JP2011006130A - Liquid level detector for tanks - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the level of a fluid at the bottom of a tank irrespective of a displacement of the tank depending on the amount of storage.SOLUTION: A fluid level detector 80 for a tank is composed of, for configuration, a fluid level measuring section 60, a holder 61 for the measuring section, a fluid level detecting sensor 62, an oil level detecting sensor 64, a fluid level indicating section 66 and a displacement absorbing mechanism 68. The fluid level measuring section 60 is composed of an upper measuring pipe 60A and a lower measuring pipe 60B which is extended down, on its own, to a position where it comes in contact with the bottom of the tank. The measuring section displacement absorbing mechanism 68 is so constituted as to absorb the linear dimension of the fluid level measuring section 60 in accordance with displacements (distortion) in a vertical direction of an underground tank 20, and is equipped with a tank distortion detecting sensor 65 that detects relative displacements of the upper measuring pipe 60A and the lower measuring pipe 60B involved with a displacement in a vertical direction of the underground tank 20 as a distortion in a vertical direction of the underground tank 20.

Description

  The present invention relates to a tank liquid level detector, and more particularly, to a tank liquid level detector configured to detect that water has accumulated at the bottom of a tank that stores oil.

  For example, in an oil supply device installed in a gas station, oil is stored by pumping up an oil solution stored in an underground tank buried underground (see, for example, Patent Document 1).

  In the underground tank, water gradually accumulates in the tank, and when the water level rises, there is a possibility that water is supplied to the fuel tank together with the oil liquid through the suction port at the lower end of the suction pipe. As a cause of water accumulation in the underground tank, for example, when the liquid level in the underground tank falls due to oil suction during refueling, outside air containing moisture is introduced from the vent pipe connected to the underground tank, It is conceivable that water condensed on the inner wall of the tank accumulates at the bottom of the tank.

  In addition to the lubrication pipe, the underground tank is equipped with a level gauge mounting part, water inspection port, tank upper nozzle, etc., and if you forget to attach these caps, rainwater will enter the underground tank. May flow in. Further, when the oil liquid stored in the underground tank is biofuel ethyl alcohol, phase separation occurs when a certain amount of moisture is mixed in, and the alcohol moisture is rapidly separated and stored as water at the bottom of the underground tank.

  Therefore, a tank liquid level detector that detects the liquid level of the oil liquid in the underground tank and the water level at the bottom of the tank is inserted into the underground tank. As this kind of tank liquid level detector, as described in Patent Document 1, an oil level detection float and a water level detection float are provided in a measuring cylinder inserted in a drooping direction from the upper part of the tank. There are some which detect the oil level height from the position of the oil level detection float and detect the water level height from the position of the water level detection float.

JP-A-9-249300

  By the way, the underground tank is composed of a double shell tank formed in a cylindrical shape, and is formed in a circular shape when viewed from the side. In such an underground tank, when there is a large amount of stored oil liquid immediately after the oil liquid is unloaded from the tank truck, the cross-sectional shape of the circular underground tank is horizontally adjusted by the pressure of the stored oil liquid. It becomes a wide shape and deforms into an elliptical shape when viewed from the side.

  As the cross-sectional shape of such an underground tank is deformed according to the amount of oil stored, the vertical distance between the upper opening of the underground tank and the tank bottom becomes smaller.

  On the other hand, the liquid level detector is designed so that the lower end of the measuring unit inserted in the direction of drooping from the upper opening of the underground tank does not come into contact with the bottom of the underground tank even if the underground tank is displaced due to the unloading of oil. Is attached so that the lower end of the measuring unit is spaced upward from the bottom of the tank.

  Therefore, conventionally, the water level in the vicinity of the bottom of the tank cannot be detected, and can be detected when a certain amount of water has accumulated at the bottom of the tank, and it has been difficult to detect a small amount of water.

  In view of the above circumstances, an object of the present invention is to provide a tank liquid level detector that solves the above-described problems.

In order to solve the above problems, the present invention has the following means.
(1) The present invention includes a measuring unit inserted in a drooping direction from the tank upper opening,
An oil level detection sensor that is provided in the measurement unit and detects the oil level of the oil stored in the tank;
A water level detection sensor that is provided at a lower part of the measurement unit and detects a water level accumulated at the bottom of the tank;
In the liquid level detector for tanks, comprising a control means for displaying the measured values of the oil level and the water level by being supplied with signals from the oil level detection sensor and the water level detection sensor,
A displacement absorption mechanism that absorbs a vertical displacement associated with the deformation of the tank is provided in the measurement unit.
(2) The displacement absorbing mechanism of the present invention includes a plurality of members fitted so as to be slidable in the vertical direction, and the plurality of members slide in the vertical direction in accordance with the vertical displacement of the tank. It is characterized by that.
(3) The displacement absorption mechanism of the present invention has at least an upper measurement unit inserted from the tank upper opening, and a lower measurement unit arranged on the tank bottom,
The lower measurement unit is in contact with the tank bottom and slides vertically with respect to the upper measurement unit according to a distance from the tank upper opening to the tank bottom.
(4) The displacement absorbing mechanism of the present invention includes a tank strain detection sensor that detects a displacement in the vertical direction accompanying the deformation of the tank by a relative displacement between the upper measurement unit and the lower measurement unit,
The control means includes correction means for correcting a measured value of the oil level based on a tank distortion detected by the tank distortion detection sensor to a vertical displacement associated with the deformation of the tank.

  According to the present invention, the displacement absorption mechanism that absorbs the displacement in the vertical direction accompanying the deformation of the tank is provided in the measurement unit, so that the lower end of the measurement unit is placed on the tank bottom even if the tank is displaced according to the amount of stored oil. It is possible to maintain the contact state, and it is possible to detect even a small amount of water accumulated at the bottom of the tank. Therefore, the water level accumulated at the bottom of the tank can be detected with higher accuracy.

It is a figure which shows the structure of the oil supply equipment with which one Example of the liquid level detector for tanks by this invention was applied. It is a figure which shows the liquid level detector for tanks. It is a figure which expands and shows the lower part (A part) of the liquid level detector for tanks. It is a longitudinal cross-sectional view of the underground tank which shows the state which the oil liquid was supplied and the storage amount reduced. It is a longitudinal cross-sectional view of the underground tank which shows the state which unloaded oil liquid and the storage amount increased. It is a block diagram which shows each apparatus of a liquid level display part. It is a flowchart for demonstrating the liquid level measurement process which the control circuit of a liquid level display part performs. It is a figure which expands and shows the modification of the liquid level detector for tanks.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an oil supply facility to which an embodiment of a liquid level detector for tanks according to the present invention is applied. As shown in FIG. 1, a fueling facility 10 installed in a gas station has an underground tank 20 buried underground, a fueling device 30 installed on the ground, and a tank liquid level detector 80. The underground tank 20 is composed of, for example, a so-called FF double-shell tank made of reinforced plastic or a so-called SF double-shell tank having an iron outer shell and a reinforced plastic inner shell. And vertical distortion. Furthermore, the surroundings of the underground tank 20 are covered with earth and sand in a state of being placed on a foundation 22 solidified with concrete.

  A plurality of manholes 40A to 40C are provided between the top of the underground tank 20 and the ground surface. Inside each of the manholes 40A to 40C, pipe joints 50A to 50C connected to the top of the underground tank 20 are attached.

  A suction pipe 70A inserted to the vicinity of the bottom of the underground tank 20 is connected to the lower part of the pipe joint 50A. Further, a suction pipe 90A connected to the oil supply device 30 is communicated with a side portion of the pipe joint 50A.

  An unloading pipe 70B is connected to the lower part of the pipe joint 50B, and an oil supply pipe 90B to which an unloading hose of a tank truck is connected is connected to the side of the pipe joint 50B.

  The pipe joint 50 </ b> C communicates with an exhaust pipe 90 </ b> C that introduces exhaust from the underground tank 20 or outside air into the underground tank 20.

  FIG. 2 is a view showing a tank liquid level detector 80. FIG. 3 is an enlarged view showing a lower portion (A part) of the tank liquid level detector 80. 2 and 3, the tank liquid level detector 80 includes a liquid level measuring unit 60, a measuring unit holding body 61, an oil level detecting sensor 62, a water level detecting sensor 64, and a liquid level display. A portion 66 and a displacement absorbing mechanism 68 are included.

  The liquid level measurement unit 60 includes an upper measurement tube 60A as an upper measurement unit inserted into the underground tank 20 from the manhole 40B, and a lower measurement connected to the lower portion of the upper measurement tube 60A so as to be slidable in the vertical direction. And a lower measurement tube 60B as a part. The upper measurement tube 60A and the lower measurement tube 60B are made of a metal pipe such as stainless steel, and the lower measurement tube 60B is formed to have a larger diameter than the upper measurement tube 60A and extends to a position where it contacts the tank bottom by its own weight. .

  The displacement absorbing mechanism 68 is configured such that the lower end of the upper measuring tube 60A and the upper end of the lower measuring tube 60B are slidably fitted in the extending direction (vertical direction). The length of the liquid level measuring unit 60 is adjusted according to the vertical displacement (distortion) to absorb the tank displacement. Since the liquid level measuring unit 60 includes the displacement absorbing mechanism 68 that absorbs the tank displacement, the bottom of the liquid level measuring unit 60 is in contact with the bottom of the tank even when the underground tank 20 is deformed according to the amount of stored oil. It becomes possible to hold the water, and even a small amount of water accumulated at the bottom of the tank can be detected. Therefore, the water level detection sensor 64 can detect the water level accumulated at the bottom of the tank with higher accuracy.

  Further, the displacement absorbing mechanism 68 has a plurality of members slidably fitted in the vertical direction, and the plurality of members slide in the vertical direction so as to absorb the vertical displacement of the underground tank 20. It is configured. In the present embodiment, a small-diameter upper measuring tube 60A and a large-diameter lower measuring tube 60B are slidably fitted.

  In the displacement absorbing mechanism 68 of the present embodiment, the measurement tubes 60A and 60B having different radial dimensions are configured to slide, but a member other than the tube (for example, a rod-like member extending in the vertical direction or a rod-like member). It is good also as a structure which combines and slides the member and the to-be-penetrated member which has the hollow part which a rod-shaped member penetrates.

  In addition, the liquid level measurement unit 60 includes a tank strain detection sensor 65 that detects a relative displacement between the upper measurement pipe 60A and the lower measurement pipe 60B accompanying the vertical displacement of the underground tank 20. The tank distortion detection sensor 65 detects the vertical relative displacement between the lower end of the upper measurement pipe 60 </ b> A and the lower measurement pipe 60 </ b> B as the vertical distortion of the underground tank 20.

  The upper measurement tube 60A is provided with an oil level detection sensor 62 for detecting the level of the oil liquid. Further, a water level detection sensor 64 is provided in the lower measurement tube 60B.

  The oil level detection sensor 62 includes a cylindrical oil level float 62A that moves in the vertical direction along the outer periphery of the upper measuring tube 60A in accordance with a change in the level of the oil liquid, and a height position of the oil level float 62A. And an oil level detection unit 62B. The oil level float 62A is set so that the specific gravity is lighter than the specific gravity of the oil liquid so as to move according to the height position of the oil level L2, and a magnet is provided as a detected part.

  The oil level detection unit 62B extends in the vertical direction along the inner wall of the hollow portion of the upper measurement tube 60A. For example, the oil level detection unit 62B detects the magnetic force of the magnet provided in the oil level float 62A. The oil level detection signal corresponding to the detection position of the float 62 </ b> A is output to the liquid level display unit 66.

  The water level detection sensor 64 includes a ring-shaped water level float 64A that moves in the vertical direction along the outer periphery of the lower measurement tube 60B, and a water level detection unit 64B that detects the height position of the water level float 64A. The water level float 64A is set to 0.83 to 0.98 so that the specific gravity is heavier than the specific gravity of the oil liquid and lighter than the specific gravity of the water so as to move according to the water level L1 in the tank. Further, the water level float 64A is provided with a magnet as a detected portion. The water level detection unit 64B extends in the vertical direction along the hollow inner wall of the lower measurement tube 60B. For example, the water level detection unit 64B detects the magnetic force of a magnet provided in the water level float 64A and detects the water level float 64A. A water level detection signal corresponding to the position is output to the liquid level display unit 66.

  Since the lower measurement pipe 60B constituting the displacement absorbing mechanism 68 is fitted to the upper measurement pipe 60A so as to be movable in the vertical direction, the lower end portion is in contact with the bottom inner wall of the underground tank 20 by its own weight. Therefore, the water level detection sensor 64 allows the water level float 64A to descend to the vicinity of the tank bottom, and can detect the water level L1 of the water accumulated at the tank bottom from a low position.

  The tank strain detection sensor 65 includes a detected portion 65A provided at the upper end of the lower measurement tube 60B, and a tank strain detection portion 65B formed to extend in the vertical direction along the inner wall of the hollow portion of the upper measurement tube 60A. Have For example, the detected portion 65A is made of a magnet, and the tank strain detecting portion 65B magnetically detects the position of the detected portion 65A, and detects the relative displacement in the vertical direction between the lower end of the upper measuring tube 60A and the lower measuring tube 60B. A corresponding tank distortion detection signal is output to the liquid level display unit 66.

  Here, the displacement of the underground tank 20 according to the storage amount will be described. FIG. 4 is a vertical cross-sectional view of the underground tank 20 showing a state in which the amount of stored oil is reduced by supplying oil. As shown in FIG. 4, the underground tank 20 is molded so that the cross-sectional shape is substantially circular. The amount of storage in the underground tank 20 is gradually reduced by refueling, and the underground tank 20 is pressed by the surrounding earth pressure to have a circular cross-sectional shape.

  FIG. 5 is a longitudinal sectional view of the underground tank 20 showing a state in which the amount of stored oil has been increased by unloading the oil. As shown in FIG. 5, when the oil liquid is unloaded from the tank truck through the oil supply pipe 90B in a state where the oil liquid stored in the underground tank 20 is reduced, the oil level in the tank rises and the tank The internal pressure increases. As the tank internal pressure becomes larger than the earth pressure around the underground tank 20, the cross-sectional shape of the underground tank 20 is deformed into an elliptical shape expanded in the horizontal direction. In FIG. 5, the displacement (distortion) of the underground tank 20 is exaggerated for easy understanding.

  Thus, when the cross-sectional shape of the underground tank 20 is deformed from a circular shape to an elliptical shape, the height dimension of the underground tank 20 is reduced. Therefore, in the underground tank 20, the horizontal distortion expanded in the horizontal direction. ε1 and a vertical strain ε2 that is reduced in the vertical direction are generated.

  Here, the configuration of the liquid level display unit 66 will be described. FIG. 6 is a block diagram showing each device of the liquid level display unit 66. As shown in FIG. 6, the liquid level display unit 66 includes a control circuit 100, a liquid crystal monitor 110, a storage unit 120, and an alarm device 130. In addition to the liquid crystal monitor 110, the storage unit 120, and the alarm device 130, an oil level detection sensor 62, a water level detection sensor 64, and a tank distortion detection sensor 65 are connected to the control circuit 100.

  The control circuit 100 reads the control program stored in the storage unit 120 and displays the oil level height (oil storage amount) and the water level (water amount) according to the detection signal from each sensor on the liquid crystal monitor 110. Further, as the control program stored in the storage unit 120, the oil level height detected by the oil level detection sensor 62 is corrected according to the tank strain (vertical strain ε2) detected by the tank strain detection sensor 65, When the amount of water obtained from the water level detected by the water level detected by the control program (correction means) and the water level detection sensor 64 that cancels the fluctuation value due to the relative displacement between the upper measuring tube 60A and the lower measuring tube 60B reaches a specified value or more. A control program that issues a warning (alarm sound, alarm display) from the alarm device 130 and stores the alarm is stored.

  FIG. 7 is a flowchart for explaining the liquid level measurement process executed by the control circuit 100 of the liquid level display unit 66. As shown in FIG. 7, the control circuit 100 reads the tank strain (vertical strain ε2) detected by the tank strain detection sensor 65 in S11. In next S12, the ratio α (= ε2 / H) between the tank height H of the underground tank 20 (the tank height when empty: see FIG. 4) and the vertical strain ε2 is calculated.

  In next S13, the measured value Y1 of the oil level L2 detected by the oil level detection sensor 62 is read. Subsequently, in S14, the correction value Y1 · α is obtained by performing a correction operation so that the tank surface distortion cancels the oil level height measurement value Y1. Further, in S15, the correction value Y1 · α is subtracted from the measured value Y1 of the oil level, and the actual oil level height YA (= Y1− (Y1 · α)) corresponding to the amount of stored oil is calculated. (Correction means).

  In next S16, the total storage amount Q1 corresponding to the actual oil level height YA is calculated. The total storage amount Q1 is a total value of the storage amount Q of the oil liquid stored in the underground tank 20 and the water amount Q2 accumulated at the bottom of the tank. Subsequently, in S17, the measurement value Y2 of the water level detection sensor 64 is read, and in S18, the water amount Q2 corresponding to the shape (curvature radius) of the tank bottom is calculated. In the water level detection sensor 64, the lower end of the lower measuring pipe 60B is in contact with the bottom inner wall of the underground tank 20 by the displacement absorbing mechanism 68, so that the water level float 64A can be lowered to the vicinity of the tank bottom. Regardless of the displacement, the water level L1 of the water accumulated at the bottom of the tank can be detected from the low position. Thereby, the water level detection sensor 64 can detect the water level with higher accuracy from a small amount of stages.

  In the next S19, the water amount Q2 is subtracted from the total storage amount Q1, and the actual storage amount Q (= Q1-Q2) of the oil liquid stored in the underground tank 20 is calculated. Subsequently, the process proceeds to S20, and the actual storage amount Q and the water amount Q2 of the oil liquid are displayed on the liquid crystal monitor 110. Furthermore, in S21, it is checked whether or not the measurement value Y2 of the water level detection sensor 64 is equal to or less than a preset water level upper limit value Y0.

  In S21, when the measured value Y2 of the water level detection sensor 64 is equal to or lower than the water level upper limit value Y0 (in the case of NO), the process returns to S11, and the processes after S11 are repeated. In S21, when the measured value Y2 of the water level detection sensor 64 reaches the water level upper limit value Y0 (in the case of YES), the process proceeds to S22, and the water level L1 accumulated at the bottom of the tank is provided at the lower end of the suction pipe 70A. It is determined that the water suction port has been reached and the alarm device 130 informs that the water level is abnormal.

  As a result, on the gas station, it is possible to request a maintenance company to perform a water draining operation for removing water accumulated at the bottom of the underground tank 20.

  Here, a modified example will be described.

  FIG. 8 is an enlarged view showing a modification of the tank liquid level detector. As shown in FIG. 8, the tank liquid level detector 80A of the modified example is provided with a spring receiver 60C on the outer periphery of the upper measurement tube 60A, and between the spring receiver 60C and the upper end of the lower measurement tube 60B, An urging member 60D made of a coil spring is wound thereon. The biasing member 60 </ b> D generates a biasing force that presses the lower measurement pipe 60 </ b> B downward, and the lower end of the lower measurement pipe 60 </ b> B is held in contact with the bottom inner wall of the underground tank 20.

  Therefore, even if the underground tank 20 is displaced in the horizontal direction and the vertical direction (see FIG. 5) according to the change in the amount of stored oil, the lower end of the lower measuring pipe 60B constituting the displacement absorbing mechanism 68 is always at the bottom of the underground tank 20. It is urged to be in contact with the bottom inner wall. Therefore, the water level detection sensor 64 allows the water level float 64A to descend to the vicinity of the tank bottom, and can detect the water level L1 of the water accumulated at the tank bottom from a low position.

  In the above embodiment, the underground tank installed at the gas station has been described as an example. However, the present invention can be applied to an underground tank of a facility having a fueling facility other than the gas station, or a tank installed on the ground. Of course, it can be applied.

  In the above-described embodiment, the configuration in which the displacement absorption mechanism 68 is provided in the lower part of the liquid level measurement unit 60 has been described as an example. However, the present invention is not limited to this. Alternatively, the displacement absorbing mechanism 68 may be provided at a plurality of locations at different heights of the liquid level measuring unit 60.

  In the above-described embodiment, the underground tank is exemplified as the FF double shell tank or the SF double shell tank. However, the present invention is not limited to this, and the present invention can be applied to other structures. Yes.

DESCRIPTION OF SYMBOLS 10 Oil supply equipment 20 Underground tank 30 Oil supply apparatus 40A-40C Manhole 50A-50C Pipe joint 60 Liquid level measurement part 60A Upper measurement pipe 60B Lower measurement pipe 60C Spring receiver 60D Energizing member 61 Measurement part holding body 62 Oil level detection sensor 62A Oil Surface float 62B Oil level detection unit 64 Water level detection sensor 64A Water level float 64B Water level detection unit 65 Tank strain detection sensor 65A Detected unit 65B Tank strain detection unit 66 Liquid level display unit 68 Displacement absorption mechanism 70A Suction pipe 70B Unloading Pipe 80 Tank level detector 90A Suction pipe 90B Lubrication pipe 90C Ventilation pipe 100 Control circuit 110 Liquid crystal monitor 120 Storage unit 130 Alarm

Claims (4)

A measurement unit inserted in a drooping direction from the tank upper opening,
An oil level detection sensor that is provided in the measurement unit and detects the oil level of the oil stored in the tank;
A water level detection sensor that is provided at a lower part of the measurement unit and detects a water level accumulated at the bottom of the tank;
In the liquid level detector for tanks, comprising a control means for displaying the measured values of the oil level and the water level by receiving signals from the oil level detection sensor and the water level detection sensor
A liquid level detector for a tank, wherein a displacement absorption mechanism for absorbing a vertical displacement accompanying the deformation of the tank is provided in the measurement unit.   The displacement absorbing mechanism is composed of a plurality of members fitted so as to be slidable in the vertical direction, and the plurality of members slide in the vertical direction in accordance with the vertical displacement of the tank. Item 2. The liquid level detector for tanks according to Item 1. The displacement absorption mechanism has at least an upper measurement unit inserted from the tank upper opening, and a lower measurement unit arranged at the tank bottom,
The lower measurement unit is in contact with the bottom of the tank and slides up and down with respect to the upper measurement unit according to a distance from the tank upper opening to the tank bottom. Liquid level detector for tank of description. The displacement absorbing mechanism has a tank strain detection sensor that detects a displacement in a vertical direction accompanying the deformation of the tank by a relative displacement between the upper measurement unit and the lower measurement unit,
The said control means has a correction means which correct | amends the amount of vertical displacement accompanying the deformation | transformation of the said tank based on the measured value of the said oil level based on the tank distortion detected by the said tank distortion detection sensor. Item 4. The liquid level detector for tanks according to Item 3.

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