Research On Quantitative Risk Assessment Method Of Gas Pipeline Based On Data Statistics And Scenario Simulation

As one of the urban public infrastructures,gas pipeline is a double-edged sword that outweighs the disadvantages.On the one hand,the importance of gas determines that gas pipelines are an indispensable lifeline in the development of urban modernization.On the other hand,accidents such as gas pipeline leakage,fire and explosion are major threats to urban public safety.In recent years,the endless stream of gas pipeline accidents has highlighted the importance of quantitative risk assessment.Aiming at the lack of basic data,the strong subjective dependence,the immature simulation of the consequences of fire and explosion accidents,and the nonprominent characteristics of gas pipelines in the process of quantitative risk assessment of gas pipelines,a quantitative risk assessment method for gas pipelines based on data statistics and scenario simulation is proposed.The main research contents and results are as follows:(1)A method for evaluating the failure probability of gas pipelines based on failure data and modification factors is proposed.The statistical data of the pipeline failure database are analyzed,and the basic failure probability calculation model of the gas pipeline is established.The gas pipeline modification factor index system is constructed,and the modification factor indices are divided into three groups: a quantitative index,a semi-quantitative index and a qualitative index,according to the difficulty in quantifying each index.This three groups of modification factor indices are used to modify and update the basic failure probability.The application results show that this method can reduce the subjective dependence of failure probability assessment and improve the accuracy of quantitative results when the risk assessment data are scarce.(2)The leakage state of gas pipeline is divided into two types: steady state and unsteady state.The calculation methods of gas leakage rate in pipeline with different diameter holes are analyzed,which lay the foundation for gas pipeline leakage jet fire and explosion accident scenario simulation.A 3D numerical calculation model of gas pipeline leakage jet fire accident scenario is established to simulate the whole dynamic process of gas pipeline leakage,diffusion and jet fire.The simulation results are compared with the existing experimental results,which basically coincided with each other and verified the accuracy of the 3D model.On this basis,the thermal radiation influence range of gas pipeline jet fire under different working conditions is analyzed.The results show that the flame height and thermal radiation influence range are closely related to the internal pressure,pipe diameter,wind speed and the obstacle congestion level around the pipeline.As a reference,the influence distance of gas pipeline fire and explosion accidents that have occurred at home and abroad is counted.The flame height and thermal radiation influence distance of jet fire are studied.Considering the influence of wind speed around the pipeline,the empirical formula of the potential impact radius of pipeline accidents given in ASME B31.8S-2016 is revised.An empirical formula for the thermal radiation influence distance of gas pipeline jet fire depending on the variation of internal pressure,pipe diameter and wind speed is proposed.The revised formula is in good agreement with the simulation results,and the error is within acceptable range.(3)Based on the data of pipeline parameters,building distribution and environmental conditions in Manhattan gas pipeline explosion accident,a 3D numerical calculation model of the explosion accident scenario is constructed to simulate the whole dynamic process of gas pipeline leakage,diffusion and explosion.The simulation results were compared with those in the accident investigation report.This two results basically coincided with each other,and the accuracy of the model was verified.On this basis,the explosion shock wave overpressure influence range of gas pipeline under different working conditions is analyzed.The results show that obstacles inhibit the diffusion of natural gas and stimulate the propagation of explosion shock wave.The explosion shock wave overpressure influence range is closely related to the internal pressure,pipe diameter,wind speed,ignition time and the obstacle congestion level around the pipeline,but it is random and the quantitative relationship is unpredictable.The influence distance of gas pipeline explosion shock wave overpressure is studied,and compared with that of jet fire thermal radiation.The results show that,in general,for gas pipelines,the influence distance of explosion shock wave overpressure is smaller than that of jet fire thermal radiation.(4)A monetary quantitative assessment method of failure consequences based on influence distance and hazard acceptor is proposed.Combining with failure probability assessment,a quantitative risk matrix is used to implement risk classification control of gas pipeline.Taking a town gas pipeline as an example,engineering application demonstration is carried out,relevant data are collected,failure probability and consequences of the pipeline are evaluated,and risk space of the gas pipeline is constructed.Distribution map can accurately identify high-consequence and high-risk areas.