JP2000002614A - Tank inspecting device and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a tank inspection device to accurately defect locations such as micro through holes in a tank in a short time without the necessity for any scaffold or using any gas detecting solution and to enable the device to be automated as well. SOLUTION: After a gas to be inspected is injected to the outer surface side of a tank, a float body 2 is operated from a location distant from the inner surface of the tank to place an inspecting device formed by arranging a plurality of gas sensors 1 installed on the surface of the float 2 close to the inner surface of the tank, and the detection of leakage of the gas to be inspected in a part of predetermined area is performed at once. By this, inspection on through holes in the part of a predetermined area is performed. When each gas sensor 1 notifies inspectors of the detection of leakage of the gas to be inspected, the locations of leakage of the gas to be inspected are marked with a marker 4 provided according to each gas sensor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a tank for inspecting the presence or absence of a defect such as a through-hole which causes a fluid leak from a tank and searching for a defective portion.

[0002]

2. Description of the Related Art After a tank is manufactured, it is necessary to inspect for defects such as through holes which may cause fluid leakage, and to search for a defective portion. Conventionally, this tank inspection is performed in the following procedure.

That is, after the tank is manufactured, a scaffold for inspection is erected inside the tank, and a gas detection liquid that changes color by a test gas (for example, ammonia gas) is applied to the inner surface of the tank, and the outer surface of the tank (the outer surface of the tank and the heat insulating layer) is applied. The gap between the gas detection liquid and ammonia gas was charged into the tank, and the discoloration of the applied gas detection liquid was examined by visual observation to see if the ammonia gas passed through defects such as through holes and leaked to the tank inner surface. inspect.

[0004]

As described above, conventionally,
The tank inspection was performed by applying a gas detection liquid to the inside of the tank and then visually monitoring the discoloration of the gas detection liquid for the ammonia gas charged on the outside of the tank to leak to the inside of the tank. Such problems existed. Since all scaffolds need to be erected in the tank,
A large amount of work is required for disassembly, and a large amount of work time and cost is required. The tank inner surface may be damaged during scaffolding or dismantling, and repair may be required. As the inspection work, cleaning the inside surface of the tank, applying a gas detection liquid, charging ammonia gas, visual inspection after a lapse of a predetermined time,
Although the work of wiping and cleaning the gas detection liquid is performed, the work is performed on a scaffold, and measures to prevent a fall or the like are required. If the tank is large, it takes tens of hours or more for ammonia gas to spread throughout the tank, penetrate through holes, react with the gas detection liquid applied on the inner surface, and change color after the ammonia gas is charged. And waiting time occurs, resulting in poor efficiency. Since the detection accuracy of the through-hole depends on the thickness of the applied gas detection liquid, the detection accuracy varies. In other words, since the gas detection liquid changes color by contacting and reacting with the ammonia gas for a predetermined time or more, when the coating film thickness is small, the ammonia gas permeates the gas detection liquid film in a short time, and If the contact time cannot be long, and the coating film thickness is large, the discoloration of the gas detection liquid film due to the ammonia gas remains inside the film and does not appear on the gas detection liquid film surface. In either case, detection of the through-hole may not be possible. Appropriate gas detection liquid coating thickness is 50 ± 10μ
m, but it takes time and effort to control and apply the film thickness in this range.

A technical object of the present invention is to make it possible to accurately and quickly detect a defective portion such as a minute through-hole in a tank without using a gas detecting liquid, and to make automation possible. It is in.

[0006]

According to the tank inspection method of the present invention, after the test gas is charged into the outer surface of the tank, the floating body is operated from a position distant from the inner surface of the tank and attached to the surface of the floating body. An inspection device consisting of a plurality of gas sensors arranged close to the inner surface of the tank and detecting the leak of the gas to be detected in a predetermined area at one time, inspects the through-hole in the predetermined area, and tests each gas sensor. When it is notified that the gas leak has been detected, marking is performed on each leak location of the test gas detected by each gas sensor. It is characterized in that the tank inner surface is scanned by sequentially performing these series of steps while moving the floating body along the tank inner surface.

In the apparatus used in this method, a predetermined number of gas sensors for detecting a gas to be detected are arranged on the surface of the floating body, and a holder is mounted so that each measurement surface is in the same direction. Along with each gas sensor of the holder, independently, a marker for marking a leak point of the test gas detected by each gas sensor is installed, and a floating body or a moving vehicle electrically connected to the floating body is provided with a marker. An informing means for informing that the gas sensor has detected leakage of the test gas is provided.

In the method and apparatus of the present invention, the test gas may be, for example, ammonia gas, carbon dioxide gas, helium gas, acetylene gas, laughing gas, or the like. The gas sensors that can be used are roughly classified into an electrochemical sensor and a ceramic sensor. Further, when ammonia gas is used as the test gas, for example, a constant potential electrolytic sensor classified as an electrochemical sensor, a semiconductor sensor classified as a ceramic sensor, a hot wire semiconductor sensor, or the like can be used. When using another gas as the test gas, it depends on the type of gas,
It is possible to use a sensor having a detection principle such as a thermal conductivity type, a galvanic cell type, a non-dispersive infrared type, and a mass spectrometer type.
In addition, the gas sensor only needs to be able to install markers corresponding thereto, and the number and the number of rows are not limited. Further, the marker may be set to automatically mark the tank surface when the corresponding gas sensor detects the leakage of the gas to be detected, and the marker corresponding to the gas sensor that has detected the leakage of the gas to be detected may be an operator. May be selected by a selection switch to perform a marking operation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. Hereinafter, the first of the present invention.
The tank inspection method according to the embodiment and the apparatus used in this method will be described with reference to FIGS. FIG. 1 is a configuration diagram schematically showing the relationship between a gas sensor unit and a floating body of a tank inspection device according to the first embodiment, and a movable trolley electrically connected thereto, and FIG. 2 is a plan view of the gas sensor unit. FIG. 3 is an explanatory view of a method for inspecting a tank using the apparatus of the first embodiment. FIG. 4 is a graph showing the detection performance when an ammonia gas sensor is employed in the apparatus of the first embodiment. FIG. 5 is a circuit diagram for explaining the principle of detection of a potentiostatic electrolytic sensor, which is an ammonia gas sensor, and FIG. 6 is a detection diagram of a semiconductor sensor, which is also an ammonia gas sensor. It is a circuit diagram for explaining a principle.

In the tank inspection apparatus of the first embodiment, as shown in FIGS. 1 and 2, a plurality of gas sensors 1...
2 × 40) and attached to the surface (here, the upper surface) of a floating body 2 made of a transparent material (for example, vinyl) so that the measurement surfaces 1a having a diameter of 30 mm of each gas sensor 1 are in the same direction. 60x1
The 200 mm range can be inspected at a time. In the vicinity of each gas sensor 1 in the holder 3, a marker 4 composed of an ink jet marking nozzle for marking a leak location of the test gas detected by each gas sensor 1 is installed independently, A gas detection lamp 5 is provided on the surface (here, the lower surface) of the floating body, which is easily attached to the gas, as first notification means for notifying that each of the gas sensors 1 has detected leakage of the test gas.
Further, the movable cart 12 electrically connected to the floating body has a gas sensor 1, a gas detection lamp 5, a marker 4, and so on.
A control device 6 connected to the above is installed. The rectangular holder 3 is made of a lightweight material (for example, aluminum, plastic, or styrene foam) to reduce the load on the floating body 2 and to reduce the load on the floating body 2.
Part is housed in the concave pocket formed in the bottom of the pocket, and it is detachably fixed to the bottom of the pocket with adhesive tape etc.
This prevents the helium gas loaded in the floating body 2 from leaking from the inspection device mounting portion.

The control device 6 includes at least each gas sensor 1
Are detected by each of the gas sensors 1 on the basis of coordinates set in advance, and a display 7 having a function as a second notification means for identifying and indicating that the leakage of the test gas has been detected for each sensor. A controller 8 having a calculating means for calculating the leaked portion of the test gas by calculation, a recorder 9 for recording the calculation result, and a driving power supply 11 composed of a battery are provided. The controller 8 further has functions such as sensitivity adjustment of the gas sensors 1,..., Setting of a timer for keeping the inspection apparatus close to the inner surface 16a of the tank 16 to be inspected, control of marking, and the like.

At four corners in the holder 3, distance sensors 19 are arranged so that their distance measurement surfaces are in the same direction as the measurement surfaces 1a of the gas sensors 1, and are connected to the control device 6. I have. Further, a proximity detection lamp 21 is provided on the surface (here, the lower surface) of the floating body that is easily visible to the operator to notify the operator that the measurement surface 1a of each gas sensor 1 has been positioned close to the tank inner surface 16a. The determination as to whether or not the measurement surface 1a of each gas sensor 1 is close to the tank inner surface 16a is based on the determination that each of the distances from the tank inner surface 16a detected by each of the distance sensors 19 is equal to or less than a predetermined distance (for example, 3 mm or less). The control device 6 determines that the vehicle is near when the condition is satisfied, and turns on the proximity detection lamp 21. In addition,
13 is a levitating body operation cord, and 14 is a cable.

Next, a method for inspecting a tank using the apparatus of the first embodiment will be described. In the apparatus of the first embodiment, ammonia gas is used as a test gas,
As the gas sensor, a potentiostatic electrolytic sensor shown in FIG. 5 capable of detecting ammonia gas is used, but the semiconductor sensor shown in FIG. 6 or a hot-wire semiconductor sensor (not shown) can be used as the gas sensor. .

As shown in FIG. 5, the potentiostatic electrolytic sensor has three electrodes, a working electrode (WE), a counter electrode (CE), and a comparison electrode (RE), as is well known. Each electrode is immersed in an electrolytic solution and held by an electrolytic cell, and each electrode is connected to a potentiostat circuit. Therefore, when gas is ventilated to the working electrode (WE) which is kept at a constant potential with respect to the comparison electrode (RE), the working electrode (WE)
And a counter electrode (CE) occur simultaneously, and an electrolytic current i flows in an external circuit. Since the electrolytic current i is proportional to the gas concentration according to Faraday's law, the gas concentration can be measured by measuring the electrolytic current i.

As shown in FIG. 6, the semiconductor sensor comprises an n-type semiconductor made of metal oxide (SnO ₂ ), two electrodes, and a heater coil, as shown in FIG. Let me. When the activated semiconductor comes into contact with the reducing gas, the resistance value between the electrodes changes. Therefore, the gas concentration can be measured by extracting the resistance with a voltage.

As is well known, a hot wire type semiconductor sensor has a structure in which a metal oxide semiconductor is frozen on a platinum wire coil, and has the same basic principle as a semiconductor type sensor.

The inspection of the tank 16 is carried out mainly on a welded portion where a leak may be present. First, a test gas, that is, an ammonia gas, is charged into the outer surface of the tank (a gap between the outer surface of the tank and the heat insulating layer). Next, the worker operates the levitating body 2 holding the inspection device from a position distant from the tank inner surface 16a with the levitating body operation string 13 to carry the tip of the holder 3 of the inspection device to the welding portion of the tank inner surface 16a. At this position, the levitating body operation cord 13 is released, and the tip of the holder 3 is brought close to and pressed against the tank inner surface 16a by utilizing the buoyancy of the levitating body 2 until the proximity detection lamp 21 is turned on (FIG. 3). When the proximity detection lamp 21 is turned on, the measurement surfaces 1a of the gas sensors 1
a, this state is maintained for a predetermined time (for example, 1
Minutes). The measurement of the sensor proximity holding time is performed by manually operating a timer (not shown) by the operator, or by the controller 8 automatically operating a built-in timer in conjunction with the lighting of the proximity detection lamp 21. Thus, a range of 60 × 1200 mm is inspected at a time.

If the gas detection lamp 5 does not turn on even after one minute, the operation string 13 of the floating body 2 is pulled to separate the floating bodies 2, that is, the gas sensors 1 from the tank inner surface 16a. 2 to the next inspection point,
Perform the same operation as described above. Since the levitating body 2 is made of a transparent material, the adjacent inspection point can be visually recognized through the levitating body 2. These series of operations are performed on the tank inner surface 16.
By repeating while sequentially moving along the welding line of a,
The tank inner surface 16a is scanned.

The time (1 minute) during which the measurement surface 1a of each gas sensor 1 is held close to the tank inner surface 16a.
When the gas detection lamp 5 is turned on, the leakage point is confirmed by the indicator 7 of the control device 6, and the switch (not shown) of the marker 4 at the corresponding point is pressed to mark the leakage point and detect the leakage point. The recorded coordinate data of the leak location is recorded in the recorder 9.

This marking operation can be performed by the controller 8 by setting the automatic mode. That is, the controller 8 grasps the positions of the gas sensors 1 in the holder 3 and the corresponding markers 4. When the leak is detected, the gas sensor that detects the leak using the detection signal as a trigger is provided. The marker 4 corresponding to 1 is actuated to automatically eject ink to the leak location, and the recorder 9 automatically records the coordinate data of the detected leak location.

Calibration of each of the gas sensors 1 is performed by allowing the gas to be detected to pass through a calibration reference material having a through hole having a standard size and detecting the gas by the gas sensor 1.

The gas detection performance of the ammonia gas sensor of the constant potential electrolysis type used in the first embodiment is as shown in the experimental result diagram of FIG. In FIG. 4, the vertical axis indicates the minimum detection limit through-hole diameter, and the horizontal axis indicates the distance between the through-hole and the measurement surface of the gas sensor. In this experiment, 1-5μ
A cell provided with a through-hole standard material having a through-hole of m was filled with ammonia gas, and the relationship between the distance between the measurement surface of the gas sensor and the through-hole of the standard material and the detection limit minimum through-hole diameter was examined. Things.

As is apparent from FIG. 4, the smaller the distance between the measurement surface of the gas sensor and the through hole of the standard material, the smaller the through hole can be detected, and the apparatus of the first embodiment is used. According to the tank inspection method, it was confirmed that it was possible to detect even a through hole having a diameter of 1 μm. That is, as a result of the experiment, it was found that it is important to make the measurement surface of the gas sensor close to the inner surface of the tank in order to enable detection of a smaller through hole.

Next, the effect of the first embodiment will be described with reference to a depth dimension of 20 m manufactured by welding and joining stainless steel plates.
Width 20m, height 20m, capacity 8000m ³ , inner surface area 2
An example in which the present invention is applied to detection of a through hole in a tank having a length of 400 m ² and a welding line length of 4000 m will be described in comparison with a conventional gas detection liquid application method. In this case, the concentration 2
A 5% ammonia gas was charged, and the inside of the tank was inspected 24 hours after the charging so that the ammonia gas spread over the entire tank and was diluted to a concentration of about 1 to 2%. In addition, the time for approaching the inner surface of the tank for detecting the through-hole by the device of the first embodiment was set to 1 minute per unit.

Inspection required time T (inspection work only) In the case of the embodiment, T = (T1 10 T2) · L / (W · 60) = 83 hours → 10.4 days (8 hours / day) T1: Holding time 1 minute T2 : Marking time for moving and positioning 10 minutes 0.5 L: Total length of welding line 4000 m W: Inspection sensor length 1.2 m Other required time In the case of the embodiment, the circulation time 24 hours (1 day) after charging ammonia gas 8 hours (1 day) That is, the total number of days required for the inspection work is 12.4 days in the case of the first embodiment. The levitation body was carried in a folded state in the tank, helium gas was charged therein, and after the inspection work, the helium gas was recovered, folded again, and carried out.

In the case of the comparative example In other words, when the tank of the same size was inspected by the conventional gas detection liquid application method, the scaffold was erected 5 days, the ammonia gas was charged, the reaction wait time was 2 days (during this time, the tank inner surface was Liquid application) Visual inspection 4 days Wiping and cleaning of detection liquid 2 days Scaffold dismantling 5 days Total 18 days

That is, according to the tank inspection method of the first embodiment, the number of days required for the inspection can be remarkably reduced as compared with the comparative example, and the total number of days required for the operation can be reduced by 5.6 days. Was.

In the case of the embodiment, the number of workers and man-hours required for the inspection are as follows. Ammonia gas charging 5 people x 1 day Floating body loading, preparation, clearing, unloading 5 people x 1 day Inspection 2 people x 10.4 days Total work man-hours 31 persons / day In the case of the comparative example (gas detection liquid application method) Scaffolding erection 10 persons x 5 days Ammonia gas charging 5 persons x 1 day Visual inspection 10 persons x 4 days Sensing liquid wiping and cleaning 10 persons x 2 Day Scaffold dismantling 10 people x 5 days Total work man-hours 165 people / day

That is, according to the tank inspection method of the first embodiment, the number of workers and man-hours required for the inspection can be significantly reduced as compared with the comparative example. 134 people / day could be reduced.

Embodiment 2 FIG. 7 is a configuration diagram schematically showing the relationship between a gas sensor unit and a floating body of a tank inspection device according to a second embodiment of the present invention, and a movable truck electrically connected thereto, and FIG. Plan view of FIG. 9
FIG. 4 is an explanatory view of a method of inspecting a tank using the apparatus of the second embodiment. In each figure, the same parts as those of the first embodiment are denoted by the same reference numerals.

As shown in FIGS. 7 and 8, the tank inspection apparatus of the second embodiment uses the measurement surfaces 1Aa... Of a plurality of gas sensors 1A. (Shown on the right side of the figure)
Are formed in an array (here, 40 pieces per row: 1
* 40 array), and the surface of a mountain-shaped floating body 2A made of a transparent material (for example, vinyl or the like) such that the measurement surfaces 1Aa having a diameter of 30 mm are in the same direction in the unfolded state of each gas sensor 1A. (In this case, the upper surface) is held by the chevron-shaped holder 3A.
A range of 1200 mm can be inspected at a time. When the corner portion of the tank inner surface 16a is related to three surfaces as shown in the center of FIG. 9, only the measurement surface of the gas sensor located at the center of the sensor array is formed on three surfaces, and the three-surface gas sensor is connected to the tank corner. A sensor array having a mountain-shaped (two-sided) measurement surface similar to that described above is radially arranged along (three directions), and the surface of a three-sided mountain-shaped floating body 2B made of a transparent material (for example, vinyl) is used. Here, it is attached to the upper surface).

Each of the gas sensors 1A in the holder 3A.
In the vicinity of one side, a marker 4A composed of an ink jet marking nozzle for marking a leaked portion of the test gas detected by each gas sensor 1A.
Are installed, and each gas sensor 1 in the holder 3A is installed.
A. Spacers 31 made of polystyrene are provided on the other side.

Further, a gas detection lamp 5 is provided on the surface of the floating body (here, the lower surface), which is easily visible to the operator, as first informing means for informing that the gas sensors 1A... ing. Further, the movable cart 12 electrically connected to the floating body 2A has gas sensors 1A.
And a control device 6 connected to the gas detection lamp 5, the markers 4A, and the like. The holder 3A is
It is made of a lightweight material (for example, aluminum, plastic, or styrene foam) to reduce the load on the levitating body 2A, and is partially housed in a concave pocket formed in the levitating body 2A, so that a pocket bottom is formed. The helium gas loaded in the floating body 2 is prevented from leaking from the mounting portion of the inspection device.

The control device 6 includes at least each gas sensor 1
A is provided with a function as a second notification means for identifying and notifying that each of the sensors A has detected the leakage of the test gas by each sensor, and each gas sensor 1A. The controller 8 includes a controller 8 having a calculating means for calculating a leaked portion of the detected test gas by calculation, a recorder 9 for recording the calculation result, and a driving power supply 11 including a battery. The controller 8 further has functions such as sensitivity adjustment of each gas sensor 1A, setting of a timer for keeping the inspection device close to the inner surface 16a of the tank 16 to be inspected, control of marking, and the like.

At the four corners in the holder 3A, distance sensors 19A...
Are arranged in the same direction as the measurement surface 1Aa of A ...
It is connected to the control device 6. Further, each gas sensor 1 is provided on the surface (here, the lower surface) of the floating body which is easily visible to the operator.
A proximity detection lamp 21 is provided to notify an operator that the measurement surface 1Aa of A ... has approached the tank inner surface 16a. Whether or not the measurement surface 1Aa of each gas sensor 1A is close to the tank inner surface 16a is determined by determining that the distance to the tank inner surface 16a detected by each distance sensor 19A is not more than a predetermined distance (for example, 3 mm or less). The control device 6 determines that the vehicle is near when the condition is satisfied, and turns on the proximity detection lamp 21. In addition, 13 is a levitating body operation cord, and 14 is a cable.

Next, a method for inspecting a tank using the apparatus of the second embodiment will be described. Also in the apparatus of the second embodiment, ammonia gas is used as a test gas,
A constant potential electrolytic sensor capable of detecting ammonia gas is used as a gas sensor.

The inspection of the tank 16 is carried out mainly on a welded portion where a leak may be present. First, a test gas, that is, an ammonia gas, is charged into the outer surface of the tank (a gap between the outer surface of the tank and the heat insulating layer). Next, the worker operates the levitating body 2A holding the inspection device from a position away from the tank inner surface 16a with the levitating body operation cord 13, and carries the tip of the holder 3A of the inspection device to the welding portion of the tank inner surface 16a. At this position, the levitating body operation cord 13 is released, and the tip of the holder 3A is brought close to and pressed against the tank inner surface 16a by using the buoyancy of the levitating body 2A until the proximity detection lamp 21 is turned on (FIG. 9). When the proximity detection lamp 21 is turned on, the measurement surface 1Aa of each gas sensor 1A is close to the tank inner surface 16a, and this state is maintained for a predetermined time (for example, one minute). The measurement of the sensor proximity holding time is performed by manually operating a timer (not shown) by the operator, or by the controller 8 automatically operating a built-in timer in conjunction with the lighting of the proximity detection lamp 21. As a result, 30 × 1200 in the unfolded state
Inspect the range of mm at a time.

If the gas detection lamp 5 does not turn on after one minute, the operation string 13 of the floating body 2A is pulled, and the floating body 2
A, that is, each gas sensor 1A is separated from the tank inner surface 16a, and in that state, the floating body 2A is moved to an adjacent inspection point, and the same operation as described above is performed. In the next inspection part, since the floating body 2A is made of a transparent material, the floating body 2A
Can be seen through. By repeating these series of operations while sequentially moving along the welding line on the tank inner surface 16a, the tank inner surface 16a is scanned.

The measurement surface 1Aa of each gas sensor 1A.
If the gas detection lamp 5 is turned on within the time (1 minute) in which the...
The switch 7 (not shown) of the marker 4A at the corresponding location is pressed to mark the leak location, and the recorder 9 records coordinate data of the detected leak location.

Also in the second embodiment, the marking operation can be performed by the controller 8 by setting the operation mode to the automatic mode. That is, in the controller 8, each gas sensor 1
The position of A ... in the holder 3A and the corresponding markers 4A ... are known, and when leakage is detected,
The detection signal is used as a trigger to activate the marker 4A corresponding to the gas sensor 1A that has detected the leak, to automatically eject ink to the leak location, and to automatically record the coordinate data of the detected leak location in the recorder 9. Let it.

The inspection of the vertical surface of the tank inner surface 16a is performed by using the floating body 2 described in the first embodiment as shown in FIG. Gas sensors 1 are arranged close to the tank inner surface 16a.

[0042]

As described above, according to the tank inspection method of the present invention, after the test gas is charged into the outer surface of the tank,
By operating the float from a position away from the tank inner surface, an inspection device consisting of a plurality of gas sensors attached to the surface of the float is installed close to the tank inner surface, and detection of gas leakage of a predetermined area at once can be detected. By performing the inspection of the through-hole of the predetermined area portion, when it is notified that the leak of the test gas has been detected by each gas sensor, to mark the leak location of the test gas detected by each gas sensor, respectively, Since these series of steps were performed sequentially while moving the floating body along the tank inner surface, the tank inner surface was scanned,
Eliminates the need for a large-scale scaffold, allows a small number of people to accurately and quickly detect defective locations such as minute through holes in the tank without using a gas detection liquid, cleans the inside of the tank, applies the detection liquid, visually inspects the gas, and detects the gas detection liquid. Work such as wiping and cleaning of
There is no waiting time for the reaction between the test gas and the detection liquid, the automation becomes easy, and the cost for inspection can be greatly reduced.

Further, a wide variety of gas sensors used in the apparatus used in this method have been developed and are commercially available, and may be appropriately selected and used, and there is no need to newly develop a sensor. However, the cost can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a relationship between a gas sensor unit and a floating body of a device used in a tank inspection method according to a first embodiment of the present invention, and a movable trolley electrically connected thereto.

FIG. 2 is a plan view of a gas sensor unit of the tank inspection device according to the first embodiment.

FIG. 3 is an explanatory diagram of a tank inspection method according to the first embodiment.

FIG. 4 is a diagram showing the detection performance when an ammonia gas sensor is employed in the device according to the first embodiment, as a relationship between the distance between the through-hole and the sensor and the minimum detection-limit through-hole;

FIG. 5 is a circuit diagram for explaining the detection principle of the potentiostatic sensor.

FIG. 6 is a circuit diagram for explaining the detection principle of the semiconductor sensor.

FIG. 7 is a configuration diagram schematically showing a relationship between a gas sensor unit and a floating body of a device used in a tank inspection method according to a second embodiment of the present invention, and a movable trolley electrically connected thereto.

FIG. 8 is a plan view of a gas sensor unit of the tank inspection device according to the second embodiment.

FIG. 9 is an explanatory diagram of a tank inspection method according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1, 1A gas sensor 1a, 1Aa Gas sensor measurement surface 2, 2A, 2B Floating body 3, 3A holder 4, 4A marker 5 Gas detection lamp (notifying means) 7 Display (notifying means) 12 Moving trolley 13 Floating body operation cord 16 Tank 16a Tank inner surface

Claims (2)

[Claims] 1. A step of charging a test gas to an outer surface of a tank, and operating a floating body having an inspection device having a plurality of gas sensors arranged on the surface from a position away from the inner surface of the tank. The inspection device is located near the tank inner surface, the leak of the gas to be detected in a predetermined area is detected at a time, and the process of inspecting the through hole is performed, and it is notified that the leak of the gas to be detected is detected by each gas sensor. And marking each leak location of the test gas detected by each gas sensor, and scanning the tank inner surface by sequentially performing each of the steps while moving the floating body along the tank inner surface. A tank inspection method characterized by the following. 2. A holder comprising a predetermined number of gas sensors for detecting a gas to be detected arranged on the surface of the floating body and holding the measurement surfaces in the same direction, and a holder in the vicinity of each gas sensor of the holder. Independently, a marker is installed to mark the leak location of the test gas detected by each gas sensor, and each of the gas sensors is attached to the floating body or a movable carriage electrically connected to the floating body. A tank inspecting device provided with an informing means for informing that a leak of water has been detected.