JPS58131519A - Supervising method of vibration of rotating body - Google Patents

Abstract

PURPOSE:To attain the early detection and quick processing of abnormal phenomena by using past data for the rate of variation for vibration of a turbine generator to forecast the abnormal phenomena by the method of least square. CONSTITUTION:Each vibration detector 5 detects respective shaft vibration and generates an oscillating signal. The signal is transmitted to a vibration supervising and forecasting device 7 through an amplifier 6. An input scanning part 9 scans the oscillation signal of each sahft at a fixed period and converts the signal into a digital value. The digital value is inputted to a rate of vibration calculating part 10. The rate of variation for amplitude is obtained by primarily approximating ten data in total consisting of nine amplitude values found for the past nine seconds in each second and an amplitude value entered at that time by the method of least square and finding the gradient i.e., the rate of variation. A pattern discriminating part 11 discriminates whether the combination of the rate of variation for amplitude and the amplitude values is located in a safety area, a caution area or a stop area, and outputs an alarm meassage to a display device 14 in case of the safety or caution area and a turbine stop command in case of the stop area.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for monitoring vibrations of a rotating body such as a turbine generator.

Generally, when monitoring the vibration of a rotating body such as a turbine generator, the vibration of the rotating body is detected, and when the vibration 111g value of the detected vibration signal exceeds a predetermined value, it is regarded as abnormal and an alarm is issued. Monitoring is carried out by means such as emitting a message.

In addition to monitoring the imaging amplitude as described above, there is also a method of monitoring the rate of change in vibration amplitude.

It is almost impossible to avoid vibration phenomena in a rotating body, and although there are differences in the magnitude of vibration amplitude, vibrations are almost always detected in books. Therefore, if an abnormality in the rotating body can be detected as soon as possible from the detected vibration signal, the problem can be avoided. It is also true that most abnormal phenomena rarely occur suddenly at a certain point in time, and that some symptoms appear in advance.

However, with conventional vibration monitoring methods, the vibration amplitude value at a certain point,
Alternatively, it was simply a method of monitoring the vibration amplitude value at a certain point in time, and monitoring the vibration of the rotating body based on whether it exceeded nine predetermined values set independently for each.

Therefore, in some cases, the countermeasures could not be taken in time. For this reason, it may be possible to set the predetermined value of the vibration amplitude signal or its rate of change to a low value, but this could only be the result of monitoring at that point in time, and such monitoring would be of great concern to the operator. Improvements are needed in terms of communication such as warning displays and early detection of abnormalities, and predictive warning output is also required.

The present invention has been made in view of the above points, and is a turbine generator that can predict the rate of change of the turbine generator's turbulence by the least squares method using past data, and can detect and treat abnormal phenomena early. The object of the present invention is to provide a vibration monitoring method.

Hereinafter, specific examples of the present invention will be described.

FIG. 1 shows a case where bearing vibration of a rotating body is detected, and an alarm is issued by determining two factors, the vibration amplitude value and the vibration amplitude change rate, on a two-dimensional plane. The horizontal axis is the amplitude change rate, the vertical axis is the vibration amplitude value, and the safety range S is set on this plane.
This is an example of 1 caution area A1 stop area T. The point on this plane is A
If it goes into T, a caution warning will be issued, and if it goes into T, the turbine will be stopped.

This is characterized by setting a safety area, a warning area, and a trip area, respectively, based on the correlation between the imaging width and the vibration amplitude change rate. This method provides better monitoring accuracy than setting limit values for each individual item.

FIG. 2 shows a block diagram of the turbine generator and vibration monitoring device.

The turbine generator includes a low pressure turbine 1, an intermediate pressure turbine 2,
It is composed of a high pressure turbine 3 and a generator 4.

The vibration monitoring device includes a vibration detector 5, an amplifier 6, a vibration monitoring and prediction device 7, and a turbine control device 8.

The vibration detector 5 detects the low pressure, intermediate pressure and high pressure turbines 1.2.
Two of them are disposed on each shaft of the generator 3 and the generator 4.

The vibration monitoring and prediction device 7 includes a human power scanning section 9 and a rate of change calculation section 1.
0, a pattern determination section 11, a pattern display section 12, a prediction calculation section 13, and a display device 14. The display device 13 uses a CRT because the current digital display lacks display capability.

Next, the effect will be explained.

The vibration detector 5 detects shaft vibration of each axis and generates a vibration signal. This vibration signal is transmitted to a vibration monitoring and prediction device 7 via an amplifier 6.

The input scanning section 9 scans the vibration signals of each axis at regular intervals and converts them into digital values. This digital value is calculated by the rate of change calculation section l.
It is input to O.

The amplitude change rate is calculated using 10 amplitude values: 9 amplitude values X + (i = 1.2...9) for the past 9 seconds captured at 1-second intervals and the currently captured amplitude value Xso. Data is used. Specifically, the amplitude change rate is determined by first-order approximation of each data using the least squares method to obtain the slope, that is, the change rate.

Data displays include amplitude value display for each bearing, amplitude change rate display for each bearing, periodic display of amplitude vibration value for each bearing, periodic display of amplitude change rate for each bearing, and other displays. Each display is digitally displayed depending on the selection.The rate of change calculating section 10 calculates the rate of change in the following manner.

As shown in FIG. 3, a vibration signal is obtained for one shaft vibration, scanned and digitally converted from the past N-1 values Xt (i=t) at intervals of TO seconds.

A total of N amplitude values X+(1=1.2...N
). Using the least squares method from these amplitude values, linear approximation is performed using the following equation, and the slope, that is, the rate of change is calculated.

t I= tt+ (11) To −(2
) The pattern determination unit 11 determines whether the set PM (XN, XN) of the death loss width change rate X obtained in this way and the amplitude value XN is in the safety range S1, the caution range, or the stop range T. I do. Each region is shown in FIG. This pattern can be automatically switched to several types depending on the rotation speed of the turbines 1, 2.3 (7). The pattern determination unit 11 inputs an alarm message output to the display device 14 if the determination results in the safety range S or the caution range A, and if the result is the stop range TK6, issues a turbine stop command. This turbine stop command is input to the turbine control device 8.

Turbine control device 8 controls the turbine based on this command.

Vibration phenomena do not occur instantaneously, but usually appear gradually. It is important to detect this trend early.

For this reason, the pattern display unit 12 displays the set PHI, Pwz or PM of the amplitude change rate XN and the flea width value XN of the past n points.
, is remembered. This stored output is plotted on display 14 as shown in FIG. Since the calculation of the rate of change is performed every scanning period To seconds, the plot is also updated every To seconds.

Suppose that n points are now plotted.

When a new point p*, n+1 is calculated after llo seconds,
The oldest displayed point p+H is deleted, resulting in p112 to PM. l is displayed.

Next, prediction calculation will be explained.

Now, the pattern display section 12 displays n data PHI (XN
I, Xwt), Pwz (X'N2, X
Suppose that N2) to PMII(X')l-,XN,) are stored.

The prediction calculation unit 13 uses the above data to approximate its change tendency using a linear equation using the method of small squares.

This approximation is shown in the following equation.

X=aX+b...(5
) b=(Xs) a(, l(J
・”(7) In this way, the past vibration state is approximated by a linear equation,
Assuming that the vibration state will continue according to this linear equation,
It is predicted how many seconds it will take to reach the caution area A or the stop area T. Regarding this linear equation, -be. Equation (5) can be rewritten as the following equation.

dX(t) X(t) = a −+ b −(
10t Solving this differential equation yields the following solution.

The constant cld is an integral constant, and this integral constant is determined as follows.

If we take the time origin 1=0 of equation (11) at the present moment, t=0
The initial condition in is given by X N* HXNm.

Strictly speaking, since it is a first-order approximation, the initial value is XNmH
Although it does not match Xw@, it can be substituted with a sufficient approximation.

Therefore, by setting t=O and X(t)=Xs- in equation (11), the integral constant C becomes as follows.

C=XN, -b...0 Therefore, the formula (11j becomes).

As described above, according to the present invention, it is possible to predict the rate of change in vibration amplitude, and an improvement in safety can be expected.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the patterns defined in each area of safety area, caution area, and stop area, and Fig. 2 is an illustration of the vibration protection I! of the turbine generator of the present invention. FIG. 3 is an explanatory diagram for explaining the calculation of the amplitude change rate, and FIG. 4 is an explanatory diagram for the prediction calculation. DESCRIPTION OF SYMBOLS 1... Low pressure turbine, 4... Generator, 5... Vibration detector, 7... Vibration monitoring and prediction device, Death... Turbine control device, 9... Input scanning part, 10... Change rate calculation unit, 11...) Turn determination unit, 12... Pattern display unit, 13... Prediction calculation unit, 14... Display device.

Claims (1)

[Claims] 1. In a method of monitoring the vibration of a rotating body, the vibration of the rotating body is detected, the detected vibration signal is sampled, and the vibration amplitude values of a predetermined number of samples are calculated by the least squares method from the current point onward. A linear approximation straight line is calculated, a current vibration amplitude change rate is sequentially estimated from the slope of the -order approximation straight line, and the vibration of the rotating body is monitored based on the estimated vibration amplitude change rate. Vibration monitoring method for rotating bodies.