Induction heating of large-diameter thin-walled elbow based on skin effect

The large-diameter thin-walled elbow is widely applied in oil and gas pipeline engineering, and it is mainly manufactured by means of local induction heating and hydraulic pushing and bending. Therefore, the accurate matching between the hydraulic pushing speed and the induction heating parameters is the important factor affecting the quality of elbows. Considering the uncertainty of skin effect on heating result in the process of induction heating, the key parameters based on skin effect were investigated after the induction heating theory was analyzed. Then, the effects of all technological parameters on Joule heat distribution in the induction heating process of pipes were analyzed by virtue of finite element simulation calculation method. And finally, parameter sets were optimized by means of orthogonal tests. It is indicated that the effects of variation gradient of three parameters (current frequency, current density and pipe-inductor distance) on the skin effect shall be analyzed comprehensively in the design of induction heating device, so that the optimal parameter set can be obtained and the accurate design parameters for its matching elbow pushing speed can be provided. And consequently, field debugging and production efficiency of equipment is improve d significantly while the quality of elbow is ensured.