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Aboveground Storage Tanks (AST) & Fuel Terminals
Aboveground Storage Tanks (AST) & Fuel Terminals
API 653 Storage Tank Bottom Plate MFL Inspection Scope
High-Speed Magnetic Flux Leakage Floor Mapping & Ultrasonic Sizing
Primary NDT Techniques:MFLUT
Targeted Damage Mechanisms
- Soil-side Bottom Pitting
- Product-side Acid Corrosion
- Floor Plate Lap Weld Cracking
Key Inspection Challenges Resolved
- Soil-side pitting on floor undersides is invisible from the top surface.
- Tank outages have tight schedule windows requiring high square-footage scan speeds.
- Plate thickness variations and floor coatings complicate defect sizing.
Standard Field Inspection Workflow
1
Floor Surface Prep & Grid Layout
Clean floor plates to remove sludge and heavy scale. Lay out digital grid coordinates matching tank floor plate arrangement drawing.
2
Motorized MFL Floor Scanning
Drive 64-channel MFL floor scanner (e.g. Eddyfi SIMS) at speeds up to 1 m/s. Capture dual Hall-effect sensor data for top vs. bottom pit discrimination.
3
UT Defect Verification & Sizing
Follow up all MFL defect signals above 20% loss threshold with high-precision UT thickness gauge or Crawler UT to measure exact remaining pit depth.
4
API 653 Remaining Life Calculation
Input minimum floor thickness readings into API 653 formula to establish next out-of-service inspection interval.
Recommended Hardware & Probes
- Eddyfi SIMS / Silverwing MFL Scanner
- Olympus 38DL Plus UT Thickness Gauge
Governing Inspection Standards
- API Standard 653 Tank Inspection
- EEMUA Publication 159
- ASNT SNT-TC-1A
Ready to Execute This Scope?