United States
Environmental Protection
Agency
Office of Solid Waste
and Emergency Response
(5104 A)
EPA 550-F-09-004
September 2009
www.epa.gov/OEM
CHEMICAL SAFETY
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.
We are 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, State Emergency Response Commissions
(SERCs), Local Emergency Planning Committees (LEPCs), emergency responders, and
others review this information and consider whether additional action is needed to
address the hazards.
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 2 million-gallons. In several of
the tank failures cited in this alert, the tanks
were built by either Carolyn Equipment
Company ofFairfield, 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.
While all users of aboveground liquid
storage tanks should take appropriate steps
to maintain tank integrity, owners of tanks
produced by these two manufacturers are
advised to take extra precautions to guard
against tank failure.
Accidents
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.
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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 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.
11/12/2008 in Virginia: A 2-million gallon
tank of urea ammonium nitrate fertilizer
ruptured, seriously injuring two workers.
The released liquid fertilizer overtopped the
secondary containment berm surrounding
the tank, partially flooded an adjacent
residential neighborhood, and contaminated
the southern branch of the Elizabeth River.
Nearby residents were ordered to evacuate
for several days.
Hazard Awareness
Defective Welds
In the incidents cited, all of the above-
ground liquid storage tanks that failed
appeared to have had defective welds.
Several of the tanks were produced by either
Carolyn Equipment Company or Nationwide
Tanks Incorporated. Both companies have
since gone out of business. These 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.
Increased Hazard During First Fill
According to American Petroleum Institute
(API) Standard 653, "Tank Inspection,
Repair, Alteration, and Reconstruction,"
tanks are more likely to fail when being
filled to the maximum level for the first
time. Additionally, hydrostatic testing places
greater than usual stresses on a tank shell,
and therefore presents another potential
failure scenario. Facilities should be aware
of the additional hazard associated with
initial fill and hydrostatic testing, and
develop procedures or policies to prevent or
mitigate failures that may occur at these
times.
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Rupture Hazard from Liquid Storage Tanks
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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
The Fertilizer Institute (TFI) has published
uniform industry inspection and
maintenance guidelines for aboveground
liquid fertilizer storage tanks. According to
the TFI guidelines, liquid fertilizer storage
tanks should be designed and constructed
according to API Standard 650, "Welded
Steel Tanks for Oil Storage," and
inspections of existing tanks should be based
on API-653, but with modifications for the
unique characteristics of tanks storing liquid
fertilizer. 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.
Operational Hazards and Maintenance
Tank buyers should insist on seeing the
tank's 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 fusion of the welds joining shell
plates.
Once a tank 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 several other methods. A vacuum box
can identify localized problems. The
vacuum box, approximately 6 inches by 30
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Rupture Hazard from Liquid Storage Tanks
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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,
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 with the
methodology described in API Std 579-
1/ASME FFS-1 "Fitness for Service." Any
tanks that do not meet the acceptance
requirements set by API Std 579-1/ASME
FFS-1 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.
• 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 problems identified during
inspections by conducting repairs or, if
necessary, replacing the tank.
• Replace, repair, or modify any and all
tanks not meeting the standards set forth
in API-Std 579-1/ASME FFS-1
methodology.
• Be on the alert for new tank regulations,
standards, or recommended practices.
• Locate storage tanks and design and
construct their secondary containment
systems so as to separate the contents of
a leaking or collapsing tank from the
rest of the facility and to prevent any
leakage from going offsite.
Develop an emergency plan that
addresses a catastrophic tank failure.
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.
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Rupture Hazard from Liquid Storage Tanks
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Information Resources
References with information about the
hazards of catastrophic storage tank 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:
http://www.epa.gov/emergencies/docs/chem
/cat-tnks.pdf
Statutes and Regulations
• Clean Air Act Section 112(r)(l) -
General Duty
• EPA's Risk Management Program Rule
[40 CFR 68]
• OSHA Process Safety Management
Standard [29 CFR 1910.119]
• EPA Spill Prevention, Control and
Countermeasure Plan regulations [40
CFR 112]
Investigation Reports and Safety Videos
The U.S. Chemical Safety and Hazard
Investigation Board (CSB) is an independent
federal agency charged with investigating
industrial chemical accidents. The CSB
conducts root cause investigations of
chemical accidents affixed industrial
facilities, publishes investigation reports,
produces safety videos, and makes
recommendations to plants, regulatory
agencies, industry organizations, and labor
groups:
Investigation Report: Allied Terminals, Inc.
- Catastrophic Tank Collapse, Report No.
2009-03-I-VA
U.S. Chemical Safety and Hazard
Investigation Board
2175 K Street, NW, Suite 650
Washington, DC 20037-1809
Phone: 202-261-7600
Web site: http://www.csb.gov
Codes and Standards
The Fertilizer Institute (TFI) has published
guidelines for inspection and maintenance
ofaboveground liquid fertilizer storage
tanks:
Aboveground Storage Tanks of Liquid
Fertilizer: Recommended Inspection
Guidelines
The Fertilizer Institute
820 First Street, N.E., Suite 430
Washington, DC 20002
The American Petroleum Institute (API) has
tank standards and guidelines on safe
API Standard 579-1/ASME FFS-1 - Fitness
for Service
API Standard 620 - Design and
Construction of Large, Welded, Low-
Pressure Storage Tanks
API Standard 650 - Welded Steel Tanks for
Oil Storage
API Standard 653 - Tank Inspection,
Repair, Alteration, and Reconstruction
American Petroleum Institute
1120LStNW
Washington DC 20005
Phone: 202-682-8000
Web site: http://www.api.org
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
1828 LStNW, Suite 906
Washington DC 20036
Phone: 800-843-2863
or 202-785-3756
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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 AWS QC-1 (Quality Control)
Welding Inspector and has guidelines on
safe welding.
American Welding Society
550 NW LeJeune Road
Miami, FL 33126
Phone: 800-443-9353
or 305-443-9353
Web site: http://www.amweld.org
For More Information:
Call the Superfund, TRI, EPCRA, Risk Management Program,
and Oil Information Center
800-424-9346 or 703-412-9810
TDD 800-553-7672 or 703-412-3323
Visit the OEM Home Page at:
www.epa.gov/emergencies
Notice: The statements in this document are intended solely as guidance.
This document does not substitute for or change any applicable statutory
provisions or regulations, nor is it a regulation itself. The guidance it provides
may not be appropriate for every situation.
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