The Unsteady Thermodynamic Calculation Of Repaired Hot Oil Pipeline On Working

Northeast pipelines have been working for more than thirty years. So it has to be repaired. At present, most of the study about repair centralize at solid mechanics.The study on thermodynamics and hydraulics of excavating repaired pipeline is few. The heat lost increases and the temperature drops very quickly after digging repair. In order to ensure the safety of hot oil pipeline, it's necessary to study unstable process by thermodynamics during repair. This paper studies on excavating repair technics process without shutdown. The model of pipeline axial and radial temperature drop and pressure drop during regular function is developed. And the solution is given out. Axial temperature and pressure drop are calculated by finite difference. Radial temperature field is calculated by finite element. On this foundation of thermodynamics, the unstable excavating repair mathematics model is also developed. Both finite difference and finite element are used for solution. The influence to soil temperature field and pipeline function management by atmosphere abrupt change is studied. The conclusion that atmosphere abrupt change won't influent the gathering pipeline is proposed. The most excavating length calculation method for hot oil pipeline restricted by thermodynamics conditions is also given out. The correctness of model is tested by the combination of experimention and simulation. The normal function and excavating repair function of pipeline are analyzed. The conclusion is given out that the worst season for pipeline function is not the season with lowest atmosphere temperature. There is some delay and it depends on the depth of pipeline. Most excavating length is influenced by excavating start point and outlet oil temperature of station mostly.