JPS63184115A - Flow meter failure diagnosis device in liquid level control system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow meter failure diagnosis device used in a control system for a liquid container.

[Traditional pinching technique]

An example of the configuration of the device targeted by the present invention is shown in Fig. 2. In Fig. 2, liquid flows into a container 1 through an inflow pipe 3, and its flow rate is measured by a flow meter 7. container 1
The liquid inside passes through the outflow pipe 9 and exits to the outside.

The height of the liquid level in the container 1 is measured by a liquid level gauge 2. The output of the liquid level gauge 2 becomes the input of the liquid level controller 6.

The liquid level controller 6 inputs the output of the liquid level meter 2 and the set value 5 of the liquid level height, and controls the liquid level by PI or PID by outputting an operation signal to the flow rate control valve 4. . A flow rate control valve 4 is attached to the inflow pipe 3, and the flow rate control valve 4 is attached to the inflow pipe 3.
The opening degree is changed according to the input, and the flow rate of the liquid flowing through the inflow flow pipe 3f is changed.

In the device configured as described above, the operation of the device is 9 times as designed.
For the purpose of monitoring whether or not the operating conditions are being met, upper and lower operating conditions are set for the measured values of each indicator, and an alarm 17 is installed to issue an alarm when the measured values deviate from the operating conditions. The outfit has been done.

[Problem that the invention seeks to solve]

In Figure 1, when the flow control valve 4 is fully opened and the failure is detected, an alarm is generated when the output of the inflow flowmeter 7 exceeds the upper limit of the flow rate that can be considered under normal operating conditions. This warning has two meanings:

(1) The flow control valve is actually fully open.

(2) The inflow flowmeter 7 malfunctioned and indicated a higher flow rate than the actual flow rate.

Since the above failure (1) changes the actual operating conditions of the apparatus, it is necessary to take some kind of action to maintain the liquid level in the container 1.

Furthermore, the failure in (2) above does not change the actual operating conditions of the device, and is less urgent than the failure in (1) above. On the other hand, if measures are taken for (1) despite the fact that (2) is a failure, the operating conditions of the device will be unnecessarily disrupted.

It was impossible to distinguish between the two causes of the abnormality using only the alarm of the abnormally high flow rate of the flow meter 7, and it was difficult to issue appropriate operating instructions to the operator. ] As shown in FIG. 1, the present invention collects the operation amount of the flow rust control valve 4, the output of the liquid level gauge 2, the output of the inflow flowmeter 7, and the output of the outflow flowmeter 8 in the target device, as shown in FIG. Using the data collected by the data collection unit io and this data collection unit 10, calculate the following quantities (1) to (4), and check whether each value is within the normal operating range or abnormal on the positive side. Four calculation units 11 and 12 that output a signal representing a state of being large or abnormally large on the negative side.
, 13゜14, and when the output signal state of these four calculation units 11, 12, 13゜14 is as shown in (a) #(b) below, a signal indicating that a failure has occurred in the inflow flowmeter 7 is generated. An identifying section 15 that generates the fault, and a display section 16 that displays when the output of the identifying section 15 indicates that a failure has occurred are added.

(1) Difference between the amount of liquid increase in the container 1 determined from the output of the liquid level gauge 2 and the integral value of the difference obtained by subtracting the output of the outflow flow meter 8 from the output of the inflow flow meter 2...vl(2 ) Difference between the output of the liquid level gauge 2 and the set value 5 of the liquid level controller 6...V.

(3) Difference between the output of the inflow flowmeter 7 and the estimated flow rate of the inflow pipe 3' obtained from the input of the flow rate control valve 40...V.

(4) Integration of the difference between the increase in the amount of liquid in the container l determined from the output of the liquid level gauge 2 and the estimated flow rate of the inflow pipe 3 estimated from the input of the flow rate control valve 4 minus the output of the outflow flow meter 8 Difference with the value...v4 (&) Large error on the high side of the inflow flow meter 7 ■ The value of v8 is abnormal on the low side ■ The value of V is normal ■ The value of V is abnormal on the high side ■ v4 The value of is normal.) Large error on the low side of the inflow flow meter 7■ The value of vl is abnormal on the high side.■ The value of V is normal.■ The value of V is abnormal on the low side.■ The value of v4 is normal. ] The present invention [A large indication error of the inflow flowmeter 7 has occurred]
In order to confirm that [a flow control valve abnormality is unlikely], an abnormality with a large error in the indicated value of the inflow flow meter 7 will not cause an abnormality in the true state of the process, but an abnormality in the flow control valve 4 will cause no abnormality. From the perspective that the true state of the Fi process changes and affects other parts, we focus on the following four quantities, and determine how each failure affects the following four quantities. Perform a diagnosis.

The symbols used in the following description are as follows.

L: Liquid level height A (L) of container 1: Cross-sectional area at height L of container 1 Fl: Indication value of inflow flowmeter 7 Fo: Indication value of outflow flowmeter 8 U: Input to flow f control valve 4 Signal fO(u): Obtained from the characteristics of the flow control valve 4 during normal operation. Value of the liquid flow rate estimation function through the 9-flow TV 4-node valve 4. La: Steady value of the liquid level height in the container 1. T: To obtain the above La. Time to take the time average of (1)
Amount of liquid stored in container 1 calculated from each meter reading at a certain point t
Since the amount of liquid accumulated in the container 1 from 1 to t1 after an appropriate time TI is equal to the difference between the amount of liquid that has flowed in and the amount of liquid that has flowed out, the following value is calculated.

Here, the amount determined by equation (1) is referred to as the liquid storage amount.

vl is a value that is zero regardless of whether the flow rate control valve 4 is out of order, but if the error of the inflow flow meter 7 becomes large, the value will deviate from zero.

If the inflow flow meter 7 has a large positive error, vl will be a negative value, and if the inflow flow meter 7 has a large negative error, vl will be a positive value. In reality, taking into account the errors that flowmeters and liquid level gauges always have, and in order to determine that ■ is far from zero, we set an upper limit v1h and a lower limit vIL of the allowable error value of the vl value. An abnormality is detected when these upper limit values are exceeded.

(2) Deviation from the steady value of the liquid level gauge If the flow control valve 4 fails, liquid level control becomes impossible and the indicated value of the liquid level gauge 2 deviates from the steady value. The value of this deviation is V
, the calculation of the steady value of the indicated value of the level gauge 2 uses, for example, the average of the indicated values of the level gauge 2 for an appropriate time interval T before a certain point in time.

In order to judge the deviation from the steady value, set an appropriate tolerance range, and judge when the deviation from the steady value exceeds the tolerance value. If the above-mentioned steady-state value is used, the value of (2) can be given, for example, by the following equation.

t: Current time (3) Difference between the indicated value of the inflow flow meter 7 and the inflow flow rate estimated from the input to the flow rate control valve 4.As long as there is no change in the upstream pressure of the flow rate control valve 4, the flow rate control valve 4 is opened. A functional relationship is established between the temperature and the flow rate flowing through the flow rate control valve 4.

There is also a one-to-one correspondence between the input to the flow rate control valve 4 and the valve opening, so the input to the flow rate control valve 4 and the flow! If the relationship between the flow rate of liquid flowing through the control valve 4 is determined in advance, the flow rate of the liquid flowing through the valve 4 can be estimated from the input to the flow control valve 4. If we take the difference between the estimated flow rate value and the indicated value of the inflow flowmeter 7 and let this be V, then the value of V, = F'i - Fc(u) Due to failure, the value will be far from zero.

Conversely, if V is zero, it is necessary to suspect another failure. Similarly to the above two quantities, an abnormality is detected for the value of (2) when it deviates from the allowable range.

(4) Calculate the liquid volume balance value in the container 1 from the indicated value of the liquid level gauge 2, the indicated value of the outflow flow meter 8, and the inflow flow estimated from the input to the flow fth control valve 4 from the same viewpoint as v1 above. , the liquid volume balance value of the container 1 is determined, but at this time, the flow rate flowing into the container 1 is estimated from the input to the flow rate adjustment valve 4 mentioned in the above (3), rather than the indicated value of the inflow flow meter 7. However, the inflow flow rate is used. This value v4 is given by the following equation.

Here 1. ．． 1! The meaning of is the same as in equation (1).

(2) The value of 4 is different from the value of vl; it remains zero even if the inflow flowmeter 7 fails, but it becomes a value that moves away from zero when the flow rate control valve 4 fails. ■Anomalies in the value of 4 are determined by deviation from the appropriate tolerance range, similar to the value of V-work.

Now, when the above four values (V□, V, , V, , V,) are calculated and an abnormality is detected based on the judgment criteria described above, the failure of the inflow flow meter is confirmed by the following method.

(&) Large error on the high side of inflow flow meter 7 ■ The value of vl is abnormal on the low side ■ The value of V is normal ■ The value of V is abnormal on the high side ■ The value of V4 is normal (b) Inflow Flow meter 7 has a large error on the low side ■ The value of V is abnormal on the high side ■ The value of V is normal ■ The value of V is abnormal on the low side ■ The value of v4 is normal Which of the above (a) and ω) However, it is confirmed that the liquid level gauge 2 and the outflow flow meter 8 are normal by checking ■ and ■. In other words, if the liquid level gauge 2 is abnormal, ■.

■ indicates an abnormality. Further, if the outflow flow meter 8 is abnormal, the abnormality will appear in (2).

[Example] FIG. 1 shows the equipment configuration in the present invention. The role played by each part in the diagram in the above-described diagnosis will be explained. Note that the explanation of the parts that overlap with the parts shown in FIG. 2 described in the section of the prior art will be omitted.

In Figure 1, the data collection unit 10 inputs the output of the liquid level meter 2, the output of the inflow flowmeter 7, the set value 5 of the liquid level controller 6, and the output of the outflow flowmeter 8, and 4 each calculation unit 1
Distribute input to 1, 12, 13, and 14.

The first calculation unit 11 calculates the value of v8, determines whether it is abnormal or not using the method described above in the section 9 (1).
Outputs three status signals: positive side abnormality and negative side abnormality.

The second calculation unit 12 calculates the value of V, determines whether it is abnormal or not using the method described in the section of operation (2) above, and determines whether it is normal or not.
Outputs three status signals: positive side abnormality and negative side abnormality.

The third calculation unit 13 calculates the value of (■), determines whether it is abnormal or not using the method described in the section of action (3) above, and determines whether it is normal or not.
Outputs three status signals: positive side abnormality and negative side abnormality.

The fourth calculation unit 14 calculates the value of v4, determines whether it is abnormal or not using the method described in the section of action (4) above.
Outputs three status signals: positive side abnormality and negative side abnormality.

The identification unit 15 includes each of the calculation units 11 e I J # 1
3 Use the output of a14 as input, and perform the above (a), O))
The abnormality in the inflow flow meter 7 is identified by the method of
Outputs a normal two-state signal.

The display section 16 inputs the output of the identification section 15, and when the same person's power indicates that a failure has occurred, the display section 16 displays this by, for example, a lamp or the like.

In the above-mentioned embodiment, the operation of the inflow flowmeter 7 was mainly explained for failure diagnosis in a configuration in which the flow control valve 4 installed in the inflow pipe 3 is controlled by the liquid level controller 6. The present invention is not limited to this, but can similarly be applied to failure diagnosis of an outflow flow meter when, for example, a flow control valve is provided in the outflow pipe 9 and the flow control valve is controlled by a liquid level controller. .

〔Effect of the invention〕

As described above, according to the flowmeter failure diagnosis device for a liquid level control system of the present invention, it is possible to accurately determine the failure of each flowmeter on the inflow side and the outflow side, and to detect abnormal flowmeter output. In some cases, the operator can be notified of the cause of the abnormality without confusing it with a failure of the flow control valve.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a device configuration as an embodiment of the present invention, and FIG. 2 is a detailed device configuration diagram illustrating a conventional technique. 1... Container, 2... Liquid level gauge, 3... Inflow pipe, 4...
...Flow rate control valve, 5...Liquid level controller setting value, 6...
Liquid level controller, 7... Inflow flowmeter, 8... Outflow flowmeter, 9... Outflow pipe, 10... Data collection unit, 11...
・First calculation unit, 12...Second calculation unit, 13...
Third calculation section, 14...Fourth calculation section, 15'' identification section, 16...Display section, 17...Alarm device. Applicant's representative Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] A container equipped with a liquid level gauge, an inflow pipe for flowing liquid into the container, an outflow pipe for flowing liquid out of the container, a flow rate control valve provided in the inflow pipe or the outflow pipe, and a flow rate control valve for the liquid level gauge. A liquid level controller that operates the flow rate control valve based on an output and a set liquid level value, an inflow flowmeter that measures the flow rate of the inflow pipe, and an outflow flowmeter that measures the flow rate of the outflow pipe. The apparatus comprises a data collection unit that collects the operation amount of the flow rate control valve and each output of the liquid level gauge, inflow flowmeter, and outflow flowmeter; Based on the data, calculate the difference between the amount of liquid increase in the container calculated from the output of the liquid level meter and the integral value of the difference obtained by subtracting the output of the outflow flowmeter from the output of the inflow flowmeter, and calculate the calculation result. The first calculation unit outputs a three-value status signal of [normal/abnormally large on the positive side/abnormally large on the negative side], and the difference between the output of the liquid level gauge and the liquid level setting value is calculated. A second calculation unit outputs a three-value status signal similar to the above based on the calculation result, and calculates the difference between the estimated inflow pipe flow rate obtained from the output of the inflow flowmeter and the input of the flow rate control valve. a third calculation unit that outputs a three-value status signal similar to the above based on the calculation result; and an inflow pipe estimated from the increase in liquid in the container obtained from the output of the liquid level gauge and the input of the flow rate control valve. Subtract the output of the outflow flow meter from the estimated flow rate, find the difference between the difference and the integral value, and use the same calculation result as above.
A fourth calculation unit outputs a value status signal, and receives four types of three-value status signals obtained from each of these calculation units, and determines the [positive side] of the inflow flowmeter or outflow flowmeter based on the specific pattern state of the signal. large error/large negative error], an identification section generates a signal indicating that a failure has occurred in the flowmeter, and an identification section that generates a signal indicating that a failure has occurred in the flowmeter. 1. A flowmeter failure diagnosis device for a liquid level control system, comprising a display section that displays this fact.