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 (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
