Guided Wave Inspection (GWI/LRGW) uses mechanical stress waves to propagate though elongated structures while guided by its boundaries. The wave travels along the distance with little loss of energy. It uses very low ultrasonic frequencies.

Advantages

• Long range inspection – has the potential to achieve hundreds of meters of inspection range.
• Limited access – insulated line with minimal insulation removal, corrosion under supports without need for lifting, inspection at elevated locations with minimal need for scaffolding, and inspection of road crossings and buried pipes.
• Data is fully recorded.
• Fully automated data collection protocols.

Disadvantages

• Interpretation of data is highly operator dependant.
• It is difficult to find small pitting.
• Not very effective at inspection areas that are close to accessories.
• Needs good procedures.