The waves propagate up to three feet into the annular plate. When corrosion, pitting, erosion are present the ultrasonic waves mode convert and are received by the same transducer.
its also being used to test for corrosion under pipe supports, corrosion at soil air interfaces, and similar difficult to access locations.

Graphic Figure One depicts the transducer placement on the chime plate propagating long range ultrasonic waves into the annular plate.

The sound reflects at top side or underside corrosion providing a C-scan image of the defect. The signal strength at the defect provides evidence of the depth and overall morphology of the defects.

Applications:

• Tank Floor Annular Plate Testing
• Testing Concrete Coated Interfaces
• Testing Under Pipe Supports
• Tank Dyke Piping Interfaces
• Scan Under Vessel Supports

Limitations of this technique are:

• Top or Bottom Side Differentiation
• Must Have 2″ Space for Probe Placement

This is considered as one method for determining the integrity of tank annular plates where the highest probability of corrosion exists to help prioritize out of service tank maintenance requirements.