Applications of Encoded Phased Arrays
Michael Moles, Olympus NDT
48 Woerd Avenue, Waltham, MA, USA 02453
Tel: +14168314428
E-mail: [email protected]
Introduction
Initially the paper will describe phased arrays and how
they work with illustrations of their advantages for encoded
linear scanning. This will follow with specific examples
of complete inspection systems, e.g. HydroFORM for
measuring corrosion, Cobra for smaller diameter piping
welds, WeldROVER for inspecting large diameter pipes,
PipeWIZARD for inspecting pipeline girth welds, and in-line
inspection systems for pipe mills. Portable developments
typically include the OmniScan MX2, though the Focus
LT® is transportable.
How Phased Arrays Work
Phased arrays have been well documented recently (1-3),
so in depth details on their operation are not required.
Briefly, an array consists of a series of electrically-isolated
elements, each with its own connector, time delay circuits
and analog-to-digital card. The arrays themselves can be
linear (the most common type), 2D matrix, or circular or
“specials”. The elements in the arrays are typically pulsed
in groups, with “phasing”. Phasing involves adjusting
the pulsing of the elements to provide constructive and
destructive interference, or “phasing”.
In practice, there are two methods of using industrial phased
arrays: manual (4) and encoded (5). The differences are
laid out in (6), but essentially encoded linear scanning (or
automated) phased arrays permit full data collection – with
recorded location. Consequently, the data can be audited,
analyzed and reconstructed.
What Phased Arrays Can Do
Phasing allows focusing, sweeping and steering of the
beams, as shown in Figure 1.
Figure 1: Illustrations of E-scans, S-scans and DDF
• Speed
• Flexibility
• Auditable
• Better defect detection
• Defect sizing capability
Realistically, the decreased overall operating costs and
advanced imaging are the prime reasons that phased
arrays have become so commercially successful in a short
time. In addition, phased arrays do not change the physics
of ultrasound; they are primarily a method of generating
and receiving signals.
Not surprisingly, there are disadvantages of phased arrays
as well. All the usual ultrasonic issues arise (coupling, worn
wedges, array choice, dead zones etc). In addition, less
obvious issues also arise: grating lobes, optimal angles for
S-scans, calibrating over range, and in particular – training
(7).
Typical Applications of Phased Arrays
Given the huge range of possible applications for
phased arrays, it is perhaps not surprising that there is
a wide variety of applications. In practice, maybe 2/3 of
the applications are for weld inspections, with various
aerospace applications following behind. This paper will
describe several weld (and other) inspections of varying
degrees of complexity, and all of them use linear (1D)
arrays.
1. Corrosion Mapping. Olympus has developed the
HydroFORM, a linear corrosion mapping array using a
water path and holder (8). This array is normally semiautomated, i.e. the scanner is encoded but not motorized.
Figure 2 shows a photograph of the HydroFORM scanner.
The arrays need to be tailored to the application, e.g.
plate dimensions, materials etc. They also need to be
code-compliant, if a code is specified. In general, using
phased arrays with encoded linear scanning offers major
advantages over competing technologies like manual
ultrasonics or radiography, such as:
Figure 2: Photograph of HydroFORM corrosion mapping
scanner.
HydroFORM is typically run from an OmniScan MX2
instrument, to provide results like those shown in Figure 3.
Keywords: p
hased array ultrasonics, encoded linear scan, corrosion measurement, weld inspection, in-line systems
www.cinde.ca
CINDE Journal t Vol.33 t No.5 t September/October 2012
9
F
E
A
T
U
R
E
A
R
T
I
C
L
E
philosophy of providing solutions, not just equipment. The
scanner has been designed as an add-on to the OmniScan
MX2, and operates exactly as any phased array-TOFD
combination would on the instrument. Naturally, all the
usual requirements for phased array (and TOFD) apply:
training, calibration, data collection and analysis.
F
E
A
T
U
R
E
A
R
T
I
C
L
E
Figure 3: Scan image of corroded part using multiple
displays (MX display).
In this particular instance, high corrosion areas can be
easily detected, on both the B-scan and the C-scan.
2. Small Diameter Pipe Inspections. The Cobra scanner
for small diameter pipes has been developed with low
clearance and focusing to minimize beam spread. This is
also a semi-automated system, since it is easier to push
probes around a small pipe with limited access than to
motorize them. (This scanning option is included in ASME
Mandatory Appendix V, as it is also encoded). This is
essentially a bracelet scanner, and fits mechanically onto
a pipe for both ferritic and austenitic steels. Figure 4 shows
a photograph of the Cobra scanner.
Figure 5: WeldROVER scanner.
The WeldROVER is very straightforward to use, and
connects directly onto the OmniScan. It is controlled
by a handheld device with only a couple of buttons.
WeldROVER can scan pipes from 100 mm and up to
flat plate. Unlike Cobra, WeldROVER can hold a pair of
phased arrays, plus a TOFD pair for complete scanning.
It does not have a drive controller as such, but is directed
by the operator using a rod at the back along a lasercontrolled path along the weld.
Figure 4: Photo of Cobra scanner
This scanner works on pipe diameters from 20 mm to
110 mm. It has been designed for boiler tubes and other
applications where pipes are in close proximity or for
applications where radiation safety, speed or coverage
are critical. Again, the initial Cobra used 7.5 MHz focused
arrays, but Olympus has received requests for frequencies
down to 2.25 MHz and up to 10, for longitudinal waves and
even for TOFD applications.
3. Large Diameter Pipes. Weld ROVER has been
developed (see Figure 5) for larger pipe diameters. The
WeldROVER is compact, versatile, and well designed for
code-compliant applications in keeping with the Olympus
10
CINDE Journal t Vol.33 t No.5 t September/October 2012
Figure 6: Screen shot of typical image from OmniScan.
4. Pipeline AUT. Pipeline automated ultrasonic testing was
originally developed in Alberta by NOVA and TransCanada
Pipelines, and uses a linear (i.e. a mechanical scan around
the weld axis) approach. As equipment has developed, it
has evolved from a few transducers to phased arrays,
with added TOFD and other techniques. Despite wellestablished codes (9, 10, 11), the requirements for AUT
equipment kept growing, e.g. seamless pipe, austenitics,
double-jointing, improved sizing accuracy for examples.
Not surprisingly with the demand for shipping oil and gas,
www.cinde.ca
pipelines are being constructed all over the world in a wide
variety of conditions (see Figure 7 for example).
Figure 9: Photo of
part of on-line ERWPA inspection
system.
Figure 7: Pipeline AUT being performed in a desert
(Courtesy of Absolute NDE)
Recently, Olympus came out with a new PipeWIZARD
V4, which is an advanced phased array unit with special
features (12). Specifically, PipeWIZARD V4 has software
updated to a recent version of TomoView, an improved
umbilical, changes in the driver box, TOFD pre-amp,
much faster data transfer, the computer itself, and updated
instrumentation. The new (downsized) PipeWIZARD V4
instrument box is shown in Figure 8.
These systems are driven from a QuickScan LT PA
(or multiple QuickScan units), which permits rapid and
repeatable scanning over the whole arc of the array
(see Figure 10). These systems also include automatic
calibration, end of tube inspection and other useful
features.
Figure 10: QuickScan
LT PA instrument,
designed for high
PRF.
Many Other Uses for Phased Arrays
Figure 8: Photos of old V2 instrument box at left, and new
V4 instrument box at right.
5. In-Line Inspection Systems (Pipe Mills). Olympus
has developed specific phased array systems for several
pipe mills, e.g. rotating in-line phased array systems, ERW
(Electrical Resistance Welds) on and off-line, and bar and
rotating bar – usually in conjunction with eddy current
arrays. These systems work well, but the market is volatile
(as it is for PipeWIZARD). These systems cost maybe $1-4
million each, and Olympus partners with systems builders
for the mechanics. Figure 9 shows an example of part of
an ERW-PA system.
www.cinde.ca
Early on in the development of phased arrays, Olympus
(then R/D Tech) wrote a paper on their applications (13).
These included:
• Butt weld inspections
• Austenitic weld inspections
• T-weld inspections of bridge structures
• Turbine root inspections
• HIC – Hydrogen Induced Cracking
• Flange corrosion under gasket
• Nozzle inspections
• Bridge bolt inspections
• Spindle/shaft inspections
• Thread inspections for the US Army
• Landing gear inspections
• Laser weld inspections
• Composites
Many of these applications have matured and become fully
commercial (e.g. butt welds, bolts, turbine roots, flanges,
CINDE Journal t Vol.33 t No.5 t September/October 2012
11
F
E
A
T
U
R
E
A
R
T
I
C
L
E
landing gear, composites), though some (e.g. nozzles) are
still being worked on. Some are predominately manual
(e.g. HIC and landing gear), though several of the
welding applications are, or could be, automated. Since
writing this early paper (13), there have been many more
applications – and many have come from customers, not
from manufacturers.
Summary
F
E
A
T
U
R
E
A
R
T
I
C
L
E
This article has been fun to prepare. Basically, phased
arrays are the “new boy” on the block, though they
still require training and experience. More and more
applications keep coming, and there are likely still more
to be discovered. The main advantages of phased arrays
are:
• Speed (i.e. cost-effectiveness)
• Imaging
• Flexibility for changes in set-up and procedures
• Data storage for auditing and review
• Reproducibility
Acknowledgements
This article was assembled from many sources, mostly
within Olympus NDT. These sources include FrancoisCome Beaupre, Chris Magruder, Christophe Imbert, Simon
Alain, Sebastien Rigault, Mark Carte and many others.
References
1. R
/D Tech, “Introduction to Phased Array Ultrasonic
Technology Applications – R/D Tech Guideline”,
published by R/D Tech (now Olympus NDT), August
2004, www.rd-tech.com, now www.olympus-ims.com/en
g
2. O
lympus NDT, “Advances in Phased Array Ultrasonic
Technology Applications”, published Q1, 2007.
3. Olympus NDT, “Phased Array Testing – Basic Theory
for Industrial Applications”, November 2010
4. ASME Section V Article 4 Mandatory Appendix IV,
“Phased Array Manual Raster Techniques using Linear
Arrays”, July 2010.
5. ASME Section V Article 4 Mandatory Appendix V,
“Phased Array E-Scan and S-scan Linear Scanning
Examination Techniques”, July 2010.
6. J. M. Davis and M. Moles, “Phased Arrays vs. Phased
Arrays - Beam Sweeping vs. Encoded Data Collection”,
Materials Evaluation Back to Basics, June 2007, page
539.
7. T. Armitt, “Phased Arrays Not The Answer To Every
Application”, 6th European Conference on NDT, Berlin,
2006, Paper No. 177.
8. M. Carte, K. Sinclair and J. Skidmore, “Corrosion
Mapping with Phased Array Ultrasonics”, 13th Middle
East Corrosion Conference, Bahrain, 2010.
9. M. Moles and E.A. Ginzel, “Phased Array for Small
Diameter, Thin-Walled Piping Inspections”, 5th Middle
East Conference on NDT, Bahrain, 2009.
10. ASTM E-1961, “Standard Practice for Mechanized
Ultrasonic Inspection of Girth Welds using Zonal
Discrimination with Focused Probes”, Updated 2011,
ASTM
11. DNV OS-F101, “Appendix E – Automated Ultrasonic
Girth Weld Testing”, October 2007.
12. API 1104, 19th Edition, “Welding of Pipelines and
Related Facilities”, API, September 1999.
13. J. Granillo and M. Moles, “Portable Phased Array
Applications”, Materials Evaluation, April 2005, p. 394.
h
CINDE Invites you to submit your papers:
Technical, Research or Articles & Pictures of Interest
Visit: www.cinde.ca/journal/submit.shtml
12
CINDE Journal t Vol.33 t No.5 t September/October 2012
www.cinde.ca