JPH04215046A - Detecting method for internal residue in steel pipe - Google Patents

Abstract

PURPOSE:To detect internal residues at a real time by radiating microwaves through a pipe end propagate the microwaves through a steel pipe, and calculating modulation of the frequency thereof and attenuation of a power. CONSTITUTION:Axes coincide with each other for setting in a state that a circular waveguide discharge port 3 is separated approximate 10mm away from a seam welded pipe 4, and a microwave receiving port 6 is set in a similar manner described above to the one pipe end. The microwave receiving port 6 is connected to a spectrum analyzer 8 and/or a microwave power meter 4 through a transmission cable 7. When a cut-off frequency is oscillated by means of a microwave oscillator 1 and microwaves are transmitted and received through a transmission cable 2, if remaining beads are present in a pipe, modulation of a frequency and attenuation of power transmission occur. Since even when the seam welded pipe 4 is not defective, it has slight unevenness in an outside diameter, thickness, and a bend, attenuation of microwave propagation and modulation of a propagating frequency occur, but they are approximately 5%. Attenuation of a propagation power and modulation of a propagating frequency are premeasured, a measuring result is compared with those occurring owing to remaining beads, and residues in a pipe is easily detected.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting internal residues in steel pipes.

0002

[Prior Art] Conventionally, internal residues of steel pipes, such as internal bead debris left inside ERW steel pipes, have been removed by placing a group of fluorescent lamps at one end of the pipe and looking into the inside of the pipe from the other end. Visual inspection is common.

0003

[Problems to be Solved by the Invention] When visually inspecting the internal residue of a steel pipe, for example, if the pipe has a small diameter and has bends, it is difficult to inspect the pipe, and there is a possibility of erroneous detection. The present invention advantageously solves this problem.

0004

[Means for Solving the Problems] The gist of the present invention is to radiate electromagnetic waves from the pipe end when detecting internal residue in a steel pipe,
This is a method for detecting internal residues in a steel pipe, which comprises propagating electromagnetic waves using the steel pipe as a circular waveguide, and detecting internal residues by measuring the frequency modulation and/or power attenuation of the electromagnetic waves. In other words, electromagnetic waves are radiated from internally cut bead debris of small-diameter ERW pipes, etc., and the electromagnetic waves are frequency modulated and/or
Alternatively, power attenuation can be measured and detected with high accuracy.

[0005]

[Function] In general, a tubular body with good conductivity has an outer diameter of D,
Letting the wall thickness be t, it acts as a circular waveguide in the microwave band given by the following equation.

Therefore, if a bead remains in a part or the entire length of the steel pipe, the equivalent result is that the wall thickness t increases to t + Δt, and the propagation frequency and propagation mode change, resulting in a decrease in the conductivity. This is observed as increased propagation attenuation and frequency modulation of electromagnetic waves in wave tubes. Practically speaking, the size where bead residue becomes a problem is D=20.
35 mm, t=1 to 4 mm, and the circular waveguide propagation frequency for this is in the 5.6 to 10.9 GHz band.

The present invention will be explained in detail below with reference to FIG. 1, taking as an example the case where it is applied to a small diameter electric resistance welded pipe.

The small-diameter electric resistance welded pipe 4 has an outer diameter of 25 mm, a wall thickness of 3.0 mm, and a length of 600 mm, and there is bead residue 5 inside that was cut immediately after the pipe was made and remained without being removed. exists. Bead residue 5 is short and 1
If it is long, it may extend from 00mm to the entire length. The electric resistance welded pipe 4 is stopped on a skid that is fed horizontally one by one on a finishing line in a manufacturing factory. At the stop position, the microwave oscillator 1 oscillates at a frequency determined from the outer diameter and wall thickness of the steel pipe, and the circular waveguide discharge port 3 is separated from the ERW pipe 4 by about 10 mm via the electric transmission cable 2. Align and set the axes. At the same time, at the other tube end, move the microwave receiving port 6 10 mm from the tube end.
Align the axes with a distance of about mm and set. The microwave receiving port 6 is connected via a transmission cable 7 to a microwave band spectrum analyzer 8 and/or a microwave power meter 9.

[0009] When microwaves are transmitted and received in this manner, if there is bead debris in the pipe, frequency modulation and power transmission attenuation occur due to this.

0010

[Example] Fig. 2 shows the data obtained by implementing the present invention and actually measured the propagation power attenuation, and Fig. 3 shows the data obtained by actually measuring the propagation frequency modulation.
Shown below.

Even in good quality ERW tubes 4, there are some variations in outer diameter, wall thickness, and bending, so there is some variation between the circular waveguide outlet 3 or the microwave reception port 6 and the ERW tube 4. Wave propagation attenuation and propagation frequency modulation occur, but both ±
It is about 5%, and by measuring the propagation power attenuation and/or propagation frequency modulation degree of a good product in advance and comparing it with that caused by bead residue, it is possible to easily detect the residue in the pipe.

[0012] In order to further increase the detection sensitivity, one end of the tube is sealed and a microwave oscillator and a sensor for detecting electromagnetic waves are placed at the other end to reduce the degree of frequency modulation and/or attenuation of the propagation power of the electromagnetic waves due to the residue. It is good to detect the rate.

Furthermore, if the present invention is applied to a conductive tubular body whose inner surface is close to a mirror surface and has a high degree of roundness, and the detection accuracy is improved, it becomes possible to detect flaws on the inner surface.

[0014]

According to the present invention, it is possible to automatically detect residues in a small diameter pipe in real time, and it is also possible to reliably detect short bead residues that were overlooked by conventional visual inspection.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the method of the present invention.

FIG. 2 is a diagram showing data obtained by measuring the propagation power attenuation of electromagnetic waves using the method of the present invention.

FIG. 3 is a diagram showing data obtained by measuring propagation frequency modulation of electromagnetic waves using the method of the present invention.

[Explanation of symbols]

1 Microwave oscillator 2 Electrical transmission cable 3 Circular waveguide outlet 4 Small diameter ERW pipe 5 Bead residue 6 Microwave receiving port 7 Electrical transmission cable 8 Spectrum analyzer 9. Microwave power meter

Claims (1)

[Claims] [Claim 1] When detecting internal residue in a steel pipe, electromagnetic waves are radiated from the pipe end, the electromagnetic waves are propagated through the steel pipe as a circular waveguide, and the frequency modulation and/or power attenuation of the electromagnetic waves are measured. A method for detecting internal residues in steel pipes, the method comprising detecting internal residues.