CN102200529B - Ultrasonic transducer for detecting by insertion into stainless steel corrugated pipe - Google Patents

Abstract

An ultrasonic transducer that can be inserted into the stainless steel bellows for detection, is arranged at one end of the bellows, the permanent magnet (2) is inserted into the iron core (3) inside the bellows (1), and the two ends of the iron core (3) are and the middle part are provided with several isolation steps, and the part between every two adjacent isolation steps is surrounded by enameled wire, and the winding direction is changed every time the enameled wire passes through an isolation step; two permanent magnets (2) are adsorbed on the iron core (3 ) on both sides. The invention uses a permanent magnet to generate a bias magnetic field in the iron core. When an alternating voltage is applied to both ends of the enameled wire, local mechanical vibrations will be generated in the corrugated tube, and the detection of the entire corrugated tube can be realized. The sensor in the present invention can be inserted into the bellows for long-distance detection, and the detection signal is simple and clear, which is easy to analyze, thereby reducing the detection cost, and can be applied to stainless steel bellows in service in industrial sites with high tube bundle density and compact spatial distribution. detection.

Description

Ultrasonic transducers that can be inserted into stainless steel bellows for detection

technical field

The invention relates to an ultrasonic transducer that can be inserted into a stainless steel bellows for detection, and belongs to the technical field of acoustic sensors. Its function is to convert the electromagnetic energy generated by the sensor into mechanical energy (sound energy) Energy) analysis to detect the presence or absence of defects in stainless steel bellows.

Background technique

Nowadays, eddy current testing technology is mainly used for non-destructive testing of condenser stainless steel bellows. However, the eddy current inspection method needs to be detected point by point in actual detection, which is time-consuming and laborious, and it is difficult to carry out mass inspection. At the same time, the bundle density of stainless steel bellows is relatively high, and the spatial distribution is compact, so it is difficult to carry out effective inspection by ordinary inspection methods. The high economy and high efficiency of real-time state inspection are essential, so it is necessary to design an ultrasonic transducer that can be inserted into the stainless steel bellows for detection to meet the engineering requirements of in-service inspection of bellows.

Contents of the invention

The object of the present invention is to realize rapid and long-distance detection in the stainless steel bellows of the condenser by providing an ultrasonic transducer that can be inserted into the stainless steel bellows for detection.

The present invention is an ultrasonic transducer that can be inserted into the interior of a stainless steel bellows for detection, which is realized by the following technical means:

An ultrasonic transducer that can be inserted into the stainless steel corrugated tube for detection. It is installed at one end of the corrugated tube. The permanent magnet 2 is inserted into the iron core 3 inside the corrugated tube 1. The two ends and the middle part of the iron core 3 are provided with several isolation Steps, the parts between every two adjacent isolation steps are surrounded by enameled wires, and the enameled wires change the winding direction every time they pass through an isolation step; two permanent magnets 2 are adsorbed on both sides of the iron core 3 .

The outer diameter of the aforementioned iron core (3) is the same as the inner diameter of the bellows.

The outer diameter of the aforementioned permanent magnet (2) is the same as the inner diameter of the iron core (3).

Compared with the prior art, the present invention has the following obvious advantages and beneficial effects:

The invention uses a permanent magnet to generate a bias magnetic field in the iron core. When an alternating voltage is applied to both ends of the enameled wire, according to the law of electromagnetic field, local mechanical vibration will be generated in the bellows, and this vibration will flow from the excitation source to the two The direction propagates at the same time. When it encounters the end face or defect of the bellows, it will reflect and be captured by the receiving sensor, so that the detection of the entire bellows can be realized. The sensor in the present invention can be inserted into the bellows for long-distance detection, and the detection signal is simple and clear, which is easy to analyze, thereby reducing the detection cost, and can be applied to stainless steel bellows in service in industrial sites with high tube bundle density and compact spatial distribution. detection.

Description of drawings

Fig. 1 is the overall installation schematic diagram of the present invention;

Fig. 2 is a schematic diagram of coil winding on the iron core 3;

Fig. 3 is the schematic diagram of the receiving signal when using the piezoelectric chip self-excitation self-receiving;

FIG. 4 is a schematic diagram of a received signal when a piezoelectric chip is used to stimulate the reception of the present invention.

In the figure, 1, steel strand, 2, permanent magnet, 3, iron core, 4, enameled wire.

Detailed ways

Provide following embodiment in conjunction with the content of the inventive method:

The structure of this embodiment is shown in Fig. 1, comprises permanent magnet 2, and the iron core 3 that inserts bellows 1 inside, the two ends and the middle part on the appearance of iron core 3 are all provided with isolation steps, between every two isolation steps The parts in between are surrounded by enameled wires 4, and the winding direction is changed every time the enameled wires 4 pass through an isolation step. Two permanent magnets 2 are attached to both sides of the iron core 3, and the outer diameters of the permanent magnets 2 and the iron core 3 are the same as the inner diameter of the bellows, so as to be inserted into the inside of the bellows and make the enameled wire 4 as close as possible to the inner wall of the bellows.

In this embodiment, the outer diameter of the stainless steel bellows of the condenser is 25 mm, the wall thickness is 0.7 mm, the pitch is 10 mm, and the wave height is 0.5 mm. The total length of the corrugated pipe sample is 3780mm. The sensor is installed at the end face of the straight pipe section of the corrugated pipe. The piezoelectric ring is evenly distributed with 16 pieces. The selected piezoelectric ceramic chip is 7mm long, 3mm wide, and 0.5mm thick. The vibration type is length Telescopic type. A single audio signal with a peak-to-peak value of 300mV modulated by a Hanning window for 20 oscillation cycles is generated by a function generator, and the selected frequency is 240kHz. The excitation signal is amplified by the power amplifier, loaded on the piezoelectric chip, and then excites the L(0, 2) mode guided wave signal in the bellows, which will be reflected after propagating to the end face of the bellows, and then transformed Received by the sensor, displayed on the digital oscilloscope, and stored in the computer through the port.

A circumferential crack is processed on the bellows, the circumferential length is 10mm, the axial width is 0.4mm, and the center position is 1500mm away from the piezoelectric plate ring. The received signal when the piezoelectric chip is self-excited and self-received is shown in Figure 3. Using The received signal when the piezoelectric wafer is used to stimulate the present invention to receive is shown in FIG. 4 . It can be seen from the test results that in addition to the end face echo, the crack defect echo is clearly identifiable, and the axial position of the defect can be calculated by reading the arrival time of the defect wave packet, that is, the identification and positioning of the defect can be realized. Compared with the self-excited and self-received detection results received by the piezoelectric chip excitation, the detection signal has less clutter and a higher signal-to-noise ratio, but the amplitude is relatively small.

The experimental results show that the L(0,2) mode guided wave is suitable for detecting cracks in bellows, and the use of electromagnetic acoustic transducers can further improve the detection results and increase the detection range. The experimental results have verified the feasibility of ultrasonic guided waves in the detection of bellows defects, and the ultrasonic transducer inserted into the bellows can be applied to the in-service conditions of stainless steel bellows in industrial sites with high tube bundle density and compact spatial distribution. The detection also lays a certain foundation for the in-service detection of bellows.

Claims (3)

1. An ultrasonic transducer that can be inserted into a stainless steel bellows for internal detection, is arranged at one end in the bellows, and is characterized in that: a permanent magnet (2) and an iron core (3) are inserted into the inside of the bellows (1), and the iron core ( 3) The two ends and the middle part of the exterior are provided with several isolation steps, and the part between every two adjacent isolation steps is surrounded by enameled wire, and the enameled wire changes the winding direction every time it passes through an isolation step; two permanent magnets (2) Adsorbed on the two ends of the iron core (3) surface. 2. An ultrasonic transducer that can be inserted into a stainless steel bellows for detection according to claim 1, wherein the outer diameter of the iron core (3) is the same as the inner diameter of the bellows. 3. An ultrasonic transducer that can be inserted into a stainless steel bellows for detection according to claim 1, wherein the outer diameter of the permanent magnet (2) is the same as the inner diameter of the iron core (3).

Images