Cogitation on Safety Evaluation of Shutdown and Restart of Buried Waxy Crude Pipelines

The general comment is made on the research advance of shutdown and restart in buried waxy crude pipelines. The main reasons of the deviations between calculated result of temperature drop and restart pressure and measured ones are originated from the uncertainties of crude oil rheology, environmental and operating parameters, inappropriate assumptions of real conditions in developed mathematical models, and the lack of the quantitative description of the shear and thermal history effect on the waxy crude. The imperfection of evaluating the safety of shutdown and restart of buried waxy crude pipelines by decided method has been discussed. Moreover, the difficulties and challenges in studying shutdown and restart are pointed out. In addition, studies on evaluating the safety of shutdown and restart are also put forward.