API-653 is the standard for 50-feet or taller tanks along with tanks that are greater than 30-feet in diameter. It covers the maintenance, inspection, alteration, and repair of steel and must be performed by a professional, licensed inspector.
An API-653 inspection reviews tank specifications, construction, release detection methods, and spill control. It allows different types of inspection to examine aboveground tanks components such as:
- Visual
- Ultrasonic
- Liquid Penetrant
- Magnetic Particle
- Radiography
- Vacuum Box
- And more
When it comes to the structure of the tank, API-653 standards take into account minimum remaining thickness, minimum required thickness, and maximum corrosion rate. Some other factors assessed under API-653 to examine whether the tank is tilting or settling in the ground improperly include:
- Out of plane
- Rigid Body Tilting
- Uniform
- Dish Type
- Edge Settlement
- Localized Dispersions
An API-653 external inspection is required every five years while an API-653 internal inspection is required every ten years. Monthly, it is recommended under API-653 for site owner/operator’s inspector to thoroughly assess the overall tank condition without removing the aboveground tank from service.