Reliability Analysis For Girth Weld On Pipelines

For long-distance oil and gas pipelines,pipeline construction is actually a vast project which involves long-distance welding process.Because of technology and artificial factors,girth weld is prone to include defects during the welding process.Pipeline is often subject to a series of adverse conditions,including cyclic loading,pressure fluctuation,corrosion,high temperature,shock and so on,which seriously impair the performance of pipeline,and then pipeline happens accident.Girth weld defect is one of the underlying causes,which leads to early damage to welded structure and arouses catastrophic accident.It is necessary to study the reliability of girth weld.It provides theoretical guidance for the safe operation of oil and gas pipelines.Reliability analysis for girth weld on pipelines is studyed from three aspects.Firstly,Data was collected and a statistical analysis on material properties parameters of X60,X70 and X80 pipelines girth weld are made,including girth weld tensile strength,girth weld impact energy and girth weld fracture toughness.The best distributions of parameters are recommended and distributions parameters are given.Secondly,based on stress condition and strain condition,the limit state equations for girth weld of pipelines are constructed,respectively.Then,Monte Carlo method is used to conduct reliability analysis for girth weld on pipelines with defects.Thirdly,according to the definition of sensitivity,Monte Carlo method is introduced in sensitivity analysis for parameters,which affect failure for girth weld on pipelines.The main factors affecting the reliability for girth weld on pipelines are determined.