Enhancements in Pulsed Eddy Current Examination of Insulated Component Dr. Vincent DEMERS-CARPENTIER, Dr. Maxime ROCHETTE, Marc GRENIER, Charles TREMBLAY, Dr. Marco Michele SISTO, Martin TURGEON Presented by: Michel BEZEMER
PEC Working Principle (1/3) PEC consists in the analysis of the transient eddy current inside a conductive component following a sharp electromagnetic transition. There are 3 phases: 1. The emission phase (the pulse) during which the probe injects magnetic fields that penetrate and stabilize in the component thickness 1 Excitation pulse Time 1 Magnetic response Time 2 Eddyfi NDT Inc. 2009 2016
PEC Working Principle (2/3) PEC consists in the analysis of the transient eddy current inside a conductive component following a sharp electromagnetic transition. There are 3 phases: 2. The cut-off phase which induces strong eddy currents into the component when the magnetic field emission is stopped abruptly 2 Excitation pulse Time 2 Magnetic response Time 3 Eddyfi NDT Inc. 2009 2016
PEC Working Principle (3/3) PEC consists in the analysis of the transient eddy current inside a conductive component following a sharp electromagnetic transition. There are 3 phases: 3. The reception phase during which magnetic sensors measure the decay of the eddy currents as they diffuse into the material thickness 3 Excitation pulse Time 3 Magnetic response Time 4 Eddyfi NDT Inc. 2009 2016
Voltage - Log scale (v) Voltage - Log scale (v) A-Scan in Reception Phase Early in the A-scan: Eddy currents diffuse in the WT as if they are in an infinite wall The decay rate follows a power law relation that: Produces a straight line in a Log-Log scale Produces a rapid Log-Log drop Scale in a Log-Lin scale Log-Lin Scale V t a V t a 1 10 100 Time - Log scale (ms) 0 50 100 150 Time - Linear scale (ms) 5 Eddyfi NDT Inc. 2009 2016
Voltage - Log scale (v) Voltage - Log scale (v) A-Scan in Reception Phase Later in the A-scan Eddy currents reach the far side of the WT The decay rate follows an exponential relation that: Produces a rapid drop in a Log-Log scale Produces a straight Log-Log line Scale in a Log-Lin scale Log-Lin Scale V e t τ V e t τ 1 10 100 Time - Log scale (ms) 0 50 100 150 Time - Linear scale (ms) 6 Eddyfi NDT Inc. 2009 2016
Voltage - Log scale (v) Voltage - Log scale (v) A-Scan in Reception Phase Thinner wall thicknesses change the shape of the A-scan Shorter eddy current diffusion time Quicker signal drop in a Log-Log scale Different slope in a Log-Lin scale 1 2 3 4 Log-Log Scale Log-Lin Scale Region of interest with Lyft 1 10 100 Time - Log scale (ms) 0 50 100 150 Time - Linear scale (ms) 7 Eddyfi NDT Inc. 2009 2016
Voltage - Log scale (v) PEC Reinvented Two major advantages: Shorter acquisition time Mostly immune to signal amplitude variations Log-Lin Scale 1 2 3 4 15 25 35 45 55 65 75 85 Time - Linear scale (ms) 8 Eddyfi NDT Inc. 2009 2016
What is Pulsed Eddy Current? 1 Pulse Stop Listen 3 Excitation pulse Time Excitation pulse Time Excitation pulse 2 Time 1 2 3 Time Time Time Magnetic response Magnetic response Magnetic response Allows the measurement of wall thickness at high lift off 9 Eddyfi NDT Inc. 2009 2016
A World of Applications Corrosion under Insulation (CUI) Scab Corrosion Flow Accelerated Corrosion (FAC) 10 Eddyfi NDT Inc. 2009 2016
A World of Applications Corrosion under Insulation (CUI) Potential applications include: Insulated pipes Tanks Vessels Sphere legs Any carbon steel with insulation or cladding 11 Eddyfi NDT Inc. 2009 2016
Introducing Lyft - PEC Reinvented FAST Dynamic mode (unique to Lyft): Probe moving speed up to 100mm/s (4in/s) No need for grid marking the sample, just straight lines RELIABLE Less operator-dependent Less affected by lift-off variations and weather jacket overlaps Not sensitive to probe motion VERSATILE Galvanized steel weather jacket, and scab/blistering-capable Works at lift offs up to 12 (300 mm) Wall thickness up to 4 (100 mm) Through concrete, polymer coating and chicken wire Near metallic structures such as nozzles, flanges, pipe supports Lyft system 12 Eddyfi NDT Inc. 2009 2016
What Pulsed Eddy Currents doesn t do Pulsed Eddy Current work best on large corrosion patches, especially at high lift off. Pulsed Eddy Current does not detect: Cracks Small pitting 13 Eddyfi NDT Inc. 2009 2016
Where does Lyft fit in the NDE Tool Belt? Permits expansion of inspection scope and frequency without increasing schedule Can inspect in-service components Monitoring without shut down (high or low temperature components) Does not require removal insulation or cladding Broader screening permits more focused application of RT and UT 14 Eddyfi NDT Inc. 2009 2016
Measuring Defects Through Insulation What happens when the probe scans over a defect? Wall Thickness 2 1.5 1 0.75 0.5 0.25 Wall Relative Thickness 100% 75% 50% 37.5% 25% 12.5% Measured Thickness 100% 77.2% 49.8% 36.0% 24.9% 13.1% 15 Eddyfi NDT Inc. 2009 2016
Measuring Defects Through Insulation What happens when the probe scans over a defect? Scanning a defect smaller than the footprint leads to undersizing 16 Eddyfi NDT Inc. 2009 2016
What is Undersizing? Lab mockup sample Flat bottom holes Plate WT 0.5 (12.7 mm) Insulation height 2 (50.8 mm) Sample 17 Eddyfi NDT Inc. 2009 2016
What is Undersizing? Lab mockup sample Flat bottom holes Plate WT 0.5 (12.7 mm) A B Insulation height 2 (50.8 mm) Defect Diameter Real WT Measured WT A 3 66% 89.5% C B 6 33% 66.8% C 3 33% 85.7% 18 Eddyfi NDT Inc. 2009 2016
Signal - Log Scale (V) Signal - Log Scale (V) What is the signal like when we undersize? Log - Log Scale Log - Lin Scale 2 20 Time - Log Scale (ms) 2 22 42 Time - Lin Scale (ms) Nominal + Defect = Actual Signal 19 Eddyfi NDT Inc. 2009 2016
Signal - Log Scale (V) Compensated Wall Thickness Isolate the defect contribution from the signal We use an analytical equation for each component of the signal Analyze a defective region rather than a single data point Log - Lin Scale 2 22 42 Time - Log Scale (ms) 20 Eddyfi NDT Inc. 2009 2016
Compensating for the Undersizing Phenomenon Lab mockup sample Flat bottom holes Plate WT 0.5 (12.7 mm) Insulation height 2 (50.8 mm) Defect Diameter Real WT Measured WT Compensated WT A 3 66% 89.5% 67.1% B 6 33% 66.8% 36.7% C 3 33% 85.7% 39.8% 21 Eddyfi NDT Inc. 2009 2016
Compensated Wall Thickness on Real Corrosion Scab corrosion Plate WT Insulation 0.35 (8.9 mm) None Sample 22 Eddyfi NDT Inc. 2009 2016
Compensated Wall Thickness on Real Corrosion Scab corrosion 57% Plate WT Insulation 0.35 (8.9 mm) None 52% Sample 29% 32% 23 Eddyfi NDT Inc. 2009 2016
Compensated Wall Thickness on Real Corrosion Scab corrosion Plate WT 0.35 (8.9 mm) Insulation None 31% 30% Sample 29% 32% 24 Eddyfi NDT Inc. 2009 2016
Conclusions Lyft is a fast, flexible and reliable screening tool which measures wall thickness through insulation and cladding Compensated Wall Thickness tool addresses the main weakness of PEC: undersizing Compensated Wall Thickness gives optimal results when applied to high resolution, low noise data sets 25 Eddyfi NDT Inc. 2009 2016
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