Patent ID: 7762137

Claim:
A method for checking a weld between a first metal pipeline and a second metal pipeline, in particular an austenitic weld, characterized in that the method comprises at least the following method steps: a. a first ultrasonic beam is transmitted to an interface between the weld and the first pipeline situated on a first side of the weld; b. a reflection of the first ultrasonic beam on the interface situated on the first side of the weld is received and a first received signal corresponding thereto is generated; c. a second ultrasonic beam different from the first ultrasonic beam is transmitted to the interface situated on the first side of the weld; d. a reflection of the second ultrasonic beam on the interface situated on the first side of the weld is received and a second received signal corresponding thereto is generated; e. the first received signal and the second received signal are processed in combination for checking the weld; wherein in step a. the first ultrasonic beam is directed such that the direction in which the first ultrasonic beam is incident on the interface between the weld and the first pipeline deviates from the normal to a surface of the interface between the weld and the first pipeline at the point where the first ultrasonic beam is incident on the interface; in step b. the reflection of the first ultrasonic beam is measured that comes from a direction that deviates from the direction in which the first ultrasonic beam would reflect on the interface according to the rule that the angle of incidence is equal to the angle of reflection, so that the first ultrasonic received signal represents a diffraction, if any, of the first ultrasonic beam on the interface between the weld and the first pipeline; in step c. the second ultrasonic beam is directed such that the direction in which the second ultrasonic beam is incident on the interface between the weld and the first pipeline at least substantially does not deviate from the normal to a surface of the interface between the weld and the first pipeline at the point where the second ultrasonic beam is incident on the interface; in step d. a reflection of the second ultrasonic beam is measured coming from a direction which, at least substantially, coincides with the direction in which the second ultrasonic beam would reflect on a surface of the interface at the point where the second beam is incident on the interface; and wherein the first ultrasonic beam and the second ultrasonic beam are directed to a same area of the interface between the first pipeline and the weld.