The Testing On Weld T Type Of Boiler Tube In Power Station By Phased Array

The boiler tube block fillet weld mainly used in power plant boilers and otherimportant equipment,inherit the welding stress, the structure stress, shear force and heatstress generated by high temperature fluctuations,produce the defects which can lead tothe boiler critical leakage.Conventional ultrasonic testing inspection is difficult todistinguish interference wave and defects wave,signal recognition of the defect isdifficult.The curvature of the reflection point result in difficult to location thedefect,lead to part of the weld no detection and other problems.The main feature ofphased array Ultrasonic technology is computercontrolled excitation（amplitude anddelay）of individual elements in a multielement probe.The excitation of piezocompositeelements can generate an ultrasonic focused beam with possibility of modifying thebeam parameters such as angle,focal distance,and focal spot size through software.Asingle crystal probe,with limited movement and beam angle,has a high probability todetect the flaw and judge the position information and type of the defect. During a scanwith mechmechanical device,data is collected based on encode position. The data isdisplayed in different views for interpretation. Typically,phased array use multiplestacked A-scans（also called “B-scans”）with different angles,time of flight and timedelays on each small piezocomposite crystal of the phased array probe. The real-timeinformation from the total number of A-scans,which are fired for a specific probeposition,are displayed in aSectorial scan or S-can,or in a electronic B-scan.Both S-scansand electronic scans provide a global image and quick information about the componentand possible discontinuities detected in the Ultrasonic range at all angles and position.So these characteristics can ensure the safety of boiler effective operation. Ultrasonicphased array inspection on the boiler tube block fillet weld is the current developmentdirection.Phased array on the T type of the boiler tube block fillet weld ultrasonic phasedarray inspection,the root and the main pipe defect detection sensitivity are low,out andinner diameter of the tube scatter sound energy seriously,the second wave of ultrasonicsignal deformation serious,more difficult to judg defects and other problems.This thesisobject is T type of the boiler tube block fillet weld,according to analysis theone-dimensional ultrasonic phased array`s acoustic characteristics and the T type of the boiler tube block fillet geometry of weld, based on CIVA9.0software simulationresults,according to sound energy distribution simulation results,established a fewprinciples such as root area detected by direct wave and middle and upper area detectedby half skip wave,and as far as possible to avoid the use of large Angle such as70°forinspection, the root、central、groove place of the main pipe and secondary pipe aredesigned respectively inspection scheme.These scheme mainly includes aboutdetermine the optimal inspection face, the choice of the probes and the wedge, scanningmode, beam angles and the distance of the probe and the welding seam centerparameters etc.Analysis "blind area" and "dead zone" of the detection,the method offlaw length and height measurement,the non-relevant indication and the false indication.Through the actual workpieceof the phased array inspection and conventionalultrasonic inspection,phased array inspection use the semi-automatic way for detectingfour division,and adding new scanning mode that focuse in the root area,the resultsprove that can effectively increase the root detection rate. At last, by cutting ofspecimens, prove phased array inspection result is correct and more accurate and moreabundant information than conventional ultrasonic testing result. The experimentalresults prove that the simulation model use in this paper is correct, The design of theinspection parameters can solve the existing problems of ultrasonic phased arrayinspection on the T type of the boiler tube block fillet weld,and made the policy andtechnology of phased array inspection on the boiler tube block fillet weld,conclusioncan be used to guide similar components of inspection process parametersdesign,possess the high practical value.