Research of Non-excavation Positioning Technology of Girth Weld in Underground Ferromagnetic Pipeline

Using the RD8000 to map pipeline routing, a non-contact metal magnetic memory detector is used to collect the tube segment signal directly above the buried ferromagnetic pipeline. The data is filtered through the Savitzky-Golay filter. It is found that when the magnetic induction normal component change gradient Kz crosses zero and the magnetic induction tangential component change gradient Ky has an extreme value, the feature position can be judged as the girth weld position. By comparing the relative distance ΔL1 of the adjacent ring welds in the magnetic signal diagram with the length ΔL2 of the construction period, the construction period number corresponding to the girth weld in the magnetic signal diagram can be matched. Finally, the GPS information collected by the magnetic memory tester is combined to determine the geographical position of the target ring weld.