API 653: Aboveground Storage Tank Inspection, Repair, Alteration, and Reconstruction

Introduction

API 653 is a widely recognized standard developed by the American Petroleum Institute (API) that governs the inspection, repair, alteration, and reconstruction of aboveground storage tanks (ASTs) primarily used in the petroleum and chemical industries. It sets minimum requirements to ensure the structural integrity, safety, and reliability of steel storage tanks after they have been placed into service. The standard covers tanks constructed under API 650 and its predecessor API 12C but can also be applied to tanks built under other codes at the owner’s discretion71.

History

API 653 was first published in January 1991 to address the growing need for standardized procedures in maintaining aboveground storage tanks. The standard has evolved through several editions, with the most recent major update released in November 2014. It complements the API 650 construction code by focusing on in-service maintenance and fitness-for-service assessment, ensuring tanks remain safe throughout their operational life7.

Scope of the Code

API 653 applies to welded or riveted, non-refrigerated and refrigerated, atmospheric pressure steel aboveground storage tanks. It covers the inspection, repair, alteration, and reconstruction of the tank’s foundation, bottom, shell, roof, attached appurtenances, and nozzles up to the first flange or welding connection. The standard ensures tanks maintain their structural integrity and safe operation throughout their service life71.

Key Sections in API 653

  • Inspection Requirements: Guidelines for visual inspections, non-destructive testing (NDT), corrosion assessment, and hydrostatic testing to evaluate tank condition.
  • Repair and Alteration Procedures: Methods and acceptance criteria for repairing damaged or corroded components and making alterations to tanks7.
  • Reconstruction: Criteria for reconstructing tanks or tank components to extend service life7.
  • Corrosion Assessment: Procedures to evaluate corrosion rates and remaining tank life, including roof, shell, and bottom assessments1.
  • Settlement Evaluation: Methods to measure and evaluate tank foundation and shell settlement to ensure stability6.
  • Fitness-for-Service: Incorporation of API 579-1/ASME FFS-1 for assessing degradation types not explicitly covered by API 6537.
  • Testing Practices: Includes hydrostatic testing, vacuum box testing, ultrasonic testing, and magnetic particle testing to verify tank integrity after repairs or alterations1.

How to Use API 653

API 653 is primarily used by certified tank inspectors, engineers, and maintenance personnel to:

  • Plan and conduct regular inspections of storage tanks.
  • Evaluate inspection data to identify corrosion, deformation, or structural weaknesses.
  • Determine repair or replacement needs based on established acceptance criteria.
  • Perform repairs, alterations, or reconstruction in compliance with the code.
  • Document inspection results and maintenance activities for regulatory compliance and asset management.
    Certification programs, such as the API 653 Aboveground Storage Tank Inspector certification, ensure inspectors have the knowledge and skills to apply the code effectively28.

Benefits of API 653

  • Safety Assurance: Helps prevent catastrophic tank failures by ensuring regular inspection and maintenance.
  • Extended Tank Life: Enables timely repairs and reconstruction to maximize asset lifespan.
  • Regulatory Compliance: Meets industry and environmental regulations for tank safety and integrity.
  • Standardized Procedures: Provides consistent inspection and repair criteria across the industry.
  • Risk Management: Identifies hazards related to corrosion, settlement, and material degradation early.

Limitations

  • Minimum Standard: API 653 sets minimum requirements; some tanks may require more frequent or detailed inspections based on service conditions.
  • Scope Restriction: It applies only to aboveground steel tanks and does not cover underground tanks or other materials.
  • Complexity: Requires trained and certified inspectors to correctly interpret and apply the code.
  • Not a Construction Code: It focuses on maintenance after construction, so it must be used in conjunction with construction standards like API 650.

Additional Details

  • API 653 integrates fitness-for-service assessments from API 579-1/ASME FFS-1 to evaluate tank degradation beyond simple visual inspection.
  • The code includes detailed formulas and procedures for calculating minimum shell thickness, allowable settlement, and corrosion allowances6.
  • Testing methods such as vacuum box and ultrasonic testing are prescribed to detect leaks and material defects1.
  • The standard emphasizes safety precautions during internal inspections and repairs to protect personnel3.

Summary

API 653 is the essential industry standard for maintaining the safety and integrity of aboveground storage tanks after they enter service. It provides comprehensive guidelines for inspection, repair, alteration, and reconstruction, helping operators manage risks, comply with regulations, and extend tank life. While it requires certified professionals for proper application, API 653 remains the cornerstone for aboveground tank maintenance worldwide.