Limit Load Calculation And Risk Assessment Of Buried Pipe

A buried piping is widely used to transport oil, gas and so on. The loading state of piping is more complicated than normal piping, therefore the safety of buried piping is very important. The consequence will be very serious if a buried piping is failure, so it is necessary to study limit load of buried piping and to perform risk assessment of buried piping.In this paper, the limit load of buried pipe, that is used in Nanjing city nature gas using engineering, was studied by finite element analysis under various groundsill character, pedestal angle and ground pressure, and the risk assessment for this piping was performed. The limit load of buried pipe was measured by experiments. The research contents and results were as follows:(1) With FEA method, the effects of various groundsill character, pedestal angle and ground pressure on the limit load of buried pipe were studied. The results show that the effects of groundsill character and pedestal angle on the limit load are little. The effect of ground pressure on the limit load is also little when the groundsill is flexible, but when the groundsill is rigid, the limit load of buried pipe is decreases rapidly as the ground pressure increases to a certain value.(2) The experimental equipment and system of buried pipe were designed, and the experiment of buried pipe was carried out successfully. The results of experiment and FEA are almost equal.(3) The limit load of buried pipe containing a local wall-thinning was studied by FEA. Calculative results of limit load by FEA is less than that calculated by normal pipe assessment method which is recommended by criterion-Safety Assessment for Pressure Vessels Containing Defects.(4) The risk assessment method of natural gas buried pipeline based on W.Kent Muhlbauer's method was improved. Then the risk of high pressure pipeline used for Nanjing city natural gas engineering was assessed. The assessment results show that the risk of this pipeline is low, and the pipeline is safe, but some measures should be adopted in keeping safety and stability of pipeline.