As previously highlighted, the difficulties encountered during AUT inspection of welds on CRA
weld overlay clad pipes result from the internal CRA layer, which induces a wavy interface
between the carbon steel and clad, and an anis
Figure 1. Due to the phenomena observed above in relation to welded clad, the standard AUT
inspection techniques using the “full skip” path
inspection of CRA weld overlay clad pipes
A
Figure 1: A) Macrograph of weld overlay clad interface with carbon steel
flat, but rather erratically wavy; B) Columnar dendrites oriented in the through
direction of the weld overlay clad.
Because skipping is not possible on t
the first ultrasonic leg.
The initial rational for inspecting girth welds on CRA
weld was to inspect several zones of the weld using a series of ul
different angles. One problem with this technique is that high angle longitudinal beams (over
70°) are very difficult to control, calibrate, and analyze, which gives rise to a blind zone in the
upper part of the weld.
Technical Innovations
To cover this blind zone, a special wedge was developed that enables the probe to ride the weld
bead, as shown on Figure 2B. This new wedge fits the AUT standard inspection head.
Weld Overlay Clad
anisotropic coarse-grained microstructure, as shown on
. n (ASTM, 1998) are inefficient for girth weld
pipes. (Institut de Soudure, 2009)