United States
Environmental Protection
Agency
Office of Solid Waste
and Emergency Response
(5104A)
EPA 550-F-01-010
September 2001
www. epa. gov/ceppo
&EPA Chemical Accidents from Electric
Power Outages
^ C n pi A! 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 chemical safety 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
Power outages and restarts could
potentially trigger a serious chemical
accident.
Electric power outages are often caused
by lightning, high wind, or ice storms,
as well as accidents at power plants
or transmission lines. Hot weather power
demands could trigger rolling blackouts.
Although planned rolling blackouts can
cause process shutdowns or upsets, they are
preferable to power system overloads and
failure, or to low voltage brownouts which
can be destructive to electrical equipment.
The recent energy crisis in California
illustrates the aggravation caused by power
outages. Power interruptions at chemical
handling facilities are a particular concern
because of the possibility of a chemical
accident. Incident data from the National
Response Center (NRC) shows that during
2000 there were about 240 chemical releases
reported due to an electric power
interruption; only a few were related to
planned rolling blackouts. A number of
releases were associated with power
resumption and restart of operations (see
Table 1).
Accidents
One accident occurred when power was
interrupted and another during restart after
power resumption.
Gramercy, Louisiana, July 1999. This plant
converts bauxite to alumina in a series of steam-
heated pressure vessels. A loss of power stopped
all pumps including those that circulated process
material through heat exchangers for cooling.
However, steam injection stayed on causing
temperatures and pressures to increase. Pressure
relief valves and piping were blocked or choked
with solid deposits hindering their ability to
relieve the increasing pressure. Several vessels
over-pressured and exploded. The force of the
explosion and release of highly corrosive caustic
material injured 29 employees and extensively
damaged the plant.
Several lessons can be learned from this
accident: Process operations must be evaluated
for the consequences associated with a power
outage to ensure that the process reaches a safe
condition. In this case, if process flow and
cooling pumps are critical to the safe state of the
process when electric power is lost, then a
backup power supply or steam driven spare or
backup pumps should be evaluated. In addition,
interlocks that stop steam heating upon loss of
flow or cooling should be considered. Finally,
pressure relieving systems must be inspected
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CHEMICAL ACCIDENTS FROMELECTRICPOPFER OUTAGES
SEPTEMBER 2001
and maintained to ensure their ability to function as
intended.
Richmond, California, May 2001. This plant was
running normally when a truck struck a utility pole,
causing a power interruption and total plant shutdown.
Shortly thereafter, sulfur dioxide (SO2) and sulfur trioxide
(SO3) began to escape from a boiler exit flue. When
power was restored a short time later, a steam turbine that
is required to keep the boiler exit flue under negative
pressure could not be immediately restarted.
Troubleshooting revealed that an automatically controlled
governor valve had malfunctioned and the turbine was
restarted. During the time the turbine could not be
restarted, residents near the plant were instructed to
remain indoors. Around 50 to 100 individuals sought
medical attention following the release.
As above, equipment or procedures critical to safe
shutdown, continued operation, or restart conditions must
be identified, maintained, tested, and kept in a ready-to-
operate state. The plant installed backup power systems
to keep the steam turbine running through a power outage.
In addition, preventative maintenance on the steam turbine
valves has been enhanced to ensure that these valves
operate properly when needed.
Table 1. Some chemical release causes reported
to the NRC during 2000:
• Fueling pump automatically restarted when
interrupted power was restored;
• Power outage during product transfer caused
tank and secondary containment overflow;
• Power outage to computer control system during
startup caused release from pressure relief;
• Utility company's hot weather power reduction
caused plant's excessive flaring;
• Power loss caused shutdown and valves did not
close;
• Scheduled power outage caused flaring; and
• Power outage caused shutdown of pollution
control device and release of material.
Hazard Identification
Find potential weak spots early or ultimately they will
find you!
When power is lost for any reason, pumps stop pumping,
compressors stop running, stirrers quit mixing, lights go
out, and instruments and controls may malfunction.
These equipment outages may lead to tank overflows,
runaway chemical reactions, temperature or pressure
increases or decreases, all of which could lead to a spill,
explosion, or fire. Even if there is no immediate release,
there may be a delayed reaction caused by thermal shock
or other factors that can compromise equipment
mechanical integrity during subsequent operation. When
power is restored even after a brief interruption, some
equipment may automatically restart before process
operations are ready while others may need to be reset and
manually restarted.
The first task is to identify and rank the process
operations or equipment that pose the most serious
potential for fire, explosion, or hazardous material release
in the event of utility interruption. A good tool that can
help identify and rank critical equipment and the
consequences to the process upon loss of power is a
formal process hazard analysis (PHA) within a sound
process safety management system (PSM). For example,
the Hazard and Operability (HazOp) or What-If analysis
techniques coupled with good employee participation is a
particularly strong combination for identifying hazards
and failure mechanisms associated with power failure and
restart. These tools and approaches can help you create
a list of process equipment (pumps, valves, instruments)
and to note exactly what happens to each device when
power fails or is restored. Don't forget to include
equipment that may be indirectly affected; for example,
pneumatic devices that quit when air pressure falls
because an electric-powered compressor stops.
Equipment should "fail-safe;" in other words, when
electric power or another utility (e.g. air or water) is lost,
the equipment and process should come to a safe
condition. And when power is restored, devices should
keep the process in a safe condition until it is ready to
resume normal operations. Table 2 shows an example list
of some devices and possible fail-safe and restored states.
Be sure to consider power dips, brief interruptions, and
losses to only some equipment in your hazard evaluation
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as unexpected and unusual circumstances may occur. For
example, some equipment may continue operating while
others trip out.
Most chemical facility operators have developed sound
contingency plans for responding to various types of plant
utility interruptions, including electric power outages.
After a power failure is over, evaluate how the process
equipment and people responded to the situation to
identify hazards and potential negative consequences that
were not previously recognized. In some cases the type
and magnitude of the disruption that occurred when power
was interrupted was not fully anticipated. In other cases
the problem was caused by adverse actions that took place
when power was restored. Power failure contingency
plans should be regularly reviewed, updated and tested.
Table 2
Sample Equipment List and Fail-Safe Modes
Device
Reactor Feed
Pump
Reactor Steam
Heat Valve
Cooling Water
Feed Valve
Reactor Vent
Valve
Reactor Mixer
Transfer Pump
Status When
Power Fails:
Off
Closed
Full open
Full open
Off
Off
When Power is
Restored:
Off - manual
restart
Closed until
reset
Open per temp.
control
Open per
pressure control
Off - manual
restart
Off - manual
restart
Problem Reduction
What actions should be taken to help neutralize the
impact of the hazards identified above?
Using the results of the hazard evaluation, make sure that
all process operations and equipment will reach a fail-safe
mode upon loss of power. Make sure that devices you
expect to operate upon loss of power are inspected,
maintained, and tested as part of your equipment
preventative maintenance program. And make sure that
operating procedures and training address these hazards.
Prepare plans and checklists and consider backup power
systems to maintain critical services as described below.
Other actions that should be taken to prevent, prepare for,
and respond to chemical emergencies triggered by power
failure and resumption can be addressed by four
categories: (1) preparing for an emergency forced
shutdown such as with a rolling blackout or an
approaching electrical storm; (2) preparing for immediate
actions from an unexpected power loss; (3) restarting
when power is restored; and (4) equipment to enhance
continuity of critical services.
1. Emergency Forced Shutdown. Sometimes there may
be a warning or brief notification, perhaps only a few
minutes, that a rolling blackout or other outage (steam,
instrument air, cooling water) is about to occur. Many
companies have developed an Emergency Forced
Shutdown Plan (EFSDP). This Plan addresses only those
priority actions that need to be taken immediately if a
power outage is imminent. The objective is to make the
best use of the short time available to bring the plant to a
safe shutdown condition and avoid unnecessary upsets
that may be driven by a loss of power. The Plan should
also address follow-up steps that could be taken if time
permits and further steps to secure the unit or process
after the outage. Finally, the Plan should also include
"load shedding" steps to shut down less important
operations, and thus conserve power, steam, cooling
water, or instrument air for the most critical operations.
This Plan should be well thought out, reviewed with all
involved employees, and periodically tested.
2. Power Outage: Immediate Action Steps. As
described above, when power dips or is interrupted
unexpectedly, equipment should reach a fail-safe
condition as specified and designed by you as a result of
your hazard evaluation. Consider developing a checklist
or other tools for employees to use to ensure that safe
conditions are reached. As described above, the checklist
might show the fail-safe mode for critical equipment and
steps such as closing valves in reactor feed lines or fuel
supplies to fired heaters, starting auxiliary power
generators, and switching to steam or diesel driven backup
pumps or compressors for critical services. In addition,
steps need to be taken to ensure that there isn't an
unintended action when power is restored and to get ready
for restart. Table 3 shows some lists of equipment and
other checks that may need to be performed after a power
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outage.
Immediately following a brief interruption, there may be
a strong desire to quickly get the process back on-line.
Rushing to put a unit, process, or certain equipment back
on-line may compound problems associated with the
outage as described below.
3. Restarting When Power is Restored. When power
is restored, there are a number of steps that should be
taken to ensure the process (1) remains in a safe mode and
(2) it is ready to return to operation. Also, if the process
remained on-line using backup systems, it must be
returned to normal operation. As mentioned above,
facilities may want to develop plans, procedures, and
checklists for restarts or restoring backup services.
Since power outages are often very short, consider
developing preplanned warm restart procedures for certain
units, processes or equipment. A warm restart procedure
addresses the unique circumstances that might arise if a
unit is not completely shutdown before power is restored
and the unit restarted.
Be sure that other necessary support utilities (steam,
instrument air, cooling water, flare gas system, fire
fighting systems, etc.) have been returned to service and
are fully operational before restarting operations.
Table 3. Sample Check Lists of steps that may
need to be performed following a Power Outage:
i/' List manually operated switches that may need
to be moved to the "off position;
i^List valves that need to be checked for proper
position;
i^List utilities such as steam, instrument air,
nitrogen blanketing, cooling water, flare system,
fuel system, radio telephone, pager
communications, etc. that need to be verified for
operability;
i/'Check backup power generators, fire fighting
systems, and other emergency response equipment
for operability;
i/Verify feedstock inventory and availability of
product storage free space;
%/List instrument controls, alarms, detection
devices, automatic shutdown or trip out devices that
must be reset or have operability verified;
i^List automatic startup power consuming
equipment that should be shut down for safety and
to minimize load demand when power is restored;
and
i^List upstream and downstream and other affected
parties to be notified of shutdown.
Caution: After a very brief outage, there may be a
temptation to quickly restart certain process operations
to avoid the hassle of warm restart or complete
shutdown and restart procedures. Explosions and
accidental releases have occurred when, for example,
fired heaters and furnaces were restarted without proper
purges or following all prescribed safety steps. Some
equipment must be brought completely down and purged,
then put back into service following prescribed steps.
The warm restart procedure must address the process
equipment that must first be stabilized and checked out
before restarting, even for a brief outage.
4. Continuity of Critical Services. As described above
in the Hazard Identification section, if there is critical
equipment that needs to operate to ensure the safe state of
the process or work area, facilities should install backup
power supplies and services. Services such as emergency
pumps, lighting, alarms, and instruments and controls,
particularly computer operated distributed control systems
(DCS) may need to operate using backup power
generators or uninterrupted power supplies (UPS). Steam
or diesel driven pumps should be considered to maintain
critical flows while a process is shutting down or
otherwise dealing with the power outage. And as with all
critical equipment and procedures, they should be
maintained, tested, and verified for operation regularly.
Caution: Backup power generators must be selected and
installed by a qualified electric service contractors or
facility personnel. It is particularly important to avoid
improper switching which can lead to power being fed
back into the regular power system. This feedback can
cause equipment damage and injury. The utility
company should be notified of the installation of any
backup generators.
Recent experiences at large, well established organizations
as well as small and medium size operations have verified
that a greater awareness of the hazards of power failure
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and restart is necessary, especially with thunderstorms
and greater electricity demands in hot weather or ice
storms in freezing weather. Facilities should re-examine
and ensure that all hazards are identified and addressed
and that equipment, procedures and staff are developed,
maintained, and ready so that chemical accidents are
prevented and those that do occur are mitigated.
Education and Training
Resources
Here are some useful resources for additional information
on power failure and backup power:
Recommended Practice for Emergency and Standby
Power Systems for Industry and Commercial
Applications.
The Institute of Electrical and Electronics Engineers,
Inc., (IEEE).
IEEE Operations Center
445 Hoes Lane, P.O. Box 1331
Piscataway, New Jersey 08855-1331 USA
732981 0060
Fax: 732 981 1721
http://www.ieee.org
Caterpillar Alban Engine Power Systems
Describes capacity ranges of portable power generating
equipment and some typical applications.
http://www.dcat.com
National Fire Protection Association (NFPA)
codes include:
NFPA 70 - National Electric Code (latest edition)
NFPA 1600 - Disaster Management (latest edition)
National Fire Protection Association
1 Batterymarch Park
P.O. Box 9101
Quincy, MA 02269-9101
617-770-3000
Customer Service: 800-344-3555
http://www.nfpa.org
Occupational Safety and Health Administration
(OSHA)
Process Safety Management (PSM)
202-219-6151
http://www.osha.gov
Mine Safety and Health Administration (MSHA)
Kaiser Aluminum accident investigation report,
including photographs, Gramercy Works Alumina
Plant Explosion, July 5, 1999.
http://www.mhsa.gov
For More Information.
Contact EPA's Emergency Planning and
Community Right-to-Know Hotline
(800) 424-9346 or (703) 412-9810
TDD (800) 553-7672
Monday-Friday, 9 AM to 6 PM, Eastern Time
444
Visit The CEPPO Home Page:
http://www.epa.gov/ceppo/
NOTICE
The statements in this document are intended solely as guidance. This document does not substitute for
EPA's or other agency regulations, nor is it a regulation itself. Site-specific application of the guidance
may vary depending on process activities, and may not apply to a given situation. EPA may revoke,
modify, or suspend this guidance in the future, as appropriate.
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