JP2007017186A - Calculation method of thinning rate of flow-accelerated corrosion, and diagnosis method of residual service life - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate pH dependency of thinning rate by flow-accelerated corrosion by hot water or erosion/corrosion and to precisely predict service life when the pH is varied. <P>SOLUTION: In the method of calculating the thinning rate by flow acceleration corrosion (FAC) by flow water at 50-250°C, the FAC thinning rate is calculated using the expression of FAC thinning rate =A×Exp(B×pH)×Fe<SP>C</SP>, where pH is a pH value of flow water, Fe is an Fe ion concentration in flow water, A, B and C are coefficients, and coefficient A is a plant coefficient peculiar to a plant. The FAC thinning rate is calculated based on past operation data including an actual measured thinning amount, an operation time, water quality pH measured value, and water quality Fe concentration measured value. The residual service life is calculated based on the calculated FAC thinning rate and residual thickness to a limit thickness. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a combined cycle exhaust heat recovery boiler combined with nuclear power generation equipment, thermal power generation equipment, gas turbine power generation, a heat exchanger of a chemical apparatus, etc., with carbon steel and Cr amount of 1% or less by flowing hot water or flowing hot water. The present invention relates to a remaining life diagnosis method and a suppression method for flow accelerated corrosion damage in CrMo steel pipes and heat transfer tubes.

  Nuclear power generation equipment (pressurized water type, boiling water type, fast breeder reactor, HTTR), thermal power generation equipment, waste heat recovery boiler (HRSG), heat exchangers for chemical equipment, such as equipment that handles flowing hot water or flowing hot water, piping, and In heat transfer tubes, thinning damage called Flow Accelerated Corrosion (FAC), sometimes called erosion / corrosion, can occur. This material damage is said to be caused by a combination of flowing water having a temperature of 50 to 250 ° C., a material of carbon steel, a water quality of low dissolved oxygen, and a pH of 9.3 or less, but the details are not clear.

  Even under the same structure and water quality conditions, the rate of thinning varies from 0 to 1 mm / 10 kh and occurs locally and suddenly, making it difficult to predict and manage.

  FIG. 8 shows a system configuration and a water-steam system of a typical exhaust heat recovery boiler. The HRSG is constituted by a combination of a economizer, an evaporator, a superheater, a drum, and related equipment and piping in order to recover exhaust heat in the exhaust gas from the gas turbine. According to FIG. 8, the high pressure superheater 11, the low pressure superheater 10, the high pressure evaporator 9, the denitration device 14, the high pressure economizer 7, the low pressure evaporator 5, and the low pressure are sequentially arranged from the upstream side of the exhaust gas from the gas turbine (not shown). The economizers 3 are arranged, the steam discharged from the steam turbine 12 is condensed by the condenser 13, supplied to the low-pressure economizer 3 by the low-pressure feed pump 2, and further pressurized by the high-pressure feed pump 6. It is configured to be supplied to the economizer 7 and fed into the drum D.

  In the HRSG economizer system, thinning damage called flow accelerated corrosion (FAC) due to flowing hot water can occur. The details of this material damage are not necessarily clear, and in particular, the effects of flow and flow velocity are not clarified, and FAC may occur unexpectedly at the shape discontinuity part even in the low flow velocity region. is there.

FIG. 4 shows a model of flow accelerated corrosion and its factor when a bend pipe is used as a representative. In FIG. 4, it represents that a fragile oxide film is generated under water quality conditions such as temperature, dissolved oxygen concentration, pH, and N ₂ H ₄ concentration. Is illustrated. In addition, thinning is accelerated by suspended wear substances, eddy currents, and drift currents. In drift parts, eddy currents and circulation flows are likely to occur, and the damaged surface often exhibits ripple marks (wind ripples or sand ripples) in which dimples are arranged. .

As a conventional technique for preventing erosion / corrosion or predicting the life, for example, as shown in Patent Document 1, it has been proposed to prevent alkaline corrosion and erosion / corrosion by controlling pH and ammonia concentration. As a conventional technique, for example, as shown in Patent Document 2, it has been proposed to manage the pipe plate thickness measurement data by erosion / corrosion in a database and predict the life.
JP 2002-180804 A JP 2001-280599 A

  FIG. 5 shows the result of arranging the flow accelerated corrosion rate by the flowing hot water or hot water investigated and collected by the inventors of the present application by temperature. Similar to the report by Chexal et al. (B. Chexal et al .: EPRI Report TR-106611-Rl 1998-7), flow accelerated corrosion becomes prominent in the temperature range of 50 to 250 ° C and peaks at 150 ° C. ing. FIG. 5 shows the data of the water quality pH of 9.1 to 9.2 and the average flow velocity of 2 to 4 m / s. As is clear from FIG. 5, there is a large variation in the thinning rate even at the same temperature. There is a problem that the rate of thinning cannot be calculated from the water quality conditions.

  When thinning is detected by periodic inspections, etc., the remaining life is diagnosed with a margin up to the wall thickness required for design (design wall thickness or limit wall thickness). For example, in the case of an initial thickness of 12 mm, a required design thickness (limit thickness) of 6 mm, and a thickness of 8 mm after operating for 10 years, the thickness reduction rate = (12−8) /10=0.4 mm / year, remaining life = (8-6) /0.4=5 years.

  If it is assumed that the wall thickness will be less than the required design thickness by the next periodic inspection, the equipment must be renewed during the current regular inspection period, but the equipment may not be renewed due to the regular inspection period or material preparation. It is necessary to take life-prolonging measures such as reducing the thickness reduction and shortening the operation time.

The most common technique for reducing the flow accelerated corrosion rate is to increase the water quality pH, and it is known that it can be practically prevented by increasing the pH to 9.4 or higher. For example, Bignold et al. : Proc 8th International Conference on Metallic Corrosion, Mainz 1981. Therefore, in water treatment with nuclear power, thermal power, HRSG, etc., ammonia (NH ₃ ) and hydrazine (N ₂ H ₄ ) are added to adjust the pH and reduce the dissolved oxygen concentration. However, an excessively a high pH, NH ₃ is on lines NH ₃ and N ₂ H ₄ occurs by decomposition, the evaporator enters the condenser via a superheater and a turbine, is condenser material Since an ammonia attack is caused to the steel alloy, there is a situation that a pH raising measure cannot be immediately adopted. Moreover, in a plant equipped with a condensate deionizer (condenser demineralizer: also referred to as “condemi”), an increase in pH leads to an increase in ionized products, resulting in an increase in the frequency of regeneration of ion exchange resins.

  On the other hand, the life expectancy has been calculated as described above, assuming that the thinning rate due to flowing water such as flow accelerated corrosion and erosion / corrosion does not change over time. It can be considered that the conventional constant speed evaluation results in an unsafe diagnosis.

  In addition, the techniques disclosed in Patent Documents 1 and 2 described above are a method for preventing thinning due to water treatment or a life prediction method based on analysis of actual data, and consideration is not given to changes with time in the thinning rate.

  The purpose of the present invention is to evaluate and diagnose the pH dependence of the rate of thinning due to flow accelerated corrosion and erosion / corrosion caused by high-temperature water, and to predict the life with high accuracy when the pH is changed. The object is to provide a high-accuracy remaining life diagnosis method in consideration of changes over time.

In order to solve the above problems, the present invention mainly adopts the following configuration.
In the method of calculating the rate of thinning by flow accelerated corrosion (FAC) with flowing hot water or flowing hot water at 50 to 250 ° C.,
The FAC thinning rate is calculated using the formula: FAC thinning rate = A × Exp (B × pH) × Fe ^C ,
Here, pH is the pH value in the flowing hot water or flowing hot water, Fe is the Fe ion concentration in the flowing hot water or flowing hot water, A, B, C are coefficients, and the coefficient A is a factor for the plant. Calculation method of flow accelerated corrosion thinning rate that is a unique plant coefficient.

  Further, in the method for calculating the flow accelerated corrosion thinning rate, the plant coefficient A is an accelerated corrosion calculated from past operation data including an actual measurement value of the thinning amount, an operation time, a water quality pH measurement value, and a water quality Fe concentration measurement value. Calculation method of thinning rate.

Moreover, in the diagnostic method of the remaining life by the damage of the flow accelerated corrosion (FAC) by 50-250 degreeC flowing hot water or flowing hot water,
The FAC thinning rate is calculated using the formula: FAC thinning rate = A × Exp (B × pH) × Fe ^C ,
Here, pH is the pH value in the flowing hot water or flowing hot water, Fe is the Fe ion concentration in the flowing hot water or flowing hot water, A, B, C are coefficients, and the coefficient A is a factor for the plant. The plant coefficient is a specific plant coefficient, and the plant coefficient A is calculated from past operation data consisting of an actual measurement value of the thinning amount, an operation time, a water quality pH measurement value, and a water quality Fe concentration measurement value,
A remaining life diagnostic method by flow accelerated corrosion damage for diagnosing the remaining life based on the FAC thinning rate, the limit wall thickness value, and the measured wall thickness value.

  According to the present invention, the pH dependence of flow accelerated corrosion of HRSG (exhaust heat recovery boiler) economizers can be predicted with high accuracy and the remaining life can be determined with high accuracy. Therefore, the power generation equipment can be operated economically and with high reliability.

  First, the basic concept of the method for calculating the flow accelerated corrosion thinning rate according to the embodiment of the present invention will be described. Flow accelerated corrosion of carbon steel with high-temperature water is based on the condition of temperature 50 to 250 ° C. (which is said to peak at around 150 ° C.) + Low dissolved oxygen concentration (30 ppb or less) + low pH (pH 9.3 or less). It is a phenomenon that occurs by combining water quality and flow. In power generation facilities and industrial plants, the temperature and flow conditions cannot be changed, so that the method of increasing dissolved oxygen concentration, increasing pH, or changing to CrMo steel is used to prevent or suppress flow accelerated corrosion.

  The increase in dissolved oxygen is a technique equivalent to boiler water supply and oxygen treatment in boiler water quality specified in JIS B-8223. However, if there are impurities, pitting corrosion occurs, so the purity of water supply and condensate is reduced. It is difficult to use for a secondary system of a PWR (Pressurized Water Reactor), an HRSG (Exhaust Heat Recovery Boiler), a chemical apparatus, a circulating boiler, and the like. Moreover, since the change to CrMo steel also leads to the renewal of large equipment, there are problems in terms of construction period and economy.

  There is a correlation between the flow accelerated corrosion rate and the feed water pH, and flow accelerated corrosion can be substantially prevented by setting the feed water pH to 9.4 or higher. FIG. 6 shows the pH dependence of the flow accelerated corrosion rate (thinning rate). The speed of various literature values was evaluated by making it dimensionless, and by increasing the pH from 9.0 to 9.4, the flow accelerated corrosion rate is reduced to 1/10 or less.

In the water supply such as PWR, thermal power, and HRSG, metal ions such as Fe ²⁺ are contained in a small amount. These metal ions change to oxides such as Fe ₃ O ₄ with an increase in pH (8.0 or more) and an increase in temperature. The present inventors have found that a metal oxide such as Fe ₃ O ₄ is a kind of ceramic and accelerates flow accelerated corrosion by flowing water due to its high hardness. It was found that the Fe ²⁺ concentration in the feed water was affected by the feed water pH, and as a result of regression analysis, it became a power law. The constitutive equation is as follows.

Predicted Fe concentration Fe = a × pH ^b (1)
Here, a and b are regression coefficients. Since the Fe concentration decreases as the pH increases, the index b takes a negative value. In addition, since the Fe concentration when the pH is changed is not uniquely determined and depends on the pH value and the Fe concentration value so far, a is a function of the actually measured values so far.

  Since the pH dependence of the flow accelerated corrosion (FAC) rate shown in FIG. 6 does not consider the Fe concentration, the pH dependence of the substantial flow accelerated corrosion (FAC) rate is an exponential law and is given by the following equation: .

FAC speed = A × Exp (B × pH) × Fe ^C (2)
Here, A, B, and C are regression indices or coefficients, and Fe is the Fe concentration (ppb) predicted by equation (1). As described above, the flow accelerated corrosion rate is affected by the flow rate, mass transfer coefficient, temperature, dissolved oxygen concentration, and Cr concentration in the material in addition to pH and Fe concentration, but these are included in the coefficient A. As will be described later, the coefficient A is specific to the part of the plant that is calculated backward from the measured value of the wall thickness or thickness reduction and the operating conditions (operating time, measured pH value, measured Fe concentration value, etc.). Coefficient (plant coefficient).

  By constructing the above equations (1) and (2), the FAC speed when the pH is changed, particularly raised, can be predicted with high accuracy. Note that the coefficient A in the equation (2) is corrected by an actual measurement value of the FAC thinning speed by the operation so far. In addition, said (1) and (2) Formula can be regressed also by an exponential law or a power law, respectively, and can be numerically expressed.

  Next, a specific example when the pH is changed in the flow accelerated corrosion thinning rate calculation method and the remaining life diagnosis method according to the embodiment of the present invention will be described. FIG. 1 shows an evaluation diagnosis flow when pH is changed in the thickness reduction rate and life prediction by flow accelerated corrosion (FAC) according to the embodiment of the present invention.

  First, the thinning rate up to the present time, the pH value of the feed water and the Fe concentration are input. The thickness reduction rate (mm / h, mm / year) can also be calculated by inputting the measurement results of the operation time (operation years), the initial wall thickness, and the wall thickness at the time of evaluation. At that time, it is desirable to measure a plurality of thicknesses to obtain a statistical maximum thinning rate. Moreover, the pH and Fe concentration of the feed water are input as average values, but if the data points are biased, it is desirable to input a weighted average value considering time or a representative average value obtained by cutting specially shifted data. .

  Next, the Fe concentration when the pH is changed is calculated by the equation (1). The FAC speed is calculated by the above equation (2). The definitions of A1 and A2 in the FAC speed equation shown in FIG. 1 will be described later. The remaining life is calculated by dividing the wall thickness up to the limit wall thickness typified by the design wall thickness (tsr) determined by the thermal nuclear technical standards by the FAC speed. If the annual operating time is almost constant, the remaining life can be calculated even in years. If the remaining life can be calculated, the renewal cycle, that is, how many times renewal is required is determined from the future operation years.

  If the remaining life or renewal time is determined according to the pH value in the future, the degree of damage to the copper alloy of the condenser due to the feed water pH will be evaluated, and the renewal time and appropriate pH will be highly accurate from the diagnosis of economics and reliability of both. Can be determined.

  The calculation method of the flow accelerated corrosion thinning rate and the remaining life diagnosis method according to the present embodiment described above are summarized as follows. That is, it can be achieved by obtaining the plant and its part-specific thinning rate in the current water quality, and calculating from the pH and Fe concentration dependence that has been previously regressed based on the rate. Specifically, it consists of the following steps.

(1) The thickness reduction rate of the evaluation target part is calculated from the results of operation time and tube thickness measurement (initial value and current thickness value). It is desirable to measure multiple points to obtain the statistical maximum thinning rate in order to improve reliability.

(2) The average or representative value of the pH and Fe concentration of the water supply up to the present time is obtained. If there is a slight change in the middle of the step, a weighted average value may be used.

(3) From the pH dependence of the Fe concentration, the Fe concentration when the pH is changed is predicted by the above equation (1).

(4) From the pH dependency and Fe concentration dependency of the FAC thinning rate, the thinning rate when the pH is changed is calculated by the above equation (2).

(5) The remaining life is calculated from the remaining thickness up to the limit thickness and the FAC thickness reduction rate calculated in (4) above.

  FIG. 2 shows a diagnostic analysis example of the remaining life and an analysis result of the water quality pH increase effect according to the embodiment of the present invention (when the FAC thinning rate is constant). This is an analysis example with an initial wall thickness of 12 mm, a wall thickness measurement result of 8 mm after 15 years of operation (current time), a limit wall thickness of 6 mm, a feed water pH of 9.1 up to the present, and an Fe concentration of up to 10 ppb. This is an example in which the annual operation time is almost constant, and if the operation time changes, the evaluation may be performed based on the operation time.

  Since it is 12-8 = 4mm thinning after 15 years of operation, the speed is 4/15 = 0.27mm / year, and the margin to the limit wall thickness (6mm) is 8-6 = 2mm, If the operation is continued under the same conditions as the current situation, 2 / 0.27 = 7.4, and 7.4 years can be calculated as the remaining life. Therefore, when the pH is increased to 9.2, 9.3 and 9.4, the remaining lifetimes can be calculated as 15 years, 29 years and 40 years or more, respectively.

  When the flow accelerated corrosion rate does not change with respect to the operating time or the number of years as shown in FIG. 2, the thinning progresses linearly. It will suffice if it is raised above. By increasing the pH to 9.4 or higher, the rate of thinning can be suppressed to a lower level and the remaining life will be greatly extended. However, the increase in pH will promote the ammonia attack of the condenser and condensate. This is not desirable in terms of the frequency of regeneration of the water purifier, and the present invention can provide an optimum pH value according to the operating life.

  As shown in the model of Fig. 4, in flow accelerated corrosion, thinning progresses, and when pitting corrosion occurs, eddy currents and circulation flows are formed, and abrasive suspended solids such as iron oxide are trapped in them. If rare, the rate of thinning increases. This is observed even with the time-lapse change of the thinning in the actual machine, and it has been experienced several times that it becomes a diagnosis on the non-safe side when it is analyzed and evaluated by the linear rule.

  FIG. 3 shows the operation and measurement data similar to FIG. 2, but the thinning progress diagram of the flow accelerated corrosion and the pH increase when the thinning rate changes with the operation years or operating hours and is accelerated over time. Shows changes in time.

  In FIG. 3, the FAC speed of the equation (2) is the following equations (3) and (4), the coefficient A is A1 × A2, A1 is a plant part coefficient, and A2 is an acceleration coefficient over time.

FAC speed = A1 × A2 × Exp (B × pH) × Fe ^C (3)
Here, A1: plant part coefficient, A2: time-dependent acceleration coefficient.

A2 = Y ^D (4)
Here, Y is the operation year or operation time, D is the time-dependent acceleration index, and D is a value calculated by regression of the flow accelerated corrosion case, and takes a value between 1.1 and 3.0. In addition, A in the equation (2) is A1 × A2 in the equation (3). Therefore, when A2 is introduced, A1 is inevitably obtained by back calculation. In the diagnosis example in FIG. 3, the remaining life to the limit wall thickness can be calculated as 3 years when the water quality remains as it is, 5 years at pH 9.2, and 9 years at pH 9.3.

As described above, in the description of the present invention, the pH dependence of the FAC rate is exponentially regressed (FAC = A × Exp (B × pH) × Fe ^C ), but power regression (FAC = D × pH ^E × Fe ^C ) can be predicted with the same accuracy, and the pH dependence of Fe concentration can be exponentially regressed. Therefore, power regression of FAC rate and exponential regression of Fe concentration are also included in the technical scope of the present invention.

  Thus, the diagnostic analysis method according to the present invention is characterized by higher accuracy because it is based on measured data. PWR, BWR, thermal power generation facility, flow accelerated corrosion with fluid hot water and fluid hot water such as HRSG, the water quality environment (temperature, pH, dissolved oxygen concentration), flow and material conditions are the same, almost the same speed It is unlikely that the thickness will be reduced, and a speed difference of up to 100 times may occur. Therefore, it was very difficult to calculate the overall thickness reduction speed, but the present invention solved the problem. It is.

  FIG. 7 shows the flow accelerated corrosion rate when the pH is increased from 9.1 to 9.4 when the Fe concentration is constant (10 ppb) without considering the pH dependence of the Fe concentration. Although it is the result evaluated only with the value, even PH 9.4 has a short remaining life, is an analysis result far from the actual, and does not become an analysis result that can be diagnosed.

  As described above, in the embodiment of the present invention, the thinning due to the flow accelerated corrosion (FAC) caused by the hot water and the high temperature water is applied to the pressurized water nuclear power (PWR) power generation facility in addition to the economizer system of the exhaust heat recovery boiler. It is generated in the secondary system, the primary system of boiling water nuclear power (BWR), and the pipes and heat transfer pipes from the condenser to the economizer of the thermal power generation facility, and the equipment including various pipes is operated safely and with high reliability. In order to achieve this, it is necessary to grasp the thinning speed at each part of the equipment with high accuracy and quantitatively determine the influence of the factors. It has been required to evaluate the effect of the corrosion control measures with high accuracy.

  Therefore, in the present invention, as the main technical idea, the rate of thinning due to flow accelerated corrosion by flowing hot water and flowing hot water at 50 to 250 ° C. is used as an index of water supply pH or a power law regression equation, and the coefficient of this equation is a plant coefficient. A, a correction index c based on the feedwater Fe concentration is introduced, and in this flow accelerated corrosion thinning rate equation, the plant coefficient A is composed of an actual value of the thinning amount, an operating time, a water quality pH measurement value, and a water quality Fe concentration measurement value. It is characterized by calculating from past operation data.

It is a figure which shows the evaluation diagnostic flow at the time of changing pH in the thinning rate by flow accelerated corrosion (FAC) which concerns on embodiment of this invention, and lifetime prediction. It is a figure which shows the diagnostic analysis example of the remaining life which concerns on embodiment of this invention, and the analysis result of the water quality pH rise effect (when FAC thinning rate is constant). It is a figure which shows the analysis analysis example of the remaining life which concerns on embodiment of this invention, and the analysis result of a water quality pH rise effect (when a FAC thinning rate is accelerated with time). It is explanatory drawing which shows the model of the flow accelerated corrosion which generate | occur | produces in a bend pipe, and its factor. It is a figure which shows the relationship between the thinning rate of the flow accelerated corrosion by flowing hot water and high temperature water, and warm water temperature. It is a figure which shows the relationship between the thinning rate of flow acceleration corrosion, and water quality pH. It is a figure which shows the analysis result at the time of water quality pH rise in the case where Fe concentration is made constant in the diagnostic analysis of a remaining life It is a block diagram which shows the conventional waste heat recovery boiler system and a water-steam system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supply water tank 2 Low pressure feed water pump 3 Low pressure economizer 4 Low pressure drum 5 Low pressure evaporator 6 High pressure feed pump 7 High pressure economizer 8 High pressure drum 9 High pressure evaporator 10 Low pressure superheater 11 High pressure superheater 12 Steam turbine 13 Condensate 14 Denitration equipment 15 Water supply chemical injection equipment 16

Claims (7)

In the method of calculating the rate of thinning by flow accelerated corrosion (FAC) with flowing hot water or flowing hot water at 50 to 250 ° C.,
The FAC thinning rate is calculated using the formula: FAC thinning rate = A × Exp (B × pH) × Fe ^C ,
Here, pH is the pH value in the flowing hot water or flowing hot water, Fe is the Fe ion concentration in the flowing hot water or flowing hot water, A, B, C are coefficients, and the coefficient A is a factor for the plant. A method for calculating the flow accelerated corrosion thinning rate characterized by a unique plant coefficient. In claim 1,
The plant coefficient A is calculated from past operation data consisting of measured values of thinning amount, operating time, measured water quality pH value, and measured water quality Fe concentration, A method for calculating an accelerated corrosion thinning rate. In the diagnostic method of remaining life due to damage of flow accelerated corrosion (FAC) caused by flowing hot water or flowing hot water of 50 to 250 ° C.,
The FAC thinning rate is calculated using the formula: FAC thinning rate = A × Exp (B × pH) × Fe ^C ,
Here, pH is the pH value in the flowing hot water or flowing hot water, Fe is the Fe ion concentration in the flowing hot water or flowing hot water, A, B, C are coefficients, and the coefficient A is a factor for the plant. The plant coefficient is a specific plant coefficient, and the plant coefficient A is calculated from past operation data consisting of an actual measurement value of the thinning amount, an operation time, a water quality pH measurement value, and a water quality Fe concentration measurement value,
A remaining life diagnosis method based on flow accelerated corrosion damage, wherein the remaining life is diagnosed based on the FAC thinning rate, the limit wall thickness value, and the measured wall thickness value. In the diagnostic method of remaining life due to damage of flow accelerated corrosion (FAC) caused by flowing water at 50 to 250 ° C. flowing through the pipe,
A first step of calculating the rate of thinning at the target site for diagnostic evaluation based on the operating time, the initial wall thickness measurement value and the current wall thickness measurement value;
A second step for obtaining an average or representative value of pH and Fe concentration of water quality up to the present time;
A third step of predicting the Fe concentration when the pH is changed from the pH dependence of the Fe concentration by using the equation: Fe = a × pH ^b a, b is a coefficient;
From the pH dependency and the Fe concentration dependency of the FAC thinning rate, the thinning rate when the pH is changed is calculated using the formula: FAC thinning rate = A × Exp (B × pH) × Fe ^C The fourth step, where A, B, and C are coefficients, the coefficient A is a plant coefficient unique to the plant, the operating time, the measured value of the thinning amount by measuring the wall thickness, the measured value of water quality pH And the water quality Fe concentration measurement value is calculated from the operation data,
A remaining life diagnosis method based on flow accelerated corrosion damage, comprising: a fifth step of calculating a remaining life from a remaining wall thickness up to a limit wall thickness and a FAC thinning rate calculated in the fourth step. In a method for suppressing damage of flow accelerated corrosion (FAC) caused by flowing hot water or flowing hot water at 50 to 250 ° C.,
The FAC thinning rate is calculated using the formula: FAC thinning rate = A × Exp (B × pH) × Fe ^C ,
Here, pH is the pH value in the flowing hot water or flowing hot water, Fe is the Fe ion concentration in the flowing hot water or flowing hot water, A, B, C are coefficients, and the coefficient A is a factor for the plant. The plant coefficient A is a specific plant coefficient, and the plant coefficient A is calculated from past operation data consisting of an actual measurement value of the thinning amount, an operation time, a water quality pH measurement value, and a water quality Fe concentration measurement value,
A flow accelerated corrosion damage suppression method characterized by obtaining a water quality pH value of a height necessary for appropriately reducing the FAC thinning rate using the characteristics of the above equation. In the diagnostic method of remaining life due to damage of flow accelerated corrosion (FAC) caused by flowing hot water or flowing hot water of 50 to 250 ° C.,
FAC thinning rate, FAC thinning rate = A1 x A2 x Exp (B x pH) x
Calculated using the formula of Fe ^C ,
Here, pH is the pH value in the flowing hot water or flowing hot water, Fe is the Fe ion concentration in the flowing hot water or flowing hot water, A1, A2, B, C are coefficients,
The coefficient A1 is a plant coefficient peculiar to the plant, and the plant coefficient A1 is calculated from the past operation data consisting of the actual measurement value of the thinning amount, the operation time, the water quality pH measurement value, and the water Fe concentration measurement value. A2 is the time acceleration factor, calculated by A2 = Y ^D, where, Y is the operating life or operating time, D is aging acceleration index,
The above FAC thinning rate indicates that it changes with the operation years or operation time Y and is accelerated over time,
A remaining life diagnosis method based on flow accelerated corrosion damage, characterized in that the remaining life is diagnosed based on the FAC thinning rate, the limit wall thickness value, and the measured wall thickness value that accelerate with time. In claim 1 or 2,
The pH dependence of the FAC thinning rate, instead of the exponential regression Exp (B × pH), power regression pH E ^E is a coefficient, meat velocity flow accelerated corrosion decrease, characterized in that calculated on the basis of the Calculation method.

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