Research On Integrity Management Of A Pipeline In Service

For an oil pipeline built in early stage in China,such key technologies as identification of high consequence area,risk assessment,defect assessment and comparison of repair structure have been researched according to changes of the social environment around the pipeline,pipe corrosion,drilling,manufacturing defects and other pipe body damages,then reasonable suggestions of pipeline operation and technical improvement are proposed for long-term safety assurance to the oil pipeline.(1)On the basis of safe distances between oil pipelines and various kinds of buildings specified in current codes and standards,the scoring method of severity of high consequence area is established.Based on accident statistics,the classification of hazard factors of pipelines and the method of determining weight of risk factors are proposed,the risk assessment index system of oil pipeline is established.The identification of high consequence area and the risk assessment of the specific pipeline are implemented,the distribution of high consequence area and the risk classification of the whole pipeline are evaluated,the proposed method is verified.(2)Full-scale burst test of pipeline with prefabricated weld defect,dent,caprepaired structure have been carried out,respectively.Some important data such as the deformation of pipe,strain and fracture have been obtained.The failure mechanism of pipeline with defects or repair structure under internal pressure are explored.Safe bearing capacity of pipeline with repair structure is tested and effects of weld defect and dents on carrying capacity are investigated.(3)A system evaluation method for corrosive defects,weld defects and dents is established.The projection algorithm about spiral weld in a pipeline derived from mechanics of fracture is proved.Based on full scale burst test,internal inspection and weld inspection of pipeline,the maximum operating pressure of the pipeline has been proposed,and the corresponding maintenance suggestions has been put forward.(4)Three finite element models of pipeline with pipe cap,reinforcing plate and sleeve respectively which is checked by test data have been established.The internal pressure of yield failure and the plastic limit internal pressure are defined.The analysis showed that the limit internal pressure can not be affected by any kind of repair structures,but the yield pressure of pipeline would be affected by different repair structures.The bearing capacity of the pipeline is measured by the yield pressure and three kinds of repair structures have been compared,and the size of the repaired structure has been optimized.