JPS60154119A - Liquid level measuring device - Google Patents

Abstract

PURPOSE:To improve the simplicity and reliability of maintenance by measuring the density and level of liquid by using a differential pressure gauge. CONSTITUTION:A liquid level signal H is led out of the differential pressure gauge 13 by introducing atmosphereic pressure in the low pressure side of the differential pressure gauge 13 by powering on a three-way solenoid valve 15 and supplied to a holding circuit through a selection switch 20. The holding circuit 21 holds the liquid level signal H before the three-way solenoid valve 15 is powered off. Once the three-way solenoid valve 15 is powered off, the low pressure side of the differential pressure side receives the hydraulic pressure of a high position corresponding to the passing of piping 16, so pressure H0rho is applied to the high pressure side of the differential pressure gauge 13 and pressure (H0-h)rho is applied to the low pressure side respectively, outputting a differential pressure signal hrho. In this case, (h) is constant, so this signal is used as a concentration signal as it is, and supplied to a holding circuit 22 through the selection switch 20 to hold the density signal rho before the power-on operation starts. Consequently, an actual liquid level signal H0 is outputted from an arithmetic circuit 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid level measuring device suitable for measuring the level of a liquid that is subject to fluctuations.

"Technical violation of the invention" In general, the density of liquids stored in liquid tanks installed in chemical plans 1~ and water and sewage systems often changes over time due to changes in their composition and environmental changes. When this liquid level is measured using a differential pressure gauge, an error occurs between the liquid level measured by the differential pressure gauge and the actual liquid level due to a change in liquid density. Therefore, it is necessary to determine the actual liquid level by correcting the liquid level measured by the differential pressure gauge based on the liquid density at that time.

FIG. 1 is a 1M4 diagram showing a conventional example of liquid level measurement involving such density changes. In Figure 1, 1 is a liquid tank, and this liquid tank 1 stores a liquid 2 whose density changes over time, for example, and the piping installed in the liquid tank. The liquid level is varied by being injected or discharged through (not shown). A pipe 6 is installed near the bottom of the liquid tank 1.
The pipe is connected to the high pressure side of the differential pressure gauge 3. Further, the low pressure side of the differential pressure side 3 is open to the atmosphere. Of course, the differential pressure gauge 3 is installed so as to measure the liquid pressure near the bottom of the C liquid tank on the high pressure side, and its output is introduced into the high pressure side. If so, the signal will be 1, which corresponds to the liquid level. On the other hand, a density meter 4 for measuring the density of the liquid 2 is installed in the liquid tank 1, and the density of the liquid 2 is determined by the density signal ρ.
It is now output as . 5 is an arithmetic circuit which inputs the liquid level signal T1 of the differential pressure gauge 3 and the density signal ρ of the densitometer 4, and calculates and outputs an actual liquid level signal Ho according to the current density of the liquid 2. In this arithmetic circuit, when the initial density of the liquid 2 detected at the time of adjusting the differential pressure gauge at the start of measurement is taken as ρ0, the actual liquid level 10 is calculated by the following equation.

1-1 o-ρ/ρ0 There is an error between digit 1 and 0.

Therefore, a stock level signal 1i14 is separately provided to obtain a density value ρ at the time of liquid level measurement, and from this, the arithmetic circuit 5 corrects the liquid level signal 1-10 by 1"J, which is a positive (1") corresponding to the density.
I set it to i47.

[Problems with blue technology] By the way, according to the above-mentioned conventional configuration, two detectors, a differential pressure gauge and a kakuda, are required to measure the actual liquid level Ho, so even if either detector fails, the measurement will not be possible. In addition, the need for more detectors may double the failure rate and cause reliability deterioration. In particular, with regard to density meters, there are currently many unstable factors in continuous measurement in process lines, and maintenance in the event of a breakdown takes a longer time compared to differential pressure gauges, which are generally used more frequently. There's a problem.

For this reason, in order to ensure measurement during maintenance, conventionally it has been necessary to take uneconomical measures such as providing two sets of detectors.

[Object of the Invention] The present invention is intended to improve the above-mentioned problems of the prior art, and its purpose is to measure the liquid level with a single differential pressure gauge (accurately measure the liquid level).
By covering the liquid level measuring device that can be
The objective is to improve ease of maintenance a3 and reliability.

[Summary of the Invention] In order to achieve the above object, the present invention corrects the actual liquid level of the liquid stored in the liquid tank based on the bitter melon variation of the liquid with respect to the detected liquid level. - In a liquid level measuring device, a differential pressure gauge is connected to the low pressure side of the differential pressure gauge, which introduces the liquid pressure near the bottom of the liquid tank J to the high pressure side, and atmospheric air is introduced into the low pressure side, and the differential pressure V If the liquid level is detected on the low pressure side, or the liquid pressure at a level nearer to the liquid level is detected on the low pressure side than on the 14 pressure side, the density is detected on the differential pressure gauge. By adopting a unique configuration for the switching control means, it is advantageous to eliminate the need for close calls.

Embodiment of the Invention FIG. 2 shows an embodiment of the liquid level measuring device according to the present invention (1 is located in Narita).

In the figure (13), 10 is a liquid 4F11c, in which is placed a liquid '11 whose density changes I'l'<C.

Near the bottom of the liquid tank 10, a color scheme 12 is provided for introducing liquid soil from the liquid 11, and the II pressure side of the differential pressure side 133 is connected to this pipe 12. Differential pressure gauge 1
The low pressure side of the liquid 11 is connected to the three-way solenoid valve 15 through a pipe 141.This three-way solenoid valve 15 either introduces the atmosphere into the low pressure side of the differential pressure J113 or controls the level of the liquid 11 from the high pressure side through the pipe 16. This system switches whether to introduce hydraulic pressure at a liquid level close to The connection is made to output a density signal obtained as the differential pressure between the two from the differential pressure gauge 13.Therefore, the other end of the piping 16 is placed at a predetermined distance 11 from the piping 12. , is connected to the liquid tank 10.The output of the differential pressure side 13 is connected to the bold circuit 21 for the liquid/level signal or the density signal via the selection switch 20, depending on the selection state of the selection switch 20. It is connected to a hold circuit 22.Furthermore, the outputs of the hold circuits 21 and 22 are connected to an arithmetic circuit 23 that calculates the actual liquid level.
Specifically, the liquid level signal and density signal detected by the differential pressure gauge 130 held by the hold circuits 21 and 22 are inputted, and the actual liquid level is determined based on a predetermined formula.

On the other hand, in the configuration described above, the valve switching of the three-way solenoid valve 15, the selection switching of the selection switch 20, and the hold circuit 21.2
The control of the signal water field in step 2 is performed by the measurement control section 24. The measurement control unit 24 includes a solenoid valve switching circuit 17 that switches the three-way solenoid valve 15, a valve switching signal to the solenoid valve switching circuit 17, a selection signal to the selection switch 20, and a selection signal to the bold circuits 21 and 22. Relay '19 which controls the output of the bold signal, and the front by relay '19. The timer circuit 18 provides timing for controlling the output of each of the signals described above. When on, the relay 19 outputs a valve switching signal to the solenoid valve switching circuit 17 to make the three-way solenoid valve 15 conductive, outputting a liquid level signal from the differential pressure gauge 13 and outputting a horn signal, and transmitting a selection signal to the selection switch 20. is output and the movable contact is connected to the hold circuit 21 side so that the liquid level signal is input to the small hold circuit 21.

When the relay 19 changes from the on state to the off state, it outputs a hold signal to the hold circuit 21 to hold the liquid level signal at that time. -h, relay 1
When OFF, 9 outputs a valve switching signal to the solenoid valve switching circuit 17 to turn the three-way solenoid valve 15 into a non-conducting state and output a density signal from the differential pressure gauge 13, and also outputs a density signal from the differential pressure gauge 13.
0 to connect the movable contact to the hold circuit 22 side so that the density signal is input to the bold circuit 22. When the relay 19 changes from the OFF state to the OFF state, it outputs a small hold signal to the hold circuit 22 to suppress the density signal at that point in time.

The arithmetic circuit 23 has the same function as the arithmetic circuit shown in FIG. According to ρ o × 11 ( , the actual liquid level signal 1” o at the current density is output.
- times of liquid level measurements are performed by obtaining a liquid level signal H and a density signal ρ from the differential pressure gauge 13.

That is, the liquid level signal T1 is extracted from the differential pressure 5+13 by energizing the three-way solenoid valve 15 to cover the low pressure side of the differential pressure 6113 with the atmosphere, and is given to the bold circuit 21 via the selection switch 20. . The bold circuit 21 receives the liquid level signal H before the energization to the three-way solenoid valve 15 is cut off.
hold. When the power to the three-way solenoid valve 1!5 is cut off, the low pressure side of the differential pressure gauge 13 receives the liquid pressure at the high position across the pipe 16, so that the high pressure side of the differential pressure 3113 has l'oρ. The pressure on the low pressure side is (1-1o -
Fl) ρ pressure is applied, and the differential pressure signal is [1ρ
The output of is given. Since [) is constant, this signal can be used as it is as the signal g, and is applied to the hold circuit 22 via the selection switch 20.

The hold circuit 22 is the hold circuit 21 for the liquid level signal 1-1.
Similarly, the density signal ρ before energization is started is held. As a result, the performance circuit 23 has a single difference 11 tears 13
The liquid level signal 1-1 and the density signal ρ of the liquid 2 when the liquid level signal is given are inputted from the liquid level signal 1-1, and an actual liquid level signal 1-10 is outputted according to the above-mentioned arithmetic expression.

Note that at least the timer circuit 18, relay 19, selection switch 20, hold circuit 21, 22, and arithmetic circuit 2
3 can be housed in the housing of the differential pressure sub-unit 13, and can be configured to be quite compact.

In the above embodiment, the timer circuit 18 controls the solenoid valve switching circuit 17 and the relay 19 to measure the liquid level. It is also possible to configure solenoid valve switching circuit 17 and relay 19 to be operated.

Roughly speaking, in this embodiment, the liquid tank is 4 t'l in size, but it goes without saying that a closed tank may also be used.

[Effects of the Invention] As explained above, according to the present invention, the actual liquid level of the liquid stored in the oil tank is corrected based on the density change of the liquid with respect to the detected liquid level. The liquid level measuring device uses a differential pressure gauge to measure the density and the liquid level.This eliminates the need to use a density meter as in the past, making maintenance easier and easier to measure. It is possible to improve reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example of liquid level measurement, and FIG. 2 shows an embodiment of a liquid level measuring device according to the present invention. 10...Liquid tank 11...Liquid 13...Differential pressure gauge 15...Three-way solenoid valve 17...Solenoid valve switching circuit 18...Timer circuit 19...Relay 20...Selection switch 21 .22
...Hold circuit 23...Arithmetic circuit 2/I...Measurement control section agent Patent attorney Yasuo Yoshitaka Figure 1

Claims (1)

[Claims] The actual liquid level of the liquid stored in the liquid tank is corrected based on the density change of the liquid with respect to the detected liquid level. A differential pressure gauge mounted on the side is connected to the low pressure side of this differential pressure gauge, and atmospheric air is introduced into the low pressure side to allow the differential pressure gauge 1 to detect the water level, or the low pressure side is compared to the high pressure side. (C) a detection switching control means for introducing a liquid pressure at a level close to the surface of the liquid and performing density detection on the differential pressure g1; ).