JP3099649B2 - Self-propelled defect detection system for tubular coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the corrosion protection coating of a tubular body, and more particularly to a steel pipe covered with an anticorrosion material at a pipe construction site or an aging process. The present invention relates to a self-propelled defect detection device that detects a portion of a coating failure, such as an air void or a blister, that has occurred in a coating, that is, a so-called air void, by nondestructive inspection.

[0002]

2. Description of the Related Art Generally, at a piping site using a coated steel pipe such as a polyethylene-coated steel pipe, a heat-shrinkable tube using a synthetic resin material such as cross-linked polyethylene is put on the welded joint to prevent corrosion of the welded joint at the site. After that, the steel pipe and the heat-shrinkable tube are heat-shrinked, and the anticorrosion coating is applied so that the heat-shrinkable tube and the factory-painted portion are adhered to each other before construction.

[0003] In the above-mentioned anticorrosion coating, when heat shrinks, as shown in FIG. 4, air remains between the steel pipe a and the heat-shrinkable tube and between the factory coating and the heat-shrinkable tube. Void c may occur. Warm, air voids may occur due to aging. b is an outer synthetic resin layer, and d is an adhesive layer. If air voids occur frequently, the anticorrosion performance of the anticorrosion coating decreases, causing corrosion, and it is necessary to find out and eliminate it. As a method of inspecting whether or not the anticorrosion coating is normally coated on the outer peripheral wall of the steel pipe, a method such as visual inspection, finger touch, or peeling of a part has been conventionally performed.

However, it is difficult to detect the presence of an air void by visual inspection or touch, and a method of peeling a part requires repairing the peeled part after inspection, which requires time and time for repair. There is a disadvantage that the cost is high. Also, adopting such an inspection method is a problem that when the pipe is narrow between the pipe and the wall surface, such as in a tunnel, it is extremely difficult to perform the test at a required location. have.

On the other hand, Japanese Patent Laid-Open No. Hei 6-118 discloses a method in which an infrared camera is used to inspect the water-containing portion of a pipe covered with a heat insulating material.
No. 040. However, the inspection method described in the above publication is designed to detect a water-containing portion by an infrared camera and does not detect air voids generated in the piping. It is fixed to the outside, the piping of the inspection part is photographed by an infrared camera, and the temperature distribution is examined to detect the water-containing part by nondestructive inspection.

Therefore, in order to detect the water-containing portion around the entire pipe, the positions of the infrared camera and the heater must be set each time. In particular, if the pipe is installed in a narrow place, the infrared camera and the heater must be set. There is a problem that installation of a camera and a heater becomes difficult.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. By mounting an infrared camera and a heater on a self-propelled carriage, air can be spread over the entire peripheral wall of the tube. It is an object of the present invention to provide a self-propelled defect detection device with a tubular body coating that can easily and reliably detect the presence of a void.

[0008]

In order to achieve the above-mentioned object, a self-propelled defect detection apparatus for coating a tubular body according to the present invention comprises: a flexible support band for tightening an outer peripheral wall of a tubular body; A bogie supported by a flexible support band and provided around the outer peripheral wall of the tubular body,
A defect detector equipped with a heater for the tube in the front of the carriage in the circumferential direction and equipped with an infrared camera behind the heater, and an image processing unit for analyzing an image taken by the infrared camera; A truck is provided with a driving body for moving the truck, and the defect detecting body is movably mounted on a rail provided on the truck.

[0009]

As shown in FIG. 4, when an air void c is present between the pipe a and the factory coating a 'and the outer synthetic resin layer b and the pressure-sensitive adhesive layer d which constitute the coating, the coating a Since the heat conductivity is lower than that of the surrounding portion having no air void, a temperature difference occurs in the cooling process. By detecting this temperature difference, the size of the air void c,
And its distribution can be analyzed.

A self-propelled defect detection device according to the present invention has a pair of bogies mutually rotatably mounted on an outer peripheral wall of a tube, and a rail is straddled between the pair of bogies, and an infrared camera and a heater are mounted on the rail. I have a body mounted. By providing a heater in the front of the cart in the circling direction and providing an infrared camera in the back, the defect detector rotates while heating the coating and covering,
The heated portion of the coating is photographed by a rear infrared camera, the photographed image is analyzed by an image processing unit, and an air void is detected based on the temperature distribution of the coating. Therefore, the presence of the air void can be simply and reliably detected over the entire peripheral wall of the tube.
In addition, since the infrared camera and the heater are driven by a self-propelled bogie, the time from heating of the heating portion of the coating device by the heater to detection can be adjusted by the orbiting speed of the self-propelled bogie. The heating temperature for the covering can be easily kept constant, and the accuracy and reliability of the detection of the air voids are improved.

[0011]

FIG. 1 is a plan view showing a state in which a self-propelled defect detection apparatus A according to an embodiment of the present invention is mounted on a tube, and FIG. 2 is a side view thereof. Self-propelled coating press A
Are a chain 2 as a flexible support band for tightening the outer peripheral wall 1a of the tube 1, a pair of carts 3, 3 'supported by the chain 2 and provided around the outer wall 1a of the tube 1 freely. A defect detector 7 movably mounted on a rail 4 erected between the trolleys 3 and 3 ′, provided with a heater 5 for the tube body 1 and mounted with an infrared camera 6 behind the heater 5, An image processing unit 8 for analyzing a video taken by the camera 6
It is composed of

Each of the carts 3 and 3 'is provided with two pairs of running wheels 9. On the carts 3 and 3', a sprocket 10 meshing with the chain 2 and a driving body for moving the cart are provided. Motors 11 are provided, respectively. The rotation of the motor 11 is transmitted to the sprocket 10 so that the cart 3 goes around the outer peripheral wall 1 a of the tube 1 along the chain 2. Since the rails 4 are provided between the trucks 3 and 3 ', the other truck 3' simultaneously goes around the outer peripheral wall 1a as one truck 3 moves.

The rail 4 is provided between support columns 3a and 3a 'which are respectively provided on the carts 3 and 3', and a defect detector 7 is movably mounted on the rail 4. The defect detector 7 can be moved along the rail 4 via driving wheels (not shown) by driving a motor 12 installed on the defect detector 7. The defect detector 7 can be moved to any position on the peripheral wall 1a of the tube 1 for detecting the air void.

An infrared lamp as a heater 5 for the tube 1 is vertically suspended by an arc-shaped arm 13 in front of the carriages 3 and 3 'in the circumferential direction of the defect detector 7. On the other hand, on the defect detector 7 behind the heater 5, an infrared camera 6 is mounted with its lens 6 a facing the tube 1.

The image processing unit 8 is installed at a position slightly distant from the tubular body 1 and comprises a display device such as a CRT and an analyzer equipped with a computer. The image processing unit 8 is connected to the infrared camera 6 by a connection cord 14. An image based on the temperature distribution of the paint covering taken by the infrared camera 6 is analyzed to detect the presence of an air void.

Next, a description will be given of a test example in which an air void detection test was performed on the following test materials using the self-propelled defect detection apparatus A described above. Test material A 750A polyethylene-lined steel pipe welded joint was coated with a heat-shrinkable tube (thickness: 3 mm) made of cross-linked polyethylene as a coating, and was artificially 6 mm in diameter and 1 mm in diameter.
As shown in FIG. 3, 5 mm and 30 mm air voids are formed at positions corresponding to 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock on the clock face, respectively.

Test Conditions As shown in FIG. 3, the test material P was placed at a distance s ₁ of 600 mm from the floor surface 15 and at a distance s ₂ of 60 from the wall surface 16.
The self-propelled defect detection device A was mounted at a position of 0 mm. The time required for the defect detector 7 to make one round around the outer peripheral wall of the steel pipe was set to 10 minutes. The coating was heated so that the surface temperature of the coating was 20 ° C. higher than the initial surface temperature before heating.
Image processing unit 8 based on a video signal from infrared camera 6
The presence of air voids was detected by analyzing the cooling process of the surface temperature of the coating. As a comparative example, an air void was detected for the above test material by visual inspection and finger touch of an inspector.

Table 1 shows the detection results of both. The position of the air void is indicated by the position of the clock face as shown in FIG.エ ア ー indicates that the air void was reliably detected, △ indicates an unclear air void, and × indicates that the air void could not be detected.
Indicated by The actual distribution of air voids was confirmed by a peeling test of the coating after the test.

[0019]

[Table 1]

As is clear from Table 1, when the self-propelled defect detection apparatus A was used, all the defects could be reliably detected. In addition, since the detection step can be performed efficiently, the time required for detection is significantly reduced. In the above test example, the surface temperature when heating the coating device was set to 20 ° C. higher than the initial surface temperature, but the heating temperature was 3 to 200 ° C.
If it is within the range, it can be detected. If the temperature exceeds 200 ° C., the coating may be deteriorated, and the temperature is preferably in the range of 5 to 30 ° C.

[0021]

According to the self-propelled defect detection device of the present invention,
Since the defect detection body equipped with the infrared camera and the heater is mounted on the peripheral wall of the tube so as to be freely rotatable, the presence of air voids can be detected easily and reliably over the entire peripheral wall of the tube. In addition, since the defect detector equipped with the infrared camera and the heater is driven by the self-propelled bogie, the time from heating of the heating part of the coating and covering to the detection by the heater until the detection speed is equal to the orbiting speed of the self-propelled bogie. In addition to the above, there is a great advantage that the heating temperature for the coating device can be easily maintained at a constant value, and the accuracy and reliability of detection of air voids are improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state in which a self-propelled defect detection apparatus for coating and covering a tubular body according to an embodiment of the present invention is mounted on the tubular body.

FIG. 2 is a side view of the self-propelled defect detection device of FIG.

FIG. 3 is an explanatory view showing a test material for detecting air voids using the self-propelled defect detection device of FIG. 1;

FIG. 4 is an explanatory view of an air void generated between a pipe and a coating device.

[Explanation of symbols]

 A Self-propelled defect detection device for coating and coating a tube 1 Tube 1a Outer peripheral wall 2 Chain (flexible support band) 3, 3 'truck 4 Rail 5 Heater 6 Infrared camera 7 Defect detector 8 Image processing unit 11 Driver

Continuing on the front page (72) Inventor Tadashi Kawamura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Motofumi Hirata 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-4-32754 (JP, A) JP-A-1-955653 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 25/72

Claims (1)

(57) [Claims] 1. A flexible support band for tightening an outer peripheral wall of a tubular body, a bogie supported by the flexible support band and provided around the outer peripheral wall of the tubular body, and a heater for the tubular body A defect detector equipped with an infrared camera behind the heater and equipped with an infrared camera behind the heater, and an image processing unit that analyzes an image captured by the infrared camera. A self-propelled defect detection apparatus with a tubular body coating, comprising a driving body for movement, and movably mounting the defect detection body on a rail provided on the carriage.