xvEPA
            United States
            Environmental Protection
            Agency
          Air and Energy Engineering
          Research Laboratory
          Research Triangle Park NC 27711
 EPA/600/8-87/034k
. August 1987
            Research and Development
Prevention Reference
Manual: Chemical
Specific

Volume 11. Control of
Accidental Releases of
Ammonia

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                                           EPA/600/8-87/034k
                                           August 1987
         PREVENTION REFERENCE MANUAL:

               CHEMICAL  SPECIFIC:
      VOLUME 11:   CONTROL OF ACCIDENTAL

              RELEASES OF AMMONIA
                      by:

                  D.S.  Davis
                  G.B.  DeWolf
                  J.D.  Quass
                   M. Stohs
              Radian  Corporation
             Austin,  Texas  78766
            Contract No.  68-02-3994
              Work Assignment 94
              EPA Project Officer

                T. Kelly Janes
Air and Energy Engineering Research Laboratory
 Research Triangle Park. North  Carolina   27711
  AIR AND ENERGY ENGINEERING RESEARCH LABORATORY
       OFFICE Of RESEARCH AND DEVELOPMENT
      U.S.  ENVIRONMENTAL PROTECTION AGENCY
        RESEARCH TRIANGLE PARK, NC 27711
                                      U.S.                          .
                                      Region 5,  L1>vary  (o:-L~j .,
                                      230 S. Deer-born Street, &co:a ICV'O
                                      Chicago, IL   $0604

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                      NOTICE

This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication.  Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.

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                                   ABSTRACT

     The accidental releases of a toxic chemical at Bhopal,  India  in  1984 was
a milestone in creating an increased public awareness  of  toxic  release
problems.  As a result of other, perhaps less dramatic incidents in the  past.
portions of the chemical industry were aware of this problem long  before these
events.  These same portions of the industry have made advances in this  area.
Interest in reducing the probability and consequences  of  accidental toxic
chemical releases that might harm workers within a process  facility and  people
in the surrounding community prompted the preparation  of  this manual  and a
planned series of companion manuals addressing accidental releases of toxic
chemicals.

     Ammonia has an IDLH (Immediately Dangerous to Life and Health) concen-
tration of 500 ppm. which makes it an acute toxic hazard.   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 facil-
ities that use 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  prac-
tices, prevention, protection and mitigation technologies,  and operation and
maintenance practices.  Conceptual cost estimates of example prevention,
protection, and mitigation measures are provided.
                               ACKNOWLEDGEMENTS

     This manual was prepared under  the  overall  guidance  and  direction  of T.
Kelly Janes, Project Officer, with the active participation of  Robert P.
Hangebrauck, William J. Rhodes, and  Jane M.  Crum, all  of  U.S. EPA.   In
addition, other EPA personnel served as  reviewers.  Radian Corporation
principal contributors involved in preparing the manual were  Graham  E.  Harris
(Program Manager), Glenn B. DeWolf (Project  Director), Daniel S. Davis,
Jeffrey D. Quass. Miriam Stohs, and  Sharon L. Wevill.  Contributions were also
provided by other staff members.  Secretarial support was provided by Roberta
J. Brouwer and others.  A special thanks is  given to many other people, both
in government and industry, who served on the Technical Advisory Group  and  as
peer reviewers.
                                     Ill

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                                TABLE OF CONTENTS

Section                                                                    Page

  ABSTRACT	•	   iii
  ACKNOWLEDGEMENTS	   ill
  FIGURES	   VI1
  TABLES  .....		  .  Viii

  1       INTRODUCTION	'..............     1
          1.1  Background .......................     1
          1.2  Purpose of this  Manual	     2
          1.3  Uses of Anhydrous  Ammonia  ...............     3
          1.4  Contents  of  this Manual  ................     3

  2       CHEMICAL CHARACTERISTICS   ......  .  .-..-.  .• .• ......     4
          2.1  Physical  Properties   .............. . .< .  .<     4
          2.2  Chemical  Properties and Reactivity .  .  .  .• . . . . ...     7
          2.3  lexicological  and  Health Effects  .  .  .  .  .  . . . . ...     8

  3       FACILITY DESCRIPTIONS AND  PROCESS  HAZARDS  ...........     11
          3.1  Manufacture  . . . .  .  .• .- .-  .  .  .  .'  .  .  .  .• . . . . .  .     11
          3.2  Processing and Consumption .•  .  .-  .  .  .  .  .  . .....  .     17
               3.2.1  Fertilizer  Production	     17
               3.2.2  Nitric  Acid Production	     27
               3.2.3  Recovery  of Ammonia from Refinery  Waste Water .  .     29
               3.2.4  The Use of  Ammonia in  the  Production of Resins   .     32
               3.2.5  The Use of  Ammonia as  a  Refrigerant	     34
               3.2.6  Neutralization of Acidic Waste Streams with
                      Ammonia	     37
               3.2.7  The Manufacture  of Hydrogen Cyanide	     38
               3.2.8  The Manufacture  of Hydrazine  ..........     41
          3.3  Repackaging  of Anhydrous Ammonia  .  .  .  .  .• .• . .• .• . .  .     43
          3.4  Storage and  Transfer  .  .  .  .  .<  .'  .  .•  .  .<  .  .• .• .- . .• .'  .     44
               3.4.1  Storage	..•.......-..-..-..     44
               3.4.2  Transfer  from  Tank Cars  and Trucks  . . . . .- .  .     51
               3.4.3  Transfer  from  Storage  Vessels  .  .  .  . .- .< . .• .  .     52
               3.4.4  Transporting Ammonia Storage Containers . . .• .•  .     53

  4       POTENTIAL CAUSES  OF RELEASES  .  ....  .<  .•  .  .  . .- . .- . .  .     54
          4.1  Process Causes ..........  .  .  .  .  . . . . . .  .     54
          4.2  Equipment Causes	     55
          4.3  Operational  Causes ..-..' .  .•  .-  .  .-  .•  .-  .  . . .- . .' .•  .-     56

  5       HAZARDS PREVENTION  AND  CONTROL  .•  .-  .  .  .  .  .  .  .• .- . .< . .  .     58
          5.1  General Considerations  .	     58
          5.2  Process Design . .• .  ......'.-..•..	     59

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                         TABLE OF CONTENTS (Continued)

Section                                                                   Page

          5.3  Physical Plant Design  .......... . . . . .• . .     59
               5.3.1  Equipment	• . • .     61
               5". 3.2  Plant Siting and Layout ............ .     78
               5.3.3  Transfer and Transport Facilities 	     80
          5.4  Protection Technologies  ........ . .• . . . . .• .     80
               5.4.1  Enclosures	 . ......     81
               5.4.2  Scrubbers	     82
          5.5  Mitigation Technologies  ....  	     85
               5.5.1  Secondary Containment Systems ..........     86
               5.5.2  Flotation Devices and Foams .• ......	     92
               5.5.3  Mitigation Techniques for Ammonia Vapor ......     93
          5.6  Operation and Maintenance Practices	     95
               5.6.1  Management Policy ................     95
               5.6.2  Operator Training ................     97
               5.6.3  Maintenance and Modification Practices  .....     99
          5.7  Control Effectiveness	     103
          5.8  Illustrative Cost Estimates for Controls .... . . . .     104
               5.8.1  Prevention and Protection Measures  .......     104
               5.8.2  Levels of Control	     104
               5.8.3  Cost Summaries	     108
               5.8.4  Equipment Specifications and Detailed Costs . . .     108
               5.8.5  Methodology	 . . .     108

  6       REFERENCES	     141

  APPENDIX A - GLOSSARY ........................     146
  APPENDIX B - TABLE B-l.  METRIC (SI) CONVERSION FACTORS .	     150
                                       VI

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                                     FIGURES

Number                                                                  Page

3-1  Conceptual diagram  of  typical  ammonia production process ....    13

3-2  Conceptual diagram  of  typical  ammonium nitrate process  ....     20

3-3  Conceptual diagram  of  typical  ammonium sulfate process  . . . .     22

3-4  Conceptual of diagram  typical  diammonium phosphate process  .- .    .24

3-5  Conceptual diagram  of  typical  urea manufacturing process  ...     26

3-6  Conceptual diagram  of  typical  nitric acid production process  .     28

3-7  Conceptual diagram  of  "WWT" waste water treatment process ...     31

3-8  Conceptual diagram  of  typical  acrylonitrile process .• .• . .< .< .     33

3-9  Conceptual diagram  of  basic vapor compression refrigeration
     cycle .' .- . .- .• .- .-  .•  .  .•  . ...  .  .1 .  ...... . .• .- . .• .     35

3-10 Conceptual diagram  of  typical  hydrogen cyanide manufacturing
     process	  .  .  .  .  .  .  .• .  . .- .• .• . . .     39

3.-11 Conceptual diagram  of  typical  hydrazine manufacturing process .     42

3-12 Conceptual diagram  of  typical  atmospheric refrigerated ammonia
     storage system	  .  . ...... .• .     46

5-1  Computer model simulation  showing the effect of diking on the
     vapor cloud generated  from a release of liquified ammonia .- . .-     90
                                      Vll

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                                    TABLES

Number                                                                    Page

2-1  Physical Properties of Anhydrous Ammonia	       5

2-2  Exposure Limits for Anhydrous Ammonia  ......  .  .  .  .  .  .  .  .       9

2-3  Predicted Human Health Effects of Exposure to Various
     Concentrations of Anhydrous Ammonia  ................   10

3-1  Anhydrous and Aqueous Ammonia Products .... .  .  .  ........   18

5-1  Some Process Design Considerations for Processes Involving Anhydrous
     Ammonia  ........... 	  .......  	   60

5-2  Maximum Safe Volume of Liquid Ammonia in Nonrefrigerated Storage
     Containers at Various Temperatures ..........  	   68

5-3  Example of Performance Characteristics for an Emergency Packed Bed
     Scrubber for Ammonia		   84

5-4  Examples of Major Prevention and Protection Measures for Ammonia
     Releases		  105

5-5  Estimated Typical Costs of Major Prevention and Protection Measures
     for Ammonia Releases 	 ...... 	  106

5-6  Summary Cost Estimates of Potential Levels of Controls for Ammonia
     Storage Tank and Stripper	  109

5-7  Example of Levels of Control for Ammonia Storage Tank	110

5-8  Example of Levels of Control for Ammonia Stripper  	  112

5-9  Estimated Typical Capital and Annual Costs Associated with Baseline
     Ammonia Storage System		  .  114

5-10 Estimated Typical Capital and Annual Costs Associated with Level 1
     Ammonia Storage System 			  115

5-11 Estimated Typical Capital and Annual Costs Associated with Level 2
     Ammonia Storage System ...............  	  117

5-12 Estimated Typical Capital and Annual Costs Associated with Baseline
     Waste Water Treatment Ammonia Stripper 	.  .  119

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                              TABLES  (Continued)

Number                                                                    Page

5-13 Estimated Typical Capital and Annual Costs Associated with Level 1
     Waste Water Treatment Ammonia Stripper . . . . . . . . . ......   120

5-14 Estimated Typical Capital and Annual Costs Associated with Level 2
     Waste Water Treatment Ammonia Stripper . .......... . . . .   121

5-15 Equipment Specifications Associated with Ammonia Storage System  . .   122

5-16 Material and Labor Costs Associated with Baseline Ammonia Storage
     System .......................... . . . .     124

5-17 Material and Labor Costs Associated with Level 1 Ammonia Storage
     System .	-.-....• .- . . . .- .... .     125

5-18 Material and Labor Costs Associated with Level 2 Ammonia Storage
     System .............. . . . . . . .• . . . . .' . .• . .     126

5-19 Equipment Specifications Associated with Waste Water Treatment
     Ammonia Stripper . . . . . . . . .• .• . . .• . .• . . . . . . . . . .     127

5-20 Material and Labor Costs Associated with Baseline Waste Water
     Treatment Ammonia Stripper . . . . . . . . . .• . . .• . . . . . . .•     128

5-21 Material and Labor Costs Associated with Level 1 Waste Water
     Treatment Ammonia Stripper ...... . .< . .• ..........     129

5-22 Material and Labor Costs Associated with Level 2 Waste Water
     Treatment Ammonia Stripper . . . . . . . . . . . . . . . . . . . .     131

5-23 Format for Total Fixed Capital Cost  . . . . .• . .< . . . . . . . .     133

5-24 Format for Total Annual Cost . . . . . . . . . .... . . ....     135

5-25 Format for Installation Costs  ........	     140
                                      IX

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                                   SECTION 1
                                 INTRODUCTION

1.1  BACKGROUND

     The  consequences  of  a large  release  of  a  toxic  chemical  can  be
devastating.  This was  clearly evidenced by the release of a cloud  of toxic
methyl  isocyanate  in Bhopal,  India  on  December 3,  1984, which  killed
approximately 2,000 people  and  injured thousands  more.   Prior to this event.
there had been other, perhaps less dramatic, releases of toxic chemicals, but
the Bhopal  incident precipitated  the  recent  public  concern for the integrity
of process  facilities which handle hazardous materials.

     Recognizing the  fact  that no  chemical plant is  free of all release
hazards and risks, a number of  concerned individuals and  organizations have
contributed to  the  development  of loss prevention as a  recognized specialty
area within the general  realm  of  engineering science.  Interest in  reducing
the probability and consequences of an accidental release of anhydrous ammonia
prompted the preparation of this manual.  This  manual  is part  of  a series of
manuals which addresses  the prevention and  control  of a large release of any
toxic chemical.  The  subjects  of  the other manuals  planned for the  series
include

     •    A user's guide,
     •    Prevention and protection technologies,
     •    Mitigation technologies, and
     •    Other chemical specific  manuals such as this one.

The manuals are based on current and historical technical literature, and they
address the design,  construction,  and operation of chemical process facilities
where accidental releases of toxic  chemicals  could  occur.   Specifically,  the

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user's guide is intended as  a  general introduction to the  subject  of toxic
chemical releases and  to the concepts which are discussed in more detail in
the other manuals.   Prevention technologies are applied  to  the design and
operation of a  process to  ensure that primary  containment  is  not  breached.
Protection technologies capture  or  destroy a toxic chemical involved in  an
incipient release after primary  containment has been breached but before an
uncontrolled release occurs.   Mitigation technologies reduce the consequences
of a release once it has occurred.

     Historically, there have been several major releases of anhydrous ammonia
in the past fifteen  years  involving numerous injuries and a number of fatali-
ties.  Primary  sources of  these  releases include pressurized  pipeline rup-
tures, failed storage tanks,  and road tanker accidents.

1.2  PURPOSE OF THIS MANUAL

     The purpose  of  this  manual  is  to provide technical information  about
anhydrous ammonia with specific emphasis placed on the prevention of  acciden-
tal releases of this chemical.   This manual addresses technological and proce-
dural issues, related  to  release prevention,  associated  with  the storage,
handling, and process  operations  involving  ammonia.   (Note:  Throughout this
manual,  "ammonia" refers only  to anhydrous ammonia  and  not to aqueous or
"aqua" ammonia.)

     This manual  is  intended as  a summary manual  for persons  charged  with
reviewing and evaluating the potential for releases at  facilities that use,
store, handle,  or generate ammonia.   It  is not intended  as  a  specification
manual,  and the reader is  often  referred to additional  technical  manuals  and
other information sources  for  more  complete information on the topics dis-
cussed.   Other  sources of  information include  manufacturers and distributors
of ammonia in addition to  technical  literature on design, operation,  and loss
prevention in facilities which handle toxic chemicals.

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1.3  USES OF ANHYDROUS AMMONIA

     Anhydrous ammonia (NHg) is a significant commodity  chemical,  produced by
the  reaction  of  hydrogen and nitrogen over a catalyst.  The  dominant  use of
this chemical is in  the  fertilizer  industry  which accounts for nearly 80% of
all  ammonia produced (1).   The  direct application of ammonia 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 production of  a  number of commercially  important
synthetic materials.

     Numerous references in  the technical  literature provide  information on
both the  manufacture and  uses  of anhydrous ammonia.   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
purification, the  preparation of cleaners  and  detergents, pulp  and  paper
manufacture,  and food and beverage treatment.

1.4  CONTENTS OF THIS MANUAL

     The five sections of  this  manual  present the relevant issues associated
with the prevention  of an  accidental  release  of anhydrous ammonia to the
atmosphere.   The physical, chemical, and toxicological  properties  of  ammonia
which create or enhance the  hazards  of an accidental release  are presented in
Section 2.   In Section 3, the manufacture,  consumption, and storage of ammonia
are discussed, and the release  hazards associated with these  operations  are
identified.   Next,  potential causes  of releases,  including  those identified in
Section 3,  are summarized  in Section  4.  Finally, Section  5 contains detailed
information  about hazards  prevention  and control.  Topics included in this
section are process  and  physical plant  designs,  protection and mitigation
technologies,  operating and maintenance practices, and  illustrative costs.

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                                   SECTION 2
                           CHEMICAL CHARACTERISTICS

     This  section  describes  the physical,  chemical and toxicological proper-
ties of anhydrous ammonia as they relate to accidental release hazards.

2.1  PHYSICAL PROPERTIES

     At atmospheric temperatures and  pressures,  anhydrous ammonia is a  pun-
gent, colorless  gas.   It may easily be  compressed  or cooled to a colorless
liquid.  Its more important physical and chemical properties are  presented  in
Table 2-1.

     Pure  liquid ammonia  is  lighter than water,  and pure gaseous ammonia is
lighter than  air.   Because  of  this  latter property, a cloud of pure  ammonia
gas will be buoyant and  rise into the  atmosphere.   However,  depending on the
pressure and  temperature, air-ammonia  mixtures which  are  denser than air may
also be  formed.   For example,  air  which is  adiabatically  saturated with
ammonia  (6.1  wt%)  has a density that  is 1.35 times the  density  of  air at
ambient conditions  (6).   Hence, a  saturated air-ammonia mixture may not
disperse very readily  and remain  close to  the ground.  Water vapor may  also
condense out of an air-ammonia  mixture, from the cooling effect of evaporating
ammonia, causing fog.  Because  of  the higher specific gravity of the cooled
air, this fog could spread laterally over the ground  (6).  Regardless of the
temperature and pressure, all air-ammonia mixtures containing more than 45 wt%
ammonia are lighter than air (6).

     Liquid anhydrous ammonia has  a  large coefficient  of expansion.   Hence,  an
overpressurization hazard exists if storage vessels have  insufficient expan-
sion space or if pipelines full of liquid ammonia may be  sealed on both  ends.
In these situations, thermal expansion of the liquid with an  increase in

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             TABLE 2-1.  PHYSICAL PROPERTIES OF ANHYDROUS AMMONIA

                                                                    Reference
CAS Registry Number

Chemical Formula

Molecular Weight

Normal Boiling Point

Melting Point

Liquid Specific Gravity (H_0=l)

Vapor Specific Gravity (air=l)

Vapor Pressure

Vapor Pressure Equation
  07664-41-7
  17.03

  -28.17 °F @ 14.7 psia

  -107.93 °F

  0.6815 ® -27.7 °F

  0.5970 @ 32 °F

  128.8 psia 9 70 °F
                               log

                           where:
Pv = A -
 B
T+C
Liquid Viscosity

Solubility in Water at
  1 a tin, wt. %
Specific Heat at Constant
  Volume (vapor)
  Pv = vapor pressure, mm Hg

   T = temperature. °C

   A = 7.36050, a constant

   B = 926.132. a constant

   C = 240.17, a constant

   0.255 cp & -33.5 °C

   32 °F     42.8
   50 °F     33.1
   68 °F     23.4
   86 °F     14.1


   0.38 Btu/(lb- °F)  @ 32 °F
                             1

                             1

                             1

                             1

                             1

                             2
                             2

                             3
                                                                (Continued)

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                             TABLE 2-1  (Continued)
                                                                    Reference
Specific Heat at Constant
  Pressure (vapor)

Specific Heat at Constant
  Pressure (liquid)

Latent Heat of Vaporization

Liquid Surface Tension
0.5 Btu/(lb-°F) @ 32 °F


1.10 Btu/(lb-°F) @ 32 °F

588.2 Btu/lb @ -27.7 °F

23.4 dynes/cm 0 52 °F
4

1

5
Additional properties useful in determining other properties from physical
property correlations:
Critical Temperature

Critical Pressure

Critical Density
270.32 °F

1639.1 psia

14.66 lb/ft-
1

1

4

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temperature can result in  containment  failure from the hydrostatic  pressure
exerted by the liquid.

     The flammahility range of ammonia in air at atmospheric pressure is  from
16% to 25% ammonia by volume, while  in oxygen the  range is  from 15%  to 79% by
volume (3).  Increasing the temperature  and  pressure  of  the ammonia broadens
the flammability  range.   Although the minimum ignition  temperature for a
mixture within the flammability limits'is relatively  high at  1562 °F (7), it
is possible for ammonia  to burn or  explode  under  some conditions such  as a
large and intense source  of  ignition combined with a high  concentration of
ammonia gas  (8).   The presence of oil or a mixture  of ammonia with other
flammable substances will also increase the fire hazard.   It has  further  been
reported  that  the presence  of iron appreciably  decreases  the  ignition
temperature (8).

     Ammonia is readily  absorbed  in  water to make ammonia  liquor (ammonium
hydroxide or aqua ammonia).  The dissolution  of  ammonia  in  water is accompa-
nied by relatively large heats  of solution.   Approximately  938  Btu of heat is
evolved when 2.2 Ib of ammonia gas is dissolved in water  (3).   The solubility
of ammonia in water at various temperatures is given in Table 2-1.

2.2  CHEMICAL PROPERTIES AND REACTIVITY

     Pure ammonia  is  a very stable  compound under normal conditions; even
slight dissociation to hydrogen and  nitrogen does not occur  at atmospheric
pressure until temperatures of  840-930 °F are reached (7).  The  products of
complete combustion of ammonia are neither toxic nor hazardous,  since they are
nitrogen and water.

     Ammonia is a highly  reactive  chemical, forming  ammonium  salts with
inorganic and organic acids.  Ammonia  reacts  with  chlorine  in dilute solution
to give chloramines,  an important reaction in water purification  (3). Because

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of the alkaline characteristics of ammonia it  is  also  used as a neutralizing
agent in a number of processes.

     It has been reported that gold, silver, and  mercury  are  each capable of
reacting with  ammonia to  form explosive compounds  (1) .   Other  explosive
materials which can be formed include metal hydrazides which are produced from
the reaction of  alkali metals and  liquid ammonia.  Acetylides,  which are
highly explosive in  the  dry state,  are  formed in the presence  of ammonia
solutions of copper,  mercury or silver salts (1).

     Most common metals do not react with dry  ammonia.  However, when mixed
with very  small  amounts  of water or water vapor, ammonia will  vigorously
attack copper,  silver, zinc,  and many  alloys,  especially those  containing
copper (9).

2.3  TOXICOLOGICAL AND HEALTH EFFECTS

     Depending  on the  concentration,  the effects  of exposure to  ammonia  gas
range from mild irritation to  severe corrosion of sensitive membranes of the
eyes,  nose, throat, and lungs  (3).  Because of  the high solubility of  ammonia
in water, it is particularly irritating to moist skin surfaces.   A concentra-
tion of  500 ppm  has  been designated as  the  IDLH  concentration (Immediately
Dangerous to Life and Health), which is based on a 30-minute exposure.  Table
2-2 presents a  summary of some of the relevant  exposure limits for ammonia gas
(10).

     The predicted human  health  effects  from  increasing  concentrations  of
ammonia gas are summarized in  Table  2-3  (1,3).  Because the pungent odor of
ammonia  is  immediately recognizable at  low concentrations,  it  is highly
unlikely that any individual would become overexposed unknowingly.  Ammonia is
not a  cumulative metabolic poison;  ammonium ions are actually  important
constituents of living systems.  However, inhalation of high levels of ammonia
gas may  have fatal consequences  as  a result of the  spasm,  inflammation  and

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edema of  the  larynx and bronchi, chemical  pneumonitis and pulmonary  edema

(11).  Exposure of the eyes to high concentrations may result in ulceration of

the conjunctiva and cornea and destruction of all ocular tissues (11).


     Contact of the skin with liquid ammonia may result in severe injury by

freezing the tissue, since liquid ammonia vaporizes  rapidly when released to

the atmosphere and  will absorb heat from any substance it contacts.   If the
skin is moist, it may also cause severe burns  from the caustic  action of the
ammonium hydroxide produced.
               TABLE 2-2.  EXPOSURE LIMITS FOR ANHYDROUS AMMONIA
Exposure
 Limit
Concentration
   (ppm)
            Description
Reference
IDLH
    500
PEL
     50
LCLO



TCLO
 30,000
     20
The concentration defined as posing        10
an immediate danger to life and health
(i.e., causes irreversible toxic
effects for a 30-minute exposure).

This concentration was determined by       10
the Occupational Safety and Health
Administration (OSHA) to be the
time-weighted 8-hour exposure limit
which should result in no adverse
effects for the average, healthy,
male worker.

This concentration is the lowest           10
published lethal concentration for
a human over a 5-minute exposure.

This concentration is the lowest           10
published concentration causing
toxic effects (irritation).

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       TABLE 2-3.   PREDICTED HUMAN HEALTH EFFECTS OF EXPOSURE TO VARIOUS
                   CONCENTRATIONS OF ANHYDROUS AMMONIA (1.3)
                                             Effect
    5

  20-50

   40

   100


 150-200


   400


   700


  1700


5000-10000

  10000
Least perceptible odor

Readily detectable odor

A few individuals may suffer slight eye irritation

Noticeable irritation of eyes and nasal passages after a few
minutes exposure

General discomfort and eye tearing; no lasting effect from
short exposure

Severe irritation of the throat, nasal passages, and upper
respiratory tract

Severe eye irritation; no permanent effect if the exposure
is limited to less than 1/2 hour

Serious coughing, bronchial spasms, burning and blistering
of the skin; less than 1/2 hour of exposure may be fatal

Serious edema, strangulation, asphyxia, rapidly fatal

Immediately fatal
                                      10

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                                   SECTION 3
                   FACILITY DESCRIPTIONS AND PROCESS HAZARDS

     This section contains brief descriptions of the processes and facilities
for the manufacture, consumption, and, storage of anhydrous ammonia in the
United States.  The purpose of this section is to identify major hazards
associated with these facilities which may directly or indirectly cause
accidental releases.  Measures taken for the prevention of these hazards are
discussed in Section 5.

3.1  MANUFACTURE (3.12)

     Anhydrous ammonia is prepared by the reaction of hydrogen and nitrogen
(the "synthesis" or "syn" gas) in the presence of a catalyst at elevated
temperatures and pressures.  The manufacturing process consists of three basic
steps:  synthesis gas preparation, purification, and ammonia synthesis.  The
first step involves the production of hydrogen and the introduction of the
stoichiometric amount of nitrogen.  In the second step, catalyst poisons
(carbon dioxide, carbon monoxide, and water) are removed from the synthesis
gas.  The third step includes the catalytic fixation of nitrogen at high
temperatures and pressures and recovery of the ammonia.  The specific
processes used by the numerous producers of ammonia primarily differ in the
source of hydrogen for synthesis gas and the temperature and pressure of the
ammonia synthesis loop.

     The main sources of hydrogen in modern ammonia plants are coal, petroleum
fractions, and natural gas, with the latter being the principal source in
commercial practice.  In general, the most economic feedstock has the highest
hydrogen to carbon ratio.  The two hydrogen generation techniques used for
processing these raw materials are partial oxidation (reaction with oxygen)
and steam reforming (reaction with steam).  Of these, steam reforming is the
                                      11

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more widely used process; partial oxidation processes are employed where
steam-reformable feeds are not available or in special situations where
favorable economic conditions exist.

     Figure 3-1 is a typical process diagram for the production  of ammonia by
steam reforming.  The first step in the preparation of the synthesis  gas  is
desulfurization of the hydrocarbon feed.  This is necessary, because  sulfur
poisons the nickel catalyst (albeit, reversibly) in the reformers, even at
very low concentrations.  Steam reforming of hydrocarbon feedstock is carried
out in the primary and secondary reformers.  The primary reformer is  a
refractory-lined furnace which contains vertically suspended tubes filled with
a nickel-based catalyst.  In the primary reformer, the feed reacts with steam
to produce hydrogen gas and carbon monoxide.  Some of the carbon monoxide also
reacts with steam in the "shift conversion" reaction to produce  carbon dioxide
and hydrogen.  The secondary reformer is a refractory-lined pressure  vessel
which contains additional reforming catalyst.  Primary reformer  effluent  gas
is mixed with air prior to entering the secondary reformer.  This serves  a
two-fold purpose; it supplies the stoichiometric amount of nitrogen,  and
it supplies oxygen for combustion which supplies the heat required for the
reforming reaction.

     After passing through waste heat boilers, the syn gas enters the purifi-
cation stage.  Regardless of the hydrogen  generation technique used,  the
unpurified syn gas contains carbon  oxides which deactivate the ammonia
synthesis catalyst and must be removed.  In the shift converters, carbon
monoxide is catalyticaliy converted to  carbon dioxide, which  is  removed more
easily than CO, and hydrogen gas.   The  next purification  step  is the  removal
of carbon dioxide.  Commercial processes generally involve absorbing  the  gas
into a solvent under pressure and then  recovering the solvent  in a  stripping
column.  The  final purification  step  involves removal of  the  residual carbon
monoxide and  carbon dioxide in a methanator and, in some  plants, cryogenic
purification.   In the methanator, CO  and CO  are catalyticaliy converted  to
methane which passes through the ammonia synthesis loop as an  inert.   The
                                       12

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                      STEAM    AIR
NATURAL > 	
GAS(CH4)C w






DESULrURIZER

AMMONIA
CONDENSER
1
*
LIQUID
NH3







PRIMARY AND
REFORMERS

AMMONIA
CONVERTER

RECYCLE
CO. C02 _ SHIFT
W CONVERTERS W

N2.H2



co2
REMOVAL
1
METHANATOR
& CRYOGENIC
PURIFICATION


Figure 3-1.  Conceptual diagram of  typical  ammonia production process.

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purpose of cryogenic purification is to remove the excess nitrogen added to
the secondary reformer.   This is done to avoid excessive loss of hydrogen and
excessive compression costs in the ammonia synthesis loop.

     The purified syn gas next flows to the final production stage which is
ammonia synthesis and recovery.  The first step is compression of the syn gas.
Synthesis pressures range from 2,000 to 10,000 psi depending on the quality of
the syn gas and certain other conditions, such as production requirements per
converter (12).  Almost without exception, all modern large-scale ammonia
plants employ steam-driven centrifugal compressors for synthesis service.  One
of the advantages of centrifugal compressors is that a minimal amount of
lubricating oil is required, as this material causes problems in the synthesis
loop.  For smaller plants, under 600 tons/day, reciprocating compressors are
still used.

     Basically, there are two classes of ammonia converters, tubular and
multiple bed.  The tubular bed reactor is limited in capacity to a maximum of
about 544 tons/day (3).  In most reactor designs, the cold inlet synthesis gas
flows through an annular space between the converter shell and the catalyst
cartridge.  This maintains the shell at a low temperature, minimizing the
possibility of hydrogen embrittlement which can occur at normal synthesis
pressures.  The inlet gas is then preheated to synthesis temperature by the
exit gas in an internal heat exchanger, after which it enters the interior of
the ammonia converter which contains the promoted iron catalyst.

     Gas recirculation in the ammonia synthesis section is necessary, because
only 9-30 percent conversion is obtained per pass over the catalyst  (12).  The
synthesis loops are generally of two types.  One type recovers ammonia product
after makeup gas-recycle compression and the other recovers ammonia product
before recycle compression.  Inerts entering with the makeup gas are removed
with a purge stream.  The ammonia is recovered by condensation which requires
refrigeration.  Since anhydrous ammonia is readily available, it is normally
used as the refrigerant.
                                       14

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     Ammonia release hazards in the production process described above occur
in the latter part of the process, specifically in the ammonia synthesis loop,
where ammonia is present in relatively pure form.  The types of equipment in
the synthesis loop include large compressors, the ammonia converter, the
ammonia condenser (plus ammonia refrigeration equipment), and the associated
piping and instrumentation.  Some previously reported and other possible
causes of equipment failure in this section include the following (13,14):

     •    Compressors
          - severe vibrations on compressor and/or turbine,
          - rotor failed,
          - compressor thrust collar broke,
          - coupling bolts failed,
          - compressor seal failed,
          - broken blades on turbine,
          - reduction gear bearing failed,  and
          - compressor 0-ring failed.

     •    Ammonia Converter
          - cracking induced by thermal shock,
          - hydrogen-induced cracking,
          - loss of feed control,  and
          - overheating of the catalyst bed.

     •    Heat  exchangers (including condensors)
          - tube failures,  and
          - loss of cooling resulting  in overpressure.

     •    Piping and instrumentation
          - relief valve did not  reseat,
          - valve packing was blown,
          - improper materials of  construction, and
          - rupture  due to corrosion/erosion  effects.
                                      15

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     Of the four major compressors in ammonia production,  the service
performed by the synthesis gas compressor is the most demanding (13).  It
discharges at the highest' pressure,  requires the most horsepower,  has an
intricate seal oil system, has the most compressor/turbine bodies, and
operates at a relatively high speed.  If the ammonia is condensed from the
synthesis loop prior to compression of the syn gas,  the ammonia content in the
compressor will be relatively low.  However, if the  ammonia is compressed with
the syn gas prior to recovery, a failure in the syn  gas compressor is a
significant release hazard.

     Ammonia plants are subjected to a thermal cycle with each shutdown and
start-up.  During planned shutdowns, the plant comes down at a slow, control-
led rate.  However, other shutdowns are unplanned,  and some plants tend to
come down rather quickly in these situations.  The  effect of rapidly reducing
the process gas temperature in the ammonia converter is the creation of high
thermal stresses.  This thermal cycle is a primary  cause of surface cracks in
the walls and outlet of the converter (14).  A second effect of cooling a
thick-wall component in high-temperature, high-pressure hydrogen service is to
supersaturate the metal with respect to hydrogen.  The excess- hydrogen is
trapped in the metal and collects in discontinuities, such as small cracks or
non-metallic inclusion, and exerts pressures high enough to initiate cracks.
Hydrogen-induced cracking may therefore magnify the  effect of thermal stress
to produce hazardous internal cracks.

     Overheating the ammonia converter could result  in uncontrollable
combustion reactions or explosions with the consequent physical breakdown of
the reactor vessel by thermal fatigue or overpressure.  Possible causes of
overheating include the following:

     •    Poor heat distribution within the reactor bed, resulting in hot
          spots;

     •    Overheating raw materials before they enter the ammonia converter;
          and
                                       16

-------
     •    Loss of composition or quantity control of raw material feeds.

     The condenser, piping, and instrumentation hazards listed above are not
specific to the ammonia production process.  Other possible causes of release
from these components are covered in Section 4.  The hazards associated with
the use of ammonia as a refrigerant are discussed in Section 3.2.5.

3.2  PROCESSING AND CONSUMPTION

     Because the uses of ammonia in the U.S. are many and diverse, the
processes discussed in this section are limited to those which 1) represent
the primary consumers of anhydrous ammonia. 2) are widespread but not large
consumers of ammonia, or 3) are especially hazardous.  Some of the numerous
minor uses of ammonia which are not discussed include the following processes:
manufacture of rubber, water purification, food and beverage treatment, the
production of pulp and paper, the preparation of cleaners and detergents, and
leather and textile treatment.

     Ammonia is also used in the manufacture of many important industrial
chemicals which are too numerous to discuss individually.  Table 3-1 lists
many of the industrial chemicals produced directly from anhydrous or aqueous
ammonia (15).  In many cases, the primary release hazards in the production
processes are associated with the ammonia storage, feed, and recovery systems,
The processes discussed in the following subsections provide specific examples
of the general hazards of ammonia processing, while the specific hazards of
ammonia storage are discussed in Section 3.4.

3.2.1  Fertilizer Production (16.17,18)

     The fertilizer industry is, by far, the largest consumer of anhydrous
ammonia in the United States, accounting for 70-80 percent of all ammonia
                                      17

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     TABLE 3-1.   ANHYDROUS AND AQUEOUS AMMONIA PRODUCTS (15)
ammonium acetate
ammonium adipate
ammonium benzoate
ammonium bicarbonate
ammonium bifluoride
ammonium binoxalate
ammonium bisulfate
ammonium bitartrate
ammonium tetraborate
ammonium bromide
ammonium carbonate
ammonium chloride
ammonium citrate
ammonium dichrornate
ammonium fluoride
ammonium fluorosilicate
ammonium gluconate
ammonium iodide
ammonium molybdate
ammonium nitrate
ammonium oxalate
ammonium perchlorate
ammonium picrate
ammonium polysulfide
ammonium salicylate
ammonium stearate
ammonium Slllfate
ammonium sulfide  (hydrosulfide)
ammonium tartrate
ammonium thiocyanate
ammonium thiosulfate
ammonium paratungstate
urea
monoammonium phosphate
diammonium phosphate
nitric oxide
acrylonitrile
caprolactam
monomethylamine
dimethylamine
hexamethylenetetramine
trimethylamine
monoethanolamine
diethanolamine
triethanolamine
hydrogen  cyanide
fatty nitrogen compounds
   (nitriles, amines,  quaternary
   ammonium compounds)
boron nitride
calcium  carbonate  (precipitated
   from calcium chloride)
hydrazine
hydrogen (high purity)
lead hydroxide
lithium  amide
methyl ethyl pyridine
sodamide
sodium cyanide
nitrogen dioxide
nitric acid
                                18

-------
 produced  in  the past decade.   In  fact,  the largest single use of ammonia is
 its  direct application as a fertilizer.  The ammonia-based fertilizers
 produced  in  the greatest quantity  include ammonium nitrate, ammonium sulfate.
 ammonium  phosphates  (mono- and di-). and urea.  In addition, nitrogen
 solutions and mixed  fertilizers are prepared which consist of combinations of
 the  various  products mentioned above along with fertilizers derived from
 elements  other than nitrogen,  e.g., phosphorus.

     In the  following paragraphs,  the processes for the manufacture of the
 three ammonium salts and urea  are  briefly discussed, and the primary process
 hazards within the fertilizer  industry are identified.  In many cases, plants
 for  the production of ammonia-based fertilizers are integrated with ammonia
 plants at the same facility, such  that the hazards of ammonia production
 presented in the Section 3.1 would also exist at this type of installation.

 Ammonium Nitrate—
     Ammonium nitrate is produced by the neutralization of nitric acid with
 anhydrous ammonia in an atmospheric or pressurized reactor.  Figure 3-2 is a
 flow diagram of a typical manufacturing process.  The reaction of ammonia with
 nitric acid is strongly exothermic.  The high heat of reaction causes flash
vaporization of water with some ammonia and nitrate going overhead.  The
 temperature of the solution in the neutralizer is controlled by regulated
 addition of the reactants and by removal of the heat.  The reactor effluent is
 approximately 83 wt% ammonium nitrate.   This product can be sold without
 further processing, or additional water can be evaporated to produce the salt
 in dry form.

     The parts of the ammonium nitrate  production process which present
ammonia release hazards are between the ammonia feed (storage)  tank and the
reaction tank or neutralizer.   Release  hazards of ammonia storage are
discussed in Section 3.4.  The neutralizer is a high hazard area because it
operates at elevated temperatures and pressures, and the neutralization
reaction is extremely exothermic.   Potential  causes  of a release include
loss of feed control and  loss  of cooling.
                                     19

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                                                  1
AMMONIA
STORAGE


AMMONIA
VAPORIZER


NEUTRALIZER
N>
O
I
                    1
                                                                   EVAPORATOR
                                     PRILL TOWER
                                         OR
                                     CRYSTALLIZER
(  AMMONIUM NITRATE
 (PRILLS OR CRYSTALS)
                                               NITRIC ACID
                           Figure 3-2.   Conceptual  diagram  of typical  ammonium nitrate  process.

-------
     Both a loss of feed control and a loss of cooling would result in
overheating of the reactor contents.  Overheating may lead to overpressure if
the vessel does not have adequate pressure relief devices, or if they fail to
operate in the correct manner.  In addition to causing excessive heat
generation, a loss of feed control may also cause overpressure if the relief
devices fail to activate.  Reactor failure (rupture) could result from the
development of temperatures or pressures which exceed design conditions.

     Solid and molten NH^NOg can be hazardous under certain conditions, e.g.,
when detonated and/or in the presence of an oxidizable substance.  However,
this property does not create a significant ammonia release hazard in the
ammonium nitrate production process, because it is highly unlikely that these
conditions will exist (especially prior to evaporation) in the parts of the
process where ammonia is present.  The explosive property of ammonium nitrate
would, however, create a hazard with respect to an ammonia release if the
storage facilities for the dry ammonium nitrate were located in close
proximity to the ammonia storage tank.

Ammonium Sulfate—
     Ammonium sulfate is produced by the reaction of by-product ammonia from
various processes with sulfuric acid.  Because of the limited number of by-
product ammonia sources, ammonium sulfate is also produced by the neutraliza-
tion of sulfuric acid with synthetic ammonia.  (The same principles and
practices are involved in the two procedures, but the synthetic raw materials
give a purer product.)  A typical process diagram for the production of
ammonium sulfate from synthetic ammonia is shown in Figure 3-3.  Anhydrous
ammonia is dissolved in water and pumped to the neutralizer where it meets a
stream of concentrated sulfuric acid (92-98% H.SO.).  The solution of ammonium
sulfate that forms is pumped into double-effect crystallizers.   The ammonium
sulfate crystals from the crystallizer are separated by centrifuging or
filtering and are dried.
                                     21

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                                               WATER
                                                                SULFURIC
                                                                 ACID
f AQUEOUS f
AMMONIA
STORAGE


AMMONIA
VAPORIZER


AMMONIA
ABSORBER
AMMUIMIA
18-26% __









ta


CENTRIFUGES
                                                                                                             AMMONIUM
                                                                                                            >  SULFATE
                                                                                                             CRYSTALS
N)
K>
                           Figure 3-3.   Conceptual diagram of  typical  ammonium sulfate process.

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     The ammonia release hazards in this process are only present between the
storage/feed systems and the point where ammonia is absorbed in water to form
the aqueous solution which is fed to the neutralizer.  These hazards are not
specific to the ammonium sulfate process and are discussed in other parts of
this manual.

Ammonium Phosphate—
     Although ammonium phosphate fertilizers are produced by several methods,
the simultaneous ammoniation and granulation process is, by far, the
predominant method.  In this process, a rolling bed of recycled undersized
ammonium phosphate particles is acidified by a spray of phosphoric acid which
is immediately neutralized by ammonia injected beneath the surface of the bed
through fixed spargers.  Alternatively, the granulation process can be
combined with a preneutralizer unit in which the phosphoric acid is first
partially neutralized with ammonia in an agitated vessel.  This process is
shown in Figure 3-4.  The heat of reaction results in a preneutralizer vessel
temperature of about 240 °F and the evaporation of about 20% of the water
present.  The hot slurry is sufficiently fluid to be distributed over the
rolling bed in the ammoniator-granulator.  In either case, an excess of
ammonia is required in the ammoniator to reach the required N:P.O,- ratio
required.  This excess is recovered by scrubbing the ammoniator-granulator
off-gases with the incoming acid.

     As in the production of the other two ammonium salts, the ammonia release
hazards are present between the ammonia storage/feed systems and the preneu-
tralizer.  The hazards of ammonia storage and handling general to all ammonia
processes  (including heat exchangers, piping, and instrumentation) are
discussed in other parts of this manual.  As with the ammonium nitrate
process, the neutralization of phosphoric acid is accompanied by a large heat
of reaction, and thus a loss of feed control or reactor cooling could lead  to
overheating and/or overpressure, possibly resulting in reactor failure with a
loss of containment of the contents.
                                      23

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                                             PHOSPHORIC
                                               ACID
NJ
                                                                             FINES RECYCLE
                        Figure 3-4.  Conceptual of diagram typical diammonium phosphate process.

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Urea—
     Urea is indirectly produced by the exothermic reaction of anhydrous
liquid ammonia and gaseous carbon dioxide at elevated temperatures and
pressures.  The initial reaction product is ammonium carbamate, which
subsequently decomposes to produce urea and water.  Urea plants are always
built in conjunction with ammonia plants, so that both reactants are obtained
from the ammonia synthesis operation.

     Figure 3-5 is a typical flow diagram for the production of urea.  The
reaction is carried out with an excess (50-100%) of liquid anhydrous ammonia
in a stainless steel- or lead-lined reactor at pressures ranging from
2000-5000 psig and temperatures of 250-380 °F.  As the reaction does not go to
completion, the unreacted gases must be separated from the reactor effluent by
heating and decompression, after which they are either recycled to the reactor
or utilized in another process.  Total recycle of the reactants is the most
common practice.  In this process, the ammonia, carbon dioxide, and ammonium
carbamate are separated from the reactor effluent in the low- and high-pres-
sure decomposers.  The low-pressure off-gas is condensed in the low-pressure
absorber, and the liquid is pumped into the high-pressure absorber for
absorption of the high-pressure decomposer gas.  Unabsorbed excess ammonia
from the high-pressure absorber is condensed in the ammonia condenser and
recycled to the reactor, as is the concentrated carbamate solution recovered
in the high-pressure absorber.  The product stream leaving the decomposers is
about 70% to 80% urea.  This product can be used as is, or it can be further
concentrated to a solid product.

     In the urea manufacturing process, ammonia is present in relatively pure
form in the ammonia recovery section (condenser and receiver), the feed system
(storage, receiver, pump, and preheater), and the carbamate reactor.  Of
these, the reactor presents the only release hazards which are specific to the
urea manufacturing process.  Release hazards are significant because of the
                                      25

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           MAKE - UP NH3
          FROM STORAGE
AMMONIA
RECEIVER
  AMMONIA
 CONDENSER
                             PUMP AND
                            PREHEATER
ro
                      l—*
                                                          NH3 -i
                                                           C02
                 HIGH AND LOW
                   PRESSURE
                  ABSORBERS
      i
REACTOR
    UREA
 HYDROLYZER
                          STRIPPER
HIGH AND LOW
  PRESSURE
DECOMPOSERS
                                                           RECYCLE
CONCENTRATION
  EQUIPMENT
UREA MELTER
 AND PRILL
  TOWER
 UREA
PRILLS
                         Figure 3-5.   Conceptual  diagram of  typical urea manufacturing process.

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high temperatures and pressures in the reactor, and because the reaction is
highly exothermic.  Therefore, a loss of cooling or feed control could result
in overheating or overpressure with subsequent reactor fracture and the loss
of containment of the reactants.  Another hazard arises from the possibility
that there will be an upset in the ammonia process resulting in unacceptable
levels of impurities in the reactants.  If, for example, the CO. were to
contain more than about 2% (volume) nitrogen and hydrogen and was somehow
mixed with air. an explosive gaseous mixture may result (19).  High tensile
steel is also susceptible to stress corrosion cracking by steam, hot water
chlorides, sulfur compounds, and nitrates.

3.2.2  Nitric Acid Production (17,20)

     Nitric acid, a major industrial chemical, is prepared by the oxidation of
ammonia.  Although its primary consumption is in the fertilizer industry.
nitric acid is also the starting material for most of the nitrogen compounds
used in the manufacture of explosives, which account for about 4-5 percent of
all ammonia produced, in addition to being a raw material in the production of
a large number of commercially important organic chemicals.

     Although the specific operating details vary among the plants which
produce nitric acid, they have in common the following three steps:  oxidation
of ammonia to nitric oxide (NO), oxidation of the nitric oxide to the dioxide
(NC^), and absorption of nitrogen oxides in water to produce nitric acid.

     Figure 3-6 is a diagram of a typical nitric acid production process.
Ammonia is evaporated and superheated before being mixed with preheated air.
Since the explosive limit of ammonia is approached at concentrations greater
than 12 mol% (at the conditions of this process). the ratio of ammonia to air
in the feed is controlled in the range 9.5-10.5 mol% ammonia.  This mixture
flows to the ammonia converter where it is reacted on a platinum-rhodium gauze
pad operating in the ranges of 1472-1760 °F and 0-120 psig.  The reaction,
which produces NO and H20. is extremely rapid and goes almost to completion.
                                      27

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                                                                                     STACK
               AIRl
ro
Qt>
                      Figure 3-6.   Conceptual diagram of typical  nitric acid production process.

-------
The NO thus produced undergoes a slow homogeneous reaction with oxygen to
yield nitrogen dioxide.  The production of NO. is favored by relatively lower
temperatures (below 300 °F).  The hot effluent gas is therefore cooled by heat
exchange with the feed gas and passes through low pressure boilers before
entering the absorption towers.  The pressure of the gas and the residence
time in route to the absorption towers can be adjusted to effect the desired
percentage oxidation of the NO.  In the absorption towers, which may be spray
towers, packed columns, or plate columns, the gas is scrubbed with weak acid
and water (steam condensate).  The normal grades of 45-65% HNO, are produced
directly in the plant; these may be concentrated to 86-99% HNO., (fuming) by
distillation under various conditions.

     Ammonia release hazards specific to the nitric acid process are a loss of
cooling or a loss of feed control to the ammonia converter.  The realization
of these hazards may result in overheating and/or overpressure of the reactor
causing failure and release of the reactor contents.  A loss of feed control
is especially hazardous, because an explosive mixture which exceeds the
flammability limits of ammonia may result.

3.2.3  Recovery of Ammonia from Refinery Waste Water (21,22)

     In the petroleum industry ammonia is used as a solvent, a refrigerant, a
corrosion inhibitor, and as a neutralizer of the acidic constituents of oil.
Additionally, in some refineries, it is recovered as a salable product from
sour water.  This process is described below; refrigeration and neutralization
processes are discussed in Sections 3.2.5 and 3.2.6, respectively.

     Waste waters from several petroleum refining processes contain
appreciable quantities of ammonia.  Typical concentrations reported in the
literature range from 3% to 10% by weight.  The "WWT Process" is a patented
process for treating these refinery wastes.  The process recovers high-purity
ammonia along with hydrogen sulfide and clean water suitable for reuse or for
discharge.  The larger WWT units produce more than 50 tons of anhydrous
ammonia per day (21).
                                      29

-------
     A typical WWT Process arrangement is shown in Figure 3-7.   The feed
consists of sour water from a degassing unit in which dissolved hydrogen,
methane* and other light hydrocarbons are removed.  The feed is pumped through
a feed heater into a reboiler stripper column.   In this column, the hydrogen
sulfide is stripped overhead while the ammonia and water are removed as the
bottoms product.  The overhead product is high purity hydrogen sulfide which
contains negligible ammonia.  The bottoms product goes directly to a second
reboiler stripper column.  The bottoms from this column is "clean" water
(typically <50 ppm NH3 and <5 ppm l^S) suitable for many in-plant reuse needs.
while the overhead product is ammonia with small amounts of hydrogen sulfide
and water.  These constituents are removed in the ammonia purification section
which consists of one or more scrubbing stages depending on the desired
purity.  The ammonia product is then compressed and condensed to salable
anhydrous liquid ammonia.  Alternatively, the ammonia product can be produced
as high-purity aqueous ammonia solution which eliminates the need for an
ammonia compressor.  Because the ammonia is handled in solution, the
production of aqueous ammonia may be less hazardous than the production of
anhydrous ammonia.  If there is no immediate use or sale for the ammonia
recovered from the second stripper, it can be incinerated in a process furnace
or special incinerator.

     The potential hazards which may result in a large release of ammonia
liquid or gas involve the latter portion of the process where ammonia is
present in relatively pure form.  This section of the process begins with the
overhead product from the second stripper and ends with the final ammonia
product storage.  Included are the ammonia stripper and condenser; one or more
#2$ scrubbers; product compressors, condensers and storage facilities; and
associated piping and instrumentation.  Process upsets specific to the WWT
Process which may lead to a large release of anhydrous ammonia include:

     •    Overheating of the ammonia stripper from excess heat to
          the ammonia stripper reboiler or a sudden decrease in
          ammonia feed; and
                                     30

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                       Hydrogen
                        Sulfkte
                       By-Product
Recycle
                                       Deaeraled
                                       Condensate
                                 Degassed  »
                                Sour Water  t
                                                                                                            Anhydrous
                                                                                                            Ammonia to
                                                                                                            By-Product
                                                                                                             Storage
                                                      Stripped
                                                       Water
                Figure 3-7.   Conceptual diagram of  "WWT" waste  water treatment  process.

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     •    Overheating of the ammonia condensers from a loss of
          cooling water.

These process upsets could potentially result in equipment failure from
overpressurization.   Additional hazards which are associated with the storage
and transfer of anhydrous ammonia are discussed in Section 3.4,  while general
causes of equipment  failure are discussed in Section 4.0.

3.2.4  The Use of Ammonia in the Production of Resins (16,17,23)

     Anhydrous ammonia and ammonia derivatives (e.g., aqueous ammonia, nitric
acid) are used in the production of a variety of resins and fibers.   These
resins are subsequently used in the manufacture of many commercially important
products in the synthetic plastics, adhesives, coatings, and textiles
industries.  This market consumes between 8 and 10 percent of all ammonia
produced in the U.S.  By far, the greatest amounts go to the production of
amino, acrylic, and  polyamide (nylon) resins, polyurethanes, and linear
polyesters (17).

     The production  of acrylonitrile (an acrylic resin) is one process which
uses anhydrous ammonia directly as a reactant.  The process, shown schematic-
ally in Figure 3-8,  involves reacting a gaseous mixture of propylene, ammonia,
and air in a ratio of 1.4:1.4:10 in the presence of a catalyst.   The three
reactants are fed to a fluidized bed reactor operating at a temperature of
750-950 °F and 5-30  psig pressure.  The reactor effluent is scrubbed in a
countercurrent absorber, and the organic materials are recovered from the
absorber water by distillation.  Hydrogen cyanide, water,  light ends, and high
boiling impurities are removed from the crude acrylonitrile by fractionation
to produce specification acrylonitrile product.  Because the conversion
obtained on a once-through basis is high, no separation or recycling of
unreacted raw materials is necessary.  However, in another commercial process
which does not have  a high conversion, the unreacted ammonia is absorbed by a
countercurrent flow of aqueous sulfuric acid to produce ammonium sulfate as a
by-product (16).

                                      32

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Water  Off Gas
                                                      Water
Crude
HCN
     Air

Ammonia

Propytone
                                                                                           Product
                                                                                         Acrytonitrite






Bo
Fe
WB
Reacta
\
rier 1
ed Pri
Her S
r


i

I
i
Absorber




*gh
assure
team
!
Acrytonitrit
Recovery
Column
!
AcetonMrita
Recovery
Column
i
e
uruoe
AcrylonHrile
fc LJohts
Column


f Product
Column
(Recycle)

Crude
' Acetonitrile
Ha
knpu
i
ivy
rities
              Figure 3-8.   Conceptual  diagram of  typical acrylonitrile  process.

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     Hazards which may lead to a large release of anhydrous ammonia in the
acrylonitrile production process involve the portions of the process where
ammonia is present in relatively pure form.  Because no ammonia recovery is
required, this only includes the section between the storage (feed) tank and
the catalytic reactor.  This section contains the storage tank, the ammonia
vaporizer (usually a solenoid valve), feed preheater, piping to the reactor, a
flow controller, and various other instrumentation.  Possible  causes of a
hazardous release from any of these components are discussed in Sections 3.4
and 4.0.  Process upsets, e.g., overheating from a loss of cooling water, are
unlikely to lead to a large release of ammonia unless coupled  with another
event such as the loss of ammonia feed control.  In  the event  of  a reactor
failure, this situation would allow excess ammonia to vent to  the atmosphere.

3.2.5  The Use  of Ammonia as a Refrigerant  (14,24)

     One of the predominant minor uses of  ammonia  (generally less than 2% of
annual production) is as a refrigerant.  Because of  its toxic  properties,
ammonia  is primarily  suitable for industrial  applications where a refrigerant
leak will not cause occupant discomfort.   For this reason also, it is
extremely important that ammonia equipment  and piping are arranged so  that
components may  be easily isolated for repair,  replacement, or  overhaul.

     Anhydrous  ammonia is used in vapor  compression  systems.   These  systems
vary from simple  single-stage refrigeration cycles to complex  multistage
compound or cascade cycles depending  on  the application.

     Figure 3-9 shows the basic refrigeration cycle  for a single-stage system.
The  four basic  components are  the compressor,  condenser, expansion valve,  and
evaporator.   High pressure liquid ammonia  flows  from the condenser  receiver
through  an  expansion  valve  to  the evaporator.  Here, heat is  absorbed from the
fluid  to be  cooled, and  the  ammonia  boils.  The  gaseous ammonia  is  then
                                       34

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u>
Ln
Expansion
  Valve
                                                         Cooling
                                                         Medium
                                                       Condenser
                                                       Evaporator
                                                         Product
                                                         Cooled
                                                                                Compressor
                   Figure  3-9.   Conceptual  diagram of basic vapor compression refrigeration cycle.

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compressed to a temperature and pressure at which the superheated vapor can be
condensed by the cooling media available for use in the condenser.  The
refrigeration cycle thus involves two pressures, high and low.  to enable a
continuous process which produces the desired cooling effect.

     Possible causes of a hazardous release from an ammonia refrigeration
system include the following:

     •    Overpressurization, and

     •    Equipment damage.

     Failure of the refrigeration compressor stops circulation of refrigerant
through the evaporator.  If the flow of the fluid being cooled is not stopped,
the pressure in the evaporator will rapidly rise causing the relief valves to
open.  If these valves are not vented to a closed system, ammonia will be
released to the atmosphere.  A similar situation can occur if cooling water to
the condenser is lost.  Again, relief valves on the condenser would open as
the pressure exceeds the limit.

     Catastrophic equipment failure could result in a large release of ammonia
liquid and/or gas.  Because refrigeration systems operate at greater than
atmospheric pressure, ammonia will quickly escape from the source of a re-
lease.

     The primary cause of refrigeration equipment problems is lack of adequate
precautions during the design, construction and installation of the system
(24).  The components of the refrigeration system which are especially vulner-
able to damage from start-up procedures and process upsets include machinery
with moving parts such as pumps and compressors.  Abnormally high process
temperatures may occur either during start-up or process upsets.  Provision
must be made for this possibility, for it can cause damaging thermal stresses
on refrigeration components and excessive boiling rates in evaporators,
causing liquid to carry over and damage the compressor.
                                      36

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     It is also important that the system is kept internally clean during
installation.  This is because ammonia is a powerful solvent, and dirt, scale,
sand, or moisture remaining in the pipes, valves and fittings will be swept
along with the suction gas to the compressor, where it is potentially harmful
to the bearings, pistons, cylinder walls, valves and lubricating oil.  When a
compressor is run for the first time, moving parts are often scratched (24).
Although damage is only minor in the beginning, scratches may progress until
they seriously affect the operation of the compressor or render it inoperative
(24).

3.2.6  Neutralization of Acidic Waste Streams with Ammonia (25)

     A variety of industrial processes generate waste streams which are acidic
in nature.  For example, sulfuric acid is used in lead-acid battery manufac-
turing processes resulting in waste streams with a pH of around 2 (25).
Regardless of the source, acidic wastes must usually be neutralized prior to
further treatment or discharge.  Owing to its alkaline properties, anhydrous
ammonia is often used as the neutralizing agent for these wastes.

     The neutralization process itself is relatively simple.  In most process-
es, anhydrous ammonia is vaporized through a solenoid valve as it leaves a
pressurized storage tank.  The gaseous ammonia flows through carbon steel
piping to a neutralization drum, pit, or tank where it is sparged into the
waste solution.  The ammonia may be piped directly into the bottom of the tank
or sent through a vertical feed pipe which is immersed in the solution.  The
quantity of ammonia fed is automatically controlled by either wastewater
flowrate or pH.

     The hazards associated with the neutralization process primarily involve
the ammonia storage system.  These hazards are general to all ammonia facili-
ties and are discussed in Section 3.4.  The only other part of the process
where ammonia is present in nearly pure form is the feed system.  However, a
failure in this system which causes too much or too little ammonia to be fed
would probably not result in a large release of anhydrous ammonia.  A slight

                                      37

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overpressurization potential would exist if the neutralization tank were a
closed system without a pressure relief device or had insufficient relief
piping volume to handle any excess gas which is not absorbed in solution.
However, because ammonia is so soluble in water, it would take a rather large
quantity to saturate an aqueous waste stream.

     One other consideration in neutralization systems is the use of suitable
materials of construction for the tank and any ammonia piping which comes into
contact with the waste solution.  Improper materials of construction may lead
to corrosion and possible equipment failure.  The type of container used as
well as the materials of construction will depend on the characteristics of
the waste.  A corrosion hazard also exists if precautions are not taken to
prevent backflow of the waste into the carbon steel ammonia piping.

3.2.7  The Manufacture of Hydrogen Cyanide (17)

     Anhydrous ammonia is a raw material in the manufacture of hydrogen
cyanide (HCN).  This chemical is a colorless, volatile liquid that is highly
flammable and very toxic.  All production of HCN in the United States is based
on the continuous catalytic reaction of air, ammonia, and methane.

     Figure 3-10 is a block diagram of a typical hydrogen cyanide manufactur-
ing process.  In this process, ammonia, methane, and air are preheated to
about 750-950 °F, mixed, and sent to a packed bed reactor.  The reactor is
typically packed with a catalytic wire gauze composed of platinum, and a
normal reaction temperature of about 2000-2200 °F is maintained.  The gaseous
effluent consists of a mixture of HCN, ammonia, and water vapor.  The crude
product mixture flows through an ammonia absorption column where the ammonia
is removed by an ammonium phosphate solution.   (Dilute sulfuric acid or
ammonium sulfate may also be used.)  The product stream  (mostly gaseous HCN)
passes to the product recovery section where it is absorbed in water,
distilled, and treated with sulfur dioxide as an inhibitor to prevent
polymerization.  The ammonium phosphate solution is first stripped of HCN,
                                      38

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CO
VO
                 Figure 3-10.   Conceptual  diagram of typical hydrogen cyanide manufacturing process.

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after which it passes to the ammonia recovery columns.   The recovered ammonia
is condensed and recycled as feed to the process.

     Hazardous areas of this process with respect  to the potential for a large
release of ammonia to the atmosphere (other than the ammonia storage and feed
systems) include the feed gas mixer, the HCN reactor, and the ammonia recovery
columns.  Specifically, the following upsets may occur which could lead to
equipment failure and the loss of containment of the reactants:

     •    Loss of feed gas composition or quantity control;

     •    Overheating of the reactor; and

     •    Loss of cooling or heating in the ammonia recovery section.

     A loss of feed gas composition is hazardous,  because a flammable mixture
of ammonia and air may form which would be especially hazardous in the
presence of methane.  In addition to posing an explosion hazard, an incorrect
feed composition or quantity could result in overheating of the reactor,
creating the potential for reactor failure from thermal fatigue or
overpressure.  Other possible causes of overheating in the reactor include
poor heat distribution within the reactor bed, resulting in hot spots, and
overheating the raw materials before they enter the reactor.  Hot spot
formation within the reactor can result in catalyst breakdown or physical
deterioration of the reactor vessel.

     Because the ammonia recovery section involves both stripping columns
(heat input) and an ammonia condenser (heat removal), a loss of flow control
or other failure affecting the heating or cooling medium could potentially
result in overheating and/or overpressure of equipment with subsequent
equipment failure and loss of containment of the process streams.
                                      40

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3.2.8  The Manufacture of Hydrazine (17.26)

     Hydrazine is produced by the partial oxidation of ammonia with chlorine,
hypochlorite, or hydrogen peroxide.  Its many uses result from a variety of
advantageous properties.  It has a high heat of combustion (hence, its use as
rocket fuel), is a strong reducing agent, an oxidizing agent under suitable
conditions, and a good completing ligand.  However, hydrazine is also a highly
reactive chemical and great care must be taken in its manufacture, handling.
and storage.

     Although there are several processes for the manufacture of hydrazine.
the predominant method is based on the oxidation of ammonia with alkaline
hypochlorite.  A typical flow diagram for this process is presented in Figure
3-11.  Liquid chlorine is first absorbed in dilute sodium hydroxide to form
sodium hypochlorite.  This chemical is then mixed with about a threefold
excess of aqueous ammonia to produce chloramine; the reaction is almost
instantaneous at a temperature of about 40 °F.  Next, a 20-30 molar excess of
anhydrous ammonia under pressure is added to the process stream, and the heat
of dilution raises the temperature to about 266 °F.  The reactor effluent
contains hydrazine, ammonia, ammonium chloride, sodium chloride, water, and
nitrogen.  The nitrogen is scrubbed with water to remove ammonia and is then
used as an inert pad to prevent decomposition of hydrazine during the
concentration steps.  The liquid effluent is preheated and sent to the ammonia
recovery section, which consists of two columns.  In the first column, ammonia
is taken overhead under pressure and recycled to the anhydrous ammonia storage
tank.  In the second column, some water and final traces of ammonia are
removed overhead.  The bottom stream from this column, consisting of water,
sodium chloride, and hydrazine. is sent on to the hydrazine recovery portion
of the process.

     Ammonia release hazards are present in this process, because ammonia is
recovered in relatively pure form and the product is hydrazine which is not
easily handled because of its highly corrosive nature and its hazardous
reactivity.  For the latter two reasons, hydrazine process equipment is
                                      41

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-P-
NJ
            NaOHJ
                                                                                                         (ANHYDROUS
                                                                                                          HYDRAZINE
                                                  NH3 + N2TO
                                                   SCRUBBER
                      Figure 3-11.   Conceptual diagram of  typical hydrazine manufacturing  process.

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stainless steel, and all vessels containing high concentrations of hydrazine
in solution are blanketed with nitrogen to prevent ignition.  Ammonia release
hazards in the ammonia recovery section are a loss of cooling to the ammonia
condenser, or overheating of the recovery columns.  Both of these failures
could lead to dangerous overheating and/or overpressure of equipment.

3.3  REPACKAGING OF ANHYDROUS AMMONIA (27)

     In addition to its use in various chemical processes, anhydrous ammonia
is also repackaged for resale and further use.  Repackaging involves a number
of procedures, the use of which depends on whether the liquid ammonia is being
transferred from tank cars into tank trucks, or from tank cars, trucks, or
bulk storage into cylinders or other portable containers.

     Filling operations may be carried out by transferring ammonia directly
from the tank car or truck to the receiving container.  However, since
demurrage begins to accrue after a short period of time, most repackagers
first transfer the ammonia to bulk (pressurized) storage before filling the
smaller containers.  Filling can be accomplished with a compressor or vapor
pump by reducing the pressure within the container being filled and at the
same time increasing the pressure within the storage tank being emptied.
Filling can also be accomplished with the use of a liquid pump.  Compressed
air should never be used to cause a flow of liquid ammonia, because oxygen
contamination in a storage vessel causes stress corrosion cracking in certain
carbon steels.  During the filling operation the receiving vessels are mounted
on scales to determine when they have been filled with the correct amount of
ammonia.  Some repackagers reweigh the vessels on a second scale to verify
that the measurements made with the first scale were accurate.

     Potential hazards in repackaging operations include the following:

     •    Contamination, such as with oxygen (latent hazard);

     •    Overpressurization of the storage vessel; and

                                      43

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     •    Overfilling of the receiving vessel.

     Stress corrosion cracking of certain carbon steels is caused by oxygen
contamination.  This hazard is discussed in more detail in Section 3.4.
Contamination with other materials could result in potentially violent
reactions.  Accidental overpressure of the storage tank could result in a
release of ammonia from the pressure relief valve if it is not vented to a
closed system.  Overfilling could cause a release from a rupture in the piping
or the receiving vessel from a pressure buildup.  A latent hazard also exists
in an overfilled vessel which goes undetected and leaves the repackaging
facility.

     Equipment used in repackaging operations should be constructed from
materials compatible with ammonia.  Suitable materials of construction for
ammonia service are discussed in Section 5.  Other potential causes of a
release include leaks in the connecting piping as a result of corrosion or
loose joint-pipe connections, cloggings of vapor or liquid pipes leading to
overpressure, and human error.

3.4  STORAGE AND TRANSFER

     All industries which use or handle ammonia in bulk quantities must have
appropriate facilities and procedures for the safe storage and transfer of
this material.  In this section, the potential hazards associated with the
storage and transfer of anhydrous ammonia common to all installations are
identified.  Proper procedures and safety precautions for the control of these
hazards for release prevention are discussed in Section 5.

3.4.1  Storage

     Liquid anhydrous ammonia is stored in either refrigerated vessels at
atmospheric pressure or in pressure vessels at ambient temperatures.  The type
of vessel used at a particular installation generally depends on the relative
costs of the two systems.  However, materials and fabrication constraints

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place an upper limit on the size of pressure vessels* such that no more than
50.000 gallons of ammonia should be stored in an unrefrigerated tank (3).  The
maximum amount of ammonia that may be stored in a particular vessel, the
"filling density", depends on the type of container and ranges from 0.56 to
0.58 times the water weight capacity of the container at 60 °F (7).

Refrigerated Storage—
     The predominant use of ammonia in the fertilizer industry has made
refrigerated storage economically attractive to producers.  This is because
the fertilizer season is relatively short, and large single-train plants which
produce ammonia year-round require large storage terminals during the off
season.  The quantities of ammonia involved make pressurized storage prohibi-
tively expensive.

     Normally, flat-bottomed, insulated, cylindrical tanks are used for
refrigerated storage of anhydrous ammonia at atmospheric pressure.  In
general, these storage tanks have design pressures of less than 15 psig and
are constructed in accordance with Appendix R of the American Petroleum
Institute (API) Standard 620 (28).  Because of the toxicity of ammonia,
however, this standard is considered as a minimum requirement, and many
installations are designed to meet stricter standards.  Although refrigerated
tanks are insulated, heat is still added to the system from the surroundings,
and thus vapor is continually generated within the tank.  It is therefore
necessary to collect, reliquify, and return the vapor to the tank.  A closed
vapor return system is necessary, not only to prevent the release of ammonia
to the atmosphere but also to prevent contamination of the stored ammonia with
oxygen.  A typical refrigerated storage system is shown schematically in
Figure 3-12.  The system in this figure extracts unwanted heat from the stored
liquid by drawing low-pressure ammonia vapor from the tank, compressing it,
and delivering it at a sufficiently high pressure for the condenser cooling
medium to reliquify it.
                                      45

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                  NH3
                 VAPOR
                   VERTICAL
                  CYLINDRICAL
                 STORAGE TANK
                                           FIRST - STAGE
                                           COMPRESSOR
  LIQUID
RETURN LINE
               FLASH
               DRUM
                                     SECOND - STAGE
                                     COMPRESSOR
CONDENSER
                       LIQUID
                        NH3
AMMONIA
PUMP


VAPORIZER
OR HEATER
TO
^ PROCESS
Figure  3-12.  Conceptual diagram of typical  atmospheric  refrigerated ammonia  storage system.

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     There are basically two types of refrigerated storage tanks, single- and
double-wall.  A single-wall tank consists of a single shell with a domed roof.
The roof and side walls are clad with insulation; the materials usually used
for insulating single-wall tanks are foamed polyurethane or polyisocyanurate,
expanded polystyrene, and foamed glass  (17).  These materials all require a
vapor seal over the entire outer surface in order to prevent moisture from
entering the insulation or the space between the insulation and the tank.  A
double-wall tank consists of an inner tank designed to store ammonia under the
required conditions, surrounded by a carbon steel outer tank.  The gap between
the shells is usually not less than 18" and is filled with a powdered insulant
(Perlite) or wool fiber.  A third type of tank is sometimes used which is a
variation of the double-wall tank.  This type of tank is called a "double-
integrity" system whereby the outer shell is designed to hold all of the
liquid in the event of a total failure of the main tank.

     Regardless of the type, all storage tanks must be supported on suitable
foundations with a layer of load-bearing insulation placed between the tank
bottom and the base.  With certain foundation designs, it is also necessary to
install a foundation heating system to prevent the temperature of the subgrade
from falling below 32 °F.  This is because the continuous formation of ice
lenses on some soils will cause the ground to heave (commonly referred to as
"frost heave11) with the resultant risk of damage to the underside of the tank.

Pressurized Storage—
     In general,  pressurized storage containers are used in conjunction with
processes which require relatively small quantities of ammonia (less than
40,000 gallons stored).  Pressurized storage tanks are generally constructed
of carbon steel according to the American Society of Mechanical Engineers
(ASME)  Code for Unfired Pressure Vessels. Section VIII,  Division I,  and with
the American National Standards Institute (ANSI)  Standards for Piping and
Fittings (29,30,31,32).  Stationary pressurized storage vessels are usually
cylindrical in shape with formed ends and may be installed with the axis
either vertical or horizontal.   Transportable cylinders are a special type of
                                      47

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pressurized storage which are used when only small quantities (usually no more
than 150 Ibs) of ammonia are required.

Storage System Hazards—
     A large release of anhydrous ammonia from a refrigerated or pressurized
storage system would result from failure of the storage vessel or its associa-
ted piping.  The failure might occur as a result of over- or underpressure of
the vessel, or as a result of weakened areas' of the vessel walls which
ruptured as a result of a very small applied stress.  Possible causes of
vessel failure include the following:

     •    Improper materials of construction,

     •    Corrosion,

     •    Overheating,

     •    Overfilling,

     •    External damage, and

     •    Failure of safety relief devices.

     The importance of using the proper materials of construction for ammonia
storage, especially refrigerated systems, cannot be overstressed.  Refrigera-
ted storage equipment is frequently subjected to subzero temperatures which
may be as low as -28 °F.  The significant difference between vessels working
at ambient temperature and refrigeration temperatures of this order is that
carbon steel vessels working at subzero temperatures are more liable to
brittle fracture under stress.  The "transition temperature" for various casts
and types of steel ranges from -58 °F to 50 °F (17).  For brittle fracture to
occur, the steel must be below its transition temperature, there must be a
notch or crack generally in association with a weld, and there must be
sufficient stress to cause plastic strain in the region where the stress is

                                      48

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 concentrated by  the notch.  Once a  fracture  is  initiated at  the notch,  it may
 propagate  at high  speed under  the influence  of  quite low applied stresses.

     A predominant internal corrosion hazard of ammonia storage tanks is
 stress corrosion cracking  (SCC) which occurs in certain carbon steels and has
 been the subject of extensive  research over  the last thirty  years.  The
 effects of SCC are several hundred  or more fine cracks invisible to the naked
 eye which  vary in  depth from less than a millimeter to the full thickness of
 the plate  (17).  The cracks always  occur in  zones of high stress, usually the
 weld deposit.  Cracking susceptibility increases with the strength of the
 steel  and  with temperature.  It is  generally agreed that the primary cause of
 SCC is contamination with oxygen; it is postulated that cracking may be
 induced in some  vessels with an oxygen concentration as low  as 1 ppm (33).
 The addition of  0.1 to 0.2 wt% of water has  been found to inhibit cracking in
 the liquid phase,  but this practice does not prevent cracking in the vapor
 phase  (34).  No  SCC has been reported in refrigerated storage vessels;  it is
 assumed that the reason for this is that any oxygen present  is removed  in the
 recompression cycle and not because of the low  temperature and pressure (33).
 As pressurized vessels are often associated with frequent transfer operations,
 contamination of the ammonia with air is a definite risk.  If prompt detection
 of SCC is  not made, a serious corrosion hazard  exists which may ultimately
 lead to complete failure of the vessel.

     In addition to stress corrosion cracking,  an external corrosion hazard
 exists if  storage vessels are in constant contact with dampness or standing
 water.  Furthermore,  if corrosive materials  are stored near ammonia storage
 vessels, fugitive emissions of these materials would enhance the possibility
 of external corrosion of an ammonia storage  tank.

     An uninsulated storage vessel  filled with ammonia at the maximum filling
 density will become liquid full at a temperature of 130 °F (7).  Thus,  an
 overheating hazard exists if ammonia is stored in an area which is located
 near flammable or incompatible materials, especially if the area is not well
ventilated or heavily trafficked,  or if storage vessels are exposed to direct

                                     49

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sunlight.  An overheating hazard exists in refrigerated storage systems
because of the dependence on the components of the refrigeration system to
maintain the low temperature of the system by removing and recompressing the
vapor phase.  If this system were to fail, the temperature in the vessel would
increase, and the pressure would eventually exceed the design pressure of the
vessel.

     Overfilling of storage vessels may occur as a result of a malfunctioning
scale, level gaging device or operator error.  An overfilled ammonia  storage
tank presents a hazard, because the temperature at which the vessel will
become liquid full is lowered.  This creates the possibility of a liquid full
container with an otherwise insignificant increase in temperature.  The
resulting hydrostatic pressure would cause the pressure relief device to vent
ammonia to the atmosphere; if the pressure relief device failed to activate, a
catastrophic release could result from vessel rupture.

     Single-wall refrigerated storage vessels are especially vulnerable to
external damage due to the ingress of moisture which will subsequently freeze
and damage the installation.  Poor vapor  sealing, which allows moisture to
enter the insulation or the space between the insulation and the tank, is
often directly responsible for insulation failures (17).  Another potential
cause of external damage is failure of the tank base heating system with the
subsequent formation of ice on the subgrade. resulting in "frost heave" which
was discussed previously.  insulation or  other forms of external damage may
also result from high winds or other severe weather conditions.  Hence,
storage vessels located in regions with a high frequency of violent  storms,
earthquakes, or high winds present a greater risk of external vessel  damage
than those located in areas with mild weather conditions.

     In  the event of an overpressure of a storage vessel, the safety  relief
valve(s) would open, allowing the pressure to be relieved by venting  ammonia
to  the atmosphere.  Likewise, if a partial vacuum were to occur  in  a
refrigerated storage vessel,  the vacuum relief valves would open and  allow
                                      50

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material  (such as air) from the discharge side  of  the relief valve  to  enter
the vessel.  If the relief valve in either of these  situations  failed  to  open,
the structural design conditions of the tank could be exceeded,  potentially
resulting in the catastrophic failure of the container.

3.4.2  Transfer from Tank Cars and Trucks

     Appropriate procedures must be followed when  transferring  ammonia from
tank cars and trucks to storage vessels to reduce  the risk of a hazardous
chemical release.   Tank cars are generally unloaded  by using a  gas  compressor
or transfer unit to create a pressure differential between the  storage vessel
and the tank car.   Tank cars may also be unloaded with the use  of a liquid
pump (1,7).  Examples of hazards associated with the unloading  of tank cars
and trucks include the following:

     •    The pressure in the tank car or truck attains the pressure
          setting of its relief valve, and ammonia vapor is vented
          to the atmosphere;

     •    The pressure in the tank car is lowered  to the extent  that
          the tank is subjected to an internal vacuum condition,
          possibly caused by a subsequent reduction  of ambient
          temperature;

     •    The vapor or liquid transfer line becomes  clogged or
          control  valve fails in the closed position resulting  in an
          overpressure of the storage vessel;

     •    Leakage  resulting from pipe corrosion or poor pipe-joint
          connections;
                                      51

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     •    Incompatible contamination in the receiving vessel which
          could result in an uncontrolled reaction with
          overpressure, or corrosion of the receiving vessel;

     •    A malfunctioning level indicating device on the receiving
          vessel resulting in an overflow of the receiving vessel;
          and

     •    Human error.

3.4.3  Transfer from Storage Vessels

     Another aspect of the transfer of liquid or vapor ammonia is its transfer
from a storage container to its designated use in the plant.  This is general-
ly accomplished with the pressure differential between the container and the
receiving vessel or process to which it is flowing.

     One hazardous transfer practice is manifolding to withdraw liquid ammonia
from two or more cylinders simultaneously.  This is because under certain
temperature conditions it is possible for liquid to flow from one cylinder
into another cylinder until it is completely filled (1).  If the valve of this
completely filled cylinder were subsequently closed, any rise in temperature
would result in a build—up of hydrostatic pressure and could result in the
rupture of the cylinder.  Because evaporation within a cylinder may cause the
ammonia to be refrigerated to a point where there is little or no flow of
ammonia vapor to a process, cylinders are often manifolded together to
increase the total vapor withdrawal rate.  Gaseous transfer between cylinders
at different temperatures in such an arrangement is likewise potentially
hazardous if there is subsequent reliquefaction and isolation of an overfilled
container.

     Nitrogen or air padding should never be used to promote the flow of
ammonia from cylinders or other storage vessels.  Hazards include dangerous
                                      52

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high pressures as a result of an increase in the ambient temperature and
oxygen contamination which causes stress corrosion cracking.  Furthermore, a
cylinder should never be warmed with a flame to increase the vapor discharge
rate because of possible pressure buildup sufficient to rupture the container.
Warming by other methods such as a water bath should be done with caution so
as to prevent accidental overpressure of the cylinder.

     Other transfer hazards include:

     •    Potential backflow of foreign material into the cylinder
          or into the upper valve chambers of the ammonia storage
          vessel;

     •    Isolation of liquid ammonia in piping between closed
          valves which could lead to bursting of the line from a
          build-up in hydrostatic pressure with a temperature
          increase; and

     •    Failure of piping connections from corrosion, improper
          materials of construction, or work hardening or fatigue.

3.4.4  Transporting Ammonia Storage Containers

     Unloading containers of ammonia from the delivery vehicle or moving them
within the plant is another aspect of the storage and transfer of this materi-
al.  In general, hazards associated with the transport of ammonia within a
closed vessel arise from failure to follow the proper transport procedures in
a safe manner.   Prevention of a hazardous release resulting from human error
is discussed in Section 5.6.
                                       53

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                                   SECTION 4
                         POTENTIAL CAUSES OF RELEASES

     The potential for a hazardous release of liquid or gaseous ammonia exists
in any type of facility which handles this material.  The possible sources of
such a release are numerous.   Large amounts of ammonia may be released from
leaks or ruptures of large storage vessels (including tank cars on-site) or
failure of process machinery  (e.g., pumps or compressors) which maintain a
large throughput of ammonia gas or liquid.  Smaller releases may occur as a
result of ruptured lines, broken gauge glasses, or leaking valves, fittings,
flanges, valve packing, or gaskets.

     In Section 3, specific release hazards associated with the manufacture,
consumption, and storage of anhydrous ammonia were identified.  In addition to
those discussed in the preceding section, there are also numerous general
hazards which, if realized, could lead to an accidental release.  Both
specific and general hazards  in ammonia facilities may be broadly classified
as process, equipment, or operational causes.  This classification is for con-
venience only.  Causes discussed below are intended to be illustrative, not
exhaustive.  More detailed discussions of possible causes of accidental re-
leases are planned for other parts of the prevention reference manual series.

4.1  PROCESS CAUSES

     Process causes are related to the fundamentals of process chemistry,
control, and general operation.  Possible process causes of an ammonia release
include:

     •    Loss of feed composition control resulting in the
          formation of ammonia-air mixtures within the flammability
          limits;
                                      54

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     •    Backflow of process reactants to an ammonia feed tank;

     •    Excess feeds in any part of a process leading to
          overfilling or overpressuring equipment or excess feed  to
          a reactor;

     •    Loss of condenser cooling to distillation units;

     •    Overheating of reaction vessels and distillation columns;
          and

     •    Overpressure in ammonia storage vessels from overheating
          as a result of fire exposure or unrelieved overfilling.

4.2  EQUIPMENT CAUSES

     Equipment causes of accidental releases result from hardware failures.
Some possible causes include:

     •    Failure of feed control systems from a loss of power,
          clogged lines, jammed valves, or instrument failure;

     •    Excessive stress on materials of construction due to
          improper fabrication, construction, or installation;

     •    Failure of pressure relief systems;

     •    Mechanical fatigue and shock in any equipment (mechanical
          fatigue could result from age, vibration, excessive
          external loadings, or stress cycling; shock could occur
          from collisions with moving equipment such as cranes  or
          other equipment in process or storage areas);
                                      55

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     •    Thermal fatigue and shock in reaction vessels,  heat
          exchangers,  and distillation columns;

     •    Equipment  constructed of high alloys, especially high
          strength alloys selected to reduce the  weight  of major
          process equipment,  which might be  especially sensitive to
          corrosion  or severe operating conditions;

     •    Brittle fracture in low temperature equipment  subjected to
          large temperature swings or creep  failure  which might
          occur in equipment  previously subjected to a fire that may
          have caused  undetected damage; and

     •    All forms  of corrosion including stress corrosion cracking
          from oxygen  contamination, pipe connections which have
          slowly corroded as  a result of contaminants entering the
          system when  cylinders are switched, and external corrosion
          from exposure to precipitation or  constant dampness.

4.3  OPERATIONAL CAUSES

     Operational causes of accidental releases are a result of incorrect
procedures or human errors.  These causes include:

     •    Overfilled storage  vessels;

     •    Improper process control system operation;

     •    Errors in loading and unloading procedures;

     •    Poor quality control resulting in  replacement  parts which
          do not meet  system specifications;
                                     56

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Inadequate maintenance in general* but especially on
pressure relief systems and other preventive and
protective devices; and

Lack of inspection and non-destructive testing of vessels
and piping to detect corrosion weakening.
                            57

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                                   SECTION 5
                        HAZARDS PREVENTION AND CONTROL

5.1  GENERAL CONSIDERATIONS

     Prevention of accidental releases relies on a combination of technologi-
cal, administrative, and operational practices.  These practices apply  to  the
design, construction, and operation of facilities where ammonia is stored  and
used.  When developing a thorough release prevention and control plan, consid-
erations must he made in the following areas:

     •    Process design,

     •    Physical plant design,

     •    Operating and maintenance practices, and

     4    Protective systems.

     In each of these  areas,  consideration must  he given to specific factors
that could  lead to  a  process upset  or  failure which  could directly  or
indirectly  cause  a hazardous release of  ammonia to the environment.   At  a
minimum, equipment and procedures should  be examined  to  ensure that they are
in  accordance  with applicable  codes,  standards, and regulations.   Further
evaluations should then be made to determine where extra protection  against a
release is  appropriate so  that stricter  equipment and procedural specifica-
tions may be developed.

     The  following subsections  discuss  specific  considerations  regarding
release prevention;  more detailed discussions may be found  in a manual on
control technologies, part of this manual series.
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5.2  PROCESS DESIGN

     Process design considerations involve  the  fundamental  characteristics  of
the processes which use ammonia.  These  considerations  include an evaluation
of how deviations  from expected process design conditions  might initiate a
series of events  that  could result in an  accidental  release.   The  primary
focus is  on how the process  is controlled  in  terms  of the basic process
chemistry and the variables of  flow,  pressure*  temperature, composition, and
quantity.   Specific considerations may  include mixing systems,  fire protec-
tion, and process control  instrumentation.   Modifications  to enhance process
integrity may result from review of these factors and might involve changes in
quantities of materials, process pressure and temperature conditions, the unit
operations,   sequence  of operations,  the process  control  strategies,  and
instrumentation used.

     Table  5-1  shows  the  relationship between  some specific process design
considerations and individual processes described in Section 3 of this manual.
This does not mean that other factors should be ignored, nor does it mean that
proper attention  to  just   the considerations in the table  ensures  a  safe
system.    The considerations listed,  and perhaps others, must  be properly
addressed if a system is to be safe,  however.

     The most significant  considerations are aimed at  preventing overheating
and/or overpressurizing systems containing ammonia.  Overheating is  hazardous
because it may lead to  overpressure which  weakens  process  equipment  and adds
to the potential for leaks at joints  and valves.   Wide  temperature  fluctua-
tions also  significantly decrease the lifespan  of  many materials of  construc-
tion,  uverpressure may occur without overheating if flowrate control  of both
gas and liquid streams is  not maintained.

5.3  PHYSICAL PLANT DESIGN

     Physical plant  design considerations  include equipment,  siting  and
layout,   and transfer/transport  facilities.   Vessels,  piping and valves,
process machinery, instrumentation, and  factors such as location of systems

                                      59

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    TABLE 5-1.  SOME PROCESS DESIGN CONSIDERATIONS FOR PROCESSES INVOLVING
                ANHYDROUS AMMONIA
Process Design Consideration
  Process or Unit Operation
Contamination (with air especially)
Flow control of ammonia feed

Temperature sensing and heating
medium flow control
Temperature sensing and cooling
medium flow control

Adequate pressure relief
Corrosion monitoring
Temperature monitoring
Level sensing and control
Feed systems, storage tanks,
SCR catalyst

All

Distillation and stripping column
reboilers, feed preheaters.
reactors

Distillation and stripping column
condensers, reactors

Storage tanks, reactors, refrigera-
tion condensers, distillation and
stripping columns,  heat exchangers

Pressurized storage tanks,
neutralization equipment

Distillation and stripping column
reboilers, storage tanks, catalytic
converters

Storage tanks, reboilers and
condensers
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and equipment  must  all be  considered.   The following  subsections  discuss
specific design aspects of facilities which handle anhydrous ammonia.

5.3.1  Equipment

     The design  of  equipment for  anhydrous ammonia calls  for  special and
up-to-date knowledge,  particularly  where  low-temperature  conditions  are
encountered.   The following paragraphs are  intended to  familiarize  the reader
with the kinds of equipment which  are used in ammonia service with specific
reference to materials  of construction,  safety devices, and safe operation.
The discussions  herein  are not intended as  specifications;  the appropriate
standards should be consulted and expert advice should always be sought in the
design and procurement of equipment for liquid ammonia duty.

Materials of Construction—
     Dry ammonia  is noncorrosive  to most  common  metals.   However,  moist
ammonia  corrodes  copper,  tin,  zinc,  and many alloys,  particularly copper
alloys.  Therefore, only  iron  or steel,  despite the  fact  they  decrease the
minimum  ignition temperature, or other nonreactive material should  be used in
contact with ammonia (8).

     Carbon and carbon-manganese steels are commonly used for various types of
equipment in ammonia  service.   As discussed  in  Section 3.4.1,  one of the
primary  concerns with ammonia storage is  the susceptibility of  certain carbon
steels to stress corrosion cracking in the presence of small amounts of oxygen
contamination.  Although  it  is  not possible to specify a particular  type  of
carbon or carbon-manganese steel which will definitely  not succumb  to stress
corrosion cracking, it  has been found that  low-strength  steels (yield less
             2
than 350 N/mm  ) are less  susceptible to  cracking than high-strength  steels,
and thermal stress relief seems to completely eliminate the mechanism  (17).
     Piping for  ammonia  service should be constructed  of  rigid steel (11).
Copper, brass  or galvanized fittings  should  not be used.  Unions, valves.
                                     61

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gauges, pressure regulators and relief devices having copper, brass  or bronze
parts are not suitable for ammonia  service.   Certain aluminum alloys may be
used  for  various components  in  ammonia  systems.  Mercury  thermometers  in
ammonia service should be avoided (3)-.

     Metallic and nonmetallic gasket  materials,  such as compressed asbestos,
graphited asbestos,  carbon steel or stainless steel spiral-wound asbestos
filled, and aluminum are suitable for ammonia service.  Ferfluorinated plastic
materials and neoprene have also been found  suitable if they are fully  con-
fined so as to prevent creep or blow out  in the event of elevated temperatures
(1).

Storage Vessels—
     A large inventory of ammonia contained in storage vessels on site repre-
sents  one  of the most  hazardous components  of  a facility which  uses  or
produces this material.   This  fact  has manifested itself in  the number of
accidental releases from  storage tanks over  the  years.   In  this section, the
different types of ammonia storage  vessels are  briefly  discussed along  with
the associated protection devices and safety  procedures  which are designed for
the prevention  of a  hazardous  release of  this  material.   For detailed
specifications of ammonia storage  systems the reader is  advised to consult
references (1) and (7).

     Anhydrous liquid ammonia is  stored  commercially at full pressure,  par-
tially refrigerated,  and fully refrigerated in vessels ranging from  two  pound
cylinders to multi-ton tanks.  In general, the quantity of  ammonia  determines
the choice of container,  which in turn influences the maximum storage pres-
sure.  Storage at ambient temperature (full  pressure) is  restricted to rela-
tively small  vessels, usually uninsulated and  cylindrical  in  shape with
rounded ends.  The most frequent sizes range from 500 to 45,000 gallons (1).
These containers must >be  designed  for pressures  of  at  least 250  psig  and
constructed in accordance with  the American   Society of Mechanical  Engineers
(ASME), Boiler and Pressure Vessel  Code,  Section VIII,  Division 1  (29).  If
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 the pressure is only partially reduced,  the  vessel is usually spherical  in
 shape and insulated.  The  pressure in a  "semi-pressure11  storage  vessel is
 selected  to  suit  the individual requirements of the site process.  This type
 of  storage is not as prevalent  today as in  the past  due  to the increasing
 amount  of ammonia which is being  stored and  transported  in  the fully
 refrigerated state.

      Full  refrigeration  of  the liquified  gas  at -27.4  °F reduces  the  pressure
 essentially  to  atmospheric. However* a slight positive pressure is necessary
 to  accommodate  minor pressure  fluctuations and to avoid negative pressure on
 the tank,  since air  must  be excluded.  Normally,  refrigerated vessels are
 flat-bottomed,  insulated,  cylindrical tanks  which are mounted  vertically.
 Tanks with design pressures of  15  psig  or  less  should be  constructed in
 accordance with American Petroleum Institute  (API)  Standard 620  (28)  as  a
 minimum, while  those with higher design pressure  should conform to the ASME
 Code cited above.

     The most probable  causes  of failure  of  an ammonia storage vessel were
 discussed in  Section 3.4 and include  corrosion and  the  buildup of  hydrostatic
 pressure  in  a liquid-full  container  caused  by overfilling  or overheating.
 Other possible  causes of storage  tank failure include brittle fracture from
 overstressing,  the  use  of  improper materials of  construction,  and external
 damage.  This section discusses the safety devices and precautions designed to
 minimize the chances of an accidental release  as  a result  of one  of these
 causes.

     Precautions should be  taken  to prevent both  internal  and external corro-
 sion of ammonia storage vessels.  Stress corrosion cracking  in ammonia  storage
 vessels is caused by  the contamination of the ammonia with air  (oxygen).   The
 primary means of preventing this  type of corrosion is  by the addition  of  at
 least 0.2%  water.   This  is not  an absolute safeguard, however,  because
 cracking can still occur in the areas  of  the  vessel which  are exposed to the
vapor phase.  Preventive  measures which may  be taken  to reduce  the risk of
 stress corrosion cracking include the following (33):

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     •    Reduce the tensile stress by thermal stress relief of the
          entire vessel;

     •    Decrease the residual welding stresses by  shotpeening  or
          stress relieving  crown  plates*  leg column  plates,  and
          bottom plates in a furnace prior to commissioning;

     •    Careful purging when commissioning; and

     •    Purge the vapor space with an oxygen free inert gas  on  a
          regular basis.

     Prevention  of external  corrosion  involves   good  housekeeping  and
maintenance practices which assure that containers are never  in  contact with
standing water or exposed to continual dampness.

     Brittle fracture of steel  is  another  potential  cause of  vessel failure.
It generally occurs in the  vicinity  of a  notch  or  crack when  the material is
below its transition temperature.   To lower the susceptibility of carbon steel
to brittle  fracture,  vessels should  either  be  built of  a steel having  a
transition temperature not higher than the design temperature, or steps should
be taken  to eliminate  plastic  strain of the  notches,  since it is  not  possible
to be certain that all surface imperfections have been eliminated  (17).   This
may be achieved by thermal stress relieving the vessel after fabrication.

     Pressure relief valves  and rupture discs are designed to allow  a con-
trolled release  of overpressurized contents. According  to American National
Standard  (ANSI) K61.1, ammonia storage containers  (with the exception of small
cylinders) should  be provided with one or more  pressure relief valves of the
spring-loaded type which are set to  discharge at a pressure not  exceeding the
design  pressure of the  container.  The  Compressed  Gas  Association  (CGA)
specifies that the maximum  discharge rate of the valve should be such that the
pressure  in  the container will not  exceed  120%  of the design pressure  (1).
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Further provisions recommended by the CGA and ANSI K61.1 include the following
(1.7):

     •    The  discharge  from pressure  relief valves  should be
          directed away from the container upward and  unobstructed
          to the open air.

     •    Vent pipes should not be  restrictive nor smaller in size
          than the pressure relief valve outlet connection.

     •    Vent pipes should have loose-fitting caps to exclude water
          and  debris but  not  restrict free discharge of vapor.   In
          addition, suitable provision should be  made  for draining
          condensate which may accumulate.

     •    Shut-off valves should not  be installed between  the
          pressure relief valves and  the container unless  the
          arrangement is such that full flow is possible  through at
          least one  nonisolated pressure relief  valve  at the re-
          quired capacity.  (Dual relief valves are usually fitted
          which can be isolated individually and  are interlocked so
          that a relief valve can be removed  for  servicing without
          losing protection of the vessel (17).)

Furthermore, it is important  to ensure  that  if the  relief  valve  lifts,  the
ammonia vapor  can be vented harmlessly.   This  may mean leading the vent to a
stack, the  height  and  position of which  is  related to work areas in the
vicinity.

     A cylinder containing less than 165 pounds of ammonia  is not  required  to
have a pressure relief device  (1).   Instead,  cylinders are designed to with-
stand very  high pressures,  as these containers are generally used indoors
where product  containment is paramount.   Regardless of  the higher design
                                     65

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pressure, these containers should be protected from  fire  and  direct exposure
to the sun,  because they are still susceptible to becoming liquid-full from an
increase in temperature.  Without a pressure relief device, overpressure would
result in a sudden rupture and complete discharge of the cylinder contents.

     Protection from overheating of larger  pressurized  storage vessels may be
provided by a shield to prevent direct exposure to the sun and by painting the
vessel with some reflective paint.

     Atmospheric and  semipressure storage  tanks  should be  equipped with
instrumentation to ensure that the design pressure is not exceeded.  This is
often done by  having  a pressure controller which  will stop and  start  the
refrigeration system as required  to maintain  tank  pressure.  Provision should
also be made to reduce  or stop any incoming  ammonia  once  the refrigeration
system is fully loaded.   In  the  event  of a  total failure of the refrigeration
plant, the pressure in the storage vessel  will  rise until it  reaches  the
design pressure of the  relief  valve,  at which time it will begin to vent  to
the atmosphere.  Therefore, a  standby  diesel  generator should  be provided in
case it is not possible to restore the power before the design pressure of the
relief valve is attained.

     Refrigerated  storage vessels operating  at atmospheric  pressure,  in
addition to having relief valves for overpressure,  must also be protected from
underpressure, since these vessels can only withstand a few inches water gauge
of vacuum.  Negative pressure  (vacuum)  relief valves are  therefore  provided
which allow warm ammonia  gas  to  flow  from the refrigeration system back into
the vessel  in the event  that  pressures below atmospheric develop  in  the
vessel.

     In  addition to venting provisions, storage vessels  should have valve
arrangements which allow  the vessel to be  isolated from the process to which
the ammonia is being fed.  Backflow of material into  the upper valve chambers
when the feed valve is  shut off  at the storage tank must  be prevented because
of the possibility of corrosion in the  feed pipe.   Other valve  specifications

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found in ANSI K61.1  require  storage  tank filling connections to be provided
with an approved combination back-pressure  check valve  and  excess  flow valve;
one double or two  single  back-pressure  check valves;  or a  positive shut-off
valve, in  conjunction with  either an  internal  back-pressure  valve or an
internal excess flow valve (7).  Each container should also be equipped with a
vapor return valve.  Furthermore,  it  is good practice to place a valve in the
liquid outlet pipe as close to the tank as possible which is capable of remote
closure in the event of a pipe failure during a transfer operation.

     To reduce the risk  of overfilling during transfer operations,  smaller
storage vessels are often mounted on a scale which will indicate the weight of
fluid in the container at all times.   All bulk storage vessels should also be
equipped with  a  reliable  liquid  level  gauge which allows  for quick  and
accurate readings.   The design and installation of an  ammonia  liquid  level
gauge should adhere to the requirements given in ANSI K61.1  (7).   Most  ammonia
storage tanks have float-type gauges whereby a float mechanism is  magnetically
coupled to a pointer which indicates percent of capacity  on a volume  basis
(1).  Although this is an accurate method  of measuring  the  level,  the
equipment is vulnerable to mechanical damage and is often supplemented  with an
additional measuring device.   A differential pressure gauge which  measures the
static head of the liquid  is one possible back-up  (17).  Each nonrefrigerated
storage container nameplate should include markings which indicate the  maximum
level to which the container may be  filled  with  liquid  ammonia between 20 °F
and 100 °F.  The  percent  of the maximum volume of  the container which may be
filled with liquid  ammonia for various temperatures is given  in  Table  5-2.
Because refrigerated, atmospheric  storage  tanks  are maintained at a fairly
constant  temperature,  they may be filled to within a  few  inches of  the
roof/wall seam.

     As an overfilled storage  vessel is a serious  hazard,  it  is  normal  for
level indicators  to be fitted with high-level alarms to  warn the operator when
the maximum filling  level has been  reached  (17).   Important level  alarms
should be connected to the vessel  separately from the level controller  in case
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TABLE 5-2.  MAXIMUM SAFE VOLUME OF LIQUID AMMONIA IN NONREFRIGERATED
            STORAGE CONTAINERS AT VARIOUS TEMPERATURES (1)

                                           Maximum Safe Volume
      Temperature of Liquid              Liquid Ammonia as  a % of
         Ammonia in Tank                  Container Water Volume
               30                                  87.3


               40                                  88.3


               50                                  89.5


               60                                  90.7


               70                                  91.8


               80                                  93.0


               90                                  94.4


              100                                  95.7
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the bottom lead line  of  the level  controller inadvertently  becomes  blocked by
oil and/or dirt.   As a  further  precaution,  a short,  vented dip pipe  can
provide protection from  overfilling  in  the  event of failure of the volume or
weight measuring device.  However,  this device will not prevent an overflow of
ammonia liquid.  Furthermore,  it will only work if there is no  other  outlet
from the vapor space and if  the  line  to the  vent system has enough capacity.
It is therefore recommended that a vessel be fitted with a relief device which
discharges to an overflow tank or  other suitable receiver if the possibility
of overfilling exists.

Process and Reaction Vessels—
     General considerations for hazard control for storage vessels  also apply
to the design and use of process and reaction vessels.   In  the latter  type of
vessels, however,  there is a greater  degree  of  risk,  as these containers are
often exposed to more severe conditions of temperature and/or pressure  than a
regular storage vessel.

     Primary considerations for process and reaction vessels include:

     •    Materials of construction,

     •    Pressure relief devices,

     •    Temperature control,

     •    Overflow protection (in addition to high level alarms), and

     •    Foundations and supports.

     The foundations and supports  for vessels are important  design  considera-
tions, especially  for large storage vessels and tall equipment such as  distil-
lation columns.  The  choice  of construction materials  is also an important
consideration particularly where low-temperature conditions  are  encountered.
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Expert advice should always be sought in the design  and  procurement  of equip-
ment for liquid ammonia duty.

     If cooling to a condenser is  lost,  overpressure may occur.  Thus, it  is
necessary to use pressure  relief valves  to protect  against leaks and ruptures
which  can  result from  overpressure.   Pressure  relief  protection is  also
necessary in the event of a fire.

     Distillation and  stripping  columns  present significant  release hazards
because they may contain large amounts of ammonia in pure form  and have a heat
input.  As they are often  located  outdoors,  external factors such as  ambient
temperature fluctuations and wind  loadings must be  properly accounted for  in
their design and construction,  especially for the support structure.

Piping-
     All ammonia piping should be extra heavy (schedule  80) steel when thread-
ed joints are used  (1).  However,  schedule 40 piping may be used when joints
are  either  welded  or joined by  flanges.  All  refrigeration system piping
should conform  to  ANSI B31.5 - American National Standard for  Refrigeration
Piping (35).  Iron  and  steel piping,  fittings,  and  valves are  suitable for
ammonia gas and  liquid.  Nonmalleable metals,  such  as cast iron, must not  be
used  for fittings  (1).   As  low  temperature embrittlement  is  a concern in
ammonia systems, material  selection must take this  into  account.  In general,
if a  material  is not notch-tough  at  the  operating  temperature, the  welds
should be subjected to post-weld heat treatment.

     Because liquid NH  expands  with temperature, bursting of  lines  due  to
hydrostatic pressure must  be prevented.   This may be accomplished with expan-
sion  chambers which should be  located at  the highest  point of  each section
that  may  be closed, trapping  liquid  NH .   Construction of these chambers
should be  in  accordance with  the  ASME Code for Unfired Pressure Vessels,
Section VIII  (29).  An  expansion chamber  device typically consists  of  a
rupture disk and a  receiver chamber  which can  hold  20—30% of  the protected
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line's capacity.  The chamber is equipped with a pressure indicator or alarm
switch set to function upon disk rupture.  Alternatively, a hydrostatic relief
valve may be installed in each section of piping in which liquid ammonia can
be isolated between shut-off valves.

     The following is a list of general  guidelines  for the safe transport of
liquid ammonia in piping systems:

     •    Piping systems should have as simple a design  as  possible
          with  a  minimum number of  joints  and connections;  flow
          should not be restricted by an excessive  number of  elbows
          and bends.

     •    Piping should be  at  least 7.5 feet  above the floor  if
          possible; provision should be made to  protect  all exposed
          piping from physical damage that might result  from  moving
          machinery, the presence  of automobiles or trucks, or any
          other undue strain that may be placed on the piping.

     •    In addition to being securely  supported,  pipes should be
          sloped with drainage provisions at the low points.

     •    Clips or hangars  should  not  fit too  tightly to allow for
          thermal expansion of the pipe.

     •    Piping should be protected from exposure  to  fire  and  high
          temperatures.

     •    A pressure reducing  regulator should  be  installed  when
          connecting to  lower pressure  piping  or  systems from
          storage vessels.
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     •    Low points should be avoided in inlet lines to relief
          valves for ammonia vapors*  because liquid can condense in
          these lines under ambient conditions.

     •    Pipelines should always  be  emptied when ammonia flow is
          not required to prevent  the possible  isolation  of  liquid
          NHn between closed valves.

Valves—
     Valves  in  ammonia service  are  discussed  in  a number  of references
(1,7,24).  Several  types  of  valves including gate,  globe, ball,  and  check
configurations are  used  in ammonia systems.  Construction may be of iron  or
steel.  Copper and copper-bearing materials must not be used  for the valve or
trim parts, because these  materials are  attacked by  ammonia  (when moisture is
present.)

     It is good practice  to  locate stop  valves in the inlet  and outlet lines
to all condensers, vessels, evaporators,  and long lengths of  pipe so they  can
be isolated  in  case of leaks and  to  facilitate pumping out.  If globe-type
valves are used they  should  be installed with  the valve  stem horizontal to
lessen the chance for dirt or scale to lodge on the valve seat or disk (24).

     Pressure regulators, solenoid valves, and thermal expansion valves should
be flanged for  easy assembly and removal.   A strainer should be used in  front
of self-contained control valves  to  protect  them  from pipe  construction
material  and  dirt (24).   Solenoid valves should be  located  upright and  pro-
tected from moisture.  A manual opening stem is useful for emergencies.

     When ammonia flow is shut off at the feed tank, the piping system between
that point and the point of application is filled with vapor.  Gradual absorp-
tion of  the  vapor in  the process fluid leaves  a vacuum which draws ammoniated
fluid back into the piping system.  This may cause serious problems,  especial-
ly if  the shut-off point  is upstream from  instruments and  other  items of
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 equipment.   A diaphragm-operated check valve held  in a closed  position by
 ammonia pressure  may  be used to prevent undesired back or reverse flows.   If
 the  ammonia  pressure  falls and  pressure  on the diaphragm becomes subatmos-
 pheric, the  valve opens and allows air to  flow  into  the  piping  system,  thus
 breaking the vacuum which would  otherwise cause  backflow of the  process  fluid.

     Excess  flow  valves should  be  considered for ammonia in vessels,  tank
 cars, and other places where unintentional  high  liquid discharge rates need to
 be  prevented.   In the  event  that a liquid discharge line is broken,  the
 resulting high flow rate would  cause  the  valve  to close off, restricting the
 escape of ammonia.

     The pressure of ammonia gas can be controlled by a pressure reducing and
 regulating valve  of steel  construction.   The valve  should be designed for the
 range of conditions under  which it  will be required to operate, taking  into
 account the  maximum and minimum flow  of ammonia gas,  its  average temperature,
 and  the average upstream and downstream pressures (1).

 Process Machinery—
     Process machinery refers to rotating or  reciprocating equipment  that may
 be used in the transfer or processing of  ammonia.   Included  in this  classifi-
 cation are pumps and compressors which may  be used  to move liquid  or gaseous
 ammonia where gas pressure padding is insufficient or inappropriate.

     Pumps— Any pump used  in  ammonia service must conform  to ANSI/DL 51 -
 American National Standard  for  Power-Operated Pumps for Anhydrous Ammonia and
 LP Gas (36).   To assure that a given  pump  is  suitable for an ammonia service
 application,   the  design engineer should  obtain information from the pump
manufacturer certifying that the pump will  perform  properly  in  this  applica-
 tion.

     Centrifugal pumps are normally used  for  pumping  liquefied   ammonia  in  a
 fully refrigerated condition  (17).   Glandless,   canned type  or  conventional
pumps fitted with either a single mechanical seal together with  a soft packed

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auxiliary gland or  a  double mechanical seal may be  used.   Canned pumps are
generally used indoors or in congested areas.  When  a glanded  pump is used a
mechanical seal is advisable followed by a  soft  packed  gland (17).  The seal
pressure should not exceed the manufacturer's recommendations,  and the  inter-
space should be vented in a safe manner.

     Pumps should be constructed with materials which are resistant to ammonia
at operating temperatures and pressures.  Lubricating oil should  be  resistant
to breakdown as a result of contact with ammonia.  In some  cases, the poten-
tial for seal leakage may rule out the use of rotating shaft seals.  Some pump
types which either isolate the seals from the process stream or eliminate them
altogether  include  canned  motor,  vertical  extended spindle  submersible.
magnetically-coupled,  and diaphragm (4).

     Net positive suction head  (NPSH)  considerations are especially  important
for ammonia, since  the liquid may be pumped near  its  boiling point.   Long
suction lines  reduce  the effective NPSH available, and if the suction  lines
are very long in relation to the NPSH available,  a vapor release vessel should
be fitted in the suction line as close to the pump as possible (17).  The pump
supply tank  should  have high and low level  alarms,  and the pump  should be
interlocked to shut off at low supply level or low discharge pressure.

     Centrifugal pumps  often have  a  recycle loop back  to the  feed container
which prevents overheating in the event that the  pump is deadheaded  (i.e.,  the
discharge valves close).  Positive displacement  pumps can be equipped with a
constant differential  relief valve capable  of  discharging the  entire capacity
of the pump into the suction port of the pump to  prevent rupture  in  the event
of deadheading.  When a positive  displacement pump  is used to  reduce the
chance of backflow, such a relief valve could defeat  this purpose  if the back
pressure were high  enough.   In  such  a  case,  the  relief  valve discharge  should
be routed somewhere other than the suction  part  of the  pump.   Pumps can also
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be protected by a differential pressure  switch  fitted  across  the  pump to trip
the  motor should a  low-pressure  condition arise.  This could be caused by
inadequate priming,  by vaporizing in the pump,  or by too low  a suction head.

      Compressors—  Ammonia compressors  include reciprocating,  centrifugal,
liquid-ring rotary,  and  non-lubricated screw compressors.   Usually two-stage
reciprocating  compressors are  used for ammonia  service,  although  rotary
compressors are also common and may be preferable if it is necessary  to  avoid
oil  contamination  (17).   Detailed  descriptions of the different types  of
compressors may be found  in the technical  literature (4).

      As  with  pumps,  materials of  construction  must be selected  which are
compatible  with  ammonia  at   the   operating conditions.   Copper  and
copper-bearing alloys must be avoided and particular  attention  paid  to  the
gland arrangement (17).  Any ammonia compressor must be designed  for  at  least
250 psig working pressure  except those used  for refrigeration service.

      A pressure relief valve  large  enough  to discharge the full  capacity  of
the compressor should be installed between the discharge of the compressor and
the high  pressure  shut-off valve.  If the  crank case is  not designed  to
withstand system pressure, it  should also  be protected with a suitable pres-
sure  relief valve.   In addition, a liquid trap should  be installed before  the
compressor suction to prevent entry of liquid into the compressor.

Miscellaneous Equipment—
      Pressure Relief Devices— Pressure relief devices for  ammonia  service
should be constructed in accordance with CGA S-1.3  -  "Pressure  Relief Device
Standards - Part  3   - Compressed Gas  Storage Containers"  (37) .   All  wetted
parts of relief valves and rupture disks should be constructed from materials
compatible with  ammonia  at the  operating temperature and  pressure.   For
balanced relief valves, the balance seals  must  also be made  of  appropriate
materials.
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     Measures should be taken to ensure that process equipment is not isolated
from its relief system.  To provide continuous pressure relief protection when
a device  requires  maintenance,  equipment may be provided  with dual  relief
systems, each sized to provide  the total  required  flow capacity.   Stop valves
installed between a vessel and its relief device should have a full port area
that is at  least  equal to that of the  pressure  relief device inlet.   These
valves should be locked open or have handles removed when the protected vessel
is in use.  If  the  discharge  is to  be piped to a closed  disposal system, the
pressure drop caused  by  the additional piping  must be considered  and  the
relief device sized accordingly.

     Some aspects of  the proper placement and  use  of pressure relief valves
have been  discussed  earlier  in this section  in  conjunction with  storage
vessels.  Additional guidelines for the correct use of pressure relief valves
include the following (7):

     •    Arrangement should be such as to minimize the possibility
          of tampering with the pressure setting adjustment;

     •    They should have direct  communication with the  vapor space
          of the container;

     •    When relief valves are put in series,  the downstream
          valves must be  large enough to accept the total potential
          relief capacity;

     •    Discharge lines of liquid  relief valves should  not  be run
          to a high point;

     •    The set-point of a relief  valve in the discharge  of a pump
          should be checked to ensure that it is higher than  the
          maximum shut-off pressure  of the pump;
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     •    The flow capacity should not be restricted  by  any connec-
          tion to it on either the upstream or downstream side; and

     •    Discharge from pressure relief valves should not  terminate
          in or beneath any building.

     Rupture disks may be used to protect pressure relief valves  from  constant
contact with the  contents  of  the storage vessel.   Rupture disks should not be
used in ammonia service where  the ruptured  disk discharges directly into  the
atmosphere.  If  the disk relieves  the  contents of the  container through a
spring-loaded pressure relief  valve,  a  small  vent should be  provided  in the
chamber between  the disk and  the valve  to  prevent any back pressure  on  the
rupture disk.  Because operating pressures  exceeding 70% of  a disk bursting
pressure may induce premature  failure, a considerable margin  should be allowed
when sizing rupture disks.

     Instrumentation— For normal  applications,  all steel  pressure,  gauges
graduated  from 0-400  psig are recommended for ammonia service (1).   For low
pressure work,  the range for the gauge  should be  one and one-half times the
maximum service pressure.

     The most  commonly  used flowmeter for  ammonia gas is  the tapered tube,
float type  (1).   For high  pressure work  the glass  tube should be  enclosed in  a
vented  shield  or,  preferably,  a steel-armored  type.  Orifice meters with
differential pressure cells  may  also be used.  Mercury manometers  should not
be used in ammonia service.   The quantity of liquid  ammonia  transferred from
one  system to  another may be measured with positive  displacement or  turbine
meters.

     Magnetic  or  rotary  gauges are preferred to  gauge  glasses (3).   Ammonia
should never  be closed into  a gauge glass,  as an  increase in pressure may
break the  glass.   Glasses  should be equipped with excess flow valves  to stop
the  flow   of ammonia  if  breakage occurs,  and  they  should have  automatic
self-closing shutoff valves which must be held  open to  take a reading  (3).
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     Instrument component failures cause about 0.6 plant  shutdowns  each year
(38).  It is projected  that  this  can  be reduced  by 36% by making all single
pressure, temperature, flow,  and level switches redundant.

5.3.2  Plant Siting and Layout

     The siting and layout of a particular ammonia facility is a complex issue
which requires careful  consideration  of  numerous  factors.   These include the
other processes in the  area,  the  proximity  of  population  centers, prevailing
winds, local terrain, and potential natural external  effects such as flooding.

     Siting of facilities or  individual  equipment  items should be done in a
manner that reduces personnel exposure, both plant and public, in the event of
a release.  Since there  are  also  other siting considerations,  there may be
trade-offs between this  requirement and others in a  process,  some  directly
safety related.  Siting should provide ready ingress  or egress in the event of
an emergency and  yet also take advantage of barriers, either man-made or
natural which could  reduce the hazards  of  releases.   Large distances between
large inventories and sensitive receptors is desirable.

     Various techniques are available  for  formally assessing a plant layout
and should be considered when planning high hazard facilities (39).

     The siting and  layout of any  facility  handling  ammonia should  adhere to
the following general guidelines:

     •    Areas in which ammonia hazards exist  should have an
          adequate number of well  marked exits  through which person-
          nel can escape quickly if necessary;  doors  should open
          outward and lead to unobstructed passageways;

     •    The plant is laid out so that, whenever possible, there
          are no confined spaces between equipment; large  distances
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          between large inventories and sensitive receptors is
          desirable;

     •    Access to platforms above ground level should be by
          stairway in preference to cat ladders, and work areas
          above ground level should have alternative means of
          escape;

     •    xhe ground under process equipment and storage vessels
          should be sloped so that fire water and liquid spillages
          flow away from equipment and then into drains, avoiding
          pools underneath equipment;

    .•    Storage facilities should be located in cool, dry, well-
          ventilated areas, away from heavily trafficked areas and
          emergency exits; and

     •    Tank car, tank truck and storage facilities should be
          located away from sources of heat, fire and explosion.

     Because heat causes thermal expansion of liquid ammonia, measures  should
be taken  to  situate piping,  storage vessels, and other ammonia equipment  so
that they are not  located  adjacent  to piping containing flammable materials,
hot process  piping,  equipment,  steam lines, and 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.  Storage should
also be situated away  from control  rooms,  offices,  utilities, and laboratory
areas.

     In the event of an emergency, there should be more than  one  entry  to  the
facility which is  accessible to  emergency  vehicles  and crews.  Storage  vessel
shut-off valves should be readily accessible.   Containment  for  liquid storage
tanks  can be provided  by diking.   Dikes  reduce evaporation rates  while
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containing the liquid.  It  is  also possible to equip a diked  area  to allow
drainage to an underground  containment  sump.   This  sump would be vented  to
either a recovery or  scrubber  system for safe removal.  A full  containment
system using a specially  constructed building is another  possible option.
This type  of  secondary containment could be  considered for large  volume.
liquid ammonia storage tanks.

5.3.3  Transfer and  Transport Facilities

     Transfer and transport facilities  where both  road vehicles and rail
tankers are loaded  or  unloaded are likely accident  areas because of  vehicle
movement and the intermittent  nature  of the operations.  Therefore,  special
attention should be  given to the design  of these  facilities.

     Before unloading, tank vehicles should be securely moored; an interlocked
barrier system is commonly  used.   Tank  cars must also  be  protected on both
ends by derailers or  on the switch end  if  located  on  a dead  end  siding-.
Sufficient space  should be available to avoid congestion of  vehicles or
personnel  during  loading  and  unloading operations.  Vehicles,  especially
trucks, should be able to move into  and out of the area without reversing.
High curbs around  transfer areas  and barriers around equipment  should be
provided to protect  equipment from vehicle collisions.

     Correct procedures must be followed when unloading and handling small
ammonia storage vessels.  Dragging,  sliding,  or  rolling cylinders, even  for
short distances,  is not acceptable.  Lifting magnets, slings of rope or chain,
or  any  other  device in which  the cylinders themselves form a part of the
carrier should never be used for transporting cylinders.

5.4  PROTECTION TECHNOLOGIES

     This  subsection  describes two  types  of  protection  technologies  for
containment and neutralization.  These are:
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     •    Enclosures; and

     •    Scrubbers.

A presentation  of  more  detailed information  on  these systems is  planned  in
other volumes of the prevention  reference manual  series.

5.4.1     Enclosures

     Enclosures  refer  to containment  structures  which capture  any ammonia
spilled  or  vented  from  storage or  process equipment, thereby  preventing
immediate  discharge of  the  chemical  to  the environment.   The  enclosures
contain  the spilled liquid  or gas  until it can be  transferred to  other con-
tainment and discharged  at  a controlled rate which would not be injurious to
people  or  the  environment,  or  transferred at a  controlled rate  to  water
scrubbers for absorption.

     Specially designed  enclosures for ammonia storage or process  equipment  do
not appear to be  in widespread  use.   The principle that it may be preferable
to  locate  toxic operations  in   the  open air has been mentioned  in  the
literature (39), along with  the opposing idea that sometimes enclosure may be
appropriate.   The  desirability  of  enclosure depends  partly  on the frequency
with which personnel must  be involved with the  equipment.   A common  design
rationale for not  having an  enclosure where  toxic  materials  are  used is  to
prevent  the  accumulation  of toxic  concentrations  within  enclosed areas.
However, if the issue is providing for secondary  containment,  total enclosure
may be appropriate.

     If  total enclosure  is  deemed appropriate for  a  given installation,  it
should be  equipped with continuous  monitoring  equipment and adequate fire
protection.  Alarm's should sound whenever  lethal  or flammable concentrations
are  detected.   Care must  be taken  when  an enclosure  is  built  around
pressurized equipment.   From an  economic standpoint,  it would not  be practical
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to design an enclosure to withstand  the  pressures  associated with the sudden
failure of a pressurized vessel.  Therefore,  if  an enclosure is built around
pressurized equipment, it  should be  equipped with some  type of explosion
protection, such as rupture plates.   These  components  are designed  to fail at
a pressure lower than  the design pressure of the enclosure,  thus  preventing
the entire structure from failing.

     An enclosure would have a ventilation system designed to draw in air  when
the enclosure was  vented.   The bottom section of an enclosure  which is  used
for stationary storage containers should be liquid tight  to  retain  any  liquid
ammonia that might  be  spilled.  Enclosures around  rail  tank cars which are
used for storage do not  normally lend themselves easily  to  effective liquid
containment.   However, containment  can be accomplished if  the  floor of the
enclosure is excavated several feet below the track level while  the  tracks are
supported at grade in the center.

     While the use  of  enclosures for secondary containment of ammonia spills
or releases is not  known to be widely used, it might  be  considered  for areas
near sensitive receptors.

5.4.2  Scrubbers

     Scrubbers are a traditional method for absorbing  toxic  gases from process
streams.  These devices  can be used for  the control of ammonia  releases from
vents and  pressure  relief discharges,  from  process equipment, or from secon-
dary containment enclosures.

     Because of its high solubility,  ammonia discharges could be absorbed in
water in any of several  types of scrubbing devices.   Types  of  scrubbers that
might be appropriate include  spray towers, packed bed  scrubbers, and Venturis.
Other types of special designs might be suitable but complex internals subject
to corrosion do not seem to be advisable.
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     Whatever type of scrubber  is  selected,  a complete  system  would include
the scrubber itself, a  liquid  feed system,  and reagent makeup  equipment.   If
such a system is used as protection  against  emergency  releases, consideration
must be given to how  it would  be activated  in time to  respond to an emergency
load.  One  approach used  in some  process  facilities  is  to  maintain  a
continuous  circulation  of scrubbing liquor through the  system.   For many
facilities this would not be practical, and the scrubber  system might be tied
into a trip system to turn it on when it is needed.  However, with  this  system
a quantity of ammonia would  be released prior to  actuation of the  scrubber
(i.e., starting up a blower and turning on the flow of liquid).

     The scrubber  system must  be  designed  so as  not  to present excessive
resistance to the flow of an emergency discharge.  The pressure drop should be
only a  small  fraction  of  the  total  pressure drop through the  emergency
discharge system.   In  general,  at  the  liquid-to-gas  ratios  required for
effective scrubbing, spray towers  have the  lowest, and Venturis  the highest
pressure drops.  While  packed  beds  may have  intermediate pressure  drops at
proper liquid-to-gas  ratios,  excessive ratios or  plugging can increase the
pressure  drop  substantially.   However,  packed  beds  have  higher  removal
efficiencies than spray  towers or Venturis.

     In addition,  the  scrubber system must be designed  to handle the "shock
wave"  generated during the initial  stages  of  the  release.   This  is
particularly important  for packed  bed  scrubbers  since  there  is a  maximum
pressure with which the  gas can enter the packed  section without damaging the
scrubber internals.

     Design of emergency scrubbers  can follow standard techniques discussed  in
the  literature,  carefully  taking into account the additional considerations
just  discussed.  An  example  of the  the  sizing of an  emergency  packed  bed
scrubber is  presented  in Table 5-3.  This example provides some idea of the
size  of  a  typical  emergency scrubber  for various flow  rates.   This  is an
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      TABLE 5-3.  EXAMPLE OF PERFORMANCE CHARACTERISTICS FOR AN EMERGENCY
                  PACKED BED SCRUBBER FOR AMMONIA


Basis:  Inlet stream of 50% NH  in 50% air.  Constant gas flow per unit
        cross-sectional area of 455 scfm/ft .

Packing:  2-inch plastic Intalox® saddles.

Pressure Drop:  0.5 inch water column

Removal Efficiency, %                        50             90
Liquid to Gas Ratio
  (gal/thousand scf)
    — at flooding                          160            160
    — operating                             80             80

Packed Height, ft.                          3.1           11.4


Column Diameter and Corresponding Gas Flow Rates for Both Removal Efficiencies


                     Column
                    Diameter                         Flow Rate
                      (ft)                            (scfm)

                      0.5                                 90
                      1.0                                360
                      2.0                              1,400
                      6.3                             14,000
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example only and  should  not  be used as the basis  for  an actual system which
might differ based on site specific requirements.

     Another approach is  the  drowning tower where the ammonia  vent  is  routed
to the bottom of a large  tank  of uncirculating wfter.  The  drowning  tower  does
not have the high contact efficiency  of the other  scrubber  types.  However,  it
can provide substantial capacity on demand as long as  the back  pressure of the
hydrostatic head does not create  a secondary hazard, by impeding an overpres-
sure relief discharge, for example.

5.5  MITIGATION TECHNOLOGIES

     If, in spite  of  all precautions, a  large  release of  anhydrous  ammonia
were to occur,  the  first  priority would be to rescue workers in the immediate
vicinity of the accident  and evacuate persons from downwind areas.   The source
of the  release  should be determined,  and the leak should be plugged to stop
the flow if this  is possible.   The next primary concern  becomes reducing  the
consequences of the released  chemical to the plant and the  surrounding commu-
nity.   Reducing the consequences  of  an accidental  release of a hazardous
chemical is  referred  to  as mitigation.   Mitigation  techniques include such
measures as physical barriers, water  sprays and  fogs,  and foams.   The purpose
of a mitigation technique is  to divert, limit,  or disperse the chemical that
has been released  to  the  atmosphere.   The mitigation  technology chosen for  a
particular chemical will  depend on the  specific properties of the  chemical
including its flammability, toxicity,  reactivity,  and those properties  which
determine its dispersion  characteristics  in the  atmosphere.

     If a release  occurs  from  a pressurized ammonia storage tank, a quantity
of liquid will  immediately flash  to its atmospheric  boiling point producing a
vapor/aerosol cloud of ammonia.  The  remaining liquid  will  cool to the normal
boiling point of -28 °F.  Heat transfer from  the air and ground will result  in
further vaporization  of  the  released  liquid.   Since the  ammonia accidentally
released from a refrigerated storage tank is already  at or below  its normal
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boiling point,  a  comparable quantity of vapor will not flash  off.  as with a
pressurized release, but heat transfer from the environment will  still quickly
cause the formation  of  a vapor  cloud.   It is therefore desirable to  minimize
the area available  for  heat transfer to  a  liquid spill which  in turn will
minimize the rate of  evaporation.   Mitigation technologies which are used  to
reduce the rate of  evaporation  of  a released liquified gas include secondary
containment systems such as impounding basins, dikes, and enclosures.

     A post-release mitigation effort requires that the source of the release
be  accessible  to  trained plant  personnel.   Therefore, the  availability of
adequate personnel  protection  is   essential.   Personnel  protection will
typically  include such  items  as  portable  breathing  air and  chemically
resistant protective clothing.

5.5.1  Secondary Containment Systems (7.40,41)

     Specific types of secondary containment  systems include excavated basins,
natural basins, earth,  steel,  or concrete  dikes,  and  high  impounding walls.
The type of  containment system best suited for  a particular  facility  will
depend on the risk  associated with an  accidental release from  that location.
The inventory of ammonia and its proximity  to other portions of the plant and
to  the community  are  primary considerations in the selection.   The secondary
containment system should have the  ability  to contain  spills with a minimum of
damage to  the  facility  and its surroundings  and with minimum  potential  for
escalation of the event.

     While it is common practice to  provide ammonia storage  tank  installations
with an earth or  concrete  dike  to  contain the liquid  into a manageable  pool
should a total  failure  of  the  main tank occur, the efficacy of a dike in the
event of a  release  from pressurized storage  has been questioned.   This is
because a sudden  loss of  pressurized containment tends to result in  ejection
of  all the contents in the  form of vapor, or  spray, leaving no  residual  liquid
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(17).  There may, however, be situations where a dike would be appropriate for
a pressurized ammonia storage vessel.

     A conventional dike is of use when refrigerated storage is involved.  The
liquid is already at atmospheric pressure, and it is assumed that  most of the
contents of the  tank will  be  contained within the confines of  the dike in the
event of  a  release from  the  tank.  ANSI  K61.1  requires  that  one of  the
following should be provided  with  any  primary refrigerated storage system;  it
has no similar provisions for pressurized  storage  (7):

     •    An adequate drainage system  underlying the storage vessels
          which terminates in an impounding  basin  having a capacity
          as large as the largest  tank served; or

     •    A diked  area  with the capacity  as large as the largest
          tank served.

These measures are designed to prevent accidental  discharge  of  liquid ammonia
from spreading to uncontrolled areas.

     The most  common  type of containment  system  is a low wall earth  dike
surrounding one  or more storage tanks.  Generally, no more  than three tanks
are enclosed within one  diked area because of increased risk.   Piping should
be  routed  over  dike walls,  and penetrations  through the walls  should be
avoided if  possible.  Vapor fences may be situated on top of  the dikes to
provide additional vapor  storage  capacity.  If there is  more than one tank in
the diked area, the tanks should be situated on berms above the maximum liquid
level attainable in the impoundment.

     Dike heights  usually range from  3  to  12  feet depending on  the area
available to achieve the  required  volumetric capacity.   The dike walls should
be liquid tight and able to withstand  the  hydrostatic pressure  and temperature
of  a spill.   It may be  necessary to construct  low  wall dikes  of  low
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temperature steel  or  concrete because  of  adverse soil conditions  or  other
specific requirements.  In addition, some experiments have led  to  the  conclu-
sion that earth dikes should be covered with a layer of clay, asphalt, plastic
film, or  a similar material  that  is impermeable  to  liquid ammonia  (42).
Otherwise, the ammonia will percolate into the ground, and the  loss of ammonia
by evaporation will be greater in the absence of an impermeable layer over  the
dike.

     A low wall dike can effectively contain the liquid portion of  an acciden-
tal release and keep  the  liquid  from entering  uncontrolled areas.   However, a
dike also  limits  access to the  tank  during a spill.   Therefore,  a remote
impounding basin  may  be considered if  a  relatively large site is  available
within a reasonable distance  of  the storage system.  With such a system, the
flow is  directed  to the basin by dikes and channels  under the  storage tanks
which are  designed to minimize  exposure  of  the  liquid to other tanks  and
surrounding facilities.  The  advantages of this type  of system  are

     •    The  spilled liquid is removed  from  the  immediate tank
          area;

     •    The  probability  of the  spilled liquid  causing further
          damage  to the tank, piping,  electrical facilities, pumps,
          and  other equipment is reduced;

     •    The  tank area is  accessible during the  spill; and

     •    Access  to the tank pumps  or  related piping for  regular
           operation,  inspection, or maintenance  is not  restricted  by
           the  impoundment.

The  impounding basin  may  be  located to use the natural topography  of the area
thus minimizing additional  excavation and diking.   A sump can also be  provided
within  the main  impounding basin  to limit  the liquid surface and ground
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contact areas.   Furthermore, the  depth of the  basin can be  increased to
provide vapor containment.

     Although few  authorities  for  ammonia facilities require  them, high  wall
impoundments may be  the  best secondary containment choice for selected sys-
tems.  Circumstances which may  warrant their use include limited storage site
area, the need  to  minimize  vapor generation rates, and/or  the tank must  be
protected from  external hazards.  Maximum vapor  generation rates will  general-
ly be lower  for a  high wall impoundment  than  for low wall  dikes  or  remote
impoundments because of  the  reduced surface contact area.  These rates can be
further reduced with the use of insulation on  the wall and  floor in the
annular space.   High impounding walls may  be  constructed of low temperature
steel, reinforced  concrete,   or  prestressed  concrete.  A  weather shield may be
provided between the tank and wall with the annular  space  remaining  open to
the atmosphere.   The available  area surrounding  the storage  tank will dictate
the minimum  height of  the wall.  The walls may  be designed  with a volumetric
capacity greater than that of the tank to provide vapor  containment.   Increas-
ing the height  of  the wall also raises the  elevation  of  any  released vapor.

     One disadvantage  of  these dikes is that  high walls around a  tank may
hinder routine  external  observation.   Furthermore,  the closer the wall is  to
the tank,  the more difficult it becomes to  access  the tank  for inspection and
maintenance.  As with low wall  dikes, piping should be routed  over the wall  if
possible.   The  closeness  of  the wall to the tank may  necessitate placement of
the pump outside  of  the  wall,  in  which case the tank outlet  (suction) line
will have  to pass through  the wall.   In  such  a situation,  a low  dike
encompassing the pipe  penetration  and  pump may be provided,  or a low  dike may
be placed around the entire wall.

     An example of the effect  of diking  as predicted by a  vapor dispersion
model is shown  in Figure  5-1 (43).   This figure  shows ammonia  vapor  clouds at
the  time when  the  farthest  distance  away  from the  source  is exposed to
concentrations  above the  IDLH.   With diking, the model predicts that  downwind
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   >>  BOO.
   • > i.oooe+oa PPM
   > > 1.00OB+O4 PPM
                     o.as
                                O.B
                                            O.7B
                                                                   1.88
             Release from  a  tank  surrounded by a 25 ft. diameter dike.
             Elapsed Time:   2 minutes
    >  500.
X - MAX CONCeNTRATXON
  •   BO9.4B PPM
0.20
            O.B
                       0.78
                                              1.88
                          Release from a tank with no dike.
                          Elapsed Time:  8 minutes
  Common Release  Conditions

  Storage Temperature = 85°F
  Storage Pressure = 148 psig
  Ambient Temperature = 85°F
                            Wind Speed = 10 mph
                            Atmospheric Stability  Class = C
                            Quantity Released = 5000  gallons
                              through a 2-inch hole
       Figure 5-1.  Computer model simulation showing the effect of diking on
                    the vapor cloud generated from a  release  of  liquified
                    ammonia.
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distances up to 1400 feet from, the  source  of  the release could be exposed to
concentrations above the  IDLH.   Two minutes  are required for the vapors to
reach the maximum down wind distance.  Without diking, the model predicts that
downwind  distances  up to  6600  feet from  the source could  be exposed  to
concentrations above the IDLH.  Eight  minutes are required for the vapors to
reach this distance.

     One further type of secondary  containment system is one which is  struc-
turally integrated with the  primary system and forms a vapor  tight enclosure
around the primary container.  Many types  of  arrangements are  possible.  These
systems may  be considered  where  protection  of  the primary  container  and
containment of vapor for events not involving foundation or wall penetration
failure are of  greatest  concern.   Drawbacks  of  an  integrated  system  are the
greater complexity  of  the structure,  the  difficulty of  access  to certain
components, and the fact that complete vapor  containment cannot  be  guaranteed
for all potential events.

     Provision should be made for  drainage of rainwater from  both impounding
basins and diked  areas.   This will  involve  the use of  sumps and separate
drainage  pumps, since  direct drainage  to  stormwater  sewers  would  presumably
allow any spilled ammonia  to follow the same route.   Alternately,  a sloped
rain hood may be used over the diked area  which  could also serve to direct the
rising vapors to a single release point  (41).  The  ground within the  enclosure
should be graded to cause  the  spilled liquid to accumulate  at one side or in
one corner.  This will help to minimize the area of ground to  which the liquid
is exposed and from which  it may  gain heat.   In areas where  it is  critical  to
minimize vapor generation,  surface  insulation may be used in the diked  area or
impoundment to  further reduce  heat transfer from  the environment to  the
spilled liquid.  The  floor of an impoundment should  be sealed with  a  clay
blanket to prevent  the ammonia  from seeping into the ground; percolation into
the ground  causes  the ground to  cool  more quickly,  increasing the  vapor
generation rate.  Absorption of the ammonia into water  in the soil  would also
release additional heat.
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5.5.2  Flotation Devices and Foams  (42,44.45,46)

     Other  possible  means  of reducing  the surface area  of spilled liquid
ammonia include placing impermeable flotation devices on the surface,  dilution
with water, and applying water-based foams.

     Placing a lid over a spilled chemical is a direct approach for  containing
the toxic vapors with nearly  100  percent efficiency.   The floating  cover may
be continuous or a distribution of light particulates.  However, being able  to
use these techniques requires acquisition  in advance  of the spill  and storage
until  needed,  and in  all  but  small  spills deployment may be difficult.
Furthermore, although particulate covers are potentially  effective,  cost is a
deterrent to their use.  Determination  of appropriate materials for applica-
tion to an  ammonia spill has been the subject  of  some research (42),  but the
use of mechanical  barriers  on an actual  spill  has not been reported  in the
literature.

     One approach to an  ammonia spill is dilution with water,  but, because of
the high heat  of solution,  the  addition of pure  water  would result  in a
violent boil-off  of  ammonia.   A water-based foam  cover provides  a  means of
diluting the ammonia with a minimum heat of solution, because water is  added
at a  slow  rate.   While  the  use of  foams  in vapor hazard control has  been
demonstrated for  a  broad range of  volatile chemicals, it  is  difficult to
accurately  quantify  the  benefits of foam  systems,  because the effects  will
vary as a function of the chemical  spilled,  foam  type, spill size,  and  atmo-
spheric conditions.  With  regard to liquified  gases,  it  has been  found that
with some materials, foams have a net positive  effect, but  with  others, foams
may exaggerate the hazard.

     When a foam cover is first applied,  an increase in the boil  off  rate  is
generally observed which causes a short-term increase in the downwind ammonia
concentration.  The initial foam cover may be destroyed by  violent boiling,  in
which  case  a second application  is necessary.   Once a continuous layer is
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formed, a net positive effect will be achieved in the downwind area  (44).  The
reduction in  downwind  concentration is a  result  of  both increased  dilution
with air, because of a  reduced vaporization rate, and the increased buoyancy
of the vapor cloud.   This latter effect is a result of  the vapor being wanned
as it rises through the blanket by heat transfer from the foam and by  the heat
of solution  of  ammonia in water; the  warmed  vapor cloud will have  greater
buoyancy and will disperse in an upward direction more rapidly.

     The extent of the downwind reduction  in concentration will  depend on the
type of  foam  used.   Research in this area has indicated that medium to high
expansion foams  (75  to  350:1)  give  significantly better results  than  do low
expansion foams  (6 to  8:1)  (44,45).   Furthermore, a high expansion  foam will
cause a smaller initial increase in boil off than a low expansion foam.

     Regardless of the  type  of foam used,  the slower the drainage rate of the
foam, the better  its performance  will  be.   A slow draining  foam will  spread
more evenly,  show more  resistance to temperature and pH effects, and collapse
more slowly.  The initial cost  for  a slowly draining foam may be higher than
for  other  foams,  but a cost  effective system will be  realized  in  superior
performance.

5.5.3  Mitigation Techniques for Ammonia Vapor (47,48)

     The extent to which the escaped ammonia vapor can be removed or dispersed
in a timely manner will  be  a function of  the quantity of vapor  released, the
ambient conditions,  and the physical characteristics  of  the  vapor cloud.  The
behavior and  characteristics of the  ammonia  cloud will  be  dependent on a
number of factors.  These include the  physical state  of the  ammonia  before its
release, the  location  of the release, and the atmospheric  and  environmental
conditions.  Many possibilities exist  concerning the shape and motion of the
vapor cloud,  and  a number  of predictive models of dispersion have been devel-
oped.  In spite  of the lower specific gravity of pure ammonia vapor, large
accidental  releases  of  ammonia have  often  resulted in the formation  of
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ammonia-air mixtures which are  denser  than the surrounding atmosphere.  This
type of vapor cloud is especially hazardous, because it will  spread laterally
and remain close to the ground.

     The primary means of dispersing as  well as removing ammonia  vapor from
the air is with  the use  of water  sprays  or fogs.   The  water is applied to the
vapor cloud by means  of  hand-held hoses  and/or stationary water-spray  barri-
ers.  For  effective  absorption,  it is important to direct  waterfog or spray
nozzles from a downwind  direction to  avoid driving the vapors  downwind more
quickly.   Other  important factors  relating to the effectiveness  of water
sprays are the  distance  of  the nozzles  from the  point of  release,  the fog
pattern, nozzle  flow rate,  pressure,  and  nozzle  rotation.  If the right
strategy is followed, a "capture zone" can be  created  downwind  of  the release
into which the ammonia vapor  will drift  and be absorbed.   In low  wind  condi-
tions, two fog nozzles should be  placed  upwind of  the release to  ensure  that
the ammonia  cloud  keeps  moving downwind  against the  water fog nozzle  pres-
sures.  If water fog is  used to  absorb  ammonia vapors  from a  diked area
containing spilled  liquid ammonia, great care must be taken not  to direct
water into the liquid ammonia itself.

     Water-spray barriers  consist of a series  of  spray nozzles  which can be
directed either  up  or  down.   If placed 30-40 feet from the point  of ammonia
release, these  barriers  are  very effective  in absorbing the ammonia vapors
passing through  without  distortion of the  ammonia cloud (47).  Several  fog
nozzles may be situated farther downwind  to  absorb  the remainder of the vapors
getting through.

     In general, techniques used  to disperse or control vapor  emissions should
emphasize  simplicity  and reliability.   In  addition to the mitigation  tech-
niques  discussed above,  physical  barriers such as  buildings and rows of trees
will help  to contain the vapor  cloud and  control its  movement.   Hence,  reduc-
ing  the consequences of  a hazardous vapor cloud can  actually  begin with a
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carefully planned layout of facilities and  the  use  of  imaginative landscaping
around major hazard sites.

5.6  OPERATION AND MAINTENANCE PRACTICES

     Accidental releases of toxic  materials result  not only from deficiencies
of design but also from deficiencies of operation.  Unfortunately, human  error
is often responsible  for  the  realization of hazards with potentially damaging
consequences.  The human error hazard manifests itself  in numerous  ways,  both
indirectly and directly.  For  example,  a lax management policy which does not
enforce safety standards might  be  indirectly responsible  for  an unnecessary
injury or fatality,  or an operator may  take the wrong  action at  a control
panel which  would  directly  lead to a hazardous release.  Aspects  of  plant
operation which  impact the magnitude  of the  risk  of  human error  include
management  policy,  operator  training,  and maintenance  and  modification
procedures.   These topics are discussed in  the  following subsections.

5.6.1  Management Policy

     Competent and effective management  plays  a vital  role in  the prevention
of accidental releases as a result of human error.   The  primary responsibili-
ties of  managers  at  chemical  plants with  large  inventories  of  hazardous
chemicals include the following (39):

     •    Ensuring worker competency;

     •    Developing,  documenting,  and enforcing standard  operating
          procedures and safety policies;

     •    Communicating and promoting feedback regarding  safety issues;

     •    Identification,  assessment, and control of hazards;  and
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     •    Regular plant audits and provisions for independent checks.

     Management is ultimately responsible for the competency of workers  hired
at facilities  which handle  hazardous  materials.  Because  of  the  serious
consequences that may  result  from  operator  error at  these installations,  the
qualifications and capabilities of prospective personnel for high hazard areas
should be carefully assessed  to ensure  that  worker skills are  matched to  job
responsibilities.  In  addition,  the skills  of competent  operators  should  be
maintained by regular training, safety meetings,  and employee reviews.

     In the chemical industry,  documentation is  generally produced which sets
forth standard  procedures  for equipment operation,  maintenance,  inspection,
hazard identification,  and  emergencies.   The enforcement of standard proce-
dures is therefore  one  of  management's most fundamental  responsibilities  in
the area of plant  safety and accident  prevention.  However,  before procedures
can be enforced,  they  must be  communicated  to  plant  personnel in  a clear,
concise style  so that  they  are thoroughly  understood.   Emphasis  should be
placed on worker safety and  the serious  consequences  of operator  error in
processes involving hazardous materials.

     Unfortunately, requiring workers  to  read  documents which  contain safety
policies is  often not  enough to ensure  that they are  fully understood  and
followed.  For  this reason,  verbal  communication should be  practiced  and
encouraged  which  emphasizes  plant  safety  and  promotes feedback.   When
management demonstrates a willingness to respond to initiatives from below and
participates  directly   with  workers  in improving  safety,  worker  morale
increases, influencing  the degree  to which standard procedures are  followed.

     Hazard  identification,   assessment, and control   is  another  area that
should be  addressed by management  to minimize  the  potential for  accidental
chemical releases.   The establishment of formal hazard  assessment  techniques
would provide management with a mechanism for  obtaining information which can
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be  used  to rank potential  problems  and decide how best  to allocate hazard
control resources.

     The  plant  safety audit is  one  of  the most frequently used methods  for
obtaining  safety related  information.   A total plant safety audit  involves  a
thorough  evaluation of a plant's design,  layout,  and procedures,  and is
specifically  aimed  at identifying  and  correcting  potentially  unsafe
conditions.   The objectives  of  these  audits  include  alerting operating
personnel  to  process hazards,  determining  if  safety  procedures need  to  be
modified,  screening  for equipment or process changes  that may have introduced
new  hazards,  assessing  the feasibility  of applying  new  hazard  control
technologies, identifying additional hazards,  and  reviewing inspection  and
maintenance  programs  (49).  In-house  safety  audits  can be  performed by
appointed  safety review committees,  or  qualified consultants or insurers  may
be brought in to provide a more  objective assessment.

5.6.2  Operator Training

     Accidental chemical  releases may result from numerous types of operator
errors  including following incorrect  operating procedures,  failing  to
recognize  critical  situations,   or by  direct  physical  mistakes,  e.g.,  by
turning the wrong valve.   For all of these  errors, the fundamental  problem may
be the operator's lack of knowledge or understanding  of process variables,
equipment operation, or emergency procedures.   It is  important  for  management
to recognize the extent to which  a comprehensive operator training  program can
decrease the  potential for accidental releases  resulting from  human error.
Some general characteristics of  quality industrial  training programs include
the following:

     •    Establishment of good working relations between management and
          personnel;

     •    Definition of trainer responsibilities and training program goals;
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     •    Use of documentation, classroom instruction, and field training  (in
          some cases supplemented with simulator training);

     •    Inclusion of procedures for normal startup and shutdown, routine
          operations,  and emergencies; and

     •    Frequent supplemental training and the use of up-to-date training
          materials.

     Employees  in  plants  which  manufacture, process,  or store  anhydrous
ammonia should be thoroughly educated about  the important  aspects  of handling
this  chemical.   These include  the proper means  of handling  and  storing,
potential consequences of  improper use and  handling,  prevention  of  spills,
cleanup procedures, maintenance  procedures,  and emergency procedures.  It is
the job of the trainer to ensure that the right type and amount of information
is supplied  at  the right time.  To do  this  he  must not only understand the
technical content of a job, but also those aspects  of  the  job  where  operators
may have difficulty.  It is  therefore advantageous  for trainers to spend time
observing and analyzing the tasks and skills they will be  teaching.

     Two types  of  training which are especially  important cover  emergencies
and safety procedures.  Emergency training includes topics such as:

     •    Recognition of alarm signals;

     •    Performance of specific functions  (e.g.,  shutdown switches);

     •    Use of emergency equipment;

     •    Evacuation procedures;

     •    Fire fighting; and
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     •    Rehearsal of emergency situations.

Safety training includes not only responses to emergency  situations,  but also
accident prevention measures.   Aspects  addressed in safety training sessions
include (39):

     •    Hazard recognition and communication;

     •    Actions to be taken in particular situations;

     •    Available safety equipment and locations;

     •    When and how to use safety equipment;

     •    Use and familiarity with relevant documentation; and

     •    First aid and CPR.

     The frequency of training  and the frequency with which training materials
are updated are important  in  maintaining strong training programs.   Chemical
processes may  be modified  to  the  extent  that  equipment changes require
operational change, and operators must be made aware of the changes and  safety
considerations  that  accompany  them  in a  timely manner.  In addition  to
operator training programs, organized management training is also beneficial
as  it  provides managers with  the perspective necessary  to  formulate good
policies and procedures and to  make  changes that will improve the quality of
the overall plant safety program.

5.6.3  Maintenance and Modification Practices

     Plant  maintenance  is necessary to  ensure the structural  integrity of
chemical processing equipment;  modifications are often necessary  to allow more
effective production.   However, since  these  activities  are  also potential
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causes of  accidental  chemical  releases,  proper maintenance  and modification
practices are important to the prevention of accidents.

     Maintenance refers to  a wide range of activities,  including preventive
maintenance, production assistance  (e.g., adjustment  of settings), servicing
(e.g., lubrication and replacement  of consumables),  running maintenance,
scheduled  repairs   during  shutdown,  and breakdown maintenance.   These
activities in turn  require  specific  operations  such as emptying, purging,  and
cleaning vessels, breaking pipelines, tank repair or demolition,  welding,  hot
tapping  (attaching  a  branch to  an  in-service line),  and  equipment  removal
(39).

     Proper maintenance and  modification programs  should be a normal part  of
plant operation and design procedures, respectively, to reduce  the chances  for
an accidental release.   Maintenance should be based on  a  priority system to
ensure that  the most critical  equipment  is taken  care of  first.   Strict
procedures should  apply to  process  modifications  to ensure that modifications
do not create unintended hazards.   Inspections  and nondestructive testing  of
vessels,   piping, and  machinery  should  be  conducted periodically  to  detect
small flaws that could eventually lead to a major release.

     Two  of the  more  common maintenance problems  are equipment identification
and equipment isolation (39).  Work performed on the wrong piece of  equipment
can have  disastrous effects, as can  failure  to completely isolate equipment
from process materials and electrical connections.  Other  potential sources of
maintenance accidents  are  improper  venting to relieve pressure,  insufficient
draining,  and not  cleaning  or  purging systems before  maintenance activities
begin.

     Permit  systems and  up-to-date  maintenance  procedures  minimize  the
potential  for accidents during maintenance operations.   Permit-to-work  systems
control maintenance activities  by specifying the work to be done, defining
individual  responsibilities,  eliminating or protecting  against hazards,  and
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ensuring  that  appropriate inspection  and  testing procedures  are followed.
Such permits generally include specific information such as  (39):

     •    The type of maintenance operations to be conducted,

     •    Descriptions and identifying codes of the equipment  to  be
          worked on,

     «    Classification of the area in which work will be conducted,

     •    Documentation of special hazards and control measures,

     •    Listing of the maintenance equipment to be used, and

     •    The date and time when maintenance work will be performed.

     Permit-to-work systems offer many advantages.   They explain the work  to
be done  to  both operating and maintenance workers.   In terms of equipment
identification and hazard identification, they provide a level of detail that
significantly reduces the potential for errors that could lead to accidents or
releases.  They also serve as historical records of maintenance activities.

     Another form  of maintenance  control  is  the maintenance information
system.  Ideally, these systems  should log the entire maintenance history  of
equipment, including preventative maintenance, inspection and  testing, routine
servicing, and breakdown or failure maintenance.  This type  of system is also
used to  track  incidents  caused by factors  such  as human error,  leaks,  and
fires which  resulted  in hazardous conditions,  downtime, or direct  repair
costs.

     One important maintenance practice  is repairing or replacing  equipment
that appears to  be headed for  failure.   A number  of testing methods  are
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available for examining the condition  of  equipment.   Some of the most  common
types of tests are listed below:

     •    Metal thickness and integrity testing,

     •    Vibration testing and monitoring, and

     •    Relief valve testing.

All  of  the above testing procedures  are  nondestructive, i.e.,  they  do not
damage the material or equipment that they test.

     Accidental releases  are  frequently the result  of  some aspect of  plant
modification.  To avoid confusion with maintenance activities,  a modification
is defined as an intentional change in process materials, equipment,  operating
procedures,  or operating  conditions (39).  Accidents  result when  equipment
integrity  and operation are not properly  assessed following modification,  or
when modifications  are made without  updating  corresponding operation  and
maintenance instructions.   Frequently, hazards created by modifications do  not
appear  in the  exact  location  of   the  change.    For example,  equipment
modifications can invalidate the arrangements  for system pressure  relief and
blowdown  or  they  can  invalidate  the  function  of  instrumentation  systems.
Several factors should be considered in  reviewing modification plans before
authorizing work.   According to Lees, these include  (39):

     •    Sufficient number and size of relief valves,

     •    Appropriate electrical area classification,

     •    Elimination of effects which could reduce  safety  standards,

     •    Use of appropriate engineering  standards.
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     •    Proper materials  of construction  and  fabrication  standards.

     •    Existing equipment not  stressed beyond  design limits,

     •    Necessary changes in operating conditions,  and

     •    Adequate instruction and training of  operation and
          maintenance teams.

5.7  CONTROL EFFECTIVENESS

     It is  difficult  to  quantify  the control effectiveness of preventive  and
protective  measures  to  reduce the  probability and magnitude of accidental
releases.    Preventive measures,  which may  involve  numerous  combinations  of
process design,  equipment design, and  operational  measures,  are  especially
difficult to quantify because they reduce a probability rather than  a  physical
quantity of  a  chemical  release.   Protective measures are more  analogous  to
traditional  pollution  control  technologies.   Thus,  they may  be easier to
quantify in  terms of  their  efficiency in minimizing  the  adverse effects of a
chemical that could be released.

     Preventive measures  reduce  the probability  of an accidental  release  by
increasing  the reliability  of both  process   systems operations and the  equip-
ment.  Control effectiveness  can thus be expressed for both  the qualitative
improvements and the quantitative improvements through probabilities.  Table
5-4  summarizes what  appear  to be some  of   the major  design,  equipment, and
operational  measures  applicable  to  the  primary hazards  identified  for the
ammonia applications  in  the U.S.   The  items listed  in this  table are for
illustration purposes only  and  do not necessarily  represent  a  satisfactory
control option for all cases.  These control options  appear to reduce  the  risk
associated with an accidental release when  viewed from a broad  perspective.
However,  there are undoubtedly specific cases where these control  options  will
not be appropriate.  Each case must  therefore be evaluated individually.   A
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presentation of more information  about  reliability in terms of probabilities
is planned for other volumes of the prevention reference manual series.

5.8  ILLUSTRATIVE COST ESTIMATES FOR CONTROLS

     This section presents  cost estimates  for different levels of control and
for specific release prevention and protection measures for  ammonia storage
and process facilities found in the United States.

5.-8.1  Prevention and Protection Measures

     Preventive measures reduce the probability  of an accidental  release from
a process or storage facility  by  increasing the reliability  of both process
systems operations and equipment.   Along with an increase in  the  reliability
of a system is an increase  in  the  capital and  annual costs associated  with
incorporating prevention  and protection measures  into  a system.   Table  5-5
presents costs for  some of  the  major  design,  equipment,  and operational
measures applicable  to  the  primary hazards identified  in  Table 5-4 for  the
ammonia applications discussed in Section 3.

5.8.2  Levels of Control

     Prevention of accidental releases relies on  a combination of technologi-
cal, administrative, and  operational practices as  they  apply  to  the design,
construction,  and operation  of facilities  where hazardous  chemicals are  used
and stored.  Inherent in  determining the degree to which these practices are
carried out is their costs.   At a minimum,  equipment  and procedures  should be
in accordance with  applicable codes,  standards,  and regulations.  However.
additional measures can be taken to provide extra  protection  against  an acci-
dental release.

     The levels  of  control  concept provides  a  means of assigning  costs to
increased levels of  prevention and  protection.   The minimum level is referred
                                       104

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       TABLE 5-4.  EXAMPLES OF MAJOR PREVENTION AND PROTECTION MEASURES
                   FOR AMMONIA RELEASES
Hazard Area
    Prevention/Protection
Ammonia flow
control

Temperature sensing
and cooling medium
flow control
Temperature sensing
and heating medium
flow control
Overpressure
Corrosion
Reactor and reboiler
temperatures

Overfilling
Atmospheric releases
from relief discharges

Storage tank or line
rupture
Redundant flow control loops;
Minimal overdesign of feed systems

Redundant temperature sensors;
Interlock flow switch to shut off
NH- feed on loss of cooling, with
relief venting to emergency scrubber
system

Redundant temperature sensors;
Interlock flow switch to shut off
NH. feed on loss of heating, with
relief venting to emergency scrubber
system

Redundant pressure relief; not
isolatable; adequate size; discharge
not restricted

Increased monitoring with more
frequent inspections; use of corrosion
coupons; visual inspections;
non-destructive testing

Redundant temperature sensing and
alarms

Redundant level sensing, alarms
and interlocks; training of
operators

Emergency vent scrubber system
Diking; foams; dilution;
neutralization; water sprays;
enclosure vented to emergency
scrubber system
                                       105

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         TABLE 5-5.   ESTIMATED TYPICAL COSTS OF MAJOR PREVENTION AND
                     PROTECTION MEASURES FOR AMMONIA RELEASE3
  Prevention/Protection Measure
Capital Cost
  (1986 $)
 Annual Cost
 (1986 $/yr)
Flow control loop

Temperature sensor

Pressure relief

  - relief valve

  - rupture disk

Interlock system for flow shut-off

Alarm system

Level sensor

  - liquid level gauge

  - load cell

Physical barriers

  - curbing

  - 3 ft. retaining wall

Diking (based on a 10,000 gal. tank)

  - 3 ft. high

  - top of tank height. 10 ft.

                •          •   b
Increased corrosion inspection
 4,000-6.000

   250-400



 1.000-2.000

 1.000-1,200

 1,500-2.000

   250-500



 1.500-2.000

10.000-15.000



750-1.000

1.500-2.000



 1.200-1,500

 7,000-7,500
  500-750

   30-50



  120-250

  120-150

  175-250

   30-75



  175-250

1,300-1,900



 120-150

 175-250



  150-175

  850-900

  200-400
       on a 10,000 gallon fixed ammonia storage tank system and a  10  tons/day
 ammonia stripper system.

 Based on 10-20 hours 0 $20/hr.
                                       106

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to as  the  "Baseline" system.  This system  consists  of  the elements required
for normal safe  operation and basic prevention  of an accidental release  of
hazardous material.

     The second level of  control  is  "Level  1".  "Level 1" includes  the  base-
line system with  added  modifications  such as improved materials  of  construc-
tion,  additional  controls,  and generally more extensive release prevention
measures.  The costs  associated with  this level are higher  than  the baseline
system costs.

     The third level  of control  is "Level 2".  This  system  incorporates both
the "Baseline" and "Level 1" systems with  additional modifications designed
specifically  for  the prevention of an  accidental  release such as  alarm and
interlock systems.  The extra  accidental  release prevention measures incorpo-
rated  into "Level  2" are  reflected in its cost, which is  much higher than  that
of the baseline system.

     When comparing  the costs of  the various levels  of control,  it is  impor-
tant to  realize  that  higher costs do not necessarily imply  improved safety.
The measures  applied must be applied correctly.   Inappropriate modifications
or add-ons may not make a system  safer.  Each added  control  option increases
the complexity  of a system.  In some cases,  the hazards  associated with the
increased complexity  may outweigh the  benefits  derived from  the particular
control  option.   Proper design and construction along with proper operational
practices are needed to assure safe operation.

     Levels of control  cost  estimates were  prepared  for a 25 ton  fixed  ammonia
storage  tank  system  with a 10,000 gal  capacity  and  a waste  water  treatment
ammonia  stripper  system with a 10 tons/day ammonia recovery  rate.  The  reader
should be  aware  that the  cost estimates  presented in  this  section are for
illustrative  purposes  only,  i.e., it is  doubtful  that any  specific  instal-
lation would  find all  of the control options listed in  these tables appro-
priate for  their purposes.  An actual  system is  likely  to  incorporate  some
                                       107

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items from each  of  the levels of  control  and also some control options not
listed here.   The purpose of these estimates is to illustrate the  relationship
between cost and control, not to provide an equipment check list.

5.8.3  Cost Summaries

     Table 5-6 presents  a summary of the total capital and  annual costs for
each of the three levels  of  controls for the ammonia storage system  and the
ammonia stripper  system.   The  costs presented  correspond  to  the systems
described in Table 5-7 and Table  5-8.   Each of the  level  costs include the
cost of the basic system  plus  any added controls.   Specific cost  information
and breakdown for each level of  control  for both the  storage  and process
facilities are .presented in Tables 5-9 through 5-14.

5.8.4  Equipment Specifications and Detailed Costs

     Equipment specifications  and details of the  capital cost  estimates for
the ammonia storage and the  ammonia  stripper systems are presented in Tables
5-15 through 5-22.

5.8.5  Methodology

Format for Presenting Cost Estimates—
     Tables are provided for control schemes associated with  storage  and pro-
cess facilities  for ammonia  showing capital, operating, and total  annual
costs.   The tables are broken down into subsections comprising vessels,  piping
and valves, process machinery,  instrumentation,  and procedures and practice.
The presentation of the  costs  in  this manner allows  for  easy comparison  of
costs for specific items, different levels, and different systems.

     Capital Cost—All capital  costs presented in this report  are shown  as
total fixed capital  costs.   Table 5-23 defines the  cost  elements  comprising
total fixed capital as it is used here.
                                       108

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       TABLE 5-6.  SUMMARY COST ESTIMATES OF POTENTIAL LEVELS OF CONTROLS
                   FOR AMMONIA STORAGE TANK AND STRIPPER
          System
Level of
Control
   Total
Capital Cost
  (1986 $)
   Total
Annual Cost
(1986 $/yr)
Ammonia Storage Tank;
25 Ton Fixed Ammonia
Tank with 10,000
Gallon Capacity
Baseline        215.000

Level #1        553,000

Level #2      1,254,000
                    26,000

                    65.000

                   146.000
Waste Water Treatment
Ammonia Stripper
with 10 Tons/Day
Ammonia Recovery
Baseline        430,000

Level #1        948,000

Level #2      1.760,000
                    59.000

                   120,000

                   197.000
                                       109

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       TABLE 5-7.   EXAMPLE OF LEVELS OF CONTROL FOR AMMONIA STORAGE TANK

         Process:   25 ton fixed ammonia storage tank
                   10.000 gal
Controls
    Baseline
   Level No. 1
    Level No. 2
Process:

Flow:
None
None
Single check-      Add second check.
valve on tank—     valve.
process feed line.
None

Add a reduced-pressure
device  with internal
air gap and relief
vent to containment
tank or scrubber.
Temperature:
None
None
Add temperature
indicator.
Pressure:
Single pressure
relief valve,
vent to atmos-
phere.  Provide
local pressure
indicator.
Add second relief
valve, secure
non-is datable.
Vent to limited
scrubber.
Add rupture disks
under relief valves.
Provide local pressure
indication on space
between disk and
valve.
Quantity:
Local level
indicator.
Add remote level
indicator.
Add level alarm.  Add
high-low level inter-
lock shut-off for both
inlet and outlet
lines.
Location:
Materials of
Construction:
Vessel:
Away from traffic. Away from traffic
                   and flammables.
Carbon steel
Tank pressure
specification:
250 psig.
Carbon steel with
increased corrosion
allowances.  (1/8
inch)

Tank pressure
specification:
300 psig.
Away from traffic,
flammables, and  other
hazardous processes.

Type 316 SS.
Tank pressure
specification:
375 psig
                                                                  (Continued)
 A reduced pressure device is a modified double check valve
                                      110

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                             TABLE 5-7  (Continued)

         Process:  25 ton fixed ammonia storage  tank

                   10,000 gal
    Controls
     Baseline
   Level No. 1
                        Level No. 2
Piping:
Process
Machinery:
Enclosures;

Diking:.


Scrubbers:

Mitigation:
Schedule 40
carbon steel.
Schedule 80
carbon steel.
Centrifugal pump.  Centrifugal pump,
carbon steel,      316 SS construc-
stuffing box       tion, double cap-
seal,              acity mechanical
                   seal.
None

None


None

None
Steel building.

3 ft high.


Water scrubber.

Water sprays.
                     Schedule 80 Type 316
                     stainless steel.

                     Magnetically-coupled
                     centrifugal pump, 316
                     SS, construction.
                     Concrete building.

                     Top of tank height,
                     10 ft.

                     Same.

                     Same.
                                        Ill

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         TABLE 5-8.   EXAMPLE OF LEVELS OF CONTROL FOR AMMONIA STRIPPER

         Process:  Waste water Treatment

         Basis:  10 tons/day ammonia recovery plant
Controls
    Baseline
   Level No. 1
    Level No. 2
Process:
Temperature:
Pressure:
Flow:
Quantity:

Mixing:

Corrosion:


Composition:

Materials of
Construction:
Provide local
temperature
control.
Provide local
pressure control.
Single pressure
relief valve.
Vent to atmos-
phere.
Provide local
flow control on
stripper feed
and heating
medium to re-
boiler.

None.

None.

Visual inspec-
tions.

None.

Carbon steel.
Enhanced tempera-
ture and flow
control.

Add redundant
temperature sensors
and alarms.  Add
remote tempera-
ture indicator.

Add redundant
pressure sensors.
Add second relief
valve.  Vent to
limited scrubber.
Add redundant flow
control loops.
None.

None.

Same.


None.

Carbon  steel with
added corrosion
allowance.
Computer control of
process.  Use of
interlock systems.

Add computer control.
Add temperature switch
and back-up cooling
system.
Add computer control.
Add rupture disks
under relief valves
and provide local and
remote pressure indi-
cator on space between
disk and valve.

Add computer control.
Add interlock flow
switch to shut off
feed on loss of cool-
ing medium.
None.

None.

Same.


None.

Type 316  stainless
steel.
                                                              (Continued)
                                       112

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                             TABLE 5-8  (Continued)

         Process:  Waste water Treatment

         Basis:  10 tons/day ammonia Recovery Plant
Controls
    Baseline
   Level No. 1
    Level No. 2
Vessel:
Piping:
Process
Machinery:
Pressure speci-
fication:  250
psig.

Schedule 40
carbon steel.
Centrifugal
pump, carbon
steel construc-
tion, stuffing
box.
Protective
Barriers:
Scrubbers :
Mitigation:
None.
None.
None.
Pressure specifi-
cation:  300 psig.
Schedule 80 car-
bon steel.
Centrifugal pump.
Type 316 stainless
steel construction.
double capacity
mechanical seal.

Curbing around
stripper.

Water scrubber.

Water sprays.
Pressure specifica-
tion:  375 psig.
Schedule 80 Type
316 stainless
steel.

Magnetically-coupled
centrifugal pump. Type
316 stainless steel
construction.
                                                        3 ft. high  retain-  ing
                                                        wall.

                                                        Same.

                                                        Same.
                                        113

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       TABLE 5-9.  ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED
                   WITH BASELINE AMMONIA STORAGE SYSTEM

                                            Capital Cost         Annual Cost
                                              (1986 $)           (1986 $/yr)
Vessels:

  Storage Tank                                186,000               22.000

Piping and Valves:

  Pipework                                      4.500                  520
  Check Valve                                     520                   60
  Ball Valves (5)                               3.200                  370
  Excess Flow Valves (2)                          950                  110
  Angle Valves (2)                              3,600                  420
  Relief Valve                                  2.000                  230

Process Machinery:

  Centrifugal Pump                             10,000                 1.200

Instrumentation:

  Pressure Gauges (4)                           1,500                  170
  Liquid Level Gauge                            1.500                  170

Procedures and Practices:

  Visual Tank Inspection (external)                                     15
  Visual Tank Inspection (internal)                                     60
  Relief Valve Inspection                                               15
  Piping Inspection                                                    300
  Piping Maintenance                                                   120
  Valve Inspection                                                      30
  Valve Maintenance                                                    350


Total Costs                                   215.000               26.000
                                       114

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       TABLE 5-10.   ESTIMATED  TYPICAL  CAPITAL AND ANNUAL COSTS ASSOCIATED
                     WITH LEVEL 1  AMMONIA STORAGE SYSTEM
                                             Capital  Cost
                                               (1986  $)
                   Annual  Cost
                    (1986 $/yr)
Vessels:

  Storage Tank

Piping and Valves:

  Pipework
  Check Valve
  Ball Valves  (5)
  Excess Flow Valves  (2)
  Angle Valves  (2)
  Relief Valves  (2)

Process Machinery:

  Centrifugal Pump

Instrumentation:

  Pressure Gauges (4)
  Flow Indicator
  Load Cell
  Remote Level Indicator

Enclosures:

  Steel Building

Scrubbers:

  Water Scrubber

Diking:

  3 ft
220,000
 12.000
  1,100
  3.200
    950
  3.600
  4.000
 20.000
  1.500
  3.700
  1,500
  1,900
 10.000
268.000
                                                1.300
26.000
 1.300
    120
    370
    110
    420
    460
 2.300
   170
   430
   170
   220
 1.200
31.000
                         160
                                                                (Continued)
                                       115

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                             TABLE 5-10 (Continued)
                                            Capital Cost         Annual Cost
                                              (1986 $)           (1986 $/yr)
Procedures and Practices:

  Visual Tank Inspection (external)                                      15
  Visual Tank Inspection (internal)                                      60
  Relief Valve Inspection                                                30
  Piping Inspection                                                     300
  Piping Maintenance                                                    120
  Valve Inspection                                                       35
  Valve Maintenance                                                     400
Total Costs                                   553.000                65.000
                                        116

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       TABLE 5-11.  ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED
                    WITH LEVEL 2 AMMONIA STORAGE SYSTEM
                                            Capital Cost
                                               (1986 $)
                   Annual Cost
                   (1986 $/yr)
Vessels:

  Storage Tank

Piping and Valves:

  Pipework
  Reduced Pressure Device
  Ball Valves  (5)
  Excess Flow Valves  (2)
  Angle Valves  (2)
  Relief Valves  (2)
  Rupture Disks  (2)

Process Machinery:

  Centrifugal Pump

Instrumentation:

  Temperature Indicator
  Pressure Gauges  (6)
  Flow Indicator
  Load Cell
  Remote Level  Indicator
  Level Alarm
  High-Low Level Shutoff

Enclosures:

  Concrete Building

Scrubbers:

  Alkaline Scrubber

Diking:

     10 ft High  Concrete Dike
877.000
  6.000
  2,700
  3.200
    950
  3.600
  4.000
  1.100
 32.000
  2.200
  2,200
  3.700
 16.000
  1.900
    740
  1.900
 19.000
268,000
  7.400
102.000
    680
    310
    370
    110
    420
    460
    130
  3.700
    260
    260
    430
  1.800
    220
     90
    220
  2,200
 31,000
    870
                                                                (Continued)
                                       117

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                             TABLE 5-11 (Continued)
                                            Capital Cost
                                              (1986 $)
                     Annual Cost
                     (1986 $/yr)
Procedures and Practices:

  Visual Tank Inspection (external)
  Visual Tank Inspection (internal)
  Relief Valve Inspection
  Piping Inspection
  Piping Maintenance
  Valve Inspection
  Valve Maintenance
                            15
                            60
                            50
                           300
                           120
                            35
                           400
Total Costs
1.254.000
146.000
                                        118

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     TABLE 5-12.  ESTIMATED  TYPICAL  CAPITAL  AND  ANNUAL  COSTS  ASSOCIATED WITH
                  BASELINE WASTE WATER  TREATMENT AMMONIA STRIPPER

                                             Capital  Cost         Annual Cost
                                               (1986  $)            (1986 $/yr)
Equipment:

  Vessels and Machinery:

     Stripping Column

     Reboiler and Condenser

     Centrifugal Pumps  (3)
Total Vessels and Machinery
Piping and Valves:
a
Instrumentation:
Q
Maintenance and Inspections:
Total Costs
260,000
117,000
53.000

430,000
31,000
14,000
6,000
8,000
59.000
o
 Costs are based on using cost factors from Peters  and Timmerhaus  (50)  and  a
 total fixed capital cost of $1.8 million  (1986 basis)  (21)  for  a  10  tons/day
 ammonia recovery plant.
                                      119

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     TABLE 5-13.   ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
                  LEVEL 1 WASTE WATER TREATMENT AMMONIA STRIPPER

                                            Capital Cost         Annual Cost
                                              (1986 $)           (1986 $/yr)
Equipment:

  Vessels and Machinery:

     Stripping Column

     Reboiler and Condenser

     Centrifugal Pumps  (3)

     Total  Vessels and Machinery3             470,000               56.000

  Piping and Valves:3                         147,000               17,000

     Relief Valve                               2,000                  240

Instrumentation:3                              53,000                6,000

  Temperature Sensor                              360                   45
  Temperature Alarm                               360                   45
  Remote Temp. Indicator                        1,800                  220
  Remote Press. Indicator                       1,800                  220
  Flow Control Loops  (2)                       11,000                1,300

Diking:

  Curbing Around Reactor                        1,200                  150

Scrubber:

  Water Scrubber                              260,000               31,000
                            a
Maintenance and Inspections:                                         8,000

  Relief Valve Inspection                                               15


Total Costs                                   948,000               120,000

Q
 Costs are based on using cost factors from Peters and Timmerhaus  (50) and  a
 total fixed capital  cost of $1.8 million  (1986 basis) (21) for a  10 tons/day)
 ammonia recovery plant.
                                       120

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    TABLE 5-14.  ESTIMATED TYPICAL CAPITAL AND ANNUAL COSTS ASSOCIATED WITH
                 LEVEL 2 WASTE WATER TREATMENT AMMONIA STRIPPER

                                               Capital Cost     Annual Cost
                                                  (1986 $)        (1986 $/yr)
Equipment:
     Vessels and Machinery:
          Stripping Column
          Reboiler and Condenser
          Centrifugal Pumps  (3)
               Total Vessels and Machinerya      1.049,000        126,000
     Piping and Valves*:                            167,000         20,000
          Relief Valve  (2)                           7,400            880
          Rupture Disk  (2)                           2.300            280

Instrumentation8:                                   53.000          6,400
     Temperature Sensor                                360             45
     Temperature Alarm                                 360             45
     Temperature Switch                                540             65
     Remote Temp. Indicator                          1,800            220
     Remote Press. Indicator                         1.800            220
     Flow Control Loops  (2)                         11,000          1,300
     Flow Interlock System                           1,800            220
     All Loops on Computer Control                  201,000          2,400

Diking:
     3 ft High Retaining Wall                        3,000            360

Scrubber:
     Water Scrubber                                 260,000         31,000

Maintenance and Inspections3:                                       8,000
     Relief Valve Inspection                                           25


Total Costs                                      1,760.000        197,000


a Costs are based on using cost factors  from  Peters and  Timmerhaus (50) and a
  total fixed capital cost of  $1.8 million  (1986 basis)  (21)  for a 10 tons/day
  ammonia recovery plant.

  Computer control costs are determined  using cost  estimating factors from
  Va1 1 e*—Ri e>fi1-ra  fS11.
Valle-Riestra  (51).
                                        121

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 TABLE 5-15.  EQUIPMENT SPECIFICATIONS ASSOCIATED WITH AMMONIA STORAGE SYSTEM
Equipment Item
       Equipment Specifications
 Reference
VESSELS:
  Storage Tank
PIPING AND VALVES:
  Pipework
  Check Valve

  Ball Valve

  Excess Flow
  Angle Valve
  Relief Valve
  Reduced Pres-
    sure Valve
  Rupture Disk
Baseline:  10,000 gal Carbon Steel
           Storage Tank, 250 psig rating
Level #1:  10,000 gal Carbon Steel with
           1/8 in. Corrosion Protection
           300 psig
Level #2:  10,000 gal Type 316 Stainless
           Steel, 375 psig rating

Baseline:  4 in. Schedule 40 Carbon Steel
Level #1:  4 in. Schedule 80 Carbon Steel
Level #2:  4 in. Schedule 80 Type 316
           Stainless Steel, 100 ft. in
           Length
4 in. Vertical Lift Check Valve, Carbon
Steel Construction
4 in. Class 300, Carbon Steel Body, Monel®
Ball and Trim
4 in. Standard Valve
4 in. Carbon Steel Construction
2 in. x 3 in. Class 300 Inlet and Outlet
Flange, Angle Body, Closed Bonnet with
Screwed Cap, Carbon Steel Body
Double Check Valve Type Service with
Internal Air Gap and Relief Valve
2 in. Monel® Disk and Carbon
Steel Holder
PROCESS MACHINERY:
  Centrifugal Pump  Baseline:

                    Level 1:
                    Level 2:
           Single Stage, Carbon Steel
           Construction, Stuffing Box
           Single Stage, Type 316 Stainless
           Steel Construction, Double
           Mechanical Seal
           Type 316 Stainless Steel Con-
           struction, Magnetically-Coupled
                                                                   50.52.53.54
55
52,56

50,52,56
52
57
52

50

53,58,59



52,60


52.60

52,60
                                                                 (Continued)
                                      122

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                            TABLE 5-15 (Continued)
Equipment Item
       Equipment Specifications
Reference
INSTRUMENTATION:
  Pressure Gauge

  Liquid Level
    Gauge
  Temperature
    Indicator
  Flow Indicator

  Level Indicator
  Load Cell
  High-low Level
    Shutoff

ENCLOSURE:
  Building
SCRUBBER:
DIKING:
Diaphragm Sealed, Hastelloy C Diaphragm,
0-1,000 psi
Differential Pressure Type                     50,61

Thermocouple, Thermowell, Electronic
Indicator                                      50,52,61
Differential Pressure Cell and Transmitter
and Associated Flowmeter                       50,61
Differential Pressure Type Indicator           50,52,61
Electronic Load Cell                           50,61,62
Solenoid Valve, Switch, and Relay System       50,52,61
Level #1:   26-Gauge Steel Walls and Roof,
            Door, Ventillation System          57
Level #2:   10 in. Concrete Walls,
            26-Gauge Steel Roof                64

Level #1 and 2:  Spray Tower, Monel® Con-
            struction, 4 ft. x 12 ft..
            Water Sprays

Level #1:   6 in. Concrete Walls,
            3 ft. high                         57
Level #2:   10 in. Concrete Walls, Top
            of Tank Height
                                       123

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            TABLE 5-16.  MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE  AMMONIA STORAGE SYSTEM
ts>



Vessels:
Storage Tank
Piping and Valves:
Pipework
Check Valves
Ball Valves (5)
Excess Flow Valves (2)
Angle Valves (2)
Relief Valve
Process Machinery:
Centrifugal Pump
Instrumentation:
Pressure Gauges (4)
Liquid Level Gauge
Total Costs
Materials
Cost


86.000

900
320
2,000
600
2.400
1.300

4,900

800
800
100.000
Labor
Cost


39,000

2.100
30
150
40
40
50

2,100

200
200
44.000
Direct
Costs
(1986 $)

125.000

3.000
350
2.150
640
2.440
1.330

7,000

1.000
1.000
144. 000
Indirect
Costs


44. 000

1.100
120
750
220
860
460

2.500

350
350
50.000
Capital
Cost


186.000

4.500
520
3.200
950
3.600
2,000

11.000

1,500
1,500
215.000

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             TABLE 5-17.  MATERIAL AND LABOR  COSTS  ASSOCIATED WITH LEVEL 1 AMMONIA STORAGE SYSTEM
NJ
Ln



Vessels:
Storage Tank
Piping and Valves :
Pipework
Check Valves
Ball Valves (5)
Excess Flow Valves (2)
Angle Valves (2)
Relief Valve (2)
Process Machinery:
Centrifugal Pump
Instrumentation:
Pressure Gauges (4)
Flow Indicator
Liquid Level Gauge
Remote Level Indicator
Enclosures:
Steel Building
Scrubbers:
Water Scrubber
Diking:
3 ft. High Concrete
Diking
Total Costs
Materials
Cost


102.000

5.300
640
2.000
600
2.400
2.600

9.300

800
2.000
800
1,000

4.600

125.000


390
259.000
Labor
Cost


46, 000

2,500
60
150
40
40
100

4.000

200
500
200
250

2,300

56.000


520
113.000
Direct
Costs
(1986 $)

148.000

7.800
700
2.150
640
2.440
2.660

13.300

1.000
2.500
1.000
1.250

6.900

181.000


900
372.000
Indirect
Costs


52.000

2.700
250
750
220
860
920

4.700

350
880
350
440

2.400

63,000


320
130.000
Capital
Cost


220, 000

12.000
1,100
3.200
950
3.600
4.000

20. 000

1.500
3.700
1.500
1,900

10. 000

268.000


1.300
553,000

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              TABLE 5-18.   MATERIAL  AND  LABOR COSTS ASSOCIATED WITH LEVEL 2 AMMONIA STORAGE SYSTEM
N5
(f*



Vessels:
Storage Tank
Piping and Valves:
Pipework
Reduced Pres. Device
Ball Valves (5)
Excess Flow Valves (2)
Angle Valves (2)
Relief Valve (2)
Rupture Disks (2)
Process Machinery:
Centrifugal Pump
Instrumentation:
Temperature Indicator
Pressure Gauges (6)
Flow Indicator
Load Cell
Remote Level Indicator
Level Alarm
High-Low Level Shut off
Enclosures:
Concrete Building
Scrubbers:
Water Scrubber
Diking:
10 ft. High
Concrete Dike
Total Costs
Materials
Cost


407.000

1.400
1.600
2.000
600
2.400
2,600
650

15.000

1.200
1.200
2.000
8.400
1.000
400
1.000

6.100

125,000


2.200
582.000
Labor
Cost


183,000

2.600
200
150
40
40
100
75

6.400

300
300
500
2.100
250
100
250

6.600

56.000


2.850
262,000
Direct
Costs
(1986 $)

590,000

4.000
1,800
2.150
640
2.440
2,660
725

21.400

1.500
1.500
2.500
10.500
1.250
500
1,250

12.700

181,000


5,000
844, 000
Indirect
Costs


207.000

1.400
630
750
220
860
920
250

7,500

530
530
880
3,700
440
180
440

4.500

63,000


1.800
295,000
Capital
Cost


877,000

6.000
2.700
3.200
950
3,600
4.000
1.100

32.000

2.200
2.200
3.700
16.000
1.900
740
1,900

19.000

268.000


7.400
1,254.000

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       TABLE 5-19.  EQUIPMENT SPECIFICATIONS ASSOCIATED WITH WASTE WATER
                    TREATMENT AMMONIA STRIPPING PROCESS
   Equipment Item
      Equipment Specification
 Reference
VESSELS AND MACHINERY:
PIPING AND VALVES:
  Pipework
  Relief Valve
  Rupture Disk
INSTRUMENTATION:
  Temp. Sensor
  Temp. Alarm
  Temp. Switch

  Remote Temp.
    Indicator
  Remote Press.
    Indicator
  Flow Control Loop

  Flow Interlock
    System

DIKING:
Ammonia Stripper and Associated Re-          21
boiler and Condenser as Defined in
Reference
Baseline:  4 in. Schedule 40
           Carbon Steel, 360 ft.             55
Level #1:  Schedule 80 Carbon Steel
Level #2:  Schedule 80 Type 316
           Stainless Steel
2 in. x 3 in. Class 300 Inlet and
Outlet Flanges, Angle Body, Closed
Bonnet with Screwed Cap, Carbon Steel
Body
2 in. Monel® Disk and Carbon
Steel Holder
Thermocouple and Associated Thermowell
Indicating and Audible Alarm
Two-Stage Switch with Independently
Set Actuation
Transmitter and Associated Electronic
Indicator
Transducer, Transmitter and Electronic
Indicator
4 in. Globe Control Valve, Flowmeter
and PID Controller
Solenoid Valve, Switch, and Relay
System
                         Level #1:  6 in. High Concrete Curbing
                         Level #2:  3 ft. High Concrete Retain-
                                    ing Wall
   52

53,58,59


50,52,61
51,58,63

50,61

50,61

50,61

50,61

50.52.57,61


   57
SCRUBBER:
Level #1 and #2:  Spray Tower, Monel*
           Construction 4 ft. x  12 ft.,
           Water Sprays                      64
                                        127

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              TABLE 5-20.  MATERIAL AND LABOR COSTS ASSOCIATED WITH BASELINE WASTE WATER
                           TREATMENT AMMONIA STRIPPER
NJ
oo
Materials Labor Direct Indirect
Cost Cost Costs Costs
Capital
Cost
(1986 $)
Equipment :
Vessels and Machinery:
Stripping column
Reboiler and Condenser
Centrifugal Pumps (3)
Total Ves. and Mach. a 125,000 56,000 181,000 45,000
Piping and Valves:3 45.000 37,000 82,000 20,000
Instrumentation:3 28,000 9,000 37,000 9,000
Total Costs 198,000 102,000 300,000 74,000





260,000
117,000
53,000
430.000
       Costs are based on using cost factors from Peters  and Timmerhaus  (50)  and  a total fixed
       capital cost of $1.8 million  (1986 basis)  (21) for a 10  tons/day  ammonia recovery plant.

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                TABLE 5-21.   MATERIAL AND LABOR  COSTS  ASSOCIATED WITH LEVEL 1 WASTE WATER
                             TREATMENT AMMONIA STRIPPER
VO
Materials Labor
Cost Cost
Direct Indirect
Costs Costs
Capital
Cost
(1986 $)
Equipment:
Vessels and Machinery:
Stripping column
Reboiler and Condenser
Centrifugal Pumps (3)
Total Ves. and Mach. a 226.000 101.000
Piping and Valves:3 77,000 25.000
Relief Valve 1,300 50
Instrumentation:3 28.000 9,000
Temperature Sensor 200 50
Temperature Alarm 200 50
Remote Temp. Indicator 1,000 250





327.000 82.000
102.000 25.000
1.350 340
37.000 9.000
250 60
250 60
1.250 310





470, 000
146. 000
2,000
53,000
360
360
1.800
                                                                                   (Continued)
       Costs are based  on using cost factors from  Peters  and  Timmerhaus (50)  and a total fixed
       capital  cost  of  $1.8 million  (1986 basis)  (21)  for a 10  tons/day ammonia recovery plant.

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TABLE 5-21 (Continued)

Remote Press. Indicator
Flow Control Loops (2)
Diking:
Curbing Around Reactor
Scrubber:
Water Scrubber
Total Costs
Materials
Cost

1,000
6,000

500

125,000
466.000
Labor
Cost

250
1,500

350

56.000
194.000
Direct
Costs
(1986 $)
1.250
7.500

850

181.000
660.000
Indirect
Costs

310
1.900

210

45.000
164,000
Capital
Cost

1,800
11.000

1.200

260.000
948.000

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        TABLE 5-22.   MATERIAL AND LABOR COSTS ASSOCIATED WITH LEVEL 2 WASTE WATER
                     TREATMENT AMMONIA STRIPPER
Materials Labor
Cost Cost
Direct
Costs
Indirect Capital
Costs Cost
(1986 $)
Equipment :
Vessels and Machinery:
Stripping column
Reboiler and Condenser
Centrifugal Pumps (3)
Total Ves. and Mach.a 504.000 226.000
Piping and Valves:3 87.000 29.000
Relief Valve (2) 5.000 100
Rupture Disk (2) 1.500 100
Instrumentation:3 28,000 9.000
Temperature Sensor 200 50
Temperature Alarm 200 50





730. 000
116.000
5.100
1,600
37. 000
250
250





182.000 1.049,000
29.000 167.000
1.300 7.400
400 2. 300
9,000 53.000
60 360
60 360
                                                                             (Continued)
Costs are based on using cost factors from Peters and Timmerhaus (50) and a total fixed
capital cost of $1.8 million (1986 basis) (21) for a 10 tons/day ammonia recovery plant.

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                                         TABLE 5-22  (Continued)
Co
N>
Materials Labor Direct
Cost Cost Costs
Indirect Capital
Costs Cost
(1986 $)
Temperature Switch 300 75 375
Remote Temp. Indicator 1,000 250 1.250
Remote Press. Indicator 1.000 250 1,250
Flow control Loops (2) 6.000 1.500 7.500
Flow Interlock System 1,000 250 1,250
All Loops on Computer 105.000 35.000 140.000
Control
Diking:
3 ft. high retaining wall 900 1. 200 2, 100
Scrubber:
Water Scrubber 125,000 56.000 181,000
Total Costs 866,000 359.000 1.225.000
95 540
310 1.800
310 1,800
1.900 11,000
310 1,800
35.000 201.000

530 3.000

45,000 260.000
305.000 1.760.000
        Computer control costs are determined using cost  estimating  factors  from Valle-Riestra
        / c- -t ^
        (51).

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                TABLE 5-23.  FORMAT FOR TOTAL FIXED CAPITAL  COST
Item No.                         Item                             Cost


   1                Total Material Cost

   2                Total Labor Cost

   3                Total Direct Cost                        Items  1+2

   4                Indirect Cost Items  (Engineering
                    & Construction Expenses)                 0.35 x Item 3a

   5                Total Bare Module Cost                   Items  (3  + 4)

   6                Contingency                              (0.05  x Item 5)

   7                Contractor's Fee                         0.05 x Item 5

   8                Total Fixed Capital  Cost                 Items  (5+6+7)


 For storage facilities, the indirect cost factor is 0.35.   For  process
 facilities, the indirect cost factor is 0.25.

 For storage facilities, the contingency cost factor is  0.05.  For process
 facilities, the contingency cost factor is 0.10.
                                      133

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     The computation of total fixed capital as shown in Table 5-23 begins with
the total direct cost for  the  system  under consideration.  This total  direct
cost is  the  total  direct installed cost of all  capital  equipment  comprising
the system.   Depending  on the specific equipment  item involved,  the  direct
capital cost was available  or  was  derived  from uninstalled equipment costs by
computing costs of installation separately.  To obtain the total fixed capital
cost,  other  costs  obtained  by  utilizing factors  are added to the total direct
costs.

     The first group of  other  cost elements is indirect costs.   These include
engineering and supervision, construction expenses, and various other  expenses
such as  administration  expenses,  for example.   These  costs  are computed by
multiplying total direct costs by a factor  shown in Table 5-23.  The factor is
approximate,   is  obtained from the cost literature, and  is based  on previous
experience with  capital  projects  of a  similar  nature.   Factors can have  a
range of  values  and vary  according to technology  area and for individual
technologies within an  area.   Appropriate  factors  were  selected  for  use in
this report based on judgement and experience.

     When the indirect costs are added  to  the total direct costs, total bare
module cost  is obtained.   Some  additional  cost elements such as contractor's
fee and contingency are calculated by applying and  adding appropriate  factors
to the total bare module cost as shown  in Table 5-23 to obtain the total fixed
capital cost.

     Annual Cost—Annual costs are obtained for each of the equipment  items by
applying a factor  for both capital recovery and for maintenance  expenses  to
the direct cost  of each  equipment  item.  Table 5-24 defines  the cost elements
and appropriate  factors  comprising these  costs.   Additional  annual costs are
incurred  for procedural  items  such as valve and vessel  inspections, for
example.  When all of these individual  costs  are added,  the  total  annual cost
is obtained.
                                      134

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                    TABLE 5-24.  FORMAT FOR TOTAL ANNUAL COST
Item No.                         Item                             Cost


   1                Total Direct Cost

   2                Capital Recovery on Equipment           0.163 x  Item  1
                    Items

   3                Maintenance Expense on Equipment        0.01 x Item 1
                    Items

   4                Total Procedural Items

   5                Total Annual Cost                       Items  (2+3+4)
                                      135

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Sources of Information—
     The costs presented in  this  report  are derived from cost information  in
existing published sources  and also from recent vendor  information.   It was
the objective of  this  effort to  present  cost levels for ammonia  process and
storage facilities using  the best costs for available sources.   The primary
sources of cost information are Peters and Timmerhaus (50). Chemical Engineer-
ing (65). and Valle-Riestra  (51)  supplemented  by  other sources and references
where necessary.  Adjustments  were  made  to update all costs  to a June  1986
dollar basis.   In addition,  for some equipment items, well-documented costs
were not available and they had to be developed from component costs.

     Costs in this document  reflect  the  "typical" or "average" representation
for specific equipment items.  This  restricts  the use  of data in  this report
to:

     •    Preliminary estimates used for policy planning,

     •    Comparison of relative costs of different levels or  systems.
          and

     •    Approximations of  costs  that might be  incurred for a specific
          application.

     The costs in this report  are considered to be "order of magnitude"  with  a
+50 percent  margin.   This  is  because the  costs  are based on preliminary
estimates and many are updated from literature sources.  Large departures  from
the design basis  of a particular system presented in this manual  or  the  advent
of a  different  technology might cause the  system cost  to vary by a greater
extent than this.  If used as  intended, however,  this document will  provide a
reasonable source of preliminary cost information for the facilities covered.
                                      136

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     When comparing costs  in  this manual to costs from other  references,  the
user should be sure the design  bases  are comparable and that  the  capital  and
annual costs as defined here are  the  same as the  costs being compared.

Cost Updating—
     A1.1 costs  in this report  are expressed  in  June 1986 dollars.   Costs
reported in the literature  were updated using cost indices for materials  and
labor.

     Costs  expressed  in  base year  dollars  may be  adjusted to dollars  for
another year by applying cost indices as  shown in the following  equation:

         ,                   , , ,              ..    new base year index
     new base year cost = old base year  cost x -,-. v	*	r—:—
              J                                 old base year index

The Chemical Engineering  (CE) Plant  Cost Index was used in updating  cost  for
this report.  For June 1986, the  index  is 316.3.

Equipment Costs—
     Most  of  the equipment costs presented  in  this manual were obtained
directly from  literature  sources of  vendor information and correspond  to a
specific design  standard.   Special cost estimating techniques,  however, were
used in determining the costs associated with  vessels,  piping systems, scrub-
bers,  diking,  and enclosures.   The  techniques used are  presented  in the
following subsections of this manual.

     Vessels—The total purchased cost  for a vessel, as dollars  per  pound of
weight of fabricated unit  f.o.b.  with carbon  steel as the basis  (January  1979
dollars) were  determined  using  the following equation from Peters and Timmer-
haus  (50):

                                                    —0 34
             Cost =  [50(Weight  of Vessel in Pounds)  u'-1^]
                                       137

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The vessel weight is determined using appropriate design equations as given by
Peters and Timmerhaus  (50)  which allow for  wall  thickness adjustments  for
corrosion allowances, for example.  The vessel weight is increased by a factor
of 0.15 for horizontal vessels  and  0.20 for  vertical vessels to  account  for
the added weight due to nozzles, manholes, and skirts or saddles.  Appropriate
factors are applied for different materials of construction as given in Peters
and Timmerhaus  (50).  The  vessel costs  are updated using  cost factors.
Finally a shipping cost amounting to 10 percent of the purchased  cost is added
to obtain the delivered equipment cost.

     Piping—Piping  costs  were  obtained  using cost  information and  data
presented by Yamartino  (55).   A  simplified  approach  is  used in which it  is
assumed that a certain length of piping containing a given number of valves,
flanges, and fittings  is contained in  the storage or process  facility,   the
data presented  by Yamartino  (55) permit  cost  determinations for  various
lengths, sizes, and  types of piping systems.   Using these factors, a represen-
tative estimate can  be  obtained for each of  the storage and  process  facili-
ties.

     Diking—Diking  costs were  estimated  using Mean's Manual  (57)  for rein-
forced concrete walls.  The following assumptions were made in determining the
costs.  The dike contains the entire contents of a tank in the event of a  leak
or release.  Two  dike  sizes are possible: a three-foot high dike,  six-inches
thick and a top-of-tank height  dike ten inches thick.  The tanks are raised
off the  ground  and  are not volumetrically included in the volume enclosed by
the diking.  These  assumptions  facilitate cost  determination for  any size
diking system.

     Enclosures—Enclosure  costs were  estimated  using Mean's Manual  (57)  for
both  reinforced  concrete  and  steel-walled  buildings.   The  buildings are
assumed  to enclose  the  same area and volume  as the top-of-tank  height  dikes.
The concrete  building is ten-inches thick with  a 26-gauge steel roof  and a
metal  door.   The steel building has 26 gauge roofing and  siding and metal
                                       138

-------
door.  The cost of a ventilation system was determined using a typical  1.000
scfm unit and  doubling  the cost to account for duct work and requirements for
the safe enclosure of hazardous  chemicals.

     Scrubbers—Scrubber  costs  were estimated  using the following  equation
from the Gard  (64) manual for spray towers based on  the  actual  cubic feet per
minute of flow at a chamber velocity of 600 feet/minute.

                        Costs =  0.235 x  (ACFM + 43.000)

                           3
A release rate of 10,000 ft /minute was assumed for  the  storage vessel  systems
and  an  appropriate rate was  determined for  process system  based on  the
quantity of  hazardous  chemicals present in the system at  any one time.  For
the ammonia  stripper system, a release rate of  10,000 ft /minute  was assumed.
In addition  to the spray tower,  the  costs also include pumps and a  storage
tank for the scrubbing  medium.   The costs  presented are updated  to June  1986
dollars.
Installation Factors—
     Installation  costs  were developed for  all  equipment items included  in
both the process and storage systems.  The costs include  both  the material and
labor  costs  for installation of a particular  piece  of  equipment.   The costs
were obtained  directly from literature  sources  and  vendor  information or
indirectly by  assuming a certain percentage of  the  purchased equipment cost
through the use of estimating factors obtained from  Peters and Timmerhaus  (50)
and Valle-Riestra  (51).   Table  5-25  lists the  cost factors used or the refer-
ence from which the  cost was obtained directly.   Many of  the  costs obtained
from the literature were updated to  June 1986 dollars using a 10 percent  per
year rate of increase for labor  and  cost  indices for materials associated with
installation.
                                       139

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                   TABLE 5-25.  FORMAT FOR INSTALLATION COSTS
Equipment Item                                         Factor or Reference


Vessels:

  Storage Tank                                               0.45
  Expansion Tank                                             0.25

Piping and Valves:

  Pipework                                                   Ref. 55
  Expansion Loop                                             Ref. 52
  Reduced Pressure Device                                    Ref. 52
  Check Valves                                               Ref. 52
  Gates Valves                                               Ref. 52
  Ball Valves                                                Ref. 52
  Excess Flow Valves                                         Ref. 52
  Angle Valves                                               Ref. 57
  Relief Valves                                              Ref. 52
  Rupture Disks                                              Ref. 52

Process Machinery:

  Centrifugal Pump                                           0.43
  Gear Pump                                                  0.43

Instrumentation:

  All Instrumentation Items                                  0.25

Enclosures:                                                  Ref. 57

Diking:                                                      Ref. 57

Scrubbers:                                                   0.45
                                        140

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                                   SECTION 6

                                  REFERENCES
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     Inc.. Arlington. VA, 1984.

 2.  Dean, J.A., (ed.).  Lange's Handbook of Chemistry.  12th  ed., McGraw-Hill
     Book Co., 1979.

 3.  Mark, H.F.; Othmer. D.F.; Overberger, C.G.; and Seaborg, G.T.,
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 4.  Perry, R.H., and Chilton, C.H.,  (eds.)  Chemical Engineers' Handbook,  5th
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 6.  Blanken, J.M.,  Behavior of Ammonia in the Event of  a Spillage.  CEP
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 7.  Safety Requirements for the Storage and Handling of Anhydrous Ammonia.
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     New York, NY,  1981.

 8.  U.S. Dept. of Health, Education, and Welfare, Criteria for  a Recommended
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 9.  Compressed Gas Association, Ammonia  (Anhydrous).  In Handbook of  .
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10.  Tatken,  R.L. and R.J. Lewis,  (eds.).  Registry of Toxic  Effects of
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11.  Air Products and Chemicals, Inc.  Specialty Gas Material Safety Data
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12.  Kent, J.A., ed.  Riegel's Handbook of Industrial Chemistry, 8th ed.,  Van
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13.  Williams. G. P..  Causes of Ammonia Plant Shutdowns.  CEP Technical
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                                      141

-------
14.  Prescott,  G.R., and F.W. Badger.  Cracking Problems in Ammonia
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15.  Lawler, G.M..   (ed.).  Chemical Origins and Markets, Fifth Edition.
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16.  Considine, D.M., (ed.).  Chemical and Process Technology Encyclopedia,
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17.  Slack, A.V., and James, G.R., (eds.).  Ammonia, Part IV, Marcel Dekker,
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18.  Lowenheim, F.A., and M.K. Moran.  Faith, Keyes, and Clark's Industrial
     Chemicals, Fourth Ed., John Wiley & Sons, 1975.

19.  Jojima, T.  Urea Reactor Failure.  CEP Technical Manual, Ammonia  Plant
     Safety and Related Facilities, Volume 21, AIChE, 1979.

20.  Mark, H.F.; Othmer, D.F.; Overberger. C.G.; and Seaborg. G.T.,
     Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.. Volume  15,  John
     Wiley & Sons,   1983.

21.  Chevron Waste Water Treating Process - WWT Process.  Chevron Research
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22.  Klett, R.J.  Treat Sour Water for Profit.  Hydrocarbon  Processing,
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23.  The Badger Company, Inc.  Acrylonitrile  (Sohio process).  Hydrocarbon
     Processing, November  1981.

24.  System Practices for Ammonia.   In 1986 Handbook - Refrigeration  Systems
     and Applications, American Society of Heating, Refrigerating and  Air
     Conditioning Engineers,  Inc., Atlanta, GA. 1986.

25.  Conversation between M.  Stohs of Radian  Corporation and a representative
     of General Battery Corporation, Reading,  PA, August 1986.

26.  Mark. H.F.; Othmer, D.F.; Overberger. C.G.; and Seaborg, G.T.,
     Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., Volume  12,  John
     Wiley & Sons,   1983.

27.  Conversation between M.  Stohs of Radian  Corporation and a representative
     of PB&S Chemical Company, Henderson. KY,  August 1986.

28.  Recommended Rules  for  Design  and  Construction  of Large  Welded
     Low-Pressure Storage Tanks.   API  Standard 620, American Petroleum
     Institute. Washington,  D.C.,  1970.
                                       142

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29.  ASME Boiler and Pressure Vessel Code.  ANSI/ASME BPV-VIII-1, American
     Society of Mechanical Engineers, New York. NY. 1983.

30.  Chemical Plant and Petroleum Refinery Piping.  ANSI/ASME B31.3, American
     National Standards Institute. Inc. New York. NY.  1980.

31.  Steel Valves.  ANSI/ASME B16.5, American National Standards Institute.
     Inc., New York, NY, 1977.

32.  Steel Pipe Flanges and Flanged Fittings.  ANSI/ASME B16.5, American
     National Standards Institute, Inc., New York, NY, 1977.

33.  Blanken, J.M.  Stress Corrosion Cracking of Ammonia Storage Spheres:
     Survey and Panel Discussion.  CEP Technical Manual, Ammonia Plant Safety
     and Related Facilities, Volume 24, AIChE, 1984.

34.  Lunde, L.  Stress Corrosion Cracking of Steels in Ammonia:  Specially
     Vapor-Phase Cracking.  CEP Technical Manual, Ammonia  Plant Safety and
     Related Facilities, Volume 24, AIChE, 1984.

35.  American National Standard for Refrigeration Piping.  ANSI B31.5,
     American National Standards Institute, Inc., New York, NY, 1974.

36.  American National Standard for Power-Operated Pumps for Anhydrous
     Ammonia and LP Gas.  ANSI/UL 51, American National Standards Institute,
     Inc., New York. NY, 1981.

37.  Pressure Relief Device Standards - Part 3 - Compressed Gas Storage
     Containers.  Pamphlet S-1.3, Compressed Gas Association,  Inc., Arlington,
     VA, 1984.

38.  Prijatel, J.  Failure Analysis of Ammonia Plant Shutdown  Instrumentation
     and Control.  CEP Technical Manual. Ammonia Plant Safety  and Related
     Facilities. Volume 24, AIChE, 1984.

39.  Lees, F.P.  Loss Prevention in the Process Industries - Hazard
     Identification, Assessment, and Control, Volumes 1 &  2, Butterworths,
     London, 1983.

40.  Aarts, J.J. and D.M. Morrison.  Refrigerated Storage  Tank Retainment
     Walls.  CEP Technical Manual, Ammonia Plant Safety and Related
     Facilities, Volume 23, American Institute of Chemical Engineers, New
     York, NY, 1981.

41.  Roberts, R.H. and S.E. Handman.  Minimize Ammonia Releases, Hydrocarbon
     Processing, March 1986.

42.  Feind, K.  Reducing Vapor Loss in Ammonia Tank Spills.  CEP Technical
     Manual, Ammonia Plant Safety and Related Facilities,  Volume  17,  American
     Institute of Chemical Engineers, New York', NY, 1975.
                                       143

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43.   Radian Laboratory Notebook Number 215.  for EPA Contract 68-02-3994. Work
     Assignnment 94,  Page 5,  1986.

44.   Hiltz, R.H. and  S.S. Gross.  The Use of Foams to Control the Vapor Hazard
     from Liquified Gas Spills.  In Control  of Hazardous Material Spills -
     Proc. 1980 National Conference on Control of Hazardous Material Spills.
     Louisville. KY.  May 1980.

45.   Clark, W.D.  Using Fire Foam on Ammonia Spills.  CEP Technical Manual,
     Ammonia Plant Safety and Related Facilities, Volume 18, American
     Institute of Chemical Engineers, New York, NY, 1976.

46.   Hiltz, R.  Part  3 - Vapor Hazard Control.  In Bennett, G.F., Feates,
     F.S., and Wilder, I.  Hazardous Materials Spills Handbook, McGraw-Hill,
     1982.

47.   Greiner,  M.L.  Emergency Response Procedures for Anhydrous Ammonia Vapor
     Release.   CEP Technical Manual, Ammonia Plant Safety and Related
     Facilities, Volume 24, American Institute of Chemical Engineers, New
     York, NY, 1984.

48.   McQuaid,  J. and  A.F. Roberts.  Loss of Containment - Its Effects and
     Control.   In Developments  '82  (Institution of Chemical Engineers Jubilee
     Symposium), London, England, April 1982.

49.   Kubias, F. 0.  Technical Safety Audit.   Presented at the Chemical
     Manufacturers Association  Process Safety Management Workshop.  Arlington,
     VA,  May 7-8. 1985.

50.   Peters, M.S. and K.D. Timmerhaus.  Plant Design and Economics  for
     Chemical Engineers.  McGraw-Hill Book Company, New York, NY,  1980.

51.   Valle-Riestra, J.F.  Project Evaluation in  the Chemical Process Irius-
     tries.  McGraw-Hill Book Company, New York, NY, 1983.

52.   Richardson Engineering Services, Inc.  The Richardson  Rapid  Construction
     Cost Estimating System, Volume  1-4, San Marcos, CA,  1986.

53.   Pikulik,  A. and H.E. Diaz.   Cost Estimating for Major  Process  Equipment.
     Chemical Engineering, October  10, 1977.

54.   Hall, R.S., J. Matley, and K.J. McNaughton.   Cost  of  Process Equipment.
     Chemical Engineering, April  5,  1982.

55.   Yamartimo, J.  Installed Cost  of Corrosion-Resistant  Piping-1978.
     Chemical Engineering, November  20,  1978.

56.   Telephone  conversation between  J.D. Quass of  Radian Corporation and a
     representative of Mark Controls Corporation.   Houston,  TX,  August  1986.
                                       144

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57.  R.S. Means Company. Inc.  Building Construction  Cost  Data 1986  (44th
     Edition). Kingston, MA.

58.  Telephone conversation between J.D. Quass  of  Radian Corporation and a
     representative of Zook Enterprises.   Chagrin  Falls, OH,  August  1986.

59.  Telephone conversation between J.D. Quass  of  Radian Corporation and a
     representative of Fike Corporation.   Houston,  TX, August 1986.

60.  Green, D.W.  (ed.).  Perry's Chemical  Engineers'  Handbook (Sixth Edition).
     McGraw-Hill Book Company, New York, NY,  1984.

61.  Liptak, B.C.  Costs of Process Instruments.   Chemical Engineering,
     September 7, 1970.

62.  Liptak, B.C.  Costs of Viscosity, Weight,  Analytical  Instruments.
     Chemical Engineering, September 21, 1970.

63.  Liptak, E.G.  Control-Panel Costs, Process Instruments.   Chemical
     Engineering, October 5.  1970.

64.  Capital and Operating Costs of Selected  Air Pollution Control Systems.
     EPA-450/5-80-002, U.S. Environmental  Protection  Agency,  1980.

65.  Cost indices obtained from Chemical Engineering.  McGraw-Hill Publishing
     Company, New York, NY, June 1974, December 1985, and  August  1986.
                                       145

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                                  APPENDIX A
                                   GLOSSARY

     This glossary defines selected terms used in the text of this manual
which might be unfamiliar to some users or which might be used differently by
different authors.

Accidental release;  The unintentional spilling, leaking, pumping, purging,
emitting, emptying, discharging, escaping, dumping, or disposing of a toxic
material into the environment in a manner that is not in compliance with a
plant's federal, state, or local environmental permits and results in toxic
concentrations in the air that are a potential health threat to the
surrounding community.

Assessment;  The process whereby the hazards which have been identified are
evaluated in order to provide an estimate for the level of risk.

Cavitation;  The formation and collapse of vapor bubbles in a flowing liquid.
Specifically the formation and collapse of vapor cavities in a pump when there
is sufficient resistance to flow at the inlet side.-

Containment/control;  A system to which toxic emissions from safety relief
discharges are routed to be controlled.  A caustic scrubber and/or flare can
be containment/control devices.  These systems may serve the dual function of
destructing continuous process exhaust gas emissions.

Creep failure;  Failure of a piece of metal as a result of creep.  Creep is
time dependent deformation as a result of stress.  Metals will deform when
exposed to stress.  High levels of stress can result in rapid deformation and
rapid failure.  Lower levels of stress can result in slow deformation and
protracted failure.
                                       146

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Deadheading;  Closing or nearly closing or blocking the discharge outlet or
piping of an operating pump or compressor.

Electromotive Series of Metals;  A list of metals and alloys arranged
according to their standard electrode potentials; which also reflects their
relative corrosion potential.

Enthalpy;  A thermodynamic property of a chemical related to its energy
content at a given condition of temperature, pressure and physical state.
Enthalpy is the internal energy added to the product of pressure times volume.
Numerical values of enthalpy for various chemicals are always based on the
change in enthalpy from an arbitrary reference pressure and temperature, and
physical state, since the absolute value cannot be measured.

Facility;  A location at which a process or set of processes are used to
produce, refine or repackage chemicals, or a location where a large enough
inventory of chemicals are stored so that a significant accidental release of
a toxic chemical is possible.

Hazard;  A source of danger.  The potential for death, injury or other forms
of damage to life and property.

Hygroscopic;  Readily absorbing and retaining moisture, usually in reference
to readily absorbing moisture from the air.

Identification;  The recognition of a situation, its causes and consequences
relating to a defined potential, e.g. Hazard Identification.

Mild steel;  Carbon steel containing a maximum of about 0.25% carbon.  Mild
steel is satisfactory for use where severe corrodents are not encountered or
where protective coatings can be used to prevent or reduce corrosion rates to
acceptable levels.
                                     147

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Mitigation;  Any measure taken to reduce the severity of the adverse effects
associated with the accidental release of a hazardous chemical.

Olefinic hydrocarbons;  A specific subgroup of aliphatic hydrocarbons sharing
the common characteristic of at least one unsaturated carbon-to-carbon atomic
bond in the hydrocarbon molecule, and with straight or branched chain
structure.

Passivation film;  A layer of oxide or other chemical compound of a metal on
its surface that acts as a protective harrier against corrosion or further
chemical reaction.

Plant;  A location at which a process or set of processes are used to produce.
refine, or repackage, chemicals.

Prevention;  Design and operating measures applied to a process to ensure that
primary containment of toxic chemicals is maintained.  Primary containment
means confinement of toxic chemicals within the equipment intended for normal
operating conditions.

Primary Containment; The containment provided by the piping, vessels and
machinery used in a facility for handling chemicals under normal operating
conditions.

Probability/potential;  A measure, either qualitative or quantitative, that an
event will occur within some unit of time.

Process;  The sequence of physical and chemical operations for the production,
refining, repackaging or storage of chemicals.

Process machinery;  Process equipment, such as pumps, compressors, heaters, or
agitators, that would not be categorized as piping and vessels.
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 Protection;  Measures  taken  to  capture or  destroy  a  toxic chemical  that has
 breached primary  containment, but before an uncontrolled release  to the
 environment has occurred.

 Qualitative Evaluation;  Assessing the risk of an  accidental  release at a
 facility in relative terms;  the end  result of the  assessment  being  a verbal
 description of the  risk.

 Quantitative Evaluation;  Assessing  the risk of an accidental release at a
 facility in numerical  terms; the end result of the assessment being some type
 of number reflects  risk, such as faults per year or mean time between failure.

 Reactivity;  The  ability of  one chemical to undergo a chemical reaction with
 another chemical.   Reactivity of one chemical is always measured  in reference
 to the potential  for reaction with itself or with  another chemical.  A chemical
 is sometimes said to be "reactive",  or have high "reactivity", without
 reference to another chemical.  Usually this means that the chemical has the
 ability to react with  common materials such as water, or common materials of
 construction such as carbon  steel.

 Redundancy;  For  control systems, redundancy is the presence  of a second piece
 of control equipment where only one  would be required.  The second  piece of
 equipment is installed to act as a backup in the event that the primary piece
 of equipment fails.  Redundant  equipment can be installed to  backup  all or
 selected portions of a control  system.

 Risk;  The probability that a hazard may be realized at any specified level in
 a given span of time.

 Secondary Containment;   Process equipment specifically designed to  contain
material that has breached primary containment before the material  is released
 to the environment and becomes  an accidental release.  A vent duct and
 scrubber that are attached to the outlet of a pressure relief device are
 examples of secondary containment.

Toxicity;   A measure of the adverse health effects of exposure to a chemical.
                                       149

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                    TABLE B-l.
    APPENDIX B
METRIC (SI) CONVERSION  FACTORS
Quantity
Length :

Area:

Volume:


Mass (weight) :


Pressure:



Temperature :

Caloric Value;
Enthalpy:

Specific-Heat
Capacity :
Density :

Concentration:

Flowrate:


Velocity :

Viscosity:
To Convert From
in
ft
in*
ft*
in3
ft3
gal
Ib
short ton (ton)
short ton (ton)
atm
mm Hg
psia
psig

°C
Btu/lb
Btu/lbmol
kcal/gmol
Btu/lb-°F

Ib/ft3
Ib/gal
oz/gal
quarts/gal
gal/min
gal /day
ft3/min
f t/min
ft/sec
centipoise (CP)
To
cm
m
cm*
m*
cm3
m3
m3
kg
Mg
metric ton (t)
kPa
kPa
kPa
kPa*
°c*
K*
kJ/kg
kJ/kgmol
kJ/kgmol
kJ/kg-°C

kg/m3
kg/m3
kg/m3
5 / 3
G^I / m
on / QLIU
m3/day
m3/min
m/min
m/sec
kg/m-s
Multiply By
2.54
0.3048
6.4516
0.0929
16.39
0.0283
0.0038
0.4536
0.9072
0.9072
101.3
0.133
6.895
((psig)+14.696)x(6.895)
(5/9)x(°F-32)
°C+273.15
2.326
2.326
4.184
4. 1868

16.02
119.8
7.490
25. 000
0.0038
0. 0038
0.0283
0.3048
0.3048
0.001
 ^Calculate as indicated
OUS GOVERNMENT PRINTING OFFICE:! 9 87 -7it8-121/ 670314
                                           150

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