Drainage pit liquid level management device and drainage pit liquid level management method

Abstract

To provide a drainage pit liquid level management device capable of accurately detecting a liquid level in a drainage pit free of the presence or absence of conductivity of liquid stored in the drainage pit and surely and automatically starting and stopping a drainage device, holding three or more output contacts, detecting even an abnormal high liquid level, and automatically starting and stopping the drainage device free of a floating matter in liquid and dirt.SOLUTION: In a drain pit liquid level management device, an electrode-type level meter 10 which detects a liquid level on the basis of an electrified state of an electrode, which gets electrified in contact with the liquid, a tilt float-type liquid meter 20 which detects a liquid level on the basis of the inclination of a float part in association with the liquid level of the liquid, and a drainage device 3 which can drain the liquid to the outside are provided in a drain pit 113. The drain pit liquid level management device controls the operation of the drainage device 3 on the basis of any of a detection signal of the electrode-type liquid meter 10 and a detection signal of the tilt float-type liquid meter 20.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a technology for managing the liquid level in a drainage pit, and in particular to a drainage pit liquid level management device and a drainage pit liquid level management method that can reliably detect the liquid level and automatically control the drainage device even when a low-conductivity liquid is accumulated in the drainage pit. [Background technology]

[0002] The power plant on the premises is equipped with a water supply facility building containing a filtered water pump for supplying construction water and water for fresh water replacement from the filtered water tank to the generator equipment, a pure water transfer pump for supplying pure water required for the operation of the power generation equipment from the pure water tank, and a fire pump for supplying fire water from the fire water tank to the fire extinguishing equipment.

[0003] In such power plants, in order to discharge water leaking from various pumps (pump drain water), the pump drain water is temporarily stored in a drainage pit together with rainwater via an underground duct installed in the basement of the water supply facility building. This drainage pit is equipped with a drainage device that constantly detects the liquid level in the pit and automatically controls the drainage pump to keep the liquid level in the drainage pit within an appropriate range. The liquid level in the pit is detected by a level gauge, but traditionally, an electrode-type level gauge (also called an electrode-type level sensor, conductivity level switch, etc.) which has no moving parts and is less susceptible to mechanical failure has been used as this level gauge (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 54-75762 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if low-conductivity pure water or filtered water leaks from a pump inside a water supply facility building and flows into a drainage pit, there is a risk that the liquid level cannot be detected even if the space between the electrodes is immersed in water. Therefore, the applicant is currently researching a drainage pit liquid level management device that can reliably detect the liquid level in a drainage pit, even if a low-conductivity liquid flows into the drainage pit, and automatically start and stop the drainage equipment based on this detection.

[0006] In this case, by adding a float type level gauge that is not affected by the conductivity of the liquid to the existing electrode type level gauge, it is effective to eliminate the inconvenience of the drainage pump not being able to start and stop by detecting the liquid level with the float type level gauge even when the electrode type level gauge cannot. However, there is a demand to add a function to sound an alarm if the liquid level in the drainage pit exceeds the drainage pump starting level for some reason and reaches an abnormal level; in other words, there is a demand to equip the drainage device with at least three contacts: a contact for detecting the liquid level that starts the drainage pump, a contact for detecting the liquid level that stops the started drainage pump, and a contact for detecting an abnormally high liquid level in the drainage pit.There is also a need to respond to the demand to be able to reliably detect the liquid level without being affected by floating objects or dirt in the liquid.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and its main objective is to provide a drainage pit liquid level management device and a drainage pit liquid level management method that can meet requirements such as the ability to accurately detect the liquid level in a drainage pit and reliably automatically start and stop the drainage equipment regardless of whether the liquid stored in the drainage pit is conductive or not, and to have three or more output contacts so that abnormally high liquid levels can be detected, and further to reliably automatically start and stop the drainage equipment regardless of floating objects or dirt in the liquid. [Means for solving the problem]

[0008] In order to achieve the above object, the drainage pit liquid level management device according to the present invention comprises: an electrode type liquid level meter that detects the liquid level based on the state of conduction of an electrode that contacts the liquid and conducts electricity; a tilt float type liquid level gauge that detects the liquid level based on the tilt of a float portion according to the liquid level; A drainage device capable of draining liquid to the outside; Installed in the drainage pit, The operation of the drainage device is controlled based on at least one of a detection signal from the electrode type liquid level gauge and a detection signal from the tilt float type liquid level gauge.

[0009] Therefore, by adding a tilt float type level gauge in addition to the electrode type level gauge, it becomes possible to detect the level of the liquid accumulated in the drainage pit regardless of the water's conductivity. Also, by adopting a tilt float type level gauge as the float type level gauge, it becomes possible to handle three or more output contacts by increasing the number of float parts. That is, in addition to the contacts that start the drainage device and the contacts that stop the operation of the drainage device, it becomes possible to further add a contact that issues an alarm when the liquid level in the drainage pit becomes abnormally high to the float type level gauge. In addition, by adopting the tilt float type, it is possible to avoid the inconvenience that can arise when adopting a float type level gauge that uses a float through which a rod is slidably inserted, namely, floating objects and dirt in the water getting between the float and the rod and hindering the smooth movement of the float. Therefore, even if the drainage pit contains water with low conductivity or water containing floating matter or dirt, it is possible to reliably detect the liquid level in the drainage pit.

[0010] Here, the three output contacts can be provided as follows: The electrode type liquid level meter is configured to be capable of detecting a first upper limit liquid level in the drainage pit, a first abnormal liquid level set to a liquid level higher than the first upper limit liquid level, and a first lower limit liquid level set to a liquid level lower than the first upper limit liquid level, The tilt float type liquid level gauge is configured to be capable of detecting a second upper limit liquid level in the drainage pit, a second abnormal liquid level set to a liquid level higher than the second upper limit liquid level, and a second lower limit liquid level set to a liquid level lower than the second upper limit liquid level, When the first upper limit liquid level or the second upper limit liquid level is detected, the drainage device may be started; when the first abnormal liquid level or the second abnormal liquid level is detected, an alarm may be issued; and when the first lower limit liquid level or the second lower limit liquid level is detected, operation of the drainage device may be stopped.

[0011] Furthermore, when a tilt float type level gauge is used as a backup for an electrode type level gauge, the second upper limit liquid level of the tilt float type level gauge is set higher than the first upper limit liquid level of the electrode type level gauge, the second abnormal liquid level of the tilt float type level gauge is set higher than the first abnormal liquid level of the electrode type level gauge, and the second lower limit liquid level of the tilt float type level gauge is set lower than the first lower limit liquid level of the electrode type level gauge. By setting it up in this manner, while using the electrode type level gauge as the main gauge, even if a large amount of water with low electrical conductivity flows into the drainage pit and the electrode type level gauge is no longer able to detect the liquid level properly, the tilt float type level gauge can still reliably detect the liquid level, making it possible for the drainage device to maintain the liquid level in the drainage pit within an appropriate range.

[0012] In addition, in order to ensure drainage of the drainage pit and to make effective use of the space within the drainage pit, it is advisable to form a groove in the bottom of the drainage pit and install the electrode type level gauge, tilt float type level gauge, and drainage device in this groove. Effect of the Invention

[0013] As described above, the drainage pit liquid level management device and drainage pit liquid level management method of the present invention make it possible to detect the liquid level regardless of whether the liquid is conductive or not (the magnitude of the conductivity), and to reliably start and stop the drainage device automatically. In addition, it is possible to have three or more output contacts, which can be used to issue an alarm when the liquid level is abnormally high. Furthermore, even if there is floating matter or dirt in the liquid accumulated in the drainage pit, it is possible to reliably detect the liquid level and reliably automatically start and stop the drainage device. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram showing the overall configuration of a water supply facility provided within the grounds of a power plant according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram explaining the drainage route from the water supply facility building to the drainage pit. [Diagram 3] FIG. 3 is a cross-sectional view showing one embodiment of a drainage pit liquid level control device of the present invention. [Figure 4] FIG. 4 is a schematic diagram illustrating an example of a liquid level detection device according to an embodiment of the present invention. [Diagram 5] Figure 5 is a schematic diagram explaining how the contacts in a tilt float type liquid level gauge turn ON and OFF depending on the inclination of the float. (a) is a diagram explaining an example in which the float starts off in a vertically hanging OFF state and tilts by more than θ1 to turn ON, and then turns OFF as the inclination decreases to less than θ2. (b) is a diagram explaining an example in which the float takes the horizontal position as the base position and tilts upward by more than θ3 to turn ON, and tilts downward from the horizontal position by more than θ4 to turn OFF. [Figure 6] FIG. 6 is a flowchart showing an example of the control operation of the drainage pit liquid level management device according to the present invention. [Figure 7] FIG. 7 is a flowchart showing another example of the control operation of the drainage pit liquid level management device according to the present invention. [Figure 8] FIG. 8 is a flowchart showing another example of the control operation of the drainage pit liquid level management device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a drainage pit liquid level management device according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a water supply facility 100 provided on the grounds of a power plant in which a drainage pit liquid level management device according to the present invention is used.

[0016] In this example, the water supply system 100 includes a filtered water tank 101, a pure water tank 102, and a fire water tank 103 located on the power plant site, as well as a water supply system building 110 equipped with pumps and other equipment for supplying the water stored in each tank to the power generation system.

[0017] The filtered water stored in the filtered water tank 101 and the pure water stored in the pure water tank 102 are supplied from the seawater desalination device 108 after seawater taken from the sea by a seawater intake pump 107 is desalinized by the seawater desalination device 108. Fresh water such as rainwater also flows into the filtered water tank 101 and is stored therein. Therefore, only the pure water supplied from the seawater desalination device 108 is stored in the pure water tank 102, but the filtered water tank 101 contains fresh water such as rainwater in addition to the pure water. The fire-extinguishing water stored in the fire-extinguishing water tank 103 is supplied with a portion of the water pumped from the pure water tank 102 by a pure water transfer pump 105, which will be described later. Therefore, the water stored in each tank has a relatively low electrical conductivity.

[0018] The pumps installed in the water supply facility building 110 include a filtered water pump 104 that pumps out the filtered water stored in the filtered water tank 101, a pure water transfer pump 105 that pumps out the pure water stored in the pure water tank 103, and a fire pump 106 that pumps out the fire water stored in the fire water tank 103 to the fire extinguishing facility of the power generation facility.

[0019] The water stored in the filtered water tank 101 is used via a filtered water pump 104 for construction work on the generator equipment, and is also used as water to replace fresh water when the flow of seawater to the heat exchanger is stopped and the water is stored. A portion of the water (pure water) stored in the pure water tank 102 is supplied to a fire water tank 103 by a pure water transfer pump 105, and the remainder is supplied to the power generation equipment and is used as make-up water for the condensate storage tank and for filling the spent nuclear fuel pool, etc. Under normal circumstances when no fire or other incident has occurred at the power generation facility, the fire pump 106 is not in operation and the water stored in the fire water tank 103 is not pumped out. However, in the event of a fire or other incident at the power generation facility, the fire pump 106 is started up and the water is supplied to the power generation facility as fire water.

[0020] In this water supply facility 100, multiple filtrate pumps 104, pure water transfer pumps 105, and fire pumps 106 are provided, and the filtrate pumps 104 and fire pumps 106 are equipped with gland packing, and the pure water transfer pump 105 is equipped with a mechanical seal mechanism. For this reason, the filtrate pump 104 and the fire pump 106 are configured to inevitably leak liquid in the shaft seal portion to cool and lubricate the packing, and the pure water transfer pump 105 leaks liquid when the shaft sealing function of the mechanical seal deteriorates, so the water supply facility building 110 needs a drainage path to discharge such leaking water (pump drain water).

[0021] Therefore, the water supply facility building 110 is provided with a drainage path 111 for draining the pump drain, as shown in FIG. 2. In this example, the drainage path 111 is provided in the basement of the water supply facility building 110, and includes a drain ditch 111a for discharging drain water from the filtered water pump 104 and the pure water transfer pump 105, and a drain ditch 111b for discharging drain water from the fire pump 106. The pump drain water discharged through these drain ditches 111a and 111b is sent to an underground duct 112 laid underground outside the water supply facility building 110, and the pump drain water discharged to this underground duct 112 is temporarily stored in a drainage pit 113 provided downstream together with rainwater, etc. The water stored in this drainage pit 113 is discharged to an external drainage ditch 114 by a liquid level management device 1 installed therein.

[0022] The drainage pit 113 is a structure formed in a concave shape with concrete on the site of the power plant. As shown in Fig. 3, for example, the drainage pit 113 is provided with an installation groove 115 that is provided next to the underground duct 112 and extends downward from the underground duct 112 at the bottom. The liquid level control device 1 including the liquid level detection device 2 and the drainage device 3 described below is installed in the installation groove 115.

[0023] The liquid level detection device 2 has an electrode type liquid level gauge 10 and a tilt float type liquid level gauge 20. Fig. 3 shows a schematic configuration of the installed state, and Fig. 4 shows a schematic diagram for explaining the liquid level detection device 2.

[0024] The electrode-type liquid level gauge 10 is a liquid level gauge that detects the liquid level based on the current flow state of two or more electrodes that are in contact with a conductive liquid. In this embodiment, the electrode-type liquid level gauge 10 has four electrodes 11, 12, 13, and 14, which are housed in a protective tube 16 made of a non-conductive material and whose upper and lower ends are open. As shown in Figure 4, this electrode-type liquid level gauge 10 has a common electrode 11 that is always immersed in liquid, an L1 water level detection electrode 12 that detects a low liquid level (first lower limit liquid level) L1, an H1 water level detection electrode 13 that detects a high liquid level (first upper limit liquid level) H1, and an HH1 water level detection electrode 14 that detects an abnormally high liquid level (first abnormal liquid level) HH1. Here, the first abnormal liquid level HH1 is set to a liquid level higher than the first upper limit liquid level H1, and the first lower limit liquid level L1 is set to a liquid level lower than the first upper limit liquid level H1, and each electrode 11 to 14 has its upper end fixed to a common base 15 and hangs down from this base 15.

[0025] The common electrode 11 corresponds to an earth electrode, and is set to have the longest length from the base 15 among the four electrodes. The lengths of the other three electrodes from the base 15 are gradually shortened in the order of the L1 water level detection electrode 12, the H1 water level detection electrode 13, and the HH1 water level detection electrode 14. Therefore, when conductive water comes into contact with the common electrode 11 and the other water level detection electrodes, a conductive state is formed between the electrodes, and the water level can be detected based on this conductive state.

[0026] The number of electrodes in the electrode type level gauge 10 may be three or five or more, but four are usually required to function as a three-contact system (a system that creates three states: pump start, pump stop, and issuance of an alarm in the event of an abnormally high water level).

[0027] Therefore, in the electrode type liquid level meter 10 according to this embodiment, a first lower limit liquid level (L1) is detected when the common electrode 11 and the L1 water level detection electrode 12 come into contact with water. Also, a first upper limit liquid level (H1) at which a pump described below needs to be started is detected when the common electrode 11 and the H1 water level detection electrode 13 come into contact with water. Also, a first abnormal liquid level (HH1) for issuing an alarm for an abnormally high water level is detected when the common electrode 11 and the HH1 water level detection electrode 14 come into contact with water. In addition, the L1 water level detection electrode 12 is used to cut off the flow of electricity to the drainage pump 31 (stopping the drainage pump) described later when the water level falls below the first lower limit liquid level (L1) and the electrical connection between the L1 water level detection electrode 12 and the common electrode 11 is cut off.

[0028] The tilt float type liquid level gauge 20 is capable of detecting the water level by turning on and off an internal microswitch by utilizing the fact that the tilt state of the float parts 21, 22, 23 changes as the water level rises and falls. The configuration of each float part 21, 22, 23 is known per se, and each float part 21, 22, 23 is assigned a different contact, with the center of buoyancy located at the tip side and the center of gravity located on the cable side (base end side). Therefore, when the liquid level rises and the float part is immersed in water, the tilt of the float part changes due to the rotation moment generated by the misalignment between the center of buoyancy and the center of gravity, and the internal steel ball moves to turn the microswitch on and off.

[0029] Each of the float elements 21, 22, 23 may be of the type that turns on when tilted at a predetermined angle (θ1) or more with respect to the vertical line and turns off when tilted at a smaller predetermined angle (θ2) or less, as shown in FIG. 5(a), or may be of the type that turns on when tilted upward by a predetermined angle (θ3) or more with respect to the horizontal line and turns off when tilted downward by a predetermined angle (θ4) or more with respect to the horizontal line, as shown in FIG. 5(b).

[0030] In this example, three floats 21, 22, 23 are provided at different heights to support a three-contact system (pump start, pump stop, and issuance of an alarm at abnormally high water level). Since the tilt float type level gauge 20 does not have a protective tube like the electrode type level gauge 10, a terminal box 25 is fixed to an installation stand 24 that is attached approximately horizontally to the wall of the drainage pit 113, a rope 26 is hung from approximately the center of a flange 25a provided at the lower end of the terminal box 25, and a weight 27 is attached to the lower end of the rope 26. The weight 27 is installed at the bottom of the drainage pit 113 (the bottom surface of the installation groove 115), and the rope 26 provided between the flange 25a and the weight 27 is attached so as not to slacken.

[0031] The three float parts 21, 22, 23 each have a cable (lead wire) 21a, 22a, 23a that hangs down from a terminal box 25 via a flange part 25a (actually, the cables 21a, 22a, 23a are inserted into the terminal box from below), and the float parts 21, 22, 23 are attached to the tip (lower end) of each cable 21a, 22a, 23a as a sensor. The rotation fulcrums of the cables 21a, 22a, 23a that are the rotation centers of the float parts 21, 22, 23, i.e., the positions of the lowest ends (lengths from the terminal box 25) that support each cable on the rope 26, are made different, and are fixed to the rope 26 with cable clips, cable ties, etc. in accordance with the operating points that turn the float parts 21, 22, 23 ON and OFF depending on the water level.

[0032] In this embodiment, as shown in Figure 3, in order to ensure on / off at three contacts for starting the drainage pump 31, stopping the drainage pump 31, and issuing an alarm in the event of an abnormally high water level, the device has a float unit (L2 detection float unit) 21 that detects the low water level (second lower limit liquid level: L2), a float unit (H2 detection float unit) 22 that detects the high water level (second upper limit liquid level: H2), and a float unit (HH2 detection float unit) 23 that detects an abnormally high water level (second abnormal liquid level: HH2) that is higher than H2. In addition, the movable range of each float part 21, 22, 23, i.e., the length from the rotation fulcrum of each cable 21a, 22a, 23a to the float part 21, 22, 23, is adjusted so that the cables 21a, 22a, 23a of adjacent float parts 21, 22, 23 do not become entangled.

[0033] Therefore, in the tilt float type liquid level gauge 20 according to this embodiment, the amount of tilt of the L2 detection float portion 21 changes, turning the internal microswitch ON, thereby detecting the second lower limit liquid level L2. Also, the amount of tilt of the H2 detection float portion 22 changes, turning the internal microswitch ON, thereby detecting the second upper limit liquid level H2. Also, the amount of tilt of the HH2 detection float portion 23 changes, turning the internal microswitch ON, thereby detecting the H2 abnormal liquid level HH2 for detecting an abnormally high water level.

[0034] Next, the drainage device 3 will be described. The drainage device 3 drains liquid to the outside, and has a drainage pump 31 that sucks up water in the drainage pit 113, and a drainage pipe 32 that drains the water sucked from the drainage pump 31 to an external drainage ditch 114. The drainage pump 31 is provided on the bottom surface of the installation ditch 115. The drainage pump 31 performs a predetermined operation by the control circuit 50 based on the detection signal of the liquid level detection device 2. The control circuit 50 controls the operation of the drainage device 3 based on at least one of the detection signal of the electrode type liquid level gauge 10 and the detection signal of the tilt float type liquid level gauge 20.

[0035] Next, the control circuit 50 will be described. The control circuit 50 has circuits for controlling the liquid level in the drainage pit 113, such as a terminal block 500 for connection to the liquid level detection device 2 as shown in Fig. 4, a known self-holding circuit using a relay switch, etc., and a circuit for output to the drainage pump 31. The terminal block 500 is provided with terminals 501, 502, 503, and 504, and wiring between the electrode type liquid level gauge 10 of the liquid level detection device 2 and the tilt float type liquid level gauge 20 is connected.

[0036] For example, the terminal 501 is connected to a wiring between the common electrode 11 of the electrode type liquid level gauge 10 and a wiring between the common wiring 29 of the tilt float type liquid level gauge 20. The terminal 502 is connected to a wiring between the L1 water level detection electrode 12 of the electrode type liquid level gauge 10 and a wiring between the L2 detection float part 21 of the tilt float type liquid level gauge 20. The terminal 503 is connected to a wiring between the H1 water level detection electrode 13 of the electrode type liquid level gauge 10 and a wiring between the H2 detection float part 22 of the tilt float type liquid level gauge 20. The terminal 504 is connected to a wiring between the HH1 water level detection electrode 14 of the electrode type liquid level gauge 10 and a wiring between the HH2 water level detection float part 23 of the tilt float type liquid level gauge 20.

[0037] For example, when terminal 503 is turned ON, the control circuit turns ON the pump start relay and activates a circuit that self-maintains that state, and then allows the drainage pump 31 to continue operating even if terminal 503 is turned OFF. In contrast, when terminal 502 is turned OFF, the self-maintaining operation of the drainage pump 31 is released, and the operation of the drainage pump 31 is stopped. Furthermore, when terminal 504 is turned ON, control circuit 50 operates a circuit that issues an alarm for an abnormally high water level, and when terminal 504 is turned OFF, control circuit 50 stops issuing the alarm.

[0038] According to this configuration, the detection signal of the electrode type level gauge 10 and the detection signal of the tilt float type level gauge 20 are connected in parallel to terminals 501 to 504 of the terminal block 500 and input to the control circuit 50 via these terminals, so that the operation of the drainage device 3 is controlled based on at least one of the detection signal of the electrode type level gauge 10 and the detection signal of the tilt float type level gauge 20. In other words, when the first upper limit liquid level (H1) or the second upper limit liquid level (H2) is detected, the drainage device (drainage pump 31) is operated, when the first abnormal liquid level (HH1) or the second abnormal liquid level (HH2) is detected, an alarm is issued, and when it is detected that the liquid level falls below the first lower limit liquid level (L1) or the second lower limit liquid level (L2), the operation of the drainage device (drainage pump 31) is stopped.

[0039] Here, when the water level detection by the electrode type liquid level gauge 10 is the main detection and the water level detection by the tilt float type liquid level gauge 20 is the secondary (backup) detection, and the drainage pump 31 and the alarm are controlled preferentially based on the water level result detected by the electrode type liquid level gauge 10, each threshold value is set to H1 <H2、HH1<HH2,L1> Just set it like L2. Furthermore, if the water level in HH1 or HH2 becomes higher than the upper end of the installation trench 115, it will no longer be possible to send water from the underground duct 112 to the drainage pit 113, so it is advisable to set it near the upper end of the installation trench 115 as a guide.

[0040] Next, an example of the operation process of the liquid level management control by the control circuit 50 in the drainage pit 113 using the electrode type liquid level gauge 10, the tilt float type liquid level gauge 20, and the drainage pump 31 will be described with reference to the flowchart shown in Fig. 6. Note that in this flowchart, the water level detection by the electrode type liquid level gauge 10 is used primarily, and the water level detection by the tilt float type liquid level gauge 20 is used as a secondary (backup) detection, i.e., H1 <H2、HH1<HH2,L1> A case where the threshold value is set as L2 will be described.

[0041] First, when the water level in the drainage pit 113 rises to the first upper limit liquid level (H1) and the H1 water level detection electrode 13 of the electrode-type liquid level gauge 10 comes into contact with the water, if the water collected in the drainage pit 113 is conductive, the common electrode 11 and the H1 water level detection electrode 13 are energized, and the H1 water level is detected by the electrode-type liquid level gauge 10 (step S10: YES). As a result, the drainage pump 31 is started to lower the water level in the drainage pit 113 (installation groove 115) (step S11).

[0042] However, if the water accumulated in the drainage pit 113 is low conductive water, even if the common electrode 11 and the H1 water level detection electrode 13 come into contact with the water, the water level of H1 cannot be detected in step S10 (step S10: NO), and the process proceeds to step S20. Then, when the H2 detection float portion 22 of the tilt float type liquid level gauge 20 detects that the water level in the drainage pit 113 is at a water level of H2, which is set higher than H1 (step S20: YES), the control circuit 50 starts the drainage pump 31 (step S21). At this time, the control circuit 50 self-maintains the operating state of the drainage pump 31. Therefore, the drainage pump 31 continues to operate even if the water level in the drainage pit 113 falls below H2 or H1.

[0043] When the drain pump 31 is started, the water in the drain pit 113 is sent to the drain ditch 114. Normally, the water level in the drain pit 113 should gradually decrease. However, if for some reason the water level in the drain pit 113 continues to rise instead of decreasing, and the water level reaches HH1 (step S12: YES), if the water is conductive, electricity will flow between the common electrode 11 and the HH1 water level detection electrode 14, and an alarm will be issued (step S13).

[0044] However, if the water accumulated in the drain pit 113 has low conductivity, the water level of HH1 cannot be detected in step S12 even if the common electrode 11 and the HH1 water level detection electrode 14 come into contact with water. In such a case, the process proceeds to step S22, where it is determined whether the HH2 float portion 23 has turned ON to detect that the water level has reached HH2 (step S22), and if it is determined that the water level has reached HH2 (step S22: YES), an alarm is issued indicating that the water level is abnormally high (step S23). The alarm indicating an abnormally high water level does not have a self-maintaining function, and the alarm is cancelled (no alarm is issued: step 30) when the water level falls below HH1 (in the case of conductive water) or below HH2 (in the case of low conductivity water).

[0045] In this way, when the water level is rising, even if the conventional electrode type level gauge 10 does not function, the tilt float type level gauge 20 functions as a backup level gauge, making it possible to reliably detect the rise in the water level.

[0046] In contrast, when the drainage pump 31 is started and the water in the drainage pit 113 is drained, causing the water level to gradually drop, the HH1 water level detection electrode 14 and the HH2 detection float part 23 will not operate, and the condition will continue without an alarm being issued. If the water is conductive, when the water level falls below L1 and there is no current flow between the common electrode 11 and the L1 water level detection electrode 12, it is detected that the water level is below L1 (step S14: YES), and the operation of the drainage pump 31 is deactivated and the drainage pump 31 is stopped (step S31). Furthermore, the condition for the pump to operate continuously (self-maintain) from the pump start water level to the stop water level is that "there is continuity of the pump stop water level in the water level detector, and there is continuity of the pump start water level during that time." Therefore, in the case of water with low conductivity, the self-maintenance function of the electrode-type water level detector does not function in the first place.

[0047] However, if the drainage pump 31 continues to operate even if the water level falls below L1 for some reason, the water level in the drainage pit 113 will continue to drop. However, if the water level falls below L2, the L2 detection float 21 of the tilt float type liquid level gauge 20 turns off, detecting that the water level has fallen below L2 (step S24: YES), and the drainage pump 31 is stopped (step S31). Therefore, the drain pump 31 can be stopped reliably by the tilt float type liquid level gauge 20 regardless of whether the water is conductive or not.

[0048] In this way, even when the water level is dropping, the tilt float type level gauge 20 functions as a backup level gauge, so it is possible to reliably stop the drainage pump. As a result, it is possible to eliminate the inconvenience of the pump running idly and being damaged.

[0049] In the above control operation examples, with regard to the operation of stopping the drainage pump 31, when the electrode type level gauge 10 detects that the water level is below L1 or when the tilt float type level gauge 20 detects that the water level is below L2, the operation state of the drainage pump 31 is released (the self-maintained operation state is released) and the drainage pump 31 is stopped. However, as shown in Figure 7, when the electrode type level gauge 10 detects that the water level is below L1 (step S14: YES) and when the tilt float type level gauge 20 detects that the water level is below L2 (step S24: YES), the drainage pump 31 may also be stopped. In this way, the drainage pump 31 will not stop until the water level falls below L2, so that it is possible to stop the drainage pump 31 before it starts to run idly while reliably draining water, regardless of whether there is an abnormality in the electrode-type liquid level gauge 10.

[0050] As a modification of Fig. 7, the drain pump 31 may be stopped only when the L2 detection float 21 detects that the water level is below L2, as shown in Fig. 8. In this configuration, the condition for stopping the drain pump 31 can be made independent of the conductivity of the water, and since there is no need to provide the L1 water level detection electrode 12, the structure of the electrode type liquid level gauge 10 can be simplified by providing three electrodes.

[0051] In this way, by using the above-mentioned drainage pit liquid level management device, even if the water accumulated in the drainage pit 113 has low conductivity and the water level cannot be detected by the electrode type liquid level gauge 40, the water level can be reliably detected by the tilt float type liquid level gauge 41, so that the drainage pump can be reliably started and stopped according to the water level in the drainage pit 113, making it possible to properly manage the water level in the drainage pit 113.

[0052] Furthermore, when a conventional float type level gauge in which a float part slides along a guide rod is installed in parallel, there is a possibility that floating objects such as garbage and dirt in the water may get in between the guide rod and the float part and adhere thereto, hindering the smooth movement of the float part. However, with this configuration in which a tilt float type level gauge is installed in parallel, even if there is a small amount of garbage floating in the water, the movement of the float part will not be hindered, and it is possible to reliably automatically drain and stop the water in the drainage pit 113.

[0053] In the above embodiment, the second upper limit liquid level H2 of the tilt float type liquid level gauge 20 is set above the first upper limit liquid level H1 of the electrode type liquid level gauge 10, the second abnormal liquid level HH2 of the tilt float type liquid level gauge 20 is set above the first abnormal liquid level HH1 of the electrode type liquid level gauge 10, and the second lower limit liquid level L2 of the tilt float type liquid level gauge 20 is set below the first lower limit liquid level L1 of the electrode type liquid level gauge 10. However, depending on the situation at the site, the second upper limit liquid level H2 may be set below the first upper limit liquid level H1, the second abnormal liquid level HH2 may be set below the first abnormal liquid level HH1, or the second lower limit liquid level L2 may be set above the first lower limit liquid level L1. Even in such a case, the water level can be reliably detected by the movement of either the electrode type liquid level gauge 10 or the tilt float type liquid level gauge 20, and the water in the drainage pit 113 can be reliably automatically discharged and stopped. [Explanation of symbols]

[0054] 1 Liquid level control device 2. Liquid level detection device 3 Drainage device 10 Electrode level gauge 20 Tilt float type liquid level gauge 21, 22, 23 Float section 31 Drainage pump 113 Drainage Pit 115 Installation groove L1 1st lower limit liquid level H1 1st upper limit liquid level HH1 1st abnormal liquid level L2 2nd lower limit liquid level H2 2nd upper limit liquid level HH2 2nd abnormal liquid level

Claims

1. an electrode type liquid level meter that detects the liquid level based on the state of conduction of an electrode that contacts the liquid and conducts electricity; a tilt float type liquid level gauge that detects the liquid level based on the tilt of a float portion according to the liquid level; A drainage device capable of draining liquid to the outside; Installed in the drainage pit, A drainage pit liquid level management device, characterized in that the operation of the drainage device is controlled based on at least one of the detection signal of the electrode type liquid level gauge and the detection signal of the tilt float type liquid level gauge.

2. The electrode type liquid level meter is capable of detecting a first upper limit liquid level in the drainage pit, a first abnormal liquid level set to a liquid level higher than the first upper limit liquid level, and a first lower limit liquid level set to a liquid level lower than the first upper limit liquid level, The tilt float type liquid level gauge is capable of detecting a second upper limit liquid level in the drainage pit, a second abnormal liquid level set to a liquid level higher than the second upper limit liquid level, and a second lower limit liquid level set to a liquid level lower than the second upper limit liquid level, A drainage pit liquid level management device as described in claim 1, which starts the drainage device when the first upper limit liquid level or the second upper limit liquid level is detected, issues an alarm when the first abnormal liquid level or the second abnormal liquid level is detected, and stops operation of the drainage device when the first lower limit liquid level or the second lower limit liquid level is detected.

3. The second upper limit liquid level of the tilt float type liquid level gauge is set higher than the first upper limit liquid level of the electrode type liquid level gauge, The second abnormal liquid level of the tilt float type liquid level gauge is set higher than the first abnormal liquid level of the electrode type liquid level gauge, The second lower limit liquid level of the tilt float type liquid level gauge is set lower than the first lower limit liquid level of the electrode type liquid level gauge.

3. The drainage pit liquid level control device according to claim 2.

4. A method for managing a liquid level in a drainage pit, comprising the steps of: A drainage pit liquid level management method characterized by controlling the operation of a drainage device capable of draining liquid to the outside based on at least one of a detection signal from an electrode type liquid level gauge that detects the liquid level based on the electrical current state of an electrode that is in contact with the liquid and conducts electricity, and a detection signal from a tilt float type liquid level gauge that detects the liquid level based on the inclination of a float portion that corresponds to the liquid level.

Images