JPH109931A - Pot for liquid level gauge and hunting preventing device of liquid level gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent hunting by a pot in a structure capable of reducing the hunting of output values from a capacitance-type liquid level gauge. SOLUTION: The probe 2 of a capacitance-type liquid level gauge 1 is suspended in a pot main body 5, and a shorter nozzle 11 for liquid injection is installed on the side of the pot main body 5. This nozzle 11 is bent downwards so that the liquid injecting opening 12 is turned toward a liquid 6 in the pot main body 5, and the liquid injecting opening 12 is formed to have an inclined end face. The tubular splash-proof cover 13 with its lower end opened is fixed in suspension so as to surround the probe 2 in the pot main body 5. A gas releasing opening 14 is formed at the upper side of the cover 13. In this structure, by bringing the nozzle 11 close to the inner side of the pot main body 5 and an injected liquid to flow down from the liquid injecting opening 12 along the inner side of the pot main body 5, the contact of splash with the probe 2 is prevented, and hunting is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pot for a capacitance type liquid level meter used in plants such as chemical and nuclear power plants, and a hunting preventing device for the liquid level meter.

[0002]

2. Description of the Related Art A capacitance type liquid level meter utilizes the fact that the capacitance of a capacitor changes depending on the dielectric constant of a substance between electrodes, and is used when liquid is in a special case such as slurry, high viscosity, and corrosiveness. In many cases, the measurement range can be wide.

A conventional capacitance type liquid level meter and its use will be described with reference to FIG. That is, in FIG. 8, the liquid level meter indicated by reference numeral 1 is
It consists of The probe 2 is mounted in the pot body 5 and converts the liquid level into a change in capacitance by being immersed in the liquid 6 in the pot body 5 and outputs a signal to a display device or the like. The pot main body 5 has a liquid injection nozzle 7 and an overflow outlet nozzle 8 on a side surface, and has a liquid discharge nozzle 9 on a bottom surface to form a pot.

[0004] As described above, the conventional capacitance type liquid level meter has no moving parts and its structure is simple, and it is relatively easy to detect the level of corrosive liquid and the level of a pot with an internal pressure. Often used for low capacity pots 5.

[0005]

In the small pot body 5 as shown in FIG. 8, the liquid injection nozzle 7 is necessarily arranged so as to approach the probe 2 of the capacitance type liquid level meter 1. I can't get it. In such a case, it is difficult to obtain a stable liquid level measurement value due to, for example, the droplets or the liquid flowing directly from the injection nozzle 7 coming into contact with the probe 2 or the surface of the liquid 6 in the pot 5 shaking. There is.

That is, the capacitance type liquid level meter 1 mounted in the pot main body 5 is hunting in which the output signal is disturbed and unstable due to the contact of the droplets and the fluctuation of the liquid level when the liquid is injected into the pot main body 5. There is a problem that the phenomenon occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a pot for a capacitance type liquid level meter and a hunting phenomenon capable of preventing a hunting phenomenon by generating a stable detection signal without disturbance of an output value. An object of the present invention is to provide a hunting prevention device that performs control to prevent hunting.

[0008]

According to a first aspect of the present invention, a capacitance type liquid level meter probe is suspended inside a pot body, and a liquid level injection nozzle is provided on a side surface of the pot body, and a nozzle is provided at a lower portion. In a capacitance type liquid level meter pot having a liquid discharge nozzle, the liquid injection port of the liquid injection nozzle is bent toward the direction of the liquid in the pot, or immersed in the liquid. It is characterized by becoming.

According to a second aspect of the present invention, there is provided a cylindrical splash prevention cover which is suspended from the upper surface of the inside of the pot body, surrounds the outside of the probe and has a gas communication port on an upper side surface and has a lower end opening. Features.

According to a third aspect of the present invention, a signal from a probe of a capacitance type liquid level meter is inputted and a signal is supplied to a remote control valve provided with a liquid injection nozzle for injecting a liquid into a pot of the liquid level meter. A process input / output device to output, a control device connected to the process input / output device, a transmission unit connected to the control device via a transmission device and a reception device, and a transmission unit connected to the transmission unit via a reception device and an instruction transmission unit. Computer connected to
A display device and an input device connected to the computer are provided.

According to a fourth aspect of the present invention, the control logic of the control device includes a pre-processing unit for receiving an input signal from the liquid level meter, and a control operation processing unit connected to the pre-processing unit. The processing unit is characterized in that the processing unit includes three stages of a process by a liquid level upper limit filter, a process by a liquid level displacement amount upper limit filter, and an average value process. The invention of claim 5 is characterized in that the capacitance type liquid level meter is fixed in the pot for the electrostatic type liquid level meter according to claim 1 or 2.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pot for a capacitance type liquid level meter according to the present invention will be described with reference to FIGS. 1 (a) and 1 (b). In FIG. 1, (a) shows a first example of a pot, (b) shows a second example of a pot, and (c) shows a third example of a pot.
In each figure, the same parts as those in FIG. 8 are denoted by the same reference numerals.

A first pot 10 shown in FIG. 1A has a probe 2 of a capacitance type liquid level meter 1 suspended in a pot body 5 and a short liquid injection nozzle is provided on a side surface of the pot body 5.
11 is installed. This short liquid injection nozzle
In 11, the liquid inlet 12 is bent downward toward the liquid 6 in the pot body 5, and the liquid inlet 12 is formed on an inclined surface.

A cylindrical splash prevention cover 13 having a lower end opening is fixedly suspended from the upper surface of the pot body 5 so as to surround the probe 2 in the pot body 5. Cover 13
A gas communication port 14 is provided on the upper side surface of the. In addition,
A liquid discharge nozzle 9 is connected to the bottom of the pot body 5.

Thus, in the first pot 10, the liquid flowing in the vicinity of the liquid injection nozzle 11 to the inner surface of the pot body 5 is transmitted along the inner surface of the pot body 5 to flow down, and thereby the capacitance is reduced. The contact of the droplets with the probe 2 of the liquid level gauge 1 can be reduced.

The second pot 15 shown in FIG.
In place of the short liquid injection nozzle 11 of the first pot 10 in (a), a long liquid injection nozzle 16 extending to near the bottom inside the pot body 5 is provided.

According to the second pot 15, the liquid injection port 17 of the long liquid injection nozzle 16 is immersed in the liquid 6 and is immersed. The inflow liquid injected into the container does not come into direct contact with the liquid, so that the generation of droplets can be prevented.

The third pot 18 shown in FIG.
In place of the short liquid injection nozzle 11 of the first pot 10 in (a), a horizontal liquid injection nozzle 19 is provided so as to penetrate the lower side surface near the bottom of the pot body 5.

According to the third pot 18, a horizontal liquid injection nozzle is provided in the inflow liquid injected in the pot body 5.
Since the liquid inlet 20 of 19 is immersed in the liquid 6 and is in a immersed state, the injected liquid does not directly contact the probe 2 of the capacitance type liquid level meter 1 to prevent the generation of droplets, There is an advantage that the structure is simpler than the first and second examples.

1 (a) to 1 (c), the provision of the cylindrical splash prevention cover 13 prevents the inflow liquid from coming into contact with the probe 2 and the liquid 6 in the pot body 5. This has the effect of acting as a damper for reducing the fluctuation of the liquid level. Further, by providing the gas communication port 14 on the upper part of the splash prevention cover 13, it is possible to prevent the occurrence of a differential pressure inside and outside the splash prevention cover 13 when the pressure of the gas phase in the pot body 5 changes. is there.

Next, an embodiment of a hunting preventing device for a capacitance type liquid level meter according to the present invention will be described with reference to FIGS. FIG. 2 shows a system incorporating the hunting prevention device according to the present invention.

In this embodiment, as a means in the case where it is necessary to stabilize the signal value from the capacitance type liquid level meter 1, the influence of the disturbance of the liquid level measurement value and the disturbance is reduced by the processing of the control device 24. It is in.

The pot body 5 in FIG. 2 is the same as that in FIG. 1 (b). A long remote liquid injection nozzle 16 is connected to a first remote control valve 21, and a liquid discharge nozzle 9 is connected to a first remote control valve 21. 2
Remote control valve 22 is connected. Capacitance type liquid level meter 1
The first remote control valve 21 is connected to a process input / output device 23. The process input / output device 23 is connected to a control device 24, and a transmission device 25 and a reception device 26 are connected to the control device 24.

The receiving device 26 is connected to a first transmitting unit 27, and the transmitting device 25 is connected to a second transmitting unit 28. Receiver 29
Is connected to the computer 30. The display device 31 and the input device 32 are connected to the computer 30. An instruction transmission unit 33 is connected to the output side of the computer 30, and the instruction transmission unit 33 is connected to the first transmission unit 27.

The first transmission unit 27 and the second transmission unit 28
To the n-th transmission device 25n and the reception device 26n are connected in parallel, and these devices 25n and 26 are connected to the second to n-th control devices 24n, and the second to n-th control devices 24n are connected to the second to n-th control devices 24n. An n-th process input / output device 23n is connected, and the second to n-th process input / output devices are connected to second to n-th capacitance type liquid level meters (not shown).

As described above, this embodiment mainly includes the plant equipment, the control device 24 for controlling the plant equipment, and the computer 30 for controlling the control device 24 and managing the entire plant.

The computer 30 is a CRT for dialogue with the operator.
And the like, a display device 31 such as a keyboard, an input device 32 such as a keyboard, a receiving device 29 for receiving information from the control device 24 via the second transmission unit 28, and an instruction from the computer 30 for the control devices 24 to 24n.
Has an instruction transmission unit 33 for transmitting via the first transmission unit 27.

The control devices 24 to 24n include transmitting devices 25 to 25n for transmitting information to the computer 30, receiving devices 26 to 26n for receiving instructions from the computer, and inputting processes from the plant and outputting control signals. Output devices 23 to 23n are provided.

A signal from the capacitance type liquid level meter 1 attached to the pot body 5 according to the first and second aspects of the present invention is input to a control device 24 via a process input / output device 23. FIG. 3 shows the control logic of the control device 24 that has received an input signal from the capacitance type liquid level meter 1.

The input signal from the capacitance type liquid level meter 1 is controlled by the logic of the pre-processing unit 34 in the control unit 24 to reduce the disturbance of the signal.
The control operation determined by the 35 logics is performed.

In the embodiment shown in FIG. 3, the control operation processing unit 35 controls the injection amount and the discharge amount of the liquid 6 in the pot body 5 in accordance with the liquid level value after the pre-processing by the pre-processing unit 34. The control signal is transmitted to the first and second remote control valves 21 and 22 for adjusting the pressure, and the operation of transmitting the information of the liquid level of the liquid 6 in the pot body 5 to the computer 30 is performed. .

The pre-processing section 34 includes a liquid level upper limit filter 36
, A process by the liquid level displacement upper limit filter 37, and a three-stage process of the average value process 38, thereby reducing the disturbance of the liquid level value.

First, the liquid level upper limit filter 36 in FIG. 3 is used when the input liquid level measurement value from the capacitance type liquid level meter 1 is higher than a liquid level upper limit set value which is a threshold value. The signal value is regarded as an abnormal value. If the abnormal value does not continue for a certain period of time, the received signal is ignored and the signal value is output while retaining the signal value before the time Δt.

If the abnormal value continues for a predetermined time or more, the abnormal value is not an abnormal value, that is, it is regarded as a normal value, and the input liquid level measurement value is output as it is. To put it simply, the liquid level upper limit filter 36 eliminates the temporarily abnormally high liquid level value when it is received.

When the control logic described with reference to FIG. 3 is implemented by software logic using a PC (programmable controller) or the like, the operation of the liquid level upper limit filter 36 is one subroutine program. This flowchart is shown in FIG.

Here, L is the received liquid level measurement value 39, Ls
Is a liquid level upper limit set value 40, C1 is a counter for storing how many times the liquid level measurement value exceeding the liquid level upper limit value is continuously scanned, C1s is a counter upper limit value, and Lm is a liquid level measurement determined as a normal value. It is a value. These variables correspond to each register of the storage device built in the PC. L
s and Cs are arbitrarily set thresholds.

First, the liquid level measurement value L is input at a constant scan period Δt (39). With reference to Ls from the storage device, it is determined whether the liquid level measurement value L does not exceed the liquid level upper limit Ls, which is a threshold value, based on whether the relationship of L <Ls is established (40). When the relationship of L <Ls holds, L
Is determined to be a normal value, and the value of L is output (41). Also, Lm in the built-in storage device is rewritten to the value of L (42),
The value of the counter C1 is reset to 1 (43).

Next, the case where the relationship L <Ls is not established will be described. With reference to the counter upper limit value C1s from the storage device, it is determined whether or not the abnormally high liquid level measurement value is continuous based on whether the relationship of C1 <C1s is established (44).
When C1 <C1s is satisfied, it is determined that an abnormally high liquid level measurement value (abnormal value) has been temporarily input, the value of Lm is output (46), and the count of the counter C1 is increased (47).
If C1 <C1s does not hold, the abnormally high liquid level measurement value is assumed to be continuous, and L is output as a normal value while avoiding the determination of an abnormal value (45).

Next, a liquid level displacement upper limit filter 37 shown in FIG.
When the input signal value is a threshold value and exceeds the liquid level displacement upper limit set value that is the displacement amount per unit time,
Similarly, the value is regarded as an abnormal value. Further, if the abnormal value continuous reception time is not abnormal to the upper limit set value which is the threshold value, the received signal is ignored, and the signal before the time Δt is held and output. That is, if the rise in the measured liquid level temporarily shows an abnormally rapid rise, it is excluded.

FIG. 5 is a flowchart showing the control logic of the liquid level displacement upper limit filter 37 in the same manner as described above. Here, L is the received output value of the liquid level upper limit filter, Ds is the liquid level displacement upper limit set value, and C2 is the number of times the liquid level measurement value exceeding the liquid level upper limit value is continuously scanned. C2s represents a counter upper limit value, and Lm represents a liquid level measurement value determined as a normal value. These variables are P
C corresponds to each register of the built-in storage device. Ds and C2s are arbitrarily set thresholds.

First, the output value of the liquid level upper limit filter is input to L (48). Lm, Ds, and C2 are referred to from the storage device to determine whether the liquid level displacement exceeds the liquid level displacement upper limit Ds, which is a threshold, depending on whether the relationship of (L−Lm) / C2 <Ds is established. It is determined whether or not (49). (L-Lm)
If the relationship of / C2 <Ds holds, L is determined to be a normal value, and the value of L is output (50). Further, Lm in the built-in storage device is rewritten to the value of L (51), and the value of the counter C2 is reset to 1 (52).

Next, the case where the relationship of (L−Lm) / C2 <Ds is not satisfied will be described. With reference to the counter upper limit value C2s from the storage device, it is determined whether or not the abnormally high liquid level displacement is continuous based on whether the relationship of C2 <C2s is established (53). When C2 <C2s holds, it is determined that a value (an abnormal value) indicating an abnormally high liquid level displacement has been input, and the value of Lm is output (57), and the counter C2
Increase the count (58).

When C2 <C2s does not hold, it is assumed that values indicating an abnormally high liquid level displacement are continuous,
L is output as a normal value while avoiding determination as an abnormal value (54). Also, Lm in the built-in storage device is rewritten to the value of L (55), and the value of the counter C2 is reset to 1 (56).

Next, in the averaging process 13 in FIG. 3, a signal change having irregularities is smoothed. The control logic is also shown in FIG. 6 as a flowchart. Where L ₁ , L ₂ ,
L ₃ ... L _N are variables for storing output values received from the upper limit filter of the liquid level displacement amount received in the past, and the output value received immediately before is L ₁ , and the output value received N-1 times before is L _N. And so on. N is an arbitrary set value, and the average interval when the scanning cycle is Δt is obtained by Δt * N.
The output value from the liquid level displacement limit filter input to L ₁ (59), after outputting the average value, the content of the L _2, L ₃ ... L _N is updated (60, 61).

(Corresponding to claim 4) The pre-processing unit of the control device according to claim 3 has been described above. Among them, the liquid level upper limit set value Ls of the liquid level upper filter is set as an arbitrary set value. Liquid level displacement upper limit value D of liquid level displacement upper limit filter
s and the set value N for determining the average interval of the average value processing.

By adding a function capable of arbitrarily changing these set values, it is possible to obtain an optimal signal according to the measurement conditions. In the case of the average value processing, for example, the output delay time and the trend record smoothing It will be set in consideration of the balance of conversion.

A method of changing the set value will be described with reference to FIG. Each of the above set values is stored in each register of the storage device built in the control device 24. The change of the set value is achieved by updating the contents of the register. In the present invention, this is achieved by the computer 30 giving an instruction to transfer the change of the set value given by the operator from the input device 32 to the control device 24 and rewrite the contents of the register. Thus, the operator can change the set value without stopping the operation while checking the trend record of the liquid level value on the display device 31.

FIG. 7 shows an embodiment of the above processing in the form of a trend record. In a sample value control system for obtaining an output signal from a capacitance type liquid level meter at a scan cycle of 5 seconds, a pot in which the electrostatic type liquid level system is installed has a shape as shown in FIG.

A liquid level upper limit filter and a liquid level upper limit in which the height of the overflow outlet 6 at 370 mm is set to the upper limit of the liquid level and the upper limit of the liquid level displacement is set to 200 mm from the pot capacity and the liquid injection flow rate. The result of passing through the filter and further processing the average value is shown in a graph.

In the figure, the trend indicated as “measurement result” indicates the output value from the capacitance type liquid level meter, the trend indicated as “judgment result” indicates the output value passed through two filters, The trend represented as “average (30 s)” indicates an output value obtained by processing the output value passed through the two filters in 30 seconds (N = 6).

In this example, it is assumed that a certain amount of liquid is stored in the pot and then sent downstream. However, according to the present embodiment, it is accurate to confirm that a certain amount of liquid has been stored. it can.

(Corresponding to claim 5) Claim 1 described above
By using the proposals corresponding to (4) to (4) in combination as in the embodiment in FIG. 2, it is possible to obtain a liquid level value with little disturbance in a pot having a capacitance type liquid level meter.

[0053]

According to the first and second aspects of the present invention, it is possible to prevent the contact of the droplet with the probe of the capacitance type liquid level meter and the fluctuation of the liquid level in the pot, which cause the disturbance of the signal from the capacitance type liquid level meter. be able to. According to the third and fourth aspects of the present invention, the signal processing can reduce disturbance and disturbance of the measured value of the capacitance type liquid level meter. The disturbance of the signal from the capacitance type liquid level meter attached to the pot according to claim 5 can be greatly reduced.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing a first example of an embodiment of a capacitance type liquid level meter pot according to the present invention,
(B) is a longitudinal sectional view showing the second example as in (a),
(C) is a longitudinal sectional view showing a third example similarly to (a).

FIG. 2 is a block diagram showing an embodiment of a hunting prevention device for a capacitance type liquid level meter according to the present invention.

FIG. 3 is a block diagram showing processing until an input signal from the electrostatic liquid level meter in FIG. 2 is set as a control operation signal.

FIG. 4 is a flowchart of a liquid level upper limit filter in FIG. 3;

FIG. 5 is a flowchart of a liquid level displacement upper limit filter in FIG. 3;

FIG. 6 is a flowchart of an average value process in FIG. 3;

FIG. 7 is a recording diagram showing a trend input and received by the hunting prevention device of the present invention from a capacitance type liquid level meter incorporated in a conventional pot in relation to the liquid level and time.

FIG. 8 is a longitudinal sectional view showing a conventional pot to which a capacitance type liquid level meter is attached.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Capacitance type liquid level meter, 2 ... Probe, 3 ... Connection fixing member, 4 ... Conductor wire, 5 ... Pot body, 6 ... Liquid, 7 ... Liquid injection nozzle, 8 ... Overflow nozzle, 9 ... Liquid discharge nozzle, 10: first pot, 11: short liquid injection nozzle, 12: liquid injection port, 13: splash prevention cover, 14: gas communication port, 15: second pot, 16: long liquid injection nozzle , 17 ... liquid inlet, 18 ... third pot, 19 ... horizontal liquid injection nozzle, 20 ... liquid inlet, 21 ... first remote control valve, 22 ... second remote control valve, 23 ... process I / O devices,
24 control device, 25 transmitting device, 26 receiving device, 27 first
, A second transmitting unit, 29 a receiving device, 30 a computer, 31 a display device, 32 an input device, 33 a command transmitting unit, 34
... pre-processing unit, 35 ... control operation processing unit, 36 ... liquid level upper limit filter, 37 ... liquid level displacement upper limit filter, 38 ... average value processing.

Claims (5)

[Claims] 1. A liquid level meter pot having a capacitance type liquid level meter probe suspended inside a pot body, a liquid level injection nozzle on a side surface of the pot body, and a liquid discharge nozzle at a lower portion. 3. The liquid level meter pot according to claim 1, wherein the liquid injection port of the liquid injection nozzle is bent toward the liquid in the pot, or is immersed in the liquid. 2. A spray cover, which is hung from the upper surface of the inside of the pot body, surrounds the outside of the probe, and has a gas communication port on its upper side surface, and has a lower end opening. The pot for liquid level meter according to 1. 3. A process input / output for inputting a signal from a probe of a capacitance type liquid level meter and outputting a signal to a remote control valve provided with a liquid injection nozzle for injecting a liquid into a pot of the liquid level meter. An apparatus, a control device connected to the process input / output device, a transmission unit connected to the control device via a transmission device and a reception device, and a computer connected to the transmission unit via a reception device and an instruction transmission unit. And a display device and an input device connected to the computer. 4. The control logic of the control device comprises a pre-processing unit for receiving an input signal from the liquid level meter, and a control operation processing unit connected to the pre-processing unit. 4. The hunting prevention device for a liquid level meter according to claim 3, wherein the hunting prevention device comprises three steps of processing by an upper limit filter, processing by a liquid level displacement upper limit filter, and average value processing. 5. The liquid level according to claim 3, wherein the capacitance type liquid level meter is fixed in the pot for the electrostatic type liquid level meter according to claim 1 or 2. Hunting prevention device for meter.