Allowable stress calculation device, allowable stress calculation method, and allowable stress calculation program

Abstract

To easily calculate an allowable stress for a piping member in which a thickness reduction with corrosion increases with the lapse of time.SOLUTION: In an allowable stress calculation device of an embodiment of the present invention, a load stress calculation unit calculates a load stress applied to a piping member when flowing a fluid in the piping member under a specific condition set by a condition setting unit, using the amount of thickness reduction calculated by a thickness reduction amount calculation unit. A creep rupture life calculation unit calculates a creep rupture life that is a period of time necessary for the piping member to cause a creep rupture when flowing the fluid flow in the piping member under the specific condition set by the condition setting unit, using the load stress calculated by the load stress calculation unit. An allowable stress calculation unit calculates an allowable stress based on the load stress calculated by the load stress calculation unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an allowable stress calculation device, an allowable stress calculation method, and an allowable stress calculation program. [Background technology]

[0002] Facilities such as power plants, petrochemical plants, and solid oxide electrolyzer cells (SOECs) include piping components. When these facilities are operated, high-temperature fluids that corrode the piping components flow through the interior of the piping components, causing deterioration over time, resulting in a decrease in the wall thickness of the piping components. As a result, the piping components may be damaged, resulting in malfunctions such as fluid leakage or ejection.

[0003] For this reason, piping materials are selected with consideration given to the occurrence of deterioration over time. For example, the thickness of piping materials is set by adding the thickness that is reduced by corrosion caused by the fluid (corrosion allowance) to the thickness that takes into account the temperature of the fluid and the stress acting on the piping materials during use. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Mamoru Fujisaki, "Corrosion margins and their actual conditions for materials in chemical equipment", Corrosion Prevention Technology Vol. 37, pp. 286-293 (1988) [Non-patent document 2] Ministry of Health, Labour and Welfare Notification No. 196, Pressure Vessel Construction Standards, Part 1, Class 1 Pressure Vessel Construction Standards, Chapter 2, Structure, Article 11 (April 30, 2003) [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-4626 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-2261 [Patent Document 3] Japanese Patent Application Publication No. 60-67837 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-22125 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-104813 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the past, it was not easy to properly calculate the allowable stress for piping components whose wall thickness decreases over time due to corrosion, making it difficult to accurately and efficiently select piping components.

[0007] Therefore, the problem that the present invention aims to solve is to provide an allowable stress calculation device, an allowable stress calculation method, and an allowable stress calculation program that can easily calculate the allowable stress for piping components whose wall thickness due to corrosion increases over time. [Means for solving the problem]

[0008] An allowable stress calculation device according to an embodiment includes a condition setting unit, a metal thinning amount calculation unit, a load stress calculation unit, a creep rupture life calculation unit, and an allowable stress calculation unit, and calculates an allowable stress allowable for a piping member when a fluid is caused to flow through the piping member under specific conditions. The condition setting unit sets the specific conditions. The metal thinning amount calculation unit calculates a metal thinning amount resulting from a reduction in the thickness of the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit. The load stress calculation unit calculates a load stress applied to the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit, using the metal thinning amount calculated by the metal thinning amount calculation unit. The creep rupture life calculation unit calculates a creep rupture life, which is a period of time required for creep rupture to occur in the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit, using the load stress calculated by the load stress calculation unit. The allowable stress calculation unit calculates the allowable stress from the load stress calculated by the load stress calculation unit. The specific conditions include at least a load condition applied to the piping member, a usage time condition for flowing a fluid through the piping member, and a target value for the creep rupture life. If the creep rupture life calculated by the creep rupture life calculation unit is longer than the usage time, the condition setting unit changes the specific conditions to conditions that increase the usage time, and then sequentially calculates the metal thinning amount, the load stress, and the creep rupture life. If the creep rupture life calculated by the creep rupture life calculation unit is shorter than the usage time, the condition setting unit changes the specific conditions to conditions that decrease the usage time, and then sequentially calculates the metal thinning amount, the load stress, and the creep rupture life. If the creep rupture life calculated by the creep rupture life calculation unit is the same as the usage time but is longer than the target value, the condition setting unit changes the specific conditions to conditions that increase the load, and then sequentially calculates the metal thinning amount, the load stress, and the creep rupture life. When the creep rupture life calculated by the creep rupture life calculation unit is the same as the usage time, and the creep rupture life calculated by the creep rupture life calculation unit is shorter than the target value, the condition setting unit changes the specific conditions to conditions with a reduced load, and then calculates the amount of metal loss, the load stress, and the creep rupture life in sequence.The allowable stress calculation unit calculates the allowable stress when the creep rupture life calculated by the creep rupture life calculation unit satisfies the usage time and target value set as the specific conditions by the condition setting unit. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram schematically showing an allowable stress calculation device 1 according to an embodiment. [Figure 2] FIG. 2 is a flow chart showing an outline of the allowable stress calculation method according to the embodiment. [Figure 3] FIG. 3 is a diagram showing the relationship between the amount of thinning Δd and the operating time t when the operating temperature is T in this embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the load stress σf and the amount of thinning Δd when the operating temperature is T in this embodiment. [Figure 5] FIG. 5 is a diagram showing the relationship between the applied stress σf and the Larson-Miller parameter LMP when the operating temperature is T in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [A] Configuration of allowable stress calculation device 1 FIG. 1 is a block diagram schematically showing an allowable stress calculation device 1 according to an embodiment.

[0011] As shown in FIG. 1, the allowable stress calculation device 1 has a condition setting unit 10, a metal thinning amount calculation unit 20, a load stress calculation unit 30, a creep rupture life calculation unit 40, and an allowable stress calculation unit 50, and calculates the allowable stress σa that can be tolerated by a piping component when a fluid is passed through the piping component under specific conditions, taking into account corrosion caused by the fluid flowing inside the piping component.

[0012] The allowable stress calculation device 1 includes a computer and a storage device, and is configured so that a computing unit functions as each component constituting the allowable stress calculation device 1 using a program stored in the storage device.

[0013] The piping member for which the allowable stress σa is calculated is, for example, a piping used in a solid oxide high-temperature steam electrolysis facility, and is made of a metal material (for example, austenitic steel).The allowable stress calculation device 1 calculates the allowable stress σa of the piping member when a high-temperature fluid (for example, a mixed gas containing 80 mol % hydrogen gas and 20 mol % water vapor) that corrodes the metal material that makes up the piping member flows inside the piping member.

[0014] Each part of the allowable stress calculation device 1 will be described.

[0015] [A-1] Condition setting section 10 The condition setting unit 10 sets specific conditions for calculating the allowable stress σa of a piping member. Here, the condition setting unit 10 sets specific conditions including the condition of the load Pi applied when a fluid is flowed through the piping member, the condition of the usage time ti for flowing the fluid through the piping member, and the target value of the creep rupture life tr.

[0016] [A-2] Thickness reduction amount calculation section 20 The wall-thinning amount calculation unit 20 calculates the wall-thinning amount Δd of the piping member when a fluid is caused to flow through the piping member under specific conditions set by the condition setting unit 10.

[0017] [A-3] Load stress calculation unit 30 The load stress calculation unit 30 calculates the load stress σf (stress acting on a piping member whose thickness has been reduced due to corrosion caused by the flow of fluid) that is applied to the piping member when a fluid is flowed through the piping member under specific conditions set by the condition setting unit 10, using the thinning amount Δd calculated by the thinning amount calculation unit 20.

[0018] [A-4] Creep rupture life calculation section 40 The creep rupture life calculation unit 40 calculates the creep rupture life tr, which is the period until creep rupture occurs in a piping component when a fluid is passed through the piping component under specific conditions set by the condition setting unit 10, using the load stress σf calculated by the load stress calculation unit 30.

[0019] [A-5] Allowable stress calculation section 50 The allowable stress calculation unit 50 calculates the allowable stress σa from the load stress σf calculated by the load stress calculation unit 30. The allowable stress calculation unit 50 executes calculation of the allowable stress σa when the creep rupture life tr calculated by the creep rupture life calculation unit 40 satisfies the usage time ti and target value trm set as specific conditions by the condition setting unit 10 (i.e., when tr=ti=trm).

[0020] [B] Allowable stress calculation method The following describes an allowable stress calculation method for calculating the allowable stress σa that can be tolerated by a piping member using the above-described allowable stress calculation device 1 (see FIG. 1).

[0021] FIG. 2 is a flow chart showing an outline of the allowable stress calculation method according to the embodiment.

[0022] [B-1] Setting specific conditions (ST10) As shown in FIG. 2, when calculating the allowable stress σa that can be tolerated by a piping member, first, specific conditions for calculating the allowable stress σa are set (ST10).

[0023] The setting of the specific conditions is executed by the condition setting unit 10. Here, the condition setting unit 10 sets the specific conditions for calculating the allowable stress σ based on input data input by an operator to an input device (not shown) such as a keyboard, for example.

[0024] Specifically, an initial load P0 is set as a condition for the load P applied to the piping member, and an initial cross-sectional area S0 is set as a condition for the cross-sectional area S of the flow path of the piping member.

[0025] The initial load P0 is the load that is expected to be applied to the piping member in the initial state before the operation of flowing a fluid through the piping member. The initial cross-sectional area S0 is the cross-sectional area of ​​the flow path in the initial state before the operation of flowing a fluid through the piping member.

[0026] Also, the use temperature T of the piping member is set. For example, 900°C is set as the use temperature T.

[0027] Also, the use time t for flowing a fluid through the piping member and the target value trm of the creep rupture life tr are set. The use time t is set to be not more than the target value trm of the creep rupture life tr (0 < t ≤ trm). For example, when the target value trm of the creep rupture life tr is 100,000 hours, the use time t is set to be not more than 100,000 hours.

[0028] [B-2] Calculation of the amount of wall thickness reduction Δd (ST20) Next, as shown in FIG. 2, the amount of wall thickness reduction Δd is calculated (ST20).

[0029] The calculation of the amount of wall thickness reduction Δd is executed by the wall thickness reduction calculation unit 20. Here, the wall thickness reduction calculation unit 20 executes the calculation of the amount of wall thickness reduction Δd using the "time power law". The amount of wall thickness reduction Δd increases as corrosion progresses in the piping member as time elapses during which a fluid flows through the piping member.

[0030] Specifically, the calculation of the amount of wall thickness reduction Δd is performed based on the following (Equation A).

[0031] Δd=(A0·exp (-Q / RT) ·t) 1 / n ···(Equation A)

[0032] Each factor shown in (Equation A) is as follows. ·n; reaction order ·A0; frequency factor ·Q; activation energy ·R; gas constant ·T; use temperature ·t; use time

[0033] The use temperature T and the use time t are the values set by the condition setting unit 10. The reaction order n, the frequency factor A0, the activation energy Q, and the gas constant R are predetermined values. The reaction order n is a coefficient that is determined when the reaction rate of the corrosion reaction occurring on the surface of a piping component is the rate-limiting step. (n is generally between 0.5 and 1, and is 0.5 if the reaction rate is diffusion-limited, and 1 if the reaction rate is reaction-limited.) The frequency factor A0 is the frequency factor in the Arrhenius equation. It has been empirically confirmed that the reaction rate constant of the corrosion reaction occurring on the surface of a piping component follows the Arrhenius equation. (When the material of the piping component is SUS316 and in an atmospheric environment with a temperature of 600 to 800°C, the frequency factor A0 is 8.92 x 10 12 μm 2 h -1 The activation energy Q is the activation energy in the Arrhenius equation. It has been empirically confirmed that the reaction rate constant of the corrosion reaction that occurs on the surface of piping components follows the Arrhenius equation. (Empirically, the activation energy Q is 150KJ / mol to 250KJ / mol.)

[0034] FIG. 3 is a diagram showing the relationship between the amount of thinning Δd and the operating time t when the operating temperature is T in this embodiment.

[0035] As shown in Fig. 3, the amount of metal thinning Δd increases with the passage of time. In other words, as the usage time t during which a fluid flows through a piping member increases, the amount of corrosion of the piping member increases, and the wall thickness of the piping member decreases. As can be seen from Fig. 3, the metal thinning calculation unit 20 can calculate the amount of metal thinning Δd corresponding to a set value of the usage time t, for example, using a function relating the usage time t and the amount of metal thinning Δd at the usage temperature T.

[0036] [B-3] Calculation of load stress σf (ST30) Next, as shown in FIG. 2, the applied stress σf is calculated (ST30).

[0037] The calculation of the load stress σf is executed by the load stress calculation unit 30. Here, the load stress calculation unit 30 uses the amount of metal thinning Δd calculated by the amount of metal thinning calculation unit 20 to calculate the load stress σf.

[0038] Specifically, the applied stress σf is calculated based on the following (Equation B).

[0039] σf=4·P / π(do-Δd) 2 ...(Formula B)

[0040] The factors shown in (Equation B) are as follows: ·P;Load ·do; initial wall thickness of piping material ·Δd; Thickness reduction amount

[0041] The load P is a value set by the condition setting unit 10. The initial wall thickness do means the wall thickness of the piping material before the fluid flow operation is performed, and is set in advance depending on the piping material. The wall thinning amount Δd is a value calculated by the wall thinning amount calculation unit 20.

[0042] FIG. 4 is a diagram showing the relationship between the load stress σf and the amount of thinning Δd when the operating temperature is T in this embodiment.

[0043] As shown in Fig. 4, the load stress σf increases as the amount of metal loss Δd increases. As can be seen from Fig. 4, the load stress calculation unit 30 can obtain the load stress σf corresponding to the value of the amount of metal loss Δd calculated by the amount of metal loss calculation unit 20, for example, by using a function relating the amount of metal loss Δd and the load stress σf at the operating temperature T.

[0044] [B-4] Calculation of creep rupture life (ST40) Next, as shown in FIG. 2, the creep rupture life tr is calculated (ST40).

[0045] The creep rupture life tr is calculated by the creep rupture life calculation unit 40. Here, the creep rupture life calculation unit 40 calculates the creep rupture life tr using the Larson-Miller parameter LMP together with the load stress σf calculated by the load stress calculation unit 30.

[0046] Specifically, the creep rupture life tr is calculated based on the following (Equation C).

[0047] LMP=h(σf)=k(t)=T(log tr+C) (Formula C)

[0048] The factors shown in (Equation C) are as follows: ·h(σf); function of applied stress σf ·k(t); function of usage time t ·C;Constant

[0049] The constant C is a value determined according to the material of the piping member. The function h(σf) is expressed, for example, by the following (Equation C1), and the function k(t) is expressed, for example, by the following (Equation C2). In (Equation C1) and (Equation C2), C1 to C4 and a1 to a4 are constants determined by experiments. h(σf)=C1σf a1 +C2σf a2 +C3σf a3 +C4σf a4 ...(Formula C1) k(t)=C1t a1 +C2t a2 +C3t a3 +C4t a4 ...(Formula C2)

[0050] FIG. 5 is a diagram showing the relationship between the applied stress σf and the Larson-Miller parameter LMP when the operating temperature is T in this embodiment.

[0051] As shown in Fig. 5, the Larson-Miller parameter LMP increases with an increase in the applied stress σf. Therefore, the creep rupture life calculation unit 40 can use, for example, a function relating the applied stress σf and the Larson-Miller parameter LMP to determine the Larson-Miller parameter LMP corresponding to the value of the applied stress σf calculated by the applied stress calculation unit 30, and can then use the determined Larson-Miller parameter LMP to calculate the creep rupture life tr using equation C.

[0052] [B-5] Creep rupture life tr compared with service time t (ST41) Next, as shown in FIG. 2, it is determined whether the creep rupture life tr is the same as the usage time t (ST41). In other words, it is determined whether the remaining life Rn obtained by subtracting the usage time t from the creep rupture life tr (that is, Rn = tr - t) is zero.

[0053] This determination is executed by the allowable stress calculation unit 50. When the creep rupture life tr calculated by the creep rupture life calculation unit 40 is different from the usage time t set as a specific condition by the condition setting unit 10 (No), the process returns to the setting of the specific condition (ST10).

[0054] At this time, when the creep rupture life tr calculated by the creep rupture life calculation unit 40 is longer than the usage time t set as a specific condition by the condition setting unit 10 (tr > t), the condition setting unit 10 changes the specific condition to a condition with an increased usage time t. That is, when the previously set usage time t is t1, t2 is set as the new usage time t by adding a predetermined usage time Δt to t1 (t2 = t1 + Δt). When the creep rupture life tr is longer than the usage time t (tr > t), the piping member is in a likely state. Therefore, as described above, the usage time t is increased. After that, based on the changed specific condition, the calculation of the wall thickness reduction amount Δd (ST20), the calculation of the load stress σf (ST30), and the calculation of the creep rupture life tr (ST40) are sequentially executed.

[0055] When the creep rupture life tr calculated by the creep rupture life calculation unit 40 is shorter than the usage time t set as a specific condition by the condition setting unit 10 (tr < t), the condition setting unit 10 changes the specific condition to a condition with a decreased usage time t. That is, when the previously set usage time t is t1, t2 is set as the new usage time t by subtracting a predetermined usage time Δt from t1 (t2 = t1 - Δt). When the creep rupture life tr is shorter than the usage time t (tr < t), the piping member is in an unlikely state. Therefore, as described above, the usage time t is decreased. After that, based on the changed specific condition, the calculation of the wall thickness reduction amount Δd (ST20), the calculation of the load stress σf (ST30), and the calculation of the creep rupture life tr (ST40) are sequentially executed.

[0056] [B-6] Comparison between the creep rupture life tr and the target value trm (ST42) On the other hand, as shown in FIG. 2, when the creep rupture life tr calculated by the creep rupture life calculation unit 40 is the same as the usage time t set as a specific condition by the condition setting unit 10 (Yes), the process proceeds to the next step (ST42). In this step, it is determined whether the creep rupture life tr is the same as the target value trm (ST42).

[0057] This determination is executed by the allowable stress calculation unit 50. When the creep rupture life tr calculated by the creep rupture life calculation unit 40 is different from the target value trm set by the condition setting unit 10 (No), the process returns to the setting of the specific condition (ST10).

[0058] At this time, when the creep rupture life tr calculated by the creep rupture life calculation unit 40 is longer than the target value trm (tr > trm), the condition setting unit 10 changes the specific condition to a condition where the load P is increased. That is, when the previously set load P is P1, a new load P2 is set as P2 = P1 + ΔP by adding a predetermined load ΔP to P1. When the creep rupture life tr is longer than the target value trm (tr > trm), since the piping member is in a likely state, the load P is increased as described above. After that, based on the changed specific condition, the calculation of the wall thickness reduction amount Δd (ST20), the calculation of the load stress σf (ST30), and the calculation of the creep rupture life tr (ST40) are sequentially executed.

[0059] Also, when the creep rupture life tr calculated by the creep rupture life calculation unit 40 is shorter than the target value trm (tr < trm), the condition setting unit 10 changes the specific condition to a condition where the load P is decreased. That is, when the previously set load P is P1, a new load P2 is set as P2 = P1 - ΔP by subtracting a predetermined load ΔP from P1. After that, based on the changed specific condition, the calculation of the wall thickness reduction amount Δd (ST20), the calculation of the load stress σf (ST30), and the calculation of the creep rupture life tr (ST40) are sequentially executed.

[0060] [B-7] Calculation of allowable stress σa (ST50) 2, if the creep rupture life tr calculated by the creep rupture life calculation unit 40 is the same as the target value trm set by the condition setting unit 10 (Yes), the process proceeds to the next step (ST50), in which the allowable stress σa is calculated (ST50).

[0061] The allowable stress σa is calculated by the allowable stress calculation unit 50. Here, the allowable stress calculation unit 50 calculates the allowable stress σa from the load stress σf calculated by the load stress calculation unit 30. In calculating the allowable stress σa, the allowable stress calculation unit 50 uses the value of the load stress σf calculated when the conditions are satisfied in steps (ST41) and (ST42).

[0062] Specifically, the allowable stress σa is calculated based on the following (Equation D).

[0063] σa=σf / SF (Equation D)

[0064] The factors shown in (Equation D) are as follows: SF: Safety factor (e.g., a value determined based on the ignition standard (1.5))

[0065] [C] Summary As described above, in this embodiment, the amount of wall thinning Δd, which is the reduction in thickness of a piping member when a fluid is passed through the piping member under specific conditions, is calculated. Then, the amount of wall thinning Δd is used to calculate the load stress σf applied to the piping member when a fluid is passed through the piping member under specific conditions. That is, the load stress σf applied to the piping member whose thickness has been reduced by the amount of wall thinning Δd is calculated. Then, the load stress σf is used to calculate the creep rupture life tr, which is the period required for creep rupture to occur in the piping member when a fluid is passed through the piping member under specific conditions. When the calculated creep rupture life tr satisfies the target value, the allowable stress σa is calculated from the calculated load stress σf.

[0066] Therefore, in this embodiment, it is possible to easily calculate the allowable stress σa that is permissible for piping components whose wall thickness decreases over time due to corrosion. As a result, it is possible to appropriately select piping components taking into account the calculated allowable stress σa value, thereby suppressing increases in costs, etc.

[0067] <Other> Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0068] 1: allowable stress calculation device, 10: condition setting section, 20: thickness reduction calculation section, 30: load stress calculation section, 40: creep rupture life calculation section, 50: allowable stress calculation section

Claims

1. An allowable stress calculation device that calculates an allowable stress that is allowable for a piping member when a fluid is caused to flow through the piping member under specific conditions, a condition setting unit that sets the specific condition; a wall-thinning amount calculation unit that calculates a wall-thinning amount that is a reduction in the thickness of the piping member when a fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit; a load stress calculation unit that calculates a load stress applied to the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit, using the amount of thinning calculated by the amount of thinning calculation unit; a creep rupture life calculation unit that calculates a creep rupture life, which is a period of time required for creep rupture to occur in the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit, using the load stress calculated by the load stress calculation unit; and an allowable stress calculation unit that calculates the allowable stress from the load stress calculated by the load stress calculation unit; and the specific conditions include at least a condition of a load applied to the piping member, a condition of a usage time during which a fluid is flowed through the piping member, and a target value of the creep rupture life; If the creep rupture life calculated by the creep rupture life calculation unit is longer than the usage time, the condition setting unit changes the specific conditions to conditions in which the usage time is increased, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; If the creep rupture life calculated by the creep rupture life calculation unit is shorter than the usage time, the condition setting unit changes the specific conditions to conditions that reduce the usage time, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; When the creep rupture life calculated by the creep rupture life calculation unit is equal to the service time, and when the creep rupture life calculated by the creep rupture life calculation unit is longer than a target value, the condition setting unit changes the specific condition to a condition in which the load is increased, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; When the creep rupture life calculated by the creep rupture life calculation unit is equal to the service time, and when the creep rupture life calculated by the creep rupture life calculation unit is shorter than a target value, the condition setting unit changes the specific conditions to conditions in which the load is reduced, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; the allowable stress calculation unit executes calculation of the allowable stress when the creep rupture life calculated by the creep rupture life calculation unit satisfies the usage time and the target value set as the specific conditions by the condition setting unit. Allowable stress calculation device.

2. The metal-thinning amount calculation unit calculates the metal-thinning amount using a "power law of time." The allowable stress calculation device according to claim 1 .

3. the creep rupture life calculation unit calculates the creep rupture life using Larson-Miller parameters; The allowable stress calculation device according to claim 1 .

4. 1. A method for calculating an allowable stress for a piping member when a fluid is caused to flow through the piping member under specific conditions, comprising: a condition setting step of setting the specific condition; a thickness reduction calculation step of calculating a thickness reduction amount of the piping member when a fluid is caused to flow through the piping member under the specific conditions set in the condition setting step; a load stress calculation step of calculating a load stress applied to the piping member when the fluid is caused to flow through the piping member under the specific conditions set in the condition setting step, using the amount of thinning calculated in the amount of thinning calculation step; a creep rupture life calculation step of calculating a creep rupture life, which is a period of time required for creep rupture to occur in the piping member when the fluid is caused to flow through the piping member under the specific conditions set in the condition setting step, using the load stress calculated in the load stress calculation step; an allowable stress calculation step of calculating the allowable stress from the load stress calculated in the load stress calculation step; and the specific conditions include at least a condition of a load applied to the piping member, a condition of a usage time during which a fluid is flowed through the piping member, and a target value of the creep rupture life; If the creep rupture life calculated in the creep rupture life calculation step is longer than the usage time, the specific conditions are changed in the condition setting step to conditions in which the usage time is increased, and then the calculation of the amount of metal loss, the calculation of the load stress, and the calculation of the creep rupture life are sequentially performed; If the creep rupture life calculated in the creep rupture life calculation step is shorter than the service time, the specific conditions are changed in the condition setting step to conditions in which the service time is reduced, and then the calculation of the amount of metal loss, the calculation of the load stress, and the calculation of the creep rupture life are sequentially performed; When the creep rupture life calculated in the creep rupture life calculation step is equal to the service time, if the creep rupture life calculated in the creep rupture life calculation step is longer than a target value, changing the specific condition in the condition setting step to a condition in which the load is increased; When the creep rupture life calculated in the creep rupture life calculation step is equal to the service time, and the creep rupture life calculated in the creep rupture life calculation step is shorter than a target value, the specific conditions are changed in the condition setting step to conditions in which the load is reduced, and then the calculation of the amount of metal loss, the calculation of the load stress, and the calculation of the creep rupture life are performed in this order; In the allowable stress calculation step, calculation of the allowable stress is performed when the creep rupture life calculated in the creep rupture life calculation step satisfies the use time and the target value set as the specific conditions in the condition setting step. Method for calculating allowable stress.

5. An allowable stress calculation program for calculating an allowable stress that is allowable for a piping member when a fluid is caused to flow through the piping member under specific conditions, the program comprising: a condition setting unit that sets the specific condition; a wall-thinning amount calculation unit that calculates a wall-thinning amount that is a reduction in the thickness of the piping member when a fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit; a load stress calculation unit that calculates a load stress applied to the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit, using the amount of thinning calculated by the amount of thinning calculation unit; a creep rupture life calculation unit that calculates a creep rupture life, which is a period of time required for creep rupture to occur in the piping member when the fluid is caused to flow through the piping member under the specific conditions set by the condition setting unit, using the load stress calculated by the load stress calculation unit; and an allowable stress calculation unit that calculates the allowable stress from the load stress calculated by the load stress calculation unit; and make the computer function as the specific conditions include at least a condition of a load applied when a fluid is flowed through the piping member, a condition of a usage time during which the fluid is flowed through the piping member, and a target value of the creep rupture life; If the creep rupture life calculated by the creep rupture life calculation unit is longer than the usage time, the condition setting unit changes the specific conditions to conditions in which the usage time is increased, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; If the creep rupture life calculated by the creep rupture life calculation unit is shorter than the usage time, the condition setting unit changes the specific conditions to conditions that reduce the usage time, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; When the creep rupture life calculated by the creep rupture life calculation unit is equal to the usage time, if the creep rupture life calculated by the creep rupture life calculation unit is longer than a target value, the condition setting unit changes the specific condition to a condition in which the load is increased, When the creep rupture life calculated by the creep rupture life calculation unit is equal to the service time, and when the creep rupture life calculated by the creep rupture life calculation unit is shorter than a target value, the condition setting unit changes the specific conditions to conditions in which the load is reduced, and then calculates the amount of metal loss, the load stress, and the creep rupture life in this order; causing the computer to function so that, when the creep rupture life calculated by the creep rupture life calculation unit satisfies the use time and the target value set as the specific conditions by the condition setting unit, the allowable stress calculation unit calculates the allowable stress; Allowable stress calculation program.

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