The Study On Shut Down And Restart Up Of Repaired Hot Oil Pipeline On Working

Since the first oil pipeline (Fushun-Daqing pipeline) was built, the hot oil pipeline of northeast has been worked for 35 years, and its using life exceed the designing life. In order to ensure of the safety of northeast oil pipeline run, now the pipeline must be heavy repaired by digging the soil. For ensure the safety of repairing and rebuilding, we should study on the problem of shut down and restart up during oil pipeline repaired.Taking into account the existing of opening segments, we establish the model of shutdown and restart up of the repairing oil pipeline. Based on the fact of pipeline, we consider buried segments, stilts segments, cross river segments and digging segments. Because of the complexity of border conditions, we adopt mathematical solution to solve the model. We obtain the axis temperature by concealed difference and gain the radial temperature of the buried segments by finite elements method. The meshing method of the area makes the nodes reduced greatly and computational speed accelerated. We study on the pressure of restart up from two sides: One is friction resistance, the other is pressure wave. We deduce the method to calculate the pressure along the pipeline by the water power equation; we calculated the pressure of station exit in view of the friction resistance and the pressure wave. For the radial temperature model of soil, we provide a method to estimate the temperature and depth of layer of constant soil temperature, as well as we establish the model of allowable shut down time, the model of the most dangerous place and the model of maximum digging length.The software named"Simulation software for hot oil pipeline during shut down and restart up"is developed. We calculated the axis temperature, radials temperature, startup pressure, allowable shut down time, the most dangerous place of not opening and opening oil pipeline etc. by the software. The results indicate that the most dangerous place is always at the end of opening segments. The allowable shut down time of opening oil pipeline is shorter than not opening oil pipeline. The results may supply references to the oil pipeline during shut down and restart up running during heavy repair.We take an experimentation of shut down and restart up of the oil pipeline at the base of Daqing oil-gas field engineering. The experimentation pipeline length is 304 meters, the diameter is 50 millimeters. The experimental device is able to auto-collect the data of the temperature and pressure during shut down and restart up. Calculate the pipeline by software and contrast the results and test data, it was found that the error was in the range of allowable, which proved the model was correct.