Abstract: In petrochemical industry, storage tanks are key equipment for storing crude oil, natural gas and other petrochemical feedstocks. Among all tank components, the bottom plate endures the most severe environmental conditions and bears the greatest pressure, making it more prone to developing defects. Consequently, it is one of the most critical parts in tank defect detection. Eddy current testing has the advantages of high detection accuracy, easy operation and no need to detect media. So it is widely used in defect detection of oil and gas pipelines, storage tanks and other equipment. However, due to the skin effect, conventional eddy current testing cannot be directly applied to ferromagnetic materials, such as those commonly used in storage tank bottom plates. This paper proposes utilizing finite element simulation to determine magnet parameters, thereby achieving pre-magnetization of ferromagnetic materials and thus addressing the skin effect problem. This method subjects the ferromagnetic materials to pre-magnetization treatment, causing it to enter saturation state.. Meanwhile, relevant experiments were conducted to validate the detection effectiveness of this method. The results demonstrate that under pre-magnetization conditions, the capability of pulsed eddy current testing to detect defects on the lower surface of ferromagnetic materials is significantly improved.

Key words: tank bottom plate, pulsed eddy current testing, skin effect, pre-magnetization