JP2507474Y2 - Probe for thin tube inspection - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an improvement in a probe for inspecting a metal thin tube such as a heat transfer tube of a steam generator for a pressurized water reactor.

[0002]

2. Description of the Related Art The outline of a steam generator used in a pressurized water nuclear reactor is as shown in FIG. 8, in which a horizontally thick tube plate b is provided under a vertically long cylindrical can a and the tube plate b is provided. A large number of inverted U-shaped heat transfer tubes p are provided on the upper side (in the figure, one is erected for convenience and is held by a plurality of support plates c in the middle thereof, and a secondary coolant w is provided above the tube plate b. ₂ is accommodated and the lower side of the tube sheet b is divided into two parts by the intermediate partition wall d. During the operation of the furnace, the high temperature and high pressure primary coolant w ₁ in the furnace is discharged from the inlet tube e into one bottom chamber. It is sent in, passes through each heat transfer tube p, exits to the other bottom chamber, and is returned to the reactor side again from the outlet tube e ′. In the process, the secondary coolant w ₂ is heated and taken out to the outside as steam. It

However, if it is used for a long period of time, the heat transfer tube P may be damaged by physical or chemical factors, and there is a risk that the radioactive primary coolant leaks out. The condition of is checked by a probe.

As the inspection probe, as shown in FIG. 9, a coil 2 connected to a power source is provided at the front end of a flexible shaft f, and on the peripheral surface of a central portion of a cylindrical body 1 made of synthetic resin (mainly ethylene tetrafluoride). And a bobbin type probe head h and a diamond-shaped capsule-shaped lead g, which are arranged so as to be held at the center of the tube by providing centering members 3 at both ends, and sequentially attach a high frequency current to the coil 2. 8, the probe head h is inserted into the heat transfer tube p from one bottom chamber as shown in FIG. 8, and the probe head h is moved back and forth through the flexible shaft f. At that time, the probe head h is moved along the coil 2 by the electromagnetic induction action. The eddy current induced in the heat transfer tube p is disturbed by the presence of scratches such as cracks, and the disturbance also disturbs the current flowing in the coil 2. You have to know the presence or absence of scratches.

[0005]

By the way, when the bobbin type probe is moved in the heat transfer tube p, that is, the metal thin tube to detect the state inside the tube, it is common to cause noise due to rattling or the like. In the above conventional probe, the coil 2
Is fitted in an annular groove formed on the circumferential surface of the cylindrical body 1 and is not expandable / contractible, and the fixing portion of the heat transfer tube p to the tube plate b is generally expanded. Therefore, in this expanded portion, the rattling of the probe is large, and the noise signal is also large accordingly, and the flaw may not be detected.

In addition, pinholes etc. were found in the previous inspection,
In the case of a pipe in which the sleeve s is internally repaired as shown in FIGS. 8 and 5, the probe can be inspected only with a probe different from the probe with the sleeve s and the probe without the probe. There is an inconvenience that the probe must be inserted from different directions in the upper and lower parts where the repair has been performed.

In view of this, even if there is a change in the inner diameter of the thin metal tube to be inspected, this invention does not require a change in the insertion direction of the probe and can detect the presence or absence of damage to the tube smoothly and reliably without causing a large amount of noise. The purpose is to do.

[0008]

Based on the above-mentioned object, the present invention, as a probe for inspecting a thin tube, firstly attaches a probe head made of a synthetic resin cylinder to the front end of a flexible shaft, and this probe head A plurality of expandable / reducible petal-shaped pieces with outer ends that are inclined rearward, spread outward, and are bent inward are provided at the center of the The piece is characterized in that a series of coils connected to a power source are attached so as to form an arcuate portion at the boundary with the outer end of each petal-like piece, and secondly, on the probe head. The feature is that a plurality of petal-shaped pieces are arranged in two rows in the front and rear, with the positions shifted in the circumferential direction. Thirdly, the coil is made into two and divided into two semi-circular parts with respect to the cross section of the probe head. It is characterized by being installed.

[0009]

EXAMPLES 1 to 3 show one embodiment of the invention, 10 there is strength as tetrafluoroboric Nichiren
In slidability good synthetic resin of the probe head is attached non-rotatably to the front end of the flexible shaft f is a cylindrical portion 11a and the conical leading portion 11b, the central portion of the cylindrical portion 11a is Te, The outer end portion 13 spreads outward while tilting rearward, that is, toward the flexible shaft f side.
On the contrary, a plurality of elastic petal-shaped pieces 13 (six in the drawing) in which a is bent obliquely inward are provided integrally at equal intervals in the circumferential direction.

From the outside to the base of the surface of each petal-shaped piece 13, a groove 14 as shown in FIG. 3 is similar to the petal-shaped piece, and has an arc at the boundary with the outer end 13a of the petal-shaped piece. A series of coils 12 connected to a power source through a lead wire 15 passing through the flexible shaft f is embedded in the groove 14 of the petaloid piece 13 in use. The arcuate portion 12a of the coil 12 arranged at the boundary of the end portion 13a is arranged to be close to the inner surface of the metal thin tube. It is preferable that the surfaces of the coil 12 and the groove 14 are thinly coated with a fluorine-based or epoxy-based resin to prevent the coil 12 from being scratched and removed.

When the probe head 10 is inserted into a metal thin tube such as a heat transfer tube while the probe head 10 is being supplied with a high-frequency current through the coil 12, the metal thin tube 20 as shown in the upper half of FIG. However, in the case of a predetermined thickness, each petal-shaped piece 13 on the cylindrical portion 11a is slightly bent inward, and the outer end boundary portion of each petal-shaped piece 13 in which the arc-shaped portion 12a of the coil 12 is embedded. Is pressed against the inner surface of the thin tube 20, and an eddy current is generated in the tube wall along the arc-shaped portion 12a of the coil due to the electromagnetic induction action based on the current flowing in the coil 12, and the eddy current when the probe head 10 is moved forward and backward. The presence or absence of a scratch on the tube is detected outside due to the disturbance of the tube.

When the probe head 10 retracts and reaches the expanded portion 20a of the metal thin tube 20, each petal-shaped piece 13 that has been deflated opens elastically and follows the change in the inner diameter of the tube well, and the outside of each The state that the end boundary is kept in pressure contact with the inner surface of the tube, the probe head 10 can be moved stably, rattling is prevented, and a large noise signal due to inner diameter change is emitted as before. Instead, the presence or absence of scratches in the expanded portion is detected. In the above description, the probe head 10 is retracted in order to make it easier to understand the operation of the petal-shaped piece 13, but the probe head 10 normally moves in the opposite direction.

On the other hand, as shown in FIG. 5, when the probe head 10 reaches the portion where the sleeve s is installed in the repair thin tube, each petal-shaped piece 13 on the cylindrical portion 1a is tapered and elastic. Therefore, it can be flexed further inward to smoothly enter the sleeve s, and the presence or absence of scratches on the repaired portion is detected as described above during the movement of the probe head 10. Further, when the probe head 10 retreats as shown by the dotted line arrow to reach the sleeve s, the outer end portions 13a of the petal-shaped pieces 13 are bent inwardly obliquely. Can enter the sleeve s without hindrance.

FIG. 6 shows a modified example in which a plurality of petal-shaped pieces 13 are circumferentially displaced on the peripheral surface of the cylindrical portion 11a so that the rear ones are located between the front ones and are arranged in two rows in front and rear. By doing so, since the dead parts between the petal-shaped pieces are covered, it is possible to prevent omission of flaws in the circumferential direction of the thin tube 20, and FIG. 7 shows each petal-shaped piece 13. Another example is shown in which the coil 12 to be attached to the probe head is divided into two semi-circular portions with respect to the cross section of the probe head, and in this case, as the probe head 10 moves, It is possible to eliminate by uniformly processing the noise signal that is evenly distributed through both coils due to the expansion and contraction of pipes evenly over the entire circumference, so that only scratch signals existing at certain points on the circumference can be deleted. It becomes easier to detect. The cylindrical portion 11a and the leading portion 11b of the probe head 10 may be separated as in the conventional case.

[0015]

As described above, according to the present invention, as a probe for inspecting a thin tube, a plurality of petal-like pieces that can be expanded / contracted and spread outward obliquely rearward are provided on the central portion of a probe head made of a synthetic resin cylindrical body. Since a series of coils connected to the power supply are attached to these, even if there is an expanded or contracted part in the metal thin tube to be inspected, it does not generate large noise and is easy and smooth in one-way operation. It is possible to detect the presence or absence of damage to the pipe, and if multiple petal-shaped pieces are arranged in two rows in the front and rear, the circumferential position of the petal-like pieces can be prevented, and the leak detection of the damage in the circumferential direction of the pipe can be prevented. Further, since the coil attached to each petal-shaped piece is a double coil and is provided separately in two semi-circular portions in the cross section of the probe head, noise is reduced and scratches can be easily detected.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention.

FIG. 2 is a front view seen from the right direction.

FIG. 3 is a sectional view taken along line XX of FIG.

FIG. 4 is a cross-sectional view of an example of a usage state.

FIG. 5 is a cross-sectional view showing another usage state.

FIG. 6 is a perspective view of a modified example.

FIG. 7 is a front view of an example in which a coil is divided into two.

FIG. 8 is a schematic cross-sectional view of a steam generator.

FIG. 9 is a perspective view of a conventional bobbin type probe.

[Explanation of symbols]

 10 probe head 11a cylindrical part 11b leading part 12 coil 12a arcuate part 13 petal-like piece 13a outer end part 14 crevice f flexible shaft

Claims (3)

(57) [Scope of utility model registration request] 1. A flexible shaft is provided with a probe head made of a synthetic resin cylindrical body at the front end thereof, and an outer end portion which tilts rearward, spreads outward, and obliquely bends inward is mounted on a central portion of the probe head. A plurality of expandable and retractable petal-shaped pieces are provided at intervals in the circumferential direction, and each petal-shaped piece has a series of coils connected to a power source at the boundary with the outer end of each petal-shaped piece. A probe for inspecting a thin tube, wherein each probe is attached so as to form a circular arc-shaped portion. 2. The probe for thin tube inspection according to claim 1, wherein a plurality of petal-shaped pieces provided on the probe head are provided in two rows in the front and rear direction so as to be displaced in the circumferential direction. 3. A probe for thin tube inspection according to claim 1, wherein the plurality of petal-shaped pieces are provided with two coils and are divided into two semi-circular portions with respect to a cross section of the probe head.