JPH06126450A - UO steel pipe weld detection method and apparatus - Google Patents

Abstract

(57) [Summary] [Purpose] Improving the accuracy of weld detection and expanding the range of objects to be detected. [Structure] UO with a pair of laser displacement meters facing each other
The UO steel pipe is placed on the outer and inner surfaces of the steel pipe, and the wall thickness of the steel pipe is calculated using the displacement distance value of the displacement gauge while rotating the UO steel pipe in the circumferential direction. The position is determined to be.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded portion detecting method and apparatus for detecting a welded portion in the circumferential direction of a UO steel pipe.

[0002]

2. Description of the Related Art As a conventional technique for detecting a welded portion of a steel pipe, there is a method disclosed in, for example, Japanese Patent Laid-Open No. 57-206592. This technology is provided near the outer circumference of the welded steel pipe.
By detecting the wall thickness of the steel pipe with a pair of ultrasonic transducers and detecting the difference between the wall thickness measurement signals to determine the voltage value, the welded part is detected and stopped at a predetermined position. This is a welding part position control method.

[0003]

By the way, the cross section of the UO steel pipe is as shown in FIG. 1 is a UO steel pipe, 9a is a base material thereof, and 9b is a welded portion. Unlike the electric resistance welded steel pipe, the welded portion on the outer surface also has a raised portion. Therefore, considering the application of the above-mentioned conventional technique to a UO steel pipe, there are the following problems and the welded portion cannot be accurately detected. That is, as a first point, in this conventional technique, it is necessary to form a laminar flow column of water between the nozzle and the outer surface of the steel pipe in order to propagate ultrasonic waves, and in the welded portion of the outer surface of the steel pipe having a raised portion, UO It is difficult to accurately form this laminar flow column while turning the steel pipe. Secondly, when ultrasonic waves are incident on the outer surface of the UO steel pipe from the water of the laminar flow column, the incident angle changes greatly due to the bulge of the outer surface welded portion, and the wall thickness cannot be accurately measured.

An object of the present invention is to accurately detect the position of a welded portion in the circumferential direction of a UO steel pipe.

[0005]

According to the method of the present invention, while rotating a UO steel pipe in the circumferential direction, the steel pipe is detected by using a detection distance value of a laser type displacement meter arranged so as to face the outer surface and the inner surface of the UO steel pipe. Is measured, and the welded portion in the circumferential direction is detected by the difference in wall thickness between the base material portion and the welded portion. The device of the present invention comprises a turning roll for rotating a UO steel pipe in a circumferential direction, a pair of opposed lasers arranged at the lower end of a steel pipe laterally supported by the turning roll for measuring the wall thickness of the steel pipe. It is equipped with a displacement meter and a computer for determining the welded part.

[0006]

In the present invention, since the laser displacement gauge having a relatively large measurement distance range is used, the displacement gauge settable range for the inner and outer surfaces of the UO steel pipe wall is greatly expanded. Therefore, the scope of application is broadened. Further, since a pair of laser type displacement gauges are arranged to face each other on the inside and outside of the steel pipe, the steel pipe wall thickness (detection value) is obtained by subtracting the detection distance of each displacement gauge from the distance between both displacement gauges. Even if the steel pipe vibrates during rotation, the detection distance of one displacement gauge becomes shorter and the detection distance of the other displacement gauge becomes longer due to the vibration, so the steel pipe wall thickness detection value does not change. That is, there is substantially no detection error due to vibration.

[0007]

FIG. 1 shows an embodiment of the present invention, and FIG.
The contents of the welding portion detection processing of the digital computer 7 shown in FIG. 1 are shown in FIG. First, in FIG. 1, 1 is UO steel pipe, 2 is U
A turning roll for rotating the O steel pipe in the circumferential direction. Reference numeral 3 is a displacement gauge for detecting the welded portion of the steel pipe 1, and a pair of displacement gauges 3 facing each other is used to reliably detect the welded portion even if vibration or the like occurs. The wall thickness is calculated by measuring the pipe inner distance (measurement distance of the pipe displacement meter) and the pipe outer distance (measurement distance of the pipe displacement meter) of each part. As the displacement meter 3, a laser displacement meter that can extend the detection range is used.

Reference numeral 4 denotes a support base for installing the displacement gauge 3 on the inner and outer surfaces of the steel pipe 1. In addition, these are installed so that the pair of displacement gauges 3 detect the lowermost end portion of the steel pipe 1 laterally supported by the turning rolls 2, and the relative position of the pair of laser type displacement gauges 3 (distance between displacement gauges). ) Is supported so that it does not change due to vibration or the like.

Numeral 5 is a displacement meter 3 when the steel pipe 1 is loaded or unloaded.
And a mechanism for retracting the support base 4.

Reference numeral 6 is an apparatus for analog / digital converting the distance detection signals of the pair of displacement gauges 3, and reference numeral 7 is a digital computer for calculating the wall thickness of the steel pipe 1 and determining the welded portion.

Reference numeral 8 is a device for outputting a welding portion detection signal output from the digital computer 7, and outputs the welding portion detection signal to a turning roll rotating device (not shown). The turning roll rotation device counts the rotation synchronizing pulse of the turning roll 2 (an electric pulse generated for one rotation of the roll 2 at a predetermined small angle), and responds to the welding portion detection signal. Initialize the count value (reset to the set value; when the set value is 0, initialize it by clearing the counter),
After this initialization, when the count value reaches the set value, the rotation of the turning roll 2 is stopped. The count value at this time is the position (rotation angle) of the welded portion with respect to the reference line (vertical line) connecting the displacement gauge 3 and the center of the steel pipe 1. When the count value (setting value) for stopping the rotation of the turning roll 2 is set to 0, the digital computer 7 generates a welding portion detection signal when the welding portion is at the position of the displacement meter 3, and The rotation of the turning roll 2 is stopped in conjunction therewith, and when the weld reaches the position of the displacement gauge 3, the rotation of the steel pipe 1 is stopped. When the count value (setting value) for stopping the rotation of the turning roll 2 is set to be equivalent to the count value of the rotation synchronizing pulse during the 180-degree rotation of the steel pipe 1, the welded portion is at the highest position in the vertical direction. When it reaches, the rotation of the turning roll 2 is stopped. That is, the rotation of the steel pipe 1 is stopped.

With reference to FIG. 2, the contents of the welded portion detection processing of the digital computer 7 will be described. When a detection instruction is given from the outside such as an operator, a host computer, the above-mentioned turning roll rotating device, etc., the computer 7 initializes a register tmax for storing the maximum value of the detected thickness. That is, the content of the register tmax is set to 0. By the time immediately before the detection instruction is given, the steel pipe 1 is placed on the turning roll 2, the roll 2 is rotationally driven at a substantially constant speed, and the support frame 4 is moved through the retracting mechanism 5 to the steel pipe. It is driven inward of the pipe so as to sandwich the pipe wall of No. 2. After the initialization, the computer 7 reads the distance detection signal of the displacement meter 3 at a predetermined cycle.
This reading is performed via the conversion device 6. Then, for each reading, the wall thickness value t of the steel pipe 1 is calculated, the judgment whether the calculated value is the maximum value (t−tmax <α?), And the processing for this judgment are performed.

The digital computer 7 has a wall thickness value t of the steel pipe 1.
Is obtained by subtracting the distance between the inside and outside of the steel pipe measured by each displacement gauge from the relative distance between the pair of displacement gauges 3. And than the thickness of the value t _n obtained up-to-date, the wall thickness t _n-1, which was measured up to that point,
When the maximum value of t _n-2 , ... t ₁ (content of register tmax) is subtracted, and the value obtained by this is below an appropriately set threshold value α (negative value) (calculation: When the wall thickness changes from rising to lowering), it is determined that the apex of the welded portion is substantially at the position of the displacement meter 3, and a welded portion detection signal is output,
The detection of the welded portion of the steel pipe 1 currently on the roller 2 is completed (“detection completed” in FIG. 2).

If the value obtained by the subtraction is greater than or equal to the threshold value α, it is checked whether the latest wall thickness value t is larger than the content of the register tmax (the maximum value so far). The wall thickness value t obtained in step 1 is updated and written in the register tmax. Until the weld is detected by this, the register t
The content of max is updated to the detected maximum value.

Next, a detailed description will be given. While rotating the UO steel pipe 1 having a diameter of about 450 to 1500 mm at a peripheral speed of about 10 mpm by the turning roll 2, about 30 c from the end of the pipe.
Based on the distance value detected by using the pair of displacement gauges 3 arranged at the position of m, a thickness of 6 to 40 mm of the steel pipe 1 is measured at a plurality of points along the circumferential direction at a detection pitch of about 3 mm. The latest calculated wall thickness value t is subtracted by the maximum wall thickness calculated by distance measurement before that, and when the difference value is negative and falls below the appropriately set threshold value 1 mm. Judges that it has passed through the welded part. On the other hand, if the difference value calculated in the same way does not exceed the above threshold value even if it is positive, zero, or negative, it is judged that it is not a welded portion, and the wall thickness value detected this time is set earlier than that. If it exceeds the maximum value of the wall thickness detected in, the maximum value of the wall thickness is updated with that value. As a result, the position of the welded portion of the steel pipe 1 was reliably detected when the welded portion of the steel pipe 1 had a build-up of, for example, 2 mm or more on the inner and outer surfaces as compared with the base material portion.

[0016]

As described above, according to the steel pipe welded portion detecting method and apparatus of the present invention, while the UO steel pipe is rotated in the circumferential direction by the turning roll, the UO steel pipe is opposed to the outer surface and the inner surface. The wall thickness of the steel pipe is detected using the detection distance value of the placed displacement meter, and the welded part in the circumferential direction is detected by the difference in the wall thickness of the base metal part and the welded part. The welded portion of the steel pipe can be accurately detected even when the height of the pipe is small, or when vibration occurs when the steel roll is rotated in the circumferential direction by the turning roll. Moreover, since a laser displacement meter having a large detection range is used, the sensor can be set in a wide range, the degree of freedom in installing the sensor and the like is high, and the applicable range of the present invention is wide.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an embodiment of a device of the present invention.

FIG. 2 is a flowchart showing the contents of a welded portion detection process of the digital computer 7 shown in FIG.

FIG. 3 is a cross-sectional view of a UO steel pipe.

[Explanation of symbols]

1: UO steel pipe 2: Turning roll 3: Displacement gauge (pair) 4: Displacement gauge support stand 5: Displacement gauge retracting mechanism 6: A / D conversion device 7: Digital computer 8: Digital output device 9a: UO steel pipe mother Material 9b: Welded part of UO steel pipe

Claims (2)

[Claims] 1. A laser type displacement meter is arranged to face each other on the outer surface and the inner surface of a UO steel pipe, and the wall thickness of the steel pipe is measured by using the detected distance value of the displacement meter while rotating the UO steel pipe in the circumferential direction, A method for detecting a welded portion of a UO steel pipe, which detects a welded portion in a circumferential direction based on a difference in wall thickness between a base material portion and a welded portion. 2. A turning roll for rotating a UO steel pipe in the circumferential direction, and a pair of opposed lasers arranged at the lower end portion of the steel pipe laterally supported by the turning roll for measuring the wall thickness of the steel pipe. A welded portion detection device for a UO steel pipe, comprising a displacement meter and a computer for determining a welded portion.