JP2001108669A - Remaining life evaluating apparatus for heat transfer tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remaining life evaluating apparatus for a heat transfer tube capable of accurately calculating a remaining life of a heat transfer tube and effectively and rapidly grasping the remaining life of each of many heat transfer tubes. SOLUTION: A ultrasonic wave is incident from an outer peripheral surface of a heat transfer tube 3, its reflected wave is measured and a scale thickness and a tube wall thickness of the tube 3 are measured by a ultrasonic oscillation measuring apparatus 1. A processor 5 stores the scale thickness and a creep rupture strength data measured for the tube of a real machine in advance, and stores a relational formula of the measured metal temperature, the scale thickness, and a steam oxidizing speed constant obtained from data of an operating time. The processor 5 calculates a remaining life time of the tube from a calculating formula obtained from the data of an internal pressure stress, the scale thickness and the metal temperature, and calculates the stress, the life time and a life consumption ratio at each lapse of a unit operating time. Thus, an accumulated value of the unit operating time calculated based on the consumption rate becomes the remaining life time of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention calculates and evaluates the remaining life of a heat transfer tube used for a superheater or a reheater of a boiler of a thermal power plant from a scale thickness, an internal stress and the like in the tube. The present invention relates to a heat transfer tube remaining life evaluation device.

[0002]

2. Description of the Related Art For example, pipes in a furnace in a boiler of a thermal power plant are renewed relatively early from the viewpoint of wall thinning. The heat transfer tube that constitutes the joint tube is a Cr-Mo tube made of heat-resistant ferritic steel, is designed under relatively severe temperature conditions, and is used for a relatively long time. However, on the inner surface of the heat transfer tube of this type of boiler, steam oxidation scale is generally generated in proportion to the operating temperature and time, and since the steam oxidation scale is generated together with the outer surface corrosion of the tube, the wall thickness of the tube is reduced. Increases with the thickness of the scale, and aging deterioration damage such as creep damage occurs due to an increase in internal pressure generation stress and deterioration of the material. For this reason, in order to use the boiler soundly, an accurate remaining life diagnosis of the heat transfer tube is required. For this reason, conventionally, a test piece was made from a tube extracted from an actual machine, and a destructive test was performed in a laboratory, or creep damage and the like were actually measured by observing the structure with a microscope to diagnose the remaining life of the tube. .

[0003]

However, such a sampling inspection from an actual machine only evaluates the remaining life of a small part of the pipes, and usually a few heaters and reheaters are used. Hundred heat transfer tubes are provided, but the difference in metal temperature is large depending on the connection position of each heat transfer tube to be connected, and there is considerable variation in the material deterioration and wall thinning occurring in each heat transfer tube. Therefore, there was a problem that it was not possible to accurately determine the remaining life of the entire heat transfer tube by a destructive test on some of the tubes.

Therefore, a method of evaluating the remaining life of this type of heat transfer tube by a so-called scale method has been proposed (for example, Japanese Patent Application Laid-Open No. Hei 6-331622). To evaluate the remaining life of the heat transfer tube by this scale method, measure the thickness of the steam oxidation scale inside the tube using an ultrasonic oscillation measurement device,
The formation of steam oxidation scale is a thermal activation process, and the logarithm of the thickness and the temperature and time parameters can be represented by a straight line.The metal temperature is calculated from these temperature and time parameters, and further, from the internal pressure of the pipe and the like. The operating stress acting on the tube is calculated, and the remaining life of the heat transfer tube is calculated from the database of the metal temperature, the operating stress, and the creep rupture strength.

However, it is difficult to create a database of the creep rupture strength of actual equipment using the conventional method of evaluating the remaining life by this type of scale method. Although the aging of the scale thickness is measured, there is a problem that it is difficult to collect long-term data of hundreds of thousands of hours, and it is difficult to construct an actually usable system.

[0006] Further, in the conventional apparatus for evaluating the remaining life by the scale method, there is no apparatus capable of displaying the remaining life of the entire tube group at a time. There is a problem that it is difficult to quickly determine whether the remaining life has expired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to accurately calculate the remaining lives of heat transfer tubes, and to accurately and quickly grasp the remaining lives of a large number of heat transfer tubes. It is an object of the present invention to provide a heat transfer tube remaining life evaluation device.

[0008]

In order to achieve the above object, a remaining life evaluation apparatus according to the first aspect of the present invention, as shown in the block diagram of FIG. The scale thickness / tube thickness measuring means 10 for measuring the scale thickness and the tube thickness of the heat transfer tube by measuring the reflected wave.
And stress calculating means 20 for calculating the internal pressure stress from the pipe thickness measured by the scale thickness / pipe wall thickness measuring means 10, the internal pressure of the heat transfer pipe, and the outer diameter of the pipe, and the metal previously measured in the heat transfer pipe of the actual machine. The relational expression of the steam oxidation rate constant is obtained and stored from the data of the temperature, the scale thickness, and the operation time, and the metal temperature of the heat transfer tube is calculated from the relational expression and the operation time and the scale thickness of the heat transfer tube to be evaluated. A metal temperature calculating means 30 to be calculated; and a storage means 25 for storing scale thickness and creep rupture strength previously measured for a heat transfer tube of an actual machine as creep rupture strength data for each scale thickness corresponding to the internal pressure stress of the heat transfer tube. Creep rupture strength is calculated by using the measured scale thickness, the creep rupture strength data for each scale thickness written in the storage means 25, and the internal pressure stress. Rupture strength calculation means 40 and remaining life time calculation means for calculating the remaining life time of the heat transfer tube using the creep rupture strength calculated by the creep rupture strength calculation means 40 and the metal temperature calculated by the metal temperature calculation means 30 45, the wall thickness reduction rate is determined from the elapse of the operation time of the heat transfer tube and the reduction in the wall thickness, and the internal pressure stress of the pipe wall thickness that decreases in accordance with the wall reduction rate is calculated for each unit operation time. And the remaining life time calculating means 45 is used to calculate the remaining life time at the time of wall thinning, calculate the life consumption rate per unit operation time, and calculate the cumulative life consumption rate by accumulating the life consumption rates. And a remaining life calculating means 50 for setting a cumulative value of the unit operation time when the cumulative life consumption rate exceeds 1 as a remaining life time of the heat transfer tube.

[0009]

In the remaining life evaluation apparatus having the above-mentioned structure, the scale thickness and the creep rupture strength of the actual heat transfer tube are measured in advance, and the creep rupture strength data for each scale thickness corresponding to the internal pressure stress of the heat transfer tube is stored in the storage means 25. To memorize. Further, a relational expression of a steam oxidation rate constant is obtained from data of a metal temperature, a scale thickness, and an operation time measured in advance in a heat transfer tube of an actual machine, and is stored.

With respect to the heat transfer tube to be evaluated, the scale thickness and tube thickness are measured by measuring the reflected wave by irradiating an ultrasonic wave from the outer peripheral surface of the tube with the scale thickness / tube thickness measuring means 10. Measure the thickness. Then, the stress calculating means 20 calculates the internal pressure stress from the pipe thickness measured by the scale thickness / pipe thickness measuring means 10, the internal pressure of the heat transfer pipe, and the pipe outer diameter. Further, the metal temperature calculating means 30 calculates the metal temperature of the heat transfer tube from the operating time of the heat transfer tube and the scale thickness using the relational expression of the steam oxidation rate constant.

Further, the creep rupture strength calculating means 40
Calculates the creep rupture strength using the measured scale thickness, the creep rupture strength data for each scale thickness written in the storage means 25, and the internal pressure stress, and the remaining life time calculation means 45 calculates the creep rupture strength calculation means 40 Is calculated using the creep rupture strength calculated by the above and the metal temperature calculated by the metal temperature calculating means 30. Then, the remaining life calculating means 50 obtains the wall thinning rate from the elapse of the operation time of the heat transfer tube and the decrease in the wall thickness, and calculates the internal pressure stress of the pipe wall thickness which decreases in accordance with the wall thinning rate per unit operation time. Then, the remaining life time at the time of thinning is calculated using the internal pressure stress and the remaining life time calculation means 45, and the life consumption rate per unit operation time is calculated. The remaining life calculating means 50 calculates the internal pressure stress, the remaining life time, and the life consumption rate every time the unit operation time elapses, and accumulates the life consumption rate to calculate the cumulative life consumption rate. Then, the cumulative value of the unit operation time when the cumulative life consumption rate exceeds 1 is the remaining life time of the heat transfer tube.

As described above, the heat transfer tube of the actual machine is
Measure the scale thickness and creep rupture strength, store them as creep rupture strength data for each scale thickness corresponding to the internal pressure stress of the heat transfer tube, and also measure the metal temperature, scale thickness, and operating time for the same heat transfer tube The relational expression of the steam oxidation rate constant is obtained from the data and stored, and the remaining life of the heat transfer tube is calculated using the data as an arithmetic expression or the like. The life can be accurately calculated.

The remaining life calculating means calculates an internal pressure stress, a remaining life time, and a life consumption rate each time the unit operation time elapses, and accumulates the life consumption rate to calculate a cumulative life consumption rate. Since the cumulative value of the unit operation time when the cumulative life consumption rate exceeds 1 is defined as the remaining life time of the heat transfer tube, as the operation time elapses, the tube thickness of the heat transfer tube decreases, and the internal pressure stress increases accordingly. It is possible to calculate an accurate remaining life in accordance with the change in.

Further, as in the second aspect of the present invention, a remaining life distribution graph displaying means is provided, and the remaining life time calculated by the remaining life calculating means for a plurality of heat transfer tubes used in the superheater or the reheater is provided. However, if the heat transfer tubes are configured to be displayed as a graph with respect to the tube row or the number of stages of the plurality of heat transfer tubes, even if a superheater or a reheater in which a large number of heat transfer tubes are arranged in a row or step shape, the actual transfer is performed. The relationship between the position of the heat pipe and the remaining life can be quickly grasped.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a configuration diagram of the remaining life evaluation device. Reference numeral 1 denotes an ultrasonic oscillation measuring device, for example, 2
The probe 2 oscillates ultrasonic waves having a frequency of about 0 MHz and detects reflected waves. This ultrasonic oscillation measuring device 1
During measurement, ultrasonic waves are oscillated and output from the probe 2 applied to the outer peripheral surface of the heat transfer tube 3, and reflected waves of the ultrasonic waves reflected from the base material layer and the scale layer of the heat transfer tube 3 are detected. The tube thickness and scale thickness of the tube 3 are measured from the reflected wave level, and the measurement data is output. FIG. 3 shows a waveform diagram of the reflected wave, where the horizontal axis represents time and the vertical axis represents the detection level of the wave. In the waveform diagram, TH corresponds to the thickness of the base material of the pipe (pipe thickness), S corresponds to the thickness of the scale, and the thickness of the pipe TH, The scale thickness S is calculated and output as measurement data.

As shown in FIG. 7, the heat transfer pipes 3 to be measured are pipes connected to an outlet header 4 of a superheater or a reheater. For example, 1 to 74) and the number of stages (for example, A to J) are given, and the measurement data of these tubes is identified by attaching the tube row number and the number of stages.

Reference numeral 5 denotes an arithmetic processing unit constituted by a personal computer or the like. The arithmetic processing unit 5 receives measurement data of the tube thickness TH and the scale thickness S from the ultrasonic oscillation measurement device 1 and inputs the measurement data using a keyboard or the like. The stress σ is calculated from the measured internal pressure, tube outer diameter, and tube wall thickness data of the heat transfer tube 3, and the operating time H, the scale thickness S, and the previously stored skein thickness S, metal temperature T, and operating time H are calculated. The metal temperature T of the heat transfer tube 3 is calculated from the relational expression. Further, the arithmetic processing unit 5 determines the remaining life evaluation curve of FIG. 6 from the creep rupture strength data for each scale thickness, the internal stress σ, and the scale thickness S stored in advance, and calculates the metal temperature T and the remaining life evaluation curve. The remaining life of the heat transfer tube 3 is calculated by using this. Their remaining life is calculated for all tubes of the superheater or reheater,
A graph showing the distribution of the remaining life with respect to the tube row or the number of stages of the heat transfer tubes is created and displayed on a display 6 such as a CRT or a liquid crystal display.

Meanwhile, it has been found that the steam oxidation scale generated in the heat transfer tube 3 exhibits a parabolic growth behavior at a constant temperature, and the oxidation rate constant k _p is k _p = d ² / t · ... (1) Here, d is the wall thickness reduction of the pipe base material (c
m) and t are time (seconds).

From the experimental value, the relational expression of the wall thickness reduction d, the time, and the temperature T during scale generation, that is, the metal temperature T (° K), is as follows from the experimental value: Log k _p = 1000a / T + b (2) When the thickness reduction d (cm) is converted into the scale thickness S (μm), and the time t (second) is replaced with the time t (hour), d ² / t = ((S / 2. 1) × 10 ⁻⁴ ) ² / (t × 3600) ·· (3), and the expression of the temperature T during the scale generation is expressed by Log (((S / 2.1) × 10 ⁻⁴ ) from the expression (2). ) ² / (t × 3600)) = 1000 a / T + b (4) Therefore, T (° K) = a / (c−2 LogS + Logt) (5) Here, a, b, and c are constants determined by various conditions.

In order to determine the constants a, b, and c, the metal temperatures T of a plurality of heat transfer tubes used in the superheater and the reheater in the boiler actually operating are measured. A part of these heat transfer tubes was withdrawn, their scale thickness S was measured by cross-section observation, and the metal temperature T
And many data of scale thickness S and operation time H were collected.

Then, using the following equation (6) obtained from the above equations (1) to (4), the steam oxidation rate constant Logk
_p is calculated, and Logk _p = (S / 2.1) × 10 ⁻⁴ ) ² / (t × 3600) (6) These steam oxidation rate constants Logk _p are calculated as shown in FIG. Is plotted on a graph with the horizontal axis representing the reciprocal of (1000 / (T + 273)) to obtain a straight line Y on these plots.

Formulating this straight line Y, Logk _p = −d × (1000 / (T + 273)) − e (7) where d and e are constants, and the above equation (3) And equation (7)
From Log (((S / 2.1) × 10 ⁻⁴ ) ² / (t × 3600)) = − d × (1000 / (T + 273)) − e (8) Becomes Then, from the above equation (8), T (° C.) + 273 = d / (f−2LogS + LogH) (9) Scale thickness S, metal temperature T ° C., and operation time H (h)
An expression indicating the relationship of r) was obtained. Here, f is a constant.

In the above equation (9), a curve obtained when the metal temperature T ° C. is changed from, for example, n ₁ ° C. to n ₁₀ ° C. is a graph in which the horizontal axis represents the operation time t and the vertical axis represents the scale thickness S. 5 is as shown in FIG. 5, and the data of the curve of this graph, that is, the data showing the relationship between the scale thickness S, the metal temperature T ° C., and the operation time H are stored in the storage unit of the arithmetic processing unit 5 by the arithmetic expression Or stored in advance as table data or the like.

Further, data of creep rupture strength (Larson Miller parameter: LM value) corresponding to the scale thickness is stored in the storage unit of the arithmetic processing unit 5 in advance. The data of this creep rupture strength (LM value) are based on the actual thickness and scale thickness of the actual and new heat transfer tubes in the superheater and reheater of a boiler used for a long time. Was measured by cross-sectional observation, a creep rupture test was performed, and the rupture test values were collected. The creep rupture strength (LM value) was, as shown in FIG. Scale thickness S
(140 μm to 800 μm), and is expressed by the following formula: LM = f (S, σ) (10)

The straight line data of the creep rupture strength (LM value) corresponding to the scale thickness S is stored in advance in the storage unit of the arithmetic processing unit 5 as an arithmetic expression or table data. In the case of a scale thickness other than a straight line, it is calculated by proportional interpolation.

On the other hand, the stress σ due to the internal pressure of the heat transfer tube 3 is stored in advance using the tube thickness TH measured by the ultrasonic oscillation measuring device 1, the tube outer diameter D _O input from a keyboard or the like, and the internal pressure P. σ = (P / 100) × (D _O /2TH−0.5) (11)

By the way, the material characteristics of the heat transfer tube vary, and it is considered that the variation of the material characteristics affects the estimation of the remaining life. For this reason, when estimating and evaluating the creep rupture strength (LM value) using the graph data of FIG. 6 from the scale thickness S and the stress σ, the concept of the safety factor for the rupture stress σ is introduced and can be selected. By multiplying a plurality of safety factors α (for example, 100% 80% 67%) by the internal pressure stress σ, an evaluation line of the creep rupture strength (LM value) is made as shown by a broken line on the graph of FIG. Uses this evaluation line to obtain the creep rupture strength (LM value) for scale thickness S and stress σ. That is, the evaluation stress σ _O used in the actual calculation is calculated from the equation σ _O = σ / α.

The relationship between the creep rupture strength (LM value), the metal temperature T, and the remaining life time of the pipe is expressed by the following formula: LM = (T + 273) × (g + Logφ) × 10 ^-3 (12) Is done. Here, g is a constant, and φ is the remaining life time of the tube.

In the above equation (12), the creep rupture strength (LM)
Value) and the metal temperature T are used to calculate the remaining life time φ of the pipe.
Since the internal pressure stress increases, it is necessary to correct the creep rupture strength (LM value) downward according to the long-term operation based on the reduced pipe wall thickness.

Therefore, since the initial thickness of the heat transfer tube 3 at the time of new material is known, the thickness reduction β
(FIG. 9) and determine a certain unit operating time (eg,
(1000 hours) At every Δt, the creep rupture strength (LM value) is calculated based on the increase in stress due to the decrease in pipe wall thickness, and the LM value is corrected downward. Using the increased stress σ _i , the remaining life time φ _{i at} that time is calculated for each unit time.

Further, the ratio of the remaining life time φ _i to the unit time Δt is defined as a life consumption rate ψ _i, and ψ _i = Δt /
It is calculated from the formula of φ _i . At the same time, the unit time Δt (1000 hours) is accumulated as the elapsed time, and the life consumption rate ψ _i is obtained for each unit time Δt, that is, every time the unit time Δt is added to the operation time H, and the accumulated values are accumulated. Cumulative life consumption rateΣ
算出 Calculate _i . When the cumulative life consumption rate Σψ _i exceeds 1, it is determined that the life is over, and finally, the elapsed time immediately before that, that is, the cumulative value of the unit time Δt is the remaining life time Φ of the heat transfer tube 3. _i-1 .

The calculation of the remaining life time Φ _i-1 is performed for all the input heat transfer tubes, and a graph of the remaining life with respect to the row of tubes is displayed for each number of tubes or for the number of tubes. Is displayed on the display 6 as a graph.

Next, the specific operation of the remaining life evaluation device will be described.
This will be described with reference to the flowcharts of FIGS.

First, the measurement data of the heat transfer tube 3 collected by the ultrasonic oscillation measuring device 1, that is, the data of the tube thickness TH and the scale thickness S is read and written into each data sheet (step 100). Each data is provided with data indicating the position of the heat transfer tubes 3 (the number of tube rows and the number of stages), and the arithmetic processing unit 5 receives the total number of tube rows and the total number of stages of the heat transfer tubes 3 from a keyboard or the like. Next, in step 110, the operating time H so far of the heat transfer tube 3 is input from a keyboard or the like.

Then, in the next step 120, the metal temperature T of each heat transfer tube 3 is calculated. This metal temperature T
Is calculated from the above equation (9) using the operation time H and the scale thickness S. That is, since the curve of the metal temperature T is represented on the graph of the operation time H and the scale thickness S as shown in FIG. 5, the curve of the metal temperature T is determined from the operation time H and the scale thickness S (corresponding to FIG. 5). If there is no curve at the position of the operating time H and the scale thickness S, the metal temperature T is calculated.

Next, in step 130, the internal pressure P (kg / cm ² ) and the outer diameter D _O (mm) of the heat transfer tube 3 actually used are inputted from a keyboard or the like. And step 140
Then, the stress σ due to the internal pressure of the heat transfer tube 3 is obtained by measuring the tube thickness TH measured by the ultrasonic oscillation measuring device 1, the input tube outer diameter D _O ,
Using the internal pressure P, it is calculated from the above equation (11).

Next, in step 150, a safety coefficient α (for example, 100% 80% 67%) is input, and a Larson Miller parameter (LM value) which becomes a creep rupture strength from the scale thickness S, stress σ, and safety coefficient α. Is calculated using the data of the equation shown in the graph of FIG. The safety factor α is used by multiplying the internal stress σ, and the evaluation stress σ _O (kg / mm ² ) is given by σ _O = σ /
The evaluation stress σ _O is calculated from the equation of α, and is shifted below the solid line corresponding to the internal pressure stress σ by multiplying by the safety factor as shown by the broken line in FIG. When there is no straight line corresponding to the scale thickness S, the Larson Miller parameter (evaluation LM value) corresponding to the evaluation stress σ _O and the scale thickness S is calculated by proportional interpolation.

Next, at step 160, the above equation (10)
The remaining life time φ ₀ of the tube is calculated by substituting the evaluation LM value and the metal temperature T into the above. Then, by adding the unit driving time to the operating time H Delta] t, obtains the operation time (H + Δt) tube wall thickness TH _i was thinning of time of, along with determining the internal pressure stress sigma _i from the tube wall thickness TH _i, said Similarly, from the scale thickness S, the internal pressure stress σ _i , and the safety coefficient α, the Larson-Miller parameter (LM value) serving as the creep rupture strength is calculated using the equation of the graph of FIG.
The remaining life time φ _i of the pipe after the elapse of the unit operation time Δt is calculated. From the remaining life time φ _i , the life consumption rate ψ
_i , and the cumulative life consumption rate Σψ _i is obtained, and the cumulative value of the unit time Δt at the time when the cumulative life consumption rate Σψ _i exceeds 1, ie, the previous unit time Δt, is the remaining life time Φ _{i− of the} heat transfer tube 3. Calculated as ₁ .

[0039] That is, as shown in the detailed flowchart of FIG. 9, first, at step 200, the pipe wall thickness TH _i during operation time Δt elapses, calculated using the thinning rate beta, then at step 210 , As described above, the changed internal pressure stress σ _i
Is calculated from the above equation (11) using the changed pipe wall thickness TH _i , pipe outer diameter D _O , and internal pressure P. Next, step 22
0, the Larson Miller parameter (L) which becomes the creep rupture strength from the scale thickness S, the internal stress σ _i , and the safety factor α
M value) is calculated using the graph data of FIG. 6 in the same manner as described above.

Then, in step 230, the unit time
The remaining life time of the tube after the elapse of Δt _i And calculate the next
At step 240, the remaining life time φ per unit time Δt
_i Life consumption rate which is the ratio of ψ_i , Ψ_i = Δt / φ_i of
Calculate from the formula and accumulate it, the cumulative life consumption rate Σψ_i To
Ask. Next, at step 250, the cumulative life consumption rate
Σψ_i Judge whether has exceeded 1 and if it does not exceed 1,
If so, the process proceeds to step 260, where the operation time H
_i To the operation time H _{i + 1} When
Then, returning to step 200 again, the operation time H_{i + 1} When
Pipe thickness TH_{i + 1}Is calculated using the thinning rate β in the same manner as above.
Put out.

Further, in the same manner as described above, the stress σ _{i + 1} is calculated, the remaining life time φ _{i + 1} is calculated, and the life consumption rate ψ _{i + 1} is calculated. Then, similarly to the above, in step 250, it is determined whether or not the cumulative life consumption rate Σψ _{i + 1} has exceeded 1, and if not, the process proceeds to step 260 again.
The unit operating time Δt is added to the operating time Hi _{+ 1} to obtain the operating time _{Hi + 2} .

As described above, by repeatedly executing the above steps 200 to 260, the operation time H elapses by the unit operation time Δt, the pipe thickness TH gradually decreases, and the stress σ gradually increases. The life consumption rate ψ gradually increases. When the cumulative life consumption rate Σψ _i exceeds 1, the process proceeds from step 250 to step 270, where the cumulative value ΣH _i− of the unit time Δt at the time when the cumulative life consumption rate Σψ _i exceeds 1 is obtained _{. 1} is the remaining life time Φ of the heat transfer tube 3
It is calculated as _i-1 .

Such calculation of the remaining life time Φ _i-1 of the heat transfer tubes 3 is performed for all the measured and input heat transfer tubes 3, and a graph of the remaining life with respect to the tube row is provided for each number of pipe stages. Is displayed as a graph of the remaining life with respect to the number of pipe stages for each pipe row as shown in FIG. In this way, by displaying the graph as a graph of the remaining life time with respect to the number of pipe rows or pipe stages, in the superheater or the reheater, for example, according to the connection position of the heat transfer pipe connected to the outlet header and used. The tendency to change the remaining life time of the tubes is well understood, and the remaining life of many heat transfer tubes is quickly and accurately grasped.
It can be used to replace tubes without waste.

[0044]

According to the remaining life evaluation device of the present invention, the heat transfer tube to be evaluated is measured by using data such as creep rupture strength or an arithmetic expression created based on data previously collected from the heat transfer tube of the actual machine. Since the remaining life is calculated using the obtained data of the pipe wall thickness and the scale thickness, it is possible to accurately calculate the actual remaining life of the heat transfer tube of the actual superheater or reheater. In addition, every time the unit operation time elapses, the internal pressure stress,
The creep rupture strength, remaining life time, and life consumption rate are calculated, and the cumulative value of the unit operation time when the cumulative life consumption rate, which is the cumulative value of the life consumption rate, exceeds 1, is calculated as the remaining life time of the heat transfer tube. Therefore, it is possible to calculate an accurate remaining life associated with an increase in the internal pressure stress according to the pipe wall thickness that decreases as the operation time elapses.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a configuration diagram of a remaining life evaluation apparatus according to an embodiment of the present invention.

FIG. 3 is a waveform diagram of a measurement reflected wave of the ultrasonic oscillation measurement device.

FIG. 4 is a graph showing a relationship between a metal temperature and a steam oxidation rate constant.

FIG. 5 is a graph showing a relationship between scale thickness, metal temperature, and operation time.

FIG. 6: Scale thickness, stress, creep rupture strength (LM)
3 is a graph showing the relationship of the values.

FIG. 7A is a plan view of an outlet of a superheater, and FIG. 7B is an enlarged sectional view thereof.

FIG. 8 is a flowchart showing the operation of the remaining life evaluation device.

FIG. 9 is a flowchart of a remaining life calculation process.

FIG. 10 is a graph output diagram of the remaining life evaluation device.

[Explanation of symbols]

 1-Ultrasonic oscillation measuring device 2-Probe 3-Heat transfer tube 5-Processing unit 6-Display

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G024 AD12 AD38 BA01 BA12 BA13 BA30 CA02 CA30 EA09 EA20 FA02 FA15 2G047 AA07 AB01 AC02 BC11 BC18 GG19 GG36 2G055 AA03 AA12 BA09 BA11 BA14 BA20 EA08 FA08

Claims (2)

[Claims] 1. A scale thickness / tube thickness measuring means for measuring a scale thickness and a tube thickness of the heat transfer tube by irradiating an ultrasonic wave from an outer peripheral surface of the heat transfer tube and measuring a reflected wave thereof; Stress calculation means for calculating the internal pressure stress from the pipe wall thickness measured by the thickness / pipe wall thickness measurement means, the internal pressure of the heat transfer pipe, and the outer diameter of the pipe; metal temperature and scale thickness measured in advance on the heat transfer pipe of the actual machine And calculating and storing a relational expression of the steam oxidation rate constant from the data of the operation time and calculating the metal temperature of the heat transfer tube from the operation time and the scale thickness of the heat transfer tube to be evaluated with the relational expression. Means for storing the scale thickness and creep rupture strength previously measured for the heat transfer tube of the actual machine as creep rupture strength data for each scale thickness corresponding to the internal pressure stress of the heat transfer tube; Creep rupture strength calculating means for calculating the creep rupture strength using the creep rupture strength data for each scale thickness and the internal pressure stress written in the storage means and the creep rupture strength calculated by the creep rupture strength calculating means A remaining life time calculating means for calculating the remaining life time of the heat transfer tube by using the strength and the metal temperature calculated by the metal temperature calculating means; and Calculate the internal pressure stress of the pipe wall thickness to be reduced according to the wall thinning rate for each unit operation time, and calculate the remaining life time at the time of thinning using the internal pressure stress and the remaining life time calculating means. Calculating the life consumption rate with respect to the unit operation time, calculating the cumulative life consumption rate by accumulating the life consumption rate, and calculating the accumulated value of the unit operation time when the cumulative life consumption rate exceeds 1 by using the heat transfer tube. After Residual life evaluating apparatus of the heat transfer tube for the remaining life calculating means for the life time, further comprising a said. 2. A remaining life displaying a remaining life time calculated by the remaining life calculating means for a plurality of heat transfer tubes used in a superheater or a reheater as a graph with respect to a tube row or the number of stages of the plurality of heat transfer tubes. 2. The apparatus according to claim 1, further comprising a distribution graph display unit.