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DACON INSPECTION TECHNOLOGIESEddy CurrentArray technology

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Surface testingConventional vs Array

Conventional Eddy Current surface testing

Advantages compared to alternatives (PT/MT):

• No paint removal

• Fast

• Environmental friendly (no use of chemicals)

• Indication of depth of defects

• Small probe• Confusing signal

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Surface testingConventional vs Array

Array Eddy Current surface testing

Advantages of ETA compared to conventional ET

• Increased coverage

• Easy to understand data presentation

• Permanent record

• Increased POD

• Encoded scans

• Big probe• Easy C-scan

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Surface testingConventional vs Array

ConventionalManual raster single coil

ET arrayWide coverage by sequential excitation

of multiple coils

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ETA Surface testingProbe explained

• Elements are the individual EC probes used to make the array probe.

• Any type of EC probe can be used as an element. For example:

• Pencil probe:

• Sliding probe:

…1 2 32

+ =Corrosion array

…1 2 32

+Surface array

=

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Surface testingProbe explained

Absolute bridge probe

Double row array

• Uniform sensitivity over the probe width

• Improved resolution that allows smaller defect detection.

• Needs an encoder to align the data in the C-scan.

• Smaller coverage for the same number of elements. Coverage

Resolution

Single row array

• Non uniform sensitivity

• Low sensitivity to cracks parallel to scan direction and between elements

Coverage

Resolution

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Surface testingProbe explained

Omni directional probe

• Sensitivity for defects in each direction

• Axial and transverse channel required to find all defects

Axial channels Transverse channels

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Surface testingWeld inspection

ConventionalMultiple scans

ET arraySingle encoded scan

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Surface testingCovering a surface

ConventionalOverlapping manual scans

ET arrayMultiple encoded scans creating a C-

scan image

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Surface testingApplications and probes

Different applications need different probes

• Surface probes

• Rigid and flexible

• Far surface corrosion

• Near and sub- surface cracks

• 5 KHz frequency

• Weld scan probes (non ferrous)

• Padded probes

• Short surface breaking cracks

• 250 or 500 KHz available

• Complex geometry probes

• Very flexible (I flex)

• Far surface corrosion

• Near and sub- surface cracks

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Surface testingApplications and probes

Different applications need different probes

• Weld scan probes (Ferrous)

• Sharck Pobe

• Carbon steel welds

• Detecting cracks in Cap, Toe and HAZ

• Sizing of cracks up to 10 mm deep

• Tangential Arrays

• Coils positioned on their side

• Axis of coil parallel to surface

• Transmit receive mode

• Eddy current parallel to surface

• Capable of dicing under a crack

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ETA tube inspection

Advantages over conventional bobbin coil tube inspections

• More sensitive to circumferential cracking

• Provides information on circumferential extent of defect

• Better accuracy for gradual (absolute) wall loss

• Can distinguish between defect signal and tube sheet signal

• No need for additional testing of tube ends for

circumferential cracking by rotating techniques

• If only testing tube ends 5 sec per tube vs 40 sec per

tube for rotating techniques

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ETA tube inspection

Sensitivity to circumferential cracking

Bobbin coil

• Eddy currents travel in

circumferential direction

• Eddy currents not

significantly disturbed by

circ. crack

Array

• Eddy currents travel parallel to the

surface

• Eddy currents are perpendicular to circ.

Crack, significantly disturbed

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ETA tube inspection

Def Hi probes

• Bobbin coils

• Arrays

• Single

or

• double

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ETA tube inspectionGradual wall loss

Bobbin coil Array

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How Can We Help?

Contact

Email : info@dacon-inspection.com

Phone : +66 (0) 33 012 484-7

www.dacon-inspection.com

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