&EPA
CEPPd)
United States
Environmental Protection
Agency
Office of Solid Waste
and Emergency Response
(5104)
EPA550-F-01-001
January 2001
Rupture Hazard from Liquid Storage Tanks
The Environmental Protection Agency (EPA) is issuing this Alert as part of its ongoing effort to
protect human health and the environment by preventing chemical accidents. EPA is striving to
learn the causes and contributing factors associated with chemical accidents and to prevent their
recurrence. Major chemical accidents cannot be prevented solely through regulatory requirements.
Rather, understanding the fundamental root causes, widely disseminating the lessons learned, and
integrating these lessons learned into safe operations are also required. EPA publishes Alerts to
increase awareness of possible hazards. It is important that facilities, SERCs, LEPCs, emergency
responders, and others review this information and take appropriate steps to minimize risk. This
document does not substitute for EPA's regulations, nor is it a regulation itself. It cannot and does
not impose legally binding requirements on EPA, states, or the regulated community, and the
measures it describes may not apply to a particular situation based upon circumstances. This
guidance does not represent final agency action and may change in the future, as appropriate.
Problem
Over the past few years, there have been
several catastrophic failures of liquid
fertilizer storage tanks resulting in property
damage and environmental contamination.
These ruptures have involved site-erected
storage tanks with capacities ranging from
500,000 to 1.5 million-gallons. The tank
failures, which prompted this alert, were all
built by either Carolyn Equipment
Company of Fairfield, Ohio, or Nationwide
Tanks Inc. of Hamilton, Ohio. Both of
these companies have since gone out
business. (Carolyn Equipment in 1990 and
Nationwide Tanks in 1995.) This alert
describes some of the tank failures and
identifies standards and precautions that
apply to aboveground liquid storage tanks.
Owners of tanks produced by these two
manufacturers are advised to take extra
precautions to guard against tank failure.
NOTE: Though all failed storage tanks
cited in this alert have been produced by
these two companies, owners of all
storage tanks should be aware of the
risks associated with operating a storage
tank.
Accident History
3/1997 in Iowa - A 1-million gallon tank
containing ammonium phosphate ruptured
and released its contents. The walls of the
ruptured tank fell onto two other tanks and
broke their valves. One tank contained
1- million gallons of a nitrogen liquid
fertilizer and the other tank held
ammonium thiosulfate. Much of the
release was contained by an earthen dike,
but immediate construction of a secondary,
temporary dike was necessary to keep the
release from flowing into the nearby
Missouri River. Cleanup involved
pumping the liquid out of the dikes and
removing all contaminated soil.
7/1999 in Michigan - A 1-million gallon
tank full of ammonium polyphosphate
ruptured and damaged three other tanks.
Fortunately, the tanks were surrounded by
earthen dikes lined with polyethylene.
This minimized the environmental damage.
1/8/2000 in Ohio - A 1-million gallon
tank of liquid fertilizer ruptured and
damaged four adjacent tanks. The wave of
liquid broke a concrete dike wall and hit
five tractor-trailer rigs, pushing two of the
rigs into the river. A total of 990,000
gallons of material were released. More
than 800,000 gallons of the liquid spilled
into the Ohio River. Sampling detected
amounts of the fertilizer mixture 100 miles
downstream, which is expected to increase
algae growth in the river. The company
has discontinued use of seven other tanks
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purchased from the same manufacturer.
3/8/2000 in Ohio - At the same facility, a 1.5-
million gallon tank of ammonium phosphate
ruptured and damaged three nearby tanks causing
them to leak. Two of the damaged tanks held
phosphoric acid and the third one held 'Ice-Melt', a
magnesium chloride mixture. The released liquid
overflowed the dike walls into nearby creeks. The
four tanks were dismantled after the incident. Over
1.8 million gallons of contaminant were recovered,
with an additional 450,000 gallons of contaminated
water recovered from the sewer system. The
release caused evacuation of a nearby school, and
the public was forced to use bottled water because
of concern that the drinking water supply may be
contaminated by the spilled chemicals.
Hazard Awareness
Defective Welds
In the incidents cited, all of the above-ground liquid
storage tanks that failed appeared to have had
defective welds. The tanks were all produced by
either Carolyn Equipment Company or Nationwide
Tanks Incorporated. Both companies have since
gone out of business. The tanks were under
warranty for only one year, and the welding of the
tanks was done by subcontractors hired by the two
companies. The companies built tanks in Michigan,
Ohio, Indiana, Illinois, Missouri, and Iowa between
1980 and 1995. Because of increased frequency in
tank failures, the Ohio Fire Division is creating a
voluntary registry of liquid storage tanks to help
track and prevent similar failures.
Chemicals Involved
The failed tanks have held liquid fertilizers, such as
ammonium phosphate, which are not considered
hazardous and are not regulated by the U.S.
Environmental Protection Agency. However, the
failure of these tanks can damage nearby tanks
containing hazardous substances and cause releases.
In some cases, accidents have involved tanks
containing hazardous materials like anhydrous
ammonia and phosphoric acid, which are used to
produce the fertilizer ammonium phosphate.
Hazard Identification
Facilities should evaluate their storage tanks for
potential catastrophic failure. Some of the factors to
consider include:
- Manufacturer's record for quality workmanship.
- Evidence of weakened or defective welds.
- Signs of corrosion around the base and direct contact
with ground and exposed to moisture.
- Exposure to high winds or frequent precipitation.
- Age of the tank.
- Close proximity to other storage tanks containing
hazardous chemicals.
Hazard Reduction/Prevention
The failure of liquid storage tanks can stem from
inadequate tank design, construction, inspection, and
maintenance. Hazard reduction and prevention starts
with good design and construction. The risk to tanks
already in service can be reduced through tank
maintenance and weld inspection. To minimize
effects from possible tank failures, there should be a
secondary containment such as a dike or a berm
surrounding the tank.
Tank Design and Construction
A tank should be designed and constructed according
to API-650, "Welded Steel Tanks for Oil Storage:"
issued by the American Petroleum Institute (API).
API-650 specifies an allowance for corrosion and for
the specific gravity of the fertilizer liquid.
In each of the tank failures mentioned, welding has
been the main cause of failure. To ensure durability
and integrity, it is imperative that the tank is welded
correctly. Several standards and specifications outline
the proper techniques and procedures for welding
including API-653, "Tank Inspection, Repair,
Alteration, and Reconstruction."
Operational Hazards and Maintenance
Tank buyers should insist on seeing the inspection
record. Although tanks should undergo a rigorous
inspection by a recognized inspection authority before
a manufacturer's job is complete, the tanks should still
be closely inspected by the buyer prior to purchasing
the unit. For liquid storage tanks, the most important
item to look for is complete penetration and complete
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fusion of the welds joining shell plates. Once atank
has been purchased, it becomes the tank owner's
duty to regularly inspect the tank. Inspection
intervals may be set by using a risk-based
inspection theory, as indicated by API-653. Various
inspection methods can be used for those tanks
already in service. Radiography is the technique
applied to all tanks designed to API-650 to ensure
that complete penetration and fusion of welded
joints has occurred. Unfortunately, this procedure
cannot detect poor mechanical properties in the
welded regions. This and other standards cover
what types of joints must be checked by a
radiograph, as well as the number of tests that must
be done. Additional inspections may be done
visually or by a vacuum box for localized problems.
The vacuum box, approximately 6 inches by 30
inches, is tightly sealed to the tank surface, and
pressure is applied. Automated ultrasonic testing
can be applied to all shell welds to examine for
cracks, fusion and penetration, and porosity with
greater resolution than radiography. It is also now
possible to conduct floor scanning while the tank is
full. Combined with chemical analysis and
hardness testing, field replication can assess the
toughness, or resistance to brittle failure of a
weldment. If damage is found during an inspection,
this needs to be assessed in accordance withAPI-
RP579 "Fitness for Service " methodology. Any
tanks that do not meet the acceptance requirements
set by API-RP579 should be repaired or replaced.
Steps for Safety
Here are some additional ways to prevent rupture
of liquid storage tanks:
- Realize the inherent risk of using and maintaining
any storage tanks.
- Identify the manufacturers of the tanks on the
property, being careful to identify any tanks built by
either company mentioned in this alert. NOTE: If
tanks were manufactured by Carolyn Equipment
Company or Nationwide Tanks of Hamilton, take
the following actions immediately:
• A close external inspection should be made
for leaks, corrosion, or any anomalies in the
surface of the tank. Vent(s) should be
checked for any blockages by foreign
materials, such as snow or ice. The
majority of the failures have occurred
during the winter months, when steel
becomes more brittle and when vents can
become blocked by snow and ice. If liquid is
drawn out of the tank when vents are plugged
or restricted, a vacuum may be pulled on the
tank causing it to collapse inward.
• If you find evidence of leakage or corrosion
during the inspection, the tank should be taken
out of service and if possible, drained.
• If there is no evidence of leakage or
corrosion, arrange for an external evaluation
by a qualified inspection agency.
• Depending on the results of the evaluation,
arrange for an internal inspection immediately
or within the year.
- Ensure that employees are aware of the hazards
associated with the failure of a liquid storage tank.
- Avoid overfilling tanks.
- Perform regular inspections of tanks. Be sure to look
for all possible risks.
- Follow up on identified problems with repairs or
replacement. Inspections are otherwise useless.
- Replace, repair, or modify any and all tanks not
meeting the standards set forth in API-579, "Fitness
for Service" methodology.
- Be on the alert for new tank regulations. (There were
recently changes made to API-653 that improved the
suggested calculations)
- Consider better mitigation in case of a leak to
separate the content of a collapsing tank from the rest
of the facility, and more importantly, prevent any
leakage from going offsite.
- Develop an emergency plan that addresses a
catastrophic tank failure.
Information Resources
References with information about the hazards of
catastrophic failures and methods of minimizing them
are listed below. Regulations potentially applicable to
storage tanks and codes and standards that may be
relevant are also included. A Chemical Safety Alert on
catastrophic fires and explosions in storage tanks is
available at www.epa.gov/swercepp/pubs/cat-tnks.pdf
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Statutes and Regulations
December 1995; and Addendum 3, December 1996).
Section 112(r) of the Clean Air Act focuses on
prevention of chemical accidents. Facilities with
regulated substances or other extremely hazardous
substances have a general duty to prevent and
mitigate accidental releases. Accident prevention
activities include identifying hazards and operating
a safe facility.
EPA 's Risk Management Program (RMP) Rule [40
CAR 68] is intended to prevent and mitigate
accidental releases of listed regulated substances.
RAMP rule requirements include development of a
hazard assessment, a prevention program, and an
emergency response program.
EPA has tank inspection regulations under the Spill
Prevention Countermeasure and Control Plan and
Oil Pollution Control Act of 1990 [40 CFR112J.
The Occupational Safety and Health
Administration's (OSHA) Process Safety
Management Standard [29 CAR 1910.119] includes
regulations on tank inspection, and conduct during
hot-work; and fire protection and prevention during
welding, brazing, and cutting [29 CAR 1910.252].
Occupational Safety and Health Administration
Phone: (202) 219-8151 - Public Information Web
site: http://www.osha.gov
Codes and Standards
The American Petroleum Institute (API) has tank
standards and guidelines on safe welding:
American Petroleum Institute
1120LStNW
Washington DC 20005
Phone: (202) 682-8000
Web site: http://www.api.org
Relevant API standards:
API Standard 620 - Design and Construction of
Large. Welded. Low-Pressure Storage Tanks, ninth
edition, February 1996 (includes Addendum 1,
December 1996)
API Standard 650 -Welded Steel Tanks for Oil
Storage, ninth edition, May 1993 (includes
Addendum 1, December 1994; Addendum 2,
API Standard 653 - Tank Inspection. Repair.
Alteration, and Reconstruction, second edition.
December 1995 (inc. Addendum 1, December 1996)
The American Society of Mechanical Engineers
(ASME) has the Pressure Vessel Code and other codes
relevant to tanks and storage vessels:
American Society of Mechanical Engineers
1828LStNW, Suite 906
Washington DC 20036
Phone: (800) 843-2863 or (202) 785-3756
Codes and standards: (212) 705-8500
Accreditation and certification programs (212)
705-8581
Web site: http://www.asme.org
The American Society of Nondestructive Testing (ANT)
certifies welding and non-destructive examination
(NDE) and non-destructive testing (NDT) inspectors:
American Society of Nondestructive Testing
P.O. Box 28518
1711 Arlingate Lane
Columbus, OH 43228
Phone: (800) 222-2768
Web site: http://www.asnt.org
The American Welding Society (A WS) certifies
welding inspectors with the designation A WS QC-1
(Quality Control) Welding Inspector and has
guidelines on safe welding.
American Welding Society
550 NW LeJeune Rd
Miami, FL 33126
Phone: (800) 443-9353 or (305) 443-9353
Web site: http://www.amweld.org
For More Information...
Contact the EPCRA Hotline at (800) 424-9346 or
(703) 412-9810 TDD (800) 553-7672
Monday-Friday 9:00 a.m. to 6:00 p.m. EST
Visit the CEPPO Home Page at www.epa.gov/ceppo
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