基于磁场强度的锅炉管内氧化皮测量精度实验

Experimental Investigation into Measurement Accuracy of Oxide Scale in Boiler Tube Based on Magnetic Field Intensity

因高温高压蒸汽作用,超临界电站锅炉受热管内易形成氧化皮,氧化皮的剥落会堵塞管道,发生超温爆管。提前探测氧化皮的状况并采取相应措施对预防爆管十分必要.文中在比较几种氧化皮探测方法的基础上,应用磁场检测法,通过实验研究了探头与管道的间隙、探头与管径的偏角、永磁体相对氧化皮的位置等因素对磁场探测结果的影响,发现间隙小于1.07mm、角度偏离中法线25.9°内、相对位置在26.4°内时,测量误差可控制在5%的工程误差以下,且探头与管道的间隙是影响磁场测量结果的主要因素;随着偏角与相对位置的增大,测得的磁场强度呈指数增长.

It is easy to form oxide scale on the surface of the stainless steel used in supercritical utility boiler tube under the action of high-temperature and high-pressure steam. As the flake of the scale may jam the boiler tube and lead to overtemperature tube burst, it is necessary to detect the scale and take some measures in advance. In this paper, several detection methods of oxide scale were compared and the magnetic-field measurement accuracy was experimentally investigated under the conditions of different clearances between the probe and the tube, different deflection angles between the probe and the tube diameter and different relative positions of the permanent magnet and the scale. It is indicated that （ 1 ） when the clearance, the deflection angle and the relative position are respectively less than 1.07mm, within 25.9° and less than 26.4°, the measurement error can be controlled within 5%; （2） the clearance between the probe and the tube is the main factor that affects the measurement; and （3） the measured magnetic field intensity exponentially increases with the deflection angle and the relative position.