What Is Guided Wave Ultrasonic Testing?
Guided Wave Ultrasonic Testing (GWUT) — also referred to as Long Range Ultrasonic Testing
(LRUT) or Guided Wave Testing (GWT) — uses low-frequency ultrasonic waves that propagate
along the length of a pipe wall, guided by the pipe geometry. A transducer ring, clamped around
the pipe at a single accessible location, transmits guided wave pulses in both directions along the
pipe. Reflections from welds, supports, features, and anomalies (corrosion, wall loss, cracks) are
recorded and displayed as a time-domain trace — with each reflection position corresponding to
a specific distance from the test point.
Long Range UT (LRUT): Inspection range typically 10–50 metres in each direction from the
transducer location. Used for rapid screening of long pipe runs, buried crossings, and insulated
lines. Detection sensitivity to cross-sectional area loss of approximately 2–9% depending on pipe
condition and attenuation.
Medium Range UT (MRUT): Inspection range typically 1–5 metres. Used where LRUT range is
insufficient due to attenuation (heavy coatings, insulation, or corroded pipe condition) or where
higher defect sensitivity is required in a targeted zone. Provides better resolution and sensitivity
at shorter range compared to LRUT.
Key advantages:
- Single access point inspection — coverage extends metres in each direction
- No requirement to remove insulation along the full inspection length
- Applicable to buried, clad, insulated, and elevated piping
- Rapid screening — metres per minute compared to point-by-point UT survey
- No couplant required — dry coupling transducer ring