JPH07218478A - Ultrasonic wave pulse echo system and method therefor - Google Patents

Abstract

PURPOSE: To heighten sensitivity for detecting the crack of a steam pipe of a nuclear reactor. CONSTITUTION: Beams emitted from a convertor 1 proceed along transmission routes 7, 8, 9 toward the wall 4 of a pipe with certain angles. The angles are larger than an incident critical angle in respective cases, and as the result parts of the beams further enter the wall 4 insides of the pipe. The two transmission routes 8, 9 are such routes as two beams join in a zone of the wall 4 of the pipe. A sound wave reflected from the route 8 at a place of the inner wall face 5 of the pipe returns to the converter through the route 9, and the reverse is conducted regarding the route 9.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ultrasonic pulse echo system comprising a transducer and a multiple reflection system for transmitting and receiving a pulsed ultrasonic signal along a first transmission path. When used, for example, to inspect the wall of a pipe, the first transmission path is substantially parallel to the wall of this pipe. The multi-reflecting system consists of a first reflecting surface and a second reflecting surface by which a beam of ultrasonic waves is directed onto the wall of the pipe and the reflected beam is returned to the transducer. The invention also relates to a method of inspecting a wall using the system.

[0002]

2. Description of the Related Art Such pulse echo
The system is known and is described in US Pat. No. 4,022,05.
No. 5 describes the use of a pair of reflecting surfaces for ultrasonic waves. Each reflective surface defines another transmission path for the wall to be inspected. One of the two alternative transmission paths is perpendicular to the wall to be examined and the second transmission path is at an angle to the wall. The vertical transmission path serves to generate a reflected signal which gives information about the thickness of the wall to be examined. The angled transmission path serves to detect irregularities such as cracks in the wall of the pipe.

A pulse echo system as in the present invention detects such cracks early for safety reasons, such as in fact detecting cracks in steam pipes of water-cooled reactor equipment. Used when it is important to do.

In practice, it has been found that most cracks that occur have a reflective surface perpendicular to the wall of the pipe in which the crack is present. Accordingly, US Pat. No. 4,022,055
The energy of the acoustic waves in the direction perpendicular to the wall of the pipe, which serves to detect the wall thickness in the signal, does not contribute to the detection of such cracks. Only the part of the energy which is transmitted and radiated at an angle to the wall to be inspected is suitable for detecting such cracks. In this case, reflection occurs at the location of such a crack and some of the ultrasonic waves travel in the opposite direction towards the transducer, where the reflection is detected. However, most of the energy is dispersed in the wall of the pipe and is not effectively used for crack detection and other purposes.

2 in European Patent A-479368.
Describes a pulse-echo system that detects two beams entering a pipe wall from a single transducer with one plane mirror and one concave mirror, and the beams intersect at 90 ° in the pipe wall. Has been done. Its purpose is to avoid crosstalk between the beams and to obtain the same path length for both beams.

It is an object of the present invention to provide a pulse echo system with great sensitivity for detecting cracks of the above type. The system of the invention can simultaneously obtain information about the wall thickness and the internal contour of the wall.

[0007]

In accordance with the invention, a transducer for transmitting and receiving a pulsed ultrasound signal along a first transmission path, and both of the first transmission path, is provided. An ultrasonic pulse echo system is provided that comprises a multi-reflector comprising a first reflecting surface and a second reflecting surface therein. The first and second reflecting surfaces respectively define another transmission path through which the ultrasonic waves originating from the transducer are reflected to the first transmission path at respective angles, and the first transmission path and the other transmission path are defined. The transmission paths of are in a common plane. The individual angles made by the further transmission paths are less than 90 ° and are chosen such that these two transmission paths meet each other. The first transmission path is parallel to the wall to be inspected, the common plane is perpendicular to the wall, and the angle of each of the other two transmission paths to the wall is the wall. Greater than the critical angle of incidence at that, so that some of the ultrasonic waves that are directed toward the wall enter the wall.

The method of inspecting a wall according to the invention emits an ultrasonic signal from a transducer along a first transmission path parallel to the wall, which is in a plane common to said first transmission path and Reflecting the signal at the first and second reflecting surfaces along another transmission path at a wall that forms an angle of less than 90 ° with respect to the wall and that is oriented greater than the critical angle of incidence, Passing at least a portion of the signal into a wall, the first and second signals
Are merged in an area within the wall and the signal reflected by the wall is detected and returned to the transducer.

Preferably, the sum of the angle of the first reflecting surface with respect to the first transmission path and the angle of the second reflecting surface with respect to the first transmission path is about 90 °. This sum is 88-92 °
Is preferred.

The sound energy transmitted by the ultrasonic transducer and reflected by the first reflecting surface is reflected by the inner surface of the wall of the pipe and after entering the wall is reflected by the outer surface of the wall of the pipe. To do. These reflected waves and the pipe wall and the second
Via a second path to and from the reflective surface of the then to the transducer. The same happens in reverse for the beam reflected at the second reflecting surface. However, since the signal reflected from the crack or defect returns from the same reflective surface it traveled through, the overall transmission path is different than the path of reflection at the inner and outer walls.

In use, the system of the present invention comprises a transmission path between the transducer, the first reflecting surface and the wall to be inspected,
And the transmission path between the transducer, the second reflecting surface and the wall intersect each other in the region of the wall, and thus by the inner and outer surfaces of the wall of the pipe to be inspected and by any irregularities present in the wall. Any reflections that occur are set back into the transducer. In the system of the invention, the behavior of the total energy transmitted by the transducer is optimized and the sensitivity of crack detection is optimized. Furthermore, in the system of the invention, information about the wall, such as its thickness, and similar information about the wall contour of the pipe, can be obtained from the reflections occurring on the inner and outer surfaces of the wall.

According to the invention, the angle of the first reflecting surface with respect to the first transmission path is between 35 and 37 °, and the angle of the second reflecting surface with respect to the first transmission path is 55 to 53 °. Best results are obtained when between. If the angle is selected by shifting 1 ° from the optimum angle setting, a difference of 6 decibels will occur in the operating characteristics.

[0013]

Embodiments of the present invention will now be described with reference to the accompanying drawings. This embodiment does not limit the invention.

Like reference numerals in the two drawings indicate like parts.

The wall 4 of the pipe having an inner wall surface 5 and an outer wall surface 6 is inspected using a pulse echo system embodying the invention. For this purpose, a pulse signal is transmitted by the ultrasonic transducer 1 in the direction of the pair of reflecting surfaces 2 and 3 operating with it. The reflecting surfaces 2 and 3 are set to have different angles with respect to the transducer 1 and are arranged offset from each other in the longitudinal direction. The transmission path 7 between the transducer 1 and the multiple reflection system consisting of the reflecting surfaces 2 and 3 is substantially parallel to the wall 4 of the pipe to be examined. The reflecting surfaces 2 and 3 reflect the ultrasonic beam entering through the transmission path 7 in the direction of the wall 4 of the pipe, and another two converging in the area of the wall of the pipe from both the reflecting surface 2 and the reflecting surface 3. Transmission paths 8, 9 to the wall of one pipe are created. The angle of each path 8, 9 with respect to the wall 4 is about 45 °. One route 8
Is facing forward. That is, it is heading in the same direction as the route 7. On the other hand, the other route 9 faces rearward. The two paths are in the same plane and in the plane containing the path 7.

In the accompanying drawings, path 7 is shown as two lines for ease of explanation, but in practice this is a single transmit beam and a return beam (as described below). is there.

The value obtained by adding the angle of the second reflecting surface 3 to the transmission path to the angle of the first reflecting surface 2 to the transmission path 7 is about 90 °. Reflection surface 2 for the first transmission path 7
Is in the range of 35 to 37 °, and the first transmission path 7
The angle of the second reflection surface 3 with respect to is preferably in the range of 55 to 53 °.

The sound wave transmitted through the transmission path 7 is reflected by the reflecting surfaces 2 and 3, and then reaches the wall 4 of the pipe through both the transmission path 8 and the transmission path 9. Upon reaching the inner surface 5 of the pipe wall 4, some of these sound waves are reflected. The beam reaching the inner surface 5 via the transmission path 8 is partially reflected and returns to the converter 1 via the path formed by the transmission path 9 and the transmission path 7.

A corresponding path is created by a beam of acoustic waves that reaches the inner surface 5 of the pipe via the transmission path 9. This beam is also reflected in the same manner, and the reflected wave passes through the transmission path 8 and the transmission path 7 in the opposite directions, and the converter 1
Return to. The total acoustic wave path lengths for these two beams are the same, so the graph shows a single signal for the inner diameter ID of the pipe as shown in FIG. 1 (where IP is the first Represents a pulse).

If another part of the energy of the ultrasonic beam reaching the pipe wall 4 via the transmission paths 8 and 9 enters the pipe wall 4 and there is no crack or defect in the pipe wall 4. (As shown in FIG. 1) is reflected by the outer wall surface 6 of the wall 4 of the pipe. Also in this case, the two beams reflected from the outer wall surface 6 return to the converter 1 by another path, and the total path lengths of these two paths are the same, and as shown in the graph of FIG. A single signal appears for the outer diameter OD. The difference in the time the signals appear for the ID and OD gives the wall thickness, and the ID signal gives information about the contour and shape of the inner wall.

If a crack is present in the wall, part of the beam sent via the transmission path 8 is reflected by this crack and returns to the converter 1 via paths 8 and 7. The total path length in this case is shorter than the total path length of the ID signal, and the pulse echo signal for the crack appears in front of the ID signal on the wall, as indicated by the arrow pointing to the right in the graph of FIG.
Similarly, the beam sent via the transmission path 9 is partially reflected by the crack and returns to the converter 1 via paths 9 and 7. The total path length of this reflected wave is longer than the reflected wave of OD,
Therefore, another pulse echo signal from the crack appears after the OD signal, as indicated by the arrow pointing to the left in the graph of FIG. In reality cracks are detected on both sides.

The attenuation of the OD signal due to cracks or defects can also be examined.

Although the present invention has been described with reference to its embodiments, the present invention is not limited to these embodiments, and many modifications can be made within the scope of the concept of the present invention.

The main features and aspects of the present invention are as follows. 1. A transducer (1) for transmitting and receiving a pulsed ultrasonic signal along a first transmission path (7), and a first reflecting surface (both of which is in the first transmission path). 2)
And a second reflecting surface (3) comprising a multi-reflecting device; said first and second reflecting surfaces each transmitting ultrasonic waves originating from the transducer at respective angles to said first transmission path (7). Defining another transmission path (8, 9) to be reflected, said first transmission path (7) and said another transmission path (8, 9) being in a common plane; The individual angles made by
The two other transmission paths are chosen to join each other,
And the wall (4) on which the first transmission path (7) is to be inspected
Parallel to the wall and the common plane is perpendicular to the wall, the angle of each of the two other transmission paths with respect to the wall is less than 90 ° and is less than the critical angle of incidence at the wall. Ultrasonic pulse-echo system that is chosen so that it is also large, so that some of the ultrasound waves that are directed toward the wall enter the wall.

2. The sum of the angle of the first reflecting surface (2) with respect to the first transmission path (7) and the angle of the first reflecting surface (3) with respect to the first transmission path (7) is about 90 °. The pulse echo system according to item 1.

3. The angle of the first reflecting surface (2) with respect to the first transmission path (7) is in the range of 35 to 37 °, and the angle of the first reflecting surface (3) with respect to the first transmission path (7) is The pulse echo system of claim 1 in the range 55-53 °.

4. Emitting an ultrasonic signal from the transducer (1) along a first transmission path (7) parallel to the wall, in the plane common to the first transmission path and at the wall to the wall. To 9
Reflecting the signal at the first and second reflecting surfaces (2,3) along another transmission path (8,9) which is oriented at an angle smaller than 0 ° and which is oriented larger than the critical angle of incidence, Passing at least part of the ultrasonic signal into the wall (4),
And a method of merging the second transmission path in an area within the wall, detecting the signal reflected by the wall and inspecting the wall (4) by ultrasonic waves returning to the transducer (1).

5. The angles of the other transmission paths (8, 9) with respect to the wall (4) are substantially equal and the wall surface (5, 9)
The method according to claim 4, wherein the signal reflected by 6) and emerging from the first reflecting surface (2) is returned to the second reflecting surface and vice versa.

6. The sum of the angle of the first reflecting surface (2) with respect to the first transmission path (7) and the angle of the first reflecting surface (3) with respect to the first transmission path (7) is about 90 °. The method according to item 4.

7. The angle of the first reflecting surface (2) with respect to the first transmission path (7) is in the range of 35 to 37 °.
The method of claim 4 wherein the angle of the first reflective surface (3) with respect to the transmission path (7) is in the range 55-53 °.

[Brief description of drawings]

FIG. 1 shows a pulse echo system embodying the present invention when inspecting a portion of a pipe wall that is free of cracks.

2 shows the pulse echo system of FIG. 1 when inspecting a portion of a pipe where cracks are present.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Converter 2 Reflective surface 3 Reflective surface 4 Wall 5 Inner wall surface 6 Outer wall surface 7 Transmission line 8 Transmission line 9 Transmission line

Claims (2)

[Claims] 1. A transducer for transmitting and receiving a pulsed ultrasonic signal along a first transmission path, and a first reflecting surface and a first both in the first transmission path. A multi-reflecting device consisting of two reflecting surfaces; said first and second reflecting surfaces each comprising a separate transmission path through which the ultrasonic waves originating from the transducer are reflected at respective angles to said first transmission path. Defining the first transmission path and the further transmission path in a common plane; the individual angles of the further transmission path are selected such that the two further transmission paths meet each other. And the first transmission path is parallel to the wall to be inspected and the common plane is perpendicular to the wall,
The angle of each of the other two transmission paths with respect to the wall is 90.
Ultrasonic waves characterized in that they are smaller than ° and larger than the critical angle of incidence at the wall, so that some of the ultrasonic waves that are directed towards the wall enter the wall. Pulse echo system. 2. An ultrasonic signal is emitted from the transducer along a first transmission path parallel to the wall, the ultrasonic signal being in a plane common to the first transmission path and at the wall relative to the wall. Reflecting the signal at the first and second transmission surfaces along another transmission path that forms an angle less than 90 ° and that is oriented greater than the critical angle of incidence, at least a portion of the ultrasonic signal at the wall Ultrasonically, characterized by passing through, merging the first and second transmission paths in an area in the wall, detecting the signal reflected by the wall and returning it to the transducer. How to inspect.