Study On The Stainless Steel Tube Oxide-scale Detection Technology In The Boiler

In recent years, people usually use stainless steel whose high temperature and corrosionresistance are better to produce pipes of superheater and reheater in the boiler of thelarge-scale thermal power unit. But after a long time running, adverse environmentalconditions would cause the oxidation of pipe walls, forming oxide-scale in the internal surfaceof the wall. When environmental conditions change dramatically, the oxide-scale is easyspalling. and the spalling oxide-scale would accumulate in the elbow of the superheater andreheater pipe, and block the pipe seriously, resulting in the heating pipes burst.In this paper, for the condition of oxide-scale blocking tubes, a non-destructive testingmethod is studied, and the detection apparatus is made for the problem of detectingoxide-scale efficiently in the tubes.Firstly, with the problem of oxide spalling in boilers appearing around the world, researchand development status about oxide spalling control technology are analyzed, and magneticnondestructive testing method was proposed to measure the thickness of the oxide.Secondly, on the basis of introducing the basic structure of boiler briefly, the reasons offormatting and spalling of oxide-scale are analyzed, and the harm for the boiler. Point out thatthe spalling oxide-scale would easily accumulate at the elbow place of the pipes insuperheater and reheater. And many aspects are analized for preventing the harms producedby the spalling oxide-scale in boiler.Thirdly, ANSYS simulation model is established for the stainless steel tube-oxidedetection. Then the simulation of the magnetic field distribution is carried out. Based on theresults of simulation, the process of detecting the oxide-scale is analized using the magneticmethod. The curve is obtained between oxide thickness and the change of BY. According tothe simulation results, magnetic measurement sensor was designed.Fourthly, the apparatus is made for detecting oxide-scale in the stainless steel tube, and is described completely, such as power module, charge module, data acquisition module,display and storage module. The main ideas of Software programming are introduced briefly.Fifthly, the pipeline oxide-scale detection test is carried out using the platform andsensors. And the curves are obtained between the voltage of detection appratus and thethickness and volume numbers of oxide. Finally, sensor calibration solutions are proposed.