2nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, New Orleans May 2000.

TABLE OF CONTENTS

What Are Eddy Current Arrays? Faster, Better, Cheaper Inspections Scan 10 to 100 Times Faster! Seeing is Believing Single-Axis Scans Faster than Raster Scans 10 to 100 Times Faster! Advantages of Array Probe Inspections Weld Inspection Turbine Blade Surface Inspection Turbine Blade Attachments and Roots Inspection Turbine Retaining Rings Inspection UT/ECT Turbine Bore Inspection SG and Other HX Tubes (X-Probe) Inspection X-Probe: What You See Is what You Get Array Probes: Practical Issues and Solutions Typical Nuclear Applications Conclusion Better, Faster, Cheaper Inspections References

What Are Eddy Current Arrays?

• Multiple eddy current coils, generally of same design, arranged in an organized pattern, in a single probe
• Array coils have similar characteristics as standard coils (size, configuration, detection capacity, sensitivity, depth reach, etc.)
• Faster, simplify inspection of complex shapes, reduce costs, make simpler scanners, lower time exposure to radiations

New technology and equipment make arrays fast and cost-effective

Faster, Better, Cheaper Inspections

• Single-axis scans, 10 to 100 times faster than raster scans
• Easy-to-handle systems, a manual scanner is often enough
• Adaptable probes, can be shaped to match complex-surface parts
• Versatile technology, can replace liquid penetrant in some applications
• Simple inspections, high-speed detection of small flaws
• Dual inspection technique, simultaneous UT/ECT without losing speed

Scan 10 to 100 Times Faster! Seeing is Believing

• Single-axis scans are faster than dual-axis
• A manual scanner isoften enough
• Can replace liquid penetrant in many applications
• High-speed detection of small flaws

Single-Axis Scans Faster than Raster Scans 10 to 100 Times Faster!

• 12 _ 6 in. plate
• Scan time under 3 seconds
• Data recorded directly on PC

Advantages of Array Probe Inspections

	Single-coil probes	Array probes
Inspectionspeed	Very slow	Very fast(10 to 100 times faster)
Analysis	C-scan and impedance plane (Lissajous)	C-scan and impedance plane (Lissajous)
Repeatability and reliability	Fair (manual) to good (automated)	Good
Records	Digital data storage(automated inspection)	Digital data storage
Scanner complexity	Medium to high(depending on part shape)	Very simple manual scanner
Table 1

	Liquid penetrant	Array probes
Inspection speed	Slow and delicate manual operations	Fast, no special preparation required
Analysis	Visual	C-scan and Lissajous
Repeatability	Operator dependent	Operator independent
Interferences from surface finish	No distinction between scratch and crack	Good, less sensitive to surface finish
Subsurface flaw detection	No	Yes
Depth determination	No	Yes
Waste production	Chemical waste	None
Automatic flawdetection	Complex and expensive	Simple
Records	None (or use of photo)	Digital data storage
Table 2

Weld Inspection

• Detection and sizing of surface-breaking cracks on welds and heat-affected zones
• Single-pass inspection at 1 ft/s (30 cm/s)
• Single pass reduces noise compared to raster scan

Turbine Blade Surface Inspection

• Flexible, single array probe allows single-pass, manual scan; eliminating the need for automated scanner
• Pit detection
• Inspection time under 2 minutes
• Data recorded directly on PC
• Digital archiving

Turbine Blade Attachments and Roots Inspection

• Array shaped to match that of the root area
• 48-channel probe
• Single-pass inspection without mechanical scanner
• Inspection under 2 seconds
• Complete inspection record

Turbine Retaining Rings Inspection

• Surface inspection with wide array probe
• Manual inspection, no need for scanner or motor drive unit
• 4 hours to complete the inspection, including setup Retaining ring section Array probe

UT/ECT Turbine Bore Inspection

• Shaft volume typically inspected with ultrasounds, and liquid penetrant for inner surface
• Eddy current may be used as liquid penetrant replacement
• Eddy current requires smaller acquisition increments than ultrasonic, and therefore, limits inspection speed
• Eddy current array offers higher resolution with acquisition increments similar to ultrasonic testing
• Example:
  • Ultrasonic inspection with 10 mm axial resolution
  • Eddy current inspection with 1 mm axial resolution
  • 10-coil eddy current array allows acquisition increments of 10 mm while maintaining the required resolution

SG and Other HX Tubes (X-Probe) Inspection

• High-density eddy current array, 40 times faster than rotating probes: 500 mm/s or 20 in./s at 30 samples/in.
• Field trials have been performed (USA and Japan)
• Analysis similar to that of rotating probe, from color 3D views and familiar Lissajous plot
• Last 20 to 50 times longer than a surface-riding rotating probe
• Significantly reduces time exposure to radiations, inspection time, and consumable costs
• EPRI qualification pending
• High-density eddy current array, 40 times faster than rotating probes: 500 mm/s or 20 in./s at 30 samples/in.
• Field trials have been performed (USA and Japan)
• Analysis similar to that of rotating probe, from color 3D views and familiar Lissajous plot
• Last 20 to 50 times longer than a surface-riding rotating probe

Fig Significantly reduces time exposure to radiations, inspection time, and consumable costs EPRI qualification pending

X-Probe: What You See Is what You Get

• High-resolution 3D imaging
• Coil pattern allows separation of circumferential from axial cracks on different channels
• Familiar Lissajous
• Data acquired at 20 in./s (500 mm/s)

• Excellent discrimination between circumferential and axial indications. Easy call on intersecting flaws
• Excellent resolution and separation on axial flaws
• Correct calls on closely spaced parallel axial flaws which could be otherwise easily confused with a circumferential flaw

Array Probes: Practical Issues and Solutions

• Require very powerful data acquisition systems
  • Array probes produce 10 to 100 times more channels than single coils
  • State-of-the-art, portable equipment handles >2,500 channels and high data rates
• Calibration, inspection monitoring too cumbersome
  • Self-test of equipment and on-line problem detection
  • Computer assisted setup and calibration: 1000's of channels in less than a minute
  • Visual monitoring from C-scan combining all channels
• Channel-by-channel analysis is too cumbersome
  • Analysis using C-scan and 3D presentation to speed up visual screening
  • Lissajous for detailed analysis on any point
  • Automated data analysis

Typical Nuclear Applications

• Turbine components
  • Turbine blades
  • Blade attachments
  • Blade roots
  • Retaining rings
  • Turbine bores (ultrasonic/eddy current)
• Welds
  • Weld surface inspections
• Tubes
  • Steam generator tubes
  • Heat exchanger tubes
• Other
  • Pressure vessel surface
  • Under cladding crack detection
  • Canopy seal inspection
  • Simultaneous ultrasonic eddy current inspections without speed loss
  • Applications requiring liquid penetrant
  • Applications using manual eddy current mapping

Conclusion

Better, Faster, Cheaper Inspections


• Single-axis scans are 10 to 100 times faster than dual-axis helix or raster scans
• Easy-to-handle systems; a manual scanner is often enough
• Fast, simple inspection of complex-surface parts by shaping array to match the surface
• Long-lasting probes; single pass leads to less wear compared to the multipass raster scan approach
• Significant reduction in time exposure to radiations
ECT array probes for fast, cost-effective inspections

References

1. Transmit-Receive Probes: "The Next Generation"; L. Obrutsky, V. Cecco, R. Lakhan, and S. Sullivan; 18th Annual EPRI Steam Generator Workshop
2. New Generation ECT Array Probe and System as High Speed Alternative to Rotating Probes; G. Lafontaine; 18th Annual EPRI Steam Generator Workshop
3. The result of Comparative Tests for a New High-Performance Multi-Array Probe; Y. Harada, K. Maeda, J. Shimone, Y. Kishi; 18th Annual EPRI Steam Generator Workshop
4. Array Probe for Steam Generator Tubes; G. Henry; 2nd Int'l Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components
5. New High-Performance ECT Array Probe for Steam Generator Tubes; K. Maeda, Y. Harada, et al.; 2nd Int'l Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components

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