JPH0474939A - Detecting device of fitting stress of double tube - Google Patents

Abstract

PURPOSE:To select a good material reliably, stably and in a non-destructive manner on the basis of whether a fitting stress of a double tube is a necessary value or not, by providing an appropriateness determinator which compares one or more signals out of ones corresponding to a waveform continuation time, a waveform area and a maximum amplitude value of a waveform of a signal processing device, with a set signal. CONSTITUTION:An elastic wave propagated in the direction of an arrow 5 is received by a reception converter 6 through a contact medium 2 and converted into an electric signal. This electric signal is subjected to an envelope detection processing by an AE measurer 7. An envelope detection waveform thus obtained is taken in an A/D converter in a signal processing device 8, AE waveform parameters are measured digitally in a sampling time of 100 usec, and based on the level thereof, it is judged by an appropriateness selector 9 whether fitting of inner and outer tubes is good or bad. According to this constitution, the precision in quality assurance of a double tube can be improved to a large extent.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to corrosion-resistant double pipes (hereinafter simply The quality of the material is determined to determine whether the fitting stress between the outer tube and inner tube of the double tube
Pseudo acoustic emission (hereinafter referred to as AE)
This invention relates to a detection device for sorting by law.

[Prior Art] A double pipe is a pipe material developed for the purpose of corrosion resistance and cost reduction; numerically, the inner pipe is made of a material with excellent corrosion resistance, and the outer pipe is made of carbon steel. The double pipe is a special public service issued in 1974-464.
As shown in the May 1999 bulletin, an inner tube and an outer tube with different components and materials made on separate tube manufacturing lines are used, the inner tube is inserted into the heated and expanded outer tube, and pressure is applied inside the inner tube. The inner and outer tubes are mechanically fitted together by thermal contraction of the outer tube after expanding the inner tube by adding a do.

If the fit of the double tube is 7mm2 or more, the inner tube will not come off or rub, and the quality of the double tube will be maintained.

Conventionally, a method for non-destructively measuring the fitting stress between the inner and outer tubes of a double tube manufactured by such a manufacturing method is known from Japanese Patent Laid-Open No. 62-828. This method is
The fitting stress between the outer tube and the inner tube is measured by distinguishing the acoustic signals generated when the double tube is hit by frequency.

[The problem that the invention tries to solve! ] Such conventional methods have problems such as the frequency of the acoustic signal being different depending on how the double tube is held, and the frequency discrimination granularity becoming low due to vibration noise at the measurement location. In addition, as a destructive measurement method, a strain gauge is attached to the inner surface of the inner tube of the tube material taken from the end of the double tube, and the residual strain in the inner tube is measured when the outer tube is cut with a saw etc. However, there are problems such as whether it can be determined by calculation or whether it is impossible to measure the fitting stress in the center of the pipe material.

In view of the problems of the prior art, the present invention provides a double pipe fitting stress measuring device that reliably non-destructively and stably selects pass/fail material to determine whether the fitting stress of the double pipe has a required value or not. The purpose is to

[Means for Solving the Problems] To achieve this object, the double tube fitting stress measuring device of the present invention includes a transmitting converter that converts a pulse generator signal into a pseudo AE signal, and a transmitting converter that converts the signal of a pulse generator into a pseudo AE signal, and the signal into an electrical signal. A receiving converter to convert, an AE measuring device to perform envelope detection processing on No. 13 of the receiving converter, a signal processing device to perform A/D conversion processing on the signal of the AE measuring device, and a waveform duration and waveform of the signal processing device. The present invention is characterized by comprising a pass/fail determiner that compares one or more of the signals corresponding to the area and the waveform maximum amplitude value with a set signal.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the electric pulse signal (FIG. 2(a)) generated by the pulse generator 1 is converted into a pseudo AE signal by the transmitting converter 4 via the couplant 2, and then An elastic wave is generated within the heavy pipe 3. The elastic waves propagated in the direction of arrow 5 are received by reception converter 6 via couplant 2 and converted into electrical signals. This electrical signal is shown in Figure 2 (
It has a waveform as shown in b), and the kneading is subjected to envelope detection processing by the AE measuring device 7 to form a waveform as shown in FIG. 2(C). This envelope detection waveform is taken into the A/D converter in the signal processing device 8, and the A/D converter in the signal processing device 8 is
E waveform parameters are digitally measured, and based on the level, a pass/fail selector 9 judges whether the fit between the inner and outer tubes is good or bad. As shown in FIG. 2, digital measurement may be performed on any of the AE waveform parameters of waveform duration T, waveform area S, and waveform maximum amplitude value (2) that exceed a predetermined threshold value Th.

Next, an actual measurement example using the device of the present invention will be described. Figure 3 shows an example of the relationship between the fit\stress and the waveform duration T determined by a destructive test. Since the two are in a proportional relationship as shown in this figure, for example, if the required fitting stress is 1
In the case of 0kgf 7mm2, the waveform duration T is 4
A pass/fail selector 9 is used to pass the case of m5ec or higher.
All you have to do is set . In addition, since there is a proportional relationship between the fitting stress of the double pipe, the waveform area S or 1, and the waveform maximum amplitude value (2), it is also possible to determine pass/fail based on stiffness.

The transmitting transducer and the receiving transducer may be arranged along the tube axis or in the circumferential direction, or on the inner or outer surface of the tube. FIG. 4 shows an example of the relationship between the distance between the bidirectional converters 4.6 and the waveform duration. As the transducer distance NL increases, the waveform duration T decreases, and when evaluating the fitting stress, it is necessary to keep the transducer distance constant. Converter path 111L
When evaluating different pipe materials, it is necessary to determine the relationship between the distance between transducers and the waveform duration in advance and correct it using the calibration curve section.

Double tube outer diameter: 88.9mmφ, outer tube wall thickness 5.0
mm, steel type of outer tube: carbon steel, wall thickness of inner tube: 1.5 mm
, Inner tube steel type: Inconel 625 (trade name), tube material length: 1.5 m double tube 2 wood, generate a pseudo AE signal, detect the waveform duration T, and judge whether the fitting stress is good or bad. did. The measurement conditions are electric pulse voltage V:
IOV, converter frequency f: 200kHz, converter path 11 [L: 1m, pulse repetition frequency fp; 20
Hz, threshold Th: 0. It was set to lV. As a result of judging whether the fitting stress was acceptable or not, the waveform duration T of the double pipe of No.] was 7.5 m5ec, and it was judged to be acceptable. As a result of measuring the fitting stress of N011 double pipe by destructive test,
There was 18kgf/III[I12. The waveform duration T of the N002 double tube was 2 m5eC, and it was determined to fail. The fitting stress of No. 2 double tubes was measured by a destructive test and was found to be 4 kgf/mm2.

[Effects of the Invention] According to the present invention, compared to the conventional method of frequency discriminating acoustic signals, the fitting stress of the double tube can be reliably maintained at the required value regardless of the method of holding the double tube or the noise at the measurement location. It is possible to non-destructively judge whether or not the material is good or bad and to sort out good or bad materials, greatly improving the accuracy of quality assurance for double pipes.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a specific example of the present invention, Fig. 2 is a diagram showing a waveform detected by a receiving converter, and Fig. 3 is an example of the relationship between fitting stress and waveform duration T determined by a destructive test. FIG. 4 is a diagram showing an example of the relationship between the distance between transducers and the waveform duration. DESCRIPTION OF SYMBOLS 1... Pulse generator, 2... Couple material, 3... Double tube, 4... Transmission transducer, 5... Propagation direction of detected elastic wave, 6... Receiving transducer, 7...AE measuring instrument, 8.
...Signal processing device, 9...Pass/fail judge, Th...Threshold value, T...Waveform duration, S...Waveform area, v
p... Waveform maximum amplitude value, L... Distance between converters, V-
...Electric pulse voltage, f...Converter frequency, fp-...
・Pulse reversal frequency.

Claims (1)

[Claims] 1. A transmitting converter (4) that converts the signal of the pulse generator (1) into a pseudo AE signal, a receiving converter (6) that converts the signal into an electrical signal, and an envelope of the signal of the receiving converter (6). The waveform duration, waveform area, and waveform of the AE measuring device (7) that performs line detection processing, the signal processing device (8) that performs A/D conversion processing on the signal of the AE measuring device (7), and the signal processing device (8). A double tube fitting stress detection device comprising a pass/fail judge (9) that compares one or more signals corresponding to the maximum amplitude value with a set signal.