Research on ultrasonic phased array system for automatic defect detection of pipeline girth welds

Traditional ultrasonic testing system has fixed focus, which is burdensome for layer inspection of welds because different layer needs different steering angle and focus ultrasonic beam to inspect. Ultrasonic phased array testing instrument can electronically steer and focus the transmission ultrasonic beams. This ability makes it very advantageous in automatic nondestructive testing in industrial field. In this article, an automatic flaw detection method on pipeline girth welds is researched and the ultrasonic phased array testing instrument is developed. Firstly, flaw detection principle of ultrasonic phased array system on girth welds and the mathematical model of the linear phased array transducer are exposed, which are basis of delay control in hardware design. Then, multi-channel acquisition system, connected to the linear ultrasonic phased array transducer is described. The hardware of single acoustic channel and the signal processing are introduced. Precise delay control of each element in the transducer is realized. Experiment results validate the good performances of ultrasonic transmission and echo composition capabilities of the system. It can be extended to automatic flaw inspection in other relative industrial fields.