KR20100033794A - Turbine life assessment method using portable hardness tester - Google Patents

Abstract

PURPOSE: A turbine life assessment method using a portable hardness tester is provided to allow a user to estimate the lifetime of equipment by portable hardness meter. CONSTITUTION: A computing device receives a hardness value of object and a driving condition values(S1, S2). Thermal stress is calculated by a simple computation of the stress of the object(S3) a life rate is obtained by adding a cliff life rate and a low cycle fatigue life rate. The residual life of the objects is obtained based on the lifetime rate(S4).

Description

Turbine life Assessment method using portable hardness tester

The present invention relates to the field of evaluating the life of a thermal power plant turbine equipment, in particular, in evaluating the life of the thermal power plant turbine equipment using the hardness test results using a portable hardness tester and in parallel with the simple stress calculation results of the turbine equipment The present invention relates to a method for evaluating the residual life of a turbine rotor and a casing for easily evaluating the remaining life.

Various types of turbines are operating in industrial plants such as power plants, and these turbine facilities require effective life management due to long-term deterioration. To date, the life assessment is based on the comprehensive analysis of the operating conditions of the turbine facility, modeling of the facility, analytical results through temperature and stress analysis, evaluation of the aging of the microstructure through facility tissue replication, and the presence of cracks through non-destructive tests. The remaining life is assessed by evaluating the residual life.

More specifically, from the start-up operation data analysis to the three-dimensional stress calculation for power plant steam turbine rotors and casings, many complicated procedures need to be calculated and processed, which requires a lot of effort and time. In particular, operation data collection at start-up is very difficult when a real-time operation data management database is not available on site, and additional efforts are required to convert the data to electronic data for use after data collection. In addition, heat transfer analysis, three-dimensional temperature distribution calculation and three-dimensional stress calculation considering the operation mode and region characteristics at the start-up require specialized programs and techniques. The results calculated through all these procedures are expected to be highly accurate, but depend on the expert's experience in computing and the accuracy of the data.

The calculated temperature and stress distribution are used as the main input data for the reliability evaluation and life evaluation of the facility. However, this evaluation is a theoretical evaluation, and evaluation tests such as a replica test, a hardness test, and a non-destructive test to evaluate the surface deterioration degree of the facility during the actual life evaluation of the facility are performed. The expert evaluates the result by comparing the test data and the theoretical analysis results. Since this series of processes takes a long time, such as diagnosis and analysis of at least five months, recently, a rapid life assessment method using test data acquired directly in the field is required.

As such, the prior art has many errors due to incompleteness of data, errors in interpretation, incompleteness of tests, and the like, and many efforts are made to improve such errors. In particular, in the field test, the hardness test is carried out through a portable hardness tester, but the results are only used to evaluate the degree of degradation of toughness and strength compared to new materials, and there is no life evaluation method using the hardness test results.

In view of the problems of the prior art, an object of the present invention is to use the hardness test results using a portable hardness tester in the evaluation of the life of turbine equipment of an industrial plant such as a thermal power plant, and the remaining life of the turbine equipment in parallel with the simple stress calculation results of the equipment. Is to provide an easy way to evaluate them. That is, using the hardness test results used only for strength evaluation at the power plant site, according to the present invention, a method for easily evaluating the remaining life of a turbine installation is provided.

According to the present invention, a portable hardness tester is connected to a measurement site selected for a turbine rotor and a casing as an object, and the temperature, as the hardness value from the portable hardness tester and the operating condition values related to the object, is evaluated to evaluate the remaining life of the object. In the method for evaluating the remaining life of the object, using a calculation device to input the hardness value, the hardness value measured at the measurement site of the object, and the operating condition values related to the object to the calculation device step; Deriving thermal stress through a simple stress calculation for calculating the stress of the object; Deriving a creep life rate and a low cycle fatigue life rate and adding each to derive a life rate; And deriving the remaining life of the object based on the lifespan consumption rate.

According to another aspect of the present invention, a portable durometer for measuring hardness in contact with a selected measurement site of a turbine rotor and a casing as an object, and a hardness value from the portable durometer and operating conditions relating to the object as temperature, pressure And a hardness value measuring the hardness at the measuring portion of the object, and operating condition values related to the object, to input the driving time to the calculation device, to evaluate the remaining life of the object. Deduce thermal stress through simple stress calculation to calculate stress, derive creep life rate and low cycle fatigue life rate, sum each to derive life rate, and derive the remaining life of the object based on the life rate And a calculation device incorporating the lower module, thereby evaluating the remaining life of the object. An apparatus for evaluating the remaining life of a turbine rotor and a casing is provided.

According to the present invention, in the life assessment of a turbine plant of an industrial plant such as a thermal power plant, by using a hardness test result using a portable hardness tester, and by the method of easily evaluating the remaining life of the turbine plant in parallel with the simple stress calculation result of the plant In addition, the hardness test results, which are used only for strength evaluation at power plant sites, can be used to easily assess the remaining life of a turbine installation.

Hereinafter, a method for evaluating the remaining life of a turbine installation according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

According to the present invention, a method for easily evaluating the remaining life of a turbine installation is provided by using a hardness test result used only for strength evaluation at a power plant site. Such a method is portable as shown in FIG. As a calculation device in which the hardness measuring device 1 and the remaining life calculation routine provided according to the present invention are incorporated, for example, the mini notebook 2 may be used in conjunction.

Having such a system, the user performs the turbine plant residual life assessment according to the invention, for which a more specific turbine plant residual life assessment method is shown in the flow chart illustrating the process according to the invention in FIG.

First, in step S1, the operating conditions and materials of the turbine facility are selected and input. At this stage basic operating information such as temperature, pressure and operating time is entered.

In the next step (S2), the hardness test using a portable hardness tester commonly used on the surface of the installation, such as rotors, casings of the turbine installation, analyzes the hardness results and enters into the database. In this step, the hardness of the location where damage occurs mainly in the turbine plant is measured and data is obtained.

Next, in step S3, the stress of the turbine installation is calculated using the simple stress method to calculate the stress of the turbine installation. That is, the stress is calculated using a simple stress analysis method for the turbine rotor and the inner casing.

Subsequently, in step S4, as described above, the input of all the information and the measurement and calculation results is completed to evaluate the final remaining life. In other words, the hardness data and the calculated stress values are used to calculate the remaining life of the target plant.

As described above, the present invention is a method for evaluating the remaining life using the hardness test results measured using a portable hardness tester and the stress results calculated by the simple stress method, and a series of processes for this are provided according to the present invention. .

(1) Input and use of basic data such as operating conditions of turbine equipment:

In the above-mentioned step S1, as mentioned, input of basic operating condition information such as operation time, temperature, and pressure is performed, which is displayed on the screen of the mini-notebook 2 as shown in FIG. The user can input through the input screen. 3 and 4 illustrate an example of a specific input screen. As shown in Figure 3, the operating conditions, such as operating time, temperature, pressure of the turbine equipment is input. FIG. 4 illustrates an input screen for selecting a material as a screen for selecting a material used in a facility to be analyzed. Selecting a material automatically links the experimental data and basic information of the material.

This process is inputted as a variable in the calculation algorithm during the final residual life assessment.

(2) Hardness measurement method using a portable hardness tester:

The next step is to measure the hardness of the location where damage occurs mainly in the turbine plant and acquire data.

5A and 5B show the position of measuring hardness for the turbine rotor and the casing.

5A shows the turbine rotor at the top and the cross section at A-A 'and B-B' of the turbine rotor at the bottom. In addition, H1-H8 represent the position which measures an actual hardness.

Figure 5b shows a turbine casing, the left and right are actually connected, but shown separately for convenience of description.

PT, MT, H, G, R in Figure 5b,

. PT (Penetration inspection Test)

. MT (Magnetic particle test): Magnetic particle inspection

. H (Hardness): Hardness Test

. R (Replica): Indicates that surface tissue replication can be applied.

Hardness test is performed by using a portable hardness tester (1) as shown in FIG. After performing the hardness test in this way, the measured hardness value according to the position of the selected equipment is stored in real time and the average of the obtained hardness values is calculated.

FIG. 6 shows an input of a hardness value measured seven times on the left side and an average hardness value calculation screen on the right side of the displayed screen.

The hardness test result is calculated as an average value, and as described below, it is used as an important variable in the final residual life assessment to evaluate the residual life.

(3) Simple stress calculation method for calculating stresses in turbine installations:

Figure 7 shows a simple stress calculation screen for the turbine rotor and casing. After entering the main dimensions of the plant, the stresses are calculated by internal algorithms. The following describes an internal algorithm for simple stress calculation.

Another major damage mechanism of the steam turbine rotor is low cycle fatigue, which is due to thermal stresses generated by the circumferential and axial temperature distribution inside the rotor at start-up and stop. Heat transfer in the rotor and the resulting stress (strain) can be calculated simultaneously using the graph. Since the stress distribution by heat transfer of the hollow cylinder cannot be solved like centrifugal stress, it is divided by a constant thickness in the circumferential direction and obtained by using one or more discretized heat transfer equations.

FIG. 8 is a graph of dimensionless thermal stress strain using steam turbine shape data, for example, showing a relationship between hardness and maximum tensile strength at room temperature for chromium-molybdenum-vanadium steel.

FIG. 8A shows the dimensionless nominal rotor surface stress curve for the biot number (hR / K) at the rotor outer surface, FIG. 8B shows the dimensionless nominal for the biot number (hR / K) at the inner surface of the casing Casing inner surface stress curve is shown.

는 다음과 같이 식(1)로 정의된다.Biot number used in Figure 8

Is defined by equation (1) as follows.

(1)

(One)

는 표면에서의 열전달계수,

은 단면에서의 두께 그리고

는 해당 재료의 열전도계수이며 일반적으로 터빈 로터 및 케이싱의 경우 Biot 수를 100으로 가정하여 응력을 구할 수 있다. 이 때 도 8a에서 무차원 응력을 구하기 위해 사용되는

는 다음과 같이 계산된다.In the above formula (1)

Is the heat transfer coefficient at the surface,

Is the thickness in cross section

Is the thermal conductivity of the material. In general, for turbine rotors and casings, the stress can be obtained assuming a biot number of 100. In this case it is used to find the dimensionless stress in Figure 8a

Is calculated as follows.

(2)

(2)

는 밀도,

는 비열, 그리고

는 시간변화를 나타낸다. 수명을 평가하고자 하는 설비의 기하학적 정보와 기본 운전정보를 입력하면 식(2)를 이용해

를 계산할 수 있고 도 8(a)및 도 8(b)로부터 무차원 응력(Dimensionless stress)을 구할 수 있다.In the above formula (2)

Is the density,

Is despicable, and

Indicates time change. Enter the geometrical information and basic operation information of the equipment whose life is to be evaluated, and use Equation (2).

Can be calculated and dimensionless stress can be obtained from FIGS. 8 (a) and 8 (b).

On the other hand, dimensionless stress is defined as follows.

(3)Dimensionless stress =

(3)

는 탄성계수,

는 열팽창계수,

는 설비표면과 중 심의 온도차를 나타내므로 도 8(a)및 도 8(b)로부터 무차원 응력(Dimensionless stress)을 구하면

,

,

을 알고 있기 때문에 최종적으로 열응력

를 구할 수 있다.In the above formula (3)

Is the modulus of elasticity,

Is the coefficient of thermal expansion,

Represents the temperature difference between the surface of the equipment and the center, so that the dimensionless stress is obtained from FIGS. 8 (a) and 8 (b).

,

,

Finally because of the thermal stress

Can be obtained.

(4) Method for evaluating remaining life of turbine equipment:

9 is a final remaining life evaluation screen for the turbine rotor and the casing, and the remaining life is evaluated using all the results calculated as described above. The following describes the internal algorithm for calculating the final residual life.

To calculate the remaining life, the creep life rate and low cycle fatigue life rate are calculated and linearly summed, respectively. The method of calculating the creep damage consumption rate is as follows.

FIG. 10 (a) is a curve showing the relationship between tensile strength and hardness of CrMoV steel, and is a graph showing the relationship between Vickers hardness and maximum tensile strength at room temperature, and the strength of the material may be indirectly predicted through the hardness value. Figure 10 (b) shows the residual life curve considering the hardness, showing the relationship between the hardness value and the temperature / break time in consideration of the stress value, breaking through the stress value and the measured hardness value calculated by the aforementioned method You can save time.

(4)

(4)

은 잔여수명(시간),

는 절대온도,

는 계산된 응력값(MPa) 그리고

는 측정된 비커스 경도값을 의미한다.Equation (4) shows a relationship with respect to Figure 10 (b)

Is the remaining life (hours),

Is absolute temperature,

Is the calculated stress value (MPa) and

Means the measured Vickers hardness value.

,

,

은 재료에 대한 크리프 수명곡선으로부터 구할 수 있다. CrMoV 강의 크리프 수명곡선은 도 11(a)에 나타냈으며 사용재 및 신재에 대한 Larson-Miller Parameter와 경도와의 관계를 알 수 있다. On the other hand,

,

,

Can be obtained from the creep life curve for the material. The creep life curve of CrMoV steel is shown in FIG. 11 (a) and the relationship between the Larson-Miller parameter and the hardness of the used and new materials can be seen.

As a result, the remaining service life can be calculated using Equation (4), and the creep lifespan rate can be obtained because the operation time can be known through the operating conditions.

Meanwhile, the method for calculating the low cycle fatigue life consumption rate is as follows. The low cycle fatigue life is calculated from the Coffin-Manson's equation (5) as shown in equation (6) using the total strain taking into account the plastic strain (Cursed CrMoV steel shown in Fig. 11 (b)). Fatigue life curve).

FIG. 10 (b) is a graph showing a low cycle fatigue life curve of CrMoV steel in the same manner as in FIG. 10 (a), and shows the total strain according to the cycle in which fracture occurs according to each material.

(5)

(5)

(6)

(6)

,

는 해당 재료에 대한 저주기 피로 수명곡선을 식(5)와 같은 형태로 변환하면서 구할 수 있다. 크리프 수명소비율과 마찬가지로 결과적으로 식(6)을 이용하여 잔여수명을 계산할 수 있고 운전조건을 통해 현재까지의 사이클 수를 알 수 있기 때문에 저주기 피로 수명 소비율을 구할 수 있다.Meanwhile, the variable in equation (6)

,

Can be found by converting the low-cycle fatigue life curve for the material into the form shown in equation (5). As with the creep life rate, the remaining life can be calculated using Eq. (6), and the low cycle fatigue life rate can be obtained because the number of cycles to date can be obtained from the operating conditions.

Finally, as shown in Equation (7), the lifetime consumption rate can be calculated by linearly adding the creep life consumption rate and the low cycle fatigue life consumption rate.

Life Consumption Rate (%) = Creep Life Consumption Rate (%) + Low Cycle Fatigue Life Consumption Rate (%) (7)

Since the lifetime consumption rate is the consumption rate of the lifetime according to the present operating time to the present, the remaining life can be finally calculated using the following equation (8).

   Remaining life (hr) = Operating time to date (hr) x (1 / Life ratio-1) (8)

By deriving the residual life by such an algorithm, the final residual life evaluation results for the turbine rotor and the casing as shown in FIG. 9 may be presented to the user.

1 is a view showing that a portable hardness measuring device and a calculation device with a built-in residual life calculation routine provided in accordance with the present invention are connected.

2 is an algorithm flow diagram of the present invention.

3 is a screen diagram for inputting basic driving information.

4 is a screen diagram for selecting a material used in the equipment to be analyzed.

FIG. 5A is a view showing a position of measuring hardness of the turbine rotor and the casing, and FIG. 5B is a cross-sectional view taken along line A-A 'and B-B in FIG. 5A.

6 is a screen diagram for calculating the average of the obtained hardness value is stored in real time measured in accordance with the position of the selected equipment.

7 is a screen diagram for calculating the stresses in the first stage grooves of the high-pressure turbine rotor and the inner casing and the boreholes of the medium-pressure turbine by a simple stress calculation method based on the geometric shape;

8A shows a dimensionless stress curve for the turbine rotor outer surface.

8b shows a dimensionless stress curve for the inner surface of the casing.

9 is a screen showing the remaining life finally calculated through the measured hardness value and the calculated stress value.

10a is a graph showing the relationship between tensile strength and hardness.

10b is a graph showing remaining life in consideration of hardness.

11A is a graph showing creep life curves.

Figure 11b is a graph showing the low cycle fatigue life curve.

Claims (4)

A calculation device for evaluating the remaining life of the object by connecting a portable hardness tester to the measurement site selected for the turbine rotor and the casing as an object, and inputting a temperature, as the hardness value from the portable hardness tester and the operating condition values related to the object. Using the method for evaluating the remaining life of the object, Inputting a hardness value of the hardness measured at the measurement portion of the object and operating condition values associated with the object to the calculation device; Deriving thermal stress through a simple stress calculation for calculating the stress of the object; Deriving a creep life rate and a low cycle fatigue life rate and adding each to derive a life rate; And And deriving the remaining life of the object based on the life consumption rate. According to claim 1, wherein the creep life rate is calculated from the following equation,

only,

Dimensionless stress

And Dimensionless stress =

Is obtained from The low cycle fatigue life consumption rate is

And

Calculated from The remaining life is calculated as the operation time (hr) x (1 / life consumption rate-1) to the present time, and the lifetime consumption rate (%) is Life Consumption Rate (%) = Creep Life Consumption Rate (%) + Low Cycle Fatigue Life Consumption Rate (%), Residual life assessment method of turbine rotor and casing. A portable hardness tester for measuring hardness in contact with selected measurement sites of a turbine rotor and a casing as an object, and In order to evaluate the remaining life of the object by inputting temperature, pressure and operating time as hardness values from the portable hardness tester and operating condition values related to the object, Inputting a hardness value of the hardness measured at the measurement portion of the object, and operating condition values related to the object to the calculation device, Deriving thermal stress through a simple stress calculation to calculate the stress of the object, Derive creep life rate and low cycle fatigue life rate and add them together to derive life rate, And a calculation device incorporating a module for deriving the remaining life of the object based on the lifespan consumption rate, thereby evaluating the remaining life of the object. The method of claim 3, The creep life rate is calculated from the following equation,

only,

Dimensionless stress

And Dimensionless stress =

Is obtained from The low cycle fatigue life consumption rate is

And

Calculated from The remaining life is calculated as the operation time (hr) x (1 / life consumption rate-1) to the present time, and the lifetime consumption rate (%) is Life Consumption Rate (%) = Creep Life Consumption Rate (%) + Low Cycle Fatigue Life Consumption Rate (%), Apparatus for evaluating the remaining life of turbine rotor and casing.

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