Reliability evaluation method for reaction kettle system in multi-failure mode considering corrosion thinning effect

Abstract

The invention relates to a method for evaluating the reliability of a reaction kettle system in a multi-failure mode by considering a corrosion thinning effect. The method comprises the following steps: acquiring a structural parameter, a working parameter and a corrosion depth data set of a target reaction kettle; acquiring corrosion rates of the target reaction kettle under different conditions according to the structure parameters, the working parameters and the corrosion depth data set of the target reaction kettle; calculating the effective thickness of the target structure of the target reaction kettle according to the corrosion rate; calculating the reliability of different structures in different failure modes according to the effective thickness of the target structure; and according to the reliability of the different structures in the different failure modes, carrying out overall reliability evaluation on the target reaction kettle. The service life of the reaction kettle can be accurately evaluated, and a basis is provided for equipment maintenance and safety management.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of reaction kettle safety evaluation, in particular to a reaction kettle system reliability evaluation method under multiple failure modes considering corrosion thinning effect. BACKGROUND

[0002] Pressure vessels often face corrosion problems in industrial applications. Traditional evaluation methods usually consider corrosion allowance, but lack comprehensive consideration of material properties, reaction temperature, medium type and reliability level. The traditional method lacks dynamic adaptability and cannot respond in real time to the influence of changes in environmental parameters such as temperature and medium concentration on the service life of the equipment. In addition, the traditional method does not fully combine stress-strength interference models and comprehensive reliability analysis of multiple failure modes, making it difficult to provide high-precision prediction results. Therefore, it is of great significance to develop a reaction kettle system reliability evaluation method under multiple failure modes considering corrosion thinning effect, which comprehensively considers the dynamic changes of corrosion rate, material strength and operating conditions, and has important significance for the safety and reliability evaluation of the reaction kettle. SUMMARY

[0003] The purpose of the present application is to provide a reaction kettle system reliability evaluation method under multiple failure modes considering corrosion thinning effect, which accurately evaluates the service life of the reaction kettle by combining stress-strength interference models and first-order second-moment method, dynamic corrosion rate calculation and multiple failure mode reliability analysis, and provides a basis for equipment maintenance and safety management.

[0004] To achieve the above-mentioned purpose, the present application provides the following scheme:

[0005] A reaction kettle system reliability evaluation method under multiple failure modes considering corrosion thinning effect, comprising:

[0006] Obtaining the structure parameters, working parameters and corrosion depth data set of the target reaction kettle;

[0007] According to the structure parameters, working parameters and corrosion depth data set of the target reaction kettle, the corrosion rate of the target reaction kettle under different conditions is obtained;

[0008] According to the corrosion rate, the target structure effective thickness of the target reaction kettle is calculated;

[0009] According to the target structure effective thickness, the reliability under different structures and different failure modes is calculated;

[0010] According to the reliability under different structures and different failure modes, the overall reliability of the target reaction kettle is evaluated.

[0011] Optionally, the structure parameters of the target reaction kettle include reaction kettle volume, cylinder inner diameter, cylinder outer diameter, nominal thickness and material.

[0012] The operating parameters of the target reactor include reaction temperature, medium concentration, and operating pressure.

[0013] Optionally, obtaining the corrosion depth dataset of the target reactor includes:

[0014] Several detection points are set for the cylinder and head area of ​​the target reactor. An ultrasonic thickness gauge is used to obtain the current remaining thickness of each detection point, and a weld gauge is used to obtain the local corrosion thickness.

[0015] The corrosion depth corresponding to each detection point is obtained based on the nominal thickness, the current remaining thickness, and the local corrosion thickness.

[0016] Based on the corrosion depth, a dataset of corrosion depths is generated for each structure of the target reactor.

[0017] Optionally, obtaining the corrosion rate of the target reactor under different conditions includes:

[0018] The corrosion rate is calculated based on the corrosion depth corresponding to each detection point in the corrosion depth dataset.

[0019] Based on the corrosion rate, the corrosion rates at each detection point under different temperatures, different medium concentrations, different temperatures, different materials, and different reactor volumes are fitted to obtain the corrosion rates under different conditions.

[0020] Optionally, calculating the effective thickness of the target structure of the target reactor based on the corrosion rate includes:

[0021] Based on the corrosion rate, the effective thickness of the target structure of the target reactor after corrosion is calculated using a normal distribution, wherein the target structure includes the cylinder and the head of the target reactor;

[0022] δ e =δ n -C1-C2;

[0023] C2 = V·t;

[0024] Where, δ e For the effective thickness, δ n C1 is the nominal thickness of the cylinder / head, C2 is the negative thickness deviation, V is the corrosion allowance, V is the corrosion rate, and t is the working time.

[0025] Optionally, based on the effective thickness of the target structure, calculating the reliability of different structures under different failure modes includes:

[0026] Based on the effective thickness of the target structure, obtain the mean effective thickness and the variance of the effective thickness.

[0027] According to the effective thickness mean value, the effective thickness variance, the critical pressure mean value, the critical pressure variance, and the stress of the cylinder / head are calculated;

[0028] According to the critical pressure mean value, the critical pressure variance, and the stress of the cylinder / head, the reliability index of the target reactor head under the critical pressure of external pressure, the reliability index of the cylinder under the critical pressure, the reliability index of the head calculated based on the yield strength, and the reliability index of the cylinder calculated based on the yield strength are calculated by using a stress-strength interference model and a first-order two-point method.

[0029] According to the reliability index, the reliability of different structures under different failure modes is obtained by using a cumulative distribution function of a standard normal distribution.

[0030] Optionally, obtaining the effective thickness mean value and the effective thickness variance comprises:

[0031]

[0032] wherein, is the effective thickness mean value, is the nominal thickness mean value, is the corrosion allowance mean value, is the effective thickness variance, μ V is the corrosion rate mean value, μ t is the working time mean value, C xi is the coefficient of variation.

[0033] Optionally, calculating the reliability index of the target reactor head under the critical pressure of external pressure comprises:

[0034]

[0035] wherein, β1 is the reliability index of the head under the critical pressure of external pressure, P2 is the external pressure calculation pressure, is the external pressure mean value, is the external pressure standard deviation, is the head critical pressure variance, P cr1 is the head critical pressure, is the head critical pressure mean value;

[0036] calculating the reliability index of the cylinder under the critical pressure comprises:

[0037]

[0038] wherein, β2 is the reliability index of the cylinder under the critical pressure, is the cylinder critical pressure mean value, P cr2 is the cylinder critical pressure, P2 is the external pressure calculation pressure, is the external pressure mean value, a critical pressure variance of the cylinder, an outer pressure standard deviation;

[0039] a reliability index of the head based on yield strength calculation is calculated:

[0040]

[0041] wherein β3 is the reliability index of the head based on yield strength calculation, μ Rel_t a mean value of yield strength at working temperature, a stress mean value of the head, σ Rel_t a standard deviation of yield strength at working temperature, S1 is a stress of the head, a stress variance of the head;

[0042] a reliability index of the cylinder based on yield strength calculation is calculated:

[0043]

[0044] wherein β4 is the reliability index of the cylinder based on yield strength calculation, S2 is a stress of the cylinder, a stress mean value of the cylinder, a stress variance of the cylinder.

[0045] Optionally, the overall reliability evaluation of the target reaction kettle comprises: obtaining the overall reliability evaluation of the target reaction kettle by multiplying the reliabilities at the cylinder structure and the head structure under internal and external pressures.

[0046] The beneficial effects of the present application are: the present application obtains the structure parameters, material parameters and working parameters of the reaction kettle according to the design drawings of the target reaction kettle; corrosion rates under different environments are calculated according to the corrosion depth data set; the effective thicknesses of the cylinder and the head of the target reaction kettle are calculated according to the corrosion rates and working time; the reliabilities under different failure modes are calculated by using the first-order second-moment method; the overall reliability evaluation of the target reaction kettle is performed according to the reliabilities under different failure modes; the reliability-working curve and the failure probability-working time curve are drawn; thus, the change of the reliability of the reaction kettle with working time is directly reflected, the performance degradation of the reaction kettle in long-term operation is accurately predicted, and then the safety and economic benefits of the reaction kettle can be improved through optimized design and maintenance strategies. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0048] Figure 1 A flow chart of a method for evaluating the reliability of a reactor system in multiple failure modes considering the effect of corrosion thinning for an embodiment of the present application;

[0049] Figure 2 A reliability operating result graph with working time for an embodiment of the present application;

[0050] Figure 3 A failure probability operating result graph with working time for an embodiment of the present application. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0052] In order to make the above objectives, characteristics and advantages of the present application more apparent, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0053] As shown in Figure 1 The present embodiment provides a method for evaluating the reliability of a reactor system in multiple failure modes considering the effect of corrosion thinning, comprising:

[0054] obtaining the structure parameters, working parameters and corrosion depth data set of the target reactor;

[0055] According to the structure parameters, working parameters and corrosion depth data set of the target reactor, the corrosion rate of the target reactor under different conditions is obtained;

[0056] According to the corrosion rate, the target structure effective thickness of the target reactor is calculated;

[0057] According to the target structure effective thickness, the reliability under different structures and different failure modes is calculated;

[0058] According to the reliability under different structures and different failure modes, the overall reliability of the target reactor is evaluated.

[0059] Further, the structure parameters of the target reactor include the reactor volume, the cylinder inner diameter, the cylinder outer diameter, the nominal thickness and the material;

[0060] The working parameters of the target reactor include the reaction temperature, the medium concentration and the working pressure.

[0061] Further, obtaining the corrosion depth data set of the target reactor comprises:

[0062] A plurality of detection points are arranged on the barrel and head region of the target reactor, and an ultrasonic thickness gauge is used to obtain the current residual thickness of each detection point, and a weld gauge is used to obtain the local corrosion thickness;

[0063] According to the nominal thickness, the current residual thickness and the local corrosion thickness, the corrosion depth corresponding to each detection point is obtained;

[0064] According to the corrosion depth, a corrosion depth data set of each structure of the target reactor is generated.

[0065] Specifically, according to the nominal thickness δ n , the current residual thickness δ R and the local corrosion depth δ L , the corrosion depth δ C corresponding to each detection point is obtained as follows: δ C = δ n - δ R + δ L .

[0066] Further, obtaining the corrosion rate of the target reactor under different conditions includes:

[0067] According to the corrosion depth corresponding to each detection point in the corrosion depth data set, the corrosion rate is calculated;

[0068] According to the corrosion rate, the corrosion rates under different medium concentrations, different temperatures, materials and reactor volumes at different temperatures of each detection point are fitted to obtain the corrosion rates under different conditions.

[0069] Specifically, according to the corrosion depth δ C corresponding to each detection point of the target reactor, the corrosion rate V is calculated as follows: Where δ c is the corrosion depth and t is the working time. The corrosion rates under different medium concentrations CC, different temperatures T, materials MM and reactor volumes L at different temperatures of each detection point are fitted to obtain the corrosion rates under different conditions, i.e. V = f (CC, MM, T, L).

[0070] Further, according to the corrosion rate, the effective thickness of the target structure of the target reactor is calculated.

[0071] According to the corrosion rate, the effective thickness of the target structure of the target reactor after corrosion is calculated using normal distribution, wherein the target structure includes the barrel and head of the target reactor.

[0072] Specifically, the corrosion allowance is calculated according to the formula C2 = V·t;

[0073] The mean value of the corrosion allowance is calculated:

[0074] According to the formula δ e = δ n -C1-C2, the effective thickness is calculated;

[0075] According to C1, The effective thickness mean value is calculated The effective thickness mean value is calculated

[0076] According to C xi The effective thickness variance is calculated The effective thickness variance is calculated

[0077] Wherein, δ e is the effective thickness, δ n is the nominal thickness of the cylinder / head, C1 is the thickness negative deviation, C2 is the corrosion allowance, V is the corrosion rate, t is the working time, is the effective thickness mean value, is the nominal thickness mean value, is the corrosion allowance mean value, is the effective thickness variance, μ V is the corrosion rate mean value, μ t is the working time mean value, C xi is the coefficient of variation.

[0078] Further, according to the effective thickness of the target structure, the reliability of different structures under different failure modes is calculated, including:

[0079] According to the effective thickness of the target structure, the effective thickness mean value and the effective thickness variance are obtained; according to the effective thickness mean value and the effective thickness variance, the critical pressure mean value, the critical pressure variance and the stress of the cylinder / head are calculated; according to the critical pressure mean value, the critical pressure variance and the stress of the cylinder / head, the reliability index of the target reactor head under external pressure at the critical pressure, the reliability index of the cylinder under the critical pressure, the reliability index of the head calculated based on the yield strength, and the reliability index of the cylinder calculated based on the yield strength are calculated by using the stress-strength interference model and the first second moment method.

[0080] According to the reliability index, the reliability of different structures under different failure modes is obtained by the cumulative distribution function of the standard normal distribution.

[0081] Specifically, based on the stress-strength interference model, the random variable y that occurs interference is represented as y=r-s, and the reliability probability of the structure is the probability that the interference random variable y>0 is obtained, Wherein, r is the intensity, s is the stress. r, s are subject to normal distribution, y is also subject to normal distribution, the mean μ y and standard deviation σ y of y are μ y = μ r - μ s , Wherein, μ r , σ r are the mean, standard deviation of material intensity; μ s , σ s are the mean, standard deviation of stress respectively. According to the first order second moment method, the reliability index The reliability P r = normcdf (β), wherein, the function normcdf () represents the cumulative distribution function of standard normal distribution.

[0082] Further, the reliability index of the target reactor head under the critical pressure of external pressure includes:

[0083]

[0084] Wherein, β1 is the reliability index of the head under the critical pressure of external pressure, P2 is the external pressure calculation pressure, is the external pressure mean, is the external pressure standard deviation, is the head critical pressure variance, P cr1 is the head critical pressure, is the head critical pressure mean;

[0085] The reliability index of the cylinder under the critical pressure is calculated:

[0086]

[0087] Wherein, β2 is the reliability index of the cylinder under the critical pressure, is the cylinder critical pressure mean, P cr2 is the cylinder critical pressure, P2 is the external pressure calculation pressure, is the external pressure mean, is the cylinder critical pressure variance, is the external pressure standard deviation;

[0088] The reliability index of the head based on the yield strength calculation is calculated:

[0089]

[0090] Wherein, β3 is the reliability index of the head based on the yield strength calculation, μ Rel_t is the mean of yield strength at working temperature, is the head stress mean, σRel_t is the standard deviation of the yield strength at the working temperature, S1 is the head stress, is the head stress variance;

[0091] The reliability index of the cylinder based on the yield strength calculation is calculated:

[0092]

[0093] wherein β4 is the reliability index of the cylinder based on the yield strength calculation, S2 is the cylinder stress, is the cylinder stress mean value, is the cylinder stress variance.

[0094] Specifically, according to the mean value of the head critical pressure and the variance the reliability index β1 of the head external pressure at the critical pressure is calculated, so as to obtain the reliability of the head structure of the reaction kettle under the external pressure failure mode, specifically including:

[0095] The calculation formula of the structure is: the head critical pressure the mean value of the head critical pressure wherein B is the external pressure stress coefficient, m1 is the head safety factor, K1 is a coefficient determined by the ratio of the long axis to the short axis of the ellipse, is the mean value of the effective thickness of the head, is the mean value of the cylinder outer diameter. The variance of the head critical pressure wherein is the standard deviation of the effective thickness of the head, is the standard deviation of the outer diameter, is the partial derivative of the critical pressure to the effective thickness, is the partial derivative of the critical pressure to the cylinder outer diameter. The reliability index of the head external pressure at the critical pressure reliability P r1 = normcdf(β1), wherein P2 is the external pressure calculation pressure, is the mean value of the external pressure, is the standard deviation of the external pressure.

[0096] According to the mean value of the cylinder critical pressure and the variance the reliability index β2 of the head external pressure at the critical pressure is calculated, so as to obtain the reliability of the head structure of the reaction kettle under the external pressure failure mode, specifically including:

[0097] The calculation formula of the structure is: the cylinder critical pressure the mean value of the cylinder critical pressure wherein B is the external pressure stress coefficient, m2 is the cylinder safety factor, is the mean value of the effective thickness of the cylinder, is the mean value of the shell outside diameter. σ is the standard deviation of the shell effective thickness, is the standard deviation of the outside diameter, is the partial derivative of the critical pressure with respect to the effective thickness, is the partial derivative of the critical pressure with respect to the shell outside diameter. The reliability index of the shell under external pressure at the critical pressure is the reliability P r2 = normcdf(β2), where P2 is the external pressure calculation pressure, is the mean value of the external pressure, is the standard deviation of the external pressure.

[0098] According to the mean value μ s1 and the variance of the head stress, the reliability index β3 of the head based on the yield strength calculation is calculated, so as to obtain the reliability of the head structure under the internal pressure failure mode, specifically comprising:

[0099] The calculation formula of the structure is: the calculation formula of the head stress is The mean value of the head stress is wherein K is a shape coefficient determined by the ratio of the major axis to the minor axis of the ellipse, μ Di , are the mean values of the stress S1, the internal pressure P1, the shell inside diameter D i and the effective thickness δ e1 . The variance of the head stress is wherein are the standard deviations of the internal pressure P1, the shell inside diameter D i and the effective thickness δ e1 , is the partial derivative of the stress S1 with respect to the internal pressure P1, is the partial derivative of the stress S1 with respect to the inside diameter D i , is the partial derivative of the stress S1 with respect to the effective thickness δ e1 . The reliability index β3 of the head based on the yield strength calculation is the reliability P r3 = normcdf(β3), wherein μ Rel_t is the mean value of the yield strength at the working temperature, and σ Rel_t is the standard deviation of the yield strength at the working temperature.

[0100] According to the mean value μ and the variance of the shell stress, the reliability index β3 of the shell based on the yield strength calculation is calculated, so as to obtain the reliability of the shell structure under the internal pressure failure mode, specifically comprising:

[0101] The calculation formula for the structure is: The calculation formula for the cylinder stress is: The average stress of the cylinder is in, These are stress s2, internal pressure P1, and inner diameter D of the cylinder, respectively. i and effective thickness δ e2 The mean; the variance of the cylinder stress is in, These are the internal pressure P1 and the inner diameter D of the cylinder, respectively. i and effective thickness δ e2 standard deviation Let S2 be the partial derivative of stress S2 with respect to internal pressure P1. For stress S2 with respect to inner diameter D i The partial derivatives, For stress S2 with respect to effective thickness δ e2 The partial derivatives. Reliability index of the cylinder based on yield strength calculation. Reliability P r4 =normcdf(β4), where μ Rel_t σ is the average yield strength at the operating temperature. Rel_t This represents the standard deviation of the yield strength at the operating temperature.

[0102] Furthermore, the overall reliability assessment of the target reactor includes obtaining the overall reliability assessment of the target reactor by multiplying the reliability of the internal and external pressure cylinder structure and the head structure.

[0103] Specifically, calculate the overall reliability P of the reactor. r :P r =P r1 ·P r2 ·P r3 ·P r4 .

[0104] The above method will be further explained below using a 500L reactor (material is 316L, working temperature is 150℃, medium is CL-constant) as an example. The reactor design parameters and reactor parameter codes involved are shown in Table 1 and Table 2.

[0105] Table 1

[0106]

[0107] Table 2

[0108]

[0109]

[0110] According to the target reactor design drawings, the structural parameters and working parameters of the reactor are obtained, including: structural parameters: reactor volume L = 500, cylinder inner diameter D = 800 mm, cylinder outer diameter D = 828 mm, nominal thickness δ = 14 mm, material MM = 1; working parameters: reaction temperature T2 = 150℃, medium concentration CC = 1.199 mol / L. i o n

[0111] A plurality of detection points are arranged on the cylinder and head region of the target reactor, and an ultrasonic thickness gauge is used to obtain the current residual thickness δ R of each detection point, and the thickness unevenness caused by corrosion is further measured by a weld gauge. L

[0112] According to the nominal thickness δ n , the current residual thickness δ R and the local corrosion depth δ L , the corrosion depth δ C of each detection point is obtained: δ C = δ n - δ R + δ L The corrosion depth corresponding to each detection area is selected to generate a corrosion depth data set for each structure of the target reactor.

[0113] According to the corrosion depth δ C of each detection point of the target reactor, the corrosion rate V is calculated: where δ c is the corrosion depth, unit: mm, t is the working time, unit: day.

[0114] The corrosion rates under different medium concentrations CC, different temperatures T, materials MM and reactor volumes L at different temperatures of each detection point are fitted, and the corrosion rates under different conditions are obtained, i.e. V = f(CC, MM, T, L).

[0115] In this embodiment, the corrosion rates under different medium concentrations CC, different temperatures T, materials MM and reactor volumes L at different temperatures of each detection point are fitted, and the corrosion rate V at 150℃ is obtained. The concentration (CC = 1.199), material (MM = 1) and volume (L = 500) are standardized to obtain CCstd, MMstd and Lstd, and are brought into the corrosion rate calculation formula when T = 150℃, i.e.

[0116] V = exp(-6.92412931-0.04034681CC std -0.92559736MM​​​​std

[0117] +0.47466423L std +0.11248140CC std ·MMstd+0.00000019CC std

[0118] .L std = 0.0413 mm / day;

[0119] in, μ CC σ CC These are the mean and standard deviation of the concentration symbol, respectively, in μ. MM σ MM These are the mean and standard deviation of the material designation, respectively, in μ. L σ L These are the mean and standard deviation of the volume symbol.

[0120] The effective thickness of the target reactor's shell and head is calculated based on the corrosion rate, and the effective wall thickness after corrosion is calculated using a normal distribution.

[0121] According to the formula C2=V·t, the corrosion allowance C2 is calculated. Based on an operating time of 80 days, C2=0.0413×80=3.3mm.

[0122] Further, the average corrosion allowance is calculated:

[0123] According to the formula δ e =δ n -C1-C2, calculate the effective thickness δ e , i.e. δ e =14-0.3-3.3=10.4mm.

[0124] Further, calculate the average effective thickness: And effective thickness variance:

[0125] Where, δ n C is the nominal thickness of the cylinder / head, C1 is the negative thickness deviation, t is the working time, and C x1 The coefficient of variation is the structural parameter; Table 3 shows the distribution form and standard deviation of random variables such as material properties and dimensions.

[0126] Table 3

[0127]

[0128] According to the effective thickness obtained, the reliability of different structures under different failure modes is calculated, and based on the stress-strength interference model, the random variable y representing interference is expressed as y=r-s, and the reliability probability of the structure is the probability of the interference random variable y>0, wherein r is the strength, s is the stress. Both r and s are subject to normal distribution, and y is also subject to normal distribution, and the mean μ y and the standard deviation σ y of y are respectively μ y =μ r -μ s , wherein μ r and σ r are respectively the mean and the standard deviation of the material strength; μ s and σ s are respectively the mean and the standard deviation of the stress. According to the first-order second-moment method, the reliability index and the reliability P r =normcdf(β) wherein the function normcdf() represents the cumulative distribution function of the standard normal distribution.

[0129] The critical pressure calculation formula of the head is The mean of the critical pressure of the head is wherein B is the external pressure stress coefficient, m1 is the head safety coefficient, K1 is the coefficient determined by the ratio of the long axis and the short axis of the ellipse, is the mean of the effective thickness of the head, is the mean of the outer diameter of the cylinder. The variance of the critical pressure of the head is

[0130]

[0131] wherein C x1 is 0.04, is the standard deviation of the effective thickness of the head, is the standard deviation of the outer diameter, is the partial derivative of the critical pressure with respect to the effective thickness, is the partial derivative of the critical pressure with respect to the outer diameter of the cylinder. The reliability index of the head external pressure under the critical pressure is P r1 =normcdf(β1)≈1 wherein C x4 is 0.02, P2 is the external pressure calculation pressure, is the mean of the external pressure, is the standard deviation of the external pressure.

[0132] According to the mean and the variance of the critical pressure of the cylinder, the reliability index β2 of the head external pressure under the critical pressure is calculated, so as to obtain the reliability of the head structure of the reaction kettle under the external pressure failure mode.

[0133] The critical pressure calculation formula of the cylinder is The mean value of the critical pressure of the cylinder is Wherein, B is the external pressure stress coefficient, m2 is the safety factor of the cylinder, is the mean value of the effective thickness of the cylinder, is the mean value of the external diameter of the cylinder. The critical pressure variance of the cylinder is

[0134]

[0135] Wherein C x1 is 0.04, is the standard deviation of the effective thickness of the cylinder, is the standard deviation of the external diameter, is the partial derivative of the critical pressure to the effective thickness, is the partial derivative of the critical pressure to the external diameter of the cylinder. The reliability index of the cylinder under external pressure at the critical pressure is The reliability P r2 = normcdf (β2) ≈ 1, wherein C x4 is 0.02, and P2 is the external pressure calculation pressure, is the mean value of the external pressure, is the standard deviation of the external pressure.

[0136] According to the mean value μ s1 and the variance of the stress of the head, the reliability index β3 of the head based on the yield strength calculation is calculated, so as to obtain the reliability of the reactor head structure under the internal pressure failure mode:

[0137] The stress calculation formula is The mean value of the stress is Wherein K is the shape coefficient, which is determined by the ratio of the major axis to the minor axis of the ellipse, μ Di , are the mean values of the stress S1, the internal pressure P1, the internal diameter D i and the effective thickness δ e1 of the cylinder respectively; the stress variance is

[0138]

[0139] Wherein, are the standard deviations of the internal pressure P1, the internal diameter D i and the effective thickness δ e1 of the cylinder respectively, is the partial derivative of the stress S1 to the internal pressure P1, is the partial derivative of the stress S1 to the internal diameter D i , is the partial derivative of the stress S1 to the effective thickness δe1 The partial derivative of the stress S2 with respect to the internal pressure P1. The reliability index β3 of the head based on yield strength calculation Reliability P r3 = normcdf(β3) ≈ 1, where C x3 = 0.07, μ Rel_t = the mean value of the yield strength at the working temperature, σ Rel_t = the standard deviation of the yield strength at the working temperature.

[0140] The reliability index β3 of the cylinder based on yield strength calculation is calculated according to the mean value μ s2 and the variance of the stress of the cylinder, so as to obtain the reliability of the pressure vessel cylinder structure under the internal pressure failure mode:

[0141] The stress calculation formula is The mean value of the stress is wherein, μ Di , are respectively the mean values of the stress S2, the internal pressure P1, the inner diameter D i and the effective thickness δ e2 ; and the stress variance is:

[0142]

[0143] wherein, are respectively the standard deviations of the internal pressure P1, the inner diameter D i and the effective thickness δ e2 , is the partial derivative of the stress S2 with respect to the internal pressure P1, is the partial derivative of the stress S2 with respect to the inner diameter D i , is the partial derivative of the stress S2 with respect to the effective thickness δ e2 . The reliability index β4 of the cylinder based on yield strength calculation Reliability P r4 = normcdf(β4) ≈ 1, where C x3 = 0.07, μ Rel_t = the mean value of the yield strength at the working temperature, σ Relt_t = the standard deviation of the yield strength at the working temperature.

[0144] According to the reliabilities under different failure modes calculated, the overall reliability of the target pressure vessel is evaluated, including: the overall reliability P r of the pressure vessel is calculated by multiplying the reliabilities of the cylinder and the head under the internal and external pressures, P r = P r1 · P r2 · P r3 · P r4≈1.

[0145] The working time corresponding to different reliabilities is shown in Table 4.

[0146] Table 4

[0147]

[0148] Therefore, if the evaluation result according to the reliability parameter of 0.99999 is that the reactor can work for 245 days, this result can provide a basis for the replacement cycle of the reactor.

[0149] The reactor reliability evaluation system provided by the embodiment considers the corrosion thinning effect, obtains the structure parameters, material parameters and working parameters of the reactor according to the target reactor design drawings, calculates the corrosion rates in different environments according to the corrosion depth data set, calculates the effective thicknesses of the cylinder and the head of the target reactor according to the corrosion rates and the working time, performs reliability calculation in different failure modes by using the first-order second-moment method, performs comprehensive evaluation of the reliability of the target reactor according to the reliabilities in different failure modes obtained by calculation, and draws the reliability-working curve and the failure probability-working time curve, as shown in FIG. 1, so as to intuitively reflect the change of the reactor reliability with the working time, accurately predict the performance degradation of the reactor in long-term operation, and then improve the safety and economic benefits of the reactor through optimization design and maintenance strategy. Figures 2-3

[0150] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.​

Claims

1. A method for reliability evaluation of a reactor system under multiple failure modes considering corrosion thinning, characterized in that, The method comprises the following steps: obtaining the structure parameters, working parameters and corrosion depth data set of a target reactor; obtaining the corrosion rate of the target reactor under different conditions according to the structure parameters, working parameters and corrosion depth data set of the target reactor; calculating the target structure effective thickness of the target reactor according to the corrosion rate; calculating the reliability under different structures and failure modes according to the target structure effective thickness; evaluating the overall reliability of the target reactor according to the reliability under different structures and failure modes.

2. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 1, characterized in that, The structure parameters of the target reactor include reactor volume, cylinder inner diameter, cylinder outer diameter, nominal thickness and material; The working parameters of the target reactor include reaction temperature, medium concentration and working pressure.

3. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 2, characterized in that, The corrosion depth data set of the target reactor comprises the following steps: setting a plurality of detection points on the cylinder and head region of the target reactor, and obtaining the current residual thickness of each detection point by using an ultrasonic thickness gauge, and obtaining the local corrosion thickness by using a weld gauge; obtaining the corrosion depth corresponding to each detection point according to the nominal thickness, the current residual thickness and the local corrosion thickness; generating the corrosion depth data set at each structure of the target reactor according to the corrosion depth.

4. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 3, characterized in that, The corrosion rate of the target reactor under different conditions comprises the following steps: calculating the corrosion rate according to the corrosion depth corresponding to each detection point in the corrosion depth data set; fitting the corrosion rate under different medium concentrations, different temperatures, materials and reactor volumes at different temperatures for each detection point according to the corrosion rate, and obtaining the corrosion rate under different conditions.

5. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 1, wherein Calculating the target structure effective thickness of the target reactor according to the corrosion rate comprises the following steps: calculating the target structure effective thickness of the target reactor after corrosion by using normal distribution, wherein the target structure includes the cylinder and head of the target reactor; δ e = δ n - C1-C2; C2=V·t; where δ e is the effective thickness, δ n is the nominal thickness of the shell / head, C1 is the negative thickness deviation, C2 is the corrosion allowance, V is the corrosion rate, and t is the service time.

6. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 5, wherein Calculating the reliability under different structures and failure modes according to the target structure effective thickness comprises the following steps: obtaining the effective thickness mean and effective thickness variance according to the target structure effective thickness; calculating the critical pressure mean, critical pressure variance and stress of the cylinder / head according to the effective thickness mean and effective thickness variance; calculating the reliability index of the target reactor head under external pressure at the critical pressure, the reliability index of the cylinder under the critical pressure, the reliability index of the head based on yield strength calculation and the reliability index of the cylinder based on yield strength calculation by using the stress-strength interference model and the first second moment method according to the critical pressure mean, critical pressure variance and stress of the cylinder / head; obtaining the reliability under different structures and failure modes by the cumulative distribution function of the standard normal distribution according to the reliability index.

7. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 6, wherein Obtaining the effective thickness mean and effective thickness variance comprises the following steps: wherein, is the average of the effective thickness, is the average of the nominal thickness, is the average of the corrosion allowance, is the variance of the effective thickness, μ V is the average of the corrosion rate, μ t is the average of the operating time, C xi is the coefficient of variation.

8. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 6, wherein Calculating the reliability index of the target reactor head under external pressure at the critical pressure comprises the following steps: Wherein, β1 is the reliability index of the head under the critical pressure of the outer pressure, P2 is the outer pressure calculation pressure, is the outer pressure mean value, is the outer pressure standard deviation, is the head critical pressure variance, P cr1 is the head critical pressure, is the head critical pressure mean value; Calculating the reliability index of the cylinder under the critical pressure: Wherein, β2 is the reliability index of the barrel at the critical pressure, P is the mean value of the critical pressure of the barrel, cr2 P is the critical pressure of the barrel, P is the variance of the critical pressure of the barrel; Calculating the reliability index of the head based on yield strength calculation: where β3 is the reliability index calculated on the basis of the yield strength of the head, μ Rel_t is the mean value of the yield strength at the working temperature, σ Rel_t is the standard deviation of the yield strength at the working temperature, S1 is the head stress, is the head stress variance, is the head stress mean value; Calculating the reliability index of the cylinder based on yield strength calculation: Wherein, β4 is the reliability index of the cylinder based on yield strength calculation, S2 is the stress of the cylinder, is the stress mean value of the cylinder, is the stress variance of the cylinder.

9. The method for reliability evaluation of a reactor system in a multiple failure mode considering corrosion thinning effect according to claim 6, wherein The whole reliability evaluation of the target reaction kettle comprises multiplying the reliabilities at the inner and outer pressure cylinder structures and the head structure to obtain the whole reliability evaluation of the target reaction kettle.

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