JPS60133363A - Detection of defect on metal surface - Google Patents

Abstract

PURPOSE:To prevent influence of vibration by a method wherein the movement of detector is stopped briefly at the scan end each time one scanning is done and the machine base is relatively moved intermittently by a length equivalent to the width of the detector with respect to the metal surface synchronizing the stop duration of the detector to inspect. CONSTITUTION:A detector 4 mounted on a swivelling device 3, a TV camera 10 covering a scanning range of the detector and a illumination lamp 11 are provided at the front of a machine base 1. The machine base 1 is loaded into a pipe 5 to be inspected and travelled therethrough to inspect the inner surface of the pipe with the detector 4 while picking up image in the inspection range with the TV camera 10. In the process, with the controlled operation of a swivel driver 33 and an intermittent driving of a travelling mechanism 2 synchronizing it, the detector 4 is stopped and fails to scan as shown by the bold chain line while the machine base is travelling while the machine base is halted while the detector 4 is performing a scanning. Thus, the detection signal of the detector will not be affected by vibration associated with the travelling of the machine base thereby permitting the outputting of a detection data with limited noise.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting defects such as corrosion and cracks occurring on the surface of a metal tube or metal plate.

In order to detect defects on the surface of a metal tube, the applicant pivots a swinging rod equipped with a magnetic flaw detector at the tip to a machine base equipped with a traveling mechanism, and swings the swinging rod inside the tube. We have already proposed a method for inspecting metal surfaces by running a machine while doing so (Japanese Patent Application Laid-Open No. 144444/1983).

Under this method, the scanning by the detector is a combination of the main scanning by the reciprocating swing of the swinging rod to which the detector is attached, and the sub-scanning by the traveling mechanism of the machine base running through the pipe. As shown in the figure, the motion of the detector drew a zigzag trajectory with respect to the metal surface.

This method is excellent in that it can automatically inspect the inner surface of the pipe, but it is susceptible to vibrations caused by the operation of the traveling mechanism and traveling drive mechanism when the machine is running, and unevenness due to corrosion or deposits on the inner surface of the pipe wall. The vibrations from traveling on the second surface are transmitted to the detector,
This causes noise to be included in the detection data.

The purpose of the present invention is to clarify an inspection method that is not affected by vibrations caused by relative movement between the machine stand and the inspection surface.

In the present invention, the movement of the detector is stopped for a short time at the scanning end for each scan of the detector, as shown in FIGS. 3 to 5, and the machine is synchronized with the stop timing of the detector. This is characterized in that the metal surface is inspected by intermittently moving relative to the metal surface by the width of the detector.

The present invention alternately performs main scanning in which the detector is reciprocated in a direction perpendicular to the metal surface inspection direction, and sub-scanning in which the detector is moved in the metal surface inspection direction. Vibrations do not affect the test data at all, and test data with less noise can be obtained.

An apparatus for inspecting the inner surface of a tube in accordance with the present invention is shown in FIGS. 1 and 2. The machine base (1) has wheels, belts,
A traveling mechanism (2) such as a caterpillar is provided on both sides, and a driving device such as an electric motor or a pulse motor is connected to each traveling mechanism (2). Under the control of the signal from 1), the movement of the machine base (1) by the traveling mechanism (2) can be switched to forward, stop, backward, etc.

At the front of the machine (1), a detector (4) attached to the swinging device (3), a television camera +1 [11] for photographing the scanning range of the detector, and a lighting lamp (11) are installed. Then, the machine (1) is inserted into the pipe (5) to be inspected, moves through the pipe, and inspects the inner surface of the pipe with the detector (4), while at the same time photographing the inspection range with a television camera (1ω).

The inspection signal output from the detector (4) and the video signal from the television camera tool are modulated into optical signals, microwave signals, or electrical signals and transmitted to an external monitoring room through a transmission circuit (12). In the monitor room, the signal transmitted from the machine (1) is demodulated, the test signal is displayed and recorded on an appropriate output device (131), and the video signal is displayed on an image device (1Φ) and recorded on an appropriate output device as necessary. For the machine (1) in the pipe, by operating the central control unit in the monitor room, commands for forward, stop, and reverse are given to the traveling drive unit, and the operation is started. can be controlled.

The detector (4) uses a method that emits ultrasonic waves, laser beams, radio waves, etc. to the inspection surface and analyzes the reflected signals, or generates a high-frequency alternating magnetic field to generate eddy currents on the tube wall, which induces self-induction of the coil or Various methods are used, such as the eddy current flaw detection method, which measures the back electromotive force or induced electromotive force generated in the coil due to mutual induction and detects disturbances in eddy current at abnormal locations on the tube wall due to corrosion or cracks. The detector (4) is attached to the lower end of the swinging rod (to) located at the front of the machine, and the swinging rod (2) freely rotates the rotating shaft (01) protruding from the upper end to the bearing device (to). At the same time as being supported, a swing drive device is connected to the rotating shaft 01).

The swing drive device uses a pulse motor or a cam mechanism, etc., to intermittently rotate the rotating shaft (311) back and forth at a set cycle and at controlled intervals, swing the swing rod, and perform detection. The detector (4) is reciprocated in the circumferential direction of the tube to scan the tube wall, and is stopped for a short time at the scanning end of the reciprocating swing of the detector 14) as shown in FIG. 3a.

The traveling drive device (1) of the machine base drives the traveling mechanism (2) while being controlled by the controller I21).
The operation of the support) is synchronized with the operation of the swing drive device, and as shown in Figure 3 a and b, one scan of the detector (4) (point A) is performed.
After that, when the detector is stopped at the scanning end (point B), advance the traveling mechanism (2) by the width of the detector (4) and stop (point 0), and then move the detector. Make one scan in the opposite direction to the previous one, stop for a short time at the other scanning end (point D), operate the traveling drive device (to), and move the traveling mechanism (2) again by the width of the detector. Let it proceed. In this way, due to the controlled operation of the swing drive device and the intermittent drive of the traveling mechanism (2) in synchronization with it, the detector (
4) Since the machine stops and does not scan while the machine is moving, and the machine stops while the detector is scanning, the detection signal of the detector may be affected by the vibration that accompanies the machine's movement. Therefore, detection data with less noise can be output.

When the detector (4) is an eddy current flaw detection probe (4ω), its diameter is about 105 m, so the distance that the traveling mechanism (2) moves forward in one intermittent drive is also restricted to about 1OI+lII+.

Therefore, in order to increase inspection efficiency, approximately 40 detectors (4) should be used.
It is necessary to swing the machine at a high speed of 4 m/min.

FIG. 5 shows another embodiment of the present invention, in which a plurality of probes (411) are arranged in the inspection direction to constitute a vertically elongated detector (4). In scanning, the width of the array length q of multiple probes is scanned and inspected at once.Every time the detector stops at the scanning end, the traveling mechanism (2) advances the distance of the array length q of the multiple probes. The output signals from multiple probes are processed using a time-sharing method, which allows the inspection efficiency to be significantly improved.
It is sent to the monitoring room using a line, and multiple output signals are simultaneously displayed and recorded on the output device (1).

When the object to be inspected is a metal plate, the movement of the detector (4) is a linear reciprocating motion on the plane of the metal plate, and the swing device and swing drive device are suitable for making the detector perform linear reciprocating motion. Of course, something similar can be used.

In addition, when carrying out the present invention, the machine base (1) is fixed to the floor, and while the person to be inspected is supported on a conveyance device such as a roller,
It is also possible to perform inspection by intermittent movement in synchronization with the reciprocating swing of the detector using a driving device.

[Brief explanation of the drawing]

FIG. 1 is a front view of the inspection device used to carry out the method of the present invention;
Figure 2 is a plan view of the same as above, Figure 3a is the movement of the detector,
The figures are graphs showing the J motion of the traveling mechanism, and Figs. 4 to 6 are graphs showing the locus of the detector. Figs. 4 and 5 are the method of the present invention, and Fig. 6 is the conventional method. It is. (1)... Machine base (2)... Traveling mechanism □□□...
Traveling drive device (3)...Rocking device country...Rocking drive device (4)...Detector tube 41) Fig. 6

Claims (1)

[Claims] ■ A detector for inspecting defects on a metal surface is scanned back and forth in a direction perpendicular to the inspection direction, and is stopped for a short time at the scanning end for each scan, and the detector is stopped at the scanning end. A metal surface defect detection method in which the metal surface and the detector are moved relative to each other by the width of the detector in synchronization with the timing of the detection. (2) The method according to claim 1, wherein the detector is a single probe, and for each scan of the detector, the metal surface and the detector are intermittently moved relative to each other by the diameter bone of the probe. ■ The detector consists of multiple probes arranged in the inspection direction, and the patent states that for each scan of the detector, the metal surface and the detector move intermittently relative to each other by the length of the array of the multiple probes. The method according to claim 1.