JP2016176866A - Method and device for leakage inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for the leakage inspection capable of improving accuracy and stability of the measurement by suppressing influences due to heating/cooling accompanied with compression and decompression.SOLUTION: A leakage inspection method determines whether there is a leakage in an object to be measured by executing pressurization introduction of a gas in a predetermined space (a portion of a main line 31, an exhaust pipe 32, a branch pipe 33, a line 34, a bypass pipe 35, a work W, and a small master Mb) including a work W of the inspection object, and then, by sealing the space and measuring a pressure change of the space after sealed. As the gas to be pressurized and introduced, an air which becomes a specifically highly humid or more without causing a dew condensation or a gas which has a specific heat higher than surrounding air and does not cause the dew condensation when pressurized and introduced into the space is used. For example, the air humidified by a humidifier 13 in such a manner that the humidity becomes 80% at the time of pressurization and introduction is supplied to an inspection device main body 6 from an air tank 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a leak inspection method and a leak inspection apparatus for inspecting leakage from a container to be inspected.

  When inspecting the sealing property of a container, a method is generally employed in which a gas such as air is introduced into the container under pressure, and then the container is sealed and a subsequent pressure change is observed.

  Moreover, in order to detect a slight leak, it is necessary to measure a pressure change with high accuracy, and therefore a differential pressure type pressure sensor is used. Specifically, a container (workpiece) to be inspected is connected to one first space of the differential pressure gauge, and a container (master) having no leakage is connected to the other second space. And gas is simultaneously introduced into both the first space and the second space to pressurize to the target pressure, and then the first space and the second space are sealed, respectively, and the difference in pressure drop between the two is measured with a differential pressure gauge. It detects (refer patent document 1).

  FIG. 14 is a diagram showing an outline of the configuration and operation of an inspection apparatus for performing the above-described inspection. In the pressurizing step, pressurized gas is introduced from the air source 100 into the inspection system including the workpiece and the master with the valves 101 to 103 opened and the exhaust valve 104 closed. During the pressurization, the gas present in the inspection system is substantially adiabatically compressed and generates heat. After the pressurization step, the valve 102 and the valve 103 are closed, and the system waits for the pressure in the workpiece and the master to be stable (the heat radiation generated in the pressurization step is completed) (equilibrium step). In the next inspection process, the pressure difference between the workpiece and the master is measured by the differential pressure gauge 105. At this time, if there is a leak in the work, a differential pressure exceeding the reference value occurs. After the inspection, the valve 101 is closed, the valves 102 and 103 are opened, and then the exhaust valve 104 is opened to exhaust the gas in the inspection system to the outside. When inspecting the next workpiece, the workpiece is replaced and the process is repeated from the pressurizing step.

  In the above inspection, since both sides of the differential pressure gauge 105 communicate with each other in the pressurization process and the exhaust process, the pressure difference applied to both sides of the differential pressure gauge 105 is a slight one generated in the inspection process even if the pressure is increased with high pressure. It is. Therefore, it is possible to use a high-precision differential pressure gauge that has a low pressure resistance but can detect a slight pressure difference.

JP 2004-6201 A

  In the leak inspection as described above, when a gas is pressurized and introduced into the workpiece or the master, the gas is adiabatically compressed and generates heat, and when the pressure is reduced after the inspection, the gas is adiabatically expanded and cooled. There is also heat dissipation from the measurement system pipeline. For this reason, there have been problems such as a large temperature change in the measurement system, a decrease in measurement accuracy, and measurement only after waiting for the temperature to stabilize. Further, heat is not only stored, but the ends of each branch including the inside of the differential pressure gauge generate heat and store heat as shown in FIG.

  That is, as shown in FIGS. 14 and 15, when compressed air is sent from the compressed air source 100 to an atmosphere release portion (for example, a replaced workpiece atmosphere release portion, a portion opened to the atmosphere at the end of measurement, etc.). For example, a part that is open to the atmosphere at room temperature at atmospheric pressure is moved by being pushed by the compressed air from the compressed air source 100, and is compressed by being driven to a downstream corner. In the example of FIG. 15, heat is generated at a gray-colored portion (heat accumulation portion), specifically, inside the work or the master, or inside the differential pressure gauge 105 or a place where the dead end is closed by the closed exhaust valve 104.・ Heat storage occurs. The above problem becomes more prominent when the leak inspection is performed by applying a high pressure such as 800 KPa or 1000 KPa.

  Furthermore, when inspecting a large workpiece (a workpiece having a large volume compared to the surface area) with high pressure, the time required to reach a stable state of heat dissipation (a state in which leakage inspection can be performed) (a settling period) However, it took a long time for the volume, and there was a problem that the inspection did not return more than expected. That is, after the pressurization is completed, the temperature of the workpiece suddenly drops due to heat dissipation, but when the temperature drops to some extent, the temperature drop suddenly becomes slow.

  There is also a problem in that it is difficult to accurately inspect the pressure because the pressure fluctuates when attempting to perform a leak inspection immediately after the end of the settling period.

  The present invention is intended to solve the above problems, and provides a leak inspection method and a leak inspection apparatus capable of improving the accuracy and stability of measurement by suppressing the influence of heat generation and cooling accompanying pressurization and decompression. It is intended to provide.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] Leak to determine whether or not there is a leak in the inspection object by sealing the space and measuring the pressure in the space after sealing after introducing gas into a predetermined space including the inspection object In the inspection method,
As the gas, air that does not condense when being introduced into the space without dew condensation, or a gas that has higher specific heat than the surrounding air and does not condense when introduced into the space under pressure is used. A leak inspection method characterized by:

  In the above-mentioned invention and the invention described in [9] below, the specific heat is larger than the predetermined humidity or the surrounding air when the pressure is introduced into the space without causing condensation, or the pressure is introduced into the space. By using a non-condensing gas, the effect of temperature change due to heat insulation change and frictional heat at the time of introducing pressure is reduced. Examples of the gas include high-humidity air that does not condense, a simple substance such as ethylene, methane, and helium, or a mixture of this with air.

[2] The leak inspection method, wherein a gas whose temperature is adjusted to be the same as or substantially the same as an ambient temperature when being pressurized and introduced into the space is used as the gas.

  In the above-mentioned invention and the invention described in [10] below, the gas introduced into the space is gradually approaching the atmospheric temperature and stabilized by heat dissipation or the like, but is the same or substantially the same as the atmospheric temperature at the stage of introduction of the pressure. Since the temperature is adjusted in advance to reach the temperature, the temperature of the gas in the space is stabilized in a short time after the introduction of pressure.

[3] The gas is stored in an air tank at a pressure higher than the target pressure of the space, introduced from the air tank to the space under reduced pressure, and at a humidity at which the gas does not condense in the air tank. The leak inspection method according to [1] or [2], wherein the leak inspection method is stored.

  In the above invention and the invention described in [11] below, the gas is stored in the air tank at a pressure higher than the target pressure of the space, and is introduced into the space from the air tank under reduced pressure. Also, the humidity is adjusted so that no condensation occurs even in the air tank.

[4] The space is a first space and a second space on both sides of the differential pressure sensor that performs the measurement,
The inspection object is included in the second space,
The leak check method according to any one of [1] to [3], wherein the sealing is performed separately for the first space and the second space.

  In the above-described invention and the invention described in [12] below, after pressure-introducing gas into the first space without leakage and the second space including the inspection object, the differential pressure between the first space and the second space is measured. . If there is a leak in the inspection target, the pressure difference between the first space and the second space increases with time.

[5] The leak inspection method according to any one of [1] to [4], wherein the gas is obtained by humidifying and compressing the air.

  In the above-mentioned invention and the invention described in [13] below, the specific heat of air increases as the amount of moisture contained in the air increases, so the specific heat is increased by humidifying the air.

[6] According to any one of [1] to [5], the density, specific heat, and thermal conductivity of the gas introduced under pressure are set to constant values in a plurality of inspections. Leak inspection method.

  In the above invention and the invention described in [14] below, stable measurement is possible regardless of the weather (temperature and atmospheric pressure).

[7] The leak inspection method according to any one of [1] to [6], wherein the gas is obtained by humidifying the heated air and the space is kept warm by a heat insulating material.

  In the above invention and the invention described in [15] below, the absolute humidity of the air can be increased by heating. Moreover, it becomes difficult to condense by insulating the space.

[8] When releasing the high-humidity air from the inspection object to the atmosphere, the air discharged from the inspection object is discharged to the outside from an openable / closable exhaust port provided in the vicinity of the inspection object. The leak inspection method according to any one of [1] to [7].

In the above-described invention and the invention described in [16] below, when high-pressure and high-humidity air is released to the atmosphere, it is rapidly cooled by adiabatic expansion, and diamond dust flutters. The diamond dust is prevented from entering the inspection apparatus main body by discharging the air discharged from the inspection object to the outside through an openable / closable exhaust port such as a valve provided in the vicinity of the inspection object.

[9] a predetermined space including an inspection object;
A gas introduction part for introducing gas under pressure into the space;
A sealing part for sealing the space after the introduction of the pressure;
A pressure sensor for measuring the pressure of the space sealed by the sealing part;
Have
When the gas introduction part is pressurized and introduced into the space as the gas, the air has a higher specific heat than the surrounding air without condensation when it is pressurized and introduced into the space, or the surrounding air is pressurized. A leak inspection apparatus characterized in that a gas that does not condense is introduced into the space under pressure.

[10] The gas introduction unit includes a temperature adjustment unit that adjusts the temperature of the gas so that when the gas is pressurized and introduced into the space, the gas introduction unit has the same or substantially the same temperature as the ambient temperature. The leak inspection apparatus according to [9], wherein the temperature is adjusted.

[11] The gas introduction unit includes an air tank that stores the gas, the gas is stored in the air tank at a pressure higher than a target pressure of the space and humidity that does not condense in the air tank, and the gas is stored in the air tank. The leak inspection apparatus according to [9] or [10], wherein the air tank is introduced into the space after being decompressed.

[12] The gas introduction unit includes a humidifier that humidifies air and a compressor, humidifies and compresses air taken from the surroundings, and stores the compressed air in the air tank. Leak inspection device.

[13] The pressure sensor is a differential pressure sensor,
The space is a first space and a second space on both sides of the differential pressure sensor,
The inspection object is included in the second space,
The leak inspection apparatus according to any one of [9] to [12], wherein the sealing unit individually seals the first space and the second space.

[14] The gas introduction section may set the density, specific heat, and thermal conductivity of the gas before introduction of pressure to constant values in a plurality of inspections. The leak inspection apparatus according to any one of the above.

[15] The gas introduction part further includes a heater, and the gas heated by the heater is humidified to obtain the gas.
The leak inspection apparatus according to any one of [9] to [14], wherein a heat insulating material that keeps the space warm is provided.

[16] When releasing the high-humidity air from the inspection object to the atmosphere, the air discharged from the inspection object is discharged to the outside through an openable and closable exhaust port provided in the vicinity of the inspection object. Any one of [9] to [15] is a leak inspection apparatus.

  According to the leak inspection method and the leak inspection apparatus according to the present invention, the accuracy and stability of measurement are improved by suppressing the influence of heat generation and cooling accompanying pressurization and decompression.

1 is a diagram showing a schematic configuration of a leak inspection apparatus according to a first embodiment of the present invention. It is a figure which shows the state which attached the manual 4-way valve to the workpiece | work W. It is a figure which shows the four opening-closing states which a manual 4-way valve can take. It is a flowchart which shows the procedure of the leak test | inspection performed with the leak test | inspection apparatus concerning 1st Embodiment. It is a figure which shows the 1st space and 2nd space in the leak test | inspection apparatus of FIG. It is a figure which shows the temperature change until predetermined time passes after an air release from the pressurization start. It is a figure which shows the leak inspection apparatus which concerns on 2nd Embodiment. It is a figure which shows the example of the leak test | inspection apparatus which concerns on 3rd Embodiment. It is a figure which shows an example of a Y-shaped residence prevention structure. It is a figure which shows an example of the stay prevention structure which combined Y character type and nozzle type. It is a figure which shows the 1st space in the leak inspection apparatus concerning a 3rd embodiment, the 2nd space, and the 3rd space. It is a flowchart which shows the test | inspection procedure in the leak test | inspection apparatus which concerns on 3rd Embodiment. It is a figure which shows the heat accumulation location which may arise in the leak inspection apparatus which concerns on 3rd Embodiment. It is a figure which shows the conventional leak test process. It is a figure which shows the heat accumulation location produced at the time of pressurization.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a leak inspection apparatus 5 according to the first embodiment of the present invention. The leak inspection apparatus 5 is an apparatus that inspects for leakage of a container (work W) to be inspected.

  The leak inspection apparatus 5 includes a gas introduction unit 10 which is a compressed gas supply source, and an inspection apparatus body 6. The inspection apparatus main body 6 has a main pipe line 31 having one end communicating with the gas introduction unit 10 and the other end provided with a connection port 31a for a work W to be inspected. The main line 31 is provided with an electropneumatic regulator 41, a first pressure sensor 42, a first on-off valve 43, and a second pressure sensor 44 in order from the upstream side where the gas introduction unit 10 is located. The electropneumatic regulator 41 functions to adjust the downstream side so as not to exceed the set pressure.

  An exhaust pipe 32 and a branch pipe 33 are branched from a predetermined location downstream of the second pressure sensor 44 in the main pipeline 31. An exhaust valve 45 is provided in the middle of the exhaust pipe 32, and the end of the exhaust pipe 32 is opened to the atmosphere through an exhaust port 32a. A manual valve 46 is inserted in the main pipeline 31 between the branch point of the exhaust pipe 32 and the connection port 31a.

  The manual valve 46 includes connection ports 1 to 3. The connection port 1 communicates with the aforementioned branching location, and the connection port 2 communicates with the connection port 31a of the workpiece W. The connection port 3 is open to the atmosphere. The manual valve 46 is manually switched between an open state and a closed state. In the open state, the manual valve 46 communicates the connection ports 1 and 2 to block the connection port 3, and in the closed state, the manual valve 46 blocks the connection port 1 and allows the connection ports 2 and 3 to communicate.

  The branch pipe 33 is connected to one connection port of the differential pressure sensor 47. A pipe 34 is connected to the other connection port of the differential pressure sensor 47, and a small master Mb is connected to the end of the pipe 34. The small master Mb is a container that has been confirmed to have a sufficiently small volume and no leakage compared to the workpiece W.

  Further, the inspection apparatus body 6 includes a bypass pipe 35 that bypasses the differential pressure sensor 47 and connects the branch pipe 33 and the pipe line 34. A second on-off valve 48 that switches the bypass pipe 35 between an open state and a closed state is interposed in the middle of the bypass pipe 35.

  A work W and a master M are connected to the connection port 31a via a manual four-way valve 50. Here, the workpiece W and the master M are attached to and detached from the connection port 31a together with the manual four-way valve 50.

  The first on-off valve 43, the second on-off valve 48, and the exhaust valve 45 employ air operated valves (spring return single-acting type) instead of solenoid valves in order to avoid heat generation of the coils. The exhaust valve 45 and the second on-off valve 48 are normally open types that are closed when driven and open when not driven, and the first on-off valve 43 is a normally closed type that opens when driven and closes when not driven. These valves have a valve body inside and a pipe mounting portion. Therefore, unlike ordinary tubes, the heat capacity is large for the internal volume.

  The first pressure sensor 42 and the second pressure sensor 44 are single pressure type pressure sensors. The rated pressure is 0 to 1000 KPa, and the measurement accuracy (error) is about ± 0.025% / full scale. Therefore, an error of about 250 Pa is included when the measurement range is 1000 KPa. The differential pressure sensor 47 breaks with a rated differential pressure of 0 to 5 KPa (rated pressure of -5 to +5 KPa) and a slight pressure (pressure difference) compared to the first pressure sensor 42 and the second pressure sensor 44 (breaking pressure is rated Approximately proportional to pressure). Instead, since there is only an error of, for example, about 2.5 Pa, a slight differential pressure can be determined and inspection can be performed with high accuracy.

  The gas introduction unit 10 adjusts the temperature of a gas having a large specific heat and sends it to the main pipeline 31. Here, the gas having a large specific heat is humidified air. The gas introduction unit 10 desires a heater 11 that heats air taken from the surroundings, an inlet temperature sensor 12 that measures the temperature of the air that enters the gas introduction unit 10 (air that has passed through the heater 11), and air that has passed through the heater 11. A humidifier 13 that humidifies the air, a humidity sensor 14 that measures the humidity of the air on the outlet side of the humidifier 13, a compressor 15 that compresses the air that has passed through the humidifier 13, and dehumidifies the pressurized and humidified air. An air cooler 16 and an air dryer 17, an air tank 18 for storing compressed air in a compressed state, a heater 19 for heating the air stored in the air tank 18, and an atmospheric pressure (atmospheric pressure) of the atmosphere are measured. A barometer 21, a temperature / humidity sensor 22 that measures the temperature and humidity of the atmosphere around the leak inspection device 5 (particularly the inspection device body 6), and the temperature of the air that exits from the gas introduction unit 10 Of the leak inspection apparatus 5 including the outlet side temperature sensor 23 that measures the humidity, the calculation unit 24 that calculates the humidity of the air after being humidified by the humidifier 11 from the target pressure and atmospheric pressure, and the gas introduction unit 10. A control unit 25 that controls the overall operation is provided. The main pipeline 31 communicates with the outlet of the air tank 18.

  When the gas introduction unit 10 pressurizes and introduces gas from the air tank 18 into the inspection apparatus main body 6 so as to achieve a target pressure, the humidity at which no dew condensation occurs in the piping of the inspection apparatus main body 6 or in the workpiece W, for example, inspection The target is a relative humidity of about 80 to 100% (relative humidity during pressurization) within the apparatus body 6. The air tank 18 is a pressurized gas whose humidity and temperature are adjusted so that the humidity of the gas is approximately 80 to 100% and the temperature is substantially equal to the ambient temperature when introduced into the pipe in the inspection apparatus body 6. To store. The target pressure is set to 400 to 1000 KPa, for example.

  The purpose of humidification by the humidifier 13 is to set the humidity of the compressed air that comes out of the air dryer 17 and accumulates in the air tank 18 to about 80 to 100% even in the winter when the ambient air taken in by the gas introduction unit 10 is dry. This is because (relative humidity during pressurization).

  The conventional air dryer has the following structure. That is, the humid hot air from the compressor 15 is pre-cooled by heat exchange with the humid (dehumidified) cold air coming out of the air dryer in the heat exchanger in the air dryer, and further, the air cooler is heated to a predetermined temperature by the chlorofluorocarbon gas. To be cooled. Thereby, moisture in the air is condensed and cooled and dehumidified. That is, the humidity is 100% (relative humidity at pressurization is 100%). Thereafter, heat exchange (remaining heat) with hot air entering the heat exchanger in the air dryer is performed to reduce the humidity, and then the air is discharged from the air dryer. That is, dry air is supplied from the air dryer.

  However, with this structure, it is not possible to achieve the purpose of humidification in the gas introduction unit 10 such that the relative humidity during pressurization is approximately 80 to 100%. Therefore, the air dryer 17 used in the gas introduction unit 10 does not use the heat exchanger that performs the pre-cooling and preheating described above (or has a low capacity) without reducing the humidity of the air from the air dryer 17 (or controlling the reduction range). In addition to using a mechanism that exits at high humidity, the temperature of the air that exits from the air dryer 17 is substantially the same as the temperature of the air (atmosphere temperature) that enters the gas introduction unit 10 (or a temperature that is lower by a predetermined temperature). Adjust the temperature. This prevents condensation on the downstream side of the air dryer 17, for example, inside the inspection apparatus body 6, the air tank 18, and the piping between the inspection apparatus body 6 to the air tank 18 (or the air dryer 17).

  It should be noted that the minimum temperature for approximately one day including nighttime is stored, and the air dryer is preferably set at a slightly lower humidity, such as 85% humidity (humidity during pressurization), in order to obtain a humidity that does not condense even at the lowest temperature. You may make it start from 17. If the temperature of the air entering the gas introduction unit 10 in winter is different from the temperature of the atmosphere where the inspection apparatus body 6 is located, the temperature of the air entering the gas introduction unit 10 and the temperature of the air exiting from the air dryer 17 (atmosphere) The temperature of the air coming out of the air dryer 17 is not the same temperature as the temperature), and the temperature of the air at the place where the inspection apparatus main body 6 is located is the same as the temperature of the place where the inspection apparatus body 6 is located, thereby preventing condensation in the piping or the like. it can.

  In the gas introduction unit 10 shown in the present embodiment, the humidifier 13, the compressor 15, the air dryer 17, and the air tank 18 are connected in this order. For example, the humidifier 13, the compressor 15, the air tank 18, and the air dryer 17 are in this order. It doesn't matter, the order does not matter.

  FIG. 2 shows a state in which the manual four-way valve 50 is attached to the workpiece W. The manual four-way valve 50 includes connection ports 1 to 4. The connection port 1 is connected to the connection port 31 a of the main pipeline 31. One end of an intubation tube 51 to be inserted into the work W is connected to the connection port 2. One end of the outer tube 52 is connected to the connection port 3. The connection port 4 is open to the atmosphere. The other end of the outer tube 52 is connected to the entrance of the workpiece W. The inner intubation 51 passes through the peripheral wall of the outer tube 52 in the middle of the outer tube 52 and enters the outer tube 52, and thereafter, is inserted into the workpiece W through the outer tube 52. The intubation tube 51 inserted into the work W reaches the inner part of the work W, and the tip is opened near the innermost part of the work W.

  FIG. 3 shows four open / close states that the manual four-way valve 50 can take. FIG. 2A shows a “double-open” state in which the connection port 1 and the connection port 2 communicate with each other, and the connection port 3 and the connection port 4 communicate with each other. When the gas pressurized and introduced from the gas introduction unit 10 in the “both open” state flows from the connection port 1, the gas is discharged from the connection port 2 through the inner intubation 51 into the interior of the work W. Further, the outer tube 52 communicates with the outside through the connection port 4. When gas is discharged from the tip of the inner intubation 51 into the interior of the workpiece W, the air originally in the workpiece W is discharged to the outside through the outer tube 52. FIG. 2 shows a state where the manual four-way valve 50 is “double open”.

  FIG. 3B shows a “first open” state in which the connection port 1 and the connection port 2 communicate with each other and the connection port 3 and the connection port 4 are closed. FIG. 3C shows a “closed” state in which the connection port 1, the connection port 2, the connection port 3, and the connection port 4 are all closed. FIG. 3D shows a “second open” state in which the connection port 1 and the connection port 4 communicate with each other and the connection port 2 and the connection port 3 are closed. In the manual four-way valve 50, switching to each state is performed manually.

  Next, the procedure of leak inspection performed using the leak inspection apparatus 5 will be described with reference to FIG.

  The leak inspection procedure may be the same as that disclosed in Patent Document 1. The difference is that in Patent Document 1, air is introduced under pressure, but in the leak inspection apparatus 5 of the present embodiment, humidified air is introduced under pressure, and the master M (work W at the time of inspection) is dedicated. A manual four-way valve 50 is provided.

  First, the air which has been humidified, compressed and adjusted in temperature is stored in the air tank 13 of the gas introduction unit 10 (step S101). That is, the gas introduction unit 10 takes in air from the surroundings and humidifies the air with the humidifier 13. Then, the air after humidification by the humidifier 13 is compressed to a target pressure or more by the compressor 15, and is sent to the air tank 18 through the air cooler 16 and the air dryer 17 and stored. At this time, the control unit 25 adjusts the humidity and temperature so that the humidity of the gas becomes approximately 80 to 100% and the temperature is substantially equal to the ambient temperature when introduced into the pipe in the inspection apparatus body 6. The adjusted pressurized gas is stored in the air tank 18.

  Next, the entire six inspection devices are scavenged (step S102). That is, the first on-off valve 43, the exhaust valve 45, the second on-off valve 48, and the manual valve 46 are opened, and the gas supplied from the air tank 18 is supplied to the main pipe line 31, the exhaust pipe 32, the branch pipe 33, the pipe line 34, The air flows through all the pipes such as the bypass pipe 35 to scavenge these pipes. When scavenging is completed, the first on-off valve 33 is closed.

  Next, the master M is attached to the connection port 31a (step S103). The master M has the same shape and volume as the workpiece W with no leakage (having the same heat dissipation characteristics). Further, a small master Mb is attached to the end of the pipeline 34. Then, the manual valve 46 is opened, the manual four-way valve 50 attached to the master M side is set to the “both open” position, the exhaust valve 45 is closed, and the second on-off valve 48 is opened. 43 is opened again, and the gas from the air tank 18 (humidified and compressed air) is supplied to the main pipe 31, the exhaust pipe 32, the branch pipe 33, the pipe 34, the bypass pipe 35, the master M (work W at the time of inspection), Pressure is introduced into the space including the small master Mb (step S104), and after a predetermined time has elapsed, the manual four-way valve 50 is changed to the “first open” position to bring the inside of the space to a target pressure (step S105).

  At the beginning of this pressurization introduction (S104), since the manual four-way valve 50 attached to the master M side is in the “double open” position, the gas pressurized and introduced from the air tank 18 is as shown in FIG. In addition, the air that was originally inside the master M is discharged from the distal end of the inner intubation pipe 51 at the back of the inside of the master M, and from the outlet of the master M to the outside through the outer tube 52 and from the connection port 4 of the manual four-way valve 50. Discharged.

  When the manual four-way valve 50 is in the “double open” position, the target pressure is hardly reached, but the manual four-way valve 50 is set to the “first open” position after a predetermined time after scavenging in the master M is completed. After that, the pressure increases and reaches the target pressure.

  Whether or not the target pressure has been reached is confirmed by the detection value of the second pressure sensor 44. At this time, the pressure is set slightly higher than the target pressure, and the exhaust valve 45 is opened a little to reach the target pressure in order to eliminate heat accumulation at the end of the exhaust pipe 32 (position connected to the exhaust valve 45) during pressurization. May be.

  When the above space reaches the target pressure, the first on-off valve 43 is closed and the second on-off valve 48 is further closed. Thus, one of the differential pressure sensors 47 becomes a sealed space (first space R1) including the small master Mb, and the other becomes a sealed space (second space R2) including the master M. Specifically, as shown in FIG. 5, the first space R <b> 1 is a portion of the bypass pipe 35 downstream from the pipe line 34, the small master Mb, and the second opening / closing valve 48. In the figure, the first space R1 is indicated by a thick broken line. The second space R2 includes a main pipe line 31 downstream from the first on-off valve 43, an exhaust pipe 32 upstream from the exhaust valve 45, a branch pipe 33, a bypass pipe 35 on the branch pipe 33 side from the second on-off valve 48, and a master M (inspection). Time is part of work W). In the drawing, the second space R2 is indicated by a bold line.

  Note that the volume of the first space R1 is sufficiently smaller than the volume of the workpiece W. For example, the workpiece W is 150 L, and the first space R1 is 25 mL = tank bulge 13 mL + piping 12 mL.

  Thereafter, the change with time of the detected value of the differential pressure sensor 47 is measured. Using this measurement result as a reference characteristic, the ambient humidity, ambient temperature, ambient pressure, the temperature / humidity / pressure of the gas in the air tank 18, the pressurization time, the temperature of the gas in the inspection apparatus main body 6 upon completion of pressurization, etc. It is also stored together (step S107). This completes preparation for inspection.

  Next, the master M is replaced with a workpiece W, and the workpiece W is inspected for leakage. Specifically, the second open / close valve 48 is opened to connect the first space R1 and the second space R2 (step S108), and the manual valve 36 is closed and then the manual four-way valve attached to the master M side. The gas in the master M is opened to the atmosphere with 50 as the “double open” position (step S109). The gas in the master M is discharged from the manual valve 46 to the outside.

  If the gas in the master M (work W at the time of inspection) has been released, the entire inspection apparatus main body is scavenged in this state as in step S102 (step S110). When scavenging is finished, the first on-off valve 33 and the exhaust valve 35 are closed. This scavenging is performed in order to minimize the error for each measurement (referred to as measure 3).

  Next, the master M is removed and the workpiece W is attached to the connection port 31a (step S111). Then, the manual valve 36 is opened, the manual four-way valve 50 attached to the master M side is set to the “both open” position, the exhaust valve 45 is closed, and the second on-off valve 48 is opened. Is opened and the gas from the air tank 18 is pressurized and introduced into the inspection apparatus main body 6 (step S112). At this time, the inside of the workpiece W is scavenged. The manual four-way valve 50 is changed to the “first open” position after a predetermined time after scavenging of the workpiece W is completed, and the gas from the air tank 18 is further pressurized and introduced into the first and second spaces in communication. The target pressure is set (step S113).

  When the target pressure is reached, the first on-off valve 43 is closed, and the second on-off valve 48 is further closed (step S114). Thereby, one of the differential pressure sensors 47 becomes the sealed second space R2 including the workpiece W, and the other of the differential pressure sensors 47 becomes the sealed first space R1 including the small master Mb.

  Thereafter, a change with time of the detection value of the differential pressure sensor 47 is measured, and the presence of leakage of the workpiece W is determined by comparing the measurement result with the previously measured reference characteristic (step S115). That is, if there is no leakage in the workpiece W, the measurement result matches or substantially matches the reference characteristic. When air leaks from the workpiece W, the difference from the reference characteristic becomes large. For example, when the difference between the detected value at the time when a predetermined time has elapsed and the value of the reference characteristic exceeds an allowable value, it is determined that the workpiece W has a leak.

  In addition, after completion of pressurization, a predetermined time until the pressure drop due to heat dissipation (factor other than leakage) is almost settled is set as a settling time, and the value of the pressure difference when the settling time has passed for the master M is used as a reference. Get as a characteristic. Then, the pressure difference detected when the settling time elapses in the inspection of the workpiece W is compared with the pressure difference after the settling time elapses as a reference characteristic, and if the difference is less than a predetermined threshold value, the workpiece W is It may be determined that there is no leakage (inspection pass), and if it is equal to or greater than the threshold value, it is determined that there is leakage (inspection failure).

  When the inspection of the workpiece W is completed, the second on-off valve 48 is opened to connect the first space and the second space (step S116), and the manual valve 36 is closed and then the manual four-way valve attached to the workpiece W. 50 is set to the position of “both open (first open?)”, And the gas in the workpiece W is opened to the atmosphere (step S117). The gas in the work W is discharged from the manual valve 46 to the outside.

  When the next workpiece W is continuously inspected (step S118; No), the process returns to step S110 to continue the operation. When the inspection is completed (step S118; Yes), the exhaust valve 45 is opened and the workpiece W is removed. (Step S119), the work is finished.

  Note that the target humidity (humidity of gas stored in the air tank 18) when humidifying by the humidifier 13 is the inspection apparatus main body when the first on-off valve 43 and the like are opened for inspection and air is introduced under reduced pressure by the electropneumatic regulator 41. 6, the humidity at which condensation does not occur, for example, the relative humidity is approximately 80 to 100% (relative humidity during pressurization).

  In the inspection preparation and the inspection of the workpiece W, when the gas is pressurized and introduced from the air tank 18 into the first space R1 and the second space R2, the phenomenon that the gas is depressurized through the electropneumatic regulator 41 and adiabatically expands or the pressure is introduced. The temperature fluctuates due to frictional heat at the time. However, the gas supplied from the air tank 18 is humidified by the humidifier 13 as described above, and has a humidity (approximately 80% to 100%) that does not cause condensation when pressurized and introduced into the inspection apparatus body 6. The humidity is adjusted to be. Since such high-humidity air has a larger specific heat than dry low-humidity air, temperature fluctuations can be suppressed and measurement accuracy and stability can be improved.

  Furthermore, the gas introduction unit 10 adjusts the temperature of the gas in the air tank 18 so that the temperature of the gas after pressurizing and introducing the gas from the air tank 18 to the inspection apparatus body 6 substantially matches the ambient temperature. It is possible to shorten the waiting time until the temperature of the gas settles after the pressure is introduced, and the inspection can proceed efficiently.

  The air after being compressed by the compressor 15 can be humidified. For example, if the humidifier 13 is installed in the air tank 18, the compressed air is humidified. However, when humidifying after compression, the temperature in the air tank 18 changes depending on the humidification method (ultrasonic humidification, heating steam humidification). For example, when ultrasonic humidification is performed, the temperature in the air tan 18 decreases, and when heated steam humidification is performed, the temperature in the air tan 18 increases. If the gas is kept warm in the air tank 18 so as to coincide with the atmospheric temperature when the reduced pressure is introduced into the inspection apparatus body 6, condensation is less likely to occur when the reduced pressure is introduced into the inspection apparatus body 6 at the target pressure. When humidifying after compression, it becomes difficult to control the temperature so as not to cause condensation when reduced pressure is introduced into the inspection apparatus main body 6. Therefore, in the present embodiment, the air after being humidified by the humidifier 13 is compressed by the compressor 15.

  Further, the temperature, humidity, and pressure of the air entering the humidifier 13 differ depending on the weather. Therefore, in order to perform daily inspections under the same conditions regardless of the weather, the control unit 25 humidifies with the humidifier 13, compresses with the compressor 15, and the air stored in the air tank 18 has a constant density (kg / m 3). ), The humidifier 13, the compressor 15, the air cooler 16, the air dryer 17, the heater 19, and the like are controlled so as to have a constant specific heat KJ (/ kg · K) and a constant thermal conductivity W / (M · K).

  In addition, the specific heat C of air is calculated | required by the following formula | equation.

C = (Cpa · t + (γ + Cpv · t) x) / t
Cpa: Constant pressure specific heat of dry air [1.006KJ / (kg / K)]
Cpv: Constant pressure specific heat of water vapor [1.805KJ / (kg / K)]
γ: latent heat of vaporization of water at 1 atm and 0 ° C [2500KJ / kg]
t: Temperature of humid air [° C]
x: Absolute humidity [kg / kg (DA)]
The specific heat of air greatly depends on the amount of moisture (absolute humidity) contained in the air. Therefore, in order to increase the amount of moisture that can be contained in the air, the air is heated and humidified, especially in winter. To be effective.

  For example, the air taken in from the surroundings is heated by the heater 11 provided in the gas introduction unit 10 and then humidified by the humidifier 13. Even if it is heated (further compressed by the compressor 15 to generate heat), it is dissipated while it is stored in the air tank 18 and approaches the ambient temperature. Then, at the time of inspection, when guided to the main pipeline 31 and the like, the electropneumatic regulator 41 reduces the pressure (further cooling by adiabatic expansion), so that each pipeline (the first space R1, the second space R2, etc.) It is advisable to keep the temperature of the pipes) constituting the structure with a heat insulating material or with the heater 19 in the air tank 18.

  The above-mentioned heat retention is controlled by obtaining the storage temperature in the air tank 13 from the pressure after depressurization, the pressure in the air tank 18, the target pressure, etc. so that the temperature reduced by the electropneumatic regulator 41 becomes the ambient temperature. In this way, it is difficult to condense when the pressure is reduced by keeping the pipe line with a heat insulating material or by keeping the heater 19 in the air tank 18 so that the dehumidification is reduced. Can be increased.

  Here, the control and calculation performed by the gas introduction unit 10 when adjusting the humidity and temperature of the air stored in the air tank 18 to the target values will be described.

  The calculation unit 24 of the gas introduction unit 10 performs a first calculation for calculating the humidity of the air, a second calculation for calculating a storage temperature of the pressurized air in the air tank 18, and a target pressure in the inspection apparatus body 6. A third calculation or the like is performed to determine a coefficient value indicating how much the pressure in the air tank 18 is kept high. The coefficient is expressed as air pressure / target pressure stored in the air tank 18.

  The first calculation for calculating the humidity of the air is performed as follows.

The atmospheric pressure is P1, the target pressure in the inspection is P2, the temperature of the air introduced into the gas introduction unit 10 is T1, the temperature of the gas at the outlet of the air tank 18 is T2, and the saturated water vapor amount at the atmospheric pressure P1 and the temperature T1 is V1. When the saturated water vapor amount at atmospheric pressure P1 and temperature T2 is V2, and the gas in the air tank is 100% humidity,
Humidity H1 required for air under atmospheric pressure before pressurization is
H1 = V2 × compression ratio ÷ V1 × 100 = V2 × (P1 / ((P1 + P2) × coefficient)) ÷ V1 × 100
It is obtained as

  If the required humidity H1 is higher than the humidity H2 of the air before humidification under atmospheric pressure, it is necessary to humidify only by (H1-H2) with the humidifier 13, and if H1 is equal to or less than H2, the humidifier 13 humidifies. do not have to.

<Calculation Example 1>
For example, the atmospheric pressure is 100 KPa, the target pressure is 900 KPa, the target pressurization relative humidity is 100%, the coefficient is 1.3, the temperature T1 of the air introduced into the gas introduction unit 10 is 30 ° C., and the temperature T 2 of the gas at the outlet of the air tank 18 is 30 ° C. For this time, the required humidity H1 is obtained.

The compression ratio in this case is
Compression ratio = 1/13 (= atmospheric pressure 100 KPa / ((atmospheric pressure 100 KPa + 900 KPa target pressure) × factor 1.3)).

When the atmospheric temperature T1 is 30 ° C., the temperature of the compressed air supplied to the inspection apparatus body 6 (the temperature of the gas at the outlet of the air tank 18) T2 should also be 30 ° C., which is the same as the ambient temperature. Since the saturated water vapor amount V2 under atmospheric pressure and 30 ° C. is 30.4 (g / m 3), the water amount K (at 100% humidity) in the air discharged from the gas inlet 10 is
Water content K = V2 × compression ratio = 30.4 (g / m 3) × (1/13) = 2.338 (g / m 3).

If the inlet temperature T1 of the humidifier 13 is 30 ° C., the saturated water vapor amount V1 of the air on the inlet side of the humidifier 13 is 30.4 (g / m 3), which is the same as V2. Therefore, the required humidity H1 at atmospheric pressure and 30 ° C. is
H1 = V2 × compression ratio ÷ V1 × 100 = K ÷ V1 × 100 = 2.338 / 30.4 × 100 = 7.7%.

  Therefore, if the humidity at the inlet of the humidifier 13 is about 7.7% or less, humidification is performed and the air is fed to the air dryer 17 (compressor 15) as about 7.7% or more (7.7% is humidity at atmospheric pressure). For example, in summer, the temperature is high (eg, 30 ° C.) and the humidity is high (eg, 65% RH). When the output of the temperature / humidity sensor 22 for measuring the humidity of the atmosphere at this time is, for example, 65% RH, the required humidity H1 (calculation example 1) obtained from the target pressure is about 7.7%. Therefore, when the difference (7.7-65.0) is negative, the humidifier 11 is not moved (humidified) as humidification is unnecessary.

  In addition, when the atmospheric temperature of the place where the test | inspection apparatus main body 6 is placed differs from the temperature of the air which enters the gas introduction part 10, it calculates as follows.

<Calculation Example 2>
When the target pressure is 100% relative humidity, the target pressure is 420 KPa, the atmospheric pressure is 103 KPa, the temperature of the air entering the gas introduction unit 10 is 10 ° C., and the ambient temperature around the inspection apparatus body is 25 ° C.
The saturated water vapor amount at 10 ° C under atmospheric pressure is 9.4 (g / m3),
The saturated water vapor amount at 25 ° C under atmospheric pressure is 23.0 (g / m3),
From compression ratio = 103 / ((420 + 103) × 1.3) = 0.151, H1 = V2 × compression ratio ÷ V1 × 100 = 23.0 × 0.151 ÷ 9.4 × 100 = 37.1% .

  If the atmospheric temperature is 10 ° C., H1 = 15.1%. However, since the atmospheric temperature is 25 ° C., the air temperature is set to 37.1% or more, and the air dryer 17 (feeds to the compressor 15).

  For example, in winter, the temperature is low (eg, 10 ° C.) and the humidity is low (eg, 12% RH / 25 ° C.). When the output of the temperature / humidity sensor 22 for measuring the humidity of the atmosphere at this time is, for example, 12% RH / 25 ° C., the required humidity H1 (the above calculation example 2) obtained from the target pressure is about 37. Therefore, if this difference is positive (0 <(37.1% -12.0%)), it is necessary to humidify the humidifier 13 so that the humidity at atmospheric pressure is 37.1%. Move to to humidify.

  That is, this humidification does not cause a difference in humidity during pressurization between, for example, a period from spring to autumn (for example, in the case of Calculation Example 1) and a dry winter period (for example, in the case of Calculation Example 2). In other words, no difference occurs in the inspection conditions.

  Next, the 2nd calculation which calculates the storage temperature of the pressurized air in the air tank 18 is demonstrated. The storage temperature of the pressurized air in the air tank 18 is obtained as follows.

  For example, when the atmospheric pressure is 100 KPa, the target pressure is 900 KPa, and the coefficient is 1.3, the pressure in the air tank is 1200 KPa (= ((atmospheric pressure 100 KPa + 900 KPa target pressure) × factor 1.3) −atmospheric pressure 100 KPa). Becomes 900 KPa (target pressure) when the inspection apparatus body 6 is filled.

  That is, since it is filled under reduced pressure, the temperature drops when it is filled as compared with when it is in the air tank 13 (the inspection device body 6 is not a heat insulating structure, but it is a phenomenon opposite to heat generation during adiabatic compression (adiabatic expansion)). Temperature drops). If the temperature of the air in the inspection apparatus body when the pressure is introduced into the inspection apparatus body 6 under pressure and reaches the target pressure of 900 KPa, the temperature stabilizes immediately after the introduction of the pressure. It can be in the state. Therefore, air is stored in the air tank 13 at a temperature that is higher than the ambient temperature by a predetermined temperature based on the coefficient 1.3 (accurately taking into account atmospheric pressure, humidity, and the like) to achieve this state.

  At this time, the temperature increased by a predetermined temperature may be slightly lowered based on the following reason. More specifically, heat is generated by friction between the air and the piping in the inspection apparatus main body 6 at the time of pressurization at S113 and at the time of depressurization at S110 and S119 shown in FIG. 4 (friction heat generation). The magnitude of this frictional heat generation depends on the Mach number (the speed of air) (the temperature of adiabatic compression is proportional to the 0.3th power of the pressure, but if Mach 1 is exceeded, a shock wave is generated and another temperature proportional to the pressure. As the rising phenomenon occurs, it is set to less than Mach 1).

  By the way, although a certain amount of heat can be removed by scavenging in S110, the heat of frictional heat remains as the scavenging time is shortened (because the absolute amount of heat generation increases). Therefore, the heat accumulated in the frictional heat that cannot be removed by scavenging is offset by introducing air at a temperature slightly lower than the ambient temperature from the air tank 18 during pressurization in S113.

  As a result, the heat release during the settling time after pressurization (S115) is a slight heat release starting from a state in which there is almost no difference between the air temperature in the inspection apparatus body 6 and the ambient temperature. Can be achieved. As described above, the storage temperature of the pressurized air in the air tank 18 is not a temperature increased by a predetermined temperature compared to the ambient temperature, and may be slightly lower in order to offset the frictional heat generation.

  Next, the third calculation for determining the value of the coefficient indicating how much the pressure in the air tank 18 should be higher than the target pressure will be described. The coefficient may not be fixed.

  For example, when the atmospheric pressure is 100 KPa, the target pressure is 800 KPa (relative humidity at pressurization is 80%), and the coefficient is 1.3, the pressure in the air tank 18 is 1070 KPa (= ((atmospheric pressure 100 KPa + target pressure 800 KPa) × factor 1.3) -Atmospheric pressure 100 KPa). Assuming that the humidity in the 1070 KPa air tank 18 is 100% (relative humidity during pressurization), the humidity when reduced to 800 KPa is 77% as shown below.

The compression ratio when the pressure in the air tank is 1070 KPa is compression ratio = atmospheric pressure / ((atmospheric pressure + target pressure) × 1.3) = 100 / ((100 + 800) × 1.3) = 1 / 11.7. The compression ratio at the target pressure is compression ratio = atmospheric pressure / (atmospheric pressure + target pressure) = 100 / (100 + 800) = 1/9. Therefore,
Compression ratio 1 / 11.7: Humidity 100% = Compression ratio 1/9: 77%
Therefore, the humidity when the pressure is reduced to 800 KPa is 77%.

  Thus, in the case of the coefficient 1.3, if the target pressure is 800 KPa, the humidity of the gas when introduced into the inspection apparatus main body is 77%, not the desired 80%. Therefore, in the third calculation, the coefficient is changed from 1.3 to 1.25, for example. That is, the pressure in the air tank 18 is reduced from 1070 KPa to 1025 KPa with respect to the target pressure 800 KPa. In this way, although the pressurization time is extended and the inspection time is extended, the humidity at the target pressure of 800 KPa can be made approximately 80% or more (relative humidity at the time of pressurization), and the specific heat of the gas sent to the inspection apparatus main body 6 can be reduced. The effect of temperature can be reduced by increasing it.

  In addition, between the capacity | capacitance V of the air tank 18, the pressure P1 in the air tank 18, the required discharge pressure P2, use air amount (required air amount-discharge air amount) (m3), and use time t (minute). Have the following relationship:

V = Q × t ÷ ((P1-P2) × 10)
When the inspection shown in FIG. 4 is performed, scavenging expells the air originally in the workpiece W to the outside by the operation of introducing the pressurized gas with the manual four-way valve 50 in the “double open” position in S104 and S113. (Measure 1). Further, in S109 and S117, the operation of letting the gas in the workpiece W escape to the outside from the manual valve 46 (measure 2) is performed, so that the gas in the workpiece W is in the main pipeline 31 and the exhaust pipe 32 of the inspection apparatus body 6. It is discharged to the outside world without passing through.

  Countermeasures 1 and 2 are countermeasures for avoiding problems caused by the generation of diamond dust, which will be described later, but it is not necessary to perform both countermeasures 1 and 2, and either one may be used.

  Here, the problem caused by the generation of diamond dust will be described. For example, when the target pressure is 100% relative humidity (relative humidity 100% at 420 KPa = relative humidity 15.15% G = 100 × 1 / 6.6), the target pressure 420 KPa, the atmospheric pressure 103 KPa, and the ambient temperature is 25 ° C. If the gas in the master M is 25 ° C. and humidity is 40%, when the gas is introduced from the gas introduction part 10 and the inside of the inspection apparatus is pressurized to the target pressure of 420 KPa, it was originally in the master M. When the gas is compressed to 1 / 6.6 and then becomes 25 ° C. which is the same as the ambient temperature due to heat dissipation, the relative humidity is 264% (at 420 KPa 265 = 40 × 6.6).

  However, if the relative humidity at the target pressurization is 100%, the entire amount (= 264% -100%) will be condensed on the inner surface of the master M on the heat dissipation surface, and if the relative humidity at the target pressurization is lower than 100%, some Condensation is formed on the inner surface of the master M on the heat radiating surface, but the rest is consumed for increasing the humidity of the gas introduced into the master M, and the relative humidity in the master M is generally 100%. The absolute humidity at this time is 3.485 (g / m 3) (= 23 × 1 / 6.6) from 25 ° C. saturated water vapor amount = 23.0 (g / m 3) under atmospheric pressure.

  As shown in FIG. 6, the gas in the master M pressurized to 420 KPa (work W at the time of inspection) becomes, for example, close to −10 ° C. due to atmospheric release, and the absolute humidity at this time is approximately 2. Lower to 14 (g / m3). That is, diamond dust (fine ice) flies in the master M (work W at the time of inspection) for a moment (diamond dust amount 1.345 g / m3 = 3.485 g / m3-2.14 g / m3).

  For example, in the configuration of FIG. 1, when both the measures 1 and 2 described above are not performed, the diamond dust generated by the reduced pressure accumulates so as to block the pipe line where the second pressure sensor 44 is provided. That is, when the exhaust valve 45 is opened when the work W or the master M is released to the atmosphere, the gas in the master M (work W at the time of inspection) is exhausted from the inspection apparatus body 6 through the exhaust pipe 32, but the pressure is reduced. The diamond dust generated by the straight line travels straight by the inertial force, moves toward the second pressure sensor 34, and does not go toward the exhaust pipe 32.

  Since this diamond dust has a low ambient humidity (the relative humidity of 100% when pressurized to 420 KPa is 15.15% relative to the atmosphere when it is released to the atmosphere), the diamond dust evaporates immediately. To rise. If Measure 3 (scavenging before pressurization) is not performed, dew condensation occurs in the pipe by the next pressurization. In FIG. 8 (leakage inspection apparatus 5C according to the third embodiment), another measure is taken to prevent the generation of diamond dust. That is, a structure is provided in which diamond dust does not have a place where it accumulates even if it travels straight due to inertial force (Countermeasure 4).

  Next, a leak inspection apparatus 5B according to the second embodiment of the present invention will be described. In FIG. 1, the leak inspection apparatus 5 using the differential pressure sensor 47 is illustrated, but the present invention is also applied when using a single pressure type pressure sensor.

  FIG. 7 shows an example of a leak inspection apparatus 5B according to the second embodiment using a single pressure type pressure sensor. The leak inspection apparatus 5B includes a gas introduction unit 10 and an inspection apparatus body 6B. The gas introduction unit 10 is the same as the leak inspection apparatus 5. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In the leak inspection apparatus 5B, the tip portion of the branch pipe 33 provided in the inspection apparatus body 6B is different from the inspection apparatus body 6. In the leak inspection apparatus 5 </ b> B, a single pressure type pressure gauge 49 is attached to the branch pipe 33.

  In the leak inspection apparatus 5B, the first on-off valve 43 is opened while the exhaust valve 45 is open to scavenge the pipeline, and then the first on-off valve 43 is closed to finish scavenging. Next, the work W is attached to the connection port 31a, the exhaust valve 45 is closed, the first on-off valve 43 is opened, and the humidified air is pressurized and introduced into the work W. Next, the first opening / closing valve 43 is closed to seal the space containing the workpiece W. The space includes a main pipe line 31 downstream from the first opening / closing valve 43, a work W, an exhaust pipe 32 upstream from the exhaust valve 45, and a branch pipe 33 leading to a single pressure type pressure gauge 49. In this state, the output of the single pressure type pressure gauge 49 is monitored to determine whether the workpiece W is leaking.

  In the leak inspection apparatus 5B as well, by introducing a gas having a large specific heat under pressure, the influence of temperature change due to adiabatic compression or the like can be suppressed to a small extent, and measurement accuracy and stability can be improved. Moreover, the problem resulting from diamond dust is avoided by performing at least one of the above-mentioned measures 1 and 2.

  Next, a third embodiment of the present invention will be described.

  FIG. 8 shows a configuration of a leak inspection apparatus 5C according to the third embodiment. The gas introduction part 10 is the same as FIG.

  The inspection apparatus main body 6C of the leak inspection apparatus 5C includes a main pipe 61 having one end connected to the gas discharge port of the gas introduction unit 10 and the other end serving as an exhaust port 61a. An electropneumatic regulator 41, a first on-off valve 43, a second pressure sensor 44, and an exhaust valve 45 are provided in the middle of the main pipeline 61 in order from the gas introduction unit 10 side.

  The first branch pipe 62 branches from the main pipeline 61 at the first branch point B1 between the electropneumatic regulator 41 and the first on-off valve 43, and the end of the first branch pipe 62 is connected to the workpiece W and the master M before inspection. A connection port 62a for preparation for connection is provided. A branch pipe opening / closing valve 72 for opening and closing the first branch pipe 62 is provided in the middle of the first branch pipe 62.

  The second branch pipe 63 branches from the main pipeline 61 at the second branch point B2 between the first on-off valve 43 and the exhaust valve 45, and the end of the second branch pipe 63 connects the workpiece W or the master M to be inspected. This is an inspection connection port 63a. A manual valve 46 is provided in the middle of the second branch pipe 63. The second pressure sensor 44 is provided at the second branch location.

  A third branch pipe 64 branches from the main pipe 61 at a third branch point B3 between the first on-off valve 43 and the second pressure sensor 44, and the terminal end of the third branch pipe 64 is an air release port 64a. . In the third branch pipe 64, a second on-off valve 77, a small master 79, a third on-off valve 78, and a relief valve 84 are inserted in order toward the air release port 64a. The second on-off valve 77, the third on-off valve 78, and the relief valve 84 open and close the third branch pipe 64, respectively.

  The fourth branch pipe 65 branches from the main pipe 61 at the fourth branch point B4 between the second pressure sensor 44 and the exhaust valve 45, and the end of the fourth branch pipe 65 is between the relief valve 84 and the third on-off valve 78. In the meantime, it merges with the third branch pipe 64. In the fourth branch pipe 65, a third on-off valve 81, a small master 83, and a fourth on-off valve 82 are inserted toward the junction.

  The fifth branch pipe 66 branches from the third branch pipe 64 at the fifth branch point B5 between the small master 79 and the third on-off valve 78, and the branch destination is connected to one connection port of the differential pressure sensor 47. Yes. The sixth branch pipe 67 branches from the fourth branch pipe 65 at the sixth branch point B6 between the small master 83 and the fourth on-off valve 82, and the branch destination is connected to the other connection port of the differential pressure sensor 47. Yes.

  The fifth branch pipe 66 and the sixth branch pipe 67 are extremely short. In the portion provided between the first on-off valve 43 and the exhaust valve 45, the one connection port side and the other connection port side of the differential pressure sensor 47 have a symmetrical structure.

  That is, the third branch pipe 64 from the third branch point B3 to the junction of the third branch pipe 64 and the fourth branch pipe 65, the second on-off valve 77, the small master 79, the third branch pipe interposed therebetween. The on-off valve 78, their arrangement and the fifth branch pipe 66, the fourth branch pipe 65 from the fourth branch point B4 to the junction of the third branch pipe 64 and the fourth branch pipe 65, are inserted in this. The third on-off valve 81, the small master 83, the fourth on-off valve 82, their arrangement, and the sixth branch pipe 67 are symmetrical with respect to the differential pressure sensor 47. The small master 79 and the small master 83 are the same. The capacities of the small master 79 and the small master 83 are sufficiently smaller than the capacity of the workpiece W.

  The second branch point B2 is located at the center of the first on-off valve 43 and the exhaust valve 45. The length of the main pipeline 61 from the third branch point B3 to the first on-off valve 43 and the length of the main pipeline 61 from the fourth branch point B4 to the exhaust valve 45 are the same. The length of the third branch pipe 64 from the third on-off valve 78 to the junction of the third branch pipe 64 and the fourth branch pipe 65 and the fourth of the part from the fourth on-off valve 82 to the junction. The length of the branch pipe 65 is the same.

  A manual four-way valve 50 is attached to each of the workpiece W and the master M, and the workpiece W and the master M are connected to the preparation connection port 62a and the inspection connection port 63a via the manual four-way valve 50.

  The preparation on-off valve 72, the first on-off valve 43, the exhaust valve 45, the second on-off valve 77, the third on-off valve 78, the third on-off valve 81, the fourth on-off valve 82, and the relief valve 84 are all air operated. This is a valve (spring return single action type). In addition, the third on-off valve 78 and the fourth on-off valve 82 are normally open type that closes when driven and opens when not driven. The preparatory on-off valve 72, the first on-off valve 43, the exhaust valve 45, and the second on-off valve 77. The third on-off valve 81 and the relief valve 84 are both normally closed types that open when driven and close when not driven.

  In the inspection apparatus main body 6C, a retention preventing structure for preventing gas retention is provided at the second branch point B2, the third branch point B3, the fourth branch point B4, the fifth branch point B5, and the sixth branch point B6. is there.

  9 and 10 show an example of the stay prevention structure. FIG. 9 shows a Y-shaped retention prevention structure, and FIG. 10 shows a retention prevention structure combining a Y-shape and a nozzle type. The stay prevention structure uses a Y-shaped structure or a nozzle structure to perform a function of scavenging deeply into a pipe branching off at a branch point by inertia scavenging using inertia force. A Y-shaped stay prevention structure is used for the second branch point B2, the third branch point B3, the fourth branch point B4, the fifth branch point B5, and the sixth branch point B6.

  For example, in the case of the third branch point B3, since the gas that has arrived at the stay prevention structure from the first opening / closing valve 43 side (inlet side) has inertia, the direction cannot be suddenly changed at the Y-shaped part. As it is, it goes to the second on-off valve 77 (the dead end side) through the third branch pipe 64. When the second on-off valve 77 is closed, it becomes a dead end there, so that the gas staying in the dead end portion is entrained and changed in direction to the outlet side of the Y-shaped structure with the second pressure sensor 44. . In this way, the air is scavenged deep into the branch pipe.

  In the stay prevention structure shown in FIG. 10, the Y-shaped portion is the same as that in FIG. 9, and the nozzle structure is provided at the outlet portion of the Y-shaped structure. In the nozzle-type stay prevention structure with a narrow pipe diameter, the gas is increased in flow velocity at the nozzle part and discharged toward the dead end, and the gas staying in the dead end is entrained. Change direction and proceed toward the exit. In this way, the air is scavenged deep into the branch pipe.

  Next, an inspection procedure in the leak inspection apparatus 5C will be described.

In the leak inspection device 5C, once the space on both sides of the differential pressure sensor 47 is pressurized to the target pressure, the inspection can be continued one after another by exchanging the master M and the workpiece W while maintaining the state. In addition, temperature fluctuations due to adiabatic compression / expansion can be suppressed as much as possible, and inspection can be performed in a short time with high accuracy.

  In the inspection apparatus main body 6C of the leak inspection apparatus 5C, as shown in FIG. 11, the space between the third on-off valve 81, the fourth on-off valve 82, and the differential pressure sensor 47 is defined as a first space 91 and a second on-off valve 77. The space between the third on-off valve 78 and the differential pressure sensor 47 is the second space 92, and the space between the first on-off valve 43, the exhaust valve 45, the manual valve 46, the second on-off valve 77, and the third on-off valve 81. Is a third space 93.

  Specifically, the first space 91 includes a fourth branch pipe 65, a small master 83, and a sixth branch pipe 67 between the third on-off valve 81 and the fourth on-off valve 82. The second space 92 includes a third branch pipe 64, a small master 79, and a fifth branch pipe 66 between the second on-off valve 77 and the third on-off valve 78. In FIG. 11, the first space 91 and the second space 92 are indicated by bold lines. The third space 93 includes a main pipeline 61 between the first on-off valve 43 and the exhaust valve 45, a second branch pipe 63 between the second branch location B2 and the manual valve 46, a third branch location B3 and the second on-off valve. 77, the third branch pipe 64, and the fourth branch pipe 65 between the fourth branch point B4 and the third on-off valve 81. In FIG. 11, the third space 93 is indicated by a thick broken line.

  FIG. 12 shows an inspection procedure in the leak inspection apparatus 5C. First, in the same manner as in the first embodiment, air that has been humidified, compressed, and temperature-adjusted is stored in the air tank 13 of the gas introduction unit 10 (step S201). In other words, the first to third calculations described above are performed so that the temperature of the gas (at the target pressure) when introduced into the inspection apparatus main body is almost the same as the atmospheric temperature of the inspection apparatus main body and the humidity is about 80%. Based on this, the gas whose humidity and temperature are adjusted is stored in the air tank 18.

  Next, the entire interior of the inspection apparatus body is scavenged (step S202). That is, the first on-off valve 77, the third on-off valve 78, the third on-off valve 81, the fourth on-off valve 82, the relief valve 84, the exhaust valve 45, the manual valve 46, and the preparatory on-off valve 72 are opened. The on-off valve 43 is opened, and the gas supplied from the air tank 18 is caused to flow through each pipe line of the inspection apparatus body 6C to be scavenged. After scavenging for a predetermined time, the preparation on-off valve 72, the manual valve 46, the exhaust valve 45, the relief valve 84, and the first on-off valve 43 are closed. In scavenging, the first space 91, the second space 92, and the third space 93 communicate with each other.

  Next, after pressurizing the entire inside of the inspection apparatus main body to the target pressure, it is left to wait until the temperature stabilizes (step S203). Specifically, after the third on-off valve 78 and the fourth on-off valve 82 are closed, the first on-off valve 43 is opened, and the first space 91, the second space 92, and the third space 93 are communicated with each other from the air tank 18. The gas is introduced into the inspection apparatus main body under pressure. When the pressurization is completed, the first on-off valve 43 is closed.

  At this time, the gas introduced from the gas introduction unit 10 is adjusted so as to be exactly the same temperature as the ambient temperature when reduced pressure is introduced into the inspection apparatus body and the target pressure is reached. The waiting time until the inside temperature becomes stable with the ambient temperature is short. Further, the gas introduced under reduced pressure from the gas introduction part 10 does not condense, and the humidity becomes approximately 80%.

  By the way, when the scavenging time in step S202 is shortened and the scavenging is not complete, the gas remaining in the inspection apparatus main body is adiabatically compressed at the dead end portion to generate heat and form a heat pool. In FIG. 13, for example, the heat accumulation location that is generated when the air at the time of manufacturing the leak inspection apparatus 5C remains pressurized in the inspection apparatus main body 6C and is pressurized in step S203 is shown in gray. Specifically, the heat accumulation point d1 at which the main pipeline 61 stops at the exhaust valve 45, the heat accumulation point d2 at which the third branch pipe 64 stops at the third on-off valve 78, and the fourth branch pipe 65 at the fourth opening / closing. A heat accumulation point d3 where a dead end is caused by the valve 82 and a heat accumulation point d4 where the second branch pipe 63 becomes a dead end by the manual valve 46 are generated.

  Therefore, immediately before the end of pressurization in step S203, the exhaust valve 45, the third on-off valve 78, the fourth on-off valve 82, and the manual valve 46 are slightly opened to discharge the gas accumulated in the heat accumulation locations d1 to d4. And let the heat escape to the outside world. The manual valve 46 may be kept closed here. In this case, in the scavenging of S205 described later, the heat (gas) accumulated in the heat accumulation location d4 is discharged.

  In this pressurization, the fifth branch pipe 66 and the sixth branch pipe 67 are dead ends at the differential pressure sensor 47. However, the Y-shaped stay prevention structure described above scavenges, and heat accumulation is not generated. Is prevented.

  When the inside of the inspection apparatus main body reaches the target pressure, the first space 91, the second space 92, and the third space 93 are separated, and each is made a closed space (step S204). Specifically, the second on-off valve 77 and the third on-off valve 78 are closed. Thereafter, the first space 91 is maintained at the target pressure. Further, by closing the manual valve 46 when exchanging the workpiece W or the master M, the second space 92 and the third space 93 are also maintained at substantially the target pressure, and gas replacement hardly occurs.

  Next, the master M is connected to the preparation connection port 62a, the manual four-way valve 50 is set to the “both open” position, the preparation opening / closing valve 72 is opened, and the inside of the master M is scavenged. Thereafter, the manual four-way valve 50 is set to the “first open” position to increase the pressure to the target pressure, and the preparation on-off valve 72 is closed (step S205). The pressure for pressurizing the master M (the same applies to the workpiece W described later) is preferably set to the same target pressure as that in the inspection apparatus main body, but may be an arbitrary pressure.

  Next, the manual four-way valve 50 is set to the “closed” position, and the master M is removed from the preparation connection port 62a and attached to the inspection connection port 63a (step S206).

  Next, the manual valve 46 is opened, the manual four-way valve 50 is set to the “second open” position, and air between the manual valve 46 and the manual four-way valve 50 is exhausted to the outside (step S207).

  Next, the manual four-way valve 50 is set to the “first open” position so that the master M communicates with the third space 93, and the space is slightly higher than the target pressure based on the detection value of the second pressure sensor 44. After the pressure is increased, the second space 92 and the third space 93 are further communicated (step S208). For example, the pressure is increased up to 800.25 KPa (up to the error of the second pressure sensor 44) with respect to the target pressure of 800 KPa. Since the second pressure sensor 44 has a large error, even if the detected value indicates 800.25 KPa in the measurement range (full scale) 1000 KPa of the second pressure sensor 24, for example, the measurement accuracy (error) of the second pressure sensor 44. However, in the case of 0.025% / full scale, the pressure is actually in the range of 800.0-800.5 KPa. Therefore, the second space 92 and the third space 93 have a pressure higher by 0 to 0.5 KPa than the first space 91.

  Thereafter, from the detection value of the differential pressure sensor 47, the exhaust valve 45 and the relief valve 84 (the third on-off valve 78) are set so that the pressure on the second space 92 and the third space 93 side is equal to the pressure on the first space 91 side. Then, the pressure is adjusted by evacuating little by little (step S209). By doing so, the measurement error of the second pressure sensor 44 can be calibrated by the differential pressure sensor 47 and accurately pressurized to the target pressure (the same pressure as the first space 91 side).

  Since the second space 92 and the third space 93 are communicated after the third space 93 is almost pressurized to the target pressure, it is possible to prevent a large differential pressure from being applied to the differential pressure sensor 47.

  Even in the pressurization in step S208, heat is generated at the dead end unless various measures are taken. Specifically, as shown in FIG. 13, the point d5 where the fourth branch pipe 65 stops at the third on-off valve 81, the point d2 where the third branch pipe 64 stops at the third on-off valve 78, the workpiece W A heat accumulation can occur at a location d6 where the dead end is located at the back of the interior of the, and a location d1 where the main pipeline 61 becomes a dead end at the exhaust valve 45.

  However, by exhausting from the exhaust valve 45 and the relief valve 84 (opening the third on-off valve 78) in step S209, the heat at the heat accumulation points d1 and d2 is discharged to the outside. Further, heat accumulation at the heat accumulation location d5 is eliminated by the aforementioned Y-shaped retention prevention structure. Similarly, heat accumulation is prevented at the location where the fifth branch pipe 66 stops at the differential pressure sensor 47 by the stay prevention structure provided at the fifth branch location B5. And about the back | inner d6 in a master, since the inside of the master M was previously pressurized to the target pressure with the same gas by S205, there is almost no heat generation. Also, there is no condensation. The same applies to the workpiece W that is pressurized to the target pressure with the same gas in advance in S213 to be described later.

  Next, as in the first embodiment, reference characteristics are measured (step S210). As described above, at the time of pressurization, almost no heat is accumulated in the heat accumulation location, and when the target pressure is reached, the gas whose temperature and humidity are adjusted so as to coincide with the ambient temperature is supplied from the gas introduction unit 10. Since the reduced pressure is introduced, the time until the temperature inside the inspection apparatus body stabilizes (the settling time) can be short.

  When the measurement of the reference characteristics is completed, the second opening / closing valve 77 is closed to separate the second space 92 and the third space 93 (step S211). Next, the manual valve 46 is set to the “closed” position, the master M is released to the atmosphere, and the master M is removed from the inspection connection port 63a together with the manual four-way valve 50 (step S212). The gas in the master M is discharged from the manual valve 46 to the outside, and the above-mentioned diamond dust problem does not occur.

  Next, the workpiece W is connected to the preparation connection port 62a, and after scavenging as in the case of the master M, the pressure is increased to the target pressure (step S213).

  Next, the manual four-way valve 50 is set to the “closed” position, the workpiece W is removed from the preparation connection port 62a, and attached to the inspection connection port 63a (step S214). In addition, about the workpiece | work W, the operation | work which pressurizes to a target pressure is performed one after another, and the thing removed from the connection port 62a for preparation is left for a while in a storage place until the internal gas temperature corresponds to ambient temperature, and then And connected to the inspection connection port 63a. By so doing, it is possible to stabilize the temperature at the storage location while inspecting another workpiece W.

  Next, the manual valve 46 is opened, the manual four-way valve 50 is set to the “second open” position, and the air between the manual valve 46 and the manual four-way valve 50 is exhausted (purged) to the outside (step S215). ).

  Next, the manual four-way valve 50 is set to the “first open” position to communicate the workpiece W with the third space 93, and the space is slightly higher than the target pressure based on the detection value of the second pressure sensor 44. After the pressure is increased, the second space 92 and the third space 93 are further communicated (step S216). Then, from the detection value of the differential pressure sensor 47, the exhaust valve 45 and the relief valve 84 (the third on-off valve 78) are set so that the pressure on the second space 92 and the third space 93 side is equal to the pressure on the first space 91 side. Then, the air is exhausted little by little to adjust the pressure in the third space 93 to the same pressure as that in the first space 91 (step S217). Since the second space 92 and the third space 93 are communicated after the third space 93 is almost pressurized to the target pressure, a large differential pressure is prevented from being applied to the differential pressure sensor 47.

  Again, as described in steps S208 and S209, the occurrence of heat accumulation is prevented by the exhaust and Y-shaped structure during fitting. Moreover, since the inside of the workpiece W is pre-filled with the same gas in S213, heat generation and condensation do not occur.

  Next, as in the first embodiment, the workpiece W is inspected for leakage (step S218). As described above, almost no heat is accumulated in the heat accumulation area during pressurization, and when the target pressure is reached, the temperature / humidity is adjusted so that the humidity is approximately 80% with the ambient temperature and no condensation. Since the adjusted gas is introduced from the gas introduction unit 10, the time until the temperature in the inspection apparatus main body is stabilized (static time) can be short. Also, there is no condensation. Steps S <b> 205 to S <b> 209 and S <b> 213 to S <b> 217 are the same operation, and the conditions can be made the same at the time of reference specific measurement and at the time of inspection.

  When the inspection is completed, the second opening / closing valve 77 is closed, and the second space 92 and the third space 93 are separated (step S219). Next, the manual valve 46 is set to the “closed” position, the workpiece W is released to the atmosphere, and the workpiece W is removed from the inspection connection port 63a together with the manual four-way valve 50 (step S220). Since the gas in the work W is discharged to the outside through the manual valve 46 without passing through the inside of the inspection apparatus main body, the above-described problem of diamond dust does not occur.

  When the next workpiece W is inspected continuously (step S221; No), the process moves to step S213 and the operation is continued. If the inspection is finished (step S221; Yes), this process is finished. At this time, the second on-off valve 77 and the third on-off valve 81 are opened to connect the first space 91, the second space 92, and the third space 93, and then the exhaust valve 45 is opened.

  Thus, in the leak inspection apparatus 5C, even when the master M and the workpiece W are replaced, the first space 91 and the second space 92 on both sides of the differential pressure sensor 47 are maintained at substantially the same pressure. A large differential pressure is not applied to both sides of the sensor 47, and a high-precision differential pressure sensor 47 can be used to perform inspection under high pressure.

  In addition, the first space 91, the second space 92, and the third space 92 are maintained at a target pressure and a state in which almost no gas is exchanged even when the master @M or the work @W is exchanged. Is done. For this reason, there is little heat_generation | fever and it can test | inspect several workpiece | work @W in a short time on the same conditions.

  Here, the case where the inspection pressure is switched will be described.

  First, as an inspection preparation, the first space 91 and the second space 92 are pressurized to a target pressure and then cooled to a stable state. For example, the previous test is the target pressure (900 KPa) as shown in Calculation Example 1 exemplified in the first embodiment, and the current test is the target pressure (420 KPa) as shown in Calculation Example 2. In this case, scavenging in the inspection apparatus main body 6C of the leak inspection apparatus 5C is performed by the following method.

  That is, in the previous inspection, the target pressure is 900 KPa (atmosphere temperature 30 ° C.), and the gas stored in the gas introduction unit 10 has a pressure of 1200 KPa (= ((100 + 900) × 1.3) -100) and a humidity of 100% ( (Humidity at the time of pressurization) Therefore, when converted into absolute humidity, it becomes 2.3 (= 30.4 × 1/13) (g / m3).

  If the current test is at a target pressure of 420 KPa (atmosphere temperature 25 ° C), the absolute humidity will be 3.5 (= 23.0 × 1/13) (g / m3). The humidity of the air remaining in the first space 91 and the second space 92 (for example, absolute humidity 2.3 g / m 3) and the humidity of the air used for the current inspection (for example, absolute humidity 3.5 g / m 3) Therefore, the humidity (specific heat) of the air in the second space 92 and the third space 93 where the air in the space is replaced little by little for each inspection and the air in the first space 91 that is not replaced at all is different. It will be different and an error will occur for each measurement.

  Therefore, when the inspection conditions are different, the air in the first space 91 and the second space second space 92 (also the third space 93) is replaced in advance. This scavenging is also performed before the first examination. This is because the air in the first space 91, the second space 92, and the third space 93 is filled with the air when the inspection device body 6C of the leak inspection device 5C is assembled.

  The scavenging associated with the switching of the inspection condition before the inspection uses the penetrating type small masters 79 and 83 while using the Y-shaped retention prevention structure and the nozzle-type retention prevention structure as shown in FIG. (Inertia scavenging).

  For example, in the leak inspection apparatus 5 of FIG. 1, the dead ends (gray portions of FIG. 5) on both sides of the differential pressure sensor 47 are portions that cannot be scavenged well and require time to change air. 8, by providing a Y-shaped stay prevention structure at the location where the bypass pipe 35 branches from the branch pipe 33 and the location where the bypass pipe 35 merges with the branch pipe 33, the scavenging gas is made inertial. The dead pressure of the differential pressure sensor 47 is reached by force, and scavenging (inertial scavenging) is performed in which the gas in that portion is involved (inertial scavenging) (the small master is made through-type or removed every scavenging).

  Thereby, replacement of air required for inspection pressure change or the like can be performed quickly, the air in the first space R1 and the second space R2 becomes the same, and the same physical constant (control the humidity of the inspection gas, Comparison can be made with air having the same specific heat) under the same temperature and pressure.

  Next, the point of eliminating the heat generation at the heat accumulation location by scavenging will be described in more detail.

  For example, when the atmospheric pressure is 100 KPa, the target pressure is 800 KPa, and the coefficient is 1.25, the gas is stored in the air tank 18 at 1025 KPa (= ((atmospheric pressure 100 KPa + 800 KPa target pressure) × coefficient 1.25) −atmospheric pressure 100 KPa). . If the humidity in the air tank 18 at this time is approximately 100%, when the gas is introduced from the gas introduction unit 10 to the inspection device body 6C of the leak inspection device 5C under reduced pressure, the humidity of the gas is approximately 80% (relative to the pressurization). Humidity).

  As described above, the heat generation in S203 is caused by the control of discharging the gas accumulated in the heat accumulation points d1 to d4 to the outside by slightly opening the exhaust valve 45 and the like immediately before the pressurization and the Y-shaped retention prevention structure. The heat generated in S208 and S216 is eliminated by opening the exhaust valve 45 and the like by pressure matching control for discharging the heat accumulated in the heat accumulation locations d1, d2, and d5 to the outside and the Y-shaped retention prevention structure. It will be resolved.

  However, the heat of the heat generation point d6 in the master M or the workpiece W is not eliminated by the above-described control or stay prevention structure. In the leak inspection apparatuses 5 and 5C, the work W and the master M are preliminarily purged with the gas introduced from the gas introduction unit 10 to prevent the heat generation point d6 from generating heat. It becomes like this.

  For example, the atmospheric pressure is 100 KPa, the target pressure is 800 KPa, the atmospheric temperature is 30 ° C., the atmospheric humidity is 65% RH, the coefficient (according to the third calculation) is 1.3 → 1.25, the humidity in the air tank is approximately 100% (relative humidity at pressurization) ) When the humidity of the air sent to the inspection apparatus main body 6C of the leak inspection apparatus 5C is approximately 80% (relative humidity during pressurization) (temperature is the ambient temperature by the second calculation), the air is introduced from the air tank 18 to the workpiece W. The pressurized air sent toward is 30 ° C. (temperature when the target pressure is 800 KPa), which is the same as the ambient temperature, and has a humidity of approximately 80% (humidity when the target pressure is 800 KPa).

  However, if no prior scavenging is performed, the air originally in the work W is filled with the same atmospheric temperature as 30 ° C. (atmospheric pressure) and atmospheric humidity of 65% (atmospheric relative humidity). There are many cases. The air in the work W generates heat by heating (heat generation point d6 in FIG. 13), and this heat convects and moves upward in the work W (tank), but approaches the ambient temperature with time (see FIG. 6). The leak inspection ends when the ambient temperature approaches 30 ° C. (for example, within about +0 to + 10 ° C.). At this time, the following phenomenon is expected in the workpiece W (tank).

  That is, the air in the workpiece W having a relative humidity of 65% at atmospheric pressure has a volume of 1/9 (= −100 KPa / (800 KPa + 100 KPa)) after pressurization, whereby the humidity is 585% (= 65% × 9 Target pressure 800 KPa pressurization humidity at 30 ° C.). That is, when heat is released with time as shown in FIG. 6, water vapor (gas) changes to water (liquid) in the tank, and latent heat is released with it. In other words, the settling time until the work W leakage inspection is completed is extended by latent heat radiation. Furthermore, a water film partially covers the inner surface of the tank.

  By the way, if the gas to be put into the workpiece W is the same during inspection and during actual use, the amount of leaked gas that is a criterion for inspection and the allowable amount of gas allowed during actual use The same reference value can be used for. However, containers that use liquids inside (for example, stainless steel hot water storage tanks (all stainless steel) used in electric water heaters, copper heat exchangers (copper fins and copper tubes used in instant water heaters), etc. ), Etc.) is the workpiece W, the allowable leakage value of liquid allowed in actual use must be converted into the amount of gas leakage, and the inspection allowable leakage value (gas) must be set.

  In this conversion, conversion is performed using the difference in viscosity coefficient. However, if water droplets (water film) are attached to the part where leakage occurs in the workpiece W (tank), the leakage inspection standard must use the amount of liquid leakage. However, as described above, in the inspection, when the water film partially covers the inner surface of the tank, it is not known whether water droplets (water film) are attached to the leaking part ( Leak plugging phenomenon).

  In addition, the fluctuation of pressure change that seems to have gone through the cycle of condensation-> heat radiation disturbance-> dripping-> heat radiation recovery occurs when trying to perform a leak test after the end of the static period (immediately after the leak test). It is difficult to inspect accurately (pressure fluctuation phenomenon).

  Therefore, in the inspection apparatus main body 6C of the leak inspection apparatus 5C according to the present embodiment, the downstream side of the electropneumatic regulator 41 is branched into two hands in order to prevent the above-described dew condensation in the workpiece W, and at the atmospheric pressure before the inspection. Replace the air in the workpiece W with a relative humidity of 65% (at 30 ° C) with air at a relative humidity of 80% (at 30 ° C) at 800 KPa = 8.9% (at 30 ° C) relative humidity at atmospheric pressure. This solves the above problem. Similarly, in the leak inspection apparatuses 5 and 5B, the same solution is achieved by scavenging the inside of the workpiece W with the gas introduced from the gas introduction unit 10.

  Further, a manual four-way valve 50 is attached to the workpiece W so that air sent from the gas introduction unit 10 and atmospheric air (for example, relative humidity 65% (at 30 ° C.)) are not mixed. At this time, the pressure of the air confined in the workpiece W may be an atmospheric pressure, a negative pressure, or a target pressure.

  By the way, the non-work W side (connection port 1 side) of the manual four-way valve 50 attached to the work W is filled with air (for example, relative humidity 65% (at 30 ° C.)), and further the inspection of the inspection apparatus main body 6C. The connection port 63a is also filled with the atmosphere, and the relative humidity at atmospheric pressure is 65% between the manual valve 46 and the manual four-way valve 50 in FIG. 8 when attaching to the workpiece W in step S214 in FIG. The atmosphere of (at 30 ° C.) is sealed.

  Therefore, in step S215 (S207 in the case of the master M), the manual four-way valve 50 is temporarily set to “second open” and purged to prevent unconditioned air from flowing into the workpiece W. Yes. As a result, not only the air in the first space 91 and the second space 92 but also the air in the work W and between the manual valve 46 and the manual four-way valve 50 are the same, and the air with the same physical constant is used. Comparison (leakage inspection) can be performed.

  By the way, a gas (for example, an atmosphere) other than the gas sent from the gas introduction unit 10 is contained in the workpiece W or a pipe between the manual four-way valve 50 and the manual valve 46 attached to the workpiece W. Therefore, because the work W and piping are filled with air that does not have the same physical constant as the gas sent from the gas introduction unit 10, condensation occurs during pressurization, causing problems such as leakage blockage. However, in the leak inspection device 5C, a structure that enables inertia scavenging (residence prevention structure), control such as opening the exhaust valve 45 and the like to match the target pressure (including “scavenging elimination of heat generation points”), etc. This has been solved.

  For example, when the inspection apparatus main body 6C of the leak inspection apparatus 5C is assembled (manufactured), the internal air remaining at the end of the branch pipe is removed, and for example, the inspection apparatus main body 6C of the leak inspection apparatus 5C and the gas The gas (atmosphere) in the pipe between the inspection apparatus main body 6C and the gas introduction unit 10 when the introduction unit 10 is connected is scavenged.

  By the way, in order to prevent condensation, for example, when assembling the leak inspection apparatuses 5, 5B, 5C, it may be assembled in an environment where the humidity is “0”. However, in that case, the leak inspection is performed with air different from the physical constant of the gas sent from the gas introduction unit 10, and the comparison under the air condition with the same physical constant cannot be performed, which is meaningless.

  The leak inspection apparatuses 5, 5B, and 5C according to the present invention have a feature that they can be inspected with a gas having a large specific heat that is hardly affected by temperature by being humidified even in winter. This is particularly effective when testing in dry areas (Egypt, Morocco, etc.) because it can be tested with humidified air throughout the year.

  Next, a method for manufacturing the workpiece W for leak inspection will be described. The leak inspection devices 5, 5B, 5C according to the present embodiment are to be inspected by using a container with a liquid inside (for example, a stainless hot water hot water storage tank (all stainless steel used in an electric water heater)). , A copper heat exchanger (copper fins and copper tubes) as used in instant water heaters, and made by welding (or a plastic hot water hot water storage tank by injection molding).

  If the workpiece W as a container to be used with gas inside is subjected to a leak inspection, the amount of gas leakage can be easily set as an allowable leakage allowable value. In other words, if the gas to be put into the workpiece W is the same during inspection and during actual use, the amount of leakage gas used as a criterion for inspection and the allowable amount of gas allowed during actual use The same reference value can be used for. However, when gas is used for inspection of workpieces that contain liquid, the allowable leakage value of liquid allowed during actual use is converted into the amount of gas leakage, and the allowable leakage value (gas) for inspection is set. Must.

  In this conversion, conversion is performed using the difference in the kinematic viscosity coefficient. The workpiece W as a container to be inspected in the present invention is manufactured, and incorporated in the apparatus after passing the leak inspection. For example, in the case of an instantaneous water heater, water is passed through the shipping inspection (including the work W incorporated inside), but when the stainless hot water hot water storage tank is like the work W, it is built into the equipment. Only after being transported to the construction site is water passed through the product incorporating the workpiece W. In other words, the workpiece W is made of water without being passed through from the part processed into a container (for example, a stainless steel plate, a copper plate, a copper pipe, etc.) to the shape of the container until leak inspection. It is not washed.

  By the way, reference characteristics (steps S107 and S210) are obtained based on the master M that should be the same as the workpiece W, and a plurality of workpieces W are inspected for leaks. ), The weight of each part is slightly different due to the manufacturing error between them, affecting the leak inspection (disturbance) The difference in weight of the workpiece W or the like used in the present embodiment is different from the base material used in the parts (differing in specific heat), for example, the weight does not differ depending on the internal water or the like (with the workpiece W or the like). Since there is no mixing of disturbances with different specific heats, “removal of disturbances with different specific heats is unnecessary”), the difference in weight is the difference in the weight of the base material. Therefore, in order to correct the weight difference with the master M, the weight difference is corrected by inserting a correction part made of the same material as the base material into the work W or in the part connected to the connection port 31a. (“Disturbance prevention using the same specific heat compensation component” with the workpiece W etc.)

  Of course, the materials and weights of the parts connected to the connection ports 31a and 63a and the accessories other than the locations connected to the connection ports 31a and 63a are the same so that there is no difference between the workpieces W and the like. The heat capacity is adjusted by using the same heavy object ("Preventing disturbance caused by parts and accessories connected to the connection port").

  After preventing such various disturbances, the temperature equalizing operation is started. That is, if the temperature differs between the workpieces W and the like, the leakage inspection is affected by the amount of retained heat, so that it is removed (“disturbance prevention by adjusting the amount of retained heat”). The above-described disturbance prevention is preferably performed by the day before the reference characteristic or inspection, as in steps S201 to S204.

  By the way, the heat generated by the adiabatic compression is different from the gas introduced into the inspection apparatus main bodies 6, 6B, 6C of the leak inspection apparatuses 5, 5B, 5C in the inspection (for example, a gas having a different temperature due to the previous inspection and heat dissipation) This is because, for example, gases having different humidity and temperature confined together when W is formed remain, for example, the inspection apparatus main bodies 6, 6B, 6C of the leak inspection apparatuses 5, 5B, 5C prior to the inspection. If all of the inside of the inspection apparatus main body, such as the gas in the workpiece, the gas in the workpiece W, the gas in the master M, and the gas in the differential pressure sensor 47 are vacuumed, the heat generation problem due to adiabatic compression is solved at once. It is ideal because it eliminates the gas that is the source of heat generation (however, a settling time is required instead to settle the reduced pressure cooling due to vacuum suction).

  However, even if vacuum suction is used, the gas that is the source of heat generation cannot be completely eliminated. Because no one has created a space without gas (absolute vacuum). This is the definition of JIS, and it can be understood from the fact that the vacuum is “a state of a specific space filled with a gas having a pressure lower than the atmospheric pressure”. In other words, since the gas remains even in a vacuum, heat generation due to adiabatic compression cannot be avoided.

  In the present invention, a vacuum is created by negative pressure suction, and the inspection gas from the gas introduction unit 10 is poured into the vacuum, so that the old and new gases are not replaced, but the inspection gas is introduced from the gas introduction unit 10 and added. The old and new gases were replaced by pressure scavenging. Thereby, it is not necessary to provide a vacuum pump in addition to the compressor 15.

  In addition, in the vacuum suction method, the following method can be taken. That is, the vacuum suction is caused by vacuum suction, and at this time, if pressure is applied while leaving a predetermined amount of gas, heat is generated by adiabatic compression of the remaining gas. Therefore, if switching from suction to pressurization when the reduced pressure cooling amount and the adiabatic compression heat generation amount are equal, the heat is offset and even if the suction (absolute vacuum) cannot be made completely, the purpose (measurement) Time reduction).

  However, when the pressure is applied without sufficient suction, or when the pressure is applied after excessive suction, the heat cannot be offset and an error occurs for each measurement. On the other hand, in the replacement of old and new gases by pressurized scavenging, it is sufficient if the scavenging is performed for a predetermined time or longer, and the error for each measurement can be easily converged.

  Next, a conversion calculation formula for converting the liquid leakage allowable value into the gas leakage amount will be described.

<Conversion formula using viscosity coefficient>
The flow rate leaking from the pores can be calculated using the viscosity coefficient.

Viscosity (μ Pa · s) at 20 ° C Water μ = 0.0010050 Pa · s Air μ = 0.0000181 Pa · s, pore diameter 0.1 mm (= 0.0001 m), pore length 1 mm (= 0.001 m ), Atmospheric pressure (atmospheric pressure) 101300Pa Abs, pore inlet pressure (target pressure) 300kPa G (= 401300Pa Abs), pore outlet pressure (atmospheric pressure) 0kPa G (= 101300Pa Abs) The amount is
ΔP (hereinafter referred to as water ΔP) = [pore inlet pressure] − [pore outlet pressure] (Pa Abs) = 300000 (Pa Abs)
Then,
[Water leakage amount] = π × [pore diameter] 4 × [water ΔP] / (128 × [water μ] × [pore length])
= 3.14 × 0.0001 [m] 4 × (300000 [Pa Abs]) / (128 × 0.0010050 [Pa · s] × 0.001 [m]
= 0.00000073 [m3 / s] = 0.73 [ml / s].

  On the other hand, the amount of air leakage is expressed as follows, since water is an incompressible fluid, whereas air is a compressible fluid, and hence the differential pressure (hereinafter referred to as air ΔP).

Air ΔP = ([pore inlet pressure] 2- [pore outlet pressure] 2) / (2 × [pore inlet pressure])
= 744225 (Pa Abs)
[Air leakage amount] = π × [pore diameter] 4 × [air ΔP] / (128 × [μ of air] × [length of pore])
= 3.14 × 0.0001 [m] 4 × (744225 [Pa Abs]) / (128 × 0.0000181 [Pa · s] × 0.001 [m]
= 0.00010087 [m3 / s] = 100.87 [ml / s].

Based on the [Water Leakage], a conversion factor ([Water pore inlet pressure] = [Air pore inlet pressure]) to convert [Air leak amount] from the leak inspection device )
[Air leakage] = [Water leakage] x [Conversion factor]
[Conversion factor] = [Air leakage] / [Water leakage]
= ([Pore inlet pressure] 2- [pore outlet pressure] 2) × [μ of water] / (2 × [pore inlet pressure] × [μ of air] × ([pore inlet pressure] − [ Pore outlet pressure]))
= 137.7 (= 100.87 / 0.73)

For example, when the allowable hot water leakage of a tank that stores hot water of 70 ° C at 300 [kPa G] is 10 [ml / h], the ambient temperature during inspection (= the gas temperature that fills the leak inspection device) is 20 ° C Sometimes when testing at 200 [kPa G] (when [pore inlet pressure of water] = [air inlet pressure of air]), [20 ° C. air μ] = 0.0000181 Pa · s, [70 ℃ hot water μ] = 0.0004Pa · s, atmospheric pressure (atmospheric pressure) 101300Pa Abs,
[Conversion factor] = [Air leakage] / [Water leakage]
[Air leakage amount] = π × [pore diameter] 4 × [air ΔP] / (128 × [μ of air] × [length of pore])
[Water leakage amount] = π × [pore diameter] 4 × [water ΔP] / (128 × [water μ] × [pore length])
[Conversion factor] = ([Air ΔP] × [Water μ]) / ([Air μ] × [Water ΔP])
It is represented by When calculating
[Conversion factor] = 29.28 (= 292.8 / 10)
Allowable gas leakage ([air leakage]) = 292.8 [ml / h].

However, since there is an error in the pressure sensor, it is necessary to set the allowable gas leakage amount by correcting the conversion factor in consideration of the error. here,
A: High breakdown voltage (single breakdown voltage is 1000 KPa or more, for example), error 250 Pa, measurement accuracy (error) 0.025% / full scale second pressure sensor 24 is used B: high breakdown voltage (single breakdown voltage is 1000 KPa or more, for example) A case where a differential pressure sensor that can discriminate a slight differential pressure (error 2.5 Pa, measurement accuracy (error) 0.00025% / full scale) is used will be compared and described.

  When the differential pressure sensor 25 of A is used, there is an error even if the pressure is increased up to 800.25 KPa with respect to the target pressure of 800 KPa. Therefore, it can be understood that the real pressure is a pressure in the range of 800.0 to 800.5 KPa. No (error 250 Pa). Although the amount of leakage can be measured to the same extent as B, there is an error with respect to the target pressure to be pressurized, so the pore inlet pressure used in the above calculation of the conversion coefficient changes, and a somewhat strict leakage criterion for B must be used. .

That is, in the case of A,
Air ΔP = ([901550 ± 250 Pa Abs] 2− [101300 Pa Abs] 2) / (2 × [901300 ± 250 Pa Abs])
[Conversion factor] = [Air ΔP] × [Water μ] / [Air μ] × [Water ΔP]. When calculating
[Conversion factor] = (([901550-250 Pa Abs] 2- [101300 Pa Abs] 2) / (2 × [901300-250 Pa Abs]) × [water μ] / [air μ] × [water ΔP].

When the differential pressure sensor of B is used, if the pressure is increased to 800.25 KPa with respect to the target pressure of 800 KPa, the real pressure is in the range of 800.2475 to 800.2525 KP. Therefore, for B,
Air ΔP = ([901550 ± 2.5 Pa Abs] 2− [101300 Pa Abs] 2) / (2 × [901300 ± 2.5 Pa Abs])
[Conversion factor] = [Air ΔP] × [Water μ] / [Air μ] × [Water ΔP]
[Conversion factor] = (([901550-2.5 Pa Abs] 2- [101300 Pa Abs] 2) / (2 × [901300-2.5 Pa Abs]) × [water μ] / [air μ] × [water ΔP].

  Therefore, equivalent measurement (determination) is possible by using A as a stricter determination criterion than B.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  In the embodiment, the gas having a large specific heat is humidified air. However, the gas having a large specific heat may be, for example, a simple substance such as ethylene, methane, or helium, or a mixture of this with air. Any gas that has a larger specific heat than the surrounding air and does not condense when introduced under pressure may be used.

  The configurations of the leak inspection apparatuses 5, 5B, 5C are not limited to those exemplified in the embodiment. The portion other than the gas introduction unit 10 may be arbitrary as long as it is configured to inject a gas into a test object under pressure and then seal and inspect a leak by measuring a subsequent pressure change.

  A valve body is provided at a position on the gas introduction part 10 side by a predetermined distance from an on-off valve such as the exhaust valve 45 arranged at the dead end, and the exhaust valve 45 etc. is opened just before the pressurization is completed, so that the gas at the heat accumulation location is removed. Relieve to the outside, and then close the valve body to the target pressure. That is, even if the gas in the heat reservoir is released to the outside, the exhaust valve 45 and the pipe line in the vicinity thereof have heat, so that the heat is conducted into the inspection apparatus main body by closing the valve body. To prevent.

5, 5B, 5C ... Leak inspection device 6, 6B, 6C ... Inspection device body 10 ... Gas introduction part 11 ... Heater 12 ... Incoming temperature sensor 13 ... Humidifier 14 ... Humidity sensor 15 ... Compressor 16 ... Air cooler 17 ... Air dryer 18 ... Air tank 19 ... Heater 21 ... Barometer 22 ... Temperature / humidity sensor 23 ... Exit side temperature sensor 24 ... Calculation unit 25 ... Control unit 31 ... Main pipeline 31a ... Connection port 32 ... Exhaust pipe 32a ... Exhaust port 33 ... Branch pipe 34 ... Pipe 35 ... Bypass pipe 41 ... Electro-pneumatic regulator 42 ... First pressure sensor 43 ... First on-off valve 44 ... Second pressure sensor 45 ... Exhaust valve 46 ... Manual valve 47 ... Differential pressure sensor 48 ... Second on-off valve 49 ... Pressure gauge 50 ... Manual four-way valve 51 ... Inner tube 52 ... Outer tube 61 ... Main pipeline 61a ... Exhaust port 62 ... First branch pipe 62a ... Preparation connection port 63 ... Second branch pipe 63a ... Inspection port 64 ... Third branch pipe 64a ... Atmospheric release port 65 ... Fourth branch pipe 66 ... Fifth branch pipe 67 ... Sixth branch pipe 72 ... Preparatory on-off valve 77 ... Second on-off Valve 78 ... Third on-off valve 79 ... Small master 81 ... Third on-off valve 82 ... Fourth on-off valve 83 ... Small master 84 ... Relief valve 91 ... First space 92 ... Second space 93 ... Third space B1 ... First Branch point B2 ... Second branch point B3 ... Third branch point B4 ... Fourth branch point B5 ... Fifth branch point B6 ... Sixth branch point M ... Master Mb ... Small master R1 ... First space R2 ... Second space W …work

Claims (16)

In a leak inspection method for determining whether or not there is a leak in the inspection object by sealing the space and measuring the pressure in the space after the sealing after introducing gas into a predetermined space including the inspection object ,
As the gas, air that does not condense when being introduced into the space without dew condensation, or a gas that has higher specific heat than the surrounding air and does not condense when introduced into the space under pressure is used. A leak inspection method characterized by: As the gas, a gas whose temperature is adjusted to be the same as or substantially the same as the atmospheric temperature when being introduced into the space under pressure is used. The gas is stored in an air tank at a pressure higher than the target pressure of the space, introduced from the air tank by depressurizing the space, and the gas is stored in the air tank at a humidity that does not condense in the air tank. The leak inspection method according to claim 1 or 2, characterized in that The space is a first space and a second space on both sides of the differential pressure sensor that performs the measurement,
The inspection object is included in the second space,
The leak inspection method according to any one of claims 1 to 3, wherein the sealing is performed separately for the first space and the second space. The leak inspection method according to any one of claims 1 to 4, wherein the gas is obtained by humidifying and compressing the air. 6. The leak inspection method according to claim 1, wherein the density, specific heat, and thermal conductivity of the gas introduced under pressure are set to constant values in the plurality of inspections. The leak inspection method according to any one of claims 1 to 6, wherein the air is humidified to obtain the gas, and the space is kept warm by a heat insulating material. The air discharged from the inspection object is discharged to the outside from an openable and closable exhaust port provided in the vicinity of the inspection object when releasing the high-humidity air from the inspection object to the atmosphere. The leak inspection method according to any one of 1 to 7. A predetermined space including the inspection object;
A gas introduction part for introducing gas under pressure into the space;
A sealing part for sealing the space after the introduction of the pressure;
A pressure sensor for measuring the pressure of the space sealed by the sealing part;
Have
When the gas introduction part is pressurized and introduced into the space as the gas, the air has a higher specific heat than the surrounding air without condensation when it is pressurized and introduced into the space, or the surrounding air is pressurized. A leak inspection apparatus characterized in that a gas that does not condense is introduced into the space under pressure. The gas introduction unit includes a temperature adjustment unit that adjusts the temperature of the gas, and adjusts the temperature of the gas so as to be equal to or substantially the same as the ambient temperature when pressurized and introduced into the space. The leak inspection apparatus according to claim 9. The gas introduction unit includes an air tank that stores the gas, the gas is stored in the air tank at a pressure higher than a target pressure in the space and humidity that does not condense in the air tank, and the gas is stored in the air tank from the air tank. The leak inspection apparatus according to claim 9 or 10, wherein the leak inspection apparatus is introduced into the space while reducing the pressure. The leak inspection apparatus according to claim 10, wherein the gas introduction unit includes a humidifier that humidifies air and a compressor, humidifies and compresses air taken in from the surroundings, and stores the compressed air in the air tank. . The pressure sensor is a differential pressure sensor,
The space is a first space and a second space on both sides of the differential pressure sensor,
The inspection object is included in the second space,
The leak inspection apparatus according to any one of claims 9 to 12, wherein the sealing portion seals the first space and the second space individually. 14. The gas introduction unit according to claim 9, wherein the gas introduction unit sets the density, specific heat, and thermal conductivity of the gas before the introduction of pressure to constant values in a plurality of inspections. The described leak inspection apparatus. The gas introduction part further includes a heater, humidifies the air heated by the heater to obtain the gas,
The leak inspection apparatus according to claim 9, further comprising a heat insulating material that keeps the space warm. The air discharged from the inspection object is discharged to the outside from an openable and closable exhaust port provided in the vicinity of the inspection object when releasing the high-humidity air from the inspection object to the atmosphere. Any one of 9 to 15 is a leak inspection device.