In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and to prevent the solidification of the wax fraction. The high temperature and high pressure will induce the addition...In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and to prevent the solidification of the wax fraction. The high temperature and high pressure will induce the additional stress in the pipeline, which results in the upheaval buckling of the pipeline. If such expansion is resisted, e.g., by the frictional effects of the foundation soil over a kilometer or of a pipeline, the compressive axial stress will be set up in the pipe-wall. When the stress exceeds the constraint of the foundation soil on the pipeline, suddenly-deforming will occur to release the internal stress, similar to the sudden deformation of the strut due to stability problems. The upheaval buckling may jeopardize the structural integrity of the pipeline. Therefore, effective engineering measures against this phenomenon play an important role in the submarine pipeline design. In terms of the pipeline installation and protection measures commonly used in Bohai Gulf, three engineering measures are investigated in great details. An analytical method is introduced and developed to consider the protection effect of the anti-upheaval buckling of the pipeline. The analysis results show that the amplitude of the initial imperfection has a great effect on the pipeline thermal upheaval buckling. Both trenching and burial and discrete dumping are effective techniques in preventing the pipeline from buckling. The initial imperfection and operation conditions of the pipelines determine the covered depth and the number of layers of the protection measures.展开更多
In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to ...In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buried pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis (FEA) was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.展开更多
In this paper,a theoretical solution of vertical buckling is proposed with regard to the typical initial imperfection cases of submarine pipelines.Analytical tools are applied to predicting the occurrence and conseque...In this paper,a theoretical solution of vertical buckling is proposed with regard to the typical initial imperfection cases of submarine pipelines.Analytical tools are applied to predicting the occurrence and consequence of inservice buckling of a buried heated pipeline in Bohai Gulf.An evaluation is performed to ensure the pipeline structural integrity during operation under loading conditions.Different protection measures are proposed and their validities are analyzed.Analyses show that for the same magnitude of initial imperfection,the upheaval buckling of pipeline with isolated prop model is the most likely to occur.The empathetic model represents a special sub-case of continuous prop model,and the calculated buckle temperature is between the first stage and the second stage of post-upheaval buckling of continuous prop model.And the larger the initial imperfection,the less the axial force required for the upheaval buckling.Meanwhile,it can be seen that a peak point appears on the curves of temperature difference against buckling amplitude for small initial imperfection.Besides,trenching-burial is one kind of protection measures preventing the pipeline from thermal upheaval.The covered depth-to-diameter ratio depends on the design conditions and subsoil properties.For the given pipeline in this paper,the covered depth-to-diameter ratio is recommended to be 5.展开更多
基金Project supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No.51021004)the National Natural Science Foundation of China(No.40776055)the Foundation of the State Key Laborary of Ocean Engineering (No.1002)
文摘In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and to prevent the solidification of the wax fraction. The high temperature and high pressure will induce the additional stress in the pipeline, which results in the upheaval buckling of the pipeline. If such expansion is resisted, e.g., by the frictional effects of the foundation soil over a kilometer or of a pipeline, the compressive axial stress will be set up in the pipe-wall. When the stress exceeds the constraint of the foundation soil on the pipeline, suddenly-deforming will occur to release the internal stress, similar to the sudden deformation of the strut due to stability problems. The upheaval buckling may jeopardize the structural integrity of the pipeline. Therefore, effective engineering measures against this phenomenon play an important role in the submarine pipeline design. In terms of the pipeline installation and protection measures commonly used in Bohai Gulf, three engineering measures are investigated in great details. An analytical method is introduced and developed to consider the protection effect of the anti-upheaval buckling of the pipeline. The analysis results show that the amplitude of the initial imperfection has a great effect on the pipeline thermal upheaval buckling. Both trenching and burial and discrete dumping are effective techniques in preventing the pipeline from buckling. The initial imperfection and operation conditions of the pipelines determine the covered depth and the number of layers of the protection measures.
基金Project(51021004) supported by Innovative Research Groups of the National Natural Science Foundation of ChinaProject(40776055) supported by the National Natural Science Foundation of china+1 种基金Project(1002) supported by State Key Laboratory of Ocean Engineering Foundation, ChinaProject(NCET 11 0370) supported by the Program for New Century Excellent Talents in Universities of China
文摘In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buried pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis (FEA) was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.
基金Supported by National Natural Science Foundation of China (No.40776055)
文摘In this paper,a theoretical solution of vertical buckling is proposed with regard to the typical initial imperfection cases of submarine pipelines.Analytical tools are applied to predicting the occurrence and consequence of inservice buckling of a buried heated pipeline in Bohai Gulf.An evaluation is performed to ensure the pipeline structural integrity during operation under loading conditions.Different protection measures are proposed and their validities are analyzed.Analyses show that for the same magnitude of initial imperfection,the upheaval buckling of pipeline with isolated prop model is the most likely to occur.The empathetic model represents a special sub-case of continuous prop model,and the calculated buckle temperature is between the first stage and the second stage of post-upheaval buckling of continuous prop model.And the larger the initial imperfection,the less the axial force required for the upheaval buckling.Meanwhile,it can be seen that a peak point appears on the curves of temperature difference against buckling amplitude for small initial imperfection.Besides,trenching-burial is one kind of protection measures preventing the pipeline from thermal upheaval.The covered depth-to-diameter ratio depends on the design conditions and subsoil properties.For the given pipeline in this paper,the covered depth-to-diameter ratio is recommended to be 5.