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Inspecting Turbine Dovetails with Eddy Current Array Technology
Ask an expertGas turbines are critical assets in the power generation sector. They are large and complex, and shutting them down is often quite costly. The blades in these turbines are generally attached to the rotor through an ingenious system of male and female “dovetails”. These dovetails must be inspected for defects with great efficiency to ensure safety and to maximize the life of the equipment, often in the context of life extension programs.
The Challenge
Efficiently inspect gas turbine dovetails for minute cracking, extending the life of aging equipment.
Dovetails are especially prone to fatigue cracking and Stress-Corrosion Cracking (SCC), which is defined as the growth of cracks in a corrosive environment. If left unchecked, SCC can lead to unexpected failure of normally ductile metals (e.g., INCONEL®) subjected to tensile stress, as is the case in gas turbines.
The cracking of interest here is typically small and concentrated near dovetail hooks. Conventional eddy current pencil probes and Penetrant Testing (PT) were used for several years with very limited success. The specific geometries of dovetails make inspection with these methods unreliable, if possible.
Of the two dovetail parts, inspecting the female portion has proven the most time-consuming and demanding. Inspection usually involves using slow, complex, and costly robots.
Furthermore, because there are almost as many dovetail designs as there are gas turbines, a one-size-fits-all solution such as a flexible design is virtually unthinkable, especially while wanting to preserve the level of precision necessary to effectively characterize minute cracks.
This application therefore calls for a solution that can scan female dovetails in a single pass and designed to match the dovetail’s profile.
The Solution
Eddy Current Array (ECA) probes shaped to match dovetail profiles, powered by P-Flex technology, provide a repeatable, single-pass, operator-friendly solution—without sacrificing precision or speed.
Because dovetails vary greatly in shape and size, they usually require a custom solution. The Eddy Current Array (ECA) technology in the probe remains nonetheless the same.
The P-Flex ECA probe offers a custom-fit solution for efficient, high-resolution dovetail inspections—without the need for robotics.
Why P-Flex?
Specifically designed to match dovetail profiles
- Provides stable, one-pass scanning
- Features a replaceable PCB, making it more economical over time
- Offers precise assembly, improving probe-to-probe consistency
- Compatible with Ectane® for data acquisition and Magnifi® for advanced visualization and reporting
- Thin, spring-loaded membrane ensures optimal surface contact, even in demanding conditions.
This setup enables reliable detection of cracks as small as 0.38 millimeters (mm) deep and 0.76 mm long, with full traceability and digital documentation.
While P-Flex is the recommended solution for dovetail inspection, the I-Flex probe remains a complementary option for more complex surfaces, especially when tighter radii of curvature are involved. Its flexible design adapts to various geometries while still leveraging ECA technology.
Book a Demo to determine which solution best fits your turbine components.
Ask an Expert
Benefits
- A custom-fit, one-pass, single-operator solution with precise computerized data recording.
- Custom solution shaped to specific dovetail profiles
- Custom solution designed to target your specific “hot spots” or entire dovetail profile
- Rapid, single-pass scan of regions of interest
- No harsh chemicals or hazardous waste
- Easy to handle—no need for expensive robotic solutions
- Easier interpretation with C-scan imaging
- Full computerized data recording and archiving capabilities
Beyond dovetails, turbine blades, generator slots, rotor bores, and bore holes also need to be inspected regularly, quickly, and efficiently. These applications also involve designing custom probes to fulfill highly specific sets of requirements. Over the years, Eddyfi Technologies has gained a wealth of concrete experience developing eddy current array probes for these applications. By partnering with us for your turbine application requirements, you’re not starting from scratch. Rather, you have a great head start.