JPH04166738A - Method and apparatus for detecting abnormality - Google Patents

Abstract

PURPOSE:To detect the occurrence of abnormality in an early period by investigating the correlation among two or more signals in control signals which are inputted into control apparatuses with regard to objects under inspection in a plant and sensor signals from measuring elements. CONSTITUTION:As an example, scale attachment in a reactor 4 in a chemical plant is detected. An operating circuit 20 receives a sensor signal X1 from a flowmeter 1 and expects a control signal Y1 in normal operation. When the amount of scale increases, the difference between an actual control signal Y2 and the predicted value Y1 becomes large. When the difference exceeds a threshold value, the level of the output signal of a comparator 40 becomes ON, and the abnormality in a steam feeding system is detected. Thus, the abnormality is detected in the correlation between the control signal and the correlation signal, and the deposition of the scale is indicated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an abnormality detection method and an abnormality detection apparatus for production equipment such as chemical plants.

[Prior Art 1 An example of the process by which an abnormality occurs in a conventional chemical plant will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows a system configuration of a chemical plant, and FIG. 4 shows waveforms of a sensor signal of a flow meter and a control signal instructing the opening degree of a flow rate regulating valve in the chemical plant.

In FIG. 3, a reactor 4 is supplied with raw materials and a catalyst, and a chemical reaction occurs within the reactor 4 by heating the steam.

The products produced by the chemical reaction are discharged from the reactor 4.

In order to keep the supply of steam into the reactor 4 constant, a flow rate control valve 3 and a flow meter 1 are provided in the steam supply line.

The control circuit 2 inputs the sensor signal of the flow meter 1, and maintains the amount of steam supplied to the reactor 4 within a set range by adjusting the opening degree of the flow rate regulating valve 3 based on the temperature indicated by the sensor signal. Feedback control is performed as follows.

In addition, when the flow rate indicated by the sensor signal exceeds a predetermined abnormality detection threshold, the control circuit 2 determines that the amount of steam supplied to the reactor 4 is abnormal, and issues an alarm or activates the plant. to stop.

In such a chemical plant, for example, reactor 4
A scale arises within the body, and it increases gradually (
Considering the case, microscopically, a deviation occurs between the flow rate sensor signal level and the flow rate setting signal as shown in FIG. 4, and macroscopically, the output control signal gradually increases. Furthermore, when the valve opening degree and the flow rate are balanced, that is, when the measured flow rate falls within the set range, the process in which the deviation in the flow rate sensor signal level is reduced is repeated. However, if the pressure loss progresses only slowly (ex, on the order of several days), this amount of deviation will be small, and if the sensor signal level is visually displayed on the trend display screen (ex, on the order of several hours), The signal level appears constant.

[Problem to be Solved by the Invention 1] For this reason, the conventional abnormality detection method does not detect abnormalities in the steam supply system unless there is a large flow rate fluctuation based on the flow rate deviation. Therefore, in the past, it was necessary to visually check the presence or absence of scale during periodic plant inspections.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide an abnormality detection method and apparatus that can detect abnormalities that occur in plant equipment systems and that are difficult to measure with measuring elements. .

[Means for Solving the Problems] In order to achieve such an object, the method of the present invention provides a control signal input to a control device related to an inspection target in a plant and a measurement element related to the inspection target. Determine whether or not the interrelationships between the levels of two or more specific signals among the sensor signals from the sensor have a correlation in a normal state using a correlation formula indicating the correlation, and the result of the determination is negative. The present invention is characterized in that when a determination is made, it is detected that the inspection target is abnormal.

The device of the present invention is capable of determining the mutual relationship between levels of two or more specific signals among control signals input to control equipment related to an inspection target in a plant and sensor signals from measurement elements related to the inspection target. Determining whether or not there is a correlation in normal times using a correlation formula indicating the correlation,
The present invention is characterized by comprising a determining means for outputting an abnormal pressure detection signal indicating that the test object is abnormal when the result of the determination is negative.

[Function j] The present invention selects two signals having a correlation among the sensor signals and control signals of the plant, and monitors the correlation to detect scale adhesion in a reactor or piping system, etc. It also detects abnormalities in control signal system and sensor signal system equipment.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the circuit configuration of an embodiment of the present invention.

The abnormality detection device of this embodiment detects scale adhesion in a reactor 4 of a conventional chemical plant shown in FIG.

In Figure 1, comparator lO is flow meter 1 (see Figure 3).
The threshold voltage for detecting flow abnormality is determined by manually inputting the sensor signal of
1 and the voltage of the sensor signal, and when the voltage of the sensor signal becomes greater than the threshold voltage 1, a level-on flow abnormality detection signal is generated. By measuring the level and the voltage level of the control signal and statistically analyzing the measurement results, a correlation equation between the sensor signal X and the control signal Y during normal operation is determined.This correlation equation is defined as Y= Let it be expressed as f +x+.

The subtraction circuit 20 calculates the difference between the voltage level 9 values of the expected control signal calculated by the arithmetic circuit 20 and the voltage level value of the control signal actually output from the control circuit 2 to the flow rate regulating valve 3. . This difference value is compared with the threshold voltage v2 by the comparator 40, and when the difference value becomes larger than the threshold voltage v2 due to scale adhesion to one reactor, an abnormality detection signal is output.

In such a circuit configuration, the level of the sensor signal of the flowmeter 1 does not change at time T1 in FIG. 4 when scale begins to adhere.

When the arithmetic circuit 20 in FIG. 1 receives the sensor signal of the flowmeter 1 (level x1 in FIG. 2), it predicts the level value of the control signal (level Y in FIG. 2) during normal operation.

As the scale progresses, the difference between the actual control signal (Y2) and the expected control instruction signal level value (Yl) gradually increases, and when this difference exceeds the threshold, the output signal of the comparator 40 level turns on and an abnormality in the steam supply system is detected.

Additionally, the above correlation will be broken if a short-circuit abnormality occurs in the measurement system of the flowmeter 1, if the control valve becomes stuck, or if the source pressure of the steam fluctuates, so it is difficult to detect these abnormalities. can.

The present invention is not limited to the embodiments described above, and can be implemented with various modifications as described below.

l) In the above embodiment, an abnormality such as scale adhesion in the reactor 4 was detected based on the correlation between the flow rate sensor signal and the control signal, but instead of the flow rate sensor signal, a temperature sensor that detects the temperature of the reactor 4 The correlation between the signal and the control signal to the flow regulating valve 3 may be monitored.

2) The system to be monitored is not limited to the flow rate control loop, but the present invention can also be applied to other control loops. In this case, as in this embodiment, the correlation between sensor signals and control signals having a correlation in the same control loop is monitored. Furthermore, by examining the correlation between the sensor signals of the flowmeters installed upstream and downstream of the piping system, it is possible to detect not only the process abnormality detection 8 but also the failure of the flowmeters.

3) In the above-described embodiment, the abnormality detection circuit was constructed from an analog circuit, but it may be constructed from a digital circuit using a central processing unit. At this time, the abnormality detection device can be used for general purpose if the correlation formula and threshold value are inputted from the keyboard input device.

In addition, in this digital circuit, if the sensor signal and control signal are sampled multiple times at a fixed period, for example, one hour or one day, and the average level of these signals is used,
It is possible to detect signs of abnormality over a long period of time.

4) If the sensor signal or output signal fluctuates within a certain width,
− for a predetermined number of sensor signal levels within the normal operation range.
By setting the threshold value of the comparator 40 (generally called a fluctuation threshold value) to be the threshold value of the comparator 40, it is possible to improve the accuracy of abnormality detection.

[Advantageous Effects of the Invention 1] As explained above, in the present invention, it is possible to detect the occurrence of an abnormality in a device system by examining the correlation between a plurality of signals, so the scope of investigation into the cause of the abnormality is limited. The cause of the abnormality can be identified at an early stage. Further, since it is possible to detect other types of abnormalities within the same system other than the operating state (or physical properties) of the object to be measured, there is no need to increase the number of measuring instruments. Furthermore, since we examine the correlation between sensor signals and control signals, even if the levels of sensor signals and control signals change depending on the driving rate,
There is no need to change the specifications of the components of the abnormality detection device.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of the circuit configuration of the embodiment of the present invention, Fig. 2 is an explanatory diagram showing the correlation between sensor signals and control signals in the embodiment of the invention, and Fig. 3 shows the system configuration of the conventional example. The piping diagram shown in FIG. 4 is a waveform diagram showing waveforms of control signals and sensor signals in a conventional example. DESCRIPTION OF SYMBOLS 1... Temperature sensor, 2... Control circuit, 3... Flow rate adjustment valve, 4... Reactor, 10, 40... Comparator, 20... Arithmetic circuit, 30... Subtraction circuit. Xl 7 cm, ) & number, befre wood 11 base 6 and gotetsure 3 no 31, today's number 1 each number and y1 wandering tshi number dorio [shij Tufts I Transparent screws F Sharp blade 2nd figure

Claims (1)

[Claims] 1) Each level of two or more specific signals among control signals input to control equipment related to an inspection target in a plant and sensor signals from measurement elements related to the inspection target Determining whether or not the mutual relationship has a correlation in a normal state using a correlation formula indicating the correlation, and when the result of the determination is a negative determination, it is detected that the inspection target is abnormal. An anomaly detection method characterized by: 2) When the mutual relationship between the levels of two or more specific signals among the control signals input to the control equipment related to the inspection target in the plant and the sensor signals from the measurement elements related to the inspection target is normal. Determining whether or not there is a correlation using a correlation equation indicating the correlation, and when the result of the determination is negative, outputting an abnormality detection signal indicating that the inspection target is abnormal. An abnormality detection device characterized by comprising: determination means.