United States
                    Environmental Protection
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
                    Research and Development
EPA/600/S8-87/034k Feb. 1988
&EPA         Project Summary
                    Prevention  Reference  Manual:
                    Chemical Specific, Volume  11:
                    Control of Accidental Releases of

                    D. S. Davis, G. B. DeWolf, J. D. Quass, and M. Stohs
                      The accidental  release  of a  toxic
                    chemical at Bhopal, India, in 1984 was
                    a milestone in  creating an increased
                    public awareness of toxic release prob-
                    lems. As a result of other, perhaps less
                    dramatic, incidents in the past, portions
                    of the chemical industry were aware of
                    this problem long before Bhopal. These
                    same portions of the industry have made
                    advances  in this areas.  Interest in
                    reducing  the probability and conse-
                    quences of accidental toxic chemical
                    releases that might harm workers within
                    a process facility and people  in the
                    surrounding community prompted the
                    preparation of  a  series of technical
                    manuals addressing accidental releases
                    of toxic  chemicals.  This manual is
                    chemically specific for ammonia. The
                    manual summarizes information to aid
                    regulators and  industry personnel in
                    identifying and controlling release
                    hazards associated with ammonia.
                      Reducing the risk associated with an
                    accidental release of ammonia involves
                    identifying some of the potential causes
                    of accidental releases that apply to the
                    process facilities that handle and store
                    ammonia. In this manual, examples of
                    potential  causes are identified  as are
                    specific measures that may be taken to
                    reduce the accidental release risk. Such
                    measures include recommendations on:
                    plant design practices; prevention, pro-
                    tection, and mitigation technologies;
                    and operation and maintenance prac-
                    tices. Conceptual cost estimates  of
                    example prevention,  protection, and
                    mitigation measures are provided.
  This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).

  The accidental  release of a  toxic
chemical, methyl isocyanate, in Bhopal,
India, in 1984 was a milestone in creating
an increased public awareness of toxic
release problems. There have been other
less dramatic incidents of toxic chemical
releases in the past, and the  chemical
industry was aware of this problem long
before this event. Safety and loss preven-
tion has long been a  standard part of
industry activity, and over the years
industry has made many advances in this
area. There is renewed interest, however,
in reviewing technology and procedures
for preventing, protecting against, and
mitigating accidental releases.
  As an aid to regulators and industry
personnel charged  with reducing the
probability and consequences of acci-
dental toxic chemical releases, a series of
technical manuals was  prepared that
addresses prevention, protection,  and
mitigation measures for release. This
chemical specific manual on ammonia is
part of that series.
  Ammonia is a major commodity chemi-
cal in industry. The dominant use of this
chemical is in the fertilizer industry which
accounts for nearly 80% of all  ammonia

produced. The direct application of am-
monia to the soil is, in fact, the largest
single use of the chemical. The primary
industrial uses of ammonia are as a raw
material in the manufacture of nitric acid
and as the starting material in the pro-
duction of a number of commercially im-
portant synthetic materials. In addition to
the primary uses mentioned above,
ammonia has many other minor uses in a
wide  variety of industries. Some of the
more common uses include neutralization
(especially the treatment of acidic wastes),
extraction, refrigeration, water purifica-
tion,  the  preparation of  cleaners and
detergents, pulp and paper manufacture,
and food and beverage treatment.
Potential Causes of Releases
  At  atmospheric  temperatures and
pressures, anhydrous ammonia  is  a
pungent, colorless gas that may easily be
cooled to a colorless liquid. Because liquid
anhydrous  ammonia has a  large coef-
ficient of expansion, an overpressurization
hazard exists if storage vessels have in-
sufficient expansion space or if pipelines
full of liquid ammonia are sealed at both
ends. In these situations, thermal ex-
pansion of the liquid and an  increase in
temperature can result  in containment
failure  from  the hydrostatic  pressure
exerted by the liquid.
  Failure leading to accidental releases
may be caused by process, equipment, or
operational problems. Most  of  the ac-
cidental releases of ammonia that have
occurred in the past 15 years have re-
sulted from pressurized pipeline ruptures,
failed storage tanks, and road tanker
  Possible process causes of an ammonia
release include:
   Loss of  feed  composition control
    resulting  in the  formation of am-
    monia/air mixtures within the flam-
    mability limits;
   Backflow of process reactants to an
    ammonia feed tank;
   Excess feeds in any part of a process,
    leading to overfilling or overpres-
    suring of equipment;
   Loss of condenser cooling in distilla-
    tion columns;
   Overheating of reaction vessels and
    distillation columns; and
   Overpressure  in  ammonia storage
    vessels from overheating caused by
    exposure to fire, or from unrelieved
  Equipment causes  of  accidental re-
leases result from hardware failures such
as failure of feed control systems from a
loss of  power, clogged lines, jammed
valves, or instrument failure; from  ex-
cessive stress caused by improper fabri-
cation, construction, or installation; from
failure of pressure relief systems; from
mechanical  and  thermal  fatigue and
shock; from corrosion of equipment con-
structed of high alloys; and from brittle
fracture or creep failure.  A significant
concern for anhydrous ammonia is use of
the proper alloy grade  of steel. Certain
grades of steel are prone to catastrophic
failure due to cracking or embrittlement
from anhydrous ammonia.
  Operational  causes of accidental  re-
leases result from incorrect procedures
and human error. These include: overfilled
storage vessels; improper process control
system operation; errors inloading and
unloading; poor quality control of replace-
ment parts;  inadequate  maintenance,
especially of pressure relief systems and
other preventive and protection devices;
and lack of inspection and nondestructive
testing of vessels and piping to detect
weakening from corrosion.

Hazard Prevention and Control
  Prevention of accidental releases relies
on the proper design, construction, and
operation of facilities where ammonia is
stored and used and on the  protective
systems that guard against an accidental
  Process  design involves the  basic
chemistry of a process and  how this
chemistry is affected by the variables of
flow, pressure, temperature, composition,
and quantity. Any aspect of  a  process
may be modified to enhance the integrity
of the system. Such changes could involve
the quantities of materials, process pres-
sures and temperatures, the sequence of
operations, process control strategies, and
the instrumentation used.
  The most important consideration for
systems containing ammonia is the pre-
vention  of overheating and/or overpres-
suring.  In  addition to overpressure,
overheating can  also  weaken  process
equipment and increase the probability
of leaks developing at joints and valves.
  Physical plant design covers equipment,
siting and layout, and transfer/transport
facilities. Dry ammonia is noncorrosive to
most common metals; however, moist
ammonia corrodes copper, tin, zinc, and
many alloys, especially copper alloys. Only
specific grades of steel, recommended
for ammonia service, should be used due
to the cracking or embrittlement problem
mentioned previously. Certain aluminum
alloys can be used in parts of ammonia
systems. Metallic and non metal lie gasket I
materials (e.g.,  compressed asbestos,
graphited asbestos, carbon steel or stain-
less steel  spiral-wound  asbestos,  and
aluminum) are considered suitable for
ammonia service based on current in-
dustry practice.
  The siting  and layout  of any  facility
handling  ammonia  and  of  individual
equipment should be designed to reduce
personnel  exposure  in the event of  a
release. Siting should allow ready ingress
and egress and take advantage of barriers
that reduce release exposures. Consider-
able distance between large inventories
and sensitive receptors is desirable. The
ground  under process equipment  and
storage vessels should be sloped so that
fire water and liquid spillages flow away
from  equipment into drains. Storage
facilities should  be located in cool, dry,
well-ventilated areas.
  Because heat causes significant thermal
expansion  of ammonia, piping, storage
vessels, and other equipment should not
be located adjacent to piping containing
flammable materials, hot process piping
and equipment, or other sources of direct.
or  radiant heat. Special  consideration
should be given to the location of furnaces
and other permanent sources of ignition
in the plant.                           i
  Two types  of  protection  technologies '
for containment and neutralization include
enclosures and  scrubbers. Enclosures
would capture ammonia spilled or vented
from storage or process equipment, con-
taining  the spilled liquid or gas  until  it
could be transferred to other containment
and discharged at a controlled rate or to
water scrubbers  for absorption.
  Scrubbers can also be  used for con-
trolling ammonia releases. Because of its
high solubility, ammonia discharges can
be absorbed in water in scrubbing devices
such as spray towers, packed bed scrub-
bers, and Venturis.
  If an accidental release occurs, mitiga-
tion technologies can reduce the con-
sequences.  Such  measures  include
physical barriers, water sprays and fogs,
and foams that  will divert, limit, or dis-
perse the released chemical to the atmo-
sphere.  In spite of  the  lower specific
gravity of pure ammonia vapor relative to
air, large accidental releases of ammonia
have often formed ammonia/air mixtures
that are denser than the surrounding
atmosphere. The primary  means of dis-
persing  and  removing ammonia vapor
from the air is with water sprays or fogs.
A "capture zone" can be created down-
wind of the release into which the am- j
monia vapor will drift and be absorbed.

,   Since accidental releases of toxic
 materials result not only from deficiencies
 of design but also from deficiencies of
 operation, safe operation of plants using
 ammonia requires competent,  experi-
 enced managers and staff trained in the
 proper way to handle and store ammonia.
D. Davis, G. DeWolf, J. Quass, and M.  Stohs are with Radian  Corporation,
  Austin, TX 78766.
T. Kelly Janes is the EPA Project Officer (see below).
The complete report, entitled "Prevention Reference Manual: Chemical Specific,
  Volume 11. Control of Accidental Releases of Ammonia," (Order No. PB87-
  231262/AS; Cost: $18.95, subject to change) will be available only from:
       National Technical Information Service
       5285 Port Royal Road
       Springfield. VA 22161
        Telephone: 703-487-4650
The EPA Officer can be contacted at:
       Air And Energy Engineering Research Laboratory
       U.S. Environmental Protection Agency
       Research Triangle Park, NC 27711

United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
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