Storage tanks operate at atmospheric pressure and are broken down into types based on design.
- API 650 Above Ground (Fixed / Floating Roofs) large diameter.
- API 650 Shop built.
- API 650 Guided construction.
- Cylindrical Atmospheric Process Equipment.
- Horizontal Storage Tanks.
- Slope bottom filtration tanks.
- Pump Boxes.
- Bins.
- Silos.
- Totes.
- Underground Tanks.
Certification Requirements:
- API 653.
- CGSB UT Level 1, 2, and 3.
- CGSB MT Level 1, 2, and 3.
- CGSB PT Level 1, 2, and 3.
- MFL Level 1, 2, and 3.
- Engineering – FFS, Hydro Exemption, Design, Modification, and Construction.
- Confined Space.
Storage tank designs vary significantly. The large diameter above-ground, fixed roof, internal floating roof storage tank represents the most complex design. Inspection specifications can be scaled using these inspection and construction standards into different applications.
Inspection Checklist:
The following checklist is based on API 653 and outlines basic requirements for tank owners/operators, inspection personnel and associated trades for the inspection and maintenance of above ground storage tanks.
| Inspection Component | Requirement |
|---|---|
| Construction, Design and Year Built | Verify the foundation, bottom plates, shell design including course heights, safe fill height, joint efficiency, allowable stress, roof design, coatings and insulations, nozzles, and relevant operating conditions. |
| Material requirements | Obtain material type, thickness, and corrosion allowance data from drawings, nameplate, and field checks in reference to specified codes to achieve the intended life cycle. |
| Product Compatibility | Verify the name, specific gravity, temperature, and compatibility. |
Foundation:
| Component | Required Inspection |
|---|---|
| Berm Type | Verify the design, secondary liner, berm wall height, capacity, and tank placement within the berm. |
| CP System | Check for the presence of and previous data for CP systems. |
| Walkways | Check walkways and stairways for plum, level, and corrosion. |
| Concrete | Check for cracking, spalling, exposed rebar, washout, and wear. |
| Berm Inspection | Verify if earth berm walls have been eroded by rain, check grounds, remove any vegetation from the berm, verify the capacity (Directive 55) using measurements or laser scan data. Build-up walls as required. |
Shell:
| Inspection Component | Required Inspection |
|---|---|
| Product Side Corrosion Gouges, damage, corrosion, pits, general loss. | Verify with visual inspection and non-destructive testing. |
| External Corrosion Pitting, general loss, CUI. | Verify with visual inspection and non-destructive testing. UT scanning of the shell with the wall-crawler if required. |
| Out of Round | Verify with laser scan and manual measurements. |
| Shell Settlement | Verify with settlement or laser measurements. |
| Previous Patches | Visually locate and evaluate each patch. |
| Peaking and Banding | Verify with visual and laser scan. |
| Reinforcement Pads | Verify visually. |
Bottom Plates:
| Inspection Component | Required Inspection |
|---|---|
| Nominal Thickness | Verify from manufacturer data, and nameplate, with UT verification. |
| # of Rows and Plates | Check with drawings and verify in the field. |
| Topside Gouges, damages, corrosion, pitting. | Verify in the field with pit gauges, MFL, and visual inspection. |
| Underside Pitting, general loss. | Verify with MFL and UT. Repair areas with patches and replacement as per API 653. |
| Welds | Inspect to original design code. with corrosion allowance limits. |
| Previous Patches | Verify visually in the field. Check for additional surrounding damage. |
| Settlement | Verify if the bottom plate has edge settlement, using survey data or laser scanning. |
Nozzles and Appurtenances:
| Component | Requirement |
|---|---|
| Nozzles | Verify # of nozzles, type, rating, thickness, repads, flanges, and hardware. |
| Valves | Verify type and function. |
| Expansion Joints | Determine damages based on settlement and movement. |
| Instrumentation | Verify probes, gauges, cables, grounds, hardware, radar gauges, high and low-level alarms, cable trays. |
| Heaters | Verify the overall thickness of the piping and function check. |
Fixed Roof:
| Inspection Component | Inspection Requirement |
|---|---|
| Product Side | Verify the condition of rafters, hardware, internal plate surfaces, and evaluate for hang-ups pre-entry. |
| External | Verify the condition of plates, nozzles, thief hatch, PSV’s, using UT and visual inspection. |
Coatings and Insulation:
| Inspection Component | Inspection Requirement |
|---|---|
| Visual Inspection | Verify the condition of all coatings and insulations using holiday testing, visual inspection, and other relevant examinations. Repair as required. |
Storage Tank Inspection and Repair Results – Out-of-Service:
- Determination of internal damage mechanisms.
- Material loss rates and degradation rates.
- Visual verification of internal liners and coatings.
- Visual verification of welds, piping, and other appurtenances.
- Verification of internal structures.
- Verification of settlement.
- Visual verification of floating roof seals, shims, and hardware.
- Visual inspection of external insulation.
- Repairs performed in areas of damage, or material loss to achieve the desired service interval.
- Compliance with governing codes and standards.
Storage Tank Inspection and Repair Results – In-Service:
- Ultrasonic evaluation from external surfaces.
- Visual verification of attached piping.
- Visual verification of external insulation.
- Verification of settlement.
- Compliance with governing codes and standards.
Contact: