A Guide to Probes and Scanners for Ultrasonic Corrosion Mapping of Pipelines and Tanks

Dave J. post image

By Dave Jankowski, product sales leader at GE Inspection Technologies 

Ultrasonic phased-array corrosion mapping assists in quickly scanning, detecting, profiling and sizing of pitting and erosion in pipes and tanks. Encoded scanning data allows a high degree of repeatability and ensures 100% coverage to compare asset conditions and track corrosion rates over time.

Conducting accurate, precise corrosion inspection takes more than just an ultrasonic flaw detector or A-scan thickness gauge– selecting a scanner, probe and accessory configuration for your application is a critical part of inspection planning. The right setup can make or break your inspection.

The NDT equipment industry offers a variety of scanners and probes to improve inspection productivity when mapping large surfaces for wall thickness and metal loss. This is a snapshot of the technologies available and their recommended applications.

Robotic and Motorized Scanners

Robotic or motorized corrosion scanners, such as Fast UT from GE Inspection Robotics, are particularly useful for inspection in confined spaces or overhead pipe runs, where it is unsafe or impractical to introduce a live inspector. During a maintenance turnaround where time is critical, it is often desirable to avoid the time delays and costs associated with ventilation, rigging, scaffolding or hole watch. The use of a robotic scanner or crawler can pay for itself in a single turnaround.

When selecting a robotic scanner, it’s important to ensure compatibility with your existing UT flaw detector, and to ensure that the device is certified as  intrinsically safe when it will be operating in highly hazardous environments.

Manual Scanners

Manual scanners operate in much the same way as a motorized scanner, but with the requirement of a live inspector to physically move and operate them. Because they have fewer moving parts they can be very reliable. However to ensure accurate encoding of the scanned surface area, they require strong magnets and precision mechanics. It is advisable to train operators on manual scanning carefully to ensure consistent procedures.

High quality UT instruments such as GE’s Mentor UT are compatible with a variety of commercially available aftermarket scanners and robotic systems to meet virtually any corrosion mapping need.

DM Array Probes

For corrosion inspection and mapping, it is recommended to use a multi-element array probe, such as GE’s DM phased array probes. They provide comprehensive linear coverage and excellent resolution of backwall corrosion and pitting. Curved or flat wear bars can be added to the probes to extend probe life, ensure alignment, and aid acoustic coupling to the inspection surface. The larger surface area of multi-element probes allows inspectors to cover more surface area faster, and an advanced C-scan image display provides a visual representation of wall thickness loss.

Because corrosion mapping often takes place in challenging field conditions or at high temperatures, it’s important to consider the quality of probe construction when choosing a probe supplier.

Conventional DM Probes

When initial corrosion mapping of a pipe or tank wall identifies irregularities, inspectors are often called on to conduct more specific point inspections or thickness measurements using conventional UT. To maximize inspector productivity, the best phased array UT instruments are equipped with a conventional channel so these spot-checks can be conducted with the same instrument.

Conventional dual element transducers are recommended for spot-checking and measuring remaining wall thickness in corrosion application. Dual element transducers generate sound waves with one element and receive with another – in a ‘V-path’ orientation, which increases sensitivity when examining corroded or pitted back walls.


For productive and precise corrosion inspection, software can be just as important as probe and scanning hardware. Today a new generation of “app-based” UT flaw detectors operate much like a smartphone, allowing users to customize their device interface and build error-reducing guided inspection procedures. These “apps” can automatically identify compatible probes, improve calibration consistency and lock-out unnecessary device parameters, ensuring more reliable and repeatable inspection data. In addition, remote collaboration and live streaming via wireless internet streamlines reporting and allows experts to offer second opinions on tough inspection calls.

With the right combination of probes, scanners, software and accessories, today’s NDT inspectors are speeding up corrosion inspections and improving accuracy.

Learn more about GE’s newest ultrasonic corrosion mapping instrument atwww.mentorut.com and download our popular corrosion inspection probe and scanner configuration guide at:https://www.gemeasurement.com/download/mentor-ut-probe-scanner-and-accessory-guide

Dave Jankowski is the NDT Portable Products Sales Leader for GE Inspection Technologies. He holds a masters’ degree in materials engineering from Case Western Reserve University.


Would You Do This to Your Smartphone?


By Josh Scott, GE Portables Engineering Manager

One of the best things about being an engineer is the chance to solve challenging problems with my team every day. At GE, we design and build digital inspection instruments that help industrial companies keep their operations running smoothly.

These precision instruments use ultrasound, electromagnetic current or advanced 3D visual measurement to find the tiniest cracks, pits, dents and flaws that could cause a tank or pipeline to fail or a turbine to go offline. Tolerances are measured in thousands of an inch. At the same time, these precision instruments need to be designed to stand up to harsh industrial environments, day in and day out, for years.

As technology has improved our products have become more sophisticated, with touch-screen interfaces and digital apps, much like a smartphone. They are built with onboard wireless connectivity and interchangeable probes and batteries. Imagine taking your smartphone into a desert oil field where it has to withstand sand, dust, extreme temperatures, impacts and scratches. Or imagine taking it to an Alaskan oil pipeline where it has to operate well below freezing and stand up to repeated drops into wet snow and mud.

These are the problems my team solves every day, which is why we enjoy our work so much. We shot this video in our test lab that shows the tough environmental tests our instruments go through before they leave the factory. Check it out:

The instrument that’s taking that terrible beating in the video is Mentor UT, our newest and most advanced ultrasonic array flaw detector. Mentor UT is optimized for corrosion mapping inspection in the Oil & Gas and Power Generation industries. To meet the demands of these heavy industrial applications, Mentor UT is tested to IP65 and MIL-STD-810G specifications for water resistance, dust resistance, extreme heat and humidity, cold, vibration, shock and drops.

We know our customers count on GE Inspection instruments to provide accurate readings and to work every time. That’s why we’re tough on our products before they leave the factory, and that’s why we work so hard to design quality into every unit.

Fight the High Cost of Corrosion with Advanced Ultrasonic Inspection


By Bob Ward, Senior Product Manager at GE Digital Solutions

Corrosion and erosion represents a tremendous cost to process industries in the form of lost production and unplanned repairs. In the worst case scenario unchecked corrosion can lead to catastrophic equipment failure. A well-known study published the National Association of Corrosion Engineers (NACE) indicates that the direct cost of corrosion is more than 3% of the U.S. Gross Domestic Product (GDP).

Regularly scheduled nondestructive corrosion inspections can validate corrosion rates, identify areas of concern and allow engineers and operators to better plan for maintenance. While conventional ultrasound thickness (UT) readings can be of use with regularly scheduled inspections, they do often not provide enough precision to adequately determine wall thickness losses from corrosion. Pitting cannot be reliably detected by conventional UT methods simply because the size of the defect is small compared to the area inspected.

Advances in phased array ultrasound (PAUT) techniques have now been developed to achieve the needed precision while inspecting large areas efficiently. In order to implement these techniques on a large scale the industry must find ways to overcome the high cost of training technicians, improve consistency between tests and reduce equipment costs. Fortunately, the ultrasound equipment  industry is responding to these challenges.

The high cost of training technicians is the most pressing issue, since phased array UT instruments can be complex and time-consuming to operate. Fortunately, more training institutes and colleges are incorporating phased array ultrasound technology courses, and the great benefits of phased array have resulted in more companies investing in training.

Equipment manufacturers, such as GE Inspection Technologies, are developing new “smart” inspection devices that allow the experts to simplify and customize the user interface of UT instruments so that a less experienced technician can learn and operate them quickly and easily. These devices use touch-screen “apps” to walk technicians through instrument setup, calibration and inspection procedures, which improves inspection consistency.

If a technician does not understand a step or a data signal, he or she can push a button on the device and wirelessly stream their inspection to the PC, phone, or tablet of a remote expert. These new technological developments are making it possible to realize the benefits of phased array corrosion inspection on a global scale.

The direct and indirect costs of corrosion can be staggering. With advances in inspection technologies and improved maintenance schedules, equipment manufacturers and providers are helping organizations control costs and safeguard the health of their assets.

For more information, read my recent article in Inspection Trends; Corrosion, Monitoring, Detection and Measurement  ( https://goo.gl/bQTqot)

Benefits of Digital Radiography for Process and Personal Safety

In a recent post we discussed a few advantages of digital radiography for nondestructive testing. There are, however, several benefits to transitioning to digital radiography for corrosion inspection from traditional film radiography, particularly improved safety during testing, instantaneous feedback and new possibilities for inspection.

The traditional use of film-based radiography brings with it a number of safety concerns, including:

  • High doses of radiation in the plant.
  • Maintenance of a large restricted area during the use of film-based radiography equipment.
  • The stoppage of work due to film-based radiography equipment use and the costs associated with that downtime.

Converting to digital radiography essentially eliminates those concerns. In many cases pulse type x-ray units can eliminate isotope utilization. Lower curie sources and iridium are used as opposed to cobalt when testing heavy items. Implementing a digital radiography approach limits exposure time to 10 to 45 seconds (conforming to As Low As Reasonably Achievable – ALARA – standards.)

Consider a facility that has several leaks, cracks and corrosion on 16 inch pipes. The use of film or computed radiography (CR) only allows workers to conduct three to five inspections per day without exceeding the exposure limits allowed per hour. Leveraging a digital radiography approach reduces exposure time to 30 seconds per inspection, greatly reducing exposure to plant workers. An easy rule of thumb to remember – one minute film shot equals a 40 second CR shot equals six seconds of a digital radiography shot.

With digital radiography, the instant display of the radiograph at the point of inspection makes the need for re-shots virtually impossible, eliminating the need for unnecessary exposures. The plant operators now have results almost instantly. In many cases the x-ray image may be viewed in seconds and at remote locations even thousands of miles away. This is similar to doctors sharing patient x-rays and scans in hospitals miles away from one another.

What enables the digital X-ray  workflow that addresses lack of industry expertise, geographic challenges, documentation, quality control, and remote collaboration with data integrity is the industry standard DICONDE (non- propriety).

 DICONDE is a designated ASTM E2339-04 Standard and stands for:

  • D – Digital
  • I – Imaging and
  • CO – Communication in
  • NDE – Nondestructive Evaluation

DICONDE is the backbone of a modern digital radiography workflow and supports full image integrity as well as specific transmission protocols and enables truly global operations and compatibility with other DICONDE devices.

  • Data can be readily shared between DICONDE workstations
  • Image data can be automatically pushed to multiple workstations
  • Data can be automatically pushed during non-peak working hours
  • Rhythm and the DICONDE protocol will ensure data-integrity
  • Reduction of Level 2 and Level 3 labor required


Example of a global architecture where radiography inspection, image assessment and remote diagnosis are done on different geographic locations  

Digital radiography provides new opportunities to inspect and test equipment for damaged mechanisms, particularly due to corrosion and erosion. Operators and asset owners can now conduct inspections of structures that are thicker and more complex in less time and often with lower radiation sources. New technologies and improvements may be used for both in-process inspection as well as new construction. Enhanced image quality is associated with improved measurement capabilities and increased probability of damage detection.

To read more about the benefits of digital radiography, you can find the full article here in Inspectioneering.

By Richard Mills, GE Radiography SME and ASNT Level III

Monitoring, Detecting and Measuring Corrosion

Natural objects, such as granite, and man-made structures, such as bridges, cars, ships, refineries, aircraft, are all subject to the same environmental stresses. Light, temperature changes, water, and gasses in the air all play a role in the breakdown of materials. The one major difference is just how quickly that breakdown occurs.

A general term for the degradation of man-made structures is corrosion. Scientists try to understand the mechanisms by which corrosion occurs, design barriers to corrosion, find ways to monitor the progress of corrosion, and build processes for asset maintenance and systems to reduce the overall costs of corrosion to society.

Digital X-Ray Image 1

The economic impact of corrosion has been researched at length. A well-known study published in 1999 by NACE (the National Association of Corrosion Engineers) titled The United States Cost of Corrosion Study indicates that the direct cost of corrosion is more than 3 percent of the Gross Domestic Product (GDP). Similar studies report direct costs ranging from 2 to 4.5 percent of the GDP. The real issue is where direct costs end and indirect costs begin.

Given these enormous costs, it is not surprising that there are large industries centered on:

  1. Corrosion prevention (such as additives in water systems, coating materials like paint for automobiles, etc.)
  2. Corrosion repair and maintenance
  3. Corrosion monitoring, detection, and measurement.

Regularly scheduled inspections can validate corrosion rates and allow engineers and operators to better plan for maintenance situations. While ultrasound thickness (UT) readings can be of occasional use with regularly scheduled inspections, they do not provide enough precision with the collection of manual thickness readings to adequately determine wall thickness losses from corrosion. Pitting cannot be reliably detected by conventional UT methods simply because the size of the defect is small compared to the area inspected. Phased array ultrasound (PAUT) techniques can be developed to approach the needed precision and get great coverage quickly.

The direct and indirect costs of corrosion can be staggering. With improved inspection technologies, such as digital radiography and phased array ultrasound, and maintenance schedules, equipment manufacturers and providers are helping organizations control costs and get a better handle on the health of their assets.

For more information on corrosion monitoring, detection and measurement, read Robert Ward’s article in Inspection Trends Corrosion, Monitoring, Detection and Measurement. And, for more information on GE’s phased array flaw detectors, visit here.

By Bob Ward, Senior Product Manager, Portables, GE Measurement & Control