Gas indoor stand pipe risk assessment method based on AHP

Abstract

The invention provides a gas indoor stand pipe risk assessment method based on AHP. The method comprises the following steps: step 1, dividing gas indoor stand pipes into different assessment units; 2, constructing a risk evaluation system; 3, calculating the weight by using an analytic hierarchy process, judging and comparing the importance degrees of every two risk factors, and constructing a judgment matrix; 4, establishing a scoring model S of the failure possibility of the gas indoor vertical pipe; 5, establishing a gas indoor riser failure consequence scoring model C according to the gas indoor riser failure consequence risk evaluation system and the risk factor weight; and 6, calculating a relative risk value R according to the gas indoor riser failure possibility scoring model S and the gas indoor riser failure consequence scoring model C, and determining the risk level of the evaluation unit. According to the AHP-based risk assessment method for the vertical pipe in the gas room, the working efficiency can be improved after the method is implemented, and safe operation of gas facilities in the gas room is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of urban gas pipeline risk management, and in particular to an AHP-based gas indoor riser risk assessment method. Background Art

[0002] The renovation of aging urban gas pipelines is an important livelihood project and development project. Accelerating the renovation of aging urban gas pipelines requires a comprehensive assessment of risers based on pipeline material, service life, corrosion and leakage, and safety spacing. The existing implementation plan does not provide a clear aging assessment method. Providing a risk assessment method for risers is of great significance for promoting the safe operation of gas facilities in gas households and maintaining social stability. Summary of the Invention

[0003] In view of this, the present invention discloses a risk assessment method for indoor gas risers based on AHP to perform targeted aging assessment on indoor gas risers.

[0004] The technical solution provided by the present invention is a risk assessment method for indoor gas risers based on AHP, comprising the following steps:

[0005] Step 1: Divide the gas riser into different assessment units;

[0006] Step 2: Construct a risk assessment system, including a risk assessment system for the possibility of failure of household gas risers and a risk assessment system for the consequences of failure of household gas risers;

[0007] Step 3: Based on the risk assessment system, obtain risk factors, calculate weights using the analytic hierarchy process, compare the importance of each risk factor, and construct a judgment matrix. After the judgment matrix passes the consistency test, calculate the weights of the risk factors using the judgment matrix.

[0008] Step 4: Establish a scoring model S for the possibility of failure of a household gas riser according to the risk assessment system for the possibility of failure of a household gas riser and the weight of risk factors;

[0009] Step 5: Establish a scoring model C for the consequences of failure of household gas riser pipes based on the risk assessment system for the consequences of failure of household gas riser pipes and the weights of risk factors;

[0010] Step 6: Calculate the relative risk value R based on the scoring model S for the possibility of failure of the household gas riser and the scoring model C for the consequence of failure of the household gas riser, and determine the risk level of the assessment unit.

[0011] Preferably, step 1 specifically includes:

[0012] Collect relevant information about the household gas riser, including the riser material, specifications, and commissioning time;

[0013] According to the "Guidelines for Urban Gas Pipeline Aging Assessment", based on the principle of "same material, same period", the gas risers within the assessment scope are divided into different assessment units;

[0014] Each assessment unit contains the following information: type of gas transported, pipeline length, pipe material category, pipe diameter and wall thickness, design pressure, operating pressure, completion time, commissioning time, ownership unit, operating unit, design unit, construction unit and supervision unit.

[0015] Preferably, the method for constructing the risk assessment system for the possibility of failure of the gas indoor riser is as follows: a list of influencing factors is established based on the design and construction data of the gas indoor riser and the operation, maintenance and emergency repair records; and a risk assessment system for the possibility of failure of the gas indoor riser is established by screening the factors influencing the possibility of failure of the gas indoor riser;

[0016] The data used to screen factors affecting the possibility of failure of indoor gas risers include: construction drawings, completion data, operation and maintenance and emergency repair records, urban gas design specifications, and urban gas indoor engineering construction and quality acceptance specifications;

[0017] Based on the above data, the factors affecting the failure possibility of gas riser in households are obtained, including: pipeline quality, floor penetration position treatment, interface installation, gas use environment and construction quality;

[0018] The method for constructing the risk assessment system for the consequences of failure of household gas risers is to establish a risk assessment system for the consequences of failure of household gas risers through the flammable and explosive consequences and poisoning caused by gas leakage and the phenomenon of accidents caused by high probability of misoperation.

[0019] Preferably, in step 3, the weights are calculated using the hierarchical analysis method, and the importance of each risk factor is judged and compared to construct a judgment matrix, including:

[0020] 1) Calculate the weights of risk factors identified by experts based on their scores:

[0021]

[0022] Where R j is the weight of the risk factor, Q i is the expert’s own weight; W ij The weight of risk factors evaluated by individual experts;

[0023] 2) Based on the expert scoring, the “9-scale method” is used to judge the importance of the same-level factors in pairs, and a single-factor fuzzy comprehensive evaluation is established to obtain the n-order judgment matrix A (a ij )n×n,a ijare the vectors in the judgment matrix A, representing the elements u i To u j The relative importance of the factor u i To u j the quantitative scale of the relative importance of

[0024]

[0025] Where A is the single factor evaluation matrix of failure possibility; A j is the fuzzy vector of the jth evaluation factor in the failure possibility system; u ij To evaluate the failure probability, the membership degree in the evaluation set is evaluated;

[0026] 3) Based on the hierarchical analysis method, the geometric mean method is used to solve the weights of each judgment matrix; the formula of the geometric mean method is:

[0027]

[0028] Where W i are the weight coefficients, a ij are the vectors in the judgment matrix A;

[0029] Preferably, the hierarchical analysis method is based on which the geometric mean method is used to perform geometric averaging on the row vectors of the decision matrix A and then normalizes them. The obtained row vector is the weight vector:

[0030] Multiply the elements of matrix A by columns to get a new vector;

[0031] Raise each component of the new vector to the power of n;

[0032] The obtained vector is normalized to obtain the weight vector;

[0033] The final row vector obtained is the weight distribution A.

[0034] By considering the impact of various factors on the risk of indoor risers, the weights are determined, and finally the objective weight A of each factor is obtained through calculation and deduction based on the judgment matrix;

[0035] A=(a1,a2,a3,....,a n ).

[0036] Preferably, in step 3, the judgment matrix passes the consistency test, including:

[0037] Maximum eigenvalue λ max The calculation formula is:

[0038]

[0039] (AW) i Represents the i-th element of vector AW;

[0040] The consistency test formula is:

[0041]

[0042] Where, CI is the consistency index; CR is the consistency test rate; RI is the average random consistency index; when CR≤0.1, the judgment matrix passes the consistency test;

[0043] Preferably, the scoring model S for the failure probability of the gas indoor riser in step 4 is:

[0044]

[0045] s i represents the possible risk factor of the i-th failure;

[0046] The failure probability scoring model S for the gas indoor riser is set as follows: if the following conditions exist in the evaluated pipeline, the failure probability score is adjusted to 100 points;

[0047] Pipeline components do not meet design requirements;

[0048] Working pressure exceeds design pressure;

[0049] Contain unacceptable defects;

[0050] Safety protection devices and measures do not meet design requirements.

[0051] Preferably, the scoring model C for the consequence of failure of the gas indoor riser in step 5 is:

[0052]

[0053] Ci represents the i-th failure consequence;

[0054] The gas household riser failure consequence scoring model C is set as follows:

[0055] If the following conditions exist in the assessed pipeline, the Failure Consequence Score C will be adjusted to 150 points: The gas riser is laid in a bedroom or bathroom. The riser passes through a poorly ventilated ceiling without being placed in a casing.

[0056] Preferably, the relative risk value R in step 6 is

[0057] R=SC

[0058] (8) According to the relative risk value R, the risk level is as follows:

[0059]

[0060] The AHP-based risk assessment method for indoor gas risers provided by the present invention is applicable to risers with an operating life of 20 years or more, as well as to risers with an operating life of less than 20 years but with potential safety hazards. Its implementation is of great significance for improving work efficiency, ensuring the safe operation of indoor gas facilities, and maintaining social stability.

[0061] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0063] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0064] Figure 1 This is a flow chart of the risk assessment method for indoor gas risers based on AHP of the present invention;

[0065] Figure 2 Schematic diagram of the risk assessment system for failure possibility of indoor gas riser provided by the present invention;

[0066] Figure 3 Schematic diagram of the risk assessment system for the consequences of failure of indoor gas risers provided by the present invention. DETAILED DESCRIPTION

[0067] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of systems consistent with certain aspects of the present invention, as detailed in the appended claims.

[0068] In order to solve the problems in the prior art caused by the lack of targeted aging assessment of gas risers in households, this embodiment provides a risk assessment method for gas risers in households based on AHP, including the following steps:

[0069] Step 1: Divide the gas riser into different assessment units;

[0070] Pipeline assessment units are divided according to the principle of "same material, same period" (i.e., same residential complex or residential complexes within the same area, completed and put into operation at the same time). Each assessment unit includes information such as the type of gas transported, pipeline length, pipe material type, pipe diameter and wall thickness, design pressure, operating pressure, completion date, commissioning date, ownership unit, operator, design unit, construction unit, and supervision unit.

[0071] Step 2: Construct a risk assessment system, including a risk assessment system for the possibility of failure of household gas risers and a risk assessment system for the consequences of failure of household gas risers;

[0072] The data required to study the possibility of failure of indoor risers include construction drawings, completion data, operation and maintenance and emergency repair records, urban gas design specifications, and urban gas indoor engineering construction and quality acceptance specifications.

[0073] Specific factors that affect the failure of indoor risers include: pipe quality, floor penetration location, interface installation, gas use environment and construction quality.

[0074] Step 3: Based on the risk assessment system, obtain risk factors, calculate risk factor weights using the analytic hierarchy process, compare the importance of risk factors at the same level, and construct a judgment matrix; after the judgment matrix passes the consistency test, calculate the weights of risk factors using the judgment matrix;

[0075] 1) Calculate the risk factor weights based on the scores of different experts;

[0076]

[0077] Where R j is the weight of the risk factor, Q i is the expert’s own weight; W ij is the weight of a single expert's evaluation of a factor.

[0078] 2) Using the "9-scale method", factors of the same level are judged on their importance in pairs, and a single-factor fuzzy comprehensive evaluation is established. ij is the element u i To u j the relative importance of .

[0079] Judgment scale representation element u i To u j The quantitative scale of the relative importance is shown in the following table:

[0080]

[0081] Based on the scores of each expert, the n-order judgment matrix A(a ij)n×n, the matrix constructed by each expert’s score according to the 9-scaling method is as follows:

[0082]

[0083] Where A is the single factor evaluation matrix of failure possibility; A j is the fuzzy vector of the jth evaluation factor in the failure possibility system; u ij To evaluate the possibility of failure, the membership in the evaluation set is evaluated.

[0084] 3) Based on actual experience and statistical data, the judgment matrix is ​​used and the geometric mean method, which is the most commonly used method in the hierarchical analysis method, is used to calculate the respective weights.

[0085] Perform geometric averaging on each row vector of A and then normalize them. The resulting row vector is the weight vector.

[0086] The formula for the geometric mean method is:

[0087]

[0088] Where W i are the weight coefficients, a ij are the vectors in the judgment matrix A.

[0089] The weight determination should consider the impact of various factors on the risk of indoor risers. Finally, the objective weight A of each factor is obtained through calculation and derivation based on the judgment matrix;

[0090] A=(a1,a2,a3,....,a n );

[0091] Furthermore, the specific calculation steps for obtaining the respective weights using the geometric mean method are as follows:

[0092] Multiply the elements of A by column to get a new vector;

[0093] Raise each component of the new vector to the power of n;

[0094] The obtained vector is normalized to obtain the weight vector;

[0095] The final row vector obtained is the weight distribution A.

[0096] 4)λ max The calculation formula is:

[0097]

[0098] (AW) i Represents the i-th element of vector AW.

[0099] The consistency test formula is:

[0100]

[0101] Where CI is the consistency index; CR is the consistency test rate; RI is the average random consistency index; when CR ≤ 0.1, the judgment matrix passes the consistency test.

[0102] Average random consistency index standard value RI

[0103]

[0104]

[0105] Step 4: Establish a scoring model S for the possibility of failure of a household gas riser according to the risk assessment system for the possibility of failure of a household gas riser and the weight of risk factors;

[0106] The scoring model S for the failure probability of indoor gas risers is:

[0107]

[0108] s i represents the possible risk factor of the i-th failure.

[0109] If the following conditions exist in the pipeline being evaluated, the Failure Probability score should be adjusted to 100 points.

[0110] Pipeline components do not meet design requirements;

[0111] Working pressure exceeds design pressure;

[0112] Contain unacceptable defects;

[0113] Safety protection devices and measures do not meet design requirements.

[0114] Step 5: Establish a scoring model C for the consequences of failure of household gas riser pipes based on the risk assessment system for the consequences of failure of household gas riser pipes and the weights of risk factors;

[0115]

[0116] C i represents the i-th failure consequence.

[0117] If the following conditions exist in the pipeline being evaluated, the Failure Consequence Score C should be adjusted to 150 points:

[0118] The area that is not suitable for entry or passage as specified in GB 50028 is not avoided, and the horizontal clear distance from the exterior wall of the building is less than the requirements of GB 50028 or does not comply with the requirements of GB 50028 for sectional valves.

[0119] Failure to avoid areas or facilities that should not be passed as specified in GB 50028, and failure to take safety measures.

[0120] Step 6: Calculate the relative risk value R based on the scoring model S for the possibility of failure of the household gas riser and the scoring model C for the consequence of failure of the household gas riser, and determine the risk level of the assessment unit.

[0121] The relative risk value of indoor risers is

[0122] R=SC (8)

[0123] Where R is the probability score of indoor riser failure, and C is the consequence score of indoor riser failure.

[0124] The risk levels are as follows:

[0125]

[0126] Finally, based on the calculated relative risk value of the pipeline, rectification suggestions are put forward: (1) meet the requirements for safe operation; (2) implement safety control measures and continue to operate; (3) transform within a time limit; (4) transform immediately.

[0127] This invention proposes an AHP-based risk assessment method for indoor gas risers. This method effectively and comprehensively utilizes various data, including information on indoor gas riser design, construction, operation and maintenance, and expert experience, to establish a risk assessment model for indoor gas risers. First, it analyzes and collects information to establish a risk assessment system for the likelihood of indoor gas riser failure based on five factors: pipeline quality, floor penetration location, interface installation, gas usage environment, and construction quality. Next, it uses an expert evaluation method to assess the impact of each factor, and calculates the weight of each factor using the Analytic Hierarchy Process (AHP). Finally, based on this information, it establishes a risk assessment system for the consequences of indoor gas riser failure based on factors such as medium flammability, medium toxicity, maximum leakage volume, and leakage cause, and establishes a failure consequence scoring model. Finally, a risk level is calculated, and modification recommendations are made based on the risk level. This invention addresses the existing lack of a quantitative, targeted aging assessment method for indoor gas risers. It has important practical application value for promptly identifying potential safety hazards in indoor gas risers and ensuring the safe and stable operation of urban gas pipeline systems.

[0128] Example 1

[0129] A coastal central city uses natural gas as its gas source. A large number of household gas risers are over 20 years old and present varying degrees of safety risks. An assessment method is urgently needed to assess the safety of these pipelines, determine the risk level, and propose a renovation plan based on the assessment results. This paper provides an AHP-based risk assessment method for household gas risers. Taking one assessment unit as an example, the assessment process includes the following steps:

[0130] (1) According to the "Guidelines for Urban Gas Pipeline Aging Assessment", household gas risers within the assessment scope are divided into different assessment units based on the principle of "same material, same period".

[0131] (2) The investigation found that the primary factors that caused the leakage of gas risers in the city were the pipeline itself, floor penetration treatment, interface installation quality, gas environment and construction quality. The primary factors were further divided into secondary factors. Figure 2 shown.

[0132] (3) Use the hierarchical analysis method to calculate the weights of risk factors, conduct pairwise comparisons on factors of the same level, construct a judgment matrix, integrate the expert weights, and calculate the weights of risk factors.

[0133] Five experts were invited, and their detailed information and weight coefficients are shown in Table 1:

[0134] Table 1 Calculation of weight coefficients of each expert

[0135]

[0136] The weight coefficients of the experts are (0.3, 0.25, 0.2, 0.15, 0.1);

[0137] Taking the first-level risk calculation factors in the risk assessment system for the possibility of failure of indoor gas risers as an example, the failure of indoor gas risers can be divided into five first-level analysis factors: pipeline body, floor penetration treatment, interface installation quality, gas use environment and construction quality.

[0138] Construct a judgment matrix and perform consistency test. The judgment matrix constructed by expert 1 is shown in Table 2:

[0139] Table 2 Judgment matrix constructed by expert 1

[0140]

[0141] Calculate the product m of each row element of the judgment matrix AU i :

[0142]

[0143] m1=1×3×3×5×3=135

[0144] m2=1 / 3×1×1 / 3×3×1 / 3=0.037

[0145] m3=1 / 3×3×1×3×3=9

[0146] m4=1 / 5×1 / 3×1 / 3×1×3=0.0667

[0147] m5=1 / 3×3×1 / 3×1 / 3×1=0.1111

[0148] Calculate nth root

[0149]

[0150] Pair Vector Normalization is the desired eigenvector;

[0151] but This is the desired eigenvector.

[0152]

[0153] According to formula (2), the factor weight is obtained by arithmetic mean method (W 11 ,W 12 ,W 13 ,W 14 ,W 15 )=(0.4473,0.0868,0.2603,0.0976,0.1081)

[0154] Conduct consistency judgment on the judgment matrix;

[0155]

[0156] (AW1)=1×0.4473+3×0.0868+3×0.2603+5×0.0976+3×0.1081=2.3005

[0157] (AW2)=1 / 3×0.4473+1×0.0868+1 / 3×0.2603+3×0.0976+1 / 3×0.1081=0.3912

[0158] (AW3)=1 / 3×0.4473+3×0.0868+1×0.2603+3×0.0976+3×0.1081=1.2866

[0159] (AW4)=1 / 5×0.4473+1 / 3×0.0868+1 / 3×0.2603+1×0.0976+3×0.1081=0.6269

[0160] (AW5) = 1 / 3 × 0.4473 + 3 × 0.0868 + 1 / 3 × 0.2603 + 1 / 3 × 0.0967 + 1 × 0.1081 = 0.6367 to find the maximum characteristic root λ max :

[0161]

[0162] Then the consistency index CI is calculated

[0163]

[0164] Calculate the consistency index CI

[0165] Judgment matrix n = 5, RI = 1.12, so the consistency ratio CR:

[0166]

[0167] Because CR < 0.1, the consistency requirement is met, so the pairwise judgment factor table of the judgment matrix satisfies the consistency test. In other words, the above results are valid. You can continue with the following calculations.

[0168] Similarly, the judgment matrices constructed by experts 2 to 5 are shown in Tables 3 to 6, and all meet the consistency test requirements.

[0169] Table 3 Judgment matrix constructed by expert 2

[0170]

[0171] The factor weights are obtained by arithmetic mean method (W 21 ,W 22 ,W 23 ,W 24 ,W 25 )=(0.4276,0.1033,0.2488,0.601,0.1603)

[0172] Table 4 Judgment matrix constructed by expert 3

[0173]

[0174] The factor weights are obtained by arithmetic mean method (W 31 ,W 32 ,W 33 ,W 34 ,W 35 )=(0.4596,0.1002,0.2414,0.0583,0.1405)

[0175] Table 5 Judgment matrix constructed by expert 4

[0176]

[0177] The factor weights are obtained by arithmetic mean method (W 41 ,W 42 ,W 43 ,W 44,W 45 )=(0.4188,0.1012,0.2699,0.0531,0.1507)

[0178] Table 6 Judgment matrix constructed by expert 5

[0179]

[0180] The factor weights are obtained by arithmetic mean method (W 51 ,W 52 ,W 53 ,W 54 ,W 55 )=(0.4481,0.0882,0.2607,0.0513,0.1517)

[0181] The weights of the experts' evaluation of the factors are:

[0182]

[0183] Based on the comprehensive expert weights, the weights of the first-level risk factors are calculated according to formula (1):

[0184]

[0185] Similarly, after the first-level factors are determined, the weights of the second-level factors are determined according to the above method:

[0186] The weights of the secondary factors of pipeline quality, pipeline corrosion, pipeline maintenance, and pipeline service life are (0.2376, 0.4113, 0.202, 0.1491)

[0187] The weights of the secondary factors of floor penetration treatment, namely, floor penetration casing, casing filler, and sealing condition, are (0.4742, 0.2728, 0.253).

[0188] The weights of the secondary factors of interface installation, namely, number of interfaces, interface type, number of flexible interfaces, and years of interface installation, are (0.2863, 0.2752, 0.2055, 0.2331).

[0189] The possible failure score of gas indoor riser is based on a 100-point system, and the score based on the quality of the pipeline itself is shown in Table 7:

[0190] Table 7 Pipeline ontology scores

[0191]

[0192] Table 8 Score of treatment for penetrating floor slabs

[0193]

[0194] Table 9 Interface installation scores

[0195]

[0196] Table 10 Gas usage environment scores

[0197]

[0198] Table 11 Construction quality scores

[0199]

[0200] According to the formula The total possible failure score S is calculated to be 23+2+10+2+9=46.

[0201] In the risk assessment system for the consequences of gas riser failure, the hazards of gas leakage are primarily flammability, toxicity, and the cause of the leak. The judgment matrices constructed by the five experts are shown in Tables 12 through 16.

[0202] Table 12 Judgment matrix constructed by expert 1

[0203]

[0204] Table 13 Judgment matrix constructed by expert 2

[0205]

[0206] Table 14 Judgment matrix constructed by expert 3

[0207]

[0208] Table 15 Judgment matrix constructed by expert 4

[0209]

[0210] Table 16 Judgment matrix constructed by expert 5

[0211]

[0212] After consistency testing, the judgment matrices constructed by the above experts all meet the consistency test.

[0213] The weights of the judgment matrix constructed by expert 1 are (w1, w2, w3) = (0.6370, 0.2583, 0.1047)

[0214] The weights of the judgment matrix constructed by expert 2 are (w1, w2, w3) = (0.7007, 0.2021, 0.0972)

[0215] The weights of the judgment matrix constructed by expert 3 are (w1, w2, w3) = (0.6638, 0.2270, 0.1091)

[0216] The weights of the judgment matrix constructed by expert 4 are (w1, w2, w3) = (0.5842, 0.2808, 0.1350)

[0217] The weights of the judgment matrix constructed by expert 5 are (w1, w2, w3) = (0.6638, 0.2270, 0.1091)

[0218] The weight matrix of the expert's evaluation of the factors is:

[0219]

[0220] The weights of risk factors are calculated based on the comprehensive expert weights according to formula (1).

[0221]

[0222] Similarly, after the first-level factors are determined, the weights of the second-level factors are determined according to the above method:

[0223] The secondary factor of the medium's flammability is 1;

[0224] The weights of the secondary factors of medium toxicity are natural gas, artificial coal gas, and liquefied petroleum gas (0.2222, 0.5556, 0.2222).

[0225] The secondary factors of leakage are operational errors, pipeline quality defects and poor gas environment, with weights of (0.0714, 0.3571, 0.5714)

[0226] The consequences of failure of indoor gas risers are scored on a 150-point scale.

[0227] The medium of this project is natural gas, and the medium combustibility score is 98.

[0228] Table 17 Medium toxicity scores

[0229]

[0230] Table 18 Leakage cause scores

[0231]

[0232] According to the formula The total possible failure score C is calculated to be 97+9+9=115.

[0233] According to the formula R=SC, the risk level of this assessment unit is 5290;

[0234] According to the relative risk value R, the risk level is as follows:

[0235]

[0236] The risk level is assessed as medium. Safety control measures have been implemented and operations can continue.

[0237] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These changes and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. The risk assessment method of indoor gas riser based on AHP is characterized by: The steps include: Step 1: Divide the gas riser into different assessment units; Step 2: Construct a risk assessment system, including a risk assessment system for the possibility of failure of household gas risers and a risk assessment system for the consequences of failure of household gas risers; Step 3: Based on the risk assessment system, obtain risk factors, calculate risk factor weights using the analytic hierarchy process, compare the importance of risk factors at the same level, and construct a judgment matrix; after the judgment matrix passes the consistency test, calculate the weights of risk factors using the judgment matrix; Step 4: Establish a scoring model S for the possibility of failure of a household gas riser according to the risk assessment system for the possibility of failure of a household gas riser and the weight of risk factors; Step 5: Establish a scoring model C for the consequences of failure of household gas riser pipes based on the risk assessment system for the consequences of failure of household gas riser pipes and the weights of risk factors; Step 6: Calculate the relative risk value R based on the scoring model S for the possibility of failure of the household gas riser and the scoring model C for the consequence of failure of the household gas riser, and determine the risk level of the assessment unit.

2. The AHP-based risk assessment method for indoor gas risers according to claim 1 is characterized in that: Step 1 specifically includes: Collect relevant information about the household gas riser, including the riser material, specifications, and commissioning time; According to the "Guidelines for Urban Gas Pipeline Aging Assessment," household gas risers within the assessment scope are divided into different assessment units based on the principle of "same material, same period"; Each assessment unit contains the following information: type of gas transported, pipeline length, pipe material category, pipe diameter and wall thickness, design pressure, operating pressure, completion time, commissioning time, ownership unit, operating unit, design unit, construction unit and supervision unit.

3. The AHP-based risk assessment method for indoor gas risers according to claim 1 is characterized by: The method for constructing the risk assessment system for the possibility of failure of the gas indoor riser is as follows: a list of influencing factors is established based on the design and construction data of the gas indoor riser and the operation, maintenance and emergency repair records; and a risk assessment system for the possibility of failure of the gas indoor riser is established by screening the influencing factors of the possibility of failure of the gas indoor riser; The data used to screen factors affecting the possibility of failure of indoor gas risers include: construction drawings, completion data, operation and maintenance and emergency repair records, urban gas design specifications, and urban gas indoor engineering construction and quality acceptance specifications; Based on the above data, the factors affecting the failure possibility of gas riser in households are obtained, including: pipeline quality, floor penetration position treatment, interface installation, gas use environment and construction quality; The method for constructing the risk assessment system for the consequences of failure of household gas risers is to establish a risk assessment system for the consequences of failure of household gas risers through the flammable and explosive consequences and poisoning caused by gas leakage and the phenomenon of accidents caused by high probability of misoperation.

4. The AHP-based risk assessment method for indoor gas risers according to claim 1 is characterized in that: In step 3, the weights are calculated using the analytic hierarchy process, and the importance of risk factors is compared between each other to construct a judgment matrix, including: 1) Calculate the weights of risk factors identified by experts based on their scores: Where R j is the weight of the risk factor, Q i is the expert’s own weight; W ij The weight of risk factors evaluated by individual experts; 2) Based on the expert scoring, the "9-scale method" is used to judge the importance of the same-level factors in pairs, and a single-factor fuzzy comprehensive evaluation is established to obtain the n-order judgment matrix A (a ij )n×n,a ij are the vectors in the judgment matrix A, representing the elements u i To u j The relative importance of the factor u i To u j the quantitative scale of the relative importance of Where A is the single factor evaluation matrix of failure possibility; A j is the fuzzy vector of the jth evaluation factor in the failure possibility system; u ij To evaluate the failure probability, the membership degree in the evaluation set is evaluated; 3) Based on the hierarchical analysis method, the geometric mean method is used to solve the weights of each judgment matrix; the formula of the geometric mean method is: Where W i are the weight coefficients, a ij are the vectors in the judgment matrix A.

5. The AHP-based risk assessment method for indoor gas risers according to claim 4 is characterized in that: Based on the hierarchical analysis method, the geometric mean method is used to perform geometric mean on each row vector of the decision matrix A, and then normalize it. The obtained row vector is the weight vector: Multiply the elements of matrix A by columns to get a new vector; Raise each component of the new vector to the power of n; The obtained vector is normalized to obtain the weight vector; The final row vector obtained is the weight distribution A. By considering the impact of various factors on the risk of indoor risers, the weights are determined, and finally the objective weight A of each factor is obtained through calculation and deduction based on the judgment matrix; <h2 style=";text-align:left;direction:ltr">A=(a1,a2,a3,....,a<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> )。 6. The AHP-based risk assessment method for indoor gas risers according to claim 1 is characterized in that: In step 3, the matrix is ​​judged to pass the consistency test, including: Maximum eigenvalue λ max The calculation formula is: (AW) i Represents the i-th element of vector AW; The consistency test formula is: Where CI is the consistency index; CR is the consistency test rate; RI is the average random consistency index; when CR ≤ 0.1, the judgment matrix passes the consistency test.

7. The AHP-based risk assessment method for indoor gas risers according to claim 1 is characterized in that: The scoring model S for the probability of failure of gas indoor riser described in S4 is: s i represents the possible risk factor of failure i; The failure probability scoring model S for the gas indoor riser is set as follows: if the following conditions exist in the evaluated pipeline, the failure probability score is adjusted to 100 points; Pipeline components do not meet design requirements; Working pressure exceeds design pressure; Contain unacceptable defects; Safety protection devices and measures do not meet design requirements.

8. The AHP-based risk assessment method for indoor gas risers according to claim 1 is characterized in that: The scoring model C for the consequences of failure of gas indoor riser described in S5 is: Ci represents the i-th failure consequence.

9. The AHP-based risk assessment method for indoor gas risers according to claim 1, characterized in that: The relative risk value R described in S6. R=SC (8) According to the relative risk value R, the risk level is as follows:

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