Knowledge

Phased Array Ultrasonic Testing

Inspection technique:

Phased array is an advanced pulse-echo technique utilizing multiple miniaturized transducers and time-delays to shape the ultrasonic sound beam in a desired angle and focus. Therefore the technique has a wide range of applications. A phased array probe houses an array of ultrasonic transducers which are acoustically insulated from each other. By pulsing the elements with different time-delays, the angle of the ultrasonic sound is ‘steered’ to a specific angle, focus-point or both.

Phased array has several advantages in comparison to manual pulse-echo, such as:

Digital storage of all data, location and system settings

Visualization of indications in weld and/or base material, using B-, C-, D- and S-scans (with all A-scans included)

Possibility to facilitate inspections of complex geometries

Interpretation of the data can be done after scanning.

An overlay of the geometric configuration can also be plotted over the collected data (before and after scanning) for easy defect identification, location and orientation.


Applications:

  • With phased array there is a wide range of applications, such as Weld inspection of vessels, pipelines and plates
  • Weld inspection of complex geometries, such as nozzle-welds
  • Flange face corrosion inspection
  • Fast corrosion scanning utilizing 0 degree angled wedges
  • Code case inspection in combination with Time of Flight Diffraction (TOFD) and/or pulse-echo

The outcome of a phased array report can be either a simple document with all settings and results or an extended report with all scans/views included.


We are pleased to provide services to any location around the world, pertaining as to how NDTS can help you in improving the reliability of your processes and assets.


Sector Scan Definition:

  • Focal laws of different angles generated using the same elements.
  • A-scan density and coverage is defined by the range of angles (45-70) and angle resolution (45, 46, 47, etc.)


Linear Scan Definition:

  • Focal laws generated over a series of elements using the same angle.
  • A-scan density and coverage is defined by the element step resolution. (1 element, 2 element, etc.)


Beam Steering:

  • Is the capability to modify the refracted angle of the beam generated by the array probe.
  • Allows for multiple angle inspections using a single probe
  • Applies asymmetrical (linear) focal laws


Beam Focusing:

  • Is the capability to converge the acousticenergy into a small focal spot
  • In PA, allows for focusing at different depths, using a single probe
  • Uses symmetrical (parabolic) focal laws (time delay vs. element position)


PA Transducer construction:

  • Ceramic Elements
  • Stack Bonding Technology
  • Special Backing material to reduce internal echoes


Effect of PRF:

  • Low velocity materials or thick cross-sections – pulse may not return before next pulses are transmitted
  • May cause standing echoes from colliding wave fronts
  • Called ‘ghosting’



PAUT Calibration:

  • Velocity calibration
    This calibration is needed only once for each wave mode even when using a multi-scan setup.
  • Wedge Delay calibration
    To measure the compensation for the travel of the beams through the wedge medium and account for various exit points. This ensures that indications are displayed at the correct depth.
  • Sensitivity calibration
    It equalize the sensitivity (amplitude) to a given reflector through all the angles.
  • TCG/DAC calibration
    This equalizes the amplitude level of a given reflector size at different sound path by adjusting the gain.
  • Encoder calibration
    To read the appropriate length measurements.