A novel weld penetration monitoring and control method is proposed and tested in this paper. The successful experiment results can be concluded as follows: A weld penetration monitoring and control method is proposed for the GTA pipe welding process. The method is based on observation of development of the weld pool during the welding operation.An effective control system was built and connected to common GTAW process. An easy but effective curve-fitting based
control algorithm is proposed to detect the change on the weld pool elevation, in order to indicate complete joint penetration.Smooth, consistent weld beads with complete joint penetration were obtained with both the orbital pipe welding system and manual pipe welding operations.