United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/4-88-004
October 1988
Air
ESTIMATING AIR
TOXICS EMISSIONS
FROM ORGANIC
LIQUID STORAGE
TANKS
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EPA-450/4-88-OC
October 1988
Estimating Air Toxics Emissions From
Organic Liquid Storage Tanks
By
Patrick Murphy
Midwest Research Institute
Gary, North Carolina
Contract No. 68-02-4395
EPA Project Officer: Anne A. Pope
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office Of Air And Radiation
Office Of Air Quality Planning And Standards
Research Triangle Park, North Carolina 27711
October 1988 :
Environmental Protection A»o
-i 5, Library (5PL-16)
Tr-p.rborn Street, ttoom 1670
' , .;, 60604
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This report has been reviewed by the Office Of Air Quality Planning And Standards, U.S. Environmental
Protection Agency, and approved for publication. Any mention of trade names or commercial products is not
intended to constitute endorsement or recommendation for use.
EPA-450/4-88-004
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ACKNOWLEDGEMENT
The cooperation of the American Petroleum Institute (API) is
gratefully acknowledged. We appreciate the use of API Publication 2517,
Evaporation Loss From External Floating Roof Tanks, Third Edition (in
press). Figures A-6 through A-20 have been reprinted prior to API
publication with the courtesy of the American Petroleum Institute.
iii
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TABLE OF CONTENTS
Page
LIST OF FIGURES v11
LIST OF TABLES ix
SECTION 1.0 PURPOSE OF DOCUMENT 1
SECTION 2.0 OVERVIEW OF DOCUMENT CONTENTS 3
SECTION 3.0 STORAGE TANK BACKGROUND INFORMATION 5
3.1 FIXED ROOF TANKS 5
3.2 EXTERNAL FLOATING ROOF TANKS 7
3.3 INTERNAL FLOATING ROOF TANKS 9
3.4 VARIABLE VAPOR SPACE TANKS 11
3.5 PRESSURE TANKS 12
SECTION 4.0 SOURCE CATEGORY DESCRIPTION 13
4.1 INDUSTRIAL ORGANIC CHEMICAL STORAGE TANKS 14
4.1.1 Chlorinated Solvents 16
4.1.2 Nonchlorinated Solvents 16
4.2 PETROLEUM REFINERIES 18
4.3 BULK TERMINAL STORAGE TANKS 18
SECTION 5.0 ESTIMATING AIR TOXICS EMISSIONS 21
5.1 DETERMINE TANK TYPE 24
5.2 DETERMINE ESTIMATING METHODOLOGY 24
5.3 SELECT EQUATIONS TO BE USED 25
5.3.1 Fixed Roof Tanks 25
5.3.2 External Floating Roof Tanks 28
5.3.3 Internal Floating Roof Tanks 32
5.4 IDENTIFY PARAMETERS TO BE CALCULATED OR
DETERMINED FROM TABLES 34
5.5 CALCULATE MOLE FRACTIONS IN THE LIQUID 35
5.6 CALCULATE PARTIAL PRESSURES AND TOTAL VAPOR
PRESSURE OF THE LIQUID 35
5.7 CALCULATE MOLE FRACTIONS IN THE VAPOR 36
5.8 CALCULATE MOLECULAR WEIGHT OF THE VAPOR 36
5.9 CALCULATE WEIGHT FRACTIONS OF THE VAPOR 36
5.10 CALCULATE TOTAL VOC EMITTED FROM THE TANK 37
5.11 CALCULATE AMOUNT OF EACH COMPONENT EMITTED
FROM THE TANK 37
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TABLE OF CONTENTS (continued)
Page
SECTION 6.0 REFERENCES 39
APPENDIX A. FIGURES AND TABLES A-l
APPENDIX B. GLOSSARY OF SYMBOLS AND EXAMPLES B-l
vi
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LIST OF FIGURES
Page
Figure 1. Typical fixed roof storage tank 6
Figure 2. Typical external floating roof storage tanks 8
Figure 3. Typical internal floating roof tanks 10
Figure A-l. Adjustment factor (C) for small diameter tanks A-l
Figure A-2. Turnover factor (KN) for fixed roof tanks A-2
Figure A-3. True vapor pressure (P) of crude oils
(2-15 psi RVP) A-3
Figure A-4. True vapor pressure (P) of refined petroleum liquids
like gasoline and naphthas (1-20 psi RVP) A-4
Figure A-5. Vapor pressure function (P*) A-5
Figure A-6. Rim seal loss factor for an external floating roof
welded tank with a mechanical shoe primary seal.... A-6
Figure A-7. Rim seal loss factor for an external floating roof
welded tank with a liquid-mounted resilient
filled primary seal A-7
Figure A-8. Rim seal loss factor for an external floating roof
welded tank with a vapor-mounted resilient filled
primary seal A-S
Figure A-9. Rim seal loss factor for an external floating roof
riveted tank with a mechanical shoe primary seal... A-9
Figure A-10. Roof fitting loss factor for external floating
roof access hatches A-10
Figure A-ll. Roof fitting loss factor for external floating roof
unslotted guide pole wells A-ll
Figure A-12. Roof fitting loss factor for external floating roof
slotted guide pole/sample wells A-12
Figure A-13. Roof fitting loss factor for external floating roof
gauge float wells A-13
Figure A-14. Roof fitting loss factor for external floating roof
gauge hatch/sample wells A-14
Figure A-15. Roof fitting loss factor for external floating roof
vacuum breakers A-15
Figure A-16. Roof fitting loss factor for external floating roof
roof drains A-16
Figure A-17. Roof fitting loss factor for external floating roof
adjustable roof legs A-17
vii
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LIST OF FIGURES (continued)
Figure A- 18.
Figure A- 19.
Figure A-20.
Figure A-21.
Figure A-22.
Page
Roof fitting loss factor for external floating roof
rim vents A-18
Total roof fitting loss factor for typical roof
fittings on pontoon floating roofs A-19
Total roof fitting loss factor for typical roof
fittings on double-deck floating roofs
Approximated total deck fitting loss factors (Fp)
for typical fittings in tanks with column supported
fixed roofs and either a bolted deck or a welded
tank.
Approximated total deck fitting loss factors (Fp)
for typical deck fittings in tanks with self-
supported fixed roofs and either a bolted deck or
a welded deck
A-20
A-21
A-22
viii
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LIST OF TABLES
Page
TABLE 1. CALCULATION METHODOLOGY 22
TABLE A-l. PAINT FACTORS (Fp) FOR FIXED ROOF TANKS A-23
TABLE A-2. PHYSICAL PROPERTIES OF COMMON AIR SUBSTANCES A-24
TABLE A-3. AVERAGE STORAGE TEMPERATURE (Ts) AS A FUNCTION
OF TANK PAINT COLOR I A-26
TABLE A-4. AVERAGE ANNUAL AMBIENT TEMPERATURE (Ta, °F) FOR
SELECTED U.S. LOCATIONS A-27
TABLE A-5. RIM SEAL LOSS FACTORS (K$) FOR FLOATING ROOF TANKS A-30
TABLE A-6. AVERAGE ANNUAL WIND SPEED (v, mi/h) FOR SELECTED
U.S. LOCATIONS A-31
TABLE A-7. AVERAGE CLINGAGE FACTORS (Cp) A-34
TABLE A-8. EXTERNAL ROOF FITTING LOSS/FACTORS (Kf_, Kfh)
AND TYPICAL NUMBER OF ROOF FITTINGS (Np).: A-35
TABLE A-9. TYPICAL NUMBER OF EXTERNAL FLOATING ROOF VACUUM
BREAKERS AND DRAINS A-37
TABLE A-10. TYPICAL NUMBER OF EXTERNAL FLOATING ROOF LEGS A-38
TABLE A-ll. SUMMARY OF INTERNAL FLOATING ROOF DECK FITTING LOSS
FACTORS (KF) AND TYPICAL NUMBER OF
FITTINGS (Np) A-39
TABLE A-12. TYPICAL NUMBER OF COLUMNS (Nc) AS A FUNCTION OF
TANK DIAMETER (D) FOR FLOATING ROOF TANKS
WITH COLUMN SUPPORTED FIXED ROOFS A-40
TABLE A-13. DECK SEAM LENGTH FACTORS (Sn) FOR TYPICAL DECK
CONSTRUCTIONS FOR INTERNAL FLOATING ROOF TANKS A-41
TABLE B-l. GLOSSARY OF SYMBOLS B-l
TABLE B-2. EMISSIONS FOR EXAMPLE 3 B-25
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1.0 PURPOSE OF DOCUMENT
The U. S. Environmental Protection Agency and State and local air
pollution control agencies are becoming increasingly aware of the presence
of substances in the ambient air that may be toxic at certain
concentrations. This awareness has led to an attempt to categorize air
toxics emissions by sources, such as storage tanks.
To assist groups in inventorying air emissions of potentially toxic
substances, EPA is preparing a series of documents that compiles available
information on sources and emissions of these substances. This document
deals with methods to estimate air toxics emissions from organic liquid
storage tanks. Its intended audience includes Federal, State, and local
air pollution agency personnel and others who are interested in making
estimates of air toxics emissions from storage tanks.
This document informs the reader how to (1) characterize storage
tanks, (2) select the appropriate storage tank loss equations and
parameters for estimating emissions, (3) calculate vapor pressures, mole
fractions, and molecular weights of mixtures, and (4) estimate emissions
of individual air toxics. The emphasis of this document is on presenting
equations for estimating air toxics emissions from storage tanks and
demonstrating through examples how to use the equations.
The reader is cautioned against using the emission estimates as an
exact assessment from any particular source because of the limitations of
the estimating methods and the general lack of specific source
information. If precise knowledge of emission levels is desired, the user
is advised to measure emissions of air toxics from organic liquid storage
tanks.
The storage tank emission estimating equations are based on equations
presented in AP-42, and the user is advised to consult AP-42 for addi-
tional details regarding the equations.3 This document expands
information presented in AP-42 to include methodology for estimating
emissions from mixtures stored in organic liquid storage tanks and revises
the methodology for estimating emissions from external floating roof
tanks. The revised external floating roof tank methodology includes
procedures recently developed by the American Petroleum Institute.17
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2.0 OVERVIEW OF DOCUMENT CONTENTS
This section provides an overview of the contents of this document.
It briefly outlines the nature of the material presented in the remaining
sections of this report.
Section 3 provides brief descriptions of different types of tanks and
control devices. The sources of emissions that occur from each type of
storage tank are also described.
Section 4 presents storage tank source category descriptions.
Storage tanks have been divided into usage source categories in order to
present common characteristics that are significant when estimating
emissions. Some suggestions of how to locate storage tanks are presented
in this section.
Section 5 presents descriptions of the methods recommended to make
estimates of air toxic emissions from storage tanks. The emission
estimating equations are presented along with explanations of their
appropriate use. The selection of parameters and calculation of
properties are explained in this section.
Section 6 presents the references used in this document.
Appendix A presents the physical constants of organic compounds
commonly stored in tanks and tables and figures of other data required to
use the equations. Appendix B presents four example calculations. The
examples are intended to cover a wide range of scenarios and are very
explicit. Proper use of the equations and typical assumptions are
included in the examples.
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3.0 STORAGE TANK BACKGROUND INFORMATION
This section presents descriptions of the five basic designs of
organic liquid storage vessels: fixed roof, external floating roof,
internal floating roof, variable vapor space, and pressure (low and
high). Also, the types of emissions from these tanks are discussed.
3.1 FIXED ROOF TANKS
A typical fixed roof tank is shown in Figure 1. This type of tank
consists of a cylindrical steel shell with a permanently affixed roof,
which may vary in design from cone- or dome-shaped to flat.
The design of fixed roof tanks requires an opening vent to the
atmosphere to allow for displaced air and vapors during filling,
withdrawal, and expansion due to warming. Opening vents are commonly
equipped with pressure/vacuum devices that allow the vessel to operate at
a slight internal pressure or vacuum to prevent the release of vapors
during very small changes in temperature, pressure, or liquid level. Of
current tank designs, the fixed roof tank is the least expensive to
construct and is generally considered to be the minimum acceptable
equipment for storage of organic liquids.
Two significant types of emissions from fixed roof tanks are
breathing loss and working loss. Breathing loss is the expulsion of vapor
from a tank through vapor expansion and contraction, which result from
changes in temperature and barometric pressure. During vapor contraction,
air is drawn into the tank and becomes saturated with organic vapor. Upon
subsequent expansion of the vapor, the saturated vapor is expelled from
the tank. This loss occurs without any loading or withdrawal of liquid
from the tank. For insulated tanks, no factors exist currently to
estimated breathing losses.
The combined loss from filling and emptying the tank is called
working loss. Filling loss occurs when, with an increase of the liquid
level in the tank, the pressure inside the tank exceeds the relief
pressure and vapors are expelled. Emptying loss occurs when air, drawn
into the tank during liquid removal and saturated with organic vapor, is
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Haech
Maafa«l«
Mantel.
Figure 1. Typical fixed roof storage tank.
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expelled as liquid Is subsequently pumped into the tank, thus exceeding
the capacity of the vapor space. Fixed roof emissions vary as a function
of vessel capacity, vapor pressure of the stored liquid, utilization rate
of the vessel, and atmospheric conditions at the tank location. Emissions
from fixed roof tanks can be reduced by constructing internal floating
roofs or by using add-on control devices such as vapor recovery or thermal
oxidation.
3.2 EXTERNAL FLOATING ROOF TANKS
External floating roof tanks are cylindrical vessels that have a roof
that floats on the surface of the liquid being stored. The basic
components of the tank include: (1) a cylindrical shell, (2) a floating
roof, (3) an annular rim seal attached to the perimeter of the floating
roof, and (4) roof fittings that penetrate the floating roof and serve
operational functions. The purpose of the floating roof and the seal (or
seal system) is to reduce the evaporative loss of the stored liquid.
Floating roofs are currently constructed of welded steel plates. The
present trend in floating roof construction is toward two types of
roofs: pontoon and double deck. Figure 2 shows typical external floating
roof tanks of both types. The liquid surface is completely covered by the
floating roof except at the small annular space between the roof and the
tank wall. A seal (or seal system) attached to the roof contacts the tank
wall (with small gaps, in some cases) and covers the annular space. The
seal slides against the tank wall as the roof is raised or lowered.
Floating roofs may have primary and secondary seals. Three types of
primary seals are generally usedvapor mounted, liquid mounted, and
mechanical shoe. Secondary seals are usually vapor mounted but may be
shoe mounted. External floating roof tanks have numerous roof fittings
that pass through or are attached to a floating roof to allow for
operational functions. The most common roof fittings which are sources of
evaporative losses include access hatches, guide pole wells, guide
pole/sample wells, gauge float wells, gauge hatches/sample wells, vacuum
breakers, roof drains, roof legs, and rim vents. More information on
these fittings can be found in API's forthcoming Publication 2517.1?
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-WINOOIROEII
ROLUNO LAOOEM
GAIMC HATCH/SAMPLE WEU.
GAUOE FLOAT WO.L
ANTI-MWrtON SUIOC f
ACCESS HATC
VACUUM SRCAKCR
PONTOON ACCESS HATCH
RIM VCNTI
L£G FLOOD MO
CENTER LEU
PONTOON LE8
Pontoon Type
i WINO SIROEH
KOLUNO LAOOCR
RIM VENT-
tES FLOOR PAOS
AOOF LC8
Double-Deck Type
Figure 2. Typical external floating roof storage tanks,
8
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Emissions from external floating roof tanks are the sum of standing
storage loss and withdrawal loss. The standing storage loss can be
estimated as the sum of rim seal loss and roof fitting loss. Rim seal
loss occurs from evaporation of the liquid through and past the primary
and/or secondary seals. Roof fitting loss results from roof fittings that
require openings in the floating roof. There is no deck seam loss because
the decks have welded sections. Withdrawal loss occurs as the liquid that
clings to the tank wall is exposed to the atmosphere and vaporized when
the floating roof is lowered by withdrawal of the stored liquid. Although
relatively minor losses occur from evaporation during withdrawal of stored
liquid, extremely frequent turnover of liquid in an external floating roof
tank can increase the significance of withdrawal loss.
3.3 INTERNAL FLOATING ROOF TANKS
An internal floating roof tank has both a permanent fixed roof and an
internal floating deck. Typical contact deck and noncontact deck internal
floating roof tanks are shown in Figure 3. The terms "deck" and "floating
roof" can be used interchangeably in reference to the structure floating
on the liquid inside the tank. The purpose of the internal deck is to
eliminate the "vapor space" in the tank, thereby limiting the amount of
the stored liquid that evaporates and can be emitted. The deck rises and
falls with the liquid level and either floats directly on the liquid
surface (contact deck) or rests on pontoons several inches above the
liquid surface (noncontact deck). Two basic types of internal floating
roof tanks are tanks in which the fixed roof is supported by vertical
columns within the tank and tanks with a self-supported fixed roof and no
internal support columns. Fixed roof tanks that have been retrofitted to
employ a floating deck are typically of the first type, while external
floating roof tanks that have been retrofitted to employ a floating deck
typically have a self-supported roof. Tanks initially constructed with
both a fixed roof and a floating deck may be of either type.
Contact decks can be aluminum panels with a honeycomb aluminum core
floating in contact with the liquid, or pan steel decks floating in
contact with the liquid. Noncontact decks typically have an aluminum deck
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Caacar 7aat
Hantela
Tank Support Calua
vlth CoiuBB Wali
Contact Deck Type
Poncoeu
tank Support CaluMi
with Caltan ««U
Tapor Spaca
Noacontact Deck Type
Figure 3. Typical Internal floating roof tanks.
10
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or an aluminum grid framework supported above the liquid surface by
tubular aluminum pontoons or other buoyant structures. Both types of
decks incorporate rim seals, which slide against the tank wall as the deck
moves up and down. Floating roofs may have primary and secondary seals.
Three types of primary seals are generally used: vapor mounted, liquid
mounted, and mechanical shoe. Secondary seals, which are usually vapor
mounted, are used to further reduce emissions from internal floating roof
tanks. In addition, these tanks are freely vented by circulation vents
both at the top of the fixed roof and at the top of the shell. The vents
minimize the possibility of organic vapor accumulation in concentrations
approaching the flammable range. An internal floating roof tank not
freely vented is considered a pressure tank.
Losses from internal floating roof tanks are the sum of withdrawal
and standing losses. Withdrawal losses for internal floating roof tanks
include vaporization of liquid that clings to the tank wall and columns,
if present in tanks with a column supported fixed roof. Standing storage
losses include rim seal, deck fitting, and deck seam losses. Rim seal
losses include evaporative losses from the seals. Deck fitting losses
result from penetrations in the roof by deck fittings, fixed roof column
supports, or other openings. Deck seam losses occur when roofs are
bolted. Welded roofs have no seams and thus no seam losses. Emissions
from internal floating roof tanks may be reduced by using liquid mounted
primary seals, continuous rim mounted secondary seals, welded decks,
gasketted fittings, and flexible fabric seals to cover pipe columns.
3.4 VARIABLE VAPOR SPACE TANKS
Variable vapor space tanks are equipped with expandable reservoirs to
accommodate vapor volume fluctuations attributable to temperature and
barometric pressure changes. Although variable vapor space tanks are
sometimes used independently, they are normally connected to the vapor
spaces of one or more fixed roof tanks. The two most common types of
variable vapor space tanks are lifter roof tanks and flexible diaphragm
tanks.
11
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Lifter roof tanks have a telescoping roof that fits loosely around
the outside of the main tank wall. The space between the roof and the
wall Is closed by either a wet seal, which is a trough filled with liquid,
or a dry seal, which uses a flexible coated fabric.
Flexible diaphragm tanks use flexible membranes to provide expandable
volume. They may be either separate gasholder units or integral units
mounted atop fixed roof tanks.
Variable vapor space tank losses occur during tank filling when vapor
is displaced by liquid. Loss of vapor occurs only when the tank's vapor
storage capacity is exceeded. Although an equation for estimating losses
from variable vapor space tanks is available in AP-42, the accuracy of the
equation is not documented. Losses estimated using this equation could
differ significantly from actual emissions. Therefore, emissions from
variable space tanks are not discussed further in this document.
3.5 PRESSURE TANKS
Two classes of pressure tanks are in general use, low pressure (1.5
to 14.7 pslg) and high pressure (higher than 14.7 psig). Pressure tanks
generally are used for storage of organic liquids and gases with high
vapor pressures and are found in many sizes and shapes, depending on the
operating pressure of the tank. Pressure tanks are equipped with a
pressure/vacuum vent that is set to prevent venting loss from boiling and
breathing loss from daily temperature or barometric pressure changes.
High pressure storage tanks are usually operated so that virtually no
evaporative or working losses occur. In low pressure tanks, working
losses can occur with atmospheric venting of the tank during filling and
withdrawal operations. Vapor recovery systems are generally used on low
pressure tanks to reduce working losses. No appropriate correlations are
available to estimate vapor losses from pressure tanks. Therefore, this
document does not include any further discussion of emissions from
pressure tanks.
12
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4.0 SOURCE CATEGORY DESCRIPTION
This section presents three Industrial source categories that use
storage tanks and have the potential to emit air toxics. A brief
description of each source category and available tank size and control
device information are also presented in this section. The U. S.
Environmental Protection Agency has published a document entitled "Toxic
Air Pollutant/Source CrosswalkA Screening Tool for Locating Possible
Sources Emitting Toxic Air Substances" that cross-references industrial
SIC codes, SCC codes, and air toxics for a variety of processes, including
storage tanks."* The reader is directed to that document to identify which
air toxics are known to be associated with a given industry.
Organic liquids are stored in above ground and below ground storage
tanks, both of which may be significant sources of air toxics emissions.
Underground storage tanks are defined as having 10 percent or more of
their volume (including pipes) underground. Losses from underground
storage tanks (excluding losses due to leaks in the tank system) result
from filling and withdrawal operations. An estimated 1.4 million
underground storage tanks are located in the United States. Ninety six
percent of these tanks are used to store petroleum products and the
remaining 4 percent are used to store large volumes of industrial
chemicals such as acetone, toluene, methyl ethyl ketone, methylene
chloride, styrene, chloroform, methyl isobutyl ketone, ethylene
dichloride, 1,1,1-trichloroethane, and ethylene oxide.5 Because the
accuracy of equations for estimating emissions from underground storage
tanks is not documented, emissions from those tanks are not discussed
further 1n this document.
Storage tanks can be divided into two groups based on type of stored
material: industrial organic chemicals and petroleum liquids. The
majority of storage tanks are located onsite at manufacturing and
producing facilities. Some tanks also are located at bulk terminals. Of
the total tank population, approximately 56 percent are estimated to be
located at petroleum refineries, 38 percent at organic chemical industrial
facilities, and 6 percent at bulk terminals.6 Petroleum storage tanks
generally store multicomponent liquids whereas organic chemical storage
13
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tanks usually contain single component liquids. The type of tank used to
store liquids is dependent primarily on the volume of liquid to be stored
annually and the vapor pressure of the liquid. Other factors that
influence the selection of the tank type include material stability,
safety hazards, and multiple use of tank for different liquids. The
following subsections present information about industrial organic
chemical storage tanks, petroleum refineries, and bulk terminals storage
tanks.
4.1 INDUSTRIAL ORGANIC CHEMICAL STORAGE TANKS
Most organic chemicals, with the exception of petroleum products, are
stored as single component liquids in tanks. It is assumed that the
composition of the liquids in these storage tanks is 100 percent of the
chemical.
Organic chemical storage tanks are located primarily at chemical
producing and manufacturing facilities. Some industrial organic chemicals
are stored offsite at bulk terminals. It is estimated that only a small
percentage of the total volume of industrial organic chemicals are stored
in tanks off site at bulk terminals. * The majority of emissions from
organic chemical storage tanks result from producers. About one-quarter
of air toxic emissions from organic chemical storage tanks result from
consumers. The remainder of emissions from industrial organic chemical
storage tanks originate from bulk terminal tanks.
The onsite tanks at organic chemical production and consumer
facilities are used to store raw materials, final products, and/or usable
by-products as well as waste tars, residues, and nonusable products. The
major producers of industrial organic chemicals have SIC codes 286x.
Producers are located in all areas of the U.S., with the largest plants
clustered in the Central Southern States near raw material supplies and in
the Mid-Atlantic States close to industries.
Industrial organic chemical tanks located at consuming facilities are
generally associated with industries having SIC codes 28xx. The majority
of emissions from organic chemical storage tanks located at consuming
facilities are estimated to originate from the plastics industry. Other
14
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consuming facilities that have organic chemical storage tanks manufacture
surface active agents, Pharmaceuticals, textiles, nitrogen fertilizer,
rubber and miscellaneous synthetics, and treated wood. The major types of
chemicals stored by these facilities include dyes, toners, creosote oil,
rubber processing chemicals, and plasticizers. Storage tanks present at
organic chemical consuming/manufacturing facilities are typically small,
less than 40,000 gallons. Facilities where chemicals are prepared for
distribution generally have tanks less than 20,000 gallons in size.7
Industrial organic chemical consuming facilities are fairly evenly
distributed across the U.S. with some tendency to be located in South
Atlantic and Eastern Central States.
The majority of storage tanks located at industrial organic chemical
production and manufacturing facilities are fixed roof tanks. Fixed roof
tanks are used predominantly for storing materials with vapor pressures of
5 psia or less. Although fixed roofs are used more than floating roof
tanks, volatile organic liquid storage tanks regulations will probably
result in the increasing use of floating roof tanks.
Most fixed roof tanks and internal floating roof tanks store liquids
with vapor pressures less than 5 psia and have volumes of 100,000 gallons
or less. External floating roofs are generally used to store liquid
volumes of 130,000 gallons or more. The majority of industrial organic
chemical tanks are small, with volumes of less than 20,000 gallons.
However, the majority of emissions from storage tanks are estimated to
originate from tanks with capacities greater than 20,000 gallons and which
store liquids with vapor pressures greater than 0.5 psia.7
Horizontal tanks are used widely in the Synthetic Organic Chemical
Manufacturing Industry (SOCMI). The volumes of horizontal tanks are
typically small and rarely exceed 30,000 gallons. Horizontal tanks are
preferred for separation processes. These tanks typically require add-on
control systems such as carbon adsorption or thermal oxidation.1*6
Organic liquids with vapor pressures greater than 11 psia are stored
in high pressure tanks or have a vapor recovery system. High pressure
tanks generally are used to store highly volatile and/or toxic materials.
15
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4.1.1 Chlorinated Solvents8'9
Chlorinated solvents are stored at producing and consuming
facilities. Some common chlorinated solvents are methylene chloride,
carbon tetrachloride, trichloroethylene, and perchloroethylene.
The information presented for this subsection comes from the source
assessment documents for two chlorinated solvents, methylene chloride and
trichloroethylene. The information in those documents was taken from EPA
questionnaire responses. Storage tank information was available for
facilities that produce the solvents and for facilities that use the
solvents as feedstocks in other processes. The level of control required
for the storage tanks represented in these documents may change due to
future regulations.
Almost all of the storage tanks represented in the source assessment
documents are fixed roof tanks. The tanks ranged in size from 250 to
500,000 gallons with the average size in the range of 25,000 to
50,000 gallons. In most cases, no control devices were used with the
tanks. For the few cases where a control device was used, the majority
were water-cooled condensers.
Pressure vessels of less than 1,000 gallons were reportedly being
used to store chlorinated solvents in a few cases. The only type of
storage tank other than fixed roof reported in the source assessment
documents was a contact internal floating roof tank of approximately
500,000 gallons with no control device.
4.1.2 Nonchlorinated Solvents10'l1'12
A variety of nonchlorinated solvents are stored at manufacturing
facilities. Most of these solvents are stored in small fixed roof
tanks. Some facilities use control devices; however, most small tanks
(less than 20,000 gallons) are not required to have controls. This
subsection presents information about two industries, polymeric coating
and magnetic tape manufacturing.
Polymeric coating facilities store solvents in small, fixed roof
tanks. The solvents generally stored include toluene, dimethyl formamide,
16
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acetone, methyl ethyl ketone, xylene, isopropyl alcohol, and ethyl
acetate. Toluene is the most commonly used solvent because it is
relatively inexpensive. Most polymeric coating facilities store single
solvents rather than muHicomponent solvents. Each polymeric coating
facility usually has five or less solvent storage tanks. The tank
capacity typically ranges from 1,000 to 20,000 gallons. The majority of
solvent storage tanks are underground. However, it is likely that new
solvent storage tanks will be built above ground because of concern over
potential groundwater contamination. No add-on control devices are
currently being used to control the tanks. More than 100 polymeric
coating facilities are located throughout the U.S., with the heaviest
concentration being in the Northeast. The SIC codes associated with these
facilities are 2241, 2295, 2296, 2394, 2641, 3041, 3069, and 3293.
Approximately 50 percent of the polymeric coated products are manufactured
by industries with SIC codes of 2295 and 2296 for use in automobiles.
Magnetic tape manufacturing facilities generally store multicomponent
solvents in fixed roof tanks. The solvents stored include tetrahydro-
furan, methyl ethyl ketone, methyl isobutyl ketone, toluene, and cyclo-
hexanone. The capacity for magnetic tape solvent vessels ranges from
1,000 to 20,000 gallons. The solvent tanks may be vertical or horizontal
fixed roof tanks. A few of the tanks are located underground. Most of
the tanks are operated at atmospheric pressure or slightly above.
Conservation vents are used by some facilities to minimize tank losses. A
conservation vent is a combination pressure and vacuum relief valve that
protects closed tanks from physical damage during filling and withdrawal
of liquid or from damage due to high pressure or vacuums. Conservation
vents cannot be installed in some tanks because of the resulting higher
internal pressure. Solvent storage tank emissions may also be controlled
by venting vapor into control devices such as carbon adsorbers. Proposed
regulations require new solvent tanks at magnetic tape manufacturing
facilities to install pressure relief valves or to capture and vent all
emissions to a 95 percent efficient control device. Magnetic tape
facilities are located in 15 States, with California having the largest
number of plants. The SIC codes associated with magnetic tape
manufacturers are 3679 and 3573.
17
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4.2 PETROLEUM REFINERIES13
The products stored at petroleum refineries can be divided into three
categories: low vapor pressure products, high vapor pressure products,
and crude oil. Benzene, toluene, and xylene are air toxics commonly
associated with petroleum products. Some general information about
storage practices for these three categories is presented below.
Low vapor pressure petroleum refinery products, such as fuel oil and
diesel fuel, are typically stored in large fixed roof storage tanks.
Fixed roof tanks, which have generally higher emission rates than floating
roof tanks, are allowed by Federal and State regulations to be used
because of the products' low vapor pressures. Additional control devices
(e.g., condensers) are not typically employed on these fixed roof tanks.
High vapor pressure products, such as gasoline, are typically stored
in large external floating roof tanks. These tanks range in diameter from
50 to 180 feet and are typically 30 to 50 feet high. No add-on control
devices are typically used with these tanks. Some of the tanks have been
modified to be internal floating roof tanks. External floating roof tanks
are required by State and Federal regulations to have both a primary and
secondary seal. The primary seal is usually a mechanical shoe seal and
the secondary seal is usually rim-mounted. Petroleum refineries also
store other high vapor pressure products, such as benzene, in internal
floating roof tanks that range in volume between 100,000 and
500,000 gallons.
The third category of petroleum refinery products is crude oil.
Crude oil has a wide ranging vapor pressure. Crude oil is usually stored
in large external floating roof tanks.
4.3 BULK TERMINAL STORAGE TANKS13
Bulk terminals are nonmanufacturing sites that store commodities in
large quantities. Petroleum liquid products are stored primarily at bulk
terminals, while only a small amount of industrial organic liquids are
stored at bulk terminals. The remainder of this subsection focuses on the
storage of petroleum liquids after leaving a petroleum refinery.
18
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Petroleum products are stored at two types of terminals, high volume
and low volume. External floating roof tanks are used at both high-volume
and low-volume terminals. Most of the petroleum tanks at terminals have
installed vapor recovery systems because of Federal and State regulations.
High-volume terminals are pipeline endpoints and typically have very
large external floating roof tanks. The average volume of tanks at a high
volume bulk terminal is 871,000 gallons.6 At high volume terminals, the
average smallest sized tank is estimated to be 319,000 gallons and the
average largest sized tank is estimated to be 3,600,000 gallons.7 The
majority of high-volume storage terminals are located in Texas, New
Jersey, and Louisiana. Large petroleum distribution terminals also are
located in Central and Southern States.
Low-volume terminals generally are used for local distribution of
gasoline. These tanks also have external floating roofs, but are smaller
in size than tanks at high-volume bulk terminals. Tanks at small bulk
terminals range in size from 40,000 to 100,000 gallons.
After leaving bulk terminals, gasoline is transported to local
gasoline stations. Gasoline is usually stored in underground horizontal
tanks of between 10,000 and 20,000 gallons.
19
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5.0 ESTIMATING AIR TOXICS EMISSIONS
Emissions of toxic organic compounds from storage tanks are a
function of the size and type of tank, the vapor pressure of the liquid
inside the tank, and atmospheric conditions at the tank location. Three
types of tanks are usually used to store organic liquids: fixed roof,
external floating roof, and internal floating roof. Fixed roof storage
tank emissions are the sum of breathing losses (which are due to changes
in ambient temperature or pressure) and working losses (from loading and
unloading the tank). External floating roof and internal floating roof
storage tank emissions are the sum of standing storage loss and withdrawal
loss. Standing storage loss includes rim seal loss, deck fitting loss,
and deck seam loss.
The EPA Publication AP-42 contains equations to estimate emissions of
petroleum products and volatile organic liquids from fixed roof and
external or internal floating roof tanks. These equations have been used
to obtain emission estimates for organic compounds. When using these
equations, it is important to recognize that results from the equations
are only estimates.
The following section presents the AP-42 emission estimating
equations for fixed roof tanks, external floating roof tanks, and internal
floating roof tanks and describes the methodology for the selection of
parameters and calculation of properties. Table 1 shows the calculation
methodology recommended to estimate storage tank emissions. This section
discusses each of the 11 steps in the calculation methodology.
The equations are not intended to be used in the following
applications: (1) to estimate losses from unstable or boiling stocks,
(2) to estimate losses from mixtures of hydrocarbons or petrochemicals for
which the vapor pressure is not known or cannot be readily predicted,
(3) to estimate breathing losses from insulated fixed roof tanks (the
equations for working losses are still valid), or (4) to estimate losses
from tanks in which the materials used in the rim seal system and/or roof
fittings are either deteriorated or significantly permeated by the stored
liquid.
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TABLE 1. CALCULATION METHODOLOGY
1. Determine tank type
2. Determine estimating methodology
3. Select equations to be used
4. Identify parameters to be calculated or determined from
tables
5. Calculate mole fractions in the liquid
6. Calculate partial pressures and total vapor pressure of
the liquid
7. Calculate mole fractions in the vapor
8. Calculate molecular weight of the vapor
9. Calculate weight fractions of the vapor
10. Calculate total VOC emitted from the tank
11. Calculate amount of each component emitted from the tank
22
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One of the most important parameters in estimating emissions from
storage tanks is the vapor pressure of the liquid being stored. The vapor
pressure of a liquid is a function of temperature and is affected by
process changes. The equations are more appropriate for substances with
vapor pressures of approximately 1.5 psia to 14.7 psia. The equations
have been developed for tanks having diameters greater than 20 feet and
having average wind speed ranging from 2 to 15 miles per hour. A
methodology to estimate emissions from low vapor pressure substances
stored in tanks is currently under development. Table A-2 contains vapor
178
pressure information for several common organic compounds. ' ' When two
or more compounds are present in a mixture, the resulting vapor pressure
must either be calculated analytically or determined through
measurements. The analytical method most frequently used to estimate
vapor pressure is Raoult's Law. Raoult's Law states that the vapor
pressure exerted by a component in a mixture is equal to the mole fraction
of the component times the vapor pressure of the component.
Raoult's Law in equation form is: P^ t = P° tx^, where Pj t is the
pressure exerted by component i in the mixture at temperature t, P° t is
the vapor pressure of the pure component i at temperature t, and x^ is the
mole fraction (as defined in Note (1) of Section 5.1) of component i in
the liquid mixture. Raoult's Law is valid only for compounds that form
ideal mixtures. Some mixtures behave in a nearly ideal manner because
their components have similar structures and molecular weights. Common
organic functional groups that have an effect on the ideality of a mixture
(i.e., make Raoult's Law in applicable) are:
Acid anhydride Ester
Alcohol Ether
Aldehyde Ketone
Amide Nitrile
Amine Thiol
Carboxylic acid
Mixtures that contain compounds with different functional groups will not
behave ideally. However, compounds with similar functional groups can be
assumed to behave ideally, allowing the use of Raoult's Law. Raoult's Law
cannot be applied to complex mixtures of hydrocarbons such as petroleum
stocks. If the vapor pressure of a mixture cannot be estimated accurately
23
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using Raoult's Law, it can be estimated through sampling and analysis or
chemical equilibrium data, if available.
Several examples demonstrating the use of the storage tank emission
equations are presented in Appendix B. A summary of all variables used in
the emission estimating equations is presented in Table B-l.
5.1 DETERMINE TANK TYPE
This report presents equations for estimating emissions from three
types of tanks: fixed roof, external floating roof, and internal floating
roof. Before selecting the appropriate equations, the user must
categorize the storage tank. Section 3 presents discussions and
schematics of the three types of tanks plus pressure tanks and variable
vapor space tanks. If there is a question as to what type a particular
storage tank is, Section 3 should be consulted.
5.2 DETERMINE ESTIMATING METHODOLOGY
When estimating emissions from a storage tank, the parameters used in
the equations must be determined. Usually, the identity and concentration
of the constituents in a mixture are known or can be easily calculated.
The vapor pressure of the liquid mixture must then be determined through
one of three methods: (1) read from a table, (2) calculated using
Raoult's Law if the mixture acts ideally, or (3) measured using sampling
and analysis of the vapor. The vapor pressure of mixtures such as
gasoline can be obtained from Table A-2 or Figure A-4. If the compounds
in the mixture have similar structures and molecular weights (see
Section 5.0), then Raoult's Law can be used. However, if the compounds
are dissimilar, then an accurate vapor pressure for the mixture can only
be obtained through sampling and analysis of vapor in the tank.
The molecular weight and the composition of the vapor must be
calculated if they cannot be located in a table. These parameters can be
calculated from the liquid composition and liquid component properties.
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5.3 SELECT EQUATIONS TO BE USED
AP-42 presents emission equations for three types of storage tanks:
fixed roof, external floating roof, and internal floating roof. The
equations for these tanks are presented below.
5.3.1 Fixed Roof Tanks
The following equations apply to tanks with vertical cylindrical
shells and fixed roofs. These tanks store primarily liquid and operate
approximately at atmospheric pressure. The breathing loss equations do
not apply to insulated fixed roof tanks. Total VOC losses from fixed roof
tanks can be estimated as:
LT - LB+LW (i)
where:
Ly = total loss, Ib/yr
LB = fixed roof breathing loss, Ib/yr
L^ = fixed roof working loss, Ib/yr
Breathing loss:
Fixed roof tank breathing losses can be estimated as:
pD-H-AT-FpCKc (2)
where:
My = molecular weight of vapor in storage tank, Ib/lb-mol, see Note 1
P = true vapor pressure at bulk liquid conditions, psia, see Note 2
PA = average atmospheric pressure at tank location, psia
0 = tank diameter, ft
H = average vapor space height, including roof volume correction,
ft, see Note 3
AT = average ambient diurnal temperature change, °F
Fp = paint factor, dimensionless, see Table A-l
C = adjustment factor for small diameter tanks (dimensionless), see
Figure A-l, see Note 4
25
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K£ = product factor (dimensionless), see Note 5
For horizontal tanks, see Note 6.
Working loss:
Fixed roof tank working losses can be estimated as:
"5
where:
Lw = 2.40 x 10 MyPVNKNKc
V = tank capacity, gal
N = number of turnovers per year, dimensionless
u _ total throughput per year, gal
tank capacity, gal
KN = turnover factor, dimensionless, see Figure A-2
for turnovers >36, K« * gn-
for turnovers <36, KM = 1
My, P, and Kc are as defined for Equation 2.
(3)
Notes:
(1)
where:
My can be determined by Table A-2 for selected petroleum
liquids and volatile organic liquids or estimated using the
following equation
My =
P1xi
'1
partial
PT
zM.y.
M
M1
Pi
= molecular weight of the vapor
=» molecular weight of the component i
* vapor pressure of the pure component i at the
temperature of the liquid
x^ = mole fraction of the component i in the liquid
Pj = total vapor pressure of the liquid
ppartial s Part-5al pressure of the component i
y.,. * mole fraction of the component in the
vapor
26
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The molecular weight of the vapor is dependent
upon the molecular weight and the vapor mole
fraction of each component. The mole fraction of
a component is the number of moles of that
component divided by the total number of moles in
the mixture. The number of moles of a component
in a mixture (liquid or vapor) is calculated by
dividing the weight of the component by its
molecular weight. For a given component, the
product of its liquid mole fraction and its vapor
pressure is called the partial pressure of the
component (this is Raoult's Law). This is the
amount of pressure in the vapor that is due to
that component in the liquid. The ratio of the
partial pressure of a component to the total vapor
pressure is equal to the mole fraction of that
component in the vapor.
(2) True vapor pressures for organic liquids can be
determined from Figures A-3 or A-4, Table A-2, or
by calculation. The stored liquid temperature,
T^, must be known in any case and may be
calculated by knowing the color of the tank and
the average ambient temperature in the area.
Table A-3 shows T$ as a function of ambient
temperature and tank color. Table A-4 shows
average ambient temperatures for selected U.S.
locations.
(3) If information is not available on the vapor space
height, assume H equals one half the corrected
tank height. To correct for a cone roof, the
vapor space in the cone is equal in volume to a
cylinder which has the same base diameter as the
cone and is one third the height of the cone.
(4) The small tank diameter adjustment factor, C, can
be read from Figure A-l or calculated using the
27
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following equations:
for diameter >30 feet, C = 1
for diameter <30 feet, C = 0.0771(D)-0.0013(D2)-
0.1334
(5) For crude oil, K^ » 0.65. For all other organic
liquids, KC = 1.0.
(6) The emission estimating equations presented in
Section 5.3.1 were developed for vertical fixed
roof tanks. If a user needs to estimate emissions
from a horizontal fixed roof tank, some of the
tank parameters can be modified before using the
vertical tank equations. First, by assuming that
the tank is one-half filled, the surface area of
the liquid in the tank is approximately equal to
the length of the tank times the diameter of the
tank. Next, assume that this area represents a
circle, i.e., that the liquid is in an upright
cylinder. The diameter of that circle can be
solved for and used in the equations as D. One-
half of the diameter of horizontal tank should be
used as the value for H. This method yields only
a very approximate value for emissions from
horizontal fixed roof storage tanks.
5.3.2 External Floating Roof Tanks
Floating roof tank emissions are the sum of rim seal, withdrawal, and
roof fitting losses. External floating roof tanks do not have deck seam
losses. The equations have been developed for liquids that are not
boiling, stocks with a true vapor pressure ranging from 1.5 to 14.7 psi,
average wind speeds ranging from 2 to 15 mph, and tank diameter of 20 ft
or greater. The equations are applicable to properly maintained equipment
in normal working conditions where materials used in the rim seal system
and/or roof fittings are not deteriorated or significantly permeated by
the stored liquid. Losses from poorly maintained equipment may be higher
than losses estimated using the equations.
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Emissions from external floating roof tanks can be estimated as:
where:
LT - LR+LWD+LRF
Lj = total loss, Ib/yr
1.^ = rim seal loss, Ib/yr
LWQ = withdrawal loss, Ib/yr
LRp = roof fitting loss, Ib/yr
Lg = deck seam loss, Ib/yr, = 0.0;
Rim seal loss:
Rim seal loss from floating roof tanks can be estimated by the
following equation:
1_R = KsvnP*DMvKc (5)
where:
KS = seal factor for average or tight fit seals,
lb-mol/(ft [mi/h]n yr), see Table A- 5
v = average wind speed at tank site, mi/h, see Note 1
n = seal-related wind speed exponent (dimensionless), see Table A-4
P* = vapor pressure function (dimensionless), see Note 2
where:
P = true vapor pressure at average actual liquid storage
temperature, psia, see Note 2 to Equation 1
PA = average atmospheric pressure at tank location, psia
D = tank diameter, ft
Mv = average vapor molecular weight, Ib/lb-mol, see Note 1 to
Equation 1
K£ = product factor, dimensionless, see Note 3
Figures A-6 through A-9 present graphical estimates of (K^v") for
several tank and seal types.
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Notes: (1) Wind speed data are presented in Table A-6. If the wind
speed at the tank site is not available, wind speed data
from the nearest local weather station may be used as an
approximation.
(2) P* can be calculated or read directly from Figure A-5.
(3) For all organic liquids except crude oil, KQ = 1.0. For
crude oil, K^ = 0.4.
Withdrawal loss:
The withdrawal loss from floating roof storage tanks can be estimated
using the following equation:
(0.943)QCFW NCF
LWD= D FliHrI] <7>
where:
Q = annual throughput, bbl/yr (tank capacity (bbl) times annual
turnover rate)
Cp = shell clingage factor, bbl/1,000 ft2, see Table A-7, Note 1
WL = average organic liquid density, Ib/gal, see Note 2
D = tank diameter, ft
NC = number of columns, dimension less, see Note 4
F£ = effective column diameter, ft (column perimeter [ft]/*), see
Note 5
Notes: (1) The units on this parameter, bbl/1,000 ft , are cancelled
out by the units on the constant 0.943 (see Note 3).
Therefore, if the appropriate Cp value from Table A-7 is
0.0015 bbl/1,000 ft2, the number 0.0015 should be used in
the equation for Cp.
(2) If Wj_ is not known, an average value of 5.6 Ib/gal can be
assumed for gasoline. An average value cannot be assumed
for crude oil, since densities are highly variable.
(3) The constant, 0.943, has dimensions of 1,000 ft3xgal/bbl2.
(4) For self-supporting fixed roof or an external floating roof
tank:
N = 0
30
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For internal floating roof tank with column-supported fixed
roof:
NQ = use tank-specific information, or see Table A-12
(5) For internal floating roof tank with column-supported fixed
roof, use tank-specific effective column diameter; or
Fc = 1.1 for 9-inch by 7-inch builtup columns, 0.7 for
8-inch diameter pipe columns, and 1.0 if column
construction details are not known.
Roof fitting loss:
Fitting losses from external floating roof tanks can be estimated by
the following equation:
LRF * FFP*MVKC (8)
where:
Fp = total roof fitting loss factor, Ib-mol/yr
= l(NF KF )+(NF KF ) . . . +(NF KF )]
TI ri r2 rz rn^ rn^
where:
Np - number of deck fittings of a particular type
(1 = 0,l,2,...,nf), dimensionless, see Table A-8,
A-9, A-10
Kp = roof fitting loss factor for a particular type fitting
(i = 0,l,2,...,nf), Ib-mol/yr, see Equation 9 or
Figures A-10 through A-18
n^ = total number of different types of fittings,
dimensionless
P*t Mv, Kc = as defined for Equations 5 and 6
The roof fitting loss factor for a particular roof fitting type, Kp.,
can be read directly from Figures A-10 through A-18 or calculated using
Equation 9. Figures A-10 through A-18 show roof fitting loss factors
based on wind speed for common roof fitting types. The roof fitting loss
factor for individual fitting types can also be estimated from Equation 9:
31
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F1 - fa^-
where:
Kfa = roof fitting loss factor for a particular roof fitting
type (1 = 1, 2, ..., n)(lb-mol/yr).
Kfjj = roof fitting loss factor for a particular roof fitting
1 type [i = 1, 2, ..., n][lb-niol/(nri/h)V].
m^ = roof fitting loss factor for a particular roof fitting
type (i = 1, 2, .... n)(dimension!ess).
v = average wind speed (mi/h).
The most common roof fittings and their associated roof fitting loss
factors, Kfa.t Kfjj , and m^ are presented in Table A-8.
The number of each type of roof fitting, Np.,can vary significantly
from tank to tank and should be determined for each tank under considera-
tion. If specific tank information is not available, Np can be obtained
from Tables A-8, A-9, and A-10. Table A-8 presents the typical number of
fittings associated with the most common roof fittings. Tables A-9 and
A-10 show the typical number of vacuum breakers, roof drains, and roof
legs based on tank diameter.
If no information is available on the specific type and number of
roof fittings, the total roof fitting loss factor, Fp, can be obtained
from Figures A-19 and A-20. Figures A-19 and A-20 show total roof fitting
loss factors based on tank diameter for typical roof fittings on pontoon
and double-deck floating roofs, respectively. These total loss factors
should only be used when detailed roof fitting information is not
available.
Deck seam loss:
External floating roof tanks do not have deck seam losses because
roofs are welded. Equations for deck seam losses are presented for
internal floating roof tanks in Section 5.3.3.
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5.3.3 Internal Floating Roof Tanks
The equations provided in this section are applicable only to freely
vented internal floating roof tanks. These equations are not intended to
estimate losses from closed internal floating roof tanks (tanks vented
only through a pressure/vacuum vent).
Emissions from internal floating roof tanks may be estimated as:
LT = LR+LWD+LF+LD (10)
where:
Lj = total loss, Ib/yr
Lp = rim seal loss, see Equation 5
LWD = withdrawal loss, see Equation 7
Lp = deck fitting loss, Ib/yr
LQ = deck seam loss, Ib/yr
Deck fitting losses:
Fitting losses from internal floating roof tanks can be estimated by
the following equation:
LF = FFP*MVKC (11)
where:
Fp = total deck fitting loss factor, Ib-mol/yr
- KNFlKFiHNF2Kp2)...-K(NpnKpn )]
where: ^ ^
Np = number of deck fittings of a particular type
(1 =0, 1, 2, ..., nr), dimensionless, see Table A-ll
Kp = deck fitting loss factor for a particular type fitting
(i » 0, 1, 2, ..., r\f), Ib-mol/yr, see Table A-ll
r\f = total number of different types of fittings
P*, Mv, K£ = as defined in Equations 5 and 6.
The value of Fp may be calculated by using actual tank-specific data for
the number of each fitting type (Np) and then multiplying by the fitting
loss factor for each fitting (Kp). Values of fitting loss factors and
typical number of fittings are presented in Table A-ll. Where tank-
specific data for the number and kind of deck fittings are unavailable,
33
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then Fp can be approximated according to tank diameter. Figures A-21 and
A-22 present Fp plotted against tank diameter for column-supported fixed
roofs and self-supported fixed roofs, respectively.
Deck seam loss:
Welded internal floating roof tanks do not have deck seam losses.
Deck seam losses may be present for tanks with bolted decks. Deck seam
loss can be estimated by the following equation:
LQ = KgSgDVMvKc (12)
where:
K0 = deck seam loss per unit seam length factor, Ib-mol/ft yr
= 0.0 for welded deck and external floating roof tanks,
=0.34 for bolted deck
Sg = deck seam length factor, ft/ft
"deck
where:
Lseam = total length of deck seams, ft
Adeck = area of deck» ft2 = IT D /4
D» P*, Mv, K£ = as defined for Equations 5 and 6
If the total length of the deck seam is not known, Table A-13 can be
used to determine SQ. For a deck constructed from continuous metal sheets
with a 7 ft spacing between the seams, a value of 0.14 ft/ft can be
used. A value of 0.33 can be used for Sg when a deck is constructed from
rectangular panels 5 ft by 7.5 ft. Where tank-specific data concerning
width of deck sheets or size of deck panels are unavailable, a default
value for Sg can be assigned. A value of 0.20 ft/ft2 can be assumed to
represent the most common bolted decks currently in use.
5.4 IDENTIFY PARAMETERS TO BE CALCULATED OR DETERMINED FROM TABLES
Once the correct emission estimating equations have been identified,
the user must identify the variables that are not specified by given
34
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conditions. By determining which factors (such as the number of columns
in an internal floating roof tank) are not known and which can be
determined from tables (e.g., the paint factor, the wind velocity
exponent), the user can decide which calculation steps need to be
performed.
5.5 CALCULATE MOLE FRACTIONS IN THE LIQUID
This step is only necessary if the vapor pressure of the liquid is
estimated using Raoult's Law. The number of moles of a component in a
mixture (liquid or vapor) is equal to the weight of the component in the
mixture divided by the molecular weight of the component. The mole
fraction of a component is the number of moles of the component divided by
the total number of moles in the mixture, including itself. Often mole
fractions are calculated from weight fractions. For example, a stored
liquid might be known to be 50 weight percent toluene, 35 weight percent
benzene, and 15 weight percent aniline. By looking at an arbitrary amount
of the liquid (1,000 pounds), the mole fractions of the three components
can be determined. This is demonstrated in Part 5 of Example B-l. The
mole fractions calculated for a mixture using an arbitrary amount of
liquid are valid no matter what amount of the mixture is actually present.
5.6 CALCULATE PARTIAL PRESSURES AND TOTAL VAPOR PRESSURE OF THE LIQUID
This step is required only when the vapor pressure of the stored
liquid is not known. Vapor presures of organic compounds are located in
Table A-2. Vapor pressures for certain compounds also can be calculated
using regression equations. ' If the mixture behaves ideally, Raoult's
Law is used to calculate the partial pressure of each component in the
mixture. As explained in Section 5.0, Raoult's Law states that the mole
fraction of the component in the liquid (x^) times the vapor pressure of
the component at the storage temperature (Pj j) is equal to the partial
pressure for that component. The sum of the partial pressures for all
components in the mixture is the vapor pressure of the mixture. This is
demonstrated in Step 6 of Example B-l.
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5.7 CALCULATE MOLE FRACTIONS IN THE VAPOR
This step is only required when the weight fractions or the molecular
weight of the vapor is not known. The mole fraction of a component in a
vapor mixture is equal to the partial pressure of the component divided by
the total vapor pressure of the liquid:
1 rtotal
This is demonstrated in Step 7 of Example B-l.
5.8 CALCULATE MOLECULAR WEIGHT OF THE VAPOR
This step is required only when the molecular weight of the vapor is
not known. Since molecular weight is a molar quantity, the molecular
weight of the vapor is dependent on the mole fractions of components in
the vapor. This calculation is shown in Step 8 of Example B-l.
5.9 CALCULATE WEIGHT FRACTIONS OF THE VAPOR
This step is required only when the weight fractions of the vapor are
not known. Vapor phase weight fractions for many mixtures are available
in VOC species data manuals (see Reference 14). Weight fractions can also
be calculated using the mole fractions from Step 7. For example, the
vapor phase mole fractions might have been calculated as 50 percent
toluene, 25 percent benzene, and 25 percent aniline. By looking at an
arbitrary amount of the vapor (1,000 moles), the weight fractions of the
three components can be determined. This is demonstrated in Step 9 of
Example B-l. The weight fractions calculated for a mixture using an
arbitrary amount of vapor are valid no matter what amount of the mixture
is actually present.
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5.10 CALCULATE TOTAL VOC EMITTED FROM THE TANK
Using the equations identified in Step 3 and the parameters
calculated in Steps 4 through 8, the total VOC emitted from the storage
tank can be calculated. This calculation is shown in Step 10 of
Example B-l.
5.11 CALCULATE AMOUNT OF EACH COMPONENT EMITTED FROM THE TANK
The amount of each component emitted from the tank is the weight
fraction of that component in the vapor (calculated in Step 9) times the
amount of total VOC emitted (calculated in Step 10). For example, if a
tank emits 1,000 pounds of VOC and the vapor weight fraction for benzene
is 0.15, then 150 pounds of benzene is emitted. The liquid volume of a
component emitted can be calculated by dividing the weight of the
component emitted by the density (Ib/gal) of the component. This is
demonstrated in Step 11 of Example B-l.
37
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6.0 REFERENCES
1. 52 FR 11420. Standards of Performance for New Stationary Sources:
Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid
Storage Vessels), Final Rule. April 8, 1987.
2. Letter from Jim Walters, API, to Anne Pope, U. S. EPA on May 11,
1988.
3. Compilation of Air Pollutant Emission Factors, Fourth Edition
(AP-42). U. S. Environmental Protection Agency, Office of Air and
Radiation, Office of Air Quality Planning and Standards. Research
Triangle Park, North Carolina. September 1985.
4. U. S. Environmental Protection Agency. Toxic Air Pollutant/Source
Crosswalk-A Screening Tool for Locating Possible Sources Emitting
Toxic Air Substances. Office of Air Quality Planning and Standards.
Research Triangle Park, North Carolina. EPA-450/4-87-023a.
December 1987.
5. UST Press Release. EPA Proposes Leak Detection and Cleanup For
Underground Storage Tanks. April 2, 1987.
6. U. S. Environmental Protection Agency. VOC Emissions From Volatile
Organic Liquid Storage TanksBackground Information for Promulgated
Standards. EPA-450/3-81-003b. January 1987.
7. U. S. Environmental Protection Agency. VOC Emissions From Volatile
Organic Liquid Storage TanksBackground Information for Proposed
Standards. Draft EIS. Office of A1r Quality Planning and
Standards. Research Triangle Park, North Carolina.
EPA-450/3-81-003a. April 1981.
8. Radian Corporation. Source Assessment of Methylene Chloride
Emissions, Final Report. Prepared for the U. S. Environmental
Protection Agency, Research Triangle Park, North Carolina. DCN
No. 231-020-19-06-02. p. 2-9 to 2-12 and p. 3-11 to 3-12.
9. Radian Corporation. Source Assessment of Trichloroethylene
Emissions, Final Report. Prepared for the U. S. Environmental
Protection Agency, Research Triangle Park, North Carolina. DCN
No. 231-020-19-06-07. p. 3-4 to 3-6. August 1985.
10. U. S. Environmental Protection Agency. Polymeric Coating of
Supporting SubstratesBackground Information for Proposed Standards,
Draft EIS. Office of Air Quality Planning and Standards. Research
Triangle Park, North Carolina. EPA-450/3-85-022a. April 1987.
39
-------
11. U. S. Environmental Protection Agency. Magnetic Tape Manufacturing
IndustryBackground Information for Proposed Standards, Draft EIS.
Office of Air Quality Planning and Standards. Research Triangle
Park, North Carolina. EPA-450/3-85-029a. December 1985.
12. 51 FR 2996. Standards of Performance for New Stationary Sources;
Magnetic Tape Manufacturing Industry, Proposed Rule. January 22,
1986.
13. Telecon. Murphy, P. B., MRI, to Moody, W. T., MRI. December 22,
1987.
14. U. S. Environmental Protection Agency. Air Emissions Species
Manual. Volume I. Volatile Organic Compound (VOC) Species
Profiles. Research Triangle Park, North Carolina.
EPA-450/2-89-003a. April 1988.
15. Handbook of Physics and Chemistry, pp. D-212 through D-215, 67th
Edition. CRC Press, Inc., 1986.
16. "The Properties of Gases and Liquids," Reid, Robert C. et al.
McGraw-Hill, Inc. 1977.
17. API Publication 2517 "Evaporation Loss From External Floating-Roof
Tanks," Draft Revised December 14, 1987.
40
-------
APPENDIX A.
FIGURES AND TABLES
-------
ADJUSTMENT FACTOR, C
o o o o *-
*
3 K» *. 01 0» C
4
f
/
/
f
/
/
A
t
s
s
s
s
j*
*>
**
z*
^
0 10 20 30
TANK DIAMETER, D (ft)
Figure A-l. Adjustment factor (C) for small diameter tanks.
A-l
-------
0.8
0.6
0.4
0.2
100 200 300
400
TURNOVERS PER YEAR, N
ANNUAL THROUGHPUT
TANK CAPACITY
NOTE: FOR 36 TURNOVERS PER YEAR OR LESS, KN = 1.0
FOR 36 TURNOVERS OR MORE PER YEAR,
180+N
= ~~
Figure A-2. Turnover factor (KN) for fixed roof tanks.
A-2
-------
r- O.S
8
7
9
10
11
' 12
13
14
13
| 2
3
_ 4
S
10
I 15
140
130
120 =
110 =
100 =
90
-= s
IM
70 = >
= Q
I 1
80 -i I
IZ u
.4*
40 =
30 H
20 \
10 i
Figure A-3. True vapor pressure (P) of crude oils (2-15 psi RVP)
A-3
-------
0.20
0.30
^0.40
' O.SO
^0.80
0.70
I 0.80
0.90
p- i.oo
r
120
110 -
100
90-
IF
*
a
k
^- 100
,00
r- 4.00
t*2^-
P- 8.00
L 7.00
=. 100
=- 9.00
iao
11.0
no
13.0
16.0
17.0
=-iau»
£-19.0
C-20.0
t-21.0
P-22.0
P-23.0
=-24.0
9
a
70^ 5
; >
-: c
^» S
60 3
t-
: a
5 * SLOPC Of THC ASTM OlSTIUATION
CUMVf AT 10 PERCENT EVAPORATED
. OtG f AT 18 PEHCSNT MINUS PEG f AT S PERCENT
10
IN TH« AKINCS Of DISTILLATION DATA
THE FOLLOWING AVfMAGf VALUE OP S MAY BE USED:
MOTOR GASOLINE 3
AVIATION GASOLINE 2
UGHT NAPHTHA (9-14 LB RVPI 3.5
NAPHTHA a-8 LB RVPt 15
30
20-=
10-2
J
Nt.n Da*hcU line illuMratc* vimpte pniMcm for RVP > III pmimfc per V^IKH* inch. ja»>4ine
SOL'RC E: Nomtwjph Jrjwn fnmt inc Jau of in* MJIHHIV! Buivaa t
r. ' »: .< F
Figure A-4. True vapor pressure (P) of refined petroleum liquids like
gasoline and naphthas (1-20 psi RVP).
A-4
-------
to
9
8
.7
8
1
I
0.1
.07
.OB
.04
.03
.02
0.01
_
-
-
-
-
5
E
-
-
-
-
-
-
M
=/
-
f
1
\
f
/
1
>
X
f
\
<
1
ll
/
X
/
^
X
f-
V14.7
Wfw*:
i
1
i
1
i
P\ "
iT?J
l.7poui»
^
\
IV
dtpcrv
|
uan im
I
/
^
h atnoli
f
/-
/-
/ -
-
-
^
^
_
-
-
-
-
-
5
^
^
I 0
9
3
01
09
08
07
06
OS
(X
03
02
OOt
78 9 10
TRUE VAPOM PfttSSUNC. />fo*Ml
11
12 13
.NOTt. DMtod liM illmtraM* tampte problem foe ^ - 9.4 pounds par iqvart inch ataotuic.
Figure A-5. Vapor pressure function (P*).
A-5
-------
100
50
'o
S
10
O
H
U
co
CO
O
H-3
0.5
0.1
Z3
Primary Only
Primary And Shoe-
Mounted Secondary
Primary And Rim-
Mounted Secondary
Average Fit Seal
Tight Fit Seal
1 5 10 15 30
WIND SPEED (mi/hr)
Figure A-6. Rim seal loss factor for an external floating roof welded
tank with a mechanical shoe primary seal.
A-6
-------
100
Cft
O
i-l
>,
*!
r^H
'o
s
jg
o<
8
U
£
CO
CO
O
J
J
^
CO
s
HH
C^
>->
O
O
LA
.1
/5'
/
I/
Primary Only
Primary And
'Weather Shield
. Primary And Rim-
Mounted Secondary
Avg. Fit Seal
-- Tight Fit Seal
1 5 10 15
WIND SPEED (mi/hr)
30
Figure A-7. Rim seal loss factor for an external floating roof
welded tank with a liquid-mounted resilient filled primary seal.
A-7
-------
RIM SEAL LOSS FACTOR (Ibmole/ft yr)
H-* Lft
i > Ul O O
_L t./, O O O O
/
/ /
/ /
/ /
f I >
//f
' /,'
t
/
1
I/
1
'/
V
/
f
I
1
1
f
1
1
/
>
/
1
f
(
/
/
/
/
/
f
t
/
1,
r
,
/
1
/
1
//
/ "*^^
/
/
/ /"^
/ /"^
y
//
x
/
i nrnary uniy
Primary And
Weather Shield
... Primary And Rim-
Mounted Secondary
i riiiidiy /AJIU.
Weather Shield
__ PTITTI^T^^ AnH Rim
Mounted Secondary
Avg. FiL Seal
Tight Fit Sea]
1 5 10 15 30
WIND SPEED (mi/hr)
Figure A-8. Rim seal loss factor for an external floating roof
welded tank with a vapor-mounted resilient filled primary seal.
A-8
-------
o
S
O
H
U
oo
00
O
CO
100
50
10
0.5
0.1
7
Primary Only
Primary And Shoe-
Mounted Secondary
Primary And Rim-
Mounted Secondary
Avg. Fit Seal
1 5 10 15 30
WIND SPEED (mi/hr)
Figure A-9. Rim seal loss factor for an external floating roof
riveted tank with a mechanical shoe primary seal.
A-9
-------
3 "8
"
.0 00
c c
DD
I
flj D
<> *-
T! W
-S-3
q ea
DO
IT
I I I I I
I I I I
o
CN
^^
^
p
00
Q
X
-------
I/I
-------
d)
3
o
X
(U
o
o
o
SSO1ONIJJLH
CM
-^
I
<:
-------
6
,J8
3
o
o
0>
Q
w
W
CU
00
Q
O
oo
1_
O)
4-1
X
at
o
4->
U
o
c
o
o
CO
._<
-------
w
ir *->
O C
-------
.a «
r^ i-^j
| ^§
S oo
u zr
T3 G
D O
*j -*
r-1 *'
§)§
S «
^<
p
i-s
fl) C3
s°
*O C2
D O
41 --H
"§>§
3l
l 1 1 1
1 1 1 1
1 1 1
]
I I I I
1 1 1 1
1 1 1 1
I 1
o
CN
s-
II
_*
it3
(U
J3
U
It}
o
o
&»
^
^^
^
P
w
o
o
en
o
o
to
f^
1
SSO19NLLLH
A-15
-------
i
I I I I
I I I I
I I I I
en
-------
t-4
13 C
1 ' ?
_KJ M <
Q Q S
*^" t^ C
me* 0
1 1 1
\^
1 1
3
2 i
3 ^
1 1
5 i
: c.
k
i
,
r
\
X
,
3
->
4
rf
S
H
ri
4
M
X
..
o
CD
Q
2
o
Q
_j
1 i i 1
\
X
1 I I 1
>~
*->
Ol
o
o
en
id
o
c
(U
-------
O "O
"-1 ft}
c *
I .S
*o c
-H
^
OJ
O
o
en
-------
8
en
o
o
4->
c
o
Q.
C
o
en
c
o
o
u
o
c
O
o
SSO1 ONLLLM dOOH 1V1O1
en
^-1
I
0)
en
A-19
-------
o
o
s-
E *.§
^ SO
-a
2
»
-a +
23
II -* JH
lit
a
i
n
O
O
0
S <
o
S-< in
- f-i O
O
2
(T3
4-»
O
SSO1 ONIJLLU dOOH 1V1O1
OJ
3
A-20
-------
a
i
o
8500
WOO
7900
6000
WOO
MOO
5000
4600
4000
3000
280
2000
1500
1000
500
i i i i
.
^
^^
/
BOLTED OfiCX(Se« NOM) /
f, « ffUMCI) Of * (1 JK) 0 + 1*U /
/,
f
1 1 1 I
//
7
i i t i
/
/A
//
/
/
/
1 ?\
' /
/
/
/
/
/ /
/
/
/ WIUOOGCK '
/ * - 0« * (1JM8) 0 + 134J
t t 1 1
til.
1 1 1 1
100 190 290 290
T«NKDMMCTEM.Otm
300
390
400
FtRinfs inetttdK (I) aeeos hatch, with un|aU«wi. uabotod cowtr (2) built-up eoiurna <*«Us. with
lidiat cow (3) adjiuuMc deck lets: (4) puft fkw wtU. with ungwlMMd. uaboted eavcn (5)
lattv wtU. *i* uafMkmd ilidiag com: (6) umpte «d|. with siit faboe ml (10 pnom opa irea): (7) I
inch diwMor nub dnin (oaly
-------
4800
4000
3300
3000
LL.
C/1
2000
1300
1000
500
BOLTED OfCX
laoaan o* «IO.TH o * iou
\
7
/
7
WBUWD OKX (SM New
P, - (0.0132) O1 - (0.79) 0 - 103.2
100 190 200 2SO
TAMCOMMCTBt.O(ll)
300
390
400
BASIS: Fttnnjs include: (I) access hatch, wnti ungasketed. unbolted cover (2) adjustable deck !«gs: (3) jauge
tio.tt *cU, wuh uafukncd. unbotod cow. (4) sampte wcU. with slit fabric scat 110 percent open ami: iJi l-
inch diwnrar SB* dnins (oniy on botad deck): and (6) vKimm breaket with pskcted weighted mectumcal
xmmm This bvit VMS dem*4 from a survey of usen and nunufxtuRrs. Othtr tlmnp may be typically used
witiua pMkokr conpeoiet or orfsiuzMioa* w reflea standards and/or sptafiaaoM of thai group.
NOTTS: If no specific infommnoa is available, assume welded decks are the most comm
in UM in tanks with self-supporting fixed roots.
m/typical type currently
Figure A-22. Approximated total deck fitting loss factors (Fp) for
typical deck fittings in tanks with self-supported fixed roofs and
either a bolted deck or a welded deck. (This figure is to be used only
when tank specific data on the number and kind of deck fittings are
unavailable.)
A-22
-------
TABLE A-l. PAINT FACTORS (Fp) FOR FIXED ROOF TANKS
Tank
Roof
White
Aluminum (specular)
White
Aluminum (specular)
White
Aluminum (diffuse)
White
Light gray
Medium gray
color
Shell
White
White
Aluminum (specular)
Aluminum (specular)
Aluminum (diffuse)
Aluminum (diffuse)
Gray
Light gray
Medium gray
Paint
factors (F0)
Paint condition
Good
1.00
1.04
1.16
1.20
1.30
1.39
1.30
1.33
1.40
Poor
1.15
1.18
1.24
1.29
1.38
1.46
1.38
1.44a
1.58a
Estimated from the ratios of the seven preceding paint factors.
A-23
-------
2S
CJ
I
on
OQ
oo
s
PROPERTIES
esj
8
1^-
11«:
*-
- 3.S
oo vn *r r*. P-» o o
O
O
<». a» CM a>
00
M - O
O O O
oo C* «*
ai ^v csi o ot
g
3 oS
^ odd
**» <"M «H ^ OO <** O O O 9 ** ^" <*l -« odd f\i - ^ d V
*- ^ OD - «r 10 cf* m m -*
o o o o
CM CD O CM 49 vQ O» O O» *
> ^r CM CNt OOO c\i O * O *^
33
v«o >o u> f
So r
7- «-S£
,-8 2^ tZS
0»4IO O* > u O O
ji *- U U ** O
P*T «..- =«
si
^ "S O O 41
4=jC««~ f
wwOJ= _< t. 4/
u a> ^- u w ii 41 4» **
S 2 2-5SSS -«5^^
ooo-
jq3'w_a^a.a o o ^- ' V>«
tcMcaauu u u fM*«4iai -w S..C .
! aaeuu 5 5 o w * "3 ^ Q 5 a " 5 ^ .
^21! 5-5
rii^^:
A-24
-------
28
S
-S
8
CM
I
* *3
5 a * <9
Ills
O -w m
o *a JR
S
d^-c
Q tn~* CM to O* --O f-ToO U» WT» O CM ** O « O*
CM O% fl d4 r^ CM O ***
doJdfV ^do^fi (*icod^-d d^ (M Ot WV (Mr^><
^* CM r^. rs. <
ID ** OO ,*rf -W U H- nt»»
SS ".
fc ?
S V
I I
a *s
£ «
I 5
** <*
2 I"
8 %
s 1
** ^
I ?
. §.
S 3
Iff 4->
S ~
3 8
O t-
a: a. c
u -3
U ') U
o o «o
<4. a. Q.-*J
Of > IQ iq
A-25
-------
TABLE A-3. AVERAGE ANNUAL STORAGE TEMPERATURE (To)
AS A FUNCTION OF TANK PAINT COLOR
Average
annual storage
Tank color temperature, TS
White
Aluminum
Gray
Black
TA+3.5
TA+5.0
T^ is the average annual ambient temperature in degrees
Fahrenheit.
A-26
-------
TABLE A-4. AVERAGE ANNUAL AMBIENT TEMPERATURE (Ta,
U.S. LOCATIONS
F) FOR SELECTED
Birmingham, Ala.
Huntsvi 1 le, Ala.
Mobile, Ala.
Montgomery, Ala.
Anchorage, Alaska
Annette, Alaska
Barrow, Alaska
Barter Island, Alaska
Bethel, Alaska
Settles, Alaska
Big Delta, Alaska
Cold Bay, Alaska
Fairbanks, Alaska
Gulkana, Alaska
Homer, Alaska
Juneau, Alaska
King Salmon, Alaska
Kodiak, Alaska
Kotzebue, Alaska
McGrath, Alaska
Nome, Alaska
St. Paul Island, Alaska
Talkeetna, Alaska
Unalakleet, Alaska
Valdez, Alaska
Yakutat, Alaska
Flagstaff, Ariz.
Phoenix, Ariz.
Tucson, Ariz.
WinslOM, Ariz.
Yuma, Ariz.
Fort Smith, Ariz.
Little Rock, Ark.
North Little Rock, Ark.
Bakersf ield, Calif.
Bishop, Cat if.
Blue Canyon, Cal if.
Eureka , Ca 1 i f .
Fresno, Cal if .
Long Beach, Cal if .
Los Angeles, Calif.
International Airport
Los Angeles, Cal if .
Mount Shasta, Cal if .
Red Bluff, Cal if.
Sacramento , Ca 1 i f .
San Diego, Cal if .
San Francisco, Calif.
International Airport
San Francisco, Calif. City
Santa Barbara , Ca 1 i f .
Santa Mar la, Ca 1 i f .
62.0
60.6
67.5
64.9
35.3
45.4
9.1
9.6
28.4
21.2
27.4
37.9
23.9
26.5
36.6
40.0
32.8
40.7
20.9
25.0
25.5
34.3
32.6
26.4
38.3
38.6
45.4
71.2
68.0
54.9
73.8
60.8
61.9
61.7
65.5
56.0
50.4
52.0
62.6
63.9
62.6
65.3
49.5
62.9
60.6
63.8
56.6
56.8
58.9
56.8
Stockton , Ca 1 i f .
Alasosa, Colo.
Colorado Springs, Colo.
Denver, Colo.
Grand Junction, Colo.
Pueblo, Colo.
Bridgeport, Conn.
Hartford, Conn.
Mi Imington, Del .
Wash., D.C. -Dulles Airport
Wash. O.C. -National Airport
Apalachicol a, Fla.
Daytona Beach, Fla.
Fort Myers, Fla.
Gainsvi lie, Fla.
Jackson vi Me, Fla.
Key West, Fla.
Miami, Fla.
Orlando, Fla.
Pensaco la, Fla.
Tal lahassee, Fla.
Tampa, Fla.
Vero Beach, Fla.
West Palm Beach, Fla.
Athens, Ga.
Atlanta, Ga.
Augusta, Ga.
Columbus, Ga.
Macon, Ga.
Savannah, Ga.
Hi lo, Hawai i
Honolulu, Hawai i
Kahu 1 u i , Hawa i i
Lihua, Hawai i
Boise, Idaho
Lewiston, Idaho
Pocatello, Idaho
Cairo, III.
O'Hare Airport, Chicago, III.
Moline, III.
Peoria, III.
Rock ford, III.
Springfield, III.
Evan vi lie, Ind.
Fort Wayne, Ind.
Indianapol is, Ind.
South Bend, Ind.
Des Moines, Iowa
Dubuque, Iowa
Sioux City, Iowa
Waterloo, Iowa
Concordia, Kans.
Dodge City, Kans.
Good land, Kans.
Topeka, Kans.
61.6
41.2
48.9
50.3
52.7
52.8
51.8
49.8
54.0
53.9
57.5
68.2
70.3
73.9
68.6
68.0
77.7
75.7
72.4
68.0
67.2
72.0
72.4
74.6
61.4
61.2
63.2
64.3
64.7
65.9
73.6
77.0
75.5
75.2
51.1
52.1
46.6
59.1
49.2
49.5
50.4
47.8
52.6
55.7
49.7
52.1
49.4
49.7
46.3
48.4
46.1
53.2
55.1
50.7
54.1
(continued)
A-27
-------
TABLE A-4. (continued)
Wichita, Kans.
Cincinnati, Ky. Airport
Jackson, Ky.
Lexington, Ky.
Louisvi 1 le, Ky.
Paducah, Ky.
Bacon Rouge, La.
Lake Charles, La.
New Orleans, La.
Sheveport, La.
Caribou, Maine
Portland, Maine
Baltimore, Md.
Blue Hill Observation, Mass.
Boston, Mass.
Worcester, Maine
Alpena, Mich.
Detroit, Mich.
Flint, Mich.
Grand Rapids, Mich.
Noughton Lake, Mich.
Lansing, Mich.
Marquette, Mich.
Maskegon, Mich.
Sauft St. Marie, Mien.
Duluth, Minn.
International Falls, Minn.
Minnesota-St. Paul, Minn.
Rochester, Minn.
Saint Cloud, Minn.
Jackson, Miss.
Meridian, Miss.
Tupelo, Miss.
Columbia, Mo.
Kansas City, Missouri Airport
Kansas City, Mo.
St. Louis, Mo.
Springfield, Mo.
Billings, Mont.
Glasgow, Mont.
Great Falls, Mont.
Havre, Mont.
Helena, Mont.
Kali spell, Mont.
Miles City, Mont.
Missoula, Mont.
Grand Island, Nebr.
Lincoln, Nebr.
Norfolk, Nebr.
North Platte, Nebr.
Omaha, Nebr. Eppley Airport
Omaha, Nebr. City
Scottsbluff, Nebr.
Valentine, Nebr.
Elko, Nev.
56.4
53.4
52.6
54.9
56.2
57.2
67.5
68.0
68.2
68.4
38.9
45.0
55.1
48.6
51.5
46.8
42.2
48.6
46.8
47.5
42.9
47.2
39.2
47.2
39.7
38.2
36.4
44.7
43.5
41.4
64.4
64.1
61.9
34.1
56.3
59.1
55.4
55.9
46.7
41.6
44.7
42.3
43.3
42.5
45.4
44.1
49.9
50.5
46.3
48.1
51.1
49.5
48.5
46.8
46.2
Ely, Nev.
Las Vegas, Nev.
Reno, Nev.
Winnesucca, Nev.
Concord, N.H.
Mt. Washington, N.H.
Atlantic City, N.J. Airport
Atlantic City, NJ-City
Newark, N.J.
Albuquerque, N. Mex.
Clayton, N. Hex.
Roswel 1 , N. Mex.
Albany, N.Y.
Binghamton, N.Y.
Buffalo, N.Y.
New York Central Park, N.Y.
New York JFK Airport, N.Y.
New York La Guard! a
Airport, N.Y.
Rochester, N.Y.
Syracuse, N.Y.
Ashevil le, N.C.
Cape Hatteras, N.C.
Charlotte, N.C.
Greensboro High Point, N.C.
Raleigh, N.C.
Wilmington, N.C.
Bismarck, N.D.
Fargo, N.O.
Wil 1 iston, N.O.
Akron, Ohio
Cleveland, Ohio
Columbus, Ohio
Dayton, Ohio
Mansfield, Ohio
Toledo, Ohio
Youngstown, Ohio
Oklahoma City, Ok la.
Tulsa, Okla.
Astoria, Or eg.
Burns, Oreg.
Eugene, Oreg.
Medford, Oreg.
Pendleton, Oreg.
Portland, Oreg.
Salem, Oreg.
Sexton Summit, Oreg.
Guam, Pac.
Johnston, Island, Pac.
Al lentown, Pa.
Erie, Pa.
Harrisburg, Pa.
Phi ladelphia, Pa.
Pittsburg, Pa.
Avoca, Pa.
WMIiamport, Pa.
44.4
66.2
49.4
48.8
45.3
26.6
53.1
54.1
54.2
56.2
52.9
61.4
47.2
45.7
47.6
54.6
53.2
54.3
48.0
47.7
55.5
61.9
60.0
57.8
59.0
63.4
41.3
40.5
40.8
49.5
49.6
51.7
51.9
49.5
48.6
48.2
59.9
60.3
50.6
46.6
52.5
53.6
52.5
53.0
52.0
47.7
78.8
78.9
51.0
47.5
53.0
54.3
50.3
49.1
58.1
(continued)
A-28
-------
TABLE A-4. (continued)
Black Island, R.I.
Providence, R. 1 .
Charleston, S.C. , Airport
Charleston, S.C. -City
Columbia, S.C.
Greenvi 1 le-Spartanburg, S.C.
Aberdeen, S.O.
Huron, S.O.
Rapid City, S.O.
Sioux Falls, S.O.
Bristol -Johnson City, Tenn.
Chattanooga, Tenn.
Knoxv i 1 1 e , Tenn .
Memphis, Tenn.
Nashvi 1 le, Tenn.
Oak Ridge, Tenn.
Abi lene, Tex.
Anari 1 lo, Tex.
Austin, Tex.
Brownsvi Me, Tex.
Corpus Christ!, Tex.
Dallas-fort Worth, Tex.
Del Rio, Tex.
El Paso, Tex.
Galveston, Tex.
Houston, Tex.
lubbock, Tex.
Midland-Odessa, Tex.
Port Arthur, Tex.
San Angelo, Tex.
San Antonio, Tex.
Victoria, Tex.
Waco, Tex.
Wichita Falls, Tex.
Mil ford, Utah
Salt Lake City, Utah
Bur 1 i ngton , Vt .
Lynchburg, Va.
Norfolk, Va.
Richmond, Va.
Roanoke, Va.
Olympia, Wash.
Qu i 1 1 ayute , Wash .
Seattle, Wash. International
Airport
Seattle, Wash. City
Spokane, Wash.
Stampede Pass, Wash.
Wells Wells, Wash.
Yak i ma, Wash.
Beckley, W. Va.
Charleston, W. Va.
Elkins, W. Va.
Hunt i ngton, W. Va.
Green Bay, Mis.
La Cross, Wis.
50.2
50.3
64.8
64.1
63.3
60.1
43.0
44.7
46.7
45.3
55.9
59.4
58.9
61.8
59.1
57.5
64.5
57.3
68.1
73.6
72.1
66.0
69.8
63.4
69.6
68.3
59.9
63.5
68.7
65.7
68.7
70.1
67.0
63.3
49.1
51.7
44.1
56.0
59.5
57.7
56.1
49.6
48.7
51.4
52.7
47.2
59.3
54.1
49.7
50.9
54.8
49.3
55.2
43.6
46.1
Madison, Wis. 43.2
Milwaukee, Wis. 46.1
Casper, Wyo. 45.2
Cheyenne, Wyo. 45.7
Lander, Wyo. 44.4
Sheridan, Wyo. 44.6
Source: Reference 17.
A-29
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A-30
-------
TABLE A-6. AVERAGE ANNUAL WIND SPEED (v, mi/h) FOR SELECTED U.S.
LOCATIONS
Birmingham, Ala.
Huntsvi 1 le, Ala.
Mobile, Ala.
Montgomery, Ala.
Anchorage, Alaska
Annette, Alaska
Barrow, Alaska
Barter Alaska
Bethel, Alaska
Settles, Alaska
Big Delta, Alaska
Gold Bay, Alaska
Fairbanks, Alaska
Gulkana, Alaska
Homer, Alaska
Juneau, Alaska
King Salmon, Alaska
Kodiak, Alaska
Kotzebue, Alaska
McGrath, Alaska
Nome, Alaska
St. Paul Island, Alaska
Talkeetna, Alaska
Valdez, Alaska
Yakutat, Alaska
Flagstaff, Ariz.
Phoenix, Ariz.
Tucson, Ariz.
Winslow, Ariz.
Yuma, Ariz.
Fort Smith, Ark.
Little Rock, Ark.
Bakersf ietd, Cat if .
Blue Canyon, Cal if.
Eureka, Cal if .
Fresno, Cal if .
Long Beach , Ca 1 i f .
Los Angeles, Calif.
International Airport
Los Angeles, Cal if.
Mount Shasta, Cal if .
Oakland, Cal if.
Red Bluff, Calif.
Sacramento, Cal if .
San Diego, Cal if.
San Francisco, Calif.
International Airport
San Francisco, Calif. City
Santa Mar la, Ca 1 i f .
Stockton , Ca 1 i f .
Colorado Springs, Colo.
Denver, Colo.
7.3
8.1
9.0
6.7
6.8
10.6
11.8
13.2
12.8
6.7
8.2
16.9
5.4
6.8
7.2
8.4
10.7
10.6
13.0
5.1
10.7
18.3
4.5
6.0
7.4
7.3
6.3
8.2
8.9
7.8
7.6
8.0
6.4
7.7
6.8
6.4
6.4
7.5
6.2
5.1
8.2
8.6
8.1
6.8
10.5
8.7
7.0
7.5
10.1
8.8
Grand Junction, Colo.
Pueblo, Colo.
Bridgeport, Conn.
Hartford, Conn.
Wilmington, Del.
Wash., D.C. -Dulles Airport
Wash. D.C. -National Airport
Apalachicola, Fla.
Daytona Beach, Fla.
Fort Myers, Fla.
Jacksonvi lie, Fla.
Key West, Fla.
Miami, Fla.
Orlando, Fla.
Pensacola, Fla.
Tal lahassee, Fla.
Tampa, Fla.
West Palm Beach, Fla.
Athens, Ga.
Atlanta, Ga.
Auqueta, Ga.
Columbus, Ga.
Macon, Ga.
Savannah, Ga.
Hilo, Hawaii
Honolulu, Hawai i
Kahului, Hawaii
Lihua, Hawaii
Boise, Idaho
Pocatello, Idaho
Cairo, III.
Chicago, III.
Moline, Ml.
Peoria, III.
Rockford, III.
Springfield, III.
Evansvi lie, Ind.
Fort Wayne, Ind.
Indianapolis, Ind.
South Bend, Ind.
Des Moines, Iowa
Sioux City, Iowa
Waterloo, Iowa
Concord) a, Kans.
Dodge City, Kans.
Good land, Kans.
Topeka, Kans.
Wichita, Kans.
Cincinnati, Ky. Airport
Jackson, Ky.
Lexington, Ky.
Louisvil le, Ky.
Baton Rouge, La.
Lake Charles, La.
New Orleans, La.
8.1
8.7
12.0
8.5
9.2
7.5
9.3
7.9
8.8
8.2
8.2
11.2
9.2
8.6
8.4
6.5
8.6
9.5
7.4
9.1
6.5
6.7
7.7
7.9
7.1
11.6
12.8
11.9
8.9
10.2
8.5
10.3
10.0
10.1
9.9
11.3
8.2
10.2
9.6
10.4
10.9
11.0
10.7
12.3
13.9
12.6
10.2
12.4
9.1
7.0
9.5
8.3
7.7
8.7
8.2
A-31
-------
TABLE A-6. (continued)
Sheveport, La.
Caribou, Maine
Portland, Maine
Baltimore, Md.
Blue Hill Observation, Mass.
Boston, Mass.
Worcester, Mass.
Alpena, Mich.
Detroit, Mich.
Flint, Mich.
Grand Rapids, Mich.
Noughton Lake, Mich.
Lansing, Mich.
Maskegon, Mich.
Sault Ste. Marie, Mich.
Duluth, Minn.
International Falls, Minn.
Minnesota-St. Paul, Minn.
Rochester, Minn.
Saint Cloud, Minn.
Jackson, Miss.
Meridian, Miss.
Columbia, Mo.
Kansas City, Missouri Airport
Kansas City, Mo.
St. Louis, Mo.
Springfield, Mo.
Bi 1 1 ings, Mont.
Glasgow, Mont.
Great Fal Is, Mont.
Havre, Mont.
Helena, Mont.
Kalispell, Mont.
Miles City, Mont.
Missoula, Mont.
Grand Island, Nebr.
Lincoln, Nebr.
Norfolk, Nebr.
North Platte, Nebr.
Omaha, Nebr.
Scottsbluff, Nebr.
Valentine, Nebr.
Elke, Nev.
Ely, Nev.
Las Vegas, Nev.
Reno, Nev.
Winnemucca, Nev.
Concord, N.H.
Mt. Washington, N.H.
Atlantic City, N.J.
Newark, N.J.
Albuquerque, N. Mex.
Roswel 1 , N. Mex.
Albany, N.Y.
Binghamton, N.Y.
3.6
11.2
8.7
9.2
15.4
12.4
10.2
7.9
10.2
10.3
9.8
8.9
10.1
10.7
9.4
11.2
9.0
10.5
12.9
3.0
7.4
6.0
9.8
10.7
9.9
9.7
10.9
11.3
10.8
12.8
9.9
7.8
6.6
10.2
6.1
12.0
10.4
11.8
10.3
10.6
10.6
10.0
6.0
10.4
9.2
6.5
7.9
6.7
35.1
10.2
10.2
9.!
8.7
8.9
10.3
Buffalo, N.Y.
New York Central Park, N.Y.
New York La Guard i a
Airport, N.Y.
Rochester, N.Y.
Syracuse, N.Y.
Ashevil le, N.C.
Cape Hatter as, N.C.
Charlotte, N.C.
Greensboro High Point, N.C.
Raleigh, N.C.
Wi Imington, N.C.
Bismarck, N.O.
Fargo, N.D.
Wil listen, N.D.
Akron , Oh i o
Cleveland, Ohio
Columbus, Ohio
Dayton, Ohio
Mansfield, Ohio
Toledo, Ohio
Youngstown , Oh io
Oklahoma City, Okla.
Tulsa, Okla.
Astoria, Oreg.
Eugene, Oreg.
Medford, Oreg.
Pendleton, Oreg.
Portland, Oreg.
Salem, Oreg.
Sexton Summit, Oreg.
A 1 1 entown , Pa .
Erie, Pa.
Harrisburg, Pa.
Phi ladelphia, Pa.
Pittsburg, Pa. International
A i rport
Avoca, Pa.
Williamport, Pa.
San Juan, P.R.
Providence, R. 1 .
Charleston, S.C.
Columbia, S.C.
Greenvi 1 le-Spartanburg, S.C.
Aberdeen, S.D.
Huron, S.D.
Rapid City, S.D.
Sioux Fal \5, S.D.
Bristol -Johnson City, Tenn.
Chattanooga , Tenn .
Knoxvi lie, Tenn.
Memphis, Tenn.
Nashvi lie, Tenn.
Oak Ridge, Tenn.
Ab i 1 ene , Tex .
Amar i 1 1 o , Tex .
12.1
9.4
12.3
9.8
9.7
7.6
11.4
7.5
7.6
7.8
8.9
10.3
12.5
10.1
9.8
10.7
8.7
10.1
11.0
9.4
10.0
12.5
10.4
8.5
7.6
4.8
9.0
7.9
7.0
11.8
9.2
11.2
7.7
9.5
9.2
8.4
7.9
8.5
10.6
8.7
6.9
6.7
11.2
11.7
11.2
11.1
5.6
6.2
7.1
9.0
3.0
4.4
12.2
13.7
(continued)
A-32
-------
TABLE A-6. (continued)
Austin, Tex. 9.3
BrownsviIle, Tex. 11.6
Corpus Christ!, Tex. 12.0
Dallas-Port Worth, Tex. 10.8
Del Rio, Tx. 9.9
El Paso, Tex. 9.2
Galveston, Tex. 11.0
Houston, Tex. 7.8
Lubbock, Tex. 12.4
Midiand-Odessa, Tex. 11.1
Port Arthur, Tex. 9.9
San Angelo, Tex. 10.4
San Antonio, Tex. 9.4
Victoria, Tex. 10.0
Waco, Tex. 11.3
Wichita Falls, Tex. 11.7
Salt Lake City, Utah 8.8
Burlington, Vt. 8.8
Lynchburg, Va. 7.8
Norfolk, Va. 10.5
Richmond, Va. 7.5
Roanoke, Va. 3.3
Olympia, Wash. 6.7
Quillayuta, Wash. 6.1
Seattle, Wash. International 9.1
Airport
Spokans, Wash.
Walla Malta, Wash.
Yak i ma, Wash.
Beck ley, W. Va.
Charleston, W. Va.
Elkins, W. Va.
Hunt ington, W. Va.
Green Bay, Wis.
La Crosse, Wis.
Madison, Wis.
Milwaukee, Wis.
Casper, Wyo.
Cheyenne, Wyo.
Lander, Wyo.
Sheridan, Wyo.
8.7
5.3
7.1
9.3
6.4
6.2
6.5
10.1
8.8
9.8
11.6
12.9
12.9
6.9
8.1
Source: Reference 17.
A-33
-------
TABLE A-7. AVERAGE CLINGAGE FACTORS (CF)
(bbl/1,000 ft )
Liquid
Gasoline
Single component stocks
Crude oil
Light rust*
0.0015
0.0015
0.0060
Shell condition
Dense rust
0.0075
0.0075
0.030
Gunite lined
0.15
0.15
0.60
alf no specific information is available, these values can be assumed to
represent the most common condition of tanks currently in use.
A-34
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A-36
-------
TABLE A-9. TYPICAL NUMBER OF EXTERNAL FLOATING ROOF VACUUM BREAKERS
AND DRAINS4
Tank .
diameter, d (ft)D
50
100
150
200
250
300
350
400
Vacuum
Pontoon roof
1
1
2
3
4
5
6
7
breakers,
Double-deck
roof
1
1
2
2
3
3
4
4
Roof drains
Double-deck
roofc
1
1
2
3
5
7
aTh1s table was derived from a survey of users and manufacturers. The
actual number of vacuum breakers may vary greatly depending on throughput
and manufacturing prerogatives. The actual number of roof drains may
also vary greatly depending on the design rainfall and manufacturing
prerogatives. For tanks over 300 ft diameter, actual tank data or
manufacturer's recommendations may be needed for the number of roof
drains. This table should not supersede information based on actual tank
.data.
If the actual diameter is between the diameters listed in this table, use
the closest diameter listed. If midway, use the next larger diameter.
cRoof drains that drain excess rainwater into the product are not used on
pontoon floating roofs. They are, however, used on double-deck floating
roofs and are typically left "open."
A-37
-------
TABLE A-10. TYPICAL NUMBER OF EXTERNAL FLOATING ROOF LEGSa
Tank
diameter, d (ft)D
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
Vacuum
Pontoon roof
4
4
6
9
13
15
16
17
18
19
20
21
23
26
27
28
29
30
31
32
33
34
35
36
36
37
38
38
39
39
40
41
42
44
45
46
47
48
breakers
Center legs
2
4
6
7
9
10
12
16
20
24
28
33
38
42
49
56
62
69
77
83
92
101
109
118
128
138
148
156
168
179
190
202
213
226
238
252
266
281
Double-deck
roof
6
7
8
10
13
16
20
25
29
34
40
46
52
58
66
74
82
90
98
107
115
127
138
149
162
173
186
200
213
226
240
255
270
285
300
315
330
345
aThis table was derived from a survey of users and manufacturers. The
actual number of roof legs may vary greatly depending on age, floating
roof style, loading specifications, and manufacturing prerogatives. This
.table should not supersede information based on actual tank data.
DIf the actual diameter is between the diameters listed in this table, use
the closest diameter listed. If midway, use the next larger diameter.
A-38
-------
TABLE A-ll. SUMMARY OF INTERNAL FLOATING DECK FITTING LOSS FACTORS (KF)
AND TYPICAL NUMBER OF FITTINGS (Np)a
Deck fitting type
Deck
fitting loss
factor, Kp
(Ib-mol/yr)
Typical
No. of
fittings, Np
Access hatch
Bolted cover, gasketed 1.6
Unbolted cover, gasketed 11.
Unbolted cover, ungasketed 25
Automatic gauge float well
Bolted cover, gasketed 5.1
Unbolted cover, gasketed 15
Unbolted cover, ungasketed 28°
Column well
Bulltup column-sliding cover, gasketed 33
Builtup column-sliding cover, ungasketed 47°
Pipe column-flexible fabric sleeve seal 10
Pipe column-sliding cover, gasketed 19
Pipe column-sliding cover, ungasketed 32
Ladder well
Sliding cover, gasketed 56.
Sliding cover, ungasketed 76°
Roof leg or hanger well .
Adjustable 7.9°
Fixed 0
Sample pipe or well
Slotted pipe-sliding cover, gasketed 44
Slotted pipe-sliding cover, ungasketed 57
Sample well-slit fabric seal, 12°
10 percent open area
Stub drain, 1 inch diameter0 1.2
1
(see Table A-12)
Vacuum breaker
Weighted mechanical
Weighted mechanical
actuation,
actuation,
gasketed
ungasketed
0.7b
0.9
1
?For windpseeds ranging from 2 to 15 miles/h.
°If no specific information is available, this value can be assumed to
represent the most common/typical deck fittings currently used.
°Not used in welded contact internal floating decks.
dD = tank diameter, ft.
A-39
-------
TABLE A-12. TYPICAL NUMBER OF COLUMNS (Nr) AS A FUNCTION OF
TANK DIAMETER (D) FOR INTERNAL FLOATING ROOF TANKS
WITH COLUMN SUPPORTED FIXED ROOFSa
Tank diameter range Typical number
of
D (ft) columns, N
0 < D < 85
85 < D < 100
100 < D < 120
120 < 0 < 135
135 < D < 150
150 < D < 170
170 < D < 190
190 < D < 220
220 < D < 235
235 < D < 270
270 < D < 275
275 < D < 290
290 < D < 330
330 < D < 360
360 < D < 400
1
6
7
8
9
16
19
22
31
37
43
49
61
71
81
aThis table was derived from a survey of users and
manufacturers. The actual number of columns in a particular
tank may vary greatly with age, fixed roof style, loading
specifications, and manufacturing prerogatives. Data in this
table should not supercede information on actual tanks.
A-40
-------
TABLE A-13. DECK SEAM LENGTH FACTORS (SD) FOR TYPICAL DECK
CONSTRUCTIONS FOR INTERNAL FLOATING ROOF TANKS3
Typical deck seam
length factor
Deck construction SQ (ft/ft )
Continuous sheet construction"
5 ft wide sheets 0.20C
6 ft wide sheets 0.17
7 ft wide sheets 0.14
Panel construct iond
5x7.5 ft rectangular 0.33
5x12 ft rectangular 0.28
*Deck seam loss applies to bolted decks only.
= 1/W, where W = sheet width (ft).
If no specific information is available, these factors can be
assumed to represent the most common bolted decks currently
.in use.
aSD = (L+W)/LW, where W = panel width (ft) and L = panel
length (ft).
A-41
-------
APPENDIX B.
GLOSSARY OF SYMBOLS AND EXAMPLES
-------
TABLE B-l. GLOSSARY OF SYMBOLS
Symbol
Adeck
C
CF
D
FC
FP
FF
H
KC
KD
S
K'"'
*N
Ks
LB
LD
LF
LR
LRF
Lseam
LT
LW
LWD
m
Name
Area of deck
Small diameter tank adjustment
factor
Shell clingage factor
Diameter of tank
Effective column diameter
Paint factor
Total deck fitting loss factor
Vapor space height
Product factor
Deck seam loss per unit seam
length factor
roof fitting loss factor
roof fitting loss factor
Roof /deck fitting loss factor
for a particular type of
fitting (i)
Turnover factor
Seal factor
Breathing loss from a tank
Deck seam loss
Deck fitting loss
Rim seal loss
Roof fitting loss
Length of deck
Total estimated loss from a tank
Working loss from a tank
Withdrawal loss
Exponent for roof fitting
loss factor
Units
ft*
-
bbl/103 ft2
ft
ft
__
Ib-mol/yr
ft
Ib-mol/ft yr
Ib-mol/yr
Ib-mol/yr
Ib-mol/yr
lb-mol/(ft[mi/hln)
Ib/yr
Ib/yr
Ib/yr
Ib/yr
Ib/yr
ft
Ib/yr
Ib/yr
Ib/yr
Description
~
Column perimeter/ir
Correction factor for
of storage tank
color
Average vapor space height,
i nc 1 ud i ng roof vo 1 ume
correct i on
From an internal or external
floating roof tank
From an internal float
roof tank
ing
From floating roof tanks
From extern a 1 f 1 oat i ng
tank
roof
From floating roof tanks
(continued)
B-l
-------
TABLE B-l. (continued)
Symbol N
Units
Oescr i pt i on
MV, M. Molecular weight
P
P,.P
SeaI-related windspeed exponent
Total number of different types
of fittings
Number of turnovers per year
Number of columns
Number of deck fittings of a
particular type
Vapor pressure function
True vapor pressure
Ib/lb-flwl
psia
Molecular weight of vapor (or
component i) in tank
Throughput/voIume
Number of columns in column-
supported tank
True vapor pressure of
component at bulk liquid
conditions
p.
Vapor pressure of pure component psia
at temperature t
Ppartlal Partial pressure
P. Atmospheric pressure
Total vapor pressure of a
mixture
Annual tank throughput
RVP Reid vapor pressure
SD Deck seam length factor
T. Storage temperature
v Average windspeed at tank site
V Tank volume
W. Average Ii qu i d dens i ty
AT Average ambient diurnal
temperature change
x. Mole fraction of component in
1 liquid
y. Mole fraction of component in
vapor
psia
psia
psia
bbl/yr
psia
ft/ft2
F
mi/h
gal
Ib/gal
F
Average atmospheric pressure
at tank location
Tank capacity X number of
turnovers
Length/area of deck
B-2
-------
B.I CHEMICAL MIXTURE IN A FIXED ROOF TANK
Determine the yearly emission rate of product and of each component
from a vertical, fixed roof storage tank containing (for every
3,171 pounds [Ib] of liquid mixture) 2,812 Ib of benzene, 258 Ib of
toluene, and 101 Ib of cyclohexane. The tank is not heated and the
average yearly ambient temperature of the area is 67°F. The tank is
6 feet (ft) in diameter and 10 ft high and is painted white. The tank
volume is 2,100 gallons. The number of turnovers per year for the tank is
five (i.e., the throughput of the tank is 10,500 gal/yr).
Solution:
1. Determine tank type
The tank is a vertical, fixed roof storage tank.
2. Determine estimating methodology
The product is made up of three organic liquids, all of which are
miscible in each other, which make a homogenous mixture if the material is
well mixed. The tank emission rate will be based upon the properties of
the mixture. Since the components have similar structures and molecular
weights, Raoult's Law is assumed to apply to the mixture.
3. Select equations to be used
For a vertical, fixed roof storage tank, the following equations
apply:
LT = LB+LW
where:
Lw = 2.40xlQ-SMvPVNKNKc
LT = total loss, Ib/yr of VOC
LB = breathing loss, Ib/yr of VOC
Lw = working loss, Ib/yr of VOC
My = molecular weight of product vapor, Ib/lb-mol
P = true vapor pressure of product, psia
PA = atmospheric pressure, psia
D = tank diameter, ft
B-3
-------
H = average vapor space height, ft: use tank-specific values or
an assumed value of one-half the tank height
AT = average diurnal temperature change in °F
Fp = paint factor (dimensionless); see Table A-l
C = tank diameter factor (dimensionless):
for diameter >30 feet, C = 1
for diameter <30 feet,
C - 0.0771 (D)-0.0013(D2)-0.1334
K£ = product factor (dimensionless) = 1.0 for volatile organic
liquids, 0.65 for crude oil
V = tank capacity, gal
N » number of turnovers per year (dimensionless)
- throughput, qal/yr
tank capacity, gal
KM = turnover factor (dimensionless):
1 pru.M
for turnovers >36, KN = ±^-
for turnovers <36, KN = 1
4. Identify parameters to be calculated or determined from tables
In this example, the following parameters are not specified: My, P,
AT, H, PA, and Fp. Some typical assumptions that can be made are:
H = % tank height - ^(10) = 5 ft
Fp * 1.0 for clean white paint (Table A-l)
AT = 20°F
PA * atmospheric pressure = 14.7 psia
K£ » 1.0 for volatile organic liquids
The tank diameter factor can be found in Figure A-l or calculated as
follows:
C = 0.0771(6)-0.0013(6)2-0.1334
C = 0.282
The vapor pressure (P) of the liquid and the molecular weight of the
vapor (Mv) still need to be calculated.
B-4
-------
5. Calculate mole fractions in the liquid
The mole fractions of components in the liquid must be calculated in
order to calculate the vapor pressure of the liquid using Raoult's Law.
The molecular weight for each component (M^) can be read from
Table A-2.
Component Amount, Ib * M = Moles x
Benzene
Toluene
Cyclohexane
2,812
258
101
78.1
92.1
84.2
36.0
2.80
1.20
0.90
0.07
0.03
Total 40.0 1.00
M^ = molecular weight, Ib/lb-mol
x^ = moles.j/total moles = 36.0/40.0 = 0.900 for benzene
6. Calculate partial pressures and total vapor pressure of the
liquid
The vapor pressure of the mixture may be found by first obtaining the
vapor pressures of each component at the average yearly temperature from
Table A-2. For temperatures not listed in the table, interpolation
between values is required.
Vapor pressure, psia
Material
Benzene
Toluene
Cyclohexane
60° F
1.2
0.3
1.2
70°F
1.5
0.4
1.6
Because the average temperature falls between two temperature values
on the table (60°F and 70°F), interpolation between temperatures is
necessary. The vapor pressure for each component at 67°F may be
calculated through interpolation in the following manner:
Benzene
Tactual - 67°F
T! = 60°F
T2 = 70°F
P: = 1.2
P2 = 1.5
(^actual)' = 3
8-5
-------
T T P. psia (T-Tactua1). "F
1 60 1.2 (-7)
2 70 1.5 (3)
P -i-l
rbenzene at 67°F " Tj-T^
Pbenzene at 67oF
Pbenzene at 67<>F = To114'11
pbenzene at 67°F " *-4 Ps1a
Similarly, vapor pressures for the two remaining components are
calculated as:
Toluene: P(at 67°F) = 0.37 psia
Cyclohexane: P(at 67°F) = 1.5 psia
Using these vapor pressures of the pure components and the liquid
mole fractions calculated in Step 5, the partial pressures of the three
components can be calculated.
According to Raoult's Law, the partial pressure of a component is the
product of its pure vapor pressure and its liquid mole fraction.
Component P at 67 °F X xn- = ppartial
Benzene
Toluene
Cyclohexane
The vapor pressure
7. Calculate mole
1.4
0.37
1.5
of the mixture is
fractions in the
0.90
0.07
0.03
Oo
1.33 psia.
vapor
1.26
0.0259
0.045
1.33
The mole fractions of the vapor phase are based upon the partial
pressure that each component exerts (calculated in Step 6).
The total vapor pressure of the mixture is 1.33 psia; so, for
benzene,
B-6
-------
where
ybenzene = mo1e fract'ion of benzene in the vapor
ppartial = Pa^311 pressure of benzene
^total = tota^ vaP°r pressure of the mixture
Similarly for toluene and cyclohexane,
= 0.0259 = 0 Olg5
ytoluene 1.33 u'uiy!3
y = 0445 = 0.0338
J cyclohexane 1.33
The vapor phase mole fractions sum to 1.0.
8. Calculate molecular weight of the vapor
The molecular weight of the vapor is dependent upon the mole
fractions of the components in the vapor.
where
MV « molecular weight of the vapor
M.J = molecular weight of the component
y^ * mole fraction of the component in the vapor
Component M X y
Benzene
Toluene
Cyclohexane
78.1
92.1
84.2
0.947
0.0195
0.0338
1.00
73.961
1.7959
2.8459
78.6
The molecular weight of the vapor is 78.6 Ib/lb-mol.
9. Calculate weight fractions of the vapor
The weight fractions of the vapor are needed to calculate the amount
(in pounds) of each component emitted from the tank. The weight fractions
are related to the previously calculated mole fractions. First, assume
that there are 1,000 moles of vapor present. Using this assumption, the
weight fractions calculated will be valid no matter how many moles
actually are present. The number of moles for each component will be
1,000 times the mole fraction of the component
B-7
-------
No. of Weight
Component moles X M^ = Pounds ^ fraction
Benzene 947 78.1 73,961 0.941
Toluene 19.5 92.1 1,796 0.0228
Cyclohexane 33.8 84.2 2,846 0.0362
1,000 78,603 1.00
The weight fraction of each component is the pounds of that component
divided by the total pounds of the mixture. For example,
weight fract1onben2ene » = 0.941.
Simarly, toluene = 0.0228 and cyclohexane = 0.0362.
10. Calculate total VOC emitted from the tank
The total VOC emitted from the tank is calculated using the equations
identified in Step 3 and the parameters calculated in Steps 4 through 9.
LT = LB+LW
where:
LT = total loss, Ib/yr of VOC
LB = total breathing loss, Ib/yr of VOC
Lw = total working loss, Ib/yr of VOC
LB - 2.26xio-\(-^)°-sV-'Y-5 V-5Fpo
-------
LB = 23.1 Ib/yr of VOC
Lw = 2.40xlO'S MVPVNKNKC
where
Mv = 78.6 Ib/lb-mol (from Step 4)
P = 1.3 psia (from Step 6)
V = 2,100 gal (given)
N » 5 (given)
KN = 1 (from Step 3)
Kc = 1 (from Step 4)
Lw = 2.40xlO-5(78.6)(1.3)(2,100)(5)(l)(l)
Lw = 25.7 Ib/yr of VOC
LT « 23.1+25.7
LT = 48.8 Ib/yr of VOC emitted from the tank
11. Calculate amount of each component emitted from the tank
The amount of each component emitted is the weight fraction of that
component in the vapor (calculated in Step 9) times the amount of total
VOC emitted.
Component
Benzene
Toluene
Cyclohexane
For benzene,
0.941 Ib of
Weight
fraction
0.941
0.0228
0.0362
1.00
benzene.. n ..
Pounds
x48.8 Ib = emitted /yr
45.9
1.11
1.77
4O~
if \lf\r = AK Q IK nf Kon-7or
1 Ib of VOC
To calculate the liquid volume that is emitted for each component,
the density of the compound is used. The density for these three
components can be taken from Table A-2.
Component
Benzene
Toluene
Cyclohexane
Density,
Ib/gal
7.4
7.3
6.5
Amount
emitted, Ib/yr
45.9
1.11
1.77
Volume
emitted,
gal/yr
6.2
0.15
0.27
B-9
-------
where
volume, gal/yr = ;& W
B-10
-------
B.2 CHEMICAL MIXTURE IN AN EXTERNAL FLOATING ROOF TANK
Determine the yearly emission rate of a mixture that is 75 percent
benzene, 15 percent toluene, and 10 percent cyclohexane, by weight, from a
100,000 gallon external floating roof tank with a pontoon roof. The tank is
20 feet in diameter. The average yearly temperature in the area is 70°F and
the average wind speed is 10 mph. The tank has 10 turnovers per year. The
tank roof has no support columns. The tank has a mechanical shoe seal
(primary seal) and a shoe-mounted secondary seal. The tank is made of
welded steel and has a light rust covering on the inside surface of the
shell. The floating roof is equipped with the following fittings: (1) an
ungasketed access hatch with an unbolted cover, (2) an unspecified number
of ungasketed vacuum breakers with weighted mechanical actuation, and
(3) ungasketed gauge hatch/sample wells with weighted mechanical actuation.
Solution:
1. Determine tank type
The tank is an external floating roof storage tank.
2. Determine estimating methodology
The product consists of three organic liquids, all of which are
miscible in each other, which make a homogenous mixture if the material is
well mixed. The tank emission rate will be based upon the properties of
the mixture. Since the components have similar structures and molecular
weights, Raoult's Law is assumed to apply to the mixture.
3. Select equations to be used
For an external floating roof tank,
LT = LWD+LR+LRF
MF
= (0.943) QCpWL/D
Lr
RF '
LR = K$vnP*OMvKc
where:
LT « total loss, Ib/yr of VOC
LWD = withdrawal loss, Ib/yr of VOC
LR = rim seal loss from external floating roof tanks,
Ib/yr of VOC
B-ll
-------
LRF = roof fitting loss, Ib/yr of VOC
Q = product average throughput (bbl/yr)
Cp = product withdrawal shell clingage factor
(bbl/103 ft2); see Table A-7
WL = density of product (Ib/gal); 7.4 to 8.0 Ib/gal
assumed as typical range for volatile organic
liquids
D = tank diameter, ft
NQ = number of columns
= 0, there are no columns in external floating roof
tanks
F£ = effective column diameter, ft
= 0, there are no columns
Ks = seal factor, lb/-mole/(ft[mi/h])
v = average windspeed for the tank site, mi/h
n = seal windspeed exponent, dimensionless
P* » the vapor pressure function, dimensionless;
P_
p
p* , *
p °.5 2
(1+U-jH )
rt
P = the true vapor pressure of the materials stored, psia
PA = atmospheric pressure, psia = 14.7
My = molecular weight of product vapor, Ib/lb-mol
KC » product factor, dimensionless
Fp = the total deck fitting loss factor, Ib/mol/yr
nf
= Z (NF KF )=[(NF KF )+(NF KF )+...+(NF Kp )]
i * 1 hi hi hi hi hz h2 pnf Fnf
where:
Np = number of fittings of a particular type, dimensionless. Mp.
is determined for the specific tank or estimated from
Tables A-8, A-9,or A-10
B-12
-------
Kp = roof fitting loss factor for a particular type of fitting, 1 fa-
mo! /yr. Kp. is determined for each fitting type from
Table A-8 or Figures A-10 through A-18.
n.p = number of different types of fittings, dimension! ess
= 3
4. Identify parameters to be calculated or determined from tables
In this example, the following parameters are not specified: Wi_, Fp,
Cp, Ks, v, n, P, P*, Mv, and Kc. Some typical assumptions that can be
made are as follows:
v » average windspeed for the tank site = 10 mi/h
K£ = 1.0 for volatile organic liquids
CF = 0.0015 bbl/103 ft2 for tanks with light rust (from Table A-7)
Ks = 0.8 (from Table A-5)
n = 1.2 (from Table A-5)
Fpt WL, P, P*, and My still need to be calculated.
Fp is estimated by calculating the individual Kp and Np. for each of
the three types of roof fittings used in this example. For the ungasketed
access hatches with unbolted covers, the Kf value can be calculated using
information in Table A-8. For this fitting, Kfa = 2.7, Kfb = 7.1, and m =
1. There is normally one access hatch. So,
KF »
-------
For the ungasketed gauge hatch/sample wells with weighted mechanical
actuation, Table A-8 indicates that tanks normally have only one.
Figure A-14 gives Kpgauge hatch/sample well as 25 Ib-mol/yr for a wind
speed of 10 miles per hour.
Kc = 25 Ib-mol/yr
rgauge hatch/sample well
Nc = 1
rgauge hatch/samples well
Fp can be calculated as:
= I (KF )(NF )
h
= 129.7 Ib-mol/yr
5. Calculate mole fractions in the liquid
The mole fractions of components in the liquid must be calculated in
order to estimate the vapor pressure of the liquid using Raoult's Law.
For this example, the weight fractions (given as 75 percent benzene,
15 percent toluene, and 10 percent cyclohexane) of the mixture must be
converted to mole fractions. First, assume that there are 1,000 Ib of
liquid mixture. Using this assumption, the mole fractions calculated will
be valid no matter how many pounds of liquid actually are present. The
amount (pounds) of each component is equal to the weight fraction times
1,000:
Weight M1§ Ib/ Mole
Component f r act ionx 1,000 Ib = Pounds^ + lb-moles = Moles fraction
Benzene 0.75 750 78.1 9.603 0.773
Toluene 0.15 150 . 92.1 1.629 0.131
Cyclohexane 0.10 100 84.2 1.188 0.096
1.00 1,000 12.420 1.000
For example, the mole fraction of benzene in the liquid is
9.603/12.420 =0.773.
8-14
-------
6. Calculate partial pressures and total vapor pressure of the
liquid
The vapor pressure of each component at 70°F can be taken from
Table A-2. Since Raoult's Law is assumed to apply in this example, the
partial pressure of each component is the liquid mole fraction (x^) times
the vapor pressure of the component (P.,-)-
Component
Benzene
Toluene
Cyclohexane
P1 at 70° F
1.5
0.4
1.6
X x1
0.773
0.131
0.096
1.00
= ppartial
1.16
0.0524
0.154
1.37
The vapor pressure of the mixture is estimated to be 1.37 psia.
7. Calculate mole fractions in the vapor
The mole fractions of the vapor phase are based upon the partial
pressure that each component exerts (calculated in Step 6).
The total vapor pressure of the mixture is 1.37 psia. So for
benzene:
p
partial 1.16
"benzene = - ' 137 '
where:
^benzene = mole fraction Qf benzene in the vapor
ppartial = Partial pressure of benzene in the vapor, psia
P total = total vapor pressure of the mixture, psia
Similarly,
^toluene = 0.0524/1.37 = 0.0382
^cyclohexane = 0-154/1.37 = 0.112
The vapor phase mole fractions sum to 1.0.
8. Calculate molecular weight of the vapor
The molecular weight of the vapor is dependent upon the mole
fractions of the components in the vapor.
My = iM1y1
B-15
-------
where:
My = molecular weight of the vapor
M.J = molecular weight of the component
y^ = mole fraction of component in the vapor
Component M x y =
Benzene
Toluene
Cyclohexane
78.1
92.1
84.2
0.847
0.0382
0.112
1.00
66.151
3.518
9.430
79.1
The molecular weight of the vapor is 79.1 Ib/lb-mol.
9. Calculate weight fractions of the vapor
The weight fractions of the vapor are needed to calculate the amount
(in pounds) of each component emitted from the tank. The weight fractions
are related to the mole fractions calculated in Step 7. First, assume
that there are 100 moles of vapor present. Using this assumption, the
weight fractions calculated will be valid no matter how many moles
actually are present.
Mole No. of M1f lb/
Component fraction^ 100 mole = moles ^ x Ib-mole
Benzene
Toluene
Cyclohexane
0.847
0.382
0.112
Oo~
84.7
3.82
11.2
100
78.1
92.1
84.2
= Pounds.}
6,615
351.8
943.0
7,910
Weight
fraction
0.836
0.0445
0.119
1.00
The weight fraction of each component is the pounds of that component
divided by the total pounds of the mixture. For example, the weight
fraction of benzene is 6,615/7,910 = 0.836.
10. Calculate total VOC emitted from the tank
The total VOC emitted from the tank is calculated using the equations
identified in Step 3 and the parameters calculated in Steps 4 through 9.
LT = LWD+LR+LRF
LWD = 0.943 QCWL/D[1+NCFC/D]
where:
Q = 100,000 galxlO turnovers/yr (given)
= 1,000,000 galx2.381 bbl/100 gal
B-16
-------
Q = 23,810 bbl/yr
Cp = 0.0015 bbl/103 ft2 (from Table A-5)
Wj_ = l/[r (wt fraction in liquid)/(liquid density from
Table A-2)]
= 1/[(0. 75/7. 4)+(0. 15/7. 3)+(0. 10/6.5)]
= 1/(0. 101+0. 0205+0. 0154)
= 1/0.1373
= 7.3 Ib/gal
(A density range of 7.4 to 8.0 Ib/gal is typical for
volatile organic liquids.)
D = 20 ft (given)
Nc = 0 (given)
FQ » not applicable
0.943 QCFWL/D[1+-^]
[0.943(23,810)(0.0015)(7.3)/201 [1+0/201
12.3 Ib of VOC/yr
LR = KsvnP*DMvKc
Ks = 0.8 (from Step 3)
v = 10 mi/h (from Step 4)
n = 1.2 (from Step 4)
P = 1.4 psia (from Step 6)
1.4
0 c 2 (formula from Step 3)
P* = 0.0250
My = 79.1 Ib/lb-mol (from Step 8)
LR = (0.8)(10l'2)(0.0250)(20)(79.1)(1.0)
501 Ib of VOC/yr
LRF
where
FF = 129.7 Ib-mol/yr (from Step 4)
P* = 0.
.025
= 79.1 Ib/lb-mol
= 1.0 (from Step 4)
B-17
-------
LF = (129.7) (0.025)(79.1)(1.0)
Lp = 256 Ib/yr of VOC emitted
LT
LT = 12.3+501+256
LT = 770 Ib/yr of VOC emitted from tank
11. Calculate amount of each component emitted from the tank
The amount of each component emitted is the weight fraction of that
component in the vapor (calculated in Step 9) times the total amount of
VOC emitted from the tank.
Component _ Height fraction x770 Ib/yr « Pounds emitted /yr
Benzene 0.836 644
Toluene 0.0445 34.3
Cyclohexane 0.119 91.6
1.00 770
For benzene,
lb/yr of VOC = 644 lb/yr of benzene
B-18
-------
B.3 GASOLINE IN AN INTERNAL FLOATING ROOF TANK
Determine emissions of product from a 1,000,000-gallon, internal
floating roof tank containing gasoline (RVP 13). The yearly average
temperature in the area is 60°F. The annual number of turnovers for the
tank is 50. The tank is 70 ft in diameter and 35 ft high and is equipped
with a liquid-mounted primary seal plus a secondary seal. The tank's deck
is welded and equipped with the following: (1) two access hatches with an
unbolted, ungasketed cover; (2) an automatic gauge float well with an
unbolted, ungasketed cover; (3) a pipe column well with a flexible fabric
sleeve seal; (4) a siiding-cover, gasketed ladder well; (5) a fixed roof
leg; (6) a slotted sample pipe well with a gasketed sliding cover; and
(7) a weighted, gasketed vacuum breaker.
Solution;
1. Determine tank type
The following information must be known about the tank in order to
use the internal floating roof equations:
the number of columns
the effective column diameter
--the system seal description (vapor, liquid mounted; primary or
secondary seal)
the deck fitting types and the deck seam length
Some of this information depends on specific construction details, which
may not be known. In these instances, approximate values are provided for
use.
2. Determine estimating methodology
Gasoline consists of many organic compounds, all of which are
miscible in each other, which form a homogenous mixture. The tank
emission rate will be based on the properties of RVP 13 gasoline. Since
vapor pressure data have already been compiled, Raoult's Law will not be
used. The molecular weight of gasoline also will be taken from a table
and will not be calculated. Weight fractions of components will be
assumed to be available from a VOC species manual (see Reference 14).
3. Select equations to be used
LT = LW+LR+LF+L0
(0.943)QCFWL
SrfO = D
LR = KsvnP*OMvKc
LF = FFP*MVKC
B-19
-------
where:
Lj = total loss, Ib/yr
LWD = withdrawal loss, Ib/yr
LR = rim seal loss, Ib/yr
Lp = deck fitting loss, Ib/yr
LQ = deck seam loss, Ib/yr
For this example,
Q = product average throughput, bbl/yr
tank capacity (bbl/turnover)xturnovers/yr
Cp - product withdrawal shell clingage factor, bbl/10 ft
WL = density of liquid, Ib/gal
0 * tank diameter, ft
NQ = number of columns, dimensionless
FQ = effective column diameter, ft
Ks = seal factor, lb-mole/[ft [mi/h]n]
v » average wind speed for the tank site, mi/h
n = seal windspeed exponent, dimensionless
My = the average molecular weight of the product vapor, Ib/lb-mol
KQ = the product factor, dimensionless
P* = the vapor pressure function, dimensionless
P_
PA
= r> n c >
A
P = the vapor pressure of the material stored, psia
PA = average atmospheric pressure at tank location, psia
Fp = the total deck fitting loss factor, Ib-mol/yr
where:
Np - number of fittings of a particular type (dimensionless).
Mp is determined for the specific tank or estimated from
Table A-ll.
B-20
-------
Kp. = deck fitting loss factor for a particular type of fitting,
Ib-mol/yr. Kp. is determined for each fitting type from
Table A-ll.
Of = number of different types of fittings, dimensionless
Kg = the deck seam loss factor, Ib-mol/ft yr
= 0.34 for nonwelded roofs
= 0 for welded decks
deck seam length factor, ft/ft
where:
Lseam = tota^ length of deck seams, ft
2 2
Adeck = area of deck» ft = *D /4
4. Identify parameters to be calculated or determined from tables
In this example, the following parameters are not specified: Np, Fo
P, Mv, Ks, v, n, P*, Kc, FF, KD, and Sg. The density of the liquid (WL)
and the vapor pressure of the liquid (P) can be read from tables and do
not need to be calculated. Also, the weight fractions of components in
the vapor can be obtained from speciation manuals. Therefore, several
steps required in preceeding examples will not be required in this
example. In each case, if a step is not required, the reason is
presented.
The following parameters can be obtained from tables or assumptions:
KQ - 1.0 (for volatile organic liquids)
Nc = 1 (from Table A-12)
Fc = 1.0 (assumed)
Ks = 1.6 (from Table A-5)
P = 6.9 psia (from Table A-2)
Mv = 62 Ib/lb-mol (from Table A-2)
WL = 5.6 Ib/gal (from Table A-2)
CF = 0.0015 bbl/103 ft2 (from Table A-7)
v = 10 mi/h (assumed)
B-21
-------
n = 0 (from Table A-5)
Kg = 0 (for welded roofs)
SD = 0.2 ft/ft2 (from Table A-13)
Fp = values taken from Table A-ll
- I (KF.)(NF.)
= 188.7 Ib-mol/yr
P_
p* - _ £ _
6.9
TO
6.9
= 0.157
5. Calculate mole fractions 1n the liquid
This step Is not required because liquid mole fractions are only used
to calculate liquid vapor pressure, which is given in this example.
6. Calculate partial pressures and total vapor pressure of the
liquid
This step is not required because the vapor pressure of gasoline is
given.
7. Calculate mole fractions in the vapor
This step is not required because vapor mole fractions are needed to
calculate the weight fractions and the molecular weight of the vapor,
which are already specified.
B-22
-------
8. Calculate molecular weight of the vapor
This step is not required because the molecular weight of gasoline
vapor is already specified.
9. Calculate weight fractions of the vapor
The weight fractions of gasoline vapor can be obtained from a VOC
speciation manual.
10. Calculate total VOC emitted from the tank
The total VOC emitted from the tank is calculated using the equations
identified in Step 3 and the parameters specified in Step 4.
where:
where:
W
0
^c
(0.943)QCFW,
(1,000,000 gal)x(50 turnovers/yr)
(50,000,000 gal)x(2.381 bbl/100 gal)
1,190,500 bbl/yr
0.0015 bbl/103 ft2
5.6 Ib/gal
70 ft
1
- (0.943)(1.190.500)(0.0015)(5.6)-
T7U) '
LWD = 136.6 Ib/yr of VOC emitted
LR = KsDvnP*MvKc
Ks = 1.6
v = 10 mi/h
n - 0
P* = 0.157
0 = 70 ft
70
B-23
-------
Mv = 62 Ib/lb-mol
KC = 1.0
LR = (
LR = 1,090 Ib/yr of VOC emitted
LF = FFP*MVKC
where:
FF = 235.5 Ib-mol/yr
P* = 0.157
My = 62 Ib/lb-mol
Kc = 1.0
Lp = (188.7)(0.157)(62)(1.0)
Lp = 1,837 Ib/yr of VOC emitted
where:
SD = 0.2
D = 70 f t
P* = 0.157
Mv = 62 Ib/lb-mol
Kc = 1.0
L0 = (0.0)(0.2)(70)2(0.157)(62)(1.0)
LD * 0 Ib/yr of VOC
LT a LWD-HLR+LF*L0
LT = 136. 6*1 ,090+1, 837-K)
LT = 3,064 Ib/yr of VOC emitted from the tank
11. Calculate amount of each component emitted from the tank
The amount of each component emitted is the weight fraction of that
component in the vapor (obtained from a VOC species data manual and shown
in Table B-2) times the total amount of VOC emitted from the tank.
Table B-2 shows the amount emitted for each component in this example.
B-24
-------
TABLE B-2. EMISSIONS FOR EXAMPLE 3
Constituent
Weight percent
in vapor
x3,064 Ib/yr =
Pounds
emitted/yr
Air toxics
Benzene 0.77 23.5
Toluene 0.66 20.2
Ethyl benzene 0.04 1.23
o-xylene 0.05 1.53
Nontoxics
Isomers of pentane 26.78 821
N-butane 22.95 703
Iso-butane 9.83 301
M-pentane 8.56 262
Isomers of hexane 4.78 146
3-methyl pentane 2.34 71.7
Hexane 1.84 56.4
Others 21.40 656
TOO3,064
B-25
-------
B.4 CHEMICAL MIXTURE IN A HORIZONTAL FIXED ROOF TANK
Determine the yearly emission rate of product and of each component
from a horizontal above ground, fixed roof storage tank containing (for
every 1,750 Ib of liquid mixture) 1,600 Ib of benzene, 100 Ib of toluene,
and 50 Ib of cyclohexane. The tank is not heated and the average yearly
ambient temperature of the area is 67.5°F. The tank is 10 ft in diameter
and 17 ft long and the roof and shell are painted aluminum. The tank
volume is 10,000 gallons. The number of turnovers per year for the tank
is three (i.e., the throughput of the tank is 30,000 gal/yr).
Solution;
1. Determine tank type
The tank is a horizontal, fixed roof storage tank.
2. Determine estimating methodology
The product consists of three organic liquids, all of which are
miscible in each other and make a homogenous mixture if the material is
well mixed. The tank emission rate will be based upon the properties of
the mixture. Since the fixed roof equations were developed for vertical
tanks, the diameter and height of the tank will need to be calculated.
The components have similar structures and molecular weights, so Raoult's
Law will be assumed to apply.
3. Select equations to be used
For a horizontal, fixed roof storage tank, the following equations
apply:
LT = LB+LW
where:
= 2.40xlQ-SMvPVNKNKc
LT = total loss, Ib/yr of VOC
Lg = breathing loss, Ib/yr of VOC
Ly = working loss, Ib/yr of VOC
My = molecular weight of product vapor, Ib/lb-mol
P = true vapor pressure of product, psia
Pfl = atmospheric pressure, psia
D = tank diameter, ft
B-26
-------
H =» average vapor space height, ft
AT = average diurnal temperature change, °F
Fp = paint factor (dimensionless); see Table A-l;
C = tank diameter factor (dimensionless):
for diameter >30 feet, C = 1
for diameter <30 feet,
C = 0.0771 (D)-0.0013(D2)-0.1334
K£ = product factor (dimensionless) = 1.0 for volatile organic
liquids, 0.65 for crude oil
V = tank capacity, gal
N = number of turnovers per year (dimensionless)
_ throughput, gal/yr
tank capacity, gal
KN = turnover factor (dimensionless):
iafu.M
for turnovers >36, KM = ^^-
n on
for turnovers <36, KN = 1
4. Identify parameters to be calculated or determined from tables
In this example, the following parameters are not specified: Mv, P,
AT, KC, PA, C, H, and Fp. Some typical assumptions that can be made
are:
Fp = 1.2 for aluminum (specular) paint on roof and shell (see
Table A-l)
AT = 20°F
PA = atmospheric pressure = 14.7 psia
K£ = 1.0 for volatile organic liquids
Since the emission estimating equations were developed for vertical
tanks, some of the horizontal tank parameters must be modified before
using the equations. First, assume that the tank is one-half filled. The
surface area of the liquid in this case is approximately equal to the
length of the tank times the diameter of the tank. In this case, the
surface area is 17x10 - 170 ft . Next, assume that this area represents a
circle, i.e., that the liquid is in an upright cylinder. Solving for
diameter (A = 170 ft2 = irD /4) yields a diameter of 14.7 ft. Thus, a
value of 14.7 ft for D should be used in the equations. Since the tank is
B-27
-------
assumed to be one-half full, the vapor space Is equal to one-half the
diameter of the tank. Therefore, a value of 10 ftxl/2 = 5 ft for H should
be used in the equations.
The tank diameter factor (C) is calculated using a diameter of
14.7 ft.
C = 0.0771(14.7)-0.0013(14.7)2-0.1334
C = 0.719
If this tank were located underground, then the breathing losses
could be assumed to be negligible because the diurnal temperature change
(AT) would be close to zero.
The vapor pressure (P) of the liquid and the molecular weight of the
vapor (My) still need to be calculated.
5. Calculate mole fractions in the liquid
The mole fractions of components in the liquid must be calculated in
order to calculate the vapor pressure of the liquid using Raoult's Law.
The molecular weight for each component (M^) can be read from
Table A-2.
Component Amount, Ib + M^ = Moles x
Benzene
Toluene
Cyclohexane
1,600
100
50
78.1
92.1
84.2
20.5
1.09
0.594
0.92
0.049
0.027
Total 1,750 22.2 1.00
For benzene,
xbenzene a "^"benzene/*01*1 moles = 20.5/22.2 = 0.92.
6. Calculate partial pressures and total vapor pressure of the
liquid
The vapor pressure of the mixture may be found by first obtaining the
vapor pressures of each component from Table A-2. In this example, the
storage tank is painted aluminum. Therefore, the temperature of the
stored liquid must be adjusted using Table A-3. Table A-3 indicates that
the average yearly temperature must be adjusted by 2.5 degrees to account
for the aluminum tank. Therefore, vapor pressure information should be
taken from Table A-2 at 67.5+2.5 = 70° F.
B-28
-------
Vapor
pressure
at 70°F,
Component psia
Benzene 1.5
Toluene 0.4
Cyclohexane 1.6
According to Raoult's Law, the partial pressure of a component is the
product of its pure vapor pressure and its liquid mole fraction.
Component
Benzene
Toluene
Cyclohexane
Pi at 70°F
1.5
0.4
1.6
X xi
0.92
0.049
0.027
Oo~
Ppartial
1.38
0.0196
0.0432
1.44
The vapor pressure of the mixture is 1.4 psia.
7. Calculate mole fractions in the vapor
The mole fractions of the vapor phase are based upon the partial
pressure that each component exerts (calculated in Step 6).
The total vapor pressure of the mixture is 1.44 psia; so, for
benzene:
Ppartia1 1.38 n QCQ
^benzene = PJ s 1^4 " °'958
where:
ybenzene = mo^e fraction °f benzene in the vapor
ppartial ~ Part1al pressure of benzene, psia
Pj » total vapor pressure of the mixture, psia
Similarly, for toluene and Cyclohexane,
0.0196
toluene = T^T =
ycyclohexane = 1.44 = °-03
The vapor phase mole fractions sum to 1.0.
B-29
-------
8. Calculate molecular weight of the vapor
The molecular weight of the vapor is dependent upon the mole
fractions of the components in the vapor.
Mv = sM.y.
where:
My = molecular weight of the vapor, Ib/lb-mole
M.J = molecular weight of the component, Ib/lb-mole
y.j = mole fraction of the component in the vapor
Component M X y =
Benzene
Toluene
Cyclohexane
78.1
92.1
84.2
0.958
0.0136
0.03
1.00
74.82
1.253
2.526
78.6
The molecular weight of the vapor is 78.6 Ib/lb-mol.
9. Calculate weight fractions of the vapor
The weight fractions of the vapor are needed to calculate the amount
of each component emitted from the tank. The weight fractions are related
to the previously calculated mole fractions. First, assume that there are
100 moles of vapor present. Using this assumption, the weight fractions
calculated will be valid no matter how many moles actually are present.
Component
Benzene
Toluene
Cyclohexane
No. of
moles
958
13.6
30.0
1,000
X M^
78.1
92.1
84.2
Pounds^ Weight fraction
74,820
1,253
2,526
78,599
0.952
0.0159
0.0321
1.00
The weight fraction of each component is the pounds of that component
divided by the total pounds of the mixture. For example,
weight fractionbenzene = * = 0.952.
10. Calculate total VOC emitted from the tank
The total VOC emitted from the tank is calculated using the equations
identified in Step 3 and the parameters calculated in Steps 4 through 9.
B-30
-------
LT = LB+LW
where:
LT = total loss, Ib/yr of VOC
LB = total breathing loss, Ib/yr of VOC
Lw = total working loss, Ib/yr of VOC
where:
Mv = 78.6 Ib/lb-mol (from Step 8)
P = 1.4 psia (from Step 6)
PA = 14.7 psia (from Step 4)
D = 14.7 ft (from Step 4)
H = 5 ft (from Step 4)
AT = 208F (from Step 4)
Fp = 1.2 (from Step 4)
C = 0.719 (from Step 4)
Kc = 1 (from Step 4)
LB = 352 Ib/yr of VOC emitted
Lw = 2.40xlO~5 MVPVNKNKC
where:
Mv = 78.6 Ib/lb-mol (from Step 8)
P = 1.4 psia (from Step 6)
V = 10,000 gal (given)
N = 3 (given)
KN = 1 (from Step 3)
Kc = 1 (from Step 4)
Lw = 2.40xlQ-5(78.6)(1.4)(10,000)(3)(l)(l)
Lw = 79.2 Ib/yr of VOC
LT = 352+79.2
LT = 431 Ib/yr of VOC emitted from the tank
B-31
-------
11. Calculate amount of each component emitted from the tank
The amount of each component emitted is the weight fraction of that
component in the vapor (calculated in Step 9) times the amount of total
VOC emitted.
Weight Pounds
Component fraction x431 Ib/yr = emitted/yr
Benzene 0.952 410
Toluene 0.0159 6.85
Cyclohexane 0.0321 13.8
1.00 431
For benzene,
0.948 Ib of benzene
1 Ib of VOC
x431 Ib/yr of VOC = 410 Ib/yr of benzene emitted
8-32
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/4-88-004
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Estimating Air Toxics Emissions From Organic Liquid
Storage Tanks.
5. REPORT DATE
October 1988
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
Patrick Murphy
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME ANO AOORESS
Midwest Research Institute
401 Harrison Oaks Blvd.
Gary, NC 27707
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-4395
12. SPONSORING AGENCY NAME ANO AOORESS
U.S. Environmental Protection Agency
OAR, OAQPS, AQMD, PCS (MD-15)
Research Triangle Park, NC 27711
13. TYPE OF REPORT ANO PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA Project Officer: Anne A. Pope
10. ABSTRACT
To assist groups interested in inventorying air emissions of potentially toxic sub-
stances, EPA is preparing a series of documents that compiles available information
on sources and emissions of toxic substances. This document deals specifically with
methods to estimate air toxics emissions from organic liquid storage tanks. Its
intended audience includes Federal, State, and local air pollution personnel and others
interested in making estimates of toxic air pollutants emitted from organic liquid
storage tanks.
This document presents equations for estimating air toxics emissions from organic
liquid storage tanks and demonstrates through examples how to use the equations.
Information is also provided on storage tanks typically associated with source
categories.
KEY WORDS ANO DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Storage Tanks
Estimating Air Emissions
Adr Toxic Substances
Volatile Organic Liquids
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS I Tins Report!
Unclassified
21 NO. OF PAGES
20. SECURITY CLASS I Tins page/
Uriel a
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