In this article from the January 2015 World Pipelines edition, Andre Lamarre, Business Development Manager - Power Generation and Pipeline Markets at Olympus NDT, writes about trusted UT inspection methods and new technique developments used to contribute to pipeline integrity. More on Olympus ultrasonic flaw detectors: http://bit.ly/1zy3QUu Contact us: http://bit.ly/1rDmq94 Sign up for our newsletter: http://bit.ly/1j5FOTy

1. a review of new
techniques
UT:
F
or years, conventional ultrasonic testing (UT) was
the standard ultrasonic technique used to verify the
integrity of pipelines.
More recently, the development of more
advanced ultrasonic techniques have extensively improved
the efficiency of ultrasonic inspection. Phased array, time-
of-flight diffraction (TOFD), automated UT, and ultrasonic
guided waves are now the most popular advanced
ultrasonic techniques.
These advanced techniques have shown to be very
efficient in improving the integrity of pipelines, particularly
when used at specific stages in the lifecycle. They are used
during the fabrication of pipes, the construction of the
pipeline, and also during pipeline maintenance.
André Lamarre,
Olympus Scientific
Solutions
Americas, USA,
reviews popular
advanced ultrasonic
techniques used
to contribute to
pipeline integrity.
Figure 1. Operator using Olympus
UT flaw detector: EPOCH 600.
73

2. Advanced ultrasonic techniques
Conventional ultrasonic testing usually consists of a UT
flaw detector connected to an ultrasonic probe, which is
manipulated by a skilled operator. The operator interprets
an A-scan signal that represents the echo from reflectors
in the part. Conventional UT permits detection and
characterisation of flaws, but it is known to be slow and
highly operator dependent. It is also limited in that there is
no possibility to archive the data.
Phased array technology
Phased array technology is based on the capacity to
electronically modify ultrasonic beams generated by probes
that contain multiple small elements. When these elements
are excited using different time delays (focal laws), the
beam is steered at different angles and focused at different
depths. If a long probe is used, the beam can also be
multiplexed along the length of the probe, which simulates
a mechanical movement.
Phased array instruments have the capability to control
the probe and the results are displayed in a comprehensive
manner using images such as S-scan, B-scan and A-scan
plots. Phased array instruments are available as portable,
stand-alone instruments or PC-based instruments, each
offering different electronic capabilities.
Phased array technology increases the inspected volume
coverage and the flaw detection capability through its
multi-angled beam control capacity and comprehensive
imaging.
Time-of-flight diffraction
Time-of-flight diffraction (TOFD) is an ultrasonic technique
that relies on the property of defects, such as cracks, to
diffract energy when the tip is impinged by an ultrasonic
beam. Two ultrasonic transducers, one emitter and one
receiver work in tandem to inspect the volume of a weld.
When a crack is present in the weld, its tips diffract waves
back to the receiver and, using simple trigonometry,
the depth of the crack is defined. The use of the B-scan
facilitates the interpretation of the signal and increases the
probability of flaw detection.
Automated ultrasonic testing
Automated ultrasonic testing (AUT) uses powered scanners
to move and record the position of ultrasonic probes.
Different types of scanners can be adapted to perform
applications such as girth weld inspection, heat exchanger
inspection, etc. Manually driven scanners can be used
for semi-automated ultrasonic testing at a reduced cost.
Different inspection techniques, including conventional UT,
phased array and TOFD, can be used for AUT. When used in
combination they can improve the AUT speed, speed up the
process of inspection, increase the repeatability and reduce
the uncertainties induced by human operation. AUT can be
used onsite to inspect a girth weld, or in a factory to verify
the integrity of manufactured parts, such as pipes. When
integrated into the production process, AUT is referred to
an ultrasonic system.
Guided wave technology
Guided wave technology is used to locate potential
degradation such as internal or external corrosion and
metal loss in pipe. While conventional UT provides
localised inspection underneath or in the vicinity of the
sensor location, ultrasonic guided waves are able to screen
the entire pipe wall, over tens of metres, from a single
inspection position. The inspection can be done without
removing insulation from the pipe.
Advanced ultrasonics for pipe fabrication
The fabrication of pipes used for pipelines is regimented by
international standards (including the API 5L specification
and DNV standards), which define the level of integrity
required for pipes for specific applications. Since pipelines
are subjected to constant pressure and a failure could
result in catastrophe, a high level of quality is required.
Advanced ultrasonic systems allow the manufacturer to
Figure 3. Time-of-flight-diffraction principle of operation.
Figure 2. Olympus ultrasonic portable phased-array
instruments: OmniScan MX2 (left); OmniScan SX (right).
74 World Pipelines / DECEMBER 2014

3. meet these strict standards while maintaining a high rate of
productivity.
For example, industrial systems using phased-array
techniques are used to perform full-body inspection of
seamless and welded pipes. Fully automated and composed
of a series of phased array probes, industrial systems can
inspect carbon steel and high-alloyed steel pipes. Linear
flaws as well as volumetric defects can be detected. Wall
thickness variation and measurement of eccentricity are
performed simultaneously.
In such industrial environments, robust and powerful
electronics are required. Also, the use of water wedges
enables immersion of the pipe to ensure proper coupling of
the phased array probes.
Advanced ultrasonic testing during pipeline
construction
The quality of the welds between two sections of pipe is
critical to ensuring the integrity of a pipeline. Automated
ultrasonic testing that combines phased array and TOFD
permits a reliable inspection of the girth welds and provides
multiple advantages over radiography.
To be able to withstand harsh environments, such as
Middle-Eastern deserts and Siberian steppes, the automated
system has to be designed and packaged to resist over-
heating, rain, snow, sand, dust, etc.
This automated ultrasonic in situ system consists of
a pair of phased array probes, which generate multiple
beams to cover specific zones of the weld and a pair of
TOFD probes for volumetric inspection, mounted on a fully
automated scanner. The weld is inspected in its entirety
in only one pass, and the results are immediately shown
on-screen. Inspectors benefit from comprehensive strip
chart imaging to provide quick assessment of the quality of
the weld.
A major advantage that AUT has over radiography is its
capability to measure the height and depth of an indication.
When the height and depth of the indication is known,
the critical length of a flaw for the engineering critical
assessment (ECA) can be relaxed, resulting in less need for
weld repair. This has been shown to generate important
savings for pipeline contractors. In addition, AUT does not
require the use of chemicals nor proximity to radiation. AUT
inspection is also faster than radiography.
Ultrasonic guided wave testing during
pipeline maintenance
Guided wave technology is used to screen in-service pipes
and pipelines over long distances in order to localise areas
of concern.
Typically, a collar with low frequency (10 - 100 kHz)
probes is installed around a pipe. Excited by a portable
electronic unit, these transmit ultrasonic guided waves
inside the pipe wall. While travelling in the pipe, any change
of acoustic impedance due to wall reduction, corrosion, or
geometry will reflect energy back to the transducers. The
results are displayed using comprehensive imaging, such as
F-scan, C-scan, and A-scan plots, which provides the means
to identifying and localising areas of concerns.
Figure 4. Ultrasonic guided waves beam propagation principle.
Figure 6. Olympus PipeWizard in operation.
Figure 5. Zoom on the water wedges assemble of the Olympus
full-body inspection system.
Figure 7. Olympus guided wave system: UltraWave LRT.
DECEMBER 2014 / World Pipelines 75

4. This technique helps to reduce operating costs when
inspecting pipes with limited access. It is recognised as a
reliable screening method. In-depth evaluation of the area
of concern is then carried out using other techniques such
as ultrasonic phased array.
Phased array ultrasonic testing during
pipeline maintenance
To maintain the integrity of a pipeline during its lifecycle,
a maintenance programme is put in place to monitor
degradation. Corrosion is considered as the main source of
pipeline deterioration.
Corrosion evaluation of a pipeline is performed in the
ditch by a crew of operators. For the sake of practicality,
portable battery-operated phased array instruments are
used. Using a long phased array probe mounted on a water
wedge, large areas can be inspected very quickly with an
automated or semi-automated scanner. Mapping of the
inspected area is displayed on the instrument, showing the
remaining wall values in a colour-coded image known as
C-scan.
Conclusion
Advanced ultrasonic techniques contribute significantly to
the integrity of pipelines. When used during the fabrication
of pipe, and the construction or maintenance of pipelines,
these techniques optimise the accuracy, speed and
reliability of ultrasonic inspection.
The accurate and comprehensive images used by phased
array, TOFD, automated UT, and guided wave technology
offer considerable advantages for the interpretation of the
inspection results.
In addition, these techniques have shown to be reliable
replacements for radiography in ensuring pipeline integrity.
Note: this article is based on a paper presented at Pipeline Technology Conference
2014, Berlin, Germany.
Figure 8. Olympus OmniScan MX2 ultrasonic phased-array unit
with ChainScanner and Hydroform in operation for corrosion
inspection.