System and method for full-scale sampling to perform material testing on a steam turbine rotor

Abstract

The present invention is entitled "System and method for full-scale sampling to perform material testing on a steam turbine rotor." The present invention provides a method for generating a material test sample for performing material testing on a conventional steam turbine rotor, the conventional steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface. The method includes forming an annular ring of rotor material in a sample area, and forming a material test sample from a portion of the annular ring. A conventional steam turbine rotor is also described, the conventional steam turbine rotor including an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface. The steam turbine rotor has a groove formed therein, and wherein the groove is machined to be capable of removing material from the steam turbine rotor to form a sample, the sample being configured to be capable of performing material property testing and operating an improved steam turbine rotor with extended thermal stresses compared to a conventional steam turbine rotor.

Description

Technical Field

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

[0002] The steam turbine may include a rotor having a thrust balancing piston with a relief groove for relieving thermal stress outside the region of the fresh steam flow path, wherein the relief groove is axially displaced in a direction opposite to the working steam flow of the blade flow path.

[0003] As the use of renewable energy increases, the demand for power grids that operate with increased power plants and steam turbine cycles increases. Operational flexibility requirements may be limited by the life of the steam turbine because greater exposure to frequent thermal transients increases the risk of thermal fatigue cracks being initiated during cold starts, warm starts, and hot starts, as well as during load transitions and shutdowns. In addition, in steam turbines having multiple stages or turbines (e.g., high-pressure turbines and intermediate-pressure turbines), the different thermal conditions in each of the steam turbines / sections result in the rotor portion of each of the steam turbines / sections having different low-cycle fatigue lives. Therefore, maintenance schedule requirements may be out of sync, which can lead to an increase in maintenance interruptions. Although the low-cycle fatigue life of the rotor portion can be balanced by selecting rotor materials to improve toughness and ductility, there are practical limitations in achieving the purpose of selecting only rotor materials. These measures do not overcome the potential negative impact of thermal transients on the low-cycle fatigue life of the rotor.

[0004] Therefore, there is a need to monitor the life status of steam turbines. Generally speaking, theoretical assessments are performed based on minimum material properties using real but generalized operating data. For this purpose, a study of the actual mechanical behavior of the rotor in the hot section would be beneficial. In some cases, small-scale test sampling methods are used to perform fracture morphology transition temperature (FATT) assessments. Unfortunately, such methods often show large inaccuracies caused by the small sample size. In addition, for reactive drum rotors, a database of FATT data of aged in-service steam turbine rotors is usually not available. This is also the result of the lack of easily removable material that can be used to obtain test samples. In contrast, for impulse rotor steam turbines, since the rotor of the steam turbine includes a disc with no pressure drop on the corresponding stage, it is allowed to drill holes in the disc (as long as they are balanced) and retrieve sample material as needed for further study.

[0005] Therefore, there is a need to improve rotor sampling to assess the effects of thermal aging on creep rupture properties. Additionally, there is a need to improve the low cycle fatigue life of steam turbine rotor sections and to tailor the low cycle fatigue life of different sections of a steam turbine rotor to synchronize maintenance cycles of rotor sections. Summary of the Invention

[0006] A method for producing a material test sample for performing one or more material tests on a conventional steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface is provided. The method includes removing an annular ring of rotor material from a sample region selected from the inter-blade region rotor surface and the inlet region rotor surface, the removal of the annular ring forming a modified conventional steam turbine rotor; and forming the material test sample from a portion of the annular ring.

[0007] A system for retrieving a material test sample for performing one or more material tests from a conventional 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 system includes a segmented section of an annular ring of rotor material from the conventional steam turbine rotor, the annular ring being machined from a groove formed in the conventional steam turbine rotor, wherein the groove is machined to enable removal of the annular ring and formation of the material test sample.

[0008] The present invention provides an improved steam turbine rotor. The improved steam rotor includes a conventional steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface, and a groove formed in the inlet region rotor surface or the inter-blade region rotor surface of the conventional steam turbine rotor. The groove is machined to remove material from the conventional steam turbine rotor to enable at least one of performing material characterization testing and operating the improved steam turbine rotor under extended thermal stresses compared to the conventional steam turbine rotor based at least in part on the material characterization testing.

[0009] Additional features and advantages are achieved through the technology 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 and its advantages and features, refer to the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The described embodiments will be better understood from the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0011] Figure 1 is a cross-sectional view of a high-pressure steam turbine rotor including a high-pressure steam turbine inner casing according to one embodiment of the present disclosure;

[0012] Figure 2A is a partial cross-sectional view of a high-pressure steam turbine rotor and an intermediate-pressure steam turbine rotor according to one embodiment of the present disclosure;

[0013] Figure 2B is a partial cross-sectional view of a double-flow steam turbine rotor according to one embodiment of the present disclosure;

[0014] Figure 3 is an expanded cross-sectional view of a portion of a steam turbine rotor according to one embodiment, depicting the formation of blade groove BG0 in front of blade groove BG1 and taking a sample through blade groove BG0:

[0015] Figure 4A is a cross-sectional view of a portion of a steam turbine rotor, depicting the location of blade groove BG0 for obtaining a sample from the steam turbine rotor, according to one embodiment;

[0016] Figure 4B is a cross-sectional view of a portion of a steam turbine rotor according to one embodiment, depicting an initial step in forming a blade groove BG0 for obtaining a sample;

[0017] Figure 4C is a cross-sectional view of a portion of a steam turbine rotor according to one embodiment, depicting an additional step of forming a blade groove BG0 for obtaining a sample;

[0018] Figure 4D is a cross-sectional view of a portion of a steam turbine rotor according to one embodiment, depicting an annular ring of material removed from blade groove BG0 to prepare a sample;

[0019] Figure 4E According to an embodiment Figure 4D a cross-sectional view of a portion of an arcuate segment of an annular ring and a test sample taken from an annular ring removed from a steam turbine rotor;

[0020] Figure 4F is a cross-sectional view of a portion of a steam turbine rotor depicting blade grooves BG0 having filler to facilitate turbine operation according to one embodiment; and

[0021] Figure 5 is a block diagram illustration of a process flow diagram depicting sample acquisition, according to one embodiment. DETAILED DESCRIPTION

[0022] Exemplary embodiments of the present disclosure will now be described with reference to the accompanying drawings, wherein similar reference numerals are used to refer to similar elements throughout the text. In the following description, for the purpose of explanation, numerous specific details are set forth to provide a thorough understanding of the present disclosure. However, the present disclosure may be practiced without these specific details, and the present disclosure is not limited to the exemplary embodiments disclosed herein.

[0023] While various embodiments as described herein are suitable for use with and application to steam generation systems employing steam turbines, a reaction-type drum steam turbine is selected and described for clarity of illustration only. Other types of steam turbine configurations, such as steam turbines having one or more sections, drum turbines, and impulse turbines, are also applicable.

[0024] Figure 1 An example of a high-pressure steam turbine rotor 10 is shown, 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 a rotating blade (one of the rotating blades is in the Figure 4A The blades are arranged in axially spaced rows (shown in FIG. 1 ) extending circumferentially around the high-pressure steam turbine rotor 10. These blades are attached to the high-pressure steam turbine rotor 10 by means of blade grooves 13. The first row of blade grooves is generally designated BG1 and indicated at 13a, the second row of blade grooves is designated BG2 and indicated at 13b, and so on, extending through the inter-blade region rotor surface 12, depending on the number of blade stages employed in a given section of the steam turbine. Thus, the inter-blade region rotor surface 12 can be defined as the surface region of the high-pressure steam turbine rotor 10 where the blade grooves 13 are located.

[0025] The inlet region rotor surface 14 is located upstream of and immediately adjacent to the inter-blade region rotor surface 12. In operation, as steam is fed into the steam turbine, this portion of the rotor is exposed to the steam. Typically, the inlet region rotor surface 14 is shaped to direct radially fed steam into an axial direction by having a radial to axial transition surface that extends to the first upstream blade groove 13a, but other shapes are possible. In one embodiment, the inlet region rotor surface 14 and / or other areas in the inter-blade region 12 are used to provide a sample area 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 a sample, other embodiments relate to a steam turbine rotor 10 whose inter-blade region rotor surface 12 includes an area without blade grooves 13 and whose inter-blade region rotor surface 12 can be used to obtain a sample.

[0026] The piston region rotor surface 16 is positioned 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 the blade end thrust typically experienced by reaction-type steam turbines and to generate rotor thrust toward the high-pressure end of the turbine under all operating conditions. The piston may be integral with the solid rotor or retractable and locked into place. The piston region rotor surface 16 may include a stress-relief grooved rotor surface 18 located upstream of and adjacent to the inlet region rotor surface 14.

[0027] In one or more embodiments, each of the inter-blade area rotor surface 12, the inlet area rotor surface 14, the piston area 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 the surfaces 12, 14, and 16 (including the surface 18), and the radial thickness of the thermal barrier coating 19 may be uniform or may vary.

[0028] Figure 2A An exemplary embodiment of a combined high-pressure steam turbine rotor 10 and an intermediate-pressure steam turbine rotor 20 is shown in FIG. Figure 2A Also depicted are an inter-blade region rotor surface 22 and an inlet region rotor surface 24. The inter-blade region rotor surface 22 is located axially 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.

[0029] The inlet region rotor surface 24 is located upstream of and immediately adjacent to the inter-blade region rotor surface 22. As steam is fed into the steam turbine, this region of the rotor 20 is exposed to the steam. Typically, this region is shaped to direct radially fed steam into an axial direction by having a radial-to-axial transition surface extending to the first upstream blade groove 23a. In some embodiments, the steam fed to the intermediate pressure steam turbine rotor 20 may no longer be heated and may be directed from the high pressure section. Again, in one embodiment, the inlet region rotor surface 24 and / or other areas in the inter-blade region 22 are used to provide a sample area 25 for removing material as needed to provide material for material testing as described herein.

[0030] A piston region rotor surface (not shown) may be positioned proximate to inlet region rotor surface 24, such that inlet region rotor surface 24 is located between the piston region rotor surface and inter-blade region rotor surface 22, as previously described for the high pressure section. In an exemplary embodiment, each of inter-blade region rotor surface 22, inlet region rotor surface 24, and piston region rotor surface has a thermal barrier coating bonded to the respective surface.

[0031] Figure 2B , an exemplary embodiment of a dual-flow steam turbine rotor 30 is shown. The rotor 30 includes two inter-blade region rotor surfaces 32 and an inlet region rotor surface 34. The inter-blade region rotor surfaces 32 are axially disposed between rotating blades (not shown) that are circumferentially distributed on the dual-flow steam turbine rotor 30 by means of blade grooves 33 extending into the surface of the rotor 30.

[0032] The inlet region rotor surface 34 is located upstream of and immediately adjacent to the inter-blade region rotor surface 32. As steam is fed into the steam turbine, this region of the rotor 30 is exposed to the steam. Typically, this region is shaped to direct radially fed steam into an axial direction by having a radial-to-axial transition surface extending to the first upstream blade groove 33a. In some embodiments, the inter-blade region rotor surface 32 is used to provide a sample area 35 for removing material as needed to provide material for testing as described herein. Uniquely, in this figure, the inter-blade region rotor surface 32 includes a second or alternative sampling location 35 located between what will be designated as BG2 and BG3, which can also be used to remove material for material testing.

[0033] Metal materials such as stainless steel, titanium alloys, and nickel-based alloys are widely used in steam turbine rotors in the petrochemical, thermal, coal-fired, and nuclear power, automotive, and aviation industries. For example, low-alloy CrMoV steel (i.e., steel containing chromium, molybdenum, and vanadium) is typically used at temperatures up to 565°C. For supercritical applications, alloy steels with 9% Cr are used. For power plant applications operating at even higher temperatures (e.g., in the range of 700°C), nickel-based alloys can be used for rotors. These materials are manufactured to operate for extended periods under harsh conditions of high temperature, high pressure, vibration, and dynamic forces. As a result, these components will inevitably be subjected to high temperatures, creep, and fatigue damage, which will lead to deterioration of material properties and may ultimately lead to material failure. Therefore, regular testing and assessment are performed to evaluate degradation, especially for critical or expensive components. However, health monitoring and assessment can be difficult and labor-intensive, especially for large steam turbines, and can result in expensive plant downtime and delays. Therefore, methods that accelerate accurate testing are highly advantageous.

[0034] The traditional Charpy beam test is a standardized high-strain-rate test that determines how much energy a material absorbs during fracture. The absorbed energy is a measure of the material's notch toughness. It is widely used in industry as an indicator of material integrity because it is easy to prepare and perform, and the results can be obtained quickly and relatively inexpensively. The drawbacks of the Charpy beam test are that some results are only comparative, traditional fracture tests require relatively large specimens on the equipment, and after sampling, repairs often need to be made at the sampling point by welding. Furthermore, when impact testing alloys over a certain temperature range, body-centered cubic or ferritic alloys exhibit significant behavioral differences. At temperatures above the transition temperature, impact specimens tend to fracture through ductile mechanisms (typically microvoid coalescence), absorbing relatively large amounts of energy. At lower temperatures, the same impact specimens tend to fracture brittlely (typically cleaving), absorbing significantly less energy. Within the transition temperature range, specimens will typically exhibit regions with a mixture of ductile and brittle fracture.

[0035] The temperature range for the transition from one type of behavior to another type of behavior varies depending on the material being tested. The transition behavior can be defined in various ways for illustrative purposes, for example, as a minimum test result for absorbed energy, fracture morphology, lateral expansion, or a combination thereof at a specified test temperature. In some cases, the transition temperature is the temperature at which the absorbed energy or fracture morphology reaches a specified level when the test is performed over a certain temperature range. Alternatively, it may be desirable to determine the fracture morphology transition temperature (FATT) of the specimen, where FATT is the temperature at which the required minimum percentage of shear fractures (n) is obtained. FATT is a quantitative target for thermal aging, material fatigue, and crack resistance, that is, an assessment of structural integrity. It provides an important assessment of the material structure for component life. FATT enables the rotor to be evaluated to determine the fatigue level, or in other words, to determine the expected life of the component. Therefore, actual sampling of the component is beneficial for the assessment of fatigue and expected life, particularly with respect to the expected results for a given operating specification of the steam turbine rotor 10.

[0036] Now go to Figure 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. Although depicted is a steam turbine rotor 10, the depicted portions are equally applicable to the intermediate pressure rotor 20 or the dual flow rotor 30 described above. From here on, for simplicity, components of each of the high pressure rotor 10, the intermediate pressure rotor 20, and the dual flow rotor 30 will be referred to together with the descriptions that apply to each type of rotor below. In one embodiment, a portion of the blade groove 13 is depicted as extending through the inter-blade region rotor surface 12 adjacent to the inlet region rotor surface 14. As described herein, the inlet region rotor surface 14 is shaped to direct radially fed steam into an axial direction by having a radial to axial transition surface that extends to the first upstream blade groove 13a.

[0037] However, in one embodiment, other areas of the inlet region rotor surface 14 and / or the inter-blade region 12 are utilized to provide sample areas 15 for removing material for testing and FATT determinations. For example, material testing may include one or more of simple beam testing, tensile testing, hardness testing, creep testing, low cycle fatigue testing, microstructural testing, and the like.

[0038] In one embodiment, an additional initial blade groove 13i (also designated as BG0) is introduced. Initial blade groove BG0 13i has a substantially similar size and shape to the other blade grooves 13 (e.g., 13a, 13b, etc.), but this need not be the case. For example, initial blade groove 13i may be cut into the rotor surface at a selected width W1 to a first depth D1, and then may be cut to a larger, selected width W2 to an additional depth designated as D2 to form an expanded portion 17 away from the inlet region rotor surface 14. The specific profile of expanded portion 17 is selected to advantageously provide thermal and dynamic stress relief in rotors 10, 20, and / or 30. For example, it may be advantageous to cut expanded portion 17 of initial blade groove BG0 13i to have rounded corners and rounded edges across its width W2.

[0039] In some embodiments, the expanded portion 17 may have rounded corners exhibiting different geometric shapes and / or curvatures, including, but not limited to, circular, elliptical, parabolic, or polynomial functions. In one embodiment, the initial blade groove BG0 13i exhibits an expanded portion 17 having a symmetrical cross-section in at least one of the axial and radial directions. In another embodiment, the initial blade groove BG0 13i exhibits an asymmetrical expanded portion 17 in at least one of the axial and radial directions. In one embodiment, the initial blade groove BG0 13i exhibits an expanded portion 17 cross-section that is substantially circular, elliptical, or oval. In another embodiment, the initial blade groove BG0 13i exhibits a substantially identical cross-sectional shape to the other blade grooves 13, specifically the first blade groove 13a (also designated as 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.

[0040] Initial (BG0) blade grooves are currently implemented for newly constructed steam turbine rotors. In modern applications, unused blade grooves (i.e., blade grooves in which no blades are installed) are generally used to reduce fatigue stress and thermal stress at the hot section of the newly implemented rotor. However, initial blade grooves, such as BG0 13i, are not implemented on conventional rotors 10, 20, 30. Conventional rotors 10, 20, 30 also experience fatigue and damage due to their service life. Conventional rotors are particularly in need of fatigue assessment and evaluation to measure their suitability for continued use. The described embodiment first utilizes this feature to provide sampling while achieving potential enhancements in thermal stress relief of the rotor. Therefore, based on the beneficial effects of obtaining samples for performing the tests described herein, stress reduction / stress relief is achieved in the improved new blade groove geometry for the rotors 10, 20, 30. The improved stress relief can allow for faster startup and increased cycling by alleviating thermal stresses in the improved conventional rotors 10, 20, 30.

[0041] Advantageously, the material removed to form the grooves BGO 13i is machined in a manner that facilitates retrieval of a test sample 50 having a sample size sufficient to perform the test to evaluate the FATT. The particular machining and / or cutting scheme employed is not critical as long as the material is removed in a manner consistent with performing the test. In one embodiment, the sample on order for the standard simply supported beam test (which is generally rectangular and has a width of 10 millimeters (mm), a height of 10 mm, and a length of 10 mm or 20 mm or 50 mm) can be readily achieved by machining the rotor on a lathe, for example as described herein and as Figures 4A to 4F As described.

[0042] Figures 4A to 4F An exemplary cross section of a rotor 10 is shown, and an exemplary process for machining and forming initial blade slots BGO 13i in the rotor 10 and obtaining and manufacturing specimens 50 for performing fatigue and simply supported beam testing is shown. Figure 5 is a flow chart depicting an exemplary process 200 for obtaining a test sample from a conventional steam turbine rotor 10 according to one embodiment. In one embodiment, as Figure 4A As depicted, the desired initial blade slot BG0 13i is profiled using the segments designated for the sample 50 machined from the inlet region surface 14 of the rotor 10 .

[0043] Now go to Figure 4B , in a first step of process 205, a lathe 60 and a cutter blade 62 are employed to optionally remove the first slot 70 and flatten the top portion of the curved surface of the inlet region rotor surface 14 to begin forming the initial blade groove BG0 13i. At process step 210, a lathe 60 and a cutter blade 62 (which may have a different profile than the profile of the cutter blade 62 employed in step 205) are employed to remove an entry slot 72 (cross-hatched from left to right), which is cut to a width W2 and a depth D2 sufficient to provide clearance for removing material to form an undercut slot 74 (horizontally cross-hatched), as described herein. It should be understood that the width W2 is configured to provide the necessary clearance, but not so wide as to proceed further upstream (to the left as depicted) to remove any material from the region of the sample 50, nor to proceed further downstream (to the right as depicted) to remove material beyond the depicted profile of the initial blade slot 13i. Continued with reference to Figure 4B At process step 215 , a lathe 60 and a square cutting blade 62 are used to cut beneath an area of ​​the sample 50 , thereby forming an undercut slot 74 , as depicted.

[0044] Now go to Figure 4C, method 200 continues at optional process step 220, where a plurality of fasteners 80 are installed in the undercut slots 74, as needed, to stabilize and retain the material of the rotor 10 in the area of ​​the sample 50 in preparation for the subsequent removal step. In the next step 225 of process 200, a lathe 60 and cutter blade 62 can be used to remove a final slot 76 (vertical cross-hatched) axially spaced from the entry slot 72. The final slot 76 extends radially inward toward the undercut slot 74, and the cutting of the final slot 76 results in the formation of an annular ring 52 (including the sample 50) having a rectangular cross-section disposed about the circumference of the rotor 10. If desired, the optional fasteners 80 are removed at process step 230, thereby releasing the annular ring 52 of removed material to form one or more samples 50, as depicted.

[0045] Now go to Figure 4D As depicted at optional process step 235, a wedge 82 may be employed to secure the annular ring 52 for removal from the rotor 10 and the initial blade groove BG0 13i. Continuing with method 200, at process step 240, the annular ring 52 is transected at at least two locations thereof, thereby producing a plurality of arcuate sections or segments 54 having a rectangular cross-section, from which a plurality of samples 50 may be obtained.

[0046] Now go to Figure 4E , depicting an exemplary arcuate segment 54 of the annular ring 52. At process step 245, the arcuate segment 54 can be easily cut and machined into appropriate dimensions as needed to form a standardized sample 50 for impact testing. The resulting shape of the machined sample 50 can be rectangular or circular (i.e., annular). It should also be understood that other studies using samples (such as micro-segments) can be performed to study the microstructure of the material, assess hardness, determine tensile strength, etc. In one embodiment, a plurality of samples 50 are formed, each having the dimensions previously described herein, although other dimensions are also possible. The samples 50 can then be used to perform impact and simply supported beam testing, as depicted in process step 250, to facilitate evaluating the FATT of the conventional rotor 10.

[0047] Finally go to Figure 4F And as Figure 5 As depicted in process step 255, machining of the initial blade slot BG0 13i profile can be completed using machining techniques similar to those described herein. Filler material 51 having a shape complementary to blade slot BG0 13i can be installed into blade slot BG0 13i to facilitate operation of the steam turbine. The radially outer surface of filler material 51 can be flush with the inlet region rotor surface 14 to ensure that steam flowing into the inlet region is not interfered with by blade slot BG0.

[0048] In one embodiment, initial blade slots BG0 13i are formed to provide thermal and dynamic stress relief for the rotor 10. Providing such thermal stress relief via initial blade slots BG0 13i enables the conventional rotor 10 to be used with a larger temperature gradient than previously allowed. As a result, the warm-up time, startup time, and startup frequency of the steam turbine are also improved. As depicted at process step 260, the steam turbine can be operated with higher thermal stresses (such as larger thermal gradients) when compared to a conventional rotor without initial blade slots BG0 13i. For example, for a given rotor 10 and steam turbine with a specified thermal gradient limit, employing new initial blade slots BG0 13i allows the specified thermal gradient limit to be increased by approximately 1.6 times. The performance improvement in thermal gradient depends on the load scenario and future life of the steam turbine rotor 10. For the high-pressure turbine rotor 10, the thermomechanical damage per typical startup will be reduced by up to 300%, and for the dual-flow IP turbine rotor by approximately 200%.

[0049] It should be understood that although the various steps of method 200 are depicted in a particular order, they need not be strictly performed in that order and are described in such order for purposes of illustrating exemplary embodiments. Some steps may be readily 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 and processing for removing rotor material may be automated by a controller or control unit.

[0050] In addition to operational savings, the sampling systems and methods of the embodiments provide improved testing and operational capabilities by assessing the life expectancy of the steam turbine and enabling longer term operation. Specifically, utilizing the systems and methods of the present invention disclosed herein, automated equipment can be designed / planned for performing fatigue testing and FATT assessments based at least in part on the results of fatigue testing. In addition, the steam turbine rotors of the embodiments provide savings in capital and recurring costs for existing retrofit plant or boiler designs and constructions. Specifically, utilizing the systems and methods disclosed herein, existing equipment can be modified to achieve fewer restart constraints while enabling 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, a variety of cutting techniques other than cutting slots as described herein can be used to form annular rings.

[0051] An improved steam turbine rotor includes a conventional steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface, and a groove formed in the inlet region rotor surface or the inter-blade region rotor surface of the conventional steam turbine rotor. The groove is machined to remove material from the conventional steam turbine rotor to enable at least one of performing material characterization testing and operating the improved steam turbine rotor under extended thermal stresses compared to the conventional steam turbine rotor.

[0052] In addition to or in the alternative to one or more of the above features, further embodiments of the improved steam turbine rotor may include machining grooves having a first selected width and a first selected depth in the inlet region rotor surface.

[0053] In addition to one or more of the above features, or as an alternative, another embodiment of the improved steam turbine rotor may include the groove including an extension portion at the end of the groove away from the inlet area rotor surface or the inter-blade area rotor surface, and the groove is machined into the inlet area rotor surface or the inter-blade area rotor surface.

[0054] 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 expanded portion of the groove including at least one of rounded corners and rounded edges.

[0055] 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 geometries.

[0056] 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 expansion portion being substantially at least one of circular, oval, and elliptical.

[0057] 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 being at least one of symmetrical and asymmetrical in at least one of an axial direction and a radial direction.

[0058] In addition to or in addition to one or more of the above features, or as an alternative, 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 in the improved steam turbine rotor.

[0059] In addition to or in addition to one or more of the above features, further embodiments of the improved steam turbine rotor may include the conventional 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.

[0060] According to another aspect of the present disclosure, a system for retrieving a material test sample from a conventional steam turbine rotor for performing material testing is provided. The conventional steam turbine rotor includes 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 conventional steam turbine rotor. The annular ring is machined from a groove formed in the inlet region rotor surface of the conventional steam turbine rotor. The groove is machined to enable removal of the annular ring and formation of the material test sample.

[0061] In addition to or in the alternative to one or more of the above features, further embodiments of the system may include the material test sample being one of a plurality of material test samples, and the plurality of material test samples having standardized dimensions resulting from machining of the arcuate segments.

[0062] In addition to or in the alternative to one or more of the above features, further embodiments of the system may include the material test sample being one of a plurality of material test samples, and the plurality of material test samples having standardized dimensions suitable for conducting at least one of a Charpy impact test, a microstructure test, a hardness test, a creep test, a low cycle fatigue test, and a tensile test.

[0063] In addition to, or in the alternative to, one or more of the above features, 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.

[0064] In addition to or in the alternative to one or more of the above features, further embodiments of the system may include the material test sample having a width of 10 mm, a height of 10 mm, and a length selected from 10 mm, 20 mm, and 50 mm.

[0065] A method is provided for generating a material test sample for performing material testing on a conventional steam turbine rotor having an inter-blade region rotor surface and an inlet region rotor surface adjacent to the inter-blade region rotor surface. The method includes forming an annular ring of rotor material in the conventional steam turbine rotor, removing the annular ring from the conventional steam turbine rotor, and forming the material test sample from an arcuate segment of the annular ring.

[0066] In addition to or in addition to one or more of the above features, another embodiment of the method may include forming a first slot having a first selected width and a first selected depth in a radial direction to remove material from a conventional steam turbine rotor in a portion of the inlet region rotor surface; forming a second slot in an axial direction adjacent to and perpendicular to the first slot to undercut an annular ring; and forming a third slot having a second width and a second depth in a radial direction in a portion of the inlet region rotor surface axially spaced from the first slot, wherein the third slot intersects the second slot to release an annular ring of rotor material.

[0067] In addition to, or as an alternative to, one or more of the features described above, further embodiments of the method may include performing material testing on the material test sample.

[0068] In addition to or in the alternative to one or more of the features described above, further embodiments of the method may include evaluating results of material testing to assess the fracture appearance transition temperature (FATT) of a conventional steam turbine rotor.

[0069] In addition to or in the alternative to one or more of the features described above, further embodiments of the method may include predicting an extended life curve for a modified conventional steam turbine rotor based at least in part on the assessed FATT.

[0070] In addition to or in addition to one or more of the above features, or as an alternative, another embodiment of the method may include forming a first cut in a radial direction of a selected width and a selected depth before forming the first slot to remove material from a conventional steam turbine rotor at the inlet region rotor surface to flatten its curved surface.

[0071] In addition to or in addition to one or more of the above features, or as an alternative, 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 a conventional steam turbine rotor at the inlet region rotor surface, thereby flattening its curved surface.

[0072] In addition to or as an alternative to one or more of the features described above, further embodiments of the method may include securing the annular ring in the second slot with a fastener prior to forming the third slot.

[0073] In addition to, or as an alternative to, one or more of the features described above, further embodiments of the method may include securing the annular ring prior to segmenting the annular ring into two or more arcuate segments.

[0074] Finally, it should also be understood that the system and any control units (e.g., a control unit for operating the lathe 60 and cutter blade 62) may include the necessary electronics, software, memory, storage devices, databases, firmware, logic / state machines, microprocessors, communication links, displays or other visual or audio user interfaces, printing devices, and any other input / output interfaces for performing the functions described herein and / or achieving the results described herein. For example, as previously described, the system may include at least one processor and system memory / data storage structures, which may include random access memory (RAM) and read-only memory (ROM). The at least one processor of the system may include one or more conventional microprocessors and one or more supplementary coprocessors, such as a math coprocessor, etc. The data storage structures discussed herein may include appropriate combinations of magnetic, optical, and / or semiconductor memory, and may include, for example, RAM, ROM, a flash drive, an optical disk (such as a compact disk), and / or a hard disk or drive.

[0075] In addition, the software application that adapts the controller to perform the methods disclosed herein can be read from the computer-readable medium into the main memory of at least one processor. Thus, the 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 for execution to at least one processor of the system (or any other processor of the device described herein). Such media can take a variety of forms, including but not limited to non-volatile media and volatile media. Non-volatile media include, for example, optical, magnetic or optical magnetic disks, such as memory. Volatile media include dynamic random access memory (DRAM), which generally constitutes main memory. Common forms of computer-readable media include, for example, floppy disks, flexible disks, hard disks, solid-state drives (SSDs), tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, RAMs, PROMs, EPROMs or EEPROMs (electrically erasable programmable read-only memories), FLASH-EEPROMs, any other memory chips or cartridges, or any other medium that can be read by a computer.

[0076] Although in an embodiment, execution of sequences of instructions in a software application causes at least one processor to perform the methods / processes described herein, hard-wired circuitry may be used in place of or in combination with software instructions for implementing the methods / processes. Accordingly, the embodiments described herein are not limited to any specific combination of hardware and / or software.

[0077] As used herein, elements or steps listed in the singular and beginning with the word "a" or "an" should be understood as not excluding a plurality of said elements or steps, unless such exclusion is explicitly stated. In addition, reference to "one embodiment" in the described embodiment is not intended to be interpreted as excluding the existence of other embodiments that also include the enumerated features. In addition, unless explicitly stated to the contrary, embodiments that "comprise," "contain," or "have" an element or multiple elements having a particular attribute may include other such elements that do not have that attribute.

[0078] In addition, although the sizes and types of materials described herein are intended to define parameters associated with the embodiments, they should be understood as exemplary embodiments and are therefore by no means restrictive. Upon reviewing the above description, many other embodiments may be apparent to those skilled in the art. Therefore, the scope of the present disclosure should be determined with reference to the appended claims. Such descriptions may include other examples that occur to those of ordinary skill in the art, and if such other examples have structural elements identical to the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, such other examples are intended to be within the scope of the claims.

[0079] In the following claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Moreover, in the following claims, terms such as "first," "second," "third," "upper," "lower," "bottom," "top," and the like are used merely as labels and are not intended to impose numerical or positional requirements on their objects. Moreover, limitations in the following claims that are not written in mean-plus-function format are not intended to be construed as such unless and until such claim limitations expressly use the phrase "for..." following the description of the void function of other structure.

Claims

1. A method (200) for generating a material test sample (50) for performing one or more material tests on a conventional steam turbine rotor (10), the conventional steam turbine rotor having an inter-blade region rotor surface (12) and an inlet region rotor surface (14) adjacent to the inter-blade region rotor surface (12), the method (200) comprising: forming an initial slot having a selected width and a selected depth in a radial direction to remove material from the conventional steam turbine rotor at the inlet region rotor surface to flatten its curved surface; removing an annular ring (52) of rotor material selected from a sample area (15) of said inter-blade region rotor surface (12) and said inlet region rotor surface (14), said removal of said annular ring (52) forming a modified conventional steam turbine rotor; and A material test sample (50) is formed from a portion of the annular ring (52).

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

3. The method of claim 1, further comprising evaluating results of the one or more material tests to evaluate a fracture morphology transition temperature of the conventional steam turbine rotor (10). 4 . The method of claim 3 , further comprising predicting an extended life curve for the modified conventional steam turbine rotor based at least in part on the fracture morphology transition temperature.

5. The method of claim 1, wherein removing the annular ring (52) comprises: forming a first slot (70) having a first selected width and a first selected depth in a radial direction to remove material from the conventional steam turbine rotor (10), wherein the first slot is formed in a first portion of the inlet region rotor surface (14); forming a second slot in an axial direction adjacent to and perpendicular to the first slot to undercut sample material in the sample region to remove material from the conventional steam turbine rotor; as well as A third slot having a second selected width and a second selected depth is formed in the radial direction to remove material from the conventional steam turbine rotor in a second portion of the inlet region rotor surface adjacent to the sample region and axially spaced from the first slot, wherein the third slot intersects the second slot to release the annular ring of rotor material in the sample region.

6. The method of claim 5, further comprising securing the sample area with a fastener positioned in the second slot before forming the third slot.

7. The method according to claim 1, further comprising: segmenting said annular ring of rotor material; as well as removing a segmented annular ring from the rotor; and Wherein forming the material test sample from a portion of the annular ring includes machining the portion of the segmented annular ring to obtain a plurality of material test samples.

8. The method of claim 7, further comprising securing the annular ring prior to the segmenting.

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