Wang Yaxing, Sun Jie, Hu Huasheng, Hu Bo, Bin Weiqi, Shi Wen, Fu Yuewen
Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, Nanchang 330063, China.
Guangdong Institute of Special Equipment Inspection and Research, Foshan 528251, China.
Sensors (Basel). 2024 Oct 13;24(20):6599. doi: 10.3390/s24206599.
Ultra-high-pressure tubular reactors are crucial pieces of equipment for polyethylene production. Long-term operation under high temperature, high pressure, and other extremely harsh conditions can lead to various defects, with circumferential cracks posing a major safety risk. Detecting cracks is challenging, particularly when they are under a protective layer of a certain thickness. This study designed a pulsed eddy current differential probe to detect circumferential cracks in ultra-high-pressure tubular reactors, with the lift-off distance acting as a protective layer. Detection models for traditional cylindrical and semi-circular excitation differential probes were established using finite element simulations. Corresponding experiments under different lift-off conditions were carried out, and the model's accuracy was verified by the consistency between the simulation results and experimental data. The distribution of the eddy current field under different conditions and the disturbances caused by cracks at various positions to the detection signal were then calculated in the simulations. The simulation results showed that the cracks significantly disturbed the eddy current field of the semi-circular excitation differential probe compared with that of the traditional cylindrical probe. The designed differential probe effectively detected circumferential cracks of specific lengths and depths using the difference in the voltage signals. The experimental results were in agreement with the simulation results, showing that the designed probe could effectively detect 20 mm-long circumferential cracks at a lift-off of 60 mm. The experimental results also show that the probe's detection coverage area in the axial direction varied with the lift-off height. The probe design and findings are valuable for detecting cracks in ultra-high-pressure tubular reactors with protective layers.
超高压管式反应器是聚乙烯生产中的关键设备。在高温、高压等极端恶劣条件下长期运行会导致各种缺陷，其中周向裂纹构成重大安全风险。检测裂纹具有挑战性，尤其是当裂纹位于一定厚度的保护层之下时。本研究设计了一种脉冲涡流差动探头，用于检测超高压管式反应器中的周向裂纹，提离距离作为保护层。利用有限元模拟建立了传统圆柱形和半圆形激励差动探头的检测模型。在不同提离条件下进行了相应实验，并通过模拟结果与实验数据的一致性验证了模型的准确性。然后在模拟中计算了不同条件下的涡流场分布以及不同位置裂纹对检测信号的干扰。模拟结果表明，与传统圆柱形探头相比，裂纹对半圆形激励差动探头的涡流场干扰明显。所设计的差动探头利用电压信号的差异有效地检测了特定长度和深度的周向裂纹。实验结果与模拟结果一致，表明所设计的探头在提离距离为60 mm时能够有效检测20 mm长的周向裂纹。实验结果还表明，探头在轴向的检测覆盖区域随提离高度而变化。该探头设计及研究结果对于检测带有保护层的超高压管式反应器中的裂纹具有重要价值。
