JPS628023A - Diagnosis of rotary machine - Google Patents

Abstract

PURPOSE:To perform accurate diagnosis with high accuracy, by detecting acceleration at every operating condition exerting effect on the vibration characteristics of a rotary machine during the operation of the rotary machine held in a normal state. CONSTITUTION:An acceleration sensor 4 is mounted to the outside of the pump casing 3 near to the lower bearing 2 of a pump driving part 1 and reference data is taken at the time of such a good operation state that a LNG pump begins to operate. Then, a reference vibration level coming to the basis of diagnosis is set on the basis of each calculated vibration level. This reference vibration level forms a curved surface having a certain expanse in a three- dimensional space having a pump flow amount, a tank liquid level and the vibration level as coordinates axes. When the presence of the abnormality of the pump is judged, a pump vibration level is detected and the detected vibration level is divided by the reference vibration level under the same operating condition to calculate the magnification to the reference vibration level to judge whether this magnification factor exceeds the numerical value determined by experiment or experience.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for diagnosing rotating machinery, particularly applied to pumps, blowers, etc. installed in highly public LNG plants, thermal power plants, and other facilities. It is something.

[Conventional Technique #i] The proportion of rotating machines in LNG plants and other human-shaped plants or equipment is very high, and their role is also important. If any abnormality or failure occurs in these rotating machines,
Naturally, this causes economic loss, but if the accident spreads, it will develop into a major social problem. For example, LNG
The plant is used as a supply source for city gas, cold power generation equipment, etc., so LNG is pumped out from tanks.
If the G pump breaks down, it will cause a large loss to the user and also cause damage to general customers.

In order to avoid the above-mentioned problems, a diagnostic method and device for rotating machines have been proposed by the same applicant as the present application (Japanese Patent Application No. 57-173636@ or Japanese Patent Application No. 57-17
(See No. 3640). The purpose of the above proposal is to attach an acceleration sensor to a rotating machine, process the signal obtained from this sensor while the rotating machine is rotating, obtain a captured level such as acceleration or amplitude, or a vibration spectrum, and then start the rotating machine. Abnormalities in rotating machinery were diagnosed by comparing them with reference values taken at the time when the machine was in good operating condition.

[Problems to be solved by the invention] However, in general, the vibration characteristics of rotating machines, especially LNG pumps, depend on the pump flow rate and tank liquid level (or suction pressure).
There is a problem in that correct diagnosis cannot be made if standard values are set uniformly because they vary greatly depending on the operating conditions of the car.

To explain the above situation in detail, the vibration level of the pump, for example, the amplitude, generally varies three-dimensionally depending on each combination of pump flow rate Q and tank liquid level H, that is, each operating condition, as shown in Fig. 7. Changes to Therefore, a reference value is determined from the amplitude sampled under operating conditions that ignore changes in operating conditions, and an empirically determined multiplier (for example, 2
．． 5-5. If a diagnosis level a is set by multiplying the amplitude by 0) and the presence or absence of an abnormality is diagnosed based on whether the actually detected amplitude exceeds this diagnosis level a or not, the following absurdity will occur. That is, if the diagnostic level is determined based on the amplitude p1 at the operating point b1 where the flow rate and tank liquid level are minimum, the operating point b2. b3. Even if the diagnostic value (amplitude) in b4 shows an abnormal value, no abnormality can be found, and
When the diagnostic level is determined from the amplitude p4 at the operating point b4 where the flow rate and tank liquid level are maximum, the operating point b1. b2.
Even if the diagnostic value in b3 is normal, it will be diagnosed as abnormal.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and the present invention has been made to solve the above-mentioned problems. A reference vibration level is set in advance to serve as a reference for diagnosis by detecting acceleration at It is something to do.

[Function] Diagnosis is performed based on the reference level set corresponding to the operating conditions, so reliable and highly accurate diagnosis is possible.

[Example] Hereinafter, an example in which the method of the present invention is applied to an LNG pump will be described with reference to the drawings.

As shown in FIG. 2, an acceleration sensor 4 is attached to the outside of the pump casing 3 near the lower bearing 2 of the pump drive unit 1,
The reference data is collected when the LNG pump has started operating and is in good operating condition.

As shown in Figure 1, the standard data collection procedure is to draw a line where the flow rate is constant and a line where the tank liquid level H (or suction pressure) is constant over the entire operating range of the LNG pump at appropriate intervals (Q in the figure). 40m"/h, H at 5m intervals), and measure the acceleration at each operating point where each line intersects.In addition, as a measurement procedure, each tank liquid level to be measured (5, 10,
...25 m), the pump flow rate Q is the minimum flow rate of 110 m, with the suction pressure corresponding to the tank liquid level being constant.
/h to a maximum flow of 1330m”/h (3rd
(see figure), or each pump flow rate to be measured (110
, 130, ... 330111'/h), the tank liquid level H is set to a minimum liquid level of 5 m with the pump flow rate constant.
Measurements are taken from to the maximum liquid level of 25 m (see Figure 4). Then, a reference vibration level 5 (see FIG. 7), which serves as a diagnostic standard, is set based on each vibration level obtained as described above. As shown in the figure, the reference imaging level 5 forms an expanding curved surface in a three-dimensional space whose coordinate axes are the pump flow mQ1 tank liquid level H1 vibration level.

To determine whether there is an abnormality in the pump, detect the pump vibration level, divide the detected vibration level by the reference vibration level under the same operating conditions, and calculate the multiplier for the reference vibration level.
It is determined whether this magnification exceeds a numerical value determined by experiment or experience. Further, the magnification may be roughly classified into three categories: normal, caution, and abnormal, and a specific judgment may be made.

The vibration levels corresponding to each operating point (operating condition) mentioned above indicate the overall value, and when this value is frequency-analyzed, the vibration as shown in Fig. 5 for each operating point, (
For example, an amplitude) spectrum 9 is obtained.

In general, vibrations in rotating machinery such as pumps are caused by the shaft system 6, bearing 2
, 7. The internal fluid 8 is the source of vibration, and abnormalities in the shaft system 6 appear as integer frequencies based on the pump rotation speed, and abnormalities in the bearings 2.7, for example ball bearings. is related to the rotational speed of the inner and outer rings based on the number of poles, and abnormalities in the internal fluid 8 are mainly caused by cavitation and appear at high frequencies. In the case of a 1NG pump, the frequency of vibrations generated by the shaft system, bearings, and internal fluid is mainly 0 to 500H7.
, 500H2 to 10KH2, and 10KH2 to 20KH2. Therefore, by comparing the reference vibration spectrum under the same operating conditions and the vibration spectrum obtained during diagnosis for each corresponding frequency band, it is possible to diagnose the diagnosis part (shaft system, bearing, etc.) and the presence or absence of abnormality. .

Note that to compare the spectra, the peaks within each frequency band or the average values of all waveforms included in the frequency band are compared in the manner described above.

Next, an example of an apparatus for carrying out the method will be briefly described with reference to FIG. In the figure, 4 is an acceleration sensor for detecting the vibration level, 10 is a filter for removing low frequency components such as vibrations of the sensor mounting part and the entire rotating machine, 12 is an A/D converter, and 13 is a mask micro A computer system control unit; 14 is an operating condition setting device for specifying operating conditions and frequency bands during diagnosis; 15 is a vibration level detected by the acceleration sensor 4 and a reference vibration level 5;
or frequency analysis of the vibration waveform and comparison with the reference vibration spectrum 9 to determine the presence or absence of an abnormality and the location of the abnormality. The stored main memory, 17 is an auxiliary memory used during calculations, 18 is a diagnostic display unit that types out diagnostic results or displays images on a CRT, 19 is an alarm device that notifies you of an abnormality, and 20 is a device that makes an emergency stop of the machine in the event of an abnormality. A signal transmission circuit, 22 is a relay for energizing the mask microcomputer system only during diagnosis, and 23 is a power source.

In general, this device includes a slave microcomputer system 2 having a memory and a clock (none of which are shown) in order to automatically perform diagnosis at a specified time on a specified day.
4 (see the earlier application mentioned above for details).

Note that the present invention is not limited to the above-mentioned embodiments. For example, the present invention may be applied to a boiler induced draft fan instead of an LNG pump, or the operating conditions may be set to rotation instead of pump flow rate or suction pressure. Of course, various changes can be made without departing from the gist of the water-saturated invention, such as the possibility of adopting the rotational speed of the rotating shaft that governs the transverse vibration or torsional vibration of the body.

[Effects of the Invention] As described above, the present invention exhibits the following excellent effects.

(+) Since the reference vibration level for diagnosis is set in accordance with the operating conditions, accurate and highly accurate diagnosis can be performed.

(ti) By comparing the reference imaging spectrum that serves as a reference for each operating condition with the vibration spectrum detected at the time of diagnosis, it is possible to accurately and accurately diagnose the site to be diagnosed.

[Brief explanation of the drawing]

Fig. 1 is a perspective view at a diagnostic level showing an embodiment of the method of the present invention, Fig. 2 is a cutaway view of an LNG pump, and Figs. Fig. 5 is an explanatory diagram showing the change in vibration level when the pump flow rate or tank liquid level is changed; Fig. 5 is an explanatory diagram of the vibration spectrum; Fig. 6 is a block diagram showing an example of a device for carrying out the method of the present invention. 7 are explanatory diagrams showing a conventional diagnostic level setting method. In the figure, 4 indicates an acceleration sensor, 5 indicates a reference imaging level, and 9 indicates a reference vibration spectrum.

Claims (1)

[Claims] 1) During the operation of a rotary machine in good condition, acceleration is detected for each operating condition that affects the vibration characteristics of the rotary machine, and a reference vibration level serving as a diagnostic standard is set in advance. A method for diagnosing a rotating machine, characterized in that the presence or absence of an abnormality is determined by comparing the vibration level detected during diagnosis with the reference vibration level under the same operating conditions as the operating conditions at the time of diagnosis. 2) Divide the reference vibration level into required frequency bands to set a plurality of reference vibration levels, divide the vibration level at the time of diagnosis into the same frequency band as the frequency band, and set the reference vibration level for each corresponding frequency band. A method for diagnosing a rotating machine according to claim 1, in which the vibration level is compared.