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AUT Inspection of CRA-Clad
Pipeline Girth Welds

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In the field,
during pipeline construction,

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automated ultrasonic testing is used

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to inspect welds with high accuracy.

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The Olympus PipeWIZARD
is a fully automated system

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that performs phased array inspection

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on the girth welds of pipe lines.

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Increased oil and gas extraction

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necessitates the transport of more
corrosive fluids in pipelines.

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In order to minimize the damage
from corrosive elements,

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pipes are constructed with
corrosion resistant alloys (CRA).

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To limit manufacturing costs,

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pipes are not entirely
made of the CRA.

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Only a layer of the material
with enhanced properties

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is bonded to the inside
diameter of the pipe.

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CRA is also used in the welds

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that join the sections of pipes
to build the pipeline.

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When inspecting a typical
carbon steel weld

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with Phased Array pulse-echo

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or pitch-catch configurations,

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the ultrasonic beam skips
at the bottom of the part

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to reach the weld bevel and cap.

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When a material of different type

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is joined to the inside
section of the pipe,

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properties like velocity
and grain structure

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defer from the parent material.

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The skip at the bottom,

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like with standard
inspection configurations,

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becomes impossible
because the line of CRA

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will create mode conversions,

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making data analysis
extremely difficult.

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The opposite side of
the weld fusion line

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can be reached directly,
without skipping.

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But another challenge
is that CRA materials

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are generally anisotropic
and more attenuative

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resulting in a decreased
signal-to-noise ratio

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and difficult penetration
when inspecting

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the dissimilar weld with shear waves.

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In addition, the weld upper section

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with potential surface
and sub-surface indications

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remains uncovered.

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To meet these challenges,

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Olympus recommends the new
Dual Linear Array (DLA) probes

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that offer multiple advantages
for the inspection

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of dissimilar girth welds
in CRA-clad pipes.

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The 60 elements probe is
supplied in quad configuration

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split in four groups of 15 elements,

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each group acting as
transmitters or receivers.

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Different frequencies are available.

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The Dual Linear arrays probes combine

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the benefits of phased array S-scans

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with low frequency transmit
receive linear (TRL) inspection.

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The probe pulses longitudinal waves

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for better penetration
in an attenuative material.

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The wedge dual configuration

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allows the transmitter and receiver

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to be acoustically insulated,

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eliminating the need for
wedge damping material

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and large standoff required

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for longitudinal pulse echo
inspection configuration.

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The dedicated SA27 wedges

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are designed to be attached
to the PipeWIZARD scanner.

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Their small footprint
enables positioning

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the probe closer to the weld,

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resulting in shorter UT path

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for improved signal-to-noise ratio.

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The wedges are designed
based on pipe curvature

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and desired focus point.

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Depending on the environment

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and type of fluids inside the pipe,

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various combinations of materials
and thicknesses

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can be used for CRA.

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The optimum inspection technique

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will always have to be
defined for each project.

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All dissimilar welds

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and CRA-clad pipe configurations

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will bring their own challenges.

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Olympus provides tools to
support these advanced inspections.

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For more information on Olympus

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Automated Ultrasonic
testing solutions,

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contact your local representative

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or visit us online at
www.olympus-ims.com.