Water-level detection device and water-level detection method

Abstract

To provide a water-level detection device for detecting a water level of a water tank which stores water while suppressing variation in a liquid level of a water-level detection pipe to the minimum.SOLUTION: A water-level detection device 9 for detecting a water level of a water tank which stores water includes: a cylindrical water-level detection pipe 1 having a hole communicating with the water in the water tank at a lower end side; and a pressure sensor 2 which is communicably connected to the water-level detection pipe and which detects the pressure of gas existing in the water-level detection pipe. The water-level detection pipe includes: a main pipe 4 communicably connected to the pressure sensor; and an expansion pipe 5 which is communicably connected to the lower part of the main pipe and which has an expansion part 3 with an inner diameter larger than that of the main pipe.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water level detection device and a water level detection method for detecting the water level of a water receiving tank that stores water while minimizing fluctuations in the liquid level in a water level detection pipe. [Background technology]

[0002] As a water level detector for measuring the water level in a tank, Patent Documents 1 and 2 describe a water level detector in which a pipe is inserted from above to below in the tank and the air pressure in the pipe is measured.

[0003] However, the method of inserting a pipe into a tank and detecting the air pressure inside the pipe to detect the water level had the problem that it was difficult to accurately grasp the water level inside the tank because the volume of the enclosed air (enclosed gas) fluctuates greatly depending on the temperature and air pressure, causing the liquid level inside the pipe to fluctuate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 62-156835 [Patent Document 2] Japanese Patent Publication No. 2022-115042 Summary of the Invention [Problem to be solved by the invention]

[0005] Even in devices that insert a tubular water level detection tube into a water tank and detect the water level based on the air pressure inside the tube, the volume of the gas sealed inside fluctuates greatly due to fluctuations in temperature and air pressure, which causes the liquid level inside the water level detection tube to fluctuate, making it difficult to accurately determine the water level inside the water tank.

[0006] The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a water level detection device and a water level detection method for detecting the water level in a water tank that stores water while minimizing fluctuations in the liquid level in the water level detection pipe. [Means for solving the problem]

[0007] The water level detection device of the present invention comprises: (1) A water level detection device for detecting the water level of a water tank that stores water, a tubular water level detection pipe having a hole at the bottom end thereof that communicates with the water in the water tank; and a pressure sensor connected to the water level detection pipe and detecting the pressure of gas present in the water level detection pipe, The water level detection pipe comprises a main pipe connected to the pressure sensor, and an extension pipe connected to the lower part of the main pipe and having an extension part with an inner diameter larger than that of the main pipe. (2) In the water level detection device (1), the ratio A / B of the cross-sectional area A of the inner diameter of the expansion portion to the cross-sectional area B of the inner diameter of the main pipe is 3.5 or more. (3) In the water level detection device of (1) or (2), the ratio C / D of the length C from the top to the bottom of the extension part to the total length D of the water level detection pipe is 0.1 or less. (4) In (1) or (2), the water level detection device outputs the change in water level over time based on a group of moving average data of water level data calculated from individual pressure data obtained by the water level detection device. (5) A water level detection method using the water level detection device according to (1) or (2), This is a water level detection method for measuring the water level in the water tank when the highest liquid level in the water level detection pipe is lower than the top of the expansion part of the expansion pipe. [Effects of the Invention]

[0008] The configuration of the present invention makes it possible to provide a water level detection device and a water level detection method for detecting the water level in a water tank that stores water, while minimizing fluctuations in the liquid level in a tubular water level detection tube that is inserted into the water tank. Fluctuations in the water level in the receiving tank can be detected by measuring the head pressure generated by the difference between the water level in the receiving tank and the liquid level in the water level detection pipe with a pressure sensor attached to the top of the water level detection pipe. The pressure sensor indirectly measures the head pressure generated on the liquid surface in the water level detection pipe by measuring the pressure of the gas sealed inside the water level detection pipe. When the water level in the receiving tank remains constant, the volume of the gas sealed inside the water level detection pipe changes with changes in temperature in accordance with Charles' law, and the liquid level in the water level detection pipe changes. As a result, the measured water level in the receiving tank changes with changes in temperature, making it difficult to accurately detect the water level in the receiving tank. In addition, in accordance with Boyle's law, when the water level and temperature in the water tank are constant, changes in atmospheric pressure cause the volume of the gas sealed in the water level detection tube to fluctuate, which also causes the liquid level in the water level detection tube to fluctuate, which hinders accurate measurement of the water level in the water tank. By providing an expansion section at the lower end of the water level detection tube, it is possible to buffer fluctuations in the vertical direction of the liquid level inside the water level detection tube caused by changes in the volume of the gas sealed inside the water level detection tube due to temperature and air pressure, thereby minimizing errors in the water level detection value by the pressure sensor. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a main pipe / extension pipe type water level detection device 9 according to one embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a conventional water level detection device 10 that uses a single pipe of the same diameter. [Figure 3] FIG. 1 is a diagram showing the configuration of the water receiving tank (chemical liquid tank 7) and each water level detection device used in the experiment. [Figure 4] 10 is a graph of data obtained in a comparative example using a conventional water level detection device 10 that uses a single pipe. [Figure 5] 10 is a graph showing data obtained in an example of a water level detection device 9 using a main pipe and an extension pipe according to the present invention. [Figure 6]5 is a graph showing a moving average of the data of the comparative example in FIG. 4. [Figure 7] 6 is a graph showing a moving average of the data of the example in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0010] As shown in FIG. 1, the water level detection device of the present invention is a water level detection device 9 (also called a main-pipe / extension-pipe type water level detection device) that includes a water level detection pipe 1 inserted into a water tank and a pressure sensor 2 connected to the upper end of the water level detection pipe 1. The water level detection pipe 1 is equipped with a main pipe 4 and an extension pipe 5 connected to the lower end of the main pipe 4. The extension pipe 5 has an inner cross-sectional area that is clearly larger than the inner cross-sectional area of the main pipe 4 and has an extension section 3 with a hole 3a that communicates with the water in the water tank. The pressure data of the gas sealed in the main pipe 4 measured by the pressure sensor 2 is transmitted to a water level conversion means (not shown) via a signal cable 6 and converted into water level data for the water tank. The water level data of the water tank output from the water level conversion means is transmitted to a water level notification means (not shown) via at least one type of communication line, such as a public telephone line, a mobile phone line, an Internet line, a LAN line, or a dedicated line, by a water level distribution means (not shown). The water level notification means notifies the water tank manager of the water level of the water tank delivered from the water level delivery means by voice, screen display, email transmission, etc. Here, the expansion section 3 of the expansion pipe 5 refers to the internal space of the expansion pipe 5, which is located at the lower end of the water level detection pipe 1 and which can be visually confirmed to have an internal diameter that is clearly larger than that of the main pipe 4. As shown in Fig. 1, the ratio A / B of the internal cross-sectional area A of the expansion section 3 of the expansion pipe 5 to the internal cross-sectional area B of the main pipe 4 of the water level detection pipe 1 is usually 3.0 or more, and preferably 3.5 or more. If the ratio A / B is less than 1.5, it is difficult to obtain the effect of buffering and minimizing fluctuations in the liquid level inside the water level detection pipe 1 due to changes in the temperature, etc. inside the water level detection pipe 1 of the present invention. The upper limit of the inner diameter cross-sectional area of the expansion portion 3 of the expansion pipe 5 is preferably about 80% or less of the cross-sectional area of the water tank, since if it approaches the cross-sectional area of the water tank, it will be difficult to install, replace, and clean the water level detection device 9.

[0011] In the water level detection method using the water level detection device 9 of the present invention, it is preferable to measure the water level in the water tank when the liquid level inside the water level detection tube 1 is at its highest point and is lower than the top of the extension section 3 of the extension tube 5, in order to fully realize the effects of the present invention.

[0012] The range of effective device dimensions can be inferred from the actual data obtained, but it is preferable to use a formula to calculate how the liquid level in the expansion section of the water level detection tube for the device dimensions to be used will change over the temperature fluctuation range and external air pressure fluctuation range during operation, and to predict the required device dimensions.

[0013] 1, in the water level detection device 9 of the present invention, the ratio C / D, which is the length C from the upper end to the lower end of the extension section 3 of the extension pipe 5 of the water level detection pipe 1 (the height of the extension section of the extension pipe) to the total length D of the water level detection pipe 1 consisting of the main pipe 4 and the extension pipe 5 (the sum of the height of the main pipe and the height of the extension section of the extension pipe), is preferably 0.2 or less, and particularly 0.1 or less. If it is greater than 0.2, it becomes difficult to obtain the effects of the present invention. In addition, in this invention, when installing the water level detection device in the water tank, unless otherwise specified, the water level detection pipe is installed so that it is approximately perpendicular to the liquid level in the water tank, so the height and length of the water level detection pipe, extension pipe, etc. are approximately the same.

[0014] The pressure sensor 2 used in the water level detection device of the present invention can be any commercially available sensor. The head pressure acting on the gas sealed in the water level detection pipe fluctuates in conjunction with the difference in elevation between the liquid level in the water level detection pipe and the water level in the receiving tank. Therefore, the pressure of the gas sealed in the water level detection pipe increases or decreases in conjunction with the difference in elevation between the liquid level in the water level detection pipe and the water level in the receiving tank. Because the water level detection device is typically fixed to the receiving tank, the head pressure acting on the gas sealed in the water level detection pipe fluctuates primarily depending on the water level in the receiving tank. In other words, measuring the pressure of the gas sealed in the water level detection pipe provides information on fluctuations in the water level in the receiving tank. Furthermore, the water level in the receiving tank can be calculated by setting a known water level as the reference point. Furthermore, the volume of the liquid in the receiving tank can be calculated using the cross-sectional area of the receiving tank and the viscosity of the liquid in the receiving tank.

[0015] The method for calculating the moving average value of the detected water level in this invention is to sequentially average the most recent n pieces of time-series pressure data, and typically 3 to 5 pieces of data are used for the calculation. Using the moving average value is preferable because it allows for a clearer confirmation of water level fluctuations over time.

[0016] The water receiving tank in the present invention is a water receiving tank in various industrial fields that require water level management, and examples thereof include a water storage tank and a chemical tank 7 as shown in Fig. 3. The liquid whose water level is to be measured in the present invention is a liquid in various industrial fields that require water level management, and examples thereof include water and water treatment agents.

[0017] In the example, the water level detection tube is made of vinyl chloride, but a tube made of an appropriate corrosion-resistant material may be used depending on the nature of the target liquid. A hard tube that can stand upright in the liquid is preferable, but a soft tube may also be used depending on the installation environment. The shape of the expansion section may be cylindrical, bell-shaped, dish-shaped, etc., but the cross-sectional shape does not necessarily have to be circular. The expansion tube may function as a weight to prevent the water level detection tube from changing shape due to buoyancy. [Example]

[0018] The present invention will be described in more detail below with reference to examples and comparative examples.

[0019] [Example 1] to [Example 10] The test was conducted using the water level detection device 9 shown in Figure 3. A 200 L cylindrical chemical tank 7 was filled with tap water up to a water level of 180 L and heated to 50°C using an electric heater 8. A main pipe / extension pipe type water level detection device 9, which had a pressure sensor 2 attached to the upper end of a water level detection pipe 1 with a total length of 780 mm, consisting of a main pipe 4 and an extension pipe 5, was inserted vertically into the tap water in the chemical tank 7, and the lower end of the water level detection pipe 1 was fixed in a vertical position 3 cm from the bottom of the chemical tank 7. We verified whether the fluctuation in the water level measurement value when the water temperature inside the chemical tank 7 was changed from 50°C to 30°C could be reduced by adjusting the cross-sectional area ratio A / B and the length ratio C / D of the water level detection pipe 1. The dimensions of the cylindrical chemical tank 7 were 950 mm in height, 0.23 m in cross-sectional area, and 950 mm in height. 2 The test results are shown in Table 1.

[0020] [Comparative Example 1] In Comparative Example 1, tests were conducted in the same manner as in Example 1, except that a conventional single-pipe type water level detection pipe 10 using a single pipe with an inner diameter of 13 mm and a total length of 780 mm was used instead of the main pipe / extension pipe type water level detection device 9. The test results are shown in Table 1.

[0021] The results of [Example 1] to [Example 10] and [Comparative Example 1] are shown in Table 1. Here, the cross-sectional area ratio A / B is the ratio of the cross-sectional area of the main pipe (B) to the cross-sectional area of the expansion section (A), and is calculated by dividing the cross-sectional area of the expansion section (A) by the cross-sectional area of the main pipe (B). The length ratio C / D is the ratio of the length of the expansion section of the expansion pipe (C) to the total length of the water level detection pipe (D), and is calculated by dividing the length of the expansion section of the expansion pipe (C) by the total length of the water level detection pipe (D). The measured water level fluctuation rate is the rate of fluctuation of the water level measurement value when the water temperature is lowered to 30°C compared to the water level measurement value at a water temperature of 50°C, and is calculated by dividing the amount of change in the water level measurement value by the water level measurement value at a water temperature of 50°C x 100.

[0022] [Table 1]

[0023] The results in Table 1 clearly show that the water level detection device of the present invention suppresses fluctuations in measurement values due to temperature and air pressure fluctuations of the gas sealed inside the water level detection device, making it easier to determine changes in the water level in the water tank. In particular, it is preferable that the cross-sectional area ratio A / B is greater than 3.5. Examples 6 to 9, in which the height ratio C / D of the extension part is 0.1 or less, are preferred.

[0024] Comparative Example 2 The amount of liquid medicine in a square 100 L liquid medicine tank (Aquas Co., Ltd. pharmaceutical injection device: ICB type) with a width of 420 mm, depth of 570 mm, and height of 765 mm was measured using the single-pipe water level detection device 10. The liquid medicine in the tank was discharged from the tank at a rate of 0.7 L / day using a pump connected to the tank, and the measurement of the change in water level over time was verified under the condition that the amount of liquid medicine remaining in the tank decreased.

[0025] [Example 11] The test was conducted in the same manner as in Comparative Example 2, except that a main pipe / extension pipe type water level detection device 9 was used instead of the conventional single pipe type water level detection device 10, and the chemical liquid in the chemical tank was released from the chemical tank using a pump at a rate of 1.5 L / day.

[0026] Fig. 4 is a graph showing 24-hour water level change data for a chemical tank using a single-pipe type conventional water level detection device 10 for the verification of Comparative Example 2, and Fig. 5 is a graph showing 24-hour water level change data for a chemical tank using a main pipe / extension pipe type water level detection device 9 for the verification of Example 11. Fig. 5 shows that providing an extension section at the bottom end of the water level detection pipe of the present invention reduces the fluctuation range of the water level measurement value. Figure 6 is a graph in which the data in Figure 4 has been moved to average the four data points to smooth out fluctuations in measurement values due to changes in temperature during the day and night, and similarly Figure 7 is a graph in which the data in Figure 5 has been moved to average the data. Using the moving average, it was possible to obtain water level measurements with little fluctuation. However, with the conventional single-pipe water level detection device, it was not possible to grasp the state of a decrease in water level even when moving averaging was performed. [Explanation of symbols]

[0027] 1 Water level detection tube 2 Pressure Sensors 3 Extension 3a hole 4 Main manager 5 Extension tube 6 signal cables 7 Chemical tank 8 Electric heater 9 Water level detection device 10 Conventional water level detection device

Claims

1. A water level detection device for detecting the water level of a water tank that stores water, a tubular water level detection pipe having a hole at the bottom end thereof that communicates with the water in the water tank; and a pressure sensor connected to the water level detection pipe and detecting the pressure of gas present in the water level detection pipe, A water level detection device characterized in that the water level detection pipe comprises a main pipe that is connected to the pressure sensor, and an extension pipe that is connected to the lower part of the main pipe and has an extension portion with an inner diameter larger than that of the main pipe.

2. 2. The water level detection device according to claim 1, wherein the ratio A / B of the cross-sectional area A of the inner diameter of the expansion portion to the cross-sectional area B of the inner diameter of the main pipe is 3.5 or more.

3. 3. The water level detection device according to claim 1, wherein a ratio C / D of a length C from the upper end to the lower end of the extension portion to a total length D of the water level detection pipe is 0.1 or less.

4. The water level detection device according to claim 1 or 2, characterized in that the change in water level over time is output based on a group of data of moving average values of water level data calculated from individual pressure data obtained by the water level detection device.

5. A water level detection method using the water level detection device according to claim 1 or 2, comprising: A water level detection method characterized in that the water level in the water tank is measured when the highest liquid level in the water level detection pipe is lower than the top of the extension part of the extension pipe.

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