Inspectioneering Journal

Rotating Laser Profilometry Adapted for Use in Convection Furnace Tubes, Boilers and Fin-Fan Coolers

By James L. Doyle at Quest Integrated, Inc. This article appears in the May/June 1995 issue of Inspectioneering Journal.

Over the past ten years a broad family of laser-based nondestructive testing systems has been in development. These tools are used for the inspection and measurement of internal surfaces of tubes ranging in size from 5/8 inch 3-inches in diameter. Originally developed for use in marine boiler tubes for the U.S. Navy, LOTIS (TM) (Laser Optic Tube Inspection System) was developed for the location and measurement of internal features such as corrosion, pitting, and surface cracking. To date, the U.S. Navy owns eight of this type of inspection system and has inspected over 15,000 tubes on more than 75 ships. This is now a standard inspection approach for internal surfaces of naval marine boiler tubes.

In 1993, the technology spread to the inspection of commercial systems such as fossil boiler tubes, and process heat exchanger tubes. LOTIS, which employs a high-speed rotating laser caliper, generates a computer graphic map of the inside surface of the tube. Features such as ID erosion and pitting can be mapped to accuracies better than +- 0.002". Results are provided in several user-friendly computer graphic displays as well as tabular summaries. Key benefits of this technology over conventional inspection systems are accuracy and resolution. Sometimes a benefit, and occasionally a limitation is the necessity to operate in a dry environment. This is particularly important when operating in regions such as refineries and chemical plants in northern Alberta where ambient temperatures are often approaching zero degrees C.

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