Date: 2/22/2018

Through ultrasound technology, doctors use high-pitched audio waves to look beneath the skin and determine the health of a human body.

Freight railroads are exploring a similar technology that sees through steel and determines the health of railroad tracks.

Railroads have been using ultrasound inspection tools for years, but “phased array” ultrasound technology is the newest iteration of this ever-changing technology. Though earlier versions could find 90% of largely invisible defects, such as microscopic cracks, railroads knew they could do even better. After years of investment, research and development, they soon will. When phased array is deployed in the next several years, it will help railroads locate almost all of the remaining 10% of imperfections.

For more than a decade, experts in the field of non-destructive testing have been developing phased array technology for commercial use. In 2012, America’s freight railroads realized that phased array could help the industry overcome the challenges faced with conventional ultrasound inspection, such as inconclusive results from worn rails.

Working with EWI (formerly Edison Welding Institute), Dr. Matthew Witte led his project team of engineers at the Transportation Technology Center, Inc., in Pueblo, Colorado, to conduct exhaustive research and customize the phased array technology to meet the unique needs of railroads. Witte’s team also developed a computer system and accompanying software to interpret the results. Within a matter of just a few years, railroads will be able to use the technology across North America’s freight rail network.

Once phased array is operational, inspectors will be able to use it to examine a rail from multiple angles simultaneously. Like traditional ultrasound inspection techniques, phased array units will be installed on the underbelly of inspection vehicles and driven down rail tracks. As the phased array unit pulses electronic signals towards the rail, safety experts inside the inspection vehicle will monitor real-time feedback on computer screens. These inspection vehicles will travel the network, regularly monitoring the health of the system’s 140,000 miles of steel rail.

Should it uncover an issue with any rail, phased array technology will allow inspectors to switch into “high definition” mode. With the inspection vehicle stopped over the problem area, inspectors can conduct a more thorough examination of the track from hundreds of angles in a matter of minutes and achieve a level of detailed inspection that was never before possible. Railroads can pinpoint flaws much earlier and resolve them quicker than ever. Such detailed analysis will not only reduce the number of inconclusive results, but it will also provide more certainty when a problem is detected or a rail is declared healthy.

Ultimately, a definitive diagnosis and a recommended repair mean that rail lines safely stay in service.

How Phased Array Works

  • A series of crystals are arranged in patterns within a phased array inspection unit.
  • The crystals transmit electric pulses through a lubricant (typically water) at pre-determined intervals (or phases).
  • The electrical signals strike a rail and rebound toward the crystals.
  • The electrical signals return to the phased array unit and are analyzed. If the signals return as anticipated, a healthy picture of a rail emerges.
  • However, a worn or otherwise defective rail will warp the trajectory of the signal. By studying the signal’s altered course, rail inspectors will be able to identify a problem within the rail or conduct a follow-up inspection to learn more about the anomaly.