JPH0442561B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a stress monitoring device for a boiler, and is particularly suitable for stress monitoring and life management of a boiler plant operated under intermediate load, which requires frequent startup/shutdown and load change operation. The present invention relates to a boiler stress monitoring device suitable for.

[Prior art]

When the boiler starts, stops, or changes in load, the fluid temperature fluctuates greatly, creating a difference in temperature between the fluid and the pressure member. This generates thermal stress in the pressure member,
In particular, in the nozzle corner of a thick pressure-resistant part such as a header header at the outlet of a secondary superheater, a large thermal stress occurs, and the fatigue life of the pressure member is consumed. On the other hand, even during rated operation, internal pressure stress due to internal fluid pressure becomes significant, and the life of the pressure member due to creep damage is consumed due to this.

Therefore, from the safety standpoint of preventing damage to the pressure member, it is desired to suppress the life consumption of the pressure member due to starting, stopping, load changes, etc. of the boiler to below a certain allowable value. In particular, for medium-load boiler plants that require rapid and frequent startups and stops and large and frequent load changes, it is important to be able to quickly and accurately understand fatigue life consumption and provide feedback to boiler operations. is required to do so.

Conventionally, in order to suppress life consumption such as steam, for example, a life consumption diagram shown in Fig. 1 was created for each startup mode, and from this, the life consumption was counted at each startup and stop, and the life consumption of the pressure member was calculated. A method is used to manage lifespan, but errors may occur if starting and stopping are performed in a manner different from the standard mode when the main line diagram was created.

In other words, the degree of cooling of the boiler differs depending on the length of the boiler's pause or stop period, so the start-up mode (start-up mode) also varies. Since the internal pressure difference between the time and completion of startup is different, the temperature change width rate m (°C/h) and the change width Δθ _f (°C) alone are
This is because the total stress change width is not determined. Also,
In practice, this problem cannot be avoided. As a result, an error occurs in the cumulative value of life consumption, making it impossible to accurately grasp the remaining life for each startup mode, and the initially set value must be used as is for the allowable life consumption per startup. As a result, they tend to operate in a manner that speeds up their lifespan or operate on the extremely safe side.

Therefore, according to the above-mentioned conventional method, it is difficult to achieve a rapid start-up that effectively consumes the life consumption allowed for one start-up and a rapid load operation that faithfully adheres to the allowable stress. Ta.

It is an object of the present invention to be able to grasp the thermal stress and internal pressure stress of the pressure member during operation, as well as the life consumption of the pressure member based on these, for various operating modes of the boiler, and to be able to grasp the life consumption of the pressure member based on these during operation, An object of the present invention is to provide a boiler stress monitoring device that makes effective use of the allowable lifetime consumption and enables safe and rapid boiler load operation.

[Summary of the invention]

a thermal stress calculation means for detecting the temperature and flow rate of the internal fluid and the pressure member outer surface temperature at stress monitoring evaluation points set in the boiler pressure member, and calculating the thermal stress generated at the evaluation point based on these detection data; , an internal pressure stress calculation means for detecting the internal pressure of the internal fluid at the evaluation point and calculating an internal reaction force generated at the evaluation point based on the detected internal pressure; and a total sum by adding the thermal stress and the internal pressure stress. total stress calculating means for calculating stress; fatigue life consumption determining means for determining fatigue life consumption corresponding to the total stress based on design fatigue diagram data of the pressure member set and stored in advance; an initial stress calculation means for calculating an initial stress from stress/strain diagram data in correspondence with the maximum equivalent stress at which the equivalent stress reaches a maximum value and then the internal stress becomes in the tensile direction. a creep rupture life consumption determining means for determining creep rupture life consumption based on stress relaxation curve data corresponding to the initial stress; and determining a total life consumption by adding the fatigue life consumption and the creep rupture life consumption. By including the total life consumption calculation means and the allowable life consumption calculation means for calculating the remaining allowable life from the total life consumption and the set initial allowable life consumption, various boiler The purpose is to make it possible to grasp the thermal stress and internal pressure stress of the pressure member, as well as the lifetime consumption of the pressure member based on these, during operation, with respect to the operation mode.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on examples.

FIG. 2 shows the overall configuration of an embodiment of a boiler stress monitoring device to which the present invention is applied. Also,
FIG. 3 shows a flowchart of the processing procedure.

In monitoring the stress in the boiler, first, representative monitoring and evaluation points are set for each pressure member of each part of the boiler selected based on temperature conditions and pressure conditions. This evaluation point should be selected at a portion where the generated stress is large and the fatigue life consumption is significant. In the embodiment shown in FIG. 2, the nozzle corner portion 1 of the secondary superheater outlet header 200 is illustrated as an evaluation point. This part has a thick wall and is used at high temperatures around 550℃, and during unsteady conditions such as startup and stoppage, large temperature differences occur between the inner and outer surfaces in response to changes in internal fluid temperature and flow rate. The steam outlet nozzle corner part has a complicated structure, and the stress distribution is complex and the stress value is large, which is a significant part of the fatigue life consumption. In addition, the pressure of the internal fluid during steady state is as high as approximately 255 kg/cm ² , and the service life is also significantly reduced due to creep damage caused by the internal pressure.

The header 200 has temperature T _F and pressure of the internal fluid.
Detectors are provided to detect P _F , flow rate W _F , and metal outer surface temperature T _M , and each detected value is input to the boiler stress monitoring device 100 . This boiler stress monitoring device 100 is composed of a digital computer, and outputs are input to a stress indicator 2, a stress alarm 3, a life indicator 4, and a life alarm 5, respectively.

The basic function of the boiler stress monitoring device 100 is to display the deviation between the total stress and an allowable value on the stress indicator 2 during boiler operation, and to display an alarm using the stress alarm 3 when the allowable value is exceeded. In addition, the deviation from the permissible value of the life consumption per start/stop or load change is determined and displayed on the life display 4, and if the permissible value is exceeded, an alarm is displayed on the life alarm 5. . The operator looks at the stress indicator 2 and the stress alarm 3 and sets an appropriate temperature increase rate and load change rate while suppressing the stress value to a permissible value or less.

Next, an outline of the processing procedure in the boiler stress monitoring device 100 will be explained along the flowchart shown in FIG. What is shown in FIG. 3 is a procedure, such as starting and stopping, in which the temperature T _F rises and stabilizes, then falls and becomes stable, which is executed as one cycle.

First, in step 101, it is determined whether the boiler is in operation based on the presence or absence of a burner ignition signal, and if there is an ignition signal, the processes from step 102 onwards are executed.

In step 102, a creep holding time counter is reset, which is necessary for calculating the creep damage life in step 114, which will be described later. Next, in step 103, the number of operations, ie, the number of times the ignition signal is input, is counted, and this value is used in the allowable life calculation in step 119, which will be described later. In step 104, it is determined whether one cycle of operation has been completed, assuming that one cycle is from start to stop. If one cycle has not been completed, the process proceeds to the next step 105 for calculating the total internal stress. Proceed to step 117, the total life calculation step. In addition, the judgment of this cycle is
As described above, this is done by detecting changes in the rate of temperature change (temperature gradient).

In step 105, 105A~ shown in FIG.
Step 105I calculates the total internal stress of the evaluation point pressure member, which will be described in detail later.

In step 106, it is determined whether the total internal stress calculated in step 105 exceeds the allowable stress. If it does, an alarm is displayed in step 107 and the process moves to step 108. If it does not exceed the allowable stress, the process proceeds directly to step 108. The process moves to step 108, and in this step 108, those stress deviations are displayed.

In step 109, the inner principal stress difference is calculated in step 109A from the inner surface total stress obtained in step 105, and then in step 109B, fatigue life consumption is estimated from the stress amplitude.

Step 110 calculates the equivalent stress from the internal principal stress difference calculated in step 109. This equivalent stress is used in the creep damage life calculation in step 114.

Step 111 is a part for determining whether the inner circumferential direction stress of the total inner stress determined in step 105 is in the tensile direction or in the compressive direction, and corresponds to the first barrier for proceeding to the creep damage life calculation in step 114. Here, if the stress in the inner circumferential direction is in the compression direction, proceed to step 112; if the stress is in the tensile direction, proceed to step 112.
Move to 113.

Step 112 determines the maximum value of the equivalent stress calculated in step 110, stores the average temperature of the metal at this time, and returns to step 104. The maximum value obtained here is used in the creep damage life calculation in step 114.

Step 113 is the second barrier for proceeding to creep damage life calculation 114, in which it is determined whether the metal average temperature exceeds a set value for creep range determination. When the metal average temperature exceeds the set value for the first time, start the creep hold time counter and
Proceed to step 114, and if not exceed, return to step 104.

In step 115, using the maximum value of the equivalent stress obtained in step 112 and the average metal temperature at that time, the calculation is performed based on the stress strain diagram stored in advance.
Calculate the initial stress at the start of creep. Details of this initial stress calculation will be explained later.

In step 116, starting from the initial stress determined in step 115, the current stress value indicated by the creep holding time counter is determined from a pre-stored stress relaxation curve, and based on this stress value, the pre-stored stress value is determined. Estimate the creep damage life consumption from the creep rupture curve.

Next, step 117 is a step for calculating the total life consumption, and is executed based on the 1 cycle end determination given from step 104. First, step
117A, add the fatigue life consumption and creep life consumption calculated in steps 109 and 114 respectively,
Calculate the total life consumption for this cycle. Step 117B calculates the cumulative lifetime consumption from the start of boiler operation to the present. Step 117C compares the total life consumption of the current cycle with the allowable life consumption, and if it is greater than the allowable value, a warning is displayed in step 117D, and if it is less than the allowable value, the process moves directly to step 117E. In step 117E, the deviation between the total lifetime consumption and the tolerance value is displayed.

Step 118 is the part that updates the allowable life consumption per cycle, and calculates the remaining number of operations and remaining life from the cumulative number of operations determined in step 103 and the cumulative lifetime consumption determined in step 117A.
Calculate the allowable lifetime consumption per cycle.

The above is the basic content of the processing procedure of this embodiment, and the details of the main parts of the processing content will be explained below.

The inner surface total stress calculation in step 105 will be explained using FIGS. 4, 5, and 6. FIG. 4 shows the detailed processing procedure of step 105 as described above. In step 105A, evaluate the internal fluid temperature T _F , pressure P _F , flow rate W _F , and outer surface metal temperature.
_TM Import each detection data. Step 105B
calculates the Prandtl number, thermal conductivity, and kinematic viscosity system number from the steam table stored in advance, using the temperature T _F and pressure P _F of the detection data taken in the previous step 105B as parameters. In the next step 105C, the thermal conductivity is calculated using the detected data of the flow rate W _F and each coefficient obtained in the step 105B. step
105D calculates metal temperature distribution. Regarding the metal temperature distribution, as shown in Figure 5, consider a model in which the header is regarded as an infinitely long hollow cylinder and the metal is divided in the thickness direction as shown in the figure. Time j・δ _t (here, j is 1, 2) of each divided area (hereinafter referred to as node)
..., and δ _t corresponds to the temperature distribution calculation period T _S . ), T _i (j), time j・
The internal fluid temperature at δ _t is expressed as T _f (j), and the metal outer surface temperature is expressed as T _M (j), and as shown in Fig. 6, the metal temperature distribution of each node at arbitrary time j・δ _t {T _f
(j), T _p (j), T _l (j), ..., T _N-1 (j), T _M (j)} as input data 105D ₁ , metal temperature distribution calculation means 105D ₂
By solving the N-order simultaneous equations shown in the figure, the metal temperature distribution at time (j+1) δ _t of each node {T _f (j+1), T _p (j+1), T ₁ (j+1), ...,
T _N-1 (j+1), T _M (j+1)} is the output data
Obtained as 105D ₃ . In addition, in the first calculation, the internal temperature distribution of the metal at time j・δ _t is T ₀ (j)＝T ₁ (j)＝
…Calculate by setting T _N-1 (j)=T _M (j)=T _f (j). Also,
In the simultaneous equations shown in Figure 6, symbols A,
B, C, and D are shown in the following formula.

A={1/(δr) ² +1/βδ _t }/1/2δr{1/
δr+1/2r} B=1/2δr(1/δr−1/2r)/1/2δr(1/
δr+1/2r) C={1/(δr) ² −1/βδ _t }/1/2δr(1/
δr + 1/2r) D = 2hδr/λ Where, β: Thermal diffusivity λ: Thermal conductivity h: Heat transfer coefficient δr: Unit length of metal cylinder division r: Distance from the center of the cylinder In step 105E, the direction of metal thickness Find the volume average temperature of from the metal temperature distribution. step
At 105F, this volume average temperature is used as a parameter,
The Young's modulus E and linear expansion coefficient α of the metal are determined from a table stored in advance. In step 105G, the thermal stress in the r, θ, and z directions at time j· _δt is calculated using the following equations (1) to (3) expressed in polar coordinates.

σ _r (r)=Eα/1−ν{1/b ² −a ² (1−a ² /r ² )
∫ ^b _a T(r)・rdr−1/r ² ∫〓 _a T(r)rdr}……(1) σ〓(r)=Eα/1−ν{1/b ² −a ² (1+a ² / ^r2 )
∫ ^b _a T(r)・rdr＋1/r ² ∫〓 _a T(r)rdr−T(r)}……(2
) σ _z (r)=Eα/1−ν{2/b ² −a ² ∫〓 _a T(r)rdrT(
r)}...(3) Here, E: Young's modulus α: Coefficient of linear expansion ν: Poisson's ratio (=constant) a: Inner radius b: Outer radius T(r): Metal temperature at radius r Under thermal stress What was evaluated was the internal thermal stress, that is, the value at r=a (corresponding to node "0" in FIG. 5), which is expressed by the following equations (4) to (6).

σ _r (a)=0 ...(4) σ〓(a)=Eα/1−ν{2/b ² −a ² ∫ ^b _a T(r)rdr−T(a
)} ...(5) σ _z (a)=Eα/1−ν{2/b ² −a ² ∫ ^b _a T(r)rdr−T(a)
} ...(6) Next, in step 105H, from the internal fluid pressure P _F ,
The internal pressure stress in the r, θ, and z directions is calculated using the following equations (7) to (9).

σir＝−P _F …(7) σiθ＝T _H /2・P _F …(8) σiz＝DI ² /DO ² −DI ²・P _F …(9) Here, T _H : Piping meat Thickness DI: Pipe inner diameter (=2a) DO: Pipe outer diameter (=2b) Step 105I is the nozzle corner r, θ,
Let the stress concentration constant in the z direction be C _r , C〓, C _z , C _ir , C _i 〓, C _iz for each of thermal stress and internal pressure stress,
The total internal stresses σ _Tr , σ _T 〓, and σ _TZ in the r, θ, and z directions are calculated using the following equations (10) to (12). The stress concentration constant is a constant for estimating the internal stress of the nozzle corner part, which has the most severe stress condition, from the internal stress of the hollow cylindrical part obtained using the previous equations (7) to (9). This is what I was looking for.

σ _Tr =σ _ir ……(10) σ _T 〓=C〓・σ〓(a)＋C _i 〓・σ _i 〓……(11) σ _TZ ＝C _Z・σ _Z (a)＋C _iZ・σ _iZ ...(12) Return to the flowchart in Figure 3 and follow the steps.
In step 106, since the stress σ _T 〓 in the inner surface θ direction of the above equation (11) is the most severe, this is compared with the allowable stress and a warning is issued in step 107 when it exceeds the allowable value. Also, in step 108, the deviation between σ _T 〓 and the tolerance value is displayed.

Next, the procedure of fatigue life calculation in step 109 will be explained.

First, in step 109, the inner principal stress differences (S ₁ to S ₃ ) are determined by the following equations (13) to (15) based on the above equations (10) to (12).

S ₁ =σ _T 〓−σ _TZ ……(13) S ₂ =σ _TZ −σ _Tr ……(14) S ₃ =σ _Tr −σ _T 〓……(15) Next, in step 109B, the above equation is For each of the principal stress differences S ₁ to S ₃ calculated by (13) to (15), the stress amplitude is captured, and based on this, the life consumption is calculated from the design fatigue diagram. For example, as shown in FIG. 7, if the principal stress difference S ₁ shows temporal fluctuations, the total stress amplitudes Z ₁ 〓 and Z ₂ 〓 for S ₁ can be found. Similarly, for S ₂ and S ₃ , Z ₁ 〓, Z ₂ 〓, ..., Z ₁ 〓,
Z ₂ 〓, ... are respectively found.

In other words, for S ₁ , Z ₁ 〓, Z ₂ 〓 (Z ₁ 〓＞Z ₂ 〓 ) For S ₂ , Z ₁ 〓, Z ₂ 〓,…(Z ₁ 〓＞Z ₂ 〓＞…) For S ₃ , Z ₁ 〓, Z ₂ 〓,…(Z ₁ 〓＞Z ₂ 〓＞… ). Then these response amplitudes S ₁ ~S ₃
As shown in the following equation (16), the maximum values are sequentially selected from among them to obtain the stress piece amplitudes H ₁ , H ₂ , . . .

H ₁ = max {T ₁ 〓, Z ₁ 〓, Z ₁ 〓}÷2 H ₂ = max {Z ₂ 〓, Z ₂ 〓, Z ₂ 〓｝÷2 ...(16) ... ... This stress strip amplitude H ₁ , _H2 , and from the design fatigue diagram shown in Figure 8, the allowable number of repetitions _N1 ,
Find N ₂ ,... These allowable number of repetitions N ₁ ,
From the reciprocals of N ₂ ,..., the fatigue life consumption amount φ _f per cycle is calculated as shown in the following equation (17).

φ _f =1/N ₁ +1/N ₂ + (17) Further, the calculation procedure for creep damage life consumption from step 111 onwards will be explained.

The principal stress difference at the start of the boiler in the θ direction is schematically shown for the outlet header of the secondary superheater as follows:
As shown in Fig. 9, the stress changes once to the compression side, and then changes to the tension side as the pressure increases, and after reaching the initial stress σ _A , begins to relax. Creep damage life is the first
As shown in Figure 11, relaxation curves for various initial stresses σ _A are stored in the computer, and a relaxation curve corresponding to the value of the initial stress σ _A is selected.
The stress σ(T)T) and time width ΔT at the elapsed time T from the relaxation start point S of the stress relaxation curve shown in are determined. Using this σ(T), we calculate the rupture time t _r (σ(T)) from the creep rupture curve shown in Figure 11b.
The creep damage during the above ΔT is determined as Δt/t _r .

In step 111, the stress σ _T 〓 in the inner circumferential direction obtained by the previous equation (11) is in the compression direction (that is, on the negative side in Fig. 9).
If _it corresponds to Store the average metal temperature in memory.

If the stress σ _T 〓 in the inner circumferential direction changes to the tensile direction (i.e., to the positive side in Fig. 9), in step 113 the metal average temperature reaches the creep region (for example, 510°C for the secondary superheated outlet header). It is determined whether or not the stress has been reached, and once it has entered, a creep holding time counter for counting the elapsed relaxation time T after the initial stress of the stress relaxation curve is started. Then, in step 115, the initial stress σ _A is calculated.

A detailed flowchart of the initial stress calculation in step 115 is shown in FIG. The procedure for calculating the initial stress will be explained below using this flowchart and FIGS. 13 to 17.

In the example of the stress/strain diagram shown in Figure 13, the maximum equivalent stress on the compressive side occurs when the initial point is at point 0, and its value is the yield stress on the compressive side Y ₁ at the temperature at that time.
The maximum value σ _A after which the stress turns to the tensile direction
σ _A is the initial stress, which is expressed by the following equation (19).

σ _A = (σ ₂ + Y ₁ ) (F/E-1) + σ _P2 ...(19) Also, if the initial stress exceeds the yield stress Y ₃ at the rated temperature, σ _A ' in the same figure , is expressed by the following equation (20).

σ _A ′=Y ₃ + (SA−Y ₃ )F ₁ /E ₁ ...(20) Here, E ₁ : Young's modulus at rated temperature, F ₁ : High temperature tensile property slope at rated temperature, .

First, in step 115A, using the stress strain diagram shown in _FIG . Calculate Young's modulus E at

In the next step 115B, as _shown in FIG. 14, the maximum compression stress SB is calculated using _the following formula (21 ).

SB=SO−σ _P2 +σ ₂ …(21) Compare this maximum compression stress SB and yield stress −Y ₁ at step 115C, and if SB<−Y ₁ , proceed to step 115D; otherwise, proceed to step 115D. Move to step 115H.

In step 115D, the tensile side equivalent stress SA is calculated as the first
Figure 13 for the first startup, and Figure 1 for the second and subsequent startups.
It is calculated as shown in the following equation (22) using the method shown in Figure 4.

SA=(SB+ _Y1 )(F/E-1)SO...(22) This tensile side equivalent stress SA and the yield stress _Y3 at the rated temperature are compared in step 115E, and if SA> _Y3 , step Move to step 115F, otherwise move to step 115G.

In step 115F, if yield occurs on both the compression side and the tension side, the initial stress σ _A2 is calculated using the following equation (23) as shown in FIG.

σ _A2 = Y ₃ + (SA-Y ₃ ) F ₁ /E ₁ ... (23) In step 115G, the boiler is stopped as shown in Fig. 14, that is, when the stress is relaxed and has decreased to SO, the boiler is stopped. In the case of restarting, find the initial stress σ _A when yielding on the compression side.

In step 115H, the tensile equivalent stress SO is compared with the yield stress _Y3 at the rated temperature, and if SO≦ _Y3 , the process moves to step 115I, and if SO> _Y3 , the process moves to step 115J.

In step 115I, as shown in FIG. 15, when there is no yield on either the compression side or the tension side, the initial stress is the same as SO, so the initial stress σ _A1 ' is set to be equal to SO.

In step 115J, as shown in FIG. 16, when yielding occurs on the tension side without yielding on the compression side,
The initial stress σ _A2 ' is calculated using the following equation (24).

σ _A2 ′=Y ₃ + (SO−Y ₃ )F ₁ /E ₁ (24) Based on the initial stress σ _A obtained in step 115, in step 116, the 10th
Using the stress relaxation curve shown in the figure, find the stress relaxation curve to be applied by interpolation as shown in Fig. Calculate damage life.

The procedure for calculating creep damage life is shown in Figures 19 a to c.
This will be explained using the specific example shown in . Figure 19a
~c shows the applied stress relaxation curves, with creep retention times 0.1, 0.2, 0.4, 0.7,
σ(0.1), respectively, as the stress at 1.0 hours.
σ (0.2), σ (0.4), σ (0.7), and σ (1.0) are now given. Figures 19a to 19c are for explaining the method of calculating the creep damage life.If the creep retention time TG is on the left side of the intermediate time point of the above time rotation, it will coincide with the above time point. If the stress is on the right side with respect to the intermediate time point, the stress for creep damage evaluation is the stress at the time point, and the duration ΔT is set using this stress as a representative one. This is an attempt to simplify the calculation of creep damage life consumption.

According to the example in Figure 19a, the relationship between stress and its duration ΔT is: ΔT ₁ = (0.15 − 0.1) time by σ (0.1), ΔT ₂ = (0.3) by σ (0.2). −0.15) time, σ(0.4) evaluates as ΔT ₃ =(T−0.3) time. In the example of Fig. 19b, ΔT ₁ ′=(0.15−0.1) time due to σ(0.1), ΔT ₂ ′=(0.4−0.15) time due to σ(0.2), and FIG. In the example of c, σ(0.1) gives ΔT ₁ ″=(0.15−0.1) time, and σ(0.2) gives ΔT ₂ ″=(T−0.15) time.

Here, the above σ(0.1), σ(0.2), σ(0.4),...
The corresponding rupture times are given as t ₁ , t ₂ , t ₃ , . . . , respectively. From these, the creep damage life consumption φ _c is expressed as the following equations (25) to (27) for the cases shown in FIGS. 19 a to c, respectively.

φ _c = ΔT ₁ / t ₁ + ΔT ₂ / t ₂ + ΔT ₃ / t ₃ ... (25) φ _c = ΔT ₁ ′ / t ₁ + ΔT ₂ ′ / t ₂ ... (26) φ _c = ΔT ₁ ″ / t ₁ +ΔT ₂ ″/t ₂ ……(27) Creep damage life consumption φ _c determined in this way
and the fatigue life consumption φ _f , in step, the total life consumption φ _i and the cumulative total life φ _T are calculated as follows.

First, in step 117A, the total life consumption φ _i is calculated for each cycle, that is, for each cycle i, using the following equation (28).

φ _i = φ _fi + φ _ci ...(28) Next, in step 117B, the cumulative total life φ _T up to the current N cycle is calculated using the following formula (29). φ _T = _N 〓 ⁱ⁼¹ (φ _fi +φ _ci ) ...(29) In step 117C, the allowable life consumption of the set cycle i is compared with φ _pi and φ _i , and if φ _i >φ _pi , an alarm is issued in step 117D and the step
117E, the life deviation Δφ _i is calculated and displayed using the following equation (30).

Δφ _i =φ _i −φ _pi (30) As mentioned above, in step 118, the allowable life per cycle is calculated, and as reference data, for example, for each startup mode, that is, cold start mode, The allowable number of startups for warm start mode and hot start mode are initially distributed as N ^O _C , N ^O _W , and N ^O _H , respectively, and the total life consumption is initially distributed as φ ^O _TC , φ ^O _TW , and φ ^O _TH , respectively. ing. Therefore, the allowable life consumptions φ ^O _PC , φ ^O _PW , and φ ^O _PH for the initial cycle corresponding to each mode are expressed by the following equations (31).

According to this, if the number of operations in each mode up to the i-th cycle is N ⁱ _C , N ⁱ _W , N ⁱ _H and the total life consumption is φ ⁱ _TC , φ ^iTW , φ ⁱ _TH , then the next cycle (i
+1) The allowable life for each mode is calculated by the following formula (32)
It is determined by

Here, the numerator of formula (32) is the remaining allowable life,
The denominator is the remaining allowable number of operations.

In this way, according to this embodiment, it is possible to grasp the life consumption of the pressure member for each cycle of stress change caused by changes in the state of the internal fluid during operation of the boiler. Allowable life (remaining life) can be monitored.

Furthermore, according to this embodiment, the initial allowable life and allowable number of operations are set for each operation mode, and the cumulative life consumption and number of operations are determined for each boiler operation mode. The remaining allowable life and remaining number of operations for each mode can be easily determined.

〔Effect of the invention〕

According to the present invention, thermal stress, internal pressure stress, and life consumption based on these can be quickly and accurately grasped during operation for various operating modes of a boiler, and an appropriate allowable life quantity can be grasped. Therefore, it is possible to effectively utilize the lifetime consumption allowed for one startup to enable safe and rapid load operation of the boiler plant.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional lifespan management method, Fig. 2 is a configuration diagram of an embodiment of the present invention, Fig. 3 is a flowchart showing the processing procedure of the embodiment shown in Fig. 2, and Fig. 4
The figure is a flowchart showing the detailed processing procedure of the main part of the illustrated flowchart in Figure 3, Figures 5 and 6 are explanatory diagrams of the metal temperature distribution calculation method, and Figures 7 and 8 are
The figure is an explanatory diagram of the fatigue life consumption calculation method, Figures 9 to 1
Figures 1a and b are explanatory diagrams of the creep damage life calculation method, Figure 12 is a flowchart showing detailed processing procedures of the main parts of the flowchart shown in Figure 3, and Figures 13 to 13.
FIG. 17 is an explanatory diagram of the principle of initial stress calculation, and FIGS. 18 and 19 a to 19 c are concrete explanatory diagrams of the creep damage life calculation method. 1... Nozzle corner part (evaluation point), 100...
Boiler stress monitoring device.

Claims (1)

[Claims] 1. Thermal stress calculation means that detects the internal fluid temperature, flow rate, and pressure member outer surface temperature at stress monitoring evaluation points set in the boiler pressure member, and calculates the thermal stress generated at the evaluation point based on these detection data. and internal pressure stress calculation means for detecting the internal pressure of the internal fluid at the evaluation point and calculating an internal reaction force generated at the evaluation point based on the detected internal pressure, and adding the thermal stress and the internal pressure stress. a total stress calculation means for calculating a total stress; a fatigue life consumption determining means for determining a fatigue life consumption corresponding to the total stress based on preset and stored design fatigue diagram data of the pressure member; and a fatigue life consumption determining means for determining a fatigue life consumption corresponding to the total stress; and an initial stress calculation means for calculating the initial stress from the stress/strain diagram data in correspondence with the maximum equivalent stress at which the equivalent stress becomes the maximum value and the internal stress becomes in the tensile direction. means, creep rupture life consumption determining means for determining creep rupture life consumption based on stress relaxation curve data corresponding to the initial stress, and adding the fatigue life consumption and the creep rupture life consumption to determine the total life consumption. Boiler stress monitoring characterized by comprising: a total life consumption calculation means to obtain, and an allowable life consumption calculation means to calculate the remaining allowable life from the total life consumption and the set initial allowable life consumption. Device.