Patent Publication Number: US-2019195680-A1

Title: Abnormality detection device, difference vector display device, rotary machine system, abnormality detection method, and program

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an abnormality detection device, a difference vector display device, a rotary machine system, an abnormality detection method, and a program. 
     Priority is claimed on Japanese Patent Application No. 2017-245561, filed Dec. 21, 2017, the content of which is incorporated herein by reference. 
     Description of Related Art 
     Several technologies have been proposed in relation to monitoring of shaft vibration of a rotary machine such as a turbine. 
     For example, an unstable vibration monitoring device according to Japanese Unexamined Patent Application, First Publication No. 2001-142529 (hereinafter, referred to as Patent Literature 1) performs filtering for extracting only a signal of a target frequency domain from a vibration signal, and samples a filtered vibration signal. This unstable vibration monitoring device plots coordinate values by combining two consecutive sampling values such that an Nth sampling value is taken on a horizontal axis and an N+1th sampling value is taken on a vertical axis, thereby creating a pattern referred to as a phase spatial trajectory. Furthermore, this unstable vibration monitoring device rotates such that a long axis of the phase spatial trajectory is parallel to an X axis, and performs circular transformation that extends in the vertical direction. Then, this unstable vibration monitoring device determines whether there is an unstable vibration on the basis of a distance from an origin of a plot point. 
     SUMMARY OF THE INVENTION 
     It is preferable not only to detect the presence or absence of an abnormality but also to obtain information for maintenance work of a rotary machine in the monitoring of shaft vibration of the rotary machine. 
     The present invention provides an abnormality detection device, a difference vector display device, a rotary machine system, an abnormality detection method, and a program which can obtain information for maintenance work of a rotary machine. 
     According to a first aspect of the present invention, an abnormality detection device includes a vibration measurement value acquisition unit configured to acquire a measurement value of vibration of a rotation shaft for each rotation angle of the rotation shaft, the measurement value being measured by each of a plurality of shaft vibration sensors, the plurality of shaft vibration sensors being provided to be spaced apart in a diameter direction of the rotation shaft with respect to an outer circumferential surface of the rotation shaft and being provided to be spaced apart in a shaft direction of the rotation shaft, a vibration vector calculation unit configured to calculate a vibration vector, the vibration vector indicating a rotation angle at which vibration of the rotation shaft is a maximum and a magnitude of the vibration on the basis of the measurement value of the vibration, and an estimation unit configured to estimate an abnormality occurrence position in the shaft direction of the rotation shaft on the basis of a time change in the vibration vector. 
     The shaft vibration sensors may also be provided in respective diameter directions of the rotation shaft orthogonal to each other. 
     The estimation unit may estimate an abnormality occurrence position in the shaft direction of the rotation shaft on the basis of a rotation speed of the rotation shaft in addition to a time change in the vibration vector. 
     According to a second aspect of the present invention, a difference vector display device includes a vibration measurement value acquisition unit configured to acquire a measurement value of vibration of a rotation shaft for each rotation angle of the rotation shaft, the measurement value being measured by each of a plurality of shaft vibration sensors, the plurality of shaft vibration sensors being provided to be spaced apart in a diameter direction of the rotation shaft with respect to an outer circumferential surface of the rotation shaft and being provided to be spaced apart in a shaft direction of the rotation shaft, a vibration vector calculation unit configured to calculate a vibration vector, the vibration vector indicating a rotation angle at which vibration of the rotation shaft is a maximum and a magnitude of the vibration on the basis of the measurement value of the vibration, a difference vector calculation unit configured to calculate a difference vector indicating a time change in the vibration vector, and a display unit configured to display the difference vector. 
     According to a third aspect of the present invention, a rotary machine system includes a rotary machine, and an abnormality detection device, in which the rotary machine includes a rotation shaft, and a plurality of shaft vibration sensors provided to be spaced apart in a diameter direction of the rotation shaft with respect to an outer circumferential surface of the rotation shaft and provided to be spaced apart in a shaft direction of the rotation shaft, and the abnormality detection device includes a vibration measurement value acquisition unit configured to acquire a measurement value of vibration of the rotation shaft measured by the shaft vibration sensor for each rotation angle of the rotation shaft, a vibration vector calculation unit configured to calculate a vibration vector, the vibration vector indicating a rotation angle at which the vibration of the rotation shaft is a maximum and a magnitude of the vibration on the basis of the measurement value of the vibration, and an estimation unit configured to estimate an abnormality occurrence position in the shaft direction of the rotation shaft on the basis of a time change in the vibration vector. 
     According to a fourth aspect of the present invention, an abnormality detection method includes acquiring a measurement value of vibration of a rotation shaft for each rotation angle of the rotation shaft, the measurement value being measured by each of a plurality of shaft vibration sensors, the plurality of shaft vibration sensors being provided to be spaced apart in a diameter direction of the rotation shaft with respect to an outer circumferential surface of the rotation shaft and being provided to be spaced apart in a shaft direction of the rotation shaft, calculating a vibration vector, the vibration vector indicating a rotation angle at which vibration of the rotation shaft is a maximum and a magnitude of the vibration on the basis of the measurement value of the vibration, and estimating an abnormality occurrence position in the shaft direction of the rotation shaft on the basis of a time change in the vibration vector. 
     According to a fifth aspect of the present invention, a non-transitory computer-readable recording medium storing a program causes a computer to execute acquiring a measurement value of vibration of a rotation shaft for each rotation angle of the rotation shaft, the measurement value being measured by each of a plurality of shaft vibration sensors, the plurality of shaft vibration sensors being provided to be spaced apart in a diameter direction of the rotation shaft with respect to an outer circumferential surface of the rotation shaft and being provided to be spaced apart in a shaft direction of the rotation shaft, for each rotation angle of the rotation shaft, calculating a vibration vector, the vibration vector indicating a rotation angle at which vibration of the rotation shaft is a maximum and a magnitude of the vibration on the basis of the measurement value of the vibration, and estimating an abnormality occurrence position in the shaft direction of the rotation shaft on the basis of a time change in the vibration vector. 
     According to the abnormality detection device, the difference vector display device, the rotary machine system, the abnormality detection method, and the program, it is possible to obtain information for maintenance work of a rotary machine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block diagram which shows a functional configuration of a rotary machine system according to a first embodiment of the present invention. 
         FIG. 2  is a diagram which shows an example of installation positions of a shaft vibration sensor and a rotation pulse sensor in a shaft direction (a longitudinal direction) of a rotation shaft according to the first embodiment. 
         FIG. 3  is a diagram which shows an example of an installation position of a front-side shaft vibration sensor in a circumferential direction of the rotation shaft according to the first embodiment. 
         FIG. 4  is a diagram which shows an example of an installation position of a rear-side shaft vibration sensor in the circumferential direction of the rotation shaft according to the first embodiment. 
         FIG. 5  is a diagram which shows an example of an initial value of a vibration vector calculated by a vibration vector calculation unit according to the first embodiment. 
         FIG. 6  is a diagram which shows an example of a data structure of vibration vector initial value data stored in a storage unit according to the first embodiment. 
         FIG. 7  is a diagram which shows an example of a vibration vector after vibration of the rotation shaft according to the first embodiment has changed. 
         FIG. 8  is a diagram which shows a calculation example of a difference vector according to the first embodiment. 
         FIG. 9  is a diagram which shows a display example of the difference vector according to the first embodiment. 
         FIG. 10  is a diagram which shows examples of difference graphs calculated by a difference vector calculation unit according to the first embodiment for each shaft vibration sensor. 
         FIG. 11  is a diagram which shows an example of a data structure of abnormality occurrence position data stored in the storage unit according to the first embodiment. 
         FIG. 12  is a diagram which shows a display example of an abnormality occurrence position in the rotation shaft according to the first embodiment. 
         FIG. 13  is a flowchart which shows an example of a processing procedure in which an abnormality detection device according to the first embodiment generates and stores a vibration vector initial value. 
         FIG. 14  is a flowchart which shows an example of a processing procedure in which the abnormality detection device according to the first embodiment estimates an abnormality occurrence position in the rotation shaft. 
         FIG. 15  is a schematic block diagram which shows a functional configuration of a rotary machine system according to a second embodiment of the present invention. 
         FIG. 16  is a flowchart which shows an example of a processing procedure in which a difference vector display device according to the second embodiment calculates and displays a difference vector. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the present invention will be described, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of features described in the embodiments are necessarily essential to the solutions of the invention. 
     First Embodiment 
       FIG. 1  is a schematic block diagram which shows a functional configuration of a rotary machine system according to a first embodiment of the present invention. As shown in  FIG. 1 , a rotary machine system  1  includes a rotary machine  100  and an abnormality detection device  200 . The rotary machine  100  includes a rotation shaft  110 , shaft vibration sensors  120 , and an angle sensor  130 . The abnormality detection device  200  includes a communication unit  210 , an operation input unit  220 , a display unit  230 , a storage unit  280 , and a control unit  290 . The control unit  290  includes a vibration measurement value acquisition unit  291 , a vibration vector calculation unit  292 , a difference vector calculation unit  293 , and an estimation unit  294 . 
     The rotary machine  100  is a machine including a rotation shaft. In the following description, a case in which the rotary machine  100  is a steam turbine will be described as an example, but the present invention is not limited thereto. For example, the rotary machine  100  may also be a compressor or a gas turbine. 
     The rotation shaft  110  rotates in accordance with an operation of the rotary machine  100 . In the following description, a case in which the rotation shaft  110  is a rotor of a steam turbine will be described as an example. 
     The shaft vibration sensors  120  measure vibration of the rotation shaft  110 . When the rotation shaft  110  rotates, the shaft vibration sensors  120  measure the vibration of the rotation shaft  110  over the entire circumference of the rotation shaft  110 . For example, the shaft vibration sensors  120  may be configured using distance sensors, and may measure distances from the shaft vibration sensors  120  themselves to the rotation shaft  110 . 
     The angle sensor  130  measures a rotation angle (a phase) of the rotation shaft  110 . 
     Here, it is possible to configure the angle sensor  130  using a rotation pulse sensor. The rotation pulse sensor outputs a pulse waveform whenever it passes through a point fixed to a rotor (the rotation shaft  110 ) (generally indicated by a reflective tape or slit). If the rotor rotates one rotation after a certain pulse is output, another pulse is output. Since the rotation shaft  110  rotates 360 degrees at intervals between adjacent pulses, it is possible to ascertain a rotor angle at which shaft vibration is increased with the point fixed to the rotor set as a reference by observing a pulse waveform at a time at which the shaft vibration is increased. 
       FIG. 2  is a diagram which shows an example of installation positions of the shaft vibration sensors  120  and the rotation pulse sensor (the angle sensor  130 ) in a shaft direction (a longitudinal direction) of the rotation shaft  110 . A left side of the rotation shaft  110  shown in  FIG. 2  is a front side, and a right side thereof is a rear side. A line L 11  indicates a rotation center of the rotation shaft  110 . 
     In addition, bearings  140  which support the rotation shaft  110  are shown in  FIG. 2 . Of the bearings  140 , the bearing  140  on the front side of the rotation shaft  110  is referred to as a front-side bearing  141 , and the bearing  140  on the rear side of the rotation shaft  110  is referred to as a rear-side bearing  142 . 
     In addition, the shaft vibration sensors  120  and the angle sensor  130  are provided to be spaced apart in a diameter direction of the rotation shaft  110  with respect to an outer circumferential surface of the rotation shaft  110 . 
     Two of the shaft vibration sensors  120  are provided near the front-side bearing  141  or further forward on the rotation shaft  110  than the front-side bearing  141 , and two are provided near the rear-side bearing  142  or further rearward on the rotation shaft  110  than the rear-side bearing  142 . In the arrangement shown in  FIG. 2 , the shaft vibration sensors  120  positioned on the front side of the rotation shaft  110  are referred to as front-side shaft vibration sensors  121 . The shaft vibration sensors  120  positioned on the rear side of the rotation shaft  110  are referred to as rear-side shaft vibration sensors  122 . 
     In this manner, the plurality of shaft vibration sensors  120  are provided to be spaced apart in the diameter direction of the rotation shaft  110  with respect to the outer circumferential surface of the rotation shaft  110  at positions spaced apart in the shaft direction of the rotation shaft  110 . 
     The angle sensor  130  is generally provided slightly further forward on the rotation shaft  110  than the front-side shaft vibration sensors  121 . 
       FIG. 3  is a diagram which shows an example of installation positions of the front-side shaft vibration sensors  121  in the circumferential direction of the rotation shaft  110 .  FIG. 3  shows an example of a case in which the rotation shaft  110  and the front-side shaft vibration sensors  121  are seen from the front side of the rotation shaft  110 , and shows the two front-side shaft vibration sensors  121  and a cross-sectional view of the rotation shaft  110  at positions of the front-side shaft vibration sensors  121  in the shaft direction of the rotation shaft  110 . 
     The two front-side shaft vibration sensors  121  are provided in a horizontal direction and a vertical direction with respect to the rotation shaft  110 . The front-side shaft vibration sensor  121  in the horizontal direction with respect to the rotation shaft  110  is referred to as a horizontal front-side shaft vibration sensor  121   h.  The front-side shaft vibration sensor  121  in the vertical direction with respect to the rotation shaft  110  is referred to as a vertical front-side shaft vibration sensor  121   v.    
     A line L 21  is a line obtained by extending a horizontal diameter among the diameters of the rotation shaft  110 . The horizontal front-side shaft vibration sensor  121   h  is provided on the extension of the horizontal diameter among the diameters of the rotation shaft  110 . A line L 22  is a line obtained by extending a vertical diameter among the diameters of the rotation shaft  110 . The vertical front-side shaft vibration sensor  121   v  is provided on the extension of the vertical diameter among the diameters of the rotation shaft  110 . The horizontal diameter and the vertical diameter of the rotation shaft  110  are orthogonal to each other. Accordingly, the shaft vibration sensors  120  are provided in respective diameter directions of the rotation shaft  110  orthogonal to each other in the arrangement of  FIG. 3 . 
       FIG. 4  is a diagram which shows an example of installation positions of the rear-side shaft vibration sensors  122  in the circumferential direction of the rotation shaft  110 .  FIG. 4  shows an example of a case in which the rotation shaft  110  and the rear-side shaft vibration sensors  122  are seen from the front side of the rotation shaft  110 , and shows the two rear-side shaft vibration sensors  122  and a cross-sectional view of the rotation shaft  110  at positions of the rear-side shaft vibration sensors  122  in the shaft direction of the rotation shaft  110 . 
     The two rear-side shaft vibration sensors  122  are provided in the horizontal direction and the vertical direction with respect to the rotation shaft  110 . The rear-side shaft vibration sensor  122  in the horizontal direction with respect to the rotation shaft  110  is referred to as a horizontal rear-side shaft vibration sensor  122   h.  The rear-side shaft vibration sensor  122  in the vertical direction with respect to the rotation shaft  110  is referred to as a vertical rear-side shaft vibration sensor  122   v.    
     A line L 31  is a line obtained by extending the horizontal diameter among the diameters of the rotation shaft  110 . The horizontal rear-side shaft vibration sensor  122   h is provided on the extension of the horizontal diameter among the diameters of the rotation shaft  110 . A line L 32  is a line obtained by extending the vertical diameter among the diameters of the rotation shaft  110 . The vertical rear-side shaft vibration sensor  122   v  is provided on the extension of the vertical diameter among the diameters of the rotation shaft  110 . The horizontal diameter and the vertical diameter of the rotation shaft  110  are orthogonal to each other. Accordingly, the shaft vibration sensors  120  are provided in respective diameter directions of the rotation shaft  110  orthogonal to each other in an arrangement of  FIG. 4 . 
     However, the number and arrangement of the shaft vibration sensors  120  and the angle sensor  130  are not limited to those shown in  FIGS. 2 to 4 . The shaft vibration sensors  120  may be provided at three or more places in the shaft direction of the rotation shaft  110 . In addition, three or more of shaft vibration sensors  120  may also be provided in a circumferential direction of the rotation shaft  110 . Moreover, the shaft vibration sensors  120  may also be provided in an arrangement other than diameter directions of the rotation shaft  110  that are orthogonal to each other, such as being provided on an upper side and an obliquely lower side of the rotation shaft  110 . 
     A position of the angle sensor  130  is not limited to the position shown in  FIG. 2 , and may be any position as long as the rotation angle of the rotation shaft  110  can be measured. In addition, two or more angle sensors  130  may also be provided such as spare angle sensors  130  being provided. 
     The abnormality detection device  200  detects an abnormality in the vibration of the rotation shaft  110 , and estimates an occurrence position of the abnormality which causes abnormality vibration. 
     The abnormality detection device  200  is configured, for example, using a computer such as an engineering workstation (EWS) or a computer (a personal computer; PC). 
     The communication unit  210  communicates with other devices. In particular, the communication unit  210  receives sensor measurement values from each shaft vibration sensor  120  and the angle sensor  130 . 
     The operation input unit  220  includes, for example, an input device such as a keyboard or a mouse, and receives a user operation. For example, the operation input unit  220  receives a setting operation for determination conditions (for example, a determination threshold value) to determine the presence or absence of an abnormality in the vibration of the rotation shaft  110 . A user can select a level of vibration which is determined as an abnormality by setting the determination conditions. 
     The display unit  230  includes, for example, a display screen such as a liquid crystal panel or a light emitting diode (LED), and displays various types of images. In particular, the display unit  230  displays an estimation result of an abnormality occurrence position of the rotation shaft  110 . 
     The storage unit  280  stores various types of data. In particular, the storage unit  280  stores data in which a vibration situation and an abnormality occurrence position of the rotation shaft  110  are associated with each other for estimating the abnormality occurrence position of the rotation shaft  110 . In the following description, the data in which the vibration situation and the abnormality occurrence position of the rotation shaft  110  are associated with each other is referred to as abnormality occurrence position data. As will be described below, the storage unit  280  stores abnormality occurrence position data in which a rotation speed of the rotation shaft  110 , a difference vector of the rotation shaft  110  calculated by the difference vector calculation unit  293 , an abnormality occurrence position in the shaft direction of the rotation shaft  110 , and an abnormality occurrence position in the circumferential direction of the rotation shaft  110  are associated with each other. The storage unit  280  stores an abnormality occurrence position data group in which a plurality of pieces of abnormality occurrence position data are converted into a database. 
     The storage unit  280  is configured to use a storage device included in the abnormality detection device  200 . 
     The control unit  290  performs various types of processing by controlling each unit of the abnormality detection device  200 . The control unit  290  is configured by a central processing unit (CPU) included in the abnormality detection device  200  reading a program from the storage unit  280  and executing it. 
     The vibration measurement value acquisition unit  291  acquires a measurement value of the vibration of the rotation shaft  110  measured by the shaft vibration sensors  120  for each rotation angle of the rotation shaft  110 . Specifically, the vibration measurement value acquisition unit  291  associates a measurement value of the vibration of the rotation shaft  110  measured by the shaft vibration sensors  120  with an angle on the rotation shaft with an inter-pulse of the rotation pulse sensor set as 360 degrees for each shaft vibration sensor  120 , and acquires a measurement value of one round of vibration of the rotation shaft  110  (for example, measurement values of distances between the shaft vibration sensors  120  and the rotation shaft  110  or measurement values of displacement of the distances). 
     The vibration measurement value acquisition unit  291  may also extract data for one round of the rotation shaft  110  from the measurement value of the vibration of the rotation shaft  110  measured by the shaft vibration sensors  120 . Alternatively, the vibration measurement value acquisition unit  291  may acquire the measurement value of the vibration of the rotation shaft  110  for a plurality of rounds of the rotation shaft  110  measured by the shaft vibration sensor  120 , and may also calculate an average for each rotation angle. 
     The vibration vector calculation unit  292  calculates a vibration vector which indicates an angle on a rotor (the rotation shaft  110 ) at which the vibration of the rotation shaft  110  is a maximum and a magnitude of the vibration on the basis of the measurement value of the vibration acquired by the vibration measurement value acquisition unit  291 . 
     The vibration vector calculation unit  292  calculates a vibration vector for each shaft vibration sensor  120 . However, a unit in which the vibration vector calculation unit  292  calculates the vibration vector is not limited to each shaft vibration sensor  120 . For example, the vibration vector calculation unit  292  may calculate a vibration vector associated with the plurality of shaft vibration sensors  120  on the basis of an average of the measurement value of the vibration measured by the plurality of shaft vibration sensors  120 . 
       FIG. 5  is a diagram which shows an example of an initial value of a vibration vector calculated by the vibration vector calculation unit  292 . A coordinate axis of the graph of  FIG. 5  shows the magnitude of vibration and polar coordinates of a circumferential angle to a rotation pulse reference point on the rotation shaft  110 . The rotation pulse reference point is indicated by, for example, a reflective tape or slit. 
     A vector B 11  shows an example of a vibration vector. A vibration vector indicates an angle on the rotation shaft (an angle from the rotation pulse reference point) at which the shaft vibration of the rotation shaft  110  at the measured number of rotations measured by the vibration measurement value acquisition unit  291  is a maximum 
       FIG. 6  is a diagram which shows an example of a data structure of vibration vector initial value data stored in the storage unit  280 . 
     In the example of  FIG. 6 , the vibration vector initial value data stores magnitudes of a phase and vibration as vibration vector initial values of each of the horizontal front-side shaft vibration sensor  121   h,  the vertical front-side shaft vibration sensor  121   v,  the horizontal rear-side shaft vibration sensor  122   h,  and the vertical rear-side shaft vibration sensor  122   v.  In addition, the vibration vector initial value data stores the number of rotations of the rotation shaft  110 . Since the vibration vector also changes if the number of rotations of the rotation shaft  110  changes, the storage unit  280  stores the vibration vector initial value data for each rotation speed of the rotation shaft  110 . 
     Alternatively, in a case in which the abnormality detection device  200  operates only when the rotation shaft  110  rotates at a predetermined speed such as performing abnormality detection only when the rotation shaft  110  rotates at a rated speed, the “number of rotations” column in the vibration vector initial value data is unnecessary. The storage unit  280  may store a vibration vector initial value at a predetermined speed. 
       FIG. 7  is a diagram which shows an example of a vibration vector after the vibration of the rotation shaft  110  has changed. A coordinate axis of the graph of  FIG. 7  shows the same polar coordinates as that of the graph of  FIG. 5 . 
     A vector B 12 , like the vector B 11  in  FIG. 5 , shows an example of the vibration vector according to a vibration measurement value of the shaft vibration sensor  120 . When the vibration changes due to, for example, an occurrence of an abnormality such as a crack in the rotation shaft  110 , the vibration vector also changes from the vector B 11  to the vector B 12 . 
     In the following description, a vibration vector obtained based on a vibration measurement value measured by the shaft vibration sensor  120  is referred to as a vibration vector of the shaft vibration sensor  120 . 
     The difference vector calculation unit  293  calculates a difference vector. A difference vector herein is a vector indicating a time change in the vibration vector. Specifically, the difference vector is a vector obtained by subtracting the vibration vector initial value of a corresponding shaft vibration sensor  120  from a vibration vector of the vibration measurement value of the shaft vibration sensor  120 . 
       FIG. 8  is a diagram which shows a calculation example of the difference vector. A coordinate axis of the graph of  FIG. 8  shows the same polar coordinates as that of the graph of  FIG. 5 . 
     In  FIG. 8 , the vector B 11  which is a vibration vector initial value described with reference to  FIG. 5 , and a vector B 12  which is a vibration vector described with reference to  FIG. 7  are shown. The vector B 13  is a vector obtained by subtracting the vector B 11  from the vector B 12 , and corresponds to an example of the difference vector. 
       FIG. 9  is a diagram which shows a display example of the difference vector. A coordinate axis of the graph of  FIG. 9  shows the same polar coordinates as that of the graph of  FIG. 5 . 
     In  FIG. 9 , the vector B 13  which is a difference vector described with reference to  FIG. 8  is shown to start from the origin of a coordinate axis. 
       FIG. 10  is a diagram which shows examples of difference graphs calculated by the difference vector calculation unit  293  for each shaft vibration sensor  120 . A coordinate axis of each graph of  FIG. 10  shows polar coordinates in the same manner as the graph of  FIG. 5 . In  FIG. 10 , difference vectors of each of the horizontal front-side shaft vibration sensor  121   h,  the vertical front-side shaft vibration sensor  121   v,  the horizontal front-side shaft vibration sensor  121   h,  and the vertical front-side shaft vibration sensor  121   v  are shown. 
     In this manner, the difference vector calculation unit  293  calculates a difference vector for each shaft vibration sensor  120  (for each unit in which the vibration vector calculation unit  292  calculates a vibration vector). 
     The estimation unit  294  estimates an abnormality occurrence position in the shaft direction of the rotation shaft  110  on the basis of a time change in the vibration vector. Specifically, apart from the actual measurement values described above, a shaft vibration analysis is performed on the rotary machine  100  to be evaluated. In the shaft vibration analysis, a calculated value of a change in the vibration vector (an effect vector) of each of the horizontal direction and the vertical direction of each bearing position when unit imbalance is installed at each position in the shaft direction of the rotor is converted into a database. Then, a unit imbalance position of a calculated value with which these vectors are closest is selected by comparing a difference vector of the vibration vector between before the occurrence of an abnormality and after the occurrence of an abnormality with an effect vector of the calculated database. 
       FIG. 11  is a diagram which shows an example of a data structure of abnormality occurrence position data stored in the storage unit  280 . 
     In the example of  FIG. 11 , the abnormality occurrence position data includes the “number of rotations” column, a “phase” column and a “magnitude of vibration” column for each shaft vibration sensor  120 , and a “shaft direction position” of an abnormality occurrence position column. 
     The “rotation speed” column stores the rotation speed of the rotation shaft  110 . As the rotation speed of the rotation shaft  110 , for example, the control unit  290  calculates the number of rotations according to the rotation pulse sensor (the angle sensor  130 ). 
     Alternatively, in a case in which the abnormality detection device  200  operates only when the rotation shaft  110  rotates at a predetermined speed such as performing abnormality detection only when the rotation shaft  110  rotates at a rated speed, the “rotation speed” column in the abnormality occurrence position data is unnecessary. 
     The “rotation angle” column and the “magnitude of vibration” for each shaft vibration sensor  120  store a rotation angle and the magnitude of vibration in the vibration vector of a corresponding shaft vibration sensor  120 . 
     A “front and rear position” column and a “circumferential position” column of an abnormality occurrence position store an abnormality occurrence position in the rotation shaft  110  at a position in the shaft direction of the rotation shaft  110  and a position in the circumferential direction thereof. The shaft direction of the rotation shaft  110  (a longitudinal direction of the rotation shaft  110 ) is also referred to as a front and rear direction of the rotation shaft  110 . 
     A method of acquiring abnormality occurrence position data stored in the storage unit  280  is not limited to a specific method. 
     For example, the storage unit  280  may also store abnormality occurrence position data obtained at the time of maintenance and inspection of the rotary machine  100 . When a maintenance worker detects an abnormality of the rotation shaft  110  at the time of maintenance and inspection of the rotary machine  100 , the worker records a position in the front and rear direction of the rotation shaft  110  and a position in the circumferential direction of the rotation shaft  110  as a position of the detected abnormality. In addition, the maintenance worker reads a history of the rotation speed and vibration vector of the rotation shaft  110  in the past within a predetermined period from the maintenance and inspection from history data of the abnormality detection device  200 . Then, the maintenance worker generates the history of the rotation speed and the vibration vector of the rotation shaft  110  and abnormality occurrence position data in the front and rear direction of the rotation shaft  110 , and causes the storage unit  280  to store them. The abnormality occurrence position data obtained at the time of maintenance and inspection of the rotary machine  100  is not limited to data at the time of maintenance and inspection of the rotary machine  100  which is a target for abnormality detection, and it is also possible to use data at the time of maintenance and inspection of another rotary machine  100  of the same type. 
     Alternatively, the storage unit  280  may also store abnormality occurrence position data obtained by a real machine test of the same type of rotary machine  100 . An examination conductor causes, for example, an abnormality such as a crack or deposit to occur in the rotation shaft  110  of the rotary machine  100  to be tested, and inputs an abnormality occurrence position from the operation input unit  220 . Then, the examination conductor operates the rotary machine  100  to cause the rotation shaft  110  to rotate in a state in which an abnormality occurs in the rotation shaft  110 . In the abnormality detection device  200 , the control unit  290  calculates the rotation speed of the rotation shaft  110  and the difference vector calculation unit  293  calculates a difference vector. Then, the control unit  290  generates abnormality occurrence position data by combining the rotation speed and difference vector of the rotation shaft  110  and the abnormality occurrence position, and causes the storage unit  280  to store it. 
     Alternatively, the storage unit  280  may also store an abnormality occurrence data group in which abnormality occurrence position data obtained in each of a plurality of methods is combined. 
       FIG. 12  is a diagram which shows a display example of an abnormality occurrence position in the rotation shaft  110 . In the example of  FIG. 12 , the display unit  230  displays an abnormality occurrence position estimated by the estimation unit  294  under control of the control unit  290 . 
     The display unit  230  displays a failure occurrence position in the front and rear direction of the rotation shaft  110  in a side view in which the rotation shaft  110  is seen in the horizontal direction, and the diameter direction of the rotation shaft  110  (a direction orthogonal to the shaft direction). 
     Next, an operation of the abnormality detection device  200  will be described with reference to  FIGS. 13 and 14 .  FIG. 13  is a flowchart which shows an example of a processing procedure in which the abnormality detection device  200  generates and stores a vibration vector initial value. The abnormality detection device  200  performs processing of  FIG. 13  if a user operation instructing, for example, the generation of a vibration vector initial value is received in a state in which the rotary machine  100  is normal (in particular, in a state in which an abnormality does not occur in the rotation shaft  110 ). 
     In the processing of  FIG. 13 , the vibration measurement value acquisition unit  291  acquires a vibration measurement value for each rotation of the rotation shaft  110  (step S 11 ). The vibration measurement value acquisition unit  291  associates a measurement value of the vibration of the rotation shaft  110  measured by the shaft vibration sensor  120  with a rotation angle measurement value of the rotation shaft  110  measured by the angle sensor  130 , and acquires a vibration measurement value for each rotation angle of the rotation shaft  110 . The vibration measurement value acquisition unit  291  acquires a vibration measurement value for each rotation angle of the rotation shaft  110  for each shaft vibration sensor  120 . 
     Next, the vibration vector calculation unit  292  calculates a vibration vector based on a vibration measurement value for each rotation angle of the rotation shaft  110  acquired by the vibration measurement value acquisition unit  291  (step S 12 ). Specifically, the vibration vector calculation unit  292  detects a maximum value of the vibration and a rotation angle of the rotation shaft  110  at which the vibration has a maximum value based on a vibration measurement value for each rotation angle of the rotation shaft  110 , thereby calculating a vibration vector. 
     In addition, the control unit  290  calculates the rotation speed of the rotation shaft  110  (step S 13 ). Specifically, the control unit  290  calculates the number of rotations of the rotation shaft  110  per unit time on the basis of the rotation angle measurement value of the rotation shaft  110  measured by the angle sensor  130 . 
     Then, the vibration vector calculation unit  292  causes the vibration vector calculated in step S 12  to be stored in the storage unit  280  as a vibration vector initial value (step S 14 ). 
     As described with reference to  FIG. 6 , the vibration vector calculation unit  292  causes vibration vector initial value data including the rotation speed of the rotation shaft  110  and the vibration vector for each shaft vibration sensor  120  to be stored in the storage unit  280 . 
     After step S 14 , the processing of  FIG. 13  ends. 
     The abnormality detection device  200  may calculate and store a vibration vector initial value for each rotation speed of the rotation shaft  110 , for example, during a speed-up operation of the rotary machine  100 . 
     Alternatively, in a case in which the abnormality detection device  200  operates only when the rotation shaft  110  rotates at a predetermined speed such as performing abnormality detection only when the rotation shaft  110  rotates at a rated speed, the “rotation speed” column in the vibration vector initial value data is unnecessary. In this case, the storage unit  280  may store the vibration vector initial value data at the predetermined speed. 
     In addition, when the vibration vector in the state in which the rotary machine  100  is normal is changed due to aging and the like, the abnormality detection device  200  may update the vibration vector initial value data. For example, the abnormality detection device  200  may receive a user operation instructing the generation of a vibration vector initial value, perform the processing of  FIG. 13 , and update the vibration vector initial value data at a timing at which it is confirmed that the rotary machine  100  is normal at a periodic inspection. 
       FIG. 14  is a flowchart which shows an example of a processing procedure in which the abnormality detection device  200  estimates an abnormality occurrence position in the rotation shaft  110 . 
     For example, the abnormality detection device  200  performs the processing of  FIG. 14  if a user operation instructing abnormality detection is received. Alternatively, the processing of  FIG. 14  may be made to be automatically performed such as the abnormality detection device  200  periodically performing the processing of  FIG. 14 . 
     Steps S 21  to S 23  of  FIG. 14  are the same as steps S 11  to S 13  of  FIG. 13 . After step S 23 , the difference vector calculation unit  293  acquires a vibration vector initial value (step S 24 ). Specifically, the difference vector calculation unit  293  reads vibration vector initial value data in accordance with the number of rotations of the rotation shaft  110  obtained in step S 23  from the storage unit  280 . 
     Next, the difference vector calculation unit  293  calculates a difference vector for each shaft vibration sensor  120  (step S 25 ). Specifically, the difference vector calculation unit  293  subtracts the vibration vector initial value from the vibration vector obtained in step S 22  for each shaft vibration sensor  120 . 
     Next, the estimation unit  294  determines the presence or absence of an abnormality in the rotation shaft  110  (step S 26 ). For example, the estimation unit  294  compares a maximum value in the magnitude of vibration indicated by the vibration vector of each shaft vibration sensor  120  with a threshold value stored in advance by the storage unit  280 . When the magnitude of vibration is larger than the threshold value, the estimation unit  294  determines that there is an abnormality in the rotation shaft  110 . On the other hand, when the magnitude of vibration is equal to or less than the threshold value, the estimation unit  294  determines that there is no abnormality in the rotation shaft  110 . 
     Alternatively, the estimation unit  294  may also determine the presence or absence of an abnormality in the rotation shaft  110  on the basis of a change amount in the magnitude of vibration in addition to or instead of the magnitude of vibration indicated by a difference vector. 
     For example, the storage unit  280  stores a history of a difference vector. The estimation unit  294  calculates a magnitude of a vector obtained by subtracting a previous value from a present value of a difference vector for each shaft vibration sensor  120  as the change amount in the magnitude of vibration. The estimation unit  294  compares a maximum value of the change amount in the magnitude of vibration calculated for each shaft vibration sensor  120  with a threshold value stored in advance in the storage unit  280 . When the change amount is larger than the threshold value, the estimation unit  294  determines that there is an abnormality in the rotation shaft  110 . On the other hand, when the change amount is equal to or less than the threshold value, the estimation unit  294  determines the presence or absence of an abnormality in the rotation shaft  110  on the basis of the magnitude of vibration indicated by a difference vector. 
     When it is determined that there is no abnormality in step S 26  (NO in step S 26 ), the processing of  FIG. 14  ends. 
     On the other hand, when it is determined that there is an abnormality in step S 26  (YES in step S 26 ), the estimation unit  294  estimates an abnormality occurrence position in the rotation shaft  110  (step S 27 ). The estimation unit  294  selects (searches for) abnormality occurrence position data closest to a rotation speed obtained in step S 23  and a difference vector for each shaft vibration sensor  120  obtained in step S 25  among the abnormality occurrence position data stored in the storage unit  280 . Then, the estimation unit  294  estimates an abnormality occurrence position by reading an abnormality occurrence position from obtained abnormality occurrence position data. 
     Next, the display unit  230  displays the abnormality occurrence position estimated by the estimation unit  294  under the control of the control unit  290  (step S 28 ). For example, the display unit  230  displays an abnormality occurrence position in the shaft direction of the rotation shaft  110  and an abnormality occurrence position in the circumferential direction of the rotation shaft  110  as shown in the example of  FIG. 12 . 
     After step S 28 , the processing of  FIG. 14  ends. 
     As described above, the plurality of shaft vibration sensors  120  are provided to be spaced apart in the diameter direction of the rotation shaft  110  with respect to the outer circumferential surface of the rotation shaft  110  at positions spaced apart in the shaft direction of the rotation shaft  110 . The vibration measurement value acquisition unit  291  acquires a measurement value of the vibration of the rotation shaft  110  measured by the shaft vibration sensor  120  for each rotation angle of the rotation shaft  110 . The vibration vector calculation unit  292  calculates a vibration vector indicating a rotation angle at which the vibration of the rotation shaft  110  is a maximum and the magnitude of the vibration on the basis of the measurement value of the vibration acquired by the vibration measurement value acquisition unit  291 . The estimation unit  294  estimates an abnormality occurrence position in the shaft direction of the rotation shaft  110  on the basis of a time change in the vibration vector. 
     According to the abnormality detection device  200 , it is possible to obtain information for the maintenance work of the rotary machine  100  in that an estimation value of an abnormality occurrence position in the shaft direction of the rotation shaft  110  is obtained. 
     For example, in a previous step in which the rotary machine  100  is stopped by detecting an abnormality vibration, if an abnormality occurrence position in the shaft direction of the rotation shaft  110  can be estimated, there is a possibility that a required replacement part can be specified and prepared. When the rotary machine  100  is a steam turbine, it is possible to specify at which blade an abnormality has occurred by specifying an abnormality occurrence position in the shaft direction of the rotation shaft  110 , and a blade for replacement can be prepared in advance. 
     In addition, a maintenance worker ascertains a position estimated as a position at which an abnormality has occurred at the time of the maintenance work of the rotary machine  100 , and thereby it is expected that an abnormality can be found earlier and a possibility of overlooking an abnormality can be reduced. 
     In addition, the shaft vibration sensor  120  measures the vibration of the rotation shaft  110  in a plurality of directions among the circumferential directions of the rotation shaft  110 , thereby avoiding overlooking the vibration. 
     If the shaft vibration sensor  120  is installed only in the horizontal direction with respect to the rotation shaft  110 , if the rotation shaft  110  vibrates only in the vertical direction, a vibration measurement value measured by the shaft vibration sensor  120  is not large, and the abnormality detection device  200  may underestimate the magnitude of the vibration. On the other hand, the shaft vibration sensor  120  measures the vibration of the rotation shaft  110  in a plurality of directions among the circumferential directions of the rotation shaft  110 , and thereby, even if the rotation shaft  110  vibrates in any one direction, at least one of the vibration measurement values of the shaft vibration sensor  120  is large, and a possibility that the abnormality detection device  200  can detect a vibration is increased. 
     Moreover, the estimation unit  294  estimates an abnormality occurrence position on the basis of a time change in the vibration vector, thereby estimating an abnormality occurrence position by removing the influence of vibration at the time of the rotary machine  100  being normal, and estimating an abnormality occurrence position with high accuracy in this regard. 
     Here, the rotation shaft  110  also vibrates even when the rotary machine  100  is normal. If this vibration serves as an offset for a vibration measurement value at the time of estimating an abnormality occurrence position, it is considered that estimation accuracy of an abnormality occurrence position can be lowered. On the other hand, a vibration component at the time of the rotary machine  100  being normal is removed in a time change in the vibration vector (for example, a difference vector). The estimation unit  294  estimates an abnormality occurrence position on the basis of a time change in the vibration vector, thereby estimating an abnormality occurrence position by removing the influence of vibration at the time of the rotary machine  100  being normal, and estimating an abnormality occurrence position with high accuracy in this regard. 
     In addition, it is considered that the vibration at the time of the rotary machine  100  being normal is different for each rotary machine  100 . When the storage unit  280  stores abnormality occurrence position data obtained from another rotary machine  100  of the same type, the estimation unit  294  searches for the abnormality occurrence position data with a time change in the vibration vector set as an index, thereby performing a search by influence of individual differences for each rotary machine  100 . In this regard, the estimation unit  294  can estimate an abnormality occurrence position with high accuracy. 
     In addition, the shaft vibration sensor  120  is provided in each of the diameter directions of the rotation shaft  110  orthogonal to each other. 
     As a result, even if the rotation shaft  110  vibrates in any direction, at least one of the vibration measurement values of the shaft vibration sensor  120  is large, and a possibility that the abnormality detection device  200  can detect a vibration is increased. 
     Moreover, phase matching of the vibration vectors of two shaft vibration sensors  120  can be performed in a relatively easy manner. Phase matching of the vibration vectors herein means to align coordinates of the rotation angles of the rotation shaft  110  as shown in  FIG. 10 . 
     In addition, the estimation unit  294  estimates an abnormality occurrence position in the shaft direction of the rotation shaft  110  on the basis of the rotation speed of the rotation shaft  110  in addition to the time change in the vibration vector. If the rotation speed of the rotation shaft  110  changes, the vibration vector may also change. The estimation unit  294  estimates an abnormality occurrence position in the shaft direction of the rotation shaft  110  on the basis of the rotation speed of the rotation shaft  110  in addition to the time change in the vibration vector, thereby estimating an abnormality occurrence position with higher accuracy. 
     Second Embodiment 
       FIG. 15  is a schematic block diagram which shows a functional configuration of a rotary machine system according to a second embodiment of the present invention. As shown in  FIG. 15 , a rotary machine system  2  includes the rotary machine  100  and a difference vector display device  300 . 
     The rotary machine  100  includes the rotation shaft  110 , the shaft vibration sensor  120 , and the angle sensor  130 . The difference vector display device  300  includes the communication unit  210 , the operation input unit  220 , the display unit  230 , the storage unit  280 , and the control unit  290 . The control unit  290  includes the vibration measurement value acquisition unit  291 , the vibration vector calculation unit  292 , and the difference vector calculation unit  293 . 
     The same reference numerals ( 100 ,  110 ,  120 ,  130 ,  210 ,  220 ,  230 ,  280 ,  290 ,  291 ,  292 , and  293 ) are assigned to parts of  FIG. 15  having the same functions corresponding to respective parts of  FIG. 1 , and descriptions thereof will be omitted. 
     The rotary machine system  2  shown in  FIG. 15  is different from the rotary machine system  1  shown in  FIG. 1  in that it includes a difference vector display device  300  instead of the abnormality detection device  200 . The difference vector display device  300  is different from the abnormality detection device  200  in that it includes the estimation unit  294 . In other respects, the rotary machine system  2  is the same as the rotary machine system  1 . 
     The abnormality detection device  200  displays a result of the estimation of an abnormality occurrence position, whereas the difference vector display device  300  displays a difference vector. The display unit  230  of the difference vector display device  300 , for example, displays a difference vector of each shaft vibration sensor  120  as shown in the example of  FIG. 10  under control of the control unit  290 . 
     The display unit  230  displays a difference vector, and thereby a user of the difference vector display device  300  (an administrator of the rotary machine  100 ) can ascertain the phase and magnitude of vibration in the rotation shaft  110 , and use them as a reference for estimating an abnormality occurrence position in the rotation shaft  110 . 
     Next, an operation of the difference vector display device  300  will be described with reference to  FIG. 16 . 
       FIG. 16  is a flowchart which shows an example of a processing procedure in which the difference vector display device  300  calculates and displays a difference vector. 
     Steps S 31  to S 35  of  FIG. 16  are the same as steps S 21  to S 25  of  FIG. 14 . After step S 35 , the display unit  230  displays a difference vector obtained for each shaft vibration sensor  120  in step S 35  under the control of the control unit  290  (step S 36 ). 
     After step S 36 , the processing of  FIG. 16  ends. 
     As described above, the plurality of shaft vibration sensors  120  are provided to be spaced apart in the diameter direction of the rotation shaft  110  with respect to the outer circumferential surface of the rotation shaft  110  and provided to be spaced apart in the shaft direction of the rotation shaft  110 . The vibration measurement value acquisition unit  291  acquires a measurement value of the vibration of the rotation shaft  110  measured by the shaft vibration sensor  120  for each rotation angle of the rotation shaft  110 . The vibration vector calculation unit  292  calculates a vibration vector indicating a rotation angle at which the vibration of the rotation shaft  110  is a maximum and the magnitude of the vibration on the basis of the measurement value of the vibration acquired by the vibration measurement value acquisition unit  291 . The difference vector calculation unit  293  calculates a difference vector indicating a time change in the vibration vector. The display unit  230  displays a difference vector. The display unit  230  displays a difference vector, and thereby a user of the difference vector display device  300  (for example, an administrator of the rotary machine  100 ) can ascertain the phase and magnitude of vibration in the rotation shaft  110 , and use them as a reference for estimating an abnormality occurrence position in the rotation shaft  110 . 
     The processing of each unit may be performed by recording a program for realizing all or a part of functions of the control unit  290  in a computer-readable recording medium, and causing a computer system to read and execute the program recorded in this recording medium. “Computer system” herein includes hardware such as an OS and peripheral devices. In addition, “computer system” also includes a homepage-providing environment (or a display environment) if it uses a WWW system. 
     In addition, “computer-readable recording medium” refers to a storage device such as a portable medium such as a flexible disk, a magneto-optical disc, a ROM, a CD-ROM, and a hard disk embedded in a computer system. Moreover, the program may be one for realizing a part of the functions described above, or may be a program for realizing the functions described above in combination with a program already recorded in the computer system. 
     As described above, the embodiments of the present invention have been described in detail with reference to drawings, but a specific configuration is not limited to the embodiments, and design changes and the like within a scope not departing from the gist of this invention are also included.