Hazard Analysis And Consequence Simulation Of High Pressure Gas Transmission

The high-pressure gas pipeline is regarded as one of the most safe and economic manner for transporting natural gas. Like other engineering structures, high-pressure gas pipeline will be influenced by variety of internal and external factors, such as pipeline corrosion, material defects and third party damage, etc. resulting in pipeline leakage. Due to the characteristics of flammable, explosive and toxic characteristics of natural gas, the natural gas diffuses into the atmosphere once the high-pressure pipelines leak, if reaches a finite concentration and ignition source may cause the combustion or explosion, lead serious casualties, property losses, and the bad social and political impact. Therefore, the high-pressure natural gas pipeline leakage qualitative and quantitative risk analysis and consequence simulation is needed in order to achieve target the minimum risk and maximize effectiveness.This thesis identified potential risk and hazardous factors during the operation of high-pressure pipeline, found the risk factors which closely associated with the high-pressure pipeline natural gas leak accident. This logical reasoning process made preparations for fault tree analysis (FTA).Then the thesis utilized Qualitative FTA to find out the cause of high-pressure gas pipeline leakage. The FTA calculated the high-pressure gas pipeline leakage fault tree’s minimum cut set and got the main hazard factors which can cause high-pressure gas pipeline leakage. The major hazard factors are third party damage, corrosion, tubing defects and natural disasters. Due to lacking of enough field data and experimental data in high-pressure gas pipeline, so the fuzzy fault tree analysis (FFTA) is analyzed used to high-pressure gas pipeline system. Regard the major risk factors of high-pressure gas pipeline as the fault tree model, triangular fuzzy-number designated the probability of event and then calculated pipeline leakage probability. The method of fuzzy importance degree is utilized to get the basic event fuzzy probability order.The leakage of gas leak is the basis for the calculation of the disaster. The thesis analyzed jet theory and based on hydromechanics elementary theory, the leakage model consistent with the actual situation established. The calculation models of high-pressure gas pipeline rate is studied systematically. The models are respectively the nozzle model, the pipe model and the hole model. The range of application of every model has been determined. By comparing the leakage diffusion models systematically, the Gaussian model to simulate the gas pipeline leakage diffusion process. The thesis applied MATLAB in Gaussian smoke regiment model, got the hazardous region and researched the relationship between the hazardous region and leakage aperture, speed of wind.There is a possibly ensuing explosion and fire after high-pressure gas pipeline leakage. The thesis chose the Jet fire model, fireball model, vapor cloud explosion model to calculate different disasters in high-pressure gas pipeline and find out disasters influencing areas by choosing these hazard models scientifically. Calculation on damage of jet fire thermal radiation by solid flame model which is similar with the natural gas leak trajectory, compared to point-source model, have more comprehensive considerations and high credibility calculations. In calculating for the radius of the fireball fire damage, introducing integration to accumulate damage effect in the combustion process of fireball, which further improves the accuracy of the calculation. Gas leakage in case of delayed ignition source will lead to vapor cloud explosion, and the Mainstream model in damage calculation of vapor cloud explosion is TNT equivalent model. By obtaining the quality of TNT equivalent to the fuel, determine the scope of the damage of vapor cloud explosion. And the calculation process is simple and easy to understand, is conducive to the promotion in the analysis of actual disasters.