JP3079777B2 - Remote automatic film thickness measuring device in small diameter pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the thickness of a metal coating formed on the inner wall surface of a small-diameter pipe, and more particularly, to improving the accuracy of detecting the thickness of the metal coating. The present invention relates to a small-diameter in-pipe remote automatic film thickness measuring apparatus.

[0002]

2. Description of the Related Art An in-core housing is provided at the bottom of a reactor vessel for guiding instrumentation for detecting neutrons. As shown in FIG. 8, the in-core housing is composed of a stainless steel small-diameter tube 3 inserted and supported by a lower mirror 2 forming the bottom of the reactor vessel 1. It is inserted into the formed opening 4 and attached by welding. Since the small-diameter pipe 3 is welded from the outer peripheral portion and attached to the opening 4, the vicinity of the welded portion 5 is provided.
There is a case where the small diameter pipe 3 nearby becomes sensitized and deteriorates.
You. Therefore, the inner wall surface 6 of the small-diameter pipe 3 near the weld 5
In order to prevent the progress of deterioration or the like, a mixed powder of Cr, Ni or the like is applied in a paste form using a nozzle or the like, and the paste-like metal coating film 7 is irradiated with a laser to become a hard metal film.

[0003] As described above, since the paste of the mixed powder is applied to the inner wall surface 6 of the small-diameter pipe , the thickness of the coating film is not uniform.
And does not fall within a predetermined thickness range (0.3 to 0.8 mm).
Sometimes. Also, the part where the paste is not applied
If there is, the progress of deterioration cannot be prevented. Therefore,
Paste thickness control is required.

[0004]

Conventionally, a pasty metal coating 7 has been measured by an electromagnetic sensor. In this electromagnetic sensor, when an alternating current is applied to a probe in contact with the metal coating 7, a magnetic field is generated around the probe. Since the generated and proportional current flows through the secondary coil, the film thickness is measured from the change in the secondary current of the secondary coil according to the paste thickness. When measuring the film thickness with an electromagnetic sensor, the probe contact
Since it is provided at two places with a predetermined interval,
The measurement range is wide and the measured value is the average value
As a result, there is a large difference in film thickness within the measurement area.
If there is, the distribution of coating thickness at the peaks and valleys is detected
Can not. Also, the measured value of the secondary current varies.
There was a problem that was easy and lacked reliability.

The present invention has been made to effectively solve the above problems.

SUMMARY OF THE INVENTION The present invention relates to a metal coating formed within a small diameter tube.
And to provide a small diameter tube remote automatic film thickness measuring apparatus capable of <br/> detecting the thickness distribution of the coating film to improve the detection accuracy of the film thickness.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a reactor vessel.
Measure the thickness of the paste-like metal coating applied to the inner wall located at the weld of the small diameter pipe attached by welding
And also detects the circumferential and axial film thickness distribution of the coating.
An apparatus for that, the head and the tube axis and the tube circumferential direction of the head small diameter tube that is inserted into the small-diameter tube
A drive mechanism for moving the one in the circumferential direction in the head
It provided retractably move in the tube diameter direction while being arranged three on every 20 degrees, the upper and lower tip of the pasty metal coating
A head fixing pin for abutting against the inner wall surface to fix and hold the head in the tube, and the paste formed on the inner wall surface so as to be movable forward and backward in the tube radial direction.
An eddy current is generated in the metal coating to measure the film thickness in that area.
And an eddy current type film thickness detecting sensor for detecting the film thickness distribution in the circumferential direction and the axial direction of the coating film .

[0008]

[Function] The head fixed in the small-diameter pipe as described above,
The range of the measuring part of the film thickness of the paste metal coating of the sensor is
Because a small eddy current type film thickness detection sensor is attached,
The accuracy of film thickness detection is enhanced to improve the coating film's circumferential and axial directions.
The film thickness distribution can be detected .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, a stainless steel small-diameter tube 3 is vertically inserted as an in-core monitor housing into a lower mirror 2 forming the bottom of a reactor vessel 1, and the small-diameter tube 3 is welded downward. It is held in an opening 4 formed in the mirror 2. The inner wall surface 6 of the small-diameter pipe 3 near the welded portion 5 covers the inner wall surface 6 so as to prevent the progress of deterioration.
Metal coating with mixed powder of r, Ni etc. applied in paste form
A film 7 is formed, and this metal coating film 7 is cured by being irradiated with a laser. That is, a paste-like magnetic metal coating film is formed on the non-magnetic metal.

In particular, prior to laser irradiation, the inner wall surface 6
As a device for detecting the thickness of the paste-like metal coating film 7 formed on the small diameter pipe 3, a head 11 that can move at a predetermined pitch in the pipe axis direction and in the pipe inner circumferential direction is inserted into the small diameter pipe 3. The head 11 has a rod 12 extending downward. The rod 12 is provided with a motor (not shown) for moving the head 11 in the small-diameter pipe 3 in the pipe axis direction and the pipe inner circumferential direction at a predetermined pitch. Drive mechanism 13 is provided. A controller 14 for remotely controlling the movement of the head 11 is connected to the drive mechanism 13.

Specifically, as shown in FIG. 2, the head 11 inserted into the small-diameter tube 3 has
As shown in FIG.
Is held in the small-diameter tube 3 so that the head fixing pin 15 can be moved forward and backward. These head fixing pins 15
On the upper and lower inner wall surfaces 6 of the paste-like metal coating film 7 respectively.
The head 11 is fixedly held in contact therewith.
As a result, the head fixing pin is
15 can be fixedly held without contact. The head fixing pins 15 are provided at equal pitches in the circumferential direction of the head 11, and as shown in FIG. 4, three head fixing pins 15 are arranged at every 120 degrees in the circumferential direction of the head 11.
2 and 3, air cylinders 16 are housed in the upper and lower ends of the head 11 to move the head fixing pins 15 forward and backward, respectively. The air cylinders 16 are compressed by air supplied from an air supply pipe 16a. The head fixing pin 15 is simultaneously moved forward by an equal amount or simultaneously moved backward. Therefore, when the head fixing pin 15 is advanced, the tip of the head fixing pin 15 abuts on the inner wall surface 6 of the small diameter pipe 3, and the head 11 is fixed and held in the small diameter pipe 3, and the head fixing pin 15 is retracted. Then, the fixing of the head 11 is released. F
When the head 11 is fixedly supported, the head fixing pin 15 is
Are arranged in the circumferential direction of the pad 11 every 120 degrees.
Then, the head 11 is automatically fixed to the position of the axis of the small-diameter pipe 3.
Is determined.

The head 11 is provided with an eddy current type film thickness detecting sensor 17 for detecting the thickness of the metal coating film 7 formed on the inner wall surface 6 of the small diameter tube 3.
For example, if the detection unit is formed with a diameter of 10 mm
The head 11 is provided to be able to move forward and backward in the radial direction of the tube. That is, as shown in FIG. 2 and FIG.
1 has an opening 18 formed therein for allowing the sensor 17 to move forward and backward, and a guide 19 for guiding the movement of the sensor 17.
, And a moving mechanism for moving the sensor 17 forward and backward in the radial direction of the tube. The moving mechanism includes a lever member 22 supported in the head 11 so as to be swingable about a pin 21 and an air cylinder 23 connected to the lever member 22. The lever member 22 is connected to the rear end of the sensor 17 by engaging a pin 25 in an elongated hole 24 formed at one end, and the other end of the lever member 22 is folded back into an L shape. It is connected to the rod 26 of the air cylinder 23. Therefore, the air cylinder 2
When the rod 26 is retracted by the compressed air supplied from the air supply pipe 27 connected to the pin 3, the lever member 22 rotates counterclockwise around the pin 21 in the figure, and the sensor 17
Toward the paste metal coating film 7 at a predetermined interval.
Only in it will be facing, on the contrary, the rod 26
The forward movement causes the sensor 17 to retreat. FIG.
Is a spring, and this spring 28
Urges the sensor 17 in the backward direction.

As shown in FIG. 1, a personal computer 31 is connected to the drive mechanism 13 for controlling the head fixing pin 15 and the sensor 17 to move forward and backward. Metal film thickness is displayed recorded in real time on this computer 31,
Further, the record is displayed on the recording paper by the printer 32.

Next, the operation of the above embodiment will be described.

[0016] Prior calibration test is performed to measure the actual metal film thickness. First, to prepare paste-like metallic coating reference test pieces having different thicknesses, measuring the actual thickness dial gauge. Next, the voltage near the measurement point of the actual thickness is measured by the eddy current type film thickness detection sensor, and a correlation curve between the actual thickness by the dial gauge and the voltage value by the sensor is created. Curve.

Specifically, a reference test piece 41 as shown in FIG. 6 is manufactured. In this test piece 41, a ring groove 44 is formed in the inner wall surface 43 of a tubular base material 42 made of a non-magnetic material similar to a small-diameter pipe in the circumferential direction. A body metal paste 45 is applied. A measurement hole 46 for measurement by a dial gauge is formed in the paste 45. After setting the dial gauge at the measurement point A and measuring the paste thickness d in the test piece 41 thus configured, the eddy current sensor is applied to the measurement point B to measure the generated voltage. Can be converted to a voltage. When a voltage value is obtained from a large number of paste thickness measurement values by a dial gauge, a calibration curve as shown in FIG. 7 can be obtained.

FIG. 7 shows the correlation curve between the actual thickness of the dial gauge and the voltage value of the sensor, with the vertical axis representing the paste thickness obtained by the dial gauge and the horizontal axis representing the measurement value obtained by the eddy current sensor. In addition, a paste thickness determination curve obtained by correcting this by a predetermined value is shown. Paste thickness is within the specified range (0.3 ~
0.8 mm) is the acceptable paste thickness. Based on such a calibration test, the voltage value obtained by the eddy current type film thickness detecting sensor 17 which is actually set in the small diameter pipe 3 is converted into a value measured by a dial gauge obtained by the calibration test, and this is converted. a metal film thickness.

[0019] To actually measure the metal film thickness is the head 11 is fixed and held on the tube axis by advancing the head fixing pin 15 in the pipe diameter direction, as shown in FIG. With the head 11 fixed and held, the sensor 17 is advanced in the pipe diameter direction to obtain the metal coating thickness at the head fixed holding point. Next, after the sensor 17 and the head fixing pin 15 are retracted to release the fixation of the head 11, the measuring point is moved in the pipe inner circumferential direction and in the pipe axial direction to measure a number of points in the pipe inner circumferential direction and in the pipe axial direction. metal film thickness is measured. For example, it is measured at a pitch of 1 mm in the axial direction and at a pitch of 1 degree in the inner circumferential direction of the pipe. To change the strength of the eddy currents in response to changes in the metal film thickness, the larger the voltage value detected in accordance with the thickness increased. These sensor 17 and head fixing pin 1
The forward / backward movement of 5 is operated by the personal computer 31, and the detection result is displayed on the personal computer 31 and recorded on the recording paper 32 as needed.

If the actual paste-like metal coating thickness is detected to be out of the acceptable range, the metal coating 7 is removed, and the inner wall surface 6 of the small-diameter tube 3 is re-attached to the paste-like metal coating.
The coating film 7 will be applied.

As described above, according to the present invention, the small-diameter pipe 3 is moved in three directions from the head 11 movable in the pipe axis direction and the pipe inner circumferential direction.
To provide a head fixing pins 15 and an eddy current type film thickness detecting sensor 17 extends retractably move in the pipe diameter direction, the head
Stable fixing and holding of the small-diameter tube 3
The detection of the eddy current type film thickness detecting sensor 17 can be performed.
The position can be determined reliably. Therefore, it is possible to obtain a no variation measurement by the eddy current type film thickness detecting sensor 17, it is possible to improve the measurement accuracy of the metal film thickness. Ma
In addition, the detection unit of the eddy current type film thickness detection sensor 17 has a diameter of 10 m.
m, the film thickness distribution in the circumferential and axial directions of the coating film
It can be detected finely. In addition, paste-like metal
Since the thickness can be detected without contacting the coating film 7, the paste
The film thickness can be measured even when the metallic coating film 7 is relatively soft.
Wear.

[0022]

In summary, according to the present invention, according to the present invention, a small-diameter pipe can be moved from the head movable in the pipe axis direction and the pipe inner circumferential direction by three times.
The head fixing pin and eddy current type film thickness detection sensor extending in the
It is possible to stably hold the small-diameter pipe at the shaft center position.
The position of the eddy current type film thickness detection sensor can be
Can decide. Therefore, it is possible to obtain a no variation measurement by the eddy current type film thickness detecting sensor, it is possible to improve the measurement accuracy of the metal film thickness. Also, eddy current type film thickness detection
The sensor's detection area is small, so the coating film can be
Can be finely detected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a film thickness detecting device of the present invention.

FIG. 2 is a cross-sectional view showing a tip portion of a head.

FIG. 3 is a diagram showing a base end of a head.

FIG. 4 is a view taken along line XX of FIG. 2;

FIG. 5 is a view taken along line YY of FIG. 2;

FIG. 6 is a view showing a test piece.

FIG. 7 is a diagram showing a calibration curve.

FIG. 8 is a view showing a small-diameter tube.

[Explanation of symbols]

Reference Signs List 3 Small-diameter pipe 5 Welded part 6 Inner wall surface 7 Metal coating 11 Head 13 drive mechanism 15 Head fixing pin 17 Eddy current type film thickness detection sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-48-66864 (JP, A) JP-A-63-193357 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 7/00-7/34

Claims (1)

(57) [Claims] 1. A paste applied to an inner wall surface located at a welding portion of a small-diameter pipe attached to a reactor vessel by welding.
Measuring the thickness of the metallic coating and the circumferential direction of the coating
An apparatus for detecting a film thickness distribution in the axial direction, and the head to be inserted into the small diameter tube, the head small diameter
A drive mechanism for moving the pipe in the pipe axis direction and in the pipe inner circumferential direction;
It provided retractably move in the tube diameter direction while being arranged three on every 120 degrees in the circumferential direction in the head, tip the head to the tube in contact with the inner wall surface of the upper and lower of the pasty metal coating A head fixing pin for fixing and holding, and an eddy current is generated in the paste-like metal coating film formed on the inner wall surface and provided on the head so as to be movable forward and backward in the pipe diameter direction.
And measure the film thickness in that area to determine the circumferential and axial directions of the coating.
And an eddy current type film thickness detecting sensor for detecting a film thickness distribution of the thin film .