Acoustic Pulse Technology Streamlines Inspection

APR technology detects corrosion and severe pitting in tubes in an Italian refinery, pictured here. Source: GMA

GMA, an integrated service company headquartered in Staranzano, Italy, is known worldwide for its expertise in inspecting and maintaining condenser tubes across a wide range of industries. Customers rely on the service provider for mechanical cleaning of condensers and retubing of all types of condensers and heat exchangers. GMA has more than 30 years of experience in the field of anticorrosion, a team of distinguished technicians and specific expertise in polymeric coatings.

It is crucial for GMA to be able to offer and provide its customers with service methods that are cost-effective, minimize outage times and increase the efficiency of tube-based equipment. To meet these needs with a complete package of problem analysis and customer-specific solutions, GMA sought an easy, comprehensive and fast inspection solution.

The search for such a system resulted in GMA’s discovery of the AcousticEye (Santa Clara, CA) Dolphin tube inspection technology. AcousticEye’s acoustic pulse reflectometry (APR) technology allows GMA to provide faster and more complete inspections and problem diagnosis of tube systems than was previously possible. The result measurably reduced customer downtime and identified problems that were formerly not detectable.

“[AcousticEye] allows us to move in fast during the shutdown and perform the condenser inspection in a fraction of the time it would take to test the tubes with other conventional NDT technologies,” says Roberto Grassetti, CEO of GMA. “We can get an immediate indication of the condition of 100% of the tubes, thus allowing for quick decision making.”

“Facilities such as refineries and power companies are excited to find that tubes that were historically non-conducive to inspection are now testable, thus improving efficiency of mission critical equipment,” he adds.

APR technology performs fast detection of leaks and their positions in the reheater dryer at the Belgium Power Station. Source: GMA

Speedy and Accurate

During a scheduled maintenance outage at one of GMA’s power generation customer sites, a pressure test revealed two leaks in a carbon steel reheater dryer with u-tube bundle. Due to the geometry of the bundle and the tube material, the tubes were difficult to test with traditional sample-based inspection methods.

Using AcousticEye’s APR technology, the entire 600-tube inspection task was completed with 100% test coverage within four hours, including setup time and final analysis.

The AcousticEye Dolphin confirmed the presence of two holes which were located in the bend area of the u-tube, a physical location testable only with APR technology. In addition, the inspection revealed an additional five tubes suffering more than 80% wall loss. Although the tubes had been cleaned with pressurized air, fouling was still found to be present in a large percentage of the tubes.

As a result of the speed of the inspection with AcousticEye and the accuracy of the leak detection, the GMA team was asked to perform an additional inspection on three identical dryer reheaters with a total of 1,861 tubes by the end of the outage in four days time. An additional 18 tubes were found to have more than 80% wall loss, and were plugged as a result.

The APR test proved to be accurate and fast, and the customer was able to detect the defects and plug the tubes within the limited timeframe of the shutdown.

At an Italian refinery, GMA tested 302 tubes with the AcousticEye Dolphin for holes, blockages and pitting thresholds more than 20%. Several tubes were found to have severe pitting and holes were found within 30 centimeters of the inlet. Other tubes exhibited varying degrees of blockages.

After receiving the report, 10 tubes were pulled for physical validation; they were cut and analyzed in an independent laboratory. All the data found with the AcousticEye Dolphin was found to be consistent with the laboratory findings. The customer was highly impressed with how consistent the defect types, position and sizes were compared with the actual findings from the destructive test control.

“Facilities such as refineries and power companies are excited to find that tubes that were historically nonconducive to inspection are now testable, thus improving efficiency of mission critical equipment,” says Grassetti. “Since we have started offering tube inspection with AcousticEye, our customers are turning to us more for other services as well. Our partnership with AcousticEye has proven to be a winning opportunity both for us and our customers.”

AcousticEye USA
(713) 861-3270


  • AcousticEye’s APR technology inspected 100% of its test of 600 tubes within four hours, a fraction of the time of other inspection methods.

  • The AcousticEye Dolphin performed accurate testing in physical locations testable only with APR technology.

  • All the data found with the AcousticEye Dolphin was found to be consistent with the laboratory findings.

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