PAUT,TOFD,AUT In Lieu of RT
Pars Leading Inspection Co. Presented By: Behrouz Piranfar
9/10/2013
Techniques
Time Of Flight Diffraction (TOFD)
Contents
How it works Typical TOFD Display Defect Analysis Defect Example Application Advantage
Principle of TOFD
Transmitter
Receiver Lateral wave Upper tip Lower tip
Back-wall reflection Time-Of-Flight Diffraction (TOFD) relies on the diffraction of ultrasonic energies from 'corners' and 'ends' of internal structures (primarily defects) in a component being tested using a set of two probes.
How it works
DEFECT
PROBE
Reflection
Back
How it works
DEFECT
PROBE
Diffraction
How it works
Rx
Tx
DEFECT
Diffraction
How it works
Practically
Rx
Tx
How it works
Rx
Tx
Lateral wave + Pos
Amplitud dB
Tiemper ms
- Neg
How it works
Rx
Tx
Signal Diffracted
+ Pos
Amplitud dB
Tiemper ms
- Neg
How it works
Rx
Tx
Reflection From Back wall
+ Pos
Amplitud dB
Tiemper ms
- Neg
How it works
Data Collection 6 5 4 3 2 1 Rx
Tx
How it works
Phase Reversal + Pos
Amplitude dB
- Neg
Time = µ seconds or Millimetres
How it works
Greyscale Image Presentation
Depth
Lenght
Typical TOFD Display
Defect Analysis with Cursors
Use of cursors on top and bottom of defect to size the defect
Example – Near–Surface Breaking Defect
Lateral wave blocked Sizing by measuring crack tip
Example – Mid-wall Defect No break in lateral wave or back wall Top and bottom signals visible (if defect deep enough) Can measure lengths using hyperbolic cursors
Example – Lack of Root Penetration
Sometimes see break in back wall signal Defect can be sized using time-of-arrival Similar to other root defects
Example – Lack of Sidewall Fusion
Should see no perturbations in lateral wave or Back wall In this case, top signal is “buried” in lateral (OD) wave Can size easier if signals are clear.
Example - Porosity
Multiple small reflectors, each with hyperbolic tails. Usually can characterize, but sizing difficult.
Example – Transverse Cracks
Transverse cracks are rare, and similar to porosity, No perturbation of lateral or back wall
Example – Internal Lack of Fusion
•
Strong signal but height measurement difficult
Applications Critical plant items in construction and in-service Pressure Systems – Vessels, pipelines, pipe-work Storage facilities – Tanks, spheres Tube Vessels - Boilers, Heat Exchangers, Condensers High Temperature Inspection Up to 480˚C
Service induced defects & structural damage Corrosion/erosion profiling - especially weld root erosion Thick wall components > 300mm Clad/lining interface bond/cracking
TOFD Advantages
Excellent POD for mid-wall defects
Good detection of miss oriented defects
Can characterize surface-breaking defects
Excellent sizing for defects in transverse
Tolerable sizing for defects in linear mode
Works very well in conjunction with pulse-echo
Rapid (and relatively low cost) inspections
Permanent Record of All Parameters
Offline Interpretation and Measurement
Excellent Repeatability.
Challenges
Dead zone of ~3mm at outer surface
Additional B-scans necessary for transverse positioning
Hard to interpret
Difficult to apply to thin materials (<6mm)
Combine with MUT for exact location of defect
Techniques
Phased Array Ultrasonic Test (PAUT)
Contents
How it works Scan view Sectorial scan Electronic scan Scan plane Software Indication example Application Advantage Code Equipments
How it works A NEW ultrasound NDT technology borrowed from medical An “Array” of transducers elements in which the timing of elements’ excitation can be individually controlled to produce certain desired effects, such as steering the beam axis or focusing the beam Each element has its own connector, time delay circuit and A/D converter Elements are acoustically insulated from each other
Elements are pulsed in groups with precalculated time delays for each element; “Phasing”
How it works Transmission (Tx) Elements pulsed at controlled time intervals Control of beam direction and focusing The delays are known as Tx Focal Laws
Beam Steering
Beam Focusing
How it works
Reception (Rx) RF waveforms received by each element are delayed, then averaged Delays used to align the signals = Rx Focal Laws
•Ultrasound reflects from defect –Elements receive ultrasound at different times due to the different beam paths –Signals then aligned by electronic circuitry
Scan view
Sectorial scan
Multiple Focal Laws
Beam is swept through many angles Wide coverage of the specimen Side Drilled Holes
Back wall
Electronic scanning Each PRF cycle Aperture moves through the length of the array No raster movement required Full volumetric coverage achieved
scanning
Physical scan movement in one axis only Full axial weld coverage achieved
Scan Plane
Definition of specimen and weld geometry, coverage assessment using linear scan PAUT and representation of a typical PAUT and TOFD combination
Software A-Scan, E-Scan, and C-Scan, END View
Software Sectorial Scan, Top view , TOFD
Flaw Volumetric Position Overview Flaw volumetric position is defined as the position of the flaw relative to the weld or component. For weld inspection it is typically expressed as negative or positive in relation to the weld centerline or weld reference, and either embedded, connected to the ID, or connected to the OD. The flaw volumetric position is a key indicator for determining what SWLF flaw on weld overlay type of defect has been detected. (Slag, porosity, IP, LOF, ext.) Knowledge of the weld bevel and weld process is extremely helpful. In a V weld, IP would occur in the Sk90 (-) Sk270 (+) bottom root area, obviously. In a X weld IP would occur in the weld center. Regardless if volumetric position Weld is a requirement of the referencing Centerline code, knowing the volumetric position is necessary to make the repair. Where to excavate and how deep and long?
Flaw Volumetric Position - Overlay Weld overlays are the primary indicator for determining volumetric flaw position. Using the part and weld wizard almost any symmetrical or asymmetrical weld can be created and displayed on the S-scan.
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
Root crack
Porosity
Inclusion
Lack of root fusion
Case Study Present day NDT methodology utilizes radiography is the main method with a double wall double image technique to check the integrity of these weld joints. Natural weld defects were included in 3 pipes of 44.5 mm of diameter and 5 mm thickness with a single V configuration such as: – (i) toe crack and lack of incomplete penetration in Pipe-1 – (ii) root crack and lack of side wall fusion in Pipe-2 – (iii) an individual porosity and cluster porosities were introduced in Pipe-3 The three pipe samples were subjected to radiography and the results were analyzed The samples were also inspected utilizing the COBRA Phased Array system
Case Study
The defects are
Toe Crack
– Toe crack – Incomplete penetration Incomplete penetration
Case Study
Root Crack
These defects are – Root crack – Lack of side wall fusion
LOF
Case Study
The defects are – isolated porosity – Cluster of porosities Cluster Porosity
Applications Pressure vessels Pipelines Portable weld inspections Raw material production: ingots, billets, bars…
Aircraft: civil and defence: In-Service Inspection Military Pre-Service Inspection & In-Service Inspection Power Generation: nuclear & fossil fuel: In-Service Inspection Petrochemical: pipeline construction welds Applications can be on anything currently applying pulse-echo testing
Corrosion Mapping
Compatible with Phased array Detection of corrosion, erosion, pitting, etc. 2 in long array probe for fast acquisition
A scans acquisition Use of water box couplant efficiency
improves
Pressure Vessels Low cost and easy to use Can use conventional or PA Uses TOFD and pulse-echo Good approach for very thick walls
Need allowance for operator error Simplest mechanical solution No safety hazard, no delays Can use magnetic wheel scanner
Pipelines
AUT gives much better inspection: better detection, better resolution MUT is significantly worse, due to unfocused beams and inappropriate angles
RT and MUT would reject many more welds
Austenitic Piping PA instrument, two 5MHz 16 element probes using a splitter/umbilical, and a mechanical scanner.
1.5mm hole on near side of the weld
High Temperature Inspection
Inspection with specific probe and wedge can be carried out at high temperature in many situations. Detection and sizing up to 400˚C
Phased array weld inspection
Sample calibration Block
Construction Welding Sample crack and S-scan image
Corner Crack Inspection with 40- to 70-degree refracted angle Real-time display of S-scan and A-scan
Bolts PA Probe Threads
15 Degree Beam 15 Degree Beam
Notch #1
Notch #1 0 Degree Beam 360 Groove
360 Groove
Mode Conversions Notch #2
Notch #2 End of Bolt 0 Degree Beam
End of Bolt
PA Sectorial Scan
Boiler
High Volume – Typically large number of welds to inspect Many different configurations (diameter, thickness, etc)
Advantages
One probe covers many angles Can produce compression and shear wave No radiation hazard, chemicals and films, equipment inside pipe
Great resolution High speed inspection Instantaneous recording and evaluation of results Provides immediate feedback to the welders Reproducibility
Codes Some quick comments ASME is the most widely used code. Specifically accepts phased arrays (as do most codes) as a technology, but the techniques and procedures need to be developed. Normal procedure is to demonstrate these through a Performance Demonstration, e.g. Appendix 14 or CC 2235 in the case of ASME.
Codes Three manual code cases: CC 2451for single angle scanning, CC 2557 for manual S-scans, manual E-scans (2558) Two code cases for encoded linear scans: – linear E-scans (2599), and – linear S-scans (2600).
Codes A Standard Guide for setting up PA is available (E-2491-06) This SG requires full angular compensated gain (ACG) and TCG over the side-drilled hole calibration range for S-scans.
Equipments TD-Handy Scan
Veo-Sonatest
OmniScan® MX 2
Equipments OmniScan® MX 2 With hundreds of units being used throughout the world, the OmniScan MX is Olympus NDT’s most successful portable and modular phased array and eddy current array test instrument. The OmniScan family includes the innovative phased array and eddy current array test modules, as well as the conventional eddy current and ultrasound modules, all designed to meet the most demanding NDT requirements. The OmniScan MX offers a high acquisition rate and powerful software features—in a portable, modular instrument—to efficiently perform manual and automated inspections.
Equipments Veo-Sonatest The veo’s robust design, intuitive user interface and extensive online help brings the power of Phased Array to the field based technician. The powerful veo platform unlocks a new level of performance in a portable instrument. The Inspection Plan shows the operator in 2D and 3D where probes are positioned on the test part, simplifying the inspection setup and providing an inspection reference for reporting. Multiple scans from different probes may be displayed and evaluated at the same time. Multiple Sectorial scans, top, side and end view extractions plus C scans are all supported by the veo. TOFD and Phased array inspections can be carried out in tandem at full scanning speed and with up to 2GB data files large areas can be inspected more efficiently. Full resolution waveform data is stored directly to a removable USB data key for ease of back up and transfer to PC.
Equipments TD-Handy Scan
TD-Handy scan® Is a new hand-held multifunction advanced ultrasonic used system, the TD-Handy scan® is most successful portable phased array and TOFD test instrument. The TD-Handy scan allow the phased array and TOFD test simultaneously, and also possible to have strip chart scan which is not available by other portable equipments, all designed to meet the most demanding NDT requirements. The TDHandy scan offers a high acquisition rate and powerful software features in a portable to efficiently perform manual and automated inspections. Although the TD Handy-Scan is a small hand-held instrument weighing only 3.3 kilograms, it sports an impressive battery of features and capability.
Reporting
Techniques
Automated Ultrasonic Test (AUT)
Contents
What is AUT? History Calibration Block TOFD Phased Array Mapping Zone Discrimination Equipment AUT Advantage AUT In Iran Codes and standards Conclusion
What is AUT?
The AUT system is used for weld inspection as a combination of two or three different techniques. It provides detailed information on the position, size, and orientation of defects. Using either a conventional multi-probe, or phased array setup, the system scans a weld in a single pass. The operator is then able to view the results in a graphical presentation.
What is AUT?
The weld thickness is divided into a number of depth zones
Inspection concept is related to the weld bevel configuration Full weld inspection coverage is achieved by placing an ultrasonic probe set on both sides of the weld, each probe within the set examines a layer within the weld.
History
Initial AUT design Mid 1960 s
History
AUT Go-NoGo presentation Mid 1970 s
AUT paperchart recorder Mid 1980 s
AUT with PC presentation begin 1980 s
History
AUT paperchart recorder Mid 1980 s
Computerized AUT Mid 1990 s
Computerized AUT end 1990 s
Zone Discrimination
Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6
Weld zoned - inspect with focused waves from both sides. (Up/Down stream) Fast, reliable weld inspection (ASME/ASTM/API compliant) Mechanics simpler & more reliable Conventional UT = 1 probe per zone Phased Array = 1 probe covers all zones
Zone Discrimination
Tandem probe application
angle variation focussing tandem
Zone 2
Zone Discrimination
Зоны F5 F4 F3 F2 F1
F1
F2
F3
F4
F5
76
Scan Plane
Calibration Block A calibration plate, made of an original piece of the pipeline material to be inspected, is prepared with artificial defects such as flat bottom holes and or notches, which represent actual flaws. Artificial defects are present in each depth-zone.
Calibration Block
Calibration Block
Calibration Block
Calibration Block
Calibration Block
Capabilities
For application of the AUT, it is good practice to operate strictly according to a mutually agreed inspection procedure. To judge the results, the procedure always contains clear acceptance/rejection criteria. These criteria may be based on an Engineering Critical Assessment or Good Workmanship Standards.
Using 3 main methods (TOFD, Phased Array, Mapping) together to achieve better and more accurate results.
TOFD
A-scan
Indication
Lateral wave
Back-wall
Phased array
Probe angle
Flat bottom hole focus
Mapping The mapping feature enables the system to visualise the presence of the geometrical welding features such as the position of the weld cap and root penetration, which minimises the possibility of the system generating false calls. Furthermore this feature enables the system to cope with most existing UT procedures and acceptance criteria, because of its capability to detect and, to a certain extent, quantify volumetric defects.
Mapping
Mapping
Advantages of mapping:
Increase of inspection integrity Reducing of false calls Characterization of defects Can be combined with pulse-echo technique
TOFD , Phased array
TOFD , Phased array Phased array inspection techniques are often complimented with TOFD. TOFD is particularly beneficial for increased length and depth sizing accuracy to compliment amplitude based pulse-echo inspections. Data displayed in Tomoview 2.9 for offline analysis. Volume merge C-scan and TOFD B-scan.
Zone Discrimination •Phased array, ToFD, Pulse echo •Easy UT set-up and configuration •Configure for code complience •Meets requirements of EN 1712, API 1104, DNV 2000 FS101, ASTM E1961 •Automated or manual data evaluation •Built in reporting
Zone Discrimination
Recording Threshold
Shaded area shows TOF
Colours indicate Above / Below Acceptance thresholds
Amplitude Data
Data from Up-stream Channels
Data from
Threshold
Down-stream channels
breaking defects.
Calibration Block
LOP
LOF
Porosity
TOFD
AUT Advantages Can be used On and Offshore No radiation hazard, No chemicals and films No equipment inside pipe Hot and cold operating temperatures >100 welds/day onshore and>150 welds/day offshore Digital and real-time results, final report on a DVD
High speed inspection, High POD Instantaneous recording and evaluation of results Provides immediate feedback to the welders
AUT Advantages
AUT Equipments
PipeWizard V4
TD-Handy Scan
AUT in Iran 2004 Siri offshore pipeline by Saipem, 83 Km SP 4&5 offshore pipeline by Saipem, 190 Km 2006 Salman (EPC 3) offshore pipeline by IOEC, ~30 Km SP 8 offshore pipeline by Sadra/DOT, 100 km 2007 SP 9&10 offshore pipeline by IOEC, ~190 Km 2008 Siri-Asaluyeh offshore pipeline by IOEC, 282 Km 2009 SP 15 offshore pipeline by IOEC, ~80 Km 2010-2011-2012 SP 12 offshore pipeline by IOEC, ~440 Km Reshadat in field , ~120 Km Forozan in field , ~120 Km SP 15,16 offshore pipeline by IOEC, ~130 Km SP 15 offshore pipeline by IOEC, ~260 Km
AUT in Iran 2013 SP 19 offshore pipeline by IOEC, ~260 Km SP 20,21 ~ In progress
Total installation of pipelines using AUT in lieu of RT: ~2200 Km Range of diameters: 4” To 56” Range or Thickness: 6mm to 38mm Working hours/shift: Shifts/day: 2
12
Record per shift: 107 welds (32” main line and 4” piggy back)
Codes and standards
In 1998, the ASTM published the E-1961-98 code (reapproved in 2003), which covers key elements of AUT of girth welds – zone discrimination, rapid data interpretation, specialized calibration blocks, and configuration procedures. The E-1961 code is designed for ECA. Similarly, in 1999, the American Petroleum Institute (API) published the 20th edition of Standard 1104, which covers mechanized ultrasonic testing and radiography of girth welds. Other codes:
DNV OS-F101, BS 4515-1 2009
TOFD Acceptance codes: European norms: BS7706 and EN583_6 ASTM E-2373-04 ASME CC 2235-1
RT compare with AUT
RT compare with AUT
Reporting
Thanks for your time!
Please do not hesitate to ask for further information
Contact us for more information at: Mailing Address:
Unit 7, No 1, Allay 1, Fiyat St,
Ekbatan-Tehran Tel/Fax:
+98-21-44694583
E-mail:
[email protected]
Internet:
www.parsinspection.com
