SP001 Standard for The Inspection of Aboveground Storage Tanks

Inspection of aboveground storage tanks (ASTs) can be a critical compliance issue under the planning requirements of the U.S. Environmental Protection Agency’s rule for Spill Prevention Control and Countermeasure (SPCC). In 2000, the Steel Tank Institute released the first version of Standard for the Inspection of Aboveground Storage Tanks – the STI SP001 standard – which provides a means for AST owners to comply with EPA mandates. The standard has been updated by consensus of tank owners, tank manufacturers and other industry leaders.

Joe Mentzer is the Standards Engineer for STI/SPFA and staff liaison to the STI SP001 Committee. He can be contacted at jmentzer@steeltank.com.

Purchase SP001 Standard for The Inspection of Aboveground Storage Tanks

The SP001 Standard for The Inspection of Aboveground Storage Tanks provides inspection and evaluation criteria required to determine the suitability for continued service of aboveground storage tanks until the next scheduled inspection.

Frequently Asked Questions About SP001

Does STI SP001 comply with EPA’s requirement for tank integrity testing?

STI SP001 meets the intent of 40 CFR 112.8(c)(6) which states:

“Test or inspect each aboveground container for integrity on a regular schedule and whenever you make material repairs. You must determine, in accordance with industry standards, the appropriate qualifications for personnel performing tests and inspections, the frequency and type of testing and inspections, which take into account container size, configuration, and design (such as containers that are: shop-built, field-erected, skid-mounted, elevated, equipped with a liner, double-walled, or partially buried). Examples of these integrity tests include, but are not limited to: visual inspection, hydrostatic testing, radiographic testing, ultrasonic testing, acoustic emissions testing, or other systems of non-destructive testing. You must keep comparison records and you must also inspect the container’s supports and foundations. In addition, you must frequently inspect the outside of the container for signs of deterioration, discharges, or accumulation of oil inside diked areas. Records of inspections and tests kept under usual and customary business practices satisfy the recordkeeping requirements of this paragraph.”

Why does STI SP001 require internal inspections when one cannot easily access the inside of a small shop-fabricated tank?

STI SP001 does not mandate entry into a tank for any tank under 30,000 gallons (113,529 liters). For tanks under 30,000 gallons, either internal inspections are not required, or else an alternative is given with the use of leak-test inspections. Tanks larger than 30,000 gallons usually have manways to allow personnel entry.

Does the STI SP001 standard include inspection of fiberglass and other plastic tanks?

Overall, the standard focuses primarily on inspection of welded, carbon or stainless steel shop-fabricated and field-erected tanks. Also included is the inspection of smaller, portable containers such as 55-gallon drums, intermediate bulk containers (IBCs) and other such containers that may be of metal or plastic construction. Inspection of non-portable, shop-fabricated plastic or fiberglass tanks is not included. See the definitions within the standard for more specific questions related to size and material of construction.

The pre-2005 edition of STI SP001 gave specific instructions on the number of UT readings to be taken on every tank. This ensured that each inspector did inspections exactly alike. Does the latest edition of the standard allow a tester to take one reading on the shell of the tank and claim he tested the tank for an area where corrosion was most apt to occur?

The previous STI SP001 standard did not use a risk-based approach, but made the UT testing a requirement on all tanks in all conditions. It required thousands of readings with some tank capacities. The third and fourth editions place a much greater emphasis on a risk-based approach to the inspection process. The newer editions do specify the number of UT readings to take per square foot of surface area, but they do not necessarily establish specific areas for such readings. The STI SP001 standard expects a certified inspector to use appropriate judgment on where corrosion is most apt to occur. A certified inspector will understand the environmental, fire prevention, and life-safety issues involved. For internal inspections, the standard requires 100 percent UT of areas that cannot be visually inspected (for example, the bottom of a tank resting on the ground).

For external inspections, paragraph states:

“Take and record ultrasonic thickness testing (UTT) readings and the location of the reading of each plate or shell course in areas accessible without entering the AST. Readings must be concentrated in areas where corrosion is likely to occur. If significant internal corrosion is detected, further investigation using ultrasonic testing scans (UTS) is required.” [See the standard for definitions of UTT and UTS].

Are the AST record document and the AST checklists in Appendix C copyrighted?

No, but the rest of the standard is copyrighted. Download the SP001 AST Record and the SP001 checklists to use. Note: the AST record and the checklists are to be used in conjunction with the STI Standard SP001 and the utilization of the AST record and the checklists alone do not constitute compliance with STI SP001.  Purchase the STI Standard SP001.

My tank contains sulfuric acid (or hydrochloric acid, etc.). Can STI SP001 be used to inspect this tank?

Although the scope of the standard includes:

  • Stable, flammable and combustible liquids at atmospheric pressure
  • Liquids with operating temperatures between ambient temperature and 500 degrees F.

The 6th Edition of SP001 includes a paragraph that states:

“This Standard may be applied to ASTs containing other types of liquids as long as an individual with the appropriate training, education, and/or experience has evaluated such use and approved the application of this Standard or a modification of the Standard, including assessing the compatibility of the liquid with the AST materials to address potential failure mechanisms.”

I have a 25,000-gallon (94,607-liter) tank. Do I refer to STI SP001 or should I use API 653 as a basis for inspection?

The scope of STI SP001 includes shop-fabricated and small field-erected tanks. The scope of API 653 includes tanks built to API 650 and API 12C. This leads to an overlap in the scope of the tanks covered by the standards. Therefore, more information is needed about a tank in order to decide the best inspection standard to use.

For example, if it is a double-wall horizontal UL 142 tank, then STI SP001 probably is a better choice. If the tank has an API 650 nameplate and is located at a facility at which all of the other tanks are 500,000 gallons (1,892,150 liters) or more, then API 653 may be the better choice. Lastly, because of the risk-based inspection basis within the STI SP001 standard, the inspection schedule for many tanks is less conservative than API 653.

I have an insulated tank, and it will cost a lot of money and time to remove all of the insulation and then replace it. What must I do?

Corrosion under insulation is a serious concern because the collection of water due to a gap in the moisture barrier may lead to a previously undetected problem. Paragraph 7.5 of the STI SP001 standard states:

“Remove the insulation in areas where mold or moisture is present or points where moisture is likely to accumulate and examine the metal surface for signs of significant corrosion.”

Who can inspect a tank per STI SP001 for me?

There are two basic types of inspections included in STI SP001. Monthly, periodic inspections are to be performed by the tank owner’s inspector and qualified per paragraph 4.1.2 of the standard. External and internal formal inspections are to be performed by a certified inspector. Certified inspectors may be either an API 653 certified tank inspector with an adjunct STI SP001 certification or an STI SP001 trained and certified tank system inspector. The certification procedure for an API 653 inspectors may obtain an Adjunct STI SP001 Inspector Certification through an online program.

How can I obtain a copy of STI SP001?

Purchase the STI Standard SP001 online or by calling the STI/SPFA office.

Can API 653 Certified Inspectors inspect tanks per SP001?

STI provides an Adjunct STI SP001 Inspector Certification program for API 653 Inspectors.

What fluids contained in tanks are covered by the SPCC regulation?

View a list of SPCC regulated fluids.

Where can I find answers about the EPA SPCC rule applicability to my facility?

The EPA has a webpage devoted to SPCC frequently asked questions.

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“There are many benefits of STI/SPFA, particularly networking with members.”

Pat Rezin

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