JPH0776765B2 - Eddy current test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is one of nondestructive inspection methods, and relates to an eddy (electric) flow test method applied to maintenance inspection of heat transfer tubes of a heat exchanger. In particular, the present invention relates to a test apparatus suitable for improving test accuracy and efficiency.

[Conventional technology]

Conventional test coils are defined by being classified into two types, standard comparison type and self-comparison type, each of which has different defect detection characteristics.
Each has been used separately. As can be seen from the above-mentioned known examples, the concept of a test coil that combines them and combines the features of both was completely lacking.

The conventional technique will be described with reference to FIGS. 4 and 5.

FIG. 4 shows a method in which two test coils 11 and 12 are inserted close to each other and inserted into the tube 20. The difference between the eddy currents at the positions of the two coils, that is, the difference between the outputs of the two coils. To detect defects. It is a method that is not easily affected by background noise and is suitable for detecting local defects, and is called a self-comparative test coil.

FIG. 5 shows a method called standard comparison type in which one of the two coils, the test coil 15 is inserted into the tube 20 to be tested, and the other standard coil 16 is inserted into the standard test piece 21. Since this method detects defects and the like in the tube 20 to be tested by comparison with the standard test piece 21, it is suitable for detecting a gradually changing phenomenon such as metal thinning over a wide range and material differences. As described above, the self-comparison type (FIG. 4) and the standard comparison type (FIG. 5) have different defect detection characteristics. Both methods had to be performed separately.

[Problems to be solved by the invention]

The two types of test coils, the self-comparison type and the standard comparison type, are superior to the former in the detection of heat transfer tubes, etc. Is susceptible to background noise,
They are complementary to each other in that they are suitable for detecting thinning that changes gently over a wide range.

Therefore, only one test was inadequate and double the time required to perform both.

It is an object of the present invention to include two types of test coils and realize a highly accurate test having the characteristics of both by a single scan.

[Means for solving problems]

Means for achieving the above-mentioned object, the probe of the eddy current test device, a test coil of the standard comparison method and a plurality of test coils of the self-comparison method, at the position equidistant from the test coil of the standard comparison method, It is equipped with a plurality of self-comparison type test coils arranged so that the standard comparison type test coil and the standard comparison type standard coil that form a bridge circuit for the standard comparison type are used for the standard test piece. The test circuit of the standard comparison method and the test coil of the self comparison method are installed in a bridge circuit for the self comparison method in which a plurality of test coils of the self comparison method are incorporated so as to cancel mutual interference between the test coil of the standard comparison method and the test coil of the self comparison method. And a plurality of coils corresponding to the plurality of test coils of the self-comparison method provided for the standard test piece, Wherein the equal distance position is disposed a plurality of coils corresponding to a plurality of test coils self comparison method, the eddy current testing apparatus common power source is connected to both bridge circuits.

[Action]

Since two probe test coils with different characteristics are mounted on one probe, the test result of both methods can be obtained by one scan, and accurate judgment can be made from the results of both methods. From the self-comparison method to the plurality of test coils are equalized by disposing the plurality of self-comparison method test coils at positions equidistant from the standard comparison method test coil. When the detection result of the comparison method becomes accurate, the effect is obtained, and the accuracy is improved.

In addition, one of the two methods adopts a standard comparison method, and a standard test piece equipped with a standard comparison standard coil has a plurality of coils corresponding to a plurality of self-comparison test coils. Equipped with the same arrangement as the test coil on the test body side, interference equivalent to each method on the test body side is reproduced between each coil on the standard test piece side, and the effect of canceling both interferences on the bridge circuit side is obtained. Accuracy is improved.

Further, by making the power sources of the bridge circuits formed by the standard comparison type coil and the self-comparison type coil common, the frequencies of the respective bridges are made to coincide with each other to prevent generation of a beat signal.

〔Example〕

 First, the eddy current test method according to the present invention will be described.

FIG. 3 (B) shows a configuration in which a test coil is inserted on the inner surface of the tube to inspect the tube for material defects, and the principle of the test will be described with this example.

Reference numeral 20 denotes a cut surface of the pipe to be tested, in which two coils 11 and 12 are inserted. When an alternating current is applied to these coils, a magnetic field 31 is generated. Magnetic field 31 is a tube
An eddy current 32 is generated in 20 and this eddy current 32 forms a new magnetic field (not shown). As a result, the magnetic field interlinking the test coils 11 and 12 is the sum of the magnetic field generated by the coils themselves and the magnetic field formed by the eddy current. However, if a discontinuity such as a material defect 23 exists in the tube 20, the distribution of the eddy current 32 also becomes discontinuous and the formed magnetic field changes. As a result, the impedance of the test coil changes. The presence of the defect 23 can be detected by measuring this impedance change with a bridge circuit or the like.

FIG. 3 (A) shows a configuration example of the apparatus required for the above test, test coils 11 and 12 arranged in parallel on the probe 10, a bridge circuit 40 including these coils, and a power source 3 for the bridge.
0, amplifier 50 to increase the output of the bridge, data processing unit 6
0, a display unit 70, a recording device 80 and the like. The present invention mainly relates to the combination of the test coils 11 and 12 and the bridge power source among these configurations.

It is the present invention that both types of tests can be carried out by a single operation, and the embodiment will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a test coil according to the present invention, in which a probe 10 is provided with self-comparative test coils 11 and 12 so as to sandwich the standard comparative test coil 15 and the like. Although not shown, the standard coil (16 in FIG. 5) corresponding to the standard comparative coil is provided on a separate probe. This probe 10
Self-comparative type test is performed by the coils 11 and 12 by inserting into the tube under test, a standard comparative type test is performed by the coil 15, and two parts with the above-mentioned characteristics are provided in one operation. The test can be conducted.

Fig. 2 is for preventing the harmful signals from being generated by the interference of (the magnetic fields of) each coil when three coils are installed side by side. Coils 13 and 14 corresponding to the self-comparative coils 11 and 12 are installed on both sides of the coil 16 so that the same mutual interference that occurs in the tube under test is also generated in the standard test piece 21 and both are struck. I tried to erase it.

Also, if there is a difference in frequency or phase between the self-comparison type measurement bridge 40 and the standard comparison type bridge 43, a harmful signal such as a beat signal is generated.
Having 30 in common solves that problem.

〔The invention's effect〕

According to the present invention, it is possible to obtain the test results by both the self-comparison method and the standard comparison method by one scan, and cancel the adverse effect due to the interference of both methods, and quickly and accurately from the results of both methods. The test results can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a probe according to an embodiment of the present invention, and FIG.
FIG. 3 is a circuit configuration diagram of an embodiment of the present invention, FIG. 3 (A) is a typical configuration diagram of an eddy current test apparatus according to the present invention, and FIG. 3 (B).
Is an explanatory view of the principle of the eddy current test, FIG. 4 is an explanatory view of a test method using a self-comparative coil, and FIG. 5 is an explanatory view of a test method using a standard comparative coil. 10 ... probe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-39344 (JP, A) JP-A-57-66353 (JP, A) JP-A-57-199953 (JP, A) JP-A-50- 129284 (JP, A) Actually opened 61-15558 (JP, U)

Claims (1)

[Claims] 1. A probe of an eddy current test apparatus comprising a standard comparison type test coil and a plurality of self-comparison type test coils,
The test coil of the standard comparison method is equidistant from the test coil of the standard comparison method so that a plurality of test coils of the self-comparison method are arranged, and the test coil of the standard comparison method and the bridge circuit for the standard comparison method are provided. The standard coil of the standard comparison method is assembled to a standard test piece, and the test coil of the standard comparison method and the self-comparison method are incorporated in a bridge circuit for the self-comparison method in which a plurality of test coils of the self-comparison method are incorporated. A standard coil of the standard comparison method, which is equipped with a plurality of coils corresponding to the plurality of test coils of the self-comparison method installed to the standard test piece so as to cancel mutual interference with the test coil of the comparison method. The plurality of coils corresponding to the plurality of test coils of the self-comparison method are arranged at positions equidistant from the coils, and both bridge circuits are provided. Vortex test apparatus through a power supply is connected.