIG. 3, each heater may include a resistive or induction coil58immersed in or surrounded by a thermally conductive material such as a ceramic block60. Wiring62incorporated into or routed through the collapsible frame42and/or arms50may supply the induction coils58with power to rapidly heat the ceramic blocks60. The ceramic blocks60may in turn be placed against the stator segment22to transfer heat from the induction coils58to the stator segment22.

The means for biasing each heater44toward and/or away from the stator segment22may include a biasing element operably connected to the first frame member46and each heater44to bias each heater44toward and/or away from the first frame member46. In the particular embodiment shown inFIG. 3, the means for biasing each heater44toward and/or away from the stator segment22includes first means for biasing each heater44away from the first frame member46or toward the stator segment22and separate second means for biasing each heater44toward the first frame member46or away from the stator segment22. The structure for the first and second means may include any mechanical, pneumatic, hydraulic, or electrical device known in the art for moving one component with respect to another. For example, the first and/or second means may include a threaded engagement, a flexible coupling, a piston, a solenoid, a magnetic coupling, or other suitable device connected to the first frame member46, second frame member48, and/or heaters44to bias each heater44toward and/or away from the stator segment22. In the particular embodiment shown inFIG. 3, the first means for biasing each heater44away from the first frame member46may include a coiled spring64wrapped around one or more of the pivotal connections of the articulated portion54. In this manner, the coiled springs64may bias the articulated portion54to the expanded position, thereby moving the heaters44away from the first frame member46and toward the stator segment22. Conversely, the second means for biasing each heater44toward the first frame member46may include rack66and pinion68connections between the first and second frame members46,48. A handle or lever70pivotally connected to the pinion68may be used to rotate the pinion68counter-clockwise, causing the geared connection between the rack66and pinion68to move the heater44toward the first frame member46and away from the stator segment22.

FIG. 4provides a perspective view of a system80for heating stator segments22according to a second embodiment of the present invention. As shown, the system80again includes a collapsible frame82, one or more heaters84, and means for biasing each heater84toward and/or away from the stator segment22.

The collapsible frame82again enables the system80to be easily manipulated in the confined space between the casing12and the rotor18. In the particular embodiment shown inFIG. 4, the collapsible frame82again includes first and second frame members86,88separated by a plurality of arms90that extend radially between the first and second frame members86,88. The first and second frame members86,88may again have arcuate shapes that generally conform to an outer surface of the rotor18and the casing12and/or stator segment22, respectively, as previously described with respect to the embodiment shown inFIG. 3.

The arms90generally extend between the first and second frame members86,88to again allow relative or reciprocal movement between the first and second frame members86,88. In the particular embodiment shown inFIG. 4, each arm90includes an upper arm segment92inserted into a lower arm segment96to form an articulating piston94between the first and second frame members86,88. In this manner, the articulating piston94of each arm90may alternately push or pull the upper arm segment92to move the first frame member86radially with respect to the second frame member88.

The heaters84are again generally connected to the arms90and may include any suitable device known to one of ordinary skill in the art for transferring heat to another object, as previously discussed with respect to the embodiment shown inFIG. 3. In the particular embodiment shown inFIG. 4, the heaters84are pivotally and/or releasably connected to each arm90. Specifically, a pivotal connection98between the arms90and the heaters84may allow the angle of the heaters84to adjust to the particular angle and curvature of the stator segments22, thereby enhancing the surface-to-surface contact between the heaters84and the stator segments22. The pivotal connection98may include, for example, a ball bearing, a universal joint, or other flexible coupling that allows angular movement between the arms90and the heaters84. Alternately, or in addition, a releasable coupling100between the arms90and the heaters84enables quick removal and replacement of individual heaters44that wear out or otherwise become inoperable. The releasable coupling100may include, for example, a threaded connection, male and female fittings, a clamp, a quick release fitting, or other suitable mechanical device known in the art for releasably attaching one component to another.

In the particular embodiment shown inFIG. 4, the means for biasing each heater84toward and/or away from the stator segment22includes first means for biasing each heater84away from the first frame member86and separate second means for biasing each heater84toward the first frame member86. The structure for the first and second means may again include any mechanical, pneumatic, hydraulic, or electrical device known in the art for moving one component with respect to another. For example, the first and/or second means may include a threaded engagement, a flexible coupling, a piston, a solenoid, a magnetic coupling, or other suitable device connected to the first frame member86, second frame member88, and/or heaters84to bias each heater84toward and/or away from the stator segment22. In the particular embodiment shown inFIG. 4, the first means for biasing each heater84away from the first frame member86may include pneumatic and/or hydraulic pressure contained in the lower arm segment96to bias the upper arm segment92out of and away from the lower arm segment96. In this manner, the pneumatic and/or hydraulic pressure in the lower arm segment96may bias or move the heaters84away from the first frame member86and toward the stator segment22. Conversely, the second means for biasing each heater84toward the first frame member86may include rack102and pinion104connections between the first and second frame members86,88, with a handle or lever106to rotate the pinion104counter-clockwise to move the heater84toward the first frame member86and away from the stator segment22.

Based on the disclosure and teachings herein, one of ordinary skill in the art can readily appreciate multiple other structures and arrangements for allowing relative or reciprocal movement between the heaters44,84and the first frame member46,86or for biasing the heaters44,84toward or away from the first frame member46,86and/or stator segment22. For example, in alternate embodiments, the articulated portion54shown inFIG. 3may be replaced with any suitable structure that allows relative or reciprocal movement between the heaters44and the first frame member46. Similarly, the pinions68,104shown inFIGS. 3 and 4may be spring-biased in the clockwise direction, obviating the need for the coiled spring64shown inFIG. 3or the pressurized fluid in the lower arm segment96described with respect toFIG. 4. These and other variations are suitable equivalent structures within the scope of various embodiments of the present invention based on the disclosures and teachings herein.

FIG. 5provides a perspective view of a system110for heating stator segments22according to a third embodiment of the present invention. As shown, the system110again includes a collapsible frame112, one or more heaters114, and means for biasing each heater114toward and/or away from the stator segment22.

The collapsible frame112again enables the system110to be easily manipulated in the confined space between the casing12and the rotor18. In the particular embodiment shown inFIG. 5, the collapsible frame112again includes first and second frame members116,118separated by a plurality of arms120that extend radially between the first and second frame members116,118. The first frame member116again has an arcuate shape that generally conforms to an outer surface of the rotor18, as previously described with respect to the embodiment shown inFIGS. 3 and 4. In addition, the second frame member118may pivotally connect to adjacent heaters114so that the combined shape or contour of the second frame member118and the heaters114generally conforms to the casing12and/or stator segment22.

The arms120generally extend between the first and second frame members116,118to again allow relative or reciprocal movement between the first and second frame members116,118. In the particular embodiment shown inFIG. 5, each arm120includes an upper arm segment122inserted into a lower arm segment126to again form an articulating piston124between the first and second frame members116,118. In this manner, the articulating piston124of each arm120may alternately push or pull the upper arm segment122to move the first frame member116radially with respect to the second frame member118.

The heaters114may again include any suitable device known to one of ordinary skill in the art for transferring heat to another object, as previously discussed. In the particular embodiment shown inFIG. 5, each heater114is pivotally connected to the second frame member118. Specifically, a pivotal connection128between the second frame member118and each heater114allows the angle of the heaters114to adjust to the particular angle and curvature of the stator segments22, thereby enhancing the surface-to-surface contact between the heaters114and the stator segments22. The pivotal connection128may include, for example, a ball bearing, a universal joint, or other flexible coupling that allows angular movement between the second frame member118and the heaters114.

In the particular embodiment shown inFIG. 5, the means for biasing each heater114toward and/or away from the stator segment22includes first means for biasing each heater114away from the first frame member116and separate second means for biasing each heater114toward the first frame member116. The structure for the first and second means may again include any mechanical, pneumatic, hydraulic, or electrical device known in the art for moving one component with respect to another. For example, the first and/or second means may include a threaded engagement, a flexible coupling, a piston, a solenoid, a magnetic coupling, or other suitable device connected to the first frame member116, second frame member118, and/or heaters114to bias each heater114toward and/or away from the stator segment22. In the particular embodiment shown inFIG. 5, the first means for biasing each heater114away from the first frame member116may include a spring130connected between the first and second members116,118to bias the upper arm segment122out of and away from the lower arm segment126. In this manner, the spring130may bias or move the heaters114away from the first frame member116and toward the stator segment22. Conversely, the second means for biasing each heater114toward the first frame member116may include a handle or lever136pivotally connected to the first and second frame members116,118. Lifting the lever136shown inFIG. 5will overcome the force of the spring130to move the second frame member118, and thus the heaters114, toward the first frame member114and away from the stator segment22.

FIG. 6provides a flow diagram of a method for heating stator segments22according to one embodiment of the present invention, andFIGS. 7 and 8illustrate various positions of the system110shown inFIG. 5when positioning and operating the system110. At block140, the method may include moving the heaters114toward the first frame member116so that the heaters114and the first frame member116may fit between the casing12and the rotor18. As shown inFIG. 7, for example, the heaters114may be moved toward the first frame member116by manipulating the lever136pivotally connected to the first and second frame members116,118. As the lever136is moved toward the first frame member116, the lever136compresses the spring130connected between the first and second members116,118. As the spring130is compressed, the upper arm segment122may slide inside the lower arm segment126, moving the heaters114closer to the first frame member116.

Returning toFIG. 6, at block142, the heaters114and the first frame member116may then be inserted between the casing12and the rotor18, with the heaters114passing over the stator segment22to be heated. At block144, the heaters114may be extended from the first frame member116and towards the stator segment22to be heated, as shown inFIG. 8. The heaters114may be extended from the first frame member116by releasing the lever136and allowing the spring130to force the upper arm segment122out of the lower arm segment126, thus extending the heaters114apart from the first frame member116and toward the stator segment22. If desired, the heaters114may be pivoted and/or pressed against the stator segment22to apply additional pressure by the heaters114against the stator segment22, represented by block146inFIG. 6. The optional pivoting and/or pressing of the heaters114against the stator segment22may be accomplished, for example, by manipulating the lever136further away from the first frame member116to increase the force of the heaters114against the stator segment22.

At block148, the heaters114are energized to simultaneously heat the entire stator segment22. Depending on the particular application and ambient temperatures, the heaters114may heat the entire stator segment22to greater than 1,000 degrees Fahrenheit in approximately 5-10 minutes, providing a substantial time savings over current systems and methods. At block150, the heaters114may be de-energized and again moved toward the first frame member116so that the heaters114are retracted away from the stator segment22. At block152, the heaters114and the first frame member116may be withdrawn or removed from between the casing12and the rotor18, and the quenching process may be separately conducted to remove the stator segment22from the casing12.

One of ordinary skill in the art will readily appreciate that the systems and methods disclosed herein will substantially reduce the time to heat stator segments22while also reducing the risk of collateral damage to adjacent components. Specifically, it is anticipated that the systems and methods disclosed herein will reduce the time required to heat and quench stator segments by 12-24 hours per compressor, which provides a substantial reduction in the required outage to remove and/or replace stator segments22. In addition, the particular heaters114that may be incorporated into various embodiments may avoid the hazards associated with open flames present in existing systems, thereby reducing the risk of damaging or igniting adjacent components.