Maintenance method for gas turbine

An exhaust-side journal bearing for supporting a gas turbine rotor is disposed inside a bearing box. The bearing box is supported by a strut which extends inward from an exhaust casing, and a seal ring having an annular inner peripheral end is disposed on the bearing box. Executed during a maintenance work are: a bearing adjustment step of displacing a bearing surface of the journal bearing relative to the bearing box in a perpendicular direction perpendicular to the axial direction; and a seal ring adjustment step of displacing the inner peripheral end of the seal ring relative to the bearing box in accordance with the direction of displacement and the amount of displacement of the bearing surface.

TECHNICAL FIELD

The present invention relates to a maintenance method for a gas turbine in which a gas turbine exhaust-side journal bearing supporting a gas turbine rotor is disposed in a bearing box.

BACKGROUND ART

A gas turbine includes a compressor that compresses outside air to generate compressed air, a combustor that mixes fuel with the compressed air and combusts a mixture of the fuel and the compressed air to generate combustion gas, and a turbine that is driven by the combustion gas. Each of the compressor and the turbine includes a rotor and a casing that covers the rotor. The casing of the compressor and the casing of the turbine are connected to each other and form a gas turbine casing. Further, the rotor of the compressor and the rotor of the turbine are connected to each other and form a gas turbine rotor. The gas turbine rotor is rotatably supported on both sides thereof in an axial direction by journal bearings.

Of the two journal bearings, the journal bearing which is disposed on the exhaust side of the gas turbine is covered with a bearing box as disclosed in, for example, Patent Document 1. The bearing box is fixed by a plurality of struts that extend from the bearing box in the tangential directions of the turbine rotor. End portions of the plurality of struts are fixed to an exhaust casing that forms a part of the casing of the turbine.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Technical Problem

In a technique disclosed in Patent Document 1, there is a case in which the plurality of struts are deformed due to the long-term operation of the gas turbine and the bearing box fixed to the plurality of struts is displaced in a perpendicular direction perpendicular to the axis of the gas turbine rotor. In this case, the journal bearing provided in the bearing box is also displaced in the perpendicular direction. As a result, the gas turbine rotor, which is present at a position where the journal bearing is disposed in the axial direction, is moved in the perpendicular direction. Further, there is also a case in which the bearing box is not installed at a target position in the perpendicular direction due to assembly errors, manufacturing errors, or the like of various components. In this case, the journal bearing, which is provided in the bearing box, is also not installed at the target position in the perpendicular direction. As a result, the gas turbine rotor, which is present at the position where the journal bearing is disposed in the axial direction, is not disposed at the target position in the perpendicular direction. In these cases, a method of moving the above-mentioned exhaust casing relative to a turbine body casing, which forms a part of the casing of the turbine, in the perpendicular direction or the like is considered. However, this method has problems in that a maintenance period is lengthened and maintenance costs are also increased.

Accordingly, the invention has been made in consideration of the above-mentioned problems, and an object of the invention is to provide a maintenance method for a gas turbine that can shorten a maintenance period and reduce maintenance costs.

Solution to Problem

In order to solve the above-mentioned problems, according to an aspect of the invention, there is provided a maintenance method for a gas turbine where a gas turbine exhaust-side journal bearing for supporting a gas turbine rotor is disposed in a bearing box, the bearing box is supported by a strut extending from an exhaust casing of the gas turbine toward the inside of the exhaust casing, and a seal ring which includes an annular inner peripheral end and seals between one side and the other side thereof in an axial direction of the gas turbine rotor is provided in the bearing box. The maintenance method includes: a bearing adjustment step of displacing a bearing surface of the journal bearing relative to the bearing box in a perpendicular direction that is perpendicular to the axial direction in which the gas turbine rotor extends; and a seal ring adjustment step of displacing the inner peripheral end of the seal ring relative to the bearing box in accordance with the direction of displacement and the amount of displacement of the bearing surface.

In a case in which a plurality of struts are deformed and a bearing box fixed to the plurality of struts is displaced in a perpendicular direction perpendicular to an axis, or in a case in which a bearing box is not installed at a target position in the perpendicular direction due to assembly errors, manufacturing errors, or the like of various components, a journal bearing provided in the bearing box is also not installed at the target position in the perpendicular direction and a gas turbine rotor at a bearing position in the axial direction is not disposed at the target position in the perpendicular direction. In the maintenance method, the gas turbine rotor at the bearing position in the axial direction can be disposed at a target position in the perpendicular direction since the bearing surface of the journal bearing is displaced relative to the bearing box in the perpendicular direction perpendicular to the axial direction. In addition, in the maintenance method, the sealability of the seal ring can be ensured since the inner peripheral end of the seal ring is displaced relative to the bearing box in accordance with the direction of displacement and the amount of displacement of the bearing surface.

Here, in the maintenance method for a gas turbine, the journal bearing may include a pad on which the bearing surface is formed and a bearing housing that supports the pad from an outer peripheral side, and the bearing adjustment step may include a thickness change step of changing the thickness in the perpendicular direction of at least one component of one or more components, including the pad, disposed between an outer peripheral side of the gas turbine rotor and an inner peripheral side of the bearing housing.

Further, in any one of the above-described maintenance methods for a gas turbine, the journal bearing may include a pad on which the bearing surface is formed and a bearing housing that supports the pad from an outer peripheral side, and the bearing adjustment step may include an adjustment member disposition step of disposing a bearing surface adjustment member between the pad and the bearing housing or changing the thickness of a bearing surface adjustment member, which is disposed in advance, in the perpendicular direction.

In any one of the above-described maintenance methods for a gas turbine, the bearing adjustment step may include a thickness reduction step of cutting the bearing surface of the journal bearing.

In any one of the above-described maintenance methods for a gas turbine, the bearing adjustment step may include a bearing position change step of changing the position of the journal bearing relative to the bearing box in the perpendicular direction.

In any one of the above-described maintenance methods for a gas turbine, an annular outer peripheral end may be formed on an outer peripheral side of the annular inner peripheral end of the seal ring, and the seal ring adjustment step may include an inner peripheral end machining step of machining the seal ring so that the center of the annular inner peripheral end is eccentric to the center of the annular outer peripheral end.

In the maintenance method for a gas turbine including the inner peripheral end machining step, in the inner peripheral end machining step, a part of the inner peripheral end may be extended toward an inner peripheral side and another part of the inner peripheral end may be cut.

In any one of the above-described maintenance methods for a gas turbine, the seal ring adjustment step may include a seal ring position change step of changing the position of the seal ring relative to the bearing box in the perpendicular direction.

Any one of the above-described maintenance methods for a gas turbine may further include a displacement measurement step of measuring the amount of displacement and the direction of displacement of an actual position of the gas turbine rotor in the perpendicular direction at the bearing position with reference to a predetermined position of the gas turbine rotor in the perpendicular direction at the bearing position in the axial direction. In the bearing adjustment step, the bearing surface of the journal bearing may be displaced relative to the bearing box according to the amount of displacement in a direction opposite to the direction of displacement. In the seal ring adjustment step, the inner peripheral end of the seal ring may be displaced relative to the bearing box according to the amount of displacement in a direction opposite to the direction of displacement.

Advantageous Effects of Invention

According to an aspect of the invention, it is possible to shorten a maintenance period for a gas turbine and to reduce maintenance costs.

DESCRIPTION OF EMBODIMENTS

Embodiment

An embodiment of a maintenance method for a gas turbine according to the invention will be described in detail below with reference toFIGS. 1 to 11.

As shown inFIG. 1, a gas turbine1of this embodiment includes a compressor10that compresses outside air to generate compressed air, a plurality of combustors30that mix fuel supplied from a fuel supply source with the compressed air and combust a mixture of the fuel and the compressed air to generate combustion gas, and a turbine40that is driven by the combustion gas.

The compressor10includes a compressor rotor11that rotates about an axis Ar, a compressor casing21that covers the compressor rotor11, and an intake chamber22that guides air into the compressor casing21. The turbine40includes a turbine rotor41that rotates about the axis Ar, a turbine casing51that covers the turbine rotor41, and an exhaust chamber59that guides exhaust gas from the turbine casing51to the outside. The compressor rotor11and the turbine rotor41are connected to each other so that the axis Ar of the compressor rotor11and the axis Ar of the turbine rotor41are positioned on the same line, and form a gas turbine rotor2. In the following description, a direction in which the axis Ar extends is referred to as an axial direction Da and a direction perpendicular to the axis Ar is referred to as a perpendicular direction Dp. Further, the side of the compressor10relative to the turbine40in the axial direction Da is referred to as an upstream side or an intake side, and the side of the turbine40relative to the compressor10in the axial direction Da is referred to as a downstream side or an exhaust side.

The compressor rotor11includes a plurality of blade stages12that are arranged in the axial direction Da and a rotor body13to which the plurality of blade stages12are fixed. Each of the blade stages12includes a plurality of blades that are arranged in a circumferential direction Dc of the axis Ar. The rotor body13includes a blade fixing portion14to which the plurality of blade stages12are fixed, and a shaft portion15that extends toward the upstream side from an upstream end of the blade fixing portion14. The turbine rotor41includes a plurality of blade stages42that are arranged in the axial direction Da and a rotor body43to which the plurality of blade stages42are fixed. Each of the blade stages42includes a plurality of blades that are arranged in the circumferential direction Dc. The rotor body43includes a blade fixing portion44to which the plurality of blade stages42are fixed, and a shaft portion45that extends toward the downstream side from a downstream end of the blade fixing portion44. The turbine casing51includes a turbine body casing52that covers the blade fixing portion44of the turbine rotor41and an exhaust casing53that covers the shaft portion45of the turbine rotor41. Each of the shaft portion15of the compressor rotor11and the shaft portion45of the turbine rotor41has a columnar shape about the axis Ar.

A space between the outer peripheral side of the rotor body13of the compressor rotor11and the inner peripheral side of the compressor casing21forms a compressed air passage17in which intake air is gradually compressed. A space between the outer peripheral side of the rotor body43of the turbine rotor41and the inner peripheral side of the turbine body casing52forms a combustion gas passage47in which combustion gas flows.

The gas turbine1further includes a combustor casing25that is disposed between the compressor casing21and the turbine casing51in the axial direction Da and covers a connection portion between the compressor rotor11and the turbine rotor41. The above-mentioned plurality of combustors30are fixed to the combustor casing25. The compressor casing21, the combustor casing25, and the turbine casing51are connected to each other and form a gas turbine casing5.

The gas turbine1includes bearings that support the gas turbine rotor2so as to allow the gas turbine rotor2to rotate. The gas turbine1includes two journal bearings18and70and one thrust bearing19as the bearings. An intake-side end portion of the gas turbine rotor2is rotatably supported by one journal bearing18of the two journal bearings18and70and one thrust bearing19, and an exhaust-side end portion of the gas turbine rotor2is rotatably supported by the other journal bearing70. In other words, the shaft portion15of the compressor rotor11is rotatably supported by one journal bearing18and one thrust bearing19, and the shaft portion45of the turbine rotor41is rotatably supported by the other journal bearing70.

As shown inFIGS. 2 and 3, the journal bearing70, which supports the shaft portion45of the turbine rotor41so as to allow the shaft portion45to rotate, is covered with a bearing box60and is mounted to the bearing box60. The bearing box60includes an upper-half bearing box60athat covers the upper half of the journal bearing70and a lower-half bearing box60bthat covers the lower half of the journal bearing70. The bearing box60is fixed by a plurality of struts65that extend from the bearing box60in the tangential directions of the turbine rotor41. The outer peripheral-side end portions of the plurality of struts65are fixed to the exhaust casing53. A seal ring90is fixed to the bearing box60through a retainer95. Each of the seal ring90and the retainer95has an annular shape about the axis Ar. The seal ring90functions to seal between one side and the other side of the seal ring90in the axial direction Da in the shaft portion45of the turbine rotor41.

An outer diffuser55and an inner diffuser56, which have a cylindrical shape about the axis Ar, are disposed in the exhaust casing53. The outer diffuser55is provided along the inner peripheral surface of the exhaust casing53. The inner diffuser56is disposed on the inner peripheral side of the outer diffuser55with an interval between itself and the outer diffuser55. A space between the outer diffuser55and the inner diffuser56forms an exhaust passage57through which the combustion gas having rotated the turbine rotor41passes as exhaust gas. The bearing box60is disposed on the inner peripheral side of the inner diffuser56with an interval between itself and the inner diffuser56. All of the plurality of struts65extend from the bearing box60in the tangential directions as described above, pass through the inner diffuser56and the outer diffuser55, and are fixed to the exhaust casing53.

As shown inFIG. 4, the journal bearing70, which supports the shaft portion45of the turbine rotor41so as to allow the shaft portion45to rotate, includes pads71on which support bearing surfaces88facing the outer peripheral surface of the shaft portion45are formed, liners76that are disposed on the outer peripheral sides of the pads71, pivots77that are in contact with the liners76and support the pads71so as to allow the pads71to oscillate, and a bearing housing81on the inner peripheral side of which the pivot77is mounted.

Each of the pads71includes a pad body72on which the support bearing surface88is formed and a base75that supports the pad body72from the outer peripheral side. The support bearing surface88is a curved surface that has a radius of curvature slightly larger than the radius of the shaft portion45. The pad body72includes a body base73and a support bearing layer74that is formed on the body base73. The body base73is made of, for example, iron, chrome steel, copper, or the like. Further, the support bearing layer74is made of, for example, soft metal, such as white metal, an aluminum alloy, a copper-lead alloy, or a lead overlay, a PTFE (Polytetrafluoroethylene) resin, a PEEK (Polyetheretherketone) resin, or the like. The surface of the support bearing layer74forms the above-mentioned support bearing surface88.

A liner mounting groove75c, which is recessed toward the inner peripheral side, is formed on the outer peripheral side of the base75. The liner76is disposed in the liner mounting groove75c. The pivot77is disposed on the outer peripheral side of the liner76. The surface of the pivot77, which faces the liner76, forms a smooth curved surface77cthat is convex toward the liner76. The liner76is substantially in point contact with the curved surface77cof the pivot77, and oscillates in each direction about a portion that is in contact with the pivot77.

The bearing housing81is a cylindrical member that has a circular outer peripheral surface about the axis Ar. A semicircular inner peripheral surface, which has a radius slightly larger than the radius of the shaft portion45, is formed on an upper half81aof the bearing housing81. This inner peripheral surface forms a restraining bearing surface89that faces the outer peripheral surface of the shaft portion45. A semicircular inner peripheral surface, which has a radius larger than the radius of the inner peripheral surface of the upper half81a, is formed on a lower half81bof the bearing housing81. Pivot mounting grooves81c, which are recessed toward the outer peripheral side, are formed on this inner peripheral surface at two positions in the circumferential direction around the axis Ar. The above-mentioned pivots77are disposed in the pivot mounting grooves81c. Accordingly, the pivots77, the liners76, and the pads71are disposed between the inner peripheral surface of the lower half81bof the bearing housing81and the outer peripheral surface of the shaft portion45. A lubricant introduction hole83and a lubricant discharge hole84, which pass through the bearing housing81from the outer peripheral side to the inner peripheral side, are formed in the bearing housing81.

In the journal bearing70of this embodiment, the shaft portion45of the turbine rotor41is in contact with the support bearing surfaces88of the pads71, which are disposed on the inner peripheral side of the lower half81bof the bearing housing81, through a lubricant, and is supported by the pads71. Further, the shaft portion45of the turbine rotor41faces the restraining bearing surface89of the upper half81aof the bearing housing81, but is not in contact with the restraining bearing surface89basically. However, in a case in which abnormal vibration or the like of the turbine rotor41occurs, the shaft portion45may come into contact with the restraining bearing surface89through a lubricant. For this reason, the restraining bearing surface89is made of white metal or the like as in the case of the support bearing surface88. In this embodiment, a bearing surface87is a surface that faces the outer peripheral surface of the turbine rotor41and may come into contact with the turbine rotor41. Furthermore, the support bearing surfaces88of the bearing surface87are surfaces that are in contact with the turbine rotor41through a lubricant and function to support the turbine rotor41so as to allow the turbine rotor41to rotate. Moreover, the restraining bearing surface89of the bearing surface87is a surface that may come into contact with the turbine rotor41through a lubricant but functions to restrain the relatively large movement of the turbine rotor41in the perpendicular direction Dp without functioning to support the turbine rotor41so as to allow the turbine rotor41to rotate.

As shown inFIGS. 5 and 6, the seal ring90includes an annular tooth base91and a plurality of teeth92that protrude from the annular tooth base91to the inner peripheral side. The plurality of teeth92are arranged in the axial direction Da of the turbine rotor41. Each of the teeth92is formed over the entire area of the turbine rotor41in the circumferential direction Dc around the axis Ar. Accordingly, an inner peripheral end of each tooth92is formed in an annular shape. An outer peripheral end90oof the seal ring90is the outer peripheral end of the annular tooth base91around the axis Ar of the turbine rotor41, and an inner peripheral end90iof the seal ring90is inner peripheral ends of the annular teeth92around the axis Ar of the turbine rotor41. The retainer95is a member that has an annular shape about the axis Ar of the turbine rotor41as described above. A seal ring mounting portion96on which the seal ring90is to be mounted is formed on the inner periphery of the retainer95. Further, a portion to be mounted97, which is used to mount the retainer95on the bearing box60, is formed on the retainer95. Each of the annular seal ring90and the annular retainer95can be separated into an upper half and a lower half.

In the above-described gas turbine1of this embodiment, there is a case in which the bearing box60is not installed at a target position in the perpendicular direction Dp due to assembly errors or manufacturing errors of various components, deformation of the struts65fixing the bearing box60, or the like. In this embodiment, a maintenance method in a case in which the bearing box60is displaced vertically downward Dv1from the target position will be described by way of example. In this case, the journal bearing70positioned in the bearing box60is also displaced vertically downward Dv1. As a result, the gas turbine rotor2, which is present at a position where the exhaust-side journal bearing70is disposed in the axial direction Da, is moved vertically downward Dv1. When the gas turbine rotor2, which is present at the position where the exhaust-side journal bearing70is disposed, is moved vertically downward Dv1, a balance between a bearing load that is borne by the intake-side journal bearing18and a bearing load that is borne by the exhaust-side journal bearing70is lost. For this reason, there is also a case in which the life of each journal bearing18,70is shortened and abnormal vibration of the gas turbine rotor2is caused.

In such a case, maintenance is performed in this embodiment by a procedure shown in a flow chart ofFIG. 12.

First, the upper half of the gas turbine casing5including the exhaust casing53and the upper half of the bearing box60are disassembled as shown inFIG. 7. That is, a gas turbine upper-half casing5ais removed from a gas turbine lower-half casing5band the upper-half bearing box60ais removed from the lower-half bearing box60b(S1: casing disassembly step).

Next, the bearings and the gas turbine rotor2, which are housed in the gas turbine lower-half casing5b, are moved to the outside of the gas turbine lower-half casing5b(S2: gas turbine rotor movement step).

After that, the amount of displacement and the direction of displacement of the position of the gas turbine rotor2in the perpendicular direction Dp at a bearing position where the exhaust-side journal bearing70is disposed in the axial direction Da are measured (S3: displacement measurement step). The direction of displacement is a vertical direction Dv of the perpendicular direction Dp in this embodiment, but may not be the vertical direction Dv. Further, when a position in the perpendicular direction Dp at the bearing position of the gas turbine rotor2at the beginning of the manufacture of the gas turbine1is set as a reference position, displacement may be displacement relative to the reference position. Furthermore, when the same position as the position of the gas turbine rotor2in the perpendicular direction Dp at a position in the axial direction Da where the intake-side journal bearing18is disposed is set as the reference position of the gas turbine rotor2in the perpendicular direction Dp at the exhaust-side bearing position, displacement may be displacement relative to the reference position. In any case, a predetermined position of the gas turbine rotor2in the perpendicular direction Dp at the exhaust-side bearing position is set as a reference position.

At the time of the measurement of displacement, the removed upper-half bearing box60ais assembled with the lower-half bearing box60bagain and the gas turbine upper-half casing5ais assembled with the gas turbine lower-half casing5b, from which the gas turbine rotor2has been removed, again. The measurement of displacement is performed by, for example, the same method as a laser alignment method. Specifically, a laser oscillator and a laser detector are mounted at predetermined positions in the gas turbine casing5and laser is oscillated from the laser oscillator and is detected by the laser detector, so that the amount of displacement and the direction of displacement are measured. After the measurement of displacement, again, the gas turbine upper-half casing5ais removed from the gas turbine lower-half casing5band the upper-half bearing box60ais removed from the lower-half bearing box606.

Next, as shown inFIG. 8, the journal bearing70is adjusted so that the bearing surface87of the journal bearing70is moved relative to the bearing box60in the perpendicular direction Dp (S4: bearing adjustment step). In a case in which the bearing box60is moved vertically downward Dv as described above, in the bearing adjustment step (S4), the thickness of each of the pads71housed in the lower half81bof the bearing housing81is increased (S4a: thickness change step) and a part of the restraining bearing surface89of the upper half81aof the bearing housing81is cut (S4b: thickness reduction step). When the bearing adjustment step (S4) is performed, the position of the shaft portion45in the perpendicular direction Dp, which is determined by the support bearing surfaces88and the restraining hearing surface89, is moved vertically upward Dv2from the position of the shaft portion45that is obtained before the bearing adjustment step (S4) is performed.

The amount and direction of the increase of the thickness of each of the pads71housed in the lower half81bof the bearing housing81, and the amount and direction of the cut of the restraining bearing surface89are determined so that the position of the shaft portion45in the perpendicular direction Dp, which is determined by the support bearing surfaces88and the restraining bearing surface89, is moved by the amount of displacement, which is measured in the displacement measurement step (S3), in a direction opposite to the direction of displacement, which is measured in the displacement measurement step (S3), that is, vertically upward Dv2in this case.

Here, a method of inserting a bearing surface adjustment member79, such as a shim, between the pad body72and the base75of each pad71as shown inFIG. 8is employed as a method of increasing the thickness of the pad71. Other than the above-mentioned method, a method of replacing at least one of the pad body72and the base75of the pad71with a member having a different thickness, a method of overlaying the support bearing surface88with white metal or the like, which forms the support bearing layer74, before the thickness change step (S4a) for the pad71is performed, and the like are used as a method of increasing the thickness of the pad71.

When a part of the restraining bearing surface89is cut to form a new restraining bearing surface89, after the restraining bearing surface89is cut, the surface of a restraining bearing layer82which is made of white metal or the like and of which the surface forms the restraining bearing surface89is overlaid with white metal or the like so that the thickness of the restraining bearing layer82becomes a target thickness.

Next, as shown inFIGS. 9 and 10, the seal ring90is adjusted so that the inner peripheral end90iof the seal ring90is moved relative to the bearing box60(S5: seal ring adjustment step). In a case in which the bearing box60is moved vertically downward Dv1as described above, the inner peripheral end90iis machined in the seal ring adjustment step (S5) so that the center of the annular inner peripheral end90iis eccentric to the center of the annular outer peripheral end900of the seal ring90(S5a: inner peripheral end machining step). In the inner peripheral end machining step (S5a), a part of the inner peripheral end90iis extended toward the inner peripheral side and another part of the inner peripheral end90iis cut. In a case in which the bearing box60is moved vertically downward Dv1as described above, a lower portion of the inner peripheral end90iis extended and an upper portion of the inner peripheral end90iis cut. When the seal ring adjustment step (S5) is performed, the seal position of the seal ring90relative to the shaft portion45of which the position is determined by the bearing adjustment step (S4) can be optimized.

The amount and direction of extension of a part of the inner peripheral end90iof the seal ring90and the amount and direction of the cut of the other part of the inner end are made to correspond to the amount and direction of the increase of the thickness of each pad71and the amount and direction of the cut of the restraining bearing surface89that are determined in the bearing adjustment step (S4). That is, the amount and direction of the extension of a part of the inner peripheral end90iof the seal ring90and the amount and direction of the cut of the other part of the inner end are determined so that the position of the shaft portion45in the perpendicular direction Dp, which is determined by the inner peripheral end90iof the seal ring90, is moved by the amount of displacement, which is measured in the displacement measurement step (S3), in a direction opposite to the direction of displacement, which is measured in the displacement measurement step (S3), that is, vertically upward Dv2in this case.

Next, the bearings, which include the journal bearing70subjected to the bearing adjustment step (S4), are set on the gas turbine rotor2and the gas turbine rotor2is moved so that the gas turbine rotor2is housed in the gas turbine lower-half casing5b(S6: gas turbine rotor movement step). The setting of the journal bearing70subjected to the bearing adjustment step (S4) may be performed as described below as long as the bearing housing81can be separated into an upper half and a lower half. First, the upper half of the bearing housing81is set in the upper-half bearing box60a, the lower half of the bearing housing81is set in the lower-half bearing box60b, and the pads71, the pivots77, and the like are set in the lower half of the bearing housing81.

Next, the upper half of the seal ring90subjected to the seal ring adjustment step (S5) is mounted on the upper-half bearing box60athrough the upper half of the retainer95, and the lower half of the seal ring90is mounted on the lower-half bearing box60bthrough the lower half of the retainer95. Then, the gas turbine upper-half casing5ais assembled with the gas turbine lower-half casing5b, and the upper-half bearing box60ais assembled with the lower-half bearing box60b(S7: casing assembly step).

The maintenance of the gas turbine1of this embodiment ends in this way. As a result, as shown inFIG. 11, the position of the bearing box60in the perpendicular direction Dp is not changed, but the bearing surface87of the journal bearing70disposed in the bearing box60is displaced in the perpendicular direction Dp and the inner peripheral end90iof the seal ring90mounted on the bearing box60is displaced in the perpendicular direction Dp. For this reason, the position of the gas turbine rotor2, which is present at the exhaust-side bearing position, in the perpendicular direction Dp can be set to a target position, and sealability can be ensured between one side and the other side of the seal ring90in the axial direction Da.

A method of moving the exhaust casing53, in which the plurality of struts65are formed, vertically upward Dv2relative to the turbine body casing52is considered as a maintenance method in a case in which the bearing box60is displaced vertically downward Dv1from a target position due to assembly errors or manufacturing errors of various components, deformation of the struts65(FIGS. 2 and 3) fixing the bearing box60, or the like as described above. Flanges are fobrmed at the exhaust casing53and the turbine body casing52so that the exhaust casing53and the turbine body casing52are connected to each other as shown inFIG. 2, and a large number of bolt holes53hand52hare formed at the respective flanges. The exhaust casing53and the turbine body casing52are connected to each other by bolts58that are inserted into the respective bolt holes53hand52h. In order to perform this method, for example, the large number of bolt holes of one casing, among the bolt holes53hof the exhaust casing53and the bolt holes52hof the turbine body casing52, need to be machined in the form of elongated holes in the perpendicular direction Dp. Since a long machining time is required to form the large number of bolt holes of one casing in the form of elongated holes, the machining cost is also increased. In addition, when the exhaust casing53and the turbine body casing52are connected to each other by the bolts58, it is also necessary to prepare a jig or the like that is used to temporarily fix the exhaust casing53at a position where the exhaust casing53is moved upward relative to the turbine body casing52in accordance with the amount of displacement of the bearing box60. For this reason, this maintenance method has problems in that the maintenance period is lengthened and the maintenance cost is also increased.

In the above-described maintenance method of this embodiment, it is sufficient to perform the adjustment steps for the journal bearing70and the seal ring90that are components smaller than the exhaust casing53and the turbine body casing52. Accordingly, it is possible to shorten the maintenance period and reduce the maintenance cost.

Modification Example

The thickness change step (4a) for the pad71and the thickness reduction step (4b) are performed in the bearing adjustment step (S4) of the embodiment. However, as shown in a flow chart ofFIG. 15, a thickness change step (S4c) of changing the thickness of any one component of the liner76and the pivot77(seeFIG. 8), which are disposed between the outer peripheral side of the shaft portion45of the turbine rotor41and the inner peripheral side of the bearing housing81, in the perpendicular direction Dp may be performed instead of the thickness change step (4a) for the pad71. Further, the thickness of two or more components among the plurality of components, which are disposed between the outer peripheral side of the shaft portion45of the turbine rotor41and the inner peripheral side of the bearing housing81, may be changed in the thickness change step (S4c).

Furthermore, an adjustment member disposition step (S4d) may be performed instead of the thickness change step (4a) for the pad71. In the adjustment member disposition step (S4d) the bearing surface adjustment member79, such as a shim, is disposed between two components, which are adjacent to each other in the perpendicular direction Dp, among the plurality of components disposed between the outer peripheral side of the shaft portion45of the turbine rotor41and the inner peripheral side of the bearing housing81, that is, the pad71, the liner76, and the like (seeFIG. 8), or between a component disposed on the outermost peripheral side and the bearing housing81, or the thickness of the bearing surface adjustment member79, which is disposed in advance, in the perpendicular direction Dp is changed.

Further, a bearing position change step (S4e) of changing the position of the journal bearing70relative to the bearing box60in the perpendicular direction Dp may be performed in the bearing adjustment step (S4) instead of the thickness change step (S4aor S4c) and the thickness reduction step (S4b) that have been described above. In this case, as shown inFIG. 13, a bearing box60xis formed so as to allow the journal bearing70to relatively move in the perpendicular direction Dp inside the bearing box60x, and adjusters99that adjust the relative position of the journal bearing70in the perpendicular direction Dp inside the bearing box60xare provided. For example, bolts or the like, which pass through the bearing box60xin the perpendicular direction Dp and of which ends come into contact with the bearing housing81of the journal bearing70, can be used as the adjusters99. The position of the journal bearing70relative to the bearing box60xin the perpendicular direction Dp is changed by changing the screwing amount of the bolts, which are the adjusters99, into the bearing box60x.

Various steps performed in the bearing adjustment step (S4) have been exemplified in the above description, but two or more steps of the various steps may be performed together. For example, both the thickness change step (S4aand/or S4c) and the adjustment member disposition step (S4d) may be performed. In a case in which the20amount of displacement of the bearing box60is large, a method of performing two or more steps of the various steps together is effective to cope with the amount of the displacement.

The inner peripheral end machining step (S5a) is performed in the seal ring adjustment step (S5) of the embodiment. However, a seal ring position change step (S5b) of changing the position of the seal ring90relative to the bearing box60in the perpendicular direction Dp may be performed instead of the inner peripheral end machining step (S5a). In this case, an adjuster99a, which is used to adjust the position of the seal ring90relative to the bearing box60in the perpendicular direction Dp, is provided as shown inFIG. 14. For example, a hole98, which is long in the perpendicular direction Dp, is formed at the retainer95that is used to mount the seal ring90on the bearing box60; a screw hole66is formed in the bearing box60at a position corresponding to the hole98of the retainer95; and a bolt as the adjuster99ais screwed into the screw hole66of the bearing box60through the hole98of the retainer95. According to this structure, it is possible to adjust the position of the seal ring90relative to the bearing box60in the perpendicular direction Dp.

Here, the inner peripheral end machining step (S5a) and the seal ring position change step (S5b) have been exemplified as steps performed in the seal ring adjustment step (S5), but the two steps may be performed together. In a case in which the amount of displacement of the bearing box60is large, a method of performing the two steps together is effective to cope with the amount of the displacement. Further, in the seal ring adjustment step (S5b), an existing seal ring90may be machined or a new seal ring may be produced and the seal ring90may be replaced with the new seal ring.

In the embodiment, the seal ring adjustment step (S5) is performed after the bearing adjustment step (S4) is performed. However, the bearing adjustment step (S4) may be performed after the seal ring adjustment step (S5) is performed.

As shown inFIG. 4, the journal bearing70of the embodiment includes the bearing housing81, two pads71, two liners76, and two pivots77. However, the journal bearing is not limited to the journal bearing70of the embodiment. For example, the journal bearing may be a journal bearing that includes a bearing housing81, three or more pads71, three or more liners76, and three or more pivots77. For example, the journal bearing may be a journal bearing that does not include the liner76. The smooth curved surface77c, which is convex toward the inner peripheral side, is formed on the pivot77of the embodiment, but the curved surface77cmay be a smooth curved surface that is convex toward the outer peripheral side. That is, any configuration in which the pivot77and a component, which is in contact with the pivot77, are substantially in point contact with each other will do.

One seal ring90is mounted on the bearing box60in the embodiment, but a plurality of seal rings90may be mounted on the bearing box60. In this case, the plurality of seal rings90are arranged in the axial direction Da.

In the embodiment, a case in which the bearing box60is displaced vertically downward Dv1from a target position has been exemplified as an example of a case in which the bearing box60is not installed at a target position in the perpendicular direction Dp due to assembly errors or manufacturing errors of various components, deformation of the struts65fixing the bearing box60, or the like; and the maintenance method in that case has been shown. However, the maintenance method is not limited to a case in which the bearing box60is displaced vertically downward Dv1in the perpendicular direction Dp. For example, the maintenance method can be applied also when the bearing box60is displaced upward in a vertical direction, in a horizontal direction, and in an oblique direction which includes a vertical component and a horizontal component, among the perpendicular directions Dp.

INDUSTRIAL APPLICABILITY

According to an aspect of the invention, it is possible to shorten a maintenance period and reduce maintenance costs for a gas turbine.

REFERENCE SIGNS LIST