KR20000044060A - Interpolated umbrella type eddy current probe for non-destructively testing spiral heat pipe in steam generator - Google Patents

Abstract

PURPOSE: A probe is provided to perform a non-destructive test for curved heat pipes as well as a spiral heat pipe of a steam generator by employing eddy currents. CONSTITUTION: A protective cover(12) is connected to a flexible centering member(10) containing a spinner. Plural guide grooves(14) are formed on the side surface of the protective cover for a test coil group to be inserted to the guide grooves. Herein, the test coil group consists of a test coil(18), a support stand(16), a test coil body(32), and a leaf spring(30) moving the support stand up and down. The test coil body includes the support stand connected by a pin(28). The test coil contains an intermediate guide tube(24) and a press roll(22) having a spring(26) on a central shaft under the protective cover. A probe is folded in an umbrella type in an insertion to improve inserting property. The probe is unfolded in a withdrawal to increase fill factor while minimizing friction.

Description

Non-destructive Umbrella Type Eddy Current Probe for Nondestructive Testing of Steam Generator Spiral Heater Tubes

The present invention relates to a non-destructive inspection type umbrella type and current probe for the non-destructive inspection of the curved steam generator spiral heat transfer tube with a small radius of curvature.

The steam generator heat pipes of the nuclear power plant currently operating are ASME Code Sec. According to the requirements of XI, eddy current test is carried out during the non-destructive test as a safety test for the whole heat pipe. Eddy current test is to push the eddy current transducer guide flex-tube to both sides of the belt by pushing the push-puller installed on the outside of the steam generator manway nozzle and rotate the push puller to move the eddy current transducer It is inserted into the steam generator heat pipe. Eddy current inspection is carried out with the transducer pulled out by reverse rotation of the push puller after the transducer has advanced to the outlet on the opposite side of the heat pipe. Conventional eddy current test probes, such as the one shown in FIG. 1, have almost no slip phenomenon due to friction when the probe is inserted since the conventional steam generator heat pipe has a straight tube shape, but has a curvature radius of 500 mm or less. It is impossible to test while satisfying the fill factor (ratio of transducer outer diameter to inner diameter of the tube) by the conventional method due to friction caused by bending. In the eddy current test, the filling rate is a very important factor. In general, when the filling rate is 0.85 or less, the amplitude of the signal is very low, which makes the evaluation of the test signal very difficult. In order to solve this problem, to apply the conventional transducer of FIG. 1 to a curved tube with a small radius of curvature, a small structure and a special type of central shaft retainer satisfying the filling rate are required while eliminating the enormous frictional force generated when the transducer is inserted.

An object of the present invention was developed as an eddy current test probe during non-destructive testing to check the integrity of the spiral heat exchanger tube and the curved tube type tube of the steam generator with a small curvature radius.

The intermittent umbrella type probe for eddy current inspection of the spiral heating tube of the steam generator, which is the main point of the present invention, was connected to each other while maintaining maximum flexibility with the ultra-small body as shown in [FIG. 2] and [FIG. 3]. The protective cover that protects the inspection coil assembly is always covered before the start of the inspection or at the time of storage so that the inspection coil can be protected and the service life can be extended.This protection cover can be loosened as much as possible when inserting the transducer during the inspection to greatly reduce friction. Can be. This cover is closed at the time of insertion, that is, before the inspection, and the inspection coil is unfolded with flexibility and adaptability to the wall of the heat transfer pipe as if the umbrella is opened at the time of withdrawal, which can dramatically improve the filling rate.

In addition, in order to improve friction, a flexible centering member with elasticity and resilience is additionally installed.

1 is an interpolation probe for eddy current inspection of a conventional straight tube tube

Figure 2 is a three-dimensional shape of the interpolated umbrella type eddy current inspection transducer for spiral heat pipe

3 is a perspective view and a cross-sectional view of the interpolated umbrella type eddy current inspection transducer for spiral heat pipes

Figure 4 is an assembled perspective view of the interpolated umbrella type eddy current inspection transducer for spiral heat pipe

* Explanation of symbols for the main parts of the drawings

(10): central axis holder (12): protective cover

(14): guide gutter (16): inspection coil support

(18): Oval inspection coil (20): Coil passage

(22): Press Bunch (24): Intermediate Guide

(26): spring 28: fastening pin

(30): leaf spring (32): inspection coil body

(34): fastening wire

A perspective view and a cross-sectional view of the steam generator spiral heating tube eddy current inspection interpolation type umbrella probe of the present invention are as shown in [FIG. 3], and an assembled perspective view is as shown in [FIG. 4]. The transducer can be divided into four parts.

The central shaft retainer [10] is equipped with a spring-type flexel tube body with a flexible and resilient force and a rotary roller in the front part in order to flexibly maintain the center of the transducer in the test tube and minimize the friction. It was.

The role of the cylindrical cover of the protective cover 12 serves to protect the inspection coil and to keep the diameter of the transducer as small as possible during insertion. The protective cover can be moved from side to side along the guide gutter [14], so that the inspection coil assembly is wrapped when the transducer is inserted into the heat pipe, and the upper protective cover is opened with a slight friction when inspecting the coil. 18] make it possible to contact the inner wall of the heat pipe.

The inspection coil assembly is composed of an inspection coil [18], an inspection coil support [16], a leaf spring [30], and an inspection coil body [32]. Inspection coils are oval-shaped and arranged at intervals of 90 degrees. This inspection coil is installed on the upper part of the inspection coil support [16] which is moved up and down by the leaf spring [30]. It is folded under the protection cover before the inspection. When the protection cover is opened by friction at the same time as the inspection, the restoring force of the leaf spring is As a result, the inspection coil support is extended as the umbrella is opened so that the inspection coil contacts the inner wall of the heat transfer tube, that is, the surface of the specimen. Inspection coil body [32] is a concentric cylinder form, the outer four-piece inspection coil support with a 90-degree interval is fastened with a fastening pin [28], and the spring is blocked [26] inside and maintains the force to restore to the form before the inspection. . Inside the body, fastening wires and wires connected to the test coils pass to prevent each assembly from being separated in the worst case.

The intermediate guide tube [24] is located just below the protective cover [12] and has a spring [26] on the central axis. During the inspection of the heat pipes, the protective cover [12] is opened by external friction and the spring on the central axis of the intermediate guide tube [24]. [26] is contracted. This contracted force acts as a restoring force in the absence of frictional force to close the protective cover 12. It also protects the inspection coil by preventing the inspection coil support [16] from being excessively extended beyond the allowable limit. By adjusting the nut [27] of the central axis, it is possible to inspect the heat pipes having different inner diameters with one transducer.

(Variation of invention, example of application)

At present, the heat pipes with heat number 1 to 3 in the steam generator tube of commercial nuclear power plants have the smallest radius of curvature and are difficult to inspect while maintaining the filling rate. Inspection is possible.

Invented steam generator spiral heating tube eddy current probe for the eddy current inspection is the integrity test of all spiral tube generator heat pipes or curved pipes with a small radius of curvature that are embedded in an integral reactor, which is impossible with the prior art. Could be found. It solves the inverse relationship between friction and filling rate, dramatically improving the noise ratio compared to the test signal, providing reliability and convenience of inspection, and protecting the inspection coil from scratches, dust, impact, etc. It is possible to extend the available time.

Claims (4)

It is an interpolation type eddy current probe for eddy current inspection of curved pipe part, which is folded into an umbrella type for insertion and improves insertability when it is inserted. The protective cover 12 is connected to the installed central shaft holder 10, and a plurality of guide gutters 14 are formed on the side of the protective cover 12, and the inspection coil assembly is inserted into the inspection coil assembly. The inspection coil 18, the inspection coil support 16 and the inspection coil support 16 and the inspection coil support 16, which is mounted on the guide gutter 14 is composed of a leaf spring 30 and the inspection coil body 32 and the inspection coil Body 32 is in the form of a concentric cylinder is installed so that the inspection coil support on the outside is fastened with a fastening pin 28 and to block the spring 26 inside and the spring (2) on the right and central axis of the protective cover 12 6) The intermittent umbrella type eddy current probe for the non-destructive inspection of the steam generator spiral heat transfer tube, characterized in that the elastic guide is installed as an intermediate guide tube (24) and the press bundle (22). The method of claim 1, Non-destructive umbrella type eddy current probe for non-destructive testing of the steam generator helical heat pipe, characterized in that it comprises a central axis holder (10) for maintaining the center of the heat transfer tube of the transducer while maintaining the minimum friction with maximum elasticity and flexibility. The method of claim 1, It is characterized in that it comprises a structure to protect the inspection coil assembly and the concentric cylindrical protective cover is opened by the micro frictional force when drawn out and the contracted inspection coil support is raised to the restoring force of the leaf spring by a predetermined distance to contact the specimen. Non-destructive type umbrella type eddy current probe for non-destructive testing of steam generator spiral tube. The method of claim 1, Non-destructive umbrella type for the non-destructive testing of the steam generator spiral heat transfer pipe, characterized in that it comprises a structure in which each part is connected to each other through the inside of the body with a fastening wire (34) in case of being separated by excessive friction of each part. Eddy current transducer.