The Cross Section Of Pipelines In Service Safety Analysis

In the process of natural gas pipeline construction,it is inevitable that it will cross with various levels of highways,thus forming a highway crossing section.Highway cross section of the pipeline is buried pipelines,except by the medium,the persistent effect such as soil conditions,also from the road vehicles,such as surface subsidence,and with the increase of service life of pipe,corrosion damage,such as to greatly reduce pipeline self-bearing capacity,under the function of these factors,prone to all kinds of pipeline failure.Therefore,it is of great significance to analyze the safety of gas pipeline crossing section.This paper analyzes the safety of in-service gas pipeline crossing section.Firstly,the way of gas pipeline crossing is introduced,and the mechanical characteristics of gas pipeline crossing with and without casing are analyzed.Secondly,the finite element software ABAQUS is used to analyze the stress of the gas pipeline crossing the road with and without casing respectively,and the influence law of different factors such as running pressure,vehicle load,soil depth and pipe wall thickness on the safety of the gas pipeline is studied.Then,the stress distribution in the road crossing section of in-service gas pipeline with corrosion defects is analyzed,and the influence of operating pressure on pipeline stress is studied.Based on the plastic failure criterion,the influence of defect location and size on pipeline failure pressure is calculated and analyzed.Finally,safety analysis is carried out on the crossing section of a gas pipeline project,and safety countermeasures are put forward from two aspects of engineering technology and safety management.The main conclusions of this paper include:(1)Under the action of internal pressure,the stress of the gas pipeline crossing the highway with casing pipe or culvert increases gradually from inside to outside along the direction of wall thickness.The stress of pipeline increases approximately linearly with the increase of operating pressure.As long as the casing does not fail under the action of earth pressure and vehicle load and the pipe material meets the requirements,the pipe is safe under the action of internal pressure alone.Of course,the operating pressure should be under the design pressure,can not overload operation.(2)Under the action of vehicle load,soil mass and internal pressure,the stress and displacement of gas pipeline crossing the highway without casing are unevenly distributed.The stress of pipeline increases approximately linearly with the increase of operating pressure.Increase with the increase of vehicle load;With the increase of overburden depth,it increases,and the change rate decreases gradually.It decreases with the increase of wall thickness.(3)The failure pressure of gas pipelines with and without casing crossing the road with corrosion defects is independent of the circumferential location of the defects,while the failure pressure of the inner wall is slightly greater than that of the outer wall.With the same location,size(length,width and depth)defect,the failure pressure value of the gas pipeline with casing crossing the highway is smaller than that without casing crossing the highway.(4)For the same length and width of corrosion defects,with the increase of corrosion defect depth,the corresponding failure pressure values of gas pipelines with and without casing crossing the highway gradually decrease.From the perspective of change range,the change rate of pipeline failure pressure with defect depth is higher than that of the pipeline with casing.(5)For the same width and depth of corrosion defects,with the increase of the length of corrosion defects,the corresponding failure pressure values of gas pipelines with and without casing crossing the highway gradually decrease.But compared with defect depth defect length has less effect on failure pressure.(6)For the same length and depth of corrosion defects,with the increase of corrosion defect depth,the corresponding failure pressure values of gas pipelines with and without casing crossing the highway gradually decrease.Compared with the depth and length of the defect,the defect width has little effect on the change of the failure pressure of the gas pipeline with and without casing.