How Automated Eddy Current Analysis Boosts the Efficiency of Heat Exchanger Inspections

By Stephen Petit, Technical Writer

One of the great achievements in eddy current technology for heat exchangers is that the latest probes, handling equipment and instruments are capable of acquiring massive amounts of inspection data at exceptionally fast rates. The efficiency and productivity of the acquisition crew has never been better.

Manually analyzing the inspection results, however, is another story.

Manual analysis is a tedious, multi-step, multi-person process. After a number of tubes have been inspected, a member of the acquisition team copies the data to a memory stick or other portable device and sends it to an analyst at another location or even off site. When an analyst wants to review the inspection data for a particular tube, he or she has to find the file, open it up look for signals of interest and make a determination about what to do next. Time gained during the data acquisition process is lost many times over during manual analysis.

Automated workflows

Automated analysis software — led by Zetec’s RevospECT, the industry’s first commercially available high-powered, adaptable and scalable automated analysis system — is changing the equation.

Developed for heat exchanger inspections in power generation and industrial environments, RevospECT integrates acquisition, analysis and reporting into a single workflow. The software analyzes data as it’s being acquired by the probe operator and can produce a report almost immediately. One analyst with an automated system can be far more efficient and focused on the critical aspects of the inspection compared to multiple analysts performing manual inspections.

Automation opens up opportunities for analysts to raise their effectiveness to new levels.

For example, NDE Technology in Jackson, Michigan, was preparing to conduct an inspection at a public utility with a boiling water reactor where the condensers have roughly 12,000 titanium tubes in each water box—approximately 50,000 tubes total. Each tube is 55 feet long and has 15 support plates with a stake evenly spaced between them to help stiffen the tube bundle.

Marc Brown, Principal Level III and a partner at NDE, said his team determined that some of these stakes were slipping out of position and sliding close to the support plate, putting circumferential stress on the tubes. Under high-cycle vibration, tubes will relieve this stress by cracking axially or longitudinally.

The NDE team created a plan to map each stake’s location and monitor any movement from its original position as a way to identify high-risk tubes. “We needed to map roughly 800,000 stake locations between two reactor units,” Brown said. He estimated that doing the work manually would take at least 2,000 man-hours, with a large error factor.

With RevospECT, the team could inspect 12 tubes at a time in about three seconds. Within hours, it could produce a map of high-risk tubes caused by stakes that were not properly inserted or had moved. “The savings from plant uptime alone translated to millions of dollars for our customer,” Brown explained.

Historical comparisons

Traditionally, analysts compare eddy current inspection data with historical benchmarks so they can recognize and interpret changes in signals over time. This requires the analyst to recall files from various inspection campaigns and look for changes in the signals.

NDE used Zetec’s RevospECT HX Pro with HDC, or Historic Data Compare, to automate the process. The software can take data from a previous inspection, overlay it on top of the latest data (or any other data set) and then highlight the differences in the data streams. The ability to compare data from one inspection to another, without the variations and inconsistencies that come from manual analysis, gives asset owners confidence in their decisions about whether a flaw or defect has changed over time and needs to be addressed.

Brown said automating the analysis of historical data made NDE’s stake-mapping project feasible. “We’d done eddy current testing at this particular plant for three years straight and had compiled a large volume of data,” Brown explained. “HDC allowed us to quickly process and identify which stakes were moving and potentially putting tubes at risk. We could never have done the job manually.” Furthermore, the effectiveness of HDC increases with each inspection. The more eddy current data you can collect and run through the system, the more beneficial and valuable the comparisons can be.

As eddy current hardware continues to advance, automated analysis software ensures that you can take full advantage of your inspection-system investment. Zetec’s RevospECT eliminates bottlenecks and delivers the speed and confidence both you and your customers expect.

Zetec is a global leader in nondestructive testing (NDT) solutions for the critical inspection needs of industries the world counts on every day. To learn more, contact Zetec today!