Development Of Magnetic Flux Leakage Internal Testing System For The Heating Furnace Tube Of The Convection Chamber

To ensure the safe of furnace tube is of great significance to the safe operation of heating furnace which is one of the key equipments in petrochemical plants. Corrosion puncture is one of the main forms of furnace tube failure. However, as plenty of tubes which are encapsulated inside the furnace wall are welded as a body, there is nearly no effective testing methods for heating furnace tube at present. Based on this situation, this paper applies magnetic flux leakage(MFL) internal testing technology to the furnace tube.Firstly, on the basis of analyzing the testing condition of furnace tube, size calculation model is established considering the character of passing through 180° elbow to guide the design of the detection probe and the parameters of the magnetizer are selected with numerical simulation method by establishing MFL testing finite element model. Based on the above analysis, the process route of combination of rough testing and fine testing for furnace tube using MFL internal testing technology has been developed.To achieve the testing process, internal detection MFL system scheme has been put forward.Secondly, two kinds of MFL testing probe have been developed to match the detecting process. Both probes provide testing only for straight heating furnace tube. One testing probe which can pass through the 180° elbow of the furnace tube can scan the furnace tube of whole section of heating furnace convection chamber in the procedure of rough testing, and it has a relatively low sensitivity. In order to drive the testing probe which can pass through the 180° elbow of the furnace tube, a seal driving device has been developed.The other testing probe which is unable to pass through the 180° elbow of the furnace tube has a high sensitivity, and it is used in the procedure of fine testing. In order to pass the obstacles such as pipe welds,Magnetic force analytical model in eccentric cases has been established to guide the design of floating support unit of the testing probe which is unable to pass through the 180° elbow of the furnace tube.Then the data processing device, which includes the MFL data collection and SD card data storage device based on FPGA and MFL testing software platform, has been developed. The data collection and SD card data storage device collect the MFL datas and store these datas into the SD card to facilitate subsequent data processing. The MFL testing software platform can do some processing for MFL data stored in SD card sector, and has the function of WIFI communication.The software platform has real-time processing capability for MFL data to meet the demand of MFL detection process.Finally the performance of the system has been tested. Results show that the testing probe which can pass through the 180° elbow of the furnace tube is able to detect Φ6mm cylindrical through-hole artificial defect in the light tube and finned tube, and it does pass through the 180 °elbow through the verification of experiment.The testing probe which is unable to pass through the 180° elbow of the furnace tube can detect Φ1.6mm cylindrical through-hole artificial defect in the light tube, and can detect Φ3.2mm cylindrical through-hole artificial defect in finned tube. And the testing probe has the ability of across inner pipe weld.