JPS63150633A - Shaft vibration diagnosing device - Google Patents

Abstract

PURPOSE:To detect an abnormal indication in its early stage by converting an analog vibration signal from a vibration detector into digital data and then sampling it at 1st and 2nd sampling periods and performing Fourier transformation. CONSTITUTION:Shaft vibrations of a body 4 of rotation are detected by the vibration detector 6 and the analog signal from the detector is converted by an A/D converter 6 into the digital data. This digital data is sampled by a sampling means 23 at the 1st and 2nd different sampling periods and stored in a memory 23. Further, 1st and 2nd data groups obtained by the sampling are processed by a fast Fourier transform processor 19. A main controller 20 decides the vibration state of the body 4 of rotation according to the output of the fast Fourier transform processor 19.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a shaft vibration diagnosis device for diagnosing shaft vibration of a rotating machine such as a steam turbine generator. The present invention relates to a shaft vibration diagnosis device that determines an abnormality in shaft vibration based on a specific Fourier component, that is, a frequency component, obtained by Fourier transform.

(Prior Art) In general, in rotating machines, abnormalities tend to occur in the rotating body when the operating state suddenly changes, such as when starting or stopping.

In particular, in steam turbine generators in thermal power plants, rapid temperature changes can cause elongation and uneven stress changes in various parts, and the operating speed can even exceed the rotor's critical speed. There is also a risk of damage to the turbine. Therefore, a shaft vibration diagnostic device is attached to the steam turbine generator to monitor abnormal shaft vibration of the turbine.

FIG. 3 shows a shaft vibration diagnosis device attached to a conventional steam turbine generator, in which the rotors 4, 4, . ...
is bearing 5, 5. These bearings 5 are equipped with vibration detectors 6, which detect shaft vibration of each rotor 4.
6. ...is provided. Also attached are a tachometer 7 for detecting the number of rotations of the rotor 4, a negative 6f sensor 8 for detecting the load of the generator, and a sensor 9 for detecting temperature, pressure, etc. The central operation panel 10 includes an operation monitoring device 11, a vibration monitoring device 12, an alarm device 13, and a recorder 14, and the operation monitoring device 11 monitors each output signal from the tachometer 7 and sensors 8 and 9. The vibration monitoring device 12 monitors the shaft vibration signal from the vibration detector 6, and the alarm device 3 outputs an alarm or a trip signal when the amplitude of the shaft vibration exceeds a permissible value.

Further, the recorder 14 records the vibration amplitude and the like.

The vibration monitoring device 12 detects an abnormality in shaft vibration based on the amplitude value of the shaft vibration, but depending on the cause of the abnormality, a symptom of the abnormality often appears in the vibration frequency rather than the amplitude value of the shaft vibration. For this reason, JP-A-58-100734
No. 3 discloses an abnormality diagnosis device 15 that detects and diagnoses abnormalities at an early stage based on analysis of this vibration frequency. In this abnormality diagnosis device 15, the shaft vibration signal from the vibration monitoring device 12 is converted into a digital value by an A/D converter 16, temporarily stored in a digital memory 17, and then converted into a digital value by a fast Fourier transformer (FFT) 18. Fast Fourier transform,
1! Extract a number of specific frequency components. The +controller 19 compares the extracted frequency components with the reference value to determine abnormality, and sends the results to the display device 20 for display, and also to the hli auxiliary storage device 21 to store the data.

(Problems to be solved by the invention) In such a shaft vibration diagnosis device, when an abnormality occurs,
It is necessary to detect it in real time and take immediate action. However, in the above-mentioned device, the amplitude detection by the central operation panel 10 is done using shaft vibration signals or analog data, so it can be done almost in real time, but the frequency analysis by the abnormality diagnosis device 15 is done using digital data. The Fourier transform performed by the fast Fourier transformer 18 takes time, making real-time processing difficult. In order to monitor up to the high frequency range, it is naturally necessary to shorten the sampling period of A/D conversion, and in order to improve the phase accuracy of the Fourier-transformed frequency components, it is necessary to lengthen the sampling time. These inevitably lead to an increase in the number of data to be Fourier transformed, that is, the number of samples. As shown in Figure 4, there is a relationship of α-21ogmN between the number of samplings N and the number of Fourier calculations α, and since the Fourier processing time is proportional to the number of calculations α, as the number of samplings increases, Fourier transformation takes a long time, making real-time processing difficult.

Therefore, the purpose of the present invention is to
It is an object of the present invention to provide a shaft vibration diagnostic device that can detect and diagnose abnormalities in a rotating body of a rotating machine at an early stage by performing the following in a short time.

(Means for solving the problem) In order to achieve this object, the present invention provides a vibration detector that detects shaft vibration of a rotating body, and converts an analog vibration signal from this vibration detector into digital data. A/D conversion means; sampling means for sampling the digital data from the A/D conversion means at first and second sampling periods different from each other; and sampling means for sampling the digital data sampled at the first sampling period. memory means for storing the digital data sampled at the second data group as a first data group and the digital data sampled at the second sampling period as a second data group; The present invention is characterized by comprising a fast Fourier transform means for performing fast Fourier transform, and a control means for determining the vibration state of the -1- rotation body based on the output of the fast Fourier transform means.

(Function) The A/D conversion means converts the analog vibration signal detected by the vibration detector into digital data at a predetermined timing, and this digital data is converted into digital data by the sampling means at the first sampling period and the second sampling period. Each is sampled and sent to memory means. The memory means stores the data sampled in the first sampling period as a first data group and the data sampled in the second sampling period as a second data group, and the fast Fourier transform means stores the data sampled in the first sampling period as a second data group. Fast Fourier transform is performed on the data of and the data of the second data group, respectively,
A relatively high-order frequency component is extracted from a data group with a shorter sampling period, and a relatively low-order frequency component is extracted from a data group with a longer sampling period. The control means determines the vibration state of the rotating body based on information in a plurality of frequency ranges subjected to the fast Fourier transform.

For a data group with a long sampling period, the number of data can be significantly reduced compared to the total number of data A/D converted by the sampling means. In addition, since the sampling period for a data group with a short sampling period can be made shorter than that of a data group with a long sampling period, the number of data in this data group with a short sampling period is also significantly larger than the total number of data in the above-mentioned sampling means. can be reduced. Therefore, the processing time for Fourier transform of the first and second data groups can be significantly reduced compared to the case where all A/D converted data is subjected to Fourier transform.

(Embodiment) Hereinafter, an embodiment of the shaft vibration diagnosis device according to the present invention will be described in detail with reference to FIGS. 1 and 2, in which the same parts as in FIGS. explain.

In FIG. 1, the vibration monitoring board 12 includes a vibration detector 6.6.
The analog shaft vibration signal Av shown in FIG. This A/D converter 16 converts the analog shaft vibration signal Av into A/D based on the sampling pulse signal Bs of FIG. 2(C) which is synchronized with the rotation pulse signal As of the tachometer 7 shown in FIG. 2(b). D-convert and output digital data. The sampling means 22 samples the digital data from the A/D converter 16 at first and second sampling periods. The sampling period t2 of this first sampling period signal B is set to be sufficiently larger than the period 11 of the sampling pulse signal Bs of FIG. 2(C), as shown in FIG. The sampling period t1 of the second sampling period signal B shown in (e) is set to be the same as that of the summing pulse signal Bs.

The memory 23 has two memory parts 23A and 23B,
This memory section 23A stores the data A1 of FIG. 2(f) sampled at the first sampling period t2 as a first data group, and the second memory section 23B stores the data A1 of FIG. Data A2 in (g) is stored in memory as a second data group. The fast Fourier transformer 18 fast Fourier transforms the data A1 of the first data group stored in the first memory section 23A to extract the low frequency component C3I shown in FIG. The data A2 of the second data group stored in the memory is fast Fourier-transformed to obtain the high frequency component C32 in FIG. 2(i).
Extract. In FIGS. 2(h) and (i), the signal (1) is the rotation synchronous component of the rotor 4, and the signal (n),
(III) are a low frequency component and a high frequency component, respectively.

The main controller 9 divides the low frequency component C3I and the high frequency component C32 from the fast Fourier transformer 18 into
It also compares it with a reference value to detect signs of abnormality, sends the results to the display device 20, and sends the data to the auxiliary storage device 21. Also, the main controller/roller 19 creates a sampling pulse signal Bs synchronized with the pulse signal As based on the pulse signal As of the tachometer 7 and its own cross pulse, sends it to the A/D converter 16, and similarly , the first and second sample 1 signal B1. B2 is created and sent to the sampling means 22. The other configurations are the same as in FIG. 3.

Next, the operation of the above-mentioned shaft vibration diagnosis device will be explained.

The vibration monitoring device 12 and the alarm generator 13 are the vibration detector 6
Based on the amplitude information of analog shaft vibration signals from

The A/D converter 16 converts the analog shaft vibration signal Av into a cycle t1.
The sampling means 22 samples this digital data at a first sampling period t2 and a second sampling period t1, respectively, to obtain a first data group A1 and a second data group. Create A2.

The number of data in this first data group A1 and the second data group A2
The number of data items is set equal to N'. This number N' is equal to 2 pieces BN of all the data A/D converted by the A/D converter 16.

That is, N' -- (1) where m is an integer from 4 to 8.

The fast Fourier transformer 18 includes first memory sections 23A, 23
The first data group A1 and the second data group A2 respectively stored in B are subjected to fast Fourier transform to extract a low frequency component C5I and a high frequency component CS2. The main controller 9 detects an abnormality sign based on the low frequency component C5I and the high frequency component CS2, and displays it on the display device 22. The auxiliary storage device 21 records data CSI, CS2, etc., and uses +1r as data on changes over time.

Assuming that the number of A/D converted data, that is, the number of data N required in the conventional device, is N=210, and m in equation (2) is defined as m-8, N'=,=27. Since the number of calculations α for the fast Fourier transform is α-21ogmNα', the total calculation ratio is -0,175, which is significantly reduced by α. In this way, the abnormality diagnosis device 15 can also perform frequency analysis by quickly performing Fourier transform processing on the shaft vibration Av.

In addition, in the first embodiment, the number of data in the first data group AI and the number of data in the second data group A2 are made equal, but the number is not necessarily limited to this, and a difference may be given between them.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, A/
After sampling the digital data from the D converter in the first and second sampling periods and storing them as the first data group and the second data group, in order to perform fast Fourier transform, the number of data in the first data group and the The number of data in the two data groups can be significantly reduced compared to the number of digital data from the A/D converter, and therefore the processing time for fast Fourier transform can be significantly shortened.

Therefore, early detection of abnormality signs is possible despite frequency analysis.

Furthermore, since the number of data to be stored in the memory means is reduced, the scale of the memory can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the shaft vibration diagnosis device according to the present invention, Fig. 2 is a signal waveform diagram showing signals of each part in Fig. 1, and Fig. 3 is a conventional shaft vibration diagnosis device. FIG. 4 is a graph diagram showing the relationship between the number of fast Fourier transform calculations and the number of samplings. 4...Rotor, 6...Vibration detector, 16...A/
D converter, 19...Fast Fourier transformer, 20...
Main controller, 22... Sampling means, 23.
・Memo Applicant's Agent 11i Fujio Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A vibration detector for detecting shaft vibration of a rotating body, an A/D conversion means for converting an analog vibration signal from the vibration detector into digital data, and from this A/D conversion means sampling means for sampling the digital data at first and second sampling periods different from each other; and sampling means for sampling the digital data sampled at the first sampling period as a first data group;
a memory means for respectively storing the data sampled at the sampling period as a second data group; a fast Fourier transform means for fast Fourier transforming the data of the first data group and the data of the second data group; An apparatus for diagnosing shaft vibration of a rotating body such as a steam turbine generator, comprising: control means for determining the vibration state of the rotating body based on the output of the fast Fourier transform means. 2. The number of data in the first data group and the number of data in the second data group are each 1/m of the number of data from the sampling means (m is an integer from 4 to 8). A shaft vibration diagnosis device according to claim 1. 3. The shaft vibration diagnosis device according to claim 1, wherein the number of data in the first data group and the number of data in the second data group are equal to each other.