JP4249675B2 - Gas leak inspection system for piping in cryogenic containers - Google Patents

Description

  The present invention relates to a gas leak inspection system for piping in a cryogenic container that can specify the gas leaking location when gas leaks from the piping in a cryogenic container having piping inside.

  Conventionally, a gas leak inspection of piping in a cryogenic container has been performed using a helium leak detector. This principle is a system in which helium gas is allowed to flow through a piping system that is considered to have a gas leak, and the leaked point is detected by a helium leak detector (see Non-Patent Document 1 below).

A general helium leak inspection method is as follows.
(1) Vacuum spraying method Measured by evacuating the inside of the test object to the vacuum, spraying helium from the outside, and detecting helium that has entered the test object from the leaked part.
(2) Hood method Measurement is performed by evacuating a test object covered with a plastic bag filled with helium, and detecting helium that has entered the test object from the leak point.
(3) Sniffer method If the specimen cannot be evacuated to vacuum due to strength or other reasons, helium (or a mixed gas of helium and other gases) is pressurized and injected into the specimen, and the helium flowing out from the leak point Is measured by inhaling and detecting with a probe.
(4) Pumping method Measurement is performed by using a pumping device to place a test object in which helium has been sealed under pressure in a chamber and detecting helium flowing out under a vacuum differential pressure. It can be used for leak testing of hermetically sealed small mass production parts.
Physical Engineering Experiment 4 “Vacuum Technology”, Genichi Horikoshi, The University of Tokyo Press, P130-138

  In the conventional gas leak inspection system described above, when the helium leak detector can be brought close to the expected gas leak location, the gas leak location can be identified naturally. However, if a gas leak occurs in the container, it can be determined whether or not the gas leaks at any point in the piping system, but the helium leak detector cannot be brought close to that detailed point. It is impossible. Therefore, when damage that causes gas leakage occurs in the low-temperature container, there is only a method for checking by opening the container.

  In view of the above situation, an object of the present invention is to provide a gas leak point inspection system for piping in a cryogenic container that can accurately and quickly measure the gas leak location of piping in the cryogenic vessel. .

In order to achieve the above object, the present invention provides
[1] In a gas leak inspection system for piping in a cryogenic container, a DC magnetic field is applied to the piping system in the cryogenic container to be inspected while a liquefied gas made of a paramagnetic substance is allowed to flow to increase the inspection location. It is characterized by measuring with a sensitive magnetic sensor and identifying a gas leak point.

  [2] In the gas leak location inspection system for piping in the cryogenic container described in [1] above, the high-sensitivity magnetic sensor is a SQUID magnetic sensor.

  [3] In the gas leak location inspection system for piping in the cryogenic vessel described in [1] above, the cryogenic vessel is an outer vessel containing a superconducting coil.

  According to the present invention, the following effects can be achieved.

  (1) When a gas leak occurs in the piping in the cryogenic container, the exact damaged part can be clarified at an early stage, so that repair can be carried out at an early stage.

  (2) Since the liquefied gas made of a paramagnetic substance is vaporized at room temperature, it can be inspected without fouling the piping system.

  In a system for inspecting gas leaks in piping in a cryogenic vessel, a DC magnetic field is applied to the piping system in the cryogenic vessel to be inspected while flowing a liquefied gas made of a paramagnetic substance, and the inspection location is detected by a SQUID magnetic sensor. Measure and identify gas leak points. Therefore, when a gas leak in the piping in the cryogenic container occurs, the exact failure point can be identified at an early stage, so that the repair can be performed at an early stage. In particular, a liquefied gas made of a paramagnetic substance is vaporized at room temperature, so that it can be inspected without polluting the piping system.

  Hereinafter, embodiments of the present invention will be described in detail.

The principle of the gas leak location inspection system for piping in the cryogenic container of the present invention is as follows.
(1) A liquefied gas (for example, liquid oxygen or liquid air) made of a paramagnetic substance is magnetized in a DC magnetic field.
(2) When a liquefied gas made of a paramagnetic substance is allowed to flow through a normal piping system, a state in which the fluid is flowing along the piping can be observed with a high-sensitivity magnetic sensor by applying a DC magnetic field. In other words, when a liquefied gas consisting of a paramagnetic substance is flowed when the piping system is damaged, the magnetic sensor can observe how the liquefied gas consisting of the paramagnetic substance leaks from the damaged part of the pipe by applying a DC magnetic field. . Therefore, the leak location of the piping system can be accurately detected.

  FIG. 1 is a schematic view of a gas leak inspection system for piping in a cryogenic container showing an embodiment of the present invention.

  In this figure, 1 is an outer tank container, 2 is a first liquid chamber disposed in the outer tank container 1, 3 is a superconducting coil disposed in the first liquid chamber 2, and 4 is the first liquid chamber. The first liquefied gas in the liquid chamber 2, 5 is a vaporized gas suction port, 6 is a vaporized gas discharge port, 7 is a refrigerator, 8 is a compressor unit, and 11 is a liquefied gas made of a paramagnetic substance. A liquefied gas cylinder, 12 is a pipe, 13 is a second liquid chamber connected to the pipe 12, 14 is a second liquefied gas in the second liquid chamber 13, 21 is a DC magnetic field generator, 22 is a SQUID ( A superconducting quantum interference device (Superconducting Quantum Interference Device) magnetic sensor 23 is a measuring device connected to the SQUID magnetic sensor 22. Here, the DC magnetic field generator 21 and the SQUID magnetic sensor 22 identify (specify) the gas leak position of the pipe 12 while moving along the pipe 12 filled with a liquefied gas made of a paramagnetic substance from the outside of the outer vessel 1. To do.

  As described above, in the gas leak inspection, the liquefied gas cylinder 11 for supplying the liquefied gas made of the paramagnetic substance is connected to the pipe 12 arranged in the outer tank container 1 as the low temperature container, and the liquefaction made of the paramagnetic substance is made. Supply gas. Then, while applying a DC magnetic field by the DC magnetic field generator 21, the SQUID magnetic sensor 22 images the state of the liquefied gas made of a paramagnetic substance, so that there is no leakage of the liquefied gas made of the paramagnetic substance from the pipe 12. Measure.

  FIG. 2 is a diagram showing a measurement example in the case of a sound pipe measured by the gas leak point inspection system of the present invention, and FIG. 3 is an example in which a liquefied gas leak made of a paramagnetic substance is measured in a part of the pipe. FIG.

  When the state of the liquefied gas made of a paramagnetic substance is measured by the SQUID magnetic sensor 22 while applying a DC magnetic field by the DC magnetic field generator 21 along the pipe 12, As shown in FIG. 2, the flow path of the liquefied gas made of a paramagnetic substance can be properly imaged along the pipe 12. 2 is an image of the SQUID magnetic sensor 22 showing a state in which the flow of the liquefied gas made of a paramagnetic substance in the pipe 12 is healthy. As can be seen from the image 31, when no gas leakage occurs, liquefied gas composed of a paramagnetic substance is observed only in a portion along the pipe 12.

  On the other hand, for example, when a liquefied gas made of a paramagnetic substance leaks at a part A of the pipe 12, the liquefied gas made of a paramagnetic substance leaks from the pipe 12 as shown in an image 32 in FIG. Since it can visually recognize how to put out, it turns out that the piping 12 is damaged in this location A.

  FIG. 4 is a schematic diagram of a DC magnetic field generator and a high sensitivity magnetic sensor showing an embodiment of the present invention.

  In this figure, 41 is a SQUID magnetic sensor, 42 is a lead wire of the SQUID magnetic sensor 41, 43 is a measuring device connected to the lead wire 42, 44 is a DC magnetic field applied to a liquefied gas made of paramagnetic material in the pipe. DC magnetic field generator.

  In the present invention, since measurement is performed along the pipe 12 from the outside of the outer tank container 1 as a low temperature container, the measurement of the liquefied gas made of a paramagnetic substance is required to have high accuracy. For this purpose, the SQUID magnetic sensor 41 is used in the present invention.

  This SQUID magnetic sensor is a high-sensitivity magnetic sensor that can detect a magnetic field of 1 / 50,000,000 or less of the geomagnetism. The features are as follows: (1) The superconducting quantization phenomenon is used, and the sensitivity is 3 digits or more higher than that of the conventional magnetic sensor. (2) A wide frequency range from DC to several tens of kHz can be detected. That is, the detection sensitivity does not depend on the frequency. (3) There is a high spatial resolution. Development of SQUID using high temperature superconducting thin film enables operation at liquid nitrogen temperature (77.3K).

  As described above, the liquefied gas that is a measurement target is a liquefied gas made of a paramagnetic substance, and examples of the liquefied gas made of a paramagnetic substance include liquid oxygen and liquid air.

  Further, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

  The gas leak location inspection system for piping in a cryogenic container according to the present invention is suitable for management and maintenance of piping systems such as superconducting magnets that require quick identification of gas leak locations.

It is a schematic diagram of the gas leak location inspection system of piping in the cryogenic container which shows the Example of this invention. It is a figure which shows the example of a measurement in the case of the healthy piping measured by the gas leak location inspection system of this invention. It is a figure which shows the example by which the liquefied gas leak which consists of paramagnetic substances was measured in a part of piping measured by the gas leak location inspection system of this invention. It is a schematic diagram of a DC magnetic field generator and a high sensitivity magnetic sensor showing an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer tank container 2 1st liquid chamber 3 Superconducting coil 4 1st liquefied gas 5 Vaporized gas suction port 6 Vaporized gas discharge port 7 Refrigerator 8 Compressor unit 11 Liquefaction which supplies liquefied gas which consists of paramagnetic substances Gas cylinder 12 Piping 13 Second liquid chamber 14 Second liquefied gas 21, 44 DC magnetic field generator 22, 41 SQUID magnetic sensor 23, 43 Measuring device 31, 32 Image 42 SQUID magnetic sensor lead wire

Claims (3)

A DC magnetic field is applied to the piping system in the cryogenic vessel to be inspected while a liquefied gas made of paramagnetic material is applied, and the inspection location is measured with a high-sensitivity magnetic sensor to identify the location of the gas leak. A gas leak inspection system for piping in cryogenic containers. 2. A gas leak location inspection system for piping in a cryogenic container according to claim 1, wherein the high-sensitivity magnetic sensor is a SQUID magnetic sensor. 2. A system for inspecting gas leaks in a pipe in a cryogenic container according to claim 1, wherein the cryogenic container is an outer vessel containing a superconducting coil.

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