JP2002214019A - Liquid level monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level monitoring system which safely monitors the level of a liquid such as liquid fuels in fuel tanks without using any explosion proofed apparatus, and is available for monitoring many submerged or flooded areas, etc. SOLUTION: A pit 1 is provided in the bottom of a fuel tank T for inflow of a liquid fuel LG therein. The pressure of the fuel LG is transmitted via a pressure transfer member 2 to an intermediate medium 5 such as water sealed in a communicating tube 6, and a liquid level sensor 3 detects the displacement of the intermediate medium 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level monitoring system used for monitoring a liquid level of a liquid in a tank and for monitoring flooding and inundation of a specific area.

[0002]

2. Description of the Related Art There is already a system for detecting the liquid level of a liquid stored in a fuel tank or the like by using a liquid level meter such as a float type or an ultrasonic type and monitoring the degree of filling of the liquid.

[0003]

The conventional liquid level monitoring system basically includes a device that uses electricity around the sensor, and requires great care for explosion protection when monitoring the liquid level of flammable liquid.

[0004] In addition to requiring expensive explosion-proof equipment, the distance for laying cables is long because power is drawn to the monitoring point, which is disadvantageous in terms of system cost.

[0005] Furthermore, the objects that can be monitored are limited, and the applications are narrow. For example, in underground roads where roads are likely to be flooded by torrential rain, and in underground shopping malls where there is concern about inundation damage caused by torrential rain, etc. Although it is preferable to prevent the spread, the conventional liquid level monitoring system for detecting the liquid level is not suitable for such an application.

Accordingly, an object of the present invention is to provide a liquid level monitoring system that can provide explosion-proof properties without using expensive equipment and that can also collectively monitor flooding and flooding in many areas.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a pressure of a monitoring liquid is transmitted to an intermediate medium via a pressure transmitting member, and a pressure-receiving member which moves by receiving the pressure of the intermediate medium. Provided is a liquid level monitoring system that detects displacement by a sensor provided in a detection unit to detect a liquid level position of a monitoring liquid.

The intermediate medium referred to here may be any medium capable of transmitting pressure, and may be liquid, gas, or fixed. However, in consideration of pressure transmission efficiency and economic effects, a liquid such as water is preferable.

This liquid level monitoring system uses a nonflammable intermediate medium when monitoring a flammable liquid.

Further, it is preferable to adopt the following forms. (1) A communication pipe is provided between the monitoring point and the detection unit, and pressure is transmitted through an intermediate medium inserted in the communication pipe. (2) A flexible tank is used as the pressure transmitting member. (3) As the tank, a bottomed cylindrical bellows or a soft hollow container that expands and contracts is used. (4) A filter having shape retention is provided at the monitoring point, and the monitoring liquid that has passed through the filter is brought into contact with the pressure transmitting member. (5) A tank is provided in the detection unit, and the intermediate medium introduced into the tank is brought into contact with the pressure receiving body. (6) The tank provided in the detecting section is formed of a bottomed cylindrical bellows, and the bottom wall of the bellows acts as a pressure receiving body. (7) The pressure receiving area of the pressure transmitting member is made larger than the pressure receiving area of the pressure receiving body.

The sensor may be a sensor that distorts the optical fiber using the displacement of the pressure receiving body and measures the distortion using Brillouin scattered light which is one of the backscattered light, or a sensor that uses the pressure receiving body to deform the optical fiber. It is preferable to change the transmission loss of the optical fiber by bending or the like, and to detect a change in state based on the presence or absence of the change. However, a spot-type sensor such as a conventionally used liquid level meter can also be used.

A device that replaces the pressure of the monitoring liquid with the strain or transmission loss of the optical fiber and measures the distortion or transmission loss can determine whether or not the liquid level of the monitoring liquid has reached a specified level. The position of the liquid can be known from the amount of change in the distortion and transmission loss.

[0013]

In the present invention, the pressure change due to the change in the level of the monitoring liquid is transmitted to the pressure receiving body via the intermediate medium, and the displacement of the pressure receiving body is detected by the sensor. The detection unit by the sensor can be moved away from the monitoring point. As a result, even when monitoring highly flammable liquid fuel using an electric sensor, it is possible to use a non-flammable intermediate medium and sufficiently secure the detection unit away from the monitoring point to ensure safety. Will be possible.

In monitoring the water level of a river, it is often the case that the surface of the water to be monitored is wavy due to the wind.
The influence of the ripple can be reduced by passing through the intermediate medium.

Furthermore, since the inflow of dust and the like to the detection section is prevented by the intermediate medium, the problem that the sensor does not operate normally due to the inflow of dust and the like can be solved.

In the case where the communication pipe is provided, the pressure transmission path can be lengthened, and the detection unit is sufficiently separated from the monitoring unit for ensuring safety, and the detection unit is not easily tampered with or easily maintained. It can be installed at a place.

[0017] Further, due to the viscous resistance in the communication pipe, it is possible to further reduce the influence of the surging of the liquid surface of the monitoring liquid.

In the case of using a flexible tank as a pressure transmitting member, there is no sliding portion that generates displacement resistance, so that pressure transmission can be ensured, and the displacement of the pressure receiving portion can be reduced to reduce dust and the like. It is also possible to make it difficult to receive a return failure due to clogging. The tank is preferably a bellows or a soft hollow container which is simple and inexpensive.

The detector provided with a filter can suppress the deterioration of the movement of the pressure transmitting member due to dust, and can further reduce the influence of waving of the liquid surface due to viscous resistance when passing through the filter.

In the case where the detecting portion is provided with a tank, the pressure receiving area of the pressure receiving member can be increased to increase the displacement force of the pressure receiving member. For example, when using a float as a pressure receiving body and detecting the displacement of the float with an optical fiber, it is necessary to apply strain or bending to the optical fiber with the buoyancy of the float or a force amplified by the leverage of the float, so that the buoyancy of the float is Larger is better. If a tank is used, its buoyancy (displacement force of the pressure receiving member) can be increased to increase the sensitivity of the sensor.

In the case where the pressure receiving area of the pressure transmitting member is larger than the pressure receiving area of the pressure receiving member, if the specific gravity of the liquid to be monitored and the intermediate medium is made substantially equal, the pressure transmitting member is installed with a small displacement of the pressure transmitting member. Since the liquid at the location can be made equal to the liquid level at the pressure receiving portion of the pressure transmitting member, it is possible to reduce the influence of dust clogging and the like.

[0022]

FIG. 1 shows an embodiment of a liquid level monitoring system according to the present invention. The figure shows a system for monitoring the liquid level of a liquefied fuel tank.
Pit 1 into which the liquid fuel LG in the tank flows into the bottom of the tank
And a pressure transmitting member 2 (in the figure, a bottomed bellows) is incorporated therein (see FIG. 2).

A detecting section 4 having a liquid level sensor 3 is provided at a position sufficiently distant from the tank T. A communication pipe 6 in which an intermediate medium 5 is sealed is provided between the pit 1 at the monitoring point and the detecting section 4.
Are tied together. The intermediate medium 5 uses water, but may be another nonflammable liquid.

The liquid level sensor 3 provided in the detecting section 4 may be an existing electric liquid level meter or the like. However, in this case, a sensor of a type in which the optical fiber is distorted by the pressure of the intermediate medium 5 is preferably used. The strain generated in the optical fiber of the sensor is measured by the optical fiber strain measuring device 8, and the obtained data is sent to the monitoring and control device 9 to specify the strain generation point, and the liquid is calculated from the strain generation amount at the specified position. The position is calculated and found.

FIG. 3 shows the concept of an example of the above-mentioned sensor. Reference numeral 10 in the figure denotes a pressure receiving body (in the figure, a bottomed bellows) provided on the detection unit 4 side, and the pressure receiving body 10 expands and contracts by receiving the pressure of the intermediate medium 5 on the outer surface. A rod 11 for transmitting the displacement of the bottom wall is attached to the pressure receiving body 10, and a force transmitted through the rod 11 is amplified by a booster mechanism 12, and the amplified force is applied to the optical fiber cable 7 of FIG. The continuous optical fiber 13 is distorted (in the illustrated sensor, tensile strain is applied to the optical fiber 13 between the fixing portions 14). The amount of the distortion depends on the fluctuation of the liquid level in the tank. Therefore, the liquid level of the tank T in FIG. 1 can be monitored using a sensor as shown in FIG.

In the monitoring system shown in FIG. 1, since the detecting section 4 is sufficiently separated from the monitoring point and the liquid level is measured there, safety is ensured without using expensive explosion-proof equipment. Can be installed at a position where maintenance is easy. In addition, since the optical fiber is used as the sensor, there is no need for a power supply or a device for signal transmission in the detection unit, and in addition, there is an advantage that the collective monitoring of multiple points can be performed using one optical fiber line.

The optical fiber 13 is deformed under pressure instead of being distorted to change the transmission loss of light, and the transmission loss is measured by an optical transmission loss distribution measuring device instead of the measuring device 8 in FIG. The system can achieve the same effect.

If the pressure-receiving body 10 also employs a bottomed bellows as shown in FIG. 3, both ends of the intermediate medium are sealed to increase the reliability of the system. However, a float or the like is used instead of the pressure-receiving body of the bellows. Can also.

Further, if the displacement force applied to the pressure receiving member 10 is large, the optical fiber may be distorted by a force that has not been amplified by omitting the booster mechanism 12.

FIG. 4 shows an example of application to monitoring of inundation in an underground mall. As shown in the figure, pits 1 in which pressure transmitting members 2 are arranged are provided at locations requiring monitoring, and each pit 1 is connected to a liquid level sensor 3 provided in a detection unit 4 by a connecting pipe 6. The pressure transmitting member 2 and the liquid level sensor 3 may be the same as those described in the system of FIG.

In this system, the water H flowing into the underground shopping mall
Flows into the pit 1, and the pressure of the water H is transmitted to the intermediate medium 5 via the pressure transmitting member 2. Then, a pressure receiving body (not shown) receiving the pressure of the intermediate medium 5 is displaced, and the displacement is detected by the liquid level sensor 3. Therefore, it is possible to determine which section is flooded and how much water is generated depending on whether or not the liquid level has changed. Since this system also uses the communication pipe 6, the detection unit 4 can be brought close to the monitoring control device 9 to facilitate maintenance of the detection unit.

FIG. 5 shows an example in which a plurality of pits 1 are connected by a communication pipe 6 to communicate with the same detecting section. Although this structure cannot identify the point of inundation and detect the degree of inundation,
Since the number of sensors is reduced, there is an advantage that an economical system can be constructed when only the presence or absence of inundation needs to be determined.

As for the underground shopping mall with many floors, as shown in FIG. 6, a system for monitoring inundation for each floor may be adopted.

FIG. 7 shows a modification of the pressure transmitting member 2.
The pressure transmitting member 2 may be a piston or the like,
Since the operability due to clogging of foreign matters can be considered to have a sliding portion, the above-described bottomed bellows having no sliding portion and having a simple structure, or a soft hollow container as shown in FIG. 7 is preferable. As the soft hollow container, a rubber balloon-like one or a cloth-pulled rubber tank can be used. If the pit 1 is filled with earth and sand, the expansion and shrinkage of the rubber tank will be hindered. It is better to have a structure to prevent the inflow of water.

When there is a possibility that foreign matter such as dust enters the pit 1, it is preferable to surround the pressure transmitting member 2 with a filter 15 as shown in FIG. Filter 15
Is preferably a strong porous metal or a fine wire mesh.
If the pit 1 is provided and the monitoring liquid is allowed to enter the pit 1, it is difficult for the floating debris to enter the pit 1. However, if a filter is provided, the inflow of foreign matter is reliably prevented, and the operation stability of the pressure transmitting member is impaired. Absent.

[0036]

As described above, in the liquid level monitoring system of the present invention, pressure is transmitted through the intermediate medium, so that the detection unit where the sensor is installed is separated from the monitoring point to monitor the liquid level of the flammable liquid. In such a case, safety can be ensured by reducing equipment costs, and the detection unit can be installed at a position where maintenance is easy and a position where it is not easily tampered with.

Further, through the intermediate medium, it is possible to reduce the influence of the surging of the liquid level of the monitoring liquid or to stabilize the operation of the sensor by eliminating the inflow of dust and the like into the detecting section.

In addition, if the liquid level is detected by replacing the pressure change due to the liquid level change of the monitoring liquid with the strain change or the optical transmission loss change of the optical fiber, a power supply or a signal transmission device is required in the detecting section. Instead, there is an advantage that a single optical fiber line can perform collective monitoring at multiple points, an economically advantageous monitoring system can be realized, and monitoring of flooding, flooding, and the like can be realized by a simple system.

[Brief description of the drawings]

FIG. 1 is a diagram showing a fuel tank level monitoring system to which the present invention is applied.

FIG. 2 is an enlarged sectional view of a pit installation portion.

FIG. 3 is a diagram showing an example of a liquid level sensor.

FIG. 4 is a diagram showing an inundation monitoring system for an underground shopping mall to which the present invention is applied.

FIG. 5 is a diagram showing a modification of the system of FIG. 4;

FIG. 6 is a diagram showing a system for monitoring inundation of an underground shopping mall having a plurality of levels for each floor.

FIG. 7 is a diagram showing a modification of the pressure transmitting member.

FIG. 8 is a sectional view showing an example in which a filter is provided in a pit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pit 2 Pressure transmitting member 3 Liquid level sensor 4 Detecting unit 5 Intermediate medium 6 Communication pipe 7 Optical fiber cable 8 Optical fiber strain measuring instrument 9 Monitoring and control device 10 Pressure receiver 11 Rod 12 Boost mechanism 13 Optical fiber 14 Fixed part 15 Filter T Fuel tank LG Liquid fuel H Water

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Takashi Fujieda 4-33 Kitahama, Chuo-ku, Osaka City F-term (reference) 2F014 AB02 AC02 BA10

Claims (9)

[Claims] 1. The pressure of a monitoring liquid is transmitted to an intermediate medium via a pressure transmitting member, and the displacement of a pressure receiving member that moves in response to the pressure of the intermediate medium is detected by a sensor provided in a detection unit, and the liquid level of the monitoring liquid is detected. A liquid level monitoring system that detects the position. 2. The liquid level monitoring system according to claim 1, wherein a nonflammable liquid is used as the intermediate medium. 3. A communication pipe is provided between the monitoring point and the detector,
3. The liquid level monitoring system according to claim 1, wherein the pressure is transmitted through an intermediate medium inserted in the communication pipe. 4. The liquid level monitoring system according to claim 1, wherein a flexible tank is used as the pressure transmitting member. 5. The liquid level monitoring system according to claim 4, wherein a bottomed cylindrical bellows or a soft hollow container that expands and contracts is used as the tank. 6. A shape-preserving filter is provided at a monitoring point,
The liquid level monitoring system according to any one of claims 1 to 5, wherein the monitoring liquid that has passed through the filter is brought into contact with the pressure transmitting member. 7. The liquid level monitoring system according to claim 1, wherein a tank is provided in the detection unit, and the intermediate medium introduced into the tank is brought into contact with the pressure receiving body. 8. The liquid level monitoring system according to claim 7, wherein the tank provided in the detection section is formed of a bottomed cylindrical bellows, and a bottom wall of the bellows acts as a pressure receiving body. 9. The liquid level monitoring system according to claim 1, wherein a pressure receiving area of the pressure transmitting member is larger than a pressure receiving area of the pressure receiving body.