Wind Turbine Nondestructive Testing: What You Need to Know

Wind turbines are a growing source of renewable energy as nations around the world grow more conscious about energy consumption. According to the U.S. Department of Energy, wind could comprise 35% of the U.S. energy supply. With the increased use of turbines also comes the need to draft regular inspection procedures that can detect defects on a profound level.

There are many components of wind turbines that require regular inspection, such as probing the bearings and gear teeth, or searching for blemishes and pitting. Nondestructive testing allows analysts to detect aberrations without engaging in destructive testing procedures. For wind turbine nondestructive testing, two of the most effective approaches are ultrasonic testing (UT) and eddy current testing (ECT). 

Ultrasonic Testing of Wind Turbines

Ultrasonic nondestructive testing is a commonly used option for inspecting wind turbine blades. However, it is important to note that conventional UT cannot achieve the same level of detailed inspection parameters as specialized UT techniques such as phased array UT (PAUT), which fosters customized wave beam configurations that permit comprehensive probing techniques. Additionally, PAUT allows users to angle the wave beam in multiple directions, whereas standard UT practices only yield a fixed beaming position.

When it comes to scanning, users can configure in transverse or longitudinal directions of the blade itself. The scanning apparatus also produces faster scanning measures while ensuring thorough coverage of the testing radius.

Flexible probing procedures are especially pertinent to wind turbines, as the blade geometries and other components of the turbines feature irregular surfaces and geometries. In particular, blades typically feature composite materials and thick attenuation that can make inspections difficult. Materials that may be present within a turbine blade include:

• Fiberglass
• Resin
• Steel
• Aluminum
• Iron

The blades not only undergo heavy stress while in operation but may also come with inherent defects from the manufacturer. These defects can be hard to find without the right instrumentation. However, phased array ultrasound is specifically designed to identify and characterize small flaws in high resolution.

Further, advanced UT technologies include powerful pulses that can penetrate through thicker weld materials, reaching underlying indications that would have remained undetected. When dealing with wind turbine blades, thick welds can come in the form of fiberglass or carbon fiber, and these materials are attenuative in nature. With PAUT, analysts can detect anomalies in wind turbine materials such as pitting, corrosion, and cracking.

PAUT allows operators to find flaws quickly and fix them without delay. A quality instrument can provide instant results that are reliable and easily-digestible. Advanced features can also hasten the inspection process, allowing analysts to complete inspections more efficiently.

To get the most out of a PAUT solution, be sure to procure an instrument that’s portable and equipped with powerful software. It is important to buy from a trusted NDT manufacturer that invests in innovation and superior craftsmanship. Lesser UT instruments cannot provide the same level of resolution and flaw detection as that offered by truly cutting edge instruments.  

Eddy Current Testing of Wind Turbines

Eddy current testing is another viable and increasingly popular approach to wind turbine NDT. ECT instruments can detect malformations on a surface and near-surface level. Like UT, ECT has an advantage over other NDT methods as it does not require the use of hazardous chemicals or a constant source of electrical power. Advanced ECT instruments are conveniently portable (some compact designs are even handheld) and provide single-pass inspection features that allow analysts to thoroughly cover a larger testing radius in less time.

And, just as specialized ultrasonic testing methods offer benefits conventional UT cannot provide, so too do specialized ECT techniques have an edge over standard eddy current technology. This is where eddy current array comes into play, as ECA can provide a more detailed level of inspection of flat or unconventional surfaces.

The array function accepts surface array probes that can inspect welds composed of different geometries and material types. With a surface array probe, inspectors can detect corrosion or cracking. When searching for a suitable surface array instrument, look for the following benefits:

• Touchscreen interfacing
• Stellar software
• Multi-coil probing

The multi-coil feature is especially important due to the enhanced detection speed. When inspecting a tower, for example, a multi-coil probe can cover more ground, such as the weld bodies and weld toes. With the addition of +point coils, the array function can probe the weld toes with ease. A single-probe scan could achieve the same feat, but the analyst would have to probe on multiple occasions to complete the test. Multi-probe functionality also improves the probability of detection. 

Effective Wind Turbine Nondestructive Testing Requires the Right Instruments 

Ultrasonic testing and eddy current testing are two leading inspection methods when dealing with wind turbines due to their advanced features and added convenience. Both are adept at finding smaller flaws that are normally harder to read using other NDT methods and instruments. Both methods offer array functionality that conforms to unconventional geometries and scrutinizes flaws on a deeper level.

The instrumentation also has powerful software that reduces calibration times and enhances probe detection. The instruments also have additional features that adapt to unconventional shapes and software, with no need for multiple probe changes or frequent scanning. With wind turbine nondestructive testing, analysts can get quality results in less time, helping companies find flaws that could stall turbine function.

Zetec is a leading NDT provider of UT and ECT instrumentation for wind turbine inspections and other assets. Contact us today to get a tailor-made inspection plan and high-quality instruments.