A Study on the Electromagnetic Inspection of Large-Diameter Ropes

为评估大直径固定钢丝绳的劣化程度，研制了两套电磁检测仪系统。这些仪器磁化绳索的原理不同。用于测试直径达60 mm的绳索的电测仪有一个带有一对年轮磁极的电磁仪，以使绳索纵向磁化到饱和状态。另一种用于直径达95 mm的钢丝绳，利用两个与钢丝绳同轴的螺线管线圈，更有效地沿钢丝绳感应磁场，这些仪器中的探测器单元具有双环形霍尔效应元件阵列，用于检测钢丝绳缺陷产生的空间泄漏磁通的径向分量。将每一环向阵列划分为6个圆周段，提取各段的输出用于定位钢丝绳横截面上的缺陷。利用该仪器对某悬空屋面PWS钢丝绳进行了检测，并对检测记录进行了检验。研究结果表明，该仪器对大直径固定钢丝绳的检测是有用和有效的。通过引入新的解释方法，从检测记录中用横截面损失来估算钢丝绳的劣化，而电磁探伤估计的横截面损失与钢丝绳的实际面积损失相吻合。

In order to evaluate the degree of deterioration of large-diameter stationary wire ropes, such as cables in suspension roofings and suspension bridges, two systems of electromagnetic inspection instruments have been developed and constructed. These instruments are different in the principle to magnetize the rope. The one which is intended for testing the ropes up to 60 mm in diameter has an electromanget with a couple of annylar magnetic poles to magnetize the rope longitudinally to the saturation state. The other one for the ropes up to 95 mm in diameter utilizes two solenoidal coils coaxial with the rope, which induce magnetic field more effectively along the rope to be inspected.The detector unit in these instruments has twin annylar arrays of Hall effect elements to sense the radial component of spatial leakage flux derived from the defect in the rope. Each annylar array is divided into six circumferential segments, and the individual output of the segments can be extracted for locating the defect in the cross section of the rope.The inspection of PWS cables in a suspension roofing was carried out with the instruments, and the inspection records obtained were examined.As the result of this research these instruments have been recognized to be useful and effective for inspecting large-diameter stationary ropes. The deterioration of the rope under question has been estimated in terms of loss in the cross sectional area from the inspection records by introducing the new method of interpretation, and the cross sectional area loss estimated by electromagnetic inspection corresponded closely to the real area loss in the rope.