A method for optimizing the layout interval of a town gas pipeline cut-off valve

Abstract

The application discloses a kind of urban gas pipeline cut-off valve layout spacing optimization method, including calculating pipeline average failure probability;The average failure probability of pipeline is corrected;Respectively establish the personnel death model under the scenario of jet fire heat radiation accident, explosion overpressure accident scenario, obtain the death area of jet fire heat radiation accident, explosion overpressure accident death area;Calculate personnel death consequence value;Construct urban gas pipeline failure risk prediction model, obtain the failure risk of urban gas pipeline;Multi-objective optimization model of urban gas pipeline cut-off valve layout spacing is constructed and solved, and the optimal number of cut-off valve and corresponding layout spacing are obtained.The application is used to solve the problem that the cut-off valve layout of the secondary high-pressure and medium-pressure gas pipeline lacks quantitative specification and the design process relies heavily on engineering experience in the prior art, realizes comprehensive consideration of pipeline failure risk and cut-off valve economic cost, and provides theoretical guidance and technical support for scientific design of gas pipeline network.

Description

A method for optimizing the spacing of shut-off valves in urban gas pipelines Technical Field

[0001] This invention relates to the field of gas pipeline safety and risk management, specifically to a method for optimizing the spacing of shut-off valves in urban gas pipelines. Background Technology

[0002] As the "lifeline" of urban energy transmission, the safe operation of urban gas pipelines is directly related to public safety and social stability. In the event of a pipeline leak, promptly shutting off the shut-off valve is the most effective means of cutting off the gas supply and controlling the escalation of the accident. According to current standards such as the *Code for Design of Urban Gas Pipelines* (GB 50028-2006 (2020 Edition)) and the *Code for Gas Engineering Projects* (GB 55009-2021), only the valve spacing for high-pressure gas pipelines is clearly specified. However, for the more widely distributed and complex surrounding environments of sub-high-pressure and medium-pressure urban gas pipelines, the aforementioned existing standards have not yet made clear quantitative provisions regarding the spacing of segmented valves.

[0003] Currently, the placement of shut-off valves for sub-high-pressure and medium-pressure urban gas pipelines relies primarily on engineering experience, lacking a systematic quantitative calculation basis. This traditional experience-based placement method often fails to accurately assess the comprehensive consequences of accidents in complex environments, and when comparing different options, the consideration of input-output relationships is relatively simplistic, lacking a comprehensive quantitative decision-making mechanism that can balance safety and economic benefits. Consequently, designers struggle to scientifically determine the optimal solution when setting the number and spacing of valves on sub-high-pressure and medium-pressure urban gas pipelines. Summary of the Invention

[0004] This invention provides a method for optimizing the spacing of shut-off valves in urban gas pipelines. This method addresses the problems in existing technologies, such as the lack of quantitative standards for the layout of shut-off valves in sub-high-pressure and medium-pressure gas pipelines and the heavy reliance on engineering experience in the design process. It aims to comprehensively consider pipeline failure risks and the economic costs of shut-off valves, and solve the problems of unclear safety margins and economic benefits in traditional experience-based design methods. This provides theoretical guidance and technical support for the scientific design of gas pipeline networks.

[0005] This invention is achieved through the following technical solution:

[0006] A method for optimizing the spacing of shut-off valves in urban gas pipelines includes the following steps:

[0007] S1. Collect historical operation and failure data of urban gas pipelines and calculate the average failure probability of the pipelines; based on pipeline physical damage and pipeline management measures, correct the average failure probability of the pipelines, construct an urban gas pipeline failure probability prediction model, and obtain the corrected pipeline failure probability under different operating conditions.

[0008] S2. Considering the jet fire accident scenario and the vapor cloud explosion accident scenario respectively, establish the quantitative correlation between jet fire thermal radiation and the mortality rate, and the quantitative correlation between explosion overpressure and the mortality rate; combine the preset lethal threshold value to conduct simulation to obtain the lethal area of ​​jet fire thermal radiation accident and the lethal area of ​​explosion overpressure accident.

[0009] Combining the aforementioned jet fire accident scenario and vapor cloud explosion accident scenario, a failure consequence prediction model is constructed to calculate the personnel fatality consequence value;

[0010] S3. Determine the ignition probability, and based on the corrected pipeline failure probability and the personnel death consequence value, obtain the comprehensive risk value of personnel death;

[0011] S5. Based on the failure risk of urban gas pipelines and the total annual cost of shut-off valves, construct a multi-objective optimization model for the layout spacing of shut-off valves in urban gas pipelines; solve the multi-objective optimization model for the layout spacing of shut-off valves in urban gas pipelines to obtain the optimal number of shut-off valves and the corresponding layout spacing.

[0012] To address the lack of quantitative standards for the layout of shut-off valves in sub-high-pressure and medium-pressure gas pipelines in existing technologies, and the heavy reliance on engineering experience in the design process, this invention proposes a method for optimizing the spacing of shut-off valves in urban gas pipelines. First, based on historical operation and failure data of urban gas pipelines, this application obtains the average failure probability of the pipelines. Then, by introducing pipeline physical damage and pipeline management measures, the average failure probability is corrected, and a prediction model for the failure probability of urban gas pipelines is constructed. Based on this model, the corrected pipeline failure probabilities under different operating conditions are obtained. Next, this application considers two extreme accidents following urban gas pipeline failure: jet fire accidents and vapor cloud explosion accidents. Quantitative correlations between these two accident scenarios and the mortality rate are established. Then, simulations are conducted to obtain the lethal area corresponding to each of the two accident scenarios when the mortality probability reaches a preset lethal threshold: the lethal area of ​​a jet fire thermal radiation accident and the lethal area of ​​an explosion overpressure accident. These two lethal areas can be understood as meaning that personnel within these areas have a 100% probability of death when encountering the corresponding accident scenario. Based on the lethal areas corresponding to the two different accident scenarios, the mortality consequences are calculated. Next, this application determines the ignition probability, and then, based on the corrected pipeline failure probability and the fatality consequence value obtained in the aforementioned steps, obtains the comprehensive risk value of fatalities. Finally, based on the comprehensive risk value of fatalities and the total annual cost of the shut-off valves, a multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines is constructed; the optimal number of shut-off valves and their corresponding spacing are obtained by solving the multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines.

[0013] In this application, the historical operation and failure data of urban gas pipelines collected are preferably historical data of sub-high pressure and medium pressure gas pipelines; the urban gas pipelines to be optimized are also preferably sub-high pressure and medium pressure gas pipelines.

[0014] As can be seen, this application provides an optimized layout method for shut-off valves in sub-high-pressure and medium-pressure urban gas pipelines. This method comprehensively considers pipeline failure risk and the economic cost of shut-off valves, establishing a quantitative decision-making mechanism based on the "risk-cost-benefit ratio." This solves the problems of unclear safety margins and uncertain economic benefits in traditional empirical design methods, providing a scientific and quantitative basis for determining the optimal number and spacing of shut-off valves. This application balances the precise quantification of safety risks with the practicality of engineering applications, possessing strong scientific rigor. It helps improve the inherent safety level of gas pipeline networks and provides scientific and reasonable theoretical guidance and technical support for the scientific design of gas pipeline networks.

[0015] Furthermore, in step S1:

[0016] The average failure probability of the pipeline is calculated using the following formula:

[0017] ;

[0018] In the formula: F A The average failure probability of the pipeline; m represents the m-th year; n represents the total number of years; N m L represents the number of pipeline failures in year m. i Let be the pipeline operating length in year i;

[0019] The corrected pipeline failure probability is:

[0020] ;

[0021] In the formula: i represents the i-th working condition; PoF i Let F be the corrected pipeline failure probability under the i-th operating condition; Mi F is the management measure correction factor for the i-th working condition; Di is the physical damage correction factor for the i-th working condition.

[0022] This scheme calculates the average failure probability F of urban gas pipelines using historical operation and failure data. A Then, the historical data is categorized according to different operating conditions, and management measure correction factors and physical damage correction factors are introduced under different operating conditions to reflect individual differences in pipeline sections and establish a prediction model for the failure probability of urban gas pipelines. This allows for the calculation of the corrected pipeline failure probability corresponding to different operating conditions.

[0023] Furthermore, the management action correction factor is calculated using the following formula:

[0024] ;

[0025] In the formula: F MB F is the burial depth factor; MC For regional ranking factors; F ME For public education factors; F MS For ground identification factors; F MP For line-following frequency factor; F MM To monitor and warn of early warning factors;

[0026] The physical damage correction factor is calculated using the following formula:

[0027] ;

[0028] In the formula: F C For corrosive environment correction factor; F L F is the pipe body defect correction factor. V For third-party destruction correction factor; F P For pipe manufacturing and construction correction factors; F F V is the fatigue correction factor; C V L V V V P V F F respectively C F L F V F P F F The weight.

[0029] The management measures modification factor aims to quantify the role of human intervention in reducing risk. It is calculated by indexing the evaluation values ​​of six dimensions: pipeline burial depth, regional level, public education, ground marking, patrol frequency, and monitoring and early warning measures.

[0030] This solution introduces correction factors that reflect physical damage and management level, constructs a pipeline failure probability prediction model that reflects the differences in pipeline sections, and uses it as the basic input for valve optimization layout. This provides a quantitative calculation basis that conforms to actual operational risks for the layout of shut-off valves in sub-high pressure / medium pressure gas pipelines where there are no clear standard guidelines.

[0031] This scheme clearly defines the specific calculation methods for the management measure correction factor and the physical damage correction factor. Each factor in the formula can be adaptively quantified according to specific working conditions; no specific limitations are set here, such as by manually defining specific evaluation rules or based on expert scoring. Furthermore, the weights can also be adaptively set according to specific working conditions to satisfy V... C +V L +V V +V P+V F =1 is sufficient.

[0032] Furthermore, in step S2:

[0033] The quantitative correlation between the jet fire radiation and the mortality rate is as follows:

[0034] ;

[0035] ;

[0036] In the formula: P rp q represents the probability of death under thermal radiation exposure; t represents the exposure time; P represents the probability of death under thermal radiation exposure. dp is the probability of death under thermal radiation exposure; e is the natural logarithm.

[0037] The quantitative correlation between the explosion overpressure and the mortality rate is as follows:

[0038] ;

[0039] ;

[0040] In the formula: P rb P represents the probability of death under overpressure during a vapor cloud explosion. db Δp represents the probability of death under the overpressure of a vapor cloud explosion; Δp is the overpressure value of the explosion.

[0041] This scheme clearly defines two accident scenarios and their corresponding death models. The probability of death can be understood as a specific numerical value or score of the injury caused by the accident to a person; the higher the value or score, the more severe the consequences. The probability of death, on the other hand, is the literal probability of a person dying.

[0042] Furthermore, in step S2, the methods for obtaining the lethal area of ​​a jet fire thermal radiation accident and the lethal area of ​​an explosion overpressure accident include:

[0043] S201. Based on the quantitative correlation between the jet fire thermal radiation and the mortality rate, determine the thermal radiation intensity threshold that causes death; based on the quantitative correlation between the explosion overpressure and the mortality rate, determine the explosion overpressure threshold that causes death.

[0044] S202. Simulate the jet fire accident scenario and extract the area where the thermal radiation intensity is greater than or equal to the thermal radiation intensity threshold to obtain the lethal area of ​​the jet fire thermal radiation accident.

[0045] A simulation of a vapor cloud explosion accident scenario is performed, and the region where the explosion overpressure value is greater than or equal to the explosion overpressure threshold is extracted to obtain the lethal area of ​​the explosion overpressure accident.

[0046] This scheme, based on the combined application of probabilistic model solving and simulation techniques, obtains the lethal area under jet fire thermal radiation accidents and the lethal area under explosion accidents. The methods used in this scheme to calculate the lethal area of ​​jet fire thermal radiation accidents and the lethality of explosion overpressure accidents are scientifically sound, reasonable, and easily quantifiable, providing strong support for subsequent calculations of personnel mortality consequences.

[0047] Furthermore, in step S2, the formula for calculating the consequences of death is as follows:

[0048] ;

[0049] In the formula: C i D represents the fatality consequence of pipeline failure under the i-th operating condition; pi denoted as the population density within the influence range of the i-th working condition; S is the lethal area of ​​the jet fire thermal radiation accident; A is the lethal area of ​​the explosion overpressure accident; w1 is the weight of the jet fire thermal radiation accident; w2 is the weight of the explosion overpressure accident.

[0050] This solution innovatively proposes a specific calculation method for the value of fatal consequences. The formula combines population density, accident fatality area, and accident occurrence weight, which can accurately quantify the fatal consequences caused by pipeline failure.

[0051] Furthermore, in step S3, the comprehensive risk value of personnel mortality is calculated using the following formula:

[0052] ;

[0053] In the formula: R is the comprehensive risk value for human mortality; PoF i C represents the corrected pipeline failure probability under the i-th operating condition; i f represents the fatality rate resulting from pipeline failure under the i-th operating condition; i Let l be the ignition probability under the i-th working condition; i Let be the pipeline length under the i-th working condition; l is the total length of the urban gas pipeline to be optimized.

[0054] This solution, based on the corrected pipeline failure probability and failure consequences in multiple scenarios, combined with the ignition probability, can quickly calculate the risk value of urban gas pipeline failure caused by combustion and / or explosion. The calculation formula considers the pipeline failure probability under each operating condition, as well as the corresponding fatality consequences, ignition probability, and pipeline length, ultimately summing these factors to obtain the optimized comprehensive risk value of fatalities for urban gas pipelines.

[0055] Furthermore, in step S3, the method for determining the ignition probability includes:

[0056] Leakage scenarios in urban gas pipelines are classified into: small-hole leaks, medium-hole leaks, large-hole leaks, and complete rupture leaks; among which:

[0057] If the leakage hole diameter is ≤20mm, it is a small hole leak;

[0058] If 20mm < leakage orifice diameter ≤ 80mm, then it is a medium-hole leakage;

[0059] If 80mm < leakage orifice diameter ≤ 150mm, it is considered a large orifice leak;

[0060] If 150mm is less than the leakage orifice diameter, then it is a complete rupture leak;

[0061] Based on four different leakage scenarios, the equivalent leakage rate of the urban gas pipeline to be optimized is calculated, and the ignition probability is obtained based on the equivalent leakage rate.

[0062] The equivalent leakage rate is calculated using the following formula:

[0063] ;

[0064] In the formula: W is the equivalent leakage rate; F Ln W represents the probability percentage of the nth leakage scenario. n The leakage rate for the nth leakage scenario is calculated as follows:

[0065] when hour, ;

[0066] when hour, ;

[0067] Where: P0 is the ambient pressure; P is the pressure of the medium inside the pipeline; k is the gas adiabatic index; C d R is the leakage coefficient; E is the leakage orifice area; M is the molecular weight of natural gas; g is the ideal gas constant; T is the gas operating temperature; Y is the discharge coefficient.

[0068] In this scheme, the leakage rate for each scenario is calculated based on different leakage orifice diameters of the gas pipeline, and then the total equivalent leakage rate is obtained. During the calculation of the single-scenario leakage rate, the flow state of the leaking gas is classified, and different formulas are used depending on whether the leaking fluid is sonic or subsonic, which allows for a more accurate determination of the single-scenario leakage rate. After obtaining the equivalent leakage rate, the ignition probability can be obtained using existing technologies (such as table lookup).

[0069] Furthermore, in the multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines, the objective function is: Where, min represents taking the minimum value; J1(N) is the failure risk of urban gas pipelines; J2(N) is the total annual cost of the shut-off valve.

[0070] In this plan, As the objective function of the multi-objective optimization model, the risk reduction benefit brought by unit cost input is used as the evaluation criterion, solving the problem of difficulty in selecting the solution set in multi-objective optimization. This mechanism provides engineering designers with a clear and operable mathematical basis for determining the optimal number and spacing of shut-off valves, effectively filling the gap in the current specifications for the lack of specific quantitative regulations on the valve layout spacing of sub-high pressure / medium pressure gas pipelines, and solving the pain point of current engineering designs that rely entirely on experience.

[0071] Furthermore, the solution of the multi-objective optimization model in this application can be achieved using existing technologies, and will not be elaborated here.

[0072] Furthermore, the total annual cost of the shut-off valve is calculated using the following formula:

[0073] ;

[0074] In the formula: V PN Cost of purchasing a single shut-off valve; r d y is the shut-off valve discount rate; y is the average service life of the shut-off valve; N is the number of shut-off valves.

[0075] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0076] 1. This invention provides a method for optimizing the layout spacing of shut-off valves in urban gas pipelines. It offers an optimized layout method for shut-off valves in urban gas sub-high pressure and medium pressure pipelines. This method comprehensively considers the risk of personnel death caused by pipeline failure and the economic cost of shut-off valves, and establishes a quantitative decision-making mechanism based on the "risk-cost-benefit ratio". This solves the problems of unclear safety margin and unclear economic benefits in traditional experience-based design methods, and provides a scientific and quantitative basis for determining the optimal number and spacing of shut-off valves.

[0077] 2. The present invention provides a method for optimizing the spacing of shut-off valves in urban gas pipelines. This method balances the accurate quantification of safety risks with the practicality of engineering applications. It is highly scientific and helps to improve the inherent safety level of gas pipeline networks. It provides scientific and reasonable theoretical guidance and technical support for the scientific design of gas pipeline networks.

[0078] 3. The present invention provides a method for optimizing the spacing of shut-off valves in urban gas pipelines. By introducing correction factors that reflect physical damage and management level, a pipeline failure probability prediction model that reflects the differences in pipeline sections is constructed. This model is used as the basic input for optimizing valve layout, providing a quantitative calculation basis that conforms to actual operational risks for the layout of shut-off valves in sub-high pressure / medium pressure gas pipelines where clear specifications are lacking.

[0079] 4. The present invention provides a method for optimizing the spacing of shut-off valves in urban gas pipelines. It comprehensively considers two typical accident scenarios: jet fire and vapor cloud explosion, establishes the correlation between jet fire thermal radiation and explosion overpressure and the consequences of death, and achieves accurate quantification of accident consequences.

[0080] 5. This invention provides a method for optimizing the spacing of shut-off valves in urban gas pipelines. It uses the risk reduction benefit brought by unit cost investment as the evaluation criterion, which solves the problem of difficulty in selecting the solution set in multi-objective optimization. It provides clear and operable mathematical basis for engineering designers to determine the optimal number and spacing of shut-off valves, effectively fills the gap in the current specifications for the lack of specific quantitative regulations on the spacing of valves in sub-high pressure / medium pressure gas pipelines, and solves the pain point of current engineering design based entirely on experience. Attached Figure Description

[0081] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0082] Figure 1 is a flowchart illustrating a specific embodiment of the present invention;

[0083] Figure 2 is a simulation diagram of a jet fire accident scenario in a specific embodiment of the present invention;

[0084] Figure 3 is a simulation diagram of a vapor cloud explosion accident scenario in a specific embodiment of the present invention;

[0085] Figure 4 is a correlation curve of the change in the number of shut-off valves in a specific embodiment of the present invention. Detailed Implementation

[0086] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0087] Example 1:

[0088] Figure 1 illustrates a method for optimizing the spacing of shut-off valves in urban gas pipelines, comprising the following steps:

[0089] Step 1:

[0090] Collect historical operation and failure data of urban gas pipelines and calculate the average failure probability of the pipelines.

[0091] In this embodiment, the average failure probability of the pipeline is calculated using the following formula:

[0092] ;

[0093] In the formula: F A The average failure probability of the pipeline is expressed in times per (km·a); m represents the m-th year; n represents the total number of years; N m L represents the number of pipeline failures in year m. i The length of the pipeline in year i is expressed in km.

[0094] Based on pipeline physical damage and pipeline management measures, the average failure probability of the pipeline is corrected, and a prediction model for the failure probability of urban gas pipelines is constructed to obtain the corrected pipeline failure probability under different operating conditions.

[0095] In this embodiment, the constructed urban gas pipeline failure probability prediction model is as follows:

[0096] ;

[0097] In the formula: i represents the i-th working condition; PoF i F represents the corrected pipeline failure probability under the i-th operating condition, expressed in times per (km·a); Mi F is the management measure correction factor for the i-th working condition; Di is the physical damage correction factor for the i-th working condition.

[0098] Among them, F Mi Calculated using the following formula:

[0099] ;

[0100] In the formula: F MB F is the burial depth factor; MC For regional ranking factors; F ME For public education factors; F MS For ground identification factors; F MP For line-following frequency factor; F MM To monitor and warn of early warning factors.

[0101] Among them, F Di Calculated using the following formula:

[0102] ;

[0103] In the formula: F C For corrosive environment correction factor; F LF is the pipe body defect correction factor. V For third-party destruction correction factor; F P For pipe manufacturing and construction correction factors; F F V is the fatigue correction factor; C V L V V V P V F F respectively C F L F V F P F F The weight.

[0104] Preferably, when V C V L V V V P V F When both are unknown, take V. C =V L =V V =V P =V F =0.2.

[0105] Step Two:

[0106] First, we established quantitative correlations between jet fire thermal radiation and mortality rate, and between explosion overpressure and mortality rate.

[0107] The quantitative correlation between jet thermal radiation and mortality rate is as follows:

[0108] ;

[0109] ;

[0110] In the formula: P rp q represents the probability of death under thermal radiation exposure; q is the thermal radiation intensity, in W / m². 2 t represents exposure time in seconds; P dp is the probability of death under thermal radiation exposure; e is the natural logarithm.

[0111] The quantitative correlation between explosion overpressure and mortality rate is as follows:

[0112] ;

[0113] ;

[0114] In the formula: P rb P represents the probability of death under overpressure during a vapor cloud explosion. db∆p represents the probability of death under the overpressure of a vapor cloud explosion; ∆p is the overpressure value of the explosion, in Pa.

[0115] Subsequently, based on preset lethal thresholds, simulations were conducted to obtain the lethal area of ​​the jet fire thermal radiation accident and the lethal area of ​​the explosion overpressure accident. Specific methods include:

[0116] S201. Based on the quantitative correlation between the jet fire thermal radiation and the mortality rate, determine the thermal radiation intensity threshold that causes death; based on the quantitative correlation between the explosion overpressure and the mortality rate, determine the explosion overpressure threshold that causes death.

[0117] S202. Simulate the jet fire accident scenario and extract the area where the thermal radiation intensity is greater than or equal to the thermal radiation intensity threshold to obtain the lethal area of ​​the jet fire thermal radiation accident.

[0118] A simulation of a vapor cloud explosion accident scenario is performed, and the region where the explosion overpressure value is greater than or equal to the explosion overpressure threshold is extracted to obtain the lethal area of ​​the explosion overpressure accident.

[0119] Step 3: Determine the ignition probability, and based on the corrected pipeline failure probability and the personnel death consequence value, obtain the comprehensive risk value of personnel death.

[0120] In this embodiment, the specific formula for calculating the consequence value of death is as follows:

[0121] ;

[0122] In the formula: C i D represents the number of fatalities resulting from pipeline failure under the i-th operating condition, expressed in person. pi The population density within the area affected by the i-th working condition is expressed in people / m². 2 S represents the lethal area caused by jet fire and thermal radiation accidents, in meters. 2 A represents the area of ​​death caused by the explosion overpressure accident, in meters (m²). 2 w1 represents the weight of jet fire thermal radiation accidents; w2 represents the weight of explosion overpressure accidents.

[0123] Preferably, w1=0.38 and w2=0.62.

[0124] Calculate the overall risk value of personnel mortality:

[0125] ;

[0126] In the formula: R is the comprehensive risk value for human mortality; PoF i C represents the corrected pipeline failure probability under the i-th operating condition; i f represents the number of fatalities resulting from pipeline failure under the i-th operating condition, expressed in person; iLet be the ignition probability under the i-th working condition, in %; l i is the pipeline length under the i-th operating condition, in km; l is the total length of the urban gas pipeline to be optimized, in km.

[0127] In this embodiment, the ignition probability f i Obtained through the following method:

[0128] Leakage scenarios in urban gas pipelines are classified as: small hole leaks, medium hole leaks, large hole leaks, and complete rupture leaks.

[0129] Based on four different leakage scenarios, the equivalent leakage rate of the urban gas pipeline to be optimized is calculated, and the ignition probability is obtained based on the equivalent leakage rate.

[0130] The equivalent leakage rate is calculated using the following formula:

[0131] ;

[0132] In the formula: W is the equivalent leakage rate, in kg / s; F Ln W represents the percentage of the probability of the nth leakage scenario occurring, expressed in % . n The leakage rate for the nth leakage scenario is expressed in kg / s.

[0133] W n The calculation method is as follows:

[0134] when hour, ;

[0135] when hour, ;

[0136] Where: P0 is the ambient pressure, in MPa; P is the pressure of the medium inside the pipeline, in MPa; k is the gas adiabatic index; C d The leakage coefficient is E; the leakage orifice area is E, in m². 2 M represents the molecular weight of natural gas, in g / mol; R g is the ideal gas constant; T is the gas operating temperature in K; Y is the discharge coefficient.

[0137] Preferably, when the leakage hole is circular, C is taken as... d =1.

[0138] Preferably, the outflow coefficient Y is calculated using the following formula:

[0139] .

[0140] Step 5:

[0141] Based on the failure risk of urban gas pipelines and the total annual cost of shut-off valves, a multi-objective optimization model for the layout spacing of shut-off valves in urban gas pipelines is constructed. The optimal number of shut-off valves and their corresponding layout spacing are obtained by solving the multi-objective optimization model for the layout spacing of shut-off valves in urban gas pipelines.

[0142] In the multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines in this embodiment, the objective function is:

[0143] ;

[0144] Where min represents taking the minimum value; J1(N) is the failure risk of urban gas pipeline, J1(N)=R; J2(N) is the annual total cost of the shut-off valve.

[0145] In this embodiment, the total annual cost of the shut-off valve is calculated using the following formula:

[0146] ;

[0147] In the formula: V PN Cost of a single shut-off valve, in yuan; r d y represents the shut-off valve discount rate; y represents the average service life of the shut-off valve in years; N represents the number of shut-off valves.

[0148] Example 2:

[0149] A method for optimizing the spacing of shut-off valves in urban gas pipelines, based on Example 1, includes the following steps for solving the multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines:

[0150] After dimensionless normalization, the calculated J1(N) and J2(N) are used to construct a correlation curve of risk-cost as a function of valve number / spacing.

[0151] Calculate the fuzzy value n of the abscissa corresponding to the geometric intersection point of the two curves based on the correlation curve diagram. c Rounding down gives the starting point N of the decision interval. s : .

[0152] Determine the interval step size ΔN based on the total number of simulation schemes, and construct the asymmetric decision interval D:

[0153] ;

[0154] ;

[0155] Where, N t This represents the total number of possible solutions.

[0156] Within the decision interval D, calculate the risk-cost-benefit ratio, and select the valve quantity and spacing corresponding to the peak benefit ratio as the final optimized solution:

[0157]

[0158] In the formula: η(N) is the risk-cost-benefit ratio when the number of valves increases from N-1 to N.

[0159] Example 3:

[0160] This embodiment uses a medium-pressure gas pipeline with a total length of 4.5km, an operating pressure of 0.3MPa, and an inner diameter of 200mm as an example to illustrate the method for optimizing the spacing of shut-off valves in urban gas pipelines as described in Embodiment 1. This medium-pressure gas pipeline has three operating conditions: 2km passing through the city center, 1.5km located in a transition zone, and 1km located in the suburbs.

[0161] First, the operational length and number of failures of a typical area's gas pipeline network from 2018 to 2023 were statistically analyzed, and the results are shown in Table 1.

[0162] Table 1 Statistical Results of Historical Operation and Failure Data

[0163]

[0164] Based on the statistical results in Table 1, the average pipeline failure probability in this region is calculated to be F. A =5.644×10 -2 times / (km·a).

[0165] Next, the average failure probability of the pipeline is corrected. The rules for determining the fatigue correction factor used to calculate the physical damage correction factor are shown in Table 2; the rules for determining the values ​​of some factors used to calculate the management measure correction factor are shown in Table 3. The remaining factors are similarly determined according to relevant rules or expert scoring methods.

[0166] Table 2 Rules for Determining Fatigue Correction Factor Values

[0167]

[0168] Table 3. Rules for the Values ​​of Some Factors

[0169]

[0170] In this embodiment, the corrected pipeline failure probability is calculated to be PoF1 = 4.36 × 10⁻⁶. -3 times / (km·a), PoF2=1.26×10-2 times / (km·a), PoF3=3.02×10 -2 times / (km·a). Where PoF1 represents the corrected pipeline failure probability under the city center condition, PoF2 represents the corrected pipeline failure probability under the transition zone condition, and PoF3 represents the corrected pipeline failure probability under the suburban condition.

[0171] Subsequently, with a preset lethal threshold of 100%, and based on the quantitative correlation between jet fire thermal radiation and mortality rate, and the quantitative correlation between explosion overpressure and mortality rate, the thermal radiation intensity threshold q corresponding to 100% mortality within the range was calculated to be 37.5 kW / m². 2 The explosion overpressure threshold ∆p = 0.03 MPa.

[0172] Taking into account different shut-off valve spacings and the range of leakage consequences under different leakage scenarios (orifice diameters), the selection of pipeline leakage orifice diameters and leakage probabilities under different leakage scenarios is shown in Table 4:

[0173] Table 4. Pipeline leakage aperture and leakage probability under different leakage scenarios

[0174]

[0175] Based on the above thermal radiation intensity threshold and explosion overpressure threshold, simulation software was used to simulate the consequences of different situations. The simulation results of a typical accident (shut-off valve spacing 0.9km, leakage orifice diameter 150mm) are shown in Figures 2 and 3.

[0176] Taking a shut-off valve spacing of 1.5 km as an example, the lethal radius and lethal area under various leakage scenarios are shown in Table 5. Based on the probability proportion of each leakage scenario, the weighted sum of the accident lethal area yields a lethal area of ​​297.3 m² for the jet fire thermal radiation accident. 2 The fatal area caused by the explosion and overpressure accident was 208.14 m². 2 .

[0177] Table 5 Simulation results of various leakage scenarios when the distance between shut-off valves is 1.5 km.

[0178]

[0179] An analysis was conducted on the different spacing of shut-off valves, taking into account the city center population density of 9800 people / km². 2 The fatality rates for the city center area under different deployment spacings are shown in Table 6. Similarly, the fatality rates for the transition zone and suburbs are shown in Table 7.

[0180] Table 6. Fatal Consequences in the City Center Area with Different Shut-off Valve Spacing

[0181]

[0182] Table 7. Fatal Consequences in Transition Zones and Suburbs with Different Shut-off Valve Spacing

[0183]

[0184] Then, the overall risk value for fatalities can be calculated:

[0185] First, calculate the leakage rate W under different leakage scenarios. n The calculation results are shown in Table 8:

[0186] Table 8 Leakage rates under different leakage scenarios

[0187]

[0188] Secondly, the equivalent leakage rate W was calculated to be 3.96019 kg / s.

[0189] According to Table 9, the ignition probability can be obtained from the table. In this embodiment, f1=1.58%, and similarly, f2=1.58% and f3=0.17%.

[0190] Table 9. Ignition Probability Values

[0191]

[0192] At this point, the comprehensive risk value R of personnel mortality under different numbers and spacings of shut-off valves can be calculated, and the calculation results are shown in Table 10.

[0193] Table 10 Failure Risk Values ​​of Urban Gas Pipelines under Different Shut-off Valve Spacing

[0194]

[0195] Finally, a multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines is solved to obtain the optimal valve spacing under multi-objective optimization.

[0196] In this embodiment, the process of solving the multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines specifically includes:

[0197] Analysis of multi-objective function values: By querying the basic parameters of shut-off valves from multiple companies, the purchase cost V of a single shut-off valve can be obtained. PN =10000 yuan, discount rate r d =4.5%, average service life y=10 years.

[0198] The failure risk of urban gas pipelines and the total annual cost of shut-off valves under different shut-off valve spacings were calculated, and the results are shown in Table 11.

[0199] Table 11 Failure Risk of Urban Gas Pipelines and Total Annual Cost of Shut-off Valves under Different Shut-off Valve Spacing

[0200]

[0201] The data in Table 11 were normalized to construct the correlation curves between J1(N), J2(N) and the number of shut-off valves, as shown in Figure 4.

[0202] Based on Figure 4, calculate the x-coordinate n corresponding to the geometric intersection point of the two curves. c ,according to The starting point N of the interval is obtained. s =5; according to The calculated extension step size ΔN = 2, according to Thus, the decision interval D = [5, 7] is obtained.

[0203] Determine the optimal spacing of the shut-off valves: Within the decision interval D, calculate the risk-cost-benefit ratio of each scheme. The calculation results are shown in Table 12.

[0204] Table 12 Results of Deployment Schemes within the Decision Interval

[0205]

[0206] It can be seen that the risk-cost-benefit ratio is highest when the number of shut-off valves is 7. Therefore, the optimized number of shut-off valves for this pipeline section is 7, with a spacing of 0.75 km.

[0207] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0208] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process or method that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process or method.

Claims

1. A method for optimizing the spacing of shut-off valves in urban gas pipelines, characterized in that, Includes the following steps: S1. Collect historical operation and failure data of urban gas pipelines and calculate the average failure probability of the pipelines; Based on pipeline physical damage and pipeline management measures, the average failure probability of the pipeline is corrected, and a prediction model for the failure probability of urban gas pipelines is constructed to obtain the corrected pipeline failure probability under different operating conditions; S2, considering the jet fire accident scenario and the vapor cloud explosion accident scenario respectively, a quantitative correlation between jet fire thermal radiation and personnel mortality rate and a quantitative correlation between explosion overpressure and personnel mortality rate are established; combined with the preset lethal threshold, simulation is performed to obtain the lethal area of ​​jet fire thermal radiation accident and the lethal area of ​​explosion overpressure accident; Combining the aforementioned jet fire accident scenario and vapor cloud explosion accident scenario, a failure consequence prediction model is constructed to calculate the fatality consequence value; the quantitative correlation between the jet fire thermal radiation and the fatality rate is as follows: ； In the formula: P rp This represents the probability of death under thermal radiation exposure. q represents the intensity of thermal radiation; t represents the exposure time; P dp Let be the probability of death under thermal radiation exposure; e be the natural logarithm; the quantitative correlation between the explosion overpressure and the mortality rate is as follows: ； In the formula: P rb P represents the probability of death under overpressure during a vapor cloud explosion. db The probability of death under overpressure during a vapor cloud explosion; ∆p is the explosion overpressure value; The methods for obtaining the lethal area of ​​a jet fire thermal radiation accident and the lethal area of ​​an explosion overpressure accident include: S201, determining the lethal thermal radiation intensity threshold based on the quantitative correlation between jet fire thermal radiation and the mortality rate; determining the lethal explosion overpressure threshold based on the quantitative correlation between explosion overpressure and the mortality rate; S202, simulating a jet fire accident scenario and extracting areas with thermal radiation intensity greater than or equal to the thermal radiation intensity threshold to obtain the lethal area of ​​the jet fire thermal radiation accident; simulating a vapor cloud explosion accident scenario and extracting areas with explosion overpressure values ​​greater than or equal to the explosion overpressure threshold to obtain the lethal area of ​​the explosion overpressure accident; the formula for calculating the mortality consequence value is: In the formula: C i D represents the fatality consequence of pipeline failure under the i-th operating condition; pi S represents the population density within the impact range of the i-th working condition; S represents the lethal area of ​​a jet fire thermal radiation accident; A represents the lethal area of ​​an explosion overpressure accident; w1 represents the weight of a jet fire thermal radiation accident; w2 represents the weight of an explosion overpressure accident; S3, determine the ignition probability, and based on the corrected pipeline failure probability and the personnel death consequence value, obtain the comprehensive personnel death risk value; the comprehensive personnel death risk value is calculated using the following formula: In the formula: R is the comprehensive risk value for human mortality; PoF i C represents the corrected pipeline failure probability under the i-th operating condition; i f represents the fatality rate resulting from pipeline failure under the i-th operating condition; i Let l be the ignition probability under the i-th working condition; i Let l be the pipeline length under the i-th working condition; l is the total length of the urban gas pipeline to be optimized; S4. Based on the comprehensive risk value of personnel deaths and the annual total cost of the shut-off valve, construct a multi-objective optimization model for the layout spacing of the shut-off valves in the urban gas pipeline; solve the multi-objective optimization model for the layout spacing of the shut-off valves in the urban gas pipeline to obtain the optimal number of shut-off valves and the corresponding layout spacing.

2. The method for optimizing the spacing of shut-off valves in urban gas pipelines according to claim 1, characterized in that, In step S1: the average failure probability of the pipeline is calculated using the following formula: In the formula: F A The average failure probability of the pipeline; m represents the m-th year; n represents the total number of years; N m L represents the number of pipeline failures in year m. i Let be the pipeline operating length in year i; the urban gas pipeline failure probability prediction model is as follows: In the formula: i represents the i-th working condition; PoF i Let F be the corrected pipeline failure probability under the i-th operating condition; Mi F is the management measure correction factor for the i-th working condition; Di is the physical damage correction factor for the i-th working condition.

3. The method for optimizing the spacing of shut-off valves in urban gas pipelines according to claim 2, characterized in that, The management action correction factor is calculated using the following formula: In the formula: F MB F is the burial depth factor; MC For regional ranking factors; F ME For public education factors; F MS For ground identification factors; F MP For line-following frequency factor; F MM To monitor and warn of early warning factors, the physical damage correction factor is calculated using the following formula: In the formula: F C For corrosive environment correction factor; F L F is the pipe body defect correction factor. V For third-party destruction correction factor; F P For pipe manufacturing and construction correction factors; F F V is the fatigue correction factor; C V L V V V P V F F respectively C F L F V F P F F The weight.

4. The method for optimizing the spacing of shut-off valves in urban gas pipelines according to claim 1, characterized in that, In step S3, the method for determining the ignition probability includes: classifying the leakage scenarios of urban gas pipelines into: small-hole leakage, medium-hole leakage, large-hole leakage, and complete rupture leakage; wherein: if the leakage orifice diameter is ≤20mm, it is a small-hole leakage; if 20mm < leakage orifice diameter ≤80mm, it is a medium-hole leakage; if 80mm < leakage orifice diameter ≤150mm, it is a large-hole leakage; if 150mm < leakage orifice diameter, it is a complete rupture leakage; based on the four different leakage scenarios, the equivalent leakage rate of the urban gas pipeline to be optimized is calculated, and the ignition probability is obtained based on the equivalent leakage rate; the equivalent leakage rate is calculated using the following formula: In the formula: W is the equivalent leakage rate; F Ln W represents the probability percentage of the nth leakage scenario. n The leakage rate for the nth leakage scenario is calculated as follows: when hour, ;when hour, In the formula: P0 is the ambient pressure; P is the pressure of the medium inside the pipeline; k is the gas adiabatic index; C d R is the leakage coefficient; E is the leakage orifice area; M is the molecular weight of natural gas; g is the ideal gas constant; T is the gas operating temperature; Y is the discharge coefficient.

5. The method for optimizing the spacing of shut-off valves in urban gas pipelines according to claim 1, characterized in that, In the multi-objective optimization model for the spacing of shut-off valves in urban gas pipelines, the objective function is: Where, min represents taking the minimum value; J1(N) is the failure risk of urban gas pipelines; J2(N) is the total annual cost of the shut-off valve.

6. The method for optimizing the spacing of shut-off valves in urban gas pipelines according to claim 5, characterized in that, The total annual cost of the shut-off valve is calculated using the following formula: In the formula: V PN Cost of purchasing a single shut-off valve; r d y is the shut-off valve discount rate; y is the average service life of the shut-off valve; N is the number of shut-off valves.

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