Introduction  In the nuclear power plant, the steam pipeline is generally installed with an insulation layer on the outer wall to improve heat transfer efficiency. Currently, the main detection means for ferromagnetic pipelines are conventional ultrasound and ultrasonic guided waves. Prior to the inspection, the insulation layer on the outer wall of the pipeline needs to be removed, leading to extended inspection time, increased labor costs, and an inability to meet the requirements for high-quality development in nuclear power plants. The application of the pulsed eddy current (PEC) technique for nuclear power plants can eliminate the need for insulation layer removal, enabling non-stop online screening. The defects testing by coil placement is an essential indicator of the PEC technique.

  Method  In this paper, the modeling and simulation of the pipelines was conducted by applying ANSYS Maxwell, coaxial and vertical detection coils were designed respectively to simulate the detection capability of PEC on flat bottom defects with consistency in the lift-off distance, materials and other conditions. Sample pipes were selected from the nuclear power plant for coaxial and vertical PEC testing. The pulsed eddy current testing (PECT) results were cross-validated with ultrasonic thickness measurement, and the effects of two coil placement methods on PECT were compared.

  Result  The results show that vertical coils are more effective in defect detection compared to coaxial coils.

  Conclusion  The defects testing by coil placement has great significance for implementing PEC in the nuclear power sector.