BACKGROUND
Long Range Guided Wave (LRGW) is an advanced ultrasonic inspection techniquethat
allows large areas of pipework to be inspected from a single test position.
Compared to conventional ultrasonic methods, LRGW uses low frequency, long wavelength signals, without compromising sensitivity and with the added bonus of rapid screening capabilities as opposed to spot measurements. petrohouse utilizes the Wavemaker G3 - 3rd generation equipment that has greater sensitivity, increased reliability and improved data analysis - capable of a speedy, in service inspection to locate wall defects.
APPLICATIONS
LRGW is particularly suited to situations where there are long lengths of pipe to be inspected, with limited access, which often may be un-pigable. petrohouse also uses this technique as a rapid, baseline-screening tool to identify areas of concern. Current applications include:
- Buried / Submerged Pipe
- Road Crossings / Jump Overs
- Pipe with Restricted Access e.g. Pipe Racks
- Vertical Pipe
- Insulated Pipe (CUI)
- Un-pigable Pipe
- Offshore Risers
- Storage Sphere Supports
- Long Term Corrosion Monitoring (PIMS)
PROCEDURE
Pipework is exposed over a small area (bell holes prepared if buried pipe, insulation & coating removed, flaking material scraped off), and a 360o transducer ring is clamped in place. Ultrasonic signals are then emitted in both directions, propagating along the pipe wall, providing 100% volumetric inspection.
The configuration of the equipment, choice of transducer as well as the test parameters are all determined by a number of factors including pipe schedule, condition, substrate, coating, sensitivity, range etc…
Interpreting the results requires extensive experience as well as local knowledge of the pipework being inspected. Reflected amplitude, symmetry, phase and orientation of reflection, behavior at different frequencies and reverberations are all taken into account.