Storage Tanks

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 ComponentRequirement
Construction, Design and Year BuiltVerify 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 requirementsObtain 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 CompatibilityVerify the name, specific gravity, temperature, and compatibility.


Tank support piles with support structure.
ComponentRequired Inspection
Berm TypeVerify the design, secondary liner, berm wall height, capacity, and tank placement within the berm.
CP SystemCheck for the presence of and previous data for CP systems.
WalkwaysCheck walkways and stairways for plum, level, and corrosion.
ConcreteCheck for cracking, spalling, exposed rebar, washout, and wear.
Berm InspectionVerify 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 plate overview
Inspection ComponentRequired 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 RoundVerify with laser scan and manual measurements.
Shell SettlementVerify with settlement or laser measurements.
Previous PatchesVisually locate and evaluate each patch.
Peaking and BandingVerify with visual and laser scan.
Reinforcement PadsVerify visually.

Bottom Plates:

Preferential weld corrosion needs to be documented and repaired.
Inspection ComponentRequired Inspection
Nominal ThicknessVerify from manufacturer data, and nameplate, with UT verification.
# of Rows and PlatesCheck with drawings and verify in the field.
Gouges, damages, corrosion, pitting.
Verify in the field with pit gauges, MFL, and visual inspection.
Pitting, general loss.
Verify with MFL and UT. Repair areas with patches and replacement as per API 653.
WeldsInspect to original design code. with corrosion allowance limits.
Previous PatchesVerify visually in the field. Check for additional surrounding damage.
SettlementVerify if the bottom plate has edge settlement, using survey data or laser scanning.

Nozzles and Appurtenances:

NozzlesVerify # of nozzles, type, rating, thickness, repads, flanges, and hardware.
ValvesVerify type and function.
Expansion JointsDetermine damages based on settlement and movement.
InstrumentationVerify probes, gauges, cables, grounds, hardware, radar gauges, high and low-level alarms, cable trays.
HeatersVerify the overall thickness of the piping and function check.

Fixed Roof:

Domed roof
Inspection ComponentInspection Requirement
Product SideVerify the condition of rafters, hardware, internal plate surfaces, and evaluate for hang-ups pre-entry.
ExternalVerify the condition of plates, nozzles, thief hatch, PSV’s, using UT and visual inspection.

Coatings and Insulation:

Coating Damage at weld
Inspection ComponentInspection Requirement
Visual InspectionVerify 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.