Short Range Guided Wave Technique

Short Range Guided Wave Technique

The Short Range Guided Wave (SRUT) was designed to test the annular plate of above ground storage tanks (AST's) while the tank remains in-service and for detecting corrosion under pipe supports. The technique is based on the concept of pulsing guided laminar waves into the base material from the chime area. 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.

The technique is also being used to test for corrosion at soil air interfaces, and similar difficult to access locations.

Figure 1 depicts the transducer placement on the chime plate propagating short range ultrasonic waves into the annular plate.

Figure 2 shows the set up when inspecting under pipe supports. 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.

Figure 3 provides a visual presentation of the collected data providing distance inspected, with of inspection along with details on the indications identified.

Limitations for this technique include:
  • Top or Bottom Side Differentiation
  • 2 inch clearance for Probe Placement
  • Tank Floor Annular Plate Testing
  • Testing Concrete Coated Interfaces
  • Testing Under Pipe Supports
  • Tank Dyke Piping Interfaces
  • Scan Under Vessel Supports

SRUT has become a proven and reliable technique as one method for determining the integrity of difficult to access material and can help to prioritize and plan more intrusive inspections.

Short Range Guided Wave - Annular Plate Set-up

Figure 1: Annular Plate Set-up

Short Range Guided Wave - Corrosion Under Pipe Support Set-up

Figure 2:
Corrosion Under Pipe Support Set-up

Short Range Guided Wave - C-Scan Corrosion Map

Figure 3: C-Scan Corrosion Map

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