JPH057527Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is an eddy current type inspection for inspecting the state of change or damage in the inner diameter of heat transfer tubes mainly used in steam generators of pressurized water nuclear reactors. Concerning improvements to probes.

(Prior Technology) As is well known in steam generators for pressurized water reactors, a large number of inverted U-shaped heat transfer tubes (outer diameter approximately 22 mm, wall pressure approximately 1.3 mm, height approximately 5 m) are installed inside a vertical cylindrical can. ) are placed upright on the bottom end plate, their upright parts and horizontal ceiling parts are supported by multiple support plates, and the bottom of the end plate is divided into two by a vertical partition, one of which is used as an entrance room. The cylindrical can is filled with secondary coolant, and the high-temperature, high-pressure primary coolant inside the reactor is taken in from the inlet chamber, passed through each heat transfer tube, and then returned to the reactor from the outlet chamber. The secondary coolant is evaporated in the process. However, when such a steam generator is used for a long period of time, foreign matter (dirt) from the coolant accumulates on the surface of the heat exchanger tubes, especially on the part held by the support plate, and this builds up in the gap between the support plate and the heat exchanger tubes. Because there is a risk that the heat exchanger tubes may be corroded or deformed by penetrating into the heat exchanger tubes and leak the primary cooling member, which has strong radioactivity, the applicant will examine the state of corrosion occurrence and changes on the inner surface of the heat exchanger tubes. We previously proposed a device (probe) for this purpose. (Unexamined Japanese Patent Publication No. 64-6703) The outline thereof is shown in Fig. 5 A, B, and C. The capsule-shaped probe body 1 is made of synthetic resin or light metal and constitutes the driving part, and the cylindrical probe body 1 constitutes the detection part. The probe body consists of a probe head 2 and a number of short cylindrical beads 6 that serve as transmission parts between the two, and is approximately 2m to 4m in length.The probe body has a built-in small motor and speed reduction mechanism, and multiple A centering spring 1a is provided, while the probe head 2
is provided with a deep recess 2a in the axial direction, and in the recess 2a, a detection element 3 consisting of a substrate 3a and a column having a contact 3b at the upper end is arranged so as to be movable up and down by a pair of springs. , a non-magnetic metal plate 3c is attached to the lower surface of the substrate 3a, and this metal plate 3c
A coil 4 is provided on the bottom wall facing the head 2, and nylon whisker-shaped supports 5 are attached to the front and rear circumferential surfaces of the head 2, and bead bodies connecting the body 1 and the head 2 are attached. 6 is bendably connected to a hook-shaped link 7 having a center hole by a pin.

When inspecting the furnace, the inside of the steam generator is emptied except for the coolant, and the contact 3a is inserted into the heat exchanger tube P to be inspected with the probe head 2 at the top while pressing against the inner surface of the tube. The motor in the probe body 1 and the coil 4 in the head 2 are energized, and the head 2 is slowly rotated via the bead body 6 and the link 7 and slowly fed by an operating device to move back and forth through the tube.

During this operation, the contact 3b moves back and forth while drawing a spiral, and when it hits a deformed part in the tube,
The detector 3 moves up and down depending on the degree of deformation, and the lower metal plate 3c moves closer and closer to the coil 4. Therefore, the impedance of the coil 4 changes, and this change can be detected externally. It is designed to inspect the condition of the inner surface of the tube.

(Problem to be solved by the invention) By the way, the above-mentioned rotary probe has the advantage of being able to continuously and accurately measure the condition of the inner surface of the thin tube all around the circumference with a single detection element. The transmission part that connects the body, which is the driving part, and the head, which is the detection part, is made up of many short cylindrical beads that are large enough to come into contact with the inner surface of the tube, and are connected by links, making assembly easy. Not, and
If the length is about 4m, it will be quite heavy, and the friction with the inner surface of the tube will increase, so there is a risk that the torque transmitted by the motor will not be sufficiently transmitted to the head side, and the bead body will get stuck to the inner surface of the tube at the bend part. There are problems such as.

Therefore, this idea makes it easy to assemble the transmission part, reduces weight, and does not cause binding.
This provides a probe with good torque transmission.

(Means for Solving the Problems of the Invention) Based on the above object, this invention consists of a probe body that is connected to an operating machine and has a built-in motor and a transmission mechanism, and a probe head that has a built-in detection element and a coil facing it. The probe consists of a transmission member that connects the two, and the probe head is rotated and simultaneously moved in the axial direction to measure the inner surface of the tube.The transmission member is a flexible shaft made of a coiled metal wire, and the For this, a large diameter spherical bead body approximately equal to the inner diameter of the tube and a smaller diameter spherical bead body are placed, one large diameter spherical bead body is placed for every several small diameter spherical beads, and they are loosely fitted. It is characterized by the combination of

(Function) When in use, if the probe head is inserted from the bottom of the tube to be inspected at the top and the motor inside the probe body is activated, its rotation is decelerated and transmitted to the probe head via the flexible shaft. The head rotates slowly and at the same time moves forward and backward by the feed operation of the operating device, the contact of the inspection element slides in a spiral on the inner surface of the tube, and when it reaches a deformed part of the tube, the inspection element detects the degree of deformation. Accordingly, the impedance of the coil changes by moving downward or upward, approaching or moving away from the coil, and this change is measured externally as a mechanical value. The flexible shaft is always held at the center of the tube by the large-diameter spherical bead body, and when it reaches the curved part of the tube, it can freely bend to follow the curved state.
The rotation of the motor is transmitted to the head without any hindrance.

(Embodiment) FIGS. 1 to 4 show an embodiment of this invention. In FIG. 1, a capsule-shaped probe body 11 forming a driving section and a cylindrical probe head 12 forming a detecting section at the tip are shown. The guides 16 and 16' adjacent to these are made of synthetic resin or light metal, and are formed to have a smaller diameter than the thin tubes such as the heat transfer tube of the steam generator. An encoder 11c for detecting the directional position is housed, and a plurality of leaf springs 11e for centering the body in the pipe are attached to both sides of the circumferential surface, respectively.
A cable 21 is connected to the end cap 11d,
This cable 21 connects the body 11 to a probe operating device (not shown), and also connects the motor 11a in the body and the coil in the head to a power source via a cord 21a.

A guide tube 16 is located next to the front of the probe body 11.
is disposed, the rear half of which is pin-coupled via its spherical part 17a to a short shaft 17 that is configured to interlock with the speed reduction mechanism 11b in the body 11 so that it can rotate integrally and be bent. A socket shaft 18 is pin-coupled via a spherical portion 18a so as to be rotatable and bendable. FIG. 4 shows the combined state. On the other hand, the probe head 12 has a deep recess 12a in the axial direction, and a contact 13b such as an ore or a metal ball is placed at the upper end of the recess 12a.
A detection element 13 consisting of a column and a substrate 13a having
The base plate 13a is biased upward and held by a pair of front and rear coil springs attached to the upper surface of the head body, and when the head 12 is inserted into the pipe, the contact 13b comes into contact with the inner surface of the pipe. A metal plate 13c made of non-magnetic material such as copper or aluminum is attached to the bottom surface of the substrate 13a.
A coil 14 is fixed on the bottom wall of the recess 12a facing the metal plate 13c and spaced apart from each other at a constant interval.
Nylon whisker-shaped supports 15 are attached to both side peripheral surfaces of the head 12.

Next to the rear of the probe head 12 is a guide tube 1.
6' is disposed, the front half of which is attached to the short shaft 17' attached to the rear wall of the head 12, and its spherical part 17
a', and the socket shaft 18' is connected to the spherical part 18 in the rear part by a pin so that the socket shaft 18' can be rotated and bent as one unit through a'.
They are also rotatably and refractably pin-coupled via a'.

Then, the socket portion 18b of the socket shaft 18 on the probe body side and the socket shaft 18' on the head side
As shown in FIG. 2, both ends of a flexible shaft 19 made of multiple layers (three layers in the figure) of coiled metal wire are connected to the socket portion 18b' by caulking. On the circumferential surface between both ends, there is a large diameter spherical bead made of the same material as the body and head, with an outer diameter approximately equal to the inner diameter of the tube to hold the flexible shaft 19 in the center of the tube and prevent it from hanging down. The body 20a and small-diameter spherical bead bodies 20b, which serve as spacers and have a diameter about half of the body 20a, are loosely fitted, with one large-diameter spherical bead body 20a positioned for every several small-diameter spherical bead bodies 20b. . The material of the beads is polyacetal resin (Delrin), which is relatively lightweight and has a small coefficient of friction, making it suitable for the bead body of the probe.

In addition, the cord 21a from the power supply is connected to the short shafts 17, 1
7', the socket shafts 18, 18', and the flexible shaft 19 are connected to the coil 14 in the head 12 through their central holes.

To use it, the entire probe is inserted into the heat exchanger tube P to be inspected from the inlet chamber on one side of the bottom of the empty steam generator as shown in Fig. 3 using the operating device, with the probe head 12 at the beginning. At that time, the head 12 and the body 11 are held at the center of the tube by the support member 15 or the leaf spring 11e, and the flexible shaft 19 is held at the center of the tube by the large diameter spherical bead body 20a, and the contact of the detection element 13 is held at the center of the tube. 1
3b contacts the inner surface of the tube.

When the motor 11a in the body 11 is energized and started, its rotation is decelerated and transmitted to the probe head via the first guide tube 16, flexible shaft 19 and second guide tube 16'. The probe head 12 rotates slowly (about 4 rotations/second) and slowly moves back and forth in the tube by the feed operation of the operating device (about 10 mm/second).
Therefore, the contact 13a of the detection element slides on the inner surface of the tube in a fine spiral. In the process of such an operation, if the tube P is not deformed, the detection element 13 will not move, and the metal plate 13c on the bottom surface of the substrate will not move.
The distance between the coil 14 and the coil 14 is kept constant. On the other hand, when the tube P is deformed and the contactor 13b comes into contact with it, the detection element 13 moves downward or upward depending on the degree of deformation, causing the metal plate 13c to approach the coil 14, or As the metal plate 13c moves away, the impedance of the coil 14 changes due to the eddy current generated in the metal plate 13c, and by detecting this externally,
The state of deformation of the tube is measured.

In this way, the upright part of the heat exchanger tube P is first inspected, then the curved part and the horizontal part. When the probe reaches the curved part and the horizontal part following it, the head 12 and the body 11 A flexible shaft 19 made of a coiled metal wire connecting the tubes bends freely to adapt to the curved state of the tube, and the flexible shaft 19 has large diameter beads arranged every several small diameter spherical beads 20b on its circumferential surface. It is held in the center of the tube without hanging down by the spherical beads 20a, and only the large diameter spherical beads 20a are in contact with the inner surface of the tube, and many small diameter spherical beads 20b are not in contact with each other, and the friction is small. In addition, since no jamming occurs on the inner surface of the tube, the driving force of the motor is efficiently transmitted and the probe can be inserted smoothly.

After the inspection of one half of the heat exchanger tube is completed, the probe is removed from the tube and the other half is inspected in the same manner, and the above operation is repeated to inspect all the heat exchanger tubes.

Although the above example describes the case of inspecting heat exchanger tubes in a steam generator of a nuclear reactor, the present invention is not limited to this and can also be applied to inspections of thin tubes such as condensers and water tubes in regular boilers. Further, in the above example, the guide tube 1 is placed adjacent to the body 11 and the head 12.
6 and 16' are shown, but this is for convenience in connecting the flexible shaft 19, and these may be omitted. Further, although the above example describes the case of measuring changes in the inner diameter of a heat transfer tube, the present invention can be similarly applied to a tube flaw detection test using the same eddy current type flaw detection probe head as the probe head.

(Effects of the invention) As described above, according to this invention, a probe body that has a built-in motor and a transmission mechanism and forms a driving part;
A transmission member that connects the body and head as a type of probe that continuously measures the inner surface of a thin tube all around the circumference by connecting one detection element and a probe head, which is equipped with a coil and forming a detection section, with a transmission member. Since it is made into a flexible shaft made of coiled metal wire, it is much easier to assemble compared to the previous method in which many short cylindrical beads are connected with links, and on the circumference of the flexible shaft, By fitting large diameter spherical beads and small diameter spherical beads approximately equal to the inner diameter of the tube into the lube, one large diameter spherical bead is positioned for every several small diameter spherical beads, and a flexible shaft is formed. The bead body can be held in the center of the tube without sagging, the weight of the entire bead body is reduced, the friction with the inner surface of the tube is small, and the transmission torque of the motor can be efficiently transmitted to the head. It has the advantage that there is no risk of it hitting the inner surface of the tube and will not damage it.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of one embodiment of this invention. FIG. 2 is a perspective view of a portion of the flexible shaft. FIG. 3 is a side view showing the state of use. FIG. 4 is a sectional view taken along line X-X in FIG. 1. FIG. 5A is a partially cutaway side view showing the state of use of the prior art. Figure B is a sectional view of the probe head. In the same figure, C is Y- in figure B.
A cross-sectional view along the Y line. In the figure, 11...probe body, 11a...motor, 11b...reduction mechanism,
12... Probe head, 12a... Recess groove, 1
3...Detection element, 13a...Substrate, 13b...Contactor, 14...Coil, 15...Support material, 16,
16'...Guide cylinder, 17,17'...Short shaft, 1
8, 18'...Socket shaft, 19...Flexible shaft, 20a...Large diameter spherical bead body, 20
b...Small diameter spherical beads.

Claims (1)

[Scope of utility model registration request] It consists of a probe body that is connected to an operating device and contains a motor and a transmission mechanism, a probe head that contains a detection element and a coil that opposes it, and a transmission member that connects the two. In a probe that measures the inner surface of a tube by moving it in a direction, the transmission member is a flexible shaft made of a coiled metal wire, and on its circumferential surface are spherical beads with a large diameter approximately equal to the inner diameter of the tube and a spherical bead with a smaller diameter than this. spherical bead body and one large-diameter spherical bead body for every several small-diameter spherical bead bodies, and these are loosely fitted together.