隔水管是海洋钻井的关键设备,由于经受复杂交变应力和腐蚀环境,隔水管很容易产生应力腐蚀裂纹.针对海洋钻井隔水管应力腐蚀裂纹的特点,提出一种基于交流电磁场检测(Alternating current field measurement,ACFM)的链式阵列检测探头,建立针对隔水管表面裂纹的ACFM仿真模型,提取裂纹特征信号并分析U形载流磁心激励区域和裂纹区磁场影响范围,为阵列探头设计提供理论支持,在此基础上利用巨磁电阻(Giant magneto resistance,GMR)传感器设计基于ACFM的隔水管表面裂纹链式阵列探头检测系统,并开展隔水管裂纹检测试验.仿真和试验结果表明:单个U形磁心的激励区域为+/?40 mm,阵列激励磁心的设计间距应不大于80 mm;裂纹上方畸变磁场影响区域为+/?5 mm,传感器排布间距应不大于10 mm;利用GMR传感器设计的链式阵列ACFM探头可快速大面积定量、定位检测隔水管表面裂纹.
Drilling riser is a critical component in offshore oil & gas industry. Due to the complicated alternating stress and corrosive environment, stress corrosion cracking (SCC) is the common defect on drilling riser in service. A novelchain alternating current field measurement (ACFM) probe array is proposed to detect surface cracks on drilling riser. The finite element method (FEM) is presented for analyzing the characteristic signal of surface crack. The space between the U-shaped excitation yoke and detecting sensor is determined by simulation. Based on the results of simulation, the chain ACFM probe with giant magneto resistance (GMR) sensor array system is set up and the drilling riser surface crack detection experiment is carried out. The results show that the maximum spacing of U-shaped excitation yoke and sensor array is 80 mm and 10 mm respectively. Furthermore, the chain ACFM probe with GMR sensor array system can detect and locate the surface cracks on drilling riser rapidly and quantitatively with a single pass scanning.