JPH02208552A - Flaw detector - Google Patents

Abstract

PURPOSE:To enable the shortening of a blanking time as much as possible by detecting a pipe end by a flaw detection signal itself to eliminate effect of disturbing factors of conveying speed or the like. CONSTITUTION:In a conveying path for a steel pipe 1 being carried by a conveying roll 2, a photo sensor 3 to detect the passage of the front and rear ends of the steel pipe 1 and a through coil 4 to detect flaws are disposed in this order from the upstream side. Component coils 4a and 4b of a coil 4 are connected so as to be opposite arms of a bridge circuit 7 respectively and the coils 4a and 4b are energized by a high frequency current outputted from an oscillator 19. Under such a condition, the tip of the steel pipe 1 is detected and in addition, when a signal generated from a flaw detector meets specified requirement, this signals used as detection signal for the tip to start the detection of flaws in the steel pipe 1. The rear end is detected and in addition, when the signal emitted from the flaw detector meet specified requirements, this signal is used as detection signal for the rear end to end the detection of flaws in the steel pipe 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a flaw detection device, such as a coil-through-type automatic eddy current flaw detection device, which is installed on a conveyance path of an object to be flaw-tested.

[Prior art]

FIG. 5 is a schematic diagram showing the configuration of a conventional coil-penetrating automatic eddy current flaw detection device, as shown in the figure (1 is a steel pipe to be tested;
Reference numeral 2 denotes a conveyor roll, and a photosensor 3 is disposed in a passage area of the steel pipe 1 conveyed by the conveyor roll 2, and a timer 5 is activated by the output of the photosensor 3. A flaw detection coil 4 is arranged downstream of the photosensor 3, and the steel pipe 1 passes through it. A flaw detection device body 6 is connected to the flaw detection coil 4 . The flaw detection coil 4 generates a similar signal (tube end signal) not only when passing a defect but also when passing the tip and rear end of the steel pipe 1.
, so it is necessary to remove or invalidate it. The timer 5 is used to define the time during which the input signal from the flaw detection coil 4 is valid.

FIG. 6 is a schematic diagram showing the timing of pipe end signals on the front end and rear end sides of the steel pipe 1 detected by the flaw detector main body 6. The time t11 from when the output is turned on until it reaches the inside of the flaw detection coil 4 is a time Δt1 determined based on experience.
The time obtained by adding 1 (1+++Δt1.) is the time until the start of flaw detection. Also, the time from when the rear end of the steel pipe 1 passes the photosensor 3 and the output of the photosensor 3 is turned off until it reaches the inside of the flaw detection coil 4 is 1. Time ΔtI determined from □ based on experience! The time Dr □ - Δm, ri obtained by subtracting is the time required to complete the flaw detection.

That is, after the tip of the steel pipe 1 passes the photosensor 3 by the timer 5, (tlI+Δt++) to (tI!-
The output of the flaw detection coil 4 within the time range of Δt1□) is considered valid.

[Problem to be solved by the invention]

The above-mentioned ΔL Il+ Δtlt is the blanking time,
The tube length equivalent to this is called the blanking length, but in order to prevent the detected tube end signal from being mistaken for a signal caused by a flaw, the blanking length must be set at 200 to 400 mm.
This part becomes an undetected part, and since the undetected part is visually inspected using a detector such as an internal mirror, there is a problem that human error occurs. In order to solve these problems, it is necessary to keep the flaw detection speed constant, to test a material equivalent to the material to be tested in advance, and to set the timer 5 correctly for the start and end of the flaw detection. , in terms of the shape of the material,
Accurate setting is difficult if there is a constricted shape at the pipe end, and the flaw detection speed depends on the slip between the transport roll and the steel pipe, the dimensions of the steel pipe (outer diameter, wall thickness), and the transport roll drive device. (motor, chain, etc.), and it is extremely difficult to keep the flaw detection speed constant considering these factors. In addition, there is a problem in that it is impossible in actual operation to set the timer conditions using the same material for each flaw detection process. On the other hand, the accuracy of the photosensor and timer also needs to be taken into account when setting the blanking length.

The present invention has been made in view of the above circumstances, and its purpose is to determine the effective range of the output of the flaw detector by the signal itself obtained from the flaw detector, such as a flaw detection coil, thereby increasing the conveyance speed. It is an object of the present invention to provide a flaw detection device that can accurately detect signals at the terminals of an object to be flaw-detected without being affected by disturbance factors such as flaw detection, and can shorten the blanking length as much as possible.

[Means for Solving the Problems] The flaw detection device according to the present invention has a flaw detector facing the transport route of the object to be tested, and outputs an output when the leading and trailing ends of the object to be tested pass through the flaw detector. A flaw detector designed to nullify the signal
, the tip of the object to be tested is placed upstream of the transport path from the flaw detector.

A tube end detector detects passage of the rear end, and after the tube end detector detects the leading and trailing ends of the object to be tested, if the signal input from the flaw detector satisfies a predetermined condition, the signal is transmitted to the leading and trailing ends. A terminal signal detecting means that determines that the terminal signal is caused by passage, and a flaw detector output from detecting the end of the terminal signal at the leading end of the terminal signal detecting means to detecting the start of the terminal signal at the trailing end. It is characterized by comprising a flaw detection signal processing means.

[Effect]

When the tip of the object to be tested is detected and, in addition, the signal emitted by the flaw detector satisfies a predetermined condition, this signal is used as the tip detection signal, and flaw detection of the object to be tested is started.

On the other hand, if the rear end is detected and in addition to this the signal emitted by the flaw detector satisfies a predetermined condition, this signal is used as the rear end detection signal and the flaw detection of the object to be tested is terminated. .

[Example] Hereinafter, the present invention will be specifically explained based on drawings showing an example of a through-coil type eddy current flaw detection device. FIG. 1 is a block diagram showing the overall configuration.

In the figure, reference numeral 1 denotes a steel pipe, and the transport path of the steel pipe 1 transported by transport rolls 2 includes a photo sensor 3 that is a pipe end detector that detects passage of the tip and rear end of the steel pipe 1, and a through coil that performs flaw detection. 4 are arranged in order from the upstream side. The coils 4a and 4b of the through-hole coil 4 are connected to form opposite sides of the bridge circuit 7, respectively, and a high frequency current output from an oscillator 19 is applied to these coils 4a and 4b.

In this state, if either coil detects a defect or a tube end, a difference occurs in the impedance of both coils 4a and 4b, the balance of the bridge circuit 7 is lost, a defect signal is output from the bridge circuit 7, and the synchronous detection circuit 8.

The photosensor 3 outputs a pipe detection signal when the steel pipe 1 is present in its detection direction, and this output signal is input to a pipe end processing section 18, which will be described later.

The synchronous detection circuit 8 performs synchronous detection on the flaw detection signal input from the bridge circuit 7 based on the oscillation frequency from the oscillator 19, and outputs the result to an amplifier 9 and an amplifier 15 whose amplification is smaller than that of the amplifier 9. .

The flaw detection signal input to the amplifier 9 is amplified and output to the phase adjuster 10. The phase adjuster 10 adjusts the phase of the input signal and outputs it to the band pass filter 11 and balance circuit 14.

The balance circuit 14 is a circuit that controls the output of the synchronous detection circuit 8 to be zero at all times. In order to erase it on the output side, the output signal of the phase adjuster IO is fed back to the output side of the synchronous detection circuit 8 only while an output permission signal output from a tube end processing section 18, which will be described later, is being input.

Further, the flaw detection signal input to the band pass filter 11 has components in a predetermined frequency band extracted, and is input to the flaw determination circuit 13 via the delay circuit 12 .

On the other hand, the flaw detection signal input to the amplifier 15 is amplified and input to the amplitude calculators 1 and 6. The amplitude calculator 16 performs analog calculations on the amplitude of the input signal, and sends the results of this calculation to the A/
It is converted into a digital quantity through a D converter 17 and output to a tube end processing section 18 consisting of a microprocessor.

The output signals of the ^/D converter 17 and the photosensor 3 are input to the tube end processing section 18.
determines the tip and rear end of the tube based on these input signals, and outputs an output permission signal to the flaw judgment circuit 13 for permitting the output of the balance circuit 14 and the flaw judgment circuit 13 .

Next, based on the time chart of FIG. 2 and the flowchart of FIG. The contents of the calculation will be explained.

When the tip of the steel pipe 1 reaches the photosensor 3, the photosensor 3 turns on its output as shown in photosensor output (a) in FIG. When the output of the photosensor 3 is turned on (step 1), the tube end processing unit 18 samples the output of the A/D converter 17 as D+, Dz...DT-1+D7... with timing based on the internal clock signal. (Step 2). When the tip of the steel pipe l passes through the flaw detection coil 4, the tube tip detection signal F shown in the flaw detection signal (b), which is the output signal of the bandpass filter 11, and the tube tip amplitude signal Wl shown in the amplitude calculator output (c) are generated. can get.

In the tube end processing section 18, DT exceeds a predetermined value A (step 3), then decreases (step 4), and Di
Under the condition that becomes smaller than A, D ar Dt-+
When ≦α (α is a constant determined empirically) (step 5), the pipe end processing unit 18 outputs the output permission signal to the flaw determination circuit 13 as shown in the pipe end processing unit output (d). (Step 6).

In this state where the output of the flaw determination circuit 13 is permitted, if a flaw exists in the steel pipe 1, a flaw signal P7. Pg appears, and these are output from the flaw judgment circuit 13 as shown in the flaw judgment circuit output (e).

Next, when the rear end of the steel pipe 1 approaches the photosensor 3, the photosensor output is turned off as shown in photosensor output (a). When the output of the photosensor 3 is turned off (step 7), the tube end processing section 18 changes the output of the ^/D converter 17 to D according to the timing based on its internal clock signal.
+, Dz...DT-ItD,... (Step 8). Front and rear end detection signal R shown in flaw detection signal (b) and tube tip amplitude signal W shown in amplitude calculator output (c)
2 is obtained. In the tube end processing section 18, DT D
When t-I≧β (β is an empirically determined constant) (step 9), the output of the output permission signal that is already being output to the flaw determination circuit 13 is canceled (step 1).
0).

In the flaw detection signal obtained in this way, since the trailing edge detection signal is removed before the flaw detection signal, only the flaw signal is obtained.

Next, a description will be given of a flaw detection method for flaw detection of a steel pipe whose tip has a constricted shape.

FIG. 4 is a schematic diagram showing a flaw detection method for the orifice tube.

Now, when the tip of the tube has a constricted shape like the constricted tube 40 shown in FIG. Mouth diaphragm detection signal F+ and shoulder detection signal F as if the tip was detected
2 is obtained. Therefore, the mouth constriction detection signal F is recognized as the tube tip signal, and the shoulder detection signal Fz that appears next
There is an inconvenience that the signal may be mistakenly recognized as a defect signal.

In order to prevent the above-mentioned inconvenience, when testing the orifice tube 40, the two photosensors 31 and 32 are connected to the orifice tube 40.
A pulse oscillator 20
will be newly installed in the flaw detection equipment. In such a flaw detection device for a diaphragm tube, the outputs of the photosensors 31 and 32 are input to the pulse oscillator 20.

In the pulse oscillator 20, the aperture tube 4 is
The time difference between the tube end detection signals inputted from the two photosensors 31 and 32 upon passage of 0 is measured, and the transport speed of the orifice tube 40 is determined from the time difference. Then, the pulse oscillator 2 is configured to oscillate one pulse signal for the unit length of the orifice tube 40 based on the determined conveyance speed.
0, a pulse signal is output to the tube end processing section 18.

The tube end processing section 18 stores in advance the orifice length Ll of the orifice tube 40.
The photosensor 32 and the flaw detection coil 4 on the downstream side of the conveyance path
Sampling the data as described above until the number of pulses obtained by adding the number of pulses corresponding to the distance between the two and the number of pulses corresponding to, for example, half of the aperture length stored in advance Avoid doing so.

In this way, the orifice constriction portion detection signal F of the orifice constriction tube 40
, becomes invalid, the tip detection of the orifice tube 40 that is input to the tube end processing section 18 is only the shoulder detection signal F2, and the tube end processing section 18 converts the shoulder detection signal F2 into the plain end as described above. Since it is processed in the same way as the tube tip signal F in the case of , flaw detection can be performed without the above-mentioned inconvenience.

〔effect〕

As described in detail above, in the present invention, the pipe end is detected using the flaw detection signal itself, so it is not affected by the conveying speed. Therefore, it becomes possible to shorten the blanking length as much as possible.

Note that the present invention is applicable not only to steel pipes but also to other materials, and is not limited to penetrating eddy current flaw detection devices but can also be applied to eddy current flaw detection devices using other sensors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of the device of the present invention, and FIG.
Fig. 3 is a time chart for explaining the operation of the device of the present invention, Fig. 3 is a flowchart showing the processing procedure of the tube end treatment section, Fig. 4 is a schematic diagram showing the flaw detection method for a choke tube, and Fig. 5 is a conventional device. FIG. 6 is a time chart for explaining the operation of the conventional device. 3...Photo sensor 4...Flaw detection coil 13...
Flaw determination circuit 18... At the time of pipe end treatment section Applicant
Sumitomo Metal Industries Co., Ltd. Representative Patent Attorney Kono
Noboru F2

Claims (1)

[Scope of Claims] 1. A flaw detection device in which a flaw detector is placed facing the transport path of the object to be tested, and the signals output when the front and rear ends of the object to be tested pass through the flaw detector are nullified. The apparatus includes: a tube end detector arranged upstream of the transport route than the flaw detector for detecting passage of the leading and trailing ends of the object to be tested; and a tube end detector detecting the leading and trailing ends of the object to be tested. a terminal signal detection means for determining that the signal input from the flaw detector satisfies a predetermined condition as a terminal signal caused by passing the first and rear ends; and a terminal at the tip of the terminal signal detection means. 1. A flaw detection apparatus comprising flaw detection signal processing means for validating flaw detector output from detection of the end of a signal to detection of the start of a terminal signal at the rear end.