Ultrasonic Phased Array Procedures for Rapid
Inspection of Piping Welds
1014656
WARNING: Please read the
Export Control Agreement
on the back cover.
Effective December 6, 2006, this report has been made publicly available in accordance
with Section 734.3(b)(3) and published in accordance with Section 734.7 of the U.S. Export
Administration Regulations. As a result of this publication, this report is subject to only
copyright protection and does not require any license agreement from EPRI. This notice
supersedes the export control restrictions and any proprietary licensed material notices
embedded in the document prior to publication.
Ultrasonic Phased Array Procedures for
Rapid Inspection of Piping Welds
1014656
Technical Update, December 2006
EPRI Project Managers
D. MacDonald
M. Dennis
J. Landrum
G. Selby
ELECTRIC POWER RESEARCH INSTITUTE
3420 Hillview Avenue, Palo Alto, California 94304-1338 ▪ PO Box 10412, Palo Alto, California 94303-0813 ▪ USA
800.313.3774 ▪ 650.855.2121 ▪ askepri@epri.com ▪ www.epri.com
DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES
THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF
WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI).
NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY
PERSON ACTING ON BEHALF OF ANY OF THEM:
(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH
RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM
DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED
RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS
SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR
(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING
ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED
OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS
DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN
THIS DOCUMENT.
ORGANIZATION(S) THAT PREPARED THIS DOCUMENT
Electric Power Research Institute (EPRI)
This is an EPRI Technical Update report. A Technical Update report is intended as an informal report of
continuing research, a meeting, or a topical study. It is not a final EPRI technical report.
NOTE
For further information about EPRI, call the EPRI Customer Assistance Center at 800.313.3774 or
e-mail askepri@epri.com.
Electric Power Research Institute and EPRI are registered service marks of the Electric Power
Research Institute, Inc.
Copyright © 2006 Electric Power Research Institute, Inc. All rights reserved.
CITATIONS
This document was prepared by
Electric Power Research Institute (EPRI)
Nondestructive Evaluation (NDE) Center
1300 W.T. Harris Blvd.
Charlotte, NC 28262
Principal Investigators
D. MacDonald
M. Dennis
J. Landrum
G. Selby
This document describes research sponsored by EPRI.
This publication is a corporate document that should be cited in the literature in the following
manner:
Ultrasonic Phased Array Procedures for Rapid Inspection of Piping Welds, EPRI, Palo Alto, CA:
2006. 1014656
iii
ABSTRACT
In 2001, EPRI NDE Center personnel successfully completed an Appendix VIII qualification of
an automated phased array ultrasonic examination procedure for flaw detection and length sizing
in austenitic and ferritic piping welds. As demonstrated by the EPRI team, a phased array
approach to piping examinations offers improvements in speed, coverage, and reliability. These
improvements have the potential of lowering the costs and increasing the confidence in piping
examinations by reducing qualification costs, radiation exposure, need for re-scans, and repairs.
The automated phased array procedure was further enhanced in 2003, as the EPRI NDE Center
reduced this similar metal weld piping examination technique from three to one phased array
probe. This single phased array probe approach was successfully qualified through the
Performance Demonstrative Initiative in 2004. The qualified procedure and supporting
documents can be found in the appendices of this report.
v
CONTENTS
1 INTRODUCTION ....................................................................................................................1-1
2 QUALIFICATION OF AUTOMATED PHASED ARRAY UT FOR SIMILAR-METAL PIPING
WELDS ......................................................................................................................................2-1
Phased Array Probe.............................................................................................................2-1
Circumferential Flaws...........................................................................................................2-2
Axial Flaws ...........................................................................................................................2-5
EPRI NDE Center Appendix VIII Qualification .....................................................................2-7
Phased Array Procedure Commercialization .......................................................................2-9
3 SINGLE PHASED ARRAY PROBE FOR PIPING .................................................................3-1
Preliminary Activities ............................................................................................................3-1
Detection and Length Sizing Results ...................................................................................3-7
4 SUMMARY .............................................................................................................................4-1
5 REFERENCES .......................................................................................................................5-1
A PROCEDURE FOR AUTOMATED SINGLE PHASED-ARRAY PROBE ULTRASONIC
FLAW DETECTION AND LENGTH SIZING IN AUSTENITIC AND FERRITIC PIPING WELDS
(EPRI-SPA-1) ........................................................................................................................... A-1
List 1 - Material & Examination Thickness Ranges............................................................. A-4
List 2- Phased Array System Hardware List ....................................................................... A-6
List 3 Phased Array Transducer Essential Variables .......................................................... A-7
List 4 Phased Array Wedge Essential Parameters ............................................................. A-8
List 5 Phased Array Focal Laws.......................................................................................... A-9
List 6- Material Velocities .................................................................................................. A-19
List 7 Line Scan Examinations .......................................................................................... A-23
B APPENDIX ............................................................................................................................ B-1
C APPENDIX ............................................................................................................................ C-1
Introduction ......................................................................................................................... C-1
Experiments ........................................................................................................................ C-2
Conclusions......................................................................................................................... C-5
Recommendations .............................................................................................................. C-5
vii
LIST OF FIGURES
Figure 1-1 Probe Motion for Line Scan Technique ....................................................................1-1
Figure 2-1 Examination Volume (A-B-C-D) for Pipe Weld Inspection........................................2-1
Figure 2-2 Phased Array Probe Scan Pattern for Circumferential Flaws...................................2-2
Figure 2-3 Phased Array Probe Scan Pattern for Circumferential Flaws...................................2-3
Figure 2-4 Phased Array Probe Configuration for Circumferential Flaws ..................................2-3
Figure 2-5 Phased Array Imaging of Circumferential IGSCC ....................................................2-4
Figure 2-6 Phased Array Probe/Wedge Design for Axial Flaws (Counter-Clockwise Scan)......2-5
Figure 2-7 Phased Array Probe Counter-Clockwise Scan Pattern for Axial Flaws ....................2-6
Figure 2-8 Phased Array Probe Clockwise Scan Pattern for Axial Flaws ..................................2-6
Figure 2-9 Phased Array Image of Axial IGSCC........................................................................2-7
Figure 2-10 Phased Array Approach to Similar Metal Pipe Weld Examinations........................2-8
Figure 3-1 Phased Array Probe/Wedge for Circumferential and Axial Flaws ............................3-2
Figure 3-2 Austenitic Weld Sample Containing EDM Notches ..................................................3-3
Figure 3-3 Shear Wave Ultrasonic Image (Circumferential & Axial EDM Notches) ...................3-4
Figure 3-4 Shear Wave Ultrasonic Image (Circumferential & Axial Flaws)................................3-5
Figure 3-5 Longitudinal Wave Ultrasonic Image (Circumferential Flaws) ..................................3-6
Figure 3-6 Drawing of 12-inch Austenitic Pipe Sample..............................................................3-7
Figure 3-7 Axial Flaw E Detection Results (-45° and + 45° Skew Angles) ................................3-8
Figure 3-8 Axial Flaw F Detection Results (-45° and + 45° Skew Angles).................................3-8
Figure 3-9 Circumferential Flaw B Detection & Length Sizing Results (40° to 70° Beam Angles)
...................................................................................................................................................3-9
Figure 3-10 Circumferential Flaw C Detection & Length Sizing Results (40° to 70° Beam Angles)
.................................................................................................................................................3-10
ix
LIST OF TABLES
Table 2-1 Probe for Automated Phased Array Examination of Pipe Welds ...............................2-1
Table 3-1 Circumferential Flaw Length Sizing Results ............................................................3-12
xi
1
INTRODUCTION
The objective of the EPRI NDE Center phased array program is to exploit the benefits of
increased speed, coverage, and accuracy afforded by this technology. To implement this
objective, EPRI is assisting NDE service providers by developing and qualifying phased array
procedures.
The phased array approach enables acoustic beam steering and focusing. An “array” is a type of
ultrasonic transducer that has been segmented into many individual, parallel elements. Each
element is operated independently. By controlling the timing, or “phase”, of each element’s
excitation, a single array probe can be made to simulate many different conventional probes. In
this manner, a region of a component may be scanned electronically in milliseconds instead of
scanned mechanically in a few seconds.
Conventional automated UT procedures employ at least five scans on each side of the weld to
detect both circumferential and axial flaws. Phased array technology offers a means to reduce
the scanning time by simplifying the scan pattern. Instead of the slow, two-dimensional “raster
scan” pattern necessary to scan a weld joint using conventional methods, the phased array probe
may simply be scanned along the length of the weld in a “line scan” pattern to achieve similar
results (see Figure 1-1).
Figure 1-1
Probe Motion for Line Scan Technique
1-1
2
QUALIFICATION OF AUTOMATED PHASED ARRAY
UT FOR SIMILAR-METAL PIPING WELDS
The EPRI NDE Center has developed automated phased array UT techniques to examine pipe
welds. The key advantage of automated inspection is that all the waveforms are recorded, along
with the transducer position for each waveform, so that imaging software can produce threedimensional views of the data volume. These views are the most powerful tools for accurate
interpretation of the data and also allow the data to be viewed at any time after the inspection.
Figure 2-1 shows the required examination volume (rectangle, A-B-C-D) for pipe weld
inspection.
Figure 2-1
Examination Volume (A-B-C-D) for Pipe Weld Inspection
Phased Array Probe
EPRI’s phased array procedure for detection and length sizing in similar-metal piping welds is
based on 4 x 7 1.5 MHz array probes. The array is configured for use with interchangeable
plastic wedges. Table 2-1 gives the number of array elements, the frequency, and the relative
size of this probe.
Table 2-1
Probe for Automated Phased Array Examination of Pipe Welds
Elements
Frequency (MHz)
4x7
1.5
Aperture Size
12 mm x 20 mm
(0.472-inch x 0.787-inch)
2-1
Circumferential Flaws
For circumferential flaws, two 4 x 7 arrays are mounted on a dual, side-by-side wedge for
suppression of internal wedge echoes. The wedge is optimized for production of shear waves. A
dual, longitudinal-wave wedge is also used when access is available from only one side of a
stainless steel weld.
Probe skewing has been found to be a useful discriminator between intergranular stress corrosion
cracking (IGSCC) and geometry responses in conventional ultrasonic inspection. The 4 x 7
arrays provide electronic beam skewing, as well as, beam angle steering. The arrays were used
to steer the beam angle between 40° and 70°, in 1°-increments (a sector scan) and skew this fan
of beams at three distinct angles: -15°, 0°, and +15° (see Figure 2-2). Additional higher- and
lower-gain sector scans at 0° skew are performed to enhance dynamic range.
CL
Weld
Probe
Figure 2-2
Phased Array Probe Scan Pattern for Circumferential Flaws
The position and number of phased array line scans performed to examine a weld is a function of
the amount of coverage desired and range of angles in the sector scan (40° to 70° probe angles,
in this case). A two-line scan approach was adopted and found to provide adequate information.
The axial positions of the scan lines are determined by the pipe wall thickness and weld crown
width to provide examination angles of about 45° to 55° in the examination volume (see Figure
2-3).
2-2
Figure 2-3
Phased Array Probe Scan Pattern for Circumferential Flaws
The small footprint dual array probe (see Figure 2-4) was used to acquire a total of 125 A-scans
at each probe position. This approach proved effective for detecting all the circumferential flaws
in the qualification sample set including field-removed IGSCC.
Figure 2-4
Phased Array Probe Configuration for Circumferential Flaws
2-3
Figure 2-5 shows the phased array ultrasonic images from a practice specimen containing
circumferential IGSCC.
Figure 2-5
Phased Array Imaging of Circumferential IGSCC
2-4
Axial Flaws
For detection of axial flaws, the phase array approach closely mimics the most successful
conventional techniques, that is scanning the beam index point as close as possible to the weld
crown with at least two different probe skews. A single 4 x 7 array is mounted on a wedge
designed to direct shear waves toward the weld root at about a 50° counter-clockwise skew. The
array is mounted with its long, 7-element axis nominally parallel with the weld, so that the center
of the acoustic footprint on the pipe surface is as close as possible to the weld crown toe (see
Figure 2-6).
Figure 2-6
Phased Array Probe/Wedge Design for Axial Flaws (Counter-Clockwise Scan)
A second 4 x 7 array is mounted on a similar wedge that is cut to look clockwise. The wedge
design allows the array to interrogate the weld with limited sector scans at five different probe
skew angles, using a total of 55 beam angle/skew angle combinations. Two scan strokes are
performed. The first stroke is positioned to provide optimum detection of flaws located very
near the weld root, and the second is optimized for flaws near the front of the examination
volume (see Figures 2-7 and 2-8).
2-5
CL
Weld
Probe
Figure 2-7
Phased Array Probe Counter-Clockwise Scan Pattern for Axial Flaws
CL
Weld
Probe
Figure 2-8
Phased Array Probe Clockwise Scan Pattern for Axial Flaws
The successful Appendix VIII qualification demonstrated the effectiveness of this approach for
detecting for a range of misoriented axial flaws in austenitic pipe welds including field-removed
IGSCC.
Figure 2-9 shows the phased array ultrasonic images from an axial IGSCC.
2-6
Figure 2-9
Phased Array Image of Axial IGSCC
EPRI NDE Center Appendix VIII Qualification
EPRI has documented the successful Appendix VIII qualification of a single procedure for
phased array examination of ferritic, austenitic (non-IGSCC) and austenitic (IGSCC) pipe welds
for flaw detection and length sizing [1]. This procedure covers pipe diameters from 305 to
1270 mm (12 to 50 inches) and thicknesses from 12 to 127 mm (0.5 to 5.0 inches).
The phased array approach uses 1.5 MHz 2D array probes that enable acoustic beam steering and
skewing. The qualified procedure uses three separate probes (two looking circumferentially and
one looking axially). Each probe is scanned parallel to the weld using rapid two-stroke line
scans on each side of the weld (see Figure 2-10). The axial position of the probes is determined
from wall thickness and weld crown width.
2-7
Figure 2-10
Phased Array Approach to Similar Metal Pipe Weld Examinations
This procedure was successfully qualified through the Performance Demonstration Initiative
(PDI). EPRI personnel performed the qualification. In addition to providing excellent
information about the effectiveness of the technique, the qualification gave PDI its first
experience on how to qualify a phased array procedure that takes full advantage of electronic
beam steering and skewing. PDI had qualified phased array procedures before, but those
procedures used arrays to generate only a few beam angles (mimicking several conventional
probes) and used conventional, detailed raster scan patterns. The EPRI procedure uses over 200
beam/skew directions, with a very limited line scan pattern, so there was a learning curve on how
to deal with the quite different set of essential variables. The EPRI procedure poses some new
qualification problems. Several technical justifications were prepared in order to address them.
With normal wear and tear, individual array elements will cease to function. This can be the
result of failure of connections within the array, failure of cables, or failure of individual
channels within the phased array instrument. In order for the qualification to be valid for a
somewhat degraded array probe, cable, or system, the qualification was performed with some of
the elements – about 25% of them - deliberately turned off.
Experiments were performed to determine the effect of disabling different random selections of
elements and the effect of disabling a worst-case selection of elements. No significant difference
in performance was found between the selections of elements to turn off. The only significant
effect was the loss of a few dB of sensitivity according to the loss of active area. No selection of
disabled elements had a significant effect on detection and location of flaw indications.
Conventional procedures require measurement of the index point and beam angle for each probe
that is used. For this procedure, it would not be practical to measure the index and angle for each
of the over 200 beam directions that it uses. Instead, calibration is performed using the recorded
sector-scan display from reference reflectors, such as side-drilled holes and verification that the
depths of the holes are imaged correctly. In this way, a few of the beam angles are verified, and
if they are as they should be, then all the other angles should be correct as well. Anything that
would affect one beam angle – modification of the wedge, for example – will affect all.
2-8
The purpose of the reference sensitivity is to facilitate the comparison of an indication’s
amplitude between two observations that might be years apart. It would not be practical to
establish separate reference sensitivity for each beam angle and skew. Instead, the reference
sensitivity is measured for one selected beam angle for each array/wedge combination. This is
sufficient because any difference between inspections that would affect the sensitivity of one
beam angle would affect all the others in the same way.
EPRI has prepared software tools that form a part of the procedure. These tools are also specific
to the R/D Tech FOCUS system and TomoView software. One of the tools (EPRI Phased Array
Toolkit) calculates the focal laws, or phase programming, that the instrument will use to generate
the proper beam angles and skews for the examination. The other tool (EPRI Piping Phased
Array Workbook) generates the scan plan, calibration sheets, and examination report sheets for
each inspection.
Phased Array Procedure Commercialization
EPRI moved quickly with utility advisors and vendors to make phased array technology
commercially available. This was based on the success of the phased array ultrasonic Appendix
VIII qualification for piping [1]. Commercialization was accomplished by coordinating the
phase array technique development with a vendor, so that when the technique was ready, the
vendor would be ready to deliver it. EPRI assisted a vendor in expanding the procedure to fit
their field examination requirements. Notably, extending the diameter range down to 102mm
(4-inch), the thickness range down to 6mm (0.237 inch), and the cable length out to 100m (300foot). Commercial phased array pipe examination inspection services are now available and are
being applied (Peach Bottom, Fall 2002; Japan, Spring 2003). In addition, this technique has
been used for a basis in developing manual phased array procedures for piping.
2-9
3
SINGLE PHASED ARRAY PROBE FOR PIPING
Preliminary Activities
Recently, EPRI NDE Center staff developed and qualified through the Performance
Demonstrative Initiative (PDI) an automated inspection technique for the detection and length
sizing of IGSCC and non-IGSCC in ferritic and austenitic piping welds using ultrasonic phased
array technology with three two-dimensional piezoelectric phased array probes. This technique
utilized the advantage of the two-dimensional phased array transducers in order to electronically
generate the multiple beam and skew angles, which would ordinarily be accomplished
mechanically using conventional ultrasonic methods. Using the multiple beam and skew angles
also made it possible to replace the conventional raster scan pattern with a faster line scan pattern
parallel to the weld. After successfully qualifying a three-probe phased array technique, the next
objective is to develop and qualify a single probe phased array technique for the examination of
circumferential and axial flaws in piping welds which performs the same functions as the
previous technique but in an overall faster and simpler manner.
The single ultrasonic phased array probe for examining circumferential and axial flaws in piping
welds is made up of 2D piezoelectric arrays. In addition, multiple wedges contoured for outside
pipe diameters ranging from 101.6mm (4-inch) to 1270mm (50-inch) will be manufactured to
cover a large range of pipe sizes. (Figure 3-1) These probe/wedge combinations make it possible
to generate and inspect with both longitudinal and shear waves without additional wedges or
acquisition setups.
3-1
Figure 3-1
Phased Array Probe/Wedge for Circumferential and Axial Flaws
3-2
In order to investigate the functionality of the single phased array probe, an austenitic weld
sample containing circumferential and axially-oriented inside surface connected EDM notches
(5 mm height) was examined with multiple line scans using shear wave beam angles from 40° to
60° and skew angles from ±15° to ±80° (Figures 3-2 and 3-3).
Figure 3-2
Austenitic Weld Sample Containing EDM Notches
3-3
Figure 3-3
Shear Wave Ultrasonic Image (Circumferential & Axial EDM Notches)
R/D Tech’s TomoView software was used to combine the contributions from these 200 angles
into merged images based on signal amplitude. Figure 3-3 illustrates merged volume corrected
“VC-Top (C)” and “VC-Side (B)” views showing all fifteen indications in the austenitic EDM
notch sample. The vertical (green) and horizontal (blue) axes shown in the “VC-Top” view are
the directions perpendicular and parallel to the circumferential weld respectively. As can be seen
in the “VC-Top” image above, the EDM notches are placed at various axial locations from the
centerline of the weld that results in a “V” shape for ten axial notches positioned closest to the
circumferential notch. The “VC-Side” view in Figure 3-3 shows the indications around the
circumference (blue axis) and throughout the thickness (purple axis) of the pipe. In both the
“VC-Top” and “VC-Side” images, the ultrasonic responses from the notches skewed ±80°
produced the lowest amplitude, however, the signal-to-noise ratio is adequate for detection.
3-4
A different austenitic weld sample containing fabricated (non-IGSCC) flaws was also used to
test the functionality of the single probe technique using two line scans with shear wave beam
angles from 40° to 60°; skew angles from ±15° to ±68°; longitudinal wave beam angles from 40°
to 65°; and skew angles from –15° to +15° (Figures 3-4 & 3-5).
Figure 3-4
Shear Wave Ultrasonic Image (Circumferential & Axial Flaws)
3-5
Figure 3-5
Longitudinal Wave Ultrasonic Image (Circumferential Flaws)
Figure 3-4 shows the volume corrected merged “VC-Top” and “VC-Side” shear wave ultrasonic
images from the austenitic weld sample containing one far-side circumferential flaw, two nearside circumferential flaws, and one near-side axially oriented flaw. Furthermore, ultrasonic
responses from the weld root and reflections in the wedge can also be seen in the images. This
wedge noise should be significantly reduced with the addition of damping material incorporated
in the next wedge design revision. Figure 3-5 shows the volume corrected merged “VC-Top”
and “VC-Side” longitudinal wave ultrasonic images from the same austenitic weld sample. This
data was collected using an additional channel in the same acquisition setup file. The
longitudinal wave beam angles serve as confirmation of the far side flaw detection shown in the
shear wave data.
These preliminary results provide reassurance that the single probe/wedge design is capable of
detecting both circumferentially and axially-oriented flaws in piping welds. The ultrasonic
images shown in Figures 3-3 through 3-5 are comparable to the results from the original threeprobe technique.
3-6
Detection and Length Sizing Results
The results from the preliminary activities were used to refine the ultrasonic settings and
essential parameters of the automated single probe phased array technique. These refinements
included slight changes in the inspection angles and the selection of the worst-case selection of
elements to deactivate for the PDI demonstration.
A 304.8 mm (12-inch) OD, 17.1 mm (0.674-inch) thick austenitic pipe sample containing
fabricated circumferential and axial defects of various lengths and heights was examined using
the updated phased array procedure. A drawing of this pipe specimen can be found in Figure 3-6.
Figures 3-7 and 3-8 show successful axial flaw detections in the “VC-Side” view using the -45°
and +45° shear wave skew angles for flaws “E“ and “F” respectively. No effort was made to size
these defects as length sizing of axial flaws is not a requirement of the PDI qualification process
for piping. Utilizing shear wave beam angles from 40° to 70°, satisfactory detection and length
sizing evaluations for the circumferential cracks are illustrated in Figures 3-9 through
3-12 for flaws “B”, “C”, “D”, and “A”. Table 3-1 presents the length sizing measurements and
the associated errors for the circumferential flaws. The largest error of 9.58 mm (0.377-inch) was
observed for circumferential Flaw “D”. The root mean of the squared error (RMS) for length
sizing over these four circumferential defects was only 6.87 mm (0.270-inch).
Figure 3-6
Drawing of 12-inch Austenitic Pipe Sample
3-7
+45° Skew
Detection
-45° Skew
Detection
Figure 3-7
Axial Flaw E Detection Results (-45° and + 45° Skew Angles)
+45° Skew
Detection
-45° Skew
Detection
Figure 3-8
Axial Flaw F Detection Results (-45° and + 45° Skew Angles)
3-8
Figure 3-9
Circumferential Flaw B Detection & Length Sizing Results (40° to 70° Beam Angles)
3-9
Figure 3-10
Circumferential Flaw C Detection & Length Sizing Results (40° to 70° Beam Angles)
3-10
Figure 3-11. Circumferential Flaw D Detection & Length Sizing Results (40° to 70° Beam
Angles)
3-11
Figure 3-12. Circumferential Flaw A Detection & Length Sizing Results (40° to 70° Beam
Angles)
Table 3-1
Circumferential Flaw Length Sizing Results
Flaw
True Length
(mm)
True Length
(in)
Measured
Length
Measured
Length
(mm)
(in)
Length Error
(mm)
Length Error
(in)
B
89.63
3.529
97.00
3.819
7.37
0.290
C
145.16
5.715
148.67
5.853
3.50
0.138
D
42.44
1.671
52.02
2.048
9.58
0.377
A
39.49
1.555
45.01
1.772
5.52
0.217
RMS Length Error = 6.87 mm (0.270 in)
These detection and length sizing results on fabricated flaws using the automated single-probe
phased array procedure were acceptable. This technique has been finalized and the procedure
was successfully qualified through PDI for ferritic and austenitic similar metal weld piping,
including IGSCC for nominal outside pipe diameters of 152.4 mm (6-inch) and greater in 2004.
The qualified procedure and supporting documents can be found in the appendices of this report.
3-12
4
SUMMARY
Phased array UT technologies have been applied to improve pipe weld inspection speed and
reliability. PDI qualifications now exist for phased array examination of ferritic piping and
austenitic piping. An ISI vendor is currently using EPRI automated phased array pipe weld
examination technology at various power plants. EPRI NDE Center sponsors are benefiting
from availability of qualified phased array procedures. EPRI has reduced the inspection time of
its automated phased array examination procedure for piping by combining the functions of the
qualified three-probe procedure into a single probe technique. In 2004 this enhanced single
probe technique was successfully demonstrated through the PDI process for the detection and
length sizing of flaws (including IGSCC) in similar metal piping welds. EPRI is currently
seeking vendor collaboration of this efficient array technology for field implementation.
4-1
5
REFERENCES
1. D. MacDonald Phased Array Ultrasound Piping Examination Procedure. EPRI Technical
Report 1006980. October 2002.
2. J. Landrum M. Dennis, G. Selby, and D. MacDonald. Procedure for Automated Single
Phased-Array Probe Ultrasonic Flaw Detection and Length Sizing in Ferritic and
Austenitic Piping Welds (EPRI-SPA-1). August 2004.
5-1
A
PROCEDURE FOR AUTOMATED SINGLE PHASEDARRAY PROBE ULTRASONIC FLAW DETECTION AND
LENGTH SIZING IN AUSTENITIC AND FERRITIC
PIPING WELDS (EPRI-SPA-1)
A-1
PROCEDURE FOR AUTOMATED SINGLE
PHASED-ARRAY PROBE ULTRASONIC
FLAW DETECTION AND LENGTH SIZING
IN FERRITIC AND AUSTENITIC PIPING
WELDS (EPRI-SPA-1)
Approved by:
_____________________________________
_____________________________________
_____________________________________
_____________________________________
A-3
1. SCOPE
1.1.
This procedure defines the method and requirements for contact, automated phased array
ultrasonic examination of full penetration piping butt welds and adjacent base materials from
the Outside Diameter (OD) surface.
1.2.
This procedure is applicable to the diameter and thickness ranges for austenitic stainless steel
and ferritic carbon steel materials as listed below. This includes austenitic stainless steel
piping systems susceptible to intergranular stress corrosion cracking (IGSCC).
List 1 - Material & Examination Thickness Ranges
Material
Diameter Range
PDI
Field Applicability
Demonstration
Thickness Range
PDI
Field Applicability
Demonstration
Wrought
Austenitic
6” NPS to 36.0"
6” NPS and
Greater
0.432” to 2.625"
0.332” to 3.125"
Ferritic
6” NPS to 50.0"
6” NPS and
Greater
0.432” to 3.85"
0.332” to 4.85"
1.3.
The techniques described within this procedure address the detection and length sizing of
discontinuities within the examination volume. Depth sizing is not addressed.
1.4.
Where dual side access is available, examinations shall always be performed from both sides
of the weld. Where dual side access is not possible, the examination shall be performed from
a single side of the weld.
1.5.
The weld crown condition may be mechanically conditioned or in the "as-welded" condition.
1.6.
This procedure has been demonstrated in accordance with the requirements of the American
Society of Mechanical Engineers (ASME) Code, Section XI, Appendix VIII, 1995 Edition with
Addenda through 2000, as modified the Performance Demonstration Initiative (PDI) program
description. This demonstration was also conducted in accordance with the requirements of
the Federal Register, Part II, Nuclear Regulatory Commission, 10 CFR Part 50, Industry
Codes and Standards; Amended Requirements; Final Rule, Dated 26 September, 2002.
1.7.
This procedure is qualified for;
1.7.1.
Detection and length sizing of circumferentially oriented flaw indications in austenitic and
ferritic material where dual side access is available or if the flaw indications are located
on the near side of a single side access configuration.
1.7.2.
Detection and length sizing of circumferentially oriented flaw indications in ferritic material
where only single side access is available.
1.7.3.
Detection of axially oriented flaws in austenitic and ferritic material where dual side
access is available or if the flaw indications are located on the near side of a single side
access configuration
A-4
1.8.
This procedure is not qualified for;
1.8.1.
Detection or length sizing of circumferentially oriented flaw indications in austenitic
material when only single side access is available and the flaw is located on the far side
of the weld, however guidance is provided. The techniques identified in this procedure
have been demonstrated to be representative of “best effort" technology for single side
detection of far side defects parallel to the weld.
1.8.2.
Length sizing axially oriented flaws regardless of location.
2. REFERENCES
2.1.
American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section
XI, including Appendix VIII, 1995 Edition with the 2000 Addenda of Appendix VIII.
2.2.
Receipt Inspection of Single Phased Array Probe Transducer and Wedges for Piping Welds.
A White Paper in support of Procedure for Automated Phased Array Ultrasonic Flaw Detection
and Length Sizing in Austenitic And Ferritic Piping Welds (EPRI-SPA-1). EPRI NDE Center,
October 2003.
2.3.
Effect of De-activating Some of the Elements of a Phased Array Probe. A White Paper in
support of Procedure for Automated Single Phased-Array Probe Ultrasonic Flaw Detection
and Length Sizing in Ferritic and Austenitic Piping Welds (EPRI-SPA-1). EPRI NDE Center,
October 2003.
2.4.
Reference Sensitivity Measurement and Recording for Phased Array Pipe Inspection. A
White Paper in support of Procedure for Automated Phased Array Ultrasonic Flaw Detection
and Length Sizing in Austenitic And Ferritic Piping Welds (EPRI-PA-1). EPRI NDE Center,
October 2001.
2.5.
EPRI Phased Array Toolkit V1.0 User Manual. EPRI NDE Center, September 2001.
2.6.
EPRI Piping Single Phased Array Probe Workbook User Manual. EPRI NDE Center, October
2003.
3. PERSONNEL
3.1.
Personnel performing examinations, reviewing and evaluating recorded data to this procedure
shall be certified to Level II or III in accordance with their employers’ written certification
program.
3.2.
Data acquisition operators do not require PDI qualifications. Data acquisition operators can
perform ultrasonic calibrations; however, qualified data analysis personnel shall perform
validation of calibration and examination essential parameters.
3.3.
Data analysis personnel shall have current PDI qualification status for the material type,
diameter, thickness, and access limitation (if any) for the component being examined.
Qualification ranges and limitations are listed on the Performance Demonstration Qualification
Summary (PDQS) for each qualified individual. Qualified data analysis personnel are
responsible for assuring that all acquired data meets the technique requirements and quality
standards specified within this procedure.
3.4.
Personnel, whose involvement is limited to mounting tracks, positioning the automatic scanner
or verifying transducer position, etc., need not be certified.
A-5
4. EQUIPMENT
4.1.
Ultrasonic Instrument
4.1.1.
The R/D Tech digitized ultrasonic data acquisition and analysis system with TomoView
Version 2.2 Revision Q14. Later revisions of the software shall also be considered
equivalent if they contain, as a minimum, the same data merging tools and image views
as described within this procedure and the revision has been validated through R/D
Tech’s software configuration control process. That process must contain provisions to
assure that no change has been made to any of the parameters that have an affect on
the sensitivity and accuracy of the signal amplitude and time outputs of the software
whether displayed, recorded, or automatically processed. This also applies to addition of
mathematical modules, which aid the data analysis with positioning flaws and adjusting
for geometric configurations.
4.1.2.
The R/D Tech digitized ultrasonic data acquisition equipment shall be utilized. The
system consists of the hardware named in List 2 below. If the essential variable
hardware is substituted, the provisions of ASME Section XI, Appendix VIII-4110 must be
met.
List 2- Phased Array System Hardware List
Essential
Nonessential
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Description
TomoScan III/PA, Manufacturer: R/D-Tech
Pulser Card
Piggy Pulser/Receiver Card
Delay Receiver Card
Delay Piggy Card
Back Plane Card
Mother Card
CPU Card
MIM Card RS422
MIM Clock Card
Interface board µTomo
PIM Hyper / Hyper Pim 03
Voltage Switcher
µ TOMO board
µ TOMO : VxWorks
FOCUS : VxWorks
Data Acquisition computer (PC) and external
storage device
Scanner with appropriate search unit gimbals
Non-ultrasonic cabling, including network cables
and umbilical cable
Note: Revision letters in some cases can be instrument specific.
A-6
Model Number
EQUX114C
EWUX-203E
EQUX167B
EQUX169B
4.1.1
4.2.
Lists 9A through 9K and Lists 10A through 10F identify the essential and nonessential instrument settings. Essential settings are mandatory and shall be set as
indicated. No adjustments to the nonessential ultrasonic parameters can be made
without the knowledge and concurrence of the qualified Data Analyst.
Ultrasonic Phased Array Transducers
4.2.1.
This procedure utilizes arrays that use a minimum of 28 elements arranged in a twodimensional (2D) matrix. Single array configurations (pulse-echo) are used for the
detection of axial flaws. Dual array configurations (pitch-catch) are for the detection of
circumferential flaws. Figure 1 provides further detail.
4.2.2.
The phased array transducers that have been qualified for examinations are listed in the
applicable PDI Table 1 document for this procedure.
4.2.3.
Replacement phased array transducers of the same manufacturer, model number,
number and arrangement of elements, element sizes, element spacing, element shapes,
and nominal frequency (i.e., different serial number) may be used without re-qualification.
Replacement transducers not of the same manufacture, that are of the same number and
arrangement of elements, element sizes, element spacing, and frequency may be used
providing the provisions of ASME Section XI, Appendix VIII-4110 are met.
4.2.4.
Phased array transducer essential parameters are identified in List 3.
List 3 Phased Array Transducer Essential Variables
Element Axis Element Axis
Manf.
Model
Freq.
Number
Agfa
115-000-206 1.5 MHz
No. of
Element
Elements Arrangement
56
7x8
A-7
Element Element Element Element
Length
(MM)
2.25
Spacing
(MM)
2.30
Width
(MM)
1.35
Spacing
(MM)
1.40
Figure 1 Phased Array Transducers
4.3.
Phased Array Transducer Wedges
4.3.1.
Phased array transducer wedges allow for the formation of several beam angles and
beam skews simultaneously. Wedges are typically cut two-dimensionally, with one
dimension (wedge cut) controlling the refracted angle(s) produced and the other
dimension (roof angle) affecting beam focusing or skewing capabilities.
4.3.2.
The phased array transducer wedges that have been qualified for examinations are listed
in the applicable PDI Table 1 document for this procedure.
4.3.3.
Replacement wedges of the same manufacturer, model, number, material, angles, and
dimensions may be used without re-qualification. Replacement wedges not of the same
manufacture, that are of the same material, angles, and dimensions may be used
providing the provisions of ASME Section XI, Appendix VIII-4110 are met.
4.3.4.
Transducer wedge essential parameters are identified in List 4.
List 4 Phased Array Wedge Essential Parameters
Manf.
Model
Number
Wedge Cut Roof
Contour
Beam
Flaw Type
Config.
Primary
Angle
Angle
Agfa 360-151-019
30°
0°
(OD)
Direction
Wedge Design
(Note 1)
(Figure 9)
Flat
UPST or DNST Circ/Axial Dual/ Single
45° Shear
Agfa 360-152-004
30°
0°
36” NPS UPST or DNST Circ/Axial Dual/ Single
45° Shear
Agfa 360-152-005
30°
0°
20” NPS UPST or DNST Circ/Axial Dual/ Single
45° Shear
Agfa 360-152-006
30°
0°
12” NPS UPST or DNST Circ/Axial Dual/ Single
45° Shear
Agfa 360-152-007
30°
0°
6” NPS UPST or DNST Circ/Axial Dual/ Single
45° Shear
Note 1: Flat transducer wedges shall be used on components greater than 50” in diameter. The 36” NPS
wedges shall be used on components greater than or equal to 35” in diameter. The 20” NPS wedges shall
be used on components greater than 16” in diameter. The 12” NPS wedges shall be used on components
greater than 8” in diameter. The 6” NPS wedges shall be used on 6” NPS piping. The preceding should
be used as a guide in determining the appropriate wedge to be used for a particular pipe size. For each
examination the wedge that best matches the outside diameter of the pipe should be used.
A-8
4.4.
Phased Array Focal Laws
4.4.1.
A phased array focal law is a group of parameters (gains, delays, skews, filters, etc.)
applied simultaneously by the Tomoscan III/PA system during pulse transmission and
reception to create a desired beam in the material. The timing of the elements' excitation
can be individually controlled to produce certain desired effects, such as multiple
examination angles or steering the beam axis. A single focal law typically generates a
single beam angle. Combining several focal laws creates a focal law “group”. Figure 2
provides further detail.
4.4.2.
The phased array focal law groups that have been qualified for examinations in
accordance with this procedure are identified in List 5.
List 5 Phased Array Focal Laws
Focal
Law
Group
Beam
Direction
1a
2
UPST or
DNST
UPST or
DNST
LKLT
3
LKRT
1b
Beam
Angles
Minimum Beam
Angle
Resolution
Skews
Mode
UT Channel
Name/#
UT
Channel #
40° - 70°
1°
0°, -15°, +15°
Shear Wave
4070S
1
43° - 70°
1°
0°, -15°, +15°
4370L
4
35° - 60°
2.5°
Left 3560S
2
35° - 60°
2.5°
-35°,-45°, -52.5°, 60°, -67.5
35°, 45°, 52.5°, 60°,
67.5°
Longitudinal
Wave
Shear Wave
Shear Wave
Right 3560S
3
A-9
Figure 2 Phased Array Focal Laws
4.5.
Mounting phased array transducers
4.5.1.
The arrays are positioned so that the first element of each array is located at the rear of
the wedge and is the furthest element from the center of the cork in the lateral direction.
(see Figure 3)
Figure 3 Array Placements
A-10
4.6.
Ultrasonic cable configurations
4.6.1.
The cable type, maximum length, and maximum number of intermediate connectors are
specified in Figure 4 and in applicable Table 1 document for this procedure. The
maximum cable length identified may be exceeded by a length of 1-meter (3.3’) to allow
for cable manufacturing tolerances.
4.6.2.
Phased Array Transducer Cable (Integral)
a.
b.
4.6.3.
a.
b.
c.
4.6.4
a.
b.
c.
4.6.5
a.
b.
Hypertronics 160-pin male connector
Length: 10 meters (~ 33’)
Extension Cables
Two Hypertronics 160-pin male to 160-pin female, 64 RG-178
Length: each 44.5 meters (~146’)
Type: RG-178
Intermediate Y Cables
Hypertronics “Y” cable: two 160-pin females into one 160-pin male
Hypertronics “Y” cable: two 160-pin males into one 160-pin female
Length: 10.6 meters (~35’)
Cable Adapter (112-140-264)
Hypertronics 160-pin female to 160-pin male
Length: 0.15 meters (~0.5’)
A-11
Figure 4 Cable Diagram
A-12
4.7.
Motion Control/Manipulator
4.7.1.
4.8.
An encoded manipulator calibrated to provide accurate positioning shall be utilized. The
manipulator shall be capable of performing the scanning and indexing requirements of
this procedure. In addition, the scanner shall have the ability to provide adequate force to
keep the search unit coupled to the pipe surface.
Ultrasonic Couplant
4.8.1.
4.9.
The ultrasonic couplant or demin water to be used shall be in sufficient quantities to
maintain adequate acoustic contact between the search unit and component, and shall
be approved by the Owner for use.
Calibration and Reference Blocks
4.9.1.
Calibration blocks shall be used to establish a reference sensitivity level from which
subsequent examinations may be compared. The calibration block design shall be the
Basic Calibration Block described in III-3400 of the ASME B & PV Code Section XI
(Appendix III) or an alternative calibration block as approved and /or provided by the
owner.
4.9.2.
The Phased Array Reference Blocks shall be made of the same material type (carbon or
stainless steel) as the component being examined. The Phased Array Reference Blocks
are described in Figure 5.
4.9.3.
For calibration for 6” NPS piping either a 4” or 6” NPS pipe section shall be used, in lieu
of the Phased Array Reference Block. The pipe section shall contain a circumferential
notch, a notch of the same depth rotated 45° clockwise, and a notch of the same depth
rotated 45° counterclockwise. All three notches shall be located on the inside surface.
The depth shall be as specified for the Basic Calibration Block described in III-3400 of the
ASME B&PV Code Section XI (Appendix III). The thickness of the pipe section shall be
at least ¾”.
4.9.4.
Reference blocks (i.e. IIW, DSC, Rompas, etc.) used for establishing linear screen
ranges shall be made of the same material type (carbon or stainless steel) as the
component being examined. Reference blocks used for verifying phased array channel
count and performing calibration verifications (cal checks) may be made of any suitable
material provided that adequate time base and amplitude verification points can be
established.
4.10.
When desired, contour gauges may be used to obtain OD surface profiles to aid in the
evaluation of indications.
A-13
Figure 5 Phased Array Reference Block
A-14
4.11.
Phased Array Software
4.11.1. The “EPRI Piping Single Phased Array Probe Workbook V1.0 Rev0.0.xls” shall be used
to develop scan plans, create “Focal Depth Files” (*.adf), create “merge.ini” files, and
record examination information. Later revisions of the software shall be considered
equivalent if they allow the generation of equivalent scan patterns, “Focal Depth Files”,
and “merge.ini” files, and if the revision has been validated through the software
configuration control process.
4.11.2. The “EPRI Phased Array Toolkit V1.0 Rev0” shall be used to calculate all focal laws
uploaded into TomoView Version 2.2 Revision Q14. Later revisions of the software shall
be considered equivalent if they allow the generation of equivalent beam and skew
angles for the minimum number of transmitting and receiving elements and if the revision
has been validated through the software configuration control process.
5. CALIBRATION
5.1.
5.2.
General Information
5.1.1.
Select the appropriate search unit and wedge combination for the examination to be
performed. Refer to Lists 3 & 4 for search unit/wedge configurations. Connect the
search unit and wedge combination to the Tomoscan III/PA system.
5.1.2.
The default measurement system in TomoView 2.2Q14 is “Metric” and shall not be
changed during calibration, data setup, or data acquisition. Ensure that the “Bypass
Analysis” box under “Preferences” is checked.
5.1.3.
Input all pre-determined essential and non-essential instrument UT settings identified in
List 9A – 9K into TomoView into Channel #1.
5.1.4.
Create ultrasonic channels 2 through 4 by copying channel 1. Rename each channel
using the ultrasonic channel name in List 5. For channel 4 (4370L) the “Wave” should be
changed to “Longitudinal”, the “Sound velocity” should be updated (See List 6), and the
Time base Range should also be updated. (See 5.5.4).
5.1.5.
Load the appropriate focal law file for the current ultrasonic channel. (See List 5)
Active Channel Count
5.2.1.
An active channel count shall be performed for each search unit prior to a series of
exams or any time that system irregularity is suspected. The following steps should be
used to perform an active channel count.
a.
Apply a special focal law that allows viewing individually the responses of each
element. This special focal law shall be included in a setup file named “single probe
element check01.acq”.
b.
Place the search unit on a block, which contains an appropriate reflector, and obtain a
response. Observe the number of channels that are not operating (a non-operative
channel might result from a failure of the channel’s piezoelectric element, cabling,
pulser, or receiver).
A-15
c.
5.3.
If at least 21 of the channels are functioning the system is considered to be
acceptable. The procedure demonstration was performed with 7 of the elements
turned off.
Focal Law Creation
5.3.1.
Focal laws shall be created or approved by the qualified Data Analyst.
5.3.2.
The “EPRI Piping Single Phased Array Probe Workbook V1.0 Rev0.0.xls” shall be used
to create the appropriate “Focal Depth File” (*.adf) and “Procedure Input Files” (*.epi) for
a given wedge, focal depth, and pipe specimen. This “Procedure Input File” shall then be
loaded into the “EPRI Phased Array Toolkit” by the user to generate the corresponding
“Focal Law File” (*.law). All focal law files shall be generated using the “EPRI Phased
Array Toolkit”.
5.3.3.
Focal law files are created based on the following items:
a.
Material velocity (List 6), transducer (List 3), wedge (List 4), and pipe diameter.
b.
Focal law “Groups” shall be created with the appropriate wave mode (see List 5). The
“Focal Depth File” and “Procedure Input File” generated by the “EPRI Piping Single
Phased Array Probe Workbook V1.0 Rev0.0.xls” automatically provides the correct
beam angles and skew angles. This file should then be loaded into the “EPRI Phased
Array Toolkit” to insure that the correct focal law “Groups” are used.
c.
For piping with a nominal thickness greater than or equal to 0.5 inch (16.51mm), the
focal depth shall be equal to the thickness of the pipe ±0.25” (6.35 mm). For piping
with a nominal thickness less than 0.5 inch (14.9mm), the focal depth shall be equal to
three times the thickness of the pipe, with a ±0.25” (6.35mm) tolerance on the focal
depth.
Note: Pipe thickness shall be based on the average wall thickness of the upstream and downstream
sides of the weld measured at the weld toes. If dual sided access is not available, and the weld crown is
ground flush, the measured thickness at the weld centerline should be used. When the weld crown
configuration precludes an accurate thickness reading, the pipe thickness of the accessible side should
be used.
A-16
5.3.4.
Both upstream and downstream focal law files are generated and named automatically
by the “EPRI Phased Array Toolkit” software in one calculation. Focal law files (*.law)
should be named using the following convention:
“Material Type”“Pipe Diameter”_”Wedge Part #”_”Minimum Beam Angle””Maximum Beam Angle”
“Mode”“’FD’””FocalDepth””_””Beam Direction”
a.
“Material Type” shall be “SS” for austenitic materials and “CS” for ferritc materials.
b.
Focal law files for looking downstream scans (Probe Skew of 270o) shall have a suffix
of “_LkDn”. Focal law files for looking upstream scans (Probe Skew of 90o) shall have
a suffix of “_LkUp”.
Example: Shear wave focal law files for an austenitic pipe, 305mm diameter using wedge
118-340-373” at a focal depth of 17mm would be as follows:
Material & Pipe Dia.
Wedge Part #.
Min. & Max. Angles, Mode,and Focal depth(FD#)
“SS406_123-456-798_4070SFD32_LkUp.law” (looking upstream)
“SS406_123-456-798_4070SFD32_LkDn.law” (looking downstream).
5.3.5.
Focal law files are loaded into TomoView using the following process:
a.
Select/activate the appropriate ultrasonic channel. (See List 5)
b.
Click on the Tomoview Focal Law Calculator Icon
from a file", then click “Next”.
c.
Click "Browse" and select the appropriate file.
d.
Click "Replace” to replace the current set of focal laws with the focal laws from the file.
e.
Click "Finish" to load the focal laws into TomoView.
A-17
and choose "Read a sector
5.4.
5.5.
5.3.6.
After all the applicable focal laws have been loaded the “Time base Start” should be set
to “0”. The “Time base Start” should also be set to “0” after establishing the system delay.
5.3.7.
The focal law filename should be input on the scan plan.
Focal Law Verification
5.4.1.
Focal Law Verification shall be completed for each ultrasonic channel (1 through 4).
5.4.2.
Focal laws shall be verified prior to each examination on an appropriate (CS or SS)
reference block similar to the block shown in Figure 5. The following process should be
used for focal law verification:
a.
Split the setup screen to display two windows, one an “S-scan” and the other an “Online A-scan”.
b.
Use the cursor in the “S-scan” window to select the focal law for a beam/skew angle
of 45°/0° for ultrasonic channels 1 and 4; 45°/±45° for ultrasonic channels 2 and 3.
c.
Using the appropriate reference block adjust the probe position and rotation to
maximize the amplitude of the response from the appropriate reflector. For 6”
contoured wedges, the appropriate reflector is an ID notch in the reference block
defined in Paragraph 4.9.3. For wedges contoured for 12” and larger diameters, the
appropriate reflector is the SDH that is closest to the thickness of the component, in
the reference block defined in Paragraph 4.9.2.
d.
Without moving the search unit, use the S-scan cursors to measure the depth of the
reflector. For the Phased Array Reference Block defined in Paragraph 4.9.2, measure
the depths of both the SDH closest to the thickness of the component and the SDH at
the next shallower depth.
e.
If the measured depths are accurate (±10% of the true depth) then the focal laws’
beam angles are considered accurate. The actual and measured depths should be
recorded on the calibration data sheet.
Ultrasonic Calibration
5.5.1.
General Information
a.
Initial system calibrations shall be performed prior to an examination or series of
examinations. A system calibration check (calibration verification) shall be performed
as required by paragraph 5.7.
b.
The basic calibration data and the digitized A-Scan data acquired during examinations
may be stored on any appropriate storage media.
c.
All initial and final calibration and calibration verification times and data shall be
recorded on the calibration data sheet. A copy of the calibration data sheet shall be
included in the Examination Report.
d.
A linear time base representing metal path shall be established. The time base shall
be calibrated using an appropriate reference block (CS or SS) with known reflector
distances.
A-18
5.5.2.
Acoustic Velocity Setting
a.
Acoustic velocity settings for search unit modes of propagation and material types are
shown in List 6.
List 6- Material Velocities
Material
Carbon Steel
Stainless Steel
5.5.3.
The system delay is established using a beam angle/skew angle of 45o/0o for
ultrasonic channels 1 and 4, and 45°/±45° for ultrasonic channels 2 and 3 on an
appropriate reference block. The reference block shall provide appropriate reflectors,
such as a 2-inch and/or 4-inch radius. For 6” NPS an ID notch should be used. Peak
the signal from the reflector, and then adjust the system delay until the peak of the
reflector signal is at the correct time base location.
Time Base (Range) Size
a.
Weld profile and component thickness information shall be reviewed prior to
calibration to aid in the development of scan plans and establishing an appropriate
time base size.
b.
The time base size shall be sufficient to provide adequate coverage of the required
examination volume from each side of the weld. Sufficient allowance should be
provided for material thickness and/or sound path variation. The following guidelines
should be used for establishing time base size, based on the thickness T:
1.
2.
5.6.
Velocity Shear
US Units
Metric Units
in./sec.
m/sec.
127165
3230
124016
3150
System Delay Setting
a.
5.5.4.
Velocity Longitudinal
US Units
Metric Units
in./sec.
m/sec.
231890
5890
227165
5770
For nominal thicknesses greater than or equal to 0.5 inch, the minimum time base
shall be Min.TB =(T+0.25”)/cos(70o) and the maximum time base shall be Max.TB
=((Tx1.5)+0.25”)/cos(70o).
For nominal thicknesses less than 0.5 inch, the minimum time base shall be
Min.TB =(3T+0.25”)/cos(70o) and the maximum time base shall be Max.TB
=((3Tx1.5)+0.25”)/cos(70o).
Reference Sensitivity
5.6.1.
Reference sensitivity shall be established for all ultrasonic channels (1 through 4) using
an ASME basic calibration block, or for 6” NPS, using the reference block defined in
Paragraph 4.9.3. Establish the reference sensitivity using the following process:
a.
Peak the signal from the ID notch using a beam angle/skew angle of 45o/0o for
ultrasonic channels 1 and 4, and 45°/±45° for ultrasonic channels 2 and 3 and adjust
the amplitude to approximately 80% full screen height (FSH).
A-19
b.
5.7.
Record the calibration block name, array part #, wedge part #, focal law filename,
beam angle, skew angle, metal path, amplitude, noise level, and gain setting on the
calibration data sheet included in “EPRI Piping Single Phased Array Probe Workbook
V1.0 Rev0.xls”.
Calibration Verification (Cal check)
5.7.1.
Calibration Verification shall be completed for all ultrasonic channels (1 through 4).
5.7.2.
The following process shall be used to establish calibration verification measurements:
a.
Using the same focal law used to establish reference sensitivity (see 5.6), obtain and
maximize a response from a known reflector in a reference block such as the phased
array reference block or an appropriate reference block.
b.
Adjust the signal amplitude to approximately 80% full screen height (FSH).
c.
Record the identification of the reference block, the identification of the selected
reflector, the gain setting, metal path position and amplitude of this reflector.
5.7.3.
Time base and amplitude calibration points shall be recorded during the initial calibration
and verified:
a.
Prior to a series of examinations
b.
At the completion of a series of examinations
c.
At intervals not to exceed 12 hr
d.
After any interruption in system continuity (e.g., power interruptions, activation of new
examination setups, etc.)
e.
After any instance of suspected system irregularity.
5.7.4.
Acceptance criteria for calibration check
a.
Time base response from reference reflector has not changed by more than ± 10% of
the original position.
b.
Amplitude response from reference notch reflector has not changed by more than ± 3
dB of the original response. Amplitude changes of 3dB or more shall be investigated
to the extent necessary to determine the cause and provide corrective action. If the
amplitude has decreased by 3dB or more an active channel count should be
performed using the process outlined in paragraph 5.2.
c.
At least 21 beam elements in each array are operating.
5.7.5.
If any calibration verification fails to meet these requirements, all examinations since the
last successful calibration check shall be voided and the affected components shall be reexamined.
5.7.6.
Any change in search units, wedges, focal laws, or UT instruments from that used during
the initial calibration shall be cause for re-calibration. When replacing cables of the same
size, type, length and number of intermediate connectors as used during the original
calibration, it is acceptable to perform a calibration check and active channel count only.
A-20
6. EXAMINATION
6.1.
General Requirements
6.1.1.
Prior to examination, the system operator shall verify that all pre-determined essential
and non-essential instrument settings identified in Lists 9A through 9K and Lists 10A
through 10F are set as specified in this procedure.
6.1.2.
Weld profile and component thickness information shall be available prior to examination.
6.1.3.
The reference system (Lo, Wo) shall be established per Reference 2.1.
6.1.4.
The coordinate systems for circumferential and axial flaw examinations can be found in
Figure 6. The scanner shall be “inverted” appropriately such that the positive and
negative “Scan” and “Index” directions are maintained for all scans. The positive Index
axis shall be opposite the flow direction in the pipe. The positive Scan direction shall be
clockwise while looking in the flow direction.
Figure 6 Examination Coordinate System
A-21
6.2.
Required Examination Volume and Surface Condition Requirements
6.2.1.
The required examination volume as identified in Figure 10 shall be scanned from both
sides of the weld when accessible. Welds that cannot be examined from at least one (1)
side shall be reported to the Owner for disposition.
Figure 7 Examination Volume
6.3.
6.2.2.
The examination shall be performed from the OD surface of the piping component to be
examined. The surface shall be free of irregularities, loose material, or coatings, which
interfere with the ultrasonic wave transmission. Areas where ultrasonic contact is
inadequate shall be documented as limitations and reported to the Owner for disposition.
6.2.3.
When using shear waves to examine austenitic piping, it is important that the wedge
footprint is on base metal. In some cases, weld crowns are blended with the base metal
so smoothly that the axial location of the weld toe is not visible. On each side of the weld
that will be scanned, if the location of the toe is not visible, the location of the toe shall be
identified using etchants, small magnets, or other means.
Scan Plans
6.3.1.
Each weld shall be scanned in accordance with a scan plan developed using the “EPRI
Piping Single Phased Array Probe Workbook V1.0 Rev0.xls”. Scan plans shall be
developed or approved by a qualified data analyst.
6.3.2.
Scan plans shall be prepared prior to each examination. Scan plans shall provide the
system operator with the scan parameters to be applied and additionally identify the scan
coordinates that bound the area to be scanned. The component geometry and/or
contour of the area of interest and adjacent scan surfaces shall be evaluated to
determine coverage and scan distances. If minor scan parameter changes are required
as a result of actual conditions encountered (e.g., wider than expected crown widths,
physical obstructions, etc.) the changed values shall be recorded.
6.3.3.
The following scan plan information shall be input into the ultrasonic examination system:
a.
Scan Offset and Index offset information shall be entered in “UT Settings” under the
“Probe” tab in “Modify Probe-T”.
b.
Scan Start, Scan Stop, and Scan Resolution, along with Index Start, Index Stop, and
Index Resolution shall be entered in “Inspection Settings” under the “Sequence” tab.
A-22
c.
Scan file name using a file naming convention that uniquely identifies information for
each exam conducted. The “EPRI Piping Single Phased Array Probe Workbook V1.0
Rev0.xls” automatically suggest an appropriate scan file name. Specific information
recommended for each examination data file name includes:
•
•
•
•
•
•
6.4.
Weld ID
Wedge number
Minimum and maximum beam angles
Focal depth
Beam direction
Wave Mode
Scan Patterns (Line Scans)
6.4.1.
The maximum scan speed shall be determined from the “Acquisition Rate” and “Scan
Resolution” of “1 mm” . The maximum scan speed shall be 95% of the product of the
“Acquisition Rate” and the “Scan Resolution”. For example, the maximum scan speed
with an acquisition rate of 8 Hz and scan resolution of “1 mm” is “7.6 mm/s”.
6.4.2.
List 7 identifies the minimum number, and required positions of scan lines for each
examination. Additional scan lines may be requested by the qualified data analyst to
further interrogate suspect indications or to compensate for geometrical uncertainties
(offset weld root, tapers, etc.).
List 7 Line Scan Examinations
Thickness
Access
>0.500”
Dual Side
>0.500”
Single Side
≤0.500”
Dual Side
≤0.500”
Single Side
Propagation
Minimum # of Lines
Positions
4
6.4.3
4
6.4.4
Shear
4
6.4.3
Shear
4
6.4.4
Shear & Longitudinal (Stainless Only)
Shear & Longitudinal (Stainless Only)
Note: The longitudinal wave mode (channel 4) is not required for dual side access or carbon steel
material or pipe thickness less than or equal to 0.5”.
6.4.3.
Scan Positions (Dual Side Access)
The scan positions are illustrated in Figure 8.
a.
When possible, the transducer position for the first scan line will be such that a 45°
beam angle with a 52.5° skew strikes the inside surface at the centerline of the weld.
If the weld crown width prevents this from occurring then the transducer position for
the first scan line will be with the front of the wedge as close as possible to the weld
toe. The wedge footprint must be on base material when examining austenitic
materials with any crown conditions, or when examining ferritic materials with nonflush weld crowns. [The 45o/52.5o beam angle is actually the angle at the opposite
surface]
A-23
b.
The transducer position for the last scan line will be such that a 45° beam angle with a
0° skew strikes the inside surface at the back of the examination volume. If the
separation between the first and second scan lines are less than T/2 then the
transducer position for the second scan line will be changed to T/2 from the first scan
line. The second and third scan lines shall be positioned between the first and fourth
lines, to provide a constant axial scan increment.
c.
For piping that is less than or equal to 0.5” thick, the scan lines are determined as
defined in “a” and “b” above, but assuming that the thickness for the last scan line is
three times the actual thickness, so that the examination is configured for the 3/2 veepath. (See Figure 9)
Figure 8 Dual Side Access Technique (T>0.500”)
Figure 9 Dual Side Access Technique (T≤0.500”)
A-24
6.4.4.
Scan Positions (Single Side Access)
The scan positions are illustrated in Figure 10.
a.
When possible, the transducer position for the first scan line will be such that a 45°
beam angle with a 52.5° skew strikes strikes the inside surface at the far-side edge of
the examination volume. This will require that the wedge be positioned on the weld.
If the weld crown contour prevents this from occurring with adequate contact, then the
transducer position for the first scan line will be with the front of the wedge as close as
possible to the weld toe. The wedge footprint must be on base material when
examining austenitic materials with any crown conditions, or when examining ferritic
materials with non-flush weld crowns. [The 45o/52.5o beam angle is actually the angle
at the opposite surface]
b.
The transducer position for the last scan line will be such that a 45° beam angle with a
0° skew strikes the inside surface at the back of the examination volume. If the
separation between the first and second scan lines are less than T/2 then the
transducer position for the second scan line will be changed to T/2 from the first scan
line. The second and third scan lines shall be positioned between the first and fourth
lines, to provide a constant axial scan increment.
c.
For piping that is less than or equal to 0.5” thick, the scan lines are determined as
defined in “a” and “b” above, but assuming that the thickness for the last scan line is
three times the actual thickness, so that the examination is configured for the 3/2 veepath. (See Figure 11)
Figure 10 Single Side Access Technique (T>0.500”)
A-25
Figure 11 Single Side Access Technique (T≤0.500”)
6.5.
Scan Sensitivity
6.5.1.
For channel 1 using shear waves, the scanning sensitivity shall be initially determined by
selecting the beam angle from “Group 1a” at 0° skew which the forward scan line strikes
the weld centerline at the inside surface and adjusting the acquisition gain until the
material noise in the area of the weld root is between 2% and 5% FSH. For channel 4
using longitudinal waves, the scanning sensitivity shall be initially determined by selecting
the beam angle from “Group 1b” at 0° skew which the forward scan line strikes the weld
centerline at the inside surface and adjusting the acquisition gain until the material noise
in the area of the weld root is between 4% and 8% FSH.
6.5.2.
For channels 2 and 3, the scanning sensitivity shall be initially determined by selecting
the beam angle from “Group 2 or 3” at 52.5o skew which strikes the weld centerline at the
inside surface and adjusting the acquisition gain until the material noise in the area of the
weld root is between 2% and 5% FSH.
6.5.3.
During scanning the system operator shall verify equipment operation and search unit
contact by observing data acquisition displays. It is recommended that both the “S-Scan”
view, and a “DynAC-Side” view for a focal law which strikes the inside surface near the
weld root, should be displayed while acquiring data. If the operator notices that the initial
scanning sensitivity has been set inappropriately (too high or too low) whereas responses
in the area of the weld root are absent or excessively saturated, the scan shall be
stopped, scan gain shall be adjusted appropriately, and the affected data shall be
recollected.
6.6.
Supplemental scans may be required by the qualified Data Analyst to obtain additional
information. Supplemental examinations are acceptable provided they are not used to
overturn the results of examinations obtained with the primary qualified examination technique
described within the procedure, or obtain coverage in lieu of the qualified technique.
6.7.
Ensure examinations are performed in accordance with this procedure and the Scan Plan.
Where examination limitations are encountered document these on the examination report
and advise the qualified Data Analyst.
A-26
7. DATA ANALYSIS
7.1.
Pre-Analysis Verifications
7.1.1.
Weld fabrication and examination data histories, if available, should be reviewed prior to
analysis of the ultrasonic examination data.
7.1.2.
Prior to analyzing data, the Data Analyst shall ensure the quality of the data by verifying
the following:
a.
All data has been collected in accordance with requirements of this procedure.
b.
All required examinations have been performed and scan limitations documented.
c.
The necessary data records and scan plans are completed.
d.
A thickness and contour has been performed or provided.
e.
Adequate search unit contact has been achieved. Isolated instances of lack of contact
may be accepted provided that no more than 3 adjacent acquisition positions are
empty of data in the direction of scanning and the area does not contain flaw or
suspected flaw indications that require evaluation.
f.
Areas that do not meet the acceptance criteria stated above shall be reexamined. If
repeated examinations do not achieve acceptable scans, the total amount of missed
coverage shall be calculated.
A-27
7.2.
Initial Data Analysis Set-up
7.2.1.
All examination data files shall be initially evaluated utilizing the data analysis layout
views identified in Figure 12.
Figure 12 Phased Array Analysis Layout
Volume Corrected Side B Merge
Volume Corrected Top C Merge
Volume Corrected End D Merge
Note: The Volume Corrected End D Merge is optional for Axial flaw evaluations.
A-28
7.2.2.
Focal Law Merge Files
a.
Individual focal laws are merged to create special volumetric merge views for the
analysis system display. The “EPRI Piping Single Phased Array Probe Workbook”
shall be utilized to create a “Batch Volumetric Merge” file (*.bvm) and “Volumetric
Merge” files (“.vmc) for initial data evaluation. These merged views can be activated
from the “Tools” drop-down menu under “change channels”.
b.
The merged views identified in List 9 were utilized as a template for the processes
used to qualify this procedure and shall each be viewed as a minimum data analysis
requirement. Additional merge views can be created using the workbook or from the
analysis system software.
List 8 Layout Merge Views
Beam Directions LKUP or LKDN
Merge Channel Name
MERGE 4070S SKW -15
MERGE 4070S SKW 0
MERGE 4070S SKW +15
MERGE 5570S SKW 0
MERGE 4070S All Ref
MERGE 3560 SKW -35
MERGE 3560 SKW -45
MERGE 3560 SKW -52.5
MERGE 3560 SKW -60
MERGE 3560 SKW -67.5
MERGE 3560 SKW All MERGE 3560 SKW +35
MERGE 3560 SKW +45
MERGE 3560 SKW +52.5
MERGE 3560 SKW +60
MERGE 3560 SKW +67.5
MERGE 3560 SKW All +
MERGE 4370L SKW -15
MERGE 4370L SKW 0
MERGE 4370L SKW +15
MERGE 5570L SKW 0
MERGE 4370L All Ref
Merge Details
Merge all angles from 40° - 70° at (-) 15° Skew only (Shear)
Merge all angles from 40° - 70° at 0° Skew only (Shear)
Merge all angles from 40° - 70° at (+) 15° Skew only (Shear)
Merge only angles from 55° - 70° at 0° Skew (Shear)
Merge all angles from 40° - 70° at all skews (Shear)
Merge all angles from 35° - 60° at (- ) 35° Skew only
Merge all angles from 35° - 60° at (- ) 45° Skew only
Merge all angles from 35° - 60° at (-) 52.5° Skew only
Merge all angles from 35° - 60° at (-) 60° Skew only
Merge all angles from 35° - 60° at (-) 67.5° Skew only
Merge all angles from 35° - 60°and all (-)skews
Merge all angles from 35° - 60° at (+ ) 35° Skew only
Merge all angles from 35° - 60° at (+ ) 45° Skew only
Merge all angles from 35° - 60° at (+) 52.5° Skew only
Merge all angles from 35° - 60° at (+) 60° Skew only
Merge all angles from 35° - 60° at (+) 67.5° Skew only
Merge all angles from 35° - 60°and all (+)skews
Merge all angles from 43° - 70° at (-) 15° Skew only (Longitudinal)
Merge all angles from 43° - 70° at 0° Skew only (Longitudinal)
Merge all angles from 43° - 70° at (+) 15° Skew only (Longitudinal)
Merge only angles from 55° - 70° at 0° Skew (Longitudinal)
Merge all angles from 43° - 70° at all skews (Longitudinal)
A-29
7.3.
Evaluation of Ultrasonic Data
7.3.1.
Load the appropriate data file.
a.
Ensure all volume-corrected views are in the projection mode.
b.
Activate each pane and set all measurement units to inches, with two decimal places
of precision, or set all to millimeters with one decimal place of precision. Set the
USOUND setting to “True Depth”.
c.
Under the “Edit Pane Properties” icon select the “Parameters” tab and verify that all
parameters are correct (sound velocity, delay, offsets, etc.).
d.
In all the merged volume corrected displays adjust the gate cursors to envelop the
entire scan area. After this evaluation, these gates can be manipulated to display
specific regions of the weld length or volume for pattern interpretation and
comparison. For axial flaw channels, the “Index” and “Depth” gates shall be adjusted
so that the signal responses from the internal wedge noise is not displayed in the “VCTop” and “VC-Side” views.
e.
For each merged channel, analyze the volumetric images to identify areas that exhibit
deviation from the component geometrical or metallurgical interface responses. The
amplitude color palette range will require adjustment to provide resolution of the
various reflectors throughout the scan. The analyst must assure that the data is
evaluated from the background noise level and above. Several palette ranges should
be evaluated in order to provide optimum image contrast and to ensure that flaw
indications are not masked with the background noise. The following are examples of
conditions that may warrant additional analysis:
1.
Localized high amplitude indications; or
2.
Indications which exhibit throughwall depth; or
3.
Indications which are offset from normal geometry, such as the weld centerline,
root, or counter bore areas; or
4.
Indications that display unique response as compared to benchmark responses.
f.
7.4.
When analyzing data from piping that is less than 0.5” thick, two additional good
practices should be followed:
1.
When evaluating data for circumferential defects, the top view should be evaluated
with the projection gates enveloping the ½-vee path, and again with the gates
enveloping the 3/2-vee path. The gates should be set to exclude geometric and
metallurgical reflectors occurring at or near the full-vee path.
2.
When evaluating data for axial defects, care should be taken to evaluate each
skew angle individually, using the “Change Channel” function. This is to ensure
that each flaw is viewed at its best signal-to-noise ratio.
Discrimination of Indications
7.4.1.
The following conditions should be considered for determination of geometrical
indications. Note: These items should not be considered mandatory criteria for
A-30
classifying indications as geometry, but are listed as significant points to consider by the
data analyst during evaluation of suspect areas
a.
The indication appears at or near the centerline of the weld or other documented
geometrical condition (i.e., counter bore). This information can be evaluated against
the thickness and contour information.
b.
The indication can be seen across the entire length of the scan (either continuously or
intermittently) at consistent amplitude and position responses.
c.
The indication possesses very little or no echo dynamic travel in the depth direction.
d.
When a comparison is made between responses from a lower and higher beam angle
merges, the indication responses are significantly lower or not detected with the
higher beam angles.
e.
When a comparison is made between the 0° skew merges and the 15° skew merges
the indication responses are significantly lower or not detected with the 15° skew
merges.
f.
The indication displays patterns or signal responses (multiples), which can be
indicative of mode converted shear wave signals from the use of longitudinal wave
search units or mode converted signals from counter bore.
7.4.2.
The following conditions should be considered for determination of metallurgical
indications. Note: These items should not be considered mandatory criteria for
classifying indications as metallurgical indications, but are listed as significant points to
consider by the data analyst during evaluation of suspect areas.
a.
The indication appears at or near one of the welds’ acoustical interfaces.
b.
The indication is not connected to a surface.
c.
Similar indications can be seen at varying amplitudes 360° intermittently.
7.4.3.
The following conditions should be considered for determination of flaw indications.
Note: These items should not be considered mandatory flaw confirmation criteria, but are
listed as significant points to consider by the data analyst during evaluation of suspect
areas.
a.
The indication has a high signal-to-noise ratio. This information can be supported by
raising the upper and lower amplitude thresholds of the color palette and observing
signal-to-noise ratio contrast across the length of the component.
b.
The indication response is isolated from common geometrical benchmark responses
(e.g., root geometry, counterbore).
c.
The indication displays several areas of unique and inconsistent amplitude peaks.
d.
When a comparison is made between responses from a lower and higher beam angle
merges, the indication responses are at comparable or higher amplitude with the
higher beam angles.
e.
For circumferential flaws, the responses maintain good signal to noise ratio when
viewing either of the skew merges.
A-31
f.
During axial flaw scans a skew angle detects a reflector which can be contributed to
an axial component in an area adjacent to a suspect circumferential indication.
g.
The indication has defined start and end points. (May not apply to axial flaws).
h.
The indication possesses echo dynamic responses indicating reflector depth. Due to
flaw orientation this information may be displayed in the Volume Corrected Side B
Merge as a significant pattern of response displayed above and/or below the
measured material thickness.
i.
For circumferential flaws, the indication can be confirmed from the opposite side of the
weld. This information may not be available if the ultrasonic beam is required to
propagate through austenitic weld material.
j.
For axial flaws, the indication can be confirmed from alternative beam skews.
7.4.4.
The following information should be additionally considered during the evaluation of each
suspected indication in austenitic welds where access is limited to a single side and the
ultrasonic beam is required to propagate through austenitic weld material.
a.
The indication is not related to adverse conditions caused by the austenitic weld
material (e.g., beam redirect or beam steering).
b.
The shear wave and/or longitudinal wave search units show an isolated indication that
is located on the far side of the weld.
c.
The indication response is repeatable during additional or supplemental scans.
d.
The indication possesses echo dynamic responses indicating reflector depth. Due to
flaw orientation this information may be displayed in the Volume Corrected Side B
Merge as a significant pattern of response displayed above or below the measured
material thickness.
7.4.5.
Once the analyst has determined that an indication is a flaw, the following items should
be considered to determine if the flaw is surface-connected.
a.
The shear wave indication is projected at the inside surface. For axial flaws, the
indication may image beyond the inside surface.
b.
When viewing the merged B or D Scan images, there is no clear separation between
the flaw and the inside surface geometry.
c.
Indications from longitudinal wave search units have an accompanying shear wave
component signal present confirming the location detected by the L-wave component.
d.
Consideration should be given for single side examinations in austenitic materials
where the sound beam must penetrate through the weld material (far side flaws).
Determining indication surface connection may be difficult due to beam redirection
and component thickness uncertainty.
7.4.6.
a.
Circumferential Flaw Length Sizing (Ultrasonic Channels 1 & 4)
Length sizing should generally be performed utilizing 0° skew data from the
examinations performed on the same side of the weld as the indications. However, if
component geometry provides limitations (e.g., longitudinal weld obstructions, welded
A-32
attachments, etc.) or the flaw orientation provides improved and satisfactory UT
responses, then 0° skew data from opposite side examinations may be used to
provide additional information to the same side data. Also, some flaws that are of
nominally circumferential orientation are actually skewed to some degree, and in such
cases the +15° or the -15° skewed images might produce a similar or better signal-tonoise ratio as the 0° skewed images. In these cases, the +15° or -15° skewed data
may be used in conjunction with the 0° skew data to make length measurements.
b.
The flaw length shall be determined by locating and recording search unit
circumferential position at the end points where the flaw signal is no longer present
(full amplitude drop).
c.
This technique provides the outside diameter length dimension which is longer than
the actual inside diameter dimension due to pipe curvature; therefore to calculate the
flaw length at the ID surface, use the following formula:
(ID/OD) x OD flaw length dimension = ID flaw dimension.
7.4.7.
Flaw Positioning
a.
In general, the flaw shall be positioned in the axial (Y) and the circumferential (X)
direction using the data from the merge view that was used to determine the final flaw
length.
b.
Due to component geometrical configuration (tapers, radius, surface mismatches,
etc.) and/or inherent uncertainties associated with wave propagation in austenitic
materials, indication positioning may require detailed evaluation. Also, when using
shear waves for examination of piping that is less than 0.5” thick, axial and
circumferential position information may be less accurate at the 3/2-vee path than at
the ½-vee path. The following shall be considered during circumferential indication
positioning.
c.
1.
Evaluate the “Volume Corrected C” Merge image to identify common geometric
benchmark responses that may be available (e.g., root geometry or weld volume
responses). Determine if these responses are being displayed correctly in
relationship to the weld centerline.
2.
Evaluate the “Volume Corrected B and/or D” merges from both sides (upstream
and downstream) of the weld. Determine if the ultrasonic responses from the
indication appear reduced due to weld volume sound attenuation from one side or
another
All axial flaw indications shall be plotted or calculated to compensate for the ID/OD
ratio of the component.
A-33
8. DATA RECORDING
8.1.
Any indication of a suspected flaw shall be recorded regardless of amplitude.
8.2.
The following information shall be provided for each suspected flaw indication. It shall be
submitted in both hardcopy and electronic form:
8.3.
a.
Search unit identification, location, and orientation
b.
Flaw indication coordinates in the scan and index axis (circumferential position and
axial position relative to the weld centerline)
c.
Flaw length
d.
System image prints identifying the flaw and surrounding material conditions as
requested by the plant Owner. All printed or stored images should have the Palette
window visible, or should otherwise indicate any soft gain that has been applied.
The examination report shall include specific instrument/ calibration information and
examination information including a copy of the calibration and scan plan data sheets. The
minimum Examination Report information is listed below and is documented via hard copy or
electronic media (e.g. optical disks).
a.
All essential variable settings.
b.
Examination Report identification, date of calibration; date and time period of
examination(s)
c.
Examination procedure number and revision
d.
Names of examination personnel and NDE level
e.
Basic calibration block identification
f.
µTomoscan and Tomoscan III/PA model and serial numbers
g.
Applicable Software revision (Analysis, Collection, Focal Law Creation Software)
h.
Search unit configuration
i.
Wedge Part #
j.
Examination type (circumferential or axial)
k.
Focal law filename
l.
Extension cable type and length
m.
Calibration reflector type and location
n.
Couplant and batch number
o.
Record of the reference sensitivity including beam angles, skew angles
p.
Times of initial and final calibration and subsequent calibration checks
A-34
q.
Examination results (to be completed by the Data Analyst on the Indication Report)
r.
Scanning limitations encountered, with measurements to the nearest 0.10" (2.5 mm).
9. DATA COMPARISON
9.1.
In-service examination results shall be compared with available records from previous
examinations (PSI, ISI, special examinations, etc.). As a minimum, the following steps shall
be performed:
9.1.1.
Review prior data to determine the existence and location of flaw indications.
9.1.2.
Compare the location and length of flaw indications.
10. EVALUATION
10.1.
Initial evaluation of reportable indications shall be conducted in accordance with the applicable
ASME Boiler and Pressure Vessel Code, Section XI, Article IWA-3000.
10.2.
Final evaluation and disposition of reportable indications shall be the responsibility of the
customer.
11. RECORDS
11.1.
Records produced in accordance with this procedure shall be stored as specified by the
customer.
A-35
12. ESSENTIAL UT INSTRUMENT AND MOTION CONTROL SETTINGS
12.1.
For some UT setting parameters identified in lists 9A – 9K the input value may not be
accepted by the system as is. The system hardware will validate the input setting and display
an actual value. Some of the settings from this list are purposely identified as higher or lower
than the eventually displayed value. The validated value is the actual value and shall be
utilized for any recording.
List 9A- UT Settings (Main Screen)
Item
All laws
Interleaved
Linear
Required or Recommended/
Default Settings
Checked
Unchecked
Unchecked
Essential /
Non-Essential
Essential
Essential
Essential
List 9B- UT Settings (General Tab)
Item
Channel Gain
Focal Law Gain
Time base Start
Time base Range
Time base Mode
Required or Recommended/
Default Settings
Paragraph 6.5
0
0
Paragraph 5.5.4 (Paragraph 12.1)
Half path
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
List 9C- UT Settings (Gate Tab)
Item
Gate 0 Start
Gate 0 Length
Gate 1 Threshold
Gate 1 Start
Gate 1 Length
Gate 1 Threshold
Gate 1 Alarm Level
Gate 1 Data Pos 1
Gate 1 Data Amp 1
Gate 1 Type
Gate 2 Threshold
Gate 2 Start
Gate 2 Length
Gate 2 Threshold
Gate 2 Alarm Level
Gate 2 Data Pos 2
Gate 2 Data Amp 2
Gate 2 Type
Required or Recommended/
Default Settings
0
15
0
0
15
0
0
Unchecked
Unchecked
Maximum
0
0
15
0
0
Unchecked
Unchecked
Maximum
A-36
Essential /
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Essential
Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Non-Essential
Essential
Essential
Non-Essential
List 9D- UT Settings (DAC Tab)
Item
Enable
Required or Recommended/
Default Settings
Unchecked
Essential /
Non-Essential
Essential
List 9E- UT Settings (Digitizer Tab)
Item
Digitizing frequency
Averaging
Acquisition rate
Data sample size
Recurrence
Synchro
A-scan
Multi-Peak
A-Scan video
Compression
Required or Recommended/
Default Settings
12.5 MHz
1
Max Value
12 bits
2500 Hz
Pulse
Checked
Unchecked
Unchecked
4
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
List 9F- UT Settings (Pulser/Receiver Tab)
Item
Configuration
Pulser Element number
Voltage (all channels)
Pulse width
Receiver
Scale type
Rectification
High-pass
Low-pass
Smoothing
Required or Recommended/
Default Settings
Phased array pulse echo
1
200 V
333 ns
Pulser
LIN
Bipolar
0.5 MHz
5 MHz
No smoothing
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
List 9G- UT Settings (Probe Tab)
Item
Wave
Sound velocity
Probe name
Modify Probe-T (Wedge delay)
Modify Probe-T (Scan axis
offset)
Modify Probe-T (Index axis
offset)
Modify Probe-T (Refracted
angle)
Modify Probe-T (Skew angle)
Required or Recommended/
Default Settings
List 5
List 6
Probe
Paragraph 5.5.3
Paragraph 6.3.3
Essential /
Non-Essential
Essential
Essential
Non-essential
Essential
Essential
Essential
Paragraph 6.3.3
0
Essential
0
Essential
A-37
Modify Probe-R (Wedge delay)
Modify Probe-R (Scan axis
offset)
Modify Probe-R (Index axis
offset)
Modify Probe-R (Refracted
angle)
Modify Probe-R (Skew angle)
Modify Law (Wedge delay)
Modify Law (Scan axis offset)
Do Not Change
Do Not Change
Essential
Essential
Do Not Change
Essential
Do Not Change
Essential
Do Not Change
Do Not Change
Essential
Essential
Essential
Do Not Change
Modify Law (Index axis offset)
Modify Law (Refracted angle)
Modify Law (Skew angle)
Do Not Change
Do Not Change
Do Not Change
Essential
Essential
Essential
List 9H- UT Settings (Alarms Tab)
Item
Output line
Not
Not Synchro
Not Synchro
Not Gate 1
Not Gate 1
Not Gate 2
Not Gate 2
Not Gate 3
Not Gate 3
Not Gate 4
Not Gate 4
Required or Recommended/
Default Settings
Alarm 1
Unchecked
Unchecked
Unused
Unchecked
Unused
Unchecked
Unused
Unchecked
Unused
Unchecked
Unused
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
List 9I- UT Settings (I/O Tab)
Item
General outputs #1
General outputs #2
General outputs #3
General outputs #4
General outputs #5
General outputs #6
Required or Recommended/
Default Settings
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
Essential
List 9J- UT Settings (Transmitter Tab)
Item
First element
Current element
On
Delay
Required or Recommended/
Default Settings
Do Not Change
Do Not Change
Do Not Change
Do Not Change
A-38
Essential /
Non-Essential
Essential
Essential
Essential
Essential
List 9K- UT Settings (Receiver Tab)
Item
First element
Current element
On
Delay
Gain
Sum gain
12.2.
Required or Recommended/
Default Settings
Do Not Change
Do Not Change
Do Not Change
Do Not Change
Do Not Change
Do Not Change
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
Essential
The inspection settings provided in Lists 10A through 10D are specific for the UT instrument
and motion control system (including manipulator) that was qualified during performance
demonstration. Additionally, Lists 10E – 10F provide settings if a MCDU motion control
system is used. Any alternative motion control systems (including manipulators) is acceptable
for use as long as they can perform the scanning requirements identified within this procedure.
When alternative motion control systems are utilized, the requirements identified for scan and
index resolutions and scan and index speeds shall be maintained.
List 10A- Inspection Settings (Sequence Tab)
Item
Fire on
Type
Index axis preset
Range
Stop
Scan Start
Scan Stop
Scan Resolution
Scan Speed
Scan Unit
Scan Preset
Scan Preset value
Index Start
Index Stop
Index Resolution
Index Speed
Index Unit
Index Preset
Index Preset value
Required or Recommended/
Default Settings
Encoder
Bidirectional
None
Unselected
Selected
Paragraph 6.3.3
Paragraph 6.3.3
1 mm (Maximum)
Paragraph 6.4.1
Mm
Never
0
Paragraph 6.3.3
Paragraph 6.3.3
Paragraph 6.3.3
38.1 mm/s (Maximum)
Mm
Never
0
A-39
Essential /
Non-Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Essential
Non-Essential
Non-Essential
Essential
Essential
Essential
Essential
Essential
Non-Essential
Non-Essential
List 10B- Inspection Settings (Sequence Controls Tab)
Item
Use current sequence only
Show file size
Enable pause acquisition
Item
Encoder 1 Name
Required or Recommended/
Essential /
Default Settings
Non-Essential
Checked
Essential
Unchecked
Essential
Unchecked
Essential
List 10C- Inspection Settings (Encoders Tab)
Required or Recommended/
Default Settings
Any
Essential /
Non-Essential
Non-essential
Encoder 1/Wheels (Type)
Quadrature
Non-essential
Encoder 1/Wheels (Resolution)
Paragraph 4.7
Non-essential
Encoder 1/Wheels (Invert)
Paragraph 6.1.4
Non-essential
Encoder 2 Name
Any
Non-essential
Encoder 2/Arm (Type)
Quadrature
Non-essential
Encoder 2/Arm (Resolution)
Paragraph 4.7
Non-essential
Encoder 2/Arm (Invert)
Paragraph 6.1.4
Non-essential
Save
Unchecked
Non-essential
List 10D- Inspection Settings (Options Tab)
Item
Directory
Required or Recommended/
Default Settings
Any
Essential /
Non-Essential
Non-essential
Root name
Any
Non-essential
Counter value
Any
Non-essential
Prompt
Selected
Non-essential
External File
Unchecked
Non-essential
A-40
List 10E- Inspection Settings (MCDU control Tab w/ MCDU)
Item
Motor 1/Wheels (Tuning Speed)
Motor 1/Wheels (Invert polarity)
Motor 1/Wheels (Destination)
Motor 1/Wheels (Joystick)
Motor 2/Arm (Tuning Speed)
Motor 2/Arm (Invert polarity)
Motor 2/Arm (Destination)
Motor 2/Arm (Joystick)
Required or Recommended/
Default Settings
12 mm/s
See Paragraph 6.1.4
0
Unchecked
25 mm/s
See Paragraph 6.1.4
0
Unchecked
Essential /
Non-Essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
List 10F- Inspection Settings (MCDU I/O Tab w/ MCDU)
Item
Required or Recommended/
Default Settings
Essential /
Non-Essential
Motor 1/Wheels (High limit switch)
Motor 1/Wheels (Invert limit)
Motor 1/Wheels (Invert home)
Motor 1/Wheels (Invert index)
Motor 2/Arm (High limit switch)
Motor 2/Arm (Invert limit)
Motor 2/Arm (Invert home)
Motor 2/Arm (Invert index)
Relay 0
Relay 1
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Unchecked
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
Non-essential
A-41
B
APPENDIX
Receipt Inspection of Single Phased Array Probe Transducer and Wedges for Piping
Welds
A White Paper
in support of
“Procedure for Automated Single Phased-Array Probe Ultrasonic Flaw Detection and
Length Sizing in Ferritic and Austenitic Piping Welds (EPRI-SPA-1)”
This White Paper describes steps that EPRI takes to ensure proper functionality when receiving a
new phased array probe.
1
2
3
Purpose
a. This document defines a set of measurements performed by EPRI upon initial
receipt of phased array transducers and wedges.
b. The purpose of the measurements is to verify that all the array’s elements are
functioning and that they are wired to the correct pins on the array’s connector,
and to verify that the wedge produces the correct beam angles and skews, with
the correct beam exit points.
Array active element count
a. The array (without a wedge) is placed on a flat block. instrument.
b. The instrument is programmed with a special set of focal laws. The first focal law
pulses only element number 1 and receives using only element number 1. The
second law uses only element number 2. In this fashion, the number of focal
laws is equal to the number of elements, and each element has a unique focal
law.
c. The set of focal laws is executed and the resultant sector scan is recorded.
d. The sector scan is displayed. The responses of interest are the reflections from
the contact surface.
e. Record the numbers of any elements that do not produce a response. These are
the dead elements. The response amplitudes for all the active elements should
be about the same, within 6dB or so.
i. Dead elements will be apparent by the lack of any ultrasonic response.
ii. The sound path for each backwall response should be the same for all
elements.
Array active element count and wiring check
a. The array is mounted on a wedge and connected to the phased array instrument.
b. The instrument is programmed with a special set of focal laws. The first focal law
pulses only element number 1 and receives using only element number 1. The
second law uses only element number 2. In this fashion, the number of focal
laws is equal to the number of elements, and each element has a unique focal
law.
c. The set of focal laws is executed, once, in air, not coupled to any test block. The
resultant sector scan is recorded.
d. The sector scan is displayed. The responses of interest are the reflections from
the contact surface of the wedge (in air, for this test).
B-1
e. Record the numbers of any elements that do not produce a response. These are
the dead elements. The response amplitudes for all the active elements should
be about the same, within 6dB or so.
i. The responses from the elements located toward the top of the wedge
might be lower, because they have a longer plastic path; if necessary,
this measurement can be repeated without a wedge on a flat plate, using
the backwall responses to compare element amplitudes.
ii. Dead elements will be apparent by the lack of any ultrasonic response.
f. Verify that the sound paths of the wedge surface responses follow the expected
pattern.
i. For a linear array, the sound path for the element lowest on the wedge
should be the shortest. The sound path for the element highest on the
wedge should be the longest. The sound paths for all the elements
between should appear at the expected sound paths relative to the
endmost elements. If elements are mis-wired, this will be apparent in the
pattern of sound paths. An example is shown in Figure 1, which shows a
sector scan produced by two 64-element arrays that are nominally
identical, mounted on 18-degree wedges.
1. The horizontal axis of the display is time, the vertical axis is
element number, and the colors represent amplitude. The red
area at the left is the initial pulse.
2. The image contains two diagonal responses, one smooth and
one choppy. The smooth one is the response of the elements in
one of the arrays, which was wired correctly. The time step from
one element to the next is constant. The choppy one is from the
other array, which was wired incorrectly; blocks of four elements
were transposed alternately along the array. It’s immediately
apparent that the wiring is incorrect.
3. Note that the amplitude of the response from the elements
lowest on the wedge (shortest time – toward the left in the
image) is much higher than the amplitude of the elements
highest on the wedge. This is due to attenuation in the plastic,
so this test would not be appropriate for testing the constancy of
element sensitivity per item 3e(i) above.
ii. For a matrix array, the principle is the same but the pattern of sound
paths is a little more complex.
4
Wedge verification – beam skew (Method 1)
a. These steps are performed only if the array/wedge combination is intended to
perform a skewing function. This will be the case for some 2D arrays, and for
linear arrays that are mounted laterally on the wedge.
b. The array is mounted on the wedge and connected to the phased array
instrument.
c. Consider the set of beam angles and skews that the array/wedge combination
will be called upon to generate. Identify, for each beam skew, the highest and
lowest beam angles that will be used. Program the system with focal laws that
will generate these angle/skew combinations in the material of interest.
d. For each focal law (angle/skew combination) identified in step (c), perform the
following steps:
i. Set the instrument to display a live A-scan using the selected focal law.
ii. Place the probe at the center of the 4” radius of an IIW block, or
alternative reference block such as the one shown in Figure 4, of the
material of interest. Rotate the probe to obtain the response from the
radiused surface.
B-2
5
6
iii. Maximize the response by rotating the probe and adjusting its axial
position on the block.
iv. When the response is maximized, measure the skew of the probe. Here
is one good way to do this:
1. Draw a pencil line on the reference block along one edge of the
wedge.
2. Remove the wedge. Use a sliding T-bevel tool to preserve the
angle of the pencil line relative to the side of the reference block.
3. Use a protractor to measure the angle from the T-bevel.
v. Record the measured skew.
e. Make a record, such as a chart or table, of the measured skews versus the
programmed (intended) skews.
f. The RMS value of the skew errors (measured minus intended) should be less
than 3 degrees.
i. A few settings might have skew errors greater than 3 degrees. Keep
these cases in mind if these specific, higher-error focal laws will be used
in a function that requires high accuracy of skew.
ii. The average skew error should be close to zero degrees. If there is a
significantly nonzero skew error, while the RMS value of the error is
small, then the wedge is biased; it is not cut the way it was supposed to
be. Test the wedge using a flat focal law (same delay for all elements)
and an IIW block to determine what its actual angles are.
Wedge verification – beam skew (Method 2)
a. These steps are performed only if the array/wedge combination is intended to
perform a skewing function. This will be the case for some 2D arrays, and for
linear arrays that are mounted laterally on the wedge.
b. The array is mounted on the wedge and connected to the phased array
instrument.
c. Consider the set of beam angles and skews that the array/wedge combination
will be called upon to generate. Identify, for each beam skew, the highest and
lowest beam angles that will be used. Program the system with focal laws that
will generate these angle/skew combinations in the material of interest.
d. Collect ultrasonic data on a sample with skewed notches or flaws. (See Figure 5)
e. If all the skewed notches or flaws are detected then the generated skew angles
are adequate for inspection and are valid. (See Figure 6)
Wedge verification – beam angles
a. Steps b-e below are to be performed at each skew value that the probe will be
used for. If the skew angles have already been verified then steps b-e below are
to be performed at the zero degree skew value.
b. Program the instrument to generate a sector scan at a specific skew value of
interest, focusing at a specific depth of interest.
c. Place the probe on a side-drilled hole block such as the one in Figure 4. Rotate
the probe to the programmed skew value, so that the beams are pointed at the
holes.
d. Perform a single scan stroke toward the holes. Record the sector scans along
with the encoded probe position. Acquire data at a spacing of 0.1” or less. (See
Figure 7)
e. (This step contains features specific to R/Dtech’s TomoView software.) In
analysis mode, perform a volumetric merge of the data. Display the VolumeCorrected Side View of the merged data. Use cursors to measure the error in
depth position and axial position of the SDH nearest the focal depth. Record the
error.
f. The error in the measured depth position of the selected SDH should be less
than 10%, for array/wedge combinations and focal laws to be used for crack
detection and length sizing in piping. Other applications may require greater
accuracy.
B-3
Figure 1. Sector scan used for testing two 64-element arrays for correct wiring. The top half
shows the response of an array that is wired correctly; the bottom half shows the response of an
array that is wired incorrectly.
Figure 2. Sector and A-scan used for testing “single” phased array probe without wedge.
Channels 93-96 and Channels 123 to 125 are inactive by design.
B-4
Figure 3. Sector and A-scan used for testing “single” phased array probe with 30 degree wedge.
Channels 93-96 and Channels 123 to 125 are inactive by design.
B-5
Hole #
1
2
3
4
5
6
7
8
9
Figure 4. Alternative calibration block.
B-6
Location From Top (in)
0.250
0.500
0.750
1.000
1.500
2.000
2.500
3.000
3.500
Figure 5. Austenitic Weld Sample Containing EDM Notches (Notch skew angle in degrees shown above
notch).
Figure 6. Shear Wave Ultrasonic Image (Circumferential & Axial EDM Notches)
B-7
Figure 7. Scan of reference block using 45-degree shear and longitudinal waves.
Wave Mode
Shear
Shear
Shear
Shear
Shear
Shear
Longitudinal
Longitudinal
Longitudinal
Longitudinal
Longitudinal
Longitudinal
Table. Shear and Longitudinal Wave Depth Errors
Beam Angle
Hole Depth
Hole Depth Error
(deg)
(mm)
(mm)
40
25.4
-0.30
40
38.1
0.50
45
25.4
-0.10
45
38.1
-0.30
49
25.4
-1.10
49
38.1
-1.70
43
25.4
-0.42
43
38.1
-0.30
45
25.4
-0.60
45
38.1
0.41
50
25.4
-2.26
50
38.1
-0.72
B-8
Hole Depth Error
(%)
-1.2
1.3
-0.4
-0.8
-4.3
-4.5
-1.7
-0.8
-2.4
1.1
-8.9
-1.9
C
APPENDIX
Effect of De-activating Seven out of Twenty-Eight Elements of a Phased Array Probe
A White Paper
in support of
“Procedure for Automated Single Phased-Array Probe Ultrasonic Flaw Detection and Length
Sizing in Ferritic and Austenitic Piping Welds (EPRI-SPA-1)”
This White Paper is intended to serve as supporting technical information for a demonstration of the
subject procedure in accordance with ASME Code, Section XI, Appendix VIII, as administered by the
Performance Demonstration Initiative (PDI).
Introduction
Industry experience has shown that through normal wear and tear, some of the individual array elements
in a phased array system can be expected to be eventually rendered temporarily or permanently inactive.
This might occur due to decoupling of the element from the wedge, failure of the element’s electric
connections, failure of the cable connecting the element to the instrument, or failure of the pulser or
receiver that is connected to the element. Array probes and cables are expensive, so it would not be
cost-effective to consider them to be unusable if only a few of their elements are inactive. Further, it
would not be cost-effective if a series of examinations was to be considered invalid if it was found that
during the examinations a single element had become inactive. It is necessary to be able to use a
phased array system without all its array elements operating.
EPRI’s “Procedure for Automated Single Phased-Array Probe Ultrasonic Flaw Detection and Length
Sizing in Ferritic and Austenitic Piping Welds” uses arrays that have a minimum of 28 elements arranged
in a two-dimensional matrix. The initial draft of the procedure stated that each array would be still usable
if at least 21of its elements are active, and declares that the number of active elements is an essential
variable. The demonstration of this procedure in the PDI program is planned to be performed with seven
of the elements deliberately turned off.
This White Paper presents experiments that were performed before the PDI demonstration in order to
determine which seven elements should be turned off during the demonstration. The experiments
included random selections of elements, and non-random selections intended to represent worst cases.
The report concludes that different selections of inactive elements do not produce significantly different
ultrasonic examination (UT) performance.
C-1
Experiments
Selection of elements to deactivate. Array probe manufacturers indicate that there is no industry
experience of a spatial pattern in degradation of array elements with service. There is no reason to
expect any particular element or set of elements to fail earliest. For experiments performed in support of
this document, random selections of elements were made.
The procedure uses both single-array and dual-array probe configurations. In the dual configuration, if
any significant beam-shape effects are introduced by a particular selection of inactivated elements in one
array, those effects should be mitigated by convolution with the beam-shape effects of the inactive
elements in the other array, which would presumably have a different pattern. In the single-array case,
the transmitting set of elements is the same as the receiving set of elements, so any beam-shape effects
will be maximized. Therefore, the single-array probe is the conservative case and was selected for this
investigation. This probe is used for detecting axially-oriented flaws.
In addition to the random selections of elements, the probable worst-case selection was investigated.
The row of elements nearest the weld was turned off, which has the effect of moving the beam index
away from the weld. Proximity of the beam index to the weld crown is known to be an essential
parameter for detection of axial IGSCC. No other selection of inactive elements could have as large a
negative effect on index position.
Setup. The single probe array was mounted on a wedge designed for detection of axial cracking. The
TomoScan III/PA instrument driving the probe was programmed to execute the electronic scan pattern
defined in the procedure. This electronic scan pattern includes 11 beam angles from 35° to 60°, each
produced at four skew angles from 35° to 67.5°, for a total of 55 shear beams produced at each probe
position. An austenitic pipe sample containing a Non-IGSCC axially oriented flaw was fitted with a track
for automated scanning.
Experimental design. Two different random selections of array elements were prepared using a random
number generator function in Microsoft Excel. As a worst-case non-random selection, the entire front row
of seven elements would be turned off. Finally, as a control case, a setup was prepared with no inactive
elements. Selected elements were deactivated by software control.
The programming necessary to generate a single, specific beam is called a “focal law.” All the focal laws
and scan parameters for this experiment were calculated assuming that all the elements were functional.
It would have been possible to optimize individually for each case, but in the interest of simplicity and
conservatism this was not done.
Expected results. It is expected that the effect of turning off a few elements would be to cause a loss in
sensitivity according to the reduction in radiating area:
Effect = 2 * 20 * log(21/28) = -5.0 dB
The factor of 2 accounts for the losses incurred in both transmission and reception.
It is not expected that the beam direction would be affected significantly. It is useful to think first of the
analogous situation in conventional probes, which is a partial decoupling of the transducer from the
wedge. If, for example, the transducer in a 60° probe is partially decoupled from the wedge, it’s still a 60°
probe; the only thing that has changed is the shape of the effective radiator. The angle would no more be
expected to change with this coupling degradation than it would be expected to change if a round crystal
was replaced by a square one. The determining factor is the shape of the wedge, not the shape of the
radiator.
C-2
In the case of a phased array probe, the beam direction is controlled by adjusting individually the pulse
and reception delays of each array element. Adjusting these delays is exactly analogous to changing the
angle of the wedge -- a wedge is a mechanical means of selectively delaying different parts of the sound
beam, while a phased array instrument is an electronic means of doing the same thing. For an array on
any specific wedge, using any specific focal law, turning off a few elements changes only the shape of
the radiator, not the effect of either the mechanical (wedge) or the electronic (delay law) controls on the
beam direction.
The effect of the proposed worst-case element selection would be to move the beam index farther from
the weld crown toe. It is not expected that this shift would influence the detection capability for axial
flaws.
Actual results. The data was analyzed using the Volumetric Merge function of the TomoView software.
Data from individual beam directions is not viewed individually; rather, the analyst views images
constructed using all the beam angles at once. This is the analysis method employed by the procedure.
Flaw images created using the reference case (all elements active), case 1 (random seven), case 2
(random seven), and case 3 (front seven) selections of inactive array elements are shown in the Figure 1
below respectively from top to bottom. Comparisons between the reference and inactive element cases
can also be found in Figures 2a though 2c at the end of this report. For each “VC-Side” image, the
“contour” tool was used to determine the maximum amplitude, the axial position at the maximum
amplitude, the circumferential position at the maximum amplitude, and the depth position at the maximum
amplitude in the area of the flaw. All the “VC-Side” images are shown with 9.0 dB of soft gain for display
purposes.
The images obtained using random selections of inactive elements (case 1 & case 2) are virtually
identical to one another. Differences in individual pixels can be identified, and the position of the
reflector’s maximum varies by a pixel sometimes, but these deviations are no greater than the normal
unrepeatibility of inspection results using any ultrasonic technology, and are not significant in terms of the
procedure’s objectives, which are to identify and size flaws. The effect of turning off the front row of
elements (case 3), the non-random selection that was expected to be the most conservative. The ability
to image the axial flaw was not affected. The calculated position of the reflector was not noticeably
affected in the axial direction, because of the change in the beam index position when the front row of
elements is deactivated.
C-3
Figure1. Reference, Case 1, Case 2, and Case 3 Inactive Elements Images
The quantitative effect of the different selections of inactive elements is shown in the table below.
Table. Inactive Elements Quantitative Results
Deviation from reference case (all elements turned on)
Inactive Element
Amplitude (dB) Axial position (mm) Circ. Position (mm) Depth (mm)
Random 7 (Case 1)
-4.2
0.50
0.00
1.00
Random 7 (Case 2)
-3.6
0.00
-1.00
0.50
Front 7 (Case 3)
-1.6
0.00
-1.00
0.50
Average
-3.1
0.17
-0.67
0.67
The maximum deviation in axial position of 0.5 mm is actually seen in the first random selection (case 1).
This will have no effect on data analysis, since all features in the data are offset by the same amount, and
therefore the spatial features used for flaw discrimination are not affected.
The theoretical amount of dB loss form deactivating seven out of twenty-eight elements is 5.0 dB. The
maximum dB loss (4.2 dB) can be seen from case 1. This dB loss should not impact flaw detection or
sizing because the acquisition system has 24 dB of dynamic range when collecting 12-bit data. Therefore
more bits are used to represent the amplitude of the signal (as compared to 8-bit data) and the operator is
able to scan at a lower gain setting. The color palette control can then be used in analysis to add a
sufficient amount of “soft gain” for flaw detection and sizing. As a result, setting the gain level to 4.2 dB
below the scanning sensitivity should not influence the final results.
C-4
Conclusions
EPRI makes the following conclusions based on the data presented above:
•
•
•
•
The loss of seven out of twenty-eight elements does not significantly affect detection and sizing
results.
It doesn’t matter which seven are lost.
The only significant effect of element loss is loss of sensitivity according to radiating area. This
sensitivity loss is expected to be no more than 5.0 dB.
The 24 dB dynamic range of 12-bit data and the color palette can be used during analysis to help
compensate for a 5.0 dB loss.
Recommendations
EPRI makes the following recommendations:
•
•
The PDI demonstration of this procedure should be performed with seven elements of each array
deliberately inactivated. A successful demonstration would qualify the procedure for use as long
as each array has no more than seven inactive elements.1
PDI should select promptly, or should promptly allow EPRI to select, the specific elements that
will be inactivated for the demonstration. EPRI suggests using the worst-case selection shown
above (case 1). EPRI would like to enter the qualification with data acquisition setups already
prepared, and they can’t be prepared until it’s known which elements must be turned off.
1
The only way to intentionally de-activate selected elements is by software control. The instructions that control the
elements is in the data acquisition setup file. The setup files used in the demonstration will be saved by PDI as part
of the demonstration records. It is important to note that any time the procedure will be used in the field, it would
not use the exact same setup files as were used during the demonstration, because of course it would not be desirable
to perform inspections with good elements deliberately shut off.
C-5
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
Reference Case (All Elements
On)
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
Case 1 (Random 7
Off)
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
Reference Case (All Elements
On)
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
Case 2 (Random 7
Off)
Figure 2a. Effect of deactivating
seven of the 28 elements (Reference versus Case 1). Case 1 random selection of seven deactivated
elements are shown, along with the reference case (all elements on). Inactive elements indicated in red.
Figure 2b. Effect of deactivating
seven of the 28 elements (Reference versus Case 2). Case 2 random selection of seven deactivated
elements are shown, along with the reference case (all elements on). Inactive elements indicated in red.
C-6
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
Reference Case (All Elements
On)
1
2
3
4
8
9 10 11
15 16 17 18
22 23 24 25
Case 3 (Front 7 Off)
5
12
19
26
6
13
20
27
7
14
21
28
Figure 2c. Effect of deactivating
seven of the 28 elements (Reference versus Case 3). Case 3 front row of seven deactivated
elements are shown, along with the reference case (all elements on). Inactive elements indicated in red.
C-7
WARNING: This Document contains information
classified under U.S. Export control regulations as
restricted from export outside the United States.
You are under an obligation to ensure that you
have a legal right to obtain access to this
information and to ensure that you obtain an
export license prior to any re-export of this
information. Special restrictions apply to access by
anyone that is not a United States citizen or a
permanent United States resident. For further
information regarding your obligations, please see
the information contained below in the section
entitled “Export Control Restrictions.”
Export Control Restrictions
Access to and use of EPRI Intellectual Property is
granted with the specific understanding and requirement
that responsibility for ensuring full compliance with all
applicable U.S. and foreign export laws and regulations
is being undertaken by you and your company. This
includes an obligation to ensure that any individual
receiving access hereunder who is not a U.S. citizen or
permanent U.S. resident is permitted access under
applicable U.S. and foreign export laws and regulations.
In the event you are uncertain whether you or your
company may lawfully obtain access to this EPRI
Intellectual Property, you acknowledge that it is your
obligation to consult with your company’s legal counsel
to determine whether this access is lawful. Although
EPRI may make available on a case-by-case basis an
informal assessment of the applicable U.S. export
classification for specific EPRI Intellectual Property, you
and your company acknowledge that this assessment is
solely for informational purposes and not for reliance
purposes. You and your company acknowledge that it is
still the obligation of you and your company to make
your own assessment of the applicable U.S. export
classification and ensure compliance accordingly. You
and your company understand and acknowledge your
obligations to make a prompt report to EPRI and the
appropriate authorities regarding any access to or use of
EPRI Intellectual Property hereunder that may be in
violation of applicable U.S. or foreign export laws or
regulations.
The Electric Power Research Institute (EPRI)
The Electric Power Research Institute (EPRI), with
major locations in Palo Alto, California, and Charlotte,
North Carolina, was established in 1973 as an
independent, nonprofit center for public interest
energy and environmental research. EPRI brings
together members, participants, the Institute’s
scientists and engineers, and other leading experts to
work collaboratively on solutions to the challenges of
electric power. These solutions span nearly every
area of electricity generation, delivery, and use,
including health, safety, and environment. EPRI’s
members represent over 90% of the electricity
generated in the United States. International
participation represents nearly 15% of EPRI’s total
research, development, and demonstration program.
Together…Shaping the Future of Electricity
© 2006 Electric Power Research Institute (EPRI), Inc. All rights
reserved. Electric Power Research Institute and EPRI are registered
service marks of the Electric Power Research Institute, Inc.
Printed on recycled paper in the United States of America
Electric Power Research Institute
3420 Hillview Avenue, Palo Alto, California 94304-1338 • PO Box 10412, Palo Alto, California 94303-0813 • USA
800.313.3774 • 650.855.2121 • askepri@epri.com • www.epri.com
1014656