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OmniScan MX2 Training Program Introduction to Phased Array Using the OmniScan MX2
Part 4
Please send questions and comments to: [email protected]
Intro to Phased Array Part 4 – Overview and Review.
Ø Setup and calibration of S-scan. Ø Preparation for an encoded inspection. Ø Analysis overview and flaw characterization. Ø Sizing and characterization examples.
Intro to Phased Array Part 4 – Encoded Inspection
Ø Encoders and scanners come in all shapes and sizes and are typically purchased based on the application requirements for geometry, precision, durability and speed.
Ø Encoders and scanners allow the position and orientation of the probe in one or two axis to be recorded with the MX2 phased array data allowing 2D data views such as a B-scan and C-scan.
Ø Encoded scanners can be as simple as a small wheel connected to the probe or a complex multi probe scanner with multi axis capability controlled from a computer or PLC.
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Intro to Phased Array Part 4 – Encoded Inspection cont.
Ø The scan menu is where encoders, scanners and their associated parameters are configured for the inspection.
Ø These parameters are typically configured last after the group has been created with the wizards, the UT settings have been configured, and all required calibrations completed.
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Intro to Phased Array Part 4 – Encoded Inspection One Line scan
Scan axis
Ø The one line scan can be used with either a time or encoder inspection. Ø Although a one line scan only requires a single encoder, it could have
been wired in the interface cable for either encoder 1 or 2.
Ø Intro to Phased Array Part 4 – Encoded Inspection cont. HSMT Flex (1 axis) Chain Scanner (2 axis) HSMT X03 (1 axis)
HSMT Compact (1 axis) WeldROVER (1 axis)
Cobra (1 axis)
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Intro to Phased Array Part 4 – Encoded Inspection cont.
Ø In a raster scan either encoder 1 or 2 can be assigned to monitor the scan axis.
Ø The MX2 has two encoder inputs. Whichever encoder is selected as the scan axis, the other encoder is assumed to be the index axis.
Ø In the example below, encoder 1 is assigned to the scan axis (Wheels) and encoder 2 assigned to the index (Arm).
Scan axis
Index axis Encoder 2 Encoder 1
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Intro to Phased Array Part 4 – Encoded Inspection cont.
Ø In the raster scan pictured below, the scan axis is assigned to encoder 1 (Wheel) and the index axis is assigned to encoder 2 (Clicker)
Ø The probe is moved along the scan axis, then the operator repositions the probe for the next “Stroke” and presets the C-scan on the index axis by selecting the clicker button.
Ø This creates a bi-directional inspection (C-scan) where the operator must manually control the index axis.
Scan axis
Index axis stroke 2
Index axis stroke 1
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Intro to Phased Array Part 4 – Encoded Inspection cont.
Ø The encoder origin position is used to set the encoder position when preset is selected or if configured on the start acquisition button.
Ø The preset is typically zero but can be preset for recording a series of different acquisitions. (0-100mm, 100-200mm, 200-300mm, etc.)
Intro to Phased Array Part 4 – Movie of Encoded Inspection
Intro to Phased Array Part 4 – Analysis Overview
Ø The phased array analysis section is divided into the following tasks or measurements: Ø Amplitude analysis. Ø Length sizing. Ø Depth and height sizing. Ø Volumetric position. Ø Flaw characterization. (Geometry, crack, LOF, IP, porosity, etc.)
Ø Depending on the procedure or referencing code, one or more of the above are required to make an accept\reject decision.
Ø Both the type of analysis required and the level of precision are directly related to the inspection setup, up front engineering, calibration criticality, and ultimately cost.
Ø Position C-scan analysis is covered in specific sections for corrosion mapping and composite inspection.
Intro to Phased Array Part 4 – Analysis Overview cont.
Ø The AWS D1.5 inspection is an example of an inspection code that only requires amplitude and length sizing for an indication determined not to be geometry. See AWS section for more details.
Intro to Phased Array Part 4 – Analysis Overview cont. Ø The phased array analysis consists of the following tasks and measurements:
Ø Amplitude analysis. Ø Length sizing. Ø Depth and height sizing. Ø Volumetric position. Ø Flaw characterization. Ø ASME sec VIII Div. 2 pressure vessel inspection is an example of an inspection
code that requires all of the above for flaw analysis.
Intro to Phased Array Part 4 – Amplitude Analysis – A% Readings
Ø The A% reading is the peak amplitude detected in gate A. Ø The A% reading is available for either the maximum peak (E as pictured
below) or first peak (D as below) detected in the gate as configured in Gate\Alarm>Gates>Parameters>Mode>Peak Selection.
Ø The % amplitude reading is available for both gate A (Red) or gate B (Green).
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Intro to Phased Array Part 4 – Amplitude Analysis – AdBCurve Reading
Ø The AdBCurve reading calculates the difference between the peak amplitude signal in gate A and the sizing curve level. (UT>Advanced>Reference Amplitude>Typically 80%)
Ø This reading is available for both gate A (AdBCurve) and gate B (BdBCurve). Ø In the below example of inadequate penetration the reference sensitivity was
calibrated to 80% amplitude using a notch in a piping calibration block. Ø The AdBCurve reading indicates that the 99.8% amplitude signal in gate A is 1.9
dB over the reference sensitivity of 80%. A negative number would indicate below the reference curve.
Intro to Phased Array Part 4 – Amplitude Analysis – Amplitude C-scan Ø For the S-scan weld inspection, the
amplitude C-scan is defined by the vertical focal law axis and the horizontal scan axis. (Focal laws 45-70 vs. probe movement)
Ø For each focal law, the pixel color is determined by the peak amplitude signal in gate A for that position on the scan axis. 1 pixel = 1 A-scan.
Ø The primary function of the amplitude C-scan for weld inspection is data screening and flaw length sizing.
Scan Axis (Probe movement)
Foca
l law
s 45
-70
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Intro to Phased Array Part 4 – Flaw Length Sizing Ø In the example of intermittent side wall lack of fusion (SWLF) below, the flaw
length is visualized on the C-scan and the cursors are positioned at the extremities.
Ø In this example the -6 dB drop would not result in an accurate flaw length because it is intermittent.
34.5mm
Intro to Phased Array Part 4 – ASME Flaw Length Sizing
Ø The expected flaw length sizing accuracy is typically specified as the inspection resolution in the referencing code or procedure. ASME Sec V Art 4 (2010 Edition) requires a 1mm inspection resolution for materials under 3 inches and 2mm resolution for materials over 3 inches.
Ø This would result in flaw length sizing accuracies of +\- 2mm and +\- 4mm.
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Intro to Phased Array Part 4 – Flaw Length Sizing w/ Curved Arrays
Ø Length sizing accuracy is greatly improved by the use of internally focused curved arrays, especially on small diameter piping where the reflected signal is skipping off a small curved spot on the pipe’s inner diameter surface.
Ø Both the Olympus Cobra small diameter piping system and Pipe Wizard pipeline girth weld system utilize 1D internally focused curved arrays for improved length sizing accuracy.
C-scan length sizing with flat probe. S(m-r) = 4.2mm
C-scan length sizing with internal radius focused probe. S(m-r) = 2.4mm
Intro to Phased Array Part 4 – TOFD for Improved Length sizing
Ø Phased array inspection techniques are often complimented with TOFD. Ø TOFD is particularly beneficial for increased length and depth sizing accuracy to
compliment amplitude based pulse-echo inspections. Ø TOFD is covered in detail in a later section.
OmniScan MX2 data displayed in Tomoview 2.9 for offline analysis. Volume merge C-scan and TOFD B-scan.
Intro to Phased Array Part 4 – Flaw Depth\Height Sizing Cursors
Ø In a typical weld inspection, flaw depth and height sizing is performed on the UT axis using the A-scan, B-scan, and S-scan.
Ø The three cursors used for flaw depth and height sizing are: – Data cursor. Used to visualize the A-scan and S-scan at a given position on the scan axis. – UT axis reference cursor. U(r) – UT axis measure cursor. U(m)
Reference cursor
Measure cursor
UT axis
UT axis
Reference cursor
Measure cursor
Intro to Phased Array Part 4 – Flaw Depth\Height Sizing - Angle Resolution
Ø The ability to both size and characterize flaws is dependent on the on the inspection strategy with regard to probe frequency, angle resolution (.5, 1, 2 degrees), probe aperture, beam focus (Near field), UT axis point quantity.
Ø This is especially important in a line scan from one index position where the probe cannot be skewed and repositioned for flaw signal optimization.
Intro to Phased Array Part 4 – Flaw Depth\Height Sizing - Tip Diffraction
Ø The shear wave dip diffraction technique is commonly used for crack detection and sizing and is not dependent on amplitude.
Ø Low level signals can indicate crack tips and in greatly assist in precision measurement, even if not noticeable in the C-scan.
Ø Move the data cursor while visualizing the S-scan and use the UT axis cursor to establish the deepest detected crack tip. (Pictured below at 7.96mm deep measured from the OD, and 4.54mm as measured from the ID)
Intro to Phased Array Part 4 – Flaw Depth\Height Sizing - A-scan Envelope
Ø Saving the MX2 data file with the A-scan envelope enabled assists in peaking crack tips for precision measurement.
Ø Visualize the UT axis reference cursor in the S-scan positioned at 12.42mm while manipulating the data cursor on the scan axis. Find the deepest tip signal that can clearly be differentiated from background noise.
Ø With the focal law displayed on the A-scan (60.5 degrees), peak the signal using the envelope and measure with the cursor in the center of the energy. (12.42mm below)
Ø Measure the center of the energy at the peaked position.
Ø Do not attempt to read the scales. Use gate readings and cursors for precision measurements and flaw reporting.
OmniScan MX2 Training – Flaw Depth\Height Sizing – ID Creeping Wave Ø In the example below, a phased array version of a WSY creeping wave inspection
was performed with a 55-72 degree S-scan on the clock (No encoder) for depth and height sizing of an ID connected crack.
Scan axis clock scan
Ø The 70 L-wave is peaked at 7.77mm in gate B for the through wall dimension of the deepest crack tip. (DB reading)
Ø CE1 (Collateral echo 1) is the mode converted shear wave signal (30-70-70) that is skipping into the crack on the second leg.
Ø CE2 (Collateral echo 2) when present indicates that the crack is connected to the inner surface.
L-wave Crack tip signals
L-wave crack tip signal
CE1
CE2
10L32-A1 probe SA1N60L wedge
KK WSY and Panametrics CTS
Intro to Phased Array Part 4 – Flaw Depth\Height Sizing - Volumetric Position
Ø Weld overlays are the primary indicator for determining volumetric flaw position. Ø Using the part and weld wizard almost any symmetrical or asymmetrical weld can
be created and displayed on the S-scan.
Ø The weld overlays should be considered close approximations when used to determine flaw location. The overlay is dependent on the scanner or manual probe position being maintained or entered with a high level of precision for them to be useful.
Slag Inadequate penetration OD connected crack
Intro to Phased Array Part 4 – Volumetric Position - VIA Reading
Ø The VIA reading displays the distance between the weld centerline and the maximum amplitude signal in gate A (VIA) or gate B (VIB).
Ø VIA is short for volumetric position on the index axis of the signal in gate A. It is expressed either (-) or positive relative to the weld centerline.
Ø The VIA and DA readings are the primary indicators for excavating a flaw for the repair. (Where to dig and how deep)
ID connected crack -3.88mm from weld CL Inadequate penetration at weld CL
-3.88mm
7.96mm
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Intro to Phased Array Part 4 – A-scan Flaw Characterization Ø Volumetric flaws have a very different appearance than planer flaws, and like in the
A-scan data view, the phased array view can differentiate between the two based on their appearance.
Ø Planer flaws such as root non fusion and side wall lack of fusion or geometry are indicated by a short A-scan rise and fall time or short ”Echo dynamic” similarly to an ID notch or radius reflector.
Ø Volumetric flaws like slag and porosity will have an A-scan long rise and fall time with multiple peaks.
A-scan planer indication A-scan volumetric indication
Intro to Phased Array Part 4 – Flaw S-scan Characterization
Ø Volumetric flaws have a different appearance from planer flaws, and like in the A-scan data view, the phased array view can differentiate between the two based on their signal characterization.
Ø All of the A-scan data is available in the S-scan. Nothing is lost. It is simply a view that allows multiple A-scan interpretation in one display.
Ø While visualizing the S-scan, start to imagine what the corresponding A-scan will look like for any given focal law.
Ø Note jagged, multi-faceted appearance vs. clean sharp indications.
Ø Short echo dynamic (A-scan rise and fall time) vs. long.
Side wall lack of fusion (Planer defect)
Porosity (Volumetric defect)
OmniScan MX2 Training – Analysis – Flaw Characterization Ø Max amplitude (A%) = 61.1%
measured on 61 degree focal law at 50mm on scan axis
Ø Depth (DA) = 8.68mm Ø Volume pos. (VIA) = .76mm Ø Height (Um-r) = 4.89mm Ø Scan start (Sr) = 44mm Ø Scan stop (Sm) = 55mm Ø Scan max (Data cursor) = 50mm Ø Length (Sm-r) = 11mm Ø Embedded Ø Flaw type = Porosity
