Full-scale sampling system and method for materials testing of steam turbine rotors

Abstract

To provide full-scale sampling for material testing of steam turbine rotors. The method includes forming an annular ring of rotor material within a sample area of ​​a legacy steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent the inter-blade region rotor surface, and collecting a material test sample from a portion of the annular ring. The steam turbine rotor has a groove formed therein, the groove being machined to form a sample configured to allow for at least one of removing material from the steam turbine rotor and performing material property testing, and operating the modified legacy steam turbine rotor at increased thermal stresses compared to the legacy steam turbine rotor.

Description

[Technical Field]

[0001] The present disclosure relates generally to rotors for steam turbines, and more particularly to modifications of legacy rotor configurations that enable full-scale sampling for conducting material testing to assess thermal aging and fatigue of such rotors. [Background technology]

[0002] A steam turbine may include a rotor having a thrust balance piston with a relief groove for relieving thermal stresses outside the region of the live steam flow path, the relief groove being axially displaced opposite the direction of working steam flow through the blade passage.

[0003] The increasing use of renewable energy sources is driving the need to operate electric networks with increased cycles of power plants and steam turbines. Operational flexibility requirements can be limited by the steam turbine's lifespan, as increased exposure to frequent thermal transients increases the risk of thermal fatigue cracks during cold, warm, and hot start-ups, load transitions, and shutdowns. Furthermore, for steam turbines with multiple stages or turbines (e.g., high-pressure and intermediate-pressure turbines), the different thermal conditions in each steam turbine / section can lead to different low-cycle fatigue lives for the rotor sections of each steam turbine / section. This can result in asynchronous maintenance schedule demands and increased maintenance outages. While it may be possible to balance the low-cycle fatigue lives of rotor sections by selecting rotor materials that improve toughness and ductility, there are practical limitations to achieving this goal through rotor material selection alone. These measures do not overcome the potentially adverse effects of thermal transients on the rotor's low-cycle fatigue life.

[0004] As a result, steam turbines require life monitoring. Theoretical assessments are typically based on actual, but generalized, operating data, often based on minimal material properties. To achieve this, it is beneficial to investigate the rotor's actual mechanical behavior in the hot zone. In some cases, fracture appearance transition temperature (FATT) assessments are performed using small-scale test sampling methods. However, these methods often result in significant errors due to the small sample size. Furthermore, for reaction drum-type rotors, no publicly available databases of FATT data for aging steam turbine rotors are available. This is due to the lack of readily available material from which specimens can be easily removed. Conversely, for impulse rotor steam turbines, the rotors contain pressure-free disks at each stage, allowing holes to be drilled (if balanced) to extract sample material for further investigation, if necessary.

[0005] Therefore, there is a need for improved rotor sampling to evaluate the effect of thermal aging on creep rupture properties. Additionally, there is a need to improve the low cycle fatigue life of steam turbine rotor sections, align the low cycle fatigue life of different sections of a steam turbine rotor, and synchronize multiple maintenance cycles of rotor sections. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4594948 Summary of the Invention

[0007] A method for generating a material test sample for performing one or more material tests on a legacy steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent the inter-blade region rotor surface includes removing an annular ring of rotor material in a sample area selected from the inter-blade region rotor surface and the inlet region rotor surface, creating a modified legacy steam turbine rotor by removing the annular ring, and forming a material test sample from a portion of the annular ring.

[0008] A system for extracting a material test sample for performing one or more material tests from a legacy steam turbine rotor is provided. The legacy steam turbine rotor has an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface. The system includes a segment portion of an annular ring of rotor material from the legacy steam turbine rotor, the annular ring machined from a groove formed in the legacy steam turbine rotor, the groove machined to enable removal of the annular ring and enable formation of the material test sample.

[0009] The improved steam turbine rotor includes a legacy steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent the inter-blade region rotor surface, and a groove formed in either the inlet region rotor surface or the inter-blade region rotor surface of the legacy steam turbine rotor, the groove being machined to enable removal of material from the legacy steam turbine rotor to at least one of perform material property testing and operate the improved steam turbine rotor at increased thermal stresses compared to the legacy steam turbine rotor based at least in part on the material property testing.

[0010] Additional features and advantages are realized by the techniques of the present disclosure. Other embodiments and aspects of the present disclosure are described in detail herein. For a better understanding of the present disclosure, together with its advantages and features, reference is made to the specification and drawings. [Brief explanation of the drawings]

[0011] The described embodiments will be better understood from reading the following description of non-limiting embodiments, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a cross-sectional view of a high pressure steam turbine rotor including a high pressure steam turbine inner casing according to an embodiment of the present disclosure. [Figure 2A] FIG. 1 is a partial cross-sectional view of a high pressure steam turbine rotor and an intermediate pressure steam turbine rotor according to an embodiment of the present disclosure. [Figure 2B] FIG. 1 is a partial cross-sectional view of a dual flow steam turbine rotor according to an embodiment of the present disclosure. [Figure 3] 1 is an enlarged cross-sectional view of a portion of a steam turbine rotor illustrating the formation of a blade groove BG0 in front of the blade groove BG1 and the acquisition of a sample through the blade groove BG0 according to an embodiment. [Figure 4A] 1 is a cross-sectional view of a portion of a steam turbine rotor depicting the location of a blade groove BG0 used to obtain samples from the steam turbine rotor, according to an embodiment. [Figure 4B] 1 is a cross-sectional view of a portion of a steam turbine rotor illustrating an initial step in forming a blade groove BG0 for sample acquisition, according to an embodiment. [Figure 4C] 10 is a cross-sectional view of a portion of a steam turbine rotor illustrating an additional step in forming a blade groove BG0 for sample acquisition, according to an embodiment. [Figure 4D] FIG. 10 is a cross-sectional view of a portion of a steam turbine rotor illustrating the removal of an annular ring of material from a blade groove BG0 in preparation for a sample, according to an embodiment. [Figure 4E]4E is a cross-sectional view of a portion of an arcuate segment of the annular ring of FIG. 4D and a test sample taken from the annular ring removed from a steam turbine rotor, according to an embodiment. [Figure 4F] 1 is a cross-sectional view of a portion of a steam turbine rotor illustrating a blade groove BG0 having a filler to facilitate turbine operation, according to an embodiment. [Figure 5] 10 is a process flowchart illustrating acquisition of a sample according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Exemplary embodiments of the present disclosure will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, the present disclosure may be practiced without these specific details and is not limited to the exemplary embodiments disclosed herein.

[0013] While various embodiments as described herein are suitable for application in conjunction with steam generation systems employing steam turbines, a reaction drum steam turbine is selected and described solely for clarity of illustration, and other types of steam turbine configurations, such as steam turbines having multiple sections, drum-type turbines, and impulse turbines, are equally applicable.

[0014] FIG. 1 illustrates an example of a high-pressure steam turbine rotor 10, which is typically housed in an inner casing 11. The high-pressure steam turbine rotor 10 includes an inter-blade region rotor surface 12, an inlet region rotor surface 14, and a piston region rotor surface 16. The inter-blade region rotor surface 12 is the region where rows of axially spaced rotating blades (one of which is shown in FIG. 4A ) extend circumferentially around the high-pressure steam turbine rotor 10. The blades are attached to the high-pressure steam turbine rotor 10 by blade grooves 13. A first row of blade grooves, generally designated BG1 and shown as 13a, and a second row of blade grooves, generally designated BG2 and shown as 13b, continue through the inter-blade region rotor surface 12 depending on the number of blade stages employed for a given section of the steam turbine. Thus, inter-blade rotor surface 12 may be defined as the surface area of ​​high pressure steam turbine rotor 10 where blade grooves 13 are located.

[0015] The inlet region rotor surface 14 is upstream of and immediately adjacent to the inter-blade region rotor surface 12. During operation, this portion of the rotor is exposed to steam as it is supplied to the steam turbine. Typically, the inlet region rotor surface 14 is shaped to direct radially supplied steam axially by having a radial-axial transition surface that extends to the first upstream blade groove 13a, although other shapes are possible. In embodiments, the inlet region rotor surface 14 and / or other regions within the inter-blade region 12 are employed to provide sample regions 15 for removing material as needed to provide material for material testing as described herein. For example, while some embodiments of the present disclosure describe the inlet region rotor surface 14 as being used to obtain samples, other embodiments describe the inter-blade region rotor surface 12 as including regions without blade grooves 13, with the blade region rotor surface 12 between the blades being utilized to obtain samples.

[0016] The piston region rotor surface 16 is disposed immediately adjacent to the inlet region rotor surface 14 such that the inlet region rotor surface 14 is axially located between the piston region rotor surface 16 and the inter-blade region rotor surface 12. The purpose of the piston region is to counteract end thrust of blading typical of reaction type steam turbines and to provide rotor thrust toward the high-pressure end of the turbine under all operating conditions. The piston may be either integral with the solid rotor or may be contracted and keyed into place. The piston region rotor surface 16 may include a stress relief groove rotor surface 18 upstream of and adjacent the inlet region rotor surface 14.

[0017] In one or more embodiments, each of the inter-blade region rotor surface 12, the inlet region rotor surface 14, the piston region rotor surface 16, and / or the stress relief groove rotor surface 18 has a bonded thermal barrier coating 19. The thermal barrier coating 19 may partially or completely cover surfaces 12, 14, and 16 (including surface 18), and the radial thickness of the thermal barrier coating 19 may be uniform or may vary.

[0018] An exemplary embodiment of the combined high-pressure steam turbine rotor 10 and intermediate-pressure steam turbine rotor 20 is shown in Figure 2A. Figure 2A also depicts an inter-blade region rotor surface 22 and an inlet region rotor surface 24. The inter-blade region rotor surface 22 axially lies between rotating blades (not shown) that are circumferentially distributed on the intermediate-pressure steam turbine rotor 20 by blade grooves 23 extending through the rotor surface.

[0019] The inlet region rotor surface 24 is upstream of and immediately adjacent to the inter-blade region rotor surface 22. This region of the rotor 20 is exposed to steam as it is supplied to the steam turbine. Typically, this region is configured to axially direct the radially supplied steam by having a radial-axial transition surface that extends to the first upstream blade groove 23a. In some embodiments, the steam supply to the intermediate-pressure steam turbine rotor 20 may be directed from the high-pressure section without reheating. In embodiments, the inlet region rotor surface 24 and / or other regions of the inter-blade region 22 are employed to provide a sample region 25 for removing material as needed to provide material for material testing, as described herein.

[0020] A piston region rotor surface (not shown) may be disposed immediately adjacent to inlet region rotor surface 24 such that inlet region rotor surface 24 (as previously described for the high pressure section) is located between the piston region rotor surface and inter-blade region rotor surface 22. In an exemplary embodiment, inter-blade region rotor surface 22, inlet region rotor surface 24, and piston region rotor surface each have a thermal barrier coating bonded to their respective surfaces.

[0021] An exemplary embodiment of a dual-flow steam turbine rotor 30 is shown in Figure 2B. The rotor 30 includes a dual inter-blade region rotor surface 32 and an inlet region rotor surface 34. The inter-blade region rotor surface 32 is axially disposed between rotating blades (not shown) that are circumferentially distributed on the dual-flow steam turbine rotor 30 by blade grooves 33 extending into the surface of the rotor 30.

[0022] The inlet region rotor surface 34 is upstream of and immediately adjacent to the inter-blade region rotor surface 32. This region of the rotor 30 is exposed to steam as it is delivered to the steam turbine. Typically, this region is configured to axially direct the radially delivered steam by having a radial-axial transition surface that extends to the first upstream blade groove 33a. In some embodiments, the inter-blade region rotor surface 32 is employed to provide a sample region 35 for removing material as needed to provide material for testing as described herein. Unique to this illustration, the inter-blade region rotor surface 32 includes a second (or alternative) sampling location 35 between those shown as BG2 and BG3 that may also be used to remove material to provide material testing.

[0023] Metallic materials such as stainless steels, titanium alloys, and nickel-based alloys are widely used for steam turbine rotors in the petrochemical, thermoelectric, fossil and nuclear power, automobile, and aviation industries. For example, low-alloy CrMoV steels (i.e., steels containing chromium, molybdenum, and vanadium) are commonly used at temperatures up to 565°C. In supercritical applications, steel alloys with 9% Cr are used. For power plant applications operating at even higher temperatures (e.g., near 700°C), nickel-based alloys are sometimes used for rotors. These materials are manufactured to operate for long periods under harsh conditions of high temperature, pressure, vibration, and dynamic forces. Therefore, these components inevitably suffer from high temperature, creep, and fatigue damage, which can cause degradation of material properties and ultimately lead to material failure. Therefore, periodic testing and evaluation are performed to assess degradation, especially for critical or expensive components. However, health monitoring and assessment, especially for large steam turbines, can be difficult and tedious, leading to costly plant shutdowns and delays, so a fast and accurate method of testing would be extremely useful.

[0024] Traditional Charpy tests are standardized high-strain-rate tests that measure the amount of energy absorbed by a material during fracture. The absorbed energy is an indicator of the material's notch toughness. Because they are easy to prepare and perform, and because results are obtained quickly and relatively inexpensively, they are widely used in industry as an indicator of material integrity. Disadvantages of Charpy tests include the fact that partial results are only comparative; traditional destructive testing requires a significant sample size on the equipment; and the sampled area typically requires welding repair after sampling. Furthermore, body-centered-cubic (BCC) or ferritic alloys exhibit significant differences in behavior when impact tested over a range of temperatures. Above the transition temperature, impact specimens tend to fracture by a ductile mechanism (usually microvoid coalescence), thereby absorbing relatively large amounts of energy. At lower temperatures, the same impact specimens tend to fracture in a brittle manner (usually by cleavage), absorbing much less energy. In the transition temperature range, specimens generally exhibit a region of mixed ductile and brittle fracture.

[0025] The temperature range for the transition from one type of behavior to another varies depending on the material being tested. This transition behavior can be defined in various ways for specification purposes, such as minimum test results for absorbed energy, fracture appearance, lateral expansion, or a combination thereof at a specified test temperature. In some situations, the transition temperature is the temperature at which either absorbed energy or fracture appearance reaches a specified level when tested over a temperature range. Alternatively, it may be desirable to determine the fracture appearance transition temperature (FATT) of a test specimen, which is the temperature at which a required minimum shear failure rate (n) is achieved. FATT is a quantitative target for thermal aging, material fatigue, and crack resistance, i.e., an assessment of structural integrity. It provides a critical assessment of the material structure related to component life. FATT allows for rotor evaluation and establishes the level of fatigue, or, in other words, the expected life of the component. Therefore, actual sampling of the component facilitates fatigue and life assessment, particularly with respect to expected results for a given operating profile of the steam turbine rotor 10.

[0026] Referring now to FIG. 3 , a portion 100 of a steam turbine rotor 10, 20, 30 depicts a portion of the inter-blade region rotor surface 12 (or 22, 32) and the inlet region rotor surface 14. While the steam turbine rotor 10 is depicted, the depicted portion is equally applicable to the intermediate-pressure rotor 20 or the dual-flow rotor 30, as discussed above. Hereinafter, for simplicity, the components of the high-pressure rotor 10, the intermediate-pressure rotor 20, and the dual-flow rotor 30 will be referred to collectively, with the remainder of the description applying to each type of rotor. In the embodiment, a portion of the blade groove 13 is depicted extending through a portion of the inter-blade region rotor surface 12 proximal to the inlet region rotor surface 14. As described herein, the inlet region rotor surface 14 is configured to axially direct radially supplied steam by having a radial-to-axial transition surface extending to the first upstream blade groove 13 a.

[0027] However, in this embodiment, other areas within the inlet region rotor surface 14 and / or inter-blade region 12 are utilized to provide sample areas 15 for removing material for testing and FATT determination. For example, material testing may include one or more of Charpy tests, tensile tests, hardness tests, creep tests, low cycle fatigue tests, microstructure testing, etc.

[0028] In an embodiment, an additional initial blade groove 13i (also designated BG0) is introduced. The initial blade groove BG0, 13i may be substantially similar in size and shape to the other blade grooves 13 (e.g., 13a, 13b, etc.), but this is not necessarily the case. For example, the initial blade groove 13i may be cut to a first depth D1 in the rotor surface at a selected width W1 and then cut to a further depth indicated by a larger selected width W2 to form an expanded portion 17 distal from the inlet region rotor surface 14. The particular profile for the expanded portion 17 is advantageously selected to provide thermal and dynamic stress relief in the rotors 10, 20, and / or 30. For example, it may be desirable to cut the expanded portion 17 of the initial blade groove BG0, 13i to have rounded corners and edges at its width W2.

[0029] In some embodiments, the expansion portions 17 can have rounded corners that exhibit different geometric shapes and / or curvatures, such as, but not limited to, a circle, an ellipse, a parabola, or a polynomial function. In one embodiment, the initial blade groove BG0, 13i exhibits an expansion portion 17 having a cross-section that is symmetrical in at least one of the axial and radial directions. In another embodiment, the initial blade groove BG0, 13i exhibits an expansion portion 17 that is asymmetrical in at least one of the axial and radial directions. In one embodiment, the initial blade groove BG0, 13i exhibits a substantially rounded, elliptical, or oval cross-section of the expansion portion 17. In another embodiment, the initial blade groove BG0, 13i exhibits substantially the same cross-sectional shape as the other blade grooves 13, particularly the first blade groove 13a (also designated BG1). In yet another embodiment, the initial blade groove BG0 may be larger and deeper than the first blade groove BG1, 13a. In other embodiments, the initial blade groove BG0 may be smaller and shallower than the first blade groove BG1, 13a.

[0030] Currently, steam turbine rotors are implemented with initial (BG0) blade grooves. In today's applications, unused blade grooves (i.e., blade grooves without blades installed) are commonly used to reduce fatigue and thermal stress in the hot sections of newly implemented rotors. However, legacy rotors 10, 20, and 30 do not implement initial blade grooves, e.g., BG0 and 13i. Legacy rotors 10, 20, and 30 may also experience fatigue and damage as a result of their service life. Legacy rotors, in particular, require fatigue evaluation and assessment to determine their fitness for continued service. The described embodiments first take advantage of this feature to provide sampling while simultaneously demonstrating potential enhancements to rotor thermal stress relief. As a result, stress / stress relief reductions are implemented in improved new blade groove geometries for rotors 10, 20, and 30, based on the benefits of taking samples to conduct the tests described herein. Improved stress relief may allow for faster starts and increased cycles by relieving thermal stresses in modified legacy rotors 10, 20, 30.

[0031] Advantageously, the removal of material to form grooves BG0, 13i is machined in a manner that facilitates the recovery of a test sample 50 large enough to perform testing for FATT evaluation. The particular machining and / or cutting scheme employed is not critical, provided that material is removed in a manner consistent with performing the test. In embodiments, samples on the order employed for standard Charpy testing, generally rectangular and having a width of 10 millimeters (mm), a height of 10 mm, and a length of 10 mm, 20 mm, or 50 mm, can be readily achieved by machining the rotor, for example, on a lathe, as described herein and depicted in FIGS. 4A-4F.

[0032] 4A-4F illustrate an exemplary cross-sectional view of rotor 10 and an exemplary process for machining and forming initial blade slots BG0, 13i in rotor 10, and obtaining and preparing samples 50 for fatigue and Charpy testing. FIG. 5 is a flowchart depicting an exemplary process 200 for obtaining test samples from a legacy steam turbine rotor 10 according to an embodiment. In an embodiment, a desired initial blade slot BG0, 13i profile is depicted having a designated section for sample 50 to be machined from inlet region surface 14 of rotor 10, as depicted in FIG. 4A.

[0033] 4B, in the first step of step 205, a lathe 60 and cutter blade 62 are used to optionally remove the first slot 70 and flatten the top of the curved surface of the inlet region rotor surface 14 to begin the formation of the initial blade grooves BG0, 13i. In process step 210, the lathe 60 and cutter blade 62, which may have a different profile than the cutter blade 62 employed in step 205, are used to remove an access slot 72 (cross-hatched downward from left to right), which is cut to a width W2 and depth D2 sufficient to allow clearance for material removal to form an undercut slot 74 (cross-hatched horizontally), as described herein. It should be understood that width W2 is configured to provide the necessary clearance, not so wide upstream (left as depicted) to remove any material from the region of the sample 50, nor so wide downstream (right as depicted) to remove material beyond the depicted profile for the initial blade slot 13i. With continued reference to FIG. 4B, in process step 215, a lathe 60 and right-angle cutter blade 62 are used to cut under the sample 50 area, thereby forming an undercut slot 74 as depicted.

[0034] 4C , the method 200 continues with optional process step 220, in which a plurality of fasteners 80 are installed within the undercut slots 74 as needed to stabilize and retain the rotor 10 material in the region of the samples 50 in preparation for a subsequent removal step. In the next step 225 of the process 200, a lathe 60 and cutter blade 62 may be used to remove a final slot 76 (vertical cross-hatched) axially spaced from the access slot 72. The final slot 76 extends radially inward toward the undercut slots 74, and the cutting of the final slot 76 forms an annular ring 52 (containing the samples 50) having a rectangular cross-section disposed around the circumference of the rotor 10. The optional fasteners 80 are removed as needed in process step 230, freeing the annular ring 52 of removed material for the formation of one or more samples 50, as depicted.

[0035] 4D , as depicted in optional step 235, wedges 82 may be employed to secure the annular ring 52 for removal from the rotor 10 and initial blade grooves BG0, 13i. Continuing with method 200, in step 240, the annular ring 52 is cut across its cross section in at least two locations to provide a plurality of arcuate sections or segments 54 having rectangular cross sections from which a plurality of samples 50 may be taken.

[0036] Referring now to FIG. 4E, an exemplary arcuate segment 54 of the annular ring 52 is depicted. In process step 245, the annular ring 52 is segmented, and the arcuate segments 54 can be easily cut and machined to size, as needed, to form standardized samples 50 for impact testing. The resulting shape of the machined samples 50 may be rectangular or circular (i.e., round). It should be understood that other studies employing samples (such as microsections) may also be performed to examine material microstructure, evaluate hardness, determine tensile strength, and the like. In one embodiment, multiple samples 50 are formed, each having the dimensions previously described herein, although other dimensions are possible. The samples 50 may then be employed to perform impact and Charpy tests, as depicted in process step 250, to facilitate evaluation of the FATT of the legacy rotor 10.

[0037] Finally, returning to FIG. 4F, as depicted in process step 255 of FIG. 5, machining of the initial blade slot BG0, 13i profile can be completed utilizing machining techniques similar to those described herein. Fillers 51 having a shape complementary to the blade slots BG0, 13i can be installed in the blade slots BG0, 13i to facilitate operation of the steam turbine. The radially outer surface of the fillers 51 can be flush with the inlet region rotor surface 14 so that steam entering the inlet region is not obstructed by the blade slots BG0.

[0038] In an embodiment, the initial blade slots BG0, 13i are configured to provide thermal and dynamic stress relief for the rotor 10. Providing such thermal stress relief through the initial blade slots BG0, 13i allows legacy rotors 10 with larger thermal gradients than previously tolerated. As a result, the warm-up time, start-up time, and start-up frequency of the steam turbine are also improved. As depicted in process step 260, the steam turbine can be operated with higher thermal stresses (e.g., larger thermal gradients) compared to a legacy rotor without the initial blade slots BG0, 13i. For example, for a given rotor 10 and steam turbine with a predetermined thermal gradient limit, employing the new initial blade slots BG0, 13i can increase the predetermined thermal gradient limit by approximately 1.6 times. The performance improvement against thermal gradients depends on the load regime and the future life of the steam turbine rotor 10. Typical thermomechanical damage per start-up can be reduced by a factor of up to 300% for a high-pressure turbine rotor 10 and approximately 200% for a dual-flow IP turbine rotor.

[0039] While the various steps of method 200 are depicted in a particular order, it should be understood that they need not be performed in that strict order and are described in such order merely for purposes of illustrating the example embodiment. Some steps can easily be performed in a different order. It should also be understood that one or more of the process steps of method 200 may be automated and controlled. For example, machining to remove material from the rotor and processing automated by a controller or control unit.

[0040] In addition to operational savings, the sampling systems and methods of the described embodiments provide improved testing and operational capabilities by assessing the life of steam turbines and enabling longer operation. In particular, the systems and methods disclosed herein enable automation of the design / planning of equipment for performing fatigue testing and the evaluation of FATT based at least in part on the results of fatigue testing. Furthermore, the steam turbine rotors of the described embodiments provide capital and operational cost savings in the design and construction of existing retrofitted plant or boilers. In particular, the systems and methodologies disclosed herein enable the modification of existing equipment for fewer restart constraints while achieving faster and more frequent turbine restarts. Finally, while specific methods for cutting slots and forming annular rings are described according to some embodiments, it should be understood that other techniques are possible. For example, it may be possible to employ various cutting techniques to form the annular ring beyond cutting the slots as described herein.

[0041] The improved steam turbine rotor includes a legacy steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent the inter-blade region rotor surface, and grooves formed in either the inlet region rotor surface or the inter-blade region rotor surface of the legacy steam turbine rotor, the grooves being machined to enable removal of material from the legacy steam turbine rotor and at least one of performing material property testing and operating the improved steam turbine rotor at increased thermal stresses compared to the legacy steam turbine rotor.

[0042] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include a groove machined in the inlet region rotor surface to a first selected width and a first selected depth.

[0043] In addition to or as an alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include the grooves comprising an enlarged portion at an end of the groove distal from the inlet region rotor surface or the inter-blade region rotor surface on which the grooves are machined.

[0044] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include the enlarged portion of the groove including at least one of rounded corners or rounded edges.

[0045] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include the rounded corners and rounded edges exhibiting different geometric shapes.

[0046] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include the extension portion being at least one of substantially circular, elliptical, and oval.

[0047] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include the extension portion being at least one of symmetrical and asymmetrical in at least one of the axial and radial directions.

[0048] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include an inlet region rotor surface defining a steam inlet region, and grooves extending through the inlet region rotor surface to provide additional stress relief to the improved steam turbine rotor.

[0049] In addition to or in the alternative to one or more of the features described above, further embodiments of the improved steam turbine rotor may include the legacy rotor being configured as at least one of an intermediate-pressure steam turbine rotor, a high-pressure steam turbine rotor, and a dual-flow rotor.

[0050] According to another aspect of the present disclosure, a system is provided for removing a material test sample for performing material testing from a legacy steam turbine rotor. The legacy steam turbine rotor has an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface. The material test sample is a portion of an arcuate segment of an annular ring of rotor material removed from the legacy steam turbine rotor. The annular ring is machined from a groove formed in the inlet region rotor surface of the legacy steam turbine rotor. The groove is machined to enable removal of the annular ring and enable formation of the material test sample.

[0051] In addition to or in the alternative to one or more of the features described above, further embodiments of the system may include the material test sample being one of a plurality of material test samples, the plurality of material test samples having a standardized size resulting from machining of the arcuate segment.

[0052] In addition to or in the alternative to one or more features described above, further embodiments of the system may include the material test sample being one of a plurality of material test samples, the plurality of material test samples having a standardized size suitable for performing at least one of a Charpy impact test, a microstructural test, a hardness test, a creep test, a low cycle fatigue test, and a tensile test.

[0053] In addition to or as an alternative to one or more of the features described above, further embodiments of the system may include the material test sample being substantially rectangular, while in another embodiment the material test sample is substantially circular.

[0054] In addition to or in the alternative to one or more of the features described above, further embodiments of the system may include that the material test sample has a width of 10 mm, a height of 10 mm, and a length selected from the group consisting of 10 mm, 20 mm, and 50 mm.

[0055] A method for producing a material sample for performing material testing on a legacy steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent the inter-blade region rotor surface is provided, the method including forming an annular ring of rotor material on the legacy steam turbine rotor, removing the annular ring from the legacy steam turbine rotor, and forming a material test sample from an arc segment of the annular ring.

[0056] In addition to or in the alternative to one or more of the features described above, further embodiments of the method may include forming a first slot of a first selected width and a first selected depth in a radial direction in a portion of the inlet region rotor surface to remove material from the legacy steam turbine rotor, forming a second slot axially adjacent to and perpendicular to the first slot to undercut the annular ring, and forming a third slot of a second width and a second depth in a portion of the inlet region rotor surface axially spaced from the first slot, the third slot intersecting the second slot to release the annular ring of rotor material.

[0057] In addition to or as an alternative to one or more of the features described above, further embodiments of the method may include performing a material test on the material test sample.

[0058] In addition to or in the alternative to one or more features described above, further embodiments of the method may include evaluating results of the material test to evaluate a fracture appearance transition temperature (FATT) of the legacy steam turbine rotor.

[0059] In addition to or in the alternative to one or more features described above, further embodiments of the method may include predicting an extended life profile of the improved legacy steam turbine rotor based at least in part on the evaluated FATT.

[0060] In addition to or in the alternative to one or more features described above, further embodiments of the method may include forming a radial first cut of a selected width and a selected depth to remove material from the legacy steam turbine rotor at an inlet region rotor surface to flatten its curved surface prior to forming the first slot.

[0061] In addition to or in the alternative to one or more of the features described above, further embodiments of the method may include forming an initial slot in a radial direction of a selected width and a selected depth to remove material from the legacy steam turbine rotor at an inlet region rotor surface to flatten its curved surface.

[0062] In addition to or in the alternative to one or more features described above, further embodiments of the method may include securing the annular ring with a fastener in the second slot before forming the third slot.

[0063] In addition to or in the alternative to one or more features described above, further embodiments of the method may include fixing the annular ring prior to segmenting the annular ring into two or more of the arcuate segments.

[0064] Finally, it is understood that the system and any control units (e.g., for operating the lathe 60 and cutter blade 62) may also include the electronics, software, memory, storage, databases, firmware, logic / state machines, microprocessors, communications links, displays or other visual or audio user interfaces, printing devices, and any other input / output interfaces necessary to perform the functions and / or achieve the results described herein. For example, as previously described, the system may include at least one processor and a system memory / data storage structure, which may include random access memory (RAM) and read-only memory (ROM). The system's at least one processor may include one or more conventional microprocessors and one or more auxiliary coprocessors, such as math coprocessors. The data storage structures discussed herein may include any appropriate combination of magnetic, optical, and / or semiconductor memory, and may include, for example, RAM, ROM, flash drives, optical disks (e.g., compact disks), and / or hard disks or drives.

[0065] Furthermore, software applications that adapt the controller to execute the methods disclosed herein can be loaded from a computer-readable medium into the main memory of at least one processor. Thus, embodiments of the present system can execute the methods disclosed herein in real time. As used herein, the term "computer-readable medium" refers to any medium that provides or participates in providing instructions to at least one processor of the system (or any other processor of a device described herein) for execution. Such media can take many forms, including, but not limited to, non-volatile and volatile media. Non-volatile media include, for example, optical, magnetic, or magneto-optical disks, such as memory. Volatile media include dynamic random access memory (DRAM), which typically constitutes main memory. Common forms of computer-readable media include, for example, floppy disks, flexible disks, hard disks, solid-state drives (SSDs), magnetic tape, other magnetic media, CD-ROMs, DVDs, other optical media, RAM, PROMs, EPROMs, or EEPROMs (electronically erasable programmable read-only memory), flash-EPROMs, other memory chips or cartridges, or other computer-readable media.

[0066] In embodiments, execution of sequences of instructions in a software application causes at least one processor to perform the methods / processes described herein, although hardwired circuitry may be used in place of or in combination with software instructions to implement the methods / processes described. Accordingly, embodiments as described herein are not limited to any specific combination of hardware and / or software.

[0067] As used herein, elements or steps referred to in the singular and preceded by the word "a" or "an" should be understood as not excluding a plurality of such elements or steps, unless such exclusion is expressly stated. Furthermore, references to "one embodiment" of a described embodiment are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, unless expressly stated to the contrary, embodiments that "include," "comprise," or "have" an element or elements having a particular characteristic can include additional such elements that do not have that characteristic.

[0068] Furthermore, while the dimensions and material types described herein are intended to define parameters related to the described embodiments, they should be understood as exemplary embodiments and, as such, are in no way limiting. Many other embodiments may become apparent to those skilled in the art upon reviewing the above description. Accordingly, the scope of the present disclosure should be determined with reference to the appended claims. Such description may include other examples that occur to those skilled in the art, and such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the claim language or if they include equivalent structural elements that have insubstantial differences from the claim language.

[0069] In the appended claims, the terms "including" and "in which" are used as the plain-text equivalents of the respective terms "comprising" and "wherein." Moreover, in the following claims, the terms "first," "second," "third," "upper," "lower," "below," "upper," etc. are used merely as labels and are not intended to impose numerical or positional requirements on their objects. Furthermore, any limitation of the following claims that is not written in means-plus-function form is not intended to be so construed unless such claim limitation expressly uses the phrase "means-for" following a statement of function that negates further structure. [Explanation of symbols]

[0070] 10: High pressure steam turbine rotor 11: Inner casing 12: Inter-blade region rotor surface 13: Blade groove 13a: First upstream blade groove 14: Inlet region rotor surface 15: Sample area 16: Piston region rotor surface 17: Extension 18: Stress relief groove rotor surface 19: Thermal barrier coating 20: Intermediate pressure steam turbine rotor 22: Inter-blade region rotor surface 23: Blade groove 23a: First upstream blade groove 24: Inlet region rotor surface 25: Sample area 30: Dual flow steam turbine rotor 32: Dual inter-blade region rotor surface 33: Blade groove 33a: First upstream blade groove 34: Inlet region rotor surface 35: Sample area 50: Material test sample 51: Filler 52: Annular ring 54: Arc segment 60: Lathe 62: Cutter blade 70: First slot 72: Access slot 74: Undercut slot 76: Final slot 80: Fastener 82: Wedge

Claims

1. 1. A method (200) for generating a material test sample (50) for performing one or more material tests on a legacy steam turbine rotor (10, 20, 30) having an inter-blade region rotor surface (12) and an inlet region rotor surface (14) adjacent the inter-blade region rotor surface (12), comprising: removing an annular ring (52) of rotor material at a selected sample area (15) from the inter-blade region rotor surface (12) and the inlet region rotor surface (14), the removal of the annular ring (52) creating a modified legacy steam turbine rotor; forming a material test sample (50) from a portion of the annular ring (52); A method (200) comprising:

2. forming a plurality of material test samples (50) including a material test sample (50); The method (200) of claim 1, further comprising: performing one or more material tests on one or more material test samples of the plurality of material test samples (50).

3. The method of claim 1 , further comprising evaluating results of one or more material tests to evaluate a fracture appearance transition temperature (FATT) of the legacy steam turbine rotor (10, 20, 30).

4. The method of claim 3 , further comprising predicting an extended life profile of the retrofitted legacy steam turbine rotor (10, 20, 30) based at least in part on the FATT.

5. Removal of the annular ring (52) forming a first slot (70) in a radial direction to remove material from a legacy steam turbine rotor (10, 20, 30), the first slot (70) having a first selected width and a first selected depth, the first slot (70) being formed in a first portion of an inlet region rotor surface (14); forming a second slot (72) axially adjacent to and perpendicular to the first slot (70) for removing material from the legacy steam turbine rotor (10, 20, 30) and for undercutting the material test sample (50) at the sample area (15); forming a third slot (76) radially in a second portion of the inlet region rotor surface (14) adjacent the sample region (15) for removing material from the legacy steam turbine rotor (10, 20, 30), the third slot having a second selected width and a second selected depth; Including, The second portion is axially spaced from the first slot (70); 2. The method of claim 1, wherein the third slot (76) intersects with the second slot (72) to release the annular ring (52) of rotor material at the sample region (15).

6. The method of claim 5, further comprising the step of securing the sample area (15) with a fastener (80) disposed within the second slot (72) prior to forming the third slot (76).

7. dividing an annular ring (52) of rotor material; removing the split annular ring (52) from the rotor; Including, 2. The method of claim 1, wherein forming material test samples (50) from portions of the annular ring (52) comprises machining portions of the split annular ring (52) to create a plurality of material test samples (50).

8. The method of claim 7, further comprising the step of fixing the toroidal ring (52) prior to the step of splitting the toroidal ring (52).

9. The method of claim 1, further comprising the step of forming an initial slot (13i) radially at an inlet region rotor surface (14) having a selected width and a selected depth to remove material from the legacy steam turbine rotor (10, 20, 30) and flatten its curvature prior to the step of removing the annular ring (52) of rotor material.

10. 1. A system for extracting material test samples (50) from a legacy steam turbine rotor (10, 20, 30) for performing one or more material tests, comprising: A legacy steam turbine rotor (10, 20, 30) includes an inter-blade region rotor surface (12) and an inlet region rotor surface (14) adjacent the inter-blade region rotor surface (12); The system includes a lathe (60) and a cutter blade (62) for extracting material test samples (50) from legacy steam turbine rotors (10, 20, 30), and a control unit for operating the lathe (60) and the cutter blade (62); The lathe (60) and the cutter blade (62) are controlled by the control unit. Introducing initial blade grooves (13i) into either an inter-blade region rotor surface (12) or an inlet region rotor surface (14) of a legacy steam turbine rotor (10, 20, 30); forming an annular ring (52) of rotor material containing a material test sample (50) within the initial blade groove (13i); removing an annular ring (52) containing a material test sample (50) from the legacy steam turbine rotor (10, 20, 30) and initial blade groove (13i); and extracting a material test sample (50) from a legacy steam turbine rotor (10, 20, 30) by performing an operation including:

11. The system of claim 10, wherein the annular ring (52) is machined by forming initial blade grooves (13i) in the inlet region rotor surface (14).

12. 11. The system of claim 10, wherein removing the annular ring includes cutting the annular ring into a plurality of divided sections, each section corresponding to a standardized sized material test sample for performing one or more material tests.

13. The system of claim 12 , wherein the one or more material tests include at least one of a Charpy impact test, a microstructural test, a hardness test, a creep test, a low cycle fatigue test, and a tensile test.

14. The system of claim 10, wherein the material test sample (50) is at least one of substantially rectangular and substantially circular.

15. 11. The system of claim 10, wherein the material test sample (50) has a width of 10 mm, a height of 10 mm, and a length selected from the group consisting of 10 mm, 20 mm, and 50 mm.

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