The Advantages of Eddy Current Array over Magnetic Particle and Penetrant Testing for Inspecting the Surface of Carbon Steel Welds Product Management | Tommy Bourgelas OSSA, January 2017
Apr 13, 2017
The Advantages of Eddy Current Array over Magnetic Particle and Penetrant Testing for Inspecting the Surface of Carbon Steel Welds
Product Management | Tommy Bourgelas OSSA, January 2017
Presenter: Tommy Bourgelas
Product Manager, eddy current and bond testing products
§ 16+ years experience with eddy current technology
§ Has conducted numerous trainings and provides customer support
§ Contributed to the development of several applications (eddy current array (ECA), tube testing, bond testing (BT))
§ Works on product improvement, design, and definition
Agenda § Industry problems
§ MagnaFORM™ solution
§ How it works
§ Results
§ Conclusion
Current Surface Inspection Methods (and Their Problems)
Magnetic Particle Inspection (MPI) § Globally preferred method for inspecting carbon steel welds
§ Surface-breaking defects
MPI Principles § Strong magnetic field magnetizes metal
§ Magnetic particles align in areas with discontinuities
Penetrant Testing (PT) § Alternative method to MPI — mostly applied on
complex shapes or non-ferromagnetic surfaces
§ Surface-breaking defects only
PT Principles § Paint must be stripped, and a thorough cleaning is needed before
inspection
§ Application of chemicals and dwell time
Source: mechjobs.in
Paint Pain: Removal and Re-Application § Paint needs to be removed to help ensure detection (before inspection)
§ Paint needs to be re-applied (after inspection)
Liability Concerns § Removing paint exposes bare metal
§ Accelerated corrosion rate, contamination, etc.
§ Compromised liability from the inspection itself
Environmental Impact § Paint removal requires chemicals
§ Growing environmental concerns about chemical agents
§ Chemical disposal adds to cost
Increased Costs § Paint removal and downtime are often disregarded costs
§ The entire process is much more costly than the inspection itself
Additional Limitations (MPI) § No depth sizing
§ No archiving
§ Multiple passes required
§ False indications on rough (corroded) surfaces
§ Significant repeated physical effort (holding the yoke)
Additional Limitations (PT) § “Dirty cracks” prevent penetrant from entering
§ Tighter defects (such as early stress corrosion cracking (SCC)) are almost impossible to detect with visible dye
Summary: Positive Impacts of MPI and PT § Very simple to use
§ Applicable to various parts or geometries
§ Widely used by many operators
§ Well-suited for bare metal (ferromagnetic)
§ Great sensitivity and resolution (MPI)
§ Affordable direct cost
Summary: The Negative Impacts of MPI and PT § Paint removal and re-application
– Chemicals and environmental concerns – Bare metal à liability – Downtime (entire process) – Cost of entire process
§ No sizing capability
§ No easy archiving
§ Multiple passes required
§ Low performance on tight or dirty cracks (PT)
§ Potential for false indications (rough surfaces)
The MagnaFORM™ Solution Distinctive Benefits and Features
Paint Removal is History § Eddy current sensors inspect through up to 3 mm thick paint
Single Pass Scanning § Covers the heat-affected zone (HAZ), the toe, crest, and crevices
§ Maintains detection
No More Lift-Off Headaches § Flexible array probe maintains excellent contact
§ New dynamic lift-off compensation corrects sensitivity
Durable Inspection § Rugged construction (drop tested)
§ Wear face tested on a 22 km scan before it needed replacing
Ready to Inspect § Hand scanner or semi-automated scanners
§ Works well on pressure vessels and pipes
Motorized Scan
Accessible Technology § Affordable Solution that works with an
OmniScan® MX flaw detector
§ Easy-to-use dedicated “WELD” software
Defect Depth Evaluation § Quickly evaluate defect severity for screening purposes
The Power of Imaging § Instant interpretation
§ Archive your inspection files
§ Post-inspection analysis is possible
How It Works
Basic Elements
Cart (MagnaFORM Scanner)
Eddy Current Array Probe
Encoder Cable
Position Encoder
Probe Close-Up
Detachable Connector
Sensitive Face
Pre-Shaped “Wedge”
Tool-Free Removal
1 2
3 4
Fits Most Pipes and Vessels
Flat
Large Internal Smaller External
Large External
Flexible Sensor Array
16 + 16 Sensors (two types)
Active Circuitry
Eddy Current Sensors: Multi-Layer PCB-Etched Coils
Eddy Current Technology
§ Characteristics: – Magnetic coupling – Great for surface inspection
§ Benefits: – Inspect through paint – Minimal surface preparation – Suitable for metals, including
carbon steel – Ease of use
Lift-
Off
Two Eddy Current Sensor Types
Type 1 Crack Detector
Type 2 Lift-Off Gage
0
1 2
Max
Type 1 Sensor: Crack Detector
= § PCB equivalent to a cross-wound coil
§ Ideal for carbon steel
§ Widely used in “Weld ECT Probes” (such as WeldScan probes)
§ Easily detects surface-breaking defects
§ Detects through paint, but impacted by lift-off
Crack Signal
Type 2 Sensor: Lift-Off Gage
= § Eddy current sensor
§ PCB version of a “sliding probe”
§ Stable lift-off measurement
0
1 2
Max
Lift-Off Measurement
Powerful Combination
0
1 2
Max
(Raw) Crack Signal
Lift-Off Measurement
Dynamic Lift-Off Compensation
Compensated Crack Signal
Dynamic Lift-Off Compensation
§ Dynamic = real-time software processing
§ Increases the sensitivity of crack detectors when lift-off is increased
– No/minimal lift-off = normal gain – More lift-off = more gain to crack detectors
§ Maintains uniform sensitivity independently from lift-off
Independent Sensors
16 Independent Crack Detectors
16 Independent Lift-Off Gages
16 Independent Dynamic Lift-Off Compensated Channels
+
=
MagnaFORM Scanner on a Weld
Flexible Probe
Good Contact
Increased Lift-Off
Close-Up of the Weld
Lift-Off
Raw Crack Signal
Compensated Crack Signal
MagnaFORM Representation
Live Impedance
Plane
Color Palette (Uses Vertical Amplitude)
Vertical Amplitude
C-Scan View (2D Mapping)
Index Axis (Probe Coverage)
Scan Axis (Distance or Time)
Is Sizing Possible?
0.5 mm 1 mm
2 mm 3 mm
§ The depth of surface-breaking defects has a direct effect on amplitude
§ Other variables that impact amplitude: – Lift-off (primary variable on rough surfaces/welds) – Magnetic permeability – Defect length and shape
How about the Toe of the Weld…?
0.5 mm 1 mm
2 mm 3 mm 3 mm
Sensitivity Dynamically Compensated Helps Fix Sizing
Reduced Sensitivity Due to Increased Lift-
Off (Wrong Sizing)
Probe Profile
MagnaFORM Sizing = Depth Evaluation
Selection Cursor (when Paused)
Depth Reading
Selection Length is
Taken into Account in the
Sizing Process
Results
#1 — Painted Pipe
§ Carbon steel pipe, ~ 6.5 in. OD × ~ 0.5 in. WT
§ Paint thickness: 0.007 in.
§ Machined flaws in and around the weld (electrical discharge machining (EDM))
§ Known flaw sizes
#1 — Weld Details
§ 4 weld fillets on top
§ Width of weld: ~ 1 in.
§ Rough surface
~ 1 in.
#1 — MagnaFORM Scan Circumferential Axis (360°) Coverage (~ 3 in.)
HAZ
Weld
#1 — Detection through Paint EDM in HAZ L = 18 mm Depth = 3 mm
EDM in Weld Center/Crown L = 18 mm Depth = 3 mm
EDM in Toe L = 18 mm Depth = 3 mm
EDM in Crevice L = 18 mm Depth = 3 mm
EDM in Toe L = 18 mm Depth = 3 mm
#2 — Painted Coupon
§ Carbon steel plate: ~ 3/8 in. thick
§ Paint thickness: ~ 0.003 in.
§ Induced / machined flaws in weld
Defect in Toe L = 25 mm, Linear
Defect in Crown L = 12 mm, Transverse
Simulated Porosity (Not Detected)
#2 — Results
#3 — Rough Weld with Undercut
§ Carbon steel plate, 12 in. × 14” in., ~ 0.5 in. thick
§ No paint, but a protective varnish
§ Induced flaws in the weld
§ Flaws in undercut
§ Very rough weld, 4 filler passes
#3 — Drawing
#3 — Detection Results 7 — Crack in Toe L = 15 mm, D = 2 mm
5 — Crack in Toe L = 10 mm, D = 2 mm
3 — Centerline Crack L = 10 mm, D = 2 mm
#3 — Detection Results (continued) 8 — Undercut L = 25 mm, D = 0.8 mm
6 — Crack in Undercut L = 10 mm, D = 2 +0.8 mm
4 — Crack in Undercut L = 10 mm, D = 2 + 0.8 mm
#4 — Long Defect
§ Carbon steel plate, ~ ¾ in. thick, large radius
§ No paint (previously removed for MP)
§ Presence of a continued long crack in the toe
#4 — Magnetic Particle
Exterior Interior
#4 — Results (Exterior)
#4 — Results (Interior)
#5 — Stress Corrosion Cracking (SCC)
§ Carbon steel plate, ~ 0.25 in. thick
§ No paint (previously removed for MP/PT)
§ Actual SCC (marked by hand after it was found with MP/PT)
#5 — SCC Results
#6 — Dense SCC
§ Carbon steel plate, ~ 3/8 in. thick
§ No paint (previously removed for MP/PT)
§ Actual SCC colonies all over
#6 — Wet MP Results
#7 — Dense SCC Using the MagnaFORM Probe
#7 — SCC with Corrosion
§ Carbon steel plate, ~3/8 in. thick
§ Significant corrosion
§ No paint, sandblasted to add defects
§ EDM added inside and outside the corrosion
#7 — Results EDM in Corrosion L = 10 mm, D = 3 mm
(3x) EDM L = 10 mm, D = 1 / 3 / 5 mm
Corrosion Mostly Cancelled and Compensated for Lift-Off
Conclusion
Benefits § Inspect through paint
§ Dynamic lift-off compensation
§ Single pass weld inspection
§ Stress corrosion cracking
§ Depth evaluation
§ Imaging and archiving
Thank you! Questions?
www.olympus-ims.com