NDT / NDT Exclusives

GMA Uses New APR Approach to Inspection

February 8, 2011
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Company uses new technology that minimizes outage time for customers and identifies previously undetectable tube faults.

This picture was taken during inspection. Source: GMA


GMA, an integrated service company headquartered in 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 over 30 years of experience in the field of anti-corrosion, 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 unique AcousticEye 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.

Mr. Roberto Grassetti, CEO of GMA, explains how AcousticEye has increased the company’s throughput in servicing its customers, and has actually increased their revenue from coating and cleaning of condensers:

“AcousticEye offers us the ideal solution for our customers. It 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. 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. 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.”



This is the defect map from the APR report that shows one of two tubesheets. Source: GMA

GMA Success Stories

1. Fouling in tubes: Lime scale at the Italian Power Company

A power generation customer called GMA in to evaluate the quality of its cleaning process, and to determine the presence of lime scale residue in condenser tubes after the cleaning process. In order to determine the efficiency of the cleaning method the GMA team performed an APR test using the AcousticEye Dolphin.

The GMA customer’s condenser consisted of over 11,000 tubes each with a 7/8-inch outer diameter (OD) – these tubes were not testable with conventional nondestructive testing (NDT) methods. However, the APR inspection conclusively revealed a total of up to 10% of the tubes with residual fouling.

“The task was successfully completed within a week, and the AcousticEye Dolphin proved to be a reliable and fast method for evaluating the presence and severity of fouling in the condenser tubes,” said Chiara Martellossi, head of research at GMA. “We concluded that the APR method is an excellent method of validating the cleaning process and the cleanliness of any and all condenser tubes.”



Source: GMA

2. Ultra Fast detection of leaks and their positions in the reheater/dryer at the Belgium Power Station

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-tubes 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-tubes 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 over 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 4 days time). An additional 18 tubes were found to have over 80% wall loss, and were plugged as a result.

“In conclusion, the APR test proved to be extremely accurate and fast, and the customer was able to detect the defects and plug the tubes within the limited time frame of the shutdown.”



Source: GMA

3. Detecting corrosion and severe pitting in tubes in an Italian refinery

At an Italian refinery, GMA tested 302 tubes with the AcousticEye Dolphin for holes, blockages and pitting thresholds over 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.

GMA: “We concluded that there is no better technology validation than authentication with the results from a destructive control test.”

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