Method for testing pipeline welds using ultrasonic phased arrays

A method for the non-destructive inspection of a weld between a first metal pipe and a second metal pipe, wherein the method comprises the following steps:

• forming an austenitic weld between two pipe-sections during a method of laying a pipeline,
• providing a plurality of ultrasonic transducers, able to transmit and detect ultrasonic radiation, comprising two or more ultrasonic transducers arranged as a phased array,
• emitting from the phased array a first beam of ultrasonic radiation, focussed to be incident on a first region of the weld,
• emitting from one or more of the plurality of ultrasonic transducers a second beam of ultrasonic radiation incident on a second region of the weld,
• emitting from the phased array system a third beam of ultrasonic radiation, focussed to be incident on a third region of the weld,
• at least two of the first, second and third beams being emitted substantially contemporaneously,
• detecting with one or more of the plurality of ultrasonic transducers radiation from the first, second and third regions resulting from the incidence of the first, second and third beams,
• extracting information from the detected radiation, and
• using such information to provide an indication from which the likelihood of a defect in the weld may be discerned,
• wherein at least one of the first, second and third beams is a mode converted longitudinal wave resulting from a reflection of a transverse wave on the inner wall of one of the pipes.