The Role of Videoscopes in Gas Turbine Inspections: Insights from the Field

Traditional gas turbine inspections can be time-consuming and expensive. However, a remote visual inspection can be an effective alternative to tearing equipment apart to get a look inside. Advanced videoscopes can provide excellent visibility and imaging, easy measurements, and more comprehensive reporting.

Gas turbines are and will continue to be a critical part of the energy sector. Given the pressures, temperatures, tolerances, and impact engine failure can have, knowing the mechanical health of each engine is as critical as the engine itself.

Videoscopes are instrumental in assessing that health. They allow an inspector to see, analyze, and measure items of interest inside the engine. This article explores the role of videoscopes in gas turbine inspections and discusses key videoscope capabilities that overcome common issues encountered in the field.

A videoscope is an advanced type of borescope used for remote visual inspection (RVI). A videoscope inspection on a gas turbine is generally scheduled based on the hours run and model. Additionally, forced or unplanned turnarounds or outages can occur where an emergency inspection is required to identify the cause.

During a gas turbine inspection, an RVI technician takes a videoscope, such as an Olympus IPLEX videoscope, and inserts the distal tip of the insertion tube into the turbine engine. The insertion tube of videoscopes come in a range of lengths and typically have a diameter of approximately 4 millimeters (mm) or 6 mm. The most common diameter and length for gas turbine inspection is 6 mm and 3.5 meters (11.5 feet), respectively.

1. Example videoscope inspection. Courtesy: Veracity Technology Solutions

After inserting the end of the flexible insertion tube, the technician navigates the scope to critical areas, such as the blades, vanes, and the combustion chamber. The last three inches of the insertion tube curls/articulates and is controlled by the user via a joystick. This articulation assists in the navigation because it controls the location of the insertion tube distal end as it is inserted. Once the area of interest is reached, the articulation is used to center the view of the damage or problem area on the screen (Figure 1).

When users can see the target area, they can save an image or video for collaborative analysis or reporting to the asset owner. Users can add annotations to captured images, such as circling an area or overlaying text onto an image. In most current models, annotation is simplified using the videoscope's touchscreen.

An advanced analysis method used for noted problem areas is to perform stereo measurement on indications, such as a crack on a blade. Stereo measurement quantifies the visual information on the screen and can be referenced to fault tolerance procedures, enabling the asset owner to make an informed decision on next steps.

There is more to assessing the health of a gas turbine engine than taking an image and performing measurements. While these are crucial steps, the images are then sent, managed, and reviewed—sometimes by several individuals.

Advanced videoscope manufacturers have recognized the need to provide more than a tool that produces a bright and clear image. There is a trend among these manufacturers to align with the requirements of the industry. This means that in addition to the immediate benefits of a leading-edge videoscope, features such as wireless image transfer, online image database management, and report generation are all being utilized and developed to provide inspection services.

One issue with RVI equipment is that it can be difficult to provide cohesive and quick reports to power facility owners and operators. Additionally, inspectors typically need to communicate directly with the owner and operator personnel overseeing the inspection.

Videoscopes that can improve the inspection service offered to asset owners can lead to an uptick in business. For instance, the advanced features of the Olympus IPLEX NX videoscope have proven to increase efficiency both during the inspection and when reporting the results.

Scott Kennedy, vice president of Business Development with Veracity Technology Solutions, shared some of the advantages of using the IPLEX NX videoscope. "The equipment speaks for itself, and I know our customers appreciate the benefits it provides them," explained Kennedy. "For us, the IPLEX NX videoscope is a powerful instrument for our certified borescope inspectors but is still easy enough for a plant technician to learn to use for a simple component inspection check. It's been a great tool to increase our business and provide a better service to our customers."

For Veracity, the IPLEX NX videoscope is a critical asset for performing gas turbine inspections due to three main capabilities.

Excellent Visibility and Imaging on a Large Screen. Inspection technicians and other personnel at the job site appreciate the optimal views provided by the videoscope's large 8.4-inch screen and bright, vibrant imaging. This excellent visibility comes in handy when inspecting gas turbine engines. For example, an inspector on a turbine deck can pivot the screen to a project manager who is several feet away, and the project manager can easily see and understand what is shown onscreen.

Touchscreen capabilities make the large screen size even more useful for inspections and measurements. Users can easily zoom in and out by simply pinching in or spreading two fingers on the screen. Annotating the images with text, arrows, and circles is also simpler with a touchscreen.

Depending on the inspection target, the IPLEX NX videoscope can be paired with a 4 mm, 6 mm, or 6.2 mm (containing a working channel) diameter insertion tube. The 6-mm scope is commonly used when inspecting gas turbines. To show these targets in detail with outstanding image quality, the IPLEX NX videoscope has optimized optics and a high-resolution charge-coupled device (CCD).

2. The IPLEX NX videoscope shows a brightly illuminated image. Courtesy: Veracity Technology Solutions

As this CCD requires more light to generate the same bright image compared to lower-resolution CCDs, the videoscope features intensely bright laser-diode illumination (Figure 2). The light travels through the insertion tube via a fiberoptic cable. A brighter light source is crucial in the RVI world, as the only source of light often comes from the videoscope.

Easy Measurements. Taking measurements is easy on the large touchscreen, making the task more efficient for the inspection technician. Without a touchscreen, the measurement cursor can only be moved with a joystick. Now, the user can tap in the vicinity of where the point should be placed and then use the joystick for a final refined point placement. This improved workflow enables the user to report back to the onsite project manager much faster.

The IPLEX NX videoscope also has multi-spot ranging, a feature that helps speed up the average time it takes an inspector to take a measurement. It displays five points around a circle on the live image (one in the center and four on the edge of the circle). Distances to the target on those points are displayed in real time. This way an inspector can know immediately if the measurement image is close enough in a certain area and across the entire image. This is all done in the live image before an image has been captured.

3. A 3D model (right) of the edge of a blade is used to confirm the point placement in the stereo image (left). Courtesy: Veracity Technology Solutions

Another benefit for measurements is the 3D modeling feature. Once a stereo image has been taken, the user has the option to view it as a 3D model. The 3D model helps the inspector fully understand where reference and measurement points are being placed.

3D modeling is often used when the edge of a blade is inspected, as it is common practice to place reference points on the edge of the blade. Using the 3D model, the inspector can be confident that the point is placed on the edge of the blade instead of slightly off the edge. If the point is slightly off the edge of the blade, it will be off the blade entirely and located somewhere behind the blade.

As mentioned earlier, the touchscreen makes it easy to quickly pick points. This feature is also helpful when using the 3D model. Using simple touchscreen gestures, the user can manipulate the 3D model in different ways. The user can slide one finger to rotate the model, pinch in or spread two fingers to zoom the model in and out, and slide two fingers to pan the model across the screen.

More Comprehensive Reporting. The deliverable of most inspections is a report with summary of findings, recommendations, and images to illustrate the asset status. However, the effort to generate an inspection report can be time-consuming and challenging if organizations want to adopt standardized templates.

IPLEX NX videoscopes are part of a comprehensive workflow solution designed to reduce the time and effort required to create standardized inspection reports across an entire organization. Using the ViSOL cloud solution, users can import and review inspection media from an IPLEX NX videoscope. Further, reports can be automatically generated to simplify the entire RVI workflow.

The software on the IPLEX NX videoscope is an integral part of the ViSOL solution, as it enables the inspector to customize and select the predefined inspection result or any defects at the moment of image capture. Inspection data can be embedded with the image so that the entire inspection can be seamlessly transferred to the ViSOL solution.

This information can be sent directly to the cloud or temporarily to the ViSOL desktop application during offline mode, then later synchronized to the cloud when internet connection resumes. This harmonized connection between IPLEX videoscopes and the ViSOL solution enables the RVI workflow to be more efficient, standardized, and collaborative.

The videoscope is a field-proven device for gas turbine inspections. Advanced features of modern videoscopes, such as bright, high-resolution imaging; a large, responsive touchscreen; 3D modeling; and cloud-based reporting, add greater efficiency to the inspection and reporting workflow.

—Charles Janecka is the RVI Associate Product Manager with Evident Scientific.

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