CN102520057B - Magnetostrictive guided wave sensor for detection in heat exchange tube and detection method thereof - Google Patents

Abstract

The invention discloses a magnetostrictive guided-wave sensor for the detection in a heat exchange tube and a detection method thereof. The sensor comprises a shell, an end cover fixed with one end of the shell, a conductive steel brush connected with the other side of the shell, an inner shell which is arranged in the shell and connected with the shell, an aerial socket which is arranged on the end cover and electronically connected with the conductive steel brush through direct current leads of the inner shell, a first magnetic concentrator and a second magnetic concentrator which are respectively arranged at different positions of the inner shell, and a first alternating current coil and a second alternating current coil which are respectively winded along the first magnetic concentrator and the second magnetic concentrator and are respectively electronically connected with the aerial socket. According to the invention, the whole detection process is realized by magnetic field, belonging a non-contact detection, thus the requirement of the surface conditions in the heat exchange tube to be detected is low, polishing and other special treatment are not needed, and the detection efficiency and applicability are raised.

Description

Magnetostrictive guided wave sensor for detection in heat exchange tube and detection method thereof

technical field

The invention relates to the technical field of ultrasonic non-destructive testing, in particular to a magnetostrictive guided wave sensor used for detection inside a heat exchange tube and a detection method thereof.

Background technique

With the rapid development of the petrochemical industry, the number of heat exchangers used has increased dramatically, and the number of heat exchange tubes has increased geometrically. Since the heat exchange tube is prone to failure under the interaction of corrosion and stress for a long time, it will affect the safe operation of the equipment and product quality, so it is necessary to test the heat exchange tube. At present, the detection methods for in-service heat exchange tubes mainly include far-field eddy current detection, local magnetic saturation eddy current detection, internal rotation ultrasonic phased array detection and magnetic flux leakage detection. In the detection process of the above detection methods, the sensor must pass through the detected area of the heat exchange tube. On the one hand, the moving process of the probe will lead to low detection efficiency; Affected the application of the above detection method.

Ultrasonic guided wave detection has the advantage of being able to detect a certain distance with a single point of excitation, so it can be used for heat exchange tube detection, and only need to clean the sensor placement area during the detection process without moving the sensor. The invention application of patent application number CN200480038549.4 discloses a torsional wave detection method and system for heat exchange tubes, through the coupling of the guided wave cone and the inner wall of the heat exchange tube, the magnetostrictive sensor outside the heat exchange tube is used to excite And receive the torsional wave pulse to complete the detection of the heat exchange tube, and its coupling directly affects the detection result. Therefore, this method requires a good contact condition of the inner surface and high cleaning requirements; and for the unevenness of the inner surface, special treatment such as grinding is required, which causes inconvenience in actual operation.

Contents of the invention

In view of the above defects, the object of the present invention is to provide a magnetostrictive guided wave sensor and its detection method for detection in the heat exchange tube, which only needs to place the sensor inside one end of the heat exchange tube to be tested during detection, and is in the position of The conductive steel brush at the front end of the sensor makes electrical contact with the heat exchange tube, and the sensor can realize efficient detection of the heat exchange tube without moving during the detection process.

According to one aspect of the present invention, a magnetostrictive guided wave sensor for detection in a heat exchange tube is provided, the magnetostrictive guided wave sensor comprising:

shell;

an end cap fixed to one end of the housing;

Conductive steel brushes connected to the other side of the enclosure;

an inner shell arranged inside and connected to the outer shell;

Installed on the end cover, the aviation socket is electrically connected by the DC wire passing through the inner shell and the conductive steel brush;

a first magnet concentrator and a second magnet concentrator respectively arranged at different positions of the inner casing; and

The first AC coil and the second AC coil are respectively wound on the first magnetic concentrator and the second magnetic concentrator, and are respectively electrically connected to the aviation socket.

As a further preference, the first magnetic concentrator and the second magnetic concentrator can be made of high magnetic permeability materials, such as industrial pure iron, silicon steel, low carbon steel and the like.

As a further preference, the first magnetic concentrator and the second magnetic concentrator can be fixed to the inner shell by screws.

As a further preference, both the outer shell and the inner shell are made of insulating materials.

According to another aspect of the present invention, a method for internal inspection of heat exchange tubes is provided, the method includes the following steps:

The magnetostrictive guided wave sensor is placed inside the heat exchange tube to be tested and near one end thereof;

Set a magnetic carbon brush in electrical contact with the one end of the heat exchange tube to be tested, and at the same time connect the DC power supply with the aviation socket and the magnetic carbon brush to form a circuit, thereby generating a circumferential magnetic field inside the heat exchange tube to be tested ;

Generate an electromagnetic pulse signal, amplify its power, and input it to the first AC coil wound on the first magnet concentrator, thereby forming an alternating magnetic field acting on the heat exchange tube to be detected. Under the combined action of the variable magnetic field, elastic waves of torsional mode are formed in the heat exchange tube to be detected;

When the elastic wave passes through the second AC coil wound on the second magnet concentrator, it is converted into an electrical signal due to the inverse magnetostrictive effect. At this time, the electrical signal is subjected to signal preprocessing and A/D conversion to obtain The detection result signal is obtained to complete the detection process of the heat exchange tube.

As a further preference, before using the magnetostrictive guided wave sensor to detect the heat exchange tube, the area inside the heat exchange tube where the sensor is placed is cleaned.

As a further preference, after the detection result signal is obtained, the relevant signal can be stored in the computer for subsequent processing.

According to the magnetostrictive guided wave sensor and its detection method of the present invention, since the entire detection process is realized through a magnetic field, which belongs to non-contact detection, the requirements for the inner surface of the detected heat exchange tube are low, and no special treatment such as grinding is required, thereby The detection efficiency and applicability are improved; in addition, according to the magnetostrictive guided wave sensor and its detection method of the present invention, the magnetic concentration effect of the high magnetic permeability material is utilized, and the high magnetic permeability material arranged between the DC wire and the AC coil It has a gathering effect on the alternating magnetic field, thereby improving the signal-to-noise ratio of the detection signal.

Description of drawings

Fig. 1 is a cross-sectional view of a magnetostrictive guided wave sensor for detection in a heat exchange tube according to the present invention;

Fig. 2 is a schematic diagram of a system in which a magnetostrictive guided wave sensor is used for internal detection of a heat exchange tube according to the present invention;

Fig. 3 is the cross-sectional view after increasing the magnetic concentrator in the magnetostrictive guided wave sensor according to the present invention;

Fig. 4 is the schematic diagram of the standard sample of the heat exchange tube with an outer diameter of 25mm and an inner diameter of 20m used in the specific embodiment;

Fig. 5 is to use the magnetostrictive guided wave sensor shown in Fig. 3 to detect the oscillogram of the gained signal on the standard tube;

FIG. 6 is a waveform diagram of a detection signal obtained on a standard sample tube by using the magnetostrictive guided wave sensor shown in FIG. 1 .

Detailed ways

Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Referring to FIG. 1 , FIG. 1 is a cross-sectional view of a magnetostrictive guided wave sensor for detecting inside a heat exchange tube according to the present invention. As shown in Fig. 1, the magnetostrictive guided wave sensor 2 for detecting inside the heat exchange tube according to the present invention includes an aviation socket 4, an end cover 5, an inner shell 6, a first AC coil 7, and a second AC coil 9 , DC wire 11, shell 12 and conductive steel brush 13. The end cap 5 is fixed to one end of the housing 12 , and the other end of the housing 12 is connected to a conductive steel brush 13 . In the outer shell 12, the inner shell 6 is arranged and connected with it by a suitable connection method, for example, by screws. On the end cover 5 , an aviation socket 4 is installed, and the aviation socket 4 is electrically connected to the conductive steel brush 13 through the DC wire 11 passing through the inner shell 6 . The DC conductor 11 and the conductive steel brush 13 are connected by welding. A first AC coil 7 and a second AC coil 9 are respectively wound on the inner shell 6 , and electrical connections between the first AC coil 7 , the second AC coil 9 and the aviation socket 4 can be realized respectively.

The process of using the magnetostrictive guided wave sensor according to the present invention to detect the heat exchange tube will be specifically described below with reference to FIG. 2 . As shown in Figure 2, during the detection process of the heat exchange tube 3 to be detected, the outgoing line of the DC power supply 14 is connected to the aviation socket 4, and the incoming line is connected to the magnetic carbon brush 1, and the magnetic carbon brush 1 is adsorbed on the heat exchange tube 3 to be detected Thus, a DC circuit is formed among the DC power supply 14, the conductive steel brush 13, the heat exchange tube 3 to be detected, and the magnetic carbon brush 1, and a circumferential magnetic field is generated in the heat pipe 3 to be detected.

At this time, the computer 19 controls the signal generator 16 through software to generate a pulse signal, which is input to the first AC coil 7 through the power amplifier 15, thereby generating an alternating magnetic field acting on the heat exchange tube 3 to be tested. Under the joint action of the above-mentioned alternating magnetic field and the circumferential magnetic field, an elastic wave in torsional mode is generated in the heat exchange tube 3 to be detected, and when the elastic wave passes through the second AC coil, it is converted into an electrical signal due to the inverse magnetostrictive effect, The electrical signal enters the acquisition unit of the computer 19 through the signal preprocessor 17 and the A/D converter 18, thereby realizing the whole inspection process of the heat transfer tube.

Fig. 3 is a cross-sectional view of the magnetostrictive guided wave sensor according to the present invention after adding a magnetic concentrator. As shown in Figure 3, a first magnetic concentrator 8 and a second magnetic concentrator 10 are respectively fixed on the inner shell 6 by screws, and the first AC coil 7 and the second AC coil 9 can be wound on the first magnetic concentrator 8 and the second magnetic concentrator respectively. On the second magnet concentrator 10. After research, it has been shown that because the above-mentioned high magnetic permeability material is arranged between the DC wire and the AC coil, it has a gathering effect on the alternating magnetic field, which can significantly improve the signal-to-noise ratio of the detection signal, thereby improving the accuracy of the detection of the heat exchange tube. Spend. In addition, because the high magnetic permeability material is limited to industrial pure iron, silicon steel, and low carbon steel, it is easier to process than other materials, and it is more obvious in improving the detection signal strength.

Figure 4 is a schematic diagram of a heat exchange tube standard sample with an outer diameter of 25mm and an inner diameter of 20mm. The tube length is 2m, and there is a Via defect.

FIG. 5 is a waveform diagram of a signal detected on a standard sample tube by using the magnetostrictive guided wave sensor shown in FIG. 3 . In Figure 5: the electromagnetic pulse signal detected by the magnetostrictive guided wave sensor is represented by M1, the signal passing through the second AC coil for the first time is represented by S1, the defect signal is represented by F1, the left end of the heat exchange tube to be detected The echo signal is represented by S2, and the echo signal of the right end of the heat exchange tube to be detected is represented by S3.

FIG. 6 is a waveform diagram of a detection signal obtained on a standard sample tube by using the magnetostrictive guided wave sensor shown in FIG. 1 . In Figure 6: the electromagnetic pulse signal detected by the magnetostrictive guided wave sensor is represented by M2, the signal passing through the second AC coil for the first time is represented by S4, the defect signal is represented by F2, the left end of the heat exchange tube to be detected The echo signal is represented by S5, and the echo signal of the right end of the heat exchange tube to be detected is represented by S6.

Compared with the signal in Figure 5, it can be clearly found that the signal noise generated by this method is relatively large, and the amplitude of the defect signal is reduced. Therefore, it can be proved that arranging magnet concentrators in the first and second AC coils can improve the detection effect and accuracy of the heat exchange tubes.

Claims (6)

1. A magnetostrictive guided wave sensor for detection in a heat exchange tube, the magnetostrictive guided wave sensor comprising: shell; an end cap fixed to one end of the housing; Conductive steel brushes connected to the other side of the enclosure; an inner shell arranged inside and connected to the outer shell; Installed on the end cover, the aviation socket is electrically connected by the DC wire passing through the inner shell and the conductive steel brush; a first magnet concentrator and a second magnet concentrator respectively arranged at different positions of the inner shell; and The first AC coil and the second AC coil are respectively wound on the first magnetic concentrator and the second magnetic concentrator, and are respectively electrically connected to the aviation socket. 2. The magnetostrictive guided wave sensor according to claim 1, wherein the materials of the first magnetic concentrator and the second magnetic concentrator are industrial pure iron, silicon steel or low carbon steel. 3. The magnetostrictive guided wave sensor according to claim 1 or 2, characterized in that, both the outer shell and the inner shell are made of insulating materials. 4. A method of using the magnetostrictive guided wave sensor according to any one of claims 1-3 to perform internal detection on heat exchange tubes, the method comprising the following steps: The magnetostrictive guided wave sensor is placed inside the heat exchange tube to be tested and near one end thereof; Set a magnetic carbon brush in electrical contact with the one end of the heat exchange tube to be tested, and at the same time connect the DC power supply with the aviation socket and the magnetic carbon brush to form a circuit, thereby generating a circumferential magnetic field inside the heat exchange tube to be tested ; Generate an electromagnetic pulse signal, amplify its power, and input it to the first AC coil wound on the first magnet concentrator, thereby forming an alternating magnetic field acting on the heat exchange tube to be detected. Under the combined action of the variable magnetic field, elastic waves of torsional mode are formed in the heat exchange tube to be detected; When the elastic wave passes through the second AC coil wound on the second magnet concentrator, it is converted into an electrical signal due to the inverse magnetostrictive effect. At this time, the electrical signal is subjected to signal preprocessing and A/D conversion to obtain The detection result signal is obtained to complete the detection process of the heat exchange tube. 5 . The method for internal detection of heat exchange tubes according to claim 4 , characterized in that, before the detection, the area where the sensor is placed inside the heat exchange tubes is cleaned. 5 . 6. The method for internal inspection of heat exchange tubes according to claim 4 or 5, characterized in that, after the detection result signal is obtained, the relevant signal is stored in the computer for subsequent processing.