2018 Volume 54 Issue 12 Pages 894-899
The steel tube for liquefied natural gas in a petrochemical plant is used. This steel tube of a large diameter is covered with the thermal insulation material and the sheet metal. On the inspection of the thickness or the corrosion in this steel tube, the sheet metal and the thermal insulation material are removed from the steel tube. However, much cost and time are needed for this inspection. In this paper, the pulse electromagnetic inspection method for detecting the defect in the steel tube from the upper side of the insulation material and the sheet metal is proposed. The defect is inspected by measuring of the slope of the output voltage from the maximum output voltage value obtained immediately after cutting off the pulse wave magnetic field. In addition, the proposed inspection method is investigated by the 3-D nonlinear FEM taking account of hysteresis magnetizing properties and eddy current in the steel tube.
