STI/SPFA > Fabricated Steel Products > Shop Fabricated
Tanks > SP001 Standard FAQs
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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). Steel Tank Institute in 2000 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, now in its fifth edition, 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.
FREQUENTLY ASKED QUESTIONS ABOUT SP001
Question #1: Does STI SP001 comply with EPA’s requirement for tank integrity
testing?
Answer: 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."
Question #2: Why does STI SP001 require internal inspections when one cannot easily
access the inside of a small shop-fabricated tank?
Answer: 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
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gallons usually have manways to allow personnel entry.
Question #3: Does the STI SP001 standard include inspection of fiberglass and other
plastic tanks?
Answer: 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 nonportable, 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.
Question #4: 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?
Answer: 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 7.3.1.1 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].
Question #5: Are the checklists in Appendix C copyrighted?
Answer: No, but the rest of the standard is copyrighted. Word versions of these checklists
are available here Note that these checklists are to be used in conjunction with the STI
Standard SP001 and the utilization of the checklists alone do not constitute compliance with
STI SP001. The STI Standard SP001 may be purchased here
Question #6: My tank contains sulfuric acid (or hydrochloric acid, etc.). Can STI SP001
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be used to inspect this tank?
Answer: 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."
Question #7: 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?
Answer: 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.
Question #8: 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?
Answer: 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.”
Question #9: Who can inspect a tank per STI SP001 for me?
Answer: 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
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inspector. A list of STI AST inspectors is available here. The certification procedure for an API
653 inspectors may obtain an Adjunct STI SP001 Inspector certification through a web-based
program. Click this link for more details.
Question #10: How can I obtain a copy of STI SP001?
Answer: Purchase the SP001 Standard through the STI/SPFA Store.
Question #11: Can API 653 Certified Inspectors inspect tanks per SP001?
Answer: STI provides an Adjunct Certification program for API 653 Inspectors. Click
here for additional details.
Question #12: What fluids contained in tanks are covered by the SPCC regulation?
Answer: Click here to see a list of SPCC regulated fluids.
Question #13: Where can I find answers about the EPA SPCC rule applicability to my
facility?
Answer: EPA has a webpage devoted to SPCC frequently asked questions here.
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