Tank Inspection Protocol API 653

What is API 653?

  • API 653 is the standard for tanks over 50 feet tall or having diameter greater than 30 feet.
  • Covers the maintenance, inspection, alteration and repair of steel, field-erected aboveground storage tanks (ASTs) built to API 650 or API 12C standards.
  • API 653 inspections must be performed by a licensed inspector.
  • Brittle fracture assessment are covered under API 653.
  • API 653 includes welding requirements for field erected tanks.

4 Critical Components of an API 653 inspection

1. General Tank Information: Review tank description information including:

  • Tank Specifications
  • Tank Construction
  • Release Detection Methods
  • Spill Control

2. Tank Bottom, Tank Shell, and Tank Roof Inspections: API 653 allows different types of inspection to examine the aboveground tank components including:

  • Visual
  • Ultrasonic (spot)
  • Ultrasonic (Scan)
  • Liquid Penetrant
  • Penetrating Oil
  • Magnetic Particle
  • Radiography
  • Magnetic Flux Scan
  • Vacuum Box
  • Tracer Gas


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3. Bottom, Shell and Roof: The structure of the tank is inspected to API 653 standards taking into account:

  • Minimum Remaining Thickness
  • Minimum Required Thickness
  • Maximum Corrosion Rate

4. Settlement Evaluations: Examine whether the tank is tilting or settling in the ground improperly. These factors are also assessed under API 653:

  • Out of plane
  • Rigid Body Tilting
  • Uniform
  • Dish Type
  • Edge Settlement
  • Localized Dispersions

Monthly Inspections Recommended Under API 653

  • Performed by site owner/operator’s inspector
  • Assess the overall tank condition as thoroughly as possible without removing the above ground tank from service.
  • Inspector performing monthly examination does not need to be certified, just knowledgeable.
  • Monthly records of inspections must be maintained for regulators.

API 653 External Inspections

Required Every 5 Years

  • Depending on the initial inspection findings, an external inspection may be required more frequently.
  • External inspections are conducted by a certified API 653 inspector to assess the condition of the above ground tank and determine its suitability for continued service.
  • This inspection does not require entry into the tank’s interior. Tank can remain in service.

External Inspection 4 Critical Components

  1. Inspector should review previous periodic inspection checklists and previous FEIs/FIIs
  2. Inspection should include tank thickness testing
  3. Must determine original shell thickness and establish current shell thickness
  4. Ultrasonic thickness testing can lead to ultrasonic testing scan (UTS)

API 653 Internal Inspections

Required Every 10 Years

  • Depending on the initial assessment of the tank, internal inspections may be required more frequently.
  • API 653 internal inspections are conducted by a certified inspector
  • Internal inspection assesses the internal and external condition of the above ground tank and determine its suitability for continued service.

Avoid Penalties & Fines

  • Establish a formal internal & external  inspection schedule
  • Routinely record your monthly inspection findings.

Contact one of our specialists for more advice on API 653 Inspections.