1. Detection Principle and Physical Basis
- Wall thickness detection is based on ultrasound propagation in metallic media.
- An ultrasonic probe emits high‑frequency sound pulses toward the tank wall; echoes are generated at inner and outer surfaces.
- By measuring the round‑trip time and using known sound velocity in steel, wall thickness is calculated.
- This method is non‑destructive, highly accurate, and especially suitable for uniform corrosion thinning detection on carbon steel tanks.
2. Detection Technology and Implementation Methods
- A digital ultrasonic thickness gauge with coupling agent is used for effective sound wave transmission.
- A grid is drawn on the tank wall, focusing on corrosion‑prone areas: gas‑liquid interface, weld heat‑affected zones, and bottom edge plates.
- For large tanks, automated wall‑climbing inspection robots enable scaffold‑free operation, improving efficiency and safety.
- Local suspicious areas may be further examined using magnetic particle or penetrant testing to detect surface cracks and stress corrosion.
3. Inspection Cycle and Frequency Requirements
- Wall thickness testing must be included in the annual maintenance plan, with a comprehensive measurement at least once per year.
- Inspection points should be numbered and documented at fixed locations for long‑term trend comparison.
- If the tank operates in a highly corrosive environment or localized thinning has been detected, the cycle shortens to every six months.
- Based on corrosion rate assessment, international standards recommend a maximum inspection cycle not exceeding nine years to ensure structural integrity.
4. Industry Standards and Data Management
- Testing must comply with SY/T 6620‑2014 and GB/T 37327‑2019 standards.
- Inspection data must be compiled into a written report including measurement point location, original thickness, current thickness, corrosion rate, and estimated remaining service life.
- Corrosion rate is typically conservatively estimated at 0.1 mm/year.
- Test results guide maintenance strategies, ensuring the storage tank operates within a safety margin.