Guided Ultrasonic Wave Technique (Wavemaker)

Guided Wave (UT) allows a large area of pipework to be inspected from a single transducer position.

Wavemaker Schematic Diagram

  • The Guided Wave (GW) travels along the length of the pipe and is reflected by changes in pipe stiffness (ncluding changes in acoustic impedance)
  • A symmetrical change in wall thickness generates a uniformly reflected signal whereby a localised thickness change is recorded differently.
  • A unit of piezoelectric transducers is clamped around the pipe and the GW
    are sent simultaneously in both directions along the pipe with 100% screening coverage within its diagnostic length.

Wavemaker transducerring from GUL

Example of results obtained using guided waves showing results obtained from both sides of the transducer ring

General inspection capabilities

  • Rapid inspection of both internal and external defects on long pipe sections.
  • Wavemaker technology is available both in screening and monitoring configuration (PIMS)
  • Wavemaker technology is available both with external or internal access transduction system. T-scan (internal access system) is used to screen structures such as heat exchanger tubes.
  • Wvemaker technology is also used for underwater inspection of risers and other pipelines
  • Wavemaker G3 in screening configuration can detect metal loss and cracks >1% cross-sectional area depending on given conditions. From 5% cross sectional area most defects can according to the suppliers be detected with confidence.
  • Wavemaker G3 in monitoring configuration can detect defects as small as 0.1% of the cross sectional area.
  •  Most suitable for inspection of long, un-flanged lengths of pipe.
  • Guided waves are suitable for use on pipe diameters from 16mm (3/4″) -1800 mm (72”). Inflatable rings need to be used for bigger pipes.
  • Wall thicknesses up to 75mm (3”) have been inspected.
  • No couplant is required.
  • Inspectable Materials include all metals
  • Types of Pipe: Seamless, Longitudinally welded, Spiral welded
  • Coatings: Polyurethane foam insulation, Mineral wool insulation, Epoxycoated, Tar epoxy coated, PVC coated, Painted.
  • Other: Under ideal conditions roughly 100m can be inspected in a single test. The length of pipe that can be inspected is heavily dependant on several factors and range can be much lower than ideal case.

Inspection limitations

  • Access to a surface is needed (360 degreed over 25cm axial length)
  • The method cannot pass through flanges and does not inspect flanges.
  • Standard practice is to only inspect past one bend at a time.
  • High viscosity of the pipe content (for example bitumen) will attenuate the signal and can therefore be difficult to inspect.
  • Pipes coated with attenuative coatings (e.g. soft thick and well adhered bitumen) can reduce range (or sensitivity). Coating condition and bond nature affect the ease.

Parameters affecting inspections capabilities

  • The frequency of ultrasound will govern how small or big defect can be detected but higher frequency resulting in higher sensitivity will decrease the range.
  • Type of coating utilised on pipe
  • Viscosity of pipe content will affect inspectability
  • Pipe geometries and condition.
  • Internal deposits and lining