API 653 Inspection

Certified NDT Tank Inspections

What is API 653? 

The American Petroleum Institute (API) 653 standard addresses Tank Inspection, Repair, Alteration, Relocation and Reconstruction of above ground storage tanks (ASTs) built to API 650 and it’s predecessor API 12C. API 653 provides the minimum requirements for continued service. Additionally, the API 653 code has been adopted as a widely used inspection standard for storage tanks that were built to an unknown standard, such as water towers and ceramic holding tanks.

Certified API 653 Inspectors

Our inspectors must meet certain knowledge and experience requirements to be able to apply to become an API 653 certified Inspector through the American Petroleum Institute (API) to properly interpret the standard, carefully carryout inspections, repairs and provide industry related reports,

Once approved for testing, they must pass proctored examinations to gain entry into the industry as a certified inspector, something we take great pride in and maintain with great integrity. Recertification must take place every 3 years to in order to stay up to date with the latest industry standards and practices.

API 653 Inspections – The Purpose of Inspection

Regardless of the tank, the structure and its components will degrade overtime, increasing the probability of structural failure.

Because of this degradation, inspections must take place at set intervals throughout the span of the Tank’s service life.

These inspections provide great insight into the structural integrity of the tank and its components through the use of non-destructive testing and visual inspection, allowing for the preventative maintenance needed to mitigate the probability of a hazardous discharge into the environment.

 Once approved for testing, they must pass proctored examinations to gain entry into the industry as a certified inspector, something we take great pride in and maintain with great integrity. Recertification must take place every 3 years to in order to stay up to date with the latest industry standards and practices.

API 653 – Inspection Intervals

Documented routine Inspection is to occur monthly and may be performed by an onsite operator approved by the facility’s owner and or operator. These monthly inspections should ideally use a checklist that can be adhered to consistently. If your facility is without this checklist, we can provide one to you at no cost.

External Inspections are to take place at the lesser of 1/4 life or every 5 years and shall be performed by a certified API 653 Inspector. For example, if the calculated corrosion rate suggests the remaining life of the structure is only 10 years, the next inspection interval will be set for 2.5 years. On the other hand, If the remaining life is 30 years, the 1/4 life would be 7.5 years. However, it would default to 5 years, the lesser of the fixed interval and the 1/4 life.

Ultrasonic Thickness Testing (UTT) is to take place every 5 years if the corrosion rate (CR) is unknown. Or, Lesser 1/2 life or every 15 years if the corrosion rate is known. Corrosion rate is calculated at the prior inspection. This calculation takes into account the original thickness of the steel when the tank was placed into service, or at the prior inspection, and divides the current thickness by the years since the prior measurement was taken. This will provide a reliable corrosion rate.

Internal Inspections are to take place within 10 years of being placed into service. Once this first inspection is performed, a corrosion rate will be calculated that will provide the data required to schedule the next internal inspection. The determination will be made following the less 1/2 life or 20 years rule.

NDT Testing

Our Inspectors are certified ASNT-SNT-TC-1A Non-destructive Testing (NDT) technicians, who are able to perform testing in the field such as:

  • Penetrant Dye Testing (PT)
  • Magnetic Particle Testing (MT)
  • Radiographic Testing (RT)
  • Ultrasonic Thickness Testing (UTT)

This provides them the ability to determine the weld quality, mechanical integrity &  thickness of a structure’s core components.

With this knowledge, we can calculate corrosion rates and find areas of excessive deterioration, aiding to prevent structural failure before a discharge into the environment can occur. 


In the Aftermath of the Floreffe, Pennsylvania Oil Spill of 1988, over 4 Million gallons of diesel discharged into the environment after an aboveground storage tank failed.

This failure contaminated millions of gallons of drinking water and entering dozens of fresh water streams, eventually making its way into the Ohio river. In response to this event and other similar disasters, The Environmental Protection Agency (EPA) formed the Spill Prevention, Control and Countermeasures (SPCC) regulation, an addition to the prior Oil Pollution Prevention (OPP) regulation.

The SPCC regulation’s purpose is to:

  • Provide Environmental Inspection Compliance dates.
  • Clarify and/or Tailor Specific regulatory requirements.
  • Clarify specific provisions in the Oil Pollution Prevention regulation.
  • Establish Additional technical requirements for the regulated facilities.
  • Require the Preparation of facility-unique response plans.

The EPA and the SPCC Task force work closely with the American Petroleum Institute (API) to ensure that detailed and thorough standards for inspection of ASTs, Process piping, and Pressure vessels exist and are consistently updated. These Inspections are carried out by industry trained and certified API Inspectors and Non-destructive Testing Technicians.


Extend Inspection intervals by up to 7 year and protect your facility’s investments through the use of Protective Coatings and Cathodic Protection:

  • Thin-film Liner: 2 years
  • Thin-film Liner: 5 years
  • Cathodic Protection: 5 Years
Our Aboveground Storage Tank Services


The scope of our inspections and the API 653 Standard are limited to the tank foundation, bottom, shell, structure, roof, the attached appurtenances, and nozzles up to the face of the first flange, first threaded joint, or first welding-end connection.

Pressure Leak Testing

Leak Detection is a Non-destructive Testing (NDT) technique that allows us to pressurize an empty AST under a very low PSI, we do this safely by using certified gauges and pressure regulators that read very small adjustments in the pressure input and the pressure contained. We then monitor and document changes in the internal pressure at set periods of time. This allows us to evaluate and determine the structural integrity of the tank; If there is a hole in the tank that could allow discharge of product, this test will likely reveal it to our inspectors.

Non-destructive Testing (NDT) Techniques

We’re Certified ASNT-SNT-TC-1A, allowing us to inspect using NDT testing methods such as UT, PT, MT, VT, and RT. The use of these techniques further allows us to inspect and gather quantitative data that provides great insight into the materials and structures of interest. Using this data to calculate the corrosion rate and remaining thickness of the structures’ components creates the opportunity for preventative maintenance, stopping structural failure and environmental discharge before it happens. 

Soil Sampling

If a spill has occurred, or is suspected, soil sampling may be required. In remediation projects, soil sampling is a method used to ensure the clean-up has been carried out thoroughly and sufficiently to meet state and federal regulations.

Formal Compliance Reports

All of our inspections carry with it a formal report provided to the client for their records. These reports contain the relevant observations, future inspection intervals, quantitative data, calculations and photographs of the inspection that took place.

Installation of Aboveground Storage Tanks

We address each step of the installation process, working with your group as the project manager to ensure the project is streamlined from beginning to end. You will be provided with the necessary documentation and reports to meet current compliance requirements, as well as, future maintenance and inspection requirements.