JP5224912B2 - Vibration monitoring apparatus and monitoring method - Google Patents

Description

  The present invention relates to a vibration monitoring apparatus and a monitoring method for a structure, and more particularly, to a vibration monitoring apparatus and a monitoring method for measuring vibration of a measurement object inside a structure from the outside of the structure by an ultrasonic transmission / reception apparatus.

  In a conventional non-destructive inspection apparatus, as a method for non-destructively monitoring the vibration of the inspection object inside the container or inside the flow path flowing through the container, a method of directly monitoring the vibration by providing an accelerometer on the measurement object, A method of monitoring the vibration of an object to be measured by an ultrasonic transmission / reception device provided outside is used.

  In the vibration monitoring method using ultrasonic waves, ultrasonic waves are transmitted from the ultrasonic transmission / reception device installed outside the container toward the inspection object, and are transmitted to the inspection object through the container wall and the medium in the container. The ultrasonic wave is reflected from the object to be inspected, and the ultrasonic wave is received to measure the propagation time, and converted into a distance in consideration of the propagation speed of the ultrasonic wave in the medium. By repeating this process at high speed, the vibration displacement amount of the measurement object is measured, and an abnormality of the structure of the measurement object is detected.

  As a vibration monitoring apparatus using such ultrasonic waves, Patent Document 1 discloses that ultrasonic waves are transmitted from an ultrasonic transmission / reception apparatus installed outside the pressure vessel in order to monitor the reactor internal structure in the reactor pressure vessel. It is described that the vibration of the reactor internal structure is monitored by measuring the change in the propagation time of the ultrasonic wave based on the vibration of the furnace internal structure by signal transmission and reception toward the reactor internal structure. .

Further, in Patent Document 2, in order to monitor the vibration of the rotating shaft of the electric pump installed in the container, ultrasonic waves are transmitted and received from the ultrasonic transmitting / receiving device installed outside the container toward the rotating shaft, and reflected. It is described that the waveform is subjected to signal processing using frequency analysis or the like, thereby measuring the displacement of the rotating shaft and monitoring the vibration of the electric pump.
Japanese Patent No. 3785559 JP 2004-020540 A "Ultrasonic Technology Handbook", published by Nikkan Kogyo Shimbun, 1971, p16-21

  In the conventional vibration monitoring method in which the above-mentioned accelerometer is directly attached to the inspection object, when the measurement object extends to a plurality of places, it is necessary to install a large number of accelerometers, and it affects the operation of the measurement object. There have been many problems in terms of cost and structure, such as the need for complicated wiring, and deterioration and dropout of the accelerometer.

  Further, in the vibration monitoring apparatus using the ultrasonic wave described above, it is possible to monitor the vibration of the structure inside from the outside of the container and the flow path. When an intermediate structure is present between them, most of the ultrasonic waves transmitted from the outside of the container are reflected by the intermediate structure, which causes a problem that the vibration of the measurement object cannot be accurately measured.

  In such a case, it is possible to measure the vibration of the measurement object by providing an opening in the intermediate structure so as not to interfere with the propagation of ultrasonic waves, but the structure is modified to provide an opening. There was a problem that required.

  The present invention has been made in order to solve the above-described problems, and allows ultrasonic waves to propagate efficiently even when there is an intermediate structure between a structure such as a container and a measurement object in the structure. An object of the present invention is to provide a vibration monitoring apparatus and a monitoring method capable of monitoring the vibration of a measurement object with high accuracy.

In order to solve the above-described problems, a vibration monitoring apparatus according to the present invention is a vibration monitoring apparatus for a structure having an intermediate structure between a structure and a measurement object in the structure. An ultrasonic transmission / reception device that transmits ultrasonic waves to a measurement object and receives reception waves, an A / D conversion device that converts the reception waves into digital values, and a time waveform of a received signal by performing arithmetic processing on the digital values A signal processing device that measures a vibration displacement of the measurement object from a change in shape, calculates a vibration value and a vibration frequency of the measurement object, and monitors a change in the vibration value or vibration frequency of the measurement object. An abnormality determination device for determining an abnormality, wherein the ultrasonic transmission / reception device changes a frequency of an ultrasonic wave transmitted from the ultrasonic transmission / reception device to determine a frequency at which an echo level of the received wave is maximum. In I, an ultrasonic wave of sending to the measurement object, and sets the 2 / n times the thickness of the intermediate structure where n is an integer.

The vibration monitoring method according to the present invention is an ultrasonic wave provided on an outer wall of the structure in the vibration monitoring method for a structure having an intermediate structure between the structure and the measurement object in the structure. By determining the frequency at which the echo level of the received wave is maximized by changing the frequency of the ultrasonic wave transmitted from the transmission / reception device, the wavelength of the ultrasonic wave transmitted to the measurement object is the above when n is an integer. and sets to 2 / n times the intermediate structure thickness, of the wavelength ultrasound transmits the measurement object, converts the received waves into a digital value, the received signal processing the digital values The measurement object is measured by measuring the vibration displacement of the measurement object from the change of the time waveform shape, calculating the vibration value and vibration frequency of the measurement object from the vibration displacement, and monitoring the change of the vibration value or vibration frequency. Abnormality of things Characterized in that it constant.

  According to the present invention, when there is an intermediate structure between a structure such as a container and the measurement object in the structure, the ultrasonic wave is efficiently propagated and the vibration of the measurement object is monitored with high accuracy. It is possible to provide a vibration monitoring apparatus and a monitoring method that can be used.

Hereinafter, embodiments of a vibration monitoring apparatus and a monitoring method according to the present invention will be described with reference to the drawings.
(First embodiment)
A vibration monitoring apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a case in which the vibration of the measuring object 6 inside the container is measured by the ultrasonic transmission / reception apparatus 1 installed outside the outer wall 4 of the container, but the outer wall 4 of the container and the measuring object 6 are measured. The intermediate structure 5 such as the inner wall exists between the two.

  When the ultrasonic pulse generator 21 transmits an ultrasonic pulse having a predetermined frequency indicated by the transmission waveform 2 from the ultrasonic transmission / reception apparatus 1, the transmitted ultrasonic pulse is in the fluid or gas inside the outer wall 4, the container 4. To reach the intermediate structure 5. A part of the ultrasonic pulse is reflected by the intermediate structure 5, but the other part is transmitted through the intermediate structure 5 and propagates to the measurement object 6. The ultrasonic pulse is reflected by the measuring object 6 and propagates again in the fluid or gas, the intermediate structure, and the outer wall, and the ultrasonic pulse indicated by the received waveform 3 reaches the ultrasonic transmitting / receiving apparatus 1 and is received.

The received ultrasonic pulse is converted from analog to digital by the A / D converter 22 and taken into the signal processor 23. In the signal processing device 23, the digital value of the ultrasonic pulse is arithmetically processed, and the change in the return time of the ultrasonic echo is calculated from the change in the time waveform shape of the received signal. Furthermore, the vibration displacement of the measurement object is calculated by multiplying the change in the return time by the speed of the ultrasonic wave propagating in the fluid or gas. The vibration value and vibration frequency of the measurement object 6 are calculated from the calculated vibration displacement, and these values are displayed on the display device 24, and the abnormality determination device 25 monitors changes in the vibration value and vibration frequency. The presence / absence of abnormality of the measuring object 6 to be inspected is determined.
Here, the measurement principle of the vibration monitoring apparatus according to the present invention will be described.

The ultrasonic transmittance T _I in the intermediate structure 5 between the container 4 and the measurement object 6 is such that the acoustic impedance around the intermediate structure is z ₁ , the impedance of the intermediate structure is z ₂ , and the intermediate structure plate the thickness L, and the wavelength of the ultrasonic wave that propagates through the intermediate structure in the lambda _2, represented by the following formula (1) (non-Patent Document 1).

As shown in this formula (1), the ultrasonic transmittance T _I is maximized when the thickness L of the intermediate structure becomes 2 / n times the wavelength λ ₂ in the intermediate structure 5. . In the present invention, the wavelength of the ultrasonic wave to be transmitted is changed so as to maximize the transmittance, and is set so as to obtain an optimum wavelength. Since the sound speed of ultrasonic waves is determined by temperature and material, the frequency is controlled in consideration of the parameters. Specifically, the frequency of the transmitted wave transmitted from the ultrasonic transmission / reception device 1 is changed, and the frequency at which the received echo is maximized is automatically determined.

  At this time, the time for the ultrasonic wave to reach the measuring object 6 is estimated from the design information on the dimensions and material, and the received echo in the time domain is monitored to find the frequency at which the echo level is maximum.

  When a general ultrasonic probe is used as the ultrasonic transmission / reception apparatus 1, since the width of the changeable transmission frequency is small, the frequency scanning range is limited. Therefore, it is desirable to select an ultrasonic transmission / reception apparatus having a resonance frequency close to the estimated frequency based on the design information of the structure. In addition, it is desirable to use a pulse wave having a rectangular waveform including a plurality of frequencies or a chirp wave that can efficiently use the frequency characteristics of the ultrasonic transmission / reception apparatus as the pulse signal to be transmitted. Furthermore, it is also possible to use electromagnetic ultrasonic waves (EMAT) capable of transmitting longitudinal waves that can be changed regardless of the resonance frequency of the transmission / reception device.

  FIG. 2 shows an example of the time waveform of the ultrasonic reception wave. In FIG. 2, the reception echo area (1) is an area where a transmitted pulse is received by multiple reflection in the outer wall 4. The reception echo area (2) is a multiple echo reflected from the surface of the intermediate structure 5, and the reception echo area (3) is an echo reflected from the measurement object 6.

  Therefore, the time for the ultrasonic wave to reach the measurement object 6 is estimated, the reception echo in the time domain is monitored, and the reception wave from the measurement object 6 in the reception echo area (3) is detected and analyzed.

  FIG. 3 is an enlarged view of the ultrasonic reception wave in the reception echo area (3). When the measurement object 6 vibrates in the propagation direction of the ultrasonic wave, the time until the ultrasonic wave reaches the measurement object 6 changes by the amount of vibration. Therefore, the reception wave is the reception wave 3a and the reception wave 3b. Thus, the shape moves in the time axis direction. Measurement is performed by continuously transmitting ultrasonic waves, continuously storing the received waves 3a and 3b, calculating the amount of change in the shape of the received waves 3a and 3b by a signal processing device, and multiplying by the ultrasonic velocity. The vibration amount (displacement amount) of the object 6 can be calculated.

  For example, consider a case where the measurement object 6 is in water. If the ultrasonic velocity in water is 1500 m / sec and the amount of change in the time axis direction of the received wave is 10 nsec, vibration of 1500 (m / sec) × 10 (nsec) /2=7.5 μm could be measured. It becomes. As a result, a time change of vibration as shown in FIG. 4 can be obtained. By detecting the magnitude (vibration value) and vibration frequency of the inspection object 6 from the time change of the vibration, and monitoring the fluctuation of those values, it is possible to grasp the abnormality of the inspection object.

  As shown in FIG. 5, as the ultrasonic transmission / reception apparatus 1, an ultrasonic transmission apparatus 1 a for transmission and an ultrasonic reception apparatus 1 b for reception may be provided separately. As a result, sensitivity adjustment and noise analysis of transmitted / received waves can be performed separately, so that highly accurate signal processing and vibration monitoring can be performed.

  According to the first embodiment, even when an intermediate structure such as an inner wall exists between a structure such as a container and a measurement object, ultrasonic pulses having a frequency that can propagate through the intermediate structure are transmitted and received. By using it as a wave, it is possible to measure the vibration of the measurement object with high accuracy and to monitor the occurrence of abnormality.

(Second Embodiment)
A vibration monitoring apparatus according to a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment of the present invention, the monitoring device according to the present invention is applied to monitoring of a pump shaft or monitoring of a heat transfer tube of a heat exchanger.

  FIG. 6A is an overall configuration diagram of a pumped-type vertical pump, in which an impeller is disposed at the lower end of a long pumped pipe to suck up a fluid. Generally, a vibration monitoring method is used to check whether there is any abnormality in the pump, and the acceleration of the motor unit and the shaft vibration of the rotating unit are monitored. In this vertical pump, as shown in FIG. 6A, a protective pipe 11 corresponding to the intermediate structure 5 is installed between the pumping pipe 10 and the pump shaft 12. When the vibration of the pump shaft 12 is monitored, the portion surrounded by the broken line in FIG. 6A is enlarged and the ultrasonic transmission / reception device 1 is installed outside the pumping pipe 10 as shown in FIG. The vibration of the pump shaft 12 is monitored by transmitting ultrasonic waves that pass through a certain protective tube 11.

  According to the present invention, since the rotation shaft can be monitored from the outside, the pump main body is not required to be modified, and the pump can be monitored without affecting the function of the pump.

  In addition, in a vertical pump of a type in which the pumping pipe 10 is installed in a barrel or tank (not shown), the ultrasonic transmitting / receiving device 1 is installed in the barrel or tank, and the pump is passed through the pumping pipe corresponding to an intermediate structure. It is also possible to monitor the vibration of the shaft 12.

  Further, FIG. 7 shows a case where the vibration monitoring device of the present invention is applied to vibration monitoring of a device 14 having a heat transfer tube such as a heat exchanger or a feed water heater. The vibration of the heat transfer tube 17 may increase due to wear of the support plate that supports the heat transfer tube 17, and the heat transfer tube may be damaged. In the example of FIG. 8, the baffle plate 16 exists between the container 15 and the heat transfer tube 17 that is a measurement object, but an ultrasonic pulse that propagates through the baffle plate 16 is transmitted by the ultrasonic transmission / reception device 1 provided on the outer wall. The vibration of the heat transfer tube 17 is monitored by detecting the received wave from the heat transfer tube 17.

  FIG. 8 shows a specific example of vibration monitoring. The vibration value and the vibration frequency are detected from the time change of the vibration of the pump shaft or the heat transfer tube, which is the inspection object, and the fluctuation of those values is monitored. Then, as shown in FIG. 8A, it is determined that an abnormality has occurred when the vibration value exceeds a predetermined determination criterion. Further, regarding the vibration frequency, it is determined that an abnormality has occurred when the frequency is shifted by a predetermined value or more than the normal frequency. In the above description, the vibration value and the vibration frequency are separately monitored, but it goes without saying that they may be combined.

  In the second embodiment, an example in which the vibration monitoring device according to the present invention is applied to monitoring of a pump or a heat transfer tube has been described. However, an intermediate structure is present between the detection object and the ultrasonic transmission / reception device 1. Of course, it can be applied to all structures as long as they exist.

  According to the second embodiment, even if an intermediate structure such as a protective tube or a baffle plate is present by applying the vibration monitoring device according to the present invention to a device having a pumping pump or a heat transfer tube, etc., The vibration of the pump shaft or heat transfer tube can be monitored with high accuracy and the occurrence of an abnormality can be grasped reliably.

1 is an overall configuration diagram of a vibration monitoring apparatus according to a first embodiment of the present invention. The schematic diagram of the ultrasonic wave which concerns on the 1st Embodiment of this invention. The wave form diagram of the ultrasonic wave which concerns on the 1st Embodiment of this invention. The schematic diagram of the vibration waveform concerning a 1st embodiment of the present invention. (A) is a vertical sectional view of the vibration monitoring apparatus according to the first embodiment of the present invention, (b) is a plan sectional view thereof. (A) is a general view of a pump, (b) is a schematic diagram when the vibration monitoring apparatus according to the present invention is applied to a pump. The schematic diagram at the time of applying the vibration monitoring apparatus which concerns on this invention to the apparatus which has a heat exchanger tube. (A) is a change figure of a vibration value with respect to operation time of a vibration monitoring device concerning the present invention, and (b) is a change figure of a vibration value to frequency characteristics.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... New ultrasonic transmission / reception apparatus, 1a ... Ultrasonic oscillation apparatus, 1b ... Ultrasonic reception apparatus, 2 ... Transmission waveform, 3 ... Reception waveform, 3a, 3b ... Reception wave, 4 ... Outer wall, 5 ... Intermediate structure, 6 ... objects to be measured, 10 ... pumping pipe, 11 ... protective pipe, 12 ... pump shaft, 13 ... pumping pump, 14 ... equipment, 15 ... outer wall, 16 ... baffle plate, 17 ... heat transfer pipe.

Claims (5)

In a vibration monitoring apparatus for a structure having an intermediate structure between the structure and a measurement object in the structure,
An ultrasonic transmission / reception device that is provided on the outer wall of the structure and transmits an ultrasonic wave to a measurement object and receives a reception wave; an A / D conversion device that converts the reception wave into a digital value; By measuring the vibration displacement of the measurement object from the change of the time waveform shape of the received signal, calculating the vibration value and vibration frequency of the measurement object, and monitoring the change of the vibration value or vibration frequency An abnormality determination device for determining abnormality of the measurement object,
The ultrasonic transmission / reception device changes the frequency of the ultrasonic wave transmitted from the ultrasonic transmission / reception device and determines the frequency at which the echo level of the received wave is maximized, whereby the ultrasonic wave transmitted to the measurement object A vibration monitoring apparatus characterized in that the wavelength is set to 2 / n times the thickness of the intermediate structure when n is an integer .   The vibration monitoring apparatus and monitoring method according to claim 1, wherein the ultrasonic transmission / reception apparatus includes an ultrasonic transmission apparatus and an ultrasonic reception apparatus.   A signal processing means for calculating a reception wave area from the measurement object from design information of the structure and separating the reception wave from the intermediate structure from time waveform information of the reception wave is provided. Item 3. The vibration monitoring apparatus according to item 1 or 2.   The vibration monitoring apparatus according to claim 1, wherein the transmission frequency of the ultrasonic wave includes a plurality of frequency components. In the vibration monitoring method for a structure having an intermediate structure between the structure and the measurement object in the structure,
The ultrasonic wave transmitted to the measurement object by determining the frequency at which the echo level of the received wave is maximized by changing the frequency of the ultrasonic wave transmitted from the ultrasonic transmission / reception device provided on the outer wall of the structure. the wavelength of, and sets the 2 / n times the thickness of the intermediate structure where n is an integer, and transmits ultrasonic waves of the wavelength to the measurement object, converts the received waves into a digital value The digital value is processed, the vibration displacement of the measurement object is measured from the change in the time waveform shape of the received signal, the vibration value and vibration frequency of the measurement object are calculated from the vibration displacement, and the vibration value or vibration A vibration monitoring method, wherein abnormality of the measurement object is determined by monitoring a change in frequency.

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