JPS6330983Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bearing abnormality detection device for a rotating machine.

[Conventional technology]

Plain bearings, etc. traditionally used in rotating machinery,
The optimal diameter, width, and type are selected based on usage conditions such as rotor shape, weight, and transmitted torque. Taking a steam turbine generator as an example, in a large machine, the total amount
Since it weighs over 150 tons and rotates at high speed, it goes without saying that it is desirable that the bearings that support it are strong and always in a normal state, but burnout of the bearing metal, excessive or insufficient bearing load, etc. This may cause excessive vibration and rubbing of the rotor, leading to excessive accidents such as rotor scattering accidents.

On the other hand, in recent large-capacity steam turbines,
Due to the decrease in shaft rigidity due to the increase in the size of rotating machines, unstable vibrations such as oil whips have become a problem. As a measure to prevent this oil whip, bearings are being made to have higher surface pressure. This inevitably leads to deterioration of bearing lubrication characteristics during low-speed operation, which often leads to bearing burnout. In particular, in machines that perform turning operations (rotation speed of approximately 2 rpm) for long periods of time, such as those seen in steam turbines, for a long period of one week or more, the lubrication state during low-speed operation must be managed to prevent the metal wipe phenomenon that can lead to metal burnout. Early detection or prediction of bearing abnormalities such as metal wipe (hereinafter abbreviated as metal wipe) and prevention of abnormalities are extremely important for preventive maintenance of machinery.
As mentioned above, due to the high surface pressure of bearings, complete control is becoming difficult, and metal burnout accidents are occasionally seen.

Conventionally adopted measures to deal with the above bearing abnormalities are to improve the reliability of the bearing Babbitt metal by making its structure finer and improving its mechanical strength.

Improves the roughness of the journal surface (machining finish degree) and finishes the metal burnout limit surface.

There are methods such as these, but these methods cannot be carried out unless the equipment has been sufficiently cooled down, either during the manufacture of the rotor and bearings or when the turbine is stopped during periodic inspections.

Next, general bearing metal temperature measurement and drain oil temperature measurement methods will be explained using examples as means for monitoring abnormalities during bearing operation.

Figure 1 shows a simplified cross-sectional structure of the bearing. The metal temperature measurement mentioned above uses a thermocouple 3 inside the bearing back metal 2.
This is a means for monitoring the heat generated by metal burnout, etc., by attaching a thermocouple 3b inside the cover member 4, and monitoring the heat generated by metal burnout, etc., through the waste oil. This is a means of monitoring metal burnout, etc. by measuring the

[Problem that the invention attempts to solve]

However, in the metal temperature measurement mentioned above,
The thermocouple 3a is installed on the bearing back metal 2 of the Babbitt metal 5, and is further away from the bearing sliding surface, so it can detect abnormalities even if slight metal burnout occurs, such as from uneven contact or wipes. In some cases, this may not be possible, and even if an abnormality occurs, the thermocouple 3a
It takes a certain amount of time to detect it. Similarly, in the above-mentioned drain oil temperature measurement, a certain amount of time is required until an abnormality is detected. In addition to the above-mentioned temperature measurement method, there are methods such as attaching a strain gauge to the bearing body and detecting abnormalities from the strain value, and measuring flyment changes using a gap sensor, but both detect the abnormality after it has progressed to a certain extent. Therefore, it is not only difficult to detect metal wipes that can lead to bearing burnout in the early stages, but also difficult to understand the progress of metal wipes over time from the initial stage of their occurrence.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bearing abnormality diagnosing device that can not only detect the metal wipe phenomenon immediately after it occurs, but also inform the user of its progress over time.

[Means for solving problems]

The present invention is characterized by an acoustic detection element installed at a location where ultrasonic signals generated by the bearing metal or a metal wipe on the outer surface of the bearing can be detected in a plain bearing used in a rotating machine, and the acoustic detection element. means for outputting a pulse signal when the output signal exceeds a set threshold; means for counting the pulse signal at regular intervals; and a means for determining the ratio of the period of the present invention to a count value, and detects occurrence of metal wipe using the ratio to the count value.

〔Example〕

The present invention will be explained below using the drawings.

FIG. 2 shows Babbitt temperature A, drain oil temperature B, and ultrasonic signal count number C before and after T when metal wipe occurs. The respective output values shown in FIG. 2 are data obtained by reproducing the metal wipe phenomenon, and each detector has a thermocouple installed in the Babbitt 11 and cover member 12 as shown in FIG.
3a and 13b are attached to measure the temperature, and the ultrasonic signal is sent to the acoustic sensing element 14 on the Babbitt metal 11.
This is the value obtained by counting the ultrasonic signal generated by the counter 17 after the signal is amplified by the preamplifier 15 and main amplifier 16.

As can be seen from Figure 2, the drain oil temperature and Babbitt temperature show a gradual rise in temperature from the start of operation, but the temperature change when metal wipe occurs shows that although there is a slight rise in Babbitt temperature, there is a large increase in temperature. It can be seen that there is no change.

On the other hand, the count number of the ultrasonic signal starts to rise rapidly at the same time as the metal wipe occurs, and rises at the same slope as the metal wipe progresses.

Next, FIG. 4 shows the ultrasonic signal output waveform generated by the metal wipe. The horizontal axis shows time, T
indicates when a metal wipe occurs.

As can be seen from the figure, the generation cycles of the ultrasonic signals generated by the metal wipe are almost the same, and the signal output waveforms are not only similar in size, but also
The generation cycle and magnitude of the signal waveform described above are characterized in that they hardly change from immediately after the metal wipe occurs to during the progress of the metal wipe.

As mentioned above, there is a characteristic relationship between metal wipes that can lead to bearing burnout and the accompanying ultrasonic signals, so by detecting these ultrasonic signals, the occurrence of metal wipes can be detected early. Not only that, but it is also possible to judge the progress of the metal wipe.

Next, FIG. 5 shows a block diagram of a bearing abnormality diagnosing device which is a specific embodiment of the present invention.

An acoustic detection element 22 (for example, one using a piezoelectric ceramic element) is placed at a location where an ultrasonic signal generated by the metal of the bearing 21 supporting the journal 20 or a metal wipe on the outer surface of the bearing can be detected.
is installed by crimping or gluing, and the signal obtained by the acoustic detection element 22 is sent to the turning judgment circuit 2.
Enter 3. The turning determination circuit 23 takes in the rotational speed, determines whether the vehicle is turning or is in an operating state, and inputs the output signal from the acoustic detection element 22 to the preamplifier 24 only when turning. The signal amplified by the preamplifier 24 is passed through a filter 25 to remove noise. Furthermore, the signal from which noise has been removed is amplified by the main amplifier 26, the signal is detected by the detection circuit 27, and finally the signal is detected by the comparison circuit 28.
One pulse signal is output for one ultrasonic signal shown in the figure. The pulsed signal is input to a periodicity determining circuit 29, which determines the presence or absence of a metal wipe based on the periodicity of the pulse, and passes the pulse from the comparison circuit to the counter 30 only when a metal wipe occurs. The counter 30 counts the input pulses and inputs a signal proportional to the number of pulses to the metal wipe indicator 31. The metal wipe indicator 31 determines the signal from the counter 30 and displays the occurrence of metal wipe and the progress of metal wipe.

Next, the configuration and operating principle of the periodicity determination circuit will be specifically explained. FIG. 6 shows a block diagram of the periodicity determining circuit, and FIG. 7 shows the operation of each circuit and its output waveform for ease of understanding when explaining the periodicity determining circuit.

FIG. 7 shows pulse signals output from the comparator circuit 28 before and after the metal wipe occurs.
As can be seen from the figure, if a metal wipe occurs, a periodic pulse signal is output as described above, but otherwise, that is, before a metal wipe occurs, a pulse signal that does not have periodicity due to external noise etc. A signal is output.

Next, the pulse signal is input to a gate circuit 40 shown in FIG. The gate circuit 40 has a built-in timer 41, and the timer 41 controls the gate (A) 42a and the gate (B) 42b.
are turned ON and OFF alternately as shown in FIG. 7, and the signals outputted from the comparison circuit 28 are taken out alternately.The signals outputted through the gates (A) 42a and (B) 42b are It is shown in FIG.

Next, the signals output from the gates (A) 42a and (B) 42b are input to a digital memory circuit (A) 43a and a digital memory circuit (B) 43b shown in FIG. The signals input to each of the digital memory circuits described above are input to the divider 4 shown in FIG.
4, and the ratio between the output of 43a and the output of 43b is calculated. In the divider 44, data acquisition times t ₁ , t ₂ , t ₃ , t ₄ as shown in FIG.
Every time..., the digital memory (A) 43
a, (B) 43b, and the signals inputted and stored in the memory are taken in, and the times A ₁ /B ₁ , A ₁ /B ₂ ,
Perform the calculation A ₂ /B ₂ ... (in the figure, the thick line indicates the calculation time), and only when the numerator/denominator becomes 1,
It is designed to output a DC voltage of 5V as shown in FIG. In other words, if a metal wipe occurs, the ultrasonic signal is generated periodically as described above, so the ratio of the numerator and denominator is 1:1, so it is possible to determine the presence or absence of a metal wipe. Each of the digital memory circuits described above is a digital circuit that, when a new signal is input, clears the previously stored signal and takes in the new signal.

Here, in order to make it easier to understand the calculation method by the divider 44, it will be specifically explained using FIG. 7. First, let us examine the operation of the divider at time t ₁ of data acquisition. The signal input to the divider 44 at time t ₁ via the digital memory circuit is a combination of the signal A ₁ (3 pulses) output from the gate (A) 42a and the signal from the gate (B) 42b. B ₁ (number of pulses: 1) of the output signal,
Since A ₁ /B ₁ is not 1, no signal is output from the divider 44. t Similarly for ₂ hours
Since A ₁ /B ₂ is not 1, the divider 44
There is no signal output from.

Next, when we examine time t ₃ , we find that time t ₃ is the time when metal wipes begin to occur. The signal input to the divider 44 via the digital memory circuit within time _t3 is input to the gate (A) 42a.
A ₂ (5 pulses) of the signal output from the gate (B) 42b and B ₂ (5 pulses) of the signal output from the gate (B) 42b. Since A ₂ /B ₂ is 1, the above The divider 44 outputs a DC voltage of 5V.
In reality, the ratio of the numerator to the denominator is rarely a mathematically uniform value of 1:1 due to measurement errors, so the calculation by the divider 44 involves the numerator/denominator ratio.
The denominator is set to 1±α so that an output voltage is generated even if there is an error of α.

The above-mentioned division method is a digital method, but it goes without saying that the same result as the digital method can be obtained even if the signal output from the comparison circuit 28 is converted into analog and division is performed.

Next, the signal from the divider 44 is input to an AND circuit 45 shown in FIG. 6, and ANDed with the output waveform of the comparator circuit shown in FIG. 7. The circuit output waveform is obtained.
If no metal wipe occurs, the divider 44
Since there is no output from the circuit, AND output cannot be obtained, and of course no pulses will be generated.

The metal wipe determination circuit has been specifically described above, but since there is a possibility that the above-mentioned measurement system may also receive acoustic emission signals and rubbing abnormal sound signals during measurement, it is important to note that the metal wipe determination circuit It is necessary to distinguish it from ultrasonic signals caused by

However, fortunately, acoustic/emission signals rarely occur periodically, so
It will be cut by the metal wipe determination circuit mentioned above. In addition, rubbing signals usually occur at a cycle of once per revolution, but since turning operation has a rotation speed of about 2 rpm, the cycle is extremely long even when it occurs, and it occurs with metal wipes. Because there is a significant difference in the period of the ultrasonic signal,
Like the Acoustic Emission signal, it will be cut by the metal wipe judgment circuit.

FIG. 8 shows a bearing abnormality diagnosis device which is an application example of the present invention.

An acoustic detection element 52 (for example, one using a piezoelectric ceramic element) is placed at a location where an ultrasonic signal generated by the metal of the bearing 51 supporting the journal 50 or the metal wipe on the outer surface of the bearing can be detected.
is installed by pressure bonding or gluing, and the signal obtained by the acoustic detection element 52 is sent to the turning judgment circuit 5.
Enter 3. The turning determination circuit 53 takes in the rotational speed and determines whether it is turning or an operating state, and only when turning,
The output signal from the acoustic detection element 52 is input to a preamplifier 54.

The signal amplified by the preamplifier 54 is passed through a filter 55 to remove noise. Furthermore, the signal from which noise has been removed is amplified by the main amplifier 56, the signal is detected by the detection circuit 57, and then the comparator circuit 58 generates one pulse for each ultrasonic signal shown in FIG. Output a signal. Next, the pulsed signal is input to the microcomputer 59, and the periodicity of the pulse signal is determined by the microcomputer in the same manner as the synchronization determination circuit described above.
The presence or absence of metal wipe occurrence, the metal wipe occurrence time, the progress status of metal wipe, etc. are calculated, and the results are displayed on the CRT display 60.

[Effect of idea]

As explained above, according to the present invention, not only can occurrence of bearing metal wipe be detected early, but also
You can also learn about the progress of metal wipes, and
Since it can be distinguished from signals of different types from metal wipes such as acoustic/emission signals and rubbing signals, it can be used as an online monitor for bearing abnormality detection, and has the remarkable effect of being extremely effective industrially.

Furthermore, if the above-mentioned bearing abnormality diagnosis device is used,
In addition to informing the presence or absence of a metal wipe on the CRT display surface, even if the worker misses the initial stage of the metal wipe, the occurrence time of the metal wipe can be displayed on the CRT display surface, allowing the worker to easily detect the metal wipe. You can know the time of occurrence. In addition, in order to display graphs etc. of the metal wipe progress status on the CRT display surface,
The operator has the advantage of being able to see the progress of the metal wipe at a glance, making it extremely effective as an online monitor for bearing abnormalities.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a simplified cross-sectional structure of the bearing and the installation locations of each thermocouple for measuring the bearing metal temperature and the exhaust oil temperature. FIG. 2 is a graph showing the Babbitt temperature, the drain oil temperature, and the count number of ultrasonic signal output before and after the occurrence of metal wipe. FIG. 3 shows the installation locations and measurement methods of each detector when acquiring the data shown in FIG. 2. FIG. 4 is a diagram showing the output waveform of an ultrasonic signal generated by the metal wipe. FIG. 5 is a block diagram of the bearing abnormality diagnosis device of the present invention. FIG. 6 is a block diagram showing a specific configuration of the periodicity determination circuit. FIG. 7 is a waveform diagram for explaining the operation of the periodicity determination circuit. FIG. 8 is a diagram showing a bearing abnormality diagnosis device which is an application example of the present invention. 20... Journal, 21... Bearing, 22...
Acoustic detection element, 23... Turning determination circuit, 2
4...Preamplifier, 25...Filter, 26...
Main amplifier, 27...Detection circuit, 28...Comparison circuit, 29...Periodicity determination circuit, 30...Counter, 31...Metal wipe indicator.

Claims (1)

[Scope of utility model registration request] In a sliding bearing used in a rotating machine, an acoustic detection element is installed at a location where an ultrasonic signal generated by the bearing metal or a metal wipe on the outer surface of the bearing can be detected, and the output signal of the acoustic detection element is set. a means for outputting a pulse signal when the threshold value exceeds a threshold; a means for counting the pulse signal at regular intervals; and a means for inputting the counted value and comparing it with the counted value of the previous cycle and the counted value of the current cycle. A bearing abnormality diagnosing device comprising: means for determining a ratio of the count value, and detecting occurrence of metal wipe using the ratio with the count value.