The objective optimization function was set by the summary of the insulation materials' annual sharing cost and the annual heat losing cost after insulation and the calculating model of buried hot oil pipelines' insulation economical thickness was given. The model included the burying depth's influences on around pipelines ambient temperature, the heat transfer coefficient of the outer wall insulation, and the overall heat transfer coefficient. With the help of C# programming language, a computer program was developed to optimize the thickness of insulation layer of buried hot oil pipeline with EXCEL to work out economic evaluation procedures, combining with examples of calculation. The results showed that: The determination of buried hot oil pipeline insulation thickness would have some impact on the economic benefits of the project, and it should take the double requirements into account determining the thickness on both technology and economy. That could provide a theoretical reference to the hot oil transportation construction's optimizing design.

Aiming at the problem in dynamic leakage of urban overhead gas pipeline,considering the impact of different pressure levels on leakage and diffusion, high pressure (2.0 MPa), sub high pressure (1.0 MPa) and medium pressure (0.4 MPa) three kinds of pressure grade pipe to simulate were selected.Firstly, the leakage rate of the critical flow and the sub critical flow were calculated by using the leakage rate calculation mode.Secondly, the leakage rule of different pressure pipelines was obtained.The Fluent software was used to simulate the unsteady state leakage, and the risk range of natural gas diffusion was obtained.The results showed that if the pressure in the tube was greater,the quality of residual gas in pipe and the time of leaking was higher and the risk range of natural gas was lager when the volume of pipe and the diameter of leak were fixed.With the continuous leakage of non steady state, the leakage rate was getting smaller and smaller, the risk of natural gas was also getting smaller and smaller.