Leak detector and method for detecting leaks in airtight members

Abstract

To provide a leak detector and method with which it is possible to more efficiently detect leak from an airtight member.SOLUTION: A leak detector pertaining to the present invention includes an oxidation reaction electrode, an ion exchange membrane, a reductive reaction electrode, a voltage application device, and an electrolyte aqueous solution, the ion exchange membrane being sandwiched between the oxidation reaction electrode and the reductive reaction electrode, the voltage application device applying a positive voltage to the oxidation reaction electrode and applying a negative voltage to the reductive reaction electrode. At least a portion of the reductive reaction electrode is in contact with the electrolyte aqueous solution, and an electric charge moving between the oxidation reaction electrode and the reductive reaction electrode due to an electrochemical oxidation reaction on the oxidation reaction electrode of the hydrogen to be detected, is measured as a current.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a leak detector and method that can efficiently detect leaks in airtight members. [Background technology]

[0002] Maintaining airtightness in lithium-ion batteries, compressors and piping for air conditioners and refrigerators, fuel supply pipes for cars and aircraft, high-vacuum equipment in semiconductor manufacturing equipment, process gas piping in chemical plants, spacecraft, and other devices is important not only for product reliability but also for the protection of human life and preventing accidents. In the manufacturing process of airtight components, leak checks are conducted at every stage, from the part joining and assembly processes to the final product. If a leak is discovered after the airtight component or a product containing it is completed, it will need to be discarded or repaired. Even after the product is completed, leaks can occur due to corrosion, deterioration, vibration, fatigue, and other factors during use.

[0003] There are simple methods for detecting leaks, such as submerging the airtight member in water to increase the internal pressure, or applying soapy water to the outer surface of the airtight member to increase the internal pressure, but to detect minute leaks, a method using helium is used.

[0004] In helium leak detection methods, the inside of an airtight material is depressurized while helium gas is sprayed locally onto the outer surface, and the exhaust gas is analyzed with a mass spectrometer. Since helium is almost nonexistent in the atmosphere, if there is a leak in the airtight material, helium will be detected with the mass spectrometer. Helium is inert and, being a single atom, is very small and nonpolar, and can pass through even the smallest holes, so helium leak detectors have the highest sensitivity. However, helium is expensive, and the inclusion of a mass spectrometer makes the overall device large.

[0005] Therefore, it is conceivable to use hydrogen for leak detection, which has an even lower atmospheric concentration of 0.5 ppm compared to helium, which has a concentration of 5.2 ppm, is a small molecule, and is cheaper than helium.For example, Patent Document 1 discloses a water leak detection device that supplies a mixed gas of hydrogen and nitrogen into a pipe and identifies the location of the leak based on changes in the concentration of hydrogen gas around the pipe.

[0006] Furthermore, Non-Patent Document 1 discloses a concentration cell type hydrogen sensor that includes a hydrogen permeable metal membrane made of palladium or a palladium-silver alloy and is capable of measuring hydrogen concentration even in harsh environments where conventional methods have difficulty measuring hydrogen concentration, such as in an atmosphere containing flammable gas or water vapor, or in an acidic or alkaline liquid. 60 (OSO3H) m (OH) n A hydrogen gas sensor is disclosed in which platinum-supported carbon electrodes are formed on both sides of a proton conductor made of carbon, and the hydrogen gas concentration between the electrodes is measured based on the amount of current induced by the potential difference between the electrodes. Patent Document 3 discloses an electrochemical sensor having a hydrogen-permeable diaphragm, a working electrode containing platinum that electrochemically oxidizes hydrogen, and a counter electrode. Patent Document 4 discloses a hydrogen gas sensor that includes electrodes with different chemical potentials relative to hydrogen gas and an electrolyte in contact with these electrodes, and detects hydrogen gas based on the electromotive force generated between these electrodes. Patent Document 5 discloses a hydrogen sensor that includes a solid electrolyte containing an ion conductor that conducts protons and oxide ions, and an electrode made of a material that has catalytic activity in the oxidation reaction of hydrogen. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 132517 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-270200 [Patent Document 3] Japanese Patent Application Publication No. 9-138215 [Patent Document 4] International Publication No. 2005 / 80957 Brochure [Patent Document 5] Japanese Patent Application Laid-Open No. 2003-166972 [Non-patent literature]

[0008] [Non-Patent Document 1] Hirotaka Kimura et al., Materia Japan, Vol. 59, No. 2 (2020), 99-101 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, leak detectors that use hydrogen and hydrogen sensors that electrochemically detect hydrogen are known. Therefore, it is conceivable to electrochemically detect hydrogen in a leak detector that uses hydrogen. However, even with such a hydrogen leak detector, hydrogen must be prepared separately. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a leak detector and method that can more efficiently detect leaks in airtight members. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems, and as a result have found that by using an electrolytic hydrogen pump that oxidizes hydrogen at an oxidation reaction electrode and generates hydrogen from protons or water at a reduction reaction electrode, it is possible to supply hydrogen while detecting it very efficiently, and that this pump can be used for leak testing, thereby completing the present invention. The present invention will now be described.

[0011] [1] An electrochemical device comprising an oxidation reaction electrode, an ion exchange membrane, a reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution; the ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, the voltage application device applies a positive voltage to the oxidation reaction electrode and a negative voltage to the reduction reaction electrode; At least a part of the reduction reaction electrode is in contact with the electrolytic aqueous solution, A leak detector characterized in that an electric charge that moves between the oxidation reaction electrode and the reduction reaction electrode due to an electrochemical oxidation reaction of hydrogen to be detected at the oxidation reaction electrode is measured as a current. [2] The leak detector according to [1] further includes a pressure reducing device, which reduces the pressure inside the sealed component to efficiently supply the internal gas to the oxidation reaction electrode, or efficiently supplies the gas near the outer surface of the sealed component to the oxidation reaction electrode. [3] The leak detector according to [2], wherein the pressure reducing device is an electrolytic oxygen pump. By using an electrolytic oxygen pump as the pressure reducing device, more efficient leak testing becomes possible. [4] The leak detector according to any one of [1] to [3], further comprising a pressurizing device, which makes it possible to more efficiently supply hydrogen generated from the electrolytic solution on the reduction reaction electrode side to the outer surface of the airtight member under test and more efficiently pressurize the inside of the airtight member under test. [5] The leak detector according to any one of [1] to [4], wherein the ion exchange membrane is an anion exchange membrane and the electrolytic solution is an alkaline electrolytic solution. Use of an alkaline electrolytic solution may improve the durability of the cell compared to when an acidic electrolytic solution is used. [6] The leak detector according to any one of [1] to [5], wherein the oxidation reaction electrode contains a platinum catalyst, which is an excellent electrode catalyst for oxidizing hydrogen. [7] The leak detector according to any one of [1] to [6], further comprising a mixer for mixing the hydrogen generated from the reduction reaction electrode with an inert gas. Using only the hydrogen generated from the electrolytic solution on the reduction reaction electrode side for leak testing is dangerous, but mixing the hydrogen with an inert gas enables safer leak testing.

[0012] [8] A method for detecting a leak in an airtight member, comprising: supplying the gas inside the gas-tight member to the oxidation reaction electrode of the electrolytic hydrogen pump while applying a positive voltage to the oxidation reaction electrode and a negative voltage to the reduction reaction electrode of the electrolytic hydrogen pump; measuring the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump; and a step of spraying a hydrogen-containing gas generated at the reduction reaction electrode of the electrolytic hydrogen pump onto an outer surface of the gas-tight member, the electrolytic hydrogen pump includes the oxidation reaction electrode, the ion exchange membrane, the reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution; the ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, the voltage application device applies a voltage between the oxidation reaction electrode and the reduction reaction electrode, The method, characterized in that at least a portion of the reduction reaction electrode is in contact with the aqueous electrolytic solution. [9] A method for detecting a leak in an airtight member, comprising: a step of supplying gas near the outer surface of the gas-tight member to the oxidation reaction electrode of the electrolytic hydrogen pump while applying a positive voltage to the oxidation reaction electrode and a negative voltage to the reduction reaction electrode of the electrolytic hydrogen pump; measuring the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump; and pressurizing the inside of the gas-tight member with a gas containing hydrogen generated at the reduction reaction electrode of the electrolytic hydrogen pump; the electrolytic hydrogen pump includes the oxidation reaction electrode, the ion exchange membrane, the reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution; the ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, the voltage application device applies a voltage between the oxidation reaction electrode and the reduction reaction electrode, The method, characterized in that at least a portion of the reduction reaction electrode is in contact with the aqueous electrolytic solution.

[10] The method according to [8] or [9], wherein the voltage between the oxidation reaction electrode and the reduction reaction electrode is set to exceed 1.229 V. By setting the voltage between the oxidation reaction electrode and the reduction reaction electrode to exceed 1.229 V, electrolysis of the aqueous electrolyte solution becomes possible.

[11] The method according to any one of [8] to

[10] , wherein an electrolytic oxygen pump is used to extract the gas from the inside of the airtight member. By using the electrolytic oxygen pump as a pressure reducing device, more efficient leak testing becomes possible.

[12] The method according to any one of [8] to

[11] , wherein an anion exchange membrane is used as the ion exchange membrane and an alkaline electrolytic solution is used as the electrolytic solution, whereby the durability of the cell may be improved compared to when an acidic electrolytic solution is used.

[13] The method according to any one of [8] to

[12] above, wherein the oxidation reaction electrode contains a platinum catalyst, which is an excellent electrode catalyst for oxidizing hydrogen. [Effects of the Invention]

[0013] According to the present invention, leaks in airtight members can be detected using hydrogen, which is cheaper than helium. Moreover, since hydrogen can be produced while hydrogen is being detected, it is not necessarily necessary to produce or prepare hydrogen separately. Furthermore, the power required for the present invention is very low, making it possible to implement the invention at low cost. Therefore, the present invention is industrially extremely superior as an efficient leak detection means. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of an electrolytic hydrogen pump that includes a cation exchange membrane as the ion exchange membrane. [Figure 2] FIG. 2 is a schematic diagram of a leak detector according to the present invention including a pressure reducing device. [Figure 3] FIG. 3 is a schematic diagram of an electrolytic oxygen pump that includes an anion exchange membrane as the ion exchange membrane. [Figure 4] Figure 4 is a schematic diagram of an electrolytic oxygen pump and an electrolytic hydrogen pump connected in series. [Figure 5] FIG. 5 is a schematic diagram showing an embodiment in which the presence or absence of a leak is detected using the leak detector according to the present invention while pressurizing the inside of the airtight member to be inspected. [Figure 6] FIG. 6 is a schematic diagram of a cell prepared in an example described below. [Figure 7] FIG. 7 is a schematic diagram of the electrolytic hydrogen pump system prepared in the Examples described below. [Figure 8] FIG. 8 shows the current, electromotive force (Vapp) of the hydrogen detector (fuel cell), and oxygen concentration in the circulating gas measured in the electrolytic hydrogen pump system prepared in the Examples described below. DETAILED DESCRIPTION OF THE INVENTION

[0015] First, the leak detector according to the present invention will be described. The leak detector according to the present invention includes at least an oxidation reaction electrode, an ion exchange membrane, a reduction reaction electrode, a voltage application device, and an aqueous electrolyte solution.

[0016] Ion exchange membranes are membranes that selectively allow ions to pass through, and are broadly divided into anion exchange membranes and cation exchange membranes. Anion exchange membranes are made of polymers with positively charged functional groups; cations are repelled by the positive charge and cannot pass through, while only anions can pass through. Cation exchange membranes are made of polymers with negatively charged functional groups; anions are repelled by the negative charge and cannot pass through, while only cations can pass through. Examples of anion exchange membrane materials include poly[9,9-bis(hexyl-9H-fluorene)-alt-(1,4-benzene)] with trimethylammonium groups, in which the benzene rings may be substituted with fluoro groups. Examples of cation exchange membrane materials include sulfonated polytetrafluoroethylene.

[0017] The thickness of the ion exchange membrane may be adjusted as appropriate, but is generally about 5 μm or more and 1 mm or less, and preferably 10 μm or more and 500 μm or less.

[0018] The ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, and serves to deliver ions generated by the reaction at the oxidation reaction electrode or the reduction reaction electrode to the reduction reaction electrode or the oxidation reaction electrode.

[0019] At the oxidation reaction electrode, when hydrogen is present and the ion exchange membrane is an anion exchange membrane, the reaction of the following formula (1) occurs, and when the ion exchange membrane is a cation exchange membrane, the reaction of the following formula (2) occurs. (1) H2+ 2OH - → 2H2O + 2e - (2) H2 → 2H + + 2e - Furthermore, when hydrogen is not supplied to the oxidation reaction electrode, the reaction of the following formula (3) or (4) may occur. (3) 2H2O → 4H + + O2+4e - (4) 4OH - → 2H2O + O2+ 4e -

[0020] If hydrogen is not supplied to the oxidation reaction electrode and the ion exchange membrane is a cation exchange membrane or the aqueous electrolyte solution on the reduction reaction electrode side is acidic, water is required for the reaction of the above formula (3) at the oxidation reaction electrode. If the ion exchange membrane is an anion exchange membrane and the reduction reaction electrode side is filled with an alkaline aqueous electrolyte solution, the reactions of the above formulas (1) and / or (4) proceed, producing water. However, if hydrogen is not sufficiently supplied to the oxidation reaction electrode and the reactions of the above formulas (1) and (4) do not proceed or do not proceed sufficiently, the aqueous electrolyte solution on the reduction reaction electrode side is thought to diffuse to the oxidation reaction electrode side, causing the reaction of the above formula (3) to proceed.

[0021] As the oxidation reaction electrode, for example, a conductive material such as a conductive carbon material, eg, carbon paper, can be used.

[0022] The oxidation reaction electrode preferably contains a catalyst to ensure smooth reaction. Examples of the oxidation reaction catalyst include platinum, alloys of platinum with other metals, and oxides thereof. Metals other than platinum that form alloys or oxides with platinum are not particularly limited, and examples include one or more metals selected from iron, cobalt, nickel, palladium, silver, gold, copper, ruthenium, iridium, molybdenum, rhodium, chromium, tungsten, and manganese. The oxidation reaction catalyst may be supported on a carrier. Examples of the carrier include carbon materials such as carbon black, carbon nanofibers, carbon nanotubes, and carbon woven fabric; metal oxide particles such as zirconia particles; and conductive polymers such as PEDOT / PSS, polyaniline, and polypyrrole.

[0023] At the reduction reaction electrode, water is electrolyzed and hydrogen is generated. When an acidic electrolytic solution is used, the reaction represented by the following formula (5) is thought to occur primarily, and when an alkaline electrolytic solution is used, the reaction represented by the following formula (6) is thought to occur primarily. (5) 4H + + 4e - → 2H2 (6) 4H2O + 4e - → 2H2+ 4OH -

[0024] Since water electrolysis occurs at the reduction reaction electrode, there is no need to use a catalyst, and a conductive material may be used for the reduction reaction electrode. Examples of reduction reaction electrode materials include carbon materials such as carbon rods, woven carbon cloth, and carbon sheets; metal materials such as stainless steel, titanium, nickel, aluminum, and copper; and alloy materials such as nickel-chromium alloys and nickel-tin alloys. The reduction reaction electrode may be porous to increase its specific surface area and promote the reaction, and may have interconnecting pores to transfer ions required for the reaction at the oxidation reaction electrode to the ion exchange membrane. Here, interconnecting pores refers to pores that are continuously connected from the front surface to the back surface of the reduction reaction electrode.

[0025] In the present invention, a voltage is applied between the oxidation reaction electrode and the reduction reaction electrode to generate hydrogen by electrolyzing water on the reduction reaction electrode side. Water electrolysis theoretically occurs at a voltage greater than 1.229 V, and in practice occurs at a voltage of 1.5 V or higher, so the applied voltage is preferably 1.5 V or higher. There is no particular upper limit to the applied voltage; the higher the applied voltage, the higher the efficiency of water electrolysis. However, to prevent the device from becoming too large, a voltage of 100 V or lower is preferred. The applied voltage is more preferably 50 V or lower, and even more preferably 20 V or lower. There are no particular limitations on the voltage application device, and any voltage application device may be selected appropriately depending on the voltage to be applied, as long as it can apply a constant voltage.

[0026] In the present invention, at least a portion of the reduction reaction electrode is in contact with the aqueous electrolytic solution to generate hydrogen by electrolyzing water at the reduction reaction electrode. The aqueous electrolytic solution may be in contact with the reduction reaction electrode to the extent that the water electrolysis reaction proceeds sufficiently. For example, it is preferable to send the aqueous electrolytic solution to the reduction reaction electrode side of the cell using a liquid pump and fill the reduction reaction electrode side of the cell with the aqueous electrolytic solution. The aqueous electrolytic solution refers to an aqueous solution containing ions for electrical conductivity, and may be either an acidic or alkaline aqueous electrolytic solution. Examples of acids used in acidic aqueous electrolytic solutions include inorganic acids such as hydrogen chloride, sulfuric acid, nitric acid, and perchloric acid; and organic acids such as acetic acid and citric acid. Examples of alkalis used in alkaline aqueous electrolytic solutions include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; and alkaline earth metal hydroxides such as calcium hydroxide. Salts such as sodium chloride, potassium chloride, sodium sulfate, and calcium chloride may also be added. However, using an alkaline aqueous electrolytic solution may potentially extend the life of the cell compared to an acidic aqueous electrolytic solution.

[0027] As shown in Figure 1, the reduction reaction electrode side of the cell may be filled with an aqueous electrolyte solution. However, as shown in Figure 6, the reaction may be more efficiently promoted by delivering an aqueous electrolyte solution and / or gas under positive pressure through a tube in contact with the electrode and diffusing it into the electrode having a diffusion layer or a porous electrode. Even when an aqueous electrolyte solution reservoir or a gas reservoir is provided on each electrode side as in Figure 1, delivering the aqueous electrolyte solution and / or gas under positive pressure into the electrode having a diffusion layer or a porous electrode can also promote the reaction more efficiently.

[0028] The concentration of acid or alkali in the aqueous electrolytic solution may be adjusted as appropriate within a range in which water electrolysis proceeds smoothly and the durability of the device is sufficient, and may be adjusted to, for example, 0.001 mol / L or more and 10 mol / L or less.

[0029] In the present invention, the device comprising the ion exchange membrane, oxidation reaction electrode, reduction reaction electrode, voltage application device, and aqueous electrolyte solution is sometimes referred to as an "electrolytic hydrogen pump" because hydrogen is consumed at the oxidation reaction electrode and generated at the reduction reaction electrode. A schematic diagram of an electrolytic hydrogen pump using a cation exchange membrane as the ion exchange membrane is shown in FIG. 1. As shown in FIG. 1, when hydrogen gas is supplied to the oxidation reaction electrode, it is oxidized to generate protons. The generated protons permeate the cation exchange membrane and are reduced at the reduction reaction electrode to generate hydrogen gas. Furthermore, a collector electrode may be provided on the outside of each electrode in the laminate of the ion exchange membrane, oxidation reaction electrode, and reduction reaction electrode. Stainless steel, which has excellent conductivity and is resistant to corrosion and deterioration, can be used as the material for the collector electrode.

[0030] The leak detector of the present invention preferably includes a mixing device for mixing hydrogen generated from the reduction reaction electrode of the electrolytic hydrogen pump with an inert gas. Examples of inert gases that can be used include rare gases such as helium and argon, and nitrogen. The hydrogen concentration in the hydrogen / inert gas mixture can be adjusted appropriately within a range that does not pose a risk of explosion, but can be, for example, between 1% and 10% v / v, with approximately 5±1% v / v being preferred. The gas is locally sprayed onto the outer surface of the airtight component to be tested using a pump or under pressure, or is blown into the interior of the airtight component under pressure. Note that the concentration does not refer to the partial pressure of hydrogen gas in the mixture, but rather to the ratio of the volume of hydrogen to the total volume of hydrogen and inert gas before mixing. For example, 5% v / v hydrogen gas refers to a gas mixture of hydrogen gas and inert gas in a ratio of 5:95 (v:v).

[0031] The leak detector according to the present invention preferably includes a pressurizing device for pressurizing the hydrogen-containing gas generated at the reduction reaction electrode. Such gas is preferably the above-mentioned mixed gas containing hydrogen and an inert gas.

[0032] The pressurized gas is either locally sprayed onto the outer surface of the airtight member to be tested, or supplied to the inside of the airtight member to pressurize the inside of the airtight member. When spraying the gas onto the outer surface of the airtight member, the gas pressure may be approximately 1 kPa or more and 1 MPa or less. Alternatively, since it is sufficient to spray the gas onto the outer surface of the airtight member, in this case a pump may simply be used as the pressurizing device.

[0033] When pressurizing the inside of the airtight member to be tested with the gas, it is preferable to pressurize the gas to a pressure of about 100 kPa or more and 10 MPa or less. If the pressure is 100 kPa or more, if there is a crack or the like in the airtight member, the internal gas will easily leak to the outside, and thus leaks will be more easily detected. However, since this effect may saturate, the pressure is preferably 10 MPa or less, and more preferably 5 MPa or less.

[0034] The gas pressurizing device may be appropriately selected depending on the desired pressure, and examples thereof include a diaphragm pressure pump.

[0035] The leak detector according to the present invention preferably includes a pressure reducing device. Such a pressure reducing device reduces the pressure inside the airtight member and supplies the gas inside the airtight member to the oxidation reaction electrode. It can also be used to suck gas near the outer surface of the airtight member and supply it to the oxidation reaction electrode. Figure 2 shows a schematic diagram of an example of a leak detector according to the present invention that includes a pressure reducing device. As shown in Figure 2, if the pressure inside the airtight member is reduced and a gas containing hydrogen is locally sprayed onto the outer surface, if there is a crack or the like in the airtight member, hydrogen will penetrate into the interior of the airtight member. Therefore, if the gas inside the airtight member is supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, if the gas contains hydrogen, the hydrogen will react to generate electrons, causing changes in the voltage and current between the electrodes, thereby enabling leak detection.

[0036] When reducing the pressure inside the airtight member, the internal pressure is preferably about 10 kPa or more and 100 kPa or less. If the pressure is 100 kPa or less, it can be said that leaks in the airtight member can be detected more reliably, and if the pressure is 10 kPa or more, the present invention can be implemented at relatively low cost. When supplying gas on the outer surface of the airtight member to the oxidation reaction electrode, a reduction in pressure sufficient to allow gas to be sent is sufficient.

[0037] The pressure reducing device may be any device capable of reducing the pressure inside the airtight member to an extent that allows for effective inspection of the airtight member for leaks. The pressure reducing device may be appropriately selected depending on the desired degree of pressure reduction, and examples thereof include a diaphragm pump, a scroll pump, an aspirator, a rotary pump (oil rotary pump), a mechanical booster, a dry pump, and a scroll pump.

[0038] Alternatively, an electrolytic oxygen pump may be used as the pressure reducing device. With an electrolytic oxygen pump, the pressure can be reduced by roughly the partial pressure of oxygen by simply applying a voltage between the electrodes strong enough to electrolyze water, thereby consuming the oxygen in the air inside the airtight member, and the pressure inside the airtight member can be reduced to approximately 0.8 atmospheres.

[0039] The electrolytic oxygen pump includes a reduction reaction electrode, an ion exchange membrane, an oxidation reaction electrode, a voltage application device, and an aqueous electrolyte solution. The ion exchange membrane is sandwiched between the reduction reaction electrode and the oxidation reaction electrode. The voltage application device applies a negative voltage to the reduction reaction electrode and a positive voltage to the oxidation reaction electrode, and at least a portion of the oxidation reaction electrode is in contact with the aqueous electrolyte solution. Figure 3 shows a schematic diagram of an electrolytic oxygen pump that includes an anion exchange membrane as the ion exchange membrane. As shown in Figure 3, when a gas containing oxygen is supplied to the reduction reaction electrode, the oxygen is reduced to produce hydroxide ions. The produced hydroxide ions permeate the anion exchange membrane and are oxidized to oxygen at the oxidation reaction electrode.

[0040] That is, the reaction of the following formula (7) occurs at the reduction reaction electrode of the electrolytic oxygen pump, which includes an anion exchange membrane as the ion exchange membrane, and the reaction of the following formula (8) occurs at the oxidation reaction electrode. (7) 2H2O + O2+ 4e - → 4OH - (8) 4OH - → 2H2O + O2+ 4e -

[0041] In addition, the reaction of the following formula (9) occurs at the reduction reaction electrode of the electrolytic oxygen pump, which includes a cation exchange membrane as the ion exchange membrane, and the reaction of the following formula (10) occurs at the oxidation reaction electrode. (9) 4H + + O2+ 4e - → 2H2O (10) 2H2O → 4H + + O2+ 4e -

[0042] Alternatively, as shown in Figure 4, an electrolytic oxygen pump and an electrolytic hydrogen pump can be connected in series, and the gas inside the airtight member can be supplied to the reduction reaction electrode of the electrolytic oxygen pump to reduce the oxygen partial pressure, and the resulting deoxidized gas can then be supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, tested for the presence or absence of hydrogen, and circulated to the airtight member as a circulating gas.

[0043] The interior of the airtight member under test is connected to the oxidation reaction electrode side of the electrolytic hydrogen pump by a pipe or the like, and the interior is depressurized and sealed using a pressure reducing device. Then, a hydrogen-containing gas is locally sprayed onto the outer surface of the airtight member under test. If the airtight member under test has a crack or the like, hydrogen that has infiltrated into the airtight member under test through the crack or the like will be detected by the electrolytic hydrogen pump. However, in this case, if the crack or the like is large, air may infiltrate the interior before the hydrogen-containing gas is sprayed into the crack or the like, making it necessary to depressurize the interior again. Therefore, it is preferable to install a pressure reducing device on the path connecting the interior of the airtight member under test to the oxidation reaction electrode side of the electrolytic hydrogen pump, and while depressurizing the interior of the airtight member under test, supply the exhaust gas from the pressure reducing device to the oxidation reaction electrode side of the electrolytic hydrogen pump to test for hydrogen infiltration and, ultimately, for cracks or the like.

[0044] It is also possible to connect an electrolytic hydrogen pump and an electrolytic oxygen pump in parallel to the airtight member. Because the mean free path of hydrogen is much faster than that of oxygen and the gradient of hydrogen concentration is thought to be smaller than that of oxygen concentration in the system, even if the electrolytic hydrogen pump and the electrolytic oxygen pump are connected in parallel to the airtight member, it may be possible to use the electrolytic oxygen pump to reduce the pressure inside the airtight member while using the electrolytic hydrogen pump to detect hydrogen that has entered the inside from the outside through cracks or the like.

[0045] The leak detector according to the present invention can also detect the presence or absence of a leak by pressurizing the inside of the airtight member to be inspected with a hydrogen-containing gas and supplying the gas near the outer surface of the airtight member to the oxidation reaction electrode, as shown in Fig. 5. The suitable internal pressure of the airtight member to be inspected and the pressurizing device in this embodiment are as described above.

[0046] Next, a method for detecting a leak in an airtight member according to the present invention will be described. 1. Hydrogen production process using electrolytic hydrogen pump In this step, hydrogen is produced using the electrolytic hydrogen pump. As described above, the electrolytic hydrogen pump comprises an oxidation reaction electrode, an ion exchange membrane, a reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution. The ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode. The voltage application device applies a voltage between the oxidation reaction electrode and the reduction reaction electrode, and at least a portion of the reduction reaction electrode is in contact with the aqueous electrolytic solution. When a voltage of theoretically more than 1.229 V, and practically 1.5 V or more, is applied between these electrodes, water is electrolyzed at the reduction reaction electrode, generating hydrogen. By utilizing this hydrogen, the method of the present invention can be carried out at lower cost. The voltage is preferably 100 V or less, more preferably 50 V or less, and even more preferably 20 V or less.

[0047] 2. Internal gas supply process for airtight components In this step, a voltage is applied between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump, while the gas inside the airtight member is supplied to the oxidation reaction electrode of the electrolytic hydrogen pump. This step is performed when the inside of the airtight member is depressurized to test for the presence or absence of a leak. When the inside of the airtight member is pressurized to test for the presence or absence of a leak, this step is not performed, and instead, step 3 described below is performed.

[0048] The voltage to be applied between the oxidation reaction electrode and the reduction reaction electrode can be adjusted to more than 1.229 V, and is preferably 1.5 V or more, as in the above-described Step 1. There is no particular upper limit to the voltage, but, as in the above-described Step 1, it is preferably 100 V or less, more preferably 50 V or less, and even more preferably 20 V or less.

[0049] As a method for supplying the gas inside the airtight member to the oxidation reaction electrode, the gastight member and the oxidation reaction electrode side of the electrolytic hydrogen pump may be connected by a pipe or the like and then depressurized. As a result, the gas inside the airtight member and the oxidation reaction electrode side are shared. Alternatively, the pressure inside the airtight member may be reduced by a pressure reducing device, and the resulting exhaust gas may be supplied to the oxidation reaction electrode side. Alternatively, the electrolytic oxygen pump described above may be used as the pressure reducing device, and oxygen in the gas inside the airtight member may be consumed at the reduction reaction electrode of the electrolytic oxygen pump to reduce the pressure by the amount of consumed oxygen, and the resulting reduction reaction electrode side exhaust gas may be supplied to the oxidation reaction electrode of the electrolytic hydrogen pump.

[0050] 3.External gas supply process for airtight material In this step, a voltage is applied between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump, and the inside of the airtight member is pressurized with a hydrogen-containing gas while the gas near the outer surface of the airtight member is supplied to the oxidation reaction electrode of the electrolytic hydrogen pump. Hydrogen generated on the reduction reaction electrode side of the electrolytic hydrogen pump can be used as the hydrogen supplied to the inside of the airtight member. This step is performed when the inside of the airtight member is pressurized to test for the presence or absence of a leak. When the inside of the airtight member is depressurized to test for the presence or absence of a leak, this step is not performed, and instead, step 2 described above is performed.

[0051] The voltage to be applied between the oxidation reaction electrode and the reduction reaction electrode is preferably 1.5 V or more, as in the above-mentioned Step 1. There is no particular upper limit to the voltage, but as in the above-mentioned Step 1, it is preferably 100 V or less, more preferably 50 V or less, and even more preferably 20 V or less.

[0052] As a method for supplying the gas near the outer surface of the airtight member to the oxidation reaction electrode, for example, a pressure reducing device may be used to suck in the gas near the outer surface of the airtight member and supply the exhaust gas to the oxidation reaction electrode side. As described above, an electrolytic oxygen pump may be used as such a pressure reducing device, and the exhaust gas from the reduction reaction electrode side may be supplied to the oxidation reaction electrode of the electrolytic oxygen pump. The gas near the outer surface of the airtight member is sucked in locally and evenly from the outer surface of the airtight member in order to detect leaks.

[0053] 4. Voltage / current measurement process In this step, the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump is measured, or both the voltage and the current may be measured. When hydrogen is not being supplied to the airtight member, the hydrogen concentration in the atmosphere is typically very low and constant at 0.5 ppm. Therefore, it is thought that the applied voltage is measured as is as the voltage between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump, and the measured current value is thought to be constant.

[0054] On the other hand, as will be described later, if hydrogen is supplied to the airtight member and a crack or the like is present in the airtight member, hydrogen will be supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, and changes in voltage and current will be observed.

[0055] 5. Hydrogen spraying process onto airtight components In this step, a gas containing hydrogen generated at the reduction reaction electrode of the electrolytic hydrogen pump is sprayed onto the outer surface of the airtight member. This step is performed when the inside of the airtight member is depressurized to test for the presence or absence of a leak. When the inside of the airtight member is pressurized to test for the presence or absence of a leak, this step is not performed, and instead, step 6 described below is performed.

[0056] If the amount of hydrogen generated by the electrolytic hydrogen pump is sufficient, the hydrogen can be pressurized or pumped and sprayed evenly and locally onto the outer surface of the airtight member. However, since using hydrogen alone may pose an explosion risk, it is preferable to use hydrogen mixed with an inert gas. The hydrogen content in such a mixed gas can be, for example, approximately 1 v / v% or more and 10 v / v% or less, as described above, with approximately 5±1 v / v% being preferred. Furthermore, if the amount of hydrogen generated by the electrolytic hydrogen pump is insufficient, additional hydrogen can be added. Even in this case, the hydrogen generated by the electrolytic hydrogen pump can be used, thereby reducing implementation costs. The amount of hydrogen generated by the electrolytic hydrogen pump can be adjusted by the voltage applied between the electrodes.

[0057] The amount of hydrogen sprayed onto the outer surface of the airtight member may be adjusted as needed to allow leak detection, and may be set to, for example, 1 mL / min or more and 1000 mL / min or less. A flow rate of 1 mL / min or more may enable more reliable detection of leaks in the airtight member under test. On the other hand, a flow rate of 1000 mL / min or less is sufficient for detecting minute cracks that cannot be detected visually. The flow rate is preferably 10 mL / min or more and 100 mL / min or less.

[0058] The hydrogen-containing gas is sprayed evenly and locally onto the outer surface of the airtight member to be inspected. If a crack or the like is present in the airtight member to be inspected, the hydrogen contained in the hydrogen-containing gas is drawn into the interior through the crack and is eventually supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, where it reacts.

[0059] In step 2, the gas inside the airtight member is supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, and in this step, a hydrogen-containing gas is sprayed onto the outer surface of the airtight member, while in step 4, the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump is measured. If a crack or the like is present in the airtight member under test, hydrogen will penetrate through the crack into the airtight member under test and be supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, where it will react. As a result, electrons equivalent to the amount of hydrogen reacted will be generated from the oxidation reaction electrode, causing changes in the voltage and current between the oxidation reaction electrode and the reduction reaction electrode. In other words, these changes in voltage and / or current make it possible to detect leaks in the airtight member under test.

[0060] 6. Hydrogen pressurization process inside the airtight material In this step, the inside of the airtight member is pressurized with a gas containing hydrogen generated at the reduction reaction electrode of the electrolytic hydrogen pump. Note that, when the inside of the airtight member is depressurized to test for the presence or absence of a leak, this step is not performed, and instead, step 5 described above is performed.

[0061] The gas used to pressurize the inside of the test airtight member may be hydrogen alone. The higher the hydrogen concentration of the gas, the more sensitive the leak detection. However, since the use of high-concentration hydrogen can be dangerous, as mentioned above, the hydrogen concentration of the hydrogen-containing gas used can be approximately 1 v / v% or more and 10 v / v% or less, and preferably approximately 5±1 v / v%. Furthermore, if the amount of hydrogen generated by the electrolytic hydrogen pump is insufficient, hydrogen may be added separately.

[0062] The pressure inside the airtight member may be adjusted as appropriate within a range in which leaks can be detected, and can be, for example, about 0.1 MPa or more and 1 MPa or less. If the pressure is 0.1 MPa or more, it may be possible to more reliably detect leaks in the airtight member under test. On the other hand, a pressure of 1 MPa or less is sufficient to detect minute cracks that cannot be detected visually. The pressure is preferably 0.11 MPa or more and 0.5 MPa or less.

[0063] In this step, the inside of the airtight member under test is pressurized with a hydrogen-containing gas, and in step 3, gas near the outer surface of the airtight member is supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, while in step 4, the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump is measured. If a crack or the like is present in the airtight member under test, hydrogen leaking from the inside is absorbed and supplied to the oxidation reaction electrode of the electrolytic hydrogen pump, and the oxidation reaction electrode generates electrons equivalent to the amount of hydrogen reacted, causing changes in the voltage and current between the oxidation reaction electrode and the reduction reaction electrode. In other words, these changes in voltage and / or current make it possible to detect leaks in the airtight member under test. [Example]

[0064] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the invention by making appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention.

[0065] Example 1 (1) Assembly of the electrolytic hydrogen pump system As shown in Figure 6, both sides of an anion exchange membrane (ASE-5142, manufactured by ASTM) are connected to porous nickel plates (Celmet) as reduction reaction electrodes. (R) " manufactured by Sumitomo Electric Industries, Ltd.) and platinum black-supported carbon paper with a diffusion layer ("TGP-H-60" by Chemix, platinum black loading: 1 mg / cm) as the oxidation reaction electrode. 2 The cell was sandwiched between two plates, and both sides of the cell were sealed with resin plates using gaskets to keep the cell airtight. The electrode area of ​​this cell was 1 cm 2 It was. Using the cell, an electrolytic hydrogen pump system was assembled as shown in Figure 7. A diaphragm pump ("Handy Pump DSC-2F-12W" manufactured by Denso Sangyo Co., Ltd.) was used as the pump, and the cell voltage and cell current were measured and recorded using a data logger ("GK240" manufactured by GRAPHTECH Co., Ltd.).

[0066] (2) Preliminary experiment Approximately 40 mL of hydrogen is placed in the 50 mL container shown in Figure 7, and a voltage V of 3.0 V is applied between the oxidation reaction electrode and reduction reaction electrode. cur The electrolytic hydrogen pump was operated by applying a voltage of 0.01V. The measured current and the electromotive force (V) of the hydrogen detector (fuel cell) were app ) and the oxygen concentration in the circulating gas are shown in Figure 8. As shown in Figure 8, the hydrogen concentration gradually decreased, then decreased sharply after 30 minutes. The current decreased faster than the hydrogen concentration and reached a steady state after 30 minutes. Conversely, the oxygen concentration gradually increased, then increased sharply after 30 minutes. This indicates that the presence of hydrogen in the test airtight member can be detected as a change in current value using the electrolytic hydrogen pump system according to the present invention. Furthermore, as shown in Figure 8, when hydrogen disappeared from the test airtight member, the change in current value was suppressed. In this experiment, changes in the hydrogen concentration and other factors were measured only in the gas on the oxidation reaction electrode side of the electrolytic hydrogen pump system from the container, but in reality, the hydrogen generated on the reduction reaction electrode side can be used to detect leaks in the airtight member under test. Furthermore, the increase in oxygen concentration accompanying the rapid decrease in hydrogen in the circulating gas is thought to be due to the fact that the hydrogen in the airtight member was consumed, and a reaction in which oxygen was generated from hydroxide ions and / or water occurred at the oxidation reaction electrode instead of the oxidation reaction of hydrogen. However, because the oxygen generation reaction is more difficult to occur than the oxidation reaction of hydrogen, the current, which is an indicator of the reaction, is kept lower in the absence of hydrogen than in the presence of hydrogen at a constant voltage of 3.0 V.

Claims

1. The electrochemical device includes an oxidation reaction electrode, an ion exchange membrane, a reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution, the ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, the voltage application device applies a positive voltage to the oxidation reaction electrode and a negative voltage to the reduction reaction electrode; At least a part of the reduction reaction electrode is in contact with the electrolytic aqueous solution, A leak detector characterized in that an electric charge that moves between the oxidation reaction electrode and the reduction reaction electrode due to an electrochemical oxidation reaction of hydrogen to be detected at the oxidation reaction electrode is measured as a current.

2. 2. The leak detector according to claim 1, wherein the ion exchange membrane is an anion exchange membrane, and the aqueous electrolyte solution is an alkaline aqueous electrolyte solution.

3. 3. The leak detector according to claim 1, wherein the oxidation reaction electrode contains a platinum catalyst.

4. 4. The leak detector according to claim 1, further comprising a mixer for mixing the hydrogen generated from the reduction reaction electrode with an inert gas.

5. 1. A method for detecting a leak in an airtight member, comprising: supplying the gas inside the gas-tight member to the oxidation reaction electrode of the electrolytic hydrogen pump while applying a positive voltage to the oxidation reaction electrode and a negative voltage to the reduction reaction electrode of the electrolytic hydrogen pump; measuring the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump; and a step of spraying a hydrogen-containing gas generated at the reduction reaction electrode of the electrolytic hydrogen pump onto an outer surface of the gas-tight member, the electrolytic hydrogen pump includes the oxidation reaction electrode, the ion exchange membrane, the reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution; the ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, the voltage application device applies a voltage between the oxidation reaction electrode and the reduction reaction electrode, The method, characterized in that at least a portion of the reduction reaction electrode is in contact with the aqueous electrolytic solution.

6. 1. A method for detecting a leak in an airtight member, comprising: supplying gas near the outer surface of the gas-tight member to the oxidation reaction electrode of the electrolytic hydrogen pump while applying a positive voltage to the oxidation reaction electrode and a negative voltage to the reduction reaction electrode of the electrolytic hydrogen pump; measuring the voltage or current between the oxidation reaction electrode and the reduction reaction electrode of the electrolytic hydrogen pump; and pressurizing the inside of the gas-tight member with a gas containing hydrogen generated at the reduction reaction electrode of the electrolytic hydrogen pump; the electrolytic hydrogen pump includes the oxidation reaction electrode, the ion exchange membrane, the reduction reaction electrode, a voltage application device, and an aqueous electrolytic solution; the ion exchange membrane is sandwiched between the oxidation reaction electrode and the reduction reaction electrode, the voltage application device applies a voltage between the oxidation reaction electrode and the reduction reaction electrode, The method, characterized in that at least a portion of the reduction reaction electrode is in contact with the aqueous electrolytic solution.

7. The method according to claim 5 or 6, wherein the voltage between the oxidation reaction electrode and the reduction reaction electrode is greater than 1.229 V.

8. 8. The method according to claim 5, wherein an electrolytic oxygen pump is used to extract the gas from the inside of the airtight member.

9. 9. The method according to claim 5, wherein an anion exchange membrane is used as the ion exchange membrane, and an alkaline electrolytic solution is used as the electrolytic solution.

10. The method according to any one of claims 5 to 9, wherein the oxidation reaction electrode contains a platinum catalyst.

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