Strain Calculation And Safety Analysis Of LNG Pipeline Pre-cooling Process

After the completion of the LNG terminal,the pipelines in the station can be precooled to cool the expected temperature.During the pre-cooling operation,the temperature difference during the cooling of the pipeline causes uneven shrinkage,which leads to the change of strain and stress of the pipeline.Therefore,it is necessary to conduct research on the pre-cooling operation of the pipeline.In this paper,the unloading pipeline of a domestic LNG terminal is taken as the research object,and the control variable method was adopted to conduct numerical simulation of the pre-cooling process of the pipeline.The main contents of this paper are as follows:1.Based on a domestic LNG terminal,the pre-cooling process of the unloading pipeline was investigated,and the pre-cooling effect of the pipeline was determined to be related to the pre-cooling time,inlet temperature,inlet velocity and inlet pressure of cryogenic nitrogen.2.The ICEM software was used to establish the geometric model of the pipeline and dividing the grid.Then the control variable method was used to conduct numerical simulation of the temperature field changes of the pipeline with Fluent,and the variation law of the pipeline temperature field under different pre-cooling influencing factors was obtained.At the same time,the time when the peak of temperature difference occurred in the pipeline during the pre-cooling operation under different influencing factors were determined to lay a foundation for the subsequent research.3.Fluid-structure Interaction model was established based on ANSYS Workbench,and then import the precooling time of 4000 s under the working condition of each group of the temperature field data,and the control variable method is adopted to unloading pipe of a numerical simulation of the deformation,strain and stress under different precooling factors.The variation law of the deformation,strain and stress of unloading pipeline under different pre-cooling factors are obtained.4.Based on the analysis results,some Suggestions on pre-cooling operation of LNG terminal are put forward.It is used to reduce the temperature difference of the pipeline in the pre-cooling operation,reduce the uneven shrinkage uneven contraction caused by the temperature difference,and avoid excessive deformation,strain and stress of pipeline during pre-cooling operation.