City gas pipeline risk assessment of the applicability of the method
Buried cities due to the large number of laying gas pipelines in densely populated urban areas on the ground floor, damaged pipeline leak caused the explosion, fire, accidents such as poisoning, will give residents the lives and property caused huge losses to the adverse social effects . It is risk assessment techniques to reduce the risk of accidents and the introduction of a new management techniques. In the past 30 years of research and development and application of practice, the pipeline risk assessment technology in many countries has played a significant economic and social benefits [1]. China's Tenth Five-Year plan for science and technology have been buried in the city gas pipeline as a key risk assessment research. In qualitative, quantitative and semi-quantitative risk assessment methods, semi-quantitative methods most widely used. Semi-quantitative methods to assess the main score Mushi (Muhlbauer) Act (hereinafter referred to as Mushi Act) [2] and fuzzy comprehensive evaluation (Fuzzy Assessment) Act [3]. This article summarized in the analysis of the gas pipeline risk assessment study on the basis of the status quo, the two methods in the city of buried steel gas pipeline risk assessment of the applicability of the analysis.
1 Gas Pipeline Risk Assessment Research
① foreign gas pipeline risk assessment study of the status quo
Buried pipeline risk management began as early as the 1970s. U.S. PRCI (Pipeline Research Committee Intemationa1) of the United States and Europe gas pipeline accident data and statistical classification, a summary of 22 pipe failure caused by fundamental factors [4].
In 1985, the United States Battelle Columbus Institute published a "guide to the risk of investigation," First of all pipelines in the risk analysis of the use of scoring [4]. W. K. Muhlbauer On this basis, the sum of the United States over the past 20 years oil and gas pipelines to carry out a risk assessment of technical research results, in 1992, the preparation of the famous "Pipeline Risk Management Manual", details of pipeline risk assessment expert score model, once the world And universally accepted as a buried pipeline to carry out a risk assessment of the important references [5]; in 1996 in the second edition of the book have been added to the length of a large number of different occasions, the pipeline risk assessment model of the amendment, an increase of environmentally sensitive region , Workplace stress and the evaluation of the potential human error, and details on how to make use of the risk and cost of establishing the relationship between resource allocation model [6]; in 2004, the third edition of the book is rich in the original risk management, more Clear and more specific examples of the establishment of the basic model of risk assessment procedures, an increase of oil and gas pipelines across the section of the risk assessment model approach.
As for the oil and gas pipelines understanding of the dangers of an increasing number of foreign gradual development of a new pipeline integrity management system [7], all of the factors that affect the integrity of the pipeline to carry out a comprehensive, integrated management, from the preparation of the plan, Procedures and documentation to the pipeline to carry out risk analysis to find out the possibility of the accident and the consequences of the accident, and to develop prevention and response measures on a regular basis pipeline integrity testing and evaluation, including pipeline design, construction, operation, monitoring, maintenance, replacement, Quality control and communications, and so the whole process, and pipelines running through the entire period of operation. The current management system in the long-distance oil and gas pipelines in the management of more and more attention.
In engineering applications, overseas as early as the 1960s began to pay attention to the end of the pipeline project in the pipeline service in the detection and assessment of residual strength, such as: American Petroleum Institute issued the "risk-based inspection norms" (API 581) [ 8], "added integrity of the gas pipeline system files" (ASME B31.8S) [9], "to determine the remaining strength of pipeline corrosion has been manual paper added pressure pipe norms" (ASME B31G) [10]. To the early 1990s, many oil and gas pipelines in the United States have applied a risk management techniques to guide the maintenance of the pipeline. Followed by Canada, the European countries have also joined the pipeline risk management technology development and application of the ranks. Advantica Britain through statistical analysis of a large number of pipeline information and disaster simulation in the natural gas pipeline on the risk factors for the probability analysis to quantify the consequences of the accident and on the basis of the establishment of a gas pipeline quantitative risk assessment techniques, the expert analysis software has been PIPESAFE Used in the United Kingdom and the countries of the world's high-pressure gas pipeline [10]. Canada's C-FFR has also successfully developed a pipeline maintenance and testing of risk analysis software package (PIRAMID), for the pipeline failure probability analysis of the consequences of failure and the risk calculation [11].
With the emergence of new disciplines and the development of new technologies and new methods, new technologies are also used in risk analysis of buried pipeline under study. If the literature [12] proposed the use of fuzzy neural network of buried pipeline to carry out simulation and simulated shortcomings, and buried pipeline to classify all kinds of defects. GIS technology is fast becoming the facility for management, life-cycle testing, risk analysis, coordination and management, improve the operational efficiency of the effective means. Pipeline GIS technology is widely used in the United States, Norway and other countries.
② domestic gas pipeline risk assessment study of the status quo
In the mid-1990s, China has carried out related to oil and gas pipeline safety evaluation of the study and application of a series of trials. In our country was first proposed by Professor Pan Jiahua in a comprehensive introduction in 1995 of the United States, "Pipeline Risk Management Manual" [13]. During the Ninth Five-Year Plan, China National Petroleum Corporation and the State General Administration of Quality Technology Supervision jointly organized the "oil and gas pipeline inspection and evaluation of the safety technology research," the state's key scientific and technological projects. Science and technology in the Tenth Five-Year Plan, the city gas pipeline will be a further risk assessment as a focus of research.
Domestic long-distance gas pipeline risk assessment of the fastest-growing technology. Researchers at the foreign research results on the basis of the comprehensive use of expert score, the fault tree and fuzzy math and other analytical methods, put forward a series of practical methods of evaluation [14-17].
Long-distance pipeline, the China scholar at the long-distance pipeline reliability analysis, residual strength, life prediction, risk assessment, and other aspects of a great deal of research, such as: literature [14] finite element analysis, the establishment of pipeline corrosion of non-defective line Analysis of the model, with a variety of deficiencies in the oil and gas pipeline outside the load for the stress-strain numerical simulation; the literature [15] to achieve a long-distance pipeline risk assessment of pipeline failure and the possibility of a quantitative assessment of the consequences for the Some research, put forward a risk-based oil and gas pipelines to maintain the integrity of the decision-making methods.
City gas pipeline systems, the literature [16] used fault tree analysis of liquefied petroleum gas pipeline fire explosion to analyze the causes and consequences of the establishment of a gas leak caused fire and explosion risk assessment model, a risk assessment Uncertainty and solutions. The literature [17] the use of fuzzy risk assessment methods to build a natural gas pipeline system and the failure factor consequences of system failure, and network acceptable level of risk to explore, in a more comprehensive manner taking into account the possibility of natural gas pipe network failure and the consequences of failure severity The impact of factors, overcome only rely on to assess the probability of failure brought about by the one-sidedness and limitations.
Engineering, Southwest Petroleum Institute in 2000 and China Southwest Branch of the Joint Petroleum Development of the "Gas Pipeline Risk Assessment software" in Chongqing Gas Field gas amounted to lying along the entire line of successful risk analysis and assessment of the current mark of the International General score on the law in our country has been long active oil along the trachea to reach the level of practical application [18].
As the city gas pipeline risk factors that affect many, from the design, construction, operation to third-party damage, corrosion damage, the consequences of research in the field of as many as hundreds of related factors, combined with China's city gas pipeline construction in the early and did not establish the historical data and The original design of the database, pipeline put into use after the operation entirely on artificial record, a great deal of information missing, the objective situation in the city to establish an increase of buried gas pipeline risk assessment methods and models of the difficulty of the city gas pipeline undermined the authenticity of the original data And reliability. Buried in the city gas pipeline risk assessment system has not yet formed a complete risk assessment techniques.
2 city gas pipeline and long-distance pipeline of the main differences
In the selection of risk assessment methods should often be considered evaluation of the system as well as the characteristics of the available data the situation. In practice, surveys and studies found that the city buried in the gas pipeline design, construction, management has its own inherent characteristics of its long-distance pipeline with a lot of difference, of the main problems:
① different structure of the pipeline [19, 20]
City gas pipeline network for distribution, elbow, valves, three, four and condensate pipeline, such as water tanks over the annex, 100-500 m, there is often a branch or valves, pipes Variable universal, different material pipes The situation in general. Long-distance pipeline is usually the same as the one-tube pipe, branches, and variable valve control rarely.
② pipeline planning and construction process, different
City gas pipeline network with the development of urban construction gradually and continuously expand. Pipeline construction in the early lack of a sound management system, design, construction and completion of the inspection standards are often uneven, such as anti-corrosion layer of relatively high quality defects. Long-distance pipeline is usually completed during the same period, there is a sound survey, design, construction, completion, acceptance criteria and procedures, such as the quality of the coating is relatively balanced and less defects.
③ pipeline human environment in which different
City gas pipeline in the densely populated areas, the environment surrounding the complex, in the event of a leak, fire, explosion, can cause severe casualties and property losses. Long-distance pipeline laying in the wild is usually sparsely populated areas, the distribution of surrounding buildings less easy to grasp the environmental information surrounding the incident after the little casualties.
④ pipeline where natural conditions are different
Long-distance pipeline laying in the field, covering the surface layer of soil usually suffer more against the conditions of natural forces, such as cold, lightning, heavy rains or floods, earthquakes, natural forces such conditions against the effects of long-distance pipeline is to be taken into account in [ 6]. Town buried gas pipeline due to surface cover for most of the asphalt pavement or cement, pipes from freezing conditions of natural forces such as flash floods have less impact.
⑤ different transmission media pressure
City gas pipeline in the urban area of low pressure in order to transfer [21], long-distance pipeline and the use of high-voltage transmission.
⑥ different forms of pipeline corrosion
Buried cities do not need to consider the atmospheric gas pipeline corrosion, and corrosion inside the pipe was not obvious, the main corrosion damage from the corrosive effect of the soil. Long-distance pipeline corrosion damage not only to consider soil erosion, but also corrosion and internal corrosion in the atmosphere.
⑦ pipeline corrosion protection in the form of different
China's buried pipeline, most of the city did not conduct cathodic protection, gas pipeline is very dependent on the anti-corrosion coating, anti-corrosion layer of small construction defects often can be caused by large area of pipeline corrosion. The use of all long-distance pipeline cathodic protection and corrosion inhibiting role of the double layer Corrosion outside, and cathodic protection for more than impressed current cathodic protection.
⑧ pipeline inspection and maintenance in different ways
The management of city gas pipeline is relatively passive, often conducted after police received a leaking drain the mouth to repair, maintenance after the fall; and city gas pipeline adjustable frequency, valves, condensate water tanks, such as pipe bend over, difficult to use smart pigging Device testing. Foreign long-distance pipeline has established a sound management system, the maintenance of its focus on the detection of intelligent pigging-line detection can discover the shortcomings in the pipeline system, facilitate the maintenance of predictability.
3, the city buried pipeline risk assessment of the applicability of the method
3.1 Analysis of the applicability of the law Mushi
Mushi law not only take full account of the impact of the pipeline systems of various types of safety factors (including third-party damage, corrosion, design, misoperation factor), but also to consider the danger of leakage on the transmission medium, the leakage of the state's influence , In the long-distance pipeline in the practical application of the project a success. However, due to long-distance pipeline and city gas pipeline buried a lot of difference, Mushi law can not be applied to the city of buried gas pipeline risk assessment, due to the following:
Factors and ① evaluation of the target weight approach does not apply
a. method Mushi study focused on long-distance oil and gas pipelines, and methods for the establishment of model is also related to the long-distance pipeline for oil and gas. Buried Gas Pipeline cities have their own structure and characteristics of the environment, Mushi law can not be directly applied to the city of buried gas pipeline risk assessment.
b. city gas pipeline poses the risk of a complex and include many factors inherent in the system of relations. Interaction between these factors, binding to each other, there is the shift in the internal relations. This intrinsic relationship between objective reality, making the city buried gas pipeline risks in different environmental conditions show a different picture of risk, and therefore can not ignore this intrinsic relationship. Mushi a law that is the premise of the assumption that the impact of various factors independent of each other, it is clear that this is the Mushi law in the city gas pipeline in the application of the remaining deficiencies [4].
c. Mushi proposed law would result in a pipeline accident factors into third-party damage, corrosion damage, design and misoperation factor 4, 4 this type of pipeline risk factors are scores from 0 to 100, that is, each type of factors Accounting for the weight of 25%. This deal is not quite rational, because each type of factor for the failure of the effects of different channels, each type of risk factors in the pipeline in the proportion of different.
United States Department of Transportation (Department of Transportation, referred to as the DOT) statistics, in 1931 the United States in 1986 a number of pipeline accidents, accounting for 40% of third-party damage, corrosion damage accounted for 30%. In China, some areas of the pipeline accident factors, which may vary. Statistics show that about, a city in southern China gas pipeline accident, third-party damage caused by accidents accounted for 30% of the corrosion damage caused by accidents accounted for 56%. This indicates that different countries, different environments, different conditions, different management system pipes the cause of the accident are not the same. If the pipes are used for any hard and fast score factor score system is bound to affect the outcome of the evaluation of the accuracy and usefulness.
Mushi ② law needs to provide some of the parameters of domestic hard
a. In our current urban buried gas pipeline management and operation of the system, a lot of the design, operation, operation, management and maintenance of standards and norms with Chinese characteristics, Mushi mentioned in the law and the norms of most of the measures is not Applicable to our country. Mushi as mentioned in the law known as the "address him by the system," the service system. United States Department of Transportation to address him by the conventional system is defined as: two or more of the utility companies, government departments or other underground facilities operators to establish a communication system to provide a phone number to the public as well as the mining contractor, Records of the notice requirement and that they engaged in excavation activities [6]. At present, the city's pipeline management system can not afford to adopt such measures.
b. As the city buried steel gas pipelines laid regular cement in the driveway of the road, and other municipal facilities staggered planting, a lot of testing methods such as the "tube to test potential," "secret interval measurements" will be difficult to implement, time Check the accuracy of the data difficult to ensure. Town buried steel gas pipeline distribution network was, annex large pipe, tube detector in the pipeline is difficult to carry out effective work of detection, pipe detector also be difficult to implement. These realities make the law applies to cities Mushi buried steel gas pipeline risk assessment of the above 3 (in possession of potential test, measurement and close spacing tube detector) to evaluate the contents of the score will be difficult to determine.
e. long-distance pipeline transportation as a result of media properties to be considered within the pipeline corrosion, and to consider ground pipeline corrosion in the atmosphere, these models can only be used for long-distance pipeline. As the city gas pipeline corrosion was not obvious, the majority of city gas pipeline at home and abroad are ignored in the evaluation of corrosion, and the small number of terrestrial channels, not to consider the atmosphere corrosion.
Mushi ③ law does not apply corrosion model
a. method Mushi model of corrosion, corrosion and internal corrosion in the atmosphere of the distribution of weight and value, accounting for a total assessment of the corrosion model of 40%. However, the city buried in the gas pipeline do not need to evaluate the atmospheric corrosion, and do not have the basic evaluation of the corrosion inside.
b. As a result of long-distance pipeline plus current cathodic protection, anti-corrosion layer of soil when the defect-free corrosive effects of very small Mushi corrosion on the model of soil corrosion was only re-empowered by 4.2 percent, and only to consider the soil resistivity A factor. As for the relatively high anti-corrosion layer defects without the effective implementation of the cathodic protection of the city buried gas pipeline, soil corrosion on the corrosion models have a significant impact, soil corrosion and a very elaborate procedure in the soil can not just soil corrosion resistance Judge, but also the corrosion of bacteria, soil pH, soil moisture and other factors.
c. long-distance pipeline due to stray current interference smaller, Mushi model of corrosion by stray current emphasis on empowering small, accounting for only 4.2 percent of the assessment of corrosion. The domestic city gas pipeline by the general stray current interference caused by stray current corrosion effect is very obvious, is a measure of pipeline corrosion is an important indicator.
As a result, corrosion Mushi model of the need for a corresponding adjustment to improve the checking and can be used after the city buried gas pipeline corrosion assessment.
④ Mushi is no law or under consideration
a. soil corrosion, stray current influencing factors are less Mushi law and does not take into account factors in evaluations, but as the city buried gas pipeline risk assessment, particularly the corrosion damage assessment, it is important to assess One of the indicators.
b. the city due to the laying of pipelines buried in the densely populated region, there are always illegal Zhanya, urban This is buried gas pipeline to be taken into account. Long-distance pipeline laying in the wild, no violation Zhanya, Mushi law and therefore did not consider the factors in this regard.
e. the consequences of the accident to estimate the risk assessment is an important part. Most long-distance pipeline laying wild in the open area, Mushi model only consider the consequences of the impact of population density, environmental pollution and damage to property on the ill-considered. Town buried gas pipeline should not only consider the casualties, it is also necessary to consider the loss of property, economic inputs, such as repair physical damage to the environment as well as on corporate reputation and social impact of the intangible losses.
As a result, the use of direct evaluation of city law Mushi buried steel gas pipeline will have a more serious risk of bias, it is necessary to improve the law Mushi corresponding model and the actual application only after verification.
3.2 fuzzy comprehensive evaluation of the applicability of the method of analysis
Since 1965, Zadeh fuzzy math since the creation of [22], because of its impact can be dealt with quantitative analysis and design of a variety of vague, fuzzy math has been widely used in various industrial sectors. Fuzzy comprehensive evaluation of fuzzy set theory is applied to the system of a comprehensive evaluation method, which based on fuzzy math, fuzzy relationship between the synthesis of the principles of fuzzy subsets of tectonic level to be reflected in the evaluation of the things fuzzy quantitative indicators (that is, Determine the degree of membership), and then the use of vague principles to transform the index [22].
Fuzzy comprehensive evaluation method used in gas pipeline risk assessment of the biggest advantages is that it will facilitate not only the risk of fuzzy uncertainty quantification, simple and practical, reliable science has strong operational. Fuzzy comprehensive evaluation method is more than Mushi law applicable to the city gas pipeline risk assessment, the main reason can be summarized as follows:
① with a maturity of the theoretical basis
a. fuzzy comprehensive evaluation of the theory is based on fuzzy math. Fuzzy math is the use of mathematical methods to study and deal with the "fuzzy" mathematical things. Ambiguity is the main objective things in the middle of the difference in the transition is not clear, it is an objective attribute of things, not people fail to recognize the subjective and objective reality. Fuzzy math is not accurate to become blurred, but the precise mathematical method to deal with the ambiguity of things. Using fuzzy set to express vague concept of fuzzy membership function will be to quantify, so that ambiguity with the traditional methods of mathematical analysis and processing.
b. fuzzy comprehensive evaluation to deal with the vague, imprecise or lack of the necessary information on the uncertainty of things to provide a good model. For more complex systems, as a result there are a number of system-induced accidents, the impact of the consequences of the accident fuzzy factors used to describe the methods of fuzzy sets and fuzzy to deal with these factors make the results of evaluation of the project closer to reality [23]. Buried city gas pipeline construction in the early establishment of the database did not make a lot of missing information on evaluation, fuzzy comprehensive evaluation method is to fill this gap.
c. comprehensive evaluation refers to a variety of factors, or things of the overall evaluation of the phenomenon, if such a fuzzy factors involved in the evaluation process is fuzzy comprehensive evaluation [24]. Due to the same thing with a variety of attributes, or the influence of various factors, so the evaluation process to judge the number of separate elements and some elements of the integrated form of. Is a comprehensive evaluation of the overall comprehensive evaluation of the object being to reflect the difference between, so as to achieve the target of the evaluation was to classify or sort.
d. fuzzy comprehensive evaluation method to deal with a high degree of non-linear system. Fuzzy approach particularly suited to high non-linear systems or systems of the mathematical model is not difficult to get accurate and even distressed situations cited. Fuzzy comprehensive evaluation is based on the evaluation process of non-linear characteristics put forward by its use of the fuzzy math of fuzzy algorithms for the evaluation of non-linear domain for quantization integrated so as to be comparable to quantify the results of the evaluation. As a result, fuzzy comprehensive evaluation to reduce human impact on the subjective, more objective has been to quantify the results.
② is a city gas pipeline risk assessment of the development of the
In the gas pipeline to carry out a risk assessment of the early days of the traditional idea of research is to find the cause of the failure of all gas pipelines, and on the basis of the changes in the law to determine the probability density distribution function in order to set up city gas pipeline failure probability distribution model. However, the actual course of the investigation has found that the impact of gas pipeline failure of the many factors are uncertain, and some can not be quantified. Under these circumstances, even if the establishment of a formulaic calculation of the assessment model, and the results are objective laws and that mistakes were made, a direct impact on the gas pipeline risk assessment techniques. To this end, a need to be able to deal with a number of risk factors of uncertainty is the uncertainty of parameters, as well as their mutual influence between the role of evaluation methods. As a result, the introduction of the concept of fuzzy gas pipeline semi-quantitative risk assessment, and failure to fully understand the factors and quantification of the relationship between the fuzzy, gas pipeline is to carry out an effective way to assess the risk [25].
③ more in line with the city to bury the actual situation of gas pipeline
a. fuzzy comprehensive evaluation method based on the city buried steel gas pipeline to its own characteristics and environmental characteristics and flexibility to apply to the city buried steel gas pipeline risk assessment and evaluation system to assess factors that, in view of the existing evaluation of the available information, the establishment of China's city gas pipeline to assess the actual model, to be realistic assessment of the results.
b. fuzzy comprehensive evaluation method for large and complex system of the gas pipeline risk assessment, multi-level fuzzy comprehensive evaluation will be interrelated factors unified hierarchical classification, first of all, according to the lowest levels of various factors to evaluate, and then up layer by layer Evaluation until the total came to the conclusion that the results of the evaluation.
c. buried in the city gas pipeline risk assessment, on the one hand, as a result of various factors that failure can not be quantified and models, used to be fuzzy solutions. On the other hand, the analysis will often involve human experience and to determine, for example, "good quality construction" is an ambiguous event, "soil corrosion resistance" is a fuzzy event. The fuzzy set theory is the basic functions of the use of language to express the variable parameters of non-precision [22], so in dealing with such problems than the traditional model of probability better reflect the objective reality. Recognition of ambiguity, the use of fuzzy thinking and methods, the results will be as objective as possible in order to achieve better results.
d. city buried in the gas pipeline design, construction, operation, maintenance and operation, from the people, equipment, environment and so on subjective and objective aspects of the impact of various factors on the impact of the pipeline is not independent, but related to each other , And with time, place, and other conditions vary. Failure of various factors, the link between the uncertainty of both objective and subjective uncertainties include, with a lot of ambiguity. Fuzzy comprehensive evaluation method is not cut off the various factors of the question, but give full consideration to the ambiguity of the relationship between objective reality, we can make use of fuzzy comprehensive evaluation method to solve the conventional methods can not solve the city's buried gas pipeline risk assessment .
e. city buried gas pipeline risk assessment, the impact of various factors on the pipeline's impact on the overall risk ratio is not the same, that is, the importance of various factors, not the same. Fuzzy comprehensive evaluation is not only considered all factors of nature, but also takes into account the importance of various factors. Delphi method used, AHP method to determine the weight, and other methods of evaluation of the factors that will influence the extent of the target with [0,1] to quantify the value [22], the value to reflect the size of the factors on the evaluation of the impact of the size of the object, the more value Tai said that the greater the degree of influence, in its evaluation of the system, the higher the degree of importance, so that the results of the assessment closer to the objective reality, but also more reasonable.
As a result, fuzzy comprehensive evaluation method in theory can be applied to the city of buried gas pipeline risk assessment, as a result of fuzzy comprehensive evaluation of the factors in dealing with ambiguity and uncertainty there are certain advantages, the city will have an impact on Buried Gas Pipeline Risk And their impact on the degree of reasonable quantification, and the use of traditional methods of mathematical analysis in order to be more objective than other methods reflect the city buried gas pipeline risk assessment of the outcome of the status quo.
4 Conclusion
Mushi ① model can not be directly used for city gas pipeline risk assessment. Mushi law aimed to assess the long-distance pipeline, due to the long-distance pipeline and city gas pipeline buried steel in the structure and environment, and so there is a big difference, Mushi law on the premise the assumption that corrosion and are difficult to model Apply to the city pipelines. China's unique management system, Mushi law relating to the management tool difficult to score, and the actual situation of urban pipeline also Mushi law accordingly in order to improve the application.
② fuzzy comprehensive evaluation method to deal with many factors that can affect the joint system, but also applies to city gas pipeline risk assessment. Not only does the system of evaluation in the subjective and objective can relatively uniform, and be able to quantify that is difficult to avoid some of the fuzzy concept. Fuzzy comprehensive evaluation of the ability to handle highly nonlinear, can be subjective to minimize the impact. Impact on the city buried steel gas pipeline is very complex factors that have a certain ambiguity, and people are also more subjective factors, fuzzy comprehensive evaluation of the law there are many factors which affect the city buried steel gas pipeline to carry out risk Assessment, more comprehensive and objective, scientific feasible.
1 Gas Pipeline Risk Assessment Research
① foreign gas pipeline risk assessment study of the status quo
Buried pipeline risk management began as early as the 1970s. U.S. PRCI (Pipeline Research Committee Intemationa1) of the United States and Europe gas pipeline accident data and statistical classification, a summary of 22 pipe failure caused by fundamental factors [4].
In 1985, the United States Battelle Columbus Institute published a "guide to the risk of investigation," First of all pipelines in the risk analysis of the use of scoring [4]. W. K. Muhlbauer On this basis, the sum of the United States over the past 20 years oil and gas pipelines to carry out a risk assessment of technical research results, in 1992, the preparation of the famous "Pipeline Risk Management Manual", details of pipeline risk assessment expert score model, once the world And universally accepted as a buried pipeline to carry out a risk assessment of the important references [5]; in 1996 in the second edition of the book have been added to the length of a large number of different occasions, the pipeline risk assessment model of the amendment, an increase of environmentally sensitive region , Workplace stress and the evaluation of the potential human error, and details on how to make use of the risk and cost of establishing the relationship between resource allocation model [6]; in 2004, the third edition of the book is rich in the original risk management, more Clear and more specific examples of the establishment of the basic model of risk assessment procedures, an increase of oil and gas pipelines across the section of the risk assessment model approach.
As for the oil and gas pipelines understanding of the dangers of an increasing number of foreign gradual development of a new pipeline integrity management system [7], all of the factors that affect the integrity of the pipeline to carry out a comprehensive, integrated management, from the preparation of the plan, Procedures and documentation to the pipeline to carry out risk analysis to find out the possibility of the accident and the consequences of the accident, and to develop prevention and response measures on a regular basis pipeline integrity testing and evaluation, including pipeline design, construction, operation, monitoring, maintenance, replacement, Quality control and communications, and so the whole process, and pipelines running through the entire period of operation. The current management system in the long-distance oil and gas pipelines in the management of more and more attention.
In engineering applications, overseas as early as the 1960s began to pay attention to the end of the pipeline project in the pipeline service in the detection and assessment of residual strength, such as: American Petroleum Institute issued the "risk-based inspection norms" (API 581) [ 8], "added integrity of the gas pipeline system files" (ASME B31.8S) [9], "to determine the remaining strength of pipeline corrosion has been manual paper added pressure pipe norms" (ASME B31G) [10]. To the early 1990s, many oil and gas pipelines in the United States have applied a risk management techniques to guide the maintenance of the pipeline. Followed by Canada, the European countries have also joined the pipeline risk management technology development and application of the ranks. Advantica Britain through statistical analysis of a large number of pipeline information and disaster simulation in the natural gas pipeline on the risk factors for the probability analysis to quantify the consequences of the accident and on the basis of the establishment of a gas pipeline quantitative risk assessment techniques, the expert analysis software has been PIPESAFE Used in the United Kingdom and the countries of the world's high-pressure gas pipeline [10]. Canada's C-FFR has also successfully developed a pipeline maintenance and testing of risk analysis software package (PIRAMID), for the pipeline failure probability analysis of the consequences of failure and the risk calculation [11].
With the emergence of new disciplines and the development of new technologies and new methods, new technologies are also used in risk analysis of buried pipeline under study. If the literature [12] proposed the use of fuzzy neural network of buried pipeline to carry out simulation and simulated shortcomings, and buried pipeline to classify all kinds of defects. GIS technology is fast becoming the facility for management, life-cycle testing, risk analysis, coordination and management, improve the operational efficiency of the effective means. Pipeline GIS technology is widely used in the United States, Norway and other countries.
② domestic gas pipeline risk assessment study of the status quo
In the mid-1990s, China has carried out related to oil and gas pipeline safety evaluation of the study and application of a series of trials. In our country was first proposed by Professor Pan Jiahua in a comprehensive introduction in 1995 of the United States, "Pipeline Risk Management Manual" [13]. During the Ninth Five-Year Plan, China National Petroleum Corporation and the State General Administration of Quality Technology Supervision jointly organized the "oil and gas pipeline inspection and evaluation of the safety technology research," the state's key scientific and technological projects. Science and technology in the Tenth Five-Year Plan, the city gas pipeline will be a further risk assessment as a focus of research.
Domestic long-distance gas pipeline risk assessment of the fastest-growing technology. Researchers at the foreign research results on the basis of the comprehensive use of expert score, the fault tree and fuzzy math and other analytical methods, put forward a series of practical methods of evaluation [14-17].
Long-distance pipeline, the China scholar at the long-distance pipeline reliability analysis, residual strength, life prediction, risk assessment, and other aspects of a great deal of research, such as: literature [14] finite element analysis, the establishment of pipeline corrosion of non-defective line Analysis of the model, with a variety of deficiencies in the oil and gas pipeline outside the load for the stress-strain numerical simulation; the literature [15] to achieve a long-distance pipeline risk assessment of pipeline failure and the possibility of a quantitative assessment of the consequences for the Some research, put forward a risk-based oil and gas pipelines to maintain the integrity of the decision-making methods.
City gas pipeline systems, the literature [16] used fault tree analysis of liquefied petroleum gas pipeline fire explosion to analyze the causes and consequences of the establishment of a gas leak caused fire and explosion risk assessment model, a risk assessment Uncertainty and solutions. The literature [17] the use of fuzzy risk assessment methods to build a natural gas pipeline system and the failure factor consequences of system failure, and network acceptable level of risk to explore, in a more comprehensive manner taking into account the possibility of natural gas pipe network failure and the consequences of failure severity The impact of factors, overcome only rely on to assess the probability of failure brought about by the one-sidedness and limitations.
Engineering, Southwest Petroleum Institute in 2000 and China Southwest Branch of the Joint Petroleum Development of the "Gas Pipeline Risk Assessment software" in Chongqing Gas Field gas amounted to lying along the entire line of successful risk analysis and assessment of the current mark of the International General score on the law in our country has been long active oil along the trachea to reach the level of practical application [18].
As the city gas pipeline risk factors that affect many, from the design, construction, operation to third-party damage, corrosion damage, the consequences of research in the field of as many as hundreds of related factors, combined with China's city gas pipeline construction in the early and did not establish the historical data and The original design of the database, pipeline put into use after the operation entirely on artificial record, a great deal of information missing, the objective situation in the city to establish an increase of buried gas pipeline risk assessment methods and models of the difficulty of the city gas pipeline undermined the authenticity of the original data And reliability. Buried in the city gas pipeline risk assessment system has not yet formed a complete risk assessment techniques.
2 city gas pipeline and long-distance pipeline of the main differences
In the selection of risk assessment methods should often be considered evaluation of the system as well as the characteristics of the available data the situation. In practice, surveys and studies found that the city buried in the gas pipeline design, construction, management has its own inherent characteristics of its long-distance pipeline with a lot of difference, of the main problems:
① different structure of the pipeline [19, 20]
City gas pipeline network for distribution, elbow, valves, three, four and condensate pipeline, such as water tanks over the annex, 100-500 m, there is often a branch or valves, pipes Variable universal, different material pipes The situation in general. Long-distance pipeline is usually the same as the one-tube pipe, branches, and variable valve control rarely.
② pipeline planning and construction process, different
City gas pipeline network with the development of urban construction gradually and continuously expand. Pipeline construction in the early lack of a sound management system, design, construction and completion of the inspection standards are often uneven, such as anti-corrosion layer of relatively high quality defects. Long-distance pipeline is usually completed during the same period, there is a sound survey, design, construction, completion, acceptance criteria and procedures, such as the quality of the coating is relatively balanced and less defects.
③ pipeline human environment in which different
City gas pipeline in the densely populated areas, the environment surrounding the complex, in the event of a leak, fire, explosion, can cause severe casualties and property losses. Long-distance pipeline laying in the wild is usually sparsely populated areas, the distribution of surrounding buildings less easy to grasp the environmental information surrounding the incident after the little casualties.
④ pipeline where natural conditions are different
Long-distance pipeline laying in the field, covering the surface layer of soil usually suffer more against the conditions of natural forces, such as cold, lightning, heavy rains or floods, earthquakes, natural forces such conditions against the effects of long-distance pipeline is to be taken into account in [ 6]. Town buried gas pipeline due to surface cover for most of the asphalt pavement or cement, pipes from freezing conditions of natural forces such as flash floods have less impact.
⑤ different transmission media pressure
City gas pipeline in the urban area of low pressure in order to transfer [21], long-distance pipeline and the use of high-voltage transmission.
⑥ different forms of pipeline corrosion
Buried cities do not need to consider the atmospheric gas pipeline corrosion, and corrosion inside the pipe was not obvious, the main corrosion damage from the corrosive effect of the soil. Long-distance pipeline corrosion damage not only to consider soil erosion, but also corrosion and internal corrosion in the atmosphere.
⑦ pipeline corrosion protection in the form of different
China's buried pipeline, most of the city did not conduct cathodic protection, gas pipeline is very dependent on the anti-corrosion coating, anti-corrosion layer of small construction defects often can be caused by large area of pipeline corrosion. The use of all long-distance pipeline cathodic protection and corrosion inhibiting role of the double layer Corrosion outside, and cathodic protection for more than impressed current cathodic protection.
⑧ pipeline inspection and maintenance in different ways
The management of city gas pipeline is relatively passive, often conducted after police received a leaking drain the mouth to repair, maintenance after the fall; and city gas pipeline adjustable frequency, valves, condensate water tanks, such as pipe bend over, difficult to use smart pigging Device testing. Foreign long-distance pipeline has established a sound management system, the maintenance of its focus on the detection of intelligent pigging-line detection can discover the shortcomings in the pipeline system, facilitate the maintenance of predictability.
3, the city buried pipeline risk assessment of the applicability of the method
3.1 Analysis of the applicability of the law Mushi
Mushi law not only take full account of the impact of the pipeline systems of various types of safety factors (including third-party damage, corrosion, design, misoperation factor), but also to consider the danger of leakage on the transmission medium, the leakage of the state's influence , In the long-distance pipeline in the practical application of the project a success. However, due to long-distance pipeline and city gas pipeline buried a lot of difference, Mushi law can not be applied to the city of buried gas pipeline risk assessment, due to the following:
Factors and ① evaluation of the target weight approach does not apply
a. method Mushi study focused on long-distance oil and gas pipelines, and methods for the establishment of model is also related to the long-distance pipeline for oil and gas. Buried Gas Pipeline cities have their own structure and characteristics of the environment, Mushi law can not be directly applied to the city of buried gas pipeline risk assessment.
b. city gas pipeline poses the risk of a complex and include many factors inherent in the system of relations. Interaction between these factors, binding to each other, there is the shift in the internal relations. This intrinsic relationship between objective reality, making the city buried gas pipeline risks in different environmental conditions show a different picture of risk, and therefore can not ignore this intrinsic relationship. Mushi a law that is the premise of the assumption that the impact of various factors independent of each other, it is clear that this is the Mushi law in the city gas pipeline in the application of the remaining deficiencies [4].
c. Mushi proposed law would result in a pipeline accident factors into third-party damage, corrosion damage, design and misoperation factor 4, 4 this type of pipeline risk factors are scores from 0 to 100, that is, each type of factors Accounting for the weight of 25%. This deal is not quite rational, because each type of factor for the failure of the effects of different channels, each type of risk factors in the pipeline in the proportion of different.
United States Department of Transportation (Department of Transportation, referred to as the DOT) statistics, in 1931 the United States in 1986 a number of pipeline accidents, accounting for 40% of third-party damage, corrosion damage accounted for 30%. In China, some areas of the pipeline accident factors, which may vary. Statistics show that about, a city in southern China gas pipeline accident, third-party damage caused by accidents accounted for 30% of the corrosion damage caused by accidents accounted for 56%. This indicates that different countries, different environments, different conditions, different management system pipes the cause of the accident are not the same. If the pipes are used for any hard and fast score factor score system is bound to affect the outcome of the evaluation of the accuracy and usefulness.
Mushi ② law needs to provide some of the parameters of domestic hard
a. In our current urban buried gas pipeline management and operation of the system, a lot of the design, operation, operation, management and maintenance of standards and norms with Chinese characteristics, Mushi mentioned in the law and the norms of most of the measures is not Applicable to our country. Mushi as mentioned in the law known as the "address him by the system," the service system. United States Department of Transportation to address him by the conventional system is defined as: two or more of the utility companies, government departments or other underground facilities operators to establish a communication system to provide a phone number to the public as well as the mining contractor, Records of the notice requirement and that they engaged in excavation activities [6]. At present, the city's pipeline management system can not afford to adopt such measures.
b. As the city buried steel gas pipelines laid regular cement in the driveway of the road, and other municipal facilities staggered planting, a lot of testing methods such as the "tube to test potential," "secret interval measurements" will be difficult to implement, time Check the accuracy of the data difficult to ensure. Town buried steel gas pipeline distribution network was, annex large pipe, tube detector in the pipeline is difficult to carry out effective work of detection, pipe detector also be difficult to implement. These realities make the law applies to cities Mushi buried steel gas pipeline risk assessment of the above 3 (in possession of potential test, measurement and close spacing tube detector) to evaluate the contents of the score will be difficult to determine.
e. long-distance pipeline transportation as a result of media properties to be considered within the pipeline corrosion, and to consider ground pipeline corrosion in the atmosphere, these models can only be used for long-distance pipeline. As the city gas pipeline corrosion was not obvious, the majority of city gas pipeline at home and abroad are ignored in the evaluation of corrosion, and the small number of terrestrial channels, not to consider the atmosphere corrosion.
Mushi ③ law does not apply corrosion model
a. method Mushi model of corrosion, corrosion and internal corrosion in the atmosphere of the distribution of weight and value, accounting for a total assessment of the corrosion model of 40%. However, the city buried in the gas pipeline do not need to evaluate the atmospheric corrosion, and do not have the basic evaluation of the corrosion inside.
b. As a result of long-distance pipeline plus current cathodic protection, anti-corrosion layer of soil when the defect-free corrosive effects of very small Mushi corrosion on the model of soil corrosion was only re-empowered by 4.2 percent, and only to consider the soil resistivity A factor. As for the relatively high anti-corrosion layer defects without the effective implementation of the cathodic protection of the city buried gas pipeline, soil corrosion on the corrosion models have a significant impact, soil corrosion and a very elaborate procedure in the soil can not just soil corrosion resistance Judge, but also the corrosion of bacteria, soil pH, soil moisture and other factors.
c. long-distance pipeline due to stray current interference smaller, Mushi model of corrosion by stray current emphasis on empowering small, accounting for only 4.2 percent of the assessment of corrosion. The domestic city gas pipeline by the general stray current interference caused by stray current corrosion effect is very obvious, is a measure of pipeline corrosion is an important indicator.
As a result, corrosion Mushi model of the need for a corresponding adjustment to improve the checking and can be used after the city buried gas pipeline corrosion assessment.
④ Mushi is no law or under consideration
a. soil corrosion, stray current influencing factors are less Mushi law and does not take into account factors in evaluations, but as the city buried gas pipeline risk assessment, particularly the corrosion damage assessment, it is important to assess One of the indicators.
b. the city due to the laying of pipelines buried in the densely populated region, there are always illegal Zhanya, urban This is buried gas pipeline to be taken into account. Long-distance pipeline laying in the wild, no violation Zhanya, Mushi law and therefore did not consider the factors in this regard.
e. the consequences of the accident to estimate the risk assessment is an important part. Most long-distance pipeline laying wild in the open area, Mushi model only consider the consequences of the impact of population density, environmental pollution and damage to property on the ill-considered. Town buried gas pipeline should not only consider the casualties, it is also necessary to consider the loss of property, economic inputs, such as repair physical damage to the environment as well as on corporate reputation and social impact of the intangible losses.
As a result, the use of direct evaluation of city law Mushi buried steel gas pipeline will have a more serious risk of bias, it is necessary to improve the law Mushi corresponding model and the actual application only after verification.
3.2 fuzzy comprehensive evaluation of the applicability of the method of analysis
Since 1965, Zadeh fuzzy math since the creation of [22], because of its impact can be dealt with quantitative analysis and design of a variety of vague, fuzzy math has been widely used in various industrial sectors. Fuzzy comprehensive evaluation of fuzzy set theory is applied to the system of a comprehensive evaluation method, which based on fuzzy math, fuzzy relationship between the synthesis of the principles of fuzzy subsets of tectonic level to be reflected in the evaluation of the things fuzzy quantitative indicators (that is, Determine the degree of membership), and then the use of vague principles to transform the index [22].
Fuzzy comprehensive evaluation method used in gas pipeline risk assessment of the biggest advantages is that it will facilitate not only the risk of fuzzy uncertainty quantification, simple and practical, reliable science has strong operational. Fuzzy comprehensive evaluation method is more than Mushi law applicable to the city gas pipeline risk assessment, the main reason can be summarized as follows:
① with a maturity of the theoretical basis
a. fuzzy comprehensive evaluation of the theory is based on fuzzy math. Fuzzy math is the use of mathematical methods to study and deal with the "fuzzy" mathematical things. Ambiguity is the main objective things in the middle of the difference in the transition is not clear, it is an objective attribute of things, not people fail to recognize the subjective and objective reality. Fuzzy math is not accurate to become blurred, but the precise mathematical method to deal with the ambiguity of things. Using fuzzy set to express vague concept of fuzzy membership function will be to quantify, so that ambiguity with the traditional methods of mathematical analysis and processing.
b. fuzzy comprehensive evaluation to deal with the vague, imprecise or lack of the necessary information on the uncertainty of things to provide a good model. For more complex systems, as a result there are a number of system-induced accidents, the impact of the consequences of the accident fuzzy factors used to describe the methods of fuzzy sets and fuzzy to deal with these factors make the results of evaluation of the project closer to reality [23]. Buried city gas pipeline construction in the early establishment of the database did not make a lot of missing information on evaluation, fuzzy comprehensive evaluation method is to fill this gap.
c. comprehensive evaluation refers to a variety of factors, or things of the overall evaluation of the phenomenon, if such a fuzzy factors involved in the evaluation process is fuzzy comprehensive evaluation [24]. Due to the same thing with a variety of attributes, or the influence of various factors, so the evaluation process to judge the number of separate elements and some elements of the integrated form of. Is a comprehensive evaluation of the overall comprehensive evaluation of the object being to reflect the difference between, so as to achieve the target of the evaluation was to classify or sort.
d. fuzzy comprehensive evaluation method to deal with a high degree of non-linear system. Fuzzy approach particularly suited to high non-linear systems or systems of the mathematical model is not difficult to get accurate and even distressed situations cited. Fuzzy comprehensive evaluation is based on the evaluation process of non-linear characteristics put forward by its use of the fuzzy math of fuzzy algorithms for the evaluation of non-linear domain for quantization integrated so as to be comparable to quantify the results of the evaluation. As a result, fuzzy comprehensive evaluation to reduce human impact on the subjective, more objective has been to quantify the results.
② is a city gas pipeline risk assessment of the development of the
In the gas pipeline to carry out a risk assessment of the early days of the traditional idea of research is to find the cause of the failure of all gas pipelines, and on the basis of the changes in the law to determine the probability density distribution function in order to set up city gas pipeline failure probability distribution model. However, the actual course of the investigation has found that the impact of gas pipeline failure of the many factors are uncertain, and some can not be quantified. Under these circumstances, even if the establishment of a formulaic calculation of the assessment model, and the results are objective laws and that mistakes were made, a direct impact on the gas pipeline risk assessment techniques. To this end, a need to be able to deal with a number of risk factors of uncertainty is the uncertainty of parameters, as well as their mutual influence between the role of evaluation methods. As a result, the introduction of the concept of fuzzy gas pipeline semi-quantitative risk assessment, and failure to fully understand the factors and quantification of the relationship between the fuzzy, gas pipeline is to carry out an effective way to assess the risk [25].
③ more in line with the city to bury the actual situation of gas pipeline
a. fuzzy comprehensive evaluation method based on the city buried steel gas pipeline to its own characteristics and environmental characteristics and flexibility to apply to the city buried steel gas pipeline risk assessment and evaluation system to assess factors that, in view of the existing evaluation of the available information, the establishment of China's city gas pipeline to assess the actual model, to be realistic assessment of the results.
b. fuzzy comprehensive evaluation method for large and complex system of the gas pipeline risk assessment, multi-level fuzzy comprehensive evaluation will be interrelated factors unified hierarchical classification, first of all, according to the lowest levels of various factors to evaluate, and then up layer by layer Evaluation until the total came to the conclusion that the results of the evaluation.
c. buried in the city gas pipeline risk assessment, on the one hand, as a result of various factors that failure can not be quantified and models, used to be fuzzy solutions. On the other hand, the analysis will often involve human experience and to determine, for example, "good quality construction" is an ambiguous event, "soil corrosion resistance" is a fuzzy event. The fuzzy set theory is the basic functions of the use of language to express the variable parameters of non-precision [22], so in dealing with such problems than the traditional model of probability better reflect the objective reality. Recognition of ambiguity, the use of fuzzy thinking and methods, the results will be as objective as possible in order to achieve better results.
d. city buried in the gas pipeline design, construction, operation, maintenance and operation, from the people, equipment, environment and so on subjective and objective aspects of the impact of various factors on the impact of the pipeline is not independent, but related to each other , And with time, place, and other conditions vary. Failure of various factors, the link between the uncertainty of both objective and subjective uncertainties include, with a lot of ambiguity. Fuzzy comprehensive evaluation method is not cut off the various factors of the question, but give full consideration to the ambiguity of the relationship between objective reality, we can make use of fuzzy comprehensive evaluation method to solve the conventional methods can not solve the city's buried gas pipeline risk assessment .
e. city buried gas pipeline risk assessment, the impact of various factors on the pipeline's impact on the overall risk ratio is not the same, that is, the importance of various factors, not the same. Fuzzy comprehensive evaluation is not only considered all factors of nature, but also takes into account the importance of various factors. Delphi method used, AHP method to determine the weight, and other methods of evaluation of the factors that will influence the extent of the target with [0,1] to quantify the value [22], the value to reflect the size of the factors on the evaluation of the impact of the size of the object, the more value Tai said that the greater the degree of influence, in its evaluation of the system, the higher the degree of importance, so that the results of the assessment closer to the objective reality, but also more reasonable.
As a result, fuzzy comprehensive evaluation method in theory can be applied to the city of buried gas pipeline risk assessment, as a result of fuzzy comprehensive evaluation of the factors in dealing with ambiguity and uncertainty there are certain advantages, the city will have an impact on Buried Gas Pipeline Risk And their impact on the degree of reasonable quantification, and the use of traditional methods of mathematical analysis in order to be more objective than other methods reflect the city buried gas pipeline risk assessment of the outcome of the status quo.
4 Conclusion
Mushi ① model can not be directly used for city gas pipeline risk assessment. Mushi law aimed to assess the long-distance pipeline, due to the long-distance pipeline and city gas pipeline buried steel in the structure and environment, and so there is a big difference, Mushi law on the premise the assumption that corrosion and are difficult to model Apply to the city pipelines. China's unique management system, Mushi law relating to the management tool difficult to score, and the actual situation of urban pipeline also Mushi law accordingly in order to improve the application.
② fuzzy comprehensive evaluation method to deal with many factors that can affect the joint system, but also applies to city gas pipeline risk assessment. Not only does the system of evaluation in the subjective and objective can relatively uniform, and be able to quantify that is difficult to avoid some of the fuzzy concept. Fuzzy comprehensive evaluation of the ability to handle highly nonlinear, can be subjective to minimize the impact. Impact on the city buried steel gas pipeline is very complex factors that have a certain ambiguity, and people are also more subjective factors, fuzzy comprehensive evaluation of the law there are many factors which affect the city buried steel gas pipeline to carry out risk Assessment, more comprehensive and objective, scientific feasible.
| Updated:2008.12.17 Source:International Gas Network Clicks:880