Inspection Requirements and Frequency
The schedule for testing and inspections for tank in this size range is listed below.
Periodic AST Inspections MONTHLY unless otherwise directed by the engineer in the SPCC plan.
- Performed by site owner/operator
- No need to be certified, just knowledgeable
- Checklist is included in Steel Tank Institute (STI) standard
- Records of inspections must be maintained
Formal External Inspection by certified inspector EVERY TEN YEARS
These are documented external inspection conducted by a certified inspector to assess the condition of the AST and determine its suitability for continued service without entry into the AST interior.
- Conducted by Certified Inspector
- Inspector should review previous periodic inspection checklists and previous FEIs/FIIs
- Includes ultrasonic thickness testing (UTT)
- Must determine original shell thickness and establish current shell thickness
- UTT can lead to ultrasonic testing scan (UTS)
Leak Testing by owner or owner’s designee EVERY TEN YEARS
Leak testing is a point in time test method to determine if an AST is liquid tight. Leak testing is not preventive in the sense that it provides an indication only if the AST integrity has already been breached. Therefore, it may be used as a tank integrity measure or as a supplement to other inspection procedures. LTMs may include the following technologies:
- Gas pressure decay (includes vacuum decay)
- Gas pressure soap bubble testing
- Gas tracers (e.g., helium tracer)
- Soil tracers (chemical marker)
- Mass measurement
- Level measurement
- Hydrostatic test