JPH0240524A - Reference-function determining method in method for diagnosing rotary machine - Google Patents

Abstract

PURPOSE:To obtain a reference function automatically online during the operation of a plant by processing a diagnostic index for operating conditions of a flow rate and liquid level or pressure statistically. CONSTITUTION:A plane 4 without deterioration during the normal operation is called a reference function Z. When LNG is supplied, amounts of supply Q1 - Q9 at liquid levels H1(Hmax.) - H9 from a filled up liquid level Hmax. to a lowest liquid level Hmin. are changed in a range of + or -DELTAQ for an objective amount of supply Q. Accelerations or displacements in the amounts of supply Q1 - Q9 at every level of H1 - H9 in one supply operation are measured with a vibration sensor. Diagnostic indexes Z1 - Z9 in specified sections are obtained by Fourier analysis based on said acceleration and displacement data. The reference function in a section of flow rate Q+ or -DELTAQ (section of ABCD) from the liquid level Hmax. to Hmin. is obtained. Since the reference function is obtained by a statistical method based on the diagnostic index obtained by processing the data that are measured during the operation of a rotary machine, the reference function can be obtained online accurately during the operation of a plant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to highly public LNG plants, thermal power plants,
The present invention relates to a reference function determination method in a rotating machine diagnosis method applied to pumps, blowers, etc. installed in other equipment.

[Prior Art] The proportion of rotating machines in large plants or equipment such as LNG plants is very high (and their role is also important).

When abnormalities or breakdowns occur in these rotating machines, it goes without saying that economic losses will occur, but if the accident spreads, it will develop into a major social problem.

For example, LNG plants are used as a supply source for city gas, cold power generation equipment, etc., so if the LNG pump that pumps LNG from the tank breaks down, it will cause a large loss to the user and also cause damage to general users. become. Therefore, in order to solve this problem, we installed vibration sensors on representative parts of the pump casing and measured vibrations at regular time intervals, performed Fourier analysis on the measured vibration data, and transferred it to data on the frequency axis. A diagnostic index is obtained through processing, a reference function is determined from the diagnostic index, and pump abnormality diagnosis and deterioration prediction are performed based on the reference function.

So, to explain how to find the conventional standard function,
During plant operation, when the tank liquid level reaches an appropriate level, the plant (pump) is stopped, each valve is switched to test mode, the flow rate is changed by complex valve operations, and the vibration is measured by a vibration sensor. This is recorded on a data recorder, a frequency analysis is performed using a dedicated analyzer, a diagnostic index is calculated using a computer, a reference function is determined based on the diagnostic index, and the result is input into an abnormality diagnosis device.

[Problem to be solved by the invention] However, with the conventional method of determining the reference function, it is difficult to plan operations because it is necessary to stop the plant (pump), it is difficult to set operating conditions, and it is difficult to record on a data recorder. Because the series of steps from analysis to processing to input is performed off-line, the accuracy of the reference function is low, which poses safety concerns when handling gas plants.

In view of the above-mentioned circumstances, the present invention provides a standard function that is the basis of the difference for diagnosing and predicting abnormalities in rotating bodies such as LNG pumps used in LNG plants, by measuring vibrations, processing the measured signals, and analyzing statistical data. This was done with the aim of making it possible to automatically determine on-line processing without stopping the plant.

[Means for Solving the Problems] The present invention measures and processes data on flow rate, liquid level or pressure, acceleration or displacement while a rotating machine is in operation, automatically obtains diagnostic indicators, and measures flow rate and liquid level. Alternatively, diagnostic indicators for pressure operating conditions are statistically processed to obtain a reference function.

[Function] Diagnostic indicators are obtained by processing data measured during the operation of the rotating machine, and a reference function is obtained from the diagnostic indicators using statistical methods, so the reference can be automatically and accurately set online at any time during plant operation. It becomes possible to find functions.

[Example] Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIGS. 1 to 7 (A) and (O) show an embodiment of the present invention.

FIGS. 7(A) and 7(O) are general layout diagrams of LNG storage facilities, where FIG. 7(A) shows an above-ground type, and FIG. 7<0) shows an underground type. In the figure, 1 is an LNG tank with an insulated structure, 2
3 is the LNG receiving pipe, 3 is the dispensing pump, and the LNG
LNG transported from all over the world by special ships (-
165℃) can be stored. LNG discharged from tank 1 by pump 3 is heated, gasified, and sent to consumers such as power plants, factories, and homes, but since the pump is used at extremely low temperatures and under harsh conditions, Abnormalities are likely to occur. However, this highly public facility cannot tolerate sudden breakdowns. For this reason, diagnostic and predictive functions that detect pump abnormalities in advance are essential for LNG storage facilities.

The diagnostic index, which is the standard for diagnosing the LNG pump, is explained with reference to Figure 6.The diagnostic index is obtained by Fourier transforming the acceleration or displacement measured by a vibration sensor attached to a representative position of the LNG pump to obtain the spectral distribution. After that, it is divided into certain frequencies (θ~F1, F1~F2, F2~F3), and the average values S, B, and C of the respective accelerations or displacements in each divided area are obtained. S is the average value of the shaft portion, B is the average value of the bearing portion, and C is the average value of the cavitation portion.

These values are based on the tank liquid level H(
(See Figure 7 (a) and (b)), which is greatly affected by the pump discharge flow rate Q, but other conditions such as tank internal pressure,
The effects of mixing operation and simultaneous operation of pumps in the same tank are small and can be ignored. In addition, the diagnostic index is a unique value determined by the condition of the pump, and it changes when the condition changes (replacement of bearings and bushings during periodic inspections, balance correction, installation changes, design changes, etc.), and it does not deteriorate. It is necessary to use the characteristics of diagnostic indicators in normal conditions depending on operating conditions as a reference function for diagnosing abnormalities and predicting deterioration.

FIG. 1 shows a diagnostic index 2 determined by the liquid level H when discharging LNG from the LNG tank and the discharge flow rate Q of the pump. The plane 4 in FIG. 1 during normal operation without deterioration is called the reference function 2. When discharging LNG, the tank is filled with liquid Hsax.

Dispensing is performed from the tank to the lowest liquid level H ln, but each liquid level H from the tank full liquid Hmax to the lowest liquid level Hain.
1 (Hsax, ), H2, Ha, -Hs payout amount (hlQ21Q31...Q9 is the target payout amount Q
It varies within a range of ±ΔQ. This occurs depending on the number of pumps in operation and the liquid level, and is a characteristic unique to LNG plants. Therefore, each liquid level H1 due to one dispensing
+H2rH3,...Payout amount Q+ for each Ha, Q
21 Qs+... Diagnosis index Z+, Z in a predetermined frequency area is determined by the above-mentioned Fourier analysis from the acceleration or displacement data measured by the vibration sensor at Qs.
2 r Za ,...z9 is determined, and the liquid level Hwax.

to Hmin, the area of flow rate Q±ΔQ (AB
The reference function in the DC area) will be found.

The reference function is the diagnostic index Z+ determined by one payout.
It is determined by regression analysis of l Z2 + z3 r...z9 using the least squares method. Here, regression analysis assumes an empirical formula of natural logarithm form Yn -IIkxn Yoe from data analysis, and data group x, ly
Coefficient Y by regression analysis of n. , K. That is, the first regression analysis is performed on the liquid level characteristics shown in Figure 1, and each liquid level H1 * H2 + Ha * ・
...The variation ±AQ with respect to the target dispensing flow rate Q in Ha is ignored. The equation for regression analysis is expressed as Zo-f (H, Q) = ZOQ e -K""H. (1).

Here, ZQ; diagnostic index at liquid level H1 flow rate Q (
Coefficient) ZoQ; Coefficient at liquid level H-0, flow rate Q Ho; Damping coefficient e at flow rate Q; Natural logarithm Therefore, each liquid level II r H2+ Ha +...H
For each a, obtain the diagnostic index Zt I Z2 + 23 + ... z9 using the same procedure as explained in FIG. 4Q is substituted into equation (i) to determine the diagnostic index ZQ at the liquid level H1 and flow rate Q.

If this (+) equation is drawn on a graph, it will look like curve A in Figure 2. Note that FIG. 2 shows the liquid level characteristics of the diagnostic index.

Next, it is necessary to correct the liquid level data. This correction method will be explained with reference to FIG. 2. Diagnostic indicators Z3+24+25 and Z distributed in the range of liquid level H±AH are corrected to obtain points a, b, and c on liquid level H.

Set it to the value of Z.

The data at points a, b, and c are expressed by the following equation.

When the diagnostic indicators z3゜Za, Zs distributed on the liquid level H±AH are corrected to the liquid level H, a (Za), b shown in Fig. 3 are obtained.
The data will be as shown in (Zs), c (Za),
a (Za), Q3゜b (Zs), Qs+c (Z
Perform regression analysis using a) + Qa and determine the coefficient ZQHs at the liquid level H1 flow rate Q-0 and the damping coefficient KQ)-1 at the liquid level H, then the diagnostic index ZH at the liquid level H1 flow rate Q is ZH-f ( H, Q) -ZoHe- becomes 0'''°Q ... (to). If this (to) equation is drawn on a graph, it will be as shown at the curve opening in Fig. 3. is a graph showing flow characteristics after liquid level correction.

The relationship between the liquid level and the diagnostic index shown in Figure 2 and the curve A representing it, and the relationship between the flow rate after liquid level correction and the diagnostic index shown in Figure 3 and the curve A representing it are shown on the same graph. The result will be as shown in Figure 4. FIG. 4 shows the liquid level correction procedure for the flow rate characteristics of the diagnostic index. The intersection of curve A and the mouth becomes one point on the surface representing the reference function.

When the above-mentioned calculation procedure is performed based on a large number of measured data and a graph is drawn, the result is as shown in FIG. By finding the intersection points of the curves of each diagnostic index zH and Zo, and finding the curved surface on which each intersection point rides, we can obtain the plane function Z-f (
Q, H) is determined, and this becomes the reference function.

The steps for determining the standard function are listed as follows.

(D Liquid level H(H+
, H2+...Hn) and the discharge flow rate Q (Ql, Q2...Qn) corresponding to each liquid level,
Ql r Hl + Q2, H2r...Qn, H
The acceleration and displacement at n are measured, and the acceleration and displacement are subjected to Fourier analysis and averaged in a certain frequency range, and this average value is taken as the diagnostic index Z (Z+ + z2+ . . . Zo). If the measurement interval is about 2 hours, n will be about 150.

(ID Ignoring changes in flow rate Q, the diagnostic index corresponding to liquid level H is determined by equation (i) (liquid level characteristics).

The obtained curve is shown as ■ in Figure 5.

[Phase] Select the liquid level HmHn (for example, Hl), and
The data dispersed in Hl ±AH is corrected using equation (g).

■ From the correction data, calculate the diagnostic index after liquid level correction using equation (g) (flow rate characteristics). The obtained curve is shown as ■ in Figure 5.

(v) (l ID ■) Each liquid level H2+ H3+
”・Repeat for Hn.

(By following the procedure up to the VD ω term, the coefficient (Q
-0 value) ZoH+ZQI-12・ZoH
3+...zol-1n and the damping coefficient of the flow rate characteristics at each liquid level ζKo+l KO2+KQ3+"
' Find KQn. Coefficient ZQI-11ZO)-12+
zQl-131・” zol-In is each liquid level H
The flow characteristics of 1, H2, H3, . . . Hn show the value of Q-〇, and the data is scattered on the Z-H plane. When this is regression-analyzed and expressed as an empirical formula, ZoH-'f (H) -20°e-K)-11)H・,・(,.

become.

Here, the diagnostic index (coefficient) at Zoo; Q = O1H-0, the damping coefficient of the liquid level characteristic at Kl-10;・
It shows the damping coefficient in the flow rate characteristics of H,
Assume that it changes proportionally as shown in equation (V).

Ko=f(H) - to □(, +p-H...(V) Here, Koo; damping coefficient p of liquid level H-0 ; increase/decrease rate of damping coefficient ■ (g) (V) based on formula When we find the general formula of the function, Z
−ZOHe−KQ′″Q −(Zoo e−K”°H)×. -(KQo+p-H)Q10. You will get a rabbit. Therefore, since the reference function is automatically determined based on the data obtained from one dispensing cycle, a diagnostic index is determined from the data obtained in each subsequent cycle, and this diagnostic index is compared to the reference function. Diagnosis and prediction of abnormalities and deterioration of rotating machinery is performed based on the degree of deviation.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the reference function determination method in the rotating machine diagnosis method of the present invention, (D) the reference function can be automatically determined at any time during plant operation, (ID has good accuracy due to online processing, [phase]
The method of determining the reference function becomes more rational due to the reduction in time, cost, and man-hours. ■ Changes in the characteristics of rotating machinery (wear, completion of break-in, LN
It can produce various excellent effects such as being able to respond immediately to changes in G, etc., and improving safety by eliminating the need for experiments to determine the reference function.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram of the reference function determined by the method of the present invention, Fig. 2 is a graph showing the liquid level characteristics of the diagnostic index in the method of the present invention, and Fig. 3 is a diagram showing the diagnostic index in the method of the present invention. A graph showing the flow rate characteristic after liquid level correction among the flow rate characteristics of the index, FIG. 4 is an explanatory diagram of the liquid level correction procedure for the flow rate characteristic of the diagnostic index in the method of the present invention, and FIG. 5 shows the reference function in the method of the present invention. FIG. 6 is a graph showing the relationship between frequency and acceleration or displacement of a rotating machine, and FIGS. 7(a) and 7(b) are general explanatory diagrams of LNG storage equipment. In the figure, l indicates an LNG tank, 2 indicates a receiving pipe, 3 indicates a dispensing pump, and 4 indicates a plane. Engineering ON

Claims (1)

[Claims] 1) Measure and process data on flow rate, liquid level or pressure as well as acceleration or displacement during operation of rotating machinery to automatically obtain diagnostic indicators, and statistically calculate diagnostic indicators for operating conditions of flow rate, liquid level or pressure. A method for determining a reference function in a method for diagnosing a rotating machine, characterized in that the reference function is obtained by processing the