A gas pipeline leakage positioning method based on time and risk dimension

Abstract

The application discloses a kind of gas pipeline leakage positioning method based on time and risk dimension, it is related to gas pipeline monitoring technical field, including the following steps: based on alarm positioning determination traceability range gas pipeline as preliminary traceability object;Obtain each gas pipeline and alarm pipeline maximum leakage concentration of existence, based on leakage concentration of traceability object screening;Obtain the shortest time of gas pipeline soil diffusion to connected pipeline;Obtain the connected pipeline gas diffusion time that causes alarm point to reach maximum alarm concentration;Based on soil diffusion time and connected pipeline gas diffusion time, obtain the shortest diffusion time of alarm point to reach maximum alarm concentration, based on gas pipeline soil diffusion time and connected pipeline gas diffusion time, preliminary ordering of traceability object is carried out, based on preliminary ordering result and in combination with gas pipeline leakage possibility analysis and gas pipeline soil traceability analysis, gas pipeline traceability priority is revised.

Description

Technical Field

[0001] This invention relates to the field of gas pipeline monitoring technology, specifically to a gas pipeline leak location method based on time and risk dimensions. Background Technology

[0002] With the rapid development of urban construction, various underground infrastructures are increasing, and the phenomenon of proximity and intersection with gas pipeline facilities is very common. When a buried gas pipeline leaks, it can easily spread through the soil to nearby underground spaces, thereby inducing a gas explosion accident. Therefore, for gas pipeline leak accidents, on the one hand, it is necessary to manage the pipeline hazards to eliminate or reduce the gas pipeline hazards in essence; on the other hand, it is necessary to quickly trace the leak point after the gas monitoring equipment alarms to suppress the occurrence and development of the accident.

[0003] Currently, research on gas leak prediction and tracing in the field of gas monitoring systems is limited. Most studies focus on gas diffusion in soil, and tracing techniques are confined to individual manholes. However, urban underground spaces are highly complex, with interconnected pipelines making up a significant proportion. Therefore, research on the diffusion and tracing of interconnected pipelines can provide assurance for gas safety monitoring and emergency response. For example, a gas leak tracing method and device disclosed in patent number 201810482649.x involves predicting the target gas pipeline in the gas network based on the gas diffusion characteristics in adjacent underground spaces, the monitored gas concentration values ​​in adjacent underground spaces, and the location information of the adjacent underground spaces, if a gas leak is detected in the gas pipeline network. This invention patent provides a method and device that can predict the target gas pipeline with a gas leak simply by detecting the gas concentration values ​​in adjacent underground spaces, resulting in high efficiency in gas leak tracing.

[0004] However, in real-world scenarios, gas pipelines often intersect with other adjacent pipelines. Existing technologies cannot quickly trace leaking pipelines after alarms are triggered by monitoring equipment in adjacent underground spaces, nor can they determine the priority gas pipelines for emergency repairs. Summary of the Invention

[0005] The purpose of this invention is to provide a gas pipeline leak location method based on time and risk dimensions, solving the following technical problems: To address the issues of the inability to quickly trace leaking pipelines after alarms from monitoring equipment in adjacent underground spaces and the inability to prioritize gas pipelines for emergency repairs, this invention provides technical guidance for emergency rescue by rapidly tracing gas pipeline leaks and prioritizing gas pipeline repairs based on time and pipeline leakage risk dimensions.

[0006] The objective of this invention can be achieved through the following technical solutions: A gas pipeline leak location method based on time and risk dimensions includes the following steps: S101. Based on alarm location, determine the gas pipeline within the traceability range as the initial traceability target; S102. Obtain the maximum leakage ingress concentration for each gas pipeline and alarm pipeline, and screen the source tracing objects based on the leakage ingress concentration; S103. Obtain the time t for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth ; S104. Obtain the gas diffusion time t in the connecting pipeline that causes the alarm point to reach the maximum alarm concentration. pipe ; S105, Based on the time t it takes for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth Gas diffusion time t in connecting pipelines pipe The shortest diffusion time t for the alarm point to reach the maximum alarm concentration is obtained. source , i.e. t source =t earth +t pipe ; S106, Based on the time t for gas to diffuse from the leak point through the soil to the connecting pipeline. earth and the gas diffusion time t in the connecting pipeline pipe Perform preliminary sorting of the traceable objects; S107. Based on the preliminary ranking results and combined with the gas pipeline leakage probability analysis and gas pipeline soil source tracing analysis, the gas pipeline source tracing priority is revised.

[0007] Preferably, in step S103, the relationship between the soil diffusion warning range and time is determined based on the hardened and unhardened road surfaces.

[0008] Preferably, in step S103: Based on the type of road surface above the gas pipeline, and combined with the distance L between the shortest distance point between the gas pipeline and the connecting pipeline... dis The time t takes for the gas to diffuse from the leak point through the soil to the connecting pipeline is calculated using a function: earth =solve(EWB) HSG ==L dis ,t) or t earth =solve(EWB) UHSG ==L dis ,t).

[0009] Preferably, in step S104, the connecting pipeline is divided into a waterless pipeline and a water-containing pipeline.

[0010] Preferably, in step S104, for waterless pipelines: When a single alarm point exists: Calculation of the change in concentration at the alarm point over time:

[0011] In the above formula: c(t) is the concentration value at alarm point t, m³ / m³; max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v x D is the gas diffusion velocity within the pipeline between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point, in m / s; t x is the turbulent diffusion coefficient within the pipeline between the shortest distance point of the gas pipeline and the connecting pipeline and the alarm point, in m² / s; x0 is the distance between the shortest distance point of the gas pipeline and the alarm point and the alarm point, in m; t is the diffusion time, in s; t α The unit of time is 1 second; Preferably, the diffusion time is calculated as: t pipe =solve(c(x0,t)==c0,t) Where: c0 is the maximum alarm concentration at the alarm point, m³ / m³; t pipe The gas diffusion time in the connecting pipeline is in seconds.

[0012] Preferably, when there are two or more alarm points: diffusion time t pipe :t pipe =max(t) n , t a ).

[0013] Preferably, when there are two or more gas pipeline sections t source At the same time, through the analysis of the burial depth of the gas pipeline, the deeper the gas pipeline is buried, the higher the priority of tracing its source.

[0014] Preferably, in step S107, the higher the probability of gas pipe damage and leakage and the shorter the soil diffusion time, the higher the priority of source tracing based on the results of damage and leakage probability analysis and soil source tracing analysis.

[0015] The beneficial effects of this invention are: This invention traces the source of leaks based on the changing trend of concentration monitored by monitoring equipment, data from the pipeline where the monitoring equipment is located, data from adjacent gas pipelines, and soil environmental data, using VI models, gas diffusion models, etc. This invention divides the source tracing process into three stages: first, defining gas pipelines within a 12.5m range as the source tracing targets; second, narrowing down the source targets based on theoretically predicted maximum concentrations and actual monitored maximum concentrations—that is, if the theoretically predicted maximum concentration is less than the actual monitored concentration, it indicates that the gas pipeline is unlikely to leak and is not included in the source tracing scope; similarly, only those concentrations greater than or equal to the actual monitored concentration are considered; and finally, combining leakage probability with soil source tracing analysis enables rapid source tracing of gas pipelines and prioritization of source tracing, resulting in higher accuracy in locating gas leaks. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of a gas pipeline leak location method based on time and risk dimensions according to the present invention. Figure 2 This is a schematic diagram showing the positional relationship between the gas pipeline and the connecting pipeline on the outer side in this invention; Figure 3 This is a schematic diagram showing the relationship between the gas pipeline and the connecting pipeline in the middle position in this invention; Figure 4 This is a schematic diagram showing the downstream position relationship between the gas pipeline and the connecting pipeline in this invention; Figure 5 This is a schematic diagram showing the downstream position relationship between the gas pipeline and the pipeline where the alarm point is located in this invention; Figure 6 This is a schematic diagram showing the downstream position relationship between the gas pipeline and the pipeline where the alarm point is located in this invention; Figure 7 This is a schematic diagram showing the upstream position relationship between the gas pipeline and the alarm point in this invention; Figure 8 This is a schematic diagram of the leakage hole size parameters in this invention; Figure 9 This is a schematic diagram of gas diffusion into adjacent pipelines in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 Please see Figure 1 As shown, this invention is a gas pipeline leak location method based on time and risk dimensions, comprising the following steps: S101. Based on alarm location, determine the gas pipeline within the traceability range as the initial traceability target; S102. Obtain the maximum leakage ingress concentration for each gas pipeline and alarm pipeline, and screen the source tracing objects based on the leakage ingress concentration; S103. Obtain the time t for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth ; S104. Obtain the gas diffusion time t in the connecting pipeline that causes the alarm point to reach the maximum alarm concentration. pipe ; S105, Based on the time t it takes for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth and gas diffusion time t in the connecting pipeline pipe The shortest diffusion time t for the alarm point to reach the maximum alarm concentration is obtained. source , i.e. t source =t earth +t pipe ; S106, Based on the time t for gas to diffuse from the leak point through the soil to the connecting pipeline. earth and the gas diffusion time t in the connecting pipeline pipe Perform preliminary sorting of the traceable objects; S107. Based on the preliminary ranking results and combined with the gas pipeline leakage probability analysis and gas pipeline soil source tracing analysis, the gas pipeline source tracing priority is revised.

[0020] Specifically, in step S103, the relationship between the soil diffusion warning range and time is determined based on the hardened and unhardened road surfaces: (1) Warning range and time under hardened road surface:

[0021] (2) Warning range and time for unpaved road surfaces:

[0022] In the above formula: p is the gas pipeline pressure, MPa; d is the diameter of the leak hole, mm; h g φ represents the burial depth of the gas pipeline (m); t represents the leakage time (s); and φ represents the soil porosity around the gas pipeline (cm). 3 / cm 3 S solid The soil saturation level is %; V dc The coefficient of soil viscosity, 1 / m 2 ;I dc The soil inertial drag coefficient is 1 / m; Soil diffusion time calculation: Based on the type of road surface above the gas pipeline, combined with the distance L between the shortest distance point between the gas pipeline and the connecting pipeline. dis The time it takes for the gas to diffuse from the leak point through the soil to the connecting pipeline is calculated using a function: t earth =solve(EWB) HSG ==L dis ,t) or t earth =solve(EWB) UHSG ==L dis ,t) In step S104, the connecting pipeline is divided into a waterless pipeline and a water-containing pipeline; For waterless pipelines: When a single alarm point exists: Calculation of the change in concentration at the alarm point over time:

[0023] In the above formula: c(t) is the concentration value at alarm point t, m³ / m³; c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v x D is the gas diffusion velocity within the pipeline between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point, in m / s; t The turbulence diffusion coefficient (m) is the distance between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point within the pipeline. 2 / s; x0 is the distance between the shortest distance point between the gas pipeline and the alarm point (the influence of intermediate inspection wells can be superimposed), m; t is the diffusion time, s; t α The unit of time is 1 second; Diffusion time calculation: t pipe =solve(c(x0,t)==c0,t) Where: c0 is the maximum alarm concentration at the alarm point, m³ / m³; t pipe The gas diffusion time in the connecting pipeline is expressed in seconds. When there are two or more alarm points: diffusion time t pipe :t pipe =max(t) n , t a ); Please see Figure 2 Example: Two alarm points, with the closest point between the gas pipeline and the connecting pipeline located outside the alarm point: If the maximum concentration at the remote alarm point is c 0-a > Concentration c at the nearest alarm point 0-n The gas pipeline was ruled out as the primary source of the problem. If the maximum concentration at the remote alarm point is c 0-a ≤ Concentration at the nearest alarm point c 0-n Then, the gas pipeline will be used as one of the main objects of analysis for further analysis; a. Dispersion time t of the near-field alarm point n :

[0024]

[0025] t n =solve(c n (x) n ,t)==c 0-n ,t) In the formula: c single-n For a specific time t, a gas pipeline leaks into a connecting pipeline at time x. n Instantaneous concentration at a given location, m³ / m³; c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; x n The length of the gas pipeline between the nearest point of connection to the gas pipeline and the nearest alarm point, in meters (m); v x The gas diffusion velocity within the pipeline between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point, in m / s; c 0-n The maximum alarm concentration near the alarm point, in m³ / m³; D n The turbulence diffusion coefficient between the nearest point on the gas pipeline and the alarm point, in square meters per second (m² / s); t is the diffusion time, in seconds (s). α The unit of time is 1 second; b. Dispersion time t of the remote alarm point a : Considering the characteristics of gas diffusion across wells, the concentration change at a more distant alarm point is calculated based on the concentration change during a single leak at a nearby alarm point:

[0026] t a =solve(c a (x) space ,t)==c 0-a ,t) In the formula: x space v is the length of the connecting pipeline between the two alarm points, in meters. mid and D mid c represents the gas diffusion velocity and turbulent diffusion coefficient of the connecting pipeline between the two alarm points. 0-a The maximum alarm concentration at a more distant alarm point is expressed in m³ / m³; t is the diffusion time, expressed in seconds. αThe unit of time is 1 second; Please see Figure 3 The closest point between the gas pipeline and the connecting pipeline is located between the alarm points: Proximity alarm point diffusion time t n :

[0027] t a =solve(c a (x) space ,t)==c 0-a ,t) Long-distance alarm point diffusion time t a :

[0028] t a =solve(c a (x) space ,t)==c 0-a , t In the formula: x n x is the distance between the minimum distance point between the gas pipeline and the alarm pipeline and the nearest alarm point, in meters (m). a The distance between the minimum distance point between the gas pipeline and the alarm pipeline and the most distant alarm point is m; t is the diffusion time, s; t α The unit of time is 1 second; Minimum alarm time for leakage: In S105, based on the above analysis, the time t required for the nearest alarm point to reach the maximum alarm concentration after a gas pipeline leak is calculated. n Calculate the time t it takes for a gas pipeline leak to cause the maximum alarm concentration to reach a more distant alarm point. a The maximum value of the two values ​​is the shortest time for the gas pipeline to trigger alarms at both alarm points. t pipe =max(t) n , t a ) Note: The calculation method is the same regardless of which side the shortest distance between the gas pipeline and the alarm pipeline is on.

[0029] For those with water pipes: When a single alarm point exists: Please see Figure 4 The shortest distance between the gas pipeline and the alarm pipeline is located downstream of the alarm point: a. If there is no backflow in the pipeline where the shortest distance between the gas pipeline and the alarm pipeline is located, then that pipeline is excluded as the main source tracing target. b. If there is backflow between the gas pipeline and the alarm pipeline at the point where the shortest distance is between them, then that gas pipeline will be considered as one of the primary sources for further analysis:

[0030] t pipe =solve(c(x0,t)==c0,t) In the above formula: c(t) is the concentration value at alarm point t, m³ / m³; max x0 represents the maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; x0 represents the distance between the shortest distance point between the gas pipeline and the alarm point, in meters; v n-up D represents the gas backflow diffusion velocity (m / s) between the shortest distance between the gas pipeline and the connecting pipeline and the alarm point, where there is water in the pipeline. t The turbulent diffusion coefficient (m) between the shortest distance between the gas pipeline and the connecting pipeline and the alarm point for the water pipeline. 2 / s; t is the diffusion time, s; t α The unit of time is 1 second; The shortest distance between the gas pipeline and the alarm pipeline is located upstream of the alarm point: c. Backflow exists in the pipeline where the shortest distance between the gas pipeline and the alarm pipeline is located:

[0031] t pipe= solve(c(x0,t)==c0,t) d. There is no backflow on the pipeline where the shortest distance between the gas pipeline and the alarm pipeline is located:

[0032] t pipe =solve(c(x0,t)==c0,t) In the above formula: c max x0 represents the maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; x0 represents the distance between the shortest distance point between the gas pipeline and the alarm point, in meters; v n-down The downstream diffusion velocity (m / s) of gas between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point, where there is water in the pipeline and gas is flowing backwards. w-down D is the downstream diffusion velocity of gas between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point, assuming no backflow of gas through the water pipeline; t The turbulent diffusion coefficient (m) between the shortest distance between the gas pipeline and the connecting pipeline and the alarm point for the water pipeline. 2 / s; t is the diffusion time, s; t α The unit of time is 1 second; When there are two or more alarm points: if the shortest distance between the gas pipeline and the alarm pipeline is located in the pipeline between the alarm points, then the diffusion time t pipe =max(t) up , t down ); For other cases: t pipe =max(t) n , t a ) Please see Figure 5 The closest distance between the gas pipeline and the alarm pipeline is located downstream of both alarm points: When the maximum concentration at a more distant alarm point is c 0-a >Maximum concentration c near the alarm point 0-n The gas pipeline was ruled out as the primary source of the problem. When the maximum concentration at a more distant alarm point is c 0-a ≤ Maximum concentration near alarm point c 0-n : If both exist, then the gas pipeline will be considered one of the primary sources for tracing and will be analyzed further. If one or more of them do not have backflow, the possibility of the gas pipeline leak causing each monitoring point to reach the maximum alarm concentration is low, and it will not be the main object of source tracing analysis. Proximity alarm point diffusion time t n :

[0033]

[0034] t n =solve(c n (x0, t) == c 0-n ,t) In the formula: c single-n For a specific time t, a gas pipeline leaks into a connecting pipeline at time x. n Instantaneous concentration at a given location, m³ / m³; c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; x n The length of the gas pipeline between the nearest point of connection to the gas pipeline and the nearest alarm point, in meters (m); v n-up-n D is the gas backflow diffusion velocity between the nearest point of the gas pipeline and the alarm pipeline and the nearest alarm point, in m / s; n The turbulent diffusion velocity between the nearest point of the gas pipeline and the alarm pipeline and the nearest alarm point is m² / s; t is the diffusion time, s. α The unit of time is 1 second; Long-distance alarm point diffusion time t a :

[0035] t a =solve(c up (x) mid ,t)==c 0-a ,t) In the formula: v n-up-mid D is the gas backflow diffusion velocity in the pipeline between the two alarm points, in m / s; mid The turbulent diffusion velocity in the pipeline between the two alarm points is m. 2 / s;t α The unit of time is 1 second; Please see Figure 6 The closest point between the gas pipeline and the alarm pipeline is located in the middle of the alarm point: a. If there is no backflow in the connecting pipeline between the alarm points, then the gas pipeline is excluded as the main source of the problem. b. If there is backflow in the connecting pipeline between the alarm points, then this gas pipeline will be considered as one of the main sources of the problem and will be analyzed further: Upstream alarm point diffusion time t up :

[0036] In the formula: v n-up-mid D is the gas backflow diffusion velocity in the pipeline between the two alarm points, in m / s; mid The turbulent diffusion velocity in the pipeline between the two alarm points is m. 2 / s;x up The distance between the shortest distance between the gas pipeline and the alarm pipeline and the upstream alarm point is the pipeline length, in meters (m); t is the diffusion time, in seconds (s). α The unit of time is 1 second; Downstream alarm point diffusion time t down :

[0037] In the formula: v n-down-mid x represents the downstream gas diffusion velocity in the pipeline between the two alarm points, in m / s; down The distance between the shortest distance between the gas pipeline and the alarm pipeline and the upstream alarm point is the pipeline length, in meters (m); t is the diffusion time, in seconds (s). α The unit of time is 1 second; Please see Figure 7 The shortest distance between the gas pipeline and the alarm pipeline is located upstream of the two alarm points: Near alarm point diffusion time t n :

[0038]

[0039]

[0040] t n =solve(c n (x) n ,t)==c 0-n ,t) Among them, the shortest distance point is the point where the gas pipeline and the alarm pipeline are closest; c single-n For a specific time t, a gas pipeline leaks into a connecting pipeline at time x. n Instantaneous concentration at a given location, m³ / m³; c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; x n The length of the gas pipeline between the nearest point of connection to the gas pipeline and the nearest alarm point, in meters (m); v sn D is the gas diffusion velocity in m / s between the nearest point of the gas pipeline and the alarm pipeline and the nearest alarm point. n The turbulent diffusion velocity between the nearest point of the gas pipeline and the alarm pipeline and the nearest alarm point is m² / s; t is the diffusion time, s. α The unit of time is 1 second; Long-distance alarm point diffusion time t a :

[0041]

[0042] t a =solve(c a (x) mid ,t)==c 0-a ,t) In the formula: v sw The gas diffusion velocity in the pipeline between the distant alarm point and the nearest alarm point, in m / s; x mid D is the pipeline length between the remote alarm point and the nearest alarm point, in meters. mid The turbulent diffusion velocity in the pipeline between the two alarm points is m. 2 / s;t α The unit of time is 1 second; In S105, for cases where multiple adjacent manholes alarm, tracing the source of the gas leak requires calculating the concentration diffusion time at each alarm point. The maximum required diffusion time at different alarm points is taken as the shortest time for the gas pipeline leak to cause multiple manholes to reach the maximum alarm concentration, i.e.: t pipe =max(t)up ,t down ) In the above formula: t up The time required for the upstream alarm point to reach the maximum alarm concentration, s; t down The time required for the downstream alarm point to reach the maximum alarm concentration, in seconds; Furthermore, in S106, the required diffusion time t for the proximity alarm point... n : The diffusion time of the upstream alarm point is calculated based on whether there is a backflow upstream of the alarm point:

[0043] The gas distribution at alarm point A per unit leakage time after a combustible gas leaks into the connecting pipeline can be described by the following formula:

[0044] Based on the gas pipeline diffusion VI model, the concentration at a nearby alarm point at a specific moment is:

[0045] In the above formula: c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v sn D is the gas backflow diffusion velocity between the shortest distance point between the gas pipeline and the alarm pipeline and the nearest alarm point, in m / s; n The turbulence diffusion coefficient, m, is the distance between the shortest distance point between the gas pipeline and the alarm pipeline and the nearest alarm point. 2 / s;x n The distance between the shortest distance between the gas pipeline and the alarm pipeline and the nearest alarm point, in meters (m); t α The unit of time is 1 second; Based on the above formula, the maximum alarm concentration c near the alarm point can be used as a reference. 0-n And the distance x between the shortest distance point between the gas pipeline and the alarm point and the downstream alarm point. n Calculate the gas diffusion time from the point of entry of the connecting pipeline to the nearest alarm point to reach the maximum alarm concentration by working backwards. tn=solve(c n (x) n ,t)==c 0-n ,t) Distance time t required for long-distance alarm point a : The diffusion time of the upstream alarm point is calculated based on whether there is a backflow upstream of the alarm point:

[0046] The gas distribution at alarm point A per unit leakage time after a combustible gas leaks into the connecting pipeline can be described by the following formula:

[0047] Based on the gas pipeline diffusion VI model, the concentration at alarm point B at a specific moment is:

[0048] In the above formula: c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v sw D represents the gas diffusion velocity in the intermediate pipeline at the alarm point, in m / s. mid Let m be the turbulence diffusion coefficient of the pipeline between the alarm points. 2 / s;x mid The distance between the two alarm points is in meters (m); t α The unit of time is 1 second; Based on the above formula, the maximum alarm concentration c at a more distant alarm point can be used as a reference. 0-a And the distance x between the shortest distance point between the gas pipeline and the alarm point and the downstream alarm point. mid Calculate the gas diffusion time from the point of entry into the connecting pipeline to the alarm point by working backwards; t a =solve(c a (x) mid ,t)==c 0-a ,t) Minimum diffusion time required for alarm point: In cases where multiple adjacent manholes trigger alarms, tracing the source of the gas leak requires calculating the concentration diffusion time at each alarm point. The maximum required diffusion time at each alarm point is taken as the shortest time for the gas pipeline leak to cause multiple manholes to reach the maximum alarm concentration. t pipe =max(t) n , t a ) In the above formula: t n The time required for the concentration at the nearest alarm point to reach the maximum alarm level, s; t a The time required for a distant alarm point to reach the maximum alarm concentration, in seconds; Based on the gas pipeline, the shortest time t for each alarm point to reach its maximum alarm concentration is 1. source When tracing gas pipelines, the shorter the time, the higher the priority. When two or more gas pipeline segments t exist... source At the same time, through the analysis of the burial depth of the gas pipeline, the deeper the gas pipeline is buried, the higher the priority of tracing its source.

[0049] Example 2 Soil diffusion process of gas pipelines: Maximum leakage rate of gas pipeline in soil: The above-ground leakage of a gas pipeline is expressed as follows:

[0050] The leakage amount of a gas pipeline leak into the soil can be expressed as:

[0051] Where q is the gas pipeline leakage rate, m 3 / s; p is the pipeline leakage pressure, MPa; it can be obtained directly, or the maximum pressure value corresponding to the pressure rating P of the gas pipeline can be taken. β is the ratio of the leak orifice diameter to the gas pipeline diameter, i.e., the orifice-to-pipe ratio. . The equivalent diameter of the leak outlet, calculated by default as a small hole leak, is in mm; the setting can be corrected as follows: Figure 8 As shown; Specifically, based on the soil stratification above the gas pipeline, the changes in gas leakage concentration were analyzed: Single soil layer: For gas pipeline leaks, the burial depth of the gas pipeline has a certain impact on its diffusion range. Assuming the soil environment where the gas leak diffuses is uniform and homogeneous, when the pipeline is shallow (d... f When the gas pipeline surface is less than 1.5m, the covering medium will affect the horizontal diffusion distance of the gas pipeline. Therefore, the VI model can be expressed as:

[0052] Where c is the maximum volume concentration of the gas, m³ / m³; d s The burial depth of the leaking gas pipeline is in meters (m) and d is in meters (d). f Let m be the depth of the adjacent connected pipeline, where when > hour, = L0 represents the distance, in meters, between the gas pipeline and the adjacent connected pipeline in the uncovered (pure soil) medium section; in practice, for ease of application, the default value is 0; L p The distance, in meters, between a gas pipeline and an adjacent connecting pipeline covered by a medium (such as cement, asphalt, etc.). This is a correction factor for the type of covering medium on the surface of gas pipelines, reflecting the blocking effect of the soil covering medium on the diffusion of gas into the atmosphere. The closer the value is to 0, the better the covering medium is at preventing gas from diffusing into the atmosphere. This applies when the covering medium is cement, asphalt, paving bricks, grass, or green belt. Suggested values ​​are 0.2, 0.3, 0.4, and 1. As the burial depth of gas pipelines increases, the influence of the soil surface covering medium on the lateral diffusion of gas in the soil decreases. Therefore, when the pipeline burial depth is ( (m), the surface covering medium of gas pipelines is cement, asphalt, paving bricks, grass or green belt. Suggested values ​​are 0.3, 0.45, 0.6, and 1. When the pipeline burial depth is ( When the gas pipeline surface is covered with a medium (m), it has almost no effect on the lateral diffusion of gas leaks. All values ​​are 1; Multi-layered soil: Under multi-layered soil cover conditions, the diffusion of natural gas varies in different soil media. Therefore, it is necessary to consider the effects of different cover thicknesses and effective diffusion rates. When the gas pipeline is covered by two or three layers of soil cover, the relationship between leakage diffusion concentration and distance can be expressed as:

[0053] Where n is the total number of layers, L i and D i It is the thickness and effective diffusion coefficient of layer i, calculated from the bottom. 2 / s]. The effective diffusion coefficients of different soil media were calculated based on the Buckingham model:

[0054] In the above formula, D s Let m be the gas diffusion coefficient of a certain soil medium. 2 / s; D0 is the diffusion coefficient of gas in free atmosphere at the same temperature, m 2 / s; that is, D s D0 is the ratio of the directly measured soil gas diffusion coefficient to the diffusion coefficient of the same gas in free atmosphere at the same temperature and atmospheric pressure. D0 needs to be temperature corrected using the following formula:

[0055] In the formula, , These are the temperatures before and after correction, respectively, in K. For fuel gas, take methane at... The corresponding D0 (273.15K) at 273.15K is 1.0121 × 10⁻⁶. -4 m 2 / s 3 ; The porosity of the air-filled structure can be calculated using the following formula:

[0056] In the formula: Total soil porosity ; For the unit weight of the soil column, ; For soil particle density, ; This refers to the soil volumetric water content. ; Gas inlet diffusion ratio in connecting pipeline: Assuming that the gas leaks and diffuses outward in a spherical shape, the leakage ratio that can enter adjacent pipelines after a long period of leakage can be expressed as:

[0057] Please see Figure 9 ,in, The diffusion ratio of leaked gas into adjacent connecting pipelines; d lt L is the diameter of the adjacent pipeline, in meters; l is the horizontal distance between the gas pipeline and the adjacent pipeline, in meters. If the two pipelines are on the same plane, then L = l; if the two pipelines are not on the same plane, then L = ( ), The height difference between the two pipelines; Gas diffusion process in connecting pipelines: Waterless pipeline: Gas diffusion rate: When gas diffuses into an adjacent dry, connected pipeline, since there is no other airflow affecting it, the gas will diffuse bidirectionally within the pipeline, meaning it will diffuse both upstream and downstream of the leak point. The gas diffusion velocity in each direction can then be expressed as:

[0058] Among them, v x A is the gas leakage-driven diffusion rate, m / s; A is the cross-sectional area of ​​the waterless connecting pipeline, m². 2 t is the diffusion time, in seconds; q is the maximum leakage rate of the gas pipeline in the soil, in m³ / s; Gas concentration distribution within the pipeline: Gas turbulent diffusion coefficient: The turbulent diffusion coefficient is calculated using the following formula:

[0059] Among them, v x r is the average gas diffusion velocity within the pipeline, in m / s; h The diameter of the adjacent pipeline cross section or hydraulic diameter, in meters; The friction coefficient between adjacent pipelines can be determined based on the material. As shown in the table below:

[0060] Calculate the hydraulic diameter r h For adjacent circular pipelines:

[0061] For adjacent square pipelines:

[0062] In the above formula: a is the width of the square connecting pipeline, in meters; b is the height of the square connecting pipeline, in meters.

[0063] Gas concentration distribution within the pipeline: The formula for calculating the gas distribution per unit leakage time after a combustible gas leaks into a connected pipeline is as follows:

[0064] Based on the gas pipeline diffusion VI model, the concentration at a specific location at a specific time is:

[0065] In the above formula: c max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v x D is the gas diffusion velocity within the pipeline, in m / s; t Let m be the turbulent diffusion coefficient within the pipeline. 2 / s; x is the distance between the shortest distance point between the gas pipeline and the alarm point and the point to be predicted, in meters; t is the diffusion time, in seconds; t α The unit of time is 1 second.

[0066] Water pipes are present: Air velocity in pipelines under the influence of water flow: According to Manning's equation, the water flow velocity inside the pipe is:

[0067] Where: V S S is the water flow velocity, m / s; S0 is the pipeline slope; R h The hydraulic diameter is the ratio of the fluid's cross-sectional area to its wetted perimeter. The wetted perimeter refers to the circumference of the fluid in contact with the open channel cross-section, excluding the circumference in contact with air (m); n is the Manning roughness coefficient (m). -1 / 3 ·s, with reference values ​​as shown in the table below: Manning coefficient for drainage pipes

[0068] Calculate the hydraulic diameter Rh For adjacent circular pipelines:

[0069] In the above formula: d is the diameter of the circular pipeline, in meters; h d The water level in the circular pipeline is in meters (m). For adjacent square pipelines:

[0070] In the above formula: a is the width of the square pipeline cross-section, in meters; b w The water level depth of the square pipeline is in meters. If the water level within the pipeline cannot be directly obtained, it can be calculated according to the "Outdoor Drainage Design Standard" by referring to the maximum design fullness of the drainage pipes in the table below. That is: or

[0071] Maximum design fill of drainage pipes

[0072] Under the influence of water flow, the velocity of the overhead air in the connecting pipeline has the following relationship with the water flow velocity:

[0073] Where v g The velocity of gas diffusion driven by water flow, in m / s; This is a correction factor, with a value of 0.43. According to the minimum design flow velocity specified in section 5.2.7 of the "Outdoor Drainage Design Standard," the flow velocity for sewage pipelines should be 0.6 m / s under design fullness. Therefore, it can be estimated that the minimum flow velocity affecting the diffusion of headspace gases in connected pipelines is 0.258 m / s. The maximum design flow velocity in section 5.2.5 should preferably be 5 m / s for non-metallic pipelines. Therefore, the maximum flow velocity affecting the diffusion of headspace gases in connected pipelines can be taken as 2.15 m / s.

[0074] Gas diffusion rate in pipeline

[0075] For circular pipelines, when the water level is h d When <d, the cross-sectional area of ​​gas diffusion within the connecting pipeline is:

[0076] otherwise:

[0077] In the above formula: d is the diameter of the connecting pipeline (circular), in meters; hd The water level in the connecting pipeline is in meters (m). For square pipelines

[0078] In the above formula: a is the width of the square connecting pipeline cross-section, m; b is the height of the square connecting pipeline cross-section, m; b w The water level height of the square connecting pipeline is in meters (m). Based on the above, if v x If the velocity is less than 0.258 m / s, then when the gas diffuses into the connecting pipeline, upstream backflow will definitely not occur; otherwise, gas diffusion into the pipeline may result in upstream backflow. x If the gas flow rate is greater than 2.15 m / m, then upstream backflow will definitely occur when the gas diffuses into the connecting pipeline. Gas diffusion rate under countercurrent: Gas leakage and diffusion rate in pipeline:

[0079] Among them, v xn The gas leakage velocity is denoted as A, in m / s; A is the cross-sectional area of ​​the waterless connecting pipeline, in m². 2 ; a. Upstream countercurrent diffusion rate

[0080] b. Downstream diffusion rate

[0081] Gas diffusion rate without backflow: When there is no backflow effect, all the gas leaking into the connecting pipeline flows downstream. Therefore, the gas leakage diffusion rate in the pipeline is as follows:

[0082] Among them, V xw A is the non-reverse gas diffusion velocity, m / s; A is the cross-sectional area of ​​the waterless connecting pipeline, m². 2 ; Average diffusion velocity within the gas pipeline:

[0083] Gas concentration distribution within the pipeline: Gas turbulent diffusion coefficient The turbulent diffusion coefficient is calculated using the following formula:

[0084] Where v is the cross-sectional average diffusion velocity, and r is the gas diffusion velocity determined based on the countercurrent condition, in m / s;h The diameter of the adjacent pipeline cross section or hydraulic diameter, in meters; The friction coefficient between adjacent pipelines can be determined based on the material. Calculate the hydraulic diameter rh for adjacent circular pipes:

[0085] For adjacent square pipelines:

[0086] In the above formula: a is the width of the square connecting pipeline, in meters; b is the height of the square connecting pipeline, in meters. Distribution of combustible gases in connecting pipelines: The gas distribution per unit leakage time after a combustible gas leaks into a connected pipeline is calculated using the following formula:

[0087] Based on the gas pipeline diffusion VI model, the concentration at a specific location at a specific time is:

[0088] In the above formula: c0 is the maximum concentration of gas leaking into the connecting pipeline, m³ / m³; v is the gas backflow diffusion velocity in the pipeline, m / s; D t Let m be the turbulent diffusion coefficient within the pipeline. 2 / s; x is the distance between the shortest distance point between the gas pipeline and the alarm point and the point to be predicted, in meters; t is the diffusion time, in seconds; t α The unit of time is 1 second; Determining the likelihood of gas pipeline leakage based on the highest concentration For the gas pipelines within a 12.5-meter radius of the connecting pipe section where the alarm point is located, calculate the maximum leakage concentration of each gas pipeline. By default, the leakage hole is calculated based on small hole leakage. When the maximum concentration of gas leaked into the alarm pipeline is less than the maximum monitoring concentration of the alarm point in the past 7 days, the probability of gas leaking into the alarm point in that pipeline section is low; when the maximum concentration of gas leaked into the alarm pipeline is greater than or equal to the maximum monitoring concentration of the alarm point in the past 7 days, the probability of gas leaking into the alarm point in that pipeline section is high, and this is the main analysis object of this model.

[0089] In the above formula: c max c0 represents the maximum concentration of gas that can leak into the alarm pipeline, in m³ / m³; c0 represents the maximum monitored concentration at the alarm point (single or multiple) over the past 7 days.

[0090] Example 3 For S107: Priority sorting correction: The first-priority traceable pipeline in the interconnected wells refers to the gas pipeline that ranks first in the traceability order of interconnected pipelines. First priority: Select the pipeline with the highest leakage probability score among the pipelines traced through connecting pipelines and pipelines traced through manholes as the corrected priority pipelines. When there are multiple pipelines that meet the criteria, the order is: pipelines traced through connecting pipelines first → pipelines traced through manholes first → remaining pipelines traced through manholes. Second priority: Prioritize pipelines for tracing the source of leakage in connected wells. For pipelines with a leakage probability score of <4 in the pipelines for tracing the source of leakage in independent wells, sort them in the order of priority pipelines for tracing the source of leakage in connected wells → key pipelines for tracing the source of leakage in independent wells → pipelines for tracing the source of leakage in independent wells. Third priority: After the above sorting, for the remaining pipelines, those with a leakage probability score of ≥4 points are sorted according to the original order of the tracing results of the connecting wells. Fourth priority: The remaining pipelines are sorted according to the order of the traceability results of the connecting wells.

[0091] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for locating gas pipeline leaks based on time and risk dimensions, characterized in that, Includes the following steps: S101. Based on alarm location, determine the gas pipeline within the traceability range as the initial traceability target; S102. Obtain the maximum leakage ingress concentration for each gas pipeline and alarm pipeline, and screen the source tracing objects based on the leakage ingress concentration; S103. Obtain the time t for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth ; S104. Obtain the gas diffusion time t in the connecting pipeline that causes the alarm point to reach the maximum alarm concentration. pipe ; S105, Based on the time t it takes for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth Gas diffusion time t in connecting pipelines pipe The shortest diffusion time t for the alarm point to reach the maximum alarm concentration is obtained. source , i.e. t source =t earth +t pipe ; S106, Based on the time t it takes for the gas to diffuse from the leak point through the soil to the connecting pipeline. earth and the gas diffusion time t in the connecting pipeline pipe Perform preliminary sorting of the traceable objects; S107. Based on the preliminary ranking results and combined with the gas pipeline leakage probability analysis and gas pipeline soil source tracing analysis, the gas pipeline source tracing priority is revised.

2. The gas pipeline leak location method based on time and risk dimensions according to claim 1, characterized in that, In step S104, the connecting pipeline is divided into a waterless pipeline and a water-containing pipeline.

3. The gas pipeline leak location method based on time and risk dimensions according to claim 2, characterized in that, In step S104, for waterless pipelines: When a single alarm point exists: Calculation of the change in concentration at the alarm point over time: In the above formula: c(t) is the concentration value at alarm point t, m³ / m³; max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v x D is the gas diffusion velocity within the pipeline between the shortest distance point between the gas pipeline and the connecting pipeline and the alarm point, in m / s; t denoted as , where x is the turbulence diffusion coefficient within the pipeline between the shortest distance point of the gas pipeline and the connecting pipeline and the alarm point, in m / s; x0 is the distance between the shortest distance point of the gas pipeline and the alarm point and the alarm point, in m; and t is the diffusion time, in s. t α The unit of time is 1 second.

4. The gas pipeline leak location method based on time and risk dimensions according to claim 3, characterized in that, Diffusion time calculation: t pipe =solve(c(x0,t)==c0,t) Where: c0 is the maximum alarm concentration at the alarm point, m³ / m³; t pipe The gas diffusion time in the connecting pipeline is in seconds.

5. A gas pipeline leak location method based on time and risk dimensions according to claim 2, characterized in that, For those with water pipes: When a single alarm point exists: The shortest distance between the gas pipeline and the alarm pipeline is located downstream of the alarm point: a. If there is no backflow in the pipeline where the shortest distance between the gas pipeline and the alarm pipeline is located, then that pipeline is excluded as the main source tracing target. b. If there is backflow between the gas pipeline and the alarm pipeline at the point where the shortest distance is between them, then that gas pipeline will be considered as one of the primary sources for further analysis: t pipe =solve(c(x0,t)==c0,t) In the above formula: c(t) is the concentration value at alarm point t, m³ / m³; max The maximum concentration of gas leaking into the connecting pipeline, in m³ / m³; v n-up D represents the gas backflow diffusion velocity (m / s) between the shortest distance between the gas pipeline and the connecting pipeline and the alarm point, where there is water in the pipeline. t The turbulent diffusion coefficient (m) between the shortest distance between the gas pipeline and the connecting pipeline and the alarm point for the water pipeline. 2 / s; x0 is the distance between the shortest distance point between the gas pipeline and the alarm point, in meters; t is the diffusion time, in seconds; t α The unit of time is 1 second.

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