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Phased Array ScanningTwo Types
Linear ScanningSectorial Scanning
Both describe how the elements within the array are pulsed to
create the desired acoustic beamNot to be confused with Scan
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Linear Scanning (Electronic Scan)Linear scanning is sometimes
referred to electronic scanning Is the ability to move the acoustic
beam along the axis of the array without any mechanical
movement.The beam movement is performed by time multiplexing of the
active elements across the probe aperture (ie. Electronic
scanning)Scanning extent is limited by:number of elements in
arraynumber of channels in acquisition system
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Linear ScanningSIVERT GROUP OF COMPANIESUseful for inspection of
welds without having to move or raster the probe.Numerous angle
scans can be generated across a probes aperture during a single
scan
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Sectorial ScanningSectorial scanning has the ability to scan a
complete sector of volume without any probe movement.Useful for
inspection of complex geometries, or those with space
restrictionsCombines the advantages of a wide beam and/or multiple
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Sectorial ScanningA specific number of elements (Aperture) is
defined to be used for a specific beam angle (focal law)For every
angle beam generated the entire defined element aperture is fired
to a specified time delay (focal law) Numerous beam angles are used
for coverage area during scanning. Example -30to 30 for
volumetricExample 45 to 70 for weld inspection
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DelaysSectorial Scanning
Weld Inspection
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Phased Array Scanning PhilosophySelect arrays to give adequate
coverage; need to ensure HAZ and weld zone coveredScan weld in
parallel linear motion, -> much faster.SIVERT GROUP OF COMPANIES
Left: conventional raster scan Right: phased array scan
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Probe & Wedge DesignationsProbe 5L64-A25 = 5MHzL = Linear
Array64 = # of ElementsA2 = CasingWedgeSA2-N55SSA2 = Probe CasingN
= Normal Orientation55S = 55 Optimal Refracted Shear WaveSIVERT
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Number of ElementsThe quantity of elements in a phased-array
probe is always a compromise between:Desired working range of the
probeFocusing capabilitySteering capabilityElectronic system
capabilityCost
For example, to create a probe with a large working range and a
large steering capability, a large amount of elements will be
needed, which might exceed the electronic capability of the system,
or the budget.
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ApertureDirect effect on the working range of the probe ie. Near
Field
The Near Field obtained by a probe will have a direct effect on
the focusing limitations of the probe.
Large apertures enable the ability to inspect large volumes of
area without any probe movement.SIVERT GROUP OF COMPANIES
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Phased Arrays Working RangeThe working range of the probe is the
range where the probe can be used to perform inspection.
The concept of near-field inspections: A phased-array probe can
focus within its near-field only.
All phased array inspection must be performed within the near
field, this allows for the focusing of the beam SIVERT GROUP OF
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Screen SetupThree views are generally used for detection and
evaluation on the acquisition unit.
Sectoral View: used to detect signals in the weld volume area of
interest.
A-Scan View: used for signal amplitude responses
C-Scan View: used for locating indications throughout the
recorded scan length. SIVERT GROUP OF COMPANIES
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Screen Setup S Scan
Skip & weld centerline cursors are set on the Sectoral view
after being inputted in part parameter setup.
S-Scan viewing area can then be used to ensure complete coverage
of weld volume and HAZ is achieved. This can be easily checked with
cursors
S-scan can then be used to determine signal location in regards
to depth and axial location for interpretation purposes
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Screen Setup
A-ScanTCG and sensitivity are set using A-Scan responseSignal
amplitude height for accept reject criteria is checked on
A-Scan.Signal response also used for interpretation
purposesC-ScanViewing area for C-Scan is set on the S scans using
the gate function. C-Scan gate is set to cover the weld volume from
root to cap regionIndications throughout the scan length can then
be detected and measured for length.
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Different scanning viewsSIVERT GROUP OF COMPANIES
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CalibrationsWedge Delay and Sensitivity Calibrations
PerformedNote: In most cases wedge delay is not necessary. This is
due to the high quality of probe and wedge manufacturingThin wall
materials will not require a wedge delay
TCG is performed across the entire area of interest.A 2 point
TCG is sufficient for one line scan weld inspection
Calibration and setup parameters are then saved as a setup file
on the storage card Setup files can then be opened at a later date
to use for that particular inspection
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Weld MeasurementsPipe Thickness This will be entered as the part
thickness prior to inspectionWill ensure correct skip cursors are
placed on S-Scan for indication locating and interpretation
Weld WidthThis is necessary to ensure complete coverage of the
weld volume and HAZ is achieved with the preset offset.Will also
aid in location of indications and interpretation
Note: Both measurements are to be recorded along to aid in later
analysis and repeatability of scan results.
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General Weld Visually Examined Weld to be checked throughout its
entire length for any anomaliesI.e. Undercut, Stop/Start, Weld
Spatter, Mismatch etc
Record the Following:Scan StartScan DirectionLocation ie N, S,
W, E, pipeside, tee, elbow etc.
Note: All recorded info are to be recorded to aid in later
analysis and repeatability of scan results.
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