Thrust collar machining tool and methods for in-SITU repairing of a thrust collar of a rotor shaft of a turbine

Abstract

The present disclosure is related to tools for machining a thrust collar of a rotor shaft of a turbine In particular, a steam turbine or a gas turbine. The tool comprises a support (20) and an annular unit (30) connected to the support (20). The annular unit (30) is configured for being positioned around the rotor shaft and it comprises a static ring (31) and a rotatable ring (32). The rotatable ring (32) is configured to rotate relative to the static ring (31). A cutting tool is connected to the rotatable ring (32). The support is configured to withstand the loads induced by the cutting tool during machining of the thrust collar. The present disclosure also relates to methods for repairing a thrust collar.

Description

701000-WQ-1THRUST COLLAR MACHINING TOOL AND METHODS FOR IN-SITU REPAIRING OF A THRUST COLLAR OF A ROTOR SHAFT OF A TURBINEFIELD

[0001] The present disclosure relates to tools for machining a thrust collar of a rotor shaft of a turbine. In particular, a steam or gas turbine that is used at a fossil, nuclear or renewable power plant The present disclosure also relates to methods for in-situ repairing of a thrust collar of a rotor shaft of such turbine.BACKGROUND

[0002] Modern turbines, which include gas and steam turbines, are used in a wide variety of applications, such as for power generation or for conducting industrial processes. Power generation is done, for example, at fossil, nuclear or renewable plants. The process of generating power can involve driving of a rotor of an electric generator to provide electric power as needed. Said modern turbines may generate a special type of load that is called an axial load (also known as "thrust") in addition to the torque. This thrust is observed for other machines that are called turbomachinery.

[0003] For this reason, turbomachinery may include a thrust bearing to axially support a rotor and to carry the thrust. A rotor includes a rotor shaft and moving blades. During rotation of a rotor, an axial force may be exerted by the rotor on the thrust bearing. The thrust bearing is configured to maintain the axial position of the rotor. An example of upgraded thrust bearing assembly for a rotating machine is described in PCT / EP2022 / 088092.

[0004] Thrust bearings are anchored to a foundation of a turbine and they allow for rotation of a rotor and for absorbing axial loads. There are many designs of thrust bearings. An example of such a design of a thrust bearing comprises a plurality of pads or shoes that are arranged adjacent to a thrust collar mounted on, or integral with, a rotor.

[0005] Thrust collars are subjected to high thrust during operation and so they may suffer wear or damage. There are additional factors that can induce such wear or damage on a thrust collar. Those additional factors include circumferential scoring or scratching, which may appear if debris is present in the fluid, e.g. oil. A misalignment of a rotor with respect to a thrust bearing can result in a non-uniform distribution of the loads which can also cause a localized wear. Such additional factors include also high temperatures and pressures that can lead to accelerated wear of a thrust collar, especially in case of malfunctioning of lubrication and / orcooling systems. Furthermore, insufficient lubrication can also result in increased friction between a thrust collar and pads of a thrust bearing at the corresponding contact surfaces.

[0006] In operation, dynamic loading conditions can result from fluctuations in the operating conditions, e.g. rapid changes in the flow or load. Such dynamic loading conditions can also induce premature wear of a thrust collar. As still a further example, improper operation of the turbine, e.g. sudden start / stop operations or continued operation at unfavorable conditions, can also lead to an inadequate operation of a thrust bearing system and, eventually, to increased wear of a thrust collar.

[0007] In order to account for thrust collar wear, regular inspections are conducted to identify the extent of damage. If deemed necessary, different repair operations are carried out. Such repair operations may comprise complete replacement of a thrust collar. Additionally or alternatively, said repair operations may include steps aiming at restoring acceptable mechanical and structural properties of a thrust collar. Such repair operations can comprise machining, coating, or welding to restore material in damaged areas.

[0008] In most cases, especially if significant damage is present in a thrust collar, such repair operations require removal of a thrust collar from a rotor shaft, or in case of integrally formed thrust collars, removal of a rotor shaft. Furthermore, depending on the arrangement of a thrust bearing in a turbine, complete dismantling of a rotor, and subsequent shipment to a repair site, can be required. In that particular example, a repair operation requires also shipment back of the rotor which takes a lot of time. This significantly increases the outage time of a turbine which creates prolonged lack of power or lack of operation of a particular industrial process.

[0009] The present disclosure provides examples of tools for machining a thrust collar that at least partially overcomes some of the aforementioned drawbacks. Furthermore, methods for in-situ repairing of a thrust collar by using such tools are also provided in the present disclosure.SUMMARY

[0010] In an aspect of the present disclosure, a tool for machining a thrust collar of a rotor shaft of a turbine is provided. Said turbine can be a steam turbine or a gas turbine. The tool comprises a support and an annular unit connected to the support. The annular unit is configured for being positioned around the rotor shaft and it comprises a static ring and a rotatable ring. The rotatable ring is configured to rotate relative to the static ring. Furthermore, a cutting tool is connected to the rotatable ring. Furthermore, the support is configured to withstand the loads induced by the cutting tool during machining of the thrust collar.

[0011] According to this aspect, a highly versatile repair tool is provided. The arrangementof an annular unit around the rotor shaft allows operations on the thrust collar to be carried out in situ. This enables machining without the need to dismantle a rotor, a rotor shaft, or turbine. Additionally, it avoids the need to transport any dismantled parts to a repair shop for machining. It follows that the tool allows time savings as there is no need to dismantle and to assemble parts as well as to transport to and from a repair shop. This allows to shorten any servicing time needed and so to shorten any outage. In other words, the tool allows to restore power production faster.

[0012] The repair or machining tool comprising the support and the annular unit can be implemented in a highly compact manner, thus facilitating its integration in the surrounding area of the thrust collar. The support can be located as needed in the vicinity of the thrust collar and the annular unit can be mounted on the support such that access to the thrust collar is provided. The support may be dimensioned such that loads induced by the cutting tool are properly withstood. In particular, both the mechanical parts of the support itself, and the fixations to the annular unit and to the corresponding base element, e.g. the ground or the rotor itself, may be dimensioned to allow a proper absorption and / or transfer of loads.

[0013] Furthermore, a plurality of repair operations can be implemented by adapting the cutting tool connected to the rotatable ring of the annular unit, thus increasing the flexibility of the repair tool. By providing a rotatable ring, an efficient repair operation, e.g. machining, over the complete circumference of the thrust collar can be carried out by simply rotating the rotatable ring and, accordingly, the corresponding cutting tool connected to it.

[0014] In anotheraspect of the present disclosure, a method for in-situ machining of a thrust collar of a rotor shaft of a turbine is provided. The method comprises removing a thrust bearing from the turbine, i.e. from the rotor shaft of the turbine. The method also comprises providing a support and an annular unit. The annular unit comprises a static ring and a rotatable ring configured to rotate relative to the static ring and the rotatable ring carries a cutting tool. The support is configured to withstand the loads induced by the cutting tool during machining of the thrust collar. The annular unit is attached to the support in such a way that the annular unit is positioned around the rotor shaft. The method further comprises bringing the cutting tool into contact with the thrust collar at a first position. Furthermore, the method comprises rotating the rotatable ring to carry out a repair operation, e.g. a machining operation, on the thrust collar with the cutting tool.

[0015] According to this aspect of the disclosure, a convenient method is provided which allows repair of the thrust collar without requiring dismantling of the rotor, the rotor shaft, or complete rotor. Avoiding the need to dismantle the rotor, the rotor shaft, or the entire turbine represents enormous time savings and cost reduction. Because the repair can be carried outin situ, there is also no need to transport machinery to a specific repair shop. This all allows to perform any servicing activities faster and so to restore power production faster.

[0016] The method according to this aspect of the present disclosure comprises removing the thrust bearing. Accordingly, in an example of the disclosure, the space vacated by the thrust bearing may be used to, at least partially, arrange the repair or machining tool, thus allowing an in-situ repair operation. Besides, the compact design of the tool facilitates integration in the turbine.

[0017] Throughout this disclosure, the term "thrust" or "thrust load" should be understood as an axial load in a direction of the rotational axis of a rotor or rotor shaft (or substantially parallel thereto), resulting from a non-zero sum of local axial loads. Furthermore, a cutting tool may herein be understood as any tool that is used to cut, shape, and / or remove material from a workpiece by means of machining tools as well as any abrasive tools by way of shear deformation. As is known by a skilled person, a cutting tool is made of a material that is harder than the workpiece to be machined. Moreover, machining is understood as any process of shaping metal pieces through the removal of material. Typically, machining is carried out to obtain precise and accurate parts according to specific requirements such as surface finish specifications. Examples of machining that may be carried out with examples of the tools herein provided include milling, grinding, polishing, and others.

[0018] Additional objects, advantages and features of examples of the present disclosure will become apparent to those skilled in the art upon examination of the description, or may be learned by practice.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended figures, in which:Figure 1 schematically illustrates a cross-sectional side view of a turbine;Figure 2 schematically illustrates a simplified side view of a thrust bearing assembly;Figures 3A-3C schematically illustrate perspective views of an example of a tool for machining a thrust collar in assembled (3A-3B) or exploded (3C) views;Figure 4 schematically illustrates an upper half of a first ring of a support of a tool for machining a thrust collar according to an example;Figure 5 schematically illustrates a front view of an example of a first ring of a support of a tool for machining a thrust collar;Figure 6 schematically illustrates an upper half of a second ring of a support of a tool for machining a thrust collar according to an example;Figure 7 schematically illustrates, in an exploded view, an example of an annular unit of a tool for machining a thrust collar;Figure 8 schematically illustrates a detail of an example of a connection between an annular unit and a support of a tool for machining a thrust collar;Figure 9 schematically illustrates an example of an arrangement of a tool holder for holding a cutting tool on a rotatable ring of an annular unit of a tool for machining a thrust collar;Figure 10 schematically illustrates an example of a tool holder for holding a cutting tool;Figures 11 A-11 B schematically illustrate another example of a tool holder for holding a cutting tool in two different perspective views;Figure 12 is a flow chart of a method for repairing a thrust collar according to an example;Figures 13A-13D schematically illustrate different stages in a method for repairing a thrust collar according to an example.DETAILED DESCRIPTION OF EXAMPLES

[0020] Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the teaching. For instance, features illustrated or described as part of one embodiment in this description, claims and I or figures can be used with another embodiment disclosed in the description, claims and / or figures to yield a still further embodiment that is part of this disclosure. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0021] With reference to the drawings, Figure 1 shows a cross-sectional side view of a typical double flow steam turbine 1000, comprising a high-pressure (HP) section 1100, anintermediate-pressure (IP) section 1200, and a low-pressure (LP) section with a first LP section 1420 and a second LP section 1440A generator 1520 is connected to a rotor 101 extending through HP section 1100, IP section 1200, and LP sections 1420, 1440.

[0022] In other embodiments, the steam turbine 1000 can have a different configuration. In other or same embodiments, the steam turbine 1000 may include a high-pressure (HP) section 1100 and a low-pressure section 1400 without an intermediate pressure section 1200. In other embodiments, the steam turbine 1000 may include only a high-pressure (HP) section 1100. In other embodiments, a gas turbine is used.

[0023] The steam turbine 1000 also includes a thrust bearing 152. Thus, in order to secure an axial position of the rotor 101 on which the different turbine sections are mounted, one or more thrust bearings 152 may be used. Thrust bearings 152 may be located at any point along the rotational rotor 101 , but locations with relatively small oscillation amplitudes (perpendicular to the axis of rotation of the rotational rotor 101) may be generally preferred. A thrust bearing 152 might also be located between stages of a turbine 1000. Alternatively, a thrust bearing 152 may be located downstream of the stages of the turbine and upstream of the power generation unit.

[0024] Figure 2 is a side view of a thrust bearing 152 mounted on a rotational rotor 101 of a turbine. In an example, the turbine may be a steam turbine, such as depicted in Figure 1 , or other turbomachinery.

[0025] The rotor 101 may run through an open space defined by the thrust bearing 152. The thrust bearing 152 may be coupled to a fixed structure of a turbine, e.g. a bedplate (not illustrated for reasons of simplicity), or it may be anchored to another stationary component of the system. The thrust bearing 152 may form a low friction rotational coupling with a thrust collar 106 of the rotor 101 whereas, at the same time, it may ensure the axial position of the rotor 101.

[0026] The thrust bearing 152 of the example shown in Figure 2 may comprise a plurality of thrust pads 104, 105 configured to support an axial load acting on the thrust collar 106 of the rotor 101. The plurality of thrust pads 104, 105 may be distributed circumferentially around the rotor 101 . A first set of thrust pads 104 may be arranged facing a first surface of the thrust collar 106 whereas a second set of thrust pads 105 may be arranged facing an opposite surface of the thrust collar 106. During operation, axial loads acting on the rotor 101 may push the rotor 101 in the axial direction such that either the first set of thrust pads 104 or the second set of thrust pads 105 may be actively supporting the rotor 101. Accordingly, an active side may be defined for the thrust bearing 152. On the other hand, the inactive side of the thrust bearing152 may correspond to the side that is not directly subjected to axial loads, so that the corresponding thrust pads do not actively support the rotor 101. In any case, the definition of the active and the inactive side may change during operation as the axial loads acting on the rotor 101 may change direction due to different operating conditions.

[0027] The thrust bearing 152 may also comprise a structural base 102 configured to carry the thrust pads 104, 105. The structural base 102 may comprise two structural bases 102a, 102b configured to be located at a first side and at a second side of the thrust collar 106. Furthermore the structural base 102 may also comprise a housing 131 configured to, at least partially, enclose the thrust collar 106. The housing 131 may extend axially from the first side to the second side of the thrust collar 106. The housing 131 may also enclose the two structural bases 102a, 102b.

[0028] In examples, the thrust pads 104, 105 may be made of steel faced with a tin-based babbitt metal (white metal). Alternative materials may be copper / chrome pads comprising a coating of babbitt, steel pads comprising a coating of aluminum tin, steel pads comprising a coating of polymer, solid polymer pads or steel pads comprising a coating of ceramic or cermet, among others. The thrust collar 106 may be made of steel. In other embodiments, the thrust bearing 152 is as described in any of embodiments disclosed in PCT / EP2022 / 088092.

[0029] During operation, different factors, such as misalignment between the thrust collar 106 and the thrust pads 104, 105, rapidly changing directions in the axial loads, or inadequate lubrication, may result in mechanical wear and damage of the thrust collar 106 and, more particularly, of the opposite surfaces of the thrust collar 106 configured to contact the thrust pads. For this reason, regular inspection may be carried out and repair operations may be conducted to restore the mechanical and structural properties desired for the thrust collar 106.

[0030] Figures 3A-3C provide a schematic perspective view of an example of a tool 10 for machining of a thrust collar 106. Thus, as shown in more detail below, the tool 10 may be arranged in the vicinity of a thrust bearing 152 so as to conduct maintenance and repair of thrust collars. Figures 3A and 3B provide schematic perspectives along different angles whereas Figure 3C provides an exploded view of the same tool 10.

[0031] The tool 10 for machining a thrust collar 106 of a rotor of a turbine (e.g., steam or gas turbine) shown in Figures 3A-3C comprises a support 20 and an annular unit 30 connected to the support 20. The annular unit 30 is configured for being positioned around the rotor (not shown) and it comprises a static ring 31 and a rotatable ring 32 configured to rotate relative to the static ring 31. Furthermore, a cutting tool 51 is connected to the rotatable ring 32 of the annular unit 30.

[0032] By providing a cuting tool 41 in the rotatable ring 32, a convenient repair operation may be carried out. Hence, access to the whole circumference of the thrust collar 106 can be achieved by rotating the rotatable ring 32 with respect to the static ring 31. Furthermore, in order to provide mechanical stability during the operation, a support 20, which remains static or stationary, is provided. The support 20 is configured to withstand the loads induced in the tool during repair operations e.g. machining of the surfaces of the thrust collar 106 to achieve a desired surface quality. Said configuration can include being dimensioned.

[0033] In an example, the support 20 may comprise a first substantially annular support member 21 configured for being mounted around the rotor (not shown). The first substantially annular support member 21 may comprise one or more adjustable clamps 211 for clamping to the rotor.

[0034] Figure 4 provides an example of such a first annular support member 21 . As shown in Figure 4, the clamps 211 may comprise a clamp holder 212 and a clamp block 213. The clamp block 213 may be configured to engage a rotor of a turbine. In order to provide a proper fixation to the rotor, the clamps 211 may comprise a clamp bolt 214 to adjust the precise position of the clamp block 213 with respect to the rotor.

[0035] By fixing the support 20 to the rotor, an accurate positioning between the thrust collar 106 and the tool 10 for machining the thrust collar 106 may be provided. The thrust collar 106 may either be attached or be integrally formed with the rotor. By fixing the support 20 and, consequently the tool 10, to the same system of reference, an improved alignment may be achieved.

[0036] Furthermore, the use of the rotor as a base for the tool 10 may also avoid the need of additional systems serving as a foundation. Accordingly, less parts may be required to conduct repair operations, thus reducing time and cost associated with such operations.

[0037] Adjustable clamps 211 may allow usage of the same tool 10 with different turbines. Particularly, adjustable clamps 211 may ensure proper fixation of the tool 10 to different rotors and, more particularly, to rotors exhibiting different dimensions, i.e. diameters.

[0038] In an example, a locking device may be provided to prevent rotation of the rotor 101 during the repair operation. In other words, an element preventing rotation of the rotor of the turbine and, consequently, of the rotor 101 , may be used to ensure the support 20 remains stationary during the machining operations.

[0039] As also shown in Figure 4, in an example, the first substantially annular support member 21 of the support 20 may comprise one or more centering blocks 215. The centering blocks 215 may be used to, at least partially, hold the annular unit 30. A plurality of, e.g. four,centering blocks 215 may be distributed over the circumference of the first substantially annular support member 21. In this manner, an enhanced control over the precise positioning of the annular unit 30 may be obtained. To this end, at least some of the centering blocks 215 may comprise a centering screw 216. The centering screws 216 may be used to adjust the position of the annular unit 30 and, consequently, the position of the rotatable ring 32, holding the cutting tool 41 , with respect to the center of the rotor or the rotor 101 of the turbine. This adjustment is especially relevant for servicing of older units with rotors that do not have perfect geometries.

[0040] Figure 5 schematically depicts an example of a first substantially annular support member 21 comprising four clamps 211 in a front view. The provision of four clamps 211 distributed over the circumference of the first substantially annular support member 21 provides a uniform and balanced fixation to the rotor shaft. In other examples, a different number of clamps 211 , or other attachment elements or systems for mounting the support on the rotor may be envisaged. Additionally, the clamps 211 allow to use the tool 10 at rotors of different sizes, i.e. , at machines of different power output. That provides flexibility as a single tool can be used for machines at the industrial level and at high-output power plants.

[0041] As already described with reference to Figure 4, the clamps 211 may comprise a clamp bolt 214 to adjust the precise position of the clamp block 213 of each clamp 211. In some examples comprising multiple clamps 211 , the clamp bolt 214 of each clamp 211 may be individually controlled so as to obtain a more precise and robust attachment to the rotor 101 . The tool is thus easily adjustable to different sized rotors / rotor shafts.

[0042] As shown in the exploded view of Figure 3C, the first substantially annular support member 21 may be split into a plurality of segments. Particularly, the first substantially annular support member 21 may be split into two half segments. Once in its operating state, the two half segments may define a bottom half and an upper half of the first substantially annular support member 21 . Figure 3C shows both the bottom half and the upper half whereas Figure 4 provides a more detailed view of the upper half of the first substantially annular support member 21.

[0043] Segmenting the first annular support member 21 may provide different technical effects. On the one hand, manufacturing, transportation and storing of the first annular support member 21 may be facilitated by reducing the overall dimensions of the tool 10 in the unmounted state. Furthermore, in examples of the disclosure, the different segments may be substantially equal. Thus, in cases comprising an upper half and a bottom half, these may be symmetrical and / or identical, which may facilitate manufacturing and handling of the machining tool 10.

[0044] On the other hand, installation of the first annular support member 21 may also be simplified when using segments. In particular, by segmenting the first annular support member 21 into, e.g. two parts, the tool can be more easily mounted around the rotor in an already assembled machine. As an example, a bottom half part may firstly be arranged underneath the rotor 101. Subsequently, the upper half may be arranged resting on the previously arranged bottom half and, finally, both parts may be fixed to each other. Accordingly, an effective installation may be obtained which may in particular allow in-site mounting of the first annular support member 21 around the rotor shaft without dismounting the rotor, the rotor shaft, or any other part of the rotor of the turbine.

[0045] Apart from the first substantially annular support member 21 , a second substantially annular support member 22 may also be provided as shown in Figures 3A-3C. Thus, in an example, the support 20 may comprise a second substantially annular support member 22 configured for being mounted around the rotor shaft (not shown). The second substantially annular support member 22 may comprise one or more adjustable clamps 221 for clamping to the rotor 101. Besides, the second annular support member 22 may be fixed to the first annular support member 21.

[0046] The use of a second substantially annular support member 22 may be particularly advantageous in cases requiring significant forces for the repair operation, i.e. for machining a surface of the thrust collar 106. Indeed, a single annular support member 21 may be enough for repair operations with lower loads. Nevertheless, two annular support members provide a better balancing of the force from, e.g. machining. Consequently, a faster machining is carried out. Thus, in order to keep machining forces within limits, an option may comprise using a very low rotational speed during the machining. Nevertheless, this would increase the time required for the operation and, consequently, the associated outage time.

[0047] In examples comprising a single annular support member 21 for the support 20, the size of such single annular support member 21 may be selected so as to achieve the required capability to withstand forces endured during the repair operation.

[0048] As with the first substantially annular support member 21 , the second substantially annular support member 22 may also be split into multiple segments and, more particularly, into two halves. Figure 6 provides a schematic representation of the upper half (in its mounted state) of the second substantially annular support member 22 according to an example. The adjustable clamps 221 may comprise a clamp holder 222 and a clamp block 223, the latter being configured for connection to the rotor. Furthermore, screws 225 may be used to fix the clamp holder 222 to the body of the second substantially annular support member 22. A clamp bolt 224 may also be provided to finely adjust the position of the clamp block 223 with respectto the rotor.

[0049] In an example of the present disclosure, and as shown in the exploded view of Figure 3C, the tool 10 may comprise one or more connection shafts 23 to connect the first substantially annular support member 21 and the second substantially annular support member 22.

[0050] In examples, a distance between the first annular support member 21 and the second annular support member 22 may be adjustable by adjusting the position of the first substantially annular support member 21 and the second substantially annular support member 22 along the connection shafts 23. In other examples, the connection shafts may be telescopic to adjust a distance between the annular support members. In yet further examples, different shafts with different lengths may be provided to adjust a distance between annular support members.

[0051] The use of such connection shafts 23 provides increased flexibility to the tool. Thus, the length of the connections shafts 23 may be adjusted to the space available for the servicing of the thrust collar 106. In cases comprising sufficient space, the use of comparatively larger connection shafts 23 results in an enhanced capability of the support 20 to withstand loads. Accordingly, a faster repair operation or machining is be obtained which shortens the outage time.

[0052] The same first 21 and second 22 substantially annular support members may then be used for operation in different types of turbines, exhibiting different layouts. Hence, the connection shafts 23 may be used to adapt the overall dimension of the tool 10 for machining thrust collars to the available space.

[0053] In the example depicted in Figure 3C, ten connection shafts 23 are provided. Nevertheless, a different number of connection shafts 23 may be used depending on the requirements of the specific application. Furthermore, the diameter of the connection shafts 23 may also be selected to ensure proper structural and mechanical behavior and, particularly, a proper connection between the first substantially annular support member 21 and the second substantially annular support member 22.

[0054] In an example, receptacles 226 may be provided to accommodate the connection shafts 23. Figure 6 shows an example of such receptacles 226 for the second substantially annular support member 22. Similar receptacles may be provided in the first substantially annular support member 21. In the example depicted in Figure 6, the receptacles 226 may comprise blind bores. Accordingly, in order to adjust the separation between the first substantially annular support member 21 and the second substantially annular support member 22, a set of connection shafts 23 of different lengths may be provided. Hence, thedistance may be simply adjusted by selecting connection shafts 23 of the desired length.

[0055] Nevertheless, any other type of receptacle or holding system may be provided. In particular, open holes may be provided and fixation by means of, e.g. screws, may be enabled. In this manner, the distance between the first substantially annular support member 21 and the second substantially annular support member 22 may be adjusted by sliding the first substantially annular support member 21 and / or the second substantially annular support member 22 along the connection shafts 23 before fixation.

[0056] Figure 7 schematically illustrates an example of an annular unit 30. In an example, the static ring 31 and the rotatable ring 32 of the annular unit 30 may be split into segments. Particularly, the static ring 31 and the rotatable ring 32 may be split into two half segments which, in the operating state, may correspond to a bottom half and an upper half of the static ring 31 and the rotatable ring 32.

[0057] The split of the rings of the annular unit 30 into segments may provide similar advantages to those already described with respect to the segmentation of the first 21 and second 22 substantially annular support members of the support 20. In particular, the provision of the rings into at least two segments may facilitate the in-situ operation of the tool 10 for machining a thrust collar by enabling the arrangement of the different rings around the rotor without requiring any dismounting of the rotor, or any other parts of the turbine.

[0058] In order to permit rotation of the rotatable ring 32, the rotatable ring may be rotatably mounted with respect to the static ring 31 by means of rolling or sliding elements. In the example shown in Figure 7, rollers 311 may be used to enable rotation between the rotatable ring 32 and the static ring 31. To this end, a groove 322 may be arranged in the rotatable ring 32. The groove 322 may be dimensioned so as to fit a plurality of rollers 311 , thus serving as a guide for the rotational movement. Generally speaking, the rotatable ring 32 and the static ring 31 may be associated to the rotating and static ring of a bearing system. Accordingly, any kind of rolling or sliding elements may be envisaged.

[0059] Different types of bearing elements may be used to provide adequate capability to withstand axial and / or radial loads. In particular, roller bearings may be chosen in an example due to their capability to withstand heavy radial loads. Thus, depending on the repair operation, e.g. machining of the coupling surfaces of the thrust collar 106, very heavy radial loads may be transmitted to the tool 10. In such case, the provision of rollers 311 between the static ring 31 and the rotatable ring 32 of the annular unit 30 may become advantageous. On the other hand, ball bearings may be used for applications involving lighter loads.

[0060] As also shown in the exploded view of Figure 7, the annular unit 30 in an examplemay comprise an adjusting ring 33. The adjusting ring 33 may be connected to the static ring 31 of the annular unit 30 and to the support 20 in such a way that a position and / or orientation of the adjusting ring 33 with respect to the support 20 may be adjustable.

[0061] In examples comprising such an adjusting ring 33, the adjusting ring 33 may serve at least two purposes. On the one hand, the adjusting ring 33 may increase the stiffness of the annular unit 30. On the other hand, the adjusting ring 33 may be used to help obtain precise alignment between the different parts. Thus, the adjusting ring 33 may act as the interface between the support 20 and the annular unit 30, i.e. between the first substantially annular support member 21 and the static ring 31. Adjustment may be used to ensure a proper alignment between the cutting tool 41 and the thrust collar 106. In order to provide the adjusting capability, the connection between the adjusting ring 33 and the first annular support member 21 may comprise different degrees of freedom. Thus, as shown in more detail below, the connection may allow both axial displacement in the direction of the rotor and radial displacement in a plane substantially perpendicular to the rotor.

[0062] Regarding adjustment in the radial direction, Figure 4 and Figure 5 schematically show an example in which the support 20 and, more particularly, the first substantially annular support member 21 of the support 20, may comprise a plurality of adjustable centering blocks 215 for at least partially holding the adjusting ring 33. In particular, the plurality of adjustable centering blocks 215 may be configured to adjust the position of the adjusting ring 33 in a plane substantially perpendicular to the rotor (not shown). In order to adjust the position, centering screws 216 may be provided. Thus, each of the centering blocks 215 may comprise a centering screw 216 and the centering screws 216 may be finely adjusted to move the adjusting ring 33 and, consequently, the annular unit 30 including the cutting tool 41 , in a plane perpendicular to the rotor. Such movement may allow, in particular, a precise concentric alignment between the center of the rotatable ring 32 holding the cutting tool 41 and the rotor 101. A different number of centering blocks 215 with centering screws 216 may be provided to achieve a proper control over the positioning of the adjusting ring 33. In an example, four centering blocks 215 can be envisaged.

[0063] In examples not comprising an adjusting ring 33, a similar adjustment may be obtained by engaging the centering blocks 215, with the corresponding centering screws 216, with the static ring 31 of the annular unit 30.

[0064] Figure 8 shows an example of another aspect of a connection between an adjusting ring 33 of the annular unit 30 and a first substantially annular support member 21. Apart from the centering blocks 215 depicted in Figure 5, a plurality of axial screws 217 may be provided to enable the fixation. Thus, in an example, a tool 10 may be provided wherein one or moreaxial screws 217 may be arranged to connect the adjusting ring 33 and the support 20 in an axial direction. The axial screws 217 may be configured to adjust a relative position in an axial direction of the adjusting ring 33 with respect to the support 20. To this end, a push-pull function may be implemented as shown in Figure 8 to provide a degree of freedom in the axial direction. The axial screws 217 may be configured as pull screws and corresponding tilt bushings 218 may be configured as push screws. The push-pull function may be used to finely adjust the axial position of the adjusting ring 33 and, consequently, the axial position of the annular unit 30. This function is especially relevant for older units with rotors that do not have perfect geometries.

[0065] A push-pull function may be individually provided in a plurality of axial screws 217. In this manner, not only an axial position but also an inclination with respect to a plane that is substantially perpendicular to the longitudinal axis of the rotor may be adjusted. The number of axial screws 217 may be varied depending on the required stiffness in the connection between the support 20 and the annular unit 30. In the example shown in Figure 4, four axial screws 217 are shown for the upper half of the first substantially annular support member 21 , which corresponds to a total number of eight axial screws 217. A larger number of axial screws 217, e.g. twelve or sixteen, may be preferred to increase the stiffness.

[0066] As shown in Figures 7, 8 and 9, in an example of the present disclosure, the rotatable ring 32 of the annular unit 30 may comprise an annular gear 321 on its radially outer surface. The annular gear 321 or crown may be configured for being driven by a pinion (not shown). In an example, a pinion may be driven by a motor. In this manner, a highly effective system may be provided for the rotation of the rotatable ring 32. Furthermore, an electronic drive, e.g. a variable frequency drive, may be included to control the motor, thus increasing the control over the machining operation. In other examples, different actuation systems, not requiring an annular gear, may be provided. Thus, in an example, an arrangement comprising belts and pulleys may be employed.

[0067] Figure 9 schematically illustrates an example of an arrangement of a tool holder 40 for holding a cutting tool 41 . The tool holder 40 may be connectable to the rotatable ring 32 of the annular unit 30. In particular, a support 46 may be provided to connect the tool holder 40 to the rotatable ring 32. In other examples, the support 46 may be integrally formed with the rotatable ring 32. Figure 10 provides a more detailed view of the tool holder 40 according to an example. The tool holder 40 may be provided with at least two degrees of freedom, such that the position of the cutting tool 41 may be adjustable in an axial direction substantially parallel to the rotor and in a radial direction substantially perpendicular to the axial direction. In an example, a star wheel 43 may be provided as a tool feed to adjust the radial position of thecuting tool 41 . The tool holder 40 may comprise a yoke 42 for carrying the cuting tool 41 and a guiding mechanism 44, e.g., a guide, to enable precise movement of the yoke 42 and, consequently, of the cutting tool 41 , along the radial direction.

[0068] In a variant, the star wheel 43 may be manually actuated to adjust the radial position of the cutting tool 41 along the guide 44. In another variant, an automatic actuation may be provided. In particular, a punching point or protrusion may be provided in the static ring 31 at a certain angular position, e.g. at an uppermost position, i.e. a twelve o’clock position. The punching point may be configured to engage the star wheel 43 as the tool holder 40 reaches the predetermined angular position upon rotation of the rotatable ring 32, i.e. when the tool holder 40, including the star wheel 43, is facing the punching point disposed in the static ring 31 . The punching point may engage with one of the teeth or grooves of the star wheel 43, thus inducing a rotational movement of the star wheel 43. Such rotational movement may be transferred as a longitudinal movement of the cutting tool 41 in a radial direction, i.e. along the guiding element 44.

[0069] The dimensions of the star wheel 43 and the number of teeth or grooves may be selected so as to control the degrees of the rotational movement of the star wheel 43 and, consequently, to control the radial displacement of the cutting tool 41 for each actuation, i.e. for each rotation of the rotatable ring 32. In this manner, the machining of the thrust collar may be carried out in subsequent steps as the radial position of the cutting tool 41 is adjusted at each rotation. Subsequent steps may comprise machining of the thrust collar in substantially concentric machining rings.

[0070] A further mechanism 45 may be provided to adjust the axial position of the cutting tool 41 .The axial position of the cutting tool 41 may be finely controlled to adjust the cutting depth of the machining process.

[0071] In the example shown in Figure 9, the tool holder 40 may be attached to the rotatable ring 32. Nevertheless, in other examples, the tool holder 40 may be integrally formed with the rotatable ring 32. By having a separate tool holder 40, increased flexibility can be provided as the tool holder 40 may be adapted to the cutting tool 41 intended for use in the machining operation.

[0072] Another exemplary tool holder 50 is schematically shown in Figures 11A and 11 B. As in the previous example, the tool holder 50 may be configured to hold a cutting tool 51. The tool holder 50 may comprise a support 56, used to connect the tool holder 50 to the rotatable ring 32. The tool holder 50 depicted in Figures 11A-11 B may also exhibit at least two degrees of freedom, such that the position of the cutting tool 51 may be adjusted in an axial directionsubstantially parallel to the rotor and in a radial direction substantially perpendicular to the axial direction.

[0073] In order to move the cutting tool 51 in the radial direction, an actuator or lever 53 may be provided. The lever 53 may be connected to a feed spindle 57 via a free wheel coupling 60. The free wheel coupling 60 may allow transmission of a rotational movement of the lever 53 only when the lever 53 is rotated in a certain direction. In this example, actuation, i.e. rotation, of the lever 43 in a first direction may result in a longitudinal movement of the feed spindle 57, which may translate into a radial displacement of the yoke 52 carrying the cutting tool 51. In order to control the magnitude of the radial displacement, both the spindle pitch and the rotation angle of the lever 53 may be optimized.

[0074] In a variant of the example shown in Figures 11 A-11 B, the lever 53 may be actuated manually. Nevertheless, as in the example shown in Figures 9 and 10, another variant may involve an automatic adjustment of the radial position. To this end, the tool holder 50 may comprise a starting position bolt 58 and a spring 59. The starting position bolt 58 may be adjusted so that the lever 53 is, at its initial or resting position, rotated by a certain desired angle. Then, a punching point or pin may be arranged at a defined angular position, such as at an uppermost position, i.e. a twelve o’clock position, in the static ring 31 . The punching point may be configured to push the lever 53 as the latter faces the punching point during rotation of the rotatable ring 32. The actuation of the punching point on the lever 53 may induce a rotation of the feed spindle 57. The rotation of the feed spindle 57 may then translate into a longitudinal movement of the yoke 52 carrying the cutting tool 51 along the guide 54, i.e. a longitudinal movement in the radial direction.

[0075] In order to restore the initial or resting position of the lever 53, a restoring spring 59 may be employed which applies biasing force on the lever 53 to return to the initial position. The spring 59 is shown in a disconnected state in Figures 11A-11 B but it is understood that the spring 59 may be connected to the lever 53 by, e.g. engaging with an orifice in the lever 53. The free wheel coupling 60 may be such that the rotational movement of the lever 53 when returning to its initial position as a result of the action of the spring 59, i.e., a rotational movement in an opposite direction to the rotational movement induced by the engagement with the punching point, may not be transferred to the feed spindle 57. Consequently, the radial position of the cutting tool 51 may be maintained until the next rotation, i.e. until the tool holder 50 reaches again the position of the punching point so that the lever 53 faces the punching point. When such positions is met again, the lever 53 is actuated so that the cutting tool 51 is displaced a bit further in the radial direction.

[0076] Similarly as for the tool holder 40 explained with reference to Figures 9 and 10, thedescribed actuation may result in a machining of the thrust collar in substantially concentric rings as the radial position of the cutting tool 51 is adjusted at subsequent rotations. The size of such concentric rings may be adjusted. As an example, the pitch of the spindle feed 57 and the angle of the lever 53 may be selected such that the radial displacement of the cutting tool 51 may be in a range from 0,05 to 0,20 mm per rotation. Specifically, the angle of the lever 53 may be adjusted to approximately 20° whereas the pitch of the spindle feed 57 may be in the range of 1 ,5 mm per revolution.

[0077] In a variant of the example shown in Figures 11A-11 B, a plurality of punching points or pins may be distributed over the circumference of the static ring 31. For instance, four different punching points may be arranged spaced apart by 90°. In such case, the radial position of the cutting tool 51 may be adjusted at each quarter of rotation. In order to avoid excessive radial displacements per rotation, a lower angle, e.g. 5° instead of 20°, may be used as the starting position for the lever 53. The tool holder 50 may comprise a mechanism 55 to adjust the axial position of the cutting tool 51. Such mechanism may be controlled to adjust the cutting depth during the machining operation. Indeed, accurate adjustment may be desired to increase the quality of the repair operation. In particular, a high precision may be required to ensure adequate levels of flatness on the resulting surfaces upon machining. The ability to control the axial relative position between the surface of the thrust collar to be treated and the cutting tool may provide control during the repair operation as, in particular, the axial position may be varied during the machining itself so as to control the cutting depth.

[0078] Similarly, the radial adjustment may be used to limit the extent of the area treated during the repair operation. As in the axial case, the radial relative position between the thrust collar and the cutting tool may be adjusted, not only in preparation of the repair operation, but also during the repair operation itself. As an example, a repair operation may be envisaged wherein a surface treatment, e.g. machining, is initiated at an outer radius of the thrust collar. Subsequently, the surface treatment may continue radially inwards, i.e. towards the center of the thrust collar.

[0079] Figure 12 shows a flow chart of an example of a method 100 for in-situ machining of a thrust collar 106 of a rotor 101 of a turbine. The method 100 comprises, at block 110, removing a thrust bearing 152 from the turbine. In this example, a support 20 is provided at block 120 and an annular unit 30 is provided at block 130. The annular unit 30 comprises a static ring 31 and a rotatable ring 32 configured to rotate relative to the static ring 31. Furthermore, the rotatable ring 32 carries a cutting tool 41.

[0080] The method 100 further comprises, at block 140, attaching the annular unit 30 to the support 20 such that the annular unit 30 is positioned around the rotor 101. Block 150comprises bringing the cuting tool 41 into contact with the thrust collar 106 at a first position. Subsequently, at block 160, the method 100 comprises rotating the rotatable ring 32 to carry out a machining operation on the thrust collar 106 with the cutting tool 41.

[0081] The method 100 offers significant flexibility as the thrust collar can be repaired in- situ. Hence, there is no need to dismantle the rotor from the turbine and send it to a repair site or some dedicated factory.

[0082] Even if the different blocks of method 100 have been presented in a certain order, it is understood that this order is not to be interpreted as a limiting sequence. Thus, the order of some of the blocks or steps may be modified. Furthermore, different blocks may be modified as understood by those skilled in the art. As an example, providing a cutting tool 41 on the rotatable ring 32, may be carried out either before or after attaching the annular unit 30 to the support 20 in block 140.

[0083] In examples, the method for in-situ repairing of a thrust collar may be such that, providing a support 20 in block 120, and providing an annular unit 30 in block 130, may comprise providing at least one of the support 20 and the annular unit 30 at least partially in a space previously occupied by the removed thrust bearing 152. Such an example is schematically depicted in Figures 13A-13D. Thus, Figure 13A corresponds to the initial situation wherein the thrust bearing 152 is still arranged at its working position. Figure 13B schematically depicts the situation after block 110 of the method 100, i.e. after removal of the thrust bearing 152. Subsequently, and as shown in Figure 13C, the tool 10 for repairing a thrust collar is arranged in the space that was previously occupied by the thrust bearing 152.

[0084] The arrangement in the space previously occupied by the thrust bearing 152 may provide some advantages. The space vacated after removal of the thrust bearing 152 may, in some cases, be enough to accommodate the tool 10. In this manner, a more compact repair operation, not requiring additional space, may be provided. Furthermore, the space where the thrust bearing 152 was mounted may comprise certain features, e.g. anchors or brackets, that may be used in the fixation of the support 20 of the tool 10 for machining thrust collars.

[0085] In an example, the support 20 may comprise at least an annular support member 21 with clamps 211 extending radially inwards. Providing the support in accordance with block 120 may comprise attaching the support 20 to the rotor by means of the clamps 211. The annular support member 21 may be split into several segments as illustrated before.

[0086] In this example, the clamps 211 may be adjusted individually to improve a precise fixation of the support 20 to the rotor. During the machining operation, the rotor system of the turbine and, more particularly, the rotor, may be locked so as to prevent unwanted rotation.The anti-rotating locking may be enough to withstand forces occurring during, e.g. machining of the thrust collar surfaces.

[0087] As already mentioned, a thrust bearing 152 may comprise an active side and an inactive side. Nevertheless, both surfaces of the thrust collar 106 may require maintenance and / or machining operations. Accordingly, in an example of a method (shown in Figures 13C and 13D), the method may comprise providing the support 20 and the annular unit 30 at a first side of the thrust collar 106 to carry out a repair operation on a first surface of the thrust collar 106 (see Figure 13C). Subsequently, the method may comprise dismantling the support 20 and the annular unit 30 from the first side and providing them on a second side of the thrust collar 106 to carry out a repair operation on a second surface of the thrust collar 106 (Figure 13D).

[0088] The versatility of the tool 10 described in the present disclosure may facilitate the consecutive machining operations on the two coupling surfaces of the thrust collar.

[0089] In another example, the annular unit 30 may comprise an adjusting ring 33 fixed to the static ring 31 as shown in Figures 7 or 8. The support 20 may comprise a plurality of adjustable centering blocks 215 as shown in Figure 5. Hence, in an exemplary method, attaching the annular unit 30 to the support 20 in block 140 may comprise holding the adjusting ring 33 at least partially with the adjustable centering blocks 215 and adjusting the position of the adjusting ring 33 in a plane perpendicular to the rotor with the adjustable centering blocks 215.

[0090] In examples, a tool holder 40 may be connected to the rotatable ring 32. Besides, bringing the cutting tool 41 into contact with the thrust collar at a first position may comprise adjusting an axial and / or radial position of the cutting tool 41 with the tool holder 40.

[0091] As already mentioned, the precise control of the relative position between the cutting tool 41 and the thrust collar 106 may be beneficial in order to carry out certain repair operations. This may be especially the case while conducting high precision machining of the surfaces of the thrust collar.

[0092] Different variants may be used to rotate the rotatable ring 32 of the annular unit 30. Thus, in an example, the rotatable ring 32 may comprise an annular gear 321. Accordingly, rotating the rotatable ring 132 in block 160 of the method 100 may comprise engaging a pinion driven by a motor with the annular gear 321 .

[0093] In examples of the method, axial adjustment of the cutting tool 41 to bring it into contact with a surface of the thrust collar 106 may comprise using on or more pull-push screws used for the connection of the support 20 and the annular unit 30 or, more particularly, betweena first substantially annular support member 21 of the support 20 and an adjusting ring 33 of the annular unit 30.

[0094] The tools, systems and methods disclosed in the examples of the present disclosure may be practiced in different kinds of turbines, including gas and steam turbines, and including impulse and reaction turbines. The methods and systems may further be practiced in any type of power plant as well as in industrial applications, including e.g. a fossil, renewable-energy, waste-to-energy, combined-cycle or nuclear powerplant comprising a steam turbine.

[0095] This written description uses examples to disclose the teaching, including the preferred embodiments, and also to enable any person skilled in the art to practice the teaching, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.

Claims

CLAIMS1. A tool for machining a thrust collar of a rotor shaft of a turbine, the tool comprising a support and an annular unit connected to the support, the annular unit being configured for being positioned around the rotor shaft and comprising: a static ring, a rotatable ring configured to rotate relative to the static ring, and a cutting tool connected to the rotatable ring, and wherein the support is configured to withstand the loads induced by the cutting tool during machining of the thrust collar.

2. The tool of claim 1 , wherein the support comprises a first substantially annular support member configured for being mounted around the rotor, and further comprises one or more adjustable clamps for clamping the rotor shaft3. The tool of claim 2, wherein the first substantially annular support member is split into a plurality of segments.

4. The tool of any of claims 2 or 3, wherein the support further comprises a second substantially annular support member configured for being mounted around the rotor, the second substantially annular support member comprising one or more adjustable clamps for clamping the rotor shaft, and wherein the second annular support member is fixed to the first annular support member.

5. The tool of claim 4, further comprising one or more connection shafts connecting the first annular support member and the second annular support member.

6. The tool of claim 4 or 5, wherein a distance between the first annular support member and the second annular support member is adjustable.

7. The tool of claim 6, wherein the distance between the first annular support member and the second annular support member is adjustable along connection shafts and / or byconnection shafts.

8. The tool of any of claims 1 - 7, wherein the static ring and the rotatable ring of the annular unit are split into segments, particularly into two half segments defining a bottom half and an upper half of the static ring and of the rotatable ring.

9. The tool of any previous claim, wherein the rotatable ring of the annular unit is rotatably mounted with respect to the static ring of the annular unit by means of rolling or sliding elements.

10. The tool of any previous claim, wherein the annular unit comprises an adjusting ring connected to the static ring of the annular unit and connected to the support in such a way that a position and / or orientation of the adjusting ring with respect to the support is adjustable.11 . The tool of claim 10, wherein the support comprises a plurality of adjustable centering blocks for at least partially holding the adjusting ring, wherein the plurality of adjustable centering blocks is configured to adjust the position of the adjusting ring in a plane substantially perpendicular to the rotor shaft.

12. The tool of any of claims 10 or 11 , wherein one or more axial screws are arranged to connect the adjusting ring and the support in an axial direction, the axial screws being configured to adjust an axial relative position between the adjusting ring and the support.

13. The tool of any previous claim, wherein the rotatable ring of the annular unit comprises an annular gear on a radially outer surface, the annular gear configured for being driven by a pinion.

14. The tool of any previous claim, comprising a tool holder for holding the cutting tool and connected to the rotatable ring, wherein the tool holder is provided with at least two degrees of freedom such that the position of the cutting tool is adjustable in an axial direction substantially parallel to the rotor and in a radial direction substantially perpendicular to the axial direction.

15. The tool of any previous claim, wherein the turbine is a steam turbine or a gas turbine.

16. The tool of any previous claim, wherein the turbine is installed at a fossil, gas, combined cycle, nuclear, and / or renewable power plant.

17. A method for in-situ machining of a thrust collar of a rotor of a turbine, the method comprising: removing a thrust bearing from the turbine; providing a support; attaching an annular unit to the support such that the annular unit is positioned around the rotor shaft, the annular unit comprising a static ring and a rotatable ring configured to rotate relative to the static ring, and the rotatable ring carrying a cutting tool, the support being configured to withstand the loads induced by the cutting tool during machining of the thrust collar; bringing the cutting tool into contact with the thrust collar at a first position; and rotating the rotatable ring to carry out a machining operation on the thrust collar with the cutting tool.

18. The method of claim 17, wherein at least one of the support or the annular unit are arranged at least partially in a space previously occupied by the removed thrust bearing.

19. The method of any of claims 17 or 18, wherein the support comprises an annular support member with clamps extending radially inwardly, and further wherein providing the support comprises attaching the support to the rotor shaft by means of the clamps.

20. The method of any of claims 17 to 19, comprising providing the support and the annular unit on a first side of the thrust collar to carry out a repair operation on a first surface of the thrust collar and, subsequently, dismounting the support and the annular unit from the first side and providing them on a second side of the thrust collar to carry out a repair operation on a second surface of the thrust collar.21 . The method of any of claims 17 to 20, wherein the annular unit comprises an adjusting ring fixed to the static ring and wherein the support comprises a plurality of adjustable centering blocks, and further wherein attaching the annular unit to the support comprises at least partially holding the adjusting ring with the adjustable centering blocks and adjusting the position of the adjusting ring in a plane perpendicular to the rotor with the adjustable centering blocks.

22. The method of any of claims 17 to 21 , wherein a tool holder is connected to the rotatable ring, and wherein bringing the cutting tool into contact with the thrust collar at a first position comprises adjusting an axial and / or a radial position of the cutting tool with the tool holder.

23. The method of any of claims 17 to 22, wherein the rotatable ring of the annular unit comprises an annular gear, and rotating the rotatable ring comprises engaging a pinion driven by a motor with the annular gear.

Images