JPS61265564A - Apparatus for detecting damage of rotor - Google Patents

Abstract

PURPOSE:To certainly detect damage at an early stage, by inserting a capsule type AE(acoustic emission) detector in the bore of a rotor in a slidable manner and providing an AE sensor for detecting an AE wave in the vicinity of the rotor and connecting a signal processor for processing the ZE wave. CONSTITUTION:A capsule type AE detector 15 receives the AE wave W1 generated from the contact part 16 of a casing 11 and a rotor 13 or a crack leading end part 17 and has a sensor 18 converting the AE wave W1 to an AE signal, an amplifier 19, a pulser 20 for transmitting the signal from the amplifier 19 as an AE wave W2 and a power source 21 mounted therein and is formed into a hermetically closed structure. A lubricating film 22 is formed to the outer peripheral surface of a detector 15 while the detector 15 is inserted in the bore hole 14 of the rotor 13 and AE sensors 24a, 24b for detecting the AE wave W2 transmitted from the pulser 20 are arranged to the bearings 12a, 12b supporting the rotor 13. The AE wave detected by the sensors 24a, 24b is converted to an electric signal which is, in turn, inputted to a signal processor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a damage detection device for a rotating body that can detect damage caused by rubbing, crack propagation, etc. of a rotating body at an early stage.

[Technical background of the invention and its problems]

Rubbing or the development of cracks inside the rotating body due to contact between the rotating body and the surrounding stationary body can lead to damage to the rotating body during operation and cause serious accidents, so it is important to detect this in advance. is desired.

Conventionally, as a method for detecting such damage, as shown in FIG.
CEmission) Install the sensor 2 or install the bearing 3.
An AE sensor 4 is installed at , 4, or bearing 3
A method is adopted in which changes in shaft vibration are detected by a vibration detector 8 attached to the shaft.

However, the former method of detecting the generation of AE waves using the AE sensors 2 and 4 attached to the casing 1 and the bearing 3 has a problem in that the S/N ratio is low for the reason described below.

(1) When the rotational speed exceeds 300 Orpm, background noise (mechanical noise, noise due to bearing friction, noise due to foreign matter in bearing lubricating oil, gas flow noise, etc.) increases rapidly.

(2) The amplitude of an AE wave propagating in a solid decreases as the propagation distance increases due to internal attenuation, and the degree of attenuation increases as the frequency increases. on the other hand,
The AE waves generated when rubbing or crack propagation occur are
Frequency components of 100KH2 or higher are large and are easily affected by internal attenuation.

(3) Due to diffusion, reaction at boundary surfaces, etc., even if the AE wave is a sharp impulse at the source, it has several peaks as it propagates through a solid and changes over time. The result is a gentle waveform that spreads out.

On the other hand, the latter method of detecting changes in shaft vibration using the imaging detector 8 attached to the bearing 3 has a problem in that damage cannot be detected until the damage has progressed considerably.

[Purpose of the invention]

The present invention has been developed with these points in mind, and is capable of early and reliable detection of damage caused by rubbing and crack propagation of a rotating body, and is capable of preventing serious damage. The purpose is to provide equipment.

[Summary of the invention]

The present invention provides a sensor that receives AE waves, an amplifier that amplifies this signal, a pulser that transmits the AE waves amplified by the amplifier, and a capsule-type AE detector that incorporates these power supplies at the axial center of a rotating body. An AE sensor is provided to be slidably inserted into a bore hole provided in the rotary body and to detect the AE waves transmitted from the capsule-type AE detector at a position near the rotating body. By connecting a signal processing device that processes the AE waves detected by the sensor, damage caused by rubbing of the rotating body, crack growth, etc. can be detected early and reliably. It is characterized in that the damage position can be accurately detected by moving it within the hole, and the state of the damage can also be diagnosed by processing the AE waves with a signal processing device.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIGS. 1 and 2, reference numeral 11 indicates a casing of a steam turbine, and a rotating body 13 supported by bearings 12a and 12b is rotatably disposed within the casing 11. A bore hole 14 is bored in the axial center of the rotating body 13 in the axial direction, and a capsule-type AE detector 15 is slidably inserted into the bore hole 14. .

The capsule type AE detector 15 receives the AE wave W1 generated at the contact portion 16 or the crack tip 17 between the casing 11 and the rotating body 13, as shown in FIG. 2, and converts it into an electrical signal (AE It has a built-in sensor 18 that converts into a double signal, one amplifier that amplifies this ΔE low signal, a pulser 20 that transmits the signal from this amplifier 19 as an AE wave W2, and a power supply 21 for these, and has a heat insulation effect and a noise blocking effect. It has a sealed structure, and a lubrication layer 122 is formed on its outer peripheral surface by applying a lubricant or using a self-lubricating material.This lubricant film 22 connects the bore hole 14 and the capsule-type AE detector. AE wave W at the interface with 15
,, W2 propagation characteristics can be improved, and the spaces 14a and 14b inside the bore hole 14 on both sides of the capsule-type AE detector 15 can be reliably partitioned.

Further, the sensor 18 is made of high frequency PZT which is sensitive to the AE wave W1 having a large high frequency component of 100 KH2 or more.
The pulser 20 is formed of a piezoelectric element, and the pulser 20 has five
Mechanical noise with large frequency components below 0KHz or
It is suitable for transmitting the AE wave W2 having a frequency of around 100 KHz so that it can be clearly distinguished from noise caused by bearing friction, noise caused by foreign matter in bearing lubricating oil, noise caused by gas flow noise, etc., which has a large frequency component of 0 KHz or more. It is formed from a low frequency PZT piezoelectric element. Moreover, both these P
A high-temperature PZT piezoelectric element is used as the ZT piezoelectric element so that sufficient performance can be obtained even under high-temperature conditions.

In each of the spaces 14a and 14b in the bore hole 14, both ends 13a of the rotating body 13 are provided, as shown in FIGS. 1 and 2.
, 13b, gases 23a, 23b such as cooling steam are injected at pressures P, P2 to cool the capsule type AE detector 15, and both gases 23a, 23
The capsule-type AE detector 15 is configured to slide within the bore hole 14 due to the pressure difference ΔP (P=P − P2″).

On the other hand, a bearing 12a supports the rotating body 13.

12b, the AE wave W transmitted from the pulsar 20 of the capsule type AE detector 15 is shown in FIGS. 1 and 2.
AE sensor 24a detects 2.

24b are installed respectively. And these A.E.
The AE waves detected by the sensors 24a and 24b are converted into electrical signals (AE low signals) and then input to a signal processing device 25 shown in FIG. 3.

As shown in FIG.
An amplifier 26 that amplifies the AE low signals from the E sensors 24a and 24b, a filter 27 that removes noise, a detector 28 that performs average value detection using a full wave rectification method for the AE low signals from which the noise has been removed, and an average value detection two discriminators for determining whether or not the magnitude of the AE low signal exceeds a set threshold; a counter 30 that counts the cumulative number of times that the magnitude of the average-value-detected AE low signal exceeds the set threshold; A timer 31 that measures time, a determiner 32 that determines whether the value of the cumulative number of times, the slope of its increase, and the length of the duration exceed a set threshold; It is comprised of an alarm device 33 that issues an alarm when a determination is made. Then, both AE sensors 24a are processed by this signal processing device 25.
, 24b, the state of rubbing and crack growth can be easily detected.

Next, the operation of this embodiment having such a configuration will be explained.

The AE wave W1 generated at the contact portion 16 or the crack tip 17 between the casing 11 and the rotating body 13 propagates inside the rotating body 13 and reaches the sensor 18 in the capsule-type AE detector 15.
-H is caught by. At this time, since the sensor 18 is formed of a high frequency PZ and T piezoelectric element,
The AE wave W1 having a large high frequency component of KHz or more can be received with high sensitivity, and even if the AE wave W1 is minute, it can be caught.

This AE wave W1 is converted into an electrical signal (AE low signal) within the sensor 18, amplified by the amplifier 19, and sent to the pulser 20.The AE low signal sent to the pulser 20 has a frequency of around 100 KHz. The AE wave W2 is transmitted, and this AE wave W2 is transmitted to the rotating body 13 and its bearing 12a.

12b and is detected by AE waves 24a and 24b.

At this time, the AE wave W2 has a large frequency component after 100 KHz m, so it can be caused by mechanical noise with a large frequency component below 50 KHz, noise due to bearing rIi friction, and noise in bearing lubricating oil with a large frequency component above 100 KH2. It is easy to distinguish from noise caused by foreign objects, gas flow noise, etc. Also,
It is relatively less susceptible to internal attenuation, which is a characteristic of AE waves propagating in solids. In addition, since the propagation distance is shortened, the effects of diffusion, reflection at boundary surfaces, etc. are also reduced.

Furthermore, the sensor 8 and the pulser 20 are formed of high-temperature piezoelectric elements, and are built into the capsule-type AE detector 15, which has a heat insulation effect, a sealing effect, and a noise blocking effect. It can withstand the environment. In addition, gases 23a and 23b are present in the bore hole 14.
A cooling effect can also be achieved by injecting

In addition, the capsule-type AE detector 15 has water ff1l on its circumferential surface.
l! J22 is formed, it is possible to improve the propagation characteristics of the AE waves W, W2 at the interface between the bore hole 14 and the rain space 14a within the bore hole 14.
, 14b, and the gas 23a is injected into the rain spaces 14a, 14b.

The capsule-type AE detector 15 can be freely moved within the bore hole 14 due to the pressure difference ΔP (=P − P2) between the pressure points 23b and 23b. For this reason, the AE sensors 24a, 24
By moving the capsule-type AE detector 15 to the position where the value of the AE wave W2 detected at b is the maximum, the AE
It becomes possible to accurately detect the source of the wave, that is, the damaged location.

AE wave W2 detected by the AE sensors 24a and 24b
is converted into an electric signal (AE-multiplied signal) and then sent to the signal processing device 25 for processing.

That is, the AE multiplied signal sent to the signal processing device 25 is amplified by the amplifier 26, noise is removed by the filter 27, and then the average value is detected by the detector 28 using a full-wave rectification method.

The AE multiplied signal subjected to average value detection is identified by the discriminator 29 when its magnitude exceeds a set threshold, and
The counter 30 calculates the cumulative number of times, and the timer 31
The duration is measured by . Then, the judgment device 32 judges when the value of the cumulative number of times, the slope of its increase, and the length of the duration exceed the set threshold, and a signal is output to the alarm device 33, and an alarm is issued from the alarm device 33. Sent. Thereby, the state of rubbing and crack growth can be easily detected.

FIG. 4 shows a second embodiment of the present invention, in which the bore hole 14
There are two capsule type AE detectors 15a inside.

15b to open the inside of the bore hole 14 into three spaces 14a, 1
In addition to partitioning into 4b and 14C, each space 14a and 14b
, 14c from both ends 13a, 13b and central part 13c of the rotating body 13. Cooling gas 238.23b, 23C
Two capsule-type AE detectors 15a and 15b are used to inject it and change its pressures P, P, and P3.
is moved within the bore hole 14, and the other points are the same as those of the first embodiment.

In this way, there are two capsule-type AE detectors 15a.

15b is effective when the rotating body 13 is long in the axial direction.

FIG. 5 shows a third embodiment of the present invention, in which a capsule type AE detector 15 is provided with a waveguide 34, and a bearing 3 for the waveguide 34 is provided outside the shaft end of the rotating body 13.
5 is provided, and an AE sensor 24c is installed on this bearing 35, and the AE wave W3 from the capsule type AE detector 15 is transmitted to the AE sensor 24 through the waveguide 34 and the bearing 35.
c), and other points are the same as in the first embodiment.

In this embodiment, since the AE wave propagates through a rod-shaped object such as the waveguide 34, the S/N ratio can be increased without being affected by diffusion. Therefore, this third embodiment is effective when it is necessary to particularly increase the S/N ratio.

In each of the above embodiments, the capsule type AE detector 15.1
As a means for moving 5a, 15b within the bore hole 14,
Cooling gas 23a, 23b.

23c has been described, the same effect can be obtained by using other known drive IM4 such as a feed screw.

Further, in each of the embodiments described above, the case where the invention is applied to a steam turbine has been described, but the invention is not limited to this and can be applied to any other rotating machine.

(Effects of the Invention) As explained above, the present invention has a capsule type AE detector inserted into a bore hole provided in the axial center of a rotating body, A that occurred in the
The capsule-type AE detector catches the E-waves, amplifies them, and transmits them again, which eliminates background noise during high-speed rotation, internal attenuation and diffusion of the AE waves propagating through solids, and It is less susceptible to the effects of reflection at the interface, and therefore the S/N ratio can be increased. Therefore, damage can be detected early and reliably.

Furthermore, since the capsule-type AE detector can slide within the borehole, it is possible to accurately detect the position of the AE wave generation source wherever it is.

Furthermore, since the AE waves are processed by the signal processing device, the state of rubbing and crack growth can be diagnosed.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a steam turbine showing a first embodiment of the present invention, Fig. 2 is an enlarged view of the part ■ in Fig. 1, Fig. 3 is a configuration diagram of a signal processing device, and Fig. 4 is a diagram of the present invention. The first example shows the second embodiment of
FIG. 5 is a view corresponding to FIG. 2 showing a third embodiment of the present invention, and FIG. 6 is a perspective view showing an example of a conventional damage detection device. 13-... Rotating body, 14... Bore hole, 14a, 14
b. 14 C-... Space, 15.15a, 15b-... Capsule type AE detector, 16... Contact part, 17... Crack tip, 18... Sensor, 19... Amplifier, 20・
...Pulsa, 21-...Power supply, 23a, 23b, 23c
...gas, 24a, 23. , b, 24cm AE sensor, 25-... signal processing device, 34... wave guide, 35... bearing, w, w2. w3...AE wave. Applicant's agent: Ino Mata Qinghodong 1 Tufu J2 Qin Lian

Claims (1)

[Claims] 1. A sensor that receives AE waves, an amplifier that amplifies this signal, a pulser that transmits the AE waves amplified by the amplifier, and a capsule-type AE detector that incorporates these power supplies are mounted on a rotating body. The capsule type AE is slidably inserted into a bore hole provided in the axial center of the
An AE sensor is provided to detect the AE waves transmitted from the detector, and the AE sensor is provided with an AE sensor that detects the AE waves transmitted from the detector.
A damage detection device for a rotating body, characterized in that a signal processing device for processing E waves is connected. 2. A damage detection device for a rotating body according to claim 1, wherein the AE sensor is provided in a bearing of the rotating body. 3. The damage detection device for a rotating body according to claim 1, wherein the AE sensor is provided on a bearing of a waveguide pulled out from the capsule-type AE detector. 4. Claims 1 and 2, characterized in that the sensor built into the capsule type AE detector uses a PZT piezoelectric element for high temperature and high frequency, and the pulser uses a PZT piezoelectric element for high temperature and low frequency. A damage detection device for a rotating body according to item 1 or 3. 5. Claim 1, characterized in that a fluid for cooling the capsule-type AE detector is injected into the bore hole, and the pressure of the cooling fluid causes the capsule-type AE detector to slide within the bore hole. , the damage detection device for a rotating body according to item 2, item 3, or item 4.