JP6153904B2 - Thermal spray film thickness measuring method and film thickness measuring apparatus - Google Patents

Description

  The present invention relates to a thermal spray film thickness measurement method and a film thickness measurement apparatus. More specifically, a method for measuring the thickness of a thermal sprayed film by measuring the thickness of the thermal sprayed film by an eddy current flaw detection method by contacting a sensor to an object to be inspected having an aluminum alloy thermal sprayed film formed on a tubular aluminum alloy material And a film thickness measuring apparatus.

  Conventionally, as a method for measuring the thickness of a sprayed film as described above, for example, the one shown in Patent Document 1 is known. In this method, a scale plate with a scale corresponding to a quadratic curve determined by the combination of the base alloy and the coating material alloy of the material to be measured is attached to an eddy current measurement meter, and the scale setting is made using a standard sample or the like. The thickness of the aluminum alloy is obtained from the scale of the measurement meter. Since the operator reads the scale, there are cases in which the operator varies and the accuracy decreases. Moreover, since the scale according to the quadratic curve is set, as clearly shown in this document, 300 μm is the upper limit of measurement, and further expansion of the measurement range has been desired.

Japanese Patent Publication No. 4-5324

  In view of such a conventional situation, an object of the present invention is to provide a thermal spray film thickness measuring method and a film thickness measuring apparatus capable of accurately measuring a wide range of film thickness.

  In order to achieve the above object, the thermal spray film thickness measuring method according to the present invention is characterized in that a sensor is brought into contact with a test object in which a thermal spray film of an aluminum alloy is formed on a tubular aluminum alloy material to detect eddy current flaws. In the method of measuring the film thickness of the sprayed film by the method, the sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected, and the thermal spraying is made of the same material and shape as the object to be inspected. A reference eddy current signal is measured by changing a lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having different film thicknesses, and a signal component when the lift-off distance of the reference eddy current signal is zero is measured. Based on this, a calibration curve based on a cubic polynomial is prepared in advance, the jig is brought into contact with the outer surface of the object to be inspected, and the eddy current signal is measured. When touching the outer surface It based the signal component to the calibration curve in measuring the thickness of the sprayed film.

  According to the above configuration, since the sensor is provided in the jig having a curved surface that matches the outer surface of the object to be inspected, the sensor can be stably brought into contact with the outer surface of the object to be inspected. The relative inclination of is reduced, and the measurement accuracy is improved. In addition, the curved surface can suppress variations due to the relative inclination between the sensor and the object to be inspected at the measurement location. In addition, since a calibration curve is created using a test piece having the same material and shape as the object to be inspected, the influence of the curvature shape and material of the object to be inspected can be eliminated, and the measurement accuracy is further improved. In addition, since the film thickness is obtained based on a calibration curve created by a cubic polynomial, even the film thickness of a relatively thick sprayed film can be measured with the same calibration curve with high accuracy. Furthermore, a calibration curve is created for each of a plurality of test pieces using a signal component in which the lift-off distance of the sensor with respect to the test piece is zero, and the signal of the eddy current signal when the jig is brought into contact with the outer surface of the inspection object during measurement Measure ingredients. Thus, since the output value of the eddy current signal when the lift-off distance is 0 is used, a stable eddy current signal can be obtained in combination with the above jig shape, and the film thickness of the sprayed film can be measured with high accuracy.

  The reference eddy current signal is measured and a reference signal locus of the signal is generated, a signal component when the lift-off distance is 0 is extracted from the reference signal locus, and the jig is moved from the air to the outer surface of the inspection object. Measure the eddy current signal until it comes close to contact with the outer surface, generate a signal trajectory of the signal, and extract the signal component when the jig in the signal trajectory contacts the outer surface of the object to be inspected You may do it. When extracting from the trajectory, the end of the trajectory is a signal component with a lift-off distance of zero. Also in this case, the film thickness of the sprayed film can be measured with high accuracy in the same manner as described above.

  The signal component may be a reactance component (Y component) in the impedance of the sensor. According to the inventors' experiment, as shown in FIG. 5, the Y component (reactance component) is more sensitive to film thickness variation than the X component (resistance component), and the correlation between the eddy current output and the film thickness is also high. It was found. Moreover, it has been found that the Y component can measure a thicker film thickness. That is, by using the reactance component in the impedance, it is possible to measure the film thickness over a wider range with higher accuracy.

  In order to achieve the above object, another feature of the sprayed film thickness measuring method according to the present invention is that a sensor is brought into contact with a test object in which an aluminum alloy sprayed film is formed on a tubular aluminum alloy material. In the method of measuring the film thickness of the sprayed film by the eddy current flaw detection method, the sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected, and has the same material and shape as the object to be inspected. The reference eddy current signal is generated by changing the lift-off distance of the sensor with respect to the test piece for each of the plurality of test pieces having different thicknesses of the sprayed film, and the reference signal locus of the signal is generated. A plurality of calibration curves are prepared in advance based on the second signal component extracted for each first signal component from the above, and the eddy current signal is measured by bringing the jig into contact with the outer surface of the object to be inspected. First signal of eddy current signal Select the calibration line corresponding the component, in measuring the thickness of the sprayed film on the basis of a calibration curve and the selected second signal component of the vortex signal the measurement.

  Here, the signal trajectory of the eddy current signal obtained by changing the lift-off distance is uniquely determined by the film thickness of the sprayed film, for example, as shown in FIG. It can be said that an arbitrary point on the impedance plane exists on a signal locus at a certain film thickness. Therefore, as described above, the sprayed film thickness can be measured by determining each signal component of the sensor impedance. Moreover, the lift-off distance may not be zero, and even if other deposits are formed on the sprayed film, the sprayed film thickness can be measured from there.

  Further, an eddy current signal from when the jig is brought close to the outer surface of the object to be inspected to contact with the outer surface is measured and a signal trajectory of the signal is generated. A corresponding calibration curve may be selected from the first signal component when it contacts the outer surface of the test object. Also in this case, the film thickness of the sprayed film can be measured with high accuracy in the same manner as described above.

  The first signal component may be a resistance component (X component) in the impedance of the sensor, and the second signal component may be a reactance component (Y component) in the impedance of the sensor. It was found that the Y component (reactance component) is more sensitive to film thickness fluctuations than the X component (resistance component), and the correlation between the eddy current output and the film thickness is high. Moreover, it has been found that the Y component can measure a thicker film thickness. That is, by using the reactance component in the impedance, it is possible to measure the film thickness over a wider range with higher accuracy.

  In order to achieve the above object, still another feature of the sprayed film thickness measuring method according to the present invention is that a sensor is brought into contact with a test object in which an aluminum alloy sprayed film is formed on a tubular aluminum alloy material. In the method of measuring the film thickness of the sprayed film by the eddy current flaw detection method, the sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected, and has the same material and shape as the object to be inspected. The reference eddy current signal is measured by changing the lift-off distance of the sensor with respect to the test piece for each of the plurality of test pieces having different thicknesses of the sprayed film, and a reference signal locus of the signal is generated. A calibration curve is prepared in advance based on the reference inclination of the trajectory obtained from the trajectory, and an eddy current signal from when the jig is brought close to the outer surface of the object to be inspected until it comes into contact with the outer surface is measured. It generates a signal trajectory of the signal, determine the slope of the trajectory from the signal path, in measuring the thickness of the sprayed film on the basis of the slope of the determined trajectory above calibration curve.

  Here, the signal trajectory of the eddy current signal obtained by changing the lift-off distance is uniquely determined by the film thickness of the sprayed film, for example, as shown in FIG. Therefore, the inclination of the signal locus is uniquely determined with respect to the film thickness. Therefore, as described above, the sprayed film thickness can be measured by using the slope of the signal locus. Moreover, the lift-off distance may not be zero, and even if other deposits are formed on the sprayed film, the sprayed film thickness can be measured from there.

  The inspected object may further have a non-conductive deposit on the sprayed film. In any one of the methods described above, the film thickness of the sprayed film can be measured even when another object is present on the sprayed film.

  The jig may include a pressing member that presses the sensor against an outer surface of the inspection object. Thereby, when making a sensor contact | abut to a to-be-inspected object, it can press uniformly, the relative inclination of a sensor and a to-be-inspected object can further be reduced, and a measurement precision is improved further. Moreover, the influence by the distance (lift-off) between a sensor and a to-be-inspected object can be suppressed, and the accuracy is further improved.

  Examples of the inspection object include a heat transfer tube and a lower header of an LNG vaporizer.

  In order to achieve the above object, the thermal spray film thickness measuring apparatus according to the present invention is characterized by an eddy current flaw detection by contacting a sensor to an object to be inspected having an aluminum alloy thermal spray film formed on a tubular aluminum alloy material. In the configuration in which the film thickness of the sprayed film is measured by the method, the sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected, and the thermal spraying is made of the same material and shape as the object to be inspected. A reference eddy current signal is measured by changing a lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having different film thicknesses, and a signal component when the lift-off distance of the reference eddy current signal is zero is measured. Based on this, a calibration curve based on a cubic polynomial is prepared in advance, the jig is brought into contact with the outer surface of the object to be inspected, and the eddy current signal is measured. When touching the outer surface It based the signal component to the calibration curve in measuring the thickness of the sprayed film.

  In order to achieve the above object, another feature of the apparatus for measuring a film thickness of a sprayed film according to the present invention is that a sensor is brought into contact with a test object in which an aluminum alloy sprayed film is formed on a tubular aluminum alloy material. In the configuration for measuring the film thickness of the sprayed film by the eddy current flaw detection method, the sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected, and has the same material and shape as the object to be inspected. The reference eddy current signal is generated by changing the lift-off distance of the sensor with respect to the test piece for each of the plurality of test pieces having different thicknesses of the sprayed film, and the reference signal locus of the signal is generated. A plurality of calibration curves are prepared in advance based on the second signal component extracted for each first signal component from the above, and the eddy current signal is measured by bringing the jig into contact with the outer surface of the object to be inspected. First signal of eddy current signal Select the calibration line corresponding the component, in measuring the thickness of the sprayed film on the basis of a calibration curve and the selected second signal component of the vortex signal the measurement.

  In order to achieve the above object, still another feature of the thermal spray film thickness measuring apparatus according to the present invention is that a sensor is brought into contact with a test object in which an aluminum alloy thermal spray film is formed on a tubular aluminum alloy material. In the configuration for measuring the film thickness of the sprayed film by the eddy current flaw detection method, the sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected, and has the same material and shape as the object to be inspected. The reference eddy current signal is measured by changing the lift-off distance of the sensor with respect to the test piece for each of the plurality of test pieces having different thicknesses of the sprayed film, and a reference signal locus of the signal is generated. A calibration curve is prepared in advance based on the reference inclination of the trajectory obtained from the trajectory, and an eddy current signal from when the jig is brought close to the outer surface of the object to be inspected until it comes into contact with the outer surface is measured. It generates a signal trajectory of the signal, determine the slope of the trajectory from the signal path, in measuring the thickness of the sprayed film on the basis of the slope of the determined trajectory above calibration curve.

  According to the characteristics of the thermal spray film thickness measuring method and the film thickness measuring apparatus according to the present invention, a wide range of film thicknesses can be accurately measured.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

It is the schematic of an LNG vaporizer, (a) is a front view, (b) is a side view. It is the schematic of the heat exchanger tube used as a test object, and a lower header. It is a schematic sectional drawing of the layer structure of a heat exchanger tube and a lower header. It is a block diagram of the film thickness measuring apparatus which concerns on this invention. It is a graph which shows the correlation with the film thickness value of X component and Y component, and an eddy current output. It is a figure explaining the relationship between a lift-off distance and a signal locus | trajectory. It is a figure explaining the relationship between a thermal spraying film thickness and a signal locus | trajectory. It is a figure explaining preparation of a calibration curve in a first embodiment of the present invention. It is a figure explaining calculation of the film thickness in 1st embodiment of this invention. It is the schematic of a jig | tool. It is a graph which shows the calibration curve by the test piece equivalent to a heat exchanger tube. It is a graph which shows the calibration curve by the test piece corresponding to a lower header. FIG. 9 is a view corresponding to FIG. 8 in the second embodiment of the present invention. FIG. 10 is a view corresponding to FIG. 9 in the second embodiment of the present invention. FIG. 9 is a view corresponding to FIG. 8 in the third embodiment of the present invention. FIG. 10 is a view corresponding to FIG. 9 in the third embodiment of the present invention.

Next, the first embodiment of the present invention will be described in detail with reference to FIGS.
[LNG vaporizer]
As shown in FIGS. 1 and 2, for example, the thermal spray film thickness measuring method according to the present invention includes a heat transfer tube 2 and a lower header 3 in an open rack type LNG vaporizer 1 that vaporizes LNG using seawater as a heat source. Inspected (inspected object). As shown in the figure, the LNG vaporizer 1 includes a lower header 3 to which LNG is supplied, and a plurality of heat transfer tubes 2 provided in a vertical direction from the lower header 3. A fin 2 a is provided on the upper outer peripheral surface of the heat transfer tube 2, and the upper end is connected to the upper header 4. Seawater W is supplied to the trough 5 via a pipe 6, and the seawater W overflowing from the trough 5 flows down to the lower header 3 along the outer surface of the heat transfer pipe 2. LNG is vaporized and converted into NG by heat exchange with the seawater W, and is recovered through the upper header 4.

[Heat transfer tube]
Here, in the heat transfer tube 2, as shown in FIG. 3, an aluminum alloy is used as the base material 21, and a sprayed film 22 is formed on the surface of the base material 21 by aluminum spraying. In the present embodiment, A6063 is used as the aluminum alloy material for the base material 21 and, for example, A7072 is used as the aluminum alloy used for aluminum spraying.

[Bottom header]
The lower header 3 also has a layer structure similar to that of the heat transfer tube 2, and a sprayed film 32 by aluminum spraying is formed on the surface of a base material 31 made of an aluminum alloy material. In this embodiment, A5083 is used as the aluminum alloy material for the base material 31, and A7072 is used as the aluminum alloy used for aluminum spraying, for example.

  By the way, the sprayed films 22 and 32 by the aluminum spraying function as a sacrificial anode of the aluminum alloy material of the base materials 21 and 31, and suppress corrosion and damage of the base materials 21 and 31 (sacrificial anticorrosive action). Further, the sprayed films 22 and 32 of the heat transfer tube 2 and the lower header 3 are worn (damaged) by a large amount of seawater W flowing down from the trough 5. On the other hand, thermal spraying is performed after the LNG vaporizer 1 is installed. The thickness of the film varies greatly depending on the operator, and it is difficult to identify the presence or absence of thermal spraying due to the blast treatment before thermal spraying, which may lead to construction leakage and the like. Moreover, when the film thickness is large, the adhesive strength of the sprayed films 22 and 32 may be reduced and may be peeled off. Therefore, it is important to control the film thickness of the sprayed films 22 and 32 over a wide range, and it is necessary to determine (measure) whether the film thickness is within a predetermined control value range.

[Thickness measuring device]
As shown in FIG. 2, the film thickness measuring apparatus 10 according to the present invention generally includes a jig 40 to which a sensor 11 is attached, an eddy current flaw detector 50 that processes and outputs a detected signal, and an output signal. A signal processing device 60 that performs analysis and the like and a display 70 that displays measurement results and the like are provided. The sensor 11 is brought close to the heat transfer tube 2 and the lower header 3 via the jig 40 to excite the heat transfer tube 2 and the lower header 3 to generate an eddy current. And the impedance change of the sensor 11 accompanying the change of the magnetic flux produced | generated by an eddy current is measured, and the film thickness of the sprayed films 22 and 32 is measured.

  As shown in FIG. 4, the eddy current flaw detector 50 generally includes an oscillator 51, a bridge 52, a phase shifter 53, an automatic balancer 54, an amplifier 55, and a synchronous detector 56. In the present embodiment, for example, as the sensor 11, a self-inductive self-comparison probe comprising a test coil 12 and a comparison coil 13 is used. The bridge 52 is a bridge circuit including these coils 12 and 13 and a variable resistor (not shown).

  The AC output from the oscillator 51 is applied to the test coil 12 to excite the heat transfer tube 2 and the lower header 3 and detect magnetic flux associated with the eddy current. The automatic balancer 54 makes the bridge 54 output zero. The unbalanced output between the test coil 12 and the comparison coil 13 is amplified by the amplifier 55, sent to the synchronous detector 56, and detected together with the output of the phase shifter 53. Then, the eddy current signal is taken into the signal processing device 60 via the filter 57 and the A / D converter 58 and the measurement result and the like are displayed on the display unit 70. The signal processing device 60 is composed of, for example, a personal computer (PC) connected to the eddy current flaw detection device 50.

[Signal component]
Here, as an eddy current signal in the sensor 11, an X component (resistance component) caused by lift-off (relative distance between the coil and the object to be inspected) and a Y component caused by electrical properties (electrical conductivity). (Reactance component) is obtained. An example of the result of evaluating the correlation coefficient of each component for these X component and Y component is shown in FIG. As shown in the figure, the value of the X component is saturated at about 600 μm, and it is difficult to evaluate the thickness beyond that. On the other hand, the Y component changes linearly even at about 800 μm. As for the correlation coefficient R ² , the X component is 0.8166, the Y component is 0.9908, and it was found that the Y component shows a better correlation. Therefore, it can be seen that, in the measurement of the film thickness of the aluminum sprayed film, the film thickness can be measured more accurately by using the eddy current output value of the Y component than the X component. In this embodiment, the Y component eddy current output value is used as the signal component. According to the experiments by the inventors, results similar to the above were obtained at a test frequency of 10 kHz to 400 kHz.

[Signal processing equipment]
As shown in FIG. 4, the signal processing device 60 is roughly extracted with a trajectory generator 61 that generates a signal trajectory T of the eddy current signal, and a signal component extractor 62 that extracts a signal component S from the signal trajectory T. A calibration curve creation unit 63 that creates a calibration curve C based on the signal component S and a film thickness calculation unit 64 that calculates a film thickness t from the created calibration curve C are provided. Various data such as information (base material, film thickness, material, etc.), generated signal trajectory T, created calibration curve C, measurement data, analysis result, etc. are stored in the storage unit 65. The

  The trajectory generation unit 61 generates and records a reference signal trajectory T of the reference eddy current signal in the test piece and a signal trajectory T ′ of the eddy current signal in the test objects 2 and 3. These signal trajectories T and T ′ change in accordance with the lift-off distance D of the sensor 11 on the XY plane (impedance plane). As shown in FIG. 6, the lift-off distance D decreases and the Y component of the eddy current signal decreases as the sensor 11 is brought closer to the test piece or the object 100 of the inspected objects 2 and 3 from the air (large lift-off distance). . When the sensor 11 comes into contact with the object 100 (lift-off distance D = 0), the Y component is minimized and becomes the end (right end) of the signal trajectory T. Further, in the signal trajectories T and T ′, the Y component decreases as the film thickness t of the sprayed film 102 decreases. As shown in FIG. 7, as the film thicknesses ta to c of the thermal sprayed films 102a to 102c decrease (ta> tb> tc), the Y component of the trajectory also decreases correspondingly (Ta> Tb> Tc). Thus, the signal trajectories T and T ′ are uniquely determined according to the film thickness t, and the film thickness can be measured using the signal component of the lift-off distance D = 0. Therefore, by preparing a calibration curve for the Y component of the known film thickness t in advance, the film thickness can be measured with high accuracy simply by measuring the Y component of the test objects 2 and 3.

  The signal component extraction unit 62 extracts the signal component S from the signal trajectories T and T ′ generated by the trajectory generation unit 61. In the present embodiment, as shown in FIG. 8, the Y component (Sa, Sb, Sc) when the lift-off distance D located at the end (right end) of the trajectory T is 0 is extracted from the signal trajectory T. Then, the calibration curve creation unit 63 creates a calibration curve C from the signal component S extracted by the signal component extraction unit 62. In this embodiment, as shown in FIGS. 7 and 8, a calibration curve C using a cubic polynomial based on the known film thickness (ta, tb, tc, FIG. 7) and the extracted Y components (Sa, Sb, Sc). Create

  The film thickness calculation unit 64 calculates the film thickness t by substituting the output value of the signal component of the eddy current signal in the test objects 2 and 3 into the calibration curve C. In the present embodiment, as shown in FIG. 9, when the signal component extraction unit 62 is in contact (contact) with the object to be inspected (the lift-off distance D is 0) when the sensor 11 positioned at the end (right end) of the signal trajectory T ′. ) Is substituted into the calibration curve C, and the film thickness t is calculated.

[jig]
As shown in FIG. 10, the jig 40 has a contact portion 42 having a curved surface 41 that follows the curvature of the outer surface of the heat transfer tube 2, and a through-hole 43 that penetrates the end portion of the sensor 11 is provided. . The contact portion 42 is screwed with the grip portion 45, and a cylindrical body 44 that houses the sensor 11 is housed inside the grip portion 45. The outer surface of the grip portion 45 is covered with a rubber cover 45a, for example, to suppress a change in impedance due to the outside air temperature or the like. A spring 46 is attached to one end of the cylindrical body 44 as a pressing member, and one end of the spring 46 is hooked inside an end portion 47 that is screwed with the grip portion 45. Thus, when the operator grips the grip portion 45 and presses the abutting portion 42 against the object to be inspected, the sensor 11 is arranged substantially perpendicular to the surface of the object to be inspected by the curved surface 41, and the spring 46 Pressed. Therefore, the inclination of the sensor 11 with respect to the object to be inspected can be suppressed, and the film thickness can be measured with higher accuracy. In addition, a jig 40 ′ having a contact portion 42 ′ having a curved surface 41 ′ along the curvature of the outer surface of the lower header 3 is used for the lower header 3. The sensor 11 is connected to the eddy current flaw detector 50 via a cable 49 penetrating the inside of the jig 40.

[Calibration curve]
A calibration curve is created in advance before the measurement using a plurality of test pieces (cut models) having the same material and shape as the heat transfer tube 2 and the lower header 3 and different film thicknesses of the sprayed films 22 and 32. The jigs 40 and 40 'are also used when creating a calibration curve.

  Here, the inventors conducted eddy current flaw detection using a plurality of test pieces having different film thicknesses of the sprayed film, and extracted the Y component value as the eddy current output value, and the sprayed film thickness was measured with a micrometer or the like. Measured. Comparisons of calibration curves based on the results are shown in FIGS. 11 and 12, and measured values are shown in Tables 1 and 2, respectively. 11 and Table 1 are based on a test piece equivalent to the heat transfer tube 2, and FIG. 12 and Table 2 are based on a test piece equivalent to the lower header 3.

  As shown in FIGS. 11 and 12 and Tables 1 and 2, the linear (linear approximation) calibration curve as Comparative Example 1 can partially obtain a value that approximates the film thickness measurement value, but in many film thickness ranges. It can be seen that the error greatly deviates from the actually measured value. Further, although the accuracy of the calibration curve of the quadratic polynomial (quadratic curve approximation) as the comparative example 2 is improved as compared with the linear (linear approximation) calibration curve, the film thickness range is compared with the cubic polynomial of the example. The error in the middle part of becomes larger. The correlation coefficient of the comparative example is 0.934 for Comparative Example 1 and 0.9845 for Comparative Example 2 in the case of the heat transfer tube 2, and 0.97 for Comparative Example 1 in the case of the lower header 3 and the Comparative Example. 2 was 0.9783. Further, the error (standard deviation) of the comparative example is 118 for the heat transfer tube 2 and 57 for the comparative example 2, 57 for the lower header 3 and 40 for the comparative example 2 and 40 for the comparative example 2. there were.

  On the other hand, in the calibration curve of the cubic polynomial (cubic curve approximation) of the example, the correlation coefficient is 0.9881 in the case of the heat transfer tube 2 and 0.9915 in the case of the lower header 3, Higher than 2. Further, the error (standard deviation) is 50 in the case of the heat transfer tube 2 and 25 in the case of the lower header 3, which is lower than those of the first and second comparative examples. Thus, by using a cubic polynomial calibration curve, errors can be further reduced and a wide range of film thicknesses can be accurately measured.

[Measurement procedure]
First, a plurality of test pieces having the same shape and the same material as the heat transfer tube 2 to be inspected and different from the sprayed film are prepared in advance, and a calibration curve using a cubic polynomial as shown in FIG. 11 is created. In the present embodiment, the reference eddy current signal is measured by pressing the sensor 11 against each test piece while changing the lift-off distance D of the sensor 11 with respect to the test piece using the jig 40 described above, and generating a locus. The unit 61 generates and records a reference signal trajectory for the signal. Next, the signal component extraction unit 62 extracts the value of the Y component of the lift-off distance D = 0 from each generated reference signal locus. Then, as shown in FIGS. 11 and 12, the calibration curve creation unit 63 plots the Y component value extracted as the eddy current output value on the horizontal axis, and the known film thickness value obtained by actual measurement on the vertical axis. To create a calibration curve. Since the heat transfer tube 2 and the lower header 3 are tubular bodies, their output values are affected by the curved shape. Therefore, these error factors can be eliminated by using a test piece of the same shape and the same material as that of the object to be inspected in advance when preparing the calibration curve, and the accuracy is improved.

  Next, the sensor 11 is brought close to the test piece for balance adjustment, and the phase adjustment is performed so that the lift-off noise is only the X component. Then, the sensor 11 is pressed against the heat transfer tube 2 along the curved surface 41 of the jig 40 along the outer surface of the heat transfer tube 2, and eddy current testing is performed. Similarly to the above, when the trajectory generator 61 generates and records a signal trajectory of the eddy current signal, the jig 40 (sensor 11) comes into contact with the outer surface of the heat transfer tube 2 from the signal trajectory generated by the signal component extractor 62. The Y component eddy current output value is measured. And the film thickness calculation part 64 calculates | requires a film thickness from a calibration curve based on the output value. The lower header 3 is measured in the same manner with the jig replaced.

Next, a second embodiment of the present invention will be described. In the following embodiments, members similar to those in the above embodiment are denoted by the same reference numerals.
In the first embodiment, the calibration curve C is created by extracting the Y component when the lift-off distance is 0 from the reference signal trajectory T as the signal component. However, as shown by the one-dot chain line in FIG. 3, the deposits 23, 33 (such as non-conductive coating film such as FRP coating of glass fiber reinforced plastic) are formed on the sprayed films 22, 23 of the heat transfer tube 2 and the lower header 3. If there is a foreign object), the lift-off distance does not become zero, and the lift-off distance affects the X component. Therefore, if the signal component with the lift-off distance D = 0 is used as in the first embodiment, the measurement accuracy may be reduced.

  Therefore, in the second embodiment, a plurality of calibration curves C are created for each predetermined resistance component (X component) in the impedance of the sensor 11. In the present embodiment, as shown in FIG. 13, for example, the signal component extraction unit 62 extracts Y components (Sk1 to Sk3) in the X component xk from the reference signal trajectories (T1 to T3), and the calibration curve creation unit 63 A calibration curve Ck is created from the extracted Y component. This is repeated for each predetermined X component (x1 to xn) within an arbitrary resistance component range R. In this way, a plurality of calibration curves are created in advance in consideration of the influence of the lift-off distance on the X component. In this example, the first signal component is a predetermined resistance component (X component) in the impedance of the sensor 11, and the second signal component is a predetermined reactance component (Y component) in the impedance of the sensor 11. Note that the calibration curve in this embodiment may be created by a cubic polynomial, or may be another method such as a quadratic or fourth-order polynomial, and the method is not particularly limited.

  In the measurement, a plurality of calibrations created based on the extracted X component extracted from the signal trajectory T ′ generated from the X component when the jig 40 contacts the outer surfaces of the test objects 2 and 3. Select the corresponding calibration curve from the lines. Then, the film thickness is measured by the value of the Y component when the jig 40 is in contact with the outer surfaces of the test objects 2 and 3 and the determined calibration curve. In the present embodiment, as shown in FIG. 14, the signal component extraction unit 62 extracts the X component (S′x) and the Y component (S′y) from the end (right end) of the signal trajectory T ′. Further, the film thickness calculation unit 64 determines a calibration curve to which the extracted X component S′x corresponds. For example, if the extracted X component S′x corresponds to the previous X component xk, the calibration curve Ck in FIG. 13 is selected from the plurality of calibration curves. Then, the film thickness calculator 64 calculates the film thickness t by substituting the Y component S′y extracted from the signal locus T ′ into the selected calibration curve Ck. Thereby, even if the FRP coatings 23 and 33 are formed on the sprayed films 22 and 32, for example, the sprayed film thickness can be accurately measured from above. Further, even if it is difficult to ensure a lift-off distance D = 0 between the sensor 11 and the test objects 2 and 3 during inspection for other reasons, it is possible to prevent a decrease in measurement accuracy. In addition, since a plurality of calibration curves are created in advance, the measurement accuracy is also improved. And since it is sufficient to determine the calibration curve with reference to the storage unit 65 at the time of measurement, the film thickness can be measured in real time.

Next, a third embodiment of the present invention will be described. This embodiment is also a technique for measuring the sprayed film thickness from above the deposits 23 and 33 as in the second embodiment.
In the first and second embodiments, the signal component (Y component) of the eddy current signal is used in creating the calibration curve C. In this embodiment, the gradients G and G ′ of the trajectories of the signal trajectories T and T ′ are used. . In the present embodiment, as shown in FIG. 15, for example, the reference eddy current signal is measured for each of the plurality of test pieces, and the trajectory generator 61 generates the reference signal trajectory (T4 to T6) of the signal. Then, the signal component extraction unit 62 extracts each Y component (ya4 to 6, yb4 to 6) in an arbitrary X component (xa, xb) in each reference signal trajectory (T4 to 6), and (yb−ya) / The reference inclinations G1 to G3 of the trajectory are respectively obtained from (xb−xa). Then, the calibration curve creation unit 63 creates a calibration curve Cg in advance based on the obtained reference inclinations G1 to G3 of the trajectory. Note that the calibration curve in this embodiment may also be created by a cubic polynomial, or may be another method such as a quadratic or fourth-order polynomial, and the method is not particularly limited.

  In the measurement, the trajectory gradient G ′ is obtained from the signal trajectory T ′. In the present embodiment, as shown in FIG. 16, the eddy current signal of the test objects 2 and 3 is measured, and the trajectory generator 61 generates a signal trajectory T ′ of the signal. Then, the signal component extraction unit 62 extracts each Y component (y′a, y′b) in the previous X component (xa, xb) in the signal trajectory T ′, and (y′b−y′a) / ( The inclination G ′ of the locus is obtained by xb−xa). Then, the film thickness calculation unit 64 calculates the film thickness t by substituting the obtained gradient G ′ of the locus into the calibration curve Cg. As a result, as in the second embodiment, even when it is difficult to ensure the lift-off distance D = 0 between the sensor 11 and the objects 2 and 3 during inspection, the measurement accuracy is reduced. Can be prevented.

Finally, reference is made to the possibilities of other embodiments of the invention.
In the above embodiment, A6063 was used as the aluminum alloy material for the base material 21 of the heat transfer tube 2, A5058 was used for the base material 31 of the lower header 3, and A7072 was used as the aluminum alloy used for aluminum spraying. However, these aluminum alloy materials are only examples, and the film thickness can be measured in the same manner even with other alloy materials.

  In the above embodiment, the coils 11 and 13 of the self-induction self-comparison system are used as the sensor 11, but the coil mode is not limited to the self-induction self-comparison system, and various types of coils may be applied.

  In the first embodiment, the Y component is used as the signal component. However, an X component may be used instead of the Y component. However, as described above, the embodiment is superior in terms of measurement accuracy. In the first embodiment, the reference signal trajectory T of the reference eddy current signal of the test piece measured by the trajectory generating unit 61 and the signal trajectory T ′ of the eddy current signal of the test objects 2 and 3 are generated and recorded. However, in this embodiment, the value of the signal component (that is, the lift-off distance D = 0) in a state where the sensor 11 is in contact with the test piece or the test objects 2 and 3 may be used, and the signal trajectories T and T ′ are not necessarily used. Need not be generated, and the locus generating unit 61 can be omitted. Further, for example, a reference signal trajectory T is generated, a calibration curve is created from the signal component at the end (right end) of the trajectory T, and an output value (the signal component at that time without generating a signal trajectory T ′ at the time of measurement ( (Measured value) may be substituted into the calibration curve. Further, a calibration curve is created based on the output value (measured value) when the lift-off distance D = 0 of the test piece without generating the reference signal trajectory T, and a signal trajectory T ′ is generated at the time of measurement. The value of the signal component at the end (right end) of T ′ may be extracted and substituted in the calibration curve.

  Also in the second embodiment, the X component is used as the first signal component and the Y component is used as the second signal component, but the reverse is also possible. However, as described above, the embodiment is superior in terms of measurement accuracy. In the second embodiment, the signal trajectory T ′ of the eddy current signal of the test objects 2 and 3 measured by the trajectory generating unit 61 is generated and recorded. However, in this embodiment, the value of the signal component (that is, the lift-off distance D = 0) when the sensor 11 is in contact with the test objects 2 and 3 may be used, and it is not always necessary to generate the signal locus T ′. Absent. For example, the output value (measured value) of the signal component at that time may be substituted into the calibration curve without generating the signal locus T ′ at the time of measurement.

  In the second and third embodiments, as shown in FIG. 3, the FRP film has been described as an example of the nonconductive deposit formed on the sprayed films 22 and 32, but the present invention is not limited to this. For example, it may be a non-conductive coating made of other various synthetic resins.

1: LNG vaporizer, 2: heat transfer tube (inspected object), 2a: fin, 3: lower header (inspected object), 4: upper header, 5: trough, 6: piping, 10: film thickness measuring device, 11: sensor, 12: test coil, 13: comparison coil, 21: base material, 22: sprayed film, 23: non-conductive coating (adhered matter), 31: base material, 32: sprayed film, 33: non-conductive Coating (attachment), 40, 40 ′: jig, 41, 41 ′: curved surface, 42, 42 ′: contact part, 43: through hole, 44: cylindrical body, 45: gripping part, 45a: cover , 46: spring (pressing member), 47: end, 49: cable, 50: eddy current flaw detector, 51: oscillator, 52: bridge, 53: phase shifter, 54: automatic balancer, 55: amplifier, 56: Synchronous detector, 57: filter, 58: A / D converter, 60: signal processing device (personal computer) 61: locus generation unit, 62: signal component extraction unit, 63: calibration curve creation unit, 64: film thickness calculation unit, 65: storage unit, 70: display, 100: object, 101: base material, 102 : Sprayed film, C, Cg, Ck: calibration curve, D: lift-off distance, G1 to G3: reference inclination of locus, G ′: inclination of locus, S: signal component, T, T1 to T6, Ta to Tc: reference Signal locus, T ′: Signal locus, t, ta to tc: Film thickness, W: Seawater

Claims (14)

A method for measuring a film thickness of a sprayed film by measuring a film thickness of the sprayed film by an eddy current flaw detection method by contacting a sensor to a test object in which a sprayed film of an aluminum alloy is formed on a tubular aluminum alloy material,
The sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected,
The reference eddy current signal is measured by changing the lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having the same material and the same shape as the object to be inspected and the film thickness of the sprayed film being different. A calibration curve by a cubic polynomial is prepared in advance based on the signal component when the lift-off distance of the signal is 0,
Measuring the eddy current signal by bringing the jig into contact with the outer surface of the object to be inspected,
A method for measuring a film thickness of a sprayed film, wherein the film thickness of the sprayed film is measured based on a signal component when the jig of the measured eddy current signal comes into contact with an outer surface of the inspection object and the calibration curve. The reference eddy current signal is measured and a reference signal locus of the signal is generated, a signal component when the lift-off distance is 0 is extracted from the reference signal locus, and the jig is moved from the air to the outer surface of the inspection object. Measure the eddy current signal until it comes close to contact with the outer surface, generate a signal trajectory of the signal, and extract the signal component when the jig in the signal trajectory contacts the outer surface of the object to be inspected The method for measuring a film thickness of a sprayed film according to claim 1. The thermal spray film thickness measurement method according to claim 1, wherein the signal component is a reactance component (Y component) in the impedance of the sensor. A method for measuring a film thickness of a sprayed film by measuring a film thickness of the sprayed film by an eddy current flaw detection method by contacting a sensor to a test object in which a sprayed film of an aluminum alloy is formed on a tubular aluminum alloy material,
The sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected,
The reference eddy current signal is measured while changing the lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having the same material and the same shape as the object to be inspected, and the thickness of the sprayed film is different. A plurality of calibration curves are created in advance based on second signal components extracted for each first signal component from these reference signal trajectories by generating reference signal trajectories,
Measuring the eddy current signal by bringing the jig into contact with the outer surface of the object to be inspected,
Select the corresponding calibration curve from the first signal component of the measured eddy current signal,
A method for measuring a film thickness of a sprayed film, wherein the film thickness of the sprayed film is measured based on a second signal component of the measured eddy current signal and a selected calibration curve. An eddy current signal is measured from when the jig is brought close to the outer surface of the object to be inspected and contacted with the outer surface, and a signal trajectory of the signal is generated, and the jig in the signal trajectory is the object to be inspected. 5. The method for measuring a film thickness of a sprayed film according to claim 4, wherein a corresponding calibration curve is selected from the first signal component when contacting the outer surface of the film. The thermal spray film according to claim 4 or 5, wherein the first signal component is a resistance component (X component) in the impedance of the sensor, and the second signal component is a reactance component (Y component) in the impedance of the sensor. Film thickness measurement method. A method for measuring a film thickness of a sprayed film by measuring a film thickness of the sprayed film by an eddy current flaw detection method by contacting a sensor to a test object in which a sprayed film of an aluminum alloy is formed on a tubular aluminum alloy material,
The sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected,
The reference eddy current signal is measured while changing the lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having the same material and the same shape as the object to be inspected, and the thickness of the sprayed film is different. Generate a reference signal trajectory, create a calibration curve in advance based on the reference slope of the trajectory obtained from these reference signal trajectories,
Measure the eddy current signal from the air to the outer surface of the object to be in contact with the outer surface and generate a signal locus of the signal,
Find the slope of the generated signal trajectory,
A method for measuring a film thickness of a sprayed film, wherein the film thickness of the sprayed film is measured based on the obtained inclination of the locus and the calibration curve. The method for measuring a film thickness of a sprayed film according to any one of claims 4 to 7, wherein a non-conductive deposit is further formed on the sprayed film. The method for measuring a film thickness of a sprayed film according to claim 1, wherein the jig includes a pressing member that presses the sensor against an outer surface of the inspection object. The thermal spray film thickness measuring method according to claim 1, wherein the object to be inspected is a heat transfer tube of an LNG vaporizer. The thermal spray film thickness measuring method according to claim 1, wherein the object to be inspected is a lower header of an LNG vaporizer. A thermal spray film thickness measuring apparatus for measuring the thickness of the thermal spray film by an eddy current flaw detection method by contacting a sensor to an inspection object in which an aluminum alloy thermal spray film is formed on a tubular aluminum alloy material,
The sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected,
The reference eddy current signal is measured by changing the lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having the same material and the same shape as the object to be inspected and the film thickness of the sprayed film being different. A calibration curve by a cubic polynomial is prepared in advance based on the signal component when the lift-off distance of the signal is 0,
Measuring the eddy current signal by bringing the jig into contact with the outer surface of the object to be inspected,
An apparatus for measuring a film thickness of a sprayed film, which measures the film thickness of the sprayed film based on a signal component when the jig of the measured eddy current signal comes into contact with the outer surface of the inspection object and the calibration curve. A thermal spray film thickness measuring apparatus for measuring the thickness of the thermal spray film by an eddy current flaw detection method by contacting a sensor to an inspection object in which an aluminum alloy thermal spray film is formed on a tubular aluminum alloy material,
The sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected,
The reference eddy current signal is measured while changing the lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having the same material and the same shape as the object to be inspected, and the thickness of the sprayed film is different. A plurality of calibration curves are created in advance based on second signal components extracted for each first signal component from these reference signal trajectories by generating reference signal trajectories,
Measuring the eddy current signal by bringing the jig into contact with the outer surface of the object to be inspected,
Select the corresponding calibration curve from the first signal component of the measured eddy current signal,
An apparatus for measuring a film thickness of a sprayed film that measures the film thickness of the sprayed film based on a second signal component of the measured eddy current signal and a selected calibration curve. A thermal spray film thickness measuring apparatus for measuring the thickness of the thermal spray film by an eddy current flaw detection method by contacting a sensor to an inspection object in which an aluminum alloy thermal spray film is formed on a tubular aluminum alloy material,
The sensor is provided in a jig having a curved surface that matches the outer surface of the object to be inspected,
The reference eddy current signal is measured while changing the lift-off distance of the sensor with respect to the test piece for each of a plurality of test pieces having the same material and the same shape as the object to be inspected, and the thickness of the sprayed film is different. Generate a reference signal trajectory, create a calibration curve in advance based on the reference slope of the trajectory obtained from the reference signal trajectory,
Measure the eddy current signal from the air to the outer surface of the object to be in contact with the outer surface and generate a signal locus of the signal,
Find the slope of the trajectory from the signal trajectory,
An apparatus for measuring a film thickness of a sprayed film that measures the film thickness of the sprayed film on the basis of the obtained inclination of the locus and the calibration curve.

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