When it comes to keeping storage tanks safe and compliant, ultrasonic tank inspection is the gold standard. Whether you are assessing oil and gas vessels, chemical storage, or water treatment tanks, ultrasonic testing (UT) delivers precise thickness measurements and corrosion mapping without cutting into the metal. In this guide, we’ll walk through key best practices for B-scan and C-scan inspections, share tips to avoid common pitfalls, and explain how ScanTech’s field-driven scanners and Analyst™ software can streamline your workflow.
Why Ultrasonic Tank Inspection Matters
Over time, tank walls can thin or corrode, leading to leaks or catastrophic failures. Regulatory codes like API 653 mandate regular inspections to verify wall integrity. Compared to visual checks or hydrostatic tests, ultrasonic methods provide:
- High accuracy down to 0.1 mm
- Full coverage of floor, shell, and roof surfaces
- Permanent digital records for compliance
By catching corrosion early, you can schedule repairs during planned outages and avoid unplanned downtime.
Choosing Between B-Scan and C-Scan Techniques
B-scan shows a cross-section view along a single line. It’s ideal for spot checks and weld evaluations. Your technician moves the probe along the weld seam or a vertical grid, capturing thickness changes in real time.
C-scan produces a two-dimensional map of an entire surface. Using a motorized scanner, you cover the full tank floor or sidewall in a raster pattern. Analyst™ C-scan software then generates a color-coded map, highlighting thin spots and corrosion pockets at a glance.
When to use each method:
- Use B-scan for quick weld verification or isolated checks.
- Use C-scan for a full-surface corrosion survey, especially on large or critical tanks.
Best Practices for Reliable Results
- Calibrate Before You Scan
Always perform a step-wedge test or known-thickness block check at the start of each shift. Confirm your UT probe and coupling gel deliver the correct thickness reading before moving to the tank surface. - Maintain Consistent Probe Pressure
Uneven pressure leads to fluctuating readings. Use a lightweight sled or a spring-loaded probe holder to ensure steady contact and reduce operator fatigue. - Minimize Geometric Unsharpness
Keep the probe as perpendicular to the surface as possible and avoid tilting the transducer. Any angle can blur your measurements and create false indications. - Plan Your Scan Grid
For C-scan surveys, set a grid spacing that balances speed and resolution. A typical 10 mm grid on a 20 mm thick wall yields clear maps without excessive time overhead. - Use the Right Frequency
Lower frequencies (1–2 MHz) penetrate thicker steel but sacrifice resolution. Higher frequencies (5 MHz and above) deliver sharper detail on thinner walls. Match your probe frequency to tank wall thickness.
Common Pitfalls and How to Avoid Them
- Poor Coupling: Bubbles or dry spots in the gel block your signal. Always apply fresh coupling gel and inspect for uniform coverage.
- Surface Contamination: Rust, paint, or scale can interfere. Clean or grind down inspection areas before scanning.
- Data Overload: Raw C-scan files can be large. Use Analyst™ software’s real-time filtering to highlight only readings below a critical threshold, saving time in post-processing.
How ScanTech Makes Tank Scans Easier
ScanTech’s ultrasonic scanners are built by NDT veterans who know what technicians need in the field. Our manual and automated scanners feature:
- Modular sleds for quick probe swaps
- Integrated step-wedge holders for on-the-fly calibration
- Rugged, weather-proof housings for outdoor work
Paired with Analyst™ B-scan and C-scan software, you get:
- Instant thickness display and corrosion maps
- Automated report generation in API 653-compliant formats
- Cloud archiving for easy sharing with stakeholders
Next Steps: Schedule Your Tank Scan Demo
Ready to see ScanTech ultrasonic tank inspection in action? Contact us to book a live demo, and learn how our field-driven solutions can help you catch corrosion early, reduce downtime, and stay compliant.
