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Turbine Dovetail Inspection Using Eddy Current Arrays

General description of the application

Dovetail inspection can be extremely time consuming and demanding. One of the alternatives is to use a complex robot, but it is still slow and very costly.

The system we are proposing completely covers the part to be inspected in one single pass. It uses an array of elements laid out in a probe design perfectly adapted to the part profile.

Typical inspection requirement
• Complete part coverage
• Defect sizing and positioning

Defects detected
• 0.8 mm x 0.4 mm x 0.1 mm (30 mils x 15 mils x 4 mils)
• Generally parallel to the inspection displacement

Description of the solution
• Multichannel probe
• Real-time C-scan display with pseudo-isometric view
• 24-channel probe
• Probe shaped to fit the part profile

Description of the inspection system
MultiScan MS-5800™ with MultiView™ software running on a laptop or desktop PC
• Probe with external multiplexer unit
• Optional encoder

Parts to inspect
Engine disk dovetail

Defects to be detected
Fatigue cracks

Method of inspection
The probe is balanced on the defect-free dovetail like any other ET system. After calibration on a long calibration defect, the probe is pushed inside each dovetail. The data appears in real-time on the computer screen as a C-scan.

The preferred display is the C-scan. It makes an excellent cartography of the part, especially if an encoder is used.

It is also possible to have access to the impedance plane and strip charts of each channel to make an independent analysis of each signal. This is possible because all the channels are saved individually and integrally.

MultiScan MS5800 multitechnology acquisition unit

Olympus IMS

Products Used for This Application
MultiView tube inspection acquisitions and analysis software provides voltage plane analysis, voltage plane theoretical curve, circumferential sizing overlay, calibration of three depth curves with only one reference point, voltage plane calibration without a support-plate signal and dual-driver software control. In addition, it offers offline cylindrical view, pit-depth measurement cursors, display of wall loss (%) and remaining wall, and real-time C-scan acquisition.
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