JP2023033754A - Foam leakage inspection method and vacuum box - Google Patents

Abstract

To make it easier for an inspector to check a hole in an inspection body regardless of the size of the diameter.SOLUTION: A foam leakage inspection method according to one aspect includes: applying a foaming liquid to an inspection surface of an inspection object; placing a vacuum box having a transparent window on the inspection surface; forming an inner space with the inspection surface and the vacuum box; observing the foaming liquid on the inspection surface while reducing pressure in the inner space until a differential pressure between the pressure in the inner space and the atmospheric pressure reaches a first pressure; observing the foaming liquid on the inspection surface while maintaining the differential pressure in a state of the first pressure; observing the foaming liquid on the inspection surface while further reducing the pressure in the inner space until the differential pressure reaches a second pressure from the first pressure; and observing the foaming liquid on the inspection surface while maintaining the differential pressure in a state of the second pressure.SELECTED DRAWING: Figure 2

Description

The present invention relates to a foam leak test method and a vacuum box used in the foam leak test method.

Conventionally, a foaming leak test method is known as a method for inspecting the presence or absence of a penetration defect in an inspection object (for example, Patent Literature 1). There are two types of foaming leak test methods: the pressurization method and the vacuum method. In the vacuum method in the bubble leakage test method, first, a foaming liquid is applied to the test surface of the test object, then a vacuum box having a transparent window is placed on the test surface of the test object, and the inside of the vacuum box is evacuated. The inspector observes the formation of bubbles of the bubbling liquid applied to the surface to be inspected through the window of the vacuum chamber, thereby detecting the presence or absence of holes that cause gas leakage and their locations.

JP-A-7-27656

In the foam leak test, the easiness of observation by an inspector differs depending on the size of the pore. A hole with a small diameter allows a smaller flow rate of gas to pass through than a hole with a large diameter. Therefore, the amount of foaming is small, and it is difficult for an inspector to find holes. On the other hand, in a hole having a large diameter, since the flow rate of the gas passing through the hole is large, the bubbling liquid in the vicinity of the hole is blown away by the gas passing through the hole, making it difficult to detect the hole.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a foam leak test method and a vacuum chamber that enable an inspector to easily confirm holes in an object to be inspected regardless of the size of the diameter.

In order to solve the above problems, a foaming leak test method according to an aspect of the present invention comprises applying a foaming liquid to an inspection surface of an object to be inspected, and placing a vacuum box having a transparent window on the inspection surface. an internal space is formed by the inspection surface and the vacuum box, and the internal space is depressurized until the differential pressure between the pressure in the internal space and the atmospheric pressure reaches a first pressure, and the observing the bubbling liquid and observing the bubbling liquid on the inspection surface while maintaining the differential pressure at the first pressure until the differential pressure reaches the second pressure from the first pressure; A method of observing the bubbling liquid on the inspection surface while further decompressing the internal space, and observing the bubbling liquid on the inspection surface while maintaining the state where the differential pressure is the second pressure. be.

According to the above method, the observation of the bubbling liquid under the condition that the differential pressure between the atmospheric pressure and the internal space is the first pressure and the observation of the bubbling liquid under the condition that the differential pressure is the second pressure are performed in two stages. observation. By setting the first pressure to be relatively low, when the differential pressure is reduced to the first pressure and the state of the first pressure is maintained, the bubbling liquid near the holes with relatively large diameters flows through the holes into the vacuum chamber. It is possible to suppress blowing away by the gas flowing into. Therefore, when the differential pressure is reduced to the first pressure and maintained at the first pressure, it becomes easier for the inspector to detect holes with relatively large diameters. In addition, by further decompressing the internal space to change the differential pressure from the first pressure to the second pressure, the pressure difference is reduced to the internal space through the hole compared to the case where the differential pressure is maintained at the first pressure. The total volume of incoming gas increases. As a result, the amount of bubbling in the holes increases, so that the inspector can detect holes with relatively small diameters that were difficult to observe when the differential pressure was reduced to the first pressure and held at the first pressure. easier. Therefore, according to the above method, the inspector can easily confirm the hole in the object to be inspected regardless of the size of the diameter.

Further, a vacuum box according to an aspect of the present invention is a vacuum box for a foaming leak test that is placed on an inspection surface of an inspection object, and includes a box body that forms an internal space together with the inspection surface, and the internal space. One or more pipes connected to the box, each having a first atmosphere release path, a second atmosphere release path, and a third atmosphere release path for opening to the atmosphere, and provided in the first atmosphere release path A first on-off valve, a first pressure regulating valve provided in the second atmosphere release path, a second on-off valve provided in the third atmosphere release path, and the third atmosphere release path open to the atmosphere. a second pressure regulating valve provided between the tapered end and the second on-off valve.

According to the above vacuum box, the second on-off valve and the second pressure regulating valve are arranged in series in the channel for opening the internal space to the atmosphere. When the internal space is evacuated with the first on-off valve closed and the second on-off valve open, the pressure in the internal space is regulated to the first pressure regulated by the first pressure regulating valve and the second pressure regulating valve. can. By evacuating the internal space with the first on-off valve closed and the second on-off valve closed, the pressure in the internal space can be regulated by the first pressure regulating valve to a second pressure lower than the first pressure. . Therefore, when the bubble leakage test is performed using the above-mentioned vacuum box, it is possible to easily adjust the pressure in the inner space in two stages, and as a result, the inspector can confirm the holes of the inspection object regardless of the size of the diameter. easier to do. In addition, since the first on-off valve and the first pressure regulating valve are arranged in parallel, when the first on-off valve is opened while the internal space is in a vacuum state, the internal space is quickly returned to atmospheric pressure. can be boosted.

According to the present invention, it is possible to provide a bubble leak test method and a vacuum box that make it easy for an inspector to confirm holes in an object to be inspected regardless of the size of the diameter.

1 is a schematic configuration diagram of a foaming leak test apparatus used in a foaming leak test method according to an embodiment of the present invention; FIG. It is a flowchart which shows the flow of a foaming leak test method. It is a graph which shows the relationship between the elapsed time in a foaming leak test method, and the differential pressure of the atmospheric pressure and the pressure of the space in a vacuum chamber.

Hereinafter, a foaming leak test method and a vacuum box according to an embodiment of the present invention will be described with reference to the drawings.

The foaming leak test method of this embodiment conforms to the vacuum method of JIS Z2329. That is, in the foaming leakage test method of the present embodiment, a vacuum box having a transparent window is arranged on the inspection surface after applying the foaming liquid to the inspection surface of the inspection object. After that, the internal space formed by the inspection surface and the vacuum box is evacuated by a vacuum pump, and the formation of bubbles in the bubbling liquid is observed to detect the location of gas leakage.

FIG. 1 is a schematic configuration diagram of a foaming leak test apparatus 1 used in the foaming leak test method according to the present embodiment. A foam leak test apparatus 1 includes a vacuum box 2 , a vacuum pump 3 , an exhaust pipe 4 connected to the vacuum pump 3 , and a pressure gauge 5 . In the following embodiments, as shown in FIG. 1, the concept of the vertical direction is the vertical direction when the inspection surface 101 of the inspection object 100 faces upward and the vacuum box 2 is placed on the inspection surface 101 from above. shall be consistent with the concept of However, it is used for the convenience of explanation, and does not limit the orientation of the configuration of the invention to that direction.

In the present embodiment, the test object 100 to be inspected for the presence or absence and location of leaks by the foam leak tester 1 is, for example, the bottom of a flat-bottomed cylindrical vertical storage tank. However, the type of test object 100 is not particularly limited. For example, the test object 100 may not be the bottom of the storage tank, but may be the roof or side of the storage tank. Also, the test object 100 may be a structure other than a storage tank.

[Vacuum box configuration]
The vacuum box 2 is a vacuum box for a bubble leak test that is placed on the inspection surface 101 of the inspection body 100 and used. The vacuum box 2 has a box 10 and one or more pipes 20 connected to the box 10 .

The box 10 forms an internal space S together with the inspection surface 101 of the inspection object 100 . The box 10 has a top wall 11 and a peripheral wall 12, and is formed in a substantially rectangular parallelepiped shape with an open bottom surface. The upper wall 11 has a square shape when viewed from above. The top wall 11 is transparent. The upper wall 11 is, for example, an acrylic plate. In this embodiment, the entire top wall 11 is configured as a transparent window that allows the inspector to observe the interior space S. However, the upper wall 11 may have a transparent window in its part and an opaque member in the other part. The upper wall 11 is formed with an inlet/outlet 11a and a through hole 11b.

The peripheral wall 12 is composed of four side walls provided vertically on the periphery of the top wall 11 . A lower end portion of the peripheral wall 12 is an opening edge of the vacuum chamber 2, and is a portion that contacts the inspection surface 101 when the vacuum chamber 2 is arranged on the inspection surface 101. As shown in FIG. For this reason, at least the lower end portion of the peripheral wall 12 is made of a member capable of enhancing the airtightness between the lower end portion of the peripheral wall 12 and the inspection surface 101 of the inspection body 100 . In this embodiment, the entire peripheral wall 12 is made of a sponge-like elastic body.

One or more pipes 20 have a first pipe 21 connected to the inlet/outlet 11 a of the upper wall 11 and a second pipe 22 connected to the through hole 11 b of the upper wall 11 .

Gas flows into the internal space S and gas is discharged from the internal space S through the first pipe 21 . The first pipe 21 is connected to the exhaust pipe 4 . That is, one end of the exhaust pipe 4 is connected to the first pipe 21 via the joint 4 a, and the other end of the exhaust pipe 4 is connected to the vacuum pump 3 . A flow path configured by the first pipe 21 and the exhaust pipe 4 and extending from the inlet/outlet 11 a to the vacuum pump 3 is referred to as an exhaust flow path 31 . When the vacuum pump 3 operates, the internal space S is evacuated through the exhaust passage 31 .

Further, the first pipe 21 constitutes a first atmosphere opening passage 41, a second atmosphere opening passage 42, and a third atmosphere opening passage 43 for opening the internal space S to the atmosphere.

A first on-off valve 51 is provided in the first atmosphere release passage 41 . A first pressure regulating valve 61 is provided in the second atmosphere release passage 42 . A second on-off valve 52 is provided in the third atmosphere release passage 43 . A second pressure regulating valve 62 is provided between the end portion 43 b of the third atmosphere release passage 43 that is open to the atmosphere and the second on-off valve 52 .

In this embodiment, the first atmosphere release path 41 branches from the exhaust flow path 31, the second atmosphere release path 42 branches from the first atmosphere release path 41, and the third atmosphere release path 43 branches from the exhaust flow path 31. are doing. More specifically, one end 41a of the first open-to-air channel 41 is connected to the exhaust channel 31, the other end 41b of the first open-to-air channel 41 is open to the atmosphere, and the second open-to-air channel 42 is connected to a portion between the one end 41a of the first atmosphere release passage 41 and the first on-off valve 51, and the other end 42b of the second atmosphere release passage 42 is opened to the atmosphere. One end 43a of the third open-to-air channel 43 is connected to the exhaust channel 31, and the other end 43b of the third open-to-air channel 43 is open to the atmosphere.

Therefore, in the flow path for opening the internal space S to the atmosphere, the first on-off valve 51 and the first pressure regulating valve 61 are arranged in parallel, and the second on-off valve 52 and the second pressure regulating valve 62 are arranged in parallel. are arranged in series.

The first on-off valve 51 and the second on-off valve 52 are ball valves. However, the first on-off valve 51 and the second on-off valve 52 may not be ball valves, and may be other types of on-off valves such as gate valves and butterfly valves. Also, the first on-off valve 51 and the second on-off valve 52 may be the same kind of on-off valve, or may be different kinds of on-off valves.

The first pressure regulating valve 61 and the second pressure regulating valve 62 are needle valves, respectively. However, the first pressure regulating valve 61 and the second pressure regulating valve 62 may not be needle valves, and may be other types of pressure regulating valves such as globe valves. Also, the first pressure regulating valve 61 and the second pressure regulating valve 62 may be the same type of pressure regulating valves, or may be different types of pressure regulating valves.

One end of the second pipe 22 is connected to the through hole 11 b of the upper wall 11 and the other end of the second pipe 22 is connected to the pressure gauge 5 . Therefore, the pressure in the internal space S is measured by the pressure gauge 5 . The pressure gauge 5 is, for example, a compound gauge capable of measuring both atmospheric pressure and negative pressure.

[Flow of foaming leak test]
Next, the conditions and flow of the foaming leak test method described in this embodiment will be described with reference to FIGS. FIG. 2 is a flow chart showing the flow of the foaming leak test method of this embodiment. FIG. 3 is a graph showing the relationship between the elapsed inspection time t and the pressure difference P between the atmospheric pressure and the pressure in the internal space S in the foaming leak test method of the present embodiment. The differential pressure P is a value obtained by subtracting the pressure in the internal space S from the atmospheric pressure.

(Pressure adjustment work)
Prior to the inspection work, the inspector adjusts the opening degrees of the first pressure regulating valve 61 and the second pressure regulating valve 62 according to the following procedure. With the first on-off valve 51 closed, the second on-off valve 52 closed, and both the first pressure regulating valve 61 and the second pressure regulating valve 62 fully opened, the vacuum pump 3 is operated. As a result, the pressure in the internal space S is reduced from the atmospheric pressure by the vacuum pump 3 . The inspector adjusts the opening degree of the first pressure regulating valve 61 so that the differential pressure P between the pressure in the internal space S and the atmospheric pressure reaches the second pressure P2. Subsequently, the second on-off valve 52 is opened, and the degree of opening of the second pressure regulating valve 62 is adjusted so that the differential pressure P between the pressure in the internal space S and the atmospheric pressure reaches the first pressure P1. After that, the first on-off valve 51 is opened, the pressure in the internal space S is returned to the atmospheric pressure, and the regular inspection work is started.
The opening degrees of the adjusted first pressure regulating valve 61 and the second pressure regulating valve 62 are not changed. This adjustment work is performed at the start of continuous inspection work, and does not need to be performed for each inspection.

(Coating process)
In the bubble leakage test method, first, the bubble liquid F is applied to the test surface 101 of the test object 100 (step S1).

(Placement process)
Next, the vacuum box 2 is arranged on the inspection surface 101, and the internal space S is formed by the inspection surface 101 and the vacuum box 2 (step S2).

(First decompression step)
After placing the vacuum box 2 on the inspection surface 101, the bubbling liquid on the inspection surface 101 is supplied while depressurizing the internal space S until the differential pressure P between the pressure in the internal space S and the atmospheric pressure reaches the first pressure P1. Observe F (step S3).

Specifically, the inspector closes the first on-off valve 51, opens the second on-off valve 52, and both the first pressure regulating valve 61 and the second pressure regulating valve 62 maintain their adjusted opening degrees. , the vacuum pump 3 is activated. As a result, the pressure in the internal space S is reduced from the atmospheric pressure by the vacuum pump 3, and the inspector starts observing the bubbling liquid F immediately after the internal space S starts to be depressurized. On the other hand, the first pressure regulating valve 61 and the second pressure regulating valve 62 whose opening degrees are adjusted in advance maintain the differential pressure P between the pressure in the internal space S and the atmospheric pressure at the first pressure P1.

For example, the first pressure P1 is set within a range of 20 kPa or more and less than 60 kPa. In this embodiment, the first pressure P1 is approximately 55 kPa.

(First holding step)
After depressurizing the internal space S until it reaches the first pressure P1, the bubbling liquid F on the test surface 101 is observed while maintaining the differential pressure P at the first pressure P1 (step S4). In this step, the inspector maintains the state where the differential pressure P is the first pressure P1 for the first minimum retention time T1 or longer and observes it. The first minimum holding time T1 is, for example, 10 seconds.

(Second decompression step)
After the first holding step, the bubbling liquid F on the inspection surface 101 is observed while the internal space S is further reduced in pressure until the differential pressure P reaches the second pressure P2 (step S5).

Specifically, the inspector closes the second on-off valve 52 after the first holding step. As a result, the pressure in the internal space S is further reduced by the vacuum pump 3, and the first pressure regulating valve 61, whose degree of opening is adjusted in advance, reduces the differential pressure P between the pressure in the internal space S and the atmospheric pressure to a second pressure P2. to hold.

For example, the second pressure P2 is set within a range of 30 kPa or more and 80 kPa or less. However, the second pressure P2 is set to a value higher than the first pressure P1. Further, for example, the difference ΔP between the first pressure P1 and the second pressure P2, that is, the value ΔP obtained by subtracting the first pressure P1 from the second pressure P2 is preferably set within a range of 5 kPa or more and 60 kPa or less. . In this embodiment, the second pressure P2 is approximately 70 kPa.

(Second holding step)
While maintaining the differential pressure P at the second pressure P2, the bubbling liquid F on the test surface 101 is observed (step S6). In this step, the inspector maintains the differential pressure P at the second pressure P2 for the second minimum retention time T2 or longer for observation. The second minimum holding time T2 is set longer than the first minimum holding time T1. The second minimum holding time T2 is, for example, 20 seconds.

(Atmospheric release process)
After the second holding step, the internal space S is opened to the atmosphere (step S7). Specifically, the inspector opens the first on-off valve 51 . Thereby, the pressure in the internal space S is raised to the atmospheric pressure.

When the inspection object 100 is formed with holes h, the inspector applies the bubbling liquid around the holes h in at least one step of the first decompression step, the first holding step, the second decompression step, and the second holding step. Bubbling of F can be observed. After opening the internal space S to the atmosphere, the inspector marks a portion where foaming is confirmed on the inspection surface 101 .

As described above, according to the foaming leakage test method according to the present embodiment, the foaming liquid is observed in a state where the differential pressure P between the atmospheric pressure and the internal space S is the first pressure P1, and the differential pressure P is at the second pressure P2. By setting the first pressure P1 to a relatively small value, the bubbling liquid F in the vicinity of the hole h having a relatively large diameter is caused to flow into the vacuum chamber 2 through the hole h in the first decompression process and the first holding process. You can suppress being blown away by Therefore, in the first depressurizing step and the first holding step, the inspector can easily detect the hole h having a relatively large diameter. In addition, by further decompressing the internal space S to reduce the differential pressure P to the second pressure P2, the total volume of the gas passing through the holes h from the first decompression step to the second holding step is reduced to To increase. As a result, the amount of bubbling in the hole h increases, so that the inspector can easily detect the hole h with a relatively small diameter, which was difficult to observe in the first depressurizing step and the first holding step. Therefore, according to the above method, the inspector can easily confirm the hole h of the inspection object 100 regardless of the size of the diameter.

In addition, after the first holding step, the internal space S is once opened to the atmosphere, and a point where foaming is confirmed on the inspection surface 101 is marked before the first holding step is completed. It is also conceivable to shift to two decompression steps. However, once the internal space S is opened to the atmosphere after the first holding step, the bubbling liquid F enters the holes h of the test object 100 due to the gas that has flowed into the internal space S due to the opening to the atmosphere. If the bubbling liquid F that has entered the hole h clogs the hole h, it becomes difficult to find the hole h in the subsequent second pressure reduction step and second holding step. On the other hand, in the present embodiment, since the internal space S is further decompressed without opening the internal space S to the atmosphere after the first holding step, the holes h are closed with the bubbling liquid F before the second holding step. can be suppressed.

In the vacuum box 2 of this embodiment, the second on-off valve 52 and the second pressure regulating valve 62 are arranged in series in the channel for opening the internal space S to the atmosphere. When the internal space S is evacuated with the first on-off valve 51 closed and the second on-off valve 52 open, the pressure in the internal space S is regulated by the first pressure regulating valve 61 and the second pressure regulating valve 62. The first pressure P1 can be adjusted. When the internal space S is evacuated with the first on-off valve 51 closed and the second on-off valve 52 closed, the pressure in the internal space S is reduced to a first pressure lower than the first pressure P1 regulated by the first pressure regulating valve 61 . 2 can be adjusted to pressure P2. Therefore, when the bubble leakage test is performed using the vacuum chamber 2, the pressure in the internal space S can be easily adjusted in two stages. Easier for inspectors to check. Further, since the first on-off valve 51 and the first pressure regulating valve 61 are arranged in parallel, when the first on-off valve 51 is opened while the internal space S is in a vacuum state, the internal space S is The pressure can be rapidly increased to atmospheric pressure.

[Other embodiments]
The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the gist of the present invention.

For example, the connection relationship among the exhaust flow path 31, the first open-to-air channel 41, the second open-to-air channel 42, and the third open-to-air channel 43 is not limited to that described in the above embodiment. For example, one end 42a of the second open-to-air channel 42 may be directly connected to the exhaust channel 31, or the first open-to-air channel 41 and the third open-to-air channel 43 may indirectly connect to the exhaust channel 31. may be connected to

However, another flow path is not connected between the end portion 41b of the first atmosphere opening passage 41 that is open to the atmosphere and the first on-off valve 51, and the second atmosphere opening passage 42 is open to the atmosphere. Another flow path is not connected between the closed end portion 42 b and the first pressure regulating valve 61 , and the end portion 43 b opened to the atmosphere in the third atmosphere opening passage 43 and the second on-off valve 52 No other flow path is connected between

The number of inflow/outlet ports 11a provided in the box 10 may not be one, and may be two or more. For example, the box 10 may be provided with one or more inflow/outlet ports 11a other than the inflow/outlet port 11a connected to the vacuum pump 3, and the other one or more inflow/outlet ports 11a may be provided with a first atmosphere release path 41, The second open-to-air channel 42 and the third open-to-air channel 43 may be connected. For example, the box 10 may be provided with three inflow/outlet ports 11a to which the first atmosphere opening path 41, the second atmosphere opening path 42, and the third atmosphere opening path 43 are respectively connected.

It is not always necessary to use the vacuum chamber 2 having the above configuration for the foaming leak test method of the present invention. For example, a vacuum box that does not include part or all of the third atmosphere release path 43, the second on-off valve 52, and the second pressure regulating valve 62 may be used in the foaming leak test method of the present invention.

Although the pressure gauge 5 is provided in the second pipe 22 connected to the through hole 11b of the upper wall 11 in the above embodiment, the pressure gauge may be provided in the first pipe.

The second minimum holding time T2 may be the same as the first minimum holding time T1. For example, the second minimum holding time T2 may be 10 seconds.

1: Test apparatus 2: Vacuum box 3: Vacuum pump 4: Exhaust pipe 5: Pressure gauge 10: Box 11: Upper wall 12: Peripheral wall 20: Piping 31: Exhaust flow path 41: First atmospheric release path 42: Second Atmosphere release path 43 : Third atmosphere release path 51 : First on-off valve 52 : Second on-off valve 61 : First pressure regulating valve 62 : Second pressure regulating valve 100 : Inspection body 101 : Inspection surface h : Hole F : Foaming Liquid S: Internal space

Claims (3)

Apply the foaming liquid to the inspection surface of the object to be inspected,
A vacuum box having a transparent window is placed on the inspection surface, and an internal space is formed by the inspection surface and the vacuum box;
observing the bubbling liquid on the test surface while reducing the pressure in the internal space until the pressure difference between the pressure in the internal space and the atmospheric pressure reaches a first pressure;
observing the bubbling liquid on the test surface while maintaining the differential pressure at the first pressure;
observing the bubbling liquid on the inspection surface while further reducing the pressure in the internal space until the differential pressure reaches the second pressure from the first pressure;
A foaming leak test method, wherein the foaming liquid on the test surface is observed while the differential pressure is maintained at the second pressure. maintaining the state in which the differential pressure is at the first pressure for a first minimum holding time or longer;
maintaining the state in which the differential pressure is at the second pressure for a second minimum holding time or longer;
2. The foam leak testing method of claim 1, wherein said second minimum retention time is longer than said first minimum retention time. A vacuum box for a foaming leak test placed on the inspection surface of the inspection object,
a box that forms an internal space together with the inspection surface;
one or more pipes connected to the box, each having a first atmosphere opening path, a second atmosphere opening path, and a third atmosphere opening path for opening the internal space to the atmosphere;
a first on-off valve provided in the first atmosphere open path;
a first pressure regulating valve provided in the second atmospheric release passage;
a second on-off valve provided in the third atmosphere open path;
A vacuum box, comprising: a second pressure regulating valve provided between the end portion of the third atmosphere open path that is open to the atmosphere and the second on-off valve.

Images