JP2019002807A - Scale thickness measurement device and scale thickness measurement method - Google Patents

Abstract

To provide a scale thickness measurement device which can exactly measure a thickness of each layer even if having a shape-collapsible layer constitution.SOLUTION: A scale thickness measurement device 20 in which a magnetite layer and a hematite layer adhere on an inner surface of a heat transmission pipe 9 comprises a measurement part for measuring and calculating: a surface electric resistance value when a tip of a probe sequentially contacts by the arrival of the probe at an inner surface of the heat transmission pipe 9 while penetrating the hematite layer and the magnetite layer from the hematite layer side; an electric resistance value and/or a resistance rate when the tip of the probe is located at the hematite layer, and a distance between the tip of the probe and the inner surface of the heat transmission pipe 9; an electric resistance value and/or a resistance rate when the tip of the probe is located at the magnetite layer while penetrating the hematite layer, and the distance between the tip of the probe and the inner surface of the heat transmission pipe 9; and an electric resistance value and/or a resistance rate when the tip of the probe is located at the magnetite layer, and the distance between the tip of the probe and the inner surface of the heat transmission pipe 9.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a scale thickness measuring apparatus and a scale thickness measuring method for measuring scale thicknesses deposited in multiple layers on an inner surface of a metal pipe such as a heat transfer tube.

  A power plant using a boiler and a steam turbine is known. Corrosion, scale generation and adhesion in boiler heat transfer tubes, system piping and steam supply systems to steam turbines, carryover to steam turbines, etc., depending on the water supply to the boiler used to distribute to the boiler heat transfer tubes In order to prevent this problem, water treatment is performed on the water supply. As such water treatment, for example, oxygen treatment is used. Oxygen treatment is to maintain the corrosion resistance of the steel material of the system piping and the corrosion products into the water by keeping the poorly soluble oxide in the high purity water in close contact with the surface of the steel material of the system piping and appropriately holding it. This is based on the idea that elution can be suppressed. One of the treatment methods is a combined water treatment (called CWT: Combined Water Treatment or OT: Oxygenated Feed-Water Treatment) in which dissolved oxygen coexists with weakly alkaline feed water by adding ammonia. is there.

In a plant to which CWT is applied, the scale growth rate is suppressed in the system pipe, and the hematite (Fe ₂ O ₃ ) that is generated and becomes the scale has a low solubility, thereby reducing iron elution from the system pipe. On the other hand, due to the long-term operation of the boiler, an increase in the amount of iron brought from the system piping to the boiler and a phenomenon that the hematite scale adheres to the hard scale formed on the inner surface of the boiler furnace wall pipe may be observed. The hematite scale is called a powder scale because it has a small particle size porous shape with low thermal conductivity, and it adheres to the heat transfer tube on the boiler furnace wall. It has become.
The main component of the powder scale is hematite, for example, to which iron in the feed water transported from the drain system of the feed water heater is attached. On the other hand, the main component of the hard scale is magnetite (Fe ₃ O ₄ ), which is a dense structure due to self-oxidation of the base material such as a heat transfer tube.

  When evaluating the scale attached to the inner surface of a heat transfer tube such as a furnace wall evaporator tube of a boiler, the amount of substance removed by applying ultrasonic waves may be measured as the amount of powder scale attached, but accurate quantification is difficult. It is. In addition, it is difficult to adopt the amount of powder scale adhesion by acid dissolution at the installation site of the boiler due to space and time constraints.

  As another method, a part of the heat transfer tube is extracted, brought into the analysis chamber and processed as a test piece, and then filled with resin with the scale attached, and cut obliquely to create a cut surface for observation. And by observing the cut surface with a scanning electron microscope (SEM), the thickness of the multi-layer adhesion scale may be evaluated, but the powder scale has floated off the heat transfer tube surface during resin filling, Accurate thickness measurement is difficult.

  Further, in the SEM, the observation range is narrow, and there is a possibility that it is not appropriate as an observation representative point of the deposit, and it is difficult to grasp a wide range of adhesion status.

  As described above, in the conventional method, the accuracy of the powder scale adhesion amount evaluation is insufficient, and the inspection period is prolonged, which leads to a prolonged period of regular inspection and is likely to cause economic disadvantages. There is.

  For example, in evaluating the thickness of the adhesion layer, there is a method in which the electrodes are moved and measured from a change in electric resistance value between the electrodes. Patent Document 1 below discloses an invention in which a movable electrode is moved with respect to an oxidized portion and a non-oxidized portion of a conductive refractory, and the thickness of the oxidized portion is measured.

JP-A-9-287910

However, the invention described in Patent Document 1 does not target a powder scale that is fragile and easily undergoes shape collapse, such as a hematite scale, and it is difficult to perform accurate measurement using a similar method.
If the deposit is not brittle, it is necessary to insert the movable electrode in the film thickness direction while managing the positioning accuracy of the movable electrode on the order of μm in order to measure the thickness of the deposit layer. If the impedance order is sometimes large, the thickness of the deposit can be estimated. That is, by measuring the electrical resistance value of the deposit layer from the spatial position of the movable electrode and the movable electrode at that time without obtaining an accurate electrical resistance value of the deposit layer, the tip of the movable electrode is positioned on the layer. By determining whether the position has been reached, the thickness of the layer can be estimated. In general, in order to accurately grasp the boundary between layers, it is necessary to make a judgment by overlaying multiple data. However, since it is not easy to measure multiple data in a short time, the thickness of the layer is It was only to estimate rough values.
Furthermore, when calculating the scale thickness of a heat transfer tube of a boiler, it is necessary to perform a large number of measurements at multiple locations in a pipe such as a heat transfer tube or for each of the multiple heat transfer tubes, in order to reduce the load on the operator It is desirable that the measurement per time is completed in a short time.
Furthermore, it is desirable that the measurement voltage upon measurement has a certain order value (at least in mV units) in order to reduce errors.
Since there is a relationship of measurement voltage between measurement needles = resistance to be measured × passing current, the passing voltage requires an order value (in mA units if 1Ω) in consideration of error and accuracy. Furthermore, when the internal resistance and the resistance loss of the measurement system are taken into account, a current value larger than necessary may lead to a change in the measurement system internal resistance due to heat generation, which may increase the error. In addition, when the passing current is increased more than necessary, the applied voltage also increases, so it is necessary to take measures against the operator's electric shock.

  The present invention has been made in view of such circumstances, and is a scale thickness that can easily and accurately measure the thickness of a scale layer composed of a plurality of layers attached to the inner surface of a heat transfer tube of a boiler. It is an object of the present invention to provide a measuring device and a scale thickness measuring method.

In order to solve the above problems, the scale thickness measuring apparatus and the scale thickness measuring method of the present invention employ the following means.
That is, the scale thickness measuring apparatus according to the present invention is installable in a boiler, and measures the thickness of a scale layer composed of a plurality of layers attached to the inner surface of a heat transfer tube through which boiler water flows. An apparatus comprising: a main body part; at least one probe supported in an insulated state by the main body part; a reference electrode electrically connectable to the heat transfer pipe; and the probe; An advancing / retreating means for advancing / retreating in an orthogonal direction with respect to the inner surface; an advancing / retreating amount measuring unit for calculating a relative position with the inner surface of the heat transfer tube from the advancing / retreating amount of the probe; and the probe and the reference electrode An electrical resistance measurement unit that calculates an electrical resistance value and / or resistivity from a potential difference, and a control unit that performs data processing based on the electrical resistance value and / or resistivity with respect to the advance / retreat amount.

  The probe is inserted into the scale layer, and the advance / retreat amount of the probe is calculated. Then, the electrical resistance is calculated from the potential difference between the probe and the reference electrode. As described above, the probe advancement / retraction amount and the electrical resistance value and / or the resistivity are calculated by piercing the probe, so that the thickness of each layer can be accurately measured.

  Furthermore, in the scale thickness measuring device of the present invention, the scale layer has a first layer and a second layer from the inner surface side to the surface side of the heat transfer tube, and the first layer and the second layer. The resistivity differs by an order of magnitude or more.

  Although the first layer and the second layer have different resistivity by one digit or more, it is easy to determine the position of the interface between the first layer and the second layer from the electric resistance value and / or the resistivity. Can be measured.

  Furthermore, in the scale thickness measuring apparatus of the present invention, the first layer includes a magnetite layer, and the second layer includes a hematite layer that is softer than the first layer.

  The heat transfer tube installed facing the furnace of the boiler, through which boiler water flows, has a hard magnetite layer attached to the inner surface through which the boiler water flows, and a soft hematite layer attached thereto. According to the scale thickness measuring apparatus, the change in the electrical resistance value and / or the change in the resistivity is calculated from the electrical resistance value and the distance from the metal surface, and the thickness of the magnetite layer and the hematite layer is accurately determined. Can be obtained.

  Furthermore, in the scale thickness measuring apparatus of the present invention, the main body portion includes a slide means for sliding in the longitudinal direction of the heat transfer tube, and the slide means extends in the longitudinal direction and is fixed to the heat transfer tube. Move along the rail.

  By sliding the probe along the rail, the probe can be accurately slid and moved in the longitudinal direction of the heat transfer tube. Further, if the rail is made of a conductive material and the rail is attached to a member having the same potential as the metal surface, the reference voltage at the time of measurement can be obtained from the rail.

  Furthermore, in the scale thickness measuring apparatus of the present invention, the control unit is configured to calculate the scale layer from the change amount of the electrical resistance value and / or the change amount of the resistivity with respect to the advance / retreat amount of the probe obtained by the control unit. The thickness of each multiple layer is calculated.

  The tip of the reference electrode is the same distance as the tip of the probe with respect to the surface of the heat transfer tube, and is a reference probe that can be advanced and retracted together with the probe.

  As the reference electrode, a reference probe which can be advanced and retracted together with a probe whose tip is at the same distance from the surface of the heat transfer tube can be used. The electrical resistance value and / or resistivity can be accurately measured by shortening the distance between the tip of the reference electrode and the tip of the probe.

  Furthermore, in the scale thickness measuring apparatus of the present invention, a constant current source for energizing a constant current and a voltage measuring circuit are provided between the reference probe and the probe, and the control unit includes the voltage measuring circuit. From the measured voltage value between the reference probe and the probe obtained in this way, the electrical resistance value and / or resistivity with respect to the advance / retreat amount of the probe is calculated.

  Furthermore, the scale thickness measuring device of the present invention includes a contact pressure measuring unit that measures the contact pressure applied to the probe, and / or when the contact pressure measured by the contact pressure measuring unit exceeds a threshold value, and / or When the electrical resistance value is close to zero, the advancement of the probe by the advance / retreat means is stopped.

  Furthermore, in the scale thickness measuring apparatus of the present invention, the control unit is configured to change the electrical resistance value change amount and / or resistivity change amount with respect to the probe advance / retreat amount, and the probe advance / retreat amount with respect to the probe advance / retreat amount. The thickness of each of the plurality of scale layers is calculated from the amount of change in contact pressure.

  The scale thickness measurement method of the present invention is a scale thickness measurement method for measuring the thickness of a scale layer composed of a plurality of layers attached to the inner surface of a heat transfer tube through which boiler water flows and is installed in a boiler. The probe is advanced and retracted in a direction orthogonal to the inner surface of the heat transfer tube, the amount of advancement / retraction of the probe is calculated, and the reference probe electrically connected to the heat transfer tube and the probe The electrical resistance value and / or the resistivity is calculated from the potential difference between and the data processing based on the electrical resistance with respect to the advance / retreat amount.

  Furthermore, in the scale thickness measuring method of the present invention, the probe is moved along a rail that extends in the longitudinal direction of the heat transfer tube and is fixed to the heat transfer tube.

  The thickness of the scale layer attached to the inner surface of the heat transfer tube of the boiler or the like and composed of a plurality of layers can be measured easily and accurately.

It is the schematic block diagram which showed the boiler power plant to which the scale thickness measuring apparatus of this invention is applied. It is the elements on larger scale which showed the water cooling wall which comprises the furnace of FIG. It is the fragmentary longitudinal cross-section which expanded and showed the heat exchanger tube. It is the perspective view which showed schematic structure of the scale thickness measuring apparatus which concerns on one Embodiment of this invention. It is the sectional side view which showed the principal part of FIG. It is a control block diagram of a scale thickness measuring apparatus. It is the side view which showed the probe guide. It is the schematic diagram which showed 2 probe types. It is the graph which showed the measurement example and showed the electrical resistance value and the resistivity with respect to the insertion depth of the probe. It is the sectional side view which showed the principal part of the scale thickness measuring apparatus which concerns on 3rd Embodiment.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
The first embodiment of the present invention will be described below.
FIG. 1 shows a schematic configuration of a boiler power plant 1 to which a scale thickness measuring device and a scale thickness measuring method according to the present embodiment are applied.

  The boiler power plant 1 includes a boiler 2 having a furnace 3 and a superheater (or a superheater and a reheater) 4, a steam turbine 6 that is rotationally driven by superheated steam guided from the superheater 4, and a steam turbine 6. And a condenser 7 for condensing and condensing the steam that has been expanded and finished its work. A generator 8 is connected to the steam turbine 6 to generate power by obtaining the rotational driving force of the steam turbine 6.

  Between the condenser 7 and the furnace 3, a water supply system 10 for supplying boiler water serving as water supply into the heat transfer pipe 9 of the furnace 3 is provided. The water supply system 10 is provided with a condensate pump 12, a water heater 13, a water supply pump 14, a water supply valve 15 and the like in order from the condenser 7 side. The feed water heater 13 is heated by feed steam (not shown) extracted from the steam turbine 6.

  The heat transfer tube 9 provided in the furnace 3 is made of, for example, carbon steel, low-chromium alloy steel, or stainless steel such as SUS304, and is a furnace wall tube that constitutes a water-cooled wall of the furnace 3, part of which is flame Arranged to be exposed to F. As shown in FIG. 2, a plurality of heat transfer tubes 9 are provided in parallel extending in the vertical direction via fins 11, for example. The boiler water supplied from the water supply system 10 into the heat transfer pipe 9 is operated in CWT (referred to as composite water treatment or oxygen treatment (OT)), and a certain amount of dissolved oxygen coexists with weak alkalinity. ing.

  As shown in FIG. 3, boiler water W containing iron Fe is supplied into the heat transfer tube 9, and the scale Sc may adhere so that the inside of the furnace exposed to the flame F becomes thick. The scale Sc is a hard scale layer mainly composed of magnetite formed on the inner surface of the heat transfer tube 9, and hematite is formed on the layer containing magnetite (first layer: hereinafter referred to as “magnetite layer”). It is a porous powder scale with a small particle size as a main component and a brittle adhesion layer, and is composed of a layer containing hematite (second layer: hereinafter referred to as “hematite layer”). In addition, the arrow in a figure shows the flow direction of the boiler water W. FIG. The scale thickness measuring device 20 measures the thickness of the scale Sc.

FIG. 4 shows a scale thickness measuring device 20.
The scale thickness measuring device 20 is installed near the outer surface of the heat transfer tube 9 and includes a main body portion 21, a rail 23, and a rail fixing portion 25.
The main body 21 includes at least one probe 22, an actuator (not shown) that moves the probe 22 forward and backward in the longitudinal direction of the probe 22 with respect to the scale Sc to be measured, and the main body 21. Is provided with a running portion (sliding means) (not shown) that slides in the longitudinal direction of the rail 23 with respect to the rail 23 (the vertical direction in FIG. 4 and FIG. 5). The probe 22 is supported in an insulated state with respect to the main body 21 and the rail 23. Moreover, the rail fixing | fixed part 25 is provided in the both ends of the longitudinal direction of the rail 23, for example, can be temporarily fixed to the outer surface of the heat exchanger tube 9 with the screw | thread with a magnet, a clamp mechanism, etc. At this time, the longitudinal direction of the probe 22 is substantially perpendicular to the inner surface of the heat transfer tube 9 and is substantially perpendicular to the longitudinal direction of the rail 23.

As shown in FIG. 6, the main body 21 has an electric resistance measurement unit 49 that obtains an electric resistance value calculated by measuring a current passing through the probe 22, and a travel amount traveled in the longitudinal direction of the rail 23 by the travel unit. And a travel amount measuring unit 51 that measures the amount of advance and retreat of the probe 22 that is advanced and retracted toward the scale Sc by the actuator. A computer (control unit) 32 is connected to the main body unit 21 via a measurement line 55. The computer 32 obtains the electrical resistance value calculated by the electrical resistance measurement unit 49, the travel amount measured by the travel amount measurement unit 50, the advance / retreat amount measured by the advance / retreat amount measurement unit 51, and the like. And the traveling of the rail 23 of the main body 21 and the advance / retreat of the probe 22 are controlled.
The electrical resistance measurement unit 49, the travel amount measurement unit 50, and the advance / retreat amount measurement unit 51 have sensor portions housed in the main body unit 21 and perform calculation processing of signals from each sensor by the computer 32. An arithmetic process for calculating the resistance value, the travel amount, and the advance / retreat amount may be performed.

  The probe 22 is made of a conductive material such as stainless steel (SUS304, etc.), tungsten, tungsten carbide, molybdenum, carbon nanotube, osmium alloy, silicon, etc., and at least the tip portion has a diameter of a few μm. . The probe 22 can be replaced according to the measurement target. Examples of the probe 22 to be replaced include those having different lengths and those having a tip having the same curvature as the inner surface of the heat transfer tube 9.

The probe 22 preferably has a larger diameter in order to ensure strength as the length is longer than the tip.
Further, as shown in FIG. 7, a probe guide 24 for supporting the probe 22 inside may be provided. The probe guide 24 is preferably an insulator for support, and the diameter φD1 is set to about 10 μm to 100 μm, for example, and the diameter φD2 of the probe 22 is set to 2 μm to 10 μm, for example. Since the periphery of the probe 22 is covered with an insulating probe guide 24, the contact portion between the probe 22 and the layer to be measured (the hematite layer and the magnetite layer in this embodiment) is limited to the tip of the probe 22. Therefore, the influence on the electrical resistance value by the contact area can be suppressed.

  As shown in FIG. 4, the rail 23 extends in the longitudinal direction near the outer surface of the heat transfer tube 9 so as to straddle the notch C formed in the heat transfer tube 9. Rail fixing portions 25 are provided at both end portions of the rail 23 in the longitudinal direction, and are detachably fixed to the outer surface of the heat transfer tube 9 by, for example, magnets or screws that can be clamped to the heat transfer tube 9. . The rail 23 is made of a conductive material such as metal. For this reason, since the rail 23 becomes the same potential as the heat transfer tube 9, the reference voltage at the time of measuring the current value or voltage value for calculating the electric resistance value can be acquired from the rail 23.

  The main body 21 travels along the rail 23 and is stopped at a predetermined position based on a command from the computer 32. The stop position of the main body unit 21 is calculated based on the travel amount measured by the travel amount measurement unit 50.

As shown in FIG. 5, the probe 22 advances and retreats in units of μm with respect to the heat transfer tube 9 based on a command from the computer 32, and the advance / retreat amount is measured by the advance / retreat amount measuring unit 51. The probe 22 is advanced so as to approach the inner surface of the heat transfer tube 9. When the magnetite layer 34 and the hematite layer 35 are formed on the inner surface of the heat transfer tube 9, the tip is positioned in the magnetite layer 34 or the hematite layer 35 according to the advancement / retraction amount of the probe 22. Thereby, the potential difference between the reference potential passing through the rail 23 from the surface of the heat transfer tube 9 and the probe 22 is measured, and the electric resistance value at the tip position of the probe 22 is obtained from the surface of the heat transfer tube 9 from the energized current value. be able to. The energized current value may be a constant current value as will be described later.
Further, the resistivity may be calculated according to the electric resistance value.
The resistivity is
(Resistivity) = (Electrical resistance value) × (Current passage area) / (Current passage distance)
The current passing distance is measured by the advance / retreat amount measuring unit 51 of the probe 22. The current passage area is calculated based on the size of the tip of the probe 22 (for example, the diameter φD2 in FIG. 7). However, since there is some change in the tip shape, the resistivity is corrected by temporarily measuring the existing layer in advance. More preferably.
If the tip of the probe 22 passes through the hematite layer 35 or the magnetite layer 34 and contacts the surface of the heat transfer tube 9, the electrical resistance value becomes almost zero, and if the probe 22 is further advanced, the measuring device is damaged. It is desirable to immediately stop the progress of the probe 22.

  The computer 32 obtains an electrical resistance value at each position of the tip of the probe 22 (advancing / retreating amount of the probe 22) from the electrical resistance measurement unit 49, performs a predetermined process, and adheres to the inner surface of the heat transfer tube 9. Is discriminated between a magnetite layer and a hematite layer, and the thickness of each layer is calculated.

  The computer 32 includes, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is preinstalled in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

FIG. 8 shows an example of measurement by a two-probe type. As shown in the figure, a constant current source and a voltage measuring circuit are connected between the reference probe 22R and the probe 22. In the present embodiment, the reference probe 22R is directly electrically connected to the rail 23, and a reference potential via the rail 23 is obtained from the surface of the heat transfer tube 9. By providing the reference probe 22R close to the probe 22 as shown in FIG. 8, the influence of the electrical resistance of the heat transfer tube 9 and the rail 23 (which becomes a part of the internal resistance) can be suppressed as much as possible.
The constant current source may be a constant voltage source in which a voltage is set in advance such that a current of 1 mA to 100 mA is applied, for example, but is more preferably a constant current source as described below.
For example, a constant current of 1 mA to 100 mA is applied from the constant current source. The constant current value depends on the resistivity and layer thickness of the measurement target layer, and the voltage difference between the reference probe 22R and the probe 22 via the inner surface of the heat transfer tube 9 and the measurement target layer is, for example, 0. The voltage is selected to be 1 mV to 1 mV or more, and in consideration of safety, a low voltage application that does not cause an electric shock to the operator is selected. Further, by applying a constant current and measuring, the value of the internal resistance of the measurement system such as the reference probe 22R, the probe 22 and the measurement line between them, and the probe 22 and the layer to be measured are measured. A constant current value can be selected so that the voltage drop due to contact resistance is sufficiently smaller than the voltage difference to be measured, and this voltage drop value is within a certain value regardless of the layer to be measured. The reliability of the measurement value is improved. Further, when measuring a plurality of layers having different resistivity as in this embodiment, for example, a voltage difference when measuring a layer having a low resistivity is 0.1 mV to 1 mV or more, and a layer having a high resistivity is selected. It is more preferable because an appropriate current value can be set from the accuracy of the voltage measurement system so that the voltage difference upon measurement is, for example, 1 V to 10 V or less.

  Next, the usage method of the scale thickness measuring apparatus 20 mentioned above is demonstrated. As shown in FIGS. 2 and 4, first, a notch C is formed in a part of the heat transfer tube 9 to be measured. At this time, the position of the notch C is the outer side opposite to the inner side of the furnace 3. As a result, work in the furnace 3 can be avoided, and measurement inside the furnace 3 where the scale Sc layer is easily formed thick is facilitated. The size of the notch C is such that the measurement position M can be accessed. Even if the main body 21 of the scale thickness measuring device 20 travels on the rail 23, the probe 22 is inserted and the scale Sc of the heat transfer tube 9 is inserted. Any size can be used as long as it can contact and advance. Therefore, it is not necessary to extrude several meters as in the prior art.

  An operator installs the rail 23 with respect to the outer surface of the heat exchanger tube 9 so that the notch C may be straddled. At this time, the rail 23 is temporarily fixed so as not to move with respect to the heat transfer tube 9 by a rail fixing portion 25 such as a magnet provided on the rail 23.

  Next, the rail 23 is temporarily fixed to the heat transfer tube 9 by the rail fixing portion 25, and the main body portion 21 of the scale thickness measuring device 20 is installed on the rail 23. At this time, the position of the rail 23 relative to the heat transfer tube 9 and the position of the main body 21 relative to the rail 23 are input to the computer 32 as initial positions. Thereby, the initial position in the longitudinal direction of the main body 21 with respect to the measurement position M of the heat transfer tube 9 (up and down direction in FIG. 4) is determined.

  The position of the tip of the probe 22 with respect to the main body 21 is input to the computer 32 as an initial position. Since the positional relationship between the heat transfer tube 9 and the main body portion 21 and the positional relationship between the main body portion 21 and the rail 23 are determined, the initial position of the tip of the probe 22 with respect to the surface at the measurement position M of the heat transfer tube 9 is determined. Is done.

  Then, in accordance with a command from the computer 32, the tip of the probe 22 proceeds in a horizontal direction (direction indicated by an arrow A2 in FIG. 5) while slowly approaching the inner surface of the heat transfer tube 9 in units of μm. Let The traveling speed of the tip of the probe 22 is preferably a slow speed of several μm to 1 μm / s or less so as to gradually enter the scale Sc.

The tip of the probe 22 pierces the hematite layer 35 and the magnetite layer 34 in this order, and then the tip of the probe 22 advances toward the inner surface of the heat transfer tube 9. Each position in progress of the tip of the probe 22 is sequentially measured by the advance / retreat amount measuring unit 51. At the same time, the electrical resistance value measured by the probe 22 is also sequentially measured and calculated by the electrical resistance measuring unit 49.
Then, the tip of the probe 22 pierces the scale Sc, and the tip of the probe 22 contacts the inner surface of the heat transfer tube 9. Then, the electrical resistance value at the tip of the probe 22 is almost zero (the resistivity calculated from the electrical resistance value is about several tens to several hundreds nΩm (in the case of carbon steel or low chromium alloy steel), for example. The needle 22 is in contact with the inner surface of the heat transfer tube 9, and the advancement of the probe 22 is stopped. At this position, the measurement for calculating the electric resistance value is completed.

  Here, regarding the voltage value and the current value between the tip of the probe 22 and the inner surface of the heat transfer tube 9 of the hematite layer 35 and the magnetite layer 34 which are measurement layers measured from the notch C, the hematite layer 35 and the magnetite layer 35 If moisture penetrates into the layer 34, the calculated electrical resistance value may change. In measurement, it is desirable to dry the layer to be measured inside the heat transfer tube 9, but a waiting time until measurement is required, or an additional blower for drying is required. However, in this embodiment, even in an insufficiently dried state, the voltage value or current value between the tip of the probe 22 and the inner surface of the heat transfer tube 9 is measured in a short time, and the electric resistance value or resistivity is measured. Since the relative comparison is performed, the thickness of each layer can be accurately measured without being affected by the dry state of the layer to be measured.

At the position where the electrical resistance value measured by the probe 22 becomes the electrical resistance value of the heat transfer tube 9 and becomes substantially zero, the tip of the probe 22 is in contact with the inner surface of the heat transfer tube 9. The advance of the tip is immediately stopped to prevent damage to the scale thickness measuring device 20 including the tip of the probe 22.
Thereafter, the tip of the probe 22 is retracted so as to be separated from the inner surface of the heat transfer tube 9 and returned to the initial position.
Next, after the main body portion 21 travels on the rail 23 and stops the main body portion 21 at a predetermined position, the tip end of the probe 22 is advanced and retracted as described above at another position in the longitudinal direction of the heat transfer tube 9. Measure the electrical resistance. By repeating this, electric resistance measurement at a plurality of locations in the longitudinal direction of the heat transfer tube 9 is performed.

  FIG. 9 shows a measurement result at a predetermined travel position. In the figure, the horizontal axis indicates the insertion depth, which is the amount of advancement / retraction of the tip of the probe 22, the vertical axis indicates the electrical resistance value, and the resistivity indicates. In this figure, the vertical axis indicates the logarithmic scale. Show.

  When the tip of the probe 22 is in the initial position, the tip of the probe 22 is not in contact with the hematite layer 35 and is located outside (the air) of the hematite layer 35. The resistivity (ρ1) indicates a value exceeding the measurement range.

  The tip of the probe 22 advances toward the inner surface of the heat transfer tube 9 and the electrical resistance value is calculated from the measurement of the current value and the voltage value. Furthermore, the relative relationship between the tip of the probe 22 and the inner surface of the heat transfer tube 9 is calculated. The resistivity may be calculated from the position. At the first depth t1, the electrical resistance value suddenly decreases to the first electrical resistance value R1. At this time, it is assumed that the electrical resistance value of the hematite layer 35 (for example, resistivity: ρ2: 1 kΩm to 100 kΩm) has started to be measured. The first depth t1 corresponds to the surface of the hematite layer 35. At this time, the relative position of the tip of the probe 22 and the inner surface of the heat transfer tube 9 differs depending on the thickness of the hematite layer 35, so that the absolute value of the electrical resistance value changes, but the resistivity ρ2 is stable and the order does not change greatly. You will get a value.

  When the insertion depth of the tip of the probe 22 becomes slightly deeper than the first depth t1, the electrical resistance value indicated by the probe 22 gradually decreases, and the second electrical resistance value R2 is reduced at the second depth t2. Show. The electrical resistance value that gradually decreases from the first electrical resistance value R1 to the second electrical resistance value R2 is a decrease in electrical resistance due to the thickness of the hematite layer 35. At this time, since the relative position between the tip of the probe 22 and the inner surface of the heat transfer tube 9 becomes closer, the electrical resistance value of the hematite layer 35 gradually decreases, but the resistivity ρ2 of the hematite layer 35 does not change greatly in the order. A stable value will be obtained. Therefore, the difference between the first depth t1 and the second depth t2 is the thickness of the hematite layer 35.

When the depth becomes slightly deeper from the second depth t2, the electric resistance value rapidly decreases to the third electric resistance value R3. This is considered that the electrical resistance value (for example, resistivity: ρ3: 0.001 mΩm to 0.1 mΩm) of the magnetite layer 34 is measured. From this measurement result, the second depth t2 is considered to be the position of the interface between the hematite layer 35 and the magnetite layer 34. At this time, the relative position of the tip of the probe 22 and the inner surface of the heat transfer tube 9 differs depending on the thickness of the magnetite layer 34, so that the absolute value of the electrical resistance value changes, but the resistivity ρ3 is stable and the order does not change greatly. You will get a value.
Since the resistivity of the hematite layer 35 and the magnetite layer 34 differ by one digit or more, the change of the electric resistance value becomes large at the position of the interface between the hematite layer 35 and the magnetite layer 34, and the resistivity changes rapidly by one digit or more. It is easy to determine the position of the interface.

  As the depth gradually increases from the second depth t2, the electrical resistance value indicated by the tip of the probe 22 gradually decreases, and the first electrical resistance value R1 is indicated at the first depth t1. The electrical resistance value that gradually decreases from the second electrical resistance value R2 to the first electrical resistance value R1 is a decrease in electrical resistance due to the thickness of the magnetite layer 34. At this time, since the relative position between the tip of the probe 22 and the inner surface of the heat transfer tube 9 becomes closer, the electric resistance value of the magnetite layer 34 gradually decreases, but the resistivity ρ3 of the magnetite layer 34 does not change greatly in the order. A stable value will be obtained. Therefore, the difference between the second depth t2 and the third depth t3 is the thickness of the magnetite layer 34.

When the depth is slightly increased from the second depth t2 to the third depth t3, the electric resistance value suddenly becomes about 0.1Ω or less (for example, resistivity: ρ4: 10 nΩm to 1000 nΩm (carbon steel or low chromium alloy). In the case of steel), the electric resistance value is almost zero, and it is determined that the tip of the probe 22 has reached the inner surface of the heat transfer tube 9.
Since the scale thickness measuring device 20 may be damaged if the probe 22 is further advanced when the electrical resistance value becomes substantially zero, it is desirable to immediately stop the advancement of the probe 22.

  As described above, the magnetite attached to the inner surface of the heat transfer tube 9 is obtained by measuring the position of the tip of the probe 22 and sequentially calculating the electrical resistance value and / or resistivity in the insertion depth direction of the probe 22. The thickness of the layer 34 or the hematite layer 35 can be obtained.

According to this embodiment, there exist the following effects.
The probe position of the probe 22 and the inner surface of the heat transfer tube 9 and the current value until the probe 22 reaches the inner surface of the heat transfer tube 9 through the hematite layer 35 and the magnetite layer 34 sequentially. From the measurement of the voltage value, the electric resistance value or the resistivity is calculated sequentially. Here, it can be determined that the tip of the probe 22 is in contact with the surface of the hematite layer 35 from a rapid change in electrical resistance value obtained from the probe 22 or a large change in resistivity. Furthermore, the electrical resistance value or resistivity when the probe 22 penetrates the hematite layer 35 and the tip of the probe 22 is located in the magnetite layer 34 is calculated, and when the tip of the probe 22 is located in the hematite layer. Distinguishing the inner surface of the heat transfer tube 9, the magnetite layer 34, and the hematite layer 35 from a sudden change in electrical resistance value and / or a large change in resistivity by calculating and comparing the electrical resistance value or resistivity. Can do. Since the electrical resistance value of the probe 22 suddenly changes to almost zero and / or the resistivity is greatly reduced to a low value, the tip of the probe 22 is in contact with the inner surface of the heat transfer tube 9. I can judge. The distance between the tip of the probe 22 and the inner surface of the heat transfer tube 9 when the electrical resistance value in the magnetite layer 34 is measured and changes suddenly or when the resistivity changes greatly, and the hematite layer 35 The magnetite layer 34 and the hematite layer 35 are calculated from the distance between the tip of the probe 22 and the inner surface of the heat transfer tube 9 when the electrical resistance value is calculated and changes suddenly and / or when the resistivity changes greatly. Can be obtained. Thus, since the electrical resistance value and / or the resistivity and the distance are obtained while piercing the probe 22 and changing the advance / retreat amount, the hematite layer 35 softer than the magnetite layer 34 suppresses the shape collapse, The thickness of each layer can be measured accurately.
The absolute value of the electrical resistance value changes depending on the thickness of the hematite layer 35 and the magnetite layer 34, and the relative position between the tip of the probe 22 and the inner surface of the heat transfer tube 9 changes. However, the resistivity greatly changes in order. You will get no stable value. The hematite layer 35 and the magnetite layer 34 differ in resistivity by one digit or more. For this reason, it may be easier to determine when the resistivity has changed significantly than when the electrical resistance value has changed suddenly. The distance between the tip of the probe 22 and the inner surface of the heat transfer tube 9 at this time may be easier. From this, it may be possible to measure the thickness of each layer more accurately. More preferably, both the electrical resistance value and the resistivity are judged.
Furthermore, even if the dried state of the hematite layer 35 and the magnetite layer 34 as the measurement target layers is insufficient, the voltage value and current value between the tip of the probe 22 and the inner surface of the heat transfer tube 9 are measured in a short time, Since the relative comparison of the electric resistance value and the resistivity is performed, the thickness of each layer can be measured in a short time without adding time for drying.

  By moving the tip of the probe 22 forward and backward with respect to the inner surface of the heat transfer tube 9, the tip of the probe 22 is positioned at a position where it contacts the inner surface, the magnetite layer 34, and the hematite layer 35. Thickness can be measured. Further, by moving the main body portion 21 along the rail 23, the measurement position with respect to the inner surface of the heat transfer tube 9 is changed to calculate the electrical resistance value and / or the resistivity at each position at many measurement positions. The inner surface of the heat transfer tube 9, the magnetite layer 34, and the hematite layer 35 are distinguished by the amount of change in electric resistance and / or the amount of change in resistivity, and the thickness of each layer at each measurement position in a short time. Can be measured. At this time, the thickness distribution state of the magnetite layer 34 and the hematite layer 35 is measured by the position of the tip of the probe 22 with respect to the inner surface of the heat transfer tube 9 (advancing / retreating amount of the probe 22), and the thickness of each of the layers It is possible to make a highly reliable judgment by averaging the data.

  When the electrical resistance value measured by the probe 22 is almost zero or the resistivity is low, the progress of the probe 22 is stopped. Thereby, it is possible to prevent an excessive load or load from being applied to the scale thickness measuring device 20 including the tip of the probe 22 from being damaged. For example, when the heat transfer tube 9 is a rifle tube, since the inner surface is uneven, the advance / retreat amount of the probe 22 can be suitably adjusted.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
In the first embodiment described above, the scale thickness measuring device 20 measured by the electric resistance value of the probe 22 has been described. However, in this embodiment, the scale thickness measuring device measured by the contact pressure applied to the probe 22. 20 will be described. In addition, this embodiment is the same as that of 1st Embodiment by the point which stabs a probe and measures the value of a sensor. Therefore, in the following embodiments, only differences from the first embodiment will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

In a portion where the probe 22 is supported by the main body 21 in an insulated state, a contact pressure measuring device such as a strain gauge, a piezoelectric element, or a load cell that measures the contact pressure applied to the probe 22 between the probe 22 and the support portion (see FIG. Not shown). In the configuration having the probe guide 24 as shown in FIG. 7, a contact pressure measuring device (not shown) may be provided between the probe guide 24 and the probe 22 at the base portion of the probe guide 24.
A signal from a contact pressure measuring device (not shown) is transmitted to the contact pressure measuring unit 52. The computer 32 measures the contact pressure in addition to the electrical resistance value calculated by the electrical resistance measurement unit 49, the travel amount measured by the travel amount measurement unit 50, and the advance / retreat amount measured by the advance / retreat amount measurement unit 51. The contact pressure value measured by the section 52 is obtained and various calculations are performed, and the traveling of the rail 23 of the main body section 21 and the advance / retreat of the probe 22 are controlled.
As shown in FIG. 5, the probe 22 advances and retreats with respect to the heat transfer tube 9 based on a command from the computer 32, and the advance / retreat amount is measured by the advance / retreat amount measuring unit 51. When the measurement is started, the tip of the probe 22 is pierced in the order of the hematite layer 35 and the magnetite layer 34, and each position of the tip of the probe 22 in progress (advancing / retreating amount of the probe 22) is sequentially measured by the advance / retreat amount measuring unit 51. At the same time, the contact pressure applied to the probe 22 is sequentially measured by the contact pressure measuring unit 52.
When the contact pressure at the tip of the probe 22 measured by the contact pressure measuring unit 52 exceeds a threshold value, the computer 32 determines that the tip of the probe 22 is in contact with the inner surface of the heat transfer tube 9, and the tip of the probe 22. Is stopped, and the scale thickness measuring device 20 is prevented from being damaged by further moving the probe 22 forward. Thereafter, the tip of the probe 22 is retracted so as to be separated from the inner surface of the heat transfer tube 9 and returned to the initial position.

Corresponding to the insertion depth of the probe 22 shown on the horizontal axis of FIG. 9, when the tip of the probe 22 advances toward the inner surface of the heat transfer tube 9, the contact pressure is reached at the first depth t1. The measurement value in the measurement part 52 increases rapidly. The first depth t1 is determined to be an interface between the hematite layer 35 and the outside (air) of the hematite layer 35 from a contact pressure value obtained in advance.
When the tip of the probe 22 exceeds the first depth t1, not only the contact pressure applied to the tip of the probe 22 but also the force due to the contact between the longitudinal peripheral surface of the probe 22 and the hematite layer 35 is applied. The contact pressure slightly increases with the insertion depth of the probe 22.
Further, when the insertion depth of the probe 22 is gradually increased, the measurement value in the contact pressure measurement unit 52 is rapidly increased when the depth is slightly increased from the second depth t2. From these measurement results, the second depth t2 is considered to be an interface between the hematite layer 35 and the magnetite layer 34.
When the insertion depth of the probe 22 is further increased gradually from the second depth t2, the measured value in the contact pressure measuring unit 52 is rapidly increased as the depth is increased to the third depth t3. Over. Thereby, it is determined that the tip of the probe 22 has reached the inner surface of the heat transfer tube 9.
When the measured value in the contact pressure measuring unit 52 exceeds a predetermined value, if the probe 22 is further advanced, the scale thickness measuring device 20 may be damaged. Therefore, the advancement of the probe 22 is immediately stopped. It is desirable.

  As described above, the contact pressure varies greatly depending on the position of the tip of the probe 22 according to the relationship between the electrical resistance value shown in the first embodiment and the insertion depth direction of the probe 22. By determining the amount of change in the contact pressure, the thickness of the magnetite layer 34 and the hematite layer 35 attached to the inner surface of the heat transfer tube 9 can be measured. Further, the thickness of the magnetite layer 34 and the hematite layer 35 adhering to the inner surface of the heat transfer tube 9 is measured with higher accuracy by determining the amount of change in the contact pressure in accordance with the determination of the change in the electric resistance value. Can be obtained.

According to this embodiment, there exist the following effects.
When the probe 22 passes through the hematite layer 35 and the magnetite layer 34 and reaches the inner surface of the heat transfer tube 9, the contact pressure value is sequentially measured, and from the sudden change in the contact pressure value, the inner surface of the heat transfer tube 9 The thickness of each of the magnetite layer 34 and the hematite layer 35 can be measured by distinguishing the magnetite layer 34 and the hematite layer 35 and matching the distance between the tip of the probe 22 and the inner surface of the heat transfer tube 9. it can. In addition to the sudden change in the electrical resistance value described in the first embodiment, the sudden change in the contact pressure value according to the second embodiment and the distance between the tip of the probe 22 and the inner surface of the heat transfer tube 9 are as follows. By combining them, the thicknesses of the magnetite layer 34 and the hematite layer 35 can be measured with higher accuracy and accuracy.

  When the contact pressure value applied to the probe 22 exceeds a predetermined value that is a threshold value, the advancement of the probe 22 is stopped. Thereby, even when the heat transfer tube 9 has irregularities formed on the inner surface such as a rifle tube, it is preferable to prevent the probe 22 and the scale thickness measuring device 20 from being damaged due to an excessive load or load. Can do.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
In the third embodiment, the reference probe 22R advances and retreats together with the probe 22, and measures the electrical resistance value and / or the resistivity and the contact pressure. In this embodiment, a reference probe 22R is added, but the rest is the same as the first embodiment and the second embodiment. Therefore, in the following embodiments, only differences will be described, and the same reference numerals are given to the same configurations, and the description thereof is omitted.

  As shown in FIG. 10, adjacent to the probe 22 supported by the main body 21, a reference probe 22R is arranged in parallel. At least one reference probe 22R and one probe 22 are provided, and the same reference probe 22R is adjacently arranged in parallel. The positions of the tip of the probe 22 and the tip of the reference probe 22R are set to be the same distance with respect to the inner surface of the heat transfer tube 9, or the reference position of the main body portion 21 and the rail 23. At this time, the main body portion 21 is provided with an actuator (advance / retreat means) (not shown) that advances and retracts in the longitudinal direction of the probe 22 with respect to each of the probe 22 and the reference probe 22R. The reference probe 22R advances / retreats with respect to the heat transfer tube 9 based on a command from the computer 32, and the advance / retreat amount is measured by the advance / retreat amount measuring unit 51.

The probe 22 and the reference probe 22R advance / retreat with respect to the heat transfer tube 9 based on a command from the computer 32, and the advance / retreat amount is measured by the advance / retreat amount measuring unit 51. When the measurement is started, the tips of the probe 22 and the reference probe 22R are pierced and moved in the order of the hematite layer 35 and the magnetite layer 34. The respective positions of the tips of the probe 22 and the reference probe 22R in progress are sequentially measured by the advance / retreat amount measuring unit 51, and the electrical resistance value and / or the resistivity between the probe 22 and the reference probe 22R are determined. Calculated. It is more preferable to measure the contact pressure values of the probe 22 and the reference probe 22R together as in the second embodiment. When the electrical resistance value between the probe 22 and the reference probe 22R becomes almost zero and / or when the contact pressure at the tip of the probe 22 or the reference probe 22R exceeds a predetermined value which is a threshold value, transmission is performed. It is determined that the tip of the reference probe 22R is in contact with the inner surface of the heat tube 9, and the advance of the tip of the probe 22 and the reference probe 22R is stopped. Thereby, the electrical resistance value and / or resistivity can be calculated and the contact pressure value can be measured up to a depth t3 at which the probe 22 and the reference probe 22R are in contact with the heat transfer tube 9.
Thereafter, the scale thickness can be measured by the electrical resistance value of the probe 22 as in the first embodiment.

According to this embodiment, there exist the following effects.
Since the electrical resistance value and / or resistivity between the reference probe 22R provided adjacent to a position relatively close to the probe 22 is calculated, the reference probe 22R and the tip of the probe 22 are calculated. The hematite layer 35 and the magnetite layer 34 existing between the two are extremely short distances. For this reason, the electrical conduction distance from the reference probe 22R to the probe 22 is shortened, the internal resistance of the electrical resistance measurement system is reduced, and the reliability is improved. The inner surface of the heat transfer tube 9, the magnetite layer 34, and the hematite layer 35 are distinguished from each other, and a sudden change in electrical resistance value and / or a sudden change in resistivity, and the tip of the probe 22 or the reference probe 22R are transmitted. From the distance from the inner surface of the heat tube 9, the thicknesses of the magnetite layer 34 and the hematite layer 35 can be measured with higher accuracy and accuracy. The thicknesses of the magnetite layer 34 and the hematite layer 35 may be measured from the distance between the contact pressure value of the probe 22 or the reference probe 22R and the inner surface of the heat transfer tube 9. Furthermore, the thickness of each of the magnetite layer 34 and the hematite layer 35 can be more accurately adjusted by combining a sudden change in electrical resistance value and / or a sudden change in resistivity with a sudden change in contact pressure value. High and accurate measurement.

In the above-described embodiment, the power plant using the boiler 2 has been described. However, a CWT (combined water treatment or oxygen treatment) is performed on an exhaust heat recovery boiler of a gas turbine combined power cycle (GTCC). It can also be applied to a case where OT) is operated.
In the above-described embodiment, the scale on which the magnetite layer 34 and the hematite layer 35 are attached has been described. However, the adhesion layer is not limited to this, and for example, the surface side of the magnetite layer is oxidized to become hematite. It can also be applied to existing scales. Further, the adhesion layer may not be two layers, and three or more adhesion layers can be similarly applied.

DESCRIPTION OF SYMBOLS 1 Boiler power plant 2 Boiler 3 Furnace 4 Superheater 6 Steam turbine 7 Condenser 8 Generator 9 Heat transfer pipe 10 Water supply system 12 Condensate pump 13 Feed water heater 14 Feed water pump 15 Feed water valve 20 Scale thickness measuring device 21 Main part 22 Probe 22R Reference probe 23 Rail 32 Computer (control unit)
34 Magnetite layer (first layer)
35 Hematite layer (second layer)
49 Electrical Resistance Measurement Unit 50 Travel Amount Measurement Unit 51 Advance / Retreat Amount Measurement Unit 52 Contact Pressure Measurement Unit 55 Measurement Line C Notch F Flame Fe Iron M Measurement Position Sc Scale W Boiler Water

Claims (11)

A scale thickness measuring device that can be installed in a boiler and measures the thickness of a scale layer composed of a plurality of layers attached to the inner surface of a heat transfer tube through which boiler water flows.
The main body,
At least one probe supported in an insulated state on the main body, and
A reference electrode electrically connectable to the heat transfer tube;
Advancing and retracting means for advancing and retracting the probe in a direction orthogonal to the inner surface of the heat transfer tube;
An advance / retreat amount measurement unit for calculating a relative position with the inner surface of the heat transfer tube from the advance / retreat amount of the probe;
An electrical resistance measurement unit for calculating an electrical resistance value and / or resistivity from a potential difference between the probe and the reference electrode;
A control unit that performs data processing based on the electrical resistance value and / or resistivity with respect to the advance / retreat amount;
Scale thickness measuring device with The scale layer has a first layer and a second layer from the inner surface side to the surface side of the heat transfer tube,
The scale thickness measurement apparatus according to claim 1, wherein the first layer and the second layer have different resistivity by one digit or more. The first layer includes a magnetite layer;
The scale thickness measurement apparatus according to claim 2, wherein the second layer includes a hematite layer that is softer than the first layer. The main body includes slide means for sliding in the longitudinal direction of the heat transfer tube,
The scale thickness measuring device according to any one of claims 1 to 3, wherein the sliding means moves along a rail extending in the longitudinal direction and fixed to the heat transfer tube.   The control unit calculates the thickness of each of the plurality of layers of the scale layer from the amount of change in electrical resistance value and / or the amount of change in resistivity with respect to the amount of advance and retreat of the probe obtained by the control unit. To 4. The scale thickness measuring device according to any one of 4 to 4.   The tip of the reference electrode is the same distance as the tip of the probe with respect to the surface of the heat transfer tube, and is a reference probe that can be advanced and retracted together with the probe. The scale thickness measuring device according to any one of the above. Between the reference probe and the probe, a constant current source for passing a constant current and a voltage measurement circuit,
The control unit calculates an electrical resistance value and / or a resistivity with respect to an advance / retreat amount of the probe from a voltage measurement value between the reference probe and the probe obtained by the voltage measurement circuit. The scale thickness measuring apparatus according to claim 6. A contact pressure measuring unit for measuring the contact pressure applied to the probe;
When the contact pressure measured by the contact pressure measurement unit exceeds a threshold, and / or when the electrical resistance value is close to zero,
The scale thickness measuring apparatus according to claim 1, wherein advancement of the probe by the advance / retreat means is stopped.   In addition to the amount of change in electrical resistance value and / or the amount of change in resistivity with respect to the amount of advancement / retraction of the probe, the control unit determines a plurality of scale layers from the amount of change in the contact pressure with respect to the amount of advancement / retraction of the probe The scale thickness measuring device according to claim 8 which calculates the thickness of a layer. A scale thickness measurement method for measuring the thickness of a scale layer composed of a plurality of layers attached to the inner surface of a heat transfer tube through which boiler water flows and which can be installed in a boiler,
Advancing and retracting the probe in a direction perpendicular to the inner surface of the heat transfer tube,
Calculate the relative position with the inner surface of the heat transfer tube from the amount of advance and retreat of the probe,
Calculate the electrical resistance value and / or resistivity from the potential difference between the probe and the probe electrically connected to the heat transfer tube,
A scale thickness measurement method for performing data processing based on the electrical resistance value and / or resistivity with respect to the advance / retreat amount.   The scale thickness measurement method according to claim 10, wherein the probe is moved along a rail that extends in a longitudinal direction of the heat transfer tube and is fixed to the heat transfer tube.

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