JP4257647B2 - Airtight inspection method for inner tube of double flexible tube - Google Patents

Description

  The present invention belongs to the technical field of inspecting the airtightness of the inner tube of a double flexible tube.

  Double flexible pipes, for example, double flexible pipes having a relatively small diameter and coated with a resin used for gas piping in a house, tend to be frequently used because of good workability. About the structure of the double flexible tube for gas, Fig.5 (a) shows an axial sectional view, and FIG.5 (b) shows the AA sectional view of Fig.5 (a). A gas double flexible tube (hereinafter referred to as a double flexible tube) 1 includes, for example, an inner tube (so-called corrugated tube) 1b in which a corrugated shape is formed in the axial direction and a flexible gas flows. A space 1c defined along the axial center of the inner tube 1b is provided between the outer surface of the tube 1b and a flexible outer tube 1a densely provided on the outer periphery of the inner tube 1b. The outer tube 1a of the double flexible tube is usually made of resin. The space 1c is formed at an equal angle on the inner circumference of the outer tube 1a. According to the double flexible tube 1 having the above structure, for example, even when the inner tube 1b is torn during construction, the leaked gas flows through the space 1c and is attached to the end of the double flexible tube 1. It will be detected by the detector.

  Conventionally, the double flexible tube 1 has been manufactured as follows. First, a stainless steel thin plate is formed into a cylindrical shape and welded to form a cylindrical body, and the outer periphery of the cylindrical body is corrugated in the axial direction to form the inner pipe 1b (inner pipe forming step). Next, a gas for airtightness inspection is press-fitted into the inner tube 1b, both ends of the inner tube 1b are sealed and inserted into a vacuum chamber, the vacuum chamber is set to a negative pressure, and leakage of the gas for airtightness inspection is detected. Is detected to inspect the airtightness of the inner tube 1b (airtightness inspection process). Thereafter, the outer pipe 1a is provided around the good inner pipe 1b in the airtight inspection process. (Outer tube forming step).

  According to the above-described conventional manufacturing method, the airtight inspection of the inner tube 1b can be performed with relatively high accuracy because the inner tube 1b is performed in a single state, but in the airtight inspection step, Since the upstream inner pipe forming process and the downstream outer pipe forming process, which can be carried out continuously, are separated, there is a problem that the efficiency in industrial production is lowered and it is uneconomical.

  When the double flexible tube 1 is manufactured by continuously performing the inner tube forming step and the outer tube forming step, only the inner tube 1b is provided in the state of the double flexible tube 1 with the outer tube 1a being provided around the outer tube 1a. It is necessary to check the airtightness. Furthermore, in order to economically manufacture the double flexible tube 1, it is necessary to efficiently perform the airtight inspection process.

  For example, Patent Documents 1 and 2 below disclose an example of a method for inspecting the airtightness of an inner pipe of a double pipe. The airtight inspection method of Patent Document 1 is a method mainly intended to inspect the airtightness of the inner pipe of a double gas pipe buried in the ground, and “a double pipe composed of an inner pipe and an outer pipe”. In this, the space formed by the inner tube and the outer tube is blocked in the measurement section, and an inspection gas is injected into the blocked space, an air flow is created in the inner tube, and the inspection gas is in this state. The detection part is inserted into the inner tube and moved, and the change position of the gas concentration detected by the gas detection part is specified as a leak location ".

Further, the airtight inspection method of Patent Document 2 is a method mainly intended to inspect the airtightness of the inner tube of the multiple vacuum piping of a fusion reactor, and “the outside of the tube through which the gas flows is connected to the inner tube. Gas leakage of the inner pipe of the multiple pipe having a structure in which the gas flows from the upstream side to the downstream side of both ends of the gap between the inner pipe and the outer pipe (intermediate portion) In the method of detecting a location, a carrier gas having a viscous flow property is supplied to the inner pipe and the intermediate section from the upstream side of the inner pipe and the intermediate section, and the average pressure in the intermediate section is Set to be higher than the average pressure, mix the leak test gas from the upstream side of the intermediate part into the carrier gas, and detect the leak test gas flowing into the inner pipe through the leak point of the inner pipe To do.
Japanese Patent Laid-Open No. 10-281915 JP 2001-4479 A

The airtight inspection methods of Patent Documents 1 and 2 inspect the airtightness of the inner pipe of a double pipe having a relatively large aperture and a large space (intermediate portion). This is not a suitable method for efficiently inspecting the airtightness of the inner tube of a double flexible tube of about 50 mm.
The present invention has been intensively studied by the inventors of the present invention in response to the demand for economical production of the above-mentioned double flexible tube, and can perform an airtight inspection of the inner tube of the double flexible tube efficiently. An airtight inspection method is provided.

The airtightness inspection method of the present invention has a space defined along the axis of the inner tube between the flexible inner tube and the outer peripheral surface of the inner tube, and is provided around the outer periphery of the inner tube. A method of inspecting the airtightness of the inner tube of a double flexible tube comprising a flexible outer tube, wherein the space of the wound double flexible tube is sealed and the outer tube is sealed in the space. A gas tightness inspection gas having a pressure capable of expanding the tube is supplied, the inside of the inner tube is set to a low pressure from the space, and the gas for airtightness inspection leaking from the inner tube is detected.

According to the present invention, the space of the wound double flexible tube is sealed, and the gas for airtightness inspection with a pressure capable of expanding the outer tube is injected into the space, and the inside of the inner tube of the double flexible tube is injected. The air tightness of only the inner pipe is accurately and efficiently inspected in the state of a double flexible pipe by a very simple method of lowering the pressure from the space and detecting the gas for airtight inspection leaked from the inner pipe. This makes it possible to meet the demand for economical production of double flexible tubes.

  The method for inspecting the inner tube of the double flexible tube of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of a specific embodiment of the airtightness inspection method of the present invention. FIG. 2 is a partially enlarged cross-sectional view of the sealed joint of FIG. 3, 4, and 6 are schematic configuration diagrams illustrating an example of a specific embodiment of a more preferable airtight inspection method. In the following description, the double flexible tube that is the target of the airtight inspection is the same as the double flexible tube 1 described above.

[Embodiment 1]
As shown in FIG. 1, the double flexible tube 1 has a double flexible tube 1 cut at a predetermined length, preferably a unit length to be shipped, and one end of the double flexible tube 1. A sealing joint 2 for sealing, a sealing joint 3 for sealing the other end, and a sealing joint 2 at the one end are connected to supply gas for airtightness inspection into the space 1c of the double flexible tube 1. Gas supply means 4 for airtight inspection, gas detection means for gas tightness inspection (so-called leak gas detector) 5 for detecting the gas for airtight inspection while making the inside of the inner tube 1b of the double flexible tube 1 low in pressure, Airtight inspection is carried out by the structure consisting of The sealing joint 2 that seals the one end, the gas supply means 4 for airtightness inspection, and the gas detection means 5 for airtightness inspection are connected via valves 9a and 9b that open and close at a predetermined timing. The selection of the gas for airtight inspection is not particularly limited, and one of various gases such as helium and hydrogen can be selected.

As shown in FIG. 2, one end of the outer tube 1a is peeled off so that the inner tube 1b is exposed for a predetermined length.
The sealing joint 2 that seals one end of the double flexible tube 1 can be circulated with the seal pair 21 and 22 that can seal one end of the space 1c of the double flexible tube 1 and the space 1c. A first insertion port 23 having a fluid passage 23a is provided. The one seal 22 can be in close contact with one end of the inner tube 1b, and the other seal 21 can be in close contact with one end of the outer tube 1a. Further, the sealed joint 2 includes an end portion capable of sealing one end of the inner tube 1b and a second insertion port 24 including a fluid passage 24a that can flow through the inside of the inner tube 1b. .
A sealing joint 3 that seals the other end of the double flexible tube 1 seals the other end of the space 1c and the other end of the inner tube 1b.

  The fluid passage 23a of the first insertion port 23 is connected to the gas supply means 4 for airtight inspection, and the gas supply means 4 for airtight inspection is airtight to the space 1c sealed through the fluid passage 23a. Supply inspection gas. The fluid passage 24a of the second insertion port 24 is connected to the gas detection means 5 for airtight inspection, and the gas detection means 5 for airtight inspection is connected to the inner pipe 1b via the fluid passage 24a. The air inside is sucked, and the inside of the inner tube 1b is brought to a low pressure from the space 1c. Therefore, if there is a defect in the inner pipe 1b that allows gas leakage, the gas for airtight inspection leaks into the inner pipe 1b, and the gas for airtight inspection is detected by the gas detecting means 5 for airtight inspection. The airtightness of 1b is confirmed.

  According to the above configuration, the space 1 c is sealed with the sealing joints 2 and 3, the gas for gas tightness inspection is supplied to the space 1 c with the gas supply means 4 for gas tightness inspection, and the gas detection means 5 for gas tightness inspection with the gas tightness inspection gas detection means 5. While the inside of the inner pipe 1b is set to a low pressure from the space 1c, the gas for gas tightness inspection leaked from the inner pipe 1b is detected by the gas detecting means 5 for gas tightness inspection, and the inner pipe 1b of the double flexible tube 1 is detected. It becomes possible to inspect the airtightness.

[Embodiment 2]
An example of a desirable mode of the airtightness inspection method of the present invention will be described with reference to FIG. In the figure, the same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.
In a desirable mode, the double flexible tube 1 includes a double flexible tube 1 similar to the above, a sealing joint 2, a gas supply means 4 for airtightness inspection, and a gas detection means 5 for airtightness inspection, Further, a sealing joint 2 ′ for sealing the other end of the double flexible tube 1 and a sealing joint 2 ′ at the other end are connected to each other inside the inner tube 1 b of the double flexible tube 1. An airtight inspection is performed by a configuration including a carrier gas supply unit 7 that supplies a carrier gas and a replacement detection unit 6 that detects that the space 1c of the double flexible tube 1 has been replaced with an airtight inspection gas. The sealing joint 2 'that seals the other end, the carrier gas supply means 7, and the replacement detection means 6 are connected via valves 9c and 9d that open and close at a predetermined timing.

  The sealing joint 2 ′ for sealing the other end of the double flexible tube 1 basically has the same structure as the sealing joint 2 described with reference to FIG. That is, as shown in FIG. 2, the sealing joint 2 ′ includes a seal pair 21 ′ and 22 ′ that can seal the other end of the space 1 c of the double flexible tube 1, and a fluid that can flow through the space 1 c. A third insertion opening 23 'having a passage 23'a is provided. The one seal 22 'can be brought into close contact with the other end of the inner tube 1b, and the other seal 21' can be brought into close contact with the other end of the outer tube 1a. Further, the sealing joint 2 ′ includes an end portion capable of sealing the other end of the inner tube 1b and a fourth insertion port 24 ′ including a fluid passage 24′a capable of flowing through the inner tube 1b. Have.

The fluid passage 23 ′ a of the third insertion port 23 ′ is connected to the replacement detection means 6, and the replacement detection means 6 is connected to the space 1 c with an airtight inspection gas supply means 4. Is detected, and it is detected that the space 1c has been replaced with the gas for airtightness inspection, the valve 9c is closed, and the space 1c is sealed.
The fluid passage 24'a of the fourth insertion port 24 'is connected to the carrier gas supply means 7, and the carrier gas supply means 7 enters the fluid passage 24' to the inside of the inner pipe 1b. A carrier gas is supplied via a. Although the selection of the carrier gas is not particularly limited, a gas having a higher specific gravity than the gas for airtight inspection, specifically, for example, when helium is used as the gas for airtight inspection, It is desirable to use nitrogen.

According to the above configuration, the airtightness of the inner tube 1b of the double flexible tube 1 is inspected as follows.
A double flexible tube 1 having a predetermined length is prepared. A sealing joint 2 is connected to one end of the double flexible tube 1 and a sealing joint 2 ′ is connected to the other end, and both ends of the double flexible tube 1 are sealed. The air detection test gas detection means 5 sucks the internal air of the inner pipe 1b. After the inside of the inner pipe 1b reaches a predetermined pressure, the gas for airtight inspection is supplied to the space 1c by the gas supply means 4 for airtight inspection. The replacement detection means 6 detects that the space 1c has been replaced with the gas for airtightness inspection, and closes the valve 9c. Thereafter, the valve 9d is opened, and a predetermined amount of carrier gas is supplied into the inner pipe 1b. At this time, if the gas for airtightness inspection leaks into the inner pipe 1b, the gas for airtightness inspection is quickly transported to one end by the transport gas, and the gas for airtightness inspection connected to the one end. Since it can detect rapidly with the detection means 5, it becomes possible to perform the airtight test | inspection of the inner pipe | tube 1b accurately and efficiently.

[Embodiment 3]
Another example of a desirable mode of the airtightness inspection method of the present invention will be described with reference to FIG. In the figure, the same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.
In a desirable embodiment, the double flexible tube 1 includes a sealing joint 2 and a sealing joint 3 similar to those described above, a gas supply means 4 for airtight inspection, and a gas detection means 5 for airtight inspection, and further includes a coil. An airtight inspection is performed by a configuration including the double flexible tube 1 wound in a shape. As described above, if the airtight inspection is performed in a state where the double flexible tube 1 is wound in a coil shape, the airtight inspection of the double flexible tube 1 can be performed economically without taking place for inspection. In the case of performing an airtight inspection in a state where the double flexible tube 1 is wound in a coil shape, a defect of the inner tube 1b may be blocked by the bent outer tube 1a. In order to avoid the blockage, the pressure of the gas for airtight inspection supplied to the space 1c is set to 0. 0-5 . It is desirable to expand the outer tube 1a to about 2 (Mpa).

[Embodiment 4]
Another example of a desirable mode of the airtightness inspection method of the present invention will be described with reference to FIG. In FIG. 6, the same components as those described above are denoted by the same reference numerals.

  In Embodiment 4, the double flexible tube 1 includes a sealing joint 2 that seals one end of the double flexible tube 1, a sealing joint 2 ′ that seals the other end, Gas supply means 4 for airtightness inspection connected to the sealing joint 2 via a valve 9a, and gas detection means for airtightness inspection connected to the sealing joints 2 and 2 'for sealing both ends via a valve 9b. 5 and a replacement detection means 6 connected to the sealing joint 2 'at the other end via a valve 9c is subjected to an airtight inspection.

  According to the above configuration, since the gas detection means 5 for airtightness inspection is connected to the sealing joints 2 and 2 'at both ends, for example, when the inner pipe 1b near the sealing joint 2' at the other end is defective. But the defect is detected without time delay. That is, the gas for airtightness inspection supplied from the sealing joint 2 to the space 1c moves to the other end through the space 1c, leaks from the defect on the other end side to the inner tube 1b, and passes through the sealing joint 2 ′ for airtightness inspection. Since the gas detection means 5 detects the leakage of the gas for the airtightness inspection in a shorter time than when the gas detection means 5 for the airtightness inspection is connected only to the sealed joint 2 at one end.

  In the above embodiment, the timing for supplying the gas for airtight inspection to the space 1c by the gas supply means for airtight inspection 4 and the timing for sucking the air in the inner pipe 1b by the gas detection means for airtight inspection 5 May be set appropriately. For example, if the gas for airtight inspection is simultaneously supplied to the space 1c while sucking the air inside the inner tube 1b, the airtight inspection can be performed quickly.

  The present invention is applied not only to a double flexible tube but also to a security inspection inside a tube containing a plurality of tubes such as a triple or a quadruple, and further to a large gas as well as a home gas tube as in the above embodiment. It can be applied to air tightness inspection of tubes.

It is a schematic block diagram which shows an example of the structure which performs the airtight test | inspection of the double flexible tube of this invention. It is a principal part expanded sectional view which shows the detail of the sealing joint of FIG. It is a schematic block diagram which shows another example of the structure which performs the airtight test | inspection of the double flexible tube of this invention. It is a schematic block diagram which shows another example of the structure which performs the airtight test | inspection of the double flexible tube of this invention. It is a schematic structure figure explaining the structure of a double flexible tube. It is a schematic block diagram which shows another example of the structure which performs the airtight test | inspection of the double flexible tube of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Double flexible tube, 1a outer tube, 1b inner tube, 1c space 2 (2 ') Sealing joint 3 Sealing joint 4 Gas supply means for airtight inspection 5 Gas detection means for airtight inspection 6 Replacement detection means 7 Carrier gas Supply means 9 (9a, 9b, 9c, 9d) Valve

Claims (2)

A flexible outer tube that has a space defined along the axis of the inner tube between the inner tube having flexibility and the outer peripheral surface of the inner tube and is provided around the outer periphery of the inner tube A method for inspecting the airtightness of the inner tube of a double flexible tube comprising: sealing the space of the wound double flexible tube and airtight at a pressure that allows the outer tube to expand into the space An airtight inspection method for a double flexible tube, characterized in that an inspection gas is supplied, the pressure inside the inner tube is lowered from the space, and an airtight inspection gas leaking from the inner tube is detected. The airtight inspection method for a double flexible tube according to claim 1, wherein the gas for airtight inspection leaked from the inner tube is detected at both ends of the inner tube.

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