Aboveground Storage Tank Inspections

After a recent deluge of questions regarding storage tank cleaning and inspection requirements, we wanted to share some information that we have gathered. As is often the case with regulations, the simple answer to many questions is, “It depends,” and tank inspection is no different.

With regulatory guidance from the U.S. Environmental Protection Agency (EPA) and industry standards from the American Petroleum Institute (API) and the Steel Tank Institute (STI), finding a clear-cut answer sometimes is difficult. However, understanding the requirements can help facility operators make well-informed decisions and, ultimately, better manage their risk.

EPA Requirements
The EPA references the Spill Prevention, Control and Countermeasure Act (SPCC) to prevent the release of petroleum into the waterways of the United States. Any facility with an aggregate, aboveground storage capacity greater than 1,320 gallons must comply with the SPCC requirements of 40 CFR 112. The SPCC regulations refer to the nationally recognized inspection standards provided by API and STI, with the key piece of guidance coming from API Standard 653: Tank Inspection, Repair, Alteration and Reconstruction. API 653 outlines four levels of inspection:

Routine in-service inspection
Operators should perform this inspection at least once a month. It includes visual inspection of the tank’s exterior for evidence of leaks, shell distortions, signs of settlement and corrosion. They  also should look for any deterioration in the foundation, paint coatings, insulation systems and appurtenances. Operators should document all inspections for follow-up by an authorized inspector.

Formal external visual inspection
This is similar to the routine in-service inspection, but a certified inspector must conduct it at least every five years, or at the quarter corrosion rate of the tank shell, whichever is less.

External ultrasonic thickness inspection
A certified inspector, along with an American Society of Non-Destructive Testing (ASNT) certified examiner must conduct this inspection within five years of placing the tank into service. If they do not know the corrosion rates, operators must take measurements every five years. However if the operator knows the corrosion rates, the inspection interval is the smaller of half the corrosion-rate life or fifteen years.

Internal Inspection
A certified inspector, along with an ASNT-certified examiner, must perform this inspection before the end of the corrosion life of the bottom of the tank or twenty years, whichever is less. If no corrosion rate is available, then they must perform the full inspection within ten years. An internal inspection may include a comprehensive visual inspection of the entire tank interior, ultrasonic-thickness testing of the bottom plates, magnetic-flux-leakage testing of the bottom plates, vacuum-box testing of the bottom and shell-to-bottom weld seams, settlement surveys and, in some cases, fluorescent-magnetic-particle testing of the shell-to-bottom weld seam.

HK Can Help
No wonder we have literally volumes of data regarding tank inspections! However, we hope this article helps clarify some common questions. Whether you operate a renewable fuels refinery or petroleum distribution center, Hydro-Klean has knowledgeable and experienced personnel ready to assist with all of your aboveground storage tank needs. We also maintain relationships with qualified and reputable tank inspection companies to offer complete, turnkey solutions throughout the country. For additional information, feel free to contact Hydro-Klean: 515-283-0500.

References
American Petroleum Institute Standard 653: Tank Inspection, Repair, Alteration and Reconstruction.

Steel Tank Institute Standard SP001-03, Inspection of Shop Fabricated Aboveground Storage Tanks for Storage of Combustible and Flammable Liquids. 

Spill Prevention, Control, and Countermeasure (SPCC) Guidance for Regional Inspectors "Chapter 7: Inspection, Evaluation & Testing".

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