Computed Tomography Scanning: Not Just for Medical Use

Article Summary

• Liburdi Turbine Services has been extending the life of gas turbine components for over 40 years using our in-house technologies. Computed Tomography (CT) Inspection is a crucial tool in our capabilities.
• Traditional Ultrasonic Thickness (UT) inspection, used for measuring wall thickness in internally cooled turbine blades, has limitations, especially with blades that have complex geometries or have undergone multiple repair cycles.
• To overcome these limitations, Liburdi employs CT X-Ray technology, which allows us to inspect a cross-section of the blade, ensuring that no point is subject to thinning or defects that could lead to failure.
• Liburdi's CT scanner uses a Linear Diode Array (LDA) sensor to acquire multiple images from each slice as the blade rotates, providing detailed 2D and 3D inspection scans, resulting in more confidence in the inspection results.

For over 40 years, Liburdi Turbine Services has extended the life of gas turbine components using Liburdi's in-house technologies. Computed Tomography (CT) Inspection ensures continued reliability and safe life extension of repaired components. CT technology is an enabling tool in the Liburdi suite of capabilities for extending the life of rotating components safely and robustly.

Ultrasonic thickness (UT) inspection is traditionally used to measure the wall thickness of internally cooled turbine blades. Ultrasonic wall thickness inspection measures the time ultrasonic pulses travel through the material and back to the sensor. UT inspections are performed at specific points around the airfoil of the blade.

UT inspection, however, has technological limitations in obtaining an accurate measurement for turbine blades with complex internal and external geometries. The drawbacks of UT inspection are most apparent with blades which have undergone multiple repair cycles. Additionally, UT inspection of specific points does not lend itself to a complete understanding of the internal geometry and potential defects between established measurement locations.?

To overcome the limitations of UT inspection, Liburdi performs complex inspections using computed tomography (CT) X-Ray technology. The ability to inspect a cross-section of the blade is crucial to ensure that no point of the blade is subjected to thinning or other defects that may cause a failure in service.

Figure 1: CT Scanner being loaded with turbine blades

Liburdi’s CT scanner uses a Linear Diode Array (LDA) sensor to acquire multiple images from each slice as the blade continuously rotates in the X-Ray fan beam. The fan beam offers improved high-quality results as opposed to the conventional cone beam by reducing the noise and scatter caused by the dense nickel alloy. The computer uses these scans to reconstruct an image of the tomographic slice showing the internal geometry.

Figure 2: 2D X-Ray Image generated as part of the CT inspection process

Extracting 2D and 3D inspection scans provide easy and prompt identification of critical internal structures in specific areas of interest. The slice technique allows a more detailed evaluation of internal casting geometry.

Figure 3: Section view image of Turbine Blade generated with CT System

This digital scanning process allows Liburdi to examine parts at a higher level of scrutiny, which results in more confidence in the inspection results.?

To see how our decades of superior service has helped extend turbine component life, contact Doug Nagy at [email protected] to start a conversation and learn how we can help you.