When the Difference between Success and Failure is Paper Thin


When the difference between success and failure is less than the thickness of a sheet of paper, you know all eyes are watching. Such was the case for AREVA’s Component Repair & Replacement (CR&R) metrology team who was tasked with measuring, fabricating and installing replacement in-service components with extremely tight parameters at a U.S. nuclear energy facility.

The team’s challenge was to recreate in the shop environment the as-found plant configuration of an in-service diesel generator’s intercooler spools and then to fabricate, deliver and install new spools on the existing machinery.

To fabricate the new spools, AREVA’s metrology team first had to create manufacturing specifications using 3-D measurements of the existing part with a technique called soft templating. Soft templating collects precise measurements through photogrammetry and laser-tracking technology to digitally reproduce components for fabrication.

AREVA’s laser tracker technology achieves +/- .001” three-dimensional accuracy.

AREVA’s laser tracker technology achieves +/- .001” three-dimensional accuracy.

Marrying the old with the new required a great degree of accuracy. First, the team measured the original assembly using photogrammetry that yields accuracies +/- .005” – less than the thickness of a piece of paper. Photogrammetry is a triangulation measurement process that uses a series of overlapping high-resolution digital images and a robust software package to derive accurate, three-dimensional coordinate measurements.

Next, the assembly was recreated using laser-tracking technology, with accuracies of +/- .001”, to set up templates at AREVA’s fabrication shop in Lynchburg, Virginia. The laser tracker is a real-time measurement tool that uses an interferometer, two precision encoders, and sophisticated proprietary software to calculate the three-dimensional position of a mirrored target (probe). The system follows the mirrored target over features, updating the position at a rate of one thousand times per second.

In the shop, the team completed the soft templating process to accurately recreate the as-found plant configuration of the assemblies. The team then used the precise digital template to fabricate replacement intercooler spools for the diesel generator.

The new intercooler spools were a perfect match. The AREVA team’s ability to fabricate the intercooler spools for a successful first-time fit with no safety, quality, performance or delivery concerns reduced their customer’s outage time by approximately 120 hours—a significant direct cost-savings for the facility.

When perfection counts, AREVA’s metrology team measures up to the challenge!

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