Safety Assessment Study Of Pressure Vessel In Natural Gas Station Under Low Temperature

The utilizing scope and using zone of natural gas industry of China are expanding gradually with its rapidly development.West to east gas and Shaanxi-Beijing pipeline have built many stations in winner alpine region in north.Since the temperature of pressure vessel wall in station is closing to the low temperature of external environment when the station of winner cold regions is in the transmission stopping and holding stage,the pressure vessel has the problem of low temperature servicing and the risking of low-temperature brittle fracture.Failure accidents of pressure vessels under low temperature happen and need studying on their security.Therefore,Shaanxi-Beijing pipeline is taken as the research object of this project which will carry out relevant research focused on the research safety assessment of pressure vessel in natural gas station under low temperatureThis subject conducts a system investigation about material,wall thickness,environmental limit temperature and relevant standards of vessels in winner cold regions of 1st Shaanxi-Beijing and 2nd Shaanxi-Beijing pipeline.Choosing three common material(20R,16MnR and 15MnNbR),doing tensile performance testing under different temperature and fracture toughness performance testing of different thickness and temperature,building the failure assessment diagram,studying and applying the thickness effect and building safety assessment method that focus on pressure vessels containing cracks service under low temperature.The results include the following aspects:1.Three common material of pressure vessel all present good low-temperature flexibility under the test temperature of 0?-40?,the yield strength and tensile strength of three materials increase with the decreasing of temperature,all the fractures of tensile samples and fracture toughness samples are typical tough fracture.2.Building the failure assessment diagram of three common material of pressure vessel under the low temperature of 0?-40?.The results showed that option-1 curve is the most conservative curve;option-2 curves and option-3 curves are essentially coincident when Lr is less than 0.6,when Lr is bigger than 0.6,the Kr of option-2 curves and option-3 curves in vertical or horizontal material both decrease with the reducing of temperature,the curve is closer to option-1 curve approach,this means the decreasing of material's safety area with the reducing of reducing of temperature,and the service danger is growing;option-3 curves of three material under different temperature show the higher tendency and do better in reflecting the material characters while suffering larger load.3.The toughness thickness effect of common materials of pressure vessel under low temperature is studied.The values of fracture toughness JC under low temperature all emerge the trend of first rise and then decrease with the increasing of sample thickness to the steel plate of pressure vessel.Thickness effect of 16MnR shell material after service under different temperature is not obvious,which means long time service has bigger influence to material.4.Building safety assessment method that focus on pressure vessels containing cracks service under low temperature based on the technique of failure assessment diagram.the crack of 17-Pipe dry filter which has surface crack in 1st Shaanxi-Beijing pipeline was safety assess,this led to the result that the Dry Filter is safe currently and the safety margin is 0.51.