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Introduction to Phased Array Using the OmniScan MX2 - Part Four
The document outlines the training program for the OmniScan MX2 phased array, focusing on setup, calibration, and encoded inspection techniques. It details various scanning methods, analysis procedures, and flaw characterization techniques used in ultrasonic testing. Key highlights include the use of encoders for probe positioning, amplitude and length sizing for flaw detection, and specific analysis methods related to different codes and applications.
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Introduction to Phased Array Using the OmniScan MX2 - Part Four
- 1. OmniScan MX2 TrainingProgram Introduction to Phased Array Using the OmniScan MX2 Part 4 Please send questions and comments to: [email protected]
- 2. Intro to PhasedArray Part 4 – Overview and Review. Ø Ø Ø Ø Setup and calibration of S-scan. Preparation for an encoded inspection. Analysis overview and flaw characterization. Sizing and characterization examples.
- 3. Intro to PhasedArray Part 4 – Encoded Inspection Ø Ø 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. 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. 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.
- 4. Intro to PhasedArray Part 4 – Encoded Inspection cont. Ø Ø The scan menu is where encoders, scanners and their associated parameters are configured for the inspection. 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. 4
- 5. Intro to PhasedArray Part 4 – Encoded Inspection One Line scan Ø Ø The one line scan can be used with either a time or encoder inspection. 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. Scan axis 5
- 6. Ø Intro to PhasedArray Part 4 – Encoded Inspection cont. HSMT Flex (1 axis) HSMT X03 (1 axis) HSMT Compact (1 axis) Cobra (1 axis) Chain Scanner (2 axis) WeldROVER (1 axis)
- 7. Intro to PhasedArray Part 4 – Encoded Inspection cont. Ø Ø Ø In a raster scan either encoder 1 or 2 can be assigned to monitor the scan axis. The MX2 has two encoder inputs. Whichever encoder is selected as the scan axis, the other encoder is assumed to be the index axis. In the example below, encoder 1 is assigned to the scan axis (Wheels) and encoder 2 assigned to the index (Arm). 7 Scan axis1 Encoder is Index ax 2 Encoder
- 8. Intro to PhasedArray Part 4 – Encoded Inspection cont. Ø Ø 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) 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. This creates a bi-directional inspection (C-scan) where the operator must manually control the index axis. Index axis stroke 2 Index axis stroke 1 Scan axis 8
- 9. Intro to PhasedArray Part 4 – Encoded Inspection cont. Ø Ø The encoder origin position is used to set the encoder position when preset is selected or if configured on the start acquisition button. The preset is typically zero but can be preset for recording a series of different acquisitions. (0-100mm, 100-200mm, 200-300mm, etc.) 9
- 10. Intro to PhasedArray Part 4 – Movie of Encoded Inspection
- 11. Intro to PhasedArray Part 4 – Analysis Overview Ø Ø Ø 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.) Depending on the procedure or referencing code, one or more of the above are required to make an acceptreject decision. 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. Position C-scan analysis is covered in specific sections for corrosion mapping and composite inspection.
- 12. Intro to PhasedArray 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.
- 13. Intro to PhasedArray 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.
- 14. Intro to PhasedArray 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 GateAlarm>Gates>Parameters>Mode>Peak Selection. Ø The % amplitude reading is available for both gate A (Red) or gate B (Green).
- 15. Intro to PhasedArray 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. 15
- 16. Intro to PhasedArray Part 4 – Amplitude Analysis – Amplitude C-scan Focal laws 45-70 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 Cscan for weld inspection is data screening and flaw length sizing. Scan Axis (Probe movement)
- 17. Intro to PhasedArray 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 17
- 18. Intro to PhasedArray 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.
- 19. Intro to PhasedArray 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 19
- 20. Intro to PhasedArray 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.
- 21. Intro to PhasedArray Part 4 – Flaw DepthHeight 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) UT axis Reference cursor Measure cursor UT axis Reference cursor Measure cursor
- 22. Intro to PhasedArray Part 4 – Flaw DepthHeight 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.
- 23. Intro to PhasedArray Part 4 – Flaw DepthHeight 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)
- 24. Intro to PhasedArray Part 4 – Flaw DepthHeight 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 Ø Measure the center of the energy at the peaked position. Do not attempt to read the scales. Use gate readings and cursors for precision measurements and flaw reporting.
- 25. OmniScan MX2 Training– Flaw DepthHeight 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. 10L32-A1 probe SA1N60L wedge Ø Ø 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) CE1 (Collateral echo 1) is the mode converted shear wave signal (30-70-70) that is skipping into the crack on the second leg. CE2 (Collateral echo 2) when present indicates that the crack is connected to the inner surface. KK WSY and Panametrics CTS Scan axis clock scan L-wave crack tip signal CE2 L-wave Crack tip signals CE1
- 26. Intro to PhasedArray Part 4 – Flaw DepthHeight 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
- 27. Intro to PhasedArray 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 7.96mm -3.88mm Inadequate penetration at weld CL
- 28. Intro to PhasedArray 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 28
- 29. Intro to PhasedArray 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 Ascan 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. Porosity (Volumetric defect) Side wall lack of fusion (Planer defect)
- 30. 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
- 31. Thank You! Please sendquestions and comments to: [email protected] www.olympus-ims.com