JP2000035372A - Inspection method through foaming by infrared ray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a small leakage part by allowing the temperature of foamed liquid applied to a to-be-inspected object where the inside is pressurized to differ from the temperature of a pressurized gas and extracting a part with a temperature difference from the infrared image on the surface of the inspection object. SOLUTION: For example, the leakage of an inspection object surface 2 on the meld line of a cylindrical container 1 which is pressurized by pressurized air is inspected by applying a foaming liquid at a temperature higher than the temperature of the pressurized air, for example, by approximately 3 deg.C for example by a spray 3. An image picked up by an infrared camera 4 is processed by an image-processing device 5, a part with a low temperature is extracted, and foaming position is displayed on the screen of a monitor 6 or output is made to an alarm lamp 7. Even in the case of a small hole where the diameter of a leakage part is approximately several tens of μm, a foam with a diameter of approximately several mm is generated due to a leaked gas and is identified by a temperature difference. The temperature difference between the foaming liquid and the pressurized air is preferably about 10 deg.C and a foaming liquid of a lower temperature than the temperature of the pressurized air may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a foaming liquid to a leak portion such as a pipe or a container and detecting a bubble generated by the leak using an infrared camera.

[0002]

2. Description of the Related Art In order to detect leaks such as welds and joints of pipes, tanks, pressure vessels, etc., the inside is pressurized with a gas such as air, and a foaming liquid is applied from the outer surface to detect leaks. A leak test has been conducted to detect bubbles generated from the leak and to detect a leak portion. The method of confirming the foam is performed by the naked eye.

[0003] In order to facilitate confirmation of bubbles, a coloring agent is added to the foaming liquid, and a method of coloring the bubbles or a fluorescent agent is added to the foaming liquid.
A method of irradiating a bubble with black light in a dark place and observing a fluorescent color has been used.

[0004]

However, even if a coloring agent or a fluorescent agent is used in the foaming liquid, it is difficult to detect leakage from small holes or cracks having a diameter of about several tens of micrometers with the naked eye. . Also when detecting with the naked eye. The burden on the inspector was large when there were many inspection targets.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method for detecting a minute leak portion of a test object whose inside is pressurized with a gas.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, the inside of a test object is pressurized with a gas, and a foaming liquid having a temperature difference from the gas is applied to the surface of the test object. The leaked part is detected by photographing a surface to be inspected by an infrared camera and detecting a portion of the obtained infrared image having a temperature difference.

If there is a pin pole or a crack on the surface to be inspected,
The pressurized gas inside leaks and foams are generated by the foaming liquid. The temperature of this bubble is close to the temperature of the pressurized gas. On the other hand, the temperature of the part without the pin pole or crack is close to the temperature of the applied foaming liquid. Therefore, in the infrared image of the surface to be inspected to which the foaming liquid has been applied, the bubble portion appears as a portion having a temperature difference from the other portions, and the bubble can be determined. By appropriately setting the temperature difference between the pressurized gas and the foaming liquid, a small pin pole or a crack can be detected.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a foaming inspection apparatus using infrared rays according to the present embodiment. The inspection object 1 is a cylindrical container, and the inspection object surface 2 is an area having a width of 20 to 30 mm centered on the welding line. Pressurized air (0.1 to 0.3 kgf / cm ² ) is added to the inspection object 1, and this temperature is measured. The spray 3 for applying the foaming liquid is applied to a temperature higher than the temperature of the pressurized air (for example, 3.
° C). The infrared camera 4 takes an image of the inspection target surface 2 on which the foaming liquid is applied. The image processing device 5 extracts a portion having a lower temperature than the infrared image captured by the infrared camera 4 and detects a foaming position. This infrared image is displayed on the screen of the monitor 6 so that the inspector can check the foaming position even with the naked eye. Further, the image processing apparatus 5 is provided with an alarm lamp 7 so that an alarm is issued when a low temperature portion is detected.

When the foaming liquid is applied to the surface 2 to be inspected, if there is a pin pole or a crack, the internal pressurized air leaks and bubbles are generated by the foaming liquid. The temperature of this bubble is close to the temperature of the pressurized gas. On the other hand, the temperature of the portion free from pin poles and cracks is close to the temperature of the foaming liquid at the time of application within a few seconds after application. This is due to the fact that the difference between the temperature of the surface 2 to be applied and the temperature of the foaming liquid is not so large, and the heat capacity of the foaming liquid. For this reason, in the infrared image of the inspection target surface 2 to which the foaming liquid has been applied, the bubble portion appears as a portion having a lower temperature than the other portions,
Bubbles can be identified. By setting the temperature difference between the pressurized air and the foaming liquid to about 3 ° C., a small pin pole or a crack having a diameter of several tens μm can be detected.

FIG. 2 is a view for explaining a bubble generation mechanism.
A pinhole 8 exists in the welding line on the vertical surface,
Is applied to the inspection target surface 2 including the welding line. When bubbles 10 are generated by pressurized air discharged from the pinhole 8,
The foam 10 slides on the foaming liquid 9 and moves downward. Then, the next bubble 10 is generated from the pinhole 8 and moves downward one after another. If there is a pinhole 8 on the horizontal plane, the bubbles 10 generated one after another around this pinhole 8 will be described.
Spreads.

FIG. 3 shows an infrared image when a foaming liquid is applied to a sound inspection target surface without leakage. The bright white part in the center indicates a high temperature part (approximately 29 ° C.) to which the foaming liquid has been applied, and the surrounding dark part indicates the surface of the inspection object 1 having substantially the same temperature as the pressurized air (about 26 ° C.). .

FIG. 4 shows an infrared image when a foaming liquid is applied to a surface to be inspected having leakage. The bright white portion at the center indicates a portion where the foaming liquid is applied and the temperature is high, and the dark portion around the portion indicates the surface of the test object 1 having substantially the same temperature as the pressurized air. The dark part of the white light part shows bubbles in the part of low temperature. Since the inspection target surface 2 is a vertical surface as shown in FIG. 1, the bubbles generated from the pinholes are successively lowered as shown in FIG. The temperature of the bubble at the point a with the pinhole is 26.7 ° C., the point b at the position of the falling bubble is 26.3 ° C., and the temperature at the point c away from the bubble is 29.
7 ° C., temperature at point d is 29.5 ° C., temperature at point e is 28.5
° C, and if there is a temperature difference of about 3 ° C between the pressurized air and the foaming liquid, bubbles can be accurately identified. In addition,
If the temperature difference is 1 ° C., bubbles can be identified. Even if the temperature difference is too large, the discrimination does not change.

In the above-described embodiment, the foaming liquid at a higher temperature than the pressurized air is used. However, bubbles can be similarly identified by using a foaming liquid at a lower temperature. This is because the identification of bubbles is only required if there is a temperature difference between the bubbles and their surroundings. Since it is generally easier to raise the temperature of the foaming liquid than to lower it, the temperature of the foaming liquid is usually higher than the temperature of the pressurized air.

[0014]

As is apparent from the above description, the present invention makes a difference between the temperature of the applied foaming liquid and the temperature of the foam generated by the foaming liquid, and takes an infrared image with an infrared camera.
Bubbles can be identified by detecting portions having a temperature difference.
The present invention further has the following features. Gas leaking from a minute pinhole having a diameter of several tens of μm generates bubbles having a diameter of several mm. Since the bubbles are detected, a minute leak portion can be accurately detected. Even if the leak is large and it is difficult to form bubbles, or if the bubbles burst, the leak is at the temperature of the outflowing gas, so it can be distinguished from the temperature of the surrounding foaming liquid, and the leak can be identified. If a simple heat shield is provided around the inspection position, the influence of external thermal disturbance can be eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an apparatus according to an embodiment.

FIG. 2 is a diagram illustrating generation of bubbles from a pinhole on a vertical plane.

FIG. 3 is an infrared image of a surface to be inspected without a leak.

FIG. 4 is an infrared image of an inspection target surface having a leak portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object 2 Inspection surface 3 Spray 4 Infrared camera 5 Image processing device 6 Monitor 7 Alarm lamp 8 Pinhole 9 Foaming liquid 10 Foam

Continued on the front page (72) Inventor Takeshi Ishizaki 1720, Higashi-machi, Inashiki-gun, Ibaraki Pref.

Claims (1)

[Claims] 1. An object to be inspected is pressurized with a gas, a foaming liquid having a temperature difference from the gas is applied to the surface to be inspected, and the surface to be inspected is photographed by an infrared camera. A foaming inspection method using infrared rays, wherein a leaked part is detected by detecting a part having a difference.