Could you provide advice on blade tip clearance? 

In this article:

• Explains how blade tip clearance is measured using Waygate Technologies’ borescope solution, including reference plane setup, blade edge mapping, and min/max/average clearance results for gas turbine inspections.
• Highlights key limitations and prerequisites, such as unsuitable blade geometries, image contrast requirements, and the role of 3D data quality in achieving accurate measurements.
• Shares best‑practice tips to improve accuracy and efficiency, including cursor handling, probe positioning, advisory system checks, and Auto Repeat for faster inspections.

Could you provide advice on blade tip clearance?

Functionality Notes

• The blade and shroud can have any orientation in the image.
• Not intended for use with honeycomb liners, turbine blades having outer shrouds, or blades that have irregular tip geometries by design or due to rubs.
• The clearance is measured from a reference plane determined from the 3 reference plane cursor locations. These cursors can be manually re-positioned.
• The algorithm maps the blade edge using the “Normal” 2D image (HDR images are not used). 3DPM pattern images may also be utilized where edge contrast is low in the normal 2D image.
• The pixels near the blade edge must be brighter than those just off the blade edge for successful mapping.
• The Max measurement point is visually differentiated from the Min measurement point by having a larger inactive cursor size.
• The Min and Max cursors cannot be manually re-positioned.
• The two bounding cursors, one at each end of the mapped blade edge, can be moved to exclude end portions from the min/max/average analysis.
• Long touch any shroud cursor to return all 3 shroud cursors to their automatically-chosen positions.
• Long touch either bounding cursor to return it to its automatically-chosen position.
• Use Auto Repeat to improve efficiency when making repetitive Blade Tip Clearance measurements.

Advisory System Checks:

• The system looks for several common issues that may degrade accuracy.
• Shroud 3D data quality may be reducing accuracy: The reference plane may not be accurately aligned to the liner in the vicinity of the blade tip due to excessive 3D noise, large gaps in 3D data, or insufficient liner visibility in the view.
• Blade 3D data quality may be reducing accuracy: Excessive 3D noise or large gaps in 3D data exist near the blade edge
• Move closer to target or move cursors for better results: The system may not be capable of accurately measuring a gap of the indicated size from the current tip-to-target distance
• To improve accuracy, capture image with tip optics closer to the shroud: The viewing perspective may not allow the true blade edge to be accurately mapped and measured.