Guided Wave Testing (GWT) Use of guided wave testing for the detection and monitoring of corrosion under insulation Peter Philipp Independent GWT consultant Level 3 GUL Level 3 PCN GWT BINDT-ICorr. - 12/05/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
GWT History Lamb waves identified in the 1930 s Research projects in the 1990 s Link and Thermie programs Development of dispersion curves Required faster portable computers First commercial equipment available 1999 Mid 2000 s Subsea, focussing, c-scan display, rail, permanently installed etc. 3 GWT systems developed Wavemaker (GUL) Teletest (Pi), MSS (SWRI) BINDT-ICorr. - 10/03/2013
Guided Wave Testing Standards ASTM 2011 BSI 9690 parts 1 & 2 TUV certification: GUL GWT procedure certified under EN standard 14748 NACE TG 410 2012/13 ASME Article 18 2012/13 Need for harmonization between the different standards. Standards within integrated system including legal requirements, codes and best industrial practices..; Guided Ultrasonics Ltd. 12/05/2013 4
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
Principle Transducer Standard UT Metal structure Inspected Area Transducer Ring Guided Waves Inspected area Inspected area BINDT-ICorr. - 10/03/2013
Reflection from a Feature (such as corrosion) Transducer Structure When the guided wave hits a change in cross section (or impedance), it reflects back toward the transducer BINDT-ICorr. - 12/05/2013
Dispersion curves 6.0 Longitudinal L(0,2) V gr (m/ms) 4.0 2.0 0.0 Torsional T(0,1) F(1,2) F(1,3) Black = axi -symmetric modes Red = non-axi -symmetric modes Blue = other modes that are not used by the system 0 20 40 60 80 100 BINDT-ICorr. - 12/05/2013
Backward Position of Ring Forward Series of Welds Iconic representation of identified features Decay Curves Corrosion is indicated by large red component BINDT-ICorr. - 10/03/2013
Guided Waves (Focusing) C-Scan display BINDT-ICorr. - 12/05/2013
At every change in cross section there is a reflection of the guided waves Amplitude depends on cross sectional area change The dark grey Section represents the Cross-sectional area BINDT-ICorr. - 12/05/2013
Distribution of Loss The percentage loss given by the ECL could be concentrated in a narrow portion of the pipe (e.g. a critical deep defect) could be equally distributed around the circumference (e.g. a shallow wall loss) BINDT-ICorr. - 12/05/2013
The ratio of Red to Black depends on the circumferential extent of the feature When the feature does not extend very far around the circumference, RED = BLACK Amplitude Ratio 1 0 0 50 100 Circumferential Extent (percent) When the feature extends significantly around the circumference, RED << BLACK BINDT-ICorr. - 10/03/2013
Axi-Symmetry Displayed as black and red lines BLACK lines represent axi-symmetric waves Uniform around the circumference RED lines represent non-axi-symmetric waves Varies around the circumference A symmetric weld -F4 -F3 3.0 -F2 -F1 +F1 +F2 +F3 +F4 A non-symmetric defect Amp (mv) 2.0 1.0-10.0-5.0 0.0 5.0 Distance (m) #12403 BINDT-ICorr. - 12/05/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
Why Guided Waves? 100% volumetric coverage Rapid screening In Service inspection Permanent record Significantly reduced access costs Think of costs for: scaffolding, removing insulation, digging, operating underwater BINDT-ICorr. - 10/03/2013
Rapid screening Very good at confirming clean pipe Acts as filter: point out areas where more attention is needed Everyone knows about health screening BINDT-ICorr. - 12/05/2013
In-service inspection Temperature performances from -40C to 180C the extremes of this range will require modified procedures Product low viscosity fluid does not affect torsional mode frequency range enables good performances in case of viscous fluid Pump noise, product flow signal/noise can be improved using predefined software procedures In some cases (isolated) testing is not feasible BINDT-ICorr. - 12/05/2013
Managing pipe inspection Pipeline operators need to deal with kilometres of pipelines (each site) How do operators manage the inspection now? What capabilities are offered by Guided Waves? BINDT-ICorr. - 12/05/2013
GWT and other complementary methods Prove up using other NDT methods (UT,RT, Leak detection, etc ) Use with RBI can be very powerful BINDT-ICorr. - 12/05/2013
Touch point corrosion 8 Sch 40 12 3 6 9 Guided Ultrasonics Ltd. 12/05/2013 21-16dB 12-20 0 20 40 60 F 1.2 1.0 0.8 0.6 0.4 0.2 0.0-20 0 20 40 60 Distance (ft) Amp (Linear) Clock Weld welded plate -F1 Weld Cat 1 Corrosion Support Weld Cat 3 Support Weld DAC 14% Call DAC 4% Touch point corrosion patch with pitting
Touch point corrosion 12 Sch 40 12 Pitting touch point corrosion at 6 o clock position of pipe 3 6 9 Guided Ultrasonics Ltd. 12/05/2013 22-18dB Clock 12-30.0-20.0-10.0 0.0 10.0 1.5 1.0 Amp (Linear) welded support weld Welded support Contact support Contact support -F1 Welded support Corrosion pit Weld Weld DAC 20% 0.5 Call DAC 3% 0.0-30.0-20.0-10.0 0.0 10.0 Distance (m)
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
100% Volumetric coverage What is the probability of finding a defect using UT spot check compared to Guided Waves? BINDT-ICorr. - 12/05/2013
100% Volumetric coverage What is the probability of finding a defect using UT spot check compared to Guided Waves? Example: 10 pipe, 12m length with 2 simple supports Per test: Standard UT = 0.027% area coverage Guided Wave ~ 100% area coverage BINDT-ICorr. - 12/05/2013
Monitoring using GWT - Advantages Greatly improved sensitivity Normal testing ~ 1% to 5% Monitoring in the order of 10 times better as you are detecting changes Data from all tests can be stored for setting up same test parameters and also for comparison Can use removable or permanently installed transducers Data collection after base can be done by data collectors BINDT-ICorr. - 10/03/2013
GW monitoring sensitivity Simple visual 3.0 estimate of change slow 2.0 and sometimes difficult method Amp (Linear) of interpreting 1.0 GWT data differences 0.0 +F1 +F2 0.75% CSC 0.5% CSC baseline 2.5 3.0 3.5 4.0 Distance (m) 1% CSC Guided Ultrasonics Ltd. - 12/05/2013 27
Riser monitoring results G3-163#1125 (Linear) 20.0 15.0 10.0 5.0 0.0 Weld Sea bedweld 2008 Result Weld Weld WeldWater levelweld Caisson Flange + -60-40 -20 0 G3-16#3957 (Linear) 20.0 15.0 10.0 5.0 0.0 Weld Sea bedweld 2009 Result Weld Weld WeldWater levelweld Caisson Flange + -60-40 -20 0 G3-116#1042 (Linear) 20.0 15.0 10.0 5.0 0.0 Weld Sea bedweld 2010 Result Weld Weld WeldWater levelweld Caisson Flange + -60-40 -20 0 Distance (m) Guided Ultrasonics Ltd. - 12/05/2013 28
Riser GW monitoring results: The automatically processed comparisons The yellow trace is the reflection coefficient calculated from the 2010 reading using the calibration curves. The black trace is the difference between the 2010 and baseline readings. Guided Ultrasonics Ltd. - 12/05/2013 29
Monitoring using GWT Potential problems The accuracy of comparing results must take into account the following: Unique transducer identification Ring position (for removable rings) Calibration Pipe temperature difference Transducer coupling (permanent attachment) Test parameters must be the same Ideally the software should calculate the change BINDT-ICorr. - 10/03/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
Using GWT New build considerations Design for monitoring points especially when using permanently installed transducers For example sub sea and road crossings can be installed and take base line readings Design coatings etc to maximise range (avoid thick bitumastic coatings) BINDT-ICorr. - 10/03/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
Dead zone Cannot test region of pipes close to the ring location Dead zone extending over 0.5m from ring (depends on test configuration) BINDT-ICorr. - 12/05/2013
Range 5-150 meters in each direction depending on local conditions Factors affecting range Geometry General pipe conditions Material inside pipe Attenuative surface coating BINDT-ICorr. - 12/05/2013
Difficult geometry Only test through one bend in each direction Defects at branches cannot be found reliably Flanges and Ts represent the end of the test BINDT-ICorr. - 12/05/2013
Type of defect More difficult Single isolated pit Axial cracks Small pits in welds Easier A cluster of pits Circumferential cracks Large cracks in welds CORROSION I/E - EROSION BINDT-ICorr. - 12/05/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
GWT Procedures Procedures need to be developed for: Different applications Permanent ring attachment and base test Data collection from permanent rings Comparison of monitoring data Data management BINDT-ICorr. - 10/03/2013
GWT operator training and certification The success of GWT is very operator dependant so good training/certification is crucial Some applications are more difficult The main manufacturers have different approach to training/certification PCN agreed by all GWT equipment suppliers available this year CSWIP only available for Teletest BINDT-ICorr. - 10/03/2013
Information management Managing information from NDT inspection is major issue. With Guided Waves each result contains in one file information on tens of meters of pipe. New development will enable asset integrity packages linking exact positioning of pipe features and defects (plotted on Google Earth for example) BINDT-ICorr. - 12/05/2013
Guided Waves (C-Scan) Unrolled pipe view 360 270 Angle (deg) 180 90 0 0.0 5.0 10.0 -F2 -F1 +F1-24dB +F2 +F3 +F5 +F4 2.0 Amp (Linear) 1.5 1.0 0.5 00 BINDT-ICorr. - 12/05/2013
Interpretation - Frequency scanning Time saving when collecting data Takes away responsibility from the inspector to choose best frequencies on site More information available which was not visible before when collecting single frequencies Extremely important in applications where the feature response is frequency dependent Helps distinguishing different features (e.g. defects from supports) POD BINDT-ICorr. - 12/05/2013
Typical performance on bare straight pipe (20 years old in good conditions) 100 meters range on each side Amplitude detection 1% Cross section Concentration of defect (approximate) Angle definition of defect +-22 degrees Factors reducing range discussed below BINDT-ICorr. - 12/05/2013
Applications Rapid, full coverage screening of pipes Especially cost effective in difficult to access locations Pipe racks Corrosion under insulation Road crossings Wall penetrations Rope access Road crossing Buried pipes Can reliably detect general metal loss BINDT-ICorr. - 12/05/2013
Effect of Pipe Contents Gases - no effect Liquids Almost no effect on the torsional mode Affects the longitudinal mode when the pipe is fully filled Sludge Heavy viscous deposits in the pipe attenuate the signal and reduce the test range Can be similar effect to bitumen wrapping BINDT-ICorr. - 12/05/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
This presentation Brief history of GWT How it works How good is it at identifying CUI Monitoring New build considerations Limitations Procedures and training Other GWT applications Future developments BINDT-ICorr. - 10/03/2013
Future developments Auto monitoring hardware and software Asset integrity packages linking exact positioning of pipe features and defects (plotted on Google Earth for example) Improved buried pipe capability Absolute calibration BINDT-ICorr. - 12/05/2013
Other GWT applications Tube testing boilers/heat exchangers Sub sea (diver and ROV deployed Rail Tubular structures Lampposts BINDT-ICorr. - 10/03/2013
Sub-Sea Pipe testing BINDT-ICorr. - 10/03/2013
G-Scan Rail Screening System BINDT-ICorr. - 10/03/2013
Conclusions GWT is a very versatile inspection tool Needs to be used with complementary NDT methods Can save considerable access costs More accurate when used in monitoring mode Has data record of all tests BINDT-ICorr. - 12/05/2013
Questions PQS Peter Philipp peterphilipp50@gmail.com BINDT-ICorr. - 12/05/2013