JP2018065073A - Diluted hydrogen gas generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for producing diluted hydrogen gas used as inspection gas for leakage inspection which suppresses use of a high pressure gas cylinder as much as possible, minimizes disadvantage by use of the gas cylinder, and can reduce a running cost.SOLUTION: A diluted hydrogen gas production device includes: a mixture tank to which hydrogen gas and dilution gas are introduced to produce diluted hydrogen gas obtained by diluting hydrogen; a hydrogen generator which decomposes water to produce hydrogen gas; a dilution gas supply source which supplies the dilution gas; a hydrogen gas supply flow path which guides the hydrogen gas toward the mixture tank from the hydrogen generator; a dilution gas supply flow path which guides the dilution gas toward the mixture tank from the dilution gas supply source; and gas flow rate ratio control means for controlling a ratio of a hydrogen gas flow rate guided into the mixture tank through the hydrogen gas supply path to the dilution gas flow rate guided toward the mixture tank from the dilution gas supply source.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for generating diluted hydrogen gas obtained by diluting hydrogen gas, which is used as, for example, an inspection gas in a leak inspection (leak test).

  Sufficient airtightness is often required for hollow parts containing various gases and liquids or piping for transferring gases and liquids. Therefore, these parts and piping are usually inspected to check whether leakage occurs at the final stage of the manufacturing process, the shipping stage, or the stage before use. In this type of leakage inspection, inspection gas is generally introduced into an inspection object (work), and the presence or absence of leakage of the inspection gas is detected by a gas detection device outside the inspection object.

Generally, helium (He) gas is used as such a gas for leak inspection. However, it is not necessary to use expensive 100% helium gas, and therefore, generally diluted gas such as air is mixed with high-concentration helium gas to dilute the helium gas concentration to a predetermined low concentration. Is generally used as a gas for leak inspection.
As such a gas generator for leakage inspection, for example, a gas mixing device for diluting by mixing air with high-concentration helium gas, for example, the one shown in FIG.

  The gas mixing apparatus proposed in Patent Document 1 shown in FIG. 4 basically introduces a high-concentration helium gas into the mixing tank 11 via the helium gas delivery pipe 12 and the dilution gas via the air delivery pipe 13. As a result, the inspection gas mixed in the mixing tank 11 (low-concentration helium gas diluted with air) is sent to a leak inspection apparatus (not shown) through the open / close valve 15a and the inspection gas delivery pipe 15. It is configured. A decompression valve 12c, a helium gas flow rate sensor 16, a helium gas flow rate adjustment valve 12b, and an opening / closing valve 12a are inserted into the helium gas delivery pipe 12 from the helium gas supply device 12d at the upstream end toward the mixing tank 11. ing. In addition, a pressure reducing valve 13c, an air flow rate sensor 18, an air flow rate adjusting valve 13b, and an opening / closing valve 13a are inserted into the air delivery pipe 13 from the upstream air supply device 13d toward the mixing tank 11. A pressure gauge 14 is connected to the mixing tank 11, and the open / close valves 12 a and 13 a are sequencers according to signals from the pressure gauge 14 and signals from the helium gas integrating meter 16 a and air integrating meter 18 a described below. Opening and closing control is performed by 17.

  A helium gas integrator 16 a is connected to the helium gas flow sensor 16 to calculate an integrated flow of helium gas per unit time passing through the helium gas delivery pipe 12, and an air integrator 18 The integrated flow rate of air per unit time passing through the air delivery pipe 13 is calculated.

  In such a gas mixing apparatus shown in FIG. 4, a pressure signal indicating the pressure in the mixing tank 11 from the pressure gauge 14 provided to the sequencer 17, and a helium gas delivery pipe provided from the helium gas integrator 16a. By opening and closing the open / close valves 12a and 13a by a signal of the integrated helium gas flow per unit time at 12 and a signal of the integrated air flow per unit time in the air delivery pipe 13 provided from the air integrator 18a. The amount of helium gas and the amount of air introduced into the mixing tank 11 are respectively controlled, and a test gas having a required helium gas concentration is mixed and generated in the mixing tank 11, and the inspection gas in the mixing tank 11 is also generated. Is controlled to a pressure above a certain level.

  The outline of a specific control method in the apparatus shown in FIG. 4 can be read as follows.

  When it is detected that the test gas in the mixing tank 11 has decreased and the pressure in the mixing tank 11 has fallen below a predetermined threshold, the sequencer 17 opens and closes the open / close valves 12a, 13a is opened simultaneously or with a time difference, and high-concentration helium gas and air are introduced into the mixing tank 11. At this time, the instantaneous flow rate of helium gas and the instantaneous flow rate of air passing through the delivery pipes 12 and 13 are measured by the flow rate sensors 16 and 18, and the instantaneous flow rates are integrated by the integrators 16a and 18a. Here, the amount of helium gas flowing into the mixing tank 11 is calculated by the product of the helium gas integrated flow rate per short time obtained by the accumulator 16a and the time during which the on-off valve 12a is open. On the other hand, the amount of air flowing into the mixing tank 11 is calculated by the product of the accumulated air flow per short time obtained by the accumulator 18a and the time during which the on-off valve 13a is opened. Therefore, after opening the on-off valves 12a and 13a, the pressure in the tank becomes a certain value or more, and the inflow amount of helium gas and the inflow amount of air into the mixing tank 11 obtained by the above calculation are determined in advance. When the mixture ratio is reached, the sequencer 17 closes the open / close valves 12a and 13a individually (not necessarily simultaneously).

As described above, in the gas mixing apparatus of FIG. 4, the mixing ratio of helium gas and air in the mixing tank 11 is calculated from the product of the integrated flow rate per unit time and the supply time. Control is based on the ratio of the actual inflow of air.
Here, in the gas mixing apparatus of FIG. 4, the helium gas delivery pipe 12 is provided with a helium gas flow rate adjustment valve 12b, and the air delivery pipe 13 is provided with an air flow rate regulation valve 13b. It is understood that the regulating valves 12b and 13b are not involved in the final control of the mixing ratio. Of course, it is conceivable to preliminarily set the opening degrees of these flow rate adjusting valves 12b and 13b so as to correspond to the mixing ratio to be obtained, but this is only a preliminary setting, and the final It is understood that the mixing ratio is controlled by the amount of helium gas and air actually flowing into the mixing tank 11 as described above.

  In Patent Document 1, a specific example of the helium gas supply device 12d in FIG. 4 is not described, but in practice, a helium gas cylinder in which high-concentration helium gas is stored at a high pressure must be used. . That is, in a general factory or the like, helium gas is usually not ready to be supplied to any site by permanent piping. Therefore, a helium gas cylinder must be used as the helium gas supply device 12d.

Japanese Patent No. 4329921

As described above, when a cylinder is used as a helium gas supply source, there are the following problems.
That is, if the cylinder is empty, it is necessary to interrupt the inspection and replace the cylinder with a new one. However, this type of cylinder is heavy and requires a lot of labor and time for its transportation and installation. Of course, in practice, multiple cylinders are prepared at the leak inspection site, and when one cylinder is empty, it is often switched to another cylinder, but even in that case, the cylinder is transported and installed at the leak inspection site. The same problem has to do.
In addition, when a cylinder is used as a helium gas supply source in this way, the leak inspection involves not only the site where the leak inspection is performed but also the location where the cylinder is stored. It is also necessary to manage the cylinders at remote cylinder storage locations, so the labor and labor for management cannot be ignored.

  Further, in the apparatus of Patent Document 1 shown in FIG. 4, after the internal pressure of the mixing tank decreases and the on-off valves 12a and 13a are opened, the internal pressure of the tank becomes a certain value or more, When the inflow amount of helium gas and the inflow amount of air into the mixing tank 11 obtained by calculating the product with each supply continuation time becomes a predetermined mixing ratio, the sequencer 17 opens the opening / closing valves 12a and 13a. It is supposed to be closed individually. However, in this case, in practice, there is a concern that a phenomenon that the mixing ratio deviates from the target ratio, that is, so-called overshoot occurs.

On the other hand, recently, a leak inspection apparatus using a relatively inexpensive hydrogen gas instead of expensive helium gas as a gas for leak inspection has been developed.
In this case, the high concentration hydrogen gas is not used for the leak inspection as it is, but the hydrogen gas diluted to a low concentration with the dilution gas (diluted hydrogen gas) is used as the inspection gas. In this case, it is desirable to use a gas inert to hydrogen gas, for example, nitrogen gas, as the dilution gas.

  Here, when the helium gas supply device 12d in the apparatus of Patent Document 1 shown in FIG. 4 is changed to a hydrogen gas supply device, a hydrogen gas cylinder storing nitrogen gas at high pressure is generally used as the hydrogen gas supply device. Therefore, the problem caused by using the cylinder as described above cannot be solved. Furthermore, when nitrogen gas is used as the hydrogen gas dilution gas, it is usual to use a nitrogen gas cylinder instead of the air supply device 13d in the gas mixing apparatus shown in FIG. As the number and types of the cylinders increase, the problems caused by the use of the above-mentioned cylinders become conspicuous.

  In addition, hydrogen gas is relatively inexpensive as compared with helium gas, but it requires considerable cost as long as it is purchased from a gas manufacturer as a high-pressure cylinder. Therefore, even if relatively hydrogen gas is used instead of expensive helium gas, the running cost of the leak inspection cannot be significantly reduced, which is the bottleneck of drastically reducing the running cost of the leak inspection. It was the actual situation.

  The present invention has been made against the background described above. For example, as an apparatus for generating diluted hydrogen gas used as an inspection gas in a leak inspection, the use of a high-pressure gas cylinder as a gas supply source is suppressed as much as possible. A diluted hydrogen gas generator that minimizes the disadvantages of using gas cylinders and at the same time reduces running costs and prevents the gas mixture ratio from deviating from the target (overshoot). The issue is to provide.

In order to solve the above-described problems, in the diluted hydrogen gas generation apparatus of the present invention, a hydrogen generator that generates hydrogen by the decomposition of water is used as a hydrogen gas supply source without using a hydrogen gas cylinder. We decided to reduce costs. Further, the mixing ratio (hydrogen concentration of diluted hydrogen gas) in the mixing tank is calculated as the product of the integrated flow rate and the supply duration in each gas supply channel as in the technique of Patent Document 1. Instead of controlling by the ratio of the actual inflow amount of each gas, it is controlled by the ratio of the flow rate of each gas in the supply flow path, thereby improving the controllability of the mixing ratio and preventing overshooting. I made it.
Specifically, each aspect of the present invention is as follows (1) to (5).

(1) a mixing tank for generating diluted hydrogen gas in which hydrogen gas and dilution gas are introduced to dilute hydrogen;
A hydrogen generator that decomposes water to generate hydrogen gas;
A dilution gas supply source for supplying the dilution gas;
A hydrogen gas supply flow path for introducing hydrogen gas from the hydrogen generator toward the mixing tank;
A dilution gas supply flow path for introducing the dilution gas from the dilution gas supply source toward the mixing tank;
A gas flow rate ratio control means for controlling a ratio of a hydrogen gas flow rate guided to the mixing tank through the hydrogen gas supply path and a dilution gas flow rate guided from the dilution gas supply source toward the mixing tank; A diluted hydrogen gas generator characterized by comprising:

(2) The dilution gas supply source includes a nitrogen separation device that separates and extracts nitrogen from air, and the nitrogen gas separated by the nitrogen separation device is used as the dilution gas. The diluted hydrogen gas generating device according to (1), wherein the diluted hydrogen gas generating device is guided toward the mixing tank through the dilution gas supply flow path.

(3) The gas flow rate ratio control means includes a first mass flow controller provided in the hydrogen gas supply flow path and a second mass flow controller provided in the dilution gas supply flow path. The diluted hydrogen gas generating device according to any one of (1) and (2), wherein

(4) The gas flow rate ratio control means includes a first sonic nozzle provided in the hydrogen gas supply channel and a second sonic nozzle provided in the dilution gas supply channel. In either of the position upstream of the first sonic nozzle in the hydrogen gas supply flow path and the position upstream of the second sonic nozzle in the dilution gas supply flow path, the linear movement A regulator is inserted, and an external pilot regulator is inserted on the other side. The pressure on the outlet side of the direct acting regulator is applied as a pilot pressure to the external pilot regulator. The diluted hydrogen gas generator according to any one of (1) and (2).

(5) The diluted hydrogen gas generating apparatus according to any one of (1) to (4), wherein the generated diluted hydrogen gas is an apparatus that uses the generated diluted hydrogen gas as an inspection gas for leak inspection. .

  According to the present invention, for example, as an apparatus for generating diluted hydrogen gas used as an inspection gas in a leak inspection, the use of a high-pressure gas cylinder as a gas supply source is suppressed as much as possible, and the disadvantage caused by using the gas cylinder is reduced. At the same time, the running cost can be reduced, and the controllability of the mixing ratio (hydrogen dilution) can be improved to suppress the occurrence of overshoot.

It is a block diagram which shows the dilution hydrogen gas production | generation apparatus of the 1st Embodiment of this invention. 1 is a schematic diagram showing in principle an example of a mass flow controller used in the first embodiment. It is a block diagram which shows the dilution hydrogen gas production | generation apparatus of the 2nd Embodiment of this invention. It is a block diagram which shows an example of the gas mixing apparatus for the gas production | generation for the leak test | inspection conventionally proposed.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a diluted hydrogen gas generation apparatus according to a first embodiment of the present invention. The first embodiment shows an example in which leakage inspection gas is generated by diluting high-concentration hydrogen gas with nitrogen gas.

  In FIG. 1, a mixing tank 21 is supplied with high-concentration hydrogen gas via a hydrogen gas supply flow path 22 and passes through a nitrogen gas supply flow path 23 as a dilution gas supply flow path and serves as a dilution gas. Nitrogen gas is introduced and mixed with high-concentration hydrogen gas and nitrogen gas (that is, the high-concentration hydrogen gas is diluted with nitrogen gas), and the mixed gas, that is, the low-concentration hydrogen gas diluted with nitrogen gas is supplied to the open / close valve 24. And it is set as the structure sent out to the leak inspection apparatus which is not shown in figure through the gas delivery pipe | tube 25 for a test | inspection. In the following, the high-concentration hydrogen gas is simply referred to as hydrogen gas.

  In the hydrogen gas supply flow path 22, a pressure reducing valve 27 </ b> A, a hydrogen gas mass flow controller (first mass flow controller) 28 </ b> A, and a hydrogen gas open / close valve 29 </ b> A are directed from the upstream hydrogen generator 26 to the mixing tank 21. They are inserted in that order. On the other hand, in the nitrogen gas supply channel 23, a pressure reducing valve 27 </ b> B, a nitrogen gas separation membrane module 31, a nitrogen gas mass flow controller (second mass flow controller) are directed from the air pump 30 at the upstream end toward the mixing tank 21. 28B and a nitrogen gas opening / closing valve 29B are inserted in that order.

  A pressure gauge 32 is connected to the mixing tank 21 so that the pressure in the mixing tank 11 is constantly measured. The output of the pressure gauge 32 (mixing tank pressure detection signal) is sent to the sequencer 33. The sequencer 33 is for opening / closing control of the opening / closing valves 29A, 29B in accordance with the mixing tank pressure detection signal.

  In such a first embodiment, an air pump 30 for taking in air from outside and pumping it and a membrane module 31 as a nitrogen separation device for separating nitrogen gas from air supply dilution gas. The dilution gas supply source 35 is configured. That is, as a dilution gas supply source, air is taken in the atmosphere without using a nitrogen gas cylinder, and nitrogen gas separated from the air is used as the dilution gas.

  In the first embodiment, the mass flow controllers 28A and 28B inserted in the hydrogen gas supply channel 22 and the nitrogen gas supply channel 23 measure the mass flow rate of the fluid (hydrogen gas or nitrogen gas in this embodiment). Thus, the flow rate control is performed instantaneously, and the hydrogen gas flow rate guided to the mixing tank 21 via the hydrogen gas supply flow path 22 and the dilution gas flow rate guided to the mixing tank 21 from the dilution gas supply source 35 The gas flow rate ratio control means 36 for controlling the ratio is configured.

  As the mass flow controllers 28A and 28B, general commercially available ones can be used. An example of a typical mass flow controller is shown in FIG. 2 in principle, and an outline thereof will be described below.

  The mass flow controller basically diverts the flow path 51 into a sensor-side flow path 51a and a bypass flow path 51b made of capillaries, and has a flow rate downstream of the junction 51c of the flow paths 51a and 51b. The control valve 52 is provided, the mass flow rate of the fluid passing through the sensor side flow path 51a is measured by the flow rate sensor 53, and the opening degree of the flow rate control valve 52 is controlled based on the measurement result. Specifically, the resistors 54a and 54b are wound around the upstream side and the downstream side of the sensor side channel 51a, respectively, and the resistors 54a and 54b are incorporated in the bridge circuit 55 to form the flow rate sensor 53. Then, the output of the bridge circuit 55 is amplified by the amplifier circuit 56, supplied to the comparison control circuit 58 through the correction circuit 57 as the flow measurement signal S1, and the flow measurement signal S1 is compared with the flow setting signal S2 from the outside. Then, the difference signal S3 is given to the valve drive circuit 59 to drive the solenoid-type or piezo-type valve actuator 60 to control the opening degree of the flow control valve 52.

  Here, when the fluid passes through the sensor-side channel 51a, a temperature difference occurs between the upstream and downstream resistors 54a and 54b, and the temperature difference causes a difference in electrical resistance between the resistors 54a and 54b. The flow rate measurement signal S1 corresponding to the mass flow rate of the fluid passing through the sensor side flow channel 51a is obtained by the difference output, and the mass flow rate of the fluid flowing through the flow channel 51 is set by the flow rate setting signal S2. The flow rate can be controlled immediately and accurately by the flow rate control valve 58 so that the flow rate becomes the same.

  In the first embodiment shown in FIG. 1, such mass flow controllers are provided as hydrogen gas and nitrogen gas mass flow controllers 28A and 28B in the hydrogen gas supply channel 22 and the nitrogen gas supply channel 23, respectively. By setting each flow rate, the ratio of the flow rate of the hydrogen gas flowing through the hydrogen gas supply channel 22 and the flow rate of the nitrogen gas flowing through the nitrogen gas supply channel 23 can be controlled.

  Next, the overall function of the first embodiment shown in FIG. 1 will be described.

  The hydrogen concentration of the diluted hydrogen gas used as the inspection gas in the leak inspection apparatus (not shown) from the mixing tank 21 is determined in advance. The hydrogen concentration in the leak test gas is not particularly limited, and can be appropriately selected according to the mode of the leak test, the shape of the inspection object, or the leak gas detection accuracy, but generally 1% to 20%. Is preferably within the range of 1 to 5%. If the inspection object is directly inspected in the external space without placing the inspection object in the vacuum chamber, if there is a leak, the leaked hydrogen will be released directly into the atmosphere. The hydrogen concentration of the working gas is desirably a relatively low concentration, for example, 5% or less for safety. In the following description, a representative example will be described assuming that diluted hydrogen gas having a hydrogen concentration of 5% is generated.

  In the apparatus of the first embodiment shown in FIG. 1, a hydrogen gas mass flow controller (first mass flow controller) 28 </ b> A and a nitrogen gas mass flow controller (second mass flow controller) 28 </ b> B are respectively supplied to the outlet flow rates. However, it is set so that the mixing ratio (for example, 5:95) of the inspection gas is obtained.

  At the time of leak inspection, the inspection gas (gas diluted with nitrogen so that the hydrogen concentration becomes 5%) contained in the mixing tank 21 is leaked through the open / close valve 24 and the inspection gas delivery pipe 25 (not shown). Continuously supplied to the device. Meanwhile, the pressure in the mixing tank 21 is measured by the pressure gauge 32, and the pressure measurement signal is sent to the sequencer 33. When the pressure in the mixing tank 21 drops below a predetermined pressure, the open / close valves 29A and 29B are opened, and hydrogen gas is supplied to the mixing tank 21 via the hydrogen gas supply flow path 22 by the supply operation described below. While being introduced, nitrogen gas is introduced into the mixing tank 21 through the nitrogen gas supply channel 23.

  At the upstream end of the hydrogen gas supply channel 22, water (purified water or pure water) is decomposed by the hydrogen generator 26, hydrogen gas is taken in, and introduced into the hydrogen gas mass flow controller 28A via the pressure reducing valve 27A. The Then, hydrogen gas flows out at a flow rate preset in the hydrogen gas mass flow controller 28A and is fed into the mixing tank 21 via the on-off valve 29A.

  On the other hand, at the upstream end of the nitrogen gas supply passage 23, air is taken in from the outside by the air pump 30, and the air is sent to the nitrogen gas separation membrane module 31 through the pressure reducing valve 27B, so that the nitrogen gas is separated from the air. Is done. The separated nitrogen gas is introduced into the nitrogen gas mass flow controller 28B. Then, nitrogen gas flows out at a flow rate preset in the nitrogen gas mass flow controller 28B, and is fed into the mixing tank 21 via the on-off valve 29B.

Accordingly, hydrogen gas and nitrogen gas are introduced into the mixing tank 21 at a mixing ratio corresponding to the ratio between the flow rate set in the hydrogen gas mass flow controller 28A and the flow rate set in the nitrogen gas mass flow controller 28B. The pressure in 21 rises. When the pressure in the mixing tank 21 detected by the pressure gauge 32 reaches a predetermined pressure, the sequencer 33 closes the on-off valves 29A and 29B, and the supply operation is stopped.
In this way, when the pressure in the mixing tank 21 decreases, hydrogen gas and nitrogen gas are supplied at a predetermined ratio to generate a test gas (diluted hydrogen gas) having a predetermined hydrogen concentration, and subsequently leak. Inspection can be performed.

  In the first embodiment, the hydrogen generator 26 is not particularly limited as long as it is a device that generates hydrogen by electrolyzing high-purity water (purified water), and is not particularly limited. Any device such as a hydrogen generator using a membrane can be used.

  In the first embodiment, the dilution gas supply source 35 uses a membrane module, which is a nitrogen separation device, to separate nitrogen gas from air by a so-called membrane separation method. Alternatively, nitrogen gas may be separated from air by the PSA method (adsorption method) or the like. However, among these, from the viewpoint of cost, it is most advantageous to apply a membrane separation method using a membrane module.

  In the diluted hydrogen gas generating apparatus of the first embodiment as described above, the hydrogen generator 26 that generates hydrogen by the decomposition of water is used as the hydrogen gas supply source, while the dilution gas supply source is a membrane module. Therefore, an expensive gas cylinder storing these gases is unnecessary. Therefore, the running cost of the leak inspection can be reduced. Moreover, since the operation | work which conveys and installs a heavy gas cylinder is unnecessary, the effort and labor for the operation | work are unnecessary. In addition, since there is no need to store a spare gas tank, it is not necessary to store a gas cylinder, and it is not necessary to manage the spare tank at the storage location. Siteization is possible. Furthermore, the entire apparatus can be housed in a single housing to form a single box. In addition, unlike the control method of gas mixture ratio (dilution degree) shown in Patent Document 1 (a method of controlling by the gas flow rate actually flowing into the mixing tank), the gas before the gas flows into the mixing tank. Since the gas mixture ratio (dilution degree) is set and controlled according to the gas flow ratio in each gas supply flow path, the control of the mixture ratio is good and the gas mixture ratio deviates from the target. The possibility that a situation (overshoot) will occur can be reduced.

  FIG. 3 shows a diluted hydrogen gas generation apparatus according to the second embodiment of the present invention. Note that the second embodiment also shows an example in which a high-concentration hydrogen gas is diluted with nitrogen gas to generate a leakage inspection gas, as in the first embodiment.

  In the second embodiment, sonic nozzles 43A and 43B are used as the gas flow rate control means 36 in place of the mass flow controllers 28A and 28B in the first embodiment. Furthermore, in the diluted hydrogen gas generator of the second embodiment, the direct acting regulator 41 and the external pilot regulator 42 are combined in order to equalize the pressure of the gas flowing into the sonic nozzles 43A and 43B.

  That is, in FIG. 3, the hydrogen gas supply flow path 22 includes an external pilot regulator 42 and a hydrogen gas sonic nozzle (first sonic nozzle) 43A between the hydrogen generator 26 and the open / close valve 29A. It is inserted in that order from the upstream side to the downstream side. The nitrogen gas supply channel 23 includes a direct acting regulator 41 and a nitrogen gas sonic nozzle (second sonic nozzle) 43B between the membrane module 31 of the nitrogen gas supply source 35 and the open / close valve 29B. They are inserted in that order from the upstream side to the downstream side. Further, the external pilot regulator 42 of the hydrogen gas supply passage 22 is configured such that the outlet pressure of the direct acting regulator 41 of the nitrogen gas supply passage 23 is applied as a pilot pressure via the branch passage 44.

  Here, the sonic nozzle is a throat if a throat portion with a small inner diameter is provided in the flow path of the nozzle and the ratio of the upstream pressure and the downstream pressure of the gas is kept below the critical pressure ratio. If the flow velocity in the section (minimum diameter section of the nozzle) is fixed at the sonic velocity, and the inflow pressure and the diameter of the throat section are constant, the nozzle can always generate a constant flow rate. With such a sonic nozzle, a predetermined mass flow rate can be obtained with high accuracy. Here, since the downstream flow rate of the sonic nozzle depends on the diameter of the throat portion under a constant inflow side pressure, the throat of the hydrogen gas sonic nozzle 43A inserted in the hydrogen gas supply passage 22 is used. The flow rate of the hydrogen gas introduced into the mixing tank 21 and the flow rate of the nitrogen gas are determined by determining the ratio between the diameter of the portion and the throat portion diameter of the sonic nozzle 43B for nitrogen gas inserted in the nitrogen gas supply channel 23. The ratio can be set.

  However, since the outflow side flow rate is proportional to the inflow side pressure in the sonic nozzle, if the inflow side gas pressure varies, the outflow gas flow rate also varies. Therefore, in the second embodiment, the outlet pressure of the direct acting regulator 41 provided upstream of the nitrogen gas sonic nozzle 43B in the nitrogen gas supply flow path 23 is supplied to the outside of the hydrogen gas supply flow path 22 via the branch flow path 44. By applying a pilot pressure to the pilot regulator 42, the outlet pressures of the regulators 41, 42 are controlled to be equal, and the inlet pressure of the nitrogen gas sonic nozzle 43B and the inlet pressure of the hydrogen gas sonic nozzle 43A are controlled. Are always maintained at the same pressure.

  After all, in the second embodiment shown in FIG. 3, the linear pressure regulator 41 and the external pilot regulator 42 are combined, and the inlet pressure of the sonic nozzle 43A for hydrogen gas and the inlet side of the sonic nozzle 43B for nitrogen gas are combined. The pressure is made equal, and the ratio between the throat portion diameter of the hydrogen gas sonic nozzle 43A and the throat portion diameter of the nitrogen gas sonic nozzle 43B inserted in the nitrogen gas supply channel 23 is set to an appropriate ratio. By doing so, the ratio of the flow rate of the hydrogen gas introduced into the mixing tank 21 and the flow rate of the nitrogen gas is appropriately controlled, whereby the mixing tank 21 mixes the hydrogen gas and nitrogen gas at an appropriate ratio, and the required low Diluted hydrogen gas (inspection gas) having a hydrogen concentration can be generated.

  In FIG. 3, a direct-acting regulator 41 is inserted in the nitrogen gas supply flow path 23 and an external pilot regulator 42 is inserted in the hydrogen gas supply flow path 22, but in some cases, the hydrogen gas supply is reversed. A direct acting regulator 41 may be inserted into the flow path 22, and an external pilot type regulator 42 may be inserted into the nitrogen gas supply flow path 23. In this case, the outlet pressure of the direct acting regulator 41 in the hydrogen gas supply channel 22 may be divided and applied as a pilot pressure to the external pilot regulator 42 in the nitrogen gas supply channel 23.

  Since the flow rate on the outlet side of the sonic nozzle depends on the minimum diameter of the throat part, the outlet side flow rate can be changed by replacing the nozzle with a different throat part diameter. Therefore, if you want to change the mixing ratio of the test gas (dilution of hydrogen gas with nitrogen gas), prepare several nozzles with different throat diameters in advance, and use sonic nozzles with different throat diameters as appropriate. In other words, it is possible to change the outlet flow rate of one or both of the sonic nozzles 43A and 43B, thereby changing the mixing ratio. In this case, it is also possible to change the outlet flow rate by exchanging only the throat part instead of the entire sonic nozzle device.

  In addition, when it is desired to change the mixing ratio of the inspection gas (dilution of hydrogen gas with nitrogen gas), the opening / closing valves 29A and 29B are opened without depending on the replacement of the sonic nozzle or the throat portion as described above. It is also possible to change the mixing ratio by changing the time.

Similarly to the diluted hydrogen gas generator of the first embodiment, the diluted hydrogen gas generator of the second embodiment does not require a hydrogen gas cylinder and a nitrogen gas cylinder. It can be reduced, and the work of transporting and installing heavy gas cylinders is not required, and storage and management of gas cylinders is also unnecessary, enabling on-site leak inspection, and the entire system Can be made into one box. Furthermore, as in the first embodiment, the controllability of the mixture ratio is good, and the possibility of occurrence of a situation (overshoot) in which the gas mixture ratio (hydrogen dilution) deviates from the target is reduced. Can do.
In the case of the device of Patent Document 1 shown in FIG. 4, in actual control, when the pressure is higher than a certain value after the supply into the mixing tank is started, the opening / closing valve is immediately closed. However, in the case of the second embodiment of the present invention shown in FIG. 3, compared with the apparatus of FIG. 4, there is a concern that the pressure in the tank becomes excessively high. Therefore, there is little possibility that a situation in which the pressure of the mixing tank becomes excessively high will occur.

In each of the first and second embodiments described above, nitrogen gas is used as the dilution gas. However, depending on the case, it may adversely affect the object to be inspected and may cause a hydrogen explosion. As long as it is a gas capable of diluting hydrogen without using any gas, it is allowed to use a gas other than nitrogen gas, for example, an inert gas such as Ar gas, CO ₂ gas or the like as a dilution gas.

When an inert gas, CO ₂ gas, or the like is used as the dilution gas in this way, the dilution gas supply source is the nitrogen separation in the first embodiment of FIG. 1 or the second embodiment of FIG. Instead of the membrane module 31 for the purpose, a gas cylinder storing an inert gas or a gas such as CO ₂ gas may be used. In this case as well, since hydrogen gas is generated by the decomposition of water in the hydrogen generator, a hydrogen gas cylinder as a hydrogen gas supply source is not required. Therefore, the type and number of cylinders as a total are different from those of the hydrogen gas supply cylinder. Less than if used. Therefore, labor and time for exchanging the cylinder can be minimized, and the cost of using the cylinder can be reduced.

  Furthermore, when the object (workpiece) for leak inspection is a material that is difficult to oxidize, or when oxidation of the object does not pose a problem, the use of air as the dilution gas is permitted. However, in that case, it is desirable to dilute the hydrogen with air so that the hydrogen concentration is less than 4%, preferably 3% or less. That is, even when air and hydrogen gas are mixed, hydrogen explosion is known to occur when the hydrogen concentration is 4% to 75%. Therefore, the hydrogen concentration is less than 4%, preferably If hydrogen is mixed with air so as to be 3% or less, the risk of hydrogen explosion can be avoided.

  Thus, when air is used as the dilution gas, the nitrogen separation device such as the membrane module 31 in the first embodiment of FIG. 1 or the second embodiment of FIG. 3 can be omitted. Therefore, if air is used as the dilution gas, further cost reduction can be achieved.

  In the above description, the dilute gas (hydrogen-containing mixed gas) obtained by the dilute hydrogen gas generator of the present invention is used as a gas for leak inspection, but the apparatus of the present invention is used for other purposes. Of course, the obtained diluted hydrogen gas may be used.

  The preferred embodiments of the present invention have been described above. However, these embodiments are merely examples within the scope of the gist of the present invention, and the addition of configurations within the scope not departing from the gist of the present invention, Omissions, substitutions, and other changes are possible. That is, the present invention is not limited by the above description, is limited only by the scope of the appended claims, and can be appropriately changed within the scope.

DESCRIPTION OF SYMBOLS 21 ... Mixing tank, 22 ... Hydrogen gas supply flow path, 23 ... Nitrogen gas supply flow path (dilution gas supply flow path), 26 ... Hydrogen generator, 28A ... Hydrogen gas mass flow controller (1st mass flow controller), 28B ... Mass flow controller for nitrogen gas (second mass flow controller), 31 ... Membrane module (nitrogen separator), 35 ... Gas supply source for dilution, 36 ... Gas flow ratio control means, 41 ... Direct acting regulator, 42 ... External pilot regulator, 43A ... hydrogen gas sonic nozzle (first sonic nozzle), 43B ... nitrogen gas sonic nozzle (second sonic nozzle)

Claims (5)

A mixing tank for introducing hydrogen gas and dilution gas to produce diluted hydrogen gas diluted with hydrogen;
A hydrogen generator that decomposes water to generate hydrogen gas;
A dilution gas supply source for supplying the dilution gas;
A hydrogen gas supply flow path for introducing hydrogen gas from the hydrogen generator toward the mixing tank;
A dilution gas supply flow path for introducing the dilution gas from the dilution gas supply source toward the mixing tank;
A gas flow rate ratio control means for controlling a ratio of a hydrogen gas flow rate guided to the mixing tank through the hydrogen gas supply path and a dilution gas flow rate guided from the dilution gas supply source toward the mixing tank; A diluted hydrogen gas generator characterized by comprising:   The dilution gas supply source includes a nitrogen separation device that separates and extracts nitrogen from air, and the nitrogen gas separated by the nitrogen separation device is used as the dilution gas from the predilution gas supply source. The dilute hydrogen gas generator according to claim 1, wherein the diluted hydrogen gas generator is guided toward the mixing tank through a gas supply channel.   The gas flow rate ratio control means includes a first mass flow controller provided in the hydrogen gas supply flow path and a second mass flow controller provided in the dilution gas supply flow path. The diluted hydrogen gas generator according to any one of claims 1 and 2.   The gas flow ratio control means includes a first sonic nozzle provided in the hydrogen gas supply flow path and a second sonic nozzle provided in the dilution gas supply flow path, and hydrogen gas A direct-acting regulator is provided at any one of the position upstream of the first sonic nozzle in the supply flow path and the position upstream of the second sonic nozzle in the dilution gas supply flow path. The external pilot regulator is inserted in the other, and the pressure on the outlet side of the direct acting regulator is applied as a pilot pressure to the external pilot regulator. The diluted hydrogen gas generator according to any one of claims 1 and 2. The diluted hydrogen gas generation apparatus according to any one of claims 1 to 4, wherein the generated diluted hydrogen gas is an apparatus that uses the diluted hydrogen gas as an inspection gas for leak inspection.

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