Phased Array Ultrasonic Testing Technology Of Heat Exchanger Tube-Tubesheet Welds

Mechanical scanning in both circumferential and axial is a popular scanning method on conventional ultrasonic testing system, which is applied on tube-tubesheet welds of heat exchanger. The weakness of this method are the difficulties on hard device design and processing, long cycle of detection, high cost, low efficiency of detection. Radiological testing can not detect the area type flaw of fillet welds, and the magnetic particle testing and penetrate testing can not detect internal flaws of fillet welds. In view of this situation, this paper presents the phased array ultrasonic testing technology. First, phased array parameters are analysised and optimizaied theoretically in order to achieve axial electronic linear scanning. Then, design the mechanical scanning device to control phased array probe to complete the circumferential scanning. At last, test the fillet welds flaw samples of porosity and incomplete fusion by ultrasonic detection system.First, this paper introduces the conventional testing method for tube-tubesheet welds of heat exchanger and presents the research contents of this paper in general.Then mainly presents phased array ultrasonic testing technology in theory and the acoustic mathematical model of phased array is established. In addition, the criteria of phased array probe design is the sharper main lobe beam, the lower side lobes, and no grating lobe. The simulation on the acoustic field is completed to determine phased array’s parameters with CIVA software. These parameters include array elements, inter element spacing, array element width, deflection angle, ultrasonic frequency and so on. According to the structure of heat exchange tube and fillet welds position, the mechanical scanning device is designed by UniGraphics software in order to complete the circumferential scanning. The device solves a lot of problem, such as the phased array probe water immersion, fixed, sealing, circumferential uniform rotation, etc. At last, the tests on samples with the porosity and incomplete fusion flaws is performed by ultrasonic testing system. Experiments indicate that phased array testing technology can effectively detect the porosity flaw and the incomplete fusion flaws thickness more than1mm in the welds.