Apparatus and method for inspecting a turbine blade tip shroud

An apparatus for inspecting a turbine blade tip shroud includes a frame comprising a top surface and a bottom surface that is alignable with the turbine blade tip shroud, and, at least one z-notch inspection slot that passes through the frame from the top surface to the bottom surface and is positioned to align with at least one z-notch of the turbine blade tip shroud when the frame is aligned on the turbine blade tip shroud. The apparatus further includes a removable z-notch inspection insert comprising a cross-sectional profile substantially matching the at least one z-notch inspection slot and comprising a z-notch guide face that faces the z-notch of the turbine blade tip shroud when the removable z-notch inspection insert is passed through the z-notch inspection slot

FIELD OF THE INVENTION

The present invention generally involves an apparatus and method for inspecting a turbine blade tip shroud. In particular embodiments, the apparatus may facilitate a quality inspection check for turbine blade tip shroud z-notches.

BACKGROUND OF THE INVENTION

Turbines are widely used in industrial and commercial operations. A typical commercial steam or gas turbine used to generate electrical power includes alternating stages of stationary vanes and rotating blades. The stationary vanes may be attached to a stationary component such as a casing that surrounds the turbine, and the rotating blades may be attached to a rotor located along an axial centerline of the turbine. A compressed working fluid, such as but not limited to steam, combustion gases, or air, flows through the turbine, and the stationary vanes accelerate and direct the compressed working fluid onto the subsequent stage of rotating blades to impart motion to the rotating blades, thus turning the rotor and performing work.

Compressed working fluid that leaks around or bypasses the stationary vanes or rotating blades reduces the efficiency of the turbine. To reduce the amount of compressed working fluid that bypasses the rotating blades, the casing may include stationary shroud segments that surround each stage of rotating blades, and each rotating blade may include a tip shroud at an outer radial tip. Each tip shroud may include a seal rail that extends transversely across the tip shroud to form a seal between the rotating tip shroud and the stationary shroud segments. In addition, each tip shroud may include side surfaces that interlock with complementary side surfaces of adjacent tip shrouds to prevent adjacent tip shrouds from overlapping, reduce vibrations in the rotating blades, and enhance the seal between the rotating tip shrouds and the stationary shroud segments.

Over time, the side surfaces of the tip shrouds may erode or wear, creating gaps between adjacent tip shrouds that allow the rotating blades to twist and/or vibrate and increase the amount of compressed working fluid that bypasses the rotating blades. As a result, hardened materials are typically plated onto the side surfaces and periodically inspected to determine the amount of wear to the hardened materials. If the amount of wear is excessive, the entire rotating blade may need to be replaced. Otherwise, the tip shroud may be refurbished to restore and/or increase the thickness of the hardened materials on the side surfaces.

Previous efforts have been developed to determine the amount of erosion of the hardened materials. For example, measurements of various chord lengths across the tip shroud may be used to create a detailed coordinate map of the surface of the tip shroud. However, coordinate mapping is time-consuming and produces inconsistent results due to the geometric shape of the tip shroud. As a result, an alternative apparatus and method for inspecting a turbine blade tip shroud would be welcomed in the art.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment an apparatus for inspecting a turbine blade tip shroud is disclosed. The apparatus includes a frame comprising a top surface and a bottom surface that is alignable with the turbine blade tip shroud, and, at least one z-notch inspection slot that passes through the frame from the top surface to the bottom surface and is positioned to align with at least one z-notch of the turbine blade tip shroud when the frame is aligned on the turbine blade tip shroud. The apparatus further includes a removable z-notch inspection insert comprising a cross-sectional profile substantially matching the at least one z-notch inspection slot and comprising a z-notch guide face that faces the z-notch of the turbine blade tip shroud when the removable z-notch inspection insert is passed through the z-notch inspection slot.

In another embodiment, another apparatus for inspecting a turbine blade tip shroud is disclosed. The apparatus includes a frame comprising a top surface and a bottom surface that is alignable with the turbine blade tip shroud, a first z-notch inspection slot that passes through the frame from the top surface to the bottom surface and is positioned to align with a first z-notch of the turbine blade tip shroud when the frame is aligned on the turbine blade tip shroud, and, a first removable z-notch inspection insert comprising a first cross-sectional profile substantially matching the first z-notch inspection slot and comprising a first z-notch guide face that faces the first z-notch of the turbine blade tip shroud when the first removable z-notch inspection insert is passed through the first z-notch inspection slot. The apparatus further includes a second z-notch inspection slot that passes through the frame from the top surface to the bottom surface and is positioned to align with a second z-notch of the turbine blade tip shroud when the frame is aligned on the turbine blade tip shroud, and, a second removable z-notch inspection insert comprising a second cross-sectional profile substantially matching the second z-notch inspection slot and comprising a second z-notch guide face that faces the second z-notch of the turbine blade tip shroud when the second removable z-notch inspection insert is passed through the second z-notch inspection slot.

In yet another embodiment, a method for inspecting a turbine blade tip shroud is disclosed. The method includes aligning a frame on the turbine blade tip shroud, wherein the frame comprises at least one z-notch inspection slot that passes through the top surface to the bottom surface and is positioned to align with at least one z-notch of the turbine blade tip shroud while the frame is aligned on the turbine blade tip shroud, and passing a removable z-notch inspection insert through the z-notch inspection slot, wherein a z-notch guide face of the z-notch inspection insert will pass by the at least one z-notch of the turbine blade tip shroud if the z-notch does not extend beyond the z-notch inspection slot.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present disclosure include an apparatus and method for inspecting a turbine blade tip shroud. The apparatus generally includes a frame that can be placed over the tip shroud to identify an acceptable or non-acceptable dimension of one or both of the z-notches.

FIG. 1provides a top plan view of an exemplary turbine blade tip shroud10. The tip shroud10is located at a radial tip of a rotating blade12, with the outline of the rotating blade12beneath the tip shroud10shown in phantom inFIG. 1. The tip shroud10generally includes a leading edge14and a trailing edge16that correspond to the direction of airflow over the rotating blade12. In addition, the tip shroud10includes a first side surface18generally opposed to a second side surface20, with a seal rail22extending across the tip shroud10from the first side surface18to the second side surface20. The first and second side surfaces18,20may additionally include scalloped surfaces24and hardened surfaces26designed to interlock with side surfaces of adjacent tip shrouds. For example, in the exemplary tip shroud10shown inFIG. 1, the hardened surfaces26appear as z-notches50in the first and second side surfaces18,20.

As should be appreciated to those skilled in the art, the z-notch50refers to a z-shaped profile design that reduces or substantially reduces stress in the tip shroud10. Specifically, the z-notch50can help address cracks attributable to low cycle and/or high cycle fatigue. In some embodiments, the z-notch50may be present on a new tip shroud10from original manufacturing prior to the tip shroud10seeing service. In other embodiments, the z-notch50may be present after adjusting its dimensional profile through weld build-up, blending and/or contouring from any modification operations (e.g., repair, restoration or the like).

FIG. 2provides a top perspective view of an apparatus30for inspecting a turbine blade tip shroud10according to one embodiment of the present disclosure, andFIG. 3provides a bottom perspective view of the apparatus30shown inFIG. 2. The apparatus30generally includes a frame32that is alignable with the turbine blade tip shroud10. As used herein, “alignable” and (variants thereof) refers to a design that can be independently disposed on a plurality of turbine blade tip shrouds10by engaging with the standard or expected topographical profile of the turbine blade tip shroud10so that the relative of the position of the frame32with the turbine blade tip shroud10is consistent and repeatable when aligned thereon. The frame32may be made from wood, plastic, fiberglass, metal, or any other suitably durable materials capable of maintaining their shape. The frame32includes a top surface38and a bottom surface40and may further include one or more viewing holes42or other passages to allow visual observation of the tip shroud10, and/or one or more aligning features such as a first stop34, and/or a second stop36through the frame32as will become appreciated herein.

The frame32further comprises at least one z-notch inspection slot90that passes through the frame32from the top surface38to the bottom surface40. As best illustrated inFIG. 4, the at least one z-notch inspection slot90is positioned on the frame32to align with one of the z-notches50of the turbine blade tip shroud10when the frame32is aligned on the turbine blade tip shroud10. Specifically, the z-notch inspection slot90comprises an interior edge92configured to the acceptable dimensional limits of the z-notch50itself. As should be appreciated herein, the interior edge92of the z-notch slot90may thereby align with the z-notch50of the turbine blade tip shroud10to provide a quick visual inspection guide for dimensional conformity, quality or the like. In some embodiments, such as that illustrated inFIGS. 2-5, the frame32may comprise first and second z-notch inspection slots90to individually align with first and second z-notches50respectively.

Referring now toFIG. 5, the apparatus30further comprises a removable z-notch inspection insert95that comprises a cross-sectional profile substantially matching the at least one z-notch inspection slot90. Specifically, the removable z-notch inspection insert comprises a z-notch guide face96that faces the z-notch90of the turbine blade tip shroud10(and the interior edge92of the z-notch inspection slot90) when the removable z-notch inspection insert95is passed through the z-notch inspection slot90. In use, the removable z-notch inspection insert95may be passed through the z-notch inspection slot90such that its z-notch guide face96passes by the interior edge92of the z-notch inspection slot and along the surface of the z-notch50itself. If the z-notch50has excessive material (such as from excessive weld build up, less than required finishing, or other modification operations), the removable z-notch inspection insert95will be blocked from passing through the z-notch inspection slot90by catching on the over built z-notch50. This may lead to the tip shroud10being sent for additional work prior to (re)installation in a turbine. Conversely, in some embodiments, an under-dimensioned z-notch may be identified by leaving a gap between the z-notch50and the z-notch guide face96of the z-notch inspection insert95when passed through the z-notch inspection slot90. Thus, the z-notch inspection slot90and the z-notch inspection insert95can thereby combine to provide a quick visual and/or physical quality control check on the dimensions of new or modified z-notches90of turbine bucket tip shrouds10.

Referring back toFIGS. 2-3, first and potentially second stops34,36may be positioned on the frame32to contact specific portions of the first and second side surfaces18,20, respectively to assist in aligning the frame32onto the turbine blade tip shroud10. For example, a bolt44, screw, or other device may be used to releasably attach the first stop34to a particular location on the frame32so that a first surface46of the first stop34is precisely aligned to contact a specific portion of the first side surface18of the tip shroud10. In some embodiments, the first stop34and the first surface46may be repositioned and/or re-oriented on the frame32so that the same apparatus30may be used to inspect multiple tip shrouds having different geometries.

In some embodiments, a second stop36may similarly be releasably attached to a separate particular location on the frame32so that a surface of the second stop36is precisely aligned to contact a separate specific portion of the second side surface20of the tip shroud10. However, in some embodiments, such as that illustrated inFIG. 3, the second stop36may be in sliding engagement with the frame32to contact a specific portion of the second side surface20of the turbine blade tip shroud10. For example, as shown inFIGS. 3 and 4, the frame32may include a slot48(in phantom inFIG. 3) having a predetermined length and orientation with respect to the first stop34. In particular embodiments, the slot48may be oriented perpendicular to or parallel to the first surface46, depending on the particular orientation of the first surface46of the first stop34. Alternately or in addition, the frame32may include an incremented scale adjacent to the slot48and/or second stop36to measure the amount of movement of the second stop36in the slot48. In this manner, the second stop36may ride in the slot48until the second stop36either contacts the specific portion of the second side surface20or the second stop36reaches the end of the slot48. If the second stop36contacts the specific portion of the second side surface20before reaching the end of the slot48, then the tip shroud10may be refurbished, for example, by restoring a hardened material to the first and/or second side surfaces18,20. Alternately, if the second stop36reaches the end of the slot48before contacting the specific portion of the second side surface20, then the tip shroud10may require modification before the apparatus30may be utilized to verify the dimensional acceptability of the z-notches50.

As also illustrated inFIG. 3, the apparatus30may further additionally or alternatively comprise one or more other aligning features for aligning the frame32on the turbine blade tip shroud10. In particular embodiments, the function of the one or more aligning features may be to longitudinally, transversely, and/or radially align the frame32with respect to the tip shroud10. The structure for the means may include various combinations of resilient tabs and/or projections that extend from the bottom surface40of the frame32. In the particular embodiment shown inFIG. 3, for example, the aligning features for the frame32with respect to the tip shroud10includes a plurality of resilient tabs60that extend away from the frame32. The resilient tabs60may be positioned on the frame32so that when the frame32is placed on the tip shroud10, the resilient tabs60act as bumpers or guides around the leading and/or trailing edges14,16of the tip shroud10to position the frame32longitudinally and/or transversely with respect to the tip shroud10. Alternately or in addition, the aligning features for the frame32with respect to the tip shroud10may include first projections62and/or second projections64on the bottom surface40of the frame32. As shown inFIG. 3, the first projections62may be positioned on the frame32to rest against or contact the seal rail22to position the frame32longitudinally with respect to the tip shroud10. Similarly, the second projections64may be positioned on the frame to act as spacers between the bottom surface40of the frame32and the tip shroud10. In this manner, the second projections64may position the frame32radially with respect to the tip shroud10.

Referring now additionally toFIG. 6, a method100is illustrated for inspecting a turbine blade tip shroud10. The method at least first comprises aligning a frame32on the turbine blade tip shroud10in step110. As discussed above, the frame comprises at least one z-notch inspection slot90that passes through the top surface38to the bottom surface40and is positioned to align with at least one z-notch50of the turbine blade tip shroud10while the frame32is aligned on the turbine blade tip shroud10.

The method100at least further comprises passing a z-notch inspection insert95through the z-notch inspection slot90in step120, wherein a z-notch guide face96of the z-notch inspection insert95will pass by the at least one z-notch50of the turbine blade tip shroud10if the z-notch50does not extend beyond the z-notch inspection slot90.

In some embodiments, the method100may first comprise modifying the z-notch50of the turbine blade tip shroud10in step105prior to aligning the frame32with the turbine blade tip shroud10in step110. Modifying may comprise any adjustment to the dimensional profile (e.g., size, shape, angle(s), etc.) of the z-notch50such as through weld build-up, blending and/or final contouring adjustments including from repair operations, restoration procedures or the like.

In even some embodiments, the method may comprise a quality control tollgate in step125following the attempting passing of the z-notch inspection insert95through the z-notch inspection slot90in step120. For example, if the z-notch inspection insert95cannot pass through the z-notch inspection slot90(e.g., due to an overly sized modified or repaired z-notch50), then the turbine blade tip shroud10may be sent back to step105for further modification and to repeat the overall method100. Likewise, if the z-notch inspection insert95can pass through the z-notch inspection slot90(e.g., due to and indicating an appropriately sized z-notch50), the turbine blade tip shroud10may be utilized for installation in a turbine in step130.

One of ordinary skill in the art can readily appreciate that the apparatus30and methods described herein reduce the time required to consistently inspect z-notches50for a turbine blade tip shroud10to determine, for example, the dimensional acceptability of the part. As a result, the embodiments described herein may, in part, reliably identify only those tip shrouds10requiring modification, thus assisting in the quality control associated with the inspection and refurbishment of tip shrouds10.