guided wave ultrasonic testing and LRUT basic

guided wave ultrasonic testing for pipeline inspection in oil and gas industry

Why choose guided wave ultrasonic testing pipeline inspection?

lrut gwt guided wave technology
guided wave ultrasonic testing for pipeline inspection

LRUT (Long range ultrasonic testing) or sometimes called as GWT (guided wave testing) or GWUT (Guided wave ultrasonic testing) is becoming commonplace today for ultrasonic pipeline inspection. This technology is used as excellent NDT for the screening tool. Guided wave ultrasonic pipeline inspection offer many advantages such as High productivity (km per day), access required only at discrete locations, carried out with pipe on-line ( not require shutdown) and 100% coverage except for flanges, tees and other large features. This LRUT/GWT technology come as a solution for pipeline inspection problem like restricted access, many lines not suitable for in-line inspection (ILI / pigging inspection), regular UT and RT techniques are typically not cost-effective or typical UT and RT coverage 0.1%. After conduct LRUT/GWT screening and found some anomaly or “indication”, the inspector will dig the anomaly with other NDT tools such as UT scanning or UT Flaw detector.

LRUT guided wave ultrasonic pipeline inspection and testing
guided wave ultrasonic pipeline inspection and testing

How guided wave ultrasonic testing work?

The tools create Symmetric waves that transmitted along the pipe. The waves propagate along, not through, a pipeline. The wave is reflected from changes in the cross-section in a pipeline. The amplitude of the reflection depends on the total change in the pipe wall cross-section. The percentage cross-section loss is given by the reflection amplitude, but it could be equally distributed around the circumference (e.g. a shallow wall loss) or concentrated in a narrow portion of the pipe (e.g. a critical deep defect).

guided wave ultrasonic testing
guided wave ultrasonic testing

Standard UT uses high frequency and short wavelength. Standard UT sensitive to small defects at high frequencies and use as point measurement. Guided waves ultrasonic testing use low frequency and long wavelength. GWT / LRUT sensitive to “small” defects even at low frequencies and used as rapid screening.

Guided wave ultrasonic testing development and its customer

  • 1990 D Alleyne/P Cawley Imperial College
  • 1995 Industrial sponsored project: 1st Wavemaker prototype
  • 1999 Guided Ultrasonics formed: Wavemaker SE16
  • 2005 Wavemaker G3 with dynamic frequency
  • 2007 Enhanced focussing rings and software

Companies which have bought Wavemaker or included it in their procedures include BP, Shell, PetroChina, Gazprom, Chevron, Petrobras, EON, Pemex, Conoco Phillips, Beijing Gas, Oxidental, Dow Chemicals etc. For more information about the product of Guided waves ultrasonic pipeline inspection & testing, please visit

ultrasonic pipeline inspection
Guided wave ultrasonic testing Teletest Focus

advantages of guided waves ultrasonic testing:

  • rapid screening for in-service degradation
  • the ability to scan large lengths of pipeline from a single point
  • avoidance of removal of insulation or coating (except at location of transducer tool)
  • the ability to inspect inaccessible area
  • detection of internal and external damage
  • reduction of inspection cost
Guided wave ultrasonic testing Teletest collar
Guided wave ultrasonic testing Teletest collar


  • large volume of material examined from a single point limits sensitivity and resolution
  • pipe condition ( e.g coating ) and geometry influence test performance
  • currently no means of providing flaw sizing from LRUT / GWUT which can be used to determine fitness-for-service ( currently a screening technique )


Eddyfi Technologies offers CSWIP certified training. Personnel with levels 1, 2, or 3 technique training may be examined and, if successful, certified. Examination eligibility requirements, examination format, and rules governing certificate validity and renewal comply, as a minimum, with ISO 9712(1) and EN 473(2). This certification offers the assurance that technicians are competent with the technique, which serves to give you the best available results for each inspection.

LRUT / guided wave jobs usually involved of 3-5 people, including LRUT Level 2, LRUT Level 1, UT Man, helper and driver. LRUT level 2 has the ability to operate the LRUT / Guided wave device and review and conclude the LRUT signal results (interpretation). Usually the findings (screening) of the LRUT tool will be checked in more detail using a UT tool by a UT Man who has a level 2 UT certification / qualification. The result of the UT tool is the remaining thickness of pipe that will be used by the inspector or engineer to calculate the remaining pipe strength.

Leave a Reply

Your email address will not be published. Required fields are marked *