JPS60147649A - Electromagnetic flaw detector for piping - Google Patents

Abstract

PURPOSE:To measure surely and precisely a flaw and thinning without contacting by setting an electromagnet and one or plural electromagnetic wave radiating and sensing coils or independent sensing coils to a running body without contacting with inside and outside walls of a piping. CONSTITUTION:A permanent, superconductive, or normally conductive electromagnet 3 is set to a running car 5, which is run on the inside and the outside, for example, the inside of a piping 1 by a traction rod 2, in the axial direction of the piping 1 or the direction orthogonal to this direction to generate a DC magnetic field. One or plural electromagnetic wave radiating and sensing coils 7 or independent sensing coils 7 are set to the surface of the running car 5 which faces the part where a magnetic flux 8 is flowed in the pipe, and electromagnetic waves are radiated from radiating coils 7, and reflected electromagnetic waves are detected by sensing coils 7. Thus, all flaws and thinning in the part where the running car can run are measured without water neither plants.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an element for measuring damage, corrosion, etc. of piping from the inside and outside of the pipe, and the purpose of this invention is to improve the purpose of the element by combining it with a traveling body that runs inside and outside the pipe. The present invention relates to an element that enables reliable measurement without contacting the pipe wall.

[Background of the invention]

Conventional technology is based on the ultrasonic flaw detection method, in which an ultrasonic transmitter/receiver element is attached to a moving body that can pass through the pipe, and during measurement, water is filled between the moving body and the pipe wall using a so-called water immersion method. Ultrasonic flaw detection had achieved its purpose. On the other hand, a non-contact method for testing piping involves installing an electromagnet inside or outside the pipe, and creating axial strain waves in the υ pipe through the interaction of a separately generated eddy current on the pipe surface and a magnetic field. Methods are being established to detect the presence or absence of flaws by catching the reflected waves, in which this distorted wave is mainly reflected from flaws in the radial direction. Among these methods, the former water immersion ultrasonic flaw detection method is used. This method requires the use of water and is extremely difficult to apply except for specific piping, such as condenser tubes in nuclear power plants.The latter method, which uses axial distortion waves due to the action of magnetic fields and eddy currents, is extremely difficult to apply to piping. It has the disadvantage that it can only detect flaws in the direction perpendicular to the axis, that is, in the radial direction.

[Purpose of the invention]

The object of the present invention is to eliminate the above-mentioned drawbacks, to avoid using water or couplant, and to prevent damage or corrosion in all directions of the piping by running the traveling body (or element) while keeping the element out of contact with the piping. It is an object of the present invention to provide a flaw detection element that enables reliable and precise measurement of the corresponding portion.

[Summary of the invention]

The present invention radiates electromagnetic waves into a DC magnetic field, which has been established in principle, and generates strain elastic waves inside the object to be measured through Lorentzian h due to the interaction of the eddy currents induced in the tube surface and the magnetic field. This propagates in the thickness direction of the tube, reaches a scratched or corroded surface, and is reflected there, reaching the surface of the object to be measured again, and sensing the electromagnetic waves emitted by the induced current caused by the interaction with the magnetic field. Applying the principle that accurate measurements are made by a signal processing device that is caught by a coil and connected later, permanent magnets or superconducting or normal-conducting electromagnets are installed inside and outside the tube in the axial direction of the tube or in a direction perpendicular to this. (It is possible that the element is a running body) to form the above DC magnetic field, and the surface of the DC magnet facing the tube wall, or the side of the traveling body facing the part where the magnetic flux flows in the tube. 1 on the face
It is equipped with one or more electromagnetic wave radiating coils and sensing coils or separate sensing coils, emitting electromagnetic waves of, for example, several MHz from the radiating coils, and detecting reflected electromagnetic waves with the sensing coils. Since perpendicular magnetic flux is incident on the tube surface relative to the surface, the distorted waves in the tube become transverse waves, and the distorted waves in the parallel magnetic flux section become follower waves, which can be sufficiently distinguished.

On the other hand, in order to enable flaw detection on sufficiently long tubes, and to solve the problems that arise with the measurement method in which the tube wall and the element are brought into close contact, a corresponding gap is created between the tube wall and the element, and this gap is The configuration is such that wheels or casters are attached to the traveling body to maintain a nearly constant position, and in special cases, the rotation or eccentricity of the element is performed using a separate actuator to improve measurement accuracy.

[Embodiments of the invention]

In FIG. 1, 1 is a pipe. In this case, an element for the inside of a tube has been selected as an example. This figure shows a type in which the element is towed and travels, and is moved in the axial direction of the pipe by a towing rod 2. At this time, the running is done by 5. The basic structure consists of 3 magnets, in which case they are excited by the excitation coil 4, and the DC magnetic flux forms a path through the element and the tube through the gap 12 as shown in 8. The excitation coil is supplied with current from the 6 cables. As shown in 7, the radiation and sensing coils having the following configuration are arranged in one or more tubes on the surface of the magnetic pole or on the surface of the traveling body (element) corresponding to the place where the magnetic flux in the tube is parallel to the axis of the tube. 5 This signal processing part is carried out inside the traveling body, or if the pipe diameter is sufficiently small, the signal is transmitted through 6 to the outside of the pipe. Processing is done in

Now, when a DC magnetic field is generated by 4, the radiation and sensing coil 7 emits an electromagnetic wave 13 of several MHz. When this reaches the inside of 1, Lorentzka is generated, and the distorted wave 14 hits the opposite wall at the speed of sound. When it reaches this point, a charu occurs and it reaches 7 again. In this case, the case where the wall thickness of the tube changes is shown to be the simplest, but if we obtain the time from the departure of tube 13 to the arrival of tube 16, we can obtain twice as much information about the thickness. With this element, it is possible to detect not only corrosion but also cracks, pins, etc., depending on the way the signal is processed. That is, by running this element inside and outside the pipe with a gap, it is possible to detect flaws in piping.

FIG. 2 shows an example of a device within the scope of the present claims. In other words, the piping is not a perfect circle but may have an elliptical or other shape, and in the structural example shown in Figure 1, it is possible that the magnetic flux is significantly uneven in the circumferential direction. In other words, it is effective to maintain the gap, that is, a means to keep the magnetic flux constant. For this purpose, an actuator 11 is attached to the element or a traveling body, and the structure is such that it can be rotated around O using casters 9 etc. as a guide, or the element itself is not cylindrical but has a cylindrical shape cut in the axial direction. Of course, there are devices that rotate around an axis to achieve a predetermined purpose, and all of these are included in the present invention. Further, as shown in FIG. 4, the running section is divided into a plurality of sections, and a section 7 straddles the sections.

〔Effect of the invention〕

According to the present invention, it is possible to measure flaws and wall thinning in all parts of piping while traveling inside and outside the piping, and it can be widely applied to gas pipes, electrical conduits, etc.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an example showing the basic configuration and operating principle of the present invention, and Fig. 2 is a supplementary explanation of 2゜3 shown in the claims. FIG. 3 is a schematic diagram showing the measurement theory, and FIG. 4 is a schematic diagram of an example of an application. 1... Piping, 2... Towing rod, 3, 3'...
Magnetic pole and running body, 4... Excitation coil, 5... Running vehicle, 6... Power, signal cable, 7... Radiation, sensing coil, 8... Magnetic flux, 9... Caster ( etc),
1o...Trajectory of the center of the element, 11...Actuator, 12...Gap, 13...Radiation electromagnetic wave, 1
4... forward sound wave, 15... reflected sound wave, 16... return electromagnetic wave, 17... coupling rondo. Agent Patent Attorney Akio Takahashi

Claims (1)

[Scope of Claims] 1. In an automatic running body or a towing or pushing type running body inside or outside of a pipe, a part of a single or multiple running bodies has permanent, superconducting or normal conductivity in the axial direction of the pipe or in a direction perpendicular thereto. An electromagnet is attached, and one or more electromagnetic radiation coils and sensing coils or separate sensing coils are installed on the magnetic pole surface or on the traveling body part corresponding to the part of the piping where the lines of magnetic force flow in the axial direction of the piping. An electromagnetic flaw detection element for piping featuring the following. 2. The electromagnetic flaw detection element for piping according to claim 1, wherein the magnet part, the radiation coil, and the sensing coil part of the element have an optimal gap for traveling and measurement so that they do not come into contact with the inner and outer diameters of the pipe. 3. A structure that has positioning and running wheels or casters in the radial direction, or a part or the whole of the element is equipped with pre-positioning rotating wheels or casters so that the gap between the element and the pipe wall is constant and it can travel sufficiently. 2. The electromagnetic flaw detection element for piping according to claim 1, wherein the element part can be rotated or decentered between the inside and outside of the chopstick by an external actuator.