JPH04220556A - Remote field eddy flow testing device - Google Patents

Abstract

PURPOSE:To enable an interference signal due to a pipe supporting plate to be excluded and a defect to be detected even if there is the defect at a part where the pipe supporting plate of a heat-transfer pipe is located. CONSTITUTION:A detection coil 3 which is wound around a holder 6 at a tip part of a probe guide pipe 4 is divided into two portions in reference to an axis and detection coils 3a and 3b in semi-circular rind are connected differentially. The coils 3a and 3b are generated due to excitation of an excitation coil 2, receive an electromagnetic energy which flows into a test electrically conductive pipe 1, and then sends a difference signal of the detection voltage to an impedance analyzer 10. The analyzer 10 compares frequency and phase of the difference signal of an excitation voltage of the coil 2 and the coils 3a and 3b. While operating in this manner, the guide pipe 4 moves at a constant speed within the electrically conductive pipe 1. Then, if there is a defect 1a at a part where a pipe-supporting plate 14 is located, differentially connected coils 3a and 3b detect and erase each signal at half part of the supporting plate 14 but the detection signal of the defect remains. The difference signal of this detection signal is sent to the analyzer 10 and an X-Y plotter 13 displays the defect detection signal.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an improvement of a remote field eddy current test device for detecting defects in heat transfer tubes in heat exchangers such as steam generators of sodium-cooled fast breeder reactors. This is used to inspect heat pipes during their service life.

0002

[Prior art] The principle of remote field eddy current testing is
Excitation coil 2 inserted inside tube 1 as shown in FIG.
The generated electromagnetic energy passes through the circumferential wall of the tube 1 and reaches the outside of the tube 1 as indicated by the dotted arrow, and then propagates along the outer surface of the tube 1 in the longitudinal direction, reaching a point farther away than about twice the tube diameter. At this position, it passes through the peripheral wall of the tube 1 again and returns to the inside of the tube 1. The electromagnetic energy returned to the inside of the tube 1 contains information about the tube peripheral wall, so if the detection coil 3 performs detection at a position farther away than about twice the tube diameter, defects in the tube 1 can be detected with good sensitivity. can. Also, when electromagnetic waves pass inside a conductor, a phase shift occurs in proportion to the distance traveled, so
Changes in pipe wall thickness can be detected from the phase displacement angle of the detection signal.

The configuration of an apparatus for actually performing remote field eddy current flaw detection will be explained with reference to FIG. 5. 1 is a test heat transfer tube, 2 is an excitation coil, and 3 is a detection coil. The probe guide tube 4 is wound around holders 5 and 6 fixed to the tip of the probe guide tube 4 with an interval of about twice the tube diameter of the probe guide tube 4 or more. A driving section 7 is provided at the proximal end of the probe guide tube 4 . The impedance analyzer 10 has a built-in oscillator 9, and the output from the oscillator 9 passes through an output amplifier 11 to excite the exciting coil 2. The excitation coil excitation voltage is then sent to the impedance analyzer 10. The electromagnetic energy generated by excitation of the excitation coil 2 passes through the tube 1, propagates along the outer circumference of the tube 1 in the longitudinal direction, flows into the tube 1 again, is received by the detection coil 3, and is detected by the detection voltage. is sent to the impedance analyzer 10. Note that 12 is a digivolt, and 13 is an X-Y plotter.

To explain the detection of artificial defects in a test heat exchanger tube using the conventional remote field eddy current testing apparatus configured as described above, as shown in FIG. An output is transmitted from the oscillator 9 of the analyzer 10, and the output is amplified by the output amplifier 11, and then the excitation coil 2 is excited. The excitation coil excitation voltage at this time is sent to the impedance analyzer 10. The electromagnetic energy generated by the excitation of the excitation coil 2 passes outside the heat exchanger tube 1 once, but flows into the heat exchanger tube 1 again. This flowing electromagnetic energy is received by the detection coil 3, and the detected voltage of the detection coil 3 is sent to the impedance analyzer 10. Then, a phase angle signal is obtained from the excitation voltage of the excitation coil and the detection voltage of the detection coil 3. While performing such operations, the probe guide tube 4
A defect detection signal is displayed on the X-Y plotter 13 using a phase angle signal by moving the test tube 1 at a speed of about 10 to 30 mm/sec as shown by the arrow.

[0005]

[Problems to be Solved by the Invention] However, in the remote field eddy current testing device described above, as shown in FIG. In the case where there is 1a, the defect detection signal is smaller than the signal from the tube support plate 14, so the defect detection signal is canceled by the signal from the tube support plate 14, making it impossible to detect the defect.

Therefore, the present invention provides a remote field eddy current testing device that eliminates interference signals caused by the tube support plate and makes it possible to detect defects even if there is a defect in the portion of the heat exchanger tube where the tube support plate is located. That is.

[0007]

[Means for Solving the Problems] A remote field eddy current test device of the present invention for solving the above problems has an interval on the outer periphery of the probe guide tube that is approximately twice or more the tube diameter of the test heat transfer tube. an impedance analyzer that includes a fixed detection coil and an excitation coil, a transmitter that emits an output to excite the excitation coil, and compares the height and phase of the excitation voltage of the excitation coil and the detected voltage of the detection coil; In a remote field eddy current test device consisting of an output amplifier that amplifies the output output from the detector, the detection coil is divided into a plurality of insulated parts in the circumferential direction, and the signal difference between at least one pair of detection coils is detected by the detection coil. By differentially connecting them, or by connecting each detection coil to an impedance analyzer and subtracting the output of the impedance analyzer,
It is characterized in that it can be obtained.

[0008]

[Operation] The remote field eddy current test device configured as described above detects the signal difference between at least one pair of detection coils by differentially connecting the detection coils, or by connecting each detection coil to an impedance analyzer,
This is obtained by subtracting the output of the impedance analyzer, so when detecting defects in heat exchanger tubes,
If there is a defect in the part where the tube support plate is located, the defective one of the pair of detection coils will detect the sum of the defect signal and the support plate signal, and the non-defect detection coil will detect the support plate signal. Only plate signals are detected. By taking the difference between these signals, the signal of the tube support plate is erased, and the defect signal remains without being erased. Therefore, it is possible to detect defects in the heat exchanger tube at the portion where the tube support plate is located.

[0009]

[Embodiment] An embodiment of the remote field testing apparatus of the present invention will be explained with reference to FIG. In FIG. 1, the same reference numerals as those in FIG. 5 indicate the same parts, so the explanation thereof will be omitted. The detection coil 3 wound around a holder 6 fixed at the tip of the probe guide tube 4 is divided into two axially symmetrical parts in the circumferential direction as shown in FIG. Coil 3a
, 3b are insulated, and each detection coil is differentially wired and further connected to an impedance analyzer 10.

[0010] In the remote field eddy current test apparatus configured as described above, the probe guide tube 4 is inserted into the test heat transfer tube 1 as shown in FIGS. 1 and 2, and the output is transmitted from the transmitter 9 of the impedance analyzer 10. The transmitted output is amplified by the output amplifier 11, and the excitation coil 2 is excited. At this time, the excitation coil excitation voltage is sent to the impedance analyzer 10. The electromagnetic energy generated by the excitation of the excitation coil 2 passes through the test heat exchanger tube 1, but
It flows into the test heat exchanger tube 1 again. This inflow electromagnetic energy is transferred to the differentially connected detection coil 3 of the semicircular ring.
a and 3b, and a difference signal between the detection voltages of the detection coils 3a and 3b is sent to the impedance analyzer 10. Then, the height and phase of the difference signal between the excitation coil excitation voltage and the detection voltages of the detection coils 3a and 3b are compared. While carrying out such operations, the probe guide tube 4 is moved inside the test heat exchanger tube 1 at a speed of about 10 to 30 mm/sec as shown by the arrow. As shown in FIG. 1, if there is a defect (local thinning that is not uniformly distributed in the circumferential direction) 1a in the portion of the test heat exchanger tube 1 where the tube support plate 14 is located, a pair of detection coils 3a
, 3b detect the signals of each half of the tube support plate 14 which are axially symmetrical, but since the detection coils 3a and 3b are differentially connected, the signals of each half of the tube support plate 14 are The detection signal of the defect on one half of the tube support plate 14 remains without being erased, and the difference signal of this detection signal is sent to the impedance analyzer 10, and the X-Y plotter 13 shows the amplitude change and phase. The defect detection signal due to the change is displayed, and the defect 1a of the test heat exchanger tube 1 is displayed at the part where the tube support plate 14 is located.
can be detected. Thereafter, due to the movement of the probe guide tube 4, the test heat exchanger tube 1 was
The defects 1b to 1f can be detected in the same manner as in the conventional method.

In the above embodiment, the detection coil 3 is divided axially symmetrically in the circumferential direction, and the two divided detection coils 3a and 3b are differentially connected.The detection coil 3 is shown in FIG. The detection coils 3'a to 3'i may be divided into a large number of parts in the circumferential direction, nine in this example, and connected differentially to the nine parts. Each of the detection coils 3'a to 3'i is supported on a holder 6 and is insulated from each other.

The remote field eddy current testing device of this embodiment is also used to detect defects in the test heat transfer tube 1 in the same manner as the remote field eddy current testing device of the previous embodiment.
As shown in FIG. 1, there is a defect (local thinning that is not uniformly distributed in the circumferential direction) 1 in the part where the tube support plate 14 of the test heat exchanger tube 1 is located.
a, the signals of the axially symmetrical portions of the tube support plate 14 are detected by at least one pair of detection coils, but by differentially connecting the detection coils, the signals of the axially symmetrical portions of the tube support plate 14 are detected. The signal is erased, the defect detection signal of the tube support plate 14 remains without being erased, and this difference signal is sent to the impedance analyzer 10, and the defect detection signal based on the amplitude change and phase change is displayed on the X-Y plotter 13. , it is possible to detect the defect 1a of the test heat exchanger tube 1 in the portion where the tube support plate 14 is located. Thereafter, by moving the probe guide tube 4, defects 1b to 1f of the test heat exchanger tube 1 in the portion where the tube support plate 14 is not located can be detected in the same manner as in the conventional method.

[0013]

As described above, according to the remote field eddy current testing device of the present invention, when detecting a defect in a heat transfer tube, even if there is a defect such as local thinning in the portion where the tube support plate is located, the pair of detection coils Detect the signal of the axially symmetrical tube support plate and calculate the difference between the signals by differentially connecting the detection coils, or by connecting each detection coil to an impedance analyzer and subtracting the output of the impedance analyzer. As a result, only the signal of the tube support plate is erased, and the defect signal remains without being erased. Therefore, it is possible to detect defects in the heat exchanger tube at the portion where the tube support plate is located.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the remote field eddy current testing device of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a sectional view of a detection coil in another embodiment of the remote field eddy current testing device of the present invention.

FIG. 4 is a diagram showing the principle of remote field eddy current testing.

FIG. 5 is a side view showing a conventional example of a remote field eddy current test device.

FIG. 6 is a diagram showing a state in which there is a defect in the portion of the heat exchanger tube where the tube support plate is located.

[Explanation of symbols] 1 Test heat exchanger tube 2 Excitation coil 3 Detection coils 3a, 3b A pair of divided detection coils 3'a~
3'i Multiple divided detection coils 4 Probe guide tubes 5, 6 Holder 7 Drive section 9 Transmitter 10 Impedance analyzer 11 Output amplifier

Claims (1)

[Claims] Claim 1: A detection coil and an excitation coil held and fixed on the outer periphery of the probe guide tube with an interval of approximately twice the tube diameter of the test heat exchanger tube or more, and a transmitter that emits an output to excite the excitation coil. In the remote field eddy current test device, the remote field eddy current test device includes an impedance analyzer that has a built-in impedance analyzer that compares the height and phase of the excitation voltage of the excitation coil and the detection voltage of the detection coil, and an output amplifier that amplifies the transmission output from the oscillator. The detection coil is divided and insulated into a plurality of pieces in the circumferential direction, and the signal difference between at least one pair of detection coils is detected by differentially connecting the detection coils.
Alternatively, a remote field eddy current test device characterized in that the detection coils are connected to respective impedance analyzers and the outputs of the impedance analyzers are subtracted.