A Setting-Round Process Of Pipe-End By Three-Roller For Large Pipes

The ovality of pipe ends is one of the important quality parameters for oil and gas transportation pipes.If the ovality of pipe ends does not meet the standards,it will affect the welding process between pipes,resulting in excessive welding residual stress,which poses potential risks to the safety of oil and gas transportation.Since existing processes cannot achieve continuous and high-efficiency setting-round of pipe-ends,this study proposed two three-roller setting-round process plans for pipe-ends.The two process plans can be used to setting-round different types of pipes.Based on the finite element software ABAQUS,the numerical simulation of the pipe end setting-round process of 304 stainless steel and Q235 carbon structural steel pipes was conducted,verifying the feasibility of the process,and exploring the impact of different process parameters on the rounding results.The results show that the residual stress at the pipe ends of straight pipes,tee pipes and elbows whose initial ovality exceeds the standard is small and evenly distributed after the pipe ends are setting-rounded,and the residual ovality is less than 1%,which conforms to API Spec 5L standards.Residual ovality of pipe-ends decreases with the increase of the reduction,and tends to be stable after reaching the optimum reduction.Residual ovality of pipe-ends decreases with the increase of the reciprocating bending times,and tends to be stable after reaching the optimum reciprocating bending times.There is an approximate linear relationship between the relative thickness and the optimal reduction.The shape of the transition zone of the roller has a certain influence on the setting-round result,and the roller with appropriate shape should be selected according to the different types of pipes.A three-roll pipe end setting-round experimental setup has been developed,which can be used to setting-round different types of pipes by changing the fixture.Taking the residual ovality less than 1% as the target,the pipe end setting-round experiment was carried out,and the effects of reciprocating bending times,reduction,initial ovality and relative thickness on the setting-round results were investigated.The experimental results show that the minimum residual ellipticity of the tube end can reach 0.28%,and there are no wrinkles,cracks and other defects at the pipe end.The relationship between the process parameters and the residual ovality is consistent with the numerical simulation.The simulation and experiment achieve a closed loop,and the conclusions tend to be unified.The proposed process can realize continuous setting-round of pipe-ends of straight pipes,elbows and tee pipes,improve the setting-round efficiency.In addition,the setting of process parameters is independent of initial ovality,and the process is simple to realize.