Guided Waves FAQ

Can guided waves propagate beyond elbows?

Yes, the wave can propagate beyond elbows. However, accuracy, resolution, and sensitivity are affected, dependent on the technique.

  • MRUT is less affected since the waves travel a shorter distance.
  • LRUT is more affected due to the loss of symmetric properties of the signal (affecting accuracy, sensitivity, and a reduction of probability-of-detection due to a decrease in signal-to-noise ratio). Typically, after two elbows, it is extremely difficult to evaluate the signals. The loss of symmetric properties of the signal will also affect the circumferential resolution of the defect.

Can guided waves techniques using VOLTA be used for corrosion under pipe support (CUPS) inspection?

Yes, one of the most important features of VOLTA is the possibility to combine techniques:

  • With MRUT-Lamb (PMX Scanner):
    - For inspection of pipe supports from top;
  • Axial or circumferential wave propagation, in attenuation and/or reflection modes.
  • With MRUT-SH:
    - For inspection of inaccessible areas from side (e.g. air-to-soil interface and wall penetration);
    - Increase of 30 to 40 dBs compared to MRUT-Lamb.

Can you explain how the uni-directionality function works in VOLTA?

By applying a delay in sequence between the pulses of two coils:

  • Two superimposed coils positioned at ¼ wavelength apart are also pulsed at an additional ¼ wavelength out-of-phase, thus, creating a constructive interference in one direction and destructive interference in the other. The timing of the pulsing can be reversed to switch directions.

For the MRUT-SH technique, what are the options for adhering the magnetostrictive strip?

The MRUT-SH technique requires the application of magnetostrictive strip (MS Strip), in order to generate the required magnetostrictive force. The MS Strip can be adhered via the following method:

MS Strip Adhesion Options

Double-Sided Tape – Standard (P/N 027V0086)

  • For smooth inspection material;
  • Good signal cancellation properties;
  • Easy to be removed (MS Strip can be re-used);
  • Temperature: Up to 140 °F (60 °C).

Double-Sided Tape – Rough Material (P/N 027V0083)

  • For rough inspection material;
  • Poor signal cancellation properties;
  • Requires cleaning of MS Strip, in order to be re-used;
  • Temperature: Up to 95 °F (35 °C).

Epoxy (P/N 116V0052)

  • Curing Time: ± 3 hrs;
  • Good signal cancellation properties;
  • MS Strip cannot be re-used;
  • Temperature Range: 68 °F to 104 °F (20 °C to 40 °C).