Initial state and safety of pipeline shutdown in the thermal differential batch transportation of crude oil

Different initial shutdown state for the thermal differential batch transportation pipeline corresponds to different safe shutdown time, and the shutdown safety of is a key technical issue for this transportation process. In order to obtain the influence of initial shutdown state on the safety, this paper qualitatively analyzes the features of safety of different shutdown period in one transportation cycle and quantitatively analyzes the relative safety of different initial state by introducing the concept of shutdown time and definition of dimensionless emptying time. The results show that it is most dangerous to shutdown when the oil head with high pour point reaches the inlet of pump station. There are obvious differences in dimensionless emptying time at different shutdown time, that is, the difficulty to restart at different shutdown time or safety is very different from each other and the differences increases with the increase of shutdown time. For the shutdown time with risks, the dimensionless emptying time will tend to infinite under some shutdown time, which indicates that the restart will be a failure under that shutdown time. The results can provide a technical support to the reasonable arrangement of repair schedule or qualitative judge of safe shutdown time for the thermal differential batch transportation pipeline.