JP7290995B2 - Specimen holder and cleaning system, corrosion amount measuring method and corrosion amount measuring device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a test piece holder, a cleaning system, a corrosion amount measuring method, and a corrosion amount measuring apparatus.

In order to know the state of the metal surface, the corrosion rate on the metal surface may be measured.

For example, Patent Literature 1 discloses an apparatus for measuring the resistance to corrosion (corrosion resistance) of the inner surface of a metal pipe. In this device, a pair of flanges are inserted into the interior of the metal tube so that a chamber surrounded by the inner surface of the metal tube and the flanges is formed. Then, with the room filled with seawater, the polarization resistance of the inner surface of the metal tube is measured by electrochemical measurement using a counter electrode and a reference electrode provided so as to be exposed in the room, and the polarization resistance is measured based on the polarization resistance. are used to evaluate the corrosion resistance of metal pipes.

Japanese Patent No. 2824804

By the way, when the liquid properties of the fluid flowing inside the metal pipe change, it is necessary to evaluate the amount of corrosion and the corrosion rate of the inner surface of the metal pipe every moment while the fluid is flowing inside the metal pipe. However, in the apparatus disclosed in Patent Document 1, it is not assumed that electrochemical measurements are performed while a large amount of liquid is circulated. It is thought that it will not be. Therefore, it is desired to measure the corrosion amount or corrosion rate of the inner surface of the metal pipe while circulating the liquid inside the metal pipe.

In view of the circumstances described above, at least one embodiment of the present invention provides a test strip holder and cleaning system capable of measuring the corrosion rate of a tubular test strip (metal tube) while circulating a liquid through the tubular test strip (metal tube). It is also an object of the present invention to provide a corrosion amount measuring method and a corrosion amount measuring apparatus.

(1) A test piece holder according to at least one embodiment of the present invention,
a holder body including a first holder portion and a second holder portion for holding the tubular test piece sandwiched from both sides in the axial direction of the tubular test piece;
a first channel provided in the first holder part so as to communicate with the internal channel of the tubular test piece;
a second flow path provided in the second holder portion so as to communicate with the internal flow path of the tubular test piece;
a first sealing member for sealing between the first holder portion and the tubular test piece;
a second sealing member for sealing between the second holder portion and the tubular test piece;
Prepare.

According to the above configuration (1), the tubular test piece (metal tube) is sandwiched and held between the first holder and the second holder via the sealing member, and can communicate with the internal flow path of the tubular test piece. Since the first flow path and the second flow path are provided, the fluid (cleaning liquid, etc.) can be circulated in the internal flow path of the tubular test strip via the first flow path and the second flow path. As a result, various measurements (for example, electrochemical measurements) can be performed while the liquid is circulating in the internal flow path of the tubular test piece, and the corrosion rate of the inner surface of the tubular test piece can be measured.

(2) In some embodiments, in the configuration of (1) above,
The test strip holder includes:
A conductive portion is provided between the first holder portion and the second holder portion for connecting the outer surface of the tubular test piece to a sample electrode terminal of an electrochemical measuring device.

In the above configuration (2), since the conductive portion electrically connected to the outer surface of the tubular test piece is provided between the first holder portion and the second holder portion, electrochemical A tubular test piece can be connected to the sample electrode terminal of the measuring device. Therefore, this makes it possible to perform electrochemical measurements on the tubular test piece (for example, measurement of the polarization resistance of the inner surface of the tubular test piece) while allowing the liquid to flow through the internal flow path of the tubular test piece. The corrosion rate of the inner surface of the specimen can be measured.

(3) In some embodiments, in the configuration of (1) or (2) above,
The test strip holder includes:
A fastening portion for fastening the first holder portion and the second holder portion with the tubular test piece sandwiched between the first holder portion and the second holder portion is provided.

According to the above configuration (3), the tubular test piece is sandwiched between the first holder portion and the second holder portion, and the fastening portion fastens the first holder portion and the second holder portion. Therefore, the pressure resistance and sealing performance of the test piece holder can be improved. Therefore, it is possible to obtain a test piece holder that can handle a wide range of fluid flow conditions.

(4) In some embodiments, in the configuration of (3) above,
The fastening portion is
a bolt inserted through a bolt hole provided in each of the first holder portion and the second holder portion;
a nut screwed onto the bolt;
including.

According to the configuration of (4) above, with a simple configuration including bolts and nuts, as described in (3) above, the pressure resistance and sealing performance of the test piece holder are improved, and a wide range of fluid flows. It is possible to obtain a test piece holder that can meet the conditions.

(5) In some embodiments, in the configuration of any one of (1) to (4) above,
The first holder portion is provided with a concave portion for receiving the first seal member on the end face in the pipe axis direction.

According to the above configuration (5), since the recess is provided in the end face of the first holder portion in the pipe axis direction, the first holder of the first seal member is fitted into the recess by fitting the first seal member. Positioning with respect to the part is facilitated, and sealing performance by the first sealing member can be enhanced.

(6) In some embodiments, in the configuration of (5) above,
The first seal member includes a disk portion provided so as to be in contact with the bottom surface of the recess.

According to the configuration (6) above, since the disk portion of the first seal member is in contact with the bottom surface of the recess provided in the end surface of the first holder portion, a large contact area between the first seal member and the recess is maintained. It is possible to improve the sealing performance of the first sealing member.

(7) In some embodiments, in the configuration of (6) above,
The first seal member further includes a cylindrical portion protruding from the disk portion in the tube axis direction to the side opposite to the bottom surface of the recess.

According to the above configuration (7), the first seal member has a cylindrical portion protruding from the disk portion in the tube axial direction to the side opposite to the bottom surface of the recess. By setting according to the outer diameter of the piece, it becomes easier to position the tubular test piece in the plane orthogonal to the tube axis direction. In addition, since the inner diameter of the cylindrical portion can be set according to the outer diameter of the tubular test piece,
By replacing the first seal member with one having an appropriate inner diameter size for one test piece holder, a plurality of types of tubular test pieces with different outer diameters can be used as test objects. Therefore, device manufacturing cost can be reduced.

(8) In some embodiments, in any of the above configurations (1) to (7),
The test strip holder includes:
a counter electrode provided on the holder body so as to be exposed to the first channel or the second channel and connected to a counter electrode terminal of an electrochemical measurement device;
a reference electrode provided on the holder body so as to be exposed to the first channel or the second channel and connected to a reference electrode terminal of an electrochemical measurement device;
further provide.

According to the above configuration (8), the corrosion rate of the inner surface of the tubular test piece can be measured by the polarization resistance measurement by the three-electrode method using the sample electrode, which is a tubular test piece, and the above-described counter electrode and reference electrode. . Therefore, the corrosion rate can be measured with relatively high accuracy.

(9) In some embodiments, in any of the above configurations (1) to (8),
The holder body includes a third holder portion for holding a tubular test piece other than the tubular test piece held between the first holder portion and the second holder portion,
The third holder portion is positioned to face one of the first holder portion and the second holder portion in the tube axis direction,
The test strip holder includes:
a third channel provided in the third holder part so as to communicate with the internal channel of the other tubular test piece;
a third sealing member for sealing between the third holder portion and the other tubular test piece;
Prepare.

According to the configuration (9) above, two tubular test pieces including the tubular test piece held between the first holder portion and the second holder portion and another tubular test piece held by the third holder portion Using each piece as a sample electrode, the corrosion rate of the inner surface of the tubular test piece can be measured by polarization resistance measurement by the two-electrode method. Therefore, the corrosion rate can be measured relatively easily.

(10) A heat transfer tube cleaning system according to at least one embodiment of the present invention includes:
A cleaning system for cleaning a plurality of heat transfer tubes provided in a boiler,
The test piece holder according to any one of (1) to (9) above;
a cleaning liquid circulation line connected to the plurality of heat transfer tubes for circulating a cleaning liquid through the plurality of heat transfer tubes;
a branch line branched from the cleaning liquid circulation line and connected to the first flow path or the second flow path of the test strip holder;
a temperature control unit for controlling the temperature of the cleaning liquid introduced into the test strip holder through the branch line;
a flow rate adjusting unit for adjusting the flow rate of the cleaning liquid introduced into the test strip holder through the branch line;
a control unit for controlling the temperature control unit and the flow rate control unit;
Prepare.

In order to remove the scale adhering to the inner surface of the heat transfer tube, the heat transfer tube is sometimes washed with a cleaning liquid. In this respect, according to the configuration (10) above, the cleaning liquid for cleaning the heat transfer tube can be supplied to the internal channel of the tubular test strip through the first channel or the second channel by the test strip holder. In addition, the temperature control section and the flow rate control section can control the temperature and flow rate of the cleaning liquid introduced into the test strip holder. Therefore, the flow conditions (temperature and flow rate) of the cleaning liquid in the internal channel of the tubular test piece can be adjusted according to the flow conditions on the inner surface of the heat transfer tube. Therefore, it is possible to measure the polarization resistance of the inner surface of the tubular specimen under the desired flow conditions and measure the corrosion rate.

(11) A corrosion amount measuring method according to at least one embodiment of the present invention includes:
placing the tubular test piece in the test holder according to any one of (1) to (9) above;
a step of supplying a cleaning liquid to the internal channel of the tubular test strip through the first channel and the second channel to clean the tubular test strip with the cleaning liquid;
measuring the polarization resistance of the tubular specimen during washing with the washing solution;
a step of calculating the concentration of iron derived from corrosion during the cleaning from the measurement result of the polarization resistance;
Prepare.

According to the above configuration (11), the polarization resistance of the tubular test piece is measured while the tubular test piece is washed with the washing liquid, and based on the measurement result of the polarization resistance, Since the iron concentration is calculated, the corrosion state of the surface of the tubular test piece can be properly grasped.

(12) A corrosion amount measuring method according to at least one embodiment of the present invention includes:
a step of measuring the amount of scale adhered to the test piece;
a step of predicting the iron concentration in the cleaning liquid based on the scale deposition amount, assuming that the entire amount of scale adhering to the test piece has been removed by cleaning with the cleaning liquid;
A step of measuring the polarization resistance using the test piece while washing the test piece with the cleaning solution, and calculating the concentration of corrosion-derived iron in the cleaning solution from the measurement result of the polarization resistance;
measuring the total iron concentration in the cleaning solution while cleaning the test piece with the cleaning solution;
calculating the scale-derived iron concentration in the cleaning solution from the difference between the measured total iron concentration and the calculated corrosion-derived iron concentration;
Prepare.

According to the method (12) above, the iron concentration in the cleaning solution is predicted based on the amount of scale adhered to the test piece, and the difference between the measured total iron concentration and the calculated corrosion-derived iron concentration is calculated during cleaning. Since the scale-derived iron concentration is calculated, it is possible to grasp the progress of washing of the test piece by comparing the above-mentioned predicted value of iron concentration with the scale-derived iron concentration calculated value. Therefore, it is possible to appropriately grasp the end timing of the chemical cleaning in the boiler.

(13) A corrosion amount measuring device according to at least one embodiment of the present invention,
a prediction unit that predicts the iron concentration in the cleaning liquid based on the amount of scale adhered to the test piece when it is assumed that the entire amount of scale adhering to the test piece has been removed by cleaning with the cleaning liquid;
a polarization resistance measuring unit that measures the polarization resistance using the test piece while cleaning the test piece with the cleaning solution;
a first calculation unit that calculates the concentration of corrosion-derived iron in the cleaning solution from the measurement result of the polarization resistance;
a concentration measuring unit that measures the total iron concentration in the cleaning liquid while cleaning the test piece with the cleaning liquid;
a second calculator for calculating the scale-derived iron concentration in the cleaning solution from the difference between the measured total iron concentration and the calculated corrosion-derived iron concentration;
Prepare.

According to the above configuration (13), the iron concentration in the cleaning liquid is predicted based on the amount of scale adhered to the test piece, and the difference between the measured total iron concentration and the calculated corrosion-derived iron concentration is calculated during cleaning. Since the scale-derived iron concentration is calculated, it is possible to grasp the progress of washing of the test piece by comparing the above-mentioned predicted value of iron concentration with the scale-derived iron concentration calculated value. Therefore, it is possible to appropriately grasp the end timing of the chemical cleaning in the boiler.

According to at least one embodiment of the present invention, a test piece holder and cleaning system capable of measuring the corrosion rate of the inner surface of a tubular test piece (metal tube) while circulating a liquid in the tubular test piece (metal tube), and the amount of corrosion An object of the present invention is to provide a measuring method and a corrosion amount measuring device.

1 is a schematic diagram of a cleaning system according to one embodiment; FIG. 1 is a schematic diagram of a corrosion rate measuring device according to one embodiment; FIG. 1 is a schematic diagram of a corrosion rate measuring device according to one embodiment; FIG. 1 is a schematic diagram of a corrosion rate measuring device according to one embodiment; FIG. 1 is a schematic cross-sectional view of a test strip holder according to one embodiment; FIG. 1 is a schematic cross-sectional view of a test strip holder according to one embodiment; FIG. It is an example of the graph which shows the time change of the dissolved iron density|concentration in the washing|cleaning liquid obtained by the corrosion amount measuring method which concerns on one Embodiment.

Several embodiments of the present invention will now be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, and are merely illustrative examples. do not have.

In the following embodiment, a case where an object to be cleaned in a cleaning system or a cleaning method according to one embodiment is a heat transfer tube of a boiler constituting a thermal power plant will be described, but the object to be cleaned in the present invention is limited to this. Instead, it may be, for example, a heat transfer tube of a marine boiler, a portion other than the heat transfer tube of a boiler, a heat transfer tube of a heat exchanger, or a component of a chemical plant.

FIG. 1 is a schematic diagram of a cleaning system in which test strip holders according to some embodiments are applied. A cleaning system 1 shown in FIG. 1 is configured to clean a plurality of heat transfer tubes 104 that constitute a furnace 102 of a boiler 100 .

A boiler 100 shown in FIG. 1 includes a furnace 102 arranged on a circulation line 106, a steam separator 110, and an economizer (not shown), a superheater, and the like. Water is supplied to the heat transfer tubes 104 of the furnace 102 through a circulation line 106 . In the heat transfer tube 104 of the furnace 102, the steam generated by heat exchange with the combustion heat of the fuel is supplied to the turbine (not shown) via the steam separator 110 and the superheater (not shown) to rotate the turbine rotor. rotationally driven. The steam that has finished work in the turbine is condensed in a condenser (not shown) to become water. The water produced in the condenser passes through a heater, a deaerator, an economizer, etc. (none of which are shown) provided in the circulation line 106 and is supplied to the furnace 102 again. The circulation line 106 may be provided with a pump (not shown) for pumping steam or water.

Scale mainly composed of iron oxide may adhere to the inside of the heat transfer tubes 104 constituting the furnace 102 of the boiler 100 , reducing the thermal conductivity of the heat transfer tubes. The cleaning system 1 shown in FIG. 1 is a cleaning system for removing such scale adhering to the inner surface of the heat transfer tube 104 using a cleaning liquid.

A cleaning system 1 shown in FIG. 1 includes a cleaning liquid circulation line 2 connected to a circulation line 106, and a circulation pump 4 provided in the cleaning liquid circulation line 2 for circulating the cleaning liquid. The upstream end of the cleaning liquid circulation line 2 is connected to a first connection point 105 located downstream of the steam separator 110 in the circulation line 106, and the downstream end of the cleaning liquid circulation line 2 is connected to the furnace 102 in the circulation line 106. It is connected to the second connection point 108 located upstream. That is, the cleaning liquid circulation line 2 is connected to a plurality of heat transfer tubes 104 via circulation lines 106 .

The cleaning system 1 also includes a cleaning liquid tank 8 for storing cleaning liquid, a cleaning liquid supply line 6 for supplying the cleaning liquid from the cleaning liquid tank 8 to the cleaning liquid circulation line 2, and an injection pump 10 provided in the cleaning liquid supply line 6. and including. The cleaning liquid stored in the cleaning liquid tank 8 is supplied to the cleaning liquid circulation line 2 through the cleaning liquid supply line 6 by the injection pump 10 .

The type of cleaning liquid used for cleaning the scale (that is, the cleaning liquid stored in the cleaning liquid tank 8) is not particularly limited as long as it can dissolve scale mainly containing iron oxide. Such a cleaning liquid may be, for example, a cleaning liquid containing an acid such as hydrochloric acid, or it may be a cleaning liquid containing a chelating agent or a reducing agent or a corrosion inhibitor.

The above-mentioned chelating agents include, for example, aminocarboxylic acids such as EDTA, BAPTA, DOTA, EDDS, INN, NTA, DTPA, HEDTA, TTHA, PDTA, DPTA-OH, HIDA, DHEG, GEDTA, CMGA, EDDS, and salts thereof. aminocarboxylic acid chelating agents, oxycarboxylic acids such as citric acid, gluconic acid, and hydroxyacetic acid, and oxycarboxylic acid chelating agents such as salts thereof, organic phosphoric acids such as ATMP, HEDP, NTMP, PBTC, EDTMP, and these It may be an organic phosphorus-based chelating agent such as a salt of

The above-mentioned reducing agents include, for example, various metal ions such as Fe ²⁺ and Sn ²⁺ , sulfites such as sodium sulfite, hyposulfites, oxalic acid, formic acid, ascorbic acid, elsorbic acid, pyrogallol, thiourea compounds, thiodioxide Organic compounds such as urea-based compounds and thioglycolates, hydrazine, and hydrogen may also be used.

The above-mentioned corrosion inhibitors include, for example, amphoteric surfactants, nonionic surfactants, cationic surfactants, corrosion inhibitors that form adsorptive films such as sulfur-based compounds, precipitation film-type corrosion inhibitors, and complex salts. It may be a film-forming type corrosion inhibitor or the like.

With the above-described configuration, the cleaning liquid from the cleaning liquid tank 8 is pressure-fed by the circulation pump 4, the cleaning liquid circulation line 2, the circulation line 106 downstream of the second connection point 108 and upstream of the furnace 102, and a plurality of transmission lines. It circulates through a heat tube 104 (furnace 102 ) and a circulation line 106 downstream of the furnace 102 and upstream of the first connection point 105 . When circulating the cleaning liquid in this manner, the valve 109 provided downstream of the first connection point 105 and the valve 107 provided upstream of the second connection point 108 in the circulation line 106 are closed. , the flow of water and steam circulating in circulation line 106 is stopped.

The cleaning system 1 includes a branch line 12 branching from the cleaning liquid circulation line 2, a corrosion rate measuring device 30 provided in the branch line 12, and the temperature and flow rate of the cleaning liquid introduced into the corrosion rate measuring device 30 via the branch line 12. and a temperature control unit and a flow control unit for adjusting, respectively.

An upstream end 11 and a downstream end 13 of the branch line 12 are connected to the cleaning liquid circulation line 2 respectively. A pump 14 is provided in the branch line 12 , and the cleaning liquid from the cleaning liquid circulation line 2 is drawn into the branch line 12 by the pump 14 .

The corrosion rate measuring device 30 is a device for measuring the corrosion rate of a tubular test piece, and includes a test piece holder 32 for holding the tubular test piece and an electrochemical measuring device 90 connected to the test piece holder 32. , (see FIG. 2). As this tubular test piece, one taken from one of the plurality of heat transfer tubes 104 constituting the furnace 102 can be used. When a tubular test piece is taken from the heat transfer tube 104 when the heat transfer tube 104 is chemically cleaned, the inner surface of the tubular test piece usually has scale adhered to the inner surface.

The test strip holder 32 has a cleaning liquid inlet 58 and a cleaning liquid outlet 60 connected to the branch line 12 respectively. The cleaning liquid drawn into the branch line 12 from the cleaning liquid circulation line 2 is introduced into the test piece holder 32 through the cleaning liquid inlet 58, and after passing through the internal flow path of the tubular test piece installed in the test piece holder 32, It is discharged to the branch line 12 through the cleaning liquid outlet 60 . The cleaning liquid discharged to the branch line 12 is returned to the cleaning liquid circulation line 2 via the downstream end 13 of the branch line 12 . The configuration of the corrosion rate measuring device 30 including the test piece holder 32 will be described later.

In the exemplary embodiment shown in FIG. 1, a temperature control unit for adjusting the temperature of the cleaning liquid introduced into the test strip holder 32 is provided in the branch line 12 and heats the cleaning liquid by heat generated by electrical resistance. The heater 16 is configured as follows. In another embodiment, the temperature control unit may be a heat exchanger configured to heat the cleaning liquid by exchanging heat with a heat medium.

Also, in the exemplary embodiment shown in FIG. 1 , the flow control unit for controlling the flow rate of the cleaning liquid introduced into the test strip holder 32 is the above-described pump 14 provided in the branch line 12 . The pump 14 is configured so that the discharge pressure can be adjusted by changing the rotation speed, that is, the flow rate of the cleaning liquid on the discharge side can be adjusted.

The cleaning system 1 includes a control device 20 (control unit), a flow meter 21 and a temperature sensor 22 for acquiring the temperature and flow rate of the cleaning liquid in the plurality of heat transfer tubes 104, and the temperature and flow rate of the cleaning liquid in the test strip holder 32. and a flow meter 23 and a temperature sensor 24 for acquisition.

In the exemplary embodiment shown in FIG. 1, flow meter 21 and temperature sensor 22 are provided in circulation line 106 downstream of furnace 102 .

Since the cleaning liquid flowing through the plurality of heat transfer tubes 104 joins on the downstream side of the heat transfer tubes 104, the flow rate of the cleaning liquid measured by the flow meter 21 can be regarded as the total flow rate in each of the plurality of heat transfer tubes 104. can. Therefore, by dividing the flow rate measured by the flow meter 21 by the number of heat transfer tubes 104, the flow rate per heat transfer tube 104 (or the average flow rate in each of the plurality of heat transfer tubes 104) can be calculated. can.

Also, since the temperature of the cleaning liquid flowing out from the plurality of heat transfer tubes 104 to the circulation line 106 does not change abruptly, the temperature measured by the temperature sensor 22 can be regarded as the temperature of the cleaning liquid at the outlet of the heat transfer tubes 104.

Based on the signals received from the flowmeters 21 and 23 and the temperature sensors 22 and 24, the control device 20 determines the output of the heater 16 (temperature control unit) and the number of revolutions of the pump 14 (flow control unit) (more specifically, is configured to control the frequency of the inverter for driving the motor that drives the pump 14 . Thus, controller 20 can be used to regulate the temperature and flow rate of the cleaning liquid supplied to test strip holder 32 .

2-4 are schematic diagrams of a corrosion rate measurement device 30, respectively, according to one embodiment. 5-6 are schematic cross-sectional views of a test strip holder 32 according to one embodiment. The first sealing member 46 and the second sealing member 48 shown in FIG. 6 have the same shape as the first sealing member 46 and the second sealing member 48 shown in FIGS.

As shown in FIGS. 2 to 4, the corrosion rate measuring device 30 includes a test piece holder 32 for holding a tubular test piece 200 and electrodes (a sample electrode, a counter electrode, and a reference electrode) provided on the test piece holder 32. and an electrochemical measuring device 90 having terminals to be connected.

As shown in FIGS. 2 to 4, the test piece holder 32 includes a holder body 34 including a first holder portion 36 and a second holder portion 38, a first flow path 40 provided in the first holder portion 36, a second A second flow path 42 provided in the second holder portion 38 , and a first seal member 46 and a second seal member 48 are provided. The test piece holder 32 also includes a fastening portion 50 for fastening the first holder portion 36 and the second holder portion 38 together, and a conductive portion 56 provided on the outer peripheral surface of the tubular test piece 200 .

The first holder portion 36 and the second holder portion 38 are configured to sandwich and hold the tubular test piece 200 from both sides in the axial direction of the tubular test piece 200 . The holder main body 34 including the first holder portion 36 and the second holder portion 38 may be made of an insulating material such as resin.

As shown in FIGS. 5 and 6, the tubular test strip 200 has an outer peripheral surface 202 and an inner peripheral surface 204, the inner peripheral surface 204 forming an internal flow path 201 of the tubular test strip 200. .
As shown in FIGS. 2 to 4, the first flow path 40 is provided in the first holder part 36 so as to communicate with the internal flow path 201 of the tubular test strip 200 . Also, the second flow path 42 is provided in the second holder part 38 so as to be able to communicate with the internal flow path 201 of the tubular test piece 200 . In the illustrated embodiment, the first channel 40 and the second channel are provided along the axial direction of the tubular test piece 200 .

A cleaning liquid inlet portion 58 and a cleaning liquid outlet portion 60 are provided at both ends of the holder main body 34 in the pipe axis direction. The cleaning liquid inlet portion 58 includes a joint portion 59 that connects the branch line 12 (see FIG. 1) and the second flow path 42 . The cleaning liquid outlet portion 60 includes a joint portion 61 that connects the branch line 12 and the first channel 40 . In the illustrated embodiment, the cleaning liquid outlet portion 60 is provided on the first holder portion 36 side, and the cleaning liquid inlet portion 58 is provided on the second holder portion 38 side. The cleaning liquid inlet portion 58 may be provided on the holder portion 36 side, and the cleaning liquid outlet portion 60 may be provided on the second holder portion 38 side.

The first sealing member 46 is configured to suppress leakage of cleaning liquid between the first holder portion 36 and the tubular test piece 200 . The second sealing member 48 is configured to suppress leakage of cleaning liquid between the second holder portion 38 and the tubular test piece 200 .

In the above-described embodiment, the tubular test piece 200 is sandwiched and held between the first holder portion 36 and the second holder portion 38 via the seal members 46 and 48, and communicates with the internal flow path 201 of the tubular test piece 200. Since the first channel 40 and the second channel 42 are provided, a fluid (such as a cleaning solution) can flow through the internal channel 201 of the tubular test strip 200 via the first channel 40 and the second channel 42. can be made As a result, various measurements (eg, electrochemical measurements) can be performed while the liquid is circulating in the internal flow path 201 of the tubular test piece 200, and the corrosion rate of the inner surface of the tubular test piece 200 can be measured.

The fastening portion 50 is configured to fasten the first holder portion 36 and the second holder portion 38 with the tubular test piece 200 sandwiched between the first holder portion 36 and the second holder portion 38 . . As a result, the pressure resistance and sealing performance of the test piece holder 32 can be improved. Therefore, it is possible to obtain the test strip holder 32 that can handle a wide range of fluid flow conditions.

In the exemplary embodiment shown in FIGS. 2-4, the fastening portion 50 is inserted through the bolt holes 37 provided in the first holder portion 36 and the bolt holes 39 provided in the second holder portion 38. It includes a bolt 52 and a nut 54 threaded onto the bolt 52 . In this case, with a simple configuration including the bolt 52 and the nut 54, the test strip holder 32 can have good pressure resistance and sealing performance.

In some embodiments, for example, as shown in FIGS. 5 and 6, the first holder portion 36 is provided with a concave portion 62 for receiving the first seal member 46 on the end face 36a in the tube axial direction. The recess 62 has a shape corresponding to the cross-sectional shape of the first seal member 46 . In some embodiments, as shown in FIGS. 5 and 6, for example, the second holder portion 38 is provided with a concave portion 64 for receiving the second seal member 48 on the end face 38a in the tube axial direction. . The recess 64 has a shape corresponding to the cross-sectional shape of the second seal member 48 .

As described above, since the recess 62 is provided in the end surface 36a of the first holder portion 36 in the tube axis direction, the first holder portion of the first seal member 46 is fitted into the recess 62 by fitting the first seal member 46 therein. Positioning with respect to the portion 36 is facilitated, and sealing performance by the first sealing member 46 can be enhanced. The same description applies to the recessed portion 64 provided in the second holder portion 38 as well.

In some embodiments, the first sealing member 46 includes a disk portion 120 provided to contact the bottom surface 62a of the recess 62, as shown in FIGS. 5-6, for example. The disk portion 120 is provided so as to be sandwiched between the bottom surface 62a of the recess 62 and one end surface 206 of the tubular test piece 200 in the tube axial direction. A through-hole 124 is provided in the central portion of the disk portion 120, and the internal flow path 201 of the tubular test piece 200 and the first flow path 40 can communicate with each other through the through-hole 124. there is

In some embodiments, the second seal member 48 includes a disk portion 126 provided to contact the bottom surface 62a of the recess 64, as shown in FIGS. 5-6, for example. The disk portion 126 is provided so as to be sandwiched between the bottom surface 64a of the recess 64 and the other end surface 208 of the tubular test piece 200 in the tube axial direction. A through hole 130 is provided in the central portion of the disk portion 126, and the internal flow path 201 of the tubular test piece 200 and the second flow path 42 can communicate with each other through the through hole 130. there is

As described above, since the disc portion 120 of the first seal member 46 is in contact with the bottom surface 62a of the recess 62 provided in the end surface 36a of the first holder portion 36, the contact area between the first seal member 46 and the recess 62 is can be maintained large, thereby enhancing the sealing performance of the first sealing member 46 . The same description applies to the second seal member 48 as well.

In some embodiments, for example, as shown in FIG. 6, the first seal member 46 further includes a cylindrical portion 122 that protrudes from the disk portion 120 in the tube axial direction to the side opposite to the bottom surface 62a of the recess 62. . In some embodiments, the second seal member 48 further includes a cylindrical portion 128 that protrudes from the disk portion 126 to the side opposite to the bottom surface 64a of the recess 64 in the pipe axial direction.

According to the above-described embodiment, the first seal member 46 has the cylindrical portion 122 that protrudes from the disk portion 120 on the side opposite to the bottom surface 62a of the recess 62 in the tube axial direction. is set according to the outer diameter D2 (see FIG. 6) of the tubular test piece 200, it becomes easier to position the tubular test piece 200 in the plane perpendicular to the tube axis direction. In addition, since the inner diameter of the tubular portion 122 can be set according to the outer diameter D2 of the tubular test piece 200, the first seal member 46 can have an appropriate inner diameter size for one test piece holder 32. , a plurality of types of tubular test pieces 200 having different outer diameters can be used as test objects. The same description applies to the second seal member 48 as well.

The first sealing member 46 shown in FIG. 5 and the second sealing member 48 shown in FIG. Since the first sealing member 46 shown in FIG. 5 does not have the tubular portion 122, it can be used even when the outer diameter D1 of the tubular test piece 200 is relatively large. Note that the outer diameter D1 of the tubular test piece 200 in FIG. 5 is larger than the outer diameter D2 of the tubular test piece 200 in FIG.

The conductive portion 56 (see FIGS. 2 to 4) is for connecting the outer surface of the tubular test piece 200 to the sample electrode terminal 96 of the electrochemical measuring device 90 . The conductive portion 56 is provided between the first holder portion 36 and the second holder portion 38 so as to be in contact with the outer surface of the tubular test piece 200 . Also, the conductive portion 56 can be electrically connected to the tubular test piece 200 . The conductive portion 56 and the sample electrode terminal 96 of the electrochemical measurement device 90 may be connected via a lead wire.

As described above, since the conductive portion 56 electrically connected to the outer surface of the tubular test piece 200 is provided between the first holder portion 36 and the second holder portion 38, the electric current is generated via the conductive portion 56. A tubular test piece 200 can be connected to the sample electrode terminal 96 of the chemical measurement device 90 . Therefore, as a result, it is possible to perform electrochemical measurement (for example, measurement of the polarization resistance of the inner surface of the tubular test piece 200) on the tubular test piece 200 while circulating the liquid in the internal channel 201 of the tubular test piece 200, and the measurement result , the corrosion rate of the inner surface of tubular test piece 200 can be measured.

In some embodiments, conductive portion 56 may include metal clamps that are provided to clamp tubular test strip 200 . Alternatively, in some embodiments, conductive portion 56 may be a weld provided to secure the end of the lead to the outer surface of tubular test strip 200 . The welded portion may be formed by spot welding. 5 and 6, illustration of the conductive portion 56 is omitted.

In some embodiments, for example, as shown in FIGS. 2 and 4, the test strip holder 32 includes a counter electrode 66 connected to the counter electrode terminal 92 of the electrochemical measurement device 90 and a reference electrode of the electrochemical measurement device 90. and a reference electrode 72 connected to the terminal 94 for. The counter electrode 66 may be provided on the holder body 34 so as to be exposed to the first channel 40 or the second channel 42 . The reference electrode 72 may be provided on the holder body 34 so as to be exposed to the first channel 40 or the second channel 42 . The counter electrode 66 may be a platinum electrode.

2 and 4, the counter electrode 66 and the reference electrode 72 are provided on the first holder part 36 (holder main body 34) so as to be exposed to the first flow path 40. . More specifically, the counter electrode 66 is inserted into a hole 68 provided in the first holder portion 36 so as to connect the side surface of the first holder portion 36 and the first flow channel 40, and is inserted into the first flow channel 40. 40 is supported by the first holder portion 36 via the fixing portion 80 . Further, the reference electrode 72 is inserted into a hole 74 provided in the first holder portion 36 so as to connect the side surface of the first holder portion 36 and the first flow path 40, and is exposed to the first flow path 40. In this state, it is supported by the first holder portion 36 via the fixing portion 80 .

According to the above-described embodiment, the corrosion rate of the inner surface of the tubular test piece 200 can be measured by the polarization resistance measurement by the three-electrode method using the sample electrode, the counter electrode 66 and the reference electrode 72 which are the tubular test piece 200. can. Therefore, the corrosion rate can be measured with relatively high accuracy.

In some embodiments, the holder body 34 is a separate tubular test strip 200 held between the first holder portion 36 and the second holder portion 38, for example, as shown in FIGS. A third holder portion 144 is included for holding the tubular test strip 210 . The third holder portion 144 is provided so as to face either the first holder portion 36 or the second holder portion 38 (the second holder portion 38 in FIGS. 3 and 4) in the tube axis direction. The test piece holder 32 provides a third flow path 146 provided in the third holder portion 144 so as to communicate with the internal flow path 211 of the tubular test piece 210 , and between the third holder portion 144 and the tubular test piece 210 . and a third sealing member 112 for sealing. A conductive portion 116 is provided on the outer peripheral surface of the tubular test piece 210 , and the tubular test piece 210 and the sample electrode terminal 98 of the electrochemical measurement device 90 are connected via the conductive portion 116 .

According to the above-described embodiments, there are two tubular test strips 200 held between the first holder portion 36 and the second holder portion 38 and another tubular test strip 210 held by the third holder portion 144 . Using two tubular test pieces 200 and 210 as sample electrodes, the corrosion rate of the inner surfaces of the tubular test pieces 200 and 210 can be measured by polarization resistance measurement by the two-electrode method. Therefore, the corrosion rate can be measured with a relatively simple configuration.

It should be noted that the exemplary embodiments shown in FIGS. 3 and 4 have the features described below.

The third seal member 112 is provided in a recessed portion 114 provided in the end face of the third holder portion 144 in the pipe axis direction. A seal member 148 is also provided for sealing between the second holder portion 38 and the tubular test piece 210 . The seal member 148 is provided in a recess 140 provided in the end face of the second holder portion 38 in the pipe axis direction. The third channel 146 extends along the axial direction of the tubular test piece 210 . The two tubular test strips 200 and 210 are arranged substantially coaxially, the first channel 40, the internal channel 201 of the tubular test strip 200, the second channel 42, and the internal channel 211 of the tubular test strip 210. , and the third flow path 146 form one flow path extending along the tube axis direction.

In the exemplary embodiment shown in FIGS. 3 and 4, fastening portion 50 sandwiches tubular test strip 200 between first holder portion 36 and second holder portion 38 and tubular test strip 210 is held between second holder portion 36 and second holder portion 38 . The first holder portion 36 , the second holder portion 38 , and the third holder portion 144 are configured to be fastened while sandwiched between the holder portion 38 and the third holder portion 144 . The bolt 52 of the fastening portion 50 is inserted through the bolt hole 37 provided in the first holder portion 36, the bolt hole 39 provided in the second holder portion 38, and the bolt hole 145 provided in the third holder portion 144. A nut 54 is screwed onto the bolt 52 . Note that the third holder portion 144 may be made of an insulating material such as resin.

In the exemplary embodiment shown in FIG. 4, one of the two sample electrodes (tubular test piece 200 or tubular test piece 210), a counter electrode 66 and a reference electrode 72 are used to perform polarization resistance measurements by the three-electrode method. It can be carried out. Therefore, one of the two sample electrodes (tubular test piece 200 or tubular test piece 210) is used for measurement, and if a problem occurs in one of the sample electrodes, the other sample electrode is used to Polarization resistance measurements can be continued.

In addition, in the embodiment shown in FIG. 4, the polarization resistance can be measured by the above-described three-electrode method, and the polarization resistance can be measured by the two-electrode method using two sample electrodes (tubular test piece 200 and tubular test piece 210). can also Therefore, the polarization resistance measurement can be continued by switching the measurement method between the three-electrode method and the two-electrode method, such as switching to the two-electrode method when an abnormality occurs in the reference electrode 72 or the counter electrode 66 .

Thus, according to the embodiment shown in FIG. 4, the availability of the measuring device can be improved.

Hereinafter, a corrosion amount measuring method according to one embodiment will be described with reference to FIGS. 1 and 7. FIG. FIG. 7 is an example of a graph showing temporal changes in the dissolved iron concentration in the cleaning liquid obtained by the method for measuring the amount of corrosion according to one embodiment. In the following, a method of measuring the amount of corrosion during chemical cleaning of tubular test pieces sampled from the heat transfer tubes 104 of the boiler 100 will be described.

First, heat transfer tubes to be used as test pieces are sampled from the plurality of heat transfer tubes 104 provided in the boiler 100 whose operation has been stopped, and tubular test pieces 200 are produced from the heat transfer tubes. Also, the tubular test piece 200 thus produced is placed in the test piece holder 32 . Note that the inner surface of the tubular test piece 200 obtained as described above usually has scale generated during operation of the boiler 100 adhered thereto.

Next, the cleaning liquid circulation line 2 is connected to the plurality of heat transfer tubes 104 of the boiler 100 via the circulation line 106 , and the cleaning liquid from the cleaning liquid tank 8 is circulated through the cleaning liquid circulation line 2 to heat the plurality of heat transfer tubes 104 . Wash.

A branch line 12 is connected to the cleaning liquid circulation line 2, and the cleaning liquid branched from the cleaning liquid circulation line 2 is supplied to the test piece holder 32 (corrosion rate measuring device 30) through the cleaning liquid inlet 58 and the cleaning liquid outlet 60. It flows through the second channel 42 , the internal channel 201 of the tubular test piece 200 and the first channel 40 . Then, the polarization resistance of the tubular test piece 200 is measured using the corrosion rate measuring device 30, and the concentration of iron derived from corrosion during cleaning is calculated from the measurement result of the polarization resistance.

Here, a procedure for calculating the concentration of iron derived from corrosion during cleaning from the measurement result of the polarization resistance will be described.
First, the corrosion current density i _corr can be calculated from the following formula (A) based on the measurement result R _p of the polarization resistance.
i _corr =B/R _p (A)
B in the above formula (A) is a constant.
Next, the corrosion weight loss Δm (g/cm ² ) of the base material in the tubular test piece can be calculated from the calculation result of the above formula (A) and the following formula (B).
i _corr ×t=F×Δm×z/M (B)
In the above formula (B), t is the polarization resistance measurement time (s), F is the Faraday constant, z is the valence of the iron ion (2), and M is the atomic weight of iron (55.845). is.
Then, the iron concentration C _Fe derived from base metal corrosion can be calculated from the calculation result of the above formula (B) and the following formula (C).
C _Fe = Δm × A/W (C)
A in the above formula (C) is the total inner surface property of the plurality of heat transfer tubes 104 to be chemically cleaned, and W is the amount of water retained in the cleaning liquid in the heat transfer tubes 104 .

In practice _, the polarization resistance _Rp measured by the above-described apparatus changes over time. The iron concentration C _Fe can be determined.

In addition, if the flow state inside the actual heat transfer tube 104 can be reproduced in the flow path in the test piece holder 32, the heat transfer tube 104 It is possible to accurately calculate the iron concentration C _Fe derived from the corrosion of the base material in the cleaning solution in .

In some embodiments, the following steps are further performed to reproduce the cleaning conditions (temperature and flow rate of the cleaning liquid) of the heat transfer tubes 104 in the actual boiler 100 in the test piece holder 32 (corrosion rate measuring device 30). can be

In some embodiments, the flow meter 21 and temperature sensor 22 are used to measure the flow rate F1 and temperature T1 of the cleaning liquid in the plurality of heat transfer tubes 104 while the plurality of heat transfer tubes 104 are being cleaned. The measurement results of the flow rate F1 and the temperature T1 are sent to the control device 20 .

Also, using the flowmeter 23 and the temperature sensor 24, the flow rate F2 and temperature T2 of the cleaning liquid in the internal flow path 201 of the tubular test piece 200 in the test piece holder 32 are measured. The measurement results of the flow rate F2 and the temperature T2 are sent to the control device 20 .

Based on the obtained measurement results of the flow rates F1 and F2 and the temperatures T1 and T2, the control device 20 controls the flow rate and temperature of the cleaning liquid flowing through the internal flow path 201 of the tubular test strip 200 in the test strip holder 32 to be a plurality of values. The rotational speed of the pump 14 (flow control unit) and the output of the heater 16 (temperature control unit) are controlled so that the flow rate and temperature in the heat transfer tube 104 are approximated.

The controller 20 performs feedback control (for example, P control, PI control, or PID control) on the flow rate and temperature of the cleaning liquid flowing through the internal flow path 201 of the tubular test piece 200 in the test piece holder 32 based on the above measurement results. may

For example, the control device 20 sets the flow rate F1 of the cleaning liquid in the heat transfer tube 104 as a target value, the measured value F2 of the flow rate of the cleaning liquid flowing through the internal flow path 201 of the tubular test strip 200 in the test strip holder 32, and the target value F1. Based on the deviation, the rotation speed of the pump 14 and/or the inverter frequency corresponding to this that reduces the deviation is calculated, and the calculated inverter frequency is given to the inverter as a control command value. good.

Alternatively, the control device 20 sets the temperature T1 of the cleaning liquid in the heat transfer tube 104 as a target value, and the measured value T2 of the temperature of the cleaning liquid flowing through the internal flow path 201 of the tubular test strip 200 in the test strip holder 32 and the above-mentioned target value T1. Based on the deviation, an output of the heater 16 that reduces the deviation may be calculated, and the calculated output value may be given to the heater 16 as a control command value.

According to the method according to the above-described embodiment, the temperature T2 and the flow rate F2 of the cleaning liquid introduced into the corrosion rate measuring device 30 are brought close to the flow rate F1 and the temperature T2 in the heat transfer tubes 104 of the boiler 100. Since the temperature control unit is controlled, the washing state of the heat transfer tubes 104 of the boiler 100 can be simulated in more detail within the corrosion rate measuring device 30 . Therefore, the corrosion rate measuring device 30 can be used to accurately calculate the iron concentration C _{2 Fe} in the cleaning liquid in the heat transfer tube 104 .

In the corrosion amount measuring method according to some embodiments, first, the scale adhesion amount (weight) of the scale-adhered test piece (such as the tubular test piece 200 taken from the heat transfer tube 104) is measured, and based on the measurement result Then, a predicted value Cs_est (see FIG. 7) of the iron concentration in the cleaning liquid (iron concentration _C derived from scale) is obtained assuming that the entire amount of scale adhering to the test piece has been removed by cleaning with the cleaning liquid.

Next, for example, using the corrosion rate measuring device 30 described above, the test piece is washed with the cleaning liquid, and the polarization resistance is measured using the test piece. Calculate the iron concentration C _Fe of . The procedure for calculating the iron concentration C _{2 Fe} derived from base metal corrosion based on the polarization resistance has already been described.

In addition, the total iron concentration _CT in the cleaning liquid is measured while cleaning the test piece with the cleaning liquid. That is, the cleaning solution during cleaning of the test piece is sampled, for example, at predetermined time intervals, and the total iron concentration _CT contained in the sample cleaning solution is measured by various analysis methods.

_Then , the scale-derived iron concentration _{CS is calculated from the difference between the measured value of the total iron concentration C T} obtained in this way and the calculated value of the iron concentration C _Fe derived from base metal corrosion. That is, the scale-derived iron concentration Cs can be expressed by the following formula (D).
C _S = C _T - C _Fe ... (D)

Therefore, by comparing the scale-derived iron concentration Cs calculated in this way with the predicted value Cs_est predicted in advance, it is possible to grasp the progress of cleaning of the test piece. That is, as shown in FIG. The scale-derived iron concentration Cs gradually increases as the cleaning progresses, but if the scale-derived iron concentration Cs is sufficiently close to the predicted value Cs_est, it means that most of the scale adhering to the test piece has been removed. Therefore, the end timing of the chemical cleaning of the test piece or heat transfer tube 104 can be timely determined.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and modes in which these modes are combined as appropriate.

As used herein, expressions such as "in a certain direction", "along a certain direction", "parallel", "perpendicular", "central", "concentric" or "coaxial", etc. express relative or absolute arrangements. represents not only such arrangement strictly, but also the state of being relatively displaced with a tolerance or an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which express that things are in the same state, not only express the state of being strictly equal, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
Further, in this specification, expressions representing shapes such as a quadrilateral shape and a cylindrical shape not only represent shapes such as a quadrilateral shape and a cylindrical shape in a geometrically strict sense, but also within the range in which the same effect can be obtained. , a shape including an uneven portion, a chamfered portion, and the like.
Moreover, in this specification, the expressions “comprising”, “including”, or “having” one component are not exclusive expressions excluding the presence of other components.

1 cleaning system 2 cleaning liquid circulation line 4 circulation pump 6 cleaning liquid supply line 8 cleaning liquid tank 10 injection pump 11 upstream end 12 branch line 13 downstream end 14 pump 16 heater 20 controller 21 flow meter 22 temperature sensor 23 flow meter 24 temperature sensor 30 corrosion Velocity measuring device 32 Specimen holder 34 Holder main body 36 First holder part 36a End surface 37 Bolt hole 38 Second holder part 38a End surface 39 Bolt hole 40 First flow path 42 Second flow path 46 First sealing member 48 Second sealing member 50 fastening portion 52 bolt 54 nut 56 conductive portion 58 cleaning fluid inlet portion 59 joint portion 60 cleaning fluid outlet portion 61 joint portion 62 concave portion 62 a bottom surface 64 concave portion 64 a bottom surface 66 counter electrode 68 hole 72 reference electrode 74 hole 80 fixing portion 90 electrochemical measuring device 92 Counter electrode terminal 94 Reference electrode terminal 96 Sample electrode terminal 98 Sample electrode terminal 100 Boiler 102 Furnace 104 Heat transfer tube 105 First connection point 106 Circulation line 107 Valve 108 Second connection point 109 Valve 110 Steam separator 112 Third seal Member 114 recessed portion 116 conductive portion 120 disk portion 122 cylindrical portion 124 through hole 126 disk portion 128 cylindrical portion 130 through hole 140 recessed portion 144 third holder portion 145 bolt hole 146 third flow path 148 sealing member 200 tubular test piece 201 inside Channel 202 Outer peripheral surface 204 Inner peripheral surface 206 End surface 208 End surface 210 Tubular test piece 211 Internal channel

Claims (14)

a holder body including a first holder portion and a second holder portion for holding the tubular test piece sandwiched from both sides in the axial direction of the tubular test piece;
a first channel provided in the first holder part so as to communicate with the internal channel of the tubular test piece;
a second flow path provided in the second holder portion so as to communicate with the internal flow path of the tubular test piece;
a first sealing member for sealing between the first holder portion and the tubular test piece;
a second sealing member for sealing between the second holder portion and the tubular test piece;
a counter electrode provided on the holder body so as to be exposed to the first channel or the second channel and connected to a counter electrode terminal of an electrochemical measurement device;
A specimen holder. The first holder part or the second holder part is made of an insulating material
A test strip holder according to claim 1. 3. The method according to claim 1 or 2, further comprising a conductive portion positioned between the first holder portion and the second holder portion for connecting an outer surface of the tubular test piece to a sample electrode terminal of an electrochemical measuring device. Specimen holder as described. A fastening portion for fastening the first holder portion and the second holder portion in a state in which the tubular test piece is sandwiched between the first holder portion and the second holder portion . 4. The test strip holder according to any one of 3 . The fastening portion is
a bolt inserted through a bolt hole provided in each of the first holder portion and the second holder portion;
a nut screwed onto the bolt;
5. The test strip holder of claim 4 , comprising: The test piece holder according to any one of claims 1 to 5 , wherein the first holder portion is provided with a concave portion for receiving the first seal member on an end face in the tube axis direction. 7. The test piece holder according to claim 6 , wherein the first sealing member includes a disk portion provided so as to come into contact with the bottom surface of the recess. 8. The test piece holder according to claim 7 , wherein the first seal member further includes a cylindrical portion protruding from the disk portion to the side opposite to the bottom surface of the recess in the tube axis direction. a reference electrode provided on the holder body so as to be exposed to the first channel or the second channel and connected to a reference electrode terminal of the electrochemical measurement device;
9. The test strip holder of any one of claims 1-8 , further comprising: The holder body includes a third holder portion for holding a tubular test piece other than the tubular test piece held between the first holder portion and the second holder portion,
The third holder portion is positioned to face one of the first holder portion and the second holder portion in the tube axis direction,
a third channel provided in the third holder part so as to communicate with the internal channel of the other tubular test piece;
a third sealing member for sealing between the third holder portion and the other tubular test piece;
10. The test strip holder of any one of claims 1-9 , comprising: A cleaning system for cleaning a plurality of heat transfer tubes provided in a boiler,
A test strip holder according to any one of claims 1 to 10 ;
a cleaning liquid circulation line connected to the plurality of heat transfer tubes for circulating a cleaning liquid through the plurality of heat transfer tubes;
a branch line branched from the cleaning liquid circulation line and connected to the first flow path or the second flow path of the test strip holder;
a temperature control unit for controlling the temperature of the cleaning liquid introduced into the test strip holder through the branch line;
a flow rate adjusting unit for adjusting the flow rate of the cleaning liquid introduced into the test strip holder through the branch line;
a control unit for controlling the temperature control unit and the flow rate control unit;
Heat transfer tube cleaning system. placing the tubular test strip in a test holder according to any one of claims 1 to 10 ;
a step of supplying a cleaning liquid to the internal channel of the tubular test strip through the first channel and the second channel to clean the tubular test strip with the cleaning liquid;
measuring the polarization resistance of the tubular specimen during washing with the washing solution;
a step of calculating the concentration of iron derived from corrosion during the cleaning from the measurement result of the polarization resistance;
Corrosion amount measurement method. a step of measuring the amount of scale adhered to the test piece;
a step of predicting the iron concentration in the cleaning liquid based on the scale deposition amount, assuming that the entire amount of scale adhering to the test piece has been removed by cleaning with the cleaning liquid;
A step of measuring the polarization resistance using the test piece while washing the test piece with the cleaning solution, and calculating the concentration of corrosion-derived iron in the cleaning solution from the measurement result of the polarization resistance;
measuring the total iron concentration in the cleaning solution while cleaning the test piece with the cleaning solution;
calculating the scale-derived iron concentration in the cleaning solution from the difference between the measured total iron concentration and the calculated corrosion-derived iron concentration;
Corrosion amount measurement method. a prediction unit that predicts the iron concentration in the cleaning liquid based on the amount of scale adhered to the test piece when it is assumed that the entire amount of scale adhering to the test piece has been removed by cleaning with the cleaning liquid;
a polarization resistance measuring unit that measures the polarization resistance using the test piece while cleaning the test piece with the cleaning solution;
a first calculation unit that calculates the concentration of corrosion-derived iron in the cleaning solution from the measurement result of the polarization resistance;
a concentration measuring unit that measures the total iron concentration in the cleaning liquid while cleaning the test piece with the cleaning liquid;
a second calculator for calculating the scale-derived iron concentration in the cleaning solution from the difference between the measured total iron concentration and the calculated corrosion-derived iron concentration;
Corrosion amount measuring device.

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