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Enhanced sizing accuracy for corrosion mapping using ultrasonic arrays

Project Code: 35593

Start date and planned duration: August 2023, 5 months


  • Improve the thickness measurement accuracy that can be achieved on industrial components in the presence of corrosion using novel ultrasonic testing techniques.
  • Demonstrate FMC pitch-catch can achieve equivalent thickness measurement sizing accuracy relative to ToFD.
  • Extend the applicability of FMC pitch-catch technique to enable inspection of corrosion in restricted access areas (by deployment of an asymmetric FMC setup).  

Project Outline

The project seeks to improve sizing accuracy of ultrasonic testing (UT) and phased array ultrasonic testing (PAUT) thickness measurement systems as well as offer an alternative sizing method to time of flight diffraction (ToFD), appropriate for personnel with PAUT certification.

Inspection and monitoring the degradation of metallic structures due to corrosion is a global requirement, with non-destructive testing (NDT) inspection techniques such as UT, PAUT and ToFD, routinely deployed to relevant codes/standards.

For the most accurate thickness measurement accurate knowledge of the material acoustic velocity is required. In reality calibration blocks fabricated from similar grade material can be used to calibrate velocity for inspection of a range of industrial assets. For components of unknown material grade, differences in velocity between the calibration block and component under test may reduce the accuracy of thickness measurement by as much as ~4% (e.g for austenitic steels), equating to 2mm of sizing accuracy error in a component with 50mm nominal through wall extent. 

The use of ToFD may achieve similar or improved thickness measurement accuracy to UT or PAUT, but is still dependent on accurate knowledge of material velocity as described above. Availability of qualified ToFD personnel can also be more difficult obtain, with some infrastructure operators avoiding its deployment due to a lack of qualified operators.

Industry Sectors


Oil and Gas

Benefits to Industry

Industry pull to offer improved thickness measurements for corrosion mapping:

  • Current techniques reliant on calibration blocks to determine acoustic velocity
  • Often the calibration block is a different grade material to the component under test, with one calibration block used for many applications.
  • Differences in austenitic stainless steel grade may equate to ~4%  difference in velocity, equating to a difference in thickness measurement of 2mm for a 50mm thick component.
  • Algorithms developed within the scope of this work aim to automatically assess the material acoustic velocity of the component under test, without the need for calibration step blocks or prior knowledge of the component nominal thickness.

Removal of additional training/personnel required for ToFD:

  • Trained UT/PAUT operators widely used within industry. 
  • As an additional inspection technique ToFD requires additional personnel or additional training of existing personnel.
  • PAUT/FMC pitch-catch offers a solution which examines a component with a similar approach and sizing accuracy to ToFD, but the equipment, acquisition and data interpretation can be done with PAUT training/qualifications, reducing the personnel costs.




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