Table of Contents

7.1 Organic Liquid Storage Tanks	3

7.1.1	General	3

7.1.1.1	Scope	3

7.1.1.2	Process Description	4

7.1.2	Emission Mechanisms And Control	8

7.1.2.1	Fixed Roof Tanks	8

7.1.2.2	Floating Roof Tanks	10

7.1.3	Emission Estimation Procedures	15

7.1.3.1	Routine Losses From Fixed Roof Tanks	16

7.1.3.2	Routine Losses From Floating Roof Tanks	32

7.1.3.3	Floating Roof Landing Losses	41

7.1.3.4	Tank Cleaning Emissions	53

7.1.3.5	Flashing Loss	61

7.1.3.6	Variable Vapor Space Tanks	63

7.1.3.7	Pressure Tanks	64

7.1.3.8	Variations Of Emission Estimation Procedures	65

7.1.4	Speciation Methodology	70

Figure 7.1-1. Typical fixed-roof tank	74

Figure 7.1-2. External floating roof tank (pontoon type)	75

Figure 7.1-3. External floating roof tank (double deck)	76

Figure 7.1-4. Internal floating roof tank	77

Figure 7.1-5. Domed external floating roof tank	78

Figure 7.1-6. Vapor-mounted primary seals	79

Figure 7.1-7. Liquid-mounted and mechanical shoe primary seals	80

Figure 7.1-8. Secondary rim seals	81

Figure 7.1-9. Deck fittings for floating roof tanks	82

Figure 7.1-10. Deck fittings for floating roof tanks	83

Figure 7.1-11. Slotted and unslotted guidepoles	84

Figure 7.1-12. Ladder well	85

Figure 7.1-13a. True vapor pressure of crude oils with a Reid vapor pressure

of 2 to 15 pounds per square inch	86

Figure 7. l-13a. True vapor pressure of crude oils with a Reid vapor pressure of 2 to 15 pounds per square

inch	86

Figure 7. l-14a. True vapor pressure of refined petroleum stocks with a Reid vapor pressure of 1 to 20

pounds per square inch	87

Figure 7. l-13b. Equation for true vapor pressure of crude oils with a Reid vapor pressure of 2 to 15

pounds per square inch	88

Figure 7. l-14b. Equation for true vapor pressure of refined petroleum stocks with a Reid vapor pressure

of 1 to 20 pounds per square inch	88

Figure 7.1-15. Equations to determine vapor pressure constants A and B for refined	88

Figure 7.1-16. Equations to determine vapor pressure Constants A and B for crude oil stocks	89

Figure 7.1-17. Equations for the average daily maximum and minimum liquid surface temperatures	89

Figure 7.1-18. Reserved	90

Figure 7.1-19. Vapor pressure function	91

Figure 7.1-20. Bottom conditions for landing loss	92

Figure 7.1-21. Ladder-guidepole combination with ladder sleeve	92

Figure 7.1-22. Slotted-guidepole with flexible enclosure	93

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Table 7.1-1. LIST OF ABBREVIATIONS USED IN THE TANK EQUATIONS	94

Table 7.1-2. PROPERTIES (My. Mr. PVA. Wt ) OF SELECTED PETROLEUM LIQUIDS	96

Table 7.1-3. PHYSICAL PROPERTIES OF SELECTED PETROCHEMICALS	97

Table 7.1-4. Height of the Liquid Heel and vapor space under a landed floating roof	104

Table 7.1-5. LEL VALUES FOR SELECTED COMPOUNDS	105

Table 7.1-6. PAINT SOLAR ABSORPTANCE	106

Table 7.1-7. METEOROLOGICAL DATA (Tax. Tan. V. I. Pa) FOR SELECTED U.S. LOCATIONS

	108

Table 7.1-8. RIM-SEAL LOSS FACTORS. KRa. IW and n. FOR FLOATING ROOF TANKS	144

Table 7.1-9. RESERVED	146

Table 7.1-10. AVERAGE CLINGAGE FACTORS. Cs	147

Table 7.1-11. TYPICAL NUMBER OF COLUMNS AS A FUNCTION OF TANK DIAMETER FOR

INTERNAL FLOATING ROOF TANKS WITH COLUMN- SUPPORTED FIXED ROOFS	147

Table 7.1-12. DECK-FITTING LOSS FACTORS. Ki,,. Kfh. AND m. AND TYPICAL NUMBER OF

DECK FITTINGS. Nf	148

Table 7.1-13. EXTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF VACUUM

BREAKERS. Nvh. AND DECK DRAINS. Nh	151

Table 7.1-14. EXTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF ROOF LEGS. Ni

	152

Table 7.1-15. INTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF DECK LEGS. Nk

AND STUB DRAINS. Nd	153

Table 7.1-16. DECK SEAM LENGTH FACTORS (Sr>) FOR TYPICAL DECK CONSTRUCTIONS

FOR INTERNAL FLOATING ROOF TANKS	153

Table 7.1-17. ROOF LANDING LOSSES FOR INTERNAL FLOATING ROOF TANK WITH A

LIQUID HEEL	154

Table 7.1-18. ROOF LANDING LOSSES FOREXTERNAL FLOATING ROOF TANK WITH A

LIQUID HEEL	154

Table 7.1-19. ROOF LANDING LOSSES FOR ALL DRAIN-DRY TANKS	156

Table 7.1-20. TANK CLEANING EQUATIONS - VAPOR SPACE PURGE EMISSIONS	158

Table 7.1-21. TANK CLEANING EQUATIONS - CONTINUED FORCED VENTILATION
EMISSIONS	159

7.1.5	Sample Calculations	160

7.1.6	Historical Equations	207

7.1.6.1	Average Daily Vapor Pressure Range	207

7.1.6.2	Fixed Roof Tank Working Loss	207

7.1-2

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7.1 Organic Liquid Storage Tanks
7.1.1 General
7.1.1.1 Scope

Section 7.1 presents emissions estimating methodologies for storage tanks of various types and
operating conditions. The methodologies are intended for storage tanks that are properly maintained and
in normal working condition. The methodologies do not address conditions of deteriorated or otherwise
damaged materials of construction, nor do thev address operating conditions that differ significantly from
the scenarios described herein.

Sections 7.1.3.1 and 7.1.3.2 present emissions estimating methodologies for routine emissions
from fixed roof tanks and floating roof tanks. The equations for routine emissions were developed to
estimate average annual losses for storage tanks, but provisions for applying the equations to shorter
periods of time are addressed in Section 7.1.3.8.1. The equations for routine emissions are a function of
temperatures that are derived from a theoretical energy transfer model. In order to simplify the
calculations, default values were assigned to certain parameters in the energy transfer equations. The
accuracy of the resultant equations for an individual tank depends upon how closely that tank fits the
assumptions inherent to these default values. The associated uncertainty may be mitigated by using
measured values for the liquid bulk temperature. The equations for routine emissions are not intended to
include emissions from the following events (these are addressed separately):

a)	To estimate losses that result from the landing of a floating roof. A separate methodology is
presented for floating roof landing losses in Section 7.1.3.3.

b)	To estimate losses that result from cleaning a tank. A separate methodology is presented for
tank cleaning losses in Section 7.1.3.4.

c)	To estimate losses from storage tanks containing unstable liquids, such as tanks which have
air or other gases injected into the liquid (sparging), tanks storing liquids at or above their
boiling point (boiling), or tanks storing liquids which contain gases that have the potential to
flash out of solution (flashing). Section 7.1.3.5 presents methodologies forthe estimation of
flashing losses, but Section 7.1 does not present methodologies for the estimation of sparging
or boiling losses.

d)	To estimate losses from variable vapor space tanks. Variable vapor space tanks are discussed
in Section 7.1.3.6.

e)	To estimate losses from equipment leaks associated with pressure tanks designed as closed
systems without emissions to the atmosphere. Pressure tanks are discussed in Section 7.1.3.7.

Section 7.1.3.8 addresses the following additional scenarios that are outside the scope of the
methodologies for routine emissions presented in Sections 7.1.3.1 and 7.1.3.2.

f)	Time periods shorter than one year. Certain assumptions in the equations for routine
emissions are based on annual averages, and thus the equations have greater uncertainty for a
period of time less than a year. Section 7.1.3.8.1 addresses application of the equations to
time periods shorter than one year, with the caveat that a one-month time frame is

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recommended as the shortest time period for which routine emissions should be estimated
using these methodologies.

g)	Internal floating roof tanks with closed vent systems. The equations for routine emissions
from internal floating roof tanks assume that the tank has open vents in the fixed roof.

Section 7.1.3.8.2 addresses estimation of emissions when an internal floating roof tank has
closed pressure/vacuum vents.

h)	Case-specific liquid surface temperature determination. Several parameters pertaining to
liquid surface temperature are assigned default values for incorporation into the equations for
routine emissions. Section 7.1.3.8.3 presents methodology to account forthese parameters as
variables in the estimation of emissions from a particular storage tank at a particular location.

i)	Heating cycles in fixed roof tanks. The equations for standing loss from fixed roof tanks are
based on a daily cycle of warming and cooling of the vapor space due to heat exchange
between the vapor space and ambient air through the shell and roof of the tank. This heat
exchange results in daytime expansion and nighttime contraction of vapors in the vapor
space, with each expansion causing some portion of the vapors to be expelled from the vapor
space. A similar cycle of expansion and contraction of the vapors may be driven by cyclic
heating of the bulk liquid. Section 7.1.3.8.4 provides guidance for adapting the equations for
fixed roof tank standing loss to the case of cyclic heating of the bulk liquid.

Section 7.1.4 presents calculations for applying Raoult's Law to calculate the contribution of
individual chemical species to the total emissions.

Section 7.1.5 presents worked examples, with estimated emissions shown to two significant
figures. This level of precision is chosen arbitrarily, and may overstate the accuracy of the loss estimates
given the uncertainty associated with the multiple parameters affecting emissions from storage tanks.

Section 7.1.6 contains equations that have been used historically to obtain approximate values,
but which have been replaced with more accurate equations.

7.1.1.2 Process Description1--

Storage vessels tanks containing organic liquids can be found in many industries, including
(1) petroleum producing and refining, (2) petrochemical and chemical manufacturing, (3) bulk storage
and transfer operations, and (4) other industries consuming or producing organic liquids. Organic liquids
in the petroleum industry, usually called petroleum liquids, generally are mixtures of hydrocarbons
having dissimilar true vapor pressures (for example, gasoline and crude oil). Organic liquids in the
chemical industry, usually called volatile organic liquids, are composed of pure chemicals or mixtures of
chemicals with similar true vapor pressures (for example, benzene or a mixture of isopropyl and butyl
alcohols).

Six basic tanktvpes of designs are used for organic liquid storage vesselstanks: fixed roof (vertical
and horizontal), external floating roof, domed external (or covered) floating roof, internal floating roof,
variable vapor space, and pressure (low and high). A brief description of each tank is provided below.
Loss mechanisms associated with each type of tank are provideddescribed in Section 7.1.2.

7.1-4

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The emission estimating equations presented in Section 7.1 were developed by the American
Petroleum Institute (API). API retains the copyright to these equations. API has granted permission for
the nonexclusive; noncommercial distribution of this material to governmental and regulatory agencies.
However, API reserves its rights regarding all commercial duplication and distribution of its material.
Therefore, the material presented in Section 7.1 is available for public use, but the material cannot be sold
without written permission from the American Petroleum Institute and the U. S. Environmental Protection
Agency.

7.1.1.2.1 Fixed Roof Tanks B

A typical vertical fixed roof tank is shown in Figure 7.1-1. 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. Losses from fixed roof tanks are caused by changes in temperature, pressure, and liquid
level.

Fixed roof tanks are either freely vented or equipped with a pressure/vacuum vent. The latter
allows the tanks 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. Fixed roof tanks may have additional vents or
hatches, referred to as emergency vents, to provide increased vent flow capacity in the event of excessive
pressure in the tank. Of current tank designs, the fixed roof tank is the least expensive to construct and is
generally considered the minimum acceptable equipment for storing organic liquids.

Horizontal fixed roof tanks are constructed for both above-ground and underground service and
are usually constructed of steel, steel with a fiberglass overlay, or fiberglass-reinforced polyester.
Horizontal tanks are generally small storage tanks with capacities of less than 40,000 gallons. Horizontal
tanks are constructed such that the length of the tank is not greater than six times the diameter to ensure
structural integrity. Horizontal tanks are usually equipped with pressure-vacuum vents, gauge hatches and
sample wells, and manholes to provide access to these tanks. In addition, underground tanks may be
cathodically protected to prevent corrosion of the tank shell. Cathodic protection is accomplished by
placing sacrificial anodes in the tank that are connected to an impressed current system or by using
galvanic anodes in the tank. However, internal cathodic protection against corrosion is no longer widely
used in the petroleum industry, duo to corrosion inhibitors that are now found in most refined petroleum
products.

The potential emission sources for above-ground horizontal tanks are the same as those for
vertical fixed roof tanks. Emissions from underground storage tanks are associated mainly with changes
in the liquid level in the tank. Losses due to changes in temperature or barometric pressure are minimal
for underground tanks because the surrounding earth limits the diurnal temperature change, and changes
in the barometric pressure result in only small losses.

7.1.1.2^2. External Floating Roof Tanks -B

A typical external floating roof tank (EFRT) consists of an open- toppodtop cylindrical steel shell
equipped with a roof that floats on the surface of the stored liquid. The floating roof consists of a deck,
deck fittings. and_a rim seal system. Floating decks that are currently in use are constructed of welded
steel plate and are most commonly of two general types: pontoon or double-deck. Pontoon-type and
double-deck-type external floating roof tanks are shown in Figures 7.1-2 and 7.1-3, respectively. With all

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types of external floating roof tanks, the roof rises and falls with the liquid level in the tank. External
floating decks are equipped with a rim seal system, which is attached to the deck perimeter and contacts
the tank wall. The purpose of the floating roof and rim seal system is to reduce evaporative loss of the
stored liquid. Some annular space remains between the seal system and the tank wall. The seal system
slides against the tank wall as the roof is raised and lowered. The floating deck is also equipped with deck
fittings that penetrate the deck and serve operational functions. The external floating roof design is such
that routine evaporative losses from the stored liquid are limited to losses from the rim seal system and
deck fittings (standing storage loss) and any exposed liquid on the tank walls {-that is exposed by the
lowering of the liquid level associated with the withdrawal of liquid (working loss). Because of the open-
top configuration of this tank, wind effects have a significant impact on evaporative losses from this type
of tank.

7.1.1.2.3 Internal Floating Roof Tanks B

An internal floating roof tank (IFRT) has both a permanent fixed roof and a floating roof inside.
There are two basic types of internal floating roof tanks: tanks in which the fixed roof is supported by
vertical columns within the tank, and tanks with a self-supporting fixed roof and no internal support
columns. Fixed roof tanks that have been retrofitted to use a floating roof are typically of the first type.
External floating roof tanks that have been converted to internal floating roof tanks typically have a self-
supporting roof. Newly constructed internal floating roof tanks may be of either type. The deck in internal
floating roof tanks 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). The
majority of aluminum internal floating roofs currently in service have noncontact decks. A typical internal
floating roof tank is shown in Figure 7.1-4.

Contact decks can beinclude (1) aluminum sandwich panels that are bolted together, with a
honeycomb aluminum core floating in contact with the liquid; (2) pan steel decks floating in contact with
the liquid, with or without pontoons; and (3) resin-coated, fiberglass reinforced polyester (FRP), buoyant
panels floating in contact with the liquid. Variations on these designs are also available. The majority of
internal contact floating decks currently in service are aluminum sandwich panel-type or pan steel-type.
The FRP decks are less common. The panels of pan steel decks are usually welded together.

Noncontact decks are the most common type currently in use. Typical noncontact decks are
constructed of an aluminum deck and an aluminum grid framework supported above the liquid surface by
tubular aluminum pontoons or some other buoyant structure. The noncontact decks usually have bolted
deck seams.

Installing a floating roof minimizes evaporative losses of the stored liquid. Both contact and
noncontact decks incorporate rim seals and deck fittings for the same purposes previously described for
external floating roof tanks. Evaporative losses from floating roofs may come from deck fittings,
nonwelded deck seams, and the annular space between the deck and tank wall. In addition, these tanks are
freely vented by circulation vents at the top of the fixed roof. The vents minimize the possibility of
organic vapor accumulation in the tank vapor space in concentrations approaching the flammable range.
An internal floating roof tank not freely vented is considered a pressurean internal floating roof tankT with
a closed vent system. Emission estimation methods for such tanks are not providodaddressed in A-P-
42-Section 7.1.3.8.2.

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7.1.1.2.4 Domed External Floating Roof Tanks ©

Domed external (or covered) floating roof tanks have the heavier type of deck used in external
floating roof tanks as well as a fixed roof at the top of the shell like internal floating roof tanks. Domed
external floating roof tanks usually result from retrofitting an external floating roof tank with a fixed roof.
This type of tank is very similar to an internal floating roof tank with a welded deck and a self-supporting
fixed roof. Atypical domed external floating roof tank is shown in Figure 7.1-5.

As with the internal floating roof tanks, the function of the fixed roof with respect to emissions is
not to act as a vapor barrier, but to block the wind. The estimations of rim seal losses and deck fitting
losses include a loss component that is dependent on wind speed and a loss component that is independent
of wind speed. When a tank is equipped with a fixed roof, the wind-dependent component is zero due to
the blocking of the wind by the fixed roof, leaving only the wind-independent loss component.

The type of fixed roof most commonly used is a selfisupporting aluminum dome roof, which is of
bolted construction. Like the internal floating roof tanks, these tanks are freely vented by circulation vents
at the top and around the perimeter of the fixed roof. The deck fittings and rim seals, however, are
identical to those on external floating roof tanks. In the event that the floating deck is replaced with the
lighter IFRT-type deck, the tank would then be considered an internal floating roof tank.

The distinction between a domed external floating roof tank and an internal floating roof tank is
primarily for purposes of recognizing differences in the deck fittings when estimating emissions. In
particular, the domed external floating roof deck typically has significantly taller leg sleeves than are
typical of an internal floating roof deck. The longer leg sleeves of the domed external floating roof deck
have lower associated emissions than the shorter leg sleeves of the internal floating roof deck. While a
domed external floating roof tank is distinct from an internal floating roof tank for purposes of estimating
emissions, the domed external floating roof tank would be deemed a type of internal floating roof tank
under air regulations that do not separately specify requirements for a domed external floating roof tank.

7.1.1.25 Variable Vapor Space Tanks ©

Variable vapor space tanks are equipped with expandable vapor 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.

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. A variable vapor space
tank that utilizes a flexible diaphragm will emit standing losses to the extent that the flexible diaphragm is
permeable or there is leakage through the seam where the flexible diaphragm is attached to the tank wall.

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Avariable vapor space tank losses occurwill emit vapors during tank filling when vapor is
displaced by liquid. Loss of vapor occurs only when, if the tank's vapor storage capacity is exceeded.

7.1.1.2.6 Pressure Tanks ©

Two classes of pressure tanks are in general use: low pressure (2.5 to 15 psig) and high pressure
(higher than 15 psig). Pressure tanks generally are used for storing organic liquids and gases with high
vapor pressures and are found in many sizes and shapes, depending on the operating pressure of the tank.
Low-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 can be 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 operations. No appropriate
correlations are available to estimate Vapor losses from low-pressure tanksv storing non-boiling liquids
are estimated in the same manner as for fixed roof tanks, with the vent set pressure accounted for in both
the standing and working loss equations.

7.1.2 Emission Mechanisms And Control-

Emissions from the storage of organic liquids in storage occur because of evaporative loss of the
liquid during its storage and as a result of changes in the liquid level. The emission sourcesmechanisms
vary with tank design, as does the relative contribution of each type of emission sourccmcchanism.
Emissions from fixed roof tanks are a result of evaporative losses during storage (known as breathing
losses or standing storage losses) and evaporative losses during filling and emptying operations (known
as working losses). External and internal floating roof tanks are emission sources because of evaporative
losses that occur during standing storage and withdrawal of liquid from the tank. Standing storage losses
are a result of evaporative losses through rim seals, deck fittings, and/or deck seams. The loss
mechanisms for routine emissions from fixed roof and external and internal floating roof tanks are
described in more detail in this section. Variable vapor space tanks are also emission sources because of
evaporative losses that result during filling operations. The loss mechanism for variable vapor space tanks
is also described in this section. Emissions occur from pressure tanks, as well. However, loss mechanisms
from these sources are not described in this section.

7.1.2.1 Fixed Roof Tanks ©

The two significant types of routine emissions from fixed roof tanks are storage standing and
working losses. StorageThe standing loss mechanism for a fixed roof tank is known as breathing, which is
the expulsion of vapor from a tank through vapor expansion and contraction, which are the that results
effrom changes in temperature and barometric pressure. This loss occurs without any liquid level change
in the tank. The emissions estimating methodology presented in Section 7.1 assumes the barometric
pressure to be constant, and standing losses from fixed roof tanks are attributed only to changes in
temperature. As vapors expand in the vapor space due to warming, the pressure of the vapor space
increases and expels vapors from the tank through the vent(s) on the fixed roof. If the venting is of a type
that is closed in the absence of pressure, such as a weighted-pallet pressure-vacuum vent, then vapors are
assumed to not be expelled until the pressure in the vapor space exceeds the set pressure of the vent.

The combinedevaporative loss from filling and emptying is called working loss. Evaporation
duringEmissions due to filling operations ts-aare the result of an increase in the liquid level in the tank. As

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the liquid level increases, the pressure inside the tank exceeds the relief pressurevapor space increases and
vapors are expelled from the tank. Evaporative through the vcnt(s) on the fixed roof as described above
for standing loss. No emissions are attributed to emptying, in that the increasing size of the vapor space
during emptying occurs when air drawnis assumed to exceed the rate at which evaporation increases the
volume of vapors. That is. it would be expected that flow through the vents during emptying would be
into the tank during liquid removal becomes saturated with organic vapor, and expands, thus exceeding
the capacity of the vapor space .there are no emissions actually occurring during emptying of a fixed roof
tank.

A third type of emissions from fixed roof tanks is commonly referred to as flashing losses. This
emission type is not an evaporative loss, but rather involves entrained gases bubbling out of solution
when a liquid stream experiences a pressure drop upon introduction into a storage tank. As such, it occurs
only in storage tanks that receive pressurized liquid streams containing entrained gases. This scenario is
typical of storage tanks receiving liquids from a separator in oil and gas production operations, but does
not typically occur at downstream facilities. Methodologies for estimating flashing losses are discussed
in Section 7.1.3.5.

Fixed roof tank emissions from standing and working vary as a function of vesseltank capacity,
vapor pressure of the stored liquid, utilization rate of the tank, and atmospheric conditions at the tank
location.

Several methods are used to control emissions from fixed roof tanks. Emissions from fixed roof
tanks can be controlled by installing an internal floating roof and seals to minimize evaporation of the
product being stored. The control efficiency of this method ranges from 60 to 99 percent, depending on
the type of roof and seals installed and on the type of organic liquid stored.

Fixed roof tank emissions may also be reduced by increasing the vent set pressure, and routine
emissions may be eliminated if the vent set pressure is higher than the pressure that develops in the vapor
space during normal operations. See Section 7.1.3.7 for a discussion of estimating emissions from
pressure tanks. However, the structural design of most storage tanks would not normally accommodate
internal pressures of the magnitude required to significantly reduce emissions, and thus vent set pressures
should not be altered without consideration of the tank design including all appropriate safety factors.
Subjecting a storage tank to greater pressure or vacuum than that for which the tank was designed could
potentially result in failure of the tank.

Vapor balancing is another means of emission control. Vapor balancing is probably most
common in the filling of tanks at gasoline service stations. As the storage tank is filled, the vapors
expelled from the storage tank are directed to the emptying gasoline tanker truck. The truck then
transports the vapors to a centralized station where a vapor recovery or control system ismav be used to
control emissions. Vapor balancing can have control efficiencies as high as 90 to 98 percent if the vapors
are subjected to vapor recovery or control. If the truck vents the vapor to the atmosphere instead of to a
recovery or control system, no control is achieved.

Vapor recovery systems collect emissions from storage vesselstanks and convert them to liquid
product. Several vapor recovery procedures may be used, including vapor/liquid absorption, vapor
compression, vapor cooling, vapor/solid adsorption, or a combination of these. The overall control

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efficiencies of vapor recovery systems are as high as 90 to 98 percent, depending on the methods used,
the design of the unit, the composition of vapors recovered, and the mechanical condition of the system.

In a typical thermal oxidation system, the air/vapor mixture is injected through a burner manifold
into the combustion area of an incinerator. Control efficiencies for this system can range from 96 to
99 percent.

Vapors from fixed roof tanks may also be collected and combusted. There are several types of
units at facilities used to accomplish this, including various types of flares and thermal oxidation units.

7.1.2.2 Floating Roof TanksM -B

Total-Routine emissions from floating roof tanks are the sum of withdrawal-working losses and
standing storage losses. Withdrawal losses occurThe working loss mechanism for a floating roof tank is
also known as withdrawal loss, in that it occurs as the liquid level, and thus the floating roof, is lowered
rather than raised. Some liquid remains on the inner tank wall surface and evaporates. For an internal
floating roof tank that has a column supported fixed roof, some liquid also clings to the columns and
evaporates. Evaporative loss occurs until the tank is filled and the exposed surfaces are again covered.
Standing storage losses from floating roof tanks include rim seal and deck fitting losses, and for internal
floating roof tanks alsewith welded decks, and include deck seam losses for constructions other than
welded decks. Other potential Both the working and standing storage loss mechanisms include breathing
losses as a resultfor floating roof tanks pertain to the accumulation of temperature and pressure
changes.vapors in the headspace above the floating roof. It is assumed that vapors in the headspace will
eventually be expelled from the tank, but this emissions estimating methodology does not address the rate
or time at which the vapors actually leave the tank.

Rim seal losses can occur through many complex mechanisms, but for external floating roof
tanks, the majority of rim seal vapor losses have been found to be wind induced. No dominant wind loss
mechanism has been identified for internal floating roof or domed external floating roof tank rim seal
losses. Losses can also occur due to permeation of the rim seal material by the vapor or via a wicking
effect of the liquid, but permeation of the rim seal material generally does not occur if the correct seal
fabric is used. Testing has indicated that breathing, solubility, and wicking loss mechanisms are small in
comparison to the wind-induced loss. The rim seal factors presented in this section incorporate all types
of losses.

The rim seal system is used to allow the floating roof to rise and fall within the tank as the liquid
level changes. The rim seal system also helps to fill the annular space between the rim and the tank shell
and therefore minimize evaporative losses from this area. A rim seal system may consist of just a primary
seal or a primary and a secondary seal, which is mounted above the primary seal. Examples of primary
and secondary seal configurations are shown in Figures 7.1-6, 7.1-7, and 7.1-8.

The primary seal serves as a vapor conservation device by closing the annular space between the
edge of the floating deck and the tank wall. Three basic types of primary seals are used on external
floating roofs: mechanical (metallic) shoe, resilient filled (nonmetallic), and flexible wiper seals. Some
primary seals on external floating roof tanks are protected by a weather shield. Weather shields may be of
metallic, elastomeric, or composite construction and provide the primary seal with longer life by
protecting the primary seal fabric from deterioration due to exposure to weather, debris, and sunlight.

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Internal floating roofs typically incorporate one of two types of flexible, product resistant seals: resilient
foam filled seals or wiper seals. Mechanical shoe seals, resilient filled seals, and wiper seals are discussed
below.

A mechanical shoe seal uses a light-gauge metallic band as the sliding contact with the shell of
the tank, as shown in Figure 7.1-7. The band is formed as a series of sheets (shoes) which are joined
together to form a ring, and are held against the tank shell by a mechanical device. The shoes are
normally 3 to 5 feet deep, providing a potentially largo contact area with the tank shell, when used on an
external floating roof, and are often shorter when used on an internal floating roof. Expansion and
contraction of the ring can be provided for as the ring passes over shell irregularities or rivets by jointing
narrow pieces of fabric into the ring or by crimping the shoes at intervals. The bottoms of the shoes
extend below the liquid surface to confine the rim vapor space between the shoe and the floating deck.

The rim vapor space, which is bounded by the shoe, the rim of the floating deck, and the liquid
surface, is sealed from the atmosphere by bolting or clamping a coated fabric, called the primary seal
fabric, which extends from the shoe to the rim to form an "envelope". Two locations are used for
attaching the primary seal fabric. The fabric is most commonly attached to the top of the shoe and the rim
of the floating deck. To reduce the rim vapor space, the fabric can be attached to the shoe and the floating
deck rim near the liquid surface. Rim vents can be used to relieve any excess pressure or vacuum in the
vapor space.

A resilient filled seal can be mounted to eliminate the vapor space between the rim seal and liquid
surface (liquid mounted) or to allow a vapor space between the rim seal and the liquid surface (vapor
mounted). Both configurations are shown in Figures 7.1-6 and 7.1-7. Resilient filled seals work because
of the expansion and contraction of a resilient material to maintain contact with the tank shell while
accommodating varying annular rim space widths. These rim seals allow the roof to move up and down
freely, without binding.

Resilient filled seals typically consist of a core of open-cell foam encapsulated in a coated fabric.
The seals are attached to a mounting on the deck perimeter and extend around the deck circumference.
Polyurethane-coated nylon fabric and polyurethane foam are commonly used materials. For emission
control, it is important that the attachment of the seal to the deck and the radial seal joints be vapor-tight
and that the seal be in substantial contact with the tank shell.

Wiper seals generally consist of a continuous annular blade of flexible material fastened to a
mounting bracket on the deck perimeter that spans the annular rim space and contacts the tank shell. This
type of seal is depicted in Figure 7.1-6. New tanks with wiper seals may have dual wipers, one mounted
above the other. The mounting is such that the blade is flexed, and its elasticity provides a sealing
pressure against the tank shell.

Wiper seals are vapor mounted; a vapor space exists between the liquid stock and the bottom of
the seal. For emission control, it is important that the mounting be vapor-tight, that the seal extend around
the circumference of the deck and that the blade be in substantial contact with the tank shell. Two types of
materials are commonly used to make the wipers. One type consists of a cellular, elastomeric material
tapered in cross section with the thicker portion at the mounting. Rubber is a commonly used material;
urethane and cellular plastic are also available. All radial joints in the blade are joined. The second type of
material that can be used is a foam core wrapped with a coated fabric. Polyurethane on nylon fabric and

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polyurethane foam are common materials. The core provides the flexibility and support, while the fabric
provides the vapor barrier and wear surface.

A secondary seal may be used to provide some additional evaporative loss control over that
achieved by the primary seal. Secondary seals can be either flexible wiper seals or resilient filled seals.
For external floating roof tanksmechanical shoe primary seals, two configurations of secondary seals are
available: shoe mounted and rim mounted, as shown in Figure 7.1-8. Rim mounted secondary seals are
more effective in reducing losses than shoe mounted secondary seals because they cover the entire rim
vapor space. For internal floating roof tanks, the secondary seal is mounted to an extended vertical rim
plate, above the primary seal, as shown in Figure 7.1-8. However, for some floating roof tanks, using a
secondary seal further limits the tank's operating capacity due to the need to keep the seal from interfering
with fixed roof rafters or to keep the secondary seal in contact with the tank shell when the tank is filled.

The deck fitting losses from floating roof tanks can be explained by the same mechanisms as the
rim seal losses. However.While the relative contribution of each mechanism is not known. Theto the total
emissions from a given deck fitting losses identified in this section accountis not known, emission factors
were developed for individual deck fittings by testing, thereby accounting for the combined effect of all
of the mechanisms.

Numerous fittings pass through or are attached to floating roof decks to accommodate structural
support components or allow for operational functions. Internal floating roof deck fittings are typically of
different configuration than those for external floating roof decks. Rather than having tall housings to
avoid rainwater entry, internal floating roof deck fittings tend to have lower profile housings to minimize
the potential for the fitting to contact the fixed roof when the tank is filled. Deck fittings can be a source
of evaporative loss when they require openings in the deck. The most common components that require
openings in the deck are described below.

1.	Access hatches. An access hatch is an opening in the deck with a peripheral vertical well that is
large enough to provide passage for workers and materials through the deck for construction or servicing.
Attached to the opening is a removable cover that may be bolted and/or gasketed to reduce evaporative
loss. On internal floating roof tanks with noncontact decks, the well should extend down into the liquid to
seal off the vapor space below the noncontact deck. A typical access hatch is shown in Figure 7.1-9.

2.	Gauge-floats. A gauge-float is used to indicate the level of liquid within the tank. The float
rests on the liquid surface and is housed inside a well that is closed by a cover. The cover may be bolted
and/or gasketed to reduce evaporation loss. As with other similar deck penetrations, the well extends
down into the liquid on noncontact decks in internal floating roof tanks. A typical gauge-float and well
are shown in Figure 7.1-9.

3.	Gauge-hatch/sample ports. A gauge-hatch/sample port consists of a pipe sleeve equipped with
a self closing gasketed cover (to reduce evaporative losses) and allowsthrough the deck for hand-gauging
or sampling of the stored liquid. The gauge-hatch/sample port is usually located beneath the gauger's
platform, which is mounted on top of the tank shell. A cover may be attached to the top of the opening,
and the cover may be equipped with a gasket to reduce evaporative losses. A cord may be attached to the
self closing gasketed cover so that the cover can be opened from the platform. Alternatively, the opening
may be covered with a slit-fabric seal. A funnel may be mounted above the opening to guide a sampling
device or gauge stick through the opening. A typical gauge-hatch/sample port is shown in Figure 7.1-9.

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4.	Rim vents. Rim vents are used on tanks equipped with a seal design that creates a vapor pocket
in the seal and rim area, such as a mechanical shoe seal. A typical rim vent is shown in Figure 7.1-10. The
vent is used to release any excess pressure or vacuum that is present in the vapor space bounded by the
primary-seal shoe and the floating roof rim and the primary seal fabric and the liquid level. Rim vents
usually consist of weighted pallets that rest on a gasketed covoroverthe vent opening.

5.	Deck drains. Currently two types of deck drains are in use (closed and open deck drains) to
remove rainwater from the floating deck. Open deck drains can be either flush or overflow drains. Both
types of open deck drains consist of a pipe that extends below the deck to allow the rainwater to drain into
the stored liquid. Only open deck drains are subject to evaporative loss. Flush drains are flush with the
deck surface. Overflow drains are elevated above the deck surface. Typical overflow and flush deck
drains are shown in Figure 7.1-10. Overflow drains are used to limit the maximum amount of rainwater
that can accumulate on the floating deck, providing emergency drainage of rainwater if necessary. Closed
deck drains carry rainwater from the surface of the deck though a flexible hose or some other type of
piping system that runs through the stored liquid prior to exiting the tank. The rainwater does not come in
contact with the liquid, so no evaporative losses result. Overflow drains are usually used in conjunction
with a closed drain system to carry rainwater outside the tank.

6.	Deck legs. Deck legs are used to prevent damage to fittings underneath the deck and to allow
for tank cleaning or repair, by holding the deck at a predetermined distance off the tank bottom. These
supports consist of adjustable or fixed legs attached to the floating deck or hangers suspended from the
fixed roof. For adjustable legs or hangers, the load-carrying element passcsmav pass through a well or
sleeve into the deck. With noncontact decks, the well should extend into the liquid. Evaporative losses
may occur in the annulus between the deck leg and its sleeve. A typical deck leg is shown in

Figure 7.1-10.

7.	Unslotted guidepoles and wells. A guidepole is an antirotational device that is fixed to the top
and bottom of the tank, passing through a well in the floating roof. The guidepole is used to prevent
adverse movement of the roof and thus damage to deck fittings and the rim seal system. In some cases, an
unslotted guidepole is used for gauging purposes, but there is a potential for differences in the pressure,
level, and composition of the liquid inside and outside of the guidepole. A typical guidepole and well are
shown in Figure 7.1-11.

8.	Slotted (perforated) guidepoles and wells. The function of the slotted guidepole is similar to the
unslotted guidepole but also has additional features. Perforated guidepoles can be either slotted or drilled
hole guidepoles. A typical slotted guidepole and well are shown in Figure 7.1-11. As shown in this figure,
the guide pole is slotted to allow stored liquid to enter. The same can be accomplished with drilled holes.
The liquid entering the guidepole is well mixed, havinghas the same composition as the remainder of the
stored liquid, and is at the same liquid level as the liquid in the tank. Representative samples can therefore
be collected from the slotted or drilled hole guidepole. However, Evaporative loss from the guidepole can
be reduced by some combination of modifying the guidepole or well with the addition of gaskets, sleeves.
or bvenclosures or placing a float inside the guidepole. as shown in Figures 7.1-11 and 7.1-22.

Guidepoles are also referred to as gauge poles, gauge pipes, or stilling wells.

9.	Vacuum breakers. A vacuum breaker equalizes the pressure of the vapor space across the deck
as the deck is either being landed on or floated off its legs. A typical vacuum breaker is shown in
Figure 7.1-10. As depicted in this figure, the vacuum breaker consists of a well with a cover. Attached to

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the underside of the cover is a guided leg long enough to contact the tank bottom as the floating deck
approaches. When in contact with the tank bottom, the guided leg mechanically opens the breaker by
lifting the cover off the well; otherwise, the cover closes the well. The closure may be gasketed or
ungasketed. Because the purpose of the vacuum breaker is to allow the free exchange of air and/or vapor,
the well does not extend appreciably below the deck. While vacuum breakers have historically tended to
be of the leg-actuated design described above, thev may also be vacuum actuated similar to the
pressure/vacuum vent on a fixed roof tank such that thev do not begin to open until the floating roof has
actually landed. In some cases, this is achieved by replacing the rim vent described above with a
pressure/vacuum vent.

Fittings typically used only on internal floating roof tanks include column wells, ladder wells, and
stub drains.

1.	Columns and wells. The most commonSome fixed-roof designs are normally supported from
inside the tank by means of vertical columns, which necessarily penetrate an internal floating deck. (Some
fixed roofs are entirely self-supporting from the perimeter of the roof and, therefore, have no interior
support columns.) Column wells are similar to unslotted guide pole wells on external floating roofs.
Columns are made of pipe with circular cross sections or of structural shapes with irregular cross sections
(built-up). The number of columns varies with tank diameter, from a minimum of 1 to over 50 for very
large diameter tanks. A typical fixed roof support column and well are shown in Figure 7.1-9.

The columns pass through deck openings via peripheral vertical wells. With noncontact decks,
the well should extend down into the liquid stock. Generally, a closure device exists between the top of
the well and the column. Several proprietary designs exist for this closure, including sliding covers and
fabric sleeves, which must accommodate the movements of the deck relative to the column as the liquid
level changes. A sliding cover rests on the upper rim of the column well (which is normally fixed to the
deck) and bridges the gap or space between the column well and the column. The cover, which has a
cutout, or opening, around the column slides vertically relative to the column as the deck raises and
lowers. At the same time, the cover slidcsmav slide horizontally relative to the rim of the well to
accommodate out-of-plumbness of the column. A gasket around the rim of the well reduces emissions
from this fitting. A flexible fabric sleeve seal between the rim of the well and the column (with a cutout or
opening, to allow vertical motion of the seal relative to the columns) similarly accommodates limited
horizontal motion of the deck relative to the column.

2.	Ladders and wells. Some tanks are equipped with internal ladders that extend from a manhole
in the fixed roof to the tank bottom. The deck opening through which the ladder passes is constructed
with similar design details and considerations to deck openings for column wells, as previously discussed.
A typical ladder well is shown in Figure 7.1-12.

Tanks are sometimes equipped with a ladder/guidepole combination, in which one or both legs of
the ladder is a slotted pipe that serves as a guidepole for purposes such as level gauging and sampling. A
ladder/guidepole combination is shown in Figure 7.1-21 with a ladder sleeve to reduce emissions.

3.	Stub drains. Bolted internal floating roof decks are typically equipped with stub drains to allow
any stored product that may be on the deck surface to drain back to the underside of the deck. The drains
are attached so that they are flush with the upper deck. Stub drains are approximately 1 inch in diameter
and extend down into the product on noncontact decks. A typical flush stub drain is shown in

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Figure 7.1-10. Stub drains may be equipped with floating balls to reduce emissions. The floating ball acts
as a check valve, in that it remains covering the stub drain unless liquid is present to lift it.

Deck seams in internal floating roof tanks are a source of emissions to the extent that these seams
may not be completely vapor tight if the deck is not welded. Generally, the same loss mechanisms forA
weld sealing a deck seam does not have to be structural (i.e.. may be a seal weld) to constitute a welded
deck seam for purposes of estimating emissions, but a deck seam that is bolted or otherwise mechanically
fastened and sealed with elastomeric materials or chemical adhesives is not a welded seam. Generally, the
same loss mechanisms for deck fittings apply to deck seams. The predominant mechanism depends on
whether or not the deck is in contact with the stored liquid. The deck seam loss equation accounts for the
effects of all contributing loss mochamismsmechanisms.

7.1.3 Emission Estimation Procedures

The following section presents the emission estimation procedures for fixed roof, external
floating roof, domed external floating roof, and internal floating roof tanks. These procedures are valid for
all petroleum liquids, pure volatile organic liquids^ and chemical mixtures with similar true vapor
pressures. It is important to note that in all the emission estimation procedures the physical properties of
the vapor do not include the noncondensibles (e. g., air) in the gasatmosphere but only refer to the
condensiblevolatile components of the stored liquid. For example, the vapor-phase molecular weight is
determined from the weighted average of the evaporated components of the stored liquid, and does not
include the contribution of atmospheric gases such as nitrogen and oxygen. To aid in the emission
estimation procedures, a list of variables with their corresponding definitions was developed and is
presented in Table 7.1-1.

The factors presented in AP-42 are those that are currently available and have been reviewed and
approved by the U. S. Environmental Protection Agency. As storage tank equipment vendors design new
floating decks and equipment, new emission factors may be developed based on that equipment. If the
new emission factors are reviewed and approved, the emission factors will be added to AP-42 during the
next update.

The emission estimation procedures outlined in this chapter have been used as the basis for the
development of a software program to estimate emissions from storage tanks. The software program
entitled "TANKS" is available through the Technology Transfer Network (TTN) Bulletin Board System
maintained by the U.U. S. Environmental Protection Agency- website. While this software does not
address all of the scenarios described in this chapter, is known to have errors, and is no longer supported.
it is still made available for historical purposes.

There are also commercially available storage tank emissions estimation software programs.

Users of these programs are advised to understand the extent of agreement with AP-42 Chapter 7
calculation methodology and assume responsibility of the accuracy of the output as thev have not been
reviewed or approved by the EPA.

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7.1.3.1 TetalRoutine Losses From Fixed Roof Tanks4^"14*^ -

The following equations, provided to estimate standing storage and working loss emissions, apply
to tanks with vertical cylindrical shells and fixed roofsT and to tanks with horizontal cylindrical shells.
These tanks must be substantially liquid- and vapor-tight and must operate approximately at atmospheric
pressure.^ The equations are not intended to be used in estimating losses from tanks which have air or
other gases injected into the liquid, or which store unstable or boiling stocks or from mixtures of
hydrocarbons or petrochemicals for which the vapor pressure is not known or cannot be readily predicted.
Total routine losses from fixed roof tanks are equal to the sum of the standing storage loss and working
loss:

Lt — Ls + Lw	(1-1)

where:

Lt = total routine losses, lb/yr
Ls = standing storage losses, lb/yr, see Equation 1-2
Lw = working losses, lb/yr, see Equation 1-2935

7.1.3.1.1 Standing Storage Loss

The standing storage loss, Ls. for a fixed roof tank refers to the loss of stock vapors as a result of
tank vapor space breathing. Fixed roof tank standing storage losses can be estimated from Equation l-27
which comes from the previous edition of Chapter 7 of AP 12.

Ls = 365 VvWvKeKs	(1-2)

where:

Ls =	standing storage loss, lb/yr

Vv =	vapor space volume, ft3, see Equation 1-3

Wv =	stock vapor density, lb/ft3

Ke =	vapor space expansion factor, dimensionlessper day

Ks =	vented vapor saturation factor, dimensionless

365 =	constant, the number of daily events in a year, (days/year)"4-)

Tank Vapor Space Volume. Vv - The tank vapor space volume is calculated using the following equation:

Vv={^-dAhvo	(1-3)

where:

Vv =	vapor space volume, ft3

D =	tank diameter, ft, see Equation 1-144-^ for horizontal tanks

Hvo =	vapor space outage, ft, see Equation 1 -164-»

The standing storage loss equation can be simplified by combining Equation 1-2 with Equation 1-3. The
result is Equation 1-4.

7.1-16

Liquid Storage TanksEMISSION FACTORS

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(1-4)

where:

Ls = standing storage loss, lb/yr

Ke = vapor space expansion factor,, see Equation 1-5, 1-612. or 1-213

D = diameter, ft, see Equation 1-144^ for horizontal tanks
Hvo = vapor space outage, ft, see Equation 1 -1644-: use He/2 from Equation 1-1544 for
horizontal tanks

Ks = vented vapor saturation factor, dimensionless, see Equation 1-212#

Wv = stock vapor density, lb/ft3, see Equation 1-2224
365 = constant, the number of daily events in a year, (days/year)"4)

Vapor Space Expansion Factor, Ke

The calculation of the vapor space expansion factor, Ke, depends upon the properties of the liquid
in the tank and the breather vent settings. If the liquid stock has a true vapor pressure greater than 0.1
psia, or if the breather vent settings are higher than the typical range of ±0.03 psig, see Equation 1 7. If
the liquid stored in the fixed roof tank has a true vapor pressure loss than 0.1 psia and the tank breather
vent settings are ±0.03 psig. use either Equation 1 5 or Equation 1 6. as shown in Equation 1-5. As shown
in the equation. Kf is greater than zero. If Kf is less than zero, standing losses will not occur. In that Kf
represents the fraction of vapors in the vapor space that are expelled by a given increase in temperature, a
value of 1 would indicate that the entire vapor space has been expelled. Thus the value of Kf must be less
than 1. in that it is not physically possible to expel more than 100% of what is present to begin with.

If the tank location and tank color and condition are known, Ke is calculated using the following
equation:

—Kr^——vapor space expansion factor, dimensionless
-Ti:——daily vapor temperature range, °R
¦Tax——daily maximum ambient temperature, °R
Tan——daily minimum ambient temperature, °R

	=—tank paint solar absorptance, dimensionless

—1-=—daily total solar insolation on a horizontal surface, Btu/(ft~ day)

(1-5)

where:

0.0018 ~—constant, (°R)~^
—0.72 ~—constant, dimensionless
0.028 ~—constant, (°R ft3 day)/Btu

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If the tank location is unknow n, a value of Kg can be calculated using typical meteorological
conditions for the lower 18 states. The typical value for daily solar insolation is 1,370 Btu/(ft3 day), the
daily range of ambient temperature is 21°R, the daily minimum ambient temperature is 173.5 °R, and the
tank paint solar absorptance is 0.17 for white paint in good condition. Substituting these values into
Equation 1 5 results in a value of 0.01. as shown in Equation 1 6.

	Kb-0.01	(J-6)

When the liquid stock has a true vapor pressure greater than 0.1 psia, a more accurate estimate of
the vapor space expansion factor, Kg, is obtained by Equation 1 7. As shown in the equation,
than zero. If Kb is less than zero, standing storage losses will not occur.

, - V. , . V< .v, _ „

k" ~	^

P.4 PfA

where:

A Tv =	average daily vapor temperature range, °R; see Note 1

A Pv =	average daily vapor pressure range, psi; see Note 2

A Pb =	breather vent pressure setting range, psi; see Note 3

Pa =	atmospheric pressure, psia

Pva =	vapor pressure at daily average daily liquid surface temperature, psia; see Notes 1 and 2
for Equation 1-2224-

Tla =	daily average daily liquid surface temperature, °R; see Note 3 for Equation 1 -2234

Notes:

1. The average daily vapor temperature range, A Tv- refers to the daily temperature range of the
tank vapor space averaged over all of the days in the given period of time, such as one year, and should
not be construed as being applicable to an individual day. The average daily vapor temperature range is
calculated for an uninsulated tank using the following equation: Equation 1-6.

(A 0.8 , 0.042ocr/ + 0.026(HS/D)OCS/
	Alv~	2.2 (Hs/D) +1.9) A1a+	2.2 (Hs/D) + 1.9 	

where:

	ATy =	average daily vapor temperature range. °R

	Hs =	tank shell height, ft

	D =	tank diameter, ft.

	ATa =	average daily ambient temperature range. °R; see Note 4

	or =	tank roof surface solar absorptance. dimensionless: see Table 7.1-6

	as =	tank shell surface solar absorptance. dimensionless: see Table 7.1-6

	I =	average daily total insolation factor. Btu/ft2 d: see Table 7.1-7.

API assigns a default value of H/D = 0.5 and an assumption of a,\< = a.s. resulting in the
simplified equation shown below for an uninsulated tank:22

	ATv = 0.7 ATa + 0.02 a I	(1-7)

where:

	a = average tank surface solar absorptance. dimensionless

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For purposes of estimating emissions, a storage tank should be deemed insulated only if the roof
and shell are both sufficiently insulated so as to minimize heat exchange with ambient air. If only the
shell is insulated, and not the roof, the temperature equations are independent of H /D. Also, there likely
will be sufficient heat exchange through the roof such that Equation 1-7 would be applicable.

A more accurate method of accounting for the average daily vapor temperature range. ATv. in
partially insulated scenarios is given below. When the tank shell is insulated but the tank roof is not, heat
gain to the tank from insolation is almost entirely through the tank roof and thus the liquid surface
temperature is not sensitive to Hs/D.

	ATv = 0.6 ATa + 0.02 qR I	(1-8)

In the case of a fully insulated tank maintained at constant temperature, the average daily vapor
temperature range. A Ty. should be taken as zero. This assumption that A Ty is equal to zero addresses
only temperature differentials resulting from the diurnal ambient temperature cycle. In the case of cyclic
heating of the bulk liquid, see Section 7.1.3.8.4.

-A-Tv ~ 0.72 -A-Ta + 0.028 a I	(4-8)

where:

	¦T'rTi:——daily vapor temperature range, °R

	-A-Ta——daily ambient temperature range, °R; see Note 1

	6E- ~ tank paint solar absorptance, dimensionless; see Table 7.16

	1-=—daily total solar insolation factor, Btu/ft3 d; see Table 7.1 7

2. The average daily vapor pressure range, A Pv. refers to the daily vapor pressure range at the
liquid surface temperature averaged over all of the days in the given period of time, such as one year, and
should not be construed as being applicable to an individual day. The average daily vapor pressure range
can be calculated using the following equation:

APv = Pvx-Pvn	(1-9)

where:

	A Pv = average daily vapor pressure range, psia

	Pvx = vapor pressure at the average daily maximum liquid surface temperature, psia: see Note 5

	Pvn = vapor pressure at the average daily minimum liquid surface temperature, psia: see Note 5

See Section 7.1.6.1 for a more approximate equation for APv that was used historically, but which

0.50 />' /' . V/



v rjn 2

is no longer recommended. -	L4

where:

—Pv——daily vapor pressure range, psia

—6-=—constant in the vapor pressure equation, °R; see Note 2 to Equation 121

-P^——vapor pressure at the daily average liquid surface temperature, psia; see Notes 1 and 2 to

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	Equation 1 21

-Fla——daily average liquid surface temperature, °R; see Note 3 to Equation 121
-A-T-v ~ daily vapor temperature range, °R; see Note 1

In the case of a fully insulated tank maintained at constant temperature, the average daily vapor
pressure range. A Pv. should be taken as zero, as discussed for the vapor temperature range in Note 1.

3. The breather vent pressure setting range, APb, is calculated using the following equation:

where:

A Pb = breather vent pressure setting range, psig
Pbp = breather vent pressure setting, psig
Pbv = breather vent vacuum setting, psig

If specific information on the breather vent pressure setting and vacuum setting is not available,
assume 0.03 psig for Pbp and -0.03 psig for Pbv as typical values. If the fixed roof tank is of bolted or
riveted construction in which the roof or shell plates are not vapor tight, assume that A Pb = 0, even if a
breather vent is used.

4. The average daily ambient temperature range, A Ta. refers to the daily ambient temperature
range averaged over all of the days in the given period of time, such as one year, and should not be
construed as being applicable to an individual day. The average daily ambient temperature range is
calculated using the following equation:

where:

A Ta = average daily ambient temperature range, °R
Tax = average daily maximum ambient temperature, °R
Tan = average daily minimum ambient temperature, °R

Table 7.1-7 gives historical values of Tax and Tan in degrees Fahrenheit for selected cities in the
United States. These values are converted to degrees Rankine by adding 459.7.

5. The vapor pressures associated with the average daily maximum and minimum liquid surface

temperatures, Tlx and Tln, into Equation 1-25 or 1-26 after converting the temperatures to the units
indicated for the respective equation, the vapor pressure function discussed in Notes 1 and 2 to Equation
121. If Tlx and Tln are unknown, Figure 7.1-17 can be used to calculate their values. In the case of a
fully insulated tank maintained at constant temperature, the average daily vapor pressure range. APv.
should be taken as zero.

If the liquid stored in the fixed roof tank has a true vapor pressure less than 0.1 psia and the tank
breather vent settings are not greater than ±0.03 psig. Equation 1-12 or Equation 1-13 may be used with
an acceptable loss in accuracy.

A Pb — Pbp - Pbv

(1-1044)

A Fa — Fax - Fan

(1 -11+2)

i, Pvx and Pvn, respectively, are calculated by substituting the corresponding

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If the tank location and tank color and condition are known. Kf may be calculated using the

following equation in lieu of Equation 1-5:

Kf = 0.0018 A Tv = 0.0018 TO.7 (Tax - Tan) + 0.02 PC II

(1-12)

where:

	Kf =	vapor space expansion factor, per day

	A Ty =	average daily vapor temperature range. °R

	Tax =	average daily maximum ambient temperature. °R

	Tan =	average daily minimum ambient temperature. °R

	OL =	tank surface solar absorptance. dimensionless

	I =	average daily total insolation on a horizontal surface. Btu/(ft2 day)

0.0018=	constant. ("RV1

	0.7 =	constant, dimensionless

	0.02 =	constant. (°R ft2 davVBtu

Average daily maximum and minimum ambient temperatures and average daily total insolation
can be determined from historical meteorological data for the location, or may be obtained from historical
meteorological data for a nearby location. Historical meteorological data for selected locations are given
in Table 7.1-7. where values of Tay and Tan are given in degrees Fahrenheit. These values are converted
to degrees Rankine by adding 459.7.

If the tank location is unknown, a value of Kf can be calculated using typical meteorological
conditions for the lower 48 states. The typical value for daily insolation is 1.370 Btu/ffi2 day), the average
daily range of ambient temperature is 21°R. and the tank surface solar absorptance is 0.25 for white paint
in average condition. Substituting these values into Equation 1-12 results in a value of 0.04. as shown in
Equation 1-13.

For vertical tanks, the diameter is straightforward. 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
emission estimating 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 an upright cylinder. Therefore, the effective
diameter, De, is then equal to:

Kf = 0.04

(1-13)

Diameter

D

LD

E

(1-144-3-)

where:

De = effective tank diameter, ft
L = length of the horizontal tank, ft (for tanks with rounded ends, use the overall length)

+4-06/0618

Liquid Storage Tanks

7.1-21


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D = diameter of a vertical cross-section of the horizontal tank, ft

By assuming the volume of the horizontal tank to be approximately equal to the cross-sectional
area of the tank times the length of the tank, an effective height, He, of an equivalent upright cylinder may
be calculated as:

HF =-D	(1-1544)

4

De should be used in place of D in Equation 1-4 for calculating the standing storage loss (or in
Equation 1-3, if calculating the tank vapor space volume). One-half of the effective height, He, should be
used as the vapor space outage, Hvo, in these equations. This method yields only a very approximate
value for emissions from horizontal storage tanks. For underground horizontal tanks, assume that no
breathing or standing storage losses occur (Ls = 0) because the insulating nature of the earth limits the
diurnal temperature change. No modifications to the working loss equation are necessary for either above
g ro u n dab o v c g ro u n d or underground horizontal tanks.

Vapor Space Outage

The vapor space outage, Hvo is the height of a cylinder of tank diameter, D, whose volume is
equivalent to the vapor space volume of a fixed roof tank, including the volume under the cone or dome
roof. The vapor space outage, Hvo, is estimated from:

Hvo=Hs-Hl+Hro	(1-1644)

where:

Hvo = vapor space outage, ft; use He/2 from Equation 1-1544 for horizontal tanks
Hs = tank shell height, ft

Hl = liquid height, ft; typically assumed to be at the half-full level, unless known to be
maintained at some other level
Hro = roof outage, ft; see Note 1 for a cone roof or Note 2 for a dome roof

Notes:

1.	For a cone roof, the roof outage, Hro, is calculated as follows:

Hro = 1/3 Hr	(1-1746)

where:

Hro = roof outage (or shell height equivalent to the volume contained under the roof), ft
Hr = tank roof height, ft

Hr = SrRs	(1-1842)

where:

Sr = tank cone roof slope, ft/ft; if unknown, a standard value of 0.0625 is used
Rs = tank shell radius, ft

2.	For a dome roof, the roof outage, Hro, is calculated as follows:

7.1-22

Liquid Storage TanksEMISSION FACTORS

4406/06-18


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H ro — Hr

2 6

Ei

(1 -_I94X)

where:

Hro = roof outage, ft
Rs = tank shell radius, ft
Hr = tank roof height, ft

Hr = Rr-{RR-RsT5	d-20^)

Hr = tank roof height, ft
Rr = tank dome roof radius, ft
Rs = tank shell radius, ft

The value of Rr usually ranges from 0.8D - 1.2D, where D = 2 Rs. If Rr is unknown, the tank diameter is
used in its place. If the tank diameter is used as the value for Rr, Equations 1 -194# and 1 -204-9 reduce to
Hro = 0.137 Rs and HR = 0.268 Rs.

Vented Vapor Saturation Factor, Ks

The vented vapor saturation factor, Ks, is calculated using the following equation:

K' 1 + 0.053	PrAHvo	(1-M)

where:

Ks = vented vapor saturation factor, dimensionless

Pva = vapor pressure at daily avcrage daily liquid surface temperature, psia; see Notes 1 and 2

to Equation 1-2224-
Hvo = vapor space outage, ft, see Equation 1-164^

0.053 = constant, (psia-ft)"1

Stock Vapor Density. Wv - The density of the vapor is calculated using the following equation:

Wv = Mv_Pva	(1-2224)

R Ty

where:

Wv = vapor density, lb/ft3

Mv = vapor molecular weight, lb/lb-mole; see Note 1

R = the ideal gas constant, 10.731 psia ft3/lb-mole °R
Pva = vapor pressure at daily average daily liquid surface temperature, psia; see Notes 1 and 2
	4;t-A——daily Tv = average liquid surfacovapor temperature. °R; see Note 3-6

4406/0618

Liquid Storage Tanks

7.1-23


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Notes:

1. The molecular weight of the vapor, Mv, can be determined from Table 7.1-2 and 7.1-3 for
selected petroleum liquids and volatile organic liquidsselected petrochemicals, respectively, or by
analyzing vapor samples. Where mixtures of organic liquids are stored in a tank, Mv can be calculated
from the liquid composition. The molecular weight of the vapor. Mv, is equal to the sum of the molecular
weight, Mi, multiplied by the vapor mole fraction, y,. for each component. The vapor mole fraction is
equal to the partial pressure of component i divided by the total vapor pressure. The partial pressure of
component i is equal to the true vapor pressure of component i (P) multiplied by the liquid mole fraction,
(\i). Therefore,

u,=2>< =2><

'p5^
\PvaS

(1-2332)

where:

Pva, total vapor pressure of the stored liquid, by Raoult's Law, is:

PVA =Y,Pxi	(1-2423-)

For more detailed information, please refer to Section 7.1.4.

2. True vapor pressure is defined in various ways for different purposes within the industry, such
as "bubble point'1 for transportation specifications, but for purposes of these emissions estimating
methodologies it is the sum of the equilibrium partial prossuropressures exerted by the components of a
volatile organic liquid, as defined shown in Equation 1-24. True vapor pressure may be determined by
ASTM -D 2879 £or as-ASTM D 6377 for crude oils with a true vapor pressure greater than 3.6 psia) or
obtained from standard reference texts. For certain petroleum liquids, true vapor pressure may be
predicted from Reid vapor pressure, which is the absolute vapor pressure of volatile crude oil and volatile
nonviscous petroleum liquids, except liquified petroleum gases, as determined by ASTM -D -323. True
vapor pressures for organic liquids can bo determined from Table 7.1 3. or ASTM D 5191.

Vapor pressure is sensitive to the lightest components in a mixture, and the de-gassing step in
ASTM D 2879 can remove lighter fractions from mixtures such as No. 6 fuel oil if it is not done with care
(i.e. at an appropriately low pressure and temperature). In addition, any dewatering of a sample prior to
measuring its vapor pressure must be done using a technique that has been demonstrated to not remove
the lightest organic compounds in the mixture. Alternatives to the method may be developed after
publication of this chapter.

True vapor pressure can be determined for crude oils from Reid vapor pressure using Figures 7.1-
13a and 7.1-13b. Ferfiowever. the nomograph in Figure 7.1-13a and the correlation equation in Figure
7. l-13b for crude oil are known to have an upward bias, and thus use of ASTM D 6377 is more accurate
for crude oils with a true vapor pressure greater than 3.6 psia. For light refined stocks (gasolines and
naphthas) for which the Reid vapor pressure and distillation slope are known. Table 7.1 2 or Figures 7.1-

7.1-24

Liquid Storage TanksEMISSION FACTORS

+4-06/Q6J_8


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14a and 7.1-14b can be used. For refined stocks with Reid vapor pressure below the 1 psi applicability
limit of Figures 7.1-14a and 7.1-14b. true vapor pressure can be determined using ASTM D 2879. In
order to use Figures 7.1-13a, 7.1-13b, 7.1-14a, or 7.1-14b, the stored liquid surface temperature, Tla,
must be determined in degrees Fahrenheit. See Note 3 to determine Tla.

Alternatively, true vapor pressure for selected petroleum liquid stocks, at the stored liquid surface
temperature, can be determined using the following equation:

Pj-A C\p

A -

r B ^

'la y

(1-2534)

where:

exp = exponential function
A = constant in the vapor pressure equation, dimensionless
B = constant in the vapor pressure equation, °R
Tla = daily average daily liquid surface temperature, °R; see Note 3
Pva = true vapor pressure, psia

For selected petroleum liquid stocks, physical property data including vapor pressure constants A
and B for use in Equation 1-25 are presented in Table 7.1-2. For refined petroleum stocks with Reid vapor
pressure within the limits specified in the scope of ASTM D 323. the constants A and B can be calculated
from the equations presented in Figure 7.1-15 and the distillation slopes presented in Table 7.1-24. For
crude oil stocks, the constants A and B can be calculated from Reid vapor pressure using the equations
presented in Figure 7.1-16. However, the equations in Figure 7.1-16 are known to have an upward bias.
and thus use of ASTM D 6377 is more accurate. Note that in Equation 1-2524. Tla is determined in
degrees Rankine instead of degrees Fahrenheit.

The true vapor pressure of organic liquids at the stored liquid temperature can also be estimated
by Antoine's equation:

log	.1

' B

Tt 'i +C.

la

(1-2625-)

where:

log = log 10

	A = constant in vapor pressure equation, dimensionless

B = constant in vapor pressure equation. °C
C = constant in vapor pressure equation. °C
Tla = daily-average daily liquid surface temperature, °C
Pva = vapor pressure at average liquid surface temperature, mm Hg

For organic liquidsselected pure chemicals, the values for the constants A, B, and C are listed in
Table 7.1-35-. Note that in Equation 1-2625-. Tla is determined in degrees Celsius instead of degrees
Rankine. Also, in Equation 1-2625-. Pva is determined in mm of Hg rather than psia (760 mm Hg = 14.7
psia).

4406/0618

Liquid Storage Tanks

7.1-25


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3. If the daily average liquid surface temperature, Tla, is unknow n, it is calculated using the
following oquation:The average daily liquid surface temperature. Tta. refers to the liquid surface
temperature averaged over all of the days in the given period of time, such as one year, and should not be
construed as being applicable to an individual day. While the accepted methodology is to use the average
temperature, this approach introduces a bias in that the true vapor pressure. Pva. is a non-linear function
of temperature. However, the greater accuracy that would be achieved by accounting for this logarithmic
function is not warranted, given the associated computational burden. The average daily liquid surface
temperature is calculated for an uninsulated fixed roof tank using Equation 1-27.

/	0.8 \	/	0.8

^a= 0.5-———- Taa + I0.5 +

4A(HS/D) + 3.8/ ^ V 4.4(H5/D) + 3.8
0.021 ocR I + 0.013(Hs/D) ocs I

+ ¦

4A(HS/D) + 3.8

(1-27)

-TbA ~ O.HTaa + 0.56Tb + 0.0079 a I	(4-26)

where:

Tla = daily average daily liquid surface temperature, °R
Hs = tank shell height, ft

D = tank diameter, ft,

Taa =	daily-average daily ambient temperature, °R; see Note 4

Tb =	liquid bulk temperature, °R; see Note 5

-6t~ar =	tank roof paintsurface solar absorptance, dimensionless; see Table 7.1-6

	as =	tank shell surface solar absorptance. dimensionless; see Table 7.1-6

I =	average daily total solar insolation factor, Btu/(ft2 day); see Table 7.1-7

API assigns a default value of H/D = 0.5 and an assumption of a,\< = a.s. resulting in the
simplified equation shown below for an uninsulated fixed roof tank:22

	Tt a = 0.4Taa + 0.6Tr + 0.005 a I	(1-28)

where:

	a = average tank surface solar absorptance. dimensionless

is used to calculate Pm from Figures 7.1 13a, 7.1 13b, 7.1 11a, or 7.1 11b, Tia must bo
converted from degrees Rankine to degrees Fahrenheit (°F ~ °R—160). If T^a is used to calculate Pm
from Equation 1 25, Tla must bo converted from degrees Rankino to degrees Celsius (°C ~ [°R
192J/1.8). Equation 1-2726 and Equation 1-28 should not be used to estimate liquid surface temperature
for from insulated tanks. In the case of fully insulated tanks, the average liquid surface temperature should
be based on liquid surface temperature measurements from the tank.assumed to equal the average liquid
bulk temperature (see Note 5). For purposes of estimating emissions, a storage tank should be deemed
insulated only if the roof and shell are both fully insulated so as to minimize heat exchange with ambient
air. If only the shell is insulated, and not the roof, there likely will be sufficient heat exchange through the
roof such that Equation 1-28 would be applicable.

7.1-26	Liquid Storage TanksEMISSION FACTORS	44-06/^Jl


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A more accurate method of estimating the average liquid surface temperature. Tta. in partially
insulated fixed roof tanks is given below. When the tank shell is insulated but the tank roof is not, heat
gain to the tank from insolation is almost entirely through the tank roof and thus the liquid surface
temperature is not sensitive to Hs/D.

	Tt A = 0.3 Taa + 0.7 Tb + 0.005 qR I	(1-29)

If Tt a is used to calculate Pva from Figures 7.1-13a. 7.1-13b. 7.1-14a. or 7.1-14b. Tt a must be
converted from degrees Rankine to degrees Fahrenheit (°F = °R - 459.7). If Tt a is used to calculate Pva
from Equation 1-26. Tt a must be converted from degrees Rankine to degrees Celsius (°C = l°R -
491.71/1.8).

4. The daily average daily ambient temperature, Taa, is calculated using the following equation:

Taa	(1-302?)

2

where:

Taa = daily average daily ambient temperature, °R
Tax = average daily maximum ambient temperature, °R
Tan = average daily minimum ambient temperature, °R

Table 7.1-7 gives historical values of Tax and Tan in degrees Fahrenheit for selected U.S. cities.
These values are converted to degrees Rankine by adding 459.7.

5.	The liquid bulk temperature, Tb, tsshould preferably be based on measurements or estimated
from process knowledge. For uninsulated fixed roof tanks known to be in approximate equilibrium with
ambient air, heat gain to the bulk liquid from insolation is almost entirely through the tank shell; thus the
liquid bulk temperature is not sensitive to Hs/D and may be calculated using the following equation:

Tb = Taa + 0.003^- a.s-6—II	(1 -31.2&)

where:

Tb = liquid bulk temperature, °R
Taa = daily average daily ambient temperature, °R, as calculated in Note 4
-a— as = tank shell paintsurface solar absorptance, dimensionless; see Table 7.\-6-
	I = average daily total insolation factor. Btu/ffi2 day); see Table 7.1-7.

6.	The average vapor temperature. Tv. for an uninsulated tank may be calculated using the
following equation:

^ _ [2.2(Hs/D)+1.1]Taa+0.8Tb+0.021ocrI + 0.013(Hs/D)ocsI n
1V_	2.2 (Hs/D) + 1.9		

where:

Hs = tank shell height, ft
D = tank diameter, ft.

Taa = average daily ambient temperature. °R

+4-06/0618

Liquid Storage Tanks

7.1-27


-------
	Tr =	liquid bulk temperature. °R

	-a- Or =	tank roof surface solar absorptance. dimensionless

	as =	tank shell surface solar absorptance. dimensionless

	I =	average daily total insolation factor. Btu/(ft2 day).

API assigns a default value of Hs/D = 0.5 and an assumption of a.u = a.s. resulting in the
simplified equation shown below for an uninsulated tank:22

	Tv = 0.7Taa + 0.3Tr + 0.009 a I	(1-33)

where:

	a = average tank surface solar absorptance. dimensionless

When the shell is insulated, but not the roof, the temperature equations are independent of Hs/D.

	Tv = 0.6Taa + 0.4Tr + 0.01 (fe I	(1-34)

When the tank shell and roof are fully insulated, the temperatures of the vapor space and the
liquid surface are taken as equal to the temperature of the bulk liquid.

7.1.3.1.2 Working Loss

The fixed roof tank working loss, Lw, refers to the loss of stock vapors as a result of tank filling
or emptying operations. Fixed roof tank working losses can be estimated from:

	

Lw = VqKn Kp WvKr	(1-35)

where:

Lw = working loss, lb/yr
	Mv——vapor molecular weight, lb/lb mole; see Note 1 to Equation 121

	Pw,-—vapor pressure at daily average liquid surface temperature, psia; see Notes 1 and 2 to

Equation 1 21

	Q-=—annual Vo = net working loss throughput (tank capacity Tbbll times annual turnover

rate), bbl. ft3/vr. see Note 1
Kn = working loss turnover (saturation) factor, dimensionless; see Figure 7.1 18
for turnovers > 36, Kn = (180 + N)/6N
for turnovers <36, Kn = 1

N = number of turnovers per year, dimensionless

N = IHol/(Hl,--Hlv)	(1-36^0)

where:

~ tank maximum	IHqi = the annual sum of the increases in liquid

volumelevel. ft/vr

If SHqt is unknown, it can be estimated from pump utilization records.
Over the course of a year, the sum of increases in liquid level.
IHqi. and the sum of decreases in liquid level. SHqd. will be
approximately the same. Alternatively. IHqi may be

7.1-28

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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approximated as follows:

SHot = (5.614 O) / (fa/4) D2)	(1-37)

5.614 = the conversion of barrels to cubic feet. ft3/bbl

where:

	EM—diameter, ft

Via- - J1)2 "lx

Q =	annual net throughput, bbl/vr

Hlx = maximum liquid height, ft

If the maximum liquid height is unknown, for vertical tanks use
one foot less than the shell height and for horizontal tanks use
fa/4) Dh where Dh is the diameter of the horizontal tank

Ht n = minimum liquid height, ft

If the minimum liquid height is unknown, for vertical tanks use 1
and for horizontal tanks use 0

Kp = working loss product factor, dimensionless
for crude oilsi Kp = 0.75

for all other organic liquids, Kp = 1

Using the following steps, Equation 1 29 can be simplified to combine all variables into one
equation.

Using Equation 1 21, the term "MvP-va" can be replaced with Equation 1 32.

My /'::: =Wy RTm	(1 32)

Using a combination of Equation 1 30 and Equation 1 31, the term "Q" can bo replaced with
Equation 1 33.

N Hry (7T\ 2

-0—		m2-

5.614 V4y

Assuming a standard value of Rto be 10.731 ft'psia/(lb mole °R), the result is Equation 1 31.
fO.OOlOV v	(7T\ 2

L" ~l 5614 Jt1073 '> TL4 N HLS [JO «'r

44-06/0618

Liquid Storage Tanks

7.1-29


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By assuming the temperature to be 60°F (520°R), and adding the vent setting correction factor,
Kb, the result is Equation 1 35. The vent sotting correction factor accounts for any reduction in omissions
duo to tho condensation of vapors prior to tho opening of tho vent. This correction factor will only affect
the calculation if the vent settings are greater than ±0.03 psig.

T AT U 1

( 7T >

1 n 2 r- r- nr r-

LW lV n LX \

1.4 J

\L> A jV a P " J A B



where:

—bw.——working loss, lb/yr
—N-=—number of turnovers per year, (ycar)~^

—maximum liquid height, ft
—EM—diamotor, ft

-Kr^——working loss turnover (saturation) factor, dimensionless; see Figure 7.1 18

	for turnovers > 36, Kn ~ (180 + N)/6N

	for turnovers 36, Kn-^4-

-Kp——working loss product factor, dimensionles
	for crude oils Kp ~ 0.75

for all othor organic liquids, Kp^M-

Wv = vapor density, lb/ft3, see Equation 1-2234
Kb = vent setting correction factor, dimensionless. see Note 2

for open vents and for a vent setting range up to ± 0.03 psig, Kb = 1

1. Net Working Loss Throughput.

The net working loss throughput. Vo. is the volume associated with increases in the liquid level, and is
calculated as follows:

	Vn = (£Hot)(ti/4) D2	(1-38)

where:

	ZHot = the annual sum of the increases in liquid level, ft/vr

	If IHoi is unknown. IHm can be estimated from pump utilization records. Over the course of a

year, the sum of increases in liquid level. IHm. and the sum of decreases in liquid level. IHon.
will be approximately the same. Alternatively. Vo may be approximated as follows:

	Vn =5.614 0	(1-39)

where:

	5.614 = the conversion of barrels to cubic feet. ft3/bbl

	Q = annual net throughput, bbl/vr

Use of gross throughput to approximate the sum of increases in liquid level will
significantly overstate emissions if pumping in and pumping out take place at the same
time.

2. Vent Setting Correction Factor

7.1-30	Liquid Storage TanksEMISSION FACTORS	44-06/^Jl


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When the breather vent settings are greater than the typical values of ± 0.03 psig, and the
condition expressed in Equation 1-40-36 is met, a vent setting correction factor, Kb, must be determined
using Equation 1-4132. This value of Kb will be used in Equation 1-35 to calculate working losses.

When:

A'»

PBP A

. Pi +Pa

>1.0

(1-4036)

Then:

K„ =

Pi +Pa

K

-P

VA

N

PBP +P.4 _P

VA

(1-4132)

where:

Kb = vent setting correction factor, dimensionless

Pi = pressure of the vapor space at normal operating conditions, psig

Pi is an actual pressure reading (the gauge pressure). If the tank is held at atmospheric
pressure (not held under a vacuum or held at a steady pressure) Pi would be 0.

Pa = atmospheric pressure, psia

Kn = working loss turnover (saturation) factor (dimensionless}). see Equation 1-35

	for turnovers > 36, ~ (180 + N)/6N

	for turnovers 36, K^-^4-

Pva = vapor pressure at the daily-average daily liquid surface temperature, psia; see Notes 1 and
2 to Equation 1-2224

Pbp = breather vent pressure setting, psig.

See Section 7.1.6.2 for a more approximate equation for fixed roof tank working loss that was
used historically, but which is no longer recommended. ^w 0.0010 M v I' ¦ Q A L F

4406/0618

Liquid Storage Tanks

7.1-31


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7.1.3.2 TetalRoutine Losses From Floating Roof Tanks3"5, 17 B

Total Routine floating roof tank emissions are the sum of rim seal, standing and working losses.
Routine losses from floating roof tanks may be written as:

	Lt = Ls + Lw	(2-1)

where:

	Lt = total routine loss, lb/vr

	Ls = standing loss, lb/vr; see Equation 2-2

	Lw = working (withdrawal, deck fitting, and deck seam losses. ) loss, lb/vr; see Equation 2-19

The equations presented in this subsection apply only to floating roof tanks. The equations are not
intended to be used in the following applications:

1.	To estimate losses from unstable or boiling stocks (see Section 7.1.3.5) or from mixtures of
hydrocarbons or petrochemicals for which the vapor pressure is not known or cannot readily be predicted;

2.	To estimate losses from closed internal or closed domed external floating roof tanks (tanks
vented only through a pressure/vacuum vent in the fixed roof (i.e., no open vents )4r-ef (see Section
7.1.3.8.2);

3.	To estimate losses from tanks in which the materials used in the rim seal and/or deck fittings
are either deteriorated or significantly permeated by the stored liquid^

This section contains equations for estimating emissions from floating roof tanks in two
situations: during normal operation, and during roof landings.

4.	To estimate losses that result from the landing of a floating roof (see Section 7.1.3.3); or

5.	To estimate losses that result from cleaning atank (see Section 7.1.3.4).

7.1.3.2.1 Normal OperationStanding Loss

TetalStanding losses from floating roof tanks are the sum of rim seal, deck fitting and deck seam
losses, and may be written as:

LjLs = Lr + Lwb-^-Lf + Ld	(2-1-2)

where:

	hm ~ total Ls = standing loss, lb/yr

Lr = rim seal loss, lb/yr; see Equation 2-2-3

	Lw©——withdrawal loss, lb/yr; soo Equation 2 I

Lf = deck fitting loss, lb/yr; see Equation 2-135-

Ld = deck seam loss (internal floating roof tanks only), lb/yr; see Equation 2-189

Loss factors may be estimated for deck fitting configurations that are not listed in Table 1 12, at
the zero miles per hour wind speed condition (IFRTs and CFRTs), from the following equation:

-Km ~ 0.27W



7.1-32

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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Where:

	Km——zero wind speed loss factor for a particular typo of dock fitting, in pound moles per year.

	—liquid surface area within a particular typo of dock fitting, in square inches. The liquid

surface area is the area inside the deck fitting well or leg sleeve, less any area occupied
by an obstruction in the dock fitting well or log sloovo (such as a fixod roof support
column, unslottod guidopolo, guidopolo float, or dock support log).

Tho coofficiont, 0.27, has units of pound moles por (square inches)"7*4 year, andtho exponent,
0.86, is dimensionless.

This equation is only applicable when the distance from the liquid surface to the top of the deck
fitting well or log sloovo is 12 inchos or greater. Shorter dock fitting wells or log sloovos may rosult in
higher loss rates. There are no similar algorithms available for estimating loss factors for shorter deck
fitting wells or leg sleeves.

This equation is for an uncontrolled deck fitting. Effective deck fitting controls would be
expected to result in lower loss factors than would be estimated by this equation, but there are no
algorithms available for estimating the effectiveness of deck fitting controls.

This equation is for the zero miles per hour wind speed condition. There are no algorithms
available for estimating loss factors at non zero wind speeds (EFRTs).

+4-06/0618

Liquid Storage Tanks

7.1-33


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Rim Seal Loss - Rim seal loss from floating roof tanks can be estimated using the following equation:

where:

LR = (KRa + KRbVn)DP*MvKc

Lr =	rim seal loss, lb/yr

KRa =	zero wind speed rim seal loss factor, lb-mole/ft=»yr; see Table 7.1-8

KRb =	wind speed dependent rim seal loss factor, lb-mole/(mph)nft=»yr; see Table 7.1-8

v =	average ambient wind speed at tank site, mph; see Note 1

n =	seal-related wind speed exponent, dimensionless; see Table 7.1-8

P* =	vapor pressure function, dimensionless; see Note 2

(2-33)

P* =

(p \

rK
V PA J

1 +

1-

(p \

1 VA
V PA J

(3-3)

PyA
Pa

D* — 	

o.5\2	(2-4)

1 +



)\

where:

Pva = vapor pressure at daily average daily liquid surface temperature, psia;
See Note 3 below and Notes 1 and 2 to Equation 1-2221 and Note 3

below

Pa = atmospheric pressure, psia
D = tank diameter, ft
Mv = average vapor molecular weight, lb/lb-mole; see Note 1 to Equation 1-2234.
Kc = product factor;

Kc = 0.4 for crude oils;

Kc = 1 for all other organic liquids.

Notes:

1.	If the ambient wind speed at the tank site is not available, use wind speed data from the nearest
local weather station or values from Table 7.1-79. If the tank is an internal or domed external floating roof
tank, the value of v is zero.

2.	P* can be calculated or read directly from Figure 7.1-19.

3.	The average daily liquid surface temperature. Tta. for calculation of vapor pressure. Pva. for
floating roof tanks shall be determined as follows:

For internal and domed external floating roof tanks:

7.1-34	Liquid Storage TanksEMISSION FACTORS	44-06/^Jl


-------
T _ [2.86 (Hs/D)+1.43] TAA +[3.52 (Hs/D)+3.79] TB +0.027ocR/ + 0.017(Hs/£>)ocs/
LA	6.38 (Hs/D) + 5.22	~	' " '

where:

	Tt a = average daily liquid surface temperature. °R

	Hs = tank shell height, ft

D = tank diameter, ft.

	Taa =	average daily ambient temperature. °R; see Equation 1-30

	Tr =	liquid bulk temperature. °R; see Note 5 for Equation 1-22

	or =	tank roof surface solar absorptance. dimensionless; see Table 7.1-6

	as =	tank shell surface solar absorptance. dimensionless; see Table 7.1-6

	I =	average daily total insolation factor. Btu/ffi2 day); see Table 7.1-7

API assigns a default value of H/D = 0.5 and an assumption of a,\< = a.s. resulting in the
simplified equation shown below for an uninsulated internal or domed external floating roof tank:22

	Tt A = 0.3 Taa + 0.7 Tr + 0.004 a I	(2-6)

where:

	a = average tank surface solar absorptance. dimensionless

The average daily liquid surface temperature. Tt a. for external floating roof tanks is independent
of Hs/D for a given value of Tr. Different expressions for Tt a are given for the two common types of
external floating roof deck. If the type of external floating roof deck is unknown, assume the deck to be
the steel peripheral pontoon type.

For external floating roof tanks with a steel peripheral pontoon deck (single deck center area):

	Tt A = 0.7 Taa + 0.3 Tr + 0.008 q^I	(2-7)

where the liquid bulk temperature. Tr. is preferably determined from measurements or estimated
from process knowledge, but otherwise may be estimated as follows:

Tr = Taa + r0.71 q^I + 0.485 (H/D) qsIl / (170 H/D + 57)	(2-8)

For default H/D = 0.5. when or = qs:

Tr = Taa + 0.007 q I	(2-9)

For external floating roof tanks with a steel double deck:

	Tt A = 0.3 Taa + 0.7 Tr + 0.009 q^I	(2-10)

where the liquid bulk temperature. Tr. is preferably determined from measurements or estimated
from process knowledge, but otherwise may be estimated as follows:

Tr = Taa + T0.39 q^I + 0.485 (H/D) qsIl / (170 H/D + 45)	(2-11)

For default H /D = 0.5. when or = qs:

Tr = Taa + 0.005 q I	(2-12)

3. The API recommends using the stock liquid temperature to calculate P^a for use in
Equation 2 3 in lieu of the liquid surface temperature. If the stock liquid temperature is unknown. API
recommends the following equations to estimate the stock temperature:

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Liquid Storage Tanks

7.1-35


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Tank Color



Average Annual Stock
Temperature, Ts (EF)

White



Taa + 0*

Aluminum



Taa + 2.5

Gray





Black



Taa + 5.0

Taa is the average annual ambient temperature in degrees Fahrenheit.

Withdrawal Loss The withdrawal loss from floating roof storage tanks can be estimated using
Equation 2 1.

_ (0.943)QC5Wl

Lwd

D

where:

1 ! NcFc

D

(3-4)

	Lw©——withdrawal loss, lb/yr

	Q-=—annual throughput (tank capacity [bbl] times annual turnover rate), bbl/yr

	Gs——shell clingage factor, bbl/1,000 ft3; see Table 7.1 10

	W+-——average organic liquid density, lb/gal; see Note 1

	D-=—tank diameter, ft

	0.913 -—constant, 1,000 ffcgal/bbl3

	Ne——number of fixed roof support columns, dimonsionloss; see Note 2

	fc——effective column diameter, ft (column perimeter [ft]/7i); see Note 3

Notes:

1.	A listing of the average organic liquid density for select petrochemicals is provided in
Tables 7.1 2 and 7.1 3. If Wi is not known for gasoline, an average value of 6.1 lb/gal can be assumed.

2.	For a self supporting fixed roof or an external floating roof tank:

	Ne-4:

	For a column supported fixed roof:

	Ne ~ use tank specific information or see Table 7.1 11.

3. Use tank specific effective column diameter or

Fe - 1.1 for 9 inch by 7 inch built up columns, 0.7 for 8 inch diameter pipe columns, and 1.0 if column
construction details are not known

Deck Fitting Loss - Deck fitting losses from floating roof tanks can be estimated by the following
equation:

7.1-36

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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Lf = Ff P*MvKc	(2-_I3a)

where:

Lf = the deck fitting loss, lb/yr

Ff = total deck fitting loss factor, lb-mole/yr

Ff = [(NFiKFi) + (NF2KF2) + ... +(NFnfKFnf)]	(2-146)

where:

Nf; = number of deck fittings of a particular type (i = 0,l,2,...,nf), dimensionless
Kfj = deck fitting loss factor for a particular type fitting
(i = 0,l,2,...,nf), lb-mole/yr; see Equation 2-152
nt- = total number of different types of fittings, dimensionless
P*, Mv, Kc are as defined for Equation 2-2-3.

The value of Ff may be calculated by using actual tank-specific data for the number of each
fitting type (Nf) and then multiplying by the fitting loss factor for each fitting (Kf).

The deck fitting loss factor, Kp. for a particular type of fitting, can be estimated by the following
equation:

KFl = KFai + KFbl(Kvv)m'	(2-15?)

where:

Kf; = loss factor for a particular type of deck fitting, lb-mole/yr

K|.;i = zero wind speed loss factor for a particular type of fitting, lb-mole/yr

Krv = wind speed dependent loss factor for a particular type of fitting, lb-molc/(mph)IT1=«vr

m; =	loss factor for a particular type of deck fitting, dimensionless

i = 1, 2, ..., n, dimensionless
Kv = fitting wind speed correction factor, dimensionless; see below

v =	average ambient wind speed, mph

For external floating roof tanks, the fitting wind speed correction factor, Kv, is equal to 0.7. For
internal and domed external floating roof tanks, the value of v in Equation 2-152 is zero and the equation
becomes:

KPl=KFat	(2-16&)

Loss factors K|.;i. K|.-h. and m are provided in Table 7.1-12 for the most common deck fittings used on
floating roof tanks. These factors apply only to typical deck fitting conditions and when the average
ambient wind speed is below 15 miles per hour. Typical numbers of deck fittings for floating roof tanks
are presented in Tables 7.1-11, 7.1-12, 7.1-13, 7.1-14, and 7.1-15.

4406/0618

Liquid Storage Tanks

7.1-37


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Loss factors may be estimated for deck fitting configurations that are not listed in Table 7.1-12. at
the zero miles-per-hour wind speed condition (IFRTs and Domed EFRTs). from the following equation:

	Kk = 0.27l4fiV:i 86	(2-17)

Where:

	Kfa, = zero-wind-speed loss factor for a particular type of deck fitting, in pound-moles per year.

	Af, = liquid surface area within a particular type of deck fitting, in square inches. The liquid

surface area is the area inside the deck fitting well or leg sleeve, less any area occupied
by an obstruction in the deck fitting well or leg sleeve (such as a fixed-roof support
column, unslotted guidepole. guidepole float, or deck support leg).

The coefficient. 0.27. has units of pound-moles per (square inches)" 86-vear. and the exponent.
0.86. is dimensionless.

This equation is only applicable when the distance from the liquid surface to the top of the deck
fitting well or leg sleeve is 12 inches or greater. Shorter deck fitting wells or leg sleeves may result in
higher loss rates. There are no similar algorithms available for estimating loss factors for shorter deck
fitting wells or leg sleeves.

This equation is for an uncontrolled deck fitting. Effective deck fitting controls would be
expected to result in lower loss factors than would be estimated by this equation, but there are no
algorithms available for estimating the effectiveness of deck fitting controls.

This equation is for the zero miles-per-hour wind speed condition. There are no algorithms
available for estimating loss factors at non-zero wind speeds (EFRTs).

Deck Seam Loss Neither - Deck seams that are welded deck internal floating roof tanks norare assumed
to have no deck seam loss (i.e.. Lp = 0). All external floating roof tanks have deck seam lossesroofs are
assumed to be of welded construction, and some internal floating roofs are of welded construction.
Internal floating roof tanks with bolted decks may have deck seam losses. Deck seam loss can be
estimated by the following equation:

Ld = KdSdD2P*MvKc	(2-189)

where:

Kd =

Sd =

Lseam total length of deck seams, ft

deck seam loss per unit seam length factor, lb-mole/ft-yr

0.0 for welded deck

0.14 for bolted deck; see Note

deck seam length factor, ft/ft2

Lseam
A

deck

where:

7.1-38

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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Adeck = area of deck, fit2 =	

4

D, P*, Mv, and Kc are as defined for Equation 2-33.

If the total length of the deck seam is not known, Table 7.1-16 can be used to determine Sd. For a
deck constructed from continuous metal sheets with a 7-ft spacing between the seams, a value of 0.14
ft/ft2 can be used. A value of 0.33 ft/ft2 can be used for Sd 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 Sd can be assigned. A value of 0.20 ft/ft2 can be assumed to represent the
most common bolted decks currently in use.

Note: Recently vendors of bolted decks have been using various techniques, such as gasketing the deck
seams, in an effort to reduce deck seam losses. However, emission factors are not currently
available in AP-42 that represent the emission reduction, if any, achieved by these techniques.
Some vendors have developed specific factors for their deck designs; however, use of these
factors is not recommended until approval has been obtained from the governing regulatory
agency or permitting authority. A weld seam does not have to be structural (i.e.. may be seal
welded) to constitute a welded deck seam for purposes of estimating emissions, but a deck seam
that is bolted or otherwise mechanically fastened and sealed with elastomeric materials or
chemical adhesives is not a welded seam.

7.1.3.2.2 Working (withdrawal) Loss

The working loss from floating roof storage tanks, also known as withdrawal loss, can be
estimated using Equation 2-19.

0.943 QCSWL(^ , NCFC\

Lw	D V D	(2-19)

where:

	Lw =	working (withdrawal) loss, lb/vr

	O =	annual net throughput, bbl/vr; see Note 1

	Cs =	shell clingage factor, bbl/1.000 ft2: see Table 7.1-10

	Wt =	average organic liquid density, lb/gal: see Note 2

	D =	tank diameter, ft

	0.943 =	constant. 1.000 ft3»gal/bbl2

	Nr =	number of fixed roof support columns, dimensionless: see Note 3

	Fr =	effective column diameter, ft (column perimeter I ft I/jt): see Note 4

Notes:

1. For tanks in which liquid is pumped in and out at the same time, the use of gross throughput to
estimate working loss would overstate emissions, but the overestimation would not be as significant as for
the working loss of fixed roof tanks. It would be more appropriate to express O in terms of the sum of the
decreases in liquid level ZHop. Over the course of a year, the sum of decreases in liquid level. IHon. and
the sum of increases in liquid level. IHm. will be approximately the same. The effective annual
throughput. O. may be calculated in terms of ZHop as follows:

	0= fa/4) D2(IHon/5.614)	(2-20)

+4-06/0618

Liquid Storage Tanks

7.1-39


-------
SHnn = the annual sum of the decreases in liquid level, ft/vr

	D = tank diameter, ft

5.614 = the conversion of barrels to cubic feet. ft3/bbl
If SHnn is unknown. 0 can be taken as the annual net throughput.

2.	A listing of the average organic liquid density for select petrochemicals is provided in
Tables 7.1-2 and 7.1-3. IfWr is not known for gasoline, an average value of 5.6 lb/gal can be assumed.

3.	For a self-supporting fixed roof or an external floating roof tank:
	Nr = 0.

For a column-supported fixed roof:

	Nc = use tank-specific information or see Table 7.1-11.

4. Use tank-specific effective column diameter or

Fc = 1.1 for 9-inch by 7-inch built-up columns. 0.7 for 8-inch-diameter pipe
columns, and 1.0 if column construction details are not known

7.1-40

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


-------
7.1.3.3 Floating Roof Landings^Landing Losses21

When using floating roof tanks, the roof floats on the surface of the liquid inside the tank and
reduces evaporative losses during normal oporation.routine operations. However, when the tank is
emptied to the point that the roof lands on deck legs or hangers, there is a period where the roof is not

until the tank is refilled to a sufficient level to again float the roof. Therefore, these emission
ostimatoestimation calculations are applicable each time there is a landing of the floating roof.

This model does not directly address standing idle losses for partial davs-. but it would be
conservative (i.e.. potentially overestimate reasonable to estimate the emissions) to apply the model to
episodes during which for a partial day by estimating the standing idle emissions for a single day and then
pro-rating that estimate by the number of hours that the floating roof remainswas actually landed for less
than a day.. For example, if the floating roof were landed for 6 hours, then the estimated standing idle
losses would be 6/24. or one quarter, of the estimated daily standing idle losses.

The total loss from floating roof tanks during a roof landing is the sum of the standing idle losses
and the filling losses. This relationship may be written in the form of an equation:

where:

Ltl = total losses during roof landing, lb per landing episode

Lsl = standing idle losses during roof landing, lb per landing episode

Lfl = filling losses during roof landing, lb per landing episode

The group of applicable equations to estimate the landing losses differs according to the type of
floating roof tank that is being used. The equations needed to estimate landing losses from internal
floating roof tanks are contained in Table 7.1-17; equations for external floating roof tanks are contained
in Table 7.1-18; and equations for drain-dry floating roof tanks are contained in Table 7.1-19. The
following sections explain these equations in more detail.

7.1.3,2r33.1 Standing Idle Losses

After the floating roof is landed and the liquid level in the tank continues to drop, a vacuum is
created which could cause the floating roof to collapse. To prevent damage and to equalize the pressure, a
breather vent (vacuum breaker) is actuated. Then, a vapor space is formed between the floating roof and
the liquid. The breather vent remainsmav remain open until the roof is again floated, so whenever the roof
is landed, vapor can be lost through this vcnl as well as through other deck fittings and past the rim seal.
Even in the case of a self-closing breather vent, the vapor space beneath the floating roof is vented via the
other deck fittings and the rim seal, which is effectively rendered vapor mounted once the liquid level
drops below the bottom of the rim seal. These losses are called "standing idle losses."

The three different mechanisms that contribute to standing idle losses are (1) breathing losses
from vapor space, (2) wind losses, and (3) clingage losses. The specific loss mechanism is dependent on
the type of floating roof tank and the bottom condition.

Ltl ~ ^sl + Lfl

(2-403^

I)

+4-06/0618

Liquid Storage Tanks

7.1-41


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For internal floating roof tanks with liquid remaining in the bottom (liquid heel), the breathing
losses originate from a discernible level of liquid that remains in the tank. This is typically the case for
internal floating roof tanks with nominally flat bottoms (including those built with a slight upward cone),
the breathing losses originate from a discernible level of liquid that remains in the tank at all times due to
the flatness of the tank bottom and the position of the withdrawal line4. If the remaining liquid covers the
entire bottom of the tank, this is known as a full liquid -heel-}?. The liquid evaporates into the vapor space
beneath the landed floating roof and daily changes in ambient temperature cause the tankthis vapor space
to breathe in a manner similar to a fixed roof tank. A partial liquid heel may be left in tanks with sloped
bottoms, if the withdrawal of liquid ceases while some free standing liquid remains in a sump or
elsewhere in the bottom of the tank.

For external floating roof tanks, which are not fully shielded from the surrounding atmosphere,
the-wind action across the landed floating roof can create pressure differentials that cause vapors to flow
from beneath the floating roof. The higher the wind speeds, the more vapor that can be expelled. These
are known as wind losses.

For tanks with a cone-down or shovel bottom, the floor of the tank is sloped to allow for more
thorough emptying of the tank contents, therefore, the amount of liquid diffefsremaining may differ
significantly from tanks with flat bottoms (see Figure 7.1-20). When the emptying operation drains the
tank bottom, but leaves a heel of liquid in or near the sump, the tank is considered to have a partial liquid
heel. A drain-dry condition is attained only when all of the standing liquid has been removed, including
from the bottom of the sump. However, due to sludge buildup, irregularity of the tank bottom and
roughness of the inside of the tank, a small layer of liquid can remain clinging to the sloped bottom of a
drain-dry tank. This layer of liquid will create vapor that can result in clingage losses. The amount of
vapor produced within a drain-dry tank is directly related to this clingage. Clingage factors for various
tank conditions are contained in Table 7.1-10. However, the clingage factors given in Table 7.1-10 are for
the vertical shell of the tank, which is wiped by the rim seal each time the tank is emptied. The bottom of
the tank is more nearly horizontal and is not wiped by a rim seal, and thus the clingage factors for a
vertical shell would not be directly applicable. A clingage factor of 0.15 bbl/103ft2 should be used to
represent the clingage on the tank bottom.

Standing Idle Loss for Tanks with a Liquid Heel

A constraint on the standing idle loss is added for floating roof tanks with a liquid heel in that the
total emissions cannot exceed the available stock liquid in the tank. This upper limit, represented as
LsLmaxj IS a function of the volume and density of the liquid inside the tank.

Assuming that the tank has a circular bottom and adding a volume conversion unit, the equation
can be simplified to Equation 2-423-3 and Equation 2 133-4.

L

-SLmax

(area of tank) (height of liquid) (density of liquid)

(3^2-H-)

(2-1-232

3)

7.1-42

Liquid Storage TanksEMISSION FACTORS

+4-06/0618


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^51 max = 5-9 D2 hk Wj

(3-45-3^
4)

where:

LsLmax	limit on standing idle loss, lb per landing episode

7.48 =	volume conversion factor, gal/ft3

D =	diameter of the tank, feet

hie =	effective height of the stock liquid, feet

Wi =	density of the liquid inside the tank, lb/gal

Internal Floating Roof Tank with a Liquid Heel

For internal floating roof tanks with liquid heels, the amount of "standing idle loss" depends on
the amount of vapor within the vapor space under the floating roof. Essentially, the mechanism is
identical to the breathing losses experienced with fixed roof tanks. The mechanism shown in Equation 2-
443-5 is identical to Equation 1-2.

where

Lsl =	annual breathing loss from standing storagoidle during roof landing, lb/yr

365 =	number of days in a year, days/yr

Vv =	volume of the vapor space, ft3

Wv =	stock vapor density, lb/ft3

Mv = stock vapor molecular weight, lb/lb-mole

Pva = true vapor pressure of the stock liquid, psia at the temperature beneath the landed
floating roof (given that the tank bottom is in contact with the ground, assume the
temperature to be equal to ground temperature, which is taken as the average ambient
temperature for the month in which the landing occurs, unless a different temperature is
known)

R = ideal gas constant, 10.731 (psia-ft3)/(lb-mole °R)

T\_= average vapor temperature. °R given that the tank bottom is in contact with the
ground, the temperature is assumed to be equal to ground temperature, which is taken as
the average ambient temperature for the month in which the landing occurs, unless a
different temperature is known
Ke = vapor space expansion factor, dimensionlessper day, calculated from Equation 1-5. 1-12

or 1-13 as appropriate, with the value of A Pb set equal to zero
Ks = saturation factor, dimensionless. calculated from Equation 1-21.

This equation requires adjustment, however, in that floating roof landing episodes are measured
in days rather than years. Assuming that nd equals the number of days that the tank stands idle and

Lsl= 365 Vr Wr K, Ks

(2-4432
5)

(2-44-3^
6)

4406/0618

Liquid Storage Tanks

7.1-43


-------
substituting for the stock vapor density according to Equation 2 153-6. the equation is further simplified
to Equation 2 163-7.

PvaV

RTV

(2-463^
7)

The term with the highest amount of uncertainty is the saturation of the vapor withinbcncath the
tanklanded floating roof. The factor, Ks, is estimated with the same method used to calculate the
saturation factor for fixed roof tanks in Equation 1-2120. In order to establish limits on the value of Ks,
the estimated factor is assumed to be less than or equal to the saturation factor during filling (S). (For
more information see Filling Losses.)

The bottom of the tank may be flooded with a light distillate material, such as diesel. to reduce
volatility when the original heel is a relatively volatile liquid such as gasoline. This procedure is referred
to as distillate flushing. Testing has shown that, when the characteristics of the liquid heel beneath a
landed floating roof are changed, the characteristics of the vapor space beneath the floating roof will tend
toward equilibrium with the new liquid heel within 24 hours. The values for Kf. Pva. and My in Equation
3-7 may, then, be based on the properties of the mixture resulting from distillate flushing the day
following the introduction of the distillate into the tank. Properties of this mixture would be a weighted
average of the properties of the original heel and the properties of the distillate material, proportional to
the remaining quantities of each. I add referencel

External Floating Roof Tank with a Liquid Heel

For external floating roof tanks with a liquid heel, wind affects emission releases from the tanks.
As a starting point, begin with a basic equation based on rim-seal loss. The equation, shown as Equation
2 173-8. is equivalent to Equation 2-2-3.

Lrl =	annual rim seal loss during roof landing, lb/yr

KRa =	zero wind speed rim seal loss factor, lb-mole/ft-yr

KRb =	wind speed dependent rim seal loss factor, lb-mole/((mph)n-ft-yr))

n =	seal-related wind speed loss exponent, dimensionless

(Krh, K^, and n are specific to a given configuration of rim seal)

v =	average ambient wind speed, mph

D =	tank diameter, ft

Mv =	stock vapor molecular weight, lb/lb-mole

Kc =	product factor, dimensionless

P* =	a vapor pressure function, dimensionless

Lrl = (KRa + KRb vn)D P Mv Kc

(3-m^
8)

where

7.1-44

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


-------
p =

1+

1-

fp V15
rv

kPaJ



rVA

p* — 		

fP \-i0 5^2	^

LM |1

1 +





where:

Pa = atmospheric pressure, psia

Pva = true vapor pressure of the stock liquid, psia.

Assuming that the stock properties included in the vapor pressure function will adequately
account for differences in liquid product type, Kc is assumed to equal 1. Regardless of the type of rim seal
that is in use, it is effectively rendered a Vapor-mounted" seal when the liquid level falls such that the rim
seal is no longer in contact with the liquid. The contribution of a secondary seal is neglected in that it is
offset by emissions through the deck fittings. The emissions are therefore based on the case of a welded
tank with an average-fitting vapor-mounted primary seal. According to Table 7.1-8, the values of Kra, Krb,
and n are 6.7, 0.2, and 3.0, respectively. The variables were substituted and the equation was converted
from annual emissions to daily emissions by dividing the equation by 365. A value of 10 mph is assigned
to the wind speed, so that estimated standing idle losses from an external floating roof tank will not be
less than for a typical internal floating roof tank. Lower values for the rim seal loss factors or the wind
speed should not be used. The equation for standing idle loss due to wind can be simplified for daily
omissions to Equation 3-493-10.

-'SLwincl

= 0.57 nd D P* Mv	(3-4^3-10)

where:

LsLwmd =	daily standing idle loss due to wind, lb per day-landing episode

nd =	number of days that the tank is standing idle, days

D =	tank diameter, ft

P* =	a vapor pressure function, dimensionless

Mv =	stock vapor molecular weight, lb/lb-mole

As with internal floating roof tanks with a liquid heel, distillate flushing may be used to reduce
the volatility of the liquid heel and thus the values used for the stock properties. The value for Mv. and for
Pva in the calculation of P*. may be based on the properties of the mixture resulting from distillate
flushing the day following the introduction of the distillate into the tank.

After the wind empties the vapor space above the remaining liquid heel, the liquid will continue
to produce vapor. Thus, this standing idle loss will occur every day that the tank stands idlo w ith liquid
remaining in the tank. This equation is adequate at this time, but could be revised as additional testing is
conducted and studied.

+4-06/0618

Liquid Storage Tanks

7.1-45


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Limit on Standing Idle Losses from Drain-Dry Tanks

When a drain-dry tank has been emptied, the only stock liquid available inside the tank is a small
amountthin layer that clings to the wetted surface of the tank interior (if a hool offiree-standing liquid
remains in or near a sump, or in puddles on the tank bottom, then the tank should be evaluated as having a
partial heel, and not as drain dry - see Figure 7.1-20). The slope prevents a significant amount of stock
liquid from remaining in the tank so that evaporation is much lower than from tanks with liquid heels.
Due to the limited amount of liquid clinging to the interior of the tank, as shown in Figure 7.1-20, +f+s
assumed that vapors there would net-be replenished as readily as in tanks with ano liquid heel.remaining
to replenish vapors once the clingage layer has evaporated. For this model, standing idle loss due to
clingage is a one-time event rather than a daily event, involving only evaporation of the clingage layer.

The loss due to clingage is proportional to a clingage factor, which varies with the condition of
the inside of the tank. A list of clingage factors are shown in Table 7.1-10. However, the clingage factors
given in Table 7.1-10 are for the vertical shell of the tank, which is wiped by the rim seal each time the
tank is emptied. The bottom of the tank is more nearly horizontal and is not wiped by a rim seal, and thus
the clingage factors for a vertical shell would not be directly applicable to the tank bottom.

The factors are given in terms of barrels per thousand square feet. To convert the loss to pounds,
the density of the liquid and the area of the tank bottom must be taken into account, as shown in Equation
2 20 (SeeNOTE).3-ll.

where:

Lc =	clingage loss from the drain-dry tank, lb

0.042 =	conversion factor. 1.000 gal/bbl

Cs =	clingage factor, bbl/1,000 ft2

Wi =	density of the liquid, lb/gal

Area =	area of the tank bottom, ft2

NOTE: Equation was corrected 8/2012

Among the conditions shown in Table 7.1-10, the one that best approximates a sludge-lined tank
bottom is gunite-linedr. particularly given that the tank bottom is nearly horizontal and is not wiped by a
rim seal. Assuming that gasoline is being stored in the tank, a clingage factor of 0.15 and the area term in
Equation 2 213-12 were substituted into Equation 2-203-11. which simplifies to Equation 2-223-13.

Lsl = 0.0063 W,

The clingage loss should be constrained by an upper limit equal to the filling loss for an internal
floating roof tank with a liquid heel. This is demonstrated in Equation 2-23-3-14.

Lc =0.042 CsWt(Area)

(2-203-11)

(2-243^
12)

7.1-46

Liquid Storage TanksEMISSION FACTORS

44-06/0618


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(3-33-32

14)

where:

'SLmax

maximum standing idle loss for drain-dry tanks due to clingage, lb

Wi =

density of the liquid inside the tank, lb/gal

D =

diameter of the tank, feet

PvA =

true vapor pressure of the liquid inside the tank, psia

Vv =

volume of the vapor space, ft3

R =

ideal gas constant, 10.731 psia ft3 /lb-mole °R

Tv =

average temperature of the vapor and liquid below the floating roof, °R

Mv =

stock vapor molecular weight, lb/lb-mole

LSLmax = 0.60

K lv

Therefore, the standing idle loss for drain-dry tanks, shown in Equation 3-333-13. must be less
than or equal to Equation 3-333-14. This relationship is shown by Equation 3-343-15.

< 0.60———Mv

R Tv	15)

7.1.3.3t33.2 Filling Losses

When a floating roof tank is refilled, there are additional emissions resulting from the roof being
landed. These losses are called "filling losses" and continue until the liquid reaches the level of the
floating roof.

The first contributor to filling losses is called the ""arrival" component. As liquid flows into the
tank, the vapor space botwoon the liquid and the floating roof is decreased. The displaced vapors are
expelled through the breather vent. Once the roof is refloated on the liquid surface, the breather vent
etesesrThese are the vapors that remain under the floating roof at the end of the standing idle period, but
have not been accounted for as standing idle losses. For example, in the case of a liquid heel evaporation
takes place into the vapor space beneath the landed floating roof. The vapors that are expelled from this
vapor space by breathing are accounted for as standing idle losses, and the vapors that remain upon the
commencement of refilling are deemed the arrival component of filling losses.

The second contributor to filling losses is called the "generated" component. AsThese are the
vapors created by the incoming liquid as it evaporates, additional vapors during the filling operation.
Even when filling a completely clean and gas-free tank, the incoming liquid will bo formed in the vapor
space and will also bo expelled through the breather vontgenerate a certain amount of vapors.

Internal Floating Roof TanltLimit on Filling Loss for Tanks with a Liquid Heel

For intornalA constraint on the filling loss is added for floating roof tanks with a liquid heel in that the
total emissions cannot exceed the amount of stock liquid initially left in the tank less the amount
attributed to standing idle loss, plus the vapors generated by incoming liquid upon refilling. This upper
limit, represented as Lpt™^. may be determined as follows:

	Initial amount of stock liquid = 5 .9 D2 hi,. Wi from Equation 3-4

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Liquid Storage Tanks

7.1-47


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Amount attributed to standing idle loss = L

SL

	from the applicable equation above for

the given type of tank

	Amount generated by incoming

liquid = 0.15 PvA VvMv/RTv

	from Equation 3-18

evaluated for a drain-dry tank,
to account for only the
generated component of vapors

These components of the upper limit on filling loss for a tank with a liquid heel may be combined into the
following equation:

	LFL<(5.9D2hkW,)-LSL +0.15 %^MvT	(3461

K lr

General Equation for Filling Loss

The amount of vapor that is lost during filling is directly related to the amountvolume of the
vapor space and the saturation level of the vapor within the vapor space, as shown in Equation 2-25-3-17.

Lft = (vapor space volumeMvapor concentrationMvapor mol wt)(saturation factor)	(3-17)

After substituting for the major terms in Equation 3-17. the equation can be simplified to
Equation 3-18.

Lfl ~

fPvdVy}

V ^

Mv (C„ S)

(2-253^

18)

7.1-48

Liquid Storage TanksEMISSION FACTORS

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After substituting for the major terms in Equation 2 25, the equation can be simplified to
Equation 2 26.

-U^r

<2-26)

where:

Lfl =	filling loss during roof landing, lb

Pva =	true vapor pressure of the liquid within the tank, psia

Vv =	volume of the vapor space, ft3

R =	ideal gas constant, 10.731 psia-ft3/(lb-mole-°R)

Tv =	average temperature of thew the floating roof, °R(sce Equation 3-6)

Mv = stock vapor molecular weight, lb/lb-mole

	Cf = filling saturation correction factor for wind, dimensionless

S = filling saturation factor, dimension lessdimensionless (0.60 for a full liquid heel; 0.50 for
a partial liquid heel).

This equation accounts for the arrival losses and the generated losses. The main concern with this
equation is the estimation of the saturation factor. All other components are based on the ideal gas laws.
For consistency, an accepted value of 0.6, which is used elsewhere in Chapter 7, will be used for the case
of a full liquid hool. A value of 0.5 has boon demonstrated for the case of a partial liquid hool.

Internal Floating Roof Tank with a Liquid Heel

A value of 0.6 for the filling saturation factor, which is used in Section 5.2. Table 5.2-1 for
submerged loading of tank trucks and rail cars, has been demonstrated to be suitable for the case of a full
liquid heel. A value of 0.5 has been demonstrated for the case of a partial liquid heel. In that the landed
floating roof in an internal floating roof tank or a domed external (or covered) floating roof tank is
shielded from wind by the fixed roof, the value of CSf is taken as 1.0.

External Floating Roof Tank with a Liquid Heel

For external floating roof tanks with a liquid heel, the amount of vapor lost during filling will be
less than the amount for internal floating roof tanks because of wind effects. The ""arrival" component will
behave been partially flushed out of the tank by the wind, so the preceding equation requires the
additionevaluation of a-the saturation correction factor for wind. Csf to tho saturation factor as shown in
Equation 2 27.

/The basic premise of the correction factor is that the vapors expelled by wind action will not be
present in the vapor space when the tank is refilled, so the amount of saturation is lowered. This is
demonstrated in Equation 2-2&3-19.

<2-27)

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Liquid Storage Tanks

7.1-49


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Q =1-

[one day of wind driven standing idle loss) - [one day without wind standing idle loss)
one day without wind total loss

(2-2X3^
19)

The equation for the saturation factor can be simplified based on other equations contained in this
section as shown in Equation 2-293-20 and Equation 2 303-21.

csf=i-

f {Equation 3 -10) - {Equation 3-7)^
{Equation 3 - 7) + {Equation 3-18)

(2^9-3^
20)

C„, ~ 1

0.57 nd D P Mv\-\ndKE

"d ke

\ v

P Vy
R T

My Kg

\ f
+



V

P Vy ^



'

My K

RTJ





f p Vv 1

My S

—-



1 RT

J /

<2^0)

Substituting the indicated equations, with the number of days set equal to 1 and CSf set equal to 1
in Equation 3-18 for the case without wind:

^ {O.S7-l-D-P*-Mv)-(l-KE-(^-rV^	^

Csf = 1 -

(0.57 ¦ 1 ¦ D ¦ P* ¦ Mv) - (l ¦ Ke ¦	" Mv ¦ Ks)

{i1' Ke ' (crrrf)' Mv ' Ks) + ((^>9 ' ' (1 ' S))J

(3-21)

where:

Csf = filling saturation correction factor for wind, dimensionless

na = numborset equal to 1. days of days the tank stands idle with the floating rooflanded,
dimensionless

Ke = vapor space expansion factor, dimensionless per day, calculated from Equation 1-5. 1-12
or 1-13 as appropriate, with the value of A Pr set equal to zero

f



T

, 0.50 B P

i-\	t—	rf	{2-3-1-)

t(pa - Pi

	-A-Tv—=	daily vapor temperature range, °R

-T—		average temperature of the vapor and liquid below the floating roof, °R

-B—		constant from the vapor pressure equation shown in Equation 1 21. °R

(If B is unknown, Kg may be calculated from Equation 1 5, 1 6, or 1 7, as
appropriate, with the value of Pb sot equal to zero.)

-P—		true vapor pressure of the stock liquid, psia

	Pa—=	atmospheric pressure at the tank location, psia

Vv = volume of the vapor space, ft3

7.1-50

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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hv kD2

(2-323^
22)

4

height of the vapor space under the floating roof, ft

D = tank diameter, ft

R =	ideal gas constant, 10.731 psia ft3 / lb-mole R

Mv =	stock vapor molecular weight, lb/lb-mole

Ks =	standing idle saturation factor, dimensionless

S =	filling saturation factor, dimensionless

P* =	vapor pressure function, dimensionless

Wi =	stock liquid density, lb/gal

Drain-Dry Tanks

The ""arrival" component of filling losses for drain-dry tanks is completely covered by the
""clingage" loss. Once this initial loss occurs, there is no remaining liquid inside the tank. Therefore, there
is no vapor in the tank that could be expelled by the incoming liquidTherefore. any vapors remaining in
the tank prior to introducing the incoming liquid would have already been accounted for as standing idle
loss, and thus saturation of the arrival component for drain-dry tank filling losses is taken as 0. Similarly,
a tank with a full or partial liquid heel for which evaporation of the entire heel has been accounted for as
standing idle loss should be considered to have no arrival component of filling losses, nor should a tank
that has been cleaned. Each of these scenarios is deemed "drain dry'1 for purposes of estimating the filling
loss.

However, the "generated" component remains a valid aspect of the model. Therefore, the filling
loss calculations for drain dry tanks are identical to the filling loss calculations for internal floating roof
tanks with a liquid heel. Although the equations are the same, the saturation factor will be lower for drain-
dry tanks than for tanks with a liquid heel due to the lack of an ""arrival" component. And, given the
absence of an arrival component of vapors for filling loss, the filling saturation correction factor for wind
is taken as 1.0.

AP-42 Chapter 5, Petroleum Industry, provides emission factors for the loading of gasoline and
crude oil into compartments according to the prior state of the compartment. A drain-dry tank would be
most similar to a tank that was cleaned before filling because a cleaned tank also lacks "arrival" losses.
The emission factor (0.33 lb/1000 gallons) for this kind of tank can be converted to a saturation factor by
assuming a pressure of 8 psia (the same assumption used in the formulation of the emission factor), and
substituting the molecular weight of gasoline (64 lb/lb-mole). The resulting saturation factor is 0.15. The
equation is the same as Equation 2 26 with a different assumed saturation factor.

<2-26)

where:

¦fcft——filling loss during roof landing, lb
—P-=—true vapor pressure of the liquid within the tank, psia
-¥v——volume of the vapor space, ft*

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Liquid Storage Tanks

7.1-51


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R-—ideal gas constant, 10.731 psia_-frVf_lb mole °R)

——average temperature of the vapor and liquid below the floating roof, °R
¦Mv——stock vapor molecular weight, lb/lb mole

—S-=—filling saturation factor, dimension less (0.15 for a drain dry tank).

7.1-52

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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7.1.3.4 Tank Cleaning Emissions23

The methodology presented in this section for estimating emissions associated with tank cleaning
events is expressly for the estimation of vapors that are expelled from the tank during forced ventilation.
These vapors potentially occur whenever forced ventilation of the tank is in operation while volatile
organic material remains in the tank, regardless of whether any tank cleaning is actually taking place.

For purposes of estimating emissions, tank cleaning may be characterized as comprising the steps
listed below.

Prior to commencement of forced ventilation (i.e.. not included in the tank cleaning calculations):

Normal Pumpout: As much stock liquid as possible is pumped out through the tank outlet in the
normal manner (i.e.. until the liquid level has dropped below the open end of the outlet line, and
no more liquid moves through the outlet). If the tank has a floating roof, the floating roof will
have landed on its legs and the vacuum breaker vent will have opened, causing air to be drawn
into the space beneath the floating roof. Emissions that occur during normal pumpout are
accounted for as routine emissions for fixed-roof tanks and as floating roof landing losses for
floating roof tanks, and thus the normal pumpout period does not require additional calculations
pertaining to tank cleaning.

Standing Idle: The tank may remain in the condition resulting from normal pumpout for some
period of time until the next step begins. Emissions that occur during this period are accounted
for as routine standing (breathing) loss for fixed roof tanks, and as standing idle loss during a
floating roof landing for floating roof tanks, and thus the standing idle period does not require
additional calculations pertaining to tank cleaning.

During forced ventilation (these are the steps for which additional tank cleaning calculations are
required):

a)	Vapor Space Purge: When eductors. fans, or blowers are started up. either at the top of the tank
or at a shell manhole, cleanout fitting or other shell fitting, the first air change is deemed to expel
those vapors that remain from the prior standing idle period. This first air change is
characterized as a purge of vapors from the tank. Emissions associated with subsequent air
changes are accounted for under continued forced ventilation.

A vapor space purge will occur each time that ventilation commences after a period of standing
idle without forced ventilation.

b)	Continued Forced Ventilation: Forced ventilation refers to the removal of vapors from a tank by
means of eductors. fans, or blowers. As long as volatile materials remain in the tank, some
portion of the volatile material will evaporate into the air being moved through the tank by
forced ventilation. The forced ventilation will then expel these vapors from the tank.

If forced ventilation is discontinued, such as during the overnight period, then the tank is
returned to a standing idle condition. A subsequent restarting of forced ventilation will result in
another vapor space purge followed by a period of continued forced ventilation.

+4-06/0618

Liquid Storage Tanks

7.1-53


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After the tank is clean and gas free, even if forced ventilation is continuing (not included in the tank
cleaning calculations):

Remain Clean: Once the tank has been rendered clean and gas free it may remain in the clean
condition for some period of time. While forced ventilation may continue, there would be no
further emissions in that there would be no remaining sources of vapors once the tank has been
cleaned. Thus the period of remaining clean does not require additional calculations pertaining
to tank cleaning.

Refilling: If the tank is subsequently refilled, there will be vapors generated by the incoming
stock which would then be expelled from the tank by the rising liquid level. For a fixed roof
tank, these refilling emissions are accounted for as routine working (filling) losses. For a
floating roof tank, these refilling emissions are calculated in the same manner as for the refilling
after a floating roof landing. In that the tank has been cleaned, the saturation factor for the
refilling should be 0.15. as for a drain dry tank. The refilling losses, then, do not require
additional methodology in this section pertaining to tank cleaning.

The emissions to be accounted for in this section on tank cleaning emissions, then, are those
associated with forced ventilation while volatile material remains in the tank. The equations needed to
estimate emissions resulting from forced ventilation during tank cleaning are contained in Tables 7.1-20
and 7.1-21; equations for the vapor space purge are contained in Table 7.1-20 and equations for
continued forced ventilation are contained in Table 7.1-21. The following sections explain these
equations in more detail.

where:

Lpy = total emissions due to forced ventilation during a tank cleaning event, lb

Lp_ _= vapor space purge emissions associated with the first air change following commencement

of forced ventilation, lb

LCV = emissions from continued forced ventilation following the first air change, lb
7.1.3.4.1 Vapor Space Purge Emissions

The daily breathing cycle that produces the standing idle emissions causes only a portion of the
vapors in the vapor space to be expelled from the tank. The vapors that remain in the vapor space are not
accounted for in the calculation of standing idle emissions. Commencement of forced ventilation expels
these remaining vapors from the tank. The first air change of the vapor space upon commencing forced
ventilation may be referred to as the vapor space purge, and the emissions may be estimated as follows:

Lfv = Lp + L('V

(4-1)

Lp = (Pva Vv! R Tv)MvS

(4-2)

where:

Pva = the true vapor pressure of the exposed volatile material in the tank (psia).

3

Vy = volume (ft ) of the vapor space.

R = the ideal gas constant (psia fP per lb-mole °R).

= 10.731 psia ft^ per lb-mole °R.

7.1-54

Liquid Storage TanksEMISSION FACTORS

++06/0618


-------
	Ty = the average temperature of the vapor space (°R).

	= the average ambient temperature (°R).

	My = the stock vapor molecular weight (lb/lb-mole).

	S is a saturation factor evaluated as a function of the tank type and heel condition, as

discussed later in this section

The volatility of the remaining materials may be less than the volatility of the previously stored
stock liquid, and thus an appropriate judgment should be made in assigning properties to the residual
material in the tank bottom for purposes of determining values for the true vapor pressure. Pva. and the
stock vapor molecular weight. My.

The bottom of the tank may be flooded with a light distillate material, such as diesel. to facilitate
removal of sludge from the bottom of the tank. This procedure is referred to as distillate flushing. Testing
has shown that, when the characteristics of the liquid heel beneath a landed floating roof are changed, the
characteristics of the vapor space beneath the floating roof will tend toward equilibrium with the new
liquid heel within 24 hours. The values for Pva and My in Equation 4-2 may, then, be based on the
properties of the mixture resulting from distillate flushing the day following the introduction of the
distillate into the tank. Properties of this mixture would be a weighted average of the properties of the
original heel and the properties of the distillate material, proportional to the remaining quantities of
each.24

The vapor space purge comprises the expulsion of one vapor space volume, similar to one
working-loss (filling) cycle of the vapor space. Emissions associated with subsequent air changes are
accounted for as continued forced ventilation emissions.

Fixed Roof Tanks

The volume of the vapor space for estimating working loss from a fixed-roof tank is calculated
from the maximum liquid height to which the tank may be filled. For a vapor space purge, however, the
volume of the vapor space is the entire volume under the tank roof:

	Vv_= Hyp (kD2/4)	(4-3)

where:

	Hyp = the fixed-roof tank vapor space outage (ft)

	Hyp = Hs_ h]_+ Hrp	(4-4)

where:

	Hs = the height of the tank shell (ft).

	h]_= the height of the stock liquid and sludge above the tank bottom at the tank shell (ft), and

	Hrp = the roof outage (the effective height of the vapor space enclosed by the tank roof, ft)

	= Sr D/6 for a cone-shaped roof, where Sr is the roof slope in feet per foot.

The vapor space outage. Hyp, would be slightly greater for the case of a cone-down bottom in a
tank that does not have a full liquid heel. The slope of bottoms tends to be much less than the slope of
roofs, however, and the contribution of the bottom cone to the vapor space outage would be very small

+4-06/0618

Liquid Storage Tanks

7.1-55


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compared to the full shell height.

The saturation factor for filling a fixed-roof tank is given as the turnover factor. Kn. in Equation
1-35. and defined as:

	Kn = (180+ N)/6N

where:

	N = number of turnovers per year, dimensionless

It would be advantageous to express this saturation factor in terms of days between turnovers (i.e..
days standing idle, nd). The number of days between turnovers may be expressed as follows:

	n,d_= 365 IN

and thus the equation for Kn may be rewritten as:

	Kn = (0.5 rid + l)/6	(4-5)

Recognizing that the turnover factor. Kn, is the saturation factor to be used for calculating filling
losses from a fixed-roof tank, the saturation factor. S, may be substituted for the turnover factor. Kn.

	S = (0.5 n,i + 1) / 6	(4-6)

For periods of less than one day, a value of 1 should be used for the standing idle time. nd_. This
effectively imposes a minimum value of 0.25 for the saturation factor. S. Thus a value of 0.25 should be
used for S when the vapor space purge follows a standing idle period that was limited to an overnight
cessation of forced ventilation.

The saturation factor value of 0.5 for an internal floating roof tank with a partial heel, as shown in
Equation 3-18. may be reasonably chosen as an upper bound on the value of S for a fixed roof tank vapor
space purge. It would be expected, for a given diameter of tank and type of liquid heel, that the
accumulated vapors would be less concentrated in the larger vapor space of the fixed roof tank than under
a landed floating roof, and thus a value of 0.5 should be a conservative upper bound for the fixed roof
tank vapor space purge saturation factor.

These limits are expressed as follows:

	S > 0.25	(4£71

	S < 0.5	(4-8)

Floating Roof Tanks

The volume of the vapor space for estimating the vapor space purge loss from a floating-roof tank
is limited to the space under the floating roof, in that vapors which escape past the floating roof prior to
the commencement of forced ventilation are separately accounted for as standing idle loss from the
floating roof landing event:

7.1-56

)f the vapor space under the floating roof.
Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


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	= (h^ (Hi)214).	(Ml

where:

	hy = the height (ft) of the vapor space under the floating roof for the given vapor space purge

(see Table 7.1-4)

The saturation factor. S. for the initial vapor space purge is evaluated as specified for the filling
saturation factor for a floating roof landing. This approach is conservative in that filling losses have both
an arrival component, from resident vapors, and a generated component, from vapors generated by
incoming liquid (e. g.. 25% of the filling saturation factor for an internal floating-roof tank with a full
liquid heel may be attributable to the incoming liquid - the contribution of the incoming liquid to the vapor
concentration varies with the filling scenario). The vapor space purge does not involve incoming liquid.
however, and therefore would have only the arrival component of vapors. It is conservative, therefore, to
use saturation factors that include allowance for the generated component of vapors.

When forced ventilation is discontinued overnight, then the tank cleaning process will involve a
daily cycle that includes a period of standing idle (overnight) followed by a vapor space purge (when
forced ventilation resumes the next morning). Emissions from overnight standing idle periods are
accounted for in the estimate of the next morning's vapor space purge. In that the overnight standing idle
emissions are taken as zero, there is no accounting for wind-driven losses of vapor from under external
floating roofs. These vapors must then be accounted for with the following morning's vapor space purge.
That is. the neglect of wind driven emissions during the overnight period means that the vapors must be
considered to still be present when estimating the next morning's vapor space purge, and thus there must
be no factoring down of the saturation level for the case of external floating-roof tanks. In other words. Gf
should be taken as 1.0 when the vapor space purge follows a standing idle period that was limited to an
overnight cessation of forced ventilation.

Saturation factor values to be used for floating roof tanks are summarized as follows:

Full liquid heel

	Internal floating roof tank

	S= 0.6

	External floating roof tank

	S = (0.6 Gf). where Pis evaluated as shown in Equation 3-21 with rid set to 1 for the initial

vapor space purge; for subsequent vapor space purges that follow a cessation of forced
ventilation overnight. Gf shall be taken as 1.0

Partial liquid heel

	Internal floating roof tank

	S= 0.5

	External floating roof tank

	S = (0.5 Gf). where Gf is evaluated as shown in Equation 3-21 with rid set to 1 for the initial

vapor space purge; for subsequent vapor space purges that follow a cessation of forced
ventilation overnight. Gf shall be taken as 1.0

+4-06/0618

Liquid Storage Tanks

7.1-57


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If all free flowing liquid has been removed, and only sludge remains, use the saturation factor for
a partial heel, in that there is still volatile material in the tank but not free liquid across the entire bottom.

If the heel condition is drain dry, use a saturation factor value of 0. in that evaporation of the
clingage would have already been accounted for in the estimation of the floating roof landing losses.

7.1.3.4.2 Continued Forced Ventilation Emissions

The calculation of vapor space purge emissions account for the vapors that are expelled by the
first air change of the vapor space upon commencing forced ventilation at the end of a standing idle
period. There may still be volatile materials remaining in the tank, however, that will continue to
evaporate and generate vapors, and these additional vapors are expelled by continued forced ventilation.

Continued forced ventilation emissions are calculated from the average vapor concentration in the
vapor space (which may be reported as a percent of the lower explosive limit, or %LEL). the ventilation
rate, and the length of time during which forced ventilation continues to operate. These parameters are
often known since thev may be monitored for safety reasons.

The vapor concentration may be approximated from the reading of an LEL monitor, which is
generally displayed as a percent of the LEL for the gas to which the monitor has been calibrated. LEL
values for selected calibration gases are given in Table 7.1-5. The vapor concentration may also be
approximated from the reading of an organic or toxic vapor analyzer, which may be displayed in parts per
million by volume as the calibration gas.

To determine the vapor concentration from a %LEL reading, the LEL of the calibration gas is
multiplied by the reading from the LEL monitor, after each has been divided by 100 to convert from a
percent to a decimal fraction. This gives a volume concentration (mole fraction) in terms of the calibration
gas. This concentration is corrected by a response factor (RF) to account for the difference in the
sensitivity of the LEL monitor to the actual vapors as compared to its sensitivity to the calibration gas.
When the response factor is unknown, use a value of one (RF = 1.0).

If the vapor concentration is very low, it may be below the minimum detection level of the LEL
monitor. In this case, it may be reasonable to use half the minimum detection level as the %LEL for
determining the vapor concentration.

In order to estimate the mass of vapors that are expelled from the tank by continued forced
ventilation, the vapor concentration in terms of volume must be converted to vapor density in terms of
mass. In order to convert vapor concentration to density, use the molecular weight of the calibration gas
for the LEL monitor. Uncertainty is reduced if the molecular weight of the calibration gas is similar to the
molecular weight of the stock vapors.

The continued forced ventilation emissions (LCV) estimated by the vapor concentration method

are:

	LCV = 60 Qy tv Cy (PgMCG /R TV)	(4-10)

where:

60 is the conversion of hours to minutes, min/hr
7.1-58	Liquid Storage TanksEMISSION FACTORS	44-06/^Jl


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3

	Oy = average ventilation rate during continued forced ventilation, ft /min [Note: The nominal

rated capacity of eductors. fans, or blowers should be factored by the resistance associated
with ductwork or other obstructions in order to estimate the actual air flow rate. Fan
capacity may be governed by a required number of air changes per hour.l
	= the duration of continued forced ventilation, days

	ty = the daily period of forced ventilation, hr/dav [Note: Do not include the initial time for the

vapor space purge. It would be reasonable to neglect the first half hour from each stage of
continued forced ventilation!.

	Cy = average vapor concentration by volume during continued forced ventilation.

dimensionless

	= (average LEL as displayed) (LEL of the calibration gas) RF

"average LEL as displayed'1 is the average of the % LEL readings during a given stage of
continued forced ventilation, divided by 100 to convert to a decimal fraction; LEL
readings from the first half hour may be neglected in the determination of an average
value

"LEL of the calibration gas'1 is the LEL of the gas used to calibrate the LEL monitor,
expressed as a decimal fraction
	RF = response factor, dimensionless

	= 1.0 if unknown. EPA Method 21 allows usage of a vapor monitoring instrument

without correction for the response factor, as long as the response factor is less
than 10 (40 CFRPart 60 Appendix A-7. Method 21. paragraph 8.1.1.2).
Alternatively. Cy may be obtained from an organic vapor analyzer or toxic vapor
analyzer that displays directly in terms of volume concentration, rather than displaying in
terms of LEL.

	Fa = atmospheric pressure at the tank location, psia

MCG = calibration gas molecular weight, lb/lb-mole
	R = ideal gas constant

	=	10.731 psia-ft^/db-mole °R).

	TV =	average temperature of the vapor below the floating roof. °R

	=	the average ambient temperature. °R

The vapor concentration (Cy) is limited by saturation of the vapor space. This limit may be expressed as:

Cy_<	PVA/Pn	(4-11)

where:

	PVA =	the true vapor pressure of the exposed volatile material in the tank, psia

The estimate of continued forced ventilation emissions should be compared to an upper limit
equal to the total weight of volatile sludge remaining in the tank. While there is free-standing stock liquid
remaining in the tank, the sludge may conservatively be assumed to consist entirely of stock liquid in
establishing the emissions upper limit. This limit is expressed as follows:

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LCV < 5.9D 2 hip Wj.

(4-12)

where:

	D = the tank diameter, feet

	hje = the effective height of the stock liquid and sludge for the given stage of continued forced

ventilation, ft (see Table 7.1-4)

	W]_= the density of the stock liquid, pounds per gallon

3

the constant. 5.9. has units of gal/ft (the product of the constant term n/4 and the conversion
factor 7.48 gal/ft3).

Once the free-standing stock liquid has been vacuumed out (or drained out, in the case of a drain-
dry tank), however, much of the remaining sludge consists of relatively non-volatile residue. The upper
limit on emissions from the vacuumed-out condition may assume that 20% of the sludge is volatile. This
limit is expressed as follows:

LCV	<	fa/4)(D ft)2 Fp_(dvjn.)(ET/_lb/gal)(ft/12 in.)(7.48 gal/ft3)

LCV	<	0-49 Fp_D 2 dsWl_	(4-13)

where:

	Fe	=	the fraction of the sludge with potential to evaporate (= 0.20 if unknown)

	ds	=	the average depth of sludge, inches

9

the constant. 0.49. has units of gal/(in. ft ). and the other terms are defined as shown above.

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7.1.3.5 Flashing Loss25

The equations in Section 7.1.3.1 for estimating routine emissions from fixed roof tanks do not
address the scenario of a tank storing a liquid which contains gases that have the potential to flash out of
solution. This scenario occurs when a gas-liquid mixture has been under sufficient pressure to maintain
the entrained gases in solution, but the mixture is then subjected to a drop in system pressure such that the
pressure is no longer sufficient to maintain the gases in solution. The gases will then rapidly migrate out
of the liquid, similar to carbon dioxide fizzing out of solution when a carbonated beverage container is
opened. This escape of gases from the mixture is referred to as flashing.

The most common scenario for flashing in the petroleum industry is the storage of crude oil or
condensate in the production field. Even though the produced well stream has typically been processed by
one or more separators prior to produced liquids being deposited into a storage tank, the exit pressure
from the last stage separator may be significantly greater than the pressure in the first storage tank. Thus
the produced liquid stream will experience a pressure drop upon entering the storage tank, and remaining
gases will have the potential to flash out of solution in the tank. This scenario, then, has the potential for
flashing losses in addition to routine standing and working losses.

There are numerous methodologies available for estimating flashing losses, including but not
limited to those discussed below. The accuracy of methods that rely on a site-specific sample is dependent
on how representative the sample is of production from that site, and the accuracy of methods that rely on
process simulation is dependent on how representative the modeling assumptions are of the actual
conditions at the site. The conditions to be determined by sampling or modeling are of the crude oil or
condensate properties at the last stage separator, in the oil compartment before the dump valve.

In addition to evaluating a tank with the potential for flashing losses in accordance with a method
such as those described below, the tank must also be evaluated for routine standing and working losses as
described in Section 7.1.3.1. If vapors are routed to a control device, the control efficiency of the device
should be applied to the flashing loss as well as to the standing and working losses. If vapors are routed to
a compressor for injection into a gas line or process, the control efficiency would be assumed to be 100%
whenever the compressor is on-line.

Laboratory GOR. This method involves collecting a pressurized liquid sample from a point between the
last stage separator and the first storage tank, and then analyzing the sample in a laboratory to determine
the gas-oil ratio (GOR). The sample may be taken from the oil compartment of the last stage separator,
before the dump valve, if there is a sample port available for doing so. It is imperative that the sample be
collected in a pressurized instrument, so as to prevent loss of light ends in the handling of the sample.
Specifications for collecting pressurized samples include the Gas Processors Association (GPA) standard
2174. which describes the use of floating piston cylinders and double valve cylinders.

The pressurized sample is then allowed to flash in the laboratory to ambient conditions, and the
relative volumes of gas and oil are measured to determine the standard cubic feet of flash gas generated
per barrel of crude oil or condensate produced (i.e.. the GOR). This GOR may then be multiplied by the
number of barrels produced from that well site for a given time period in order to determine the volume of
flash gas generated during that time period. The volume of flash gas may be converted to pound-moles.
and the pound-moles may be converted to mass, as shown in the following equation.

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flash gas (pounds) = (GQR) (production) (1/379.48) (MW)

where:

	GQR =	standard cubic feet (scf) of flash gas per barrel of oil

production =	barrels of oil produced

379.48 =	scf per pound-mole at standard conditions
	MW =	molecular weight of the flash gas (lb/lb-mole)

Laboratory speciation of the flash gas may be conducted to determine the molecular weight of the
gas, as well as to determine the contribution of individual constituents such as inerts (nitrogen and carbon
dioxide), methane and ethane to arrive at a value of VOC gas per barrel of oil produced.

Computer simulation modeling. The flashing losses for a given storage tank may be predicted from a
computer model that uses complex equations of state to simulate the flashing process at that tank. API
developed a computer model. E&P TANK, for the specific purpose of estimating flashing losses in
production field storage tanks. Commercial process simulation programs may also be applied to estimate
flashing losses. The accuracy achieved by any of these computer programs is improved by use of site-
specific data for the inputs, including properties obtained from laboratory analysis of pressurized liquid
samples, rather than reiving on default assumptions.

Vasquez-Beggs equation. The Vasquez-Beggs equation is a relatively simple calculation based on an
empirical correlation of the gas-oil ratio (GQR) to the separator temperature, separator pressure, gas
specific gravity, and liquid API gravity. Once the GQR has been predicted from the correlation equation,
flashing losses may be calculated in the same manner as described above for the laboratory GQR method.
As with all methods, the accuracy of the Vasquez-Beggs equation is improved if actual site-specific data
are used to determine values for the required input parameters. In that the Vasquez-Beggs equation is
based on an empirical correlation, it is considered to be invalid outside specified ranges for the input
parameters. For example, the Vasquez-Beggs equation is not suitable if the API gravity is greater than 40
degrees, and thus should not be used for estimating flashing losses from tanks storing condensate. The
Vasquez-Beggs equation is generally considered to be less accurate than the methods described above.

Direct measurement. Direct measurement of emissions at the tank vent would be a preferred approach, if
a reliable means of measurement for both the flash vapors and the amount of liquid produced during the
testing period were employed. Efforts at direct measurement should account for uncertainty in the field
measurements of vapor concentration and flow rate through the vent and in the field measurements of
volume of liquid produced during the test period, as well as variation in emission rates over time.
Uncertainty may be mitigated by use of EPA Method 25A over an extended period of time.

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7.1.3.3-6 Variable Vapor Space Tanks18 ©

Variable vapor space filling losses result when vapor is displaced by liquid during filling
operations. Since the variable vapor space tank has an expandable vapor storage capacity, this loss is not
as large as the filling loss associated with fixed roof tanks. Loss of vapor occurs only when the tank's
vapor storage capacity is exceeded. Equation 36-1 assumes that one-fourth of the expansion capacity is
available at the beginning of each transfer.

Variable vapor space system filling losses can be estimated from:

Lv =	variable vapor space filling loss, lb/1,000 gal throughput

Mv =	molecular weight of vapor in storage tank, lb/lb-mole; see Note 1 to Equation 1 -2234-

Pva =	true vapor pressure at the daily avcrage daily liquid surface temperature, psia; see Notes 1

and 2 to Equation 1-2224

Vi =	volume of liquid pumped into system, throughput, bbl/yr

V2 =	volume expansion capacity of system, bbl; see Note 1

N2 =	number of transfers into system, dimensionless; see Note 2

1.	V2 is the volume expansion capacity of the variable vapor space achieved by roof lifting or
diaphragm flexing.

2.	N2 is the number of transfers into the system during the time period that corresponds to a
throughput of Vi.

The accuracy of Equation 36-1 is not documented. Special tank operating conditions may result
in actual losses significantly different from the estimates provided by Equation 36-1. For example, if one
or more tanks with interconnected vapor spaces are filled while others are emptied simultaneously, all or
part of the expelled vapors will be transferred to the tank, or tanks, being emptied. This is called balanced
pumpingT or vapor balancing. Equation 36-1 does not account for balanced pumping, and will
overestimate losses under this condition. It should also be noted that, although not developed for use with
heavier petroleum liquids such as kerosenes and fuel oils, the equation is recommended for use with
heavier petroleum liquids in the absence of better data.

Variable vapor space tanks that rely on either a flexible diaphragm or a flexible coated fabric seal
will have additional losses to the extent that vapors leak through or past the membrane used for the
diaphragm or seal. The leakage rate through the membrane is a function of the permeability of the fabric
material from which the membrane is manufactured, and a leakage rate past the membrane is a function of
the leak tightness of the seam or seams where the membrane is attached to the tank wall. These leakage
rates depend upon the type of fabric used for the membrane and the manner in which the membrane is
attached to the tank wall.

where:

Notes:

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7.1.3.47 Pressure Tanks B

Losses occur during withdrawal and fillingroutine operations in low-pressure (2.5 to 15 psig)
tanks wkento the extent that atmospheric venting occurs. These losses are a function of the vent set
pressure, and are accounted for in the equations for routine fixed roof tank standing and working losses in
Section 7.1.3.1. High-pressure tanks are considered closed systems, with virtually no emissions. Vapor
recovery systems are often found on low pressure tanks. Fugitive losses are also associated with from
high-pressure tanks are estimated as equipment leaks, and are not addressed in the methodology for
estimating storage tank emissions, and their equipment, but with proper system maintenance, these losses
are considered insignificant. No appropriate correlations are available to estimate vapor losses from
pressure tanks.

A blanket of nitrogen gas is sometimes maintained in a storage tank for either safety or product
purity purposes, but the presence of the nitrogen gas does not reduce emissions. This is because
hydrocarbons readily evaporate into a nitrogen atmosphere, as evidenced by the fact that ambient air is
approximately 79% nitrogen. However, a nitrogen blanket is sometimes maintained in a closed or
pressurized system. In such a case, while evaporation rates would not be affected by the presence of the
nitrogen blanket, emissions may be reduced as result of the vapor space in the tank being tied to a closed
or pressurized system.

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7.1.3.5-8 Variations Of Emission Estimation Procedures B
7.1.3.8.1 Time Periods Shorter Than One Year26

All of the emission estimation procedures presented in Section 7.1.3 can be used to estimate
emissions for shorter time periods by manipulating the inputs to the equations for the time period in
question- with an associated increase in uncertainty when applying the equations to fewer tanks or
shorter time periods. Using actual data, such as the measured liquid temperature and true vapor pressure
of the stored liquid, can reduce the uncertainty in the emissions estimate.

For all of the emission estimation procedures, the true vapor pressure should be calculated from
an daily average daily liquid surface temperature should be based on the appropriate temperature and
solar insolation data for the time period over which the estimate is to be evaluated. The subsequent
calculation of the vapor pressure should be based on the corrected daily liquid surface temperature. For
example, emission calculations for the month of June would be based only on the meteorological data for
June. It is important to note that a 1-month time frame is recommended as the shortest time period for
which emissions should be estimatedr using these methodologies.

In addition to the temperature and vapor pressure corrections, the constant in the standing storage
loss equation for fixed roof tanks would need to be revised based on the actual time frame used. The
constant, 365, is based on the number of days in a year. To change the equation for a different time
period, the constant should be changed to the appropriate number of days in the time period for which
emissions are being estimated. The only change that would need to be made to the working loss equation
for fixed roof tanks would be to change the throughput per year to the throughput during the time period
for which emissions are being estimated.

Other than changing the meteorological data and the vapor pressure data, the only changes
needed for the floating roof rim seal, deck fitting, and deck seam losses would be to modify the time
frame by dividing the individual losses by the appropriate number of days or months. The only change to
the withdrawal losses would be to change the throughput to the throughput for the time period for which
emissions are being estimated.

Another variation that is frequently made to the omission estimation procedures is an adjustment
in the working or withdrawal loss equations if the tank is operated as a surge tank or constant level tank.
For constant level tanks or surge tanks where the throughput and turnovers are high but the liquid level in
the tank remains relatively constant, the actual throughput or turnovers should not bo used in the working
loss or withdrawal loss equations. For these tanks, the turnovers should be estimated by determining the
avorago chango in tho liquid hoight. Tho avorago chango in hoight should thon bo divided by tho total sholl
hoight. This adjusted turnover valuo should thon bo multipliod by tho actual throughput to obtain tho not
throughput for use in the loss equations. Alternatively, a default turnover rate of four could be used based
on data from thoso typo tanks.

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The issues that render the equations for routine emissions inappropriate for time periods shorter
than one month include, but are not limited to. the following:

a)	Temperature calculations are simplified. There are many parameters involved in a thermal
balance model for a storage tank, some of which are listed below. It has been deemed suitable
to assign default values to several of these parameters when the calculations are applied to a
large population of storage tanks located over a wide geographical area for emissions that
occur over the course of a year. However, actual values for these parameters for an individual
storage tank configuration or location, or for a particular day of the year, may deviate
significantly from the default values. Section 7.1.3.8.3 presents a more detailed discussion of
parameters affecting thermal balance in a storage tank.

1.	The angle of incident solar radiation (i.e.. the solar declination).

2.	Reflectivity of surrounding surfaces.

3.	Height to diameter ratio of the tank.

4.	Liquid level.

5.	Ambient wind speed.

6.	Thermal conductance of the floating roof.

7.	Presence of a fixed roof (versus an open top).

b)	Changes in the liquid bulk temperature. The parameters which are accounted for as variables
in the equations for routine emissions are evaluated in a manner that does not account for
short-term phenomena. For example, calculations of temperature variables in the equations
for routine emissions are based on the liquid and vapor phases within the tank having
achieved a state of thermal equilibrium. The calculations do not, however, account for how
long it may take for thermal equilibrium to be achieved after there has been a change in the
thermal balance, such as the receipt of a batch of liquid. It is demonstrated in the reference
cited in Section 7.1.3.8.3 that atypical time period for approaching thermal equilibrium may
be approximately nine days, and thus a tank that has received liquid within the prior nine days
would be expected to not be in thermal equilibrium. If measured bulk temperature is used
instead of the estimated bulk temperature when estimating emissions, the time for the liquid
to reach thermal equilibrium becomes unimportant when estimating emissions on a shorter
time-scale.

c)	Changes in ambient temperature. As ambient temperature changes, there would be an
associated change in the vapor space temperature and subsequently in the liquid surface
temperature. There would, however, be a time lag between a change in the ambient
temperature and the associated change in the liquid surface temperature. This time lag is
deemed inconsequential for the estimation of annual or monthly emissions, but would be
expected to be more significant for shorter periods of time. Shorter time periods would also
be more significantly influenced by abrupt short-term meteorological phenomena, such as
cooling due to cloud cover or precipitation.

d)	Saturation factors. The saturation level of vapors in the headspace of a fixed roof tank is a
similarly time-dependent phenomenon. The equations for routine emissions do not fully

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account for the time lag required to achieve saturation equilibrium in response to short-term
fluctuations in the values of applicable parameters.

e)	Vapor expansion rate. The calculation of standing loss for a fixed roof tank is based on the
total amount of vapor expansion that is expected to occur between the coolest night time
temperature and the warmest day time temperature. The equation does not, however,
calculate the hourly rate at which the vapor expansion takes place or the distribution of vapor
expansion over the course of a day. This hourly rate would be dependent on several of the
variables noted in (a) above, as well as on whether the tank shell is insulated. As discussed
above in Note 1 following Equation 1-5. a fixed roof tank with an insulated shell but an
uninsulated roof would be expected to have sufficient capacity for heat exchange through the
roof such that vapor space expansion would occur. However, the insulated shell may cause
the vapor space expansion to have a different hourly pattern than would be expected in the
case of an uninsulated tank shell.

f)	Vent flow capacity. In addition to not calculating the hourly rate of vapor expansion, as
noted above, the calculation of standing loss for a fixed roof tank does not take into account
whether the flow capacity of the tank vents will further limit the hourly rate at which vapors
will be expelled from the tank as a result of daytime vapor expansion.

g)	Changes in barometric pressure. The equations for routine emissions consider the barometric
pressure to be a constant for a given location, in that it has been deemed reasonable to use the
average barometric pressure when estimating emissions over the course of a year. However,
short-term changes in barometric pressure could impact short-term vapor expansion rates.

h)	Fill rate. The calculation of working loss for a fixed roof tank is based on the total volume of
vapor expelled over the course of a year, which can be thought of as the total number of
tankfuls of vapor displaced. However, the equation does not account for the hourly rate at
which a tank is filled.

i)	Standing loss for floating roof tanks. The equations for calculating routine standing losses
from floating roof tanks are based on the rate at which vapors migrate from the liquid below
the floating roof to the tank headspace above the floating roof, and do not account for the rate
at which these vapors may be eventually expelled from the tank.

i) Working loss for floating roof tanks. The calculation of working loss for a floating roof tank
is based on the evaporation of the wetted surface that is left on the inside wall of the tank
after lowering the liquid level. The calculation assumes that the entire film of liquid
evaporates, but it does not account for the hourly rate at which the film of liquid evaporates
or when the vapors are actually expelled from the tank.

k) Vapor space outage. The calculation of standing loss for a fixed roof tank is based on an
assumed vapor space outage corresponding to the average liquid height. However, at any
given point in time the tank may be nearly empty or nearly full, thus resulting in very
different scenarios of vapor space outage. For example, if the vapor space expansion factor is
0.15. that indicates 15% of the vapor space will be expelled by daytime warming, and
expelling 15% of the vapor space when the tank is nearly empty would constitute a far greater
volume than 15% of the vapor space when the tank is nearly full.

1) Vented vapor saturation factor. The saturation factor used in the calculation of standing loss
for a fixed roof tank is similarly dependent on the vapor space outage. Annual emission

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estimates are based on the average liquid height, but the calculation would indicate a lower
vapor saturation when the tank is nearly empty and a higher vapor saturation when the tank is
nearly full.

7.1.3.8.2	Internal Floating Roof Tanks with Closed Vent Systems27

The equations for routine emissions from internal floating roof tanks assume the tank has open
vents in the fixed roof. Estimation of emissions when an internal floating roof tank has closed
pressure/vacuum vents is presented in API Technical Report 2569.

The adjustment to account for the closed pressure/vacuum vents in the estimate of emissions was
found to be significant only for small diameter tanks storing relatively high volatility liquids with
infrequent turnovers. When the volatility of the stored liquid is no greater than that of diesel. then the
adjustment is generally less than 10% regardless of the tank diameter or the number of turnovers. When
the tank diameter is 60 feet or greater and the number of turnovers per year is greater than 18. then the
adjustment is generally less than 10% regardless of the volatility of the stored liquid. Given the high
degree of uncertainty associated with these calculations, and the burden of performing them, it would be
reasonable to apply a default reduction of 5% to account for the use of closed vents on a floating roof tank
in lieu of calculating a reduction specific to the given situation.

7.1.3.8.3	Case-Specific Liquid Surface Temperature Determinations22

Several parameters pertaining to liquid surface temperature are assigned default values for
incorporation into the equations for routine emissions. Methodology to account for selected parameters as
variables in the estimation of emissions from a particular storage tank at a particular location is presented
in API Manual of Petroleum Measurement Standards Chapter 19.4. Annex I.

7.1.3.8.4	Heating Cycles in Fully Insulated Fixed Roof Tanks8

The equations in Section 7.1.3.1.1 for standing loss from fixed roof tanks are based on the daily
cycle of warming and cooling of the vapor space due to heat exchange between the vapor space and
ambient air through the shell and roof of the tank. This heat exchange results in daytime expansion and
nighttime contraction of vapors in the vapor space, with each expansion cycle causing some portion of the
vapors to be expelled from the vapor space. The resulting emissions are referred to as breathing losses.

A similar cycle of expansion and contraction of vapors in the vapor space may be driven by
cyclic heating of the bulk liquid. Even in a fully insulated storage tank, in which there is minimal heat
exchange with ambient air, the temperature in the tank vapor space will cycle through a range if the bulk
liquid is heated periodically. This could occur by occasionally receiving hot stock, which then cools over
time prior to the next receipt of hot stock, or as a result of the tank being heated by some means that is
periodically turned on and off.

For uninsulated tanks or for tanks with an insulated shell but an uninsulated roof, the effect of
bulk liquid heating cycles on standing loss may be neglected because it may be random as to whether
cycles of heating the bulk liquid add to or subtract from the vapor space temperature variation driven by
the diurnal ambient temperature cycle.

For fully insulated storage tanks, however, standing loss may be driven by cyclic heating of the

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bulk liquid. The equations for routine fixed roof tank breathing loss may be adapted to the case of cyclic
heating of the bulk liquid, as shown below.

The annual breathing loss is calculated from Equation 1-4:

Ls = 365Ke

71

4D2\HvoKsWv	(1-4)

v

The variables in this equation should be evaluated for calculating heating cycle breathing losses
in the same manner as described in Section 7.1.3.1.1 for routine breathing losses, except as noted below.

The constant 365 is the number of days in a year. In that heating cycle breathing is an event that
is a function of the frequency of the heating cycle, rather than being a daily phenomenon, replace the
constant 365 with the number of heating cycles in the given time period.

The vapor space expansion factor Kk is calculated from Equation 1-5:

A7V APk -APr

KE =Y~+ p _P >°	0=51

1L4	A rK4

In a fully insulated tank, the vapor space temperature and the liquid surface temperature are both
assumed to be equal to the liquid bulk temperature. Thus the vapor temperature range A7V should be
calculated from the actual range of liquid bulk temperature in the tank, rather than using Equation 1-6 or
Equation 1-7. The actual range of liquid bulk temperature may be determined from direct measurements
or estimated from process knowledge.

	ATy= Tbx- Ten	(8-1)

where:

	Tbx = typical maximum liquid bulk temperature in the heating cycle. °R

	Ten = typical minimum liquid bulk temperature in the heating cycle. °R

The vapor pressure range A/Vis calculated from Equation 1-9.

	APy = Pit - Pvn	(1-9)

where:

Pix and Pvn are the vapor pressures at 7>,.r and Ttn. respectively, and:

	Trx = Tbx

Ttn = Trn

Similarly, the average liquid surface temperature Ttj should be taken as being equal to actual
average liquid bulk temperature, rather than being calculated from Equation 1-27 or Equation 1-28.

	Tta = Tb	(8-2)

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7.1.4 Hazardous Air Pollutants (HAP)Speciation Methodology31

In some cases it may be important to know the annual emission rate for a component (e. g., HAP)
of a stored liquid mixture. There are two basic approaches that can be used to estimate emissions for a
single component of a stored liquid mixture. One approach involves calculating the total losses based
upon the known physical properties of the mixture (i. e., gasoline) in the vapor phase and then
determining the individual component losses by multiplying the total loss by the vapor weight fraction of
the desired component. The second However, the weight fraction of a given component in the vapor
phase will vary with temperature, and thus this approach is similar to the first approach except that the
mixture properties are unknown; therefore, the mixture properties are firstvalid only at the temperature for
which the vapor weight fraction was determined based on the composition of the liquid mixture. ^

Case 1 cThe second approach is similar to the first approach except that the mixture properties in
the vapor phase are unknown; therefore, the vapor phase mixture properties are first determined based on
the composition of the liquid mixture. This involves application of Raoult's Law, which assumes ideal
behavior on the part of each of the components in the mixture. An assumption of ideal behavior has been
found to be reasonable for most hydrocarbon mixtures. The two approaches outlined above are illustrated
in Case 1 below.

An assumption of ideal behavior may not be appropriate for aqueous mixtures or mixtures
containing alcohols. The molecules of water and alcohols are polar, meaning that the individual molecules
of these substances have an attraction for one another, resulting in behavior that deviates significantly
from ideal assumptions. An illustration of speciation for an aqueous mixture is presented in Case 2 below.

Raoult's Law is also not applied to speciate working (withdrawal) loss from floating roof tanks.
The application of Raoult's Law outlined in this section assumes the fraction of the available liquid that
evaporates is very small compared to the total mass of liquid available, and thus the properties of the
remaining liquid can be assumed to be unaffected by the loss of the evaporated fraction. Floating roof
withdrawal loss, however, involves evaporation of a thin film of liquid from the wetted tank shell as the
liquid level descends. It is assumed that the entire film of liquid evaporates, and thus relative fractions of
individual components in the vapors would be the same as for the liquid.

Case 1 - If the physical properties of the mixture are known (Pva, Mv, Ml and Wl), the total
losses from the tank should be estimated using the procedures described previously for the particular tank
type. The component losses are then determined from either Equation 440-1 or 440-2. For fixed roof
tanks, the emission rate for each individual component can be estimated by:

LTi = (ZVi)(Lt)	(440-1)

where:

Lti = emission rate of component i, lb/yr
Zy. = weight fraction of component i in the vapor, lb/lb
Lt = total losses, lb/yr

For floating roof tanks, the emission rate for each individual component can be estimated by:

7.1-70

Liquid Storage TanksEMISSION FACTORS

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lTi = (Zv.XLr + Lf+Ld) + (zl,)(Lw)

(440-2)

where:

Lti = emission rate of component i, lb/yr

Zvj = weight fraction of component i in the vapor, lb/lb

Lr = rim seal losses, lb/yr

Lf = deck fitting losses, lb/yr

Ld = deck seam losses, lb/yr

Zl; = weight fraction of component i in the liquid, lb/lb

Lwb = working (withdrawal) losses, lb/yr

If Equation 440-1 is used in place of Equation 440-2 for floating roof tanks, the value obtained
will be approximately the same value as that achieved with Equation 440-2 because withdrawal losses are
typically minimal for floating roof tanks.

In order to use Equations 440-1 and 440-2. the weight fraction of the desired component in the
liquid and vapor phase is needed. The liquid weight fraction of the desired component is typically known
or can be readily calculated or determined by analysis for most mixtures. In order to calculate the weight
fraction in the vapor phase, Raoult's Law must first be used to determine the partial pressure of the
component. The partial pressure of the component can then be divided by the total vapor pressure of the
mixture to determine the mole fraction of the component in the vapor phase. Raoult's Law states that the
mole fraction of the component in the liquid (xi) multiplied by the vapor pressure of the pure component
(at the daily average daily liquid surface temperature) (P) is equal to the partial pressure (Pi) of that
component:

Pi = (P)(xi)	(440-3)

where:

Pi = partial pressure of component i, psia

P = vapor pressure of pure component i at the daily-average daily liquid surface temperature,
psia

xi = liquid mole fraction, lb-mole/lb-mole

The vapor pressure of each component can be calculated from Antoine's equation or found in
standard references, as shown in Section 7.1.3.1. In order to use Equation 440-3. the liquid mole fraction
must be determined from the liquid weight fraction by:

X: =

zuml ^

M,

(440-4)

where:

Xi =	liquid mole fraction of component i, lb-mole/lb-mole

Zl; =	weight fraction of component i in the liquid, lb/lb

Ml =	molecular weight of liquid stock, lb/lb-mole

Mi =	molecular weight of component i, lb/lb-mole

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If the molecular weight of the liquid is not known, the liquid mole fraction can be determined by
assuming a total weight of the liquid mixture (see Example 1 in Section 7.1.5).

The liquid mole fraction and the vapor pressure of the component at the daily average daily liquid
surface temperature can then be substituted into Equation 440-3 to obtain the partial pressure of the
component. The vapor mole fraction of the component can be determined from the following equation:

where:

yi = vapor mole fraction of component i, lb-mole/lb-mole
Pi = partial pressure of component i, psia
Pva = total vapor pressure of liquid mixture, psia

The weight fractions in the vapor phase are calculated from the mole fractions in the vapor phase.

where:

Zy. = vapor weight fraction of component i, lb/lb
yi = vapor mole fraction of component i, lb-mole/lb-mole

Mi = molecular weight of component i, lb/lb-mole

Mv = molecular weight of vapor stock, lb/lb-mole

The liquid and vapor weight fractions of each desired component and the total losses can be
substituted into either Equations 440-1 or 440-2 to estimate the individual component losses.

€aso 2 C For cases where the mixture properties are unknown but the composition of the liquid is
known (i. o., nonpotroloum organic mixtures), the equations presented above can bo used to obtain a
reasonable estimate of the physical properties of the mixture. For nonaqueous organic mixtures,

Equation 1 3 can be used to determine the partial pressure of each component. If Equation 1 1 is used to
determine the liquid mole fractions, the molecular weight of the liquid stock must bo known. If the
molecular woight of the liquid stock is unknown, thon the liquid molo fractions can bo determined by
assuming a weight basis and calculating the number of moles (see Example 1 in Section 7.1.5). The
partial pressure of each component can thon bo determined from Equation I 3.

Case 2 -For special cases, such as wastewater, where the liquid mixture is a dilute aqueous
solution, Henry's Law should be used instead of Raoult's Law in calculating total losses. Henry's Law
states that the mole fraction of the component in the liquid phase multiplied by the Henry's Law constant
for the component in the mixture is equal to the partial pressure (Pi) for that component. For wastewater,
Henry's Law constants are typically provided in the form of atm=»m3/g-mole.

Therefore, the appropriate form of Henry's Law equation is:

Pi

(440-5)

Pi = (Ha) (Ci)

(440-7)

7.1-72

Liquid Storage TanksEMISSION FACTORS

++06/0618


-------
where:

Pi =	partial pressure of component i, atm

Ha =	Henry's Law constant for component i, atm=»m3/g-mole

Ci =	concentration of component i in the wastewater, g-mole/m3; see Note

Section 4.3 of AP-42 presents Henry's Law constants for selected organic liquids. The partial
pressure calculated from Equation 440-7 will need to be converted from atmospheres to psia
(1 atm = 14.7 psia).

Note: Typically wastewater concentrations are given in mg/liter, which is equivalent to g/m3. To

convert the concentrations to g-mole/m3 divide the concentration by the molecular weight of the
component.

The total vapor pressure of the mixture can be calculated from the sum of the partial pressures:

Pva = ZE Pi	(440-8)

where:

Pva = vapor pressure at daily average daily liquid surface temperature, psia
Pi = partial pressure of component i, psia

This procedure can be used to determine the vapor pressure at any temperature. After computing
the total vapor pressure, the mole fractions in the vapor phase are calculated using Equation 440-5. The
vapor mole fractions are used to calculate the molecular weight of the vapor, Mv. The molecular weight
of the vapor can be calculated by:

Mv = 3E My,	(440-9)

where:

Mv = molecular weight of the vapor, lb/lb-mole
Mi = molecular weight of component i, lb/lb-mole
yi = vapor mole fraction of component i, lb-mole/lb-mole

Another variable that may need to be calculated before estimating the total losses, if it is not
available in a standard reference, is the density of the liquid, Wl. If the density of the liquid is unknown, it
can be estimated based on the liquid weight fractions of each component (see Section 7.1.5, Example 3).

All of the mixture properties are now known (Pva, Mv, and Wl). These values can now be used
with the emission estimation procedures outlined in Section 7.1.3 to estimate total losses. After
calculating the total losses, the component losses can be calculated by using either Equations 440-1 or
440-2. Prior to calculating component losses, Equation 440-6 must be used to determine the vapor weight
fractions of each component.

4406/0618

Liquid Storage Tanks

7.1-73


-------
Breather vent (open or P/V type)

Float gauge conduit

Tank roof and shell
(not insulated)

Gauge-hatch'
sample well

Roof manhole

No floating roof

Stable (nonboiling)
stock liquid

Figure 7.1-1. Typical fixed-roof tank.2"

7.1-74

Liquid Storage TanksEMlSSION FACTORS

+4-06/^18


-------
Figure 7.1-2. External floating roof tank (pontoon type}.2®

+4-06/^18

Liquid Storage Tanks

7.1-75


-------
Open top (no fixed roof)

Access hatch

Gauge hatch/
sample port

Solid guldepole
(unslotted)

-Gauge float

Rim vent

Tank shell

Overflow drain

Deck leg

Figure 7.1-3. External floating roof tank (double deck).2"

7.1-76

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


-------
¦Fixed-roof center vent

Fixed roof
(column-
supported)

Vacuum

Access hatch —'	l-Deck drain

Figure 7.1-4. Internal floating roof tank.2

(vapor-mounted)
Sample port

Ladder

Gauge float

Deck leg

Fixed-roof
support column

Tank shell

+4-06/0618

Liquid Storage Tanks

7.1-77


-------
Rim vent
Vacuum

Deck leg
(pontoon area)

Deck leg
(center area)

Overflow drain

Tank shell

Gauge float

Solid guiaepoie
(unslotted)

Gauge hatch/
sample port

Access hatch

Fixed-roof center vent

Fixed roof
(self-supporting
aluminum
dome)

Figure 7.1-5. Domed external floating roof tank.20

-78

Liquid Storage TanksEMlSSION FACTORS

+4-06/^18


-------
Liquid surface

Liquid surface

¦Tank shell

1	Flexible-wiper seal

(wiper position may vary with the
floating roofs direction of travel)

(see section views below)

Resilient-filled seal —^
(not in contact with the liquid surface)

(see section view below)

Elastomerio-coated
fabric envelope

^-Resilient
/ foam core

/— Floating
M	roof

^ . deck

Elastomeric blade

Floating
roof
deck

Rim vapor
space		

Liquid	

surface

Liquid -
surface

Elastomeric-coated
fabric envelope

—Foam core

Tank-
shell

Floating
roof
deck

Rim vapor
space	.

Figure 7.1-6. Vapor-mounted primary seals—

+4-06/06.18

Liquid Storage Tanks

7.1-79


-------
Floating roof deck

Resilient-filled seal
(bottom of seal in contact with the liquid surface)

(see section view below)

Weathershield
(not shown above)

Elastomeric-
coated
fabric
envelope.

Liquid—
surface

Resilient core
(foam or liquid-filled)

Floating
roof
deck

Floating roof deck

Primary-seal
fabric

(see section view below)

Metallic
shoe	

Rim vapor
space	

Liquid —
surface



I

-Tank shell

Primary-seal fabric

Floating
roof
deck

Figure 7.1-7. Liquid-mounted and mechanical shoe primary seals.2

7.1-80

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


-------
Rim-mounted secondary seal
over

resilient-filled primary seal

Secondary seal
(flexible wiper shown)

Rim extender

Primary seal
(resilient-filled)

Liquid
surface

Rim-mounted secondary seal
over

flexible-wiper primary seal

Secondary seal
(flexible wiper shown)

- Rim extender

Shoe-mounted secondary seal
over

mechanical-shoe primary seal

Primary seal
(mechanical
shoe)-

Liquid —
surface

¦Tank shell

Si

Secondary-seal
(shoe-mounted)

Rim-mounted secondary seal
over

mechanical-shoe primary seal

-Tank shell

Primary seal			

(mechanical
shoe)	^

Secondary-seaB
(rim-mounted)

roof
deck





r ir

Liquid <
surface







U3

BBSS® llllllil-ll

Figure 7.1-8. Secondary rim seals.2"

+4-06/0618

Liquid Storage Tanks

7.1-81


-------
Removable

Floating
roof

Well

(see section view below)

Pipe column —/	Scover

Gasket			|jl;' r_ y— Floating

* deck

(noncontact
type shown)

Floating
roof

Pipe column

Sliding
cover

(see section view below)

Handle



Access Hatch

Fixed-Roof Support Column

Gauge float	Sample Ports

Figure 7.1-9. Deck fittings for floating roof tanks.2"

Floating
roof

Float'

Removable

Cable

Well

Gauge-I
sample

(see section view below)

Slit-
fabric
sample port
roofs only)

Cord
(shov
cover open)

deck

(see section view below)

Self-

closing

cover

Pipe

sleeve

and slit-
fabric seal

~	1 cover

closed

Floating
roof
deck

tr~

roof

-82

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


-------
Screened
cover

Pipe
sleeve

Floating

root

Adjustable

Cf'""

(see section view below)

pinhole
Pin

(noncorttsct
type shown)

Screened
cover

Overflow

(see sectfon view below)

drain

(noncontact
type shown
tlii&s#te)

Deck Leg	Rim Vent

Figure 7.1-10. Deck fittings for floating roof tanks.20

Dec*;

Filiating
roof

(see section view below)

Adjustable leg
Lag

pinhole
Pin

Floating
roof
deck

Mechanical
shoe	

(see section view below)

Rim vent

-H-06/Q618

Liquid Storage Tanks

7.1-83


-------
Unslotted (solid) Guidepole

Slotted guidepole -
Roller assembly -

Slots in guidepole
(2 staggered rows
on opposite sides)

Slotted guidepole
Roller assembly-
Sliding cover

Well

¦Slotted guidepole
Roller assembly

Liquid
surface

Pole
sleeve

Slotted (perforated) Guidepole
Figure 7.1-11. Slotted and unslotted guidcpolcs.2"

7.1-84

Liquid Storage TanksEMlSSION FACTORS

+4-06/^18


-------
Floating
roof

Ladder

Sliding
cover

Gasket
Well

Liquid-

surface

{see section view below)

	Sliding

cover

deck
(noncontact
type shown)

Figure 7.1-12. Ladder well.35

-H-06/Q618

Liquid Storage Tanks

7.1-85


-------
Figure 7. l-13a. True vapor pressure of crude oils with a Reid vapor pressure
of 2 to 15 pounds per square inch.4
The nomograph in Figure 7.1-13a and the correlation equation in Figure 7.1-13b for predicting the true
vapor pressure of crude oil from the Reid vapor pressure are known to have an upward bias. When the
true vapor pressure of a crude oil is greater than 3.6 psia. it may be determined more accurately by means
of direct measurement using ASTM D 6377. A curve of true vapor pressure versus temperature may be
obtained by conducting ASTM D 6377 measurements over a range of temperatures.

7.1-86

Liquid Storage TanksEMISSION FACTORS

+4-06/06-18


-------
—	0.20

0.30
040

—	0.50

—	060
0.70

—	0.80

—	090
1.00

2 — 1.50

—	2.00

3o 1 0

4j2

120—1

no-

100-

sr

£


-------
P = exp

2,799
T +459.6.

-2.227

iog10 (RVP) -

7,261
T +459.6.

+ 12.82

Where:

P = stock true vapor pressure, in pounds per square inch absolute.

T = stock temperature, in degrees Fahrenheit.

RVP = Reid vapor pressure, in pounds per square inch.

Note:This equation was derived from a regression analysis of points read off Figure 7. l-13a over the full range
of Reid vapor pressures, slopes of the ASTM distillation curve at 10 percent evaporated, and stock
temperatures. In general, the equation yields P values that are within +0.05 pound per square inch
absolute of the values obtained directly from the nomograph.

Figure 7.1-13b. Equation for true vapor pressure of crude oils
with a Reid vapor pressure of 2 to 15 pounds per square inch.4 See note at Figure 7.1-13a.

P = exp

0.7553-

413.0
T +459.6

S log10 (RVP) -

1.854-

1,042
T +459.6

-,0.5

2,416
T +459.6

¦2.013

Where:

log10(RVP).

8,742
T +459.6

+ 15.64

P =	stock true vapor pressure, in pounds per square inch absolute.

T =	stock temperature, in degrees Fahrenheit.

RVP =	Reid vapor pressure, in pounds per square inch.

S =	slope of the ASTM distillation curve at 10 percent evaporated, in degrees Fahrenheit per percent.

Note: This equation was derived from a regression analysis of points read off Figure 7.1-14a over the full range of Reid
vapor pressures, slopes of the ASTM distillation curve at 10 percent evaporated, and stock temperatures. In general,
the equation yields P values that are within +0.05 pound per square inch absolute of the values obtained directly
from the nomograph.

Figure 7.1-14b. Equation for true vapor pressure of refined petroleum stocks
with a Reid vapor pressure of 1 to 20 pounds per square inch.4 See note at Figure 7.1-14a.

A = 15.64 - 1.854 S05 - (0.8742-0.3280 S05)ln(RVP)

B = 8,742 - 1,042 S0 5 - (1,049-179.4 S0 5)ln(RVP)
where:

RVP = stock Reid vapor pressure, in pounds per square inch
In = natural logarithm function

S = stock ASTM-D86 distillation slope at 10 volume percent
evaporation (°F/vol %)

Figure 7.1-15. Equations to determine vapor pressure constants A and B for refined

petroleum stocks Z21

7.1-88

Liquid Storage TanksEMISSION FACTORS

44-06/06J_8


-------


A = 12.82 - 0.9672 In (RVP)



B = 7,261 - 1,216 In (RVP)

where:





RVP =Reid vapor pressure, psi



In =natural logarithm function

Figure 7.1-16. Equations to determine vapor pressure Constants A and B for crude oil stocks/22

Average Daily Maximum and Minimum Liquid Surface Temperature, (°R)

Tlx = Tla + 0.25 ATv
Tln = Tla - 0.25 ATv
where:

Tlx = average daily maximum liquid surface temperature, °R

Tla is as defined in Note 3 to Equation 1-2224-

ATv is as defined in Note 1 to Equation 1 -5-7

Tln = average daily minimum liquid surface temperature, °R

Figure 7.1-17. Equations for the average daily maximum and minimum liquid surface temperatures.8

+4-06/0618

Liquid Storage Tanks

7.1-89


-------
J

1
<

bu

2
o
£

1.0

o.a
0.6
0,4
0.2

a

100

200

300

400

TURNOVER PER YEAR - ANNUAL THROUGHPUT

TANK CAPACITY

Note: For 36 turnover* per ytmt or \em, K*

1.0

Figure 7.1-18. Reserved.Turnover Factor (KN) for fixed roof tanks/

7.1-90

Liquid Storage TanksEMlSSION FACTORS

+4-06/^18


-------
12 3 4 S 6 7 8 9 10 11 12 13
Stock tnie vapor pressure. P (pounds per square inch absolute)

Notes:

1.	Broken line illustrates sample problem for P — S.4 pounds per square inch absolute.

2.	Curve is for atmospheric pressure, P^, equal to 14.7 pounds per square inch absolute.

Figure 7.1-19. Vapor pressure function.4

+4-06/0618

Liquid Storage Tanks


-------
Full Liquid Heel Partial Liquid Heel	Drain Dry

(standing liquid (standing liquid only	(no standing liquid,

across the entire bottom) in or near a sump;	only liquid is clingage)

clingage elsewhere)

Figure 7.1-20. Bottom conditions for landing loss.

20

Ladder sleeve

Figure 7.1-21. Ladder-guidepole combination with ladder sleeve.2

-92

Liquid Storage TanksEMISSION FACTORS

-1-4-06/0^18


-------
¦Flexible enclosure

-H-06/Q618

Liquid Storage Tanks

7.1-93


-------
Table 7.1-1. LIST OF ABBREVIATIONS USED IN THE TANK EQUATIONS

Variable Description

Variable Description

Variable Description

a

71

A

Adeck

Afi

B

C

Cs

Csf

Cv

tank surface solar absorptance,

dimensionless
constant (3.14159)
constant in vapor pressure equation.

dimensionless
area of deck, ft2
liquid surface area within a

particular type of deck fitting,
in2

constant in vapor pressure equation.
°R or °C

constant in vapor pressure equation.

°R or °C
shell clingage factor, bbl/1,000 ft2
filling saturation correction factor

for wind, dimensionless
average vapor concentration by

volume during continued forced
ventilatioa dimensionless
D tank diameter, ft
De effective tank diameter, ft

dg	average depth of sludge, in.

Fc effective column diameter, ft

Fg	fraction of sludge with potential to

evaporate, dimensionless
Ff total deck fitting loss factor,
lb-mole/yr

Fr	rim deck loss factor, lb mole/Ff vr

ly	deck leg height at the tank shell, ft

Hl liquid height, ft

hie	effective liquid height during roof

landing, ft
Ht n minimum liquid height, ft
Hlx
EHqd

maximum liquid height, ft
the annual sum of the decreases in
liquid level, ft/yr
EHqi the annual sum of the increases in

liquid level, ft/yr
Hr tank roof height, ft
Hr0 roof outage, ft
Hs tank shell height, ft
hv	vapor space height under landed

K,

-c

Ki

Hvo vapor space outage, ft

i	1,2,	a dimensionless

I	average daily total insolation factor,

Btu/ft2,d
product factor for floating roof

tanks, dimensionless
deck seam loss per unit seam length

factor, lb-mole/ft-yr
vapor space expansion factor, per
day

zero wind speed loss factor for a
particular type of deck fitting,
lb-mole/yr
wind speed dependent loss factor
for a particular type of deck
fitting, lb-mole/(mph)mvr
loss factor for a particular type of

deck fitting, lb-mole/yr
turnover factor, dimensionless
working loss product factor for fixed

roof tanks, dimensionless
zero wind speed rim seal loss factor,

lb-molc/ft'vr
wind speed dependent rim seal loss

factor, lb-mole/ (mph)nft,yr
vented vapor saturation factor,

dimensionless
fitting wind speed correction factor,

dimensionless
length of tank, ft

clingage factor for drain dry tanks^
lb

Lrv continued forced ventilation

emissions, lb/cleaning event
Ld deck seam loss, lb/yr
Lf deck fitting loss, lb/yr
Lfv total tank cleaning emissions due to
forced ventilatioa lb/cleaning
event

Lfl	filling loss during roof landing,

lb/landing event

Ke

KfFa:

KFb,

I'M-

Kn
KP

Kr;

Kri

Ks

Kv

L
Lc

1^	vapor space purge emissions due to

first air change from forced
ventilatioa lb/cleaning event
rim seal loss, lb/yr
rim seal loss during roof landing,

lb/landing event
standing losses, lb/yr
total length of deck seam, ft
standing loss during roof landing,

lb/landing event
total routine losses, lb/yr
emission rate of component i, lb/yr

Lr

Lrl

Ls

Lgeam

Lsl

Lt

Li\

Ltl
Lv

Lw

Mcg

total loss during roof landing,

lb/landing event
variable vapor space filling loss,

lb/1,000 gal throughput
working losses, lb/yr
molecular weight of calibration gas.

lb/lb-mole

in, loss factor for a particular type of

deck fitting, dimensionless
Mi molecular weight of component i,
lb/lb-mole

Ml molecular weight of liquid mixture,
lb/lb-mole

Mv vapor molecular weight, lb/lb-mole
N number of turnovers per year,

dimensionless
n seal-related wind speed exponent,
dimensionless

n^	number of days standing idle during

roof landing or prior to forced
ventilation, days
N: number of transfers into system,

dimensionless
Ne	number of columns

floating roof, ft

Nc number of columns, dimen-sionless
a-v duration of continued forced

ventilation, days
Nd number of drains
nf total number of different types of
fittings, dimensionless


-------
Table 7.1-1 (cont.).

Variable Description

N|.„ zero wind speed loss factor for a
particular type of deck fitting,
lb-mole/yr

NFbi wind speed dependent loss factor for
a particular type of fitting,
lb-mole/ mplV"*yr
NF[ number of deck fittings of a

particular type, dimensionless
Ni number of deck legs
Ntotal total number of moles in mixture,
lb-mole

Nvb

number of vacuum breakers

P

true vapor pressure of component i.

P*

psia

vapor pressure function.



dimensionless

Pa

atmospheric pressure, psi

APb

breather vent pressure setting range.



psig

Pbp

breather vent pressure setting, psig

Pbv

breather vent vacuum setting, psig

Pi

gauge pressure within the vapor



space, psig

P,

partial pressure of component i, psia

APV

average daily vapor pressure range.



psi

PvA

vapor pressure at average daily



liquid surface temperature, psia

PvN

vapor pressure at the average daily

minimum liquid surface
temperature, psia
Pvx vapor pressure at the average daily
maximum liquid surface
temperature, psia
Q annual net throughput, bbl/yr
Ov average ventilation rate during tank

cleaning. ft3/min
R ideal gas constant,

(10.731 psia*rt7lb-molc*°R)
Rr tank dome roof radius, ft
Rs tank shell radius, ft

S	filling saturation factor.

dimensionless

Sg	tank cone bottom slope, ft/ft

Sd deck seam length factor, ft/ft2
Sr tank cone roof slope, ft/ft
A Ta average daily ambient temperature
range, °R

Taa average daily ambient temperature,
°R

Tan average daily minimum ambient

temperature, °R
Tax average daily maximum ambient
temperature, °R

Variable Description

Tb liquid bulk temperature, °R
Trn typical minimum liquid bulk

temperature in heating cycles,
!R

Try typical maximum liquid bulk

temperature in heating cycles.
!R

Tla average daily liquid surface

temperature, °R
Tv average vapor temperature, °R

tv	daily period of forced ventilation

during tank cleaning, hr/dav
A Tv average daily vapor temperature

range, °R
v average wind speed, mph
V volume of liquid pumped into

system, bbl/yr
V2 volume expansion capacity, bbl
Vo net working loss throughput. ft3/yr
Vlx tank maximum liquid volume, ft3
Vv vapor space volume, ft3
Wi liquid density of component i, lb/ft3
Wl average organic liquid density,
lb/gal

Wv vapor density, lb/ft3
X! liquid mole fraction of component i,

lb-mole/lb-mole
yi vapor mole fraction of component i,

lb-mole/lb-mole
Z|, liquid weight fraction of

component i, lb/lb
ZV| vapor weight fraction of
component i, lb/lb

+4-06/0^18

Liquid Storage Tanks

7.1-95


-------
Table 7.1-2. PROPERTIES (My. M,.. PVA, WL) OF SELECTED PETROLEUM LIQUIDS'

Petroleum Liquid
Mixture

Vapor
Molecular
Weight3

Liquid
Molecular
Weight13

Liquid
Density3

ASTM D86
Distillation
Slope0

Vapor Pressure Equation
Constants11

True Vapor
Pressure
(at 60 °F)

Ah

Ml

Wl

S

A

B

Pva

Ib/lb-mole

Ib/lb-mole

lb/gal

°F/vol %

dimension less

°R

psia

Midcontinent Crude Oil

50

207

7.1

-

Figure 7.1-16

Figure 7.1-16

-

Refined Petroleum Stocks

-

-

-

-

Figure 7.1-15

Figure 7.1-15

-

Motor Gasoline RVP 13

62

92

5.6

3.0

11.644

5043.6

7.0

Motor Gasoline RVP 10

d)

CD
CD

92

5.6

3.0

11.724

5237.3

5.2

Motor Gasoline RVP 7

68

92

5.6

3.0

11.833

5500.6

3.5

Light Naphtha RVP 9-14

-

-

-

3.5

-

-

-

Naphtha RVP 2-8

-

-

-

2.5

-

-

-

Aviation Gasoline

-

-

-

2.0

-

-

-

Jet Naphtha (JP-4)

80

120

6.4

-

11.368

5784.3

1.3

Jet Kerosene (Jet A)

130

162

7.0

-

12.390

8933.0

0.008

No. 2 Fuel Oil (Diesel)

130

188

7.1

-

12.101

8907.0

0.006

No. 6 Fuel Oilf

130

387

7.9

-

10.781

8933.0

0.002

Vacuum Residual Oilg

190

387

7.9

-

10.104

10,475.5

0.00004

a References 10 and 11 U.S. EPA Report AP 42. Fifth Edition. November 2006^. Table 7.1 2.

b Liquid molecular weights from "Memorandum from Patrick B. Murphy, Radian/RTP to James F. Durham, EPA/CPB
Concerning Petroleum Refinery Liquid HAP and Properties Data, August 10, 1993," as adopted in versions 3.1 and 4.0 of
EPA's TANKS software.

c API 2518 June 1962^. Figure 1.Reference 4.

d For motor gasolines, see Figure 7.1-15 API 2519, 3"* edition. Figure 4;
for crude oil, see Figure 7.1-16 API 2519, 3"* edition. Figure 5;
for Jet Naphtha, Jet Kerosene, and No. 2 Fuel Oil, see Barnett and Hibbard*391—;

e Alternatively, in the absence of measured data, a value of 66 Ib/lb-mole may be assumed for all gasolines, in that the variability
shown as a function of RVP is speculative.

f This is for a blend of Vacuum Residual Oil with a light distillate cutter stock, or similar mixture. Vapor pressure constants given
will result in higher vapor pressure values than shown previously in AP-42 for Residual Oil No. 6.

g This is the straight residue from the bottom of the vacuum distillation column, prior to any further processing or blending.
Properties given for Vacuum Residual Oil are those given for Residual Fuel Oil No. 6 previously in AP-42 in API MPMS
Chapter 19.4, 2^ edition^, Table 2.

* Roforoncos 10 and 11

7.1-96

Liquid Storage TanksEMISSION FACTORS

+4-06/0718


-------
Table 7.1-3. PHYSICAL PROPERTIES OF SELECTED PETROCHEMICALS'





















Normal

Chemical
Name

CAS
Registry
No.

Molecular
Weight

Liquid
Density^
(lb/gal)





Antoine's Equation^



Boilin
Poin
(°F)

g

t









True

Constants

Temperature
Ranged

I









Vapor





















Pressure*
at 60 °F
(psia)

A

dimension less

B

(°C)

C
(°C)

Minimum
(°F)

Maximum
(°F)

I

Acetaldehyde

00075-07-0

44.05

6.5464

12.19

8.063

1,637.1

295.47

32

94

69

Acetic acid

00064-19-7

60.05

8.7277

0.176

7.557

1,642.5

233.39

63

244

244

Acetic anhydride





















{acetic acid anhydride}

00108-24-7

102.09

9.03

0.053

7.122

1,427.8

198.04

145

283

282

Acetone

00067-64-1

58.08

6.5577

2.921

7.300

1,312.3

240.71

7

454

133

Acetonitrile

00075-05-8

41.05

6.56

1.090

7.154

1,355.4

235.30

59

192

179

Aery lam id e-""*

00079-06-1

71.08

9.36

8.57E-05

11.293

3,939.9

273.16





3791

Acrylic acid





















{2-propenoic acid}

00079-10-7

72.06

8.77

1.344

5.652

648.6

154.68

68

158

282

Acrylonitrile





















{2-propenenitrile}

00107-13-1

53.06

6.73

1.383

6.942

1,255.9

231.30

-60

172

172

Allyl alcohol

00107-18-6

58.08

7.13

0.326

11.658

4,510.2

416.80

70

207

206

Allyl chloride®

00107-05-1

76.52

7.83

4.702

5.297

418.4

128.68

55

111

1131

{3-chloro-1-propene}





















Aniline

00062-53-3

93.13

8.53

0.0058

7.221

1,661.9

199.10

88

363

363

Benzene®

00071-43-2

78.11

7.32

1.171

6.906

1,211.0

220.79

46

217

176



Benz[a]anthracene'

00056-55-3

228.29



7.92E-10

11.528

5,461

273.15

219

260

820



Benzo[a]pyrene *

00050-32-8

252.31



2.29E-11

12.482

6,181

273.15

185

316

923



Benzo[ghi]perylene->

00191-24-2

276.33



2.07E-13

11.820

6,580

273.15

391

513





Biphenyl®

00092-52-4

154.21

8.68

2.37E-04

7.245

1,998.7

202.73

156

520

489



Butadiene (1,3)





















{divinyl}

00106-99-0

54.09

5.1377

30.22

6.873

941.7

240.40

-104

29

24

Butane (n)

00106-97-8

58.12

4.7877

25.67

6.725

909.7

237.00

-108

31

32

Butene (1)

00106-98-9

56.11

4.9177

30.83

7.122

1,099.2

264.89

-108

25

21

Butene (cis-2)

00590-18-1

56.11

5.1477

22.62

6.863

957.1

236.65

-94

73

39

Butene (2-methyl-1)

00563-46-2

70.13

5.43

8.257

6.862

1,047.8

232.06

34

145

88

Butene (trans-2)

00624-64-6

56.11

5.0077

24.97

6.919

982.2

242.38

-97

34

34

Butyl alcohol (n)





















{butanol (1)}

00071-36-3

74.12

6.76

0.062

7.421

1,351.6

179.81

73

244

243

Butyl alcohol (tert)





















{1,1-dimethyl ethanol}

00075-65-0

74.12

6.58

0.424

7.373

1,174.9

179.23

103

180

180

Butyl chloride (-n)





















{1-chloro-butane}

00109-69-3

92.57

7.40

1.255

6.871

1,182.9

218.27

2

173

170

Butyl ether (di-tert)

06163-66-2

130.23

6.39

0.381

6.590

1,157.7

203.05

39

228

224

Carbon disulfide

00075-15-0

76.14

10.54

4.817

6.942

1,168.6

241.53

38

176

115

-1-1-06/0? 18	Liquid Storage Tanks	7.1-97


-------






















Normal





CAS



Liquid













Boiling

CI

lemical

Registry

Molecular

Density"













Point

Ni

ime

No.

Weight

(lb/gal)





Antoine's Equation®-



(°F)













Constants



Temperature
Ranged













True



















Vapor























Pressure*

A

B

C

Minimum

Maximum













at 60 °F

dimension less

(°C)

(°C)

(°F)

(°F)













(psia)





Carbon tetrachloride

00056-23-5

153.82

13.31

1.431

6.898

1,221.8

227.41

68

172

170

Chlorobenzene

00108-90-7

112.56

9.23

0.134

6.986

1,435.7

218.03

144

269

269

Ct|ilorobutane (2)-n

00078-86-4

92.57

7.27

1.255

6.871

1,182.9

218.27

2

173

170

Chloroform

00067-66-3

119.38

12.38

2.468

7.083

1,233.1

232.20

-73

142

142

Chloroprene





















{2-chloro-1,3-butadiene}

00126-99-8

88.54

7.98

2.736

6.291

841.9

187.79

68

140

140

Chlorotoluene (o)





















{1 -chloro-2methylbenzene}

00095-49-8

126.58

9.04

0.039

7.363

1,768.1

234.76

42

319

318

Ct|irysene-t





















{benzo[a]phenanthrene}

00218-01-9

228.29

10.63

1.86E-11

12.320

6,160

273.15

185

374

838

Cresol (m)





















{3-methyl-phenol}

00108-39-4

108.14

8.63

0.0013

7.477

1,833.1

196.74

301

394

396

Cresol (o)





















{2-methyl-phenol}

00095-48-7

108.14

9.4777

0.0016

6.843

1,391.3

160.18

248

376

376

Cresol (p)





















{4-methyl-phenol}

00106-44-5

108.14

8.50104

0.00062

7.016

1,498.6

160.55

262

395

395

Cyclohexane

00110-82-7

84.16

6.4677

1.212

6.845

1,203.5

222.86

68

179

177

Cyclohexanol

00108-93-0

100.16

8.03

0.00090

5.956

111 A

91.11

201

321

320

Cyclohexanone

00108-94-1

98.14

7.91

0.0042

5.978

1,495.5

209.55

193

330

311

Cyclohexene

00110-83-8

82.14

6.77

0.110

5.872

1,221.9

223.17

98

196

181

Cyclopentane

00287-92-3

70.13

6.22

4.171

6.878

1,119.2

230.74

60

122

121

Cyclopentanone

00120-92-3

84.12

7.92

0.130

3.958

376.4

104.65

32

78

266

C\fclopentenes

00142-29-0

68.12

6.44

3.264

6.921

1,121.8

223.45





111

Decane (-n)

00124-18-5

142.28

6.09

0.011

3.085

440.6

116.25

-21

99

345

Dibromopropane (1,2)

00078-75-1

201.89

16.13

0.088

7.314

1,667.0

234.85

19

287

286

Dibromopropane (1,3)

00109-64-8

201.89

16.55

0.029

7.309

1,776.7

233.46

49

333

314

Dichloroethane (1,1)

00075-34-3

98.96

9.81

2.863

7.097

1,229.2

233.95

-77

135

135

Dichloroethane (1,2)

00107-06-2

98.96

10.4077

0.961

7.460

1,521.8

248.48

-23

211

182

Di|shloroethylene (1,2)®*"





















{1,2 dichloroethene}

00540-59-0

96.94

10.76

2.579

7.022

1,205.4

230.60

32

183

141

Di

Dhloroethylene (trans-1,2)e

00156-60-5

96.94

10.49

4.333

6.965

1,141.9

231.90

-36

185

118

Di

Dhlorotoluene (3,4)e

00095-75-0

161.03

10.49

0.0029

7.344

1,882.5

215.00

32

221

408

Diethoxyethane (1,1)

00105-57-7

118.17

6.89

0.307

7.625

1,574.0

229.47

-10

216

212

Diethoxymethane

00462-95-3

104.15

6.94

0.810

6.986

1,270.2

221.26

32

167

191

Diethyl (n,n) aniline





















{N,N-diethylbenzenamine}

00091-66-7

149.23

7.77

0.0031

8.258

2,652.8

277.32

122

425

422

Diethyl ketone





















{3-pentanone}

00096-22-0

86.13

6.7677

0.423

5.741

716.2

147.17

97

215

215

7.1-98

Liquid Storage TanksEMISSION FACTORS

44-06/Q218


-------




















Normal



CAS



Liquid













Boiling

Chemical

Registry

Molecular

Density"













Poin

t

Name

No.

Weight

(lb/gal)





Antoine's Equation®-



(°F)













Constants



Temperature
Ranged

1









True







1









Vapor





















Pressure*

A

B

C

Minimum

Maximum

1









at 60 °F

dimension less

(°C)

(°C)

(°F)

(°F)











(psia)





Diethyl sulfide

00352-93-2

90.19

6.98

0.749

7.541

1,560.5

246.59

-39

190

197

Diethylamine





















{N-ethyl ethanamine}

00109-89-7

73.14

5.89

2.712

5.737

559.1

140.18

89

141

132

Diethylbenzene (1,2)

00135-01-3

134.22

7.34

0.0094

6.990

1,577.9

200.55

206

364

361

Diethylbenzene (1,3)

00141-93-5

134.22

7.18

0.010

7.006

1,576.3

201.00

203

360

358

Diethylbenzene (1,4)

00105-05-5

134.22

7.20

0.010

7.001

1,589.3

202.02

206

365

363

Di-isopropyl ether

00108-20-3

102.17

6.04

1.877

6.842

1,135.0

218.23

74

153

155

Dimethoxyethane (1,2)

00110-71-4

90.12

7.25

0.966

6.713

1,260.5

235.83

-55

199

185

Dimethyl formamide (n,n)

00068-12-2

73.09

7.8877

0.040

6.806

1,337.7

190.50

86

194

307

Dimethyl hydrazine (1,1)

00057-14-7

60.10

6.6072

1.896

7.588

1,388.5

232.54

-32

68

146

Dimethyl phthalate-®

00131-11-3

194.18

9.94

2.25E-08

4.522

700.3

51.42

180

304

5401

Dimethylbutane (2,3)

00079-29-8

86.18

5.52

3.064

6.810

1,127.2

228.95

58

138

136

Dimethylcyclopentane (1,1)

01638-26-2

98.19

6.2677

0.932

6.830

1,226.6

222.76

60

192

190

Dimethylpentane (2,2)

00590-35-2

100.20

5.63

1.315

6.815

1,190.3

223.34

60

176

174

Dimethylpentane (2,3)

00565-59-3

100.20

5.80

0.842

6.862

1,242.6

222.34

64

195

194

Dimethylpentane (2,4)

00108-08-7

100.20

5.62

1.221

6.836

1,197.6

222.27

57

178

177

Dimethylpentane (3,3)

00562-49-2

100.20

5.79

1.029

6.831

1,231.0

225.58

56

189

187

Dioxane (1,4)

00123-91-1

88.11

8.63

0.439

7.456

1,570.1

241.85

68

221

214

Dipropyl ether





















{di-n-propyl ether}

00111-43-3

102.17

6.23

0.754

6.945

1,254.8

218.82

80

192

194

Dodecane(n)

00112-40-3

170.33

6.25

0.00093

6.981

1,625.9

180.31

259

423

421

Epichlorohydrinm_n



















I

{chloromethyl oxirane}

00106-89-8

92.52

9.85

0.194

8.229

2,086.8

273.16





241

Ethane

00074-84-0

30.07



472

6.813

659.7

256.431

-215

-100

-127

Ethanolamine (mono)

00141-43-5

61.08

8.50

0.002

7.168

1,408.9

157.06

150

340

339

Ethyl acetate

00141-78-6

88.11

7.51

1.135

7.103

1,245.7

217.96

60

168

171

Ethyl acrylate





















{ethyl ester 2-propenoic acid}

00140-88-5

100.12

7.71

0.445

7.150

1,366.1

220.47

-21

211

211

Ethyl alcohol





















{ethanol}

00064-17-5

46.07

6.59

0.648

8.247

1,670.4

232.96

32

173

173

Ethyl chloride

00075-00-3

64.51

7.4377

16.63

7.037

1,052.8

241.07

-69

55

61

Ethyl ether





















{diethyl ether}

00060-29-7

74.12

5.96

6.675

6.897

1,062.6

228.22

-10

132

94

Ethylamine

00075-04-7

45.08

5.6577

14.08

7.405

1,203.8

249.43

62

349

64

Ethylbenzene

00100-41-4

106.17

7.24

0.104

6.950

1,419.3

212.61

134

279

277

Ethylcyclopentane

01640-89-7

98.19

6.40

0.475

6.898

1,305.0

221.40

84

220

218

Ethylene





















{ethene}

00074-85-1

28.05

4 -74-155

749

6.748

584.1

254.84

-191

-120

-155

¦H-06/0^18	Liquid Storage Tanks	7.1-99


-------






















Normal

CI
Ni

lemical
ime

CAS
Registry
No.

Molecular
Weight

Liquid
Density"
(lb/gal)





Antoine's Equation®-



Boiling
Point
(°F)

1







True

Constants

Temperature
Ranged













Vapor























Pressure*
at 60 °F
(psia)

A

dimension less

B

(°C)

C
(°C)

Minimum
(°F)

Maximum
(°F)



Ethyleneoxide

00075-21-8

44.05

7.3650

17.84

8.722

2,022.8

335.81

32

89

53

Ethylpentane (3)

00617-78-7

100.20

5.83

0.701

6.880

1,254.1

220.15

70

202

200

Flljoranthene^

00206-44-0

202.25

10.45

3.96E-08

12.836

5,348.1

273.15

77

230

723

Fluorobenzene

00462-06-6

96.10

8.53

0.936

7.237

1,409.8

238.36

0

183

185

Formic acid

00064-18-6

46.03

10.18

0.516

4.876

515.0

133.74

33

93

213

Fr|eon 11®""





















{trichlorofluoromethane}

00075-69-4

137.37

12.48

10.93

6.884

1,043.0

236.88





75

Furan

00110-00-9

68.07

7.94

7.963

6.975

1,060.8

227.73

37

143

89

Furfural





















{2-furancarboxaldehyde}

00098-01-1

96.09

9.68

0.018

6.969

1,430.1

188.70

133

321

323

Heneicosane (n)

00629-94-7

296.57

6.61

6.23E-07

8.796

3,571.2

253.20

307

663

679

Heptane (n)

00142-82-5

100.20

5.71

0.541

6.903

1,268.6

216.95

79

211

209

Heptene (1)

00592-76-7

98.19

5.82

0.752

7.093

1,400.7

238.96

32

192

201

Hexadiene (1,5)

00592-42-7

82.14

5.7477

2.890

6.563

1,008.1

214.16

32

138

140

Hexane(n)

00110-54-3

86.18

5.4777

1.913

6.878

1,171.5

224.37

55

157

156

Hexanol (1)

00111-27-3

102.17

6.79

0.005

7.288

1,422.0

165.44

126

315

314

Hexene (1)

00592-41-6

84.16

5.62

2.378

6.866

1,153.0

225.85

61

148

147

Hydrogen cyanide





















{hydrocyanic acid}

00074-90-8

27.03

5.74

9.931

7.549

1,340.8

261.56

2

115

79

Isobutane





















{methylpropane (2)}

00075-28-5

58.12

4.6077

38.22

6.819

912.1

243.34

-121

11

12

Isobutene





















{methylpropene (2)}

00115-11-7

56.11

4.9277

32.18

6.522

799.1

226.54

-70

32

20

Isobutyl alcohol





















{2-methyl 1-propanol}

00078-83-1

74.12

6.69

0.096

7.306

1,237.0

171.62

176

240

226

Isooctane





















{2,2,4-trimethylpentane}

00540-84-1

114.23

5.7477

0.596

6.812

1,257.8

220.74

76

212

211

Isopentane





















{2-methyl butane}

00078-78-4

72.15

5.18

9.426

6.790

1,020.0

233.10

61

83

82

Isopentene





















{2-methyl 2-butene}

00513-35-9

70.13

5.53

6.210

6.922

1,098.6

233.26

37

159

100

Isoprene





















{2-methyl 1,3-butadiene}

00078-79-5

68.12

5.67

7.446

6.091

706.9

186.10

62

93

93

Isopropyl alcohol





















{isopropanol}

00067-63-0

60.10

6.5277

0.443

7.736

1,357.4

197.34

134

193

180

Isopropyl benzene





















{cumene}

00098-82-8

120.19

7.19

0.048

6.929

1,455.8

207.20

158

308

305

7.1-100

Liquid Storage TanksEMISSION FACTORS

44-06/Q218


-------




















Normal

Chemical
Name

CAS
Registry
No.

Molecular
Weight

Liquid
Density"
(lb/gal)





Antoine's Equation®-



Boilin
Poin
(°F)

g

t









True

Constants

Temperature
Ranged

I









Vapor





















Pressure*
at 60 °F
(psia)

A

dimension less

B

(°C)

C
(°C)

Minimum
(°F)

Maximum
(°F)

I

Isopropylbenzene





















(1-methyl-2)

00527-84-4

134.22

7.32

0.017

7.417

1,880.5

236.27

178

355

350

Methacrylonitrile





















{2-methyl 2-propenenitrile}

00126-98-7

67.09

6.68

0.886

6.999

1,353.6

238.03

-48

194

194

Methane

00074-82-8

16.04

3.53"260

4567

7.096

516.7

284.37

-262

-117

-260

Methyl acetate





















{methyl ester acetic acid}

00079-20-9

74.08

7.80

2.703

7.079

1,164.4

220.46

35

133

134

Methyl acrylate





















{methyl ester 2-propenoic

00096-33-3

86.09

7.96

1.058

7.198

1,338.7

229.63

-47

176

177

acid}





















Methyl alcohol





















{methanol}

00067-56-1

32.04

6.61

1.476

8.079

1,581.3

239.65

59

183

148

Methyl ethyl ketone





















{2-butanone}

00078-93-3

72.11

6.6877

1.081

6.864

1,150.2

209.25

106

207

176

Methyl isobutyl ketone

00108-10-1

100.16

6.6577

0.219

6.828

1,254.1

201.61

71

241

241

Methyl methacrylate

00080-62-6

100.12

7.88

0.416

8.253

1,945.6

265.58

102

192

213

Methyl propyl ether

00557-17-5

74.12

6.1455

6.017

6.563

903.6

206.46

31

103

102

Methyl styrene (alpha)®

00098-83-9

118.18

7.60

0.024

6.924

1,486.9

202.40





329



Methylcyclohexane®

00108-87-2

98.19

6.42

0.558

6.823

1,270.8

221.42

27

261

214



Methylcyclopentane

00096-37-7

84.16

6.25

1.738

6.863

1,186.1

226.04

59

163

161

Methyldichlorosilane®-"

20156-50-7

115.03

8.91

5.718

7.028

1,167.8

240.70

34

106

I

Methylene chloride

00075-09-2

84.93

11.07

5.640

7.412

1,327.0

252.68

-40

104

104

Methylhexane (2)

00591-76-4

100.20

5.66

0.799

6.882

1,240.9

220.10

65

196

194

Methylhexane (3)B

00589-34-4

100.20

5.72

0.744

6.874

1,243.8

219.63

68

199

1971

Methylpentane (2)

00107-83-5

86.18

5.4377

2.730

6.839

1,135.4

226.57

55

142

142

Methyl-tert-butyl ether®



















I

{MTBE}

01634-04-4

88.15

6.18

3.226

6.867

1,116.1

224.74

125

431

131

Morpholine e

00110-91-8

87.12

8.35

0.109

7.718

1,745.8

235.00

32

111

2631

Naphthalene

00091-20-3

128.17

8.56

0.0024

7.146

1,831.6

211.82

177

354

422

Nitrobenzene

00098-95-3

123.11

10.05

0.0022

7.091

1,727.6

199.71

273

411

412

Nitromethane

00075-52-5

61.04

9.49

0.415

7.281

1,446.2

227.52

132

277

214

Nonadecane(n)

00629-92-5

268.52

6.56

3.64E-07

33.303

28,197

725.94

91

131

624

Nonane (n)

00111-84-2

128.26

5.99

0.037

6.700

1,492.9

217.26

-64

94

303

Octadecane (n)

00593-45-3

254.49

6.4882

6.16E-07

7.207

2,069.0

161.22

346

602

592

Octane (n)

00111-65-9

114.23

5.8377

0.142

8.076

1,936.3

253.01

-70

75

258

Octanol (1)

00111-87-5

130.23

6.9077

0.00061

9.352

2,603.4

224.35

68

176

383

Octene (1)

00111-66-0

112.21

5.97

0.196

6.933

1,353.5

212.76

113

252

251

Pentachloroethane

00076-01-7

202.29

14.02

0.040

6.643

1,342.3

196.51

77

324

324

¦H-06/0^18	Liquid Storage Tanks	7.1-101


-------






















Normal

CI
Ni

lemical
ime

CAS
Registry
No.

Molecular
Weight

Liquid
Density"
(lb/gal)





Antoine's Equation®-



Boiling
Point
(°F)

1







True

Constants

Temperature
Ranged













Vapor























Pressure*
at 60 °F
(psia)

A

dimension less

B

(°C)

C
(°C)

Minimum
(°F)

Maximum
(°F)



Pentadiene (1,2)

00591-95-7

68.12

5.78

4.718

6.936

1,125.5

231.88

-76

-19

113

Pentadiene (1,4)

00591-93-5

68.12

5.52

10.06

7.035

1,108.2

241.05

-110

65

79

Pentadiene (2,3)

00591-96-8

68.12

5.80

4.223

7.263

1,256.2

239.57

-76

-15

119

Pentane (n)

00109-66-0

72.15

5.23

6.884

6.864

1,070.6

232.70

24

155

97

Pentene (1)

00109-67-1

70.13

5.35

8.671

6.786

1,014.3

229.78

55

87

88

P^ntyne (1)e

00627-19-0

68.12

5.76

5.657

6.967

1,092.5

227.18

-47

142

104

Phenanthrene

00085-01-8

178.23

8.18

3.37E-06

7.394

2,428.5

202.19

212

302

635

Phenol

00108-95-2

94.11

8.80113

0.003

7.122

1,509.7

174.20

225

359

359

Phosgene

00075-44-5

98.92

11.4577

19.43

7.146

1,072.7

243.30

47

345

46

Picoline (3)





















{3-methyl pyridine}

00108-99-6

93.13

7.98

0.064

7.054

1,484.3

211.54

165

364

291

Propane

00074-98-6

44.10

4.1277

111

6.858

819.3

248.73

-45

117

-44

Propanethiol (1)

00107-03-9

76.16

7.02

1.943

6.929

1,183.4

224.63

76

216

154

Propanethiol (2)

00075-33-2

76.16

6.80

3.590

6.877

1,113.9

226.16

51

186

131

Propyl alcohol (n)





















{propanol (1)}

00071-23-8

60.10

6.6777

0.218

8.189

1,690.9

221.35

67

207

207

Pr|opyl nitrate (n)e





















{propyl ester nitric acid}

00627-13-4

105.09

8.80

0.261

6.955

1,294.4

206.70

32

158

231

Propylamine (n)





















{1-propanamine}

00107-10-8

59.11

5.99

3.990

6.926

1,044.0

210.84

73

172

120

Propylene





















{propene}

00115-07-1

42.08

4.22

132

6.850

795.8

248.27

-161

-53

-54

Propylene glycol (1,2)m





















{1,2 propanediol}

00057-55-6

76.09

8.65

0.00094

8.208

2,085.9

203.54





368

Propylene oxide

00075-56-9

58.08

7.1732

7.101

6.970

1,065.3

226.28

-100

94

95

Pyridine

00110-86-1

79.10

8.20

0.233

7.038

1,371.4

214.65

153

307

240

Resorcinol

00108-46-3

110.11

10.6177

6.65E-06

8.398

2,687.2

210.99

305

530

532

Styrene

00100-42-5

104.15

7.56

0.066

7.095

1,525.1

216.77

86

293

295

Tetrachloroethane (1,1,1,2)

00630-20-6

167.85

12.86

0.133

6.906

1,370.4

210.25

139

266

271

Tetrachloroethane (1,1,2,2)

00079-34-5

167.85

13.32

0.037

6.091

959.6

149.78

77

266

295

Tetrachloroethylene

00127-18-4

165.83

13.54

0.213

7.056

1,440.8

223.98

82

226

250

Tetrahydrofuran

00109-99-9

72.11

7.42

2.039

6.996

1,202.9

226.33

74

211

151

Toluene

00108-88-3

92.14

7.24

0.331

7.017

1,377.6

222.64

32

122

231

Trichloroethane (1,1,1)

00071-55-6

133.40

11.18

1.650

8.761

2,210.2

308.05

22

62

165

Trichloroethane (1,1,2)

00079-00-5

133.40

12.02

0.245

6.945

1,310.3

208.74

122

237

237

Trichloroethylene

00079-01-6

131.39

12.22

0.817

6.429

974.5

187.34

64

188

189

Trichloropropane (1,2,3)

00096-18-4

147.43

11.59

0.031

7.532

1,818.9

232.52

48

316

313

Tridecane (n)

00629-50-5

184.36

6.31

2.46E-04

7.003

1,689.1

174.28

283

457

453

7.1-102

Liquid Storage TanksEMISSION FACTORS

44-06/Q218


-------




















Normal

Chemical
Name

CAS
Registry
No.

Molecular
Weight

Liquid
Density"
(lb/gal)





Antoine's Equation®-



Boilin
Poin
(°F)

g

t









True

Constants

Temperature
Ranged

I









Vapor





















Pressure4
at 60 °F
(psia)

A

dimension less

B

(°C)

C
(°C)

Minimum
(°F)

Maximum
(°F)

I

Trifluoroethane





















(1,1,2-trichloro-1,2,2f

00076-13-1

187.37

13.0577

4.376

6.880

1,099.9

227.50

-13

181

118



Trimethylbenzene (1,2,4)e

00095-63-6

120.19

7.31

0.020

7.044

1,573.3

208.56

126

388

337



Trimethylchlorosilane





















{chlorotrimethylsilane}

00075-77-4

108.64

7.1577

3.068

6.951

1,191.0

235.15

37

132

136

Trimethylpentane (2,2,3)e

00564-02-3

114.23

5.7477

0.378

6.825

1,294.9

218.42





230



Trimethylpentane (2,3,3)e

00560-21-4

114.23

6.06

0.317

6.844

1,328.1

220.38





238



Trimethylpentane (2,3,4)

00565-75-3

114.23

6.00

0.314

7.031

1,420.7

228.53

-59

308

237

Undecane(n)

01120-21-4

156.31

6.18

0.0035

6.977

1,572.5

188.02

220

387

383

Vinyl acetate





















{acetic acid ethenyl ester}

00108-05-4

86.09

7.78

1.396

7.215

1,299.1

226.97

71

162

163

Vinylidene chloride





















{1,1 -dichloro ethene}

00075-35-4

96.94

10.13

8.096

6.983

1,104.7

237.75

-19

90

88

Xylene (m)e



















I

{1,3-dimethyl benzene}

00108-38-3

106.17

7.21

0.090

7.009

1,462.3

215.11

82

331

283

Xylene (o)e



















I

{1,2-dimethyl benzene}

00095-47-6

106.17

7.3550

0.071

6.999

1,474.7

213.69

90

342

291

Xylene (p)





















{1,4-dimethyl benzene}

00106-42-3

106.17

7.19

0.097

7.021

1,474.4

217.77

56

355

281

NOTE Synonyms are shown in braces {}. Prefixes are shown in parentheses i

a Reference 22Properties are from the NIST Standard Reference Database Number 69^. except where noted otherwise.
b Liquid densities are from CRC Handbook of Chemistry and Physics, 83rd edition^. The superscript denotes the temperature in 1
superscript is given the density is for 68 °F.

Vif-n<>

Vapor pressure Pka in psia = (0.019337) 10

(7^-32)5/9+0]

where Tla is the temperature in °F.

^ Use of this equation for temperatures outside the indicated temperature range may result in loss of accuracy.

e Values of.l, B, and C and the temperature range (if any) for the 3 constant Antoine's equation are from Lange's Handbook of Chemistry&r
§ Values of A, B, and C and the temperature range for the 3 constant Antoine's equation are from Lisal et al.*34^

' Vapor pressures are calculated from the Antoine constants provided in this table.

' Values of A, B, and C and the temperature range for the 3 constant Antoine's equation are from Stephenson and MalanowskP^

k Boiling point from Lange's Handbook of Chemistn^K

"Antoine constants from API MPMS Chapter 19.1, Third Edition131 and not confirmed from a primary source.
" Density from API MPMS Chapter 19.1, Third Edition^; not confirmed from a primary source.

* Reference 11.

+4-06/0^18

Liquid Storage Tanks

7.1-103


-------
Table 7.1-4. ASTM DISTILLATION SLOPE FOR. SELECTED REFINED PETROLEUM STOCKSa
HEIGHT OF THE LIQUID HEEL AND VAPOR SPACE UNDER A LANDED FLOATING ROOF3

Scenario	Condition	Expression for height of the vapor space (hr)

General Expression Slope convention:

Sb is expressed in ft/ft; positive '?r
for cone dow n, negative for
cone up.

f, sbd
'"+ 6

j hle

Full liauid heel he -

h + ^ j hv - hd - hi

Partial liauid heel

(this condition may occur hie = the height that would result
after normal pumpout of from spreading the available
a tank with a cone-down volatile materials evenly over a
bottom or be created flat tank bottom,
during the tank cleaning hu =

process of any tank that (volume of heel, ft3) (, SB 1) )
had a full liquid heel after 2 , \ + clingagc h,, i
normal pumpout) v ) _

volume of heel, ft'1 j ( 0.01 in. j

ttD2/4 J v 12 in./ft J

No significant amount of

volatile material /?/,. = 0 /?,¦ =
remaining

(drain dry tanks or any
tank after sludge
removal)



)

Flat bottom	Sb = 0

(including slight cone-up h/L. is evaluated per the applicable /?,¦ = hj-hk {= hd-hu given Sb = 0}

bottoms)	case above.	

where:

lid = deck leg height at the tank shell, ft

hi = height of liquid at the tank shell, ft

hie = effective liquid height during roof landing, ft

hv = vapor space height under landed floating roof, ft

Sb = tank cone bottom slope, ft/ft

a Reference 23.

7.1-104

Liquid Storage TanksEMISSION FACTORS

44-06/07-18


-------
Table 7.1-5. VAPOR PRESSURE EQUATION CONSTANTS FOR. ORGANIC LIQUIDS9LEL

VALUES FOR SELECTED COMPOUNDS3

LEL

Compound	(volume percent in air)

Heptane (C7)

1.05

Hexane (C6)

1.1

Pentane (C5)

1.5

Butane (C4)

1.9

Propane (C3)

2.1

Ethane (C2)

3.0

Methane (CI)

5.0

a Reference 28.

+4-06/0^18

Liquid Storage Tanks

7.1-


-------
Table 7.1-6. PAINT SOLAR ABSORPTANCE FOR. FIXED ROOF TANKS





Reflective Condition

Surface Color

Shade or TvDe



(see Note 1)







New

Averaqe

Aaed

White



0.17

0.25

0.34

Aluminum

Specular

0.39

0.44

0.49

Aluminum

Diffuse

0.60

0.64

0.68

Beiae/Cream



0.35

0.42

0.49

Black



0.97

0.97

0.97

Brown



0.58

0.62

0.67

Grav

Liqht

0.54

0.58

0.63

Grav

Medium

0.68

0.71

0.74

Green

Dark

0.89

0.90

0.91

Red

Primer

0.89

0.90

0.91

Rust

red iron oxide

0.38

0.44

0.50

Tan



0.43

0.49

0.55

Aluminum









(see Note 2)

mill finish, unpainted

0.10

0.12

0.15

NOTE 1 Reflective condition definitions:







New: For paint, paint still retains the fresh shine of havinq been recently

applied: for mill-finish aluminum, surface is shinv. This was previously

labeled "Good."







Averaqe: For paint, paint is in qood condition, but the initial shine has

faded: for mill-finish aluminum, surface is oxidized but still briqht. The

value qiven in each case is the averaqe of the New and the Aqed values

for that case, and does not represent new data.





Aqed: For paint, paint is noticeably faded and dull: for mill-finish aluminum.

surface is dull. This was previously labeled

"Poor."





NOTE 2 This refers to aluminum as the base metal, rather than aluminum-

colored paint.

Paint Color

Paint Shade or Type

Paint Factors (a)

Paint Condition

Good

Poor

Aluminum

Specular

q 39

049

Aluminum

Diffuse

Q gQ

Q fig

Aluminum^

Mill finish, unpainted

040

04#

Beige/Cream



04£

049

Brown



0^

O^

Gray

Light

0^4

O^

Gray

Medium

Q fig

044

Green

Dark

Q gg

0^4

P p/4

TtUu

Primer

Q gg

0^4

Rust

Red iron oxide

04&

0^0

1 111

itTTT



043-

04#

White

NA

04?

044

vfotes:

a Reference 22X. If specific information is not available, a white shell and roof, with the paint in good
average condition, can be assumed to represent the most common or typical tank surface in use. If the

7.1-106

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


-------
tank roof and shell are painted a different color, a is determined from a = (a r + a s)/2; where OC r
is the tank roof paint solar absorptance and (X s is the tank shell paint solar absorptance.
bThis refers to aluminum as the base metal, rather than aluminum colored paint.

NA - not applicable.

+4-06/0^18

Liquid Storage Tanks

7.1-107


-------
^1

o

00

Table 7.1-7. METEOROLOGICAL DATA (Tax, Tan. V. L Pa) FOR SELECTED U.S. LOCATIONSa

CO
00 CO

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Birmingham, AL

T_4N

°F

31.3

34.5

42.3

49.3

57.7

65.1

69.4

68.7

63.0

50.2

41.5

34.9

50.7



Tax

°F

51.6

56.8

66.0

74.7

81.0

87.4

90.0

89.1

83.8

74.7

64.6

55.8

73.0



V

mi/hr

7.6

8.5

8.5

8.1

6.7

5.8

5.6

5.4

6.3

6.0

6.7

7.4

6.9



I

Btu/ft2/day

793

1046

1395

1744

1902

1966

1871

1775

1522

1268

888

729

1395



Pa

lb/in2

























14.45

Huntsville, AL

T_4N

°F

29.1

32.5

40.8

48.9

57.4

64.9

68.9

67.8

61.5

49.3

40.5

33.1

49.6



Tax

°F

48.2

53.4

62.8

72.5

79.3

86.5

89.1

88.9

82.8

73.0

62.4

52.5

71.1



V

mi/hr

9.2

9.8

10.1

9.4

7.8

6.7

6.3

6.0

6.9

7.4

8.5

9.4

8.1



I

Btu/ft2/day

761

983

1300

1680

1871

1997

1934

1807

1490

1236

856

666

1395



Pa

lb/in2

























14.43

Mobile, AL

T_4N

°F

39.9

42.6

50.2

57.0

64.4

70.7

73.2

72.9

68.7

57.4

49.1

43.2

57.4



Tax

°F

59.7

63.7

70.9

78.4

84.6

90.0

91.2

90.5

86.9

79.5

70.3

63.0

77.4



V

mi/hr

10.1

10.5

10.5

10.3

8.7

7.6

6.7

6.5

7.6

8.1

9.2

9.8

8.7



I

Btu/ft2/day

856

1110

1395

1712

1871

1871

1775

1649

1490

1332

983

793

1395



Pa

lb/in2

























14.65

Montgomery, AL

T_4N

°F

35.8

38.8

45.7

52.9

60.8

67.8

71.4

70.9

66.0

53.2

44.6

38.7

54.0



Tax

°F

56.3

60.8

68.5

76.5

82.9

89.4

91.0

90.3

87.1

78.3

68.7

60.3

75.7



V

mi/hr

7.6

8.1

8.3

7.4

6.0

5.6

5.6

5.1

5.8

5.6

6.5

7.4

6.7



I

Btu/ft2/day

856

1110

1427

1807

1966

2029

1934

1807

1554

1332

951

793

1458



Pa

lb/in2

























14.66

Anchorage, AK

T_4N

°F

8.4

11.5

18.1

28.6

38.8

47.1

51.6

49.5

41.5

28.8

15.1

10.0

29.1



Tax

°F

21.4

25.9

33.1

42.8

54.3

61.5

65.1

63.0

55.2

40.5

27.1

22.5

42.6



V

mi/hr

6.5

6.9

6.7

7.4

8.3

8.5

7.2

6.9

6.7

6.7

6.5

6.3

6.9



I

Btu/ft2/day

95

317

729

1141

1458

1554

1458

1110

698

349

127

63

761



Pa

lb/in2

























14.56

Annette, AK

T_4N

°F

29.7

32.2

34.0

37.0

42.3

47.8

52.0

52.3

48.0

41.9

34.7

31.5

40.3



Tax

°F

38.8

41.9

44.8

49.5

55.8

60.8

64.6

64.9

60.3

51.8

43.9

39.9

51.4



V

mi/hr

11.0

11.2

9.8

9.8

8.5

8.3

7.6

7.6

8.3

10.7

11.2

10.7

9.4



I

Btu/ft2/day

190

380

698

1110

1490

1585

1554

1268

856

444

222

159

824



Pa

lb/in2

























14.63

Barrow, AK

T_4N

°F

-19.3

-23.6

-21.1

-9.0

14.4

29.7

33.6

33.3

27.0

00
CO

-6.9

-17.1

4.1



Tax

°F

-7.4

-11.7

-9.0

4.6

24.3

38.3

45.0

42.3

33.8

18.1

3.6

-5.3

14.7


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





o

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

12.3

11.2

11.4

11.6

11.9

11.9

11.6

12.5

13.4

13.0

12.5

11.6

12.1



I

Btu/ft2/day

0

95

507

1173

1490

1554

1427

824

412

159

0

0

634



Pa

lb/in2

























14.74

Bethel, AK

T_4N

°F

0.3

-0.8

5.4

15.6

31.6

42.3

47.7

46.2

38.3

23.7

10.9

2.1

21.9



Tax

°F

12.9

12.7

21.0

31.3

48.2

58.8

62.2

59.5

52.0

35.1

22.6

14.7

36.0



V

mi/hr

14.5

15.2

14.1

13.0

11.6

11.2

10.7

11.0

11.6

12.5

13.2

14.3

12.8



I

Btu/ft2/day

127

349

793

1236

1427

1522

1363

1015

698

380

159

63

761



Pa

lb/in2

























14.55

Bettles, AK

T_4N

°F

-20.4

-18.2

-8.7

9.7

33.4

46.9

49.3

43.9

32.4

12.0

-8.9

-16.8

12.9



Tax

°F

-4.9

0.3

14.4

31.5

52.9

67.5

69.6

62.8

48.9

25.0

5.2

-1.8

30.9



V

mi/hr

6.0

6.3

7.2

7.6

7.6

7.2

6.7

6.0

6.7

6.7

6.0

5.6

6.7



I

Btu/ft2/day

32

190

634

1236

1680

1807

1585

1110

666

254

63

0

761



Pa

lb/in2

























14.33

Big Delta, AK

T_4N

°F

-11.0

-6.2

2.5

20.5

36.9

47.1

50.7

46.0

35.8

17.8

-1.7

-8.5

19.2



Tax

°F

3.0

10.6

24.4

40.3

56.7

66.4

69.6

64.8

53.2

31.3

12.7

5.4

36.5



V

mi/hr

12.1

10.5

9.2

8.5

8.5

7.8

6.5

7.2

8.5

8.7

10.3

11.6

9.2



I

Btu/ft2/day

63

254

729

1236

1617

1744

1649

1236

761

349

95

32

824



Pa

lb/in2

























13.97

Cold Bay, AK

T_4N

°F

24.1

22.8

25.0

28.6

34.9

40.8

46.0

47.1

43.2

34.9

29.8

26.6

33.6



Tax

°F

33.1

32.0

34.9

37.9

44.4

50.4

55.0

55.9

52.2

44.2

38.8

35.2

43.0



V

mi/hr

17.9

17.9

17.2

17.9

16.3

15.9

15.7

16.1

16.6

17.0

17.4

17.4

17.0



I

Btu/ft2/day

190

380

698

983

1173

1236

1173

951

698

444

222

127

698



Pa

lb/in2

























14.55

Fairbanks, AK

T_4N

°F

-18.6

-14.4

-1.7

20.5

37.9

49.5

52.5

47.1

36.1

18.1

-5.6

-14.8

17.2



Tax

°F

-1.7

7.2

23.7

41.0

59.4

70.2

72.3

66.4

54.9

32.0

10.9

1.8

36.5



V

mi/hr

3.4

4.3

5.6

6.9

7.8

7.6

6.9

6.5

6.3

5.6

3.8

3.4

5.6



I

Btu/ft2/day

32

254

729

1268

1617

1775

1617

1173

729

317

95

0

793



Pa

lb/in2

























14.42

Gulkana, AK

T_4N

°F

-13.9

-7.1

2.7

19.9

32.5

42.3

46.4

42.3

33.4

19.6

-2.6

-10.8

17.1



Tax

°F

2.5

13.6

28.0

41.5

54.9

64.2

68.4

64.8

54.1

35.2

12.7

4.6

37.0



V

mi/hr

3.6

4.9

6.0

7.6

8.3

8.5

7.6

7.8

7.2

6.3

4.0

4.0

6.3



I

Btu/ft2/day

95

317

793

1300

1617

1744

1680

1300

824

380

127

63

856



Pa

lb/in2

























13.81

King Salmon, AK

T_4N

°F

7.5

6.6

14.2

23.4

34.0

41.4

46.4

46.4

39.7

25.2

15.1

8.2

25.7


-------


D

£
&

iri

v.

EE

co

00 CO
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n

H
O

fa

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Tax

°F

22.1

22.8

30.7

39.0

50.9

58.6

63.0

61.3

54.7

39.7

29.7

23.4

41.4



V

mi/hr

11.0

11.4

11.4

11.2

11.2

11.0

10.1

10.5

10.5

10.3

10.5

11.0

10.7



I

Btu/ft2/day

159

380

761

1141

1395

1458

1363

1078

729

444

190

95

761



Pa

lb/in2

























14.58

Kodiak, AK

T_4N

°F

24.6

25.0

27.0

31.5

37.6

43.5

48.2

48.4

43.3

34.2

28.8

25.2

34.9



Tax

°F

35.1

36.1

38.8

43.7

49.5

55.6

60.4

61.9

56.7

47.1

39.9

36.3

46.8



V

mi/hr

12.3

12.3

11.9

11.6

10.3

9.2

7.6

8.1

9.2

11.0

12.1

12.3

10.5



I

Btu/ft2/day

159

349

729

1110

1363

1458

1427

1205

793

476

222

95

793



Pa

lb/in2

























14.55

Kotzebue, AK

T_4N

°F

-7.4

-11.9

-8.0

2.3

24.4

37.8

48.6

47.3

37.0

18.1

2.5

-7.4

15.3



Tax

°F

5.5

2.3

8.8

20.3

37.9

49.6

59.2

57.0

46.9

27.7

13.1

5.5

27.9



V

mi/hr

13.9

12.3

11.4

11.9

11.6

12.1

12.5

12.5

13.4

13.2

14.3

14.1

12.8



I

Btu/ft2/day

32

190

666

1300

1744

1744

1522

1046

634

285

63

0

761



Pa

lb/in2

























14.66

McGrath, AK

T_4N

°F

-17.9

-14.3

-2.9

16.0

34.5

45.1

48.9

45.0

35.4

18.0

-3.6

-14.6

15.8



Tax

°F

0.3

9.0

23.4

37.0

54.5

65.5

68.4

63.5

52.9

31.3

12.4

2.7

35.1



V

mi/hr

3.1

4.5

5.6

6.9

6.9

6.7

6.3

6.3

6.3

5.8

4.0

3.4

5.6



I

Btu/ft2/day

95

317

761

1332

1522

1617

1458

1110

698

349

127

32

793



Pa

lb/in2

























14.46

Nome, AK

T_4N

°F

-0.8

-4.5

-0.2

9.7

29.1

38.8

45.1

44.1

36.3

22.3

9.3

-0.6

19.0



Tax

°F

14.7

12.2

17.4

25.5

42.1

52.9

57.7

56.1

48.7

33.6

22.5

15.1

33.3



V

mi/hr

11.6

10.3

10.1

10.5

10.3

10.1

10.1

11.0

11.6

11.0

11.4

11.2

10.7



I

Btu/ft2/day

63

254

729

1363

1680

1744

1458

1046

666

317

95

32

793



Pa

lb/in2

























14.63

St. Paul Island, AK

T_4N

°F

22.5

18.0

19.4

23.9

31.3

37.0

42.4

44.4

40.3

33.6

28.9

24.8

30.6



Tax

°F

30.7

27.0

28.9

32.7

39.4

45.9

49.6

51.1

48.7

42.1

37.0

33.3

38.8



V

mi/hr

19.2

19.9

18.6

17.9

15.2

13.6

12.3

13.6

15.7

17.9

18.8

19.7

16.8



I

Btu/ft2/day

159

380

761

1110

1236

1268

1141

919

698

412

190

127

698



Pa

lb/in2

























14.59

Talkeetna, AK

T_4N

°F

0.7

3.9

9.9

22.5

33.8

44.4

48.9

45.7

36.7

23.2

7.9

2.8

23.4



Tax

°F

19.2

25.3

33.4

43.3

55.9

64.4

67.6

64.6

55.6

39.4

25.2

19.8

42.8



V

mi/hr

6.5

6.0

6.0

5.6

5.6

5.8

5.4

4.5

4.3

4.7

6.0

6.3

5.6



I

Btu/ft2/day

95

317

729

1300

1522

1585

1490

1141

729

380

127

63

793



Pa

lb/in2

























14.45


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Yakutat, AK

Tan

°F

18.7

21.0

23.7

29.1

36.5

43.3

47.8

46.6

41.0

34.7

25.2

21.0

32.4



Tax

°F

31.5

35.1

38.1

43.5

50.0

55.6

59.4

59.7

55.2

47.1

37.2

33.1

45.5



V

mi/hr

7.2

6.9

6.7

6.7

7.2

6.9

6.5

6.3

6.7

7.6

6.9

7.2

6.9



I

Btu/ft2/day

127

317

698

1110

1300

1395

1332

1078

698

349

159

95

729



Pa

lb/in2

























14.63

Flagstaff, AZ

T_4N

°F

15.3

17.8

21.4

26.8

33.3

41.4

50.5

48.9

41.2

30.9

22.5

15.8

30.6



Tax

°F

42.3

45.3

49.3

57.7

67.5

78.3

81.9

79.3

73.2

63.3

51.1

43.3

61.0



V

mi/hr

6.5

6.3

6.9

7.4

7.2

6.7

5.1

4.5

5.1

5.4

6.3

5.8

6.0



I

Btu/ft2/day

983

1268

1617

1997

2283

2441

2029

1871

1712

1395

1046

888

1617



Pa

lb/in2

























11.43

Phoenix, AZ

T_4N

°F

41.2

44.8

48.7

55.2

63.9

72.9

81.0

79.2

72.9

60.8

48.9

41.7

59.4



Tax

°F

65.8

70.7

75.6

84.6

93.6

103.5

106.0

103.6

98.2

88.2

74.8

66.2

85.8



V

mi/hr

5.6

6.3

7.2

7.6

7.6

7.2

7.6

7.2

6.7

6.3

5.8

5.6

6.7



I

Btu/ft2/day

1015

1363

1744

2251

2536

2663

2410

2251

1934

1554

1141

951

1807



Pa

lb/in2

























14.13

Prescott, AZ

T_4N

°F

21.9

24.1

28.0

33.4

41.2

49.8

57.9

55.8

48.7

38.1

28.6

22.3

37.6



Tax

°F

50.4

54.0

57.4

64.9

73.9

84.6

88.2

84.9

80.1

71.2

59.5

51.1

68.4



V

mi/hr

6.9

7.8

9.2

9.4

9.6

9.2

7.8

6.9

7.6

7.4

7.4

6.7

8.1



I

Btu/ft2/day

983

1236

1617

2093

2378

2536

2188

1997

1807

1458

1078

888

1680



Pa

lb/in2

























12.28

Tucson, AZ

T_4N

°F

38.7

41.0

44.6

50.4

57.9

67.8

73.6

72.1

67.5

56.7

45.7

39.7

54.7



Tax

°F

63.9

67.8

72.9

81.1

90.0

99.7

99.3

96.8

93.4

84.4

72.7

64.2

82.2



V

mi/hr

8.5

8.5

8.9

9.6

9.2

9.2

8.9

8.3

8.7

8.5

8.3

8.1

8.7



I

Btu/ft2/day

1078

1395

1775

2251

2505

2568

2251

2124

1902

1585

1205

1015

1807



Pa

lb/in2

























13.42

Fort Smith, AR

T_4N

°F

25.5

30.2

39.2

48.6

57.7

65.8

70.0

68.7

61.9

48.7

38.5

29.3

48.7



Tax

°F

48.4

53.4

64.0

74.1

80.4

88.0

93.0

92.5

85.3

75.7

62.8

51.3

72.3



V

mi/hr

8.1

8.5

9.4

8.9

7.6

6.5

6.3

6.3

6.7

6.7

7.8

8.3

7.6



I

Btu/ft2/day

824

1078

1395

1712

1902

2061

2093

1902

1522

1236

888

729

1458



Pa

lb/in2

























14.52

Little Rock, AR

T_4N

°F

29.1

33.3

42.3

50.7

59.0

67.5

71.4

69.8

63.5

50.9

41.5

33.1

51.1



Tax

°F

48.9

54.0

64.0

73.4

81.3

89.2

92.5

91.4

84.6

75.0

62.8

52.5

72.5



V

mi/hr

8.3

8.7

9.2

8.5

7.2

6.7

6.3

6.0

6.3

6.5

7.8

7.8

7.4



I

Btu/ft2/day

793

1046

1363

1680

1934

2061

2029

1871

1522

1236

856

698

1427


-------
<1

K>

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

z

hr1

o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.62

Areata, CA

T_4N

°F

38.8

40.5

41.0

41.5

45.0

48.2

50.2

50.7

48.4

45.5

42.6

39.4

44.2



Tax

°F

54.0

54.9

54.9

56.1

58.5

61.3

63.0

63.3

63.9

61.0

57.6

54.0

58.5



V

mi/hr

6.5

7.2

7.8

7.6

7.6

6.7

6.3

5.4

5.1

5.1

6.3

6.3

6.5



I

Btu/ft2/day

571

793

1141

1585

1839

1902

1871

1585

1395

983

634

507

1236



Pa

lb/in2

























14.65

Bakersfield, CA

T_4N

°F

38.7

42.6

45.9

50.2

57.4

64.0

69.6

68.5

63.5

54.9

44.8

38.3

53.2



Tax

°F

56.8

63.9

68.9

75.9

84.6

92.5

98.4

96.6

90.1

80.8

66.7

56.5

77.7



V

mi/hr

5.6

6.0

6.7

7.4

8.1

7.8

7.4

6.9

6.5

6.0

5.6

5.6

6.7



I

Btu/ft2/day

729

1046

1490

1966

2346

2568

2536

2283

1871

1395

919

666

1649



Pa

lb/in2

























14.47

Daggett, CA

T_4N

°F

36.7

41.4

46.0

51.4

59.5

67.5

73.9

72.9

65.7

55.6

44.4

36.7

54.3



Tax

°F

60.6

66.0

70.5

78.1

87.4

97.9

103.8

101.5

93.7

82.8

69.4

60.4

81.0



V

mi/hr

7.8

10.1

13.2

14.1

15.2

14.3

12.3

11.0

10.5

9.4

9.6

8.5

11.4



I

Btu/ft2/day

1015

1332

1744

2219

2505

2663

2536

2314

1997

1554

1141

919

1839



Pa

lb/in2

























13.73

Fresno, CA

T_4N

°F

37.4

40.5

43.3

47.3

53.8

60.4

65.1

63.9

58.8

50.7

42.4

37.0

50.2



Tax

°F

54.1

61.7

66.6

75.0

84.2

92.7

98.6

96.6

90.1

79.7

64.8

53.8

76.5



V

mi/hr

4.9

5.6

6.7

7.6

8.5

8.5

7.6

6.9

6.3

5.1

4.7

4.7

6.5



I

Btu/ft2/day

666

1015

1490

1997

2378

2568

2536

2283

1871

1363

856

602

1649



Pa

lb/in2

























14.56

Long Beach, CA

T_4N

°F

45.0

46.9

48.9

51.8

56.3

59.7

63.3

64.8

62.8

57.7

50.4

45.0

54.3



Tax

°F

66.7

67.6

68.0

71.4

73.2

77.0

82.8

84.0

82.0

78.4

72.1

66.9

74.1



V

mi/hr

5.6

6.3

6.9

7.4

7.4

6.9

6.7

6.7

6.3

5.6

5.6

5.1

6.5



I

Btu/ft2/day

888

1141

1490

1902

2029

2124

2314

2124

1712

1332

983

824

1585



Pa

lb/in2

























14.71

Los Angeles, CA

T_4N

°F

47.8

49.3

50.5

52.9

56.3

59.5

62.8

64.2

63.1

59.2

52.9

47.8

55.6



Tax

°F

65.7

65.8

65.5

67.5

69.1

72.0

75.4

76.6

76.6

74.5

70.3

65.8

70.3



V

mi/hr

6.9

7.6

8.5

8.9

8.7

8.5

8.3

8.3

7.8

7.4

7.2

6.7

7.8



I

Btu/ft2/day

888

1141

1522

1934

2029

2093

2251

2061

1680

1332

1015

824

1554



Pa

lb/in2

























14.68

Sacramento, CA

T_4N

°F

37.8

41.4

43.2

45.5

50.4

55.2

58.1

57.9

55.8

50.4

43.3

37.8

48.0



Tax

°F

52.7

60.1

64.0

71.1

80.2

87.8

93.2

92.1

87.3

77.9

63.1

52.7

73.6



V

mi/hr

5.6

6.9

7.8

8.1

8.7

8.9

8.5

8.1

6.9

5.6

5.6

5.6

7.2


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

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P

CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

602

951

1363

1871

2283

2505

2505

2219

1807

1268

761

539

1554



Pa

lb/in2

























14.72

San Diego, CA

T_4N

°F

48.9

50.7

52.9

55.6

59.2

61.9

65.7

67.3

65.7

61.0

54.0

48.7

57.6



Tax

°F

65.8

66.6

66.4

68.4

69.1

71.6

76.3

77.7

77.2

74.7

70.0

66.0

70.9



V

mi/hr

6.0

6.7

7.8

8.3

8.3

8.1

7.8

7.8

7.6

6.9

6.3

5.8

7.4



I

Btu/ft2/day

983

1236

1554

1934

1997

2061

2188

2061

1712

1395

1078

919

1585



Pa

lb/in2

























14.71

San Francisco, CA

T_4N

°F

41.7

45.0

45.9

47.1

49.6

52.5

54.0

55.0

55.2

51.8

47.1

42.6

48.9



Tax

°F

55.6

59.4

60.8

63.9

66.6

70.3

71.6

72.3

73.6

70.2

62.4

56.1

65.1



V

mi/hr

7.4

8.9

10.7

12.3

13.9

13.9

13.9

12.8

11.2

9.6

8.3

7.8

11.0



I

Btu/ft2/day

698

951

1332

1807

2124

2283

2314

2061

1712

1236

793

634

1490



Pa

lb/in2

























14.75

Santa Maria, CA

T_4N

°F

38.3

40.5

41.4

42.4

46.4

50.4

52.9

54.0

52.3

48.0

42.3

37.8

45.5



Tax

°F

63.9

64.8

64.2

66.9

67.8

71.1

73.2

74.1

74.8

73.9

68.7

64.2

69.1



V

mi/hr

6.3

7.2

8.3

8.5

8.9

8.3

7.2

6.7

6.3

6.3

6.7

6.3

7.2



I

Btu/ft2/day

888

1173

1554

1966

2219

2346

2378

2156

1775

1395

1015

856

1649



Pa

lb/in2

























14.62

Alamosa, CO

T_4N

°F

-3.8

4.8

15.8

23.5

32.7

41.0

47.8

45.3

36.7

24.6

12.4

-0.6

23.4



Tax

°F

33.3

39.9

48.7

58.6

68.0

77.7

82.0

79.2

72.7

62.4

47.5

35.4

58.8



V

mi/hr

7.6

7.6

10.5

11.4

10.7

10.1

8.1

7.6

6.0

7.6

8.9

5.8

8.5



I

Btu/ft2/day

951

1268

1649

2029

2251

2441

2283

2061

1775

1427

1046

856

1680



Pa

lb/in2

























11.20

Colorado Springs, CO

T_4N

°F

16.2

19.2

24.6

33.1

42.1

51.1

57.0

55.2

47.1

36.3

25.0

17.4

35.4



Tax

°F

41.4

44.6

50.0

59.7

68.7

79.0

84.4

81.3

73.6

63.5

50.7

42.3

61.5



V

mi/hr

9.2

9.6

10.5

11.4

10.7

9.6

8.9

8.5

9.2

9.4

9.4

8.9

9.6



I

Btu/ft2/day

793

1078

1427

1807

1966

2188

2124

1902

1617

1268

888

729

1490



Pa

lb/in2

























11.76

Boulder, CO

T_4N

°F

16.2

20.1

25.9

34.5

43.5

52.3

58.6

56.8

47.7

36.3

25.3

17.4

36.1



Tax

°F

43.2

46.6

52.2

61.9

70.9

81.3

88.2

85.8

76.8

66.4

52.5

44.4

64.2



V

mi/hr

8.3

8.5

9.2

9.8

9.2

8.5

8.1

7.8

7.6

7.6

7.8

8.1

8.5



I

Btu/ft2/day

761

1046

1395

1775

1966

2188

2124

1902

1585

1205

824

666

1458



Pa

lb/in2

























12.12

Eagle, CO

T_4N

°F

3.7

10.4

19.8

26.4

33.8

40.5

47.1

45.3

37.0

26.8

17.4

6.1

26.2



Tax

°F

33.8

40.6

48.4

58.6

69.1

80.1

86.0

83.3

75.0

63.3

47.1

34.9

60.1


-------


D

£
&

iri

v.

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fa

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Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

4.3

4.7

5.8

6.9

6.7

6.0

5.6

5.4

5.6

4.7

4.7

4.0

5.4



I

Btu/ft2/day

761

1046

1395

1775

2029

2283

2188

1934

1617

1236

793

666

1490



Pa

lb/in2

























11.63

Grand Junction, CO

T_4N

°F

14.5

23.5

31.3

38.5

47.8

57.0

63.9

62.2

52.9

41.5

29.5

18.7

40.1



Tax

°F

35.4

45.3

55.6

65.8

75.9

87.6

93.6

90.5

81.1

67.6

51.4

38.7

65.8



V

mi/hr

5.6

6.5

8.1

9.2

9.4

9.4

9.2

8.7

8.5

7.6

6.7

5.6

7.8



I

Btu/ft2/day

793

1110

1458

1902

2219

2441

2346

2093

1744

1300

856

698

1585



Pa

lb/in2

























12.37

Pueblo, CO

T_4N

°F

14.2

19.6

26.1

35.8

45.7

54.1

61.2

59.0

50.2

36.7

24.3

15.4

36.9



Tax

°F

45.3

50.7

57.2

67.8

76.5

87.6

93.0

89.8

81.3

70.5

56.8

46.8

68.5



V

mi/hr

8.3

8.7

10.3

11.4

11.0

10.1

9.4

8.7

8.7

8.3

8.3

8.1

9.4



I

Btu/ft2/day

856

1141

1490

1902

2124

2346

2283

2061

1712

1332

919

761

1585



Pa

lb/in2

























12.40

Bridgeport, CT

T_4N

°F

21.9

23.2

30.9

39.7

50.0

59.2

65.7

65.1

57.6

47.1

38.1

27.7

43.9



Tax

°F

36.0

37.6

46.2

56.7

66.7

75.9

81.7

81.0

74.1

64.0

53.1

41.0

59.5



V

mi/hr

13.2

13.6

13.6

13.2

11.6

10.7

10.3

10.5

11.6

11.9

13.0

13.0

12.3



I

Btu/ft2/day

602

856

1173

1490

1712

1871

1839

1649

1332

983

634

507

1205



Pa

lb/in2

























14.74

Hartford, CT

T_4N

°F

15.8

18.7

28.0

37.6

47.7

56.8

62.2

60.4

51.8

40.6

32.7

21.4

39.6



Tax

°F

33.3

36.3

46.8

59.9

71.6

80.1

84.9

82.8

74.8

63.7

51.1

37.6

60.3



V

mi/hr

8.5

8.9

9.6

9.8

8.5

7.8

7.4

6.9

6.9

7.4

8.3

8.3

8.3



I

Btu/ft2/day

602

856

1173

1458

1712

1871

1871

1617

1300

951

602

476

1205



Pa

lb/in2

























14.65

Wilmington, DE

T_4N

°F

22.5

24.8

33.1

41.7

52.2

61.5

67.1

65.8

58.3

45.7

37.0

27.7

44.8



Tax

°F

38.7

41.9

52.2

62.6

72.9

81.3

85.6

84.0

77.7

66.6

55.6

43.9

63.7



V

mi/hr

10.1

10.3

11.4

11.0

9.4

8.5

7.8

7.6

8.1

8.3

9.4

9.6

9.4



I

Btu/ft2/day

634

919

1236

1554

1775

1966

1934

1712

1395

1046

698

539

1300



Pa

lb/in2

























14.72

Daytona Beach, FL

T_4N

°F

46.9

48.4

54.0

58.6

64.9

70.9

72.5

72.9

72.0

65.1

56.3

49.6

61.0



Tax

°F

68.0

69.4

74.8

80.1

84.6

88.0

89.8

89.1

86.7

81.5

75.6

70.3

79.9



V

mi/hr

8.5

9.2

9.4

9.2

8.5

7.6

7.2

6.7

7.8

8.9

8.3

8.1

8.3



I

Btu/ft2/day

983

1236

1585

1966

2029

1934

1902

1807

1554

1332

1078

919

1522



Pa

lb/in2

























14.75

Jacksonville, FL

T_4N

°F

40.5

43.3

49.3

54.9

62.1

69.1

72.0

71.8

69.1

59.4

50.2

43.3

57.0


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Tax

°F

64.2

66.9

73.0

79.2

84.7

89.2

91.4

90.7

87.3

80.2

73.6

66.7

79.0



V

mi/hr

8.1

8.7

8.7

8.3

7.6

7.2

6.7

6.3

6.9

7.6

7.4

7.4

7.6



I

Btu/ft2/day

919

1173

1490

1871

1934

1902

1839

1712

1458

1268

1015

856

1458



Pa

lb/in2

























14.75

Key West, FL

T_4N

°F

64.9

65.7

69.1

72.1

76.1

78.4

79.5

79.3

78.4

75.6

71.2

66.7

73.0



Tax

°F

74.8

75.4

78.6

81.7

85.1

87.6

89.1

89.2

88.0

84.4

80.1

76.1

82.6



V

mi/hr

11.6

12.1

12.3

11.9

10.7

10.1

9.6

9.2

9.6

11.6

12.3

11.9

11.2



I

Btu/ft2/day

1173

1395

1744

1997

1997

1934

1934

1839

1649

1458

1205

1078

1617



Pa

lb/in2

























14.74

Miami, FL

T_4N

°F

59.2

60.4

64.2

67.8

72.1

75.0

76.3

76.6

75.9

72.1

66.7

61.5

69.1



Tax

°F

75.2

76.5

79.2

82.4

85.3

87.6

89.1

89.1

87.8

84.6

80.4

76.6

82.8



V

mi/hr

9.6

10.5

11.0

10.7

9.8

8.5

8.3

8.3

8.5

9.8

10.1

9.6

9.4



I

Btu/ft2/day

1110

1332

1649

1902

1902

1775

1839

1775

1554

1395

1173

1046

1522



Pa

lb/in2

























14.75

Tallahassee, FL

T_4N

°F

38.1

40.1

46.8

52.2

60.8

68.5

71.1

71.4

68.0

55.9

46.2

40.3

55.0



Tax

°F

63.0

66.4

73.6

80.4

86.4

90.9

91.2

91.0

88.5

81.5

73.0

65.8

79.3



V

mi/hr

6.7

7.4

7.6

7.2

6.5

5.6

5.1

5.1

6.0

6.5

6.3

6.5

6.3



I

Btu/ft2/day

919

1173

1490

1871

1997

1934

1839

1744

1554

1363

1046

856

1490



Pa

lb/in2

























14.74

Tampa, FL

T_4N

°F

50.0

51.6

56.5

60.8

67.5

72.9

74.5

74.5

72.9

65.1

57.2

52.3

63.0



Tax

°F

69.8

71.4

76.6

81.7

87.3

89.4

90.1

90.1

89.1

84.4

77.7

72.1

81.7



V

mi/hr

8.7

9.2

9.4

9.2

8.7

8.1

7.4

6.9

7.6

8.5

8.5

8.5

8.5



I

Btu/ft2/day

1015

1268

1617

1966

2029

1934

1839

1744

1554

1395

1141

983

1554



Pa

lb/in2

























14.76

West Palm Beach, FL

T_4N

°F

55.8

56.5

61.2

64.8

69.6

73.0

74.5

75.0

74.7

70.7

64.6

58.6

66.6



Tax

°F

74.5

75.9

78.8

82.0

85.6

88.2

90.0

90.0

88.5

84.9

80.1

75.9

82.9



V

mi/hr

10.3

10.7

11.4

11.0

10.3

8.7

8.3

8.3

8.7

10.7

10.7

10.3

9.8



I

Btu/ft2/day

1046

1268

1585

1871

1902

1807

1871

1775

1522

1332

1078

983

1490



Pa

lb/in2

























14.75

Athens, GA

T_4N

°F

32.0

34.7

42.1

49.8

58.1

65.8

69.4

68.7

63.0

50.7

42.3

35.1

51.1



Tax

°F

51.6

56.3

65.1

73.4

80.4

87.1

89.6

88.2

82.8

73.6

64.4

55.0

72.3



V

mi/hr

8.5

8.9

8.7

8.3

6.9

6.5

6.3

5.8

6.5

6.7

7.4

8.1

7.4



I

Btu/ft2/day

824

1078

1427

1775

1934

2029

1934

1775

1522

1268

919

761

1427



Pa

lb/in2

























14.34


-------


D

£
&

iri

v.

EE

co

00 CO
y h

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>
n

H
O

fa

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Atlanta, GA

T_4N

°F

31.5

34.5

42.4

50.2

58.6

66.2

69.4

69.1

63.5

52.0

42.8

35.1

51.3



Tax

°F

50.4

55.0

64.2

72.7

79.5

85.8

88.0

87.1

81.9

72.7

63.3

54.0

71.2



V

mi/hr

9.8

10.3

10.1

9.6

8.5

7.8

7.6

7.2

7.8

8.3

8.7

9.4

8.7



I

Btu/ft2/day

824

1078

1427

1807

1966

2029

1966

1807

1522

1300

919

761

1458



Pa

lb/in2

























14.23

Augusta, GA

T_4N

°F

32.0

34.7

42.3

48.6

57.6

65.7

70.0

69.1

63.1

50.4

41.5

34.9

50.7



Tax

°F

55.8

60.1

68.7

76.6

83.7

89.2

91.8

90.3

85.6

77.2

68.4

59.5

75.6



V

mi/hr

7.2

7.6

7.8

7.6

6.5

6.3

6.0

5.4

5.6

5.6

6.3

6.7

6.5



I

Btu/ft2/day

824

1110

1427

1807

1934

1997

1934

1744

1522

1300

951

761

1458



Pa

lb/in2

























14.69

Columbus, GA

T_4N

°F

35.2

37.6

45.1

52.2

61.0

68.4

71.8

71.4

66.4

54.1

45.0

38.1

54.0



Tax

°F

56.1

61.0

69.1

77.4

83.7

90.3

91.8

91.2

86.2

77.5

68.2

59.0

75.9



V

mi/hr

7.4

8.1

7.8

7.6

6.7

6.3

6.0

5.6

6.5

6.7

6.7

6.9

6.7



I

Btu/ft2/day

856

1110

1458

1807

1966

2029

1902

1775

1554

1332

983

793

1458



Pa

lb/in2

























14.56

Macon, GA

T_4N

°F

34.2

36.9

44.2

50.9

59.4

66.7

70.5

69.8

64.2

51.6

43.2

37.0

52.3



Tax

°F

56.7

60.8

69.4

77.7

84.6

90.1

91.9

91.0

86.4

77.9

68.7

60.3

76.3



V

mi/hr

7.6

8.5

8.5

8.3

7.2

6.9

6.7

6.3

6.5

6.5

6.7

7.4

7.2



I

Btu/ft2/day

856

1110

1458

1807

1966

1997

1902

1775

1522

1300

951

793

1458



Pa

lb/in2

























14.58

Savannah, GA

T_4N

°F

38.1

41.2

48.4

54.5

63.0

69.3

72.3

72.1

67.8

56.8

48.0

41.0

55.9



Tax

°F

59.7

62.4

70.2

77.5

84.0

88.9

91.0

89.8

85.3

77.5

70.0

62.2

76.5



V

mi/hr

8.5

9.2

9.2

8.7

7.6

7.4

7.2

6.5

7.2

7.4

7.6

7.6

7.8



I

Btu/ft2/day

888

1110

1490

1839

1966

1997

1934

1744

1490

1300

983

824

1458



Pa

lb/in2

























14.75

Hilo, HI

T_4N

°F

63.7

63.7

64.4

65.5

66.6

67.6

68.5

68.9

68.5

68.2

66.7

64.8

66.4



Tax

°F

79.9

79.9

79.5

79.9

81.1

82.8

82.9

83.7

83.8

83.1

81.3

80.1

81.5



V

mi/hr

7.8

8.1

8.1

8.1

7.8

7.6

7.4

7.2

7.2

7.2

7.4

7.6

7.6



I

Btu/ft2/day

1205

1363

1458

1522

1649

1712

1649

1680

1585

1363

1173

1110

1458



Pa

lb/in2

























14.72

Honolulu, HI

T_4N

°F

65.7

65.5

67.3

68.7

70.3

72.1

73.6

74.1

73.6

72.3

70.3

66.9

70.0



Tax

°F

80.1

80.4

81.7

82.8

84.7

86.5

87.4

88.7

88.5

86.9

84.0

81.1

84.4



V

mi/hr

9.6

9.6

11.2

11.4

11.4

12.3

12.8

12.1

11.0

10.3

10.3

9.6

11.0



I

Btu/ft2/day

1236

1490

1712

1871

2029

2061

2093

2061

1871

1585

1300

1173

1712


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£
£1

c-f

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CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.74

Kahului, HI

T_4N

°F

63.7

63.3

64.6

66.0

66.9

69.1

70.5

70.9

69.8

69.3

67.6

65.1

67.3



Tax

°F

79.9

80.1

81.1

82.2

84.2

85.8

86.7

87.6

87.6

86.4

83.7

81.1

83.8



V

mi/hr

11.6

12.1

12.8

14.1

15.0

15.9

16.6

15.9

13.9

12.3

12.8

11.2

13.6



I

Btu/ft2/day

1268

1490

1712

1871

2029

2124

2124

2061

1934

1617

1363

1236

1744



Pa

lb/in2

























14.69

Lihue, HI

T_4N

°F

65.3

65.1

66.9

68.5

70.3

72.5

73.8

74.1

73.6

72.0

70.3

67.1

70.0



Tax

°F

77.9

78.1

78.4

79.5

81.1

83.1

84.0

84.7

84.7

83.1

80.8

78.6

81.1



V

mi/hr

11.6

11.9

13.2

14.3

13.6

13.6

14.3

13.2

12.1

11.9

12.8

11.6

13.0



I

Btu/ft2/day

1173

1363

1554

1680

1871

1934

1902

1871

1775

1490

1205

1110

1585



Pa

lb/in2

























14.68

Boise, ID

T_4N

°F

21.6

27.5

31.8

36.7

43.9

52.2

57.7

56.8

48.2

39.0

31.1

22.5

39.0



Tax

°F

36.3

44.2

52.9

61.3

71.1

81.0

90.1

88.2

77.0

64.6

48.7

37.8

62.8



V

mi/hr

7.2

8.5

9.4

9.6

9.4

8.7

8.1

7.8

7.8

7.6

8.1

7.4

8.3



I

Btu/ft2/day

507

793

1205

1680

2061

2283

2410

2093

1617

1078

602

444

1395



Pa

lb/in2

























13.28

Pocatello, ID

T_4N

°F

14.4

19.8

25.9

32.4

39.6

47.3

53.1

50.9

42.8

33.4

26.1

15.8

33.4



Tax

°F

32.2

38.5

46.8

57.6

67.5

78.1

88.2

86.4

75.0

62.4

45.1

33.6

59.4



V

mi/hr

10.1

10.3

11.0

11.6

10.7

9.6

8.9

8.7

8.9

9.2

10.5

9.6

10.1



I

Btu/ft2/day

539

824

1205

1617

1966

2219

2314

1997

1585

1110

634

476

1363



Pa

lb/in2

























12.53

Chicago, IL

T_4N

°F

12.9

17.2

28.6

38.7

47.7

57.6

62.6

61.5

54.0

42.3

31.6

19.0

39.6



Tax

°F

28.9

33.4

45.9

58.6

70.2

79.5

83.7

81.9

74.8

63.3

48.4

34.0

58.6



V

mi/hr

11.6

11.4

12.1

11.9

10.3

9.4

8.3

8.1

8.9

10.1

10.7

11.0

10.3



I

Btu/ft2/day

571

824

1110

1458

1807

1997

1934

1712

1332

951

571

476

1236



Pa

lb/in2

























14.39

Moline, IL

T_4N

°F

11.3

16.0

28.0

39.4

49.8

59.5

64.6

61.9

53.2

41.7

30.7

17.4

39.6



Tax

°F

28.4

33.6

46.8

61.3

72.9

82.6

85.8

83.5

75.9

64.2

48.4

33.4

59.7



V

mi/hr

11.4

10.7

12.3

12.1

10.3

9.4

7.8

7.6

8.3

9.6

10.7

11.0

10.1



I

Btu/ft2/day

602

856

1141

1490

1807

2029

1997

1744

1363

1015

634

507

1268



Pa

lb/in2

























14.43

Peoria, IL

T_4N

°F

13.3

17.8

29.8

40.8

50.9

60.6

65.5

63.1

55.2

43.2

32.5

19.2

41.0



Tax

°F

29.8

34.9

48.0

62.1

72.9

82.2

85.6

83.1

76.8

64.8

49.8

34.5

60.4



V

mi/hr

11.0

10.7

11.9

11.4

9.6

8.5

7.6

7.4

8.1

9.2

10.5

10.5

9.6


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Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

634

888

1141

1522

1839

2029

1997

1744

1395

1015

634

507

1268



Pa

lb/in2

























14.40

Rockford, IL

T_4N

°F

9.9

14.2

26.1

36.9

47.5

57.4

62.4

60.3

52.0

40.6

29.5

16.2

37.8



Tax

°F

26.6

31.6

43.9

58.5

70.9

80.2

83.8

81.3

74.1

62.2

46.2

31.8

57.6



V

mi/hr

11.2

10.7

12.1

11.9

10.5

9.4

8.3

7.8

8.5

9.6

10.7

10.7

10.1



I

Btu/ft2/day

602

856

1110

1458

1807

1997

1934

1712

1332

951

571

476

1236



Pa

lb/in2

























14.36

Springfield, IL

T_4N

°F

16.0

20.1

31.6

42.4

52.3

61.9

66.0

63.3

55.9

44.4

34.0

21.9

42.4



Tax

°F

32.5

37.2

50.0

63.9

74.7

83.8

86.9

84.2

78.6

66.7

51.6

37.2

62.2



V

mi/hr

12.3

11.9

13.2

12.5

10.7

9.4

8.3

7.8

8.9

10.3

11.6

12.1

10.7



I

Btu/ft2/day

666

919

1173

1585

1902

2061

2029

1807

1458

1078

698

539

1332



Pa

lb/in2

























14.43

Evansville, IN

T_4N

°F

21.2

25.0

35.8

45.0

54.1

63.3

67.5

64.9

57.6

44.8

36.5

26.8

45.1



Tax

°F

38.8

43.7

55.9

67.5

76.8

86.2

89.1

87.3

80.8

69.6

55.9

43.5

66.4



V

mi/hr

8.9

8.9

9.6

9.2

7.6

6.9

6.0

5.6

6.0

6.7

8.1

8.5

7.6



I

Btu/ft2/day

666

919

1205

1585

1871

2061

1997

1807

1458

1110

729

571

1332



Pa

lb/in2

























14.56

Fort Wayne, IN

T_4N

°F

15.3

17.8

28.8

38.5

49.1

59.4

63.1

61.0

54.1

42.4

33.4

21.6

40.5



Tax

°F

30.4

34.0

46.2

59.7

71.2

81.0

84.6

82.2

75.6

63.1

49.1

35.4

59.4



V

mi/hr

11.9

11.0

12.1

11.4

9.8

9.2

8.1

7.6

8.1

9.2

10.5

11.2

10.1



I

Btu/ft2/day

571

824

1110

1458

1775

1966

1934

1680

1363

951

571

444

1236



Pa

lb/in2

























14.31

Indianapolis, IN

T_4N

°F

17.2

20.8

31.8

41.5

51.6

61.0

65.1

62.8

55.6

43.5

34.2

23.2

42.4



Tax

°F

33.6

38.3

50.9

63.3

73.8

82.8

85.5

83.7

77.5

65.8

52.0

38.5

62.1



V

mi/hr

10.5

10.3

11.4

10.5

9.2

8.3

7.4

6.9

7.6

8.5

9.8

10.3

9.2



I

Btu/ft2/day

634

888

1173

1554

1871

2061

1997

1775

1458

1046

666

507

1300



Pa

lb/in2

























14.33

South Bend, IN

T_4N

°F

16.2

18.7

29.1

38.7

48.7

58.6

63.0

61.2

53.8

42.8

33.4

22.3

40.5



Tax

°F

30.4

34.2

45.7

58.6

70.0

79.5

82.9

80.8

74.1

62.2

48.6

35.4

58.5



V

mi/hr

11.9

11.2

11.9

11.4

9.8

8.9

8.1

7.6

8.3

9.4

10.7

11.4

10.1



I

Btu/ft2/day

539

793

1078

1458

1775

1966

1902

1680

1300

919

539

444

1205



Pa

lb/in2

























14.33

Des Moines, IA

T_4N

°F

10.8

15.6

27.7

39.9

51.4

61.2

66.6

63.7

54.5

42.6

29.8

16.2

39.9



Tax

°F

28.0

33.6

46.9

61.9

73.0

82.2

86.7

84.2

75.6

64.2

48.0

32.5

59.7


-------
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|

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&

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£
£1

c-f

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P

CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

11.4

11.2

12.3

12.3

10.7

9.8

8.7

8.5

9.2

9.8

10.7

11.0

10.5



I

Btu/ft2/day

634

888

1205

1554

1839

2061

2061

1807

1395

1015

666

539

1300



Pa

lb/in2

























14.24

Mason City, IA

T_4N

°F

4.3

9.9

22.8

35.6

46.8

56.8

61.5

58.6

49.3

37.9

25.0

10.2

34.9



Tax

°F

22.1

27.5

39.9

57.0

70.5

79.9

83.7

81.0

72.1

60.4

43.0

26.4

55.2



V

mi/hr

13.2

12.3

13.2

13.2

12.1

11.0

8.9

8.5

9.6

11.0

12.1

12.5

11.4



I

Btu/ft2/day

602

856

1173

1490

1839

1997

1997

1744

1363

951

571

476

1268



Pa

lb/in2

























14.10

Sioux City, IA

T_4N

°F

7.7

13.8

25.7

38.3

50.0

59.5

64.8

62.1

52.0

39.6

26.4

12.7

37.8



Tax

°F

27.7

33.3

45.9

62.2

73.2

82.0

86.5

83.5

74.8

64.0

46.4

30.9

59.2



V

mi/hr

11.6

11.4

12.8

13.2

12.1

10.7

9.4

9.2

9.8

10.5

11.2

11.4

11.2



I

Btu/ft2/day

602

888

1205

1554

1839

2093

2061

1807

1395

1015

634

507

1300



Pa

lb/in2

























14.16

Waterloo, IA

T_4N

°F

5.4

10.6

25.0

37.0

48.7

57.6

62.2

59.0

50.0

38.5

26.2

11.7

36.0



Tax

°F

23.7

29.5

43.3

59.4

71.6

80.4

83.8

81.5

73.8

61.9

45.1

28.9

56.8



V

mi/hr

11.6

11.2

12.5

12.5

11.0

9.8

8.5

8.5

9.2

10.1

11.2

11.4

10.5



I

Btu/ft2/day

602

856

1141

1490

1807

2029

1997

1744

1363

951

602

476

1268



Pa

lb/in2

























14.29

Dodge City, KS

T_4N

°F

18.1

22.6

30.4

41.4

52.0

61.9

67.5

65.7

56.7

44.2

31.1

21.2

42.6



Tax

°F

41.5

47.3

56.7

68.0

76.3

87.1

93.0

90.7

81.3

70.7

55.2

43.9

67.6



V

mi/hr

13.2

13.4

15.0

15.0

14.1

13.4

13.0

12.3

13.0

13.0

13.2

13.2

13.4



I

Btu/ft2/day

856

1141

1490

1871

2061

2283

2283

1997

1617

1268

888

761

1554



Pa

lb/in2

























13.42

Goodland, KS

T_4N

°F

15.3

19.0

25.3

35.2

45.7

55.2

61.3

59.2

50.0

37.6

25.7

17.1

37.2



Tax

°F

41.5

45.3

52.7

63.7

72.3

83.5

89.8

87.3

78.1

66.6

51.6

42.1

64.6



V

mi/hr

12.8

12.5

14.3

14.8

13.6

12.8

12.3

11.4

12.1

11.9

12.1

12.3

12.8



I

Btu/ft2/day

793

1046

1427

1807

1997

2283

2251

1997

1617

1236

856

698

1490



Pa

lb/in2

























12.88

Topeka, KS

T_4N

°F

16.3

21.7

32.2

42.8

53.2

63.0

67.6

64.9

55.8

43.5

32.0

21.0

42.8



Tax

°F

37.0

42.6

55.0

66.9

75.7

84.2

89.2

87.4

79.7

69.1

54.0

40.5

65.1



V

mi/hr

9.8

10.1

11.9

11.6

10.3

9.4

8.5

8.1

8.3

8.7

9.6

9.4

9.6



I

Btu/ft2/day

729

951

1268

1617

1871

2061

2093

1839

1458

1110

761

602

1363



Pa

lb/in2

























14.29


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>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Wichita, KS

Tan

°F

19.2

23.7

33.6

44.4

54.3

64.6

70.0

67.8

59.2

46.6

34.0

23.0

45.0



Tax

°F

39.7

45.9

57.2

68.4

76.8

86.7

92.8

90.7

81.3

70.5

55.2

43.0

67.5



V

mi/hr

12.1

12.3

13.9

13.6

12.1

11.6

11.4

11.0

11.4

11.6

12.1

12.1

12.1



I

Btu/ft2/day

793

1046

1363

1712

1934

2124

2156

1934

1554

1205

824

698

1458



Pa

lb/in2

























14.04

Covinqton, KY

T_4N

°F

19.6

22.6

33.1

42.3

51.8

60.1

64.8

63.0

56.7

44.2

35.2

25.3

43.2



Tax

°F

36.7

40.8

53.1

64.2

73.9

82.0

85.5

84.0

77.9

66.0

53.2

41.5

63.1



V

mi/hr

10.5

10.1

11.0

10.3

8.5

7.8

6.9

6.9

7.2

8.1

9.4

10.1

8.9



I

Btu/ft2/day

602

856

1141

1522

1807

1966

1902

1744

1427

1046

666

507

1268



Pa

lb/in2

























14.30

Lexinqton, KY

T_4N

°F

22.5

25.3

35.2

44.2

53.4

61.5

65.7

64.4

57.9

46.0

37.0

27.7

45.1



Tax

°F

39.0

43.5

55.2

65.5

74.3

82.8

85.8

84.9

78.3

67.3

54.9

44.2

64.8



V

mi/hr

9.8

9.8

10.5

9.8

8.3

7.6

6.7

6.7

6.9

7.6

9.2

9.8

8.5



I

Btu/ft2/day

634

888

1173

1554

1807

1966

1902

1744

1395

1078

698

539

1300



Pa

lb/in2

























14.24

Louisville, KY

T_4N

°F

23.2

26.4

36.1

45.3

54.7

63.0

67.3

65.8

58.6

45.9

37.2

28.6

46.0



Tax

°F

40.3

44.8

56.3

67.3

75.9

83.5

87.1

85.6

80.2

69.3

56.8

45.1

66.0



V

mi/hr

9.4

9.4

10.1

9.6

8.1

7.6

6.7

6.7

6.7

7.4

8.7

9.4

8.3



I

Btu/ft2/day

634

888

1205

1585

1839

1997

1934

1775

1427

1110

698

539

1300



Pa

lb/in2

























14.50

Baton Rouqe, LA

T_4N

°F

39.6

42.4

50.2

57.9

64.8

70.3

73.2

72.7

68.7

57.0

48.9

42.4

57.4



Tax

°F

59.7

63.7

72.3

79.9

85.6

90.5

91.4

91.0

87.4

80.1

70.9

63.3

78.1



V

mi/hr

8.5

8.9

9.2

8.7

7.6

6.5

5.8

5.4

6.5

6.5

7.6

8.1

7.4



I

Btu/ft2/day

824

1110

1395

1712

1871

1902

1807

1712

1522

1363

951

793

1427



Pa

lb/in2

























14.72

Lake Charles, LA

T_4N

°F

41.2

44.1

50.7

58.6

65.7

71.6

73.6

73.0

68.5

57.9

50.0

43.5

58.3



Tax

°F

59.7

63.3

70.7

77.9

84.0

89.1

90.9

90.9

86.7

80.2

70.9

63.3

77.4



V

mi/hr

9.8

10.3

10.3

10.1

8.7

7.6

6.5

6.0

7.2

7.6

9.2

9.8

8.5



I

Btu/ft2/day

856

1141

1427

1712

1902

1997

1902

1775

1585

1363

1015

824

1458



Pa

lb/in2

























14.74

New Orleans, LA

T_4N

°F

41.7

44.4

51.6

58.5

65.1

70.9

73.0

72.9

69.4

58.6

51.1

44.8

58.5



Tax

°F

60.8

64.0

71.6

78.4

84.4

89.2

90.7

90.1

86.5

79.3

71.1

64.2

77.5



V

mi/hr

8.9

9.6

9.4

9.2

8.1

6.7

5.8

5.8

6.9

7.4

8.5

8.9

7.8



I

Btu/ft2/day

856

1141

1427

1744

1934

1934

1807

1744

1554

1363

983

824

1458


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





K>

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.75

Shreveport, LA

T_4N

°F

34.9

37.9

45.9

54.1

62.1

69.1

72.3

71.2

66.0

54.3

45.3

37.2

54.1



Tax

°F

55.4

60.6

69.3

77.2

83.1

89.8

93.0

93.0

87.3

78.6

68.0

58.5

76.3



V

mi/hr

8.7

9.4

9.8

9.4

8.3

7.4

6.9

6.5

7.2

7.2

8.5

8.7

8.1



I

Btu/ft2/day

824

1078

1395

1712

1902

2029

2029

1902

1585

1300

951

793

1458



Pa

lb/in2

























14.62

Caribou, ME

T_4N

°F

-1.7

0.7

14.9

28.9

40.1

49.1

54.5

52.2

43.2

34.3

23.7

5.5

28.8



Tax

°F

19.4

23.0

34.3

46.8

61.7

72.0

76.5

73.6

64.0

52.0

37.6

24.1

48.7



V

mi/hr

11.4

11.2

11.9

11.4

10.7

9.8

9.2

8.5

9.4

10.1

10.5

11.0

10.3



I

Btu/ft2/day

507

824

1205

1458

1649

1807

1775

1522

1141

729

444

380

1141



Pa

lb/in2

























14.37

Portland, ME

T_4N

°F

11.5

13.5

24.4

34.2

43.3

52.2

58.3

57.0

48.9

38.3

30.4

17.8

35.8



Tax

°F

30.4

33.1

41.4

52.3

63.1

72.7

78.8

77.4

69.3

58.6

46.9

35.1

54.9



V

mi/hr

9.2

9.2

9.8

9.8

9.2

8.5

7.6

7.6

7.8

8.3

8.9

8.7

8.7



I

Btu/ft2/day

602

888

1205

1490

1775

1934

1902

1712

1332

919

571

476

1236



Pa

lb/in2

























14.69

Baltimore, MD

T_4N

°F

23.4

25.9

34.2

42.4

52.5

61.9

66.7

65.7

58.5

45.9

37.0

28.2

45.1



Tax

°F

40.3

43.7

54.0

64.2

74.1

83.1

87.3

85.5

78.4

67.3

56.5

45.1

64.9



V

mi/hr

9.4

9.8

10.3

10.3

8.7

8.1

7.6

7.6

7.8

8.3

8.9

9.2

8.7



I

Btu/ft2/day

666

919

1236

1554

1775

1966

1902

1680

1395

1046

698

571

1268



Pa

lb/in2

























14.68

Boston, MA

T_4N

°F

21.6

23.0

31.3

40.3

49.8

59.2

65.1

64.0

56.8

46.9

38.3

26.8

43.5



Tax

°F

35.8

37.6

45.9

55.9

66.6

76.3

81.9

79.9

72.9

62.8

52.2

40.5

59.0



V

mi/hr

13.9

13.6

13.6

13.2

12.3

11.4

11.0

10.7

11.4

12.1

13.0

13.6

12.5



I

Btu/ft2/day

602

856

1173

1490

1775

1934

1934

1712

1363

951

602

476

1236



Pa

lb/in2

























14.72

Worchester, MA

T_4N

°F

15.1

16.5

25.0

34.7

45.1

54.0

60.1

58.6

50.5

40.5

31.3

20.1

37.6



Tax

°F

30.7

33.1

42.4

54.0

65.8

74.5

79.3

77.4

69.6

59.5

47.5

34.7

55.8



V

mi/hr

11.0

10.7

10.7

10.3

9.2

8.5

7.8

7.6

8.1

8.9

10.1

10.3

9.4



I

Btu/ft2/day

602

888

1205

1490

1744

1902

1871

1649

1332

951

602

476

1236



Pa

lb/in2

























14.20

Alpena, Ml

T_4N

°F

8.8

8.2

18.0

30.0

39.2

48.0

54.0

52.5

46.2

37.0

28.4

16.5

32.4



Tax

°F

26.4

28.2

37.9

51.6

64.8

74.5

80.2

76.8

68.4

56.8

43.0

30.9

53.2



V

mi/hr

9.2

8.7

9.4

9.4

8.5

7.8

7.4

6.9

7.4

8.1

8.9

8.7

8.5


-------
<1

K>
K>

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

507

793

1173

1490

1807

1966

1934

1617

1205

793

476

380

1173



Pa

lb/in2

























14.36

Detroit, Ml

T_4N

°F

15.6

17.6

27.0

36.9

47.1

56.3

61.3

59.5

52.5

40.8

32.2

21.4

39.0



Tax

°F

30.4

33.3

44.4

57.7

69.6

79.0

83.3

81.3

73.9

61.5

48.0

35.2

58.1



V

mi/hr

12.1

11.4

11.9

11.6

10.3

9.4

8.5

8.3

8.7

9.8

11.2

11.4

10.3



I

Btu/ft2/day

507

793

1078

1458

1775

1966

1934

1680

1300

888

539

412

1205



Pa

lb/in2

























14.39

Flint, Ml

T_4N

°F

14.2

15.6

25.5

36.0

45.7

54.7

59.7

57.9

51.1

40.5

32.2

20.7

37.8



Tax

°F

28.8

31.3

42.3

55.9

68.0

76.8

81.5

79.2

71.6

59.7

46.6

33.8

56.3



V

mi/hr

11.4

10.7

11.4

11.0

9.8

8.9

8.1

7.6

8.5

9.4

10.7

11.0

9.8



I

Btu/ft2/day

507

793

1078

1458

1775

1934

1902

1649

1268

856

507

412

1173



Pa

lb/in2

























14.33

Grand Rapids, Ml

T_4N

°F

14.7

15.8

25.3

35.4

45.7

55.2

60.4

58.5

49.8

39.0

30.2

20.7

37.6



Tax

°F

28.9

31.6

42.8

56.7

69.3

78.6

82.8

80.4

72.0

59.7

45.9

33.4

56.8



V

mi/hr

11.4

10.5

11.4

11.0

9.6

8.9

8.3

7.8

8.3

8.9

10.3

10.7

9.8



I

Btu/ft2/day

507

793

1110

1490

1807

1997

1966

1680

1300

856

507

412

1205



Pa

lb/in2

























14.31

Houghton, Ml

T_4N

°F

8.4

8.2

18.1

31.6

42.1

50.5

55.4

53.8

46.9

37.6

28.4

15.6

33.1



Tax

°F

25.3

28.0

38.1

52.7

66.0

74.8

79.5

76.5

67.8

55.8

42.1

29.5

53.1



V

mi/hr

10.1

9.2

9.8

10.1

9.2

8.5

7.6

7.4

7.8

8.7

9.6

9.6

8.9



I

Btu/ft2/day

412

698

1110

1458

1744

1902

1902

1585

1141

729

412

349

1141



Pa

lb/in2

























14.13

Lansing, Ml

T_4N

°F

13.3

14.2

24.4

35.1

45.0

54.5

59.0

56.8

49.8

39.2

30.7

19.2

36.9



Tax

°F

28.6

31.6

42.6

56.7

69.1

78.3

82.6

80.4

72.0

59.4

45.9

33.4

56.7



V

mi/hr

12.1

11.0

11.6

11.4

10.1

9.2

8.1

7.6

8.3

9.2

10.7

11.2

10.1



I

Btu/ft2/day

507

793

1110

1458

1775

1966

1934

1649

1268

856

539

412

1205



Pa

lb/in2

























14.29

Muskegon, Ml

T_4N

°F

17.8

18.0

25.3

35.4

45.1

54.3

60.3

58.8

51.4

41.5

32.7

23.4

38.7



Tax

°F

28.8

30.7

41.2

54.5

66.6

75.6

80.2

78.1

70.9

59.0

46.0

33.6

55.6



V

mi/hr

12.5

11.4

12.1

11.9

10.1

9.4

8.9

8.7

9.4

10.5

11.9

12.1

10.7



I

Btu/ft2/day

507

761

1110

1490

1871

2029

2029

1712

1300

856

507

380

1205



Pa

lb/in2

























14.40

Sault Ste. Marie, Ml

T_4N

°F

4.6

4.8

15.3

28.4

38.5

45.5

51.3

51.3

44.2

36.1

25.9

11.8

29.8



Tax

°F

21.0

23.2

32.7

48.0

62.6

70.5

76.3

73.8

65.8

54.3

39.9

26.2

49.6


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ



i

K>
U)

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

9.4

8.7

9.6

9.8

9.2

8.3

7.6

7.4

8.1

8.5

9.4

9.2

8.7



I

Btu/ft2/day

507

824

1236

1522

1807

1934

1902

1585

1110

698

444

380

1173



Pa

lb/in2

























14.34

Traverse City, Ml

T_4N

°F

13.3

11.1

20.1

31.8

41.0

51.1

57.4

55.9

49.3

39.6

30.6

19.6

35.1



Tax

°F

26.2

28.2

38.5

53.2

66.4

75.9

81.3

78.3

69.6

57.9

43.9

31.3

54.1



V

mi/hr

10.3

9.4

9.4

9.6

8.5

8.3

7.6

7.6

8.1

8.5

9.4

9.6

8.7



I

Btu/ft2/day

476

761

1110

1458

1775

1966

1934

1617

1173

761

444

380

1141



Pa

lb/in2

























14.40

Duluth, MN

T_4N

°F

-2.2

2.8

15.6

28.9

39.6

48.6

55.0

53.2

44.4

35.1

21.6

4.8

28.9



Tax

°F

16.2

21.7

32.9

48.2

61.9

71.1

77.2

73.9

63.9

52.3

35.2

20.7

47.8



V

mi/hr

11.4

10.7

11.9

11.6

11.0

10.1

8.9

8.9

9.8

10.3

11.0

10.7

10.5



I

Btu/ft2/day

507

824

1205

1522

1775

1902

1934

1617

1173

793

476

380

1173



Pa

lb/in2

























13.98

International Falls, MN

T_4N

°F

-9.9

-4.0

11.5

27.9

39.6

49.5

54.7

51.6

42.4

32.9

17.1

-2.2

25.9



Tax

°F

11.8

19.2

32.7

50.2

64.6

73.4

78.8

75.6

64.2

51.8

32.7

16.5

47.7



V

mi/hr

8.7

8.5

9.4

9.6

9.2

8.3

7.4

7.6

8.3

8.9

9.2

8.7

8.7



I

Btu/ft2/day

444

761

1173

1522

1744

1839

1839

1554

1110

698

444

349

1141



Pa

lb/in2

























14.10

Minneapolis, MN

T_4N

°F

2.8

9.1

22.6

36.1

47.7

57.6

63.1

60.3

50.4

38.8

25.2

10.2

35.2



Tax

°F

20.7

26.6

39.2

56.5

69.4

78.8

84.0

80.8

70.7

58.8

41.0

25.5

54.3



V

mi/hr

10.5

10.3

11.4

12.1

10.7

10.3

9.4

9.2

9.6

10.3

10.5

10.3

10.3



I

Btu/ft2/day

571

856

1205

1490

1807

1997

1997

1712

1300

888

539

444

1236



Pa

lb/in2

























14.30

Rochester, MN

T_4N

°F

2.7

8.1

21.4

34.5

45.5

55.2

60.1

57.6

48.6

37.6

24.4

9.3

33.6



Tax

°F

20.1

26.1

38.1

55.2

68.2

77.7

81.9

78.8

69.8

58.3

40.8

25.0

53.2



V

mi/hr

14.8

14.1

14.8

14.8

13.4

12.8

11.0

11.0

12.1

13.2

13.9

14.1

13.2



I

Btu/ft2/day

571

856

1173

1458

1775

1966

1966

1680

1268

888

539

444

1205



Pa

lb/in2

























14.04

Saint Cloud, MN

T_4N

°F

-2.4

3.7

17.6

32.0

43.3

52.2

57.6

54.9

45.3

34.3

20.3

5.0

30.4



Tax

°F

18.5

24.8

37.6

55.0

68.4

77.4

82.6

79.3

69.1

57.4

39.0

23.2

52.7



V

mi/hr

10.5

8.3

11.2

10.5

9.8

8.3

7.2

7.4

7.6

8.7

9.4

9.8

9.2



I

Btu/ft2/day

539

856

1205

1490

1775

1966

1997

1712

1268

856

539

412

1205



Pa

lb/in2

























14.18


-------
<1

K>
-1^

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Jackson, MS

Tan

°F

32.7

35.8

44.1

52.0

60.1

67.1

70.5

69.6

63.7

50.4

42.3

36.1

52.0



Tax

°F

55.6

60.1

69.3

77.4

84.0

90.7

92.5

91.9

88.0

79.2

69.3

59.5

76.5



V

mi/hr

8.3

8.5

8.9

8.3

7.2

6.3

5.8

5.6

6.5

6.5

7.6

8.5

7.4



I

Btu/ft2/day

824

1110

1427

1744

1934

2029

1966

1839

1554

1332

951

761

1458



Pa

lb/in2

























14.59

Meridian, MS

T_4N

°F

33.4

36.7

43.5

50.9

58.8

66.0

70.0

69.3

63.9

50.5

42.4

36.7

51.8



Tax

°F

56.5

61.2

69.6

77.4

83.7

90.0

92.1

91.8

86.9

77.7

68.5

60.1

76.3



V

mi/hr

7.2

7.6

7.8

7.2

5.8

5.1

4.7

4.7

5.4

5.1

6.3

7.2

6.0



I

Btu/ft2/day

824

1078

1395

1712

1871

1966

1871

1775

1522

1300

919

761

1427



Pa

lb/in2

























14.60

Columbia, MO

T_4N

°F

18.5

22.8

33.1

43.7

53.1

61.2

66.2

63.9

57.0

45.5

34.5

23.2

43.5



Tax

°F

36.7

41.4

53.2

65.7

74.1

82.8

88.5

86.7

78.8

67.6

53.6

40.3

64.0



V

mi/hr

11.2

11.2

12.3

11.9

9.6

8.7

8.3

8.1

8.7

9.8

10.7

11.0

10.1



I

Btu/ft2/day

698

951

1268

1649

1902

2093

2093

1871

1458

1110

729

602

1363



Pa

lb/in2

























14.30

Kansas City, MO

T_4N

°F

16.7

21.7

32.5

43.9

54.0

63.1

68.2

65.7

56.8

45.7

33.6

21.9

43.7



Tax

°F

34.7

40.6

52.9

65.1

74.3

83.3

88.7

86.4

78.1

67.5

52.5

38.8

63.7



V

mi/hr

11.0

11.0

12.3

12.1

10.3

9.6

9.2

8.9

9.2

10.1

10.7

10.7

10.3



I

Btu/ft2/day

698

951

1236

1617

1871

2061

2093

1839

1458

1141

729

602

1363



Pa

lb/in2

























14.27

Springfield, MO

T_4N

°F

20.5

25.0

34.3

44.1

53.2

61.9

66.6

64.9

57.7

45.9

35.4

25.3

44.6



Tax

°F

41.7

46.2

57.4

67.8

75.9

84.4

89.6

88.5

80.2

69.8

56.7

45.3

66.9



V

mi/hr

11.0

11.0

12.1

11.2

9.4

8.5

7.6

7.8

8.5

9.4

10.3

10.7

9.8



I

Btu/ft2/day

761

983

1300

1649

1871

2029

2093

1871

1490

1173

793

634

1395



Pa

lb/in2

























14.10

St Louis, MO

T_4N

°F

20.8

25.2

35.4

46.4

55.9

65.7

70.3

67.8

60.4

48.4

37.8

26.1

46.8



Tax

°F

37.8

42.6

54.7

66.9

76.1

85.3

89.2

87.3

79.9

68.5

54.7

41.7

65.5



V

mi/hr

11.0

10.7

11.9

11.6

9.6

9.2

8.5

8.1

8.5

9.2

10.3

10.7

9.8



I

Btu/ft2/day

698

919

1236

1585

1871

2029

2029

1807

1458

1110

729

571

1332



Pa

lb/in2

























14.46

Billings, MT

T_4N

°F

13.6

19.4

25.2

34.0

43.3

52.0

58.3

56.7

46.6

37.6

25.5

16.5

35.8



Tax

°F

31.8

38.7

45.9

57.0

66.7

77.5

86.7

84.7

71.6

60.6

44.4

34.3

58.3



V

mi/hr

14.1

12.3

11.2

11.4

10.5

9.6

9.4

9.4

9.8

11.0

11.6

13.2

11.2



I

Btu/ft2/day

539

824

1205

1585

1871

2124

2219

1934

1427

983

602

444

1300


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ



i

K>
Ux

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























12.92

Cut Bank, MT

T_4N

°F

7.3

12.6

18.9

28.2

37.6

45.5

49.5

48.6

39.4

31.3

19.0

10.0

28.9



Tax

°F

27.5

33.8

40.3

52.2

62.2

71.1

79.0

78.1

66.9

56.7

39.7

29.8

53.1



V

mi/hr

14.5

13.4

12.5

13.4

12.3

11.4

10.7

10.3

11.0

12.3

12.3

13.2

12.3



I

Btu/ft2/day

444

698

1110

1554

1871

2093

2188

1839

1332

888

507

349

1236



Pa

lb/in2

























12.78

Glasgow, MT

T_4N

°F

1.2

7.9

19.0

32.0

42.4

51.3

56.7

55.2

44.1

33.3

18.9

5.5

30.6



Tax

°F

19.9

27.1

39.7

56.5

67.3

77.5

84.7

83.5

70.3

58.6

39.6

25.0

54.1



V

mi/hr

9.8

10.3

11.4

12.1

12.3

11.0

11.0

11.0

11.2

10.5

9.6

10.1

10.7



I

Btu/ft2/day

476

729

1141

1490

1807

2061

2124

1807

1300

856

507

380

1236



Pa

lb/in2

























13.53

Great Falls, MT

T_4N

°F

11.7

17.2

22.8

31.8

40.8

48.6

53.2

52.2

43.5

35.8

24.3

14.5

33.1



Tax

°F

30.6

37.6

43.7

55.2

65.1

74.7

83.3

81.7

69.6

59.4

43.5

33.1

56.5



V

mi/hr

14.3

13.2

12.1

12.3

11.0

10.3

9.6

9.6

10.5

12.3

13.9

14.3

12.1



I

Btu/ft2/day

444

761

1173

1554

1839

2124

2251

1871

1363

888

539

380

1268



Pa

lb/in2

























12.88

Helena, MT

T_4N

°F

9.7

16.0

22.3

30.6

39.6

48.4

53.4

51.6

41.0

31.6

20.7

11.1

31.3



Tax

°F

29.7

36.9

44.8

56.1

65.5

75.7

84.9

83.1

69.8

58.5

42.4

31.3

56.7



V

mi/hr

6.9

7.6

8.3

9.2

8.7

8.3

7.8

7.2

7.2

6.9

6.9

6.3

7.6



I

Btu/ft2/day

476

729

1110

1522

1839

2061

2219

1871

1395

919

539

380

1268



Pa

lb/in2

























12.78

Kalispell, MT

T_4N

°F

12.7

18.1

23.9

31.1

38.5

44.1

47.1

46.2

38.7

29.5

23.7

15.4

30.7



Tax

°F

28.2

35.1

43.3

55.2

64.2

71.4

80.1

79.3

67.6

54.3

38.3

29.8

54.0



V

mi/hr

5.8

5.8

6.9

8.1

7.6

6.9

6.7

6.5

6.5

5.1

5.8

5.1

6.5



I

Btu/ft2/day

380

634

983

1363

1712

1934

2124

1775

1268

793

412

317

1141



Pa

lb/in2

























13.23

Lewistown, MT

T_4N

°F

54.9

14.2

19.6

28.8

37.2

45.1

49.8

49.1

39.9

31.6

20.5

11.7

29.7



Tax

°F

30.9

36.0

41.4

52.9

62.4

72.0

80.8

80.2

68.2

58.3

43.5

33.6

55.0



V

mi/hr

11.2

10.3

9.6

10.3

9.6

8.5

8.5

8.3

8.5

8.9

9.6

10.3

9.4



I

Btu/ft2/day

476

729

1141

1522

1807

2029

2156

1839

1332

888

539

380

1236



Pa

lb/in2

























12.65

Miles City, MT

T_4N

°F

6.3

12.9

22.3

33.8

44.6

54.1

60.6

58.5

46.6

35.4

21.7

9.3

34.0



Tax

°F

25.7

33.4

44.2

58.1

69.1

79.9

88.9

86.5

73.0

60.4

42.4

28.9

57.6



V

mi/hr

10.3

10.1

11.0

11.6

11.4

10.3

9.8

9.8

10.1

10.1

9.4

9.8

10.3


-------
<1

K>
On

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

539

824

1205

1554

1871

2156

2219

1902

1395

951

571

444

1300



Pa

lb/in2

























13.37

Missoula, MT

T_4N

°F

15.4

20.8

25.0

30.9

37.9

46.0

50.2

49.3

40.5

31.3

24.3

16.3

32.4



Tax

°F

30.0

37.4

46.6

57.6

65.7

73.9

83.5

82.2

70.9

57.0

40.6

30.2

56.3



V

mi/hr

5.4

5.8

6.7

7.8

7.6

7.4

7.4

6.7

6.3

5.1

5.6

4.9

6.5



I

Btu/ft2/day

412

666

1015

1427

1744

1997

2188

1839

1332

856

444

349

1205



Pa

lb/in2

























13.13

Grand Island, NE

T_4N

°F

11.1

16.3

26.2

38.1

49.5

59.4

64.8

62.1

51.6

39.2

26.2

14.9

38.3



Tax

°F

32.5

38.1

49.3

63.5

73.2

83.7

88.5

85.8

76.3

65.5

48.7

35.8

61.9



V

mi/hr

12.1

11.9

13.4

13.9

12.5

11.6

10.3

10.1

10.7

11.0

11.6

11.6

11.6



I

Btu/ft2/day

698

951

1300

1680

1934

2188

2156

1902

1490

1110

729

602

1395



Pa

lb/in2

























13.78

Norfolk, NE

T_4N

°F

8.4

14.2

25.0

37.6

49.3

58.6

64.0

61.2

51.1

38.7

25.5

12.7

37.2



Tax

°F

29.7

34.7

46.2

61.5

72.7

82.0

86.7

83.8

75.0

64.0

46.9

32.7

59.7



V

mi/hr

12.5

11.9

13.4

13.6

12.3

11.0

9.8

9.8

10.7

11.2

12.1

12.1

11.6



I

Btu/ft2/day

666

919

1268

1617

1902

2124

2124

1839

1427

1046

698

539

1363



Pa

lb/in2

























13.92

North Platte, NE

T_4N

°F

8.6

14.4

23.0

34.0

44.6

54.1

60.1

57.6

46.2

33.4

21.4

11.1

34.0



Tax

°F

34.5

40.8

49.8

62.4

71.8

81.7

87.8

86.0

76.6

65.7

49.5

37.2

62.1



V

mi/hr

9.4

9.6

11.6

12.5

11.4

10.1

9.6

9.2

9.6

9.4

9.4

9.2

10.1



I

Btu/ft2/day

698

983

1332

1680

1902

2156

2156

1902

1522

1141

761

602

1395



Pa

lb/in2

























13.30

Omaha, NE

T_4N

°F

11.1

16.5

27.9

40.3

51.8

61.3

66.6

63.9

54.7

43.0

29.7

16.0

40.3



Tax

°F

29.7

35.1

47.7

62.4

72.9

82.4

86.5

84.0

74.8

64.0

47.7

32.9

60.1



V

mi/hr

10.3

10.3

11.4

11.6

9.8

8.9

8.3

8.1

8.7

9.2

10.1

10.1

9.6



I

Btu/ft2/day

666

919

1236

1585

1871

2124

2093

1807

1427

1046

666

539

1332



Pa

lb/in2

























14.16

Scottsbluff, NE

T_4N

°F

11.8

16.9

22.1

31.5

41.7

52.7

58.6

55.9

45.7

33.6

22.5

12.9

33.8



Tax

°F

37.9

43.5

50.4

61.3

70.9

82.0

89.8

87.3

77.2

65.5

50.2

39.6

63.0



V

mi/hr

11.4

11.4

12.3

12.8

11.9

10.5

9.4

8.9

9.4

9.6

10.1

10.5

10.5



I

Btu/ft2/day

666

951

1300

1680

1902

2188

2219

1966

1554

1110

729

602

1395



Pa

lb/in2

























12.75

Elko, NV

T_4N

°F

13.5

19.9

25.0

29.5

36.9

44.6

50.4

48.6

38.8

29.7

22.5

14.0

31.1



Tax

°F

36.7

43.0

50.2

59.2

69.4

80.2

91.0

88.5

78.3

65.8

49.1

37.4

62.4


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





K)
<1

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

5.1

5.8

6.7

7.2

6.9

6.5

6.3

6.0

5.6

5.1

5.4

4.9

6.0



I

Btu/ft2/day

666

919

1268

1680

1997

2251

2346

2093

1712

1205

729

602

1458



Pa

lb/in2

























12.26

Ely, NV

T_4N

°F

9.3

15.4

20.7

26.1

33.6

40.6

48.0

46.6

37.2

28.2

19.0

10.6

28.0



Tax

°F

39.7

43.5

48.4

57.0

67.3

78.3

87.1

84.4

75.2

63.5

49.3

40.6

61.2



V

mi/hr

9.2

9.4

10.1

10.3

10.3

10.1

10.1

10.1

9.6

9.2

9.2

9.2

9.6



I

Btu/ft2/day

824

1078

1427

1839

2093

2378

2314

2061

1775

1300

888

698

1554



Pa

lb/in2

























11.73

Las Vegas, NV

T_4N

°F

33.6

38.8

43.9

50.7

60.3

69.4

76.3

74.1

66.2

54.3

42.6

34.0

53.8



Tax

°F

57.4

63.3

68.7

77.5

87.8

100.2

106.0

103.3

94.6

82.0

67.5

57.6

80.4



V

mi/hr

8.1

9.2

11.0

11.4

11.6

11.4

11.0

10.1

9.6

8.5

8.5

7.6

9.8



I

Btu/ft2/day

951

1268

1712

2188

2473

2663

2505

2283

1966

1490

1078

888

1807



Pa

lb/in2

























13.60

Reno, NV

T_4N

°F

20.7

24.3

29.1

33.3

40.1

46.9

51.3

49.6

41.4

32.9

26.8

19.9

34.7



Tax

°F

45.1

51.6

56.3

63.7

72.9

83.1

91.9

89.6

79.5

68.5

53.8

45.5

66.7



V

mi/hr

5.1

6.3

8.3

8.5

8.5

7.8

7.6

6.9

6.3

5.6

6.0

5.6

6.9



I

Btu/ft2/day

729

1015

1427

1871

2219

2410

2473

2188

1807

1300

824

666

1585



Pa

lb/in2

























12.57

Tonopah, NV

T_4N

°F

18.1

23.5

27.3

33.1

41.7

50.5

56.5

54.7

46.8

36.9

26.2

19.0

36.1



Tax

°F

43.9

49.3

54.5

63.0

73.0

83.5

91.0

88.3

79.5

68.2

53.2

44.4

66.0



V

mi/hr

8.3

9.2

10.7

11.0

10.3

9.6

8.9

8.5

8.7

8.5

8.5

8.3

9.2



I

Btu/ft2/day

856

1141

1522

1966

2251

2505

2473

2219

1871

1395

951

761

1649



Pa

lb/in2

























12.10

Winnemucca, NV

T_4N

°F

16.7

22.8

25.2

29.5

37.8

45.9

51.3

48.7

38.8

29.3

23.4

17.1

32.2



Tax

°F

42.1

48.9

55.0

63.0

73.0

83.1

93.0

90.7

80.1

68.2

52.3

42.6

66.0



V

mi/hr

7.2

8.1

8.7

8.9

8.9

8.7

8.5

8.1

8.1

7.6

7.8

7.6

8.3



I

Btu/ft2/day

666

919

1300

1744

2093

2346

2441

2124

1744

1205

729

602

1490



Pa

lb/in2

























12.60

Concord, NH

T_4N

°F

7.3

10.4

22.1

31.5

41.4

51.3

56.5

54.7

46.0

34.9

27.0

14.4

33.1



Tax

°F

29.8

33.1

42.8

56.3

68.9

77.4

82.4

79.9

71.6

60.6

47.1

34.2

57.0



V

mi/hr

6.7

7.2

7.8

7.8

6.7

6.5

5.6

5.4

5.4

5.6

6.7

6.7

6.7



I

Btu/ft2/day

602

888

1236

1490

1775

1934

1934

1680

1332

919

571

476

1236



Pa

lb/in2

























14.55


-------
<1

K>
o©

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Atlantic City, NJ

Tan

°F

21.4

23.5

31.3

39.4

49.6

58.6

64.8

63.5

55.6

43.7

35.8

26.2

42.8



Tax

°F

40.5

42.4

51.6

60.6

71.2

80.1

84.6

83.3

76.6

66.0

55.8

45.3

63.1



V

mi/hr

10.3

10.7

11.4

11.6

10.1

8.9

8.3

7.8

8.3

8.7

10.3

10.3

9.6



I

Btu/ft2/day

634

888

1236

1554

1775

1934

1871

1680

1395

1046

698

571

1268



Pa

lb/in2

























14.72

Newark, NJ

T_4N

°F

23.4

25.3

33.4

42.6

53.2

62.8

68.5

67.5

59.9

48.2

39.2

29.1

46.0



Tax

°F

37.8

40.5

50.7

61.9

72.3

82.2

87.1

85.5

77.5

66.7

55.4

43.0

63.3



V

mi/hr

11.0

11.4

12.1

11.6

10.3

9.6

8.9

8.9

9.4

9.4

10.5

10.7

10.3



I

Btu/ft2/day

602

856

1205

1522

1744

1902

1871

1649

1363

1015

634

507

1236



Pa

lb/in2

























14.74

Albuquerque, NM

T_4N

°F

21.7

26.4

32.2

39.6

48.6

58.3

64.4

62.6

55.2

43.0

31.3

23.2

42.3



Tax

°F

46.8

53.4

61.3

70.9

79.7

90.0

92.5

89.1

81.9

71.1

57.4

47.5

70.2



V

mi/hr

8.3

8.7

10.1

11.0

10.7

10.1

8.9

8.5

8.5

8.1

8.1

7.8

9.2



I

Btu/ft2/day

1015

1332

1712

2156

2441

2568

2378

2188

1871

1490

1110

919

1775



Pa

lb/in2

























12.15

Tucumcari, NM

T_4N

°F

21.7

25.5

32.5

41.7

50.5

59.5

64.2

62.1

55.0

43.5

33.1

23.4

42.6



Tax

°F

52.9

56.5

64.2

73.0

81.0

89.4

92.7

90.1

82.9

74.7

62.4

53.1

72.7



V

mi/hr

9.6

9.8

11.0

11.4

10.7

10.3

9.6

8.7

9.2

8.9

9.6

9.4

9.8



I

Btu/ft2/day

951

1236

1617

2029

2219

2378

2283

2061

1744

1427

1046

856

1649



Pa

lb/in2

























12.73

Albany, NY

T_4N

°F

10.9

13.8

24.4

35.1

45.3

54.7

59.5

57.7

49.5

38.7

30.7

18.1

36.7



Tax

°F

30.2

33.3

44.1

57.6

69.6

79.0

84.0

81.3

73.2

61.9

48.7

34.9

58.1



V

mi/hr

9.4

9.8

10.5

10.3

8.7

8.1

7.4

6.9

7.4

7.6

9.2

9.4

8.7



I

Btu/ft2/day

571

824

1141

1490

1744

1902

1934

1649

1300

888

539

444

1205



Pa

lb/in2

























14.59

Binghampton, NY

T_4N

°F

14.4

15.3

24.6

35.2

46.2

54.7

59.7

57.9

50.5

40.3

31.6

20.3

37.6



Tax

°F

27.9

30.0

40.5

53.4

65.5

73.8

78.6

76.5

68.5

57.4

45.0

32.7

54.1



V

mi/hr

11.2

11.0

11.6

11.4

10.1

9.2

8.3

8.3

8.7

9.6

11.0

11.2

10.1



I

Btu/ft2/day

539

793

1110

1427

1680

1839

1839

1585

1236

856

539

444

1173



Pa

lb/in2

























13.88

Buffalo, NY

T_4N

°F

17.1

17.4

25.9

36.1

46.9

56.5

61.9

60.1

53.1

42.6

34.0

22.8

39.6



Tax

°F

30.2

31.6

41.7

54.1

66.0

75.4

80.2

77.9

70.9

59.4

47.1

35.2

55.8



V

mi/hr

13.9

12.5

12.3

11.9

10.7

10.3

9.6

9.2

9.4

10.3

11.9

12.5

11.2



I

Btu/ft2/day

507

761

1078

1427

1744

1934

1902

1649

1236

824

507

412

1173


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ



i

K>

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.37

Massena, NY

T_4N

°F

4.3

6.4

19.0

32.5

43.9

52.5

57.7

55.6

47.1

37.0

27.7

11.7

33.1



Tax

°F

24.3

26.4

37.6

52.7

66.6

75.4

80.6

77.5

68.7

56.8

42.8

28.8

53.2



V

mi/hr

9.4

9.2

9.4

9.6

8.5

7.6

6.9

6.5

6.7

8.1

8.9

8.9

8.3



I

Btu/ft2/day

539

824

1173

1458

1744

1902

1934

1617

1236

824

476

412

1173



Pa

lb/in2

























14.62

New York, NY

T_4N

°F

25.3

27.0

34.9

43.9

53.8

63.0

68.4

67.3

60.1

49.6

41.2

30.7

47.1



Tax

°F

37.6

40.3

50.0

61.2

71.8

80.1

85.3

83.7

76.3

65.3

54.0

42.4

62.2



V

mi/hr

13.6

13.6

13.6

13.0

11.6

11.0

10.5

10.5

11.2

11.4

13.0

13.4

12.3



I

Btu/ft2/day

602

856

1205

1554

1807

1934

1902

1712

1363

1015

634

507

1268



Pa

lb/in2

























14.74

Rochester, NY

T_4N

°F

16.3

16.5

25.7

36.0

46.2

54.3

59.5

57.7

51.6

41.5

33.3

22.5

38.5



Tax

°F

30.9

32.5

42.6

55.9

67.8

75.7

80.8

78.1

71.8

60.4

47.8

35.8

56.7



V

mi/hr

12.1

11.2

11.2

11.4

9.6

8.9

8.3

8.1

8.3

8.9

10.3

11.0

9.8



I

Btu/ft2/day

507

761

1078

1458

1744

1934

1902

1649

1268

856

507

412

1173



Pa

lb/in2

























14.45

Syracuse, NY

T_4N

°F

14.2

15.4

25.2

35.4

46.0

53.8

59.0

57.7

51.4

41.2

33.1

21.0

37.8



Tax

°F

30.6

32.5

42.6

55.9

68.4

76.6

81.7

79.0

71.6

60.3

48.0

35.4

56.8



V

mi/hr

10.7

10.7

10.7

10.3

8.9

8.1

7.8

7.6

8.1

8.5

10.1

10.5

9.4



I

Btu/ft2/day

539

793

1110

1458

1744

1934

1902

1649

1268

856

507

412

1173



Pa

lb/in2

























14.52

Asheville, NC

T_4N

°F

24.8

27.3

35.4

42.6

50.9

58.3

62.8

61.9

55.6

43.5

35.8

28.6

43.9



Tax

°F

46.6

50.0

59.2

67.8

75.0

80.4

82.9

82.0

76.8

68.4

59.4

50.4

66.6



V

mi/hr

9.6

9.6

9.4

9.2

7.2

5.8

5.6

5.4

5.6

6.7

8.3

8.9

7.6



I

Btu/ft2/day

793

1046

1363

1712

1839

1902

1839

1680

1427

1205

856

698

1363



Pa

lb/in2

























13.66

Cape Hatteras, NC

T_4N

°F

36.7

37.6

43.5

50.7

59.5

67.5

71.8

72.0

67.6

58.3

49.3

41.2

54.7



Tax

°F

52.3

53.4

59.5

66.9

74.5

80.8

84.6

84.7

80.8

72.3

64.8

56.8

69.3



V

mi/hr

11.6

11.9

11.9

11.6

10.5

10.5

9.8

9.4

10.5

11.0

11.0

11.2

11.0



I

Btu/ft2/day

761

1046

1395

1775

1934

2029

1966

1775

1522

1173

888

698

1427



Pa

lb/in2

























14.76

Charlotte, NC

T_4N

°F

29.7

31.8

39.4

47.5

56.5

65.7

69.6

68.9

63.0

50.5

41.5

32.7

49.6



Tax

°F

48.9

53.1

62.2

71.2

78.3

85.8

88.9

87.6

81.9

72.0

62.6

52.3

70.3



V

mi/hr

7.6

8.1

8.7

8.5

7.6

6.9

6.5

6.3

6.5

6.5

6.9

7.4

7.4


-------
<1

u>
o

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

793

1046

1395

1744

1902

1997

1934

1775

1490

1236

888

729

1395



Pa

lb/in2

























14.37

Greensboro, NC

T_4N

°F

26.6

29.3

37.4

45.7

54.7

62.6

66.9

65.8

59.5

47.1

38.5

30.6

47.1



Tax

°F

46.8

50.7

60.3

69.6

77.0

83.7

86.9

85.5

79.9

70.0

60.4

50.5

68.4



V

mi/hr

7.6

8.1

8.5

8.3

7.2

6.7

6.3

6.0

6.3

6.5

7.2

7.6

7.2



I

Btu/ft2/day

761

1015

1363

1712

1902

1997

1934

1744

1458

1173

856

698

1395



Pa

lb/in2

























14.30

Raleigh-Durham, NC

T_4N

°F

28.8

31.3

38.7

46.2

55.2

63.7

68.2

67.5

61.2

48.4

39.7

32.4

48.4



Tax

°F

48.9

52.5

62.1

71.8

78.6

84.9

88.0

86.7

81.1

71.6

62.6

52.7

70.2



V

mi/hr

8.5

8.7

9.2

8.7

7.6

6.9

6.5

6.3

6.7

6.9

7.6

8.1

7.6



I

Btu/ft2/day

761

1015

1395

1744

1902

1997

1934

1744

1458

1205

856

698

1395



Pa

lb/in2

























14.53

Wilmington, NC

T_4N

°F

34.3

36.3

43.2

50.5

59.4

67.5

71.8

71.1

65.3

53.8

44.8

37.6

52.9



Tax

°F

55.2

58.1

65.7

73.9

80.8

85.5

88.5

87.6

85.3

76.8

69.1

59.4

73.8



V

mi/hr

8.7

9.4

9.6

9.8

8.7

8.3

7.6

6.9

7.6

7.6

7.8

8.3

8.5



I

Btu/ft2/day

824

1078

1427

1807

1934

1997

1902

1712

1458

1236

919

761

1427



Pa

lb/in2

























14.75

Bismarck, ND

T_4N

°F

-1.7

5.2

17.8

30.9

42.3

51.6

56.5

54.0

43.2

32.5

17.8

3.4

29.5



Tax

°F

20.1

26.4

38.5

54.9

67.8

77.2

84.4

82.8

70.9

58.6

39.4

24.4

53.8



V

mi/hr

9.8

9.4

10.3

11.2

10.7

9.4

8.5

8.7

9.2

9.6

8.9

9.2

9.6



I

Btu/ft2/day

539

824

1205

1554

1902

2093

2156

1839

1332

888

539

444

1268



Pa

lb/in2

























13.87

Fargo, ND

T_4N

°F

-3.6

2.7

17.2

32.2

43.9

53.6

58.8

56.5

45.9

34.5

19.4

3.0

30.4



Tax

°F

15.4

21.0

34.5

53.8

68.5

77.4

83.5

81.3

69.4

56.7

36.9

20.1

51.4



V

mi/hr

12.3

12.1

12.5

13.0

12.1

11.0

10.1

10.3

11.0

11.9

11.6

11.4

11.6



I

Btu/ft2/day

507

793

1173

1490

1807

1966

2029

1744

1268

856

507

412

1205



Pa

lb/in2

























14.26

Minot, ND

T_4N

°F

0.3

6.3

18.0

31.5

42.8

52.9

57.7

55.2

45.0

34.5

19.6

5.4

30.7



Tax

°F

17.6

23.4

35.4

52.9

65.8

75.6

82.0

80.4

67.6

55.8

36.1

21.7

51.3



V

mi/hr

13.6

12.5

12.8

13.0

12.5

11.4

10.5

11.0

11.9

12.5

11.9

12.5

12.1



I

Btu/ft2/day

476

761

1141

1554

1839

2029

2093

1775

1268

856

507

380

1236



Pa

lb/in2

























13.82

Akron, OH

T_4N

°F

16.9

18.9

28.6

37.9

48.2

57.0

61.5

60.1

53.8

42.6

34.2

23.5

40.3



Tax

°F

32.5

36.0

47.3

59.2

69.6

78.4

82.2

80.4

73.8

62.1

49.6

37.8

59.2


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

11.6

11.0

11.4

10.7

9.2

8.3

7.6

7.4

8.1

9.2

10.7

11.4

9.6



I

Btu/ft2/day

539

761

1078

1458

1744

1934

1902

1649

1332

919

571

444

1205



Pa

lb/in2

























14.11

Cleveland, OH

T_4N

°F

17.6

19.2

28.2

37.2

47.3

56.8

61.3

60.3

54.1

43.5

35.1

24.4

40.5



Tax

°F

31.8

35.1

46.2

57.9

68.5

78.3

82.4

80.4

73.6

62.1

50.0

37.4

58.6



V

mi/hr

12.3

11.4

11.9

11.2

9.6

9.2

8.5

8.1

8.7

9.6

11.2

11.6

10.3



I

Btu/ft2/day

507

761

1046

1458

1775

1966

1934

1680

1300

888

539

412

1205



Pa

lb/in2

























14.33

Columbus, OH

T_4N

°F

18.5

21.2

31.3

39.9

50.2

57.9

62.8

60.8

54.9

43.0

34.3

24.6

41.5



Tax

°F

34.2

37.9

50.5

62.1

72.3

80.4

83.7

82.0

76.3

64.6

51.4

39.2

61.2



V

mi/hr

9.8

9.4

10.3

9.6

8.3

7.4

6.7

6.3

6.5

7.4

8.9

9.6

8.3



I

Btu/ft2/day

571

793

1110

1458

1744

1902

1871

1680

1363

983

602

476

1205



Pa

lb/in2

























14.33

Dayton, OH

T_4N

°F

18.0

20.8

30.9

40.5

51.1

59.2

63.3

61.3

55.0

43.5

34.3

24.1

41.9



Tax

°F

34.2

37.9

50.0

61.9

72.5

81.7

84.9

82.9

76.5

64.6

51.3

39.0

61.5



V

mi/hr

11.2

10.7

11.4

11.0

9.2

8.7

7.8

7.4

7.8

8.7

10.3

10.7

9.6



I

Btu/ft2/day

602

824

1141

1490

1807

1966

1902

1712

1395

1015

634

476

1236



Pa

lb/in2

























14.23

Mansfield, OH

T_4N

°F

16.9

18.9

28.6

38.1

48.4

57.4

62.1

60.4

54.0

43.2

34.0

22.6

40.5



Tax

°F

32.2

35.1

46.6

58.6

69.3

78.3

82.0

80.1

73.8

62.2

49.3

36.9

58.6



V

mi/hr

13.2

11.6

12.5

12.3

11.0

9.4

8.5

8.3

8.9

10.1

11.6

13.0

11.0



I

Btu/ft2/day

539

793

1078

1458

1744

1934

1902

1680

1332

951

571

444

1205



Pa

lb/in2

























14.07

Toledo, OH

T_4N

°F

14.9

17.1

26.8

36.3

46.8

55.9

60.6

58.5

51.4

39.9

31.5

20.5

38.5



Tax

°F

30.2

33.4

45.5

58.8

70.5

79.9

83.5

81.3

74.5

62.4

48.6

35.2

58.6



V

mi/hr

11.2

10.5

11.4

11.0

9.4

8.5

7.4

6.9

7.6

8.5

10.1

10.3

9.4



I

Btu/ft2/day

539

824

1110

1490

1839

1997

1966

1712

1363

951

571

444

1236



Pa

lb/in2

























14.39

Youngstown, OH

T_4N

°F

16.3

18.0

27.3

36.9

46.2

54.9

59.2

57.9

51.6

41.5

33.6

22.8

38.8



Tax

°F

30.7

34.0

45.3

57.7

68.7

77.4

81.3

79.5

72.7

61.0

48.4

36.0

57.7



V

mi/hr

11.6

11.0

11.4

10.7

9.4

8.3

7.6

7.4

8.1

9.2

10.5

11.2

9.6



I

Btu/ft2/day

507

761

1046

1395

1680

1871

1839

1585

1268

888

539

412

1141



Pa

lb/in2

























14.13


-------
<1

u>
K>

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Oklahoma City, OK

Tan

°F

25.2

29.7

38.5

48.7

57.7

66.0

70.5

69.6

62.2

50.4

38.7

28.6

48.7



Tax

°F

46.8

52.2

62.1

72.0

79.2

87.3

93.4

92.5

83.8

73.6

60.4

49.8

71.1



V

mi/hr

12.3

13.0

14.1

13.6

12.5

11.0

10.7

10.3

10.7

11.4

12.3

11.9

12.1



I

Btu/ft2/day

888

1110

1458

1807

1966

2156

2188

1966

1585

1268

919

761

1522



Pa

lb/in2

























14.07

Tulsa, OK

T_4N

°F

25.0

29.5

39.0

49.8

58.8

67.6

72.9

70.5

63.0

50.7

39.6

28.9

49.6



Tax

°F

45.3

51.1

62.1

73.0

79.7

87.6

93.7

92.5

83.7

73.8

60.3

48.7

71.1



V

mi/hr

10.3

10.7

11.9

12.1

11.0

9.8

9.4

9.2

9.2

9.6

10.5

10.1

10.3



I

Btu/ft2/day

793

1046

1363

1680

1871

2029

2124

1902

1490

1205

856

698

1427



Pa

lb/in2

























14.39

Astoria, OR

T_4N

°F

36.0

37.2

38.1

40.3

44.8

49.5

52.3

52.5

48.9

44.1

40.3

36.7

43.3



Tax

°F

47.8

51.1

53.2

55.9

60.1

64.0

67.5

68.7

67.8

61.2

53.4

48.2

58.3



V

mi/hr

9.6

9.4

9.2

9.2

8.7

9.2

8.9

8.5

7.8

7.8

9.2

9.2

8.9



I

Btu/ft2/day

349

571

888

1236

1554

1680

1712

1522

1205

761

412

317

1015



Pa

lb/in2

























14.75

Burns, OR

T_4N

°F

12.9

19.2

25.0

28.9

36.0

41.5

47.1

45.0

36.3

28.0

21.9

15.1

29.8



Tax

°F

33.6

39.6

47.7

56.5

65.7

74.5

85.1

83.3

73.6

61.9

45.1

35.2

58.5



V

mi/hr

4.7

4.9

6.7

7.8

7.6

6.7

6.7

5.1

5.6

5.1

4.9

5.4

6.0



I

Btu/ft2/day

571

824

1205

1649

2029

2251

2378

2061

1617

1078

602

476

1395



Pa

lb/in2

























12.68

Eugene, OR

T_4N

°F

35.2

37.0

38.8

40.6

44.4

49.6

52.9

53.2

49.3

43.5

39.7

36.0

43.3



Tax

°F

46.4

51.4

55.9

60.4

67.1

74.1

81.7

81.9

76.3

64.6

52.3

46.2

63.1



V

mi/hr

7.6

7.8

8.3

7.8

7.4

7.6

7.8

7.4

7.4

6.5

7.8

7.6

7.6



I

Btu/ft2/day

412

634

983

1395

1744

1966

2124

1839

1395

856

444

317

1173



Pa

lb/in2

























14.56

Medford, OR

T_4N

°F

30.4

32.2

35.4

37.9

43.3

50.7

55.2

55.0

48.2

40.5

35.4

31.3

41.4



Tax

°F

45.7

53.2

58.5

64.6

72.9

82.0

90.5

90.0

82.8

69.4

52.5

44.2

67.3



V

mi/hr

3.8

4.7

5.4

5.6

5.6

6.0

5.8

5.4

4.7

3.8

3.8

3.6

4.7



I

Btu/ft2/day

476

761

1173

1649

2061

2314

2441

2124

1649

1046

539

380

1395



Pa

lb/in2

























14.07

North Bend, OR

T_4N

°F

38.8

40.5

41.2

42.4

46.6

50.7

52.5

53.1

50.5

46.8

43.2

39.7

45.5



Tax

°F

51.8

54.0

54.9

56.5

60.3

63.9

66.4

67.1

66.9

63.0

56.8

52.3

59.5



V

mi/hr

8.5

8.7

9.4

9.6

10.1

10.7

11.4

9.8

8.7

7.6

8.7

8.5

9.4



I

Btu/ft2/day

476

698

1078

1490

1807

1966

2061

1775

1427

951

571

412

1236


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ



i

U)
U)

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.76

Pendleton, OR

T_4N

°F

27.1

31.6

35.4

39.4

45.9

52.9

57.9

57.7

49.8

41.0

34.2

27.9

41.7



Tax

°F

39.7

46.9

54.1

61.3

70.0

79.5

87.8

86.2

76.3

63.7

48.9

40.5

63.0



V

mi/hr

7.4

7.6

8.5

9.2

8.7

8.5

8.3

7.8

7.6

6.9

7.2

6.9

7.8



I

Btu/ft2/day

444

666

1078

1554

1966

2188

2346

1997

1522

951

507

349

1300



Pa

lb/in2

























13.97

Portland, OR

T_4N

°F

33.6

36.1

38.7

41.4

46.9

52.9

56.5

56.8

52.0

45.0

39.6

34.9

44.4



Tax

°F

45.3

51.1

55.9

60.6

67.1

73.9

79.9

80.2

74.7

64.0

52.5

45.7

62.6



V

mi/hr

9.8

9.4

8.5

7.6

7.6

7.6

7.8

7.4

6.9

6.7

8.9

9.4

8.1



I

Btu/ft2/day

380

602

951

1332

1680

1871

1997

1712

1300

793

444

317

1110



Pa

lb/in2

























14.75

Redmond, OR

T_4N

°F

21.4

25.0

26.2

28.9

34.7

42.1

46.4

46.2

38.7

32.2

27.3

21.7

32.5



Tax

°F

41.2

47.1

52.7

59.2

67.3

76.6

85.3

83.8

75.4

64.2

48.9

41.7

62.1



V

mi/hr

7.4

7.8

8.1

8.1

7.8

7.6

7.4

6.9

6.7

6.7

7.4

6.9

7.4



I

Btu/ft2/day

539

793

1205

1680

2061

2283

2410

2093

1617

1046

602

444

1395



Pa

lb/in2

























13.18

Salem, OR

T_4N

°F

32.7

34.2

35.6

37.8

42.3

48.4

50.9

51.4

47.1

41.2

37.6

33.6

41.0



Tax

°F

46.4

51.4

55.8

60.4

66.9

74.5

81.7

82.0

75.9

64.2

52.3

46.4

63.1



V

mi/hr

7.8

7.8

8.1

7.4

6.7

6.7

6.7

6.3

6.0

5.8

8.1

7.6

7.2



I

Btu/ft2/day

412

634

983

1395

1744

1934

2093

1807

1395

856

444

349

1173



Pa

lb/in2

























14.66

Guam

T_4N

°F

71.1

70.9

71.1

72.1

72.7

72.9

72.3

72.1

72.1

72.3

73.0

72.7

72.1



Tax

°F

83.7

83.5

84.6

85.8

86.7

86.9

86.4

85.8

86.2

85.8

85.3

84.2

85.5



V

mi/hr

9.8

11.0

10.5

10.3

9.4

7.4

6.7

5.6

6.0

6.7

8.9

9.8

8.5



I

Btu/ft2/day

1395

1522

1744

1839

1807

1744

1617

1554

1554

1458

1395

1332

1585



Pa

lb/in2

























14.47

Allentown, PA

T_4N

°F

18.9

20.8

29.8

38.8

49.3

58.8

63.7

62.1

54.1

42.4

34.2

24.4

41.5



Tax

°F

34.3

37.8

48.7

60.4

71.2

80.1

84.6

82.2

75.0

63.9

51.8

39.2

60.8



V

mi/hr

10.3

10.3

11.0

10.7

9.2

8.3

7.2

7.2

7.4

8.1

9.6

9.8

9.2



I

Btu/ft2/day

602

856

1173

1490

1712

1902

1871

1649

1332

983

634

507

1236



Pa

lb/in2

























14.55

Bradford, PA

T_4N

°F

11.8

12.4

22.1

32.0

41.0

49.5

54.0

52.5

46.2

36.9

28.8

18.0

33.6



Tax

°F

26.6

29.7

40.3

52.5

64.2

72.3

76.5

74.7

67.5

56.3

43.3

31.5

53.1



V

mi/hr

9.8

9.2

9.4

9.2

7.8

6.9

5.8

5.8

6.5

7.6

9.2

9.6

8.1


-------
<1

u>

-1^

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

571

824

1141

1458

1712

1871

1839

1585

1236

888

539

444

1173



Pa

lb/in2

























13.63

Erie, PA

T_4N

°F

18.1

18.0

28.0

37.8

47.8

57.6

62.6

61.9

55.9

45.7

37.0

25.2

41.4



Tax

°F

32.5

33.6

43.5

54.5

65.8

75.4

79.9

78.4

72.1

61.0

49.5

37.8

57.0



V

mi/hr

13.6

12.3

12.5

11.9

10.7

10.1

9.4

9.4

10.3

11.6

13.6

13.9

11.6



I

Btu/ft2/day

507

761

1078

1458

1807

1997

1966

1680

1300

856

507

412

1205



Pa

lb/in2

























14.36

Harrisburg, PA

T_4N

°F

21.2

23.4

32.0

41.2

51.1

60.6

65.7

64.2

56.5

44.6

36.1

26.6

43.5



Tax

°F

36.0

39.2

50.4

62.1

72.5

81.1

85.8

83.8

76.3

64.8

52.5

40.6

62.1



V

mi/hr

8.5

8.5

9.2

9.2

7.4

6.7

6.3

5.8

6.0

6.7

7.8

8.1

7.6



I

Btu/ft2/day

634

888

1205

1522

1744

1934

1871

1680

1363

1015

634

507

1236



Pa

lb/in2

























14.58

Philadelphia, PA

T_4N

°F

22.8

24.8

33.3

42.1

52.7

61.9

67.3

66.4

58.6

46.4

37.6

28.0

45.1



Tax

°F

37.9

41.0

51.6

62.6

73.0

81.7

86.2

84.6

77.5

66.4

55.0

43.3

63.3



V

mi/hr

10.3

10.7

11.2

10.7

9.6

8.7

8.1

8.1

8.5

8.7

9.6

10.1

9.4



I

Btu/ft2/day

634

888

1205

1522

1744

1934

1902

1712

1395

1015

666

539

1268



Pa

lb/in2

























14.74

Pittsburgh, PA

T_4N

°F

18.5

20.3

29.8

38.8

48.4

56.8

61.5

60.3

53.4

42.3

34.2

24.4

40.6



Tax

°F

33.6

36.9

48.9

60.3

70.5

79.0

82.6

80.8

74.3

62.4

50.4

38.7

59.9



V

mi/hr

10.5

10.1

10.5

10.1

8.7

7.8

7.2

6.7

7.2

8.1

9.4

10.3

8.9



I

Btu/ft2/day

539

793

1110

1458

1744

1934

1871

1649

1332

951

571

444

1205



Pa

lb/in2

























14.11

Wilkes-Barre, PA

T_4N

°F

17.4

19.0

28.2

38.1

48.4

56.8

61.5

60.1

52.9

42.1

34.0

23.4

40.3



Tax

°F

31.8

34.5

45.5

57.7

69.3

77.5

81.9

79.7

72.3

61.0

48.7

36.7

58.1



V

mi/hr

8.7

8.7

9.4

9.4

8.5

7.8

7.2

6.9

7.4

7.8

8.5

8.7

8.3



I

Btu/ft2/day

571

793

1141

1458

1712

1902

1871

1649

1300

919

571

444

1205



Pa

lb/in2

























14.26

Williamsport, PA

T_4N

°F

17.1

19.2

28.6

38.1

47.8

56.7

61.5

60.4

53.1

41.5

33.6

23.9

40.1



Tax

°F

33.3

36.7

47.7

60.1

71.1

79.0

83.1

81.1

73.8

62.4

49.8

37.9

59.7



V

mi/hr

8.9

8.7

9.2

9.4

7.8

7.2

6.3

6.0

6.3

6.7

8.3

8.7

7.8



I

Btu/ft2/day

571

824

1141

1458

1712

1902

1871

1617

1268

919

571

444

1205



Pa

lb/in2

























14.47

San Juan, PR

T_4N

°F

70.9

70.5

71.6

72.9

74.5

76.1

76.8

76.6

76.3

75.6

73.9

72.3

73.9



Tax

°F

83.1

83.7

84.4

85.8

87.3

88.5

88.5

88.7

88.9

88.3

85.8

83.8

86.4


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ



i

U)

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

7.8

8.5

8.9

8.5

7.8

8.5

9.2

8.3

7.2

6.5

7.2

7.8

8.1



I

Btu/ft2/day

1363

1554

1807

1934

1839

1934

1934

1902

1744

1554

1363

1268

1680



Pa

lb/in2

























14.71

Providence, Rl

T_4N

°F

19.0

20.8

28.8

37.8

47.3

56.8

63.1

61.9

53.8

43.0

34.9

24.4

41.0



Tax

°F

36.7

38.3

46.0

57.0

67.3

76.8

82.0

80.8

74.3

64.0

53.1

41.2

59.7



V

mi/hr

11.0

11.4

12.1

12.1

10.7

9.8

9.4

9.2

9.4

9.4

10.5

10.7

10.3



I

Btu/ft2/day

602

856

1173

1490

1775

1902

1871

1649

1332

983

602

507

1236



Pa

lb/in2

























14.71

Charleston, SC

T_4N

°F

37.8

39.9

47.5

54.0

63.0

69.1

72.7

72.1

67.8

56.3

47.1

40.6

55.8



Tax

°F

57.7

61.0

68.5

75.7

82.8

87.6

90.1

89.1

84.9

77.2

69.4

61.5

75.6



V

mi/hr

8.7

9.6

9.8

9.6

8.5

8.3

7.8

7.4

7.6

8.1

8.1

8.3

8.5



I

Btu/ft2/day

856

1110

1490

1871

1966

1966

1934

1744

1490

1300

983

793

1458



Pa

lb/in2

























14.75

Columbia, SC

T_4N

°F

32.2

34.2

42.3

49.5

58.3

66.0

70.0

69.3

63.1

50.2

41.5

34.9

50.9



Tax

°F

55.2

59.4

68.2

76.5

83.5

88.9

91.6

90.1

85.1

76.3

67.8

58.8

75.0



V

mi/hr

7.2

7.6

8.1

8.1

6.9

6.5

6.0

5.6

6.0

6.0

6.3

6.9

6.7



I

Btu/ft2/day

824

1078

1427

1807

1934

1997

1934

1744

1522

1268

919

761

1427



Pa

lb/in2

























14.65

Greenville, SC

T_4N

°F

30.0

32.4

39.9

47.7

56.5

64.4

68.4

67.5

61.2

48.9

40.5

33.4

49.3



Tax

°F

50.2

54.3

63.5

72.0

79.3

85.5

88.2

86.7

81.1

72.0

62.4

53.2

70.7



V

mi/hr

7.6

8.3

8.5

8.5

7.2

6.7

6.3

6.0

6.5

6.7

7.2

7.4

7.2



I

Btu/ft2/day

824

1046

1395

1775

1902

1997

1902

1744

1490

1236

888

729

1427



Pa

lb/in2

























14.26

Huron, SD

T_4N

°F

2.3

9.1

21.7

34.0

44.8

55.6

61.7

58.8

47.3

35.4

21.7

7.9

33.4



Tax

°F

24.1

29.7

42.1

58.6

70.3

80.2

87.1

84.7

74.1

61.5

43.0

28.2

57.0



V

mi/hr

11.4

11.0

12.3

12.5

11.6

10.5

9.6

9.8

10.5

10.7

11.0

10.7

11.0



I

Btu/ft2/day

571

824

1173

1554

1839

2061

2093

1839

1395

951

602

476

1300



Pa

lb/in2

























14.05

Pierre, SD

T_4N

°F

6.6

12.0

22.6

34.9

45.7

55.8

62.1

59.9

48.6

37.0

23.5

11.1

35.1



Tax

°F

27.1

32.7

44.1

59.4

70.9

81.5

90.0

88.0

76.3

63.0

44.6

30.7

59.0



V

mi/hr

12.3

11.6

13.0

13.2

12.5

11.0

10.7

11.0

11.4

11.2

11.2

11.6

11.6



I

Btu/ft2/day

571

856

1236

1585

1902

2124

2156

1902

1427

983

634

476

1332



Pa

lb/in2

























13.82


-------
<1

u>

On

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Rapid City, SD

Tan

°F

10.8

15.3

22.3

32.2

42.3

51.6

58.3

56.1

45.5

34.9

22.8

12.7

33.6



Tax

°F

33.8

38.1

45.9

57.9

68.2

77.7

86.2

85.1

74.5

62.4

46.8

35.6

59.4



V

mi/hr

11.4

11.4

12.8

13.4

12.5

11.0

10.3

10.3

11.2

11.2

10.7

11.0

11.4



I

Btu/ft2/day

602

888

1268

1617

1902

2124

2156

1934

1490

1046

666

507

1363



Pa

lb/in2

























13.11

Sioux Falls, SD

T_4N

°F

3.4

9.7

22.6

34.9

45.9

56.1

62.2

59.4

48.7

36.0

22.6

8.6

34.2



Tax

°F

24.3

29.7

42.3

59.0

70.7

80.4

86.4

83.3

73.0

61.2

43.3

28.0

56.8



V

mi/hr

11.0

11.0

12.3

13.0

11.6

10.5

9.8

9.8

10.3

10.5

11.2

10.7

11.0



I

Btu/ft2/day

602

856

1205

1522

1839

2061

2093

1807

1363

983

602

476

1300



Pa

lb/in2

























13.98

Bristol, TN

T_4N

°F

24.3

26.8

35.4

43.0

51.6

59.9

64.0

63.1

56.7

44.2

36.0

28.2

44.4



Tax

°F

43.7

48.0

58.8

67.5

75.2

82.2

84.6

84.0

79.2

69.1

58.3

48.0

66.6



V

mi/hr

6.3

6.7

7.2

6.9

5.4

4.7

4.3

3.8

4.3

4.7

5.6

6.0

5.4



I

Btu/ft2/day

698

919

1268

1617

1807

1934

1839

1712

1427

1141

761

602

1300



Pa

lb/in2

























13.98

Chattanooga, TN

T_4N

°F

28.0

31.1

39.0

46.8

55.4

63.9

68.4

67.6

62.6

48.9

39.9

31.3

48.6



Tax

°F

46.8

52.3

61.9

71.4

78.4

86.4

89.1

88.2

82.0

72.0

61.2

50.7

70.0



V

mi/hr

6.7

7.2

7.6

7.2

5.8

5.1

4.9

4.7

4.9

4.9

5.8

6.5

6.0



I

Btu/ft2/day

761

983

1300

1680

1839

1934

1871

1744

1427

1205

824

666

1363



Pa

lb/in2

























14.42

Knoxville, TN

T_4N

°F

26.1

29.1

36.7

44.6

53.1

61.9

66.0

65.3

59.0

46.0

37.6

30.0

46.2



Tax

°F

45.9

50.9

61.3

70.3

77.5

84.6

87.1

86.7

81.1

70.5

59.9

50.2

68.9



V

mi/hr

7.6

7.8

8.3

8.3

6.7

6.3

6.0

5.6

5.6

5.6

6.7

7.2

6.7



I

Btu/ft2/day

729

951

1268

1649

1839

1966

1871

1744

1427

1173

793

634

1332



Pa

lb/in2

























14.26

Memphis, TN

T_4N

°F

30.9

34.9

43.0

52.3

61.2

68.9

72.9

71.1

64.6

52.0

42.6

34.9

52.3



Tax

°F

48.6

53.4

63.1

73.2

81.0

89.2

92.3

90.9

83.8

74.3

62.2

52.5

72.1



V

mi/hr

9.4

9.8

10.3

10.1

8.7

7.8

7.4

6.9

7.4

7.6

8.7

9.4

8.5



I

Btu/ft2/day

793

1015

1332

1712

1934

2093

2061

1902

1522

1268

856

698

1427



Pa

lb/in2

























14.62

Nashville, TN

T_4N

°F

26.4

29.8

39.0

47.5

56.7

64.8

68.9

67.6

61.2

48.4

39.6

30.9

48.4



Tax

°F

45.9

50.7

61.2

70.9

78.8

86.5

89.4

88.3

82.6

72.5

60.4

50.2

69.8



V

mi/hr

9.2

9.4

10.1

9.4

7.8

7.4

6.7

6.5

6.7

7.2

8.5

9.4

8.3



I

Btu/ft2/day

729

983

1300

1712

1902

2061

1997

1807

1490

1205

793

634

1395


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





U)

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.45

Abilene, TX

T_4N

°F

30.7

35.1

43.3

52.9

61.2

68.9

72.7

71.8

65.3

54.9

43.3

34.0

52.9



Tax

°F

54.9

59.7

68.9

77.7

84.4

91.4

95.2

94.5

86.7

77.9

66.4

57.0

76.3



V

mi/hr

11.2

11.6

13.2

13.0

12.8

11.4

10.3

9.4

9.8

10.5

11.2

10.7

11.2



I

Btu/ft2/day

983

1236

1617

1934

2061

2219

2219

1997

1649

1395

1046

919

1617



Pa

lb/in2

























13.82

Amarillo, TX

T_4N

°F

21.2

25.5

32.7

42.1

51.6

60.6

65.5

63.9

56.5

44.4

32.4

23.7

43.3



Tax

°F

48.9

52.9

61.5

71.4

79.2

87.6

91.8

89.1

81.9

72.5

59.7

50.2

70.5



V

mi/hr

13.2

13.9

15.2

15.2

14.8

13.9

13.0

11.9

12.8

13.0

13.2

12.8

13.4



I

Btu/ft2/day

951

1205

1554

1934

2093

2251

2219

1997

1649

1395

1015

856

1585



Pa

lb/in2

























12.92

Austin, TX

T_4N

°F

38.7

42.1

51.1

59.7

66.6

71.4

73.9

73.9

69.8

60.1

49.8

41.2

58.3



Tax

°F

58.8

63.3

72.0

79.3

84.7

91.0

95.0

95.5

90.5

82.0

71.8

62.1

79.0



V

mi/hr

9.6

10.3

10.5

10.1

9.4

8.5

7.8

7.6

7.8

7.8

8.9

9.2

8.9



I

Btu/ft2/day

951

1205

1490

1712

1871

2093

2156

1997

1649

1395

1046

888

1554



Pa

lb/in2

























14.42

Brownsville, TX

T_4N

°F

49.8

52.5

59.2

66.6

72.0

74.8

75.7

75.4

73.2

66.0

59.0

52.3

64.8



Tax

°F

68.9

72.1

78.4

84.0

87.8

91.0

93.4

93.6

90.3

85.3

78.3

71.8

82.9



V

mi/hr

10.5

11.9

13.2

13.4

12.8

11.4

11.2

10.3

9.4

9.2

10.5

10.7

11.2



I

Btu/ft2/day

919

1173

1458

1680

1839

2029

2061

1902

1649

1427

1078

856

1522



Pa

lb/in2

























14.72

Corpus Christi, TX

T_4N

°F

45.3

48.0

55.2

63.1

69.4

73.4

74.8

75.0

72.3

63.9

55.6

48.4

62.1



Tax

°F

64.9

69.1

75.7

81.7

86.2

90.3

93.4

93.4

89.8

83.8

75.7

68.4

81.0



V

mi/hr

12.1

13.4

14.3

14.3

12.8

11.2

11.4

11.2

11.0

10.7

12.3

12.3

12.3



I

Btu/ft2/day

888

1141

1395

1585

1744

1934

1997

1839

1585

1363

1046

856

1458



Pa

lb/in2

























14.71

El Paso, TX

T_4N

°F

29.5

34.0

40.3

48.0

56.5

64.2

68.4

66.6

61.5

49.6

38.5

30.7

48.9



Tax

°F

56.1

62.2

70.0

78.6

87.1

96.4

96.1

93.6

87.1

78.4

66.4

57.6

77.5



V

mi/hr

7.2

7.8

9.8

9.8

9.2

7.8

7.2

6.7

6.5

6.3

6.9

6.7

7.6



I

Btu/ft2/day

1110

1427

1871

2251

2473

2536

2346

2156

1871

1554

1205

1015

1807



Pa

lb/in2

























12.79

Fort Worth, TX

T_4N

°F

32.7

36.9

45.7

54.7

62.6

70.0

74.1

73.6

66.9

55.8

45.3

36.3

54.7



Tax

°F

54.1

58.8

67.8

76.3

82.9

91.9

96.4

96.3

87.8

78.4

66.7

57.6

76.3



V

mi/hr

11.4

12.1

13.0

12.8

11.6

10.3

9.6

8.9

9.4

9.8

11.0

11.0

11.0


-------
<1

u>
o©

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

919

1173

1490

1775

1966

2188

2219

2029

1649

1332

983

856

1554



Pa

lb/in2

























14.45

Houston, TX

T_4N

°F

39.7

42.6

50.0

58.1

64.4

70.5

72.3

72.0

67.8

57.6

49.6

42.3

57.4



Tax

°F

61.0

65.3

71.1

78.4

84.6

90.1

92.7

92.5

88.3

81.7

72.3

64.8

78.6



V

mi/hr

8.9

9.4

9.8

9.8

8.7

8.1

7.2

6.7

7.4

7.6

8.5

8.7

8.5



I

Btu/ft2/day

856

1078

1332

1585

1775

1902

1871

1775

1554

1332

983

793

1395



Pa

lb/in2

























14.71

Lubbock, TX

T_4N

°F

24.6

28.6

36.3

46.8

55.8

64.2

68.0

66.2

59.4

48.0

36.5

27.1

46.8



Tax

°F

52.9

57.6

66.0

75.4

83.1

90.0

91.9

89.6

82.9

74.7

63.1

54.1

73.6



V

mi/hr

12.5

13.2

14.5

15.0

14.5

13.2

11.4

10.1

10.5

11.4

11.9

11.9

12.5



I

Btu/ft2/day

983

1236

1617

1966

2124

2251

2219

1997

1649

1395

1046

888

1617



Pa

lb/in2

























13.11

Lufkin, TX

T_4N

°F

36.9

39.7

47.5

55.8

63.1

69.4

72.1

71.2

66.6

54.9

46.4

38.8

55.2



Tax

°F

58.3

63.1

71.4

79.0

84.6

90.1

93.2

93.6

88.2

80.4

70.2

61.7

77.7



V

mi/hr

7.2

7.6

8.1

7.8

6.9

5.8

5.4

5.4

5.8

5.8

6.7

7.4

6.7



I

Btu/ft2/day

856

1110

1427

1680

1871

2029

2029

1902

1617

1363

983

793

1458



Pa

lb/in2

























14.59

Midland-Odessa, TX

T_4N

°F

28.6

32.5

40.3

49.5

58.1

65.7

68.5

67.5

61.2

50.5

38.8

30.7

49.3



Tax

°F

56.5

61.5

71.2

79.9

87.4

93.4

95.4

94.1

85.5

77.4

66.2

58.5

77.2



V

mi/hr

10.7

11.4

13.0

13.2

13.0

12.5

11.2

10.5

10.3

10.3

10.7

10.5

11.4



I

Btu/ft2/day

1046

1332

1744

2061

2219

2314

2219

2061

1712

1458

1141

951

1680



Pa

lb/in2

























13.28

Port Arthur, TX

T_4N

°F

41.5

44.4

51.3

59.5

66.4

72.0

73.8

73.2

69.6

59.2

51.3

44.2

58.8



Tax

°F

60.3

64.2

71.4

78.3

84.0

89.4

91.9

91.8

87.3

80.2

71.2

64.2

77.9



V

mi/hr

10.3

11.0

11.2

11.4

9.8

8.5

7.2

6.9

8.1

8.5

9.8

10.1

9.4



I

Btu/ft2/day

856

1110

1363

1649

1839

1997

1934

1807

1585

1363

983

824

1458



Pa

lb/in2

























14.75

San Angelo, TX

T_4N

°F

30.6

34.7

43.5

52.7

61.2

66.4

69.1

68.4

64.0

53.6

42.6

33.1

51.6



Tax

°F

56.8

62.1

72.7

81.1

87.4

92.7

96.3

95.4

86.7

78.8

68.2

59.0

78.1



V

mi/hr

10.3

10.7

12.3

11.9

11.4

10.3

9.4

8.7

8.7

8.9

9.8

9.6

10.3



I

Btu/ft2/day

1015

1300

1649

1934

2061

2219

2188

2029

1680

1427

1110

951

1617



Pa

lb/in2

























13.76

San Antonio, TX

T_4N

°F

37.9

41.4

49.6

58.5

65.7

72.7

75.0

74.5

69.3

58.8

48.7

40.8

57.7



Tax

°F

60.8

65.7

73.6

80.2

85.3

91.8

95.0

95.4

89.2

81.7

72.0

63.5

79.5


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ



i

U)

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



V

mi/hr

8.7

9.4

10.1

9.8

9.8

9.6

9.4

8.5

8.5

8.5

8.5

8.5

9.2



I

Btu/ft2/day

983

1236

1522

1744

1902

2124

2188

2029

1712

1427

1078

919

1554



Pa

lb/in2

























14.33

Victoria, TX

T_4N

°F

42.4

45.3

52.9

61.0

67.6

72.7

74.7

74.1

70.3

61.0

52.3

45.1

60.1



Tax

°F

62.8

66.7

73.8

80.2

85.3

90.7

93.6

93.9

88.9

82.4

73.4

66.0

79.9



V

mi/hr

10.5

11.4

11.9

11.6

11.0

9.6

9.2

8.5

8.9

9.2

10.1

10.3

10.3



I

Btu/ft2/day

888

1141

1395

1617

1807

1966

1966

1839

1585

1363

1046

856

1458



Pa

lb/in2

























14.68

Waco, TX

T_4N

°F

34.2

37.9

46.8

56.1

64.2

70.9

74.5

73.9

67.6

56.8

46.6

37.2

55.6



Tax

°F

56.1

60.8

69.6

78.1

84.4

91.9

96.8

97.2

89.6

80.2

68.7

59.4

77.7



V

mi/hr

11.4

12.3

13.2

13.0

12.1

11.0

10.7

10.1

10.1

10.3

11.0

11.0

11.4



I

Btu/ft2/day

919

1173

1490

1744

1902

2124

2188

2029

1649

1363

1015

856

1554



Pa

lb/in2

























14.47

Wichita Falls, TX

T_4N

°F

27.7

32.2

40.6

50.4

59.2

68.0

72.7

71.4

63.9

52.2

40.6

30.7

50.7



Tax

°F

52.0

57.2

66.4

75.7

83.3

91.6

97.2

95.9

86.7

76.8

64.2

54.9

75.2



V

mi/hr

11.4

12.1

13.2

13.2

12.8

11.6

11.2

10.3

10.5

11.0

11.4

11.0

11.6



I

Btu/ft2/day

919

1173

1522

1839

2029

2188

2219

1997

1649

1332

983

824

1554



Pa

lb/in2

























14.20

Cedar City, UT

T_4N

°F

17.2

22.1

27.1

33.4

41.2

49.6

57.9

56.5

47.1

36.1

26.8

18.1

36.1



Tax

°F

41.7

46.9

52.9

61.5

72.0

83.7

90.1

87.4

79.0

66.9

52.7

43.0

64.8



V

mi/hr

6.0

6.9

8.3

8.9

8.7

8.5

8.1

7.6

7.6

6.7

7.4

6.0

7.6



I

Btu/ft2/day

856

1110

1458

1902

2219

2473

2314

2061

1807

1363

919

761

1585



Pa

lb/in2

























12.02

Salt Lake City, UT

T_4N

°F

19.2

24.6

31.5

37.9

45.7

55.4

63.7

61.9

51.1

40.3

30.9

21.6

40.3



Tax

°F

36.3

43.5

52.2

61.3

72.0

82.8

92.1

89.4

79.2

66.0

50.7

37.8

63.7



V

mi/hr

7.8

8.5

9.6

9.8

9.4

9.4

9.6

9.6

9.4

8.5

8.5

7.6

8.9



I

Btu/ft2/day

602

919

1300

1712

2061

2346

2314

2061

1649

1173

698

539

1458



Pa

lb/in2

























12.65

Burlington, VT

T_4N

°F

7.5

9.0

21.9

34.2

45.3

54.7

59.7

57.9

48.7

38.7

29.7

15.4

35.2



Tax

°F

25.2

27.5

39.4

53.6

67.3

75.7

81.1

77.9

69.1

57.0

44.1

30.4

54.0



V

mi/hr

9.6

9.2

9.6

9.4

8.9

8.5

8.1

7.6

8.3

8.7

9.8

10.1

8.9



I

Btu/ft2/day

507

824

1141

1458

1744

1902

1934

1649

1268

824

507

380

1173



Pa

lb/in2

























14.55

Lynchburg, VA

T_4N

°F

24.6

27.3

35.4

43.9

52.5

60.8

65.1

64.4

57.7

45.7

37.2

29.1

45.3


-------
<1

-1^

o

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Tax

°F

43.5

47.1

57.4

67.6

75.6

82.6

86.0

84.9

78.4

68.4

58.1

47.7

66.4



V

mi/hr

7.8

7.8

8.5

8.5

6.9

6.7

6.0

6.0

6.3

6.7

7.4

7.6

7.2



I

Btu/ft2/day

761

1015

1363

1712

1902

2061

1966

1775

1490

1173

824

666

1395



Pa

lb/in2

























14.27

Norfolk, VA

T_4N

°F

30.9

32.4

39.4

47.1

56.8

65.1

70.0

69.4

64.2

52.9

43.9

35.4

50.5



Tax

°F

47.3

49.6

57.9

66.9

75.4

82.9

86.4

85.1

79.5

69.4

61.2

52.2

67.8



V

mi/hr

11.4

12.1

12.5

11.9

10.7

10.1

9.2

8.9

9.8

10.3

10.7

11.4

10.7



I

Btu/ft2/day

729

951

1300

1617

1839

1966

1871

1712

1427

1110

793

634

1332



Pa

lb/in2

























14.75

Richmond, VA

T_4N

°F

25.7

28.0

36.3

44.6

54.1

62.8

67.5

66.4

59.0

46.6

37.9

29.8

46.6



Tax

°F

45.7

49.3

59.5

70.0

77.7

85.1

88.3

87.1

81.0

70.7

61.3

50.2

68.7



V

mi/hr

8.3

8.7

9.4

9.2

8.1

7.6

6.9

6.5

6.7

7.2

7.6

8.1

7.8



I

Btu/ft2/day

729

951

1300

1649

1839

1997

1902

1712

1427

1110

793

634

1332



Pa

lb/in2

























14.68

Roanoke, VA

T_4N

°F

25.0

27.1

35.8

43.9

52.5

60.3

64.8

63.9

56.8

44.8

37.0

28.9

45.0



Tax

°F

43.9

47.3

57.7

67.3

75.7

82.9

86.4

85.3

78.4

68.2

57.9

47.7

66.6



V

mi/hr

9.4

9.2

9.6

9.6

7.6

6.9

6.5

6.0

6.0

6.7

7.8

8.5

7.8



I

Btu/ft2/day

729

983

1300

1649

1839

1966

1871

1744

1427

1141

793

634

1332



Pa

lb/in2

























14.16

Sterling, VA

T_4N

°F

21.0

23.4

31.8

40.3

50.0

59.2

64.0

62.8

55.4

42.4

34.2

25.9

42.4



Tax

°F

40.1

43.9

54.7

65.1

74.3

82.8

87.1

85.5

79.0

67.6

56.7

45.0

65.1



V

mi/hr

8.3

8.5

9.2

8.7

7.6

6.7

6.3

5.8

6.0

6.7

7.6

7.8

7.6



I

Btu/ft2/day

666

919

1268

1585

1839

1997

1902

1712

1395

1078

729

571

1300



Pa

lb/in2

























14.59

Olympia, WA

T_4N

°F

31.6

32.7

33.6

36.1

41.0

46.4

49.3

49.5

44.8

38.8

35.1

32.2

39.2



Tax

°F

44.4

49.5

54.0

58.8

65.3

70.9

76.5

77.2

71.1

60.4

50.0

44.2

60.3



V

mi/hr

7.4

7.2

7.4

7.6

7.4

6.9

6.5

6.3

6.0

6.0

7.4

6.9

6.9



I

Btu/ft2/day

317

539

888

1268

1585

1775

1871

1617

1205

698

380

285

1046



Pa

lb/in2

























14.65

Quillayute, WA

T_4N

°F

33.6

34.9

35.2

37.2

41.7

46.6

49.5

49.6

46.2

41.4

37.2

34.3

40.6



Tax

°F

46.0

49.1

51.4

55.0

59.9

64.2

68.2

69.1

66.9

59.4

50.9

46.2

57.2



V

mi/hr

10.3

9.6

9.2

8.3

7.6

7.2

6.9

6.3

6.7

8.1

9.4

9.4

8.3



I

Btu/ft2/day

317

507

824

1173

1490

1617

1649

1427

1110

666

380

254

951



Pa

lb/in2

























14.65


-------
|o
I On

|

loo

&

-Q

£
£1

c-f

o

P

CfQ





Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual

Seattle, WA

Tan

°F

35.2

37.4

38.5

41.2

46.2

52.0

55.2

55.8

52.0

45.9

40.1

35.8

44.6



Tax

°F

45.0

49.5

52.7

57.2

63.9

70.0

75.2

75.2

69.3

59.7

50.5

45.1

59.4



V

mi/hr

9.2

8.9

8.9

8.9

8.3

8.3

7.8

7.6

7.6

7.8

8.9

8.9

8.5



I

Btu/ft2/day

317

539

888

1300

1680

1839

1934

1649

1205

698

380

254

1046



Pa

lb/in2

























14.52

Spokane, WA

T_4N

°F

20.8

25.9

29.7

34.7

41.9

49.3

54.3

54.3

45.9

36.0

28.8

21.7

36.9



Tax

°F

33.3

40.6

47.7

57.0

65.8

74.7

83.1

82.6

72.0

58.6

41.4

33.8

57.6



V

mi/hr

9.4

9.6

10.1

10.5

9.8

9.6

9.2

8.5

8.7

8.5

9.4

8.3

9.4



I

Btu/ft2/day

412

634

1015

1458

1839

2061

2219

1871

1395

856

444

349

1205



Pa

lb/in2

























13.52

Yakima, WA

T_4N

°F

21.7

26.4

30.7

35.4

42.3

49.3

53.1

52.3

44.6

35.2

28.9

22.1

36.9



Tax

°F

37.6

46.4

55.2

63.1

71.6

79.9

86.7

85.6

76.8

64.4

48.4

37.6

62.8



V

mi/hr

5.8

6.7

7.8

8.5

8.5

8.5

8.1

7.6

7.6

6.7

6.3

5.4

7.4



I

Btu/ft2/day

444

698

1141

1585

1966

2188

2283

1966

1490

951

507

349

1300



Pa

lb/in2

























14.18

Charleston, WV

T_4N

°F

23.0

25.7

35.1

42.8

51.4

59.7

64.4

63.3

56.5

44.2

36.3

28.0

44.2



Tax

°F

41.2

45.3

56.7

66.7

75.6

83.1

85.6

84.4

78.8

68.2

57.4

46.0

65.8



V

mi/hr

7.2

6.9

7.6

7.4

5.8

5.1

4.9

4.5

4.7

4.9

6.0

6.7

6.0



I

Btu/ft2/day

634

856

1173

1522

1775

1902

1839

1680

1363

1046

666

539

1236



Pa

lb/in2

























14.26

Elkins, WV

T_4N

°F

16.2

18.3

27.1

34.9

44.1

52.0

56.8

56.1

49.8

37.2

29.7

21.4

37.0



Tax

°F

37.9

41.4

52.2

61.5

70.9

77.5

80.4

79.3

73.6

63.7

52.9

42.6

61.2



V

mi/hr

7.4

7.2

7.8

7.8

6.3

4.9

4.5

4.0

4.3

5.1

6.7

7.2

6.0



I

Btu/ft2/day

602

824

1141

1427

1680

1807

1744

1585

1300

983

634

507

1205



Pa

lb/in2

























13.73

Huntington, WV

T_4N

°F

23.2

26.1

35.4

43.9

52.3

60.4

64.9

63.9

57.0

45.0

37.0

28.4

44.8



Tax

°F

40.6

44.2

56.5

66.7

75.2

81.3

84.4

83.1

78.1

67.3

55.9

45.3

64.9



V

mi/hr

7.6

7.6

8.1

7.8

6.3

5.8

5.4

5.1

5.4

5.8

7.2

7.4

6.7



I

Btu/ft2/day

634

856

1173

1522

1775

1902

1839

1649

1363

1046

666

539

1236



Pa

lb/in2

























14.33

Eau Claire, Wl

T_4N

°F

0.9

5.7

19.8

33.4

45.0

54.3

59.7

57.2

47.8

36.9

23.7

8.2

32.7



Tax

°F

20.5

26.8

39.4

56.5

69.4

78.3

83.1

80.1

70.0

58.3

40.8

25.3

54.1



V

mi/hr

8.9

8.7

9.8

10.3

9.4

8.9

8.1

7.6

8.3

8.7

9.2

8.9

8.9



I

Btu/ft2/day

539

856

1173

1458

1775

1934

1934

1649

1236

856

507

444

1205


-------
<1

-1^

K>

Q

£
Pu

in

ft

W

E

CO
00 CO

H H

O

*
hr1
>
o
H
CD

co

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



Pa

lb/in2

























14.26

Green Bay, Wl

T_4N

°F

5.7

9.5

21.4

34.0

43.7

53.4

58.8

56.8

48.7

38.5

26.8

12.6

34.2



Tax

°F

22.8

27.1

38.5

54.0

67.3

75.6

80.4

77.5

69.1

57.4

42.1

27.7

53.2



V

mi/hr

10.7

10.3

10.7

11.0

9.8

8.9

7.8

7.6

8.5

9.4

10.3

10.3

9.6



I

Btu/ft2/day

539

824

1173

1490

1807

1997

1934

1649

1236

856

507

444

1205



Pa

lb/in2

























14.36

La Crosse, Wl

T_4N

°F

5.4

10.0

23.5

37.0

48.0

57.0

62.2

59.9

51.3

40.3

27.7

12.6

36.3



Tax

°F

23.5

29.7

42.1

58.5

70.9

79.9

84.6

81.7

72.3

60.3

43.3

28.0

56.1



V

mi/hr

8.7

8.3

9.2

9.8

8.9

8.3

7.6

7.4

8.1

8.7

9.2

8.5

8.5



I

Btu/ft2/day

571

856

1173

1490

1807

1997

1966

1712

1268

888

539

444

1236



Pa

lb/in2

























14.39

Madison, Wl

T_4N

°F

7.2

11.1

23.0

34.2

44.2

54.1

59.5

56.8

48.2

37.8

26.8

13.5

34.7



Tax

°F

24.8

30.0

41.5

56.7

68.9

78.3

82.4

79.5

71.4

59.9

44.1

29.8

55.6



V

mi/hr

10.3

10.1

11.0

11.2

9.6

8.9

8.1

7.6

8.5

9.4

10.3

10.1

9.6



I

Btu/ft2/day

602

888

1173

1490

1839

2029

1966

1712

1300

888

539

476

1236



Pa

lb/in2

























14.29

Milwaukee, Wl

T_4N

°F

11.7

16.0

26.2

35.8

44.8

55.0

62.1

60.8

52.9

41.7

30.7

17.4

37.9



Tax

°F

26.1

30.0

40.5

52.9

64.2

74.8

79.9

77.7

70.5

58.6

44.8

31.3

54.3



V

mi/hr

12.3

11.9

12.3

12.3

11.0

10.3

9.6

9.4

10.1

11.2

11.9

11.9

11.2



I

Btu/ft2/day

571

824

1110

1458

1839

2029

1997

1712

1300

919

571

444

1236



Pa

lb/in2

























14.37

Casper, WY

T_4N

°F

12.0

16.0

21.7

29.5

37.9

46.9

54.0

51.8

41.5

32.2

21.7

13.6

31.6



Tax

°F

32.7

37.0

45.1

56.1

66.6

78.6

87.6

85.6

73.8

60.4

44.2

34.0

58.5



V

mi/hr

17.0

15.2

13.9

12.5

11.6

10.7

10.3

10.3

11.0

12.1

14.3

15.4

12.8



I

Btu/ft2/day

634

919

1300

1649

1934

2219

2219

1997

1554

1078

698

539

1395



Pa

lb/in2

























12.14

Cheyenne, WY

T_4N

°F

15.3

18.1

22.1

30.0

39.4

48.4

54.7

52.9

43.7

34.0

23.7

16.7

33.3



Tax

°F

37.8

40.5

45.0

54.7

64.6

74.5

82.2

80.1

71.1

60.1

46.8

38.8

57.9



V

mi/hr

15.9

14.8

14.5

14.5

13.0

11.4

10.3

10.3

11.2

12.1

13.2

14.5

13.0



I

Btu/ft2/day

698

983

1332

1680

1902

2124

2124

1871

1554

1141

761

602

1395



Pa

lb/in2

























11.76

Lander, WY

T_4N

°F

7.9

13.6

22.1

30.7

39.9

48.7

55.9

53.8

44.2

33.6

19.9

9.3

31.6



Tax

°F

31.3

37.0

45.7

55.8

66.0

77.4

86.2

83.8

72.3

59.7

42.4

32.2

57.6



V

mi/hr

5.4

5.6

6.9

7.8

8.1

7.6

7.6

7.4

6.9

6.0

5.6

5.6

6.7


-------
|o
C\

|

|oo

&

Location

Symbol

Units

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Annual



/

Btu/ft2/day

698

1015

1395

1775

2029

2251

2219

1997

1585

1141

729

602

1458



Pa

lb/in2

























12.02

Rock Springs, WY

T_4N

°F

11.1

14.4

20.7

28.4

36.9

45.7

52.9

50.7

41.0

31.3

19.9

11.8

30.4



Tax

°F

29.5

34.3

41.7

52.7

63.7

74.7

83.1

80.8

70.0

57.2

40.6

30.7

54.9



V

mi/hr

11.9

11.9

12.1

12.1

11.2

10.3

9.4

9.2

9.6

9.8

10.5

11.4

10.7



I

Btu/ft2/day

666

951

1332

1712

2029

2283

2283

2029

1649

1173

729

602

1458



Pa

lb/in2

























11.52

Sheridan, WY

T_4N

°F

8.4

14.5

21.6

30.4

39.0

47.3

53.1

51.6

41.4

31.6

19.8

10.2

30.7



Tax

°F

33.1

38.3

46.2

57.0

66.4

76.8

86.2

85.3

72.9

61.7

45.3

35.1

58.6



V

mi/hr

7.8

7.8

8.9

9.6

8.9

7.6

7.4

7.2

7.4

7.4

7.4

7.6

7.8



I

Btu/ft2/day

571

856

1236

1585

1839

2124

2188

1902

1458

983

634

507

1332



Pa

lb/in2

























12.73

r;	a References 22. 13 and 1 I Data for this table are 30-vear averages for the years 1961 through 1990. prepared by the National Renewable Energy

c	Laboratory and distributed by the National Climatic Data Center. Similar historical averages of meteorological data from nearby National Weather

Service sites or site-specific data may also be used.

o	Tax = average daily maximum ambient temperature

3	Tan = average daily minimum ambient temperature

^	V = average wind speed

g	I = average daily total insolation factor

«T	Pa = average atmospheric pressure

l

-1^


-------
Table 7.1-8. RIM-SEAL LOSS FACTORS, KRa, KRb, and n,
FOR FLOATING ROOF TANKS3

Tank Construction And

Average-Fitting Seals

KRa

KRb



Rim-Seal System

n

(lb-molc/ft-vr)

|lb-molc/(mph)"-rt-vr|

(dimensionless)

Welded Tanks

Mechanical-shoe seal







Primary onlyb

5.8

0.3

2.1

Shoe-mounted secondary

1.6

0.3

1.6

Rim-mounted secondary

0.6

0.4

1.0

Liquid-mounted seal







Primary only

1.6

0.3

1.5

Weather shield

0.7

0.3

1.2

Rim-mounted secondary

0.3

0.6

0.3

Vapor-mounted seal







Primary only

6.T

0.2

3.0

Weather shield

3.3

0.1

3.0

Rim-mounted secondary

2.2

0.003

4.3

Riveted Tanks

Mechanical-shoe seal







Primary only

10.8

0.4

2.0

Shoe-mounted secondary

9.2

0.2

1.9

Rim-mounted secondary

1.1

0.3

1.5

Tank Construction And
Rim-Seal System

Tieht-Fittined Seals

Kg,
(lb-molc/ft-vr)

Kftb

rib-mole/(mi3h)n-ft-vrl

n

(dimensionless)

Welded Tanks

Mechanical-shoe seal







Primary onlv

1.5

0.4

1.9

Shoe-mounted secondary

1.0

0.4

1.5

Rim-mounted secondary

04

04

L0

Liauid-mounted seal







Primary onlv

1.0

0.08

1.8

Weather shield

0.4

0.2

1.3

Rim-mounted secondary

02

04

04

VaDor-mountcd seal







Primary onlv

5.6

0.2

2.4

Weather shield

2.8

0.1

2.3

Rim-mounted secondary

2.2

0.02

2.6

Note: The rim-seal loss factors Ki<;,. Kkh. and n may only be used for wind speeds below 15 miles per
hour.

a References 5 and 15.

b If no specific information is available, a welded tank with an average-fitting mechanical-shoe primary
seal can be used to represent the most common or typical construction and rim-seal system in use for
external and domed external floating roof tanks.
c If no specific information is available, this value can be assumed to represent the most common or
typical rim-seal system currently in use for internal floating roof tanks.

7.1-144

Liquid Storage TanksEMISSION FACTORS

44-06/07-18


-------
d "Tight-fitting'1 means that the rim seal is maintained with no gaps greater than 1/8 in. wide between the
rim seal and the tank shell. It is not appropriate to use the values for tight-fitting seals unless the seal is
known to be maintained with gaps no greater than 1/8 in. through the full range of liquid level in the
tank.

+4-06/0^18

Liquid Storage Tanks

7.1-145


-------
Table 7.1-9. AVERAGE ANNUAL WIND SPEED (v) FOR. SELECTED U. S.

LOCATIONSaRESERVED

7.1-146

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


-------
Table 7.1-10. AVERAGE CLINGAGE FACTORS, Cs;
(bbl/103 ft2)

Product Stored

Shell Condition

Light Rust

Dense Rust

Gunite Lining

Gasoline

0.0015

0.0075

0.15

Single-component stocks

0.0015

0.0075

0.15

Crude oil

0.0060

0.030

0.60

a Reference_5-3-. If no specific information is available, the values in this table can be assumed to
represent the most common or typical condition of tanks currently in use.

Table 7.1-11. TYPICAL NUMBER OF COLUMNS AS A FUNCTION OF TANK
DIAMETER FOR INTERNAL FLOATING ROOF TANKS WITH COLUMN-
SUPPORTED FIXED ROOFS3

Tank Diameter Range D, (ft)

Typical Number
Of Columns, Nc

0 < D < 85

1

85 
-------
Table 7.1-12. DECK-FITTING LOSS FACTORS, KFa, K^,
AND m, AND TYPICAL NUMBER OF DECK FITTINGS, N,;

Fitting Type And Construction Details

Loss Factors

Typical Number Ot
Fittings, Nf

KFa
(lb-mole/yr)

K-Fb

(lb-mole/(mph)m-yr)

m

(dimensionless)

Access hatch (24 inch diameter well)







1

Bolted cover, gasketedb

1.6

0

0



Unbolted cover, ungasketed

36c

5.9

1.2



Unbolted cover, gasketed

31

5.2

1.3



Fixed roof support column welld







Nc

Round pipe, ungasketed sliding cover

31





(Table 7.1-11)

Round pipe, gasketed sliding cover

25







Round pipe, flexible fabric sleeve seal

10







Built-up column, ungasketed sliding coverc

51







Built-up column, gasketed sliding cover

33







Unslotted guide-pole and well (8 inch









diameter unslotted pole, 21 inch









diameter well)









Ungasketed sliding coverb

31

150

1.4



Ungasketed sliding cover w/pole sleeve

25

2.2

2.1



Gasketed sliding cover

25

13

2.2



Gasketed sliding cover w/pole wiper

14

3.7

0.78



Gasketed sliding cover w/pole sleeve

8.6

12

0.81



Slotted guide-pole/sample well (8 inch









diameter slotted pole, 21 inch









diameter well)e







f

Ungasketed or gasketed sliding cover

43

270

1.4



Ungasketed or gasketed sliding cover,









with float8

31

36

2.0



Gasketed sliding cover, with pole wiper

41

48

1.4



Gasketed sliding cover, with pole sleeve

11

46

1.4



Gasketed sliding cover, with pole sleeve









and pole wiper

8.3

4.4

1.6



Gasketed sliding cover, with float and









pole wiper8

21

7.9

1.8



Gasketed sliding cover, with float, pole









sleeve, and pole wiper11

11

9.9

0.89



Flexible enclosure1

21

19

L8



Gauge-float well (automatic gauge)







1

Unbolted cover, ungasketedb

14c

5.4

1.1



Unbolted cover, gasketed

4.3

17

0.38



Bolted cover, gasketed

2.8

0

0



Gauge-hatch/sample port







1

Weighted mechanical actuation,









gasketedb

0.47

0.02

0.97



Weighted mechanical actuation,









ungasketed

2.3

0

0



Slit fabric seal, 10% open areac

12







Vacuum breaker







Nvb (Table 7.1-13))

Weighted mechanical actuation,









ungasketed

7.8

0.01

4.0



Weighted mechanical actuation, gasketedb

6.2C

1.2

0.94



Deck drain (3-inch diameter)









Openb

1.5

0.21

1.7

Nd (Table 7.1-13),

90% closed

1.8

0.14

1.1



Stub drain (1-inch diameter)k

1.2





Nd (Table 7.1-15)

7.1-148

Liquid Storage TanksEMISSION FACTORS

+4-06/0718


-------


Loss Factors

Typical Number Ot
Fittings, Nf

Fitting Type And Construction Details

KFa
(lb-mole/yr)

K-Fb

(lb-mole/(mph)m-yr)

m

(dimensionless)

Deck leg (3 inch diameter). IFR-tvpe (total
sleeve length approx. 12 inches)111
Adjustable, internal floating deck0

7.9





Ni (Table 7.1-15)

Deck lea, EFR-tvpe (pontoon area of
pontoon roofs; total sleeve length approx. 30
inches)

Adjustable, pontoon area - imgasketedb
Adjustable, pontoon area - gasketed
Adjustable, pontoon area - sock

2.0
1.3
1.2

0.37
0.08
0.14

0.91
0.65
0.65

Ni (Table 7.1-14)

Deck lea, EFR-tvpe (double-deck roofs and
center area of pontoon roofs, total sleeve
lenath approx. 48 inches)

Adjustable, center area - ungasketedb
Adjustable, center area - gasketed™
Adjustable, center area - sock™

0.82
0.53
0.49

0.53
0.11
0.16

0.14
0.13
0.14

Ni (Table 7.1-14)

Deck lea or hanaer (no openina throuah deck)
Fixed

0

0

0

Ni mav be set as 0
(no openinas)

Rim vent11

Weighted mechanical actuation, ungasketed
Weighted mechanical actuation, gasketedb

0.68
0.71

1.8
0.10

1.0
1.0

1

Ladder well
Sliding cover, ungasketedc
Sliding cover, gasketed

98
56





ld

Ladder-auidepole combination well
Slidina cover, unaasketed
Ladder sleeve, unaasketed slidina cover
Ladder sleeve, aasketed slidina cover

98
65
60





ld

Note: The deck-fitting loss factors, Kh„ Ka, and m, may only be used for wind speeds below 15 miles
per hour.

a Reference 5, unless otherwise indicated.

b If no specific information is available, this value can be assumed to represent the most common or

typical deck fitting currently in use for external and domed external floating roof tanks.
c If no specific information is available, this value can be assumed to represent the most common or

typical deck fitting currently in use for internal floating roof tanks.
d Column wells and ladder wells are not typically used with self-supported fixed roofs.
e References 16,19.

1 A slotted guide pole/sample well is an optional fitting and is not typically used.There is no typical
quantity or configuration of unslotted or slotted guidepoles. and thus tank specific data should be
obtained.

8 Tests were conducted with floats positioned with the float wiper at and 1 inch above the sliding cover.
The user is cautioned against applying these factors to floats that are positioned with the wiper or top of
the float below the sliding cover ("short floats"). The emission factor for such a float is expected to be
between the factors for a guidepole without a float and with a float, depending upon the position of the
float top and/or wiper within the guidepole.
h Tests were conducted with floats positioned with the float wiper at varying heights with respect to the
sliding cover. This fitting configuration also includes a pole sleeve which restricts the airflow from the
well vapor space into the slotted guidepole. Consequently, the float position within the guidepole (at,
above, or below the sliding cover) is not expected to significantly affect emission levels for this fitting
configuration, since the function of the pole sleeve is to restrict the flow of vapor from the vapor space
below the deck into the guidepole.

+4-06/0^18

Liquid Storage Tanks

7.1-149


-------
1 EPA's Storage Tank Emission Reduction Partnership Program granted the flexible enclosure system

equivalency to the pole float system. T65 FR 19891(04/13/00)1
J Nvb = 1 for internal floating roof tanks.

k Stub drains are not used on welded contact internal floating decks.

m These loss factors were derived using the results from pontoon area deck legs with gaskets and

seeksrLoss factors for EFR-tvpe deck legs may be used for an IFR if the total height of the leg sleeves.
including the portion extending down into the liquid, is similar to that of the EFR-tvpe deck leg.
n Rim vents are used only with mechanical-shoe primary seals.

7.1-150

Liquid Storage TanksEMISSION FACTORS

44-06/Q218


-------
Table 7.1-13. EXTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF
VACUUM BREAKERS, Nvb, AND DECK DRAINS, Nda

Tank Diameter

Number Of Vacuum Breakers, NVb

Number Of Deck drains, Nd

D (feet)b

Pontoon Roof

Double-Deck Roof

50

1

1

1

100

1

1

1

150

2

2

2

200

3

2

3

250

4

3

5

300

5

3

7

350

6

4

ND

400

7

4

ND

a Reference_5-3-. This 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 deck drains may also vary greatly depending on the design rainfall and manufacturing
prerogatives. For tanks more than 350 feet in diameter, actual tank data or the manufacturer's
recommendations may be needed for the number of deck drains. This table should not be used when
actual tank data are available. ND = no data.
b If the actual diameter is between the diameters listed, the closest diameter listed should be used. If the
actual diameter is midway between the diameters listed, the next larger diameter should be used.

+4-06/0^18

Liquid Storage Tanks

7.1-151


-------
Table 7.1-14. EXTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER OF

ROOF LEGS, Nia

Tank Diameter, D (feet)b

Pontoon Roof

Number Of Legs On
Double-Deck Roof

Number Of Pontoon

Legs

Number Of Center Legs

30

4

2

6

40

4

4

7

50

6

6

8

60

9

7

10

70

13

9

13

80

15

10

16

90

16

12

20

100

17

16

25

110

18

20

29

120

19

24

34

130

20

28

40

140

21

33

46

150

23

38

52

160

26

42

58

170

27

49

66

180

28

56

74

190

29

62

82

200

30

69

90

210

31

77

98

220

32

83

107

230

33

92

115

240

34

101

127

250

35

109

138

260

36

118

149

270

36

128

162

280

37

138

173

290

38

148

186

300

38

156

200

310

39

168

213

320

39

179

226

330

40

190

240

340

41

202

255

350

42

213

270

360

44

226

285

370

45

238

300

380

46

252

315

390

47

266

330

400

48

281

345

a Reference_5-3-. This table was derived from a survey of users and manufacturers. The actual number of roof legs
may vary greatly depending on age, style of floating roof loading specifications, and manufacturing prerogatives.
This table should not be used when actual tank data are available.
b If the actual diameter is between the diameters listed, the closest diameter listed should be used. If the actual
diameter is midway between the diameters listed, the next larger diameter should be used.

7.1-152

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


-------
Table 7.1-15. INTERNAL FLOATING ROOF TANKS: TYPICAL NUMBER
OF DECK LEGS, Ni, AND STUB DRAINS, Nda

Deck fitting type

Typical Number Of Fittings, Nf

Deck leg or hanger wellb
Stub drain (1-inch diameter)'1 c

(5 + ° + D")
10 600

D2

(—)

125

a Reference 5.-4-
b D = tank diameter, ft

c Not used on welded contact internal floating decks.

Table 7.1-16. DECK SEAM LENGTH FACTORS (SD) FOR TYPICAL DECK
CONSTRUCTIONS FOR INTERNAL FLOATING ROOF TANKS3

Deck Construction

Typical Deck Seam Length Factor,
SD (ft/ft2)

Continuous sheet construction13



5 ft wide

0.20c

6 ft wide

0.17

7 ft wide

0.14

Panel constructiond



5 x 7.5 ft rectangular

0.33

5 x 12 ft rectangular

0.28

a Reference_5-4. Deck seam loss applies to bolted decks only.
b Sd = 1/W, where W = sheet width (ft).

c If no specific information is available, this value can be assumed to represent the most common bolted

decks currently in use.
d Sd = (L+W)/LW, where W = panel width (ft) and L = panel length (ft).

+4-06/0^18

Liquid Storage Tanks

7.1-153


-------
Table 7.1-17. ROOF LANDING LOSSES FOR INTERNAL FLOATING ROOF TANK WITH A

LIQUID HEELa	

Standing Idle Loss

Lsl ~ P^lT nd Kh, Mv Ks

Lsl

R T,

1V

Lsl < 5.9 D2 hk Wx

Equation 2 16

Equation 3-7

Equation 2-43-3-4

Standing Idle Saturation Factor

K c ~

1

A\

1 + 0.053 (PA,.)

1

1 + 0,0531'r , Hvo

Where Hvo is set equal to hv.

Ks
-------
Table 7.1-18. ROOF LANDING LOSSES FOREXTERNAL FLOATING ROOF TANK WITH A
LIQUID HEELa

Standing Idle Loss

Lsl = 0.57 nd D P Mv

Lsl < 5.9 D2 hle W,

Equation S-443-10
Equation 2-43-3-4

Standing Idle
Saturation Factor

Not applicable

Filling Loss
Equation

T -

{PVA

\t (c

1 II

S £

} <1

l RTJ

rpVAv;

v RTv

AJv

W, (c„. 5)

Equation 2 27

Equation 3-18

(/	\ (	(p V ^

(0 57»,DF-M„)







11 j Ke

krt ,

Mv Ks

11 j Ke

V v

vi?ry

Mv Ks







Equation 2 30

Q/ = i -

(0S7-l-D-P*-Mv)-(l-KE^PvRAT^v)-Mv-Ks

¦My(l-S) J J

¦ ) Equation 3-21

P V

'2l- TT^ '	VA V-M„

LFi< (SSD-hM)-^ + 0.15-



Equation 3-16

Filling Saturation
Factor (S)

S = 0.6 for a full liquid heel
S = 0.5 for a partial liquid heel

Reference 21.

+4-06/0^18

Liquid Storage Tanks

7.1-155


-------
Table 7.1-19. ROOF LANDING LOSSES FOR ALL DRAIN-DRY TANKS2-

Standing Idle Loss

Lsl = 0.0063 Wj

rnD^

Lsl ^ 0 60

PVT,

RT

-Mr,

L„ < 0.60 /''1' V]" Mv

sl	R T i

Equation 2-23-3-12

Equation 2 23

Equation 3-15

Standing Idle Saturation
Factor

Not applicable

Filling Loss Equation

~h

P K.

RT.

M,, S

Lfl ~

Pva Vv
v ^ Tv j

Mv (C„-

Where Gf is set equal to 1.

Equation 2 26

Equation 3-18

Filling Saturation Factor (S) S = 0.15

Reference 21.

where:

—Ls——standing idle loss por landing opisodo (lb)

—h-4——number of days tho tank stands idle with tho floating roof landed (days)
—Kg.———vapor space expansion factor (per day)

AT,, f1 0.50BP ^
-K,. =	E—J-4-

T { T(Pa-P\

--A-Tv——average daily vapor tomporaturo range (°R)

	—average temperature of the vapor and liquid below the floating roof (°R)

	6-=—constant from the vapor pressure equation shown in Equation 1 21 (°R)

	P-=—true vapor pressure of the stock liquid (psia)

—Pa——atmospheric pressure at tho tank location (psia)

—¥v——volume of the vapor space (ft'-)

-4%v——height of the vapor space under the floating roof (ft)

7.1-156

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


-------
—D-=—tank diameter (ft)

——ideal gas constant (psia ft* / lb mole R) ~ 10.731
-Mv-—stock vapor molecular weight (lb/lb mole)
—K-g.———standing idle saturation factor (dimensionless)
—S-=—filling saturation factor (dimensionless)

vapor pressure function (dimensionless)

-P* =

( P\

KPa J

1-

fp\
J

—W+——stock liquid density (lb/gal)

——effective height of the stock liquid (ft)
——filling loss per landing episode (lb)

¦€*#=	filling saturation correction factor (dimensionless)

+4-06/0^18

Liquid Storage Tanks

7.1-157


-------
Table 7.1-20. TANK CLEANING EQUATIONS - VAPOR SPACE PURGE EMISSIONS3

Vaoor Soacc Purse

L„ = ' 1: \/ S Eauation4-2

R Tv

Vaoor Soacc Volume. Vv

Fixed Roof Tank

Vv = Hvn (n D ^/4) Eauation 4-3

where:

Hvn = the fixed-roof tank vaoor soacc outage (ft)

Floating Roof Tank

T v = hv (% D ^/4) Eauation 4-9

where:

hv = the height of the vaoor soace under the landed floating roof (ft)

Saturation Factor. S

Fixed Roof Tank

S= (0.5;?rf+l)/6 Eauation 4-6

where:

n,i = oeriod of time standing idle after emotving and before commencement of
forced ventilation (davs)

S > 0.25 Eauation 4-7

S <0.5 Eauation 4-8

Floating Roof Tank (function of heel condition and tank tvpe)

S = 0.6 (V full liauid heel
S'=0.5 G oartial liauid heel
S = 0 drain drv tanks

where:

CV = 1.0 for IFRTs (and Domed EFRTs):

(V evaluated oer Eauation 3-21 for EFRTs for the initial vaoor soace ourge: set

to 1.0 for subseauent vaoor soace ourges that follow ventilation
having been shut off overnight.

a Reference 23.

7.1-158

Liquid Storage TanksEMISSION FACTORS

4406/W18


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Table 7.1-21. TANK CLEANING EQUATIONS - CONTINUED FORCED VENTILATION

EMISSIONS3

Continued Forced
Ventilation

Lcv - 60 Ov ncv tv Cv

{ Pa Mcg
{ RTV j

Eauation4-10

Prior Stock Remains

Lev < 5.9D2h,. W,



Equation 4-12

Distillate Flushing

If liauid is beins circulated throueh the tank, there would be no mass-based limit



on emissions in that the liauid is beins continually replenished. If a fixed amount



of liauid is added to the tank, emissions could not then exceed the mass of the



remaining heel dIlis the added distillate.

Only Sludee Remains

Lev < 0.49 FeD2 ds

W,

Eauation4-13

a Reference 23.

+4-06/0^18

Liquid Storage Tanks

7.1-159


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7.1.5 Sample Calculations

The examples given in this section present estimated emissions to two significant figures. This
level of precision is chosen arbitrarily, and may overstate the accuracy of the loss estimates given the
uncertainty associated with the multiple parameters affecting emissions from storage tanks.

Example 1 - Chemical Mixture in a Fixed Roof Tank

Determine the yearly emission rate of the total product mixture and each component for a
chemical mixture stored in a vertical cone roof tank in Denver, Colorado. The chemical mixture contains
(for every 3,171 lb of mixture) 2,812 lb of benzene, 258 lb of toluene, and 101 lb of cyclohexane. The
tank is 6 ft in diameter, 12 ft high, usually holds about 8 ft of product, and is painted white. The tank
liquid level typically ranges between 4.5 feet and 11.5 feet, and thus the tank working volume is
1.690-480 gallons. The number of turnovers per year for the tank is five (i.e., The throughput of the tank
is 8,450 gal/vr-K. The liquid bulk temperature is not known, but the tank is not insulated and storage
conditions are in approximate equilibrium with ambient conditions.

1.	Determine tank type. The tank is a fixed-cone roof, vertical tank.

2.	Determine estimating methodology. The product is made up of three organic liquids, all of which are
miscible in each other, which makes a homogenous mixture if the material is well mixed. The tank
emission rate will be based upon the properties of the mixture. Raoult's Law (as discussed in the HAP
Speciation Section) is assumed to apply to the mixture and will be used to determine the properties of the
mixture.

3.	Select equations to be used. For a vertical, fixed roof storage tank, the following equations apply:

Solution

(1-1)
(1-2)
(1-3529)

where:

Lt =	total loss, lb/yr

Ls =	standing storage loss, lb/yr

Lw =	working loss, lb/yr

Vv =	tank vapor space volume, ft3

Vv = n/4 D2 Hvo

Wv = vapor density, lb/ft3

(1-3)

Ke = vapor space expansion factor,

(1-2224-)

_ _ ATv , Apv-ApB

Ke	~t"

Tla Pa-Pva

Ks = vented vapor space saturation factor, dimensionless

(1^5)

7.1-160

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


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Ks =				(1-2130)

1 + 0.053 PvaHvo

D = diameter, ft
Hvo= vapor space outage, ft
Mv = molecular weight of vapor, lb/lb-mole

Pva = vapor pressure at the daily avcrage daily liquid surface temperature, psia

r> -a i + + 10.731 psia-ft3
R = ideal gas constant =	

lb-mole - °R

	Tv = average vapor temperature. °R

Tla = average daily average liquid surface temperature, E°R
A Tv = average daily vapor temperature range, E°R
A Pv = average daily vapor pressure range, psia

A Pb =	breather vent pressure setting range, psi

Pa =	atmospheric pressure, psia

	Q-=—annual Vo = net working loss throughput. bblfrVyr

Kn = working loss turnover factor, dimensionless
Kp = working loss product factor, dimensionless
	Kr = vent setting correction factor, dimensionless

4. Calculate each component of the standing storage loss and working loss functions,
a. Tank vapor space volume, Vv:

Vv = ti/4D2Hvo	(1-3)

where:

D = 6 ft (given)

For a cone roof, the vapor space outage, Hvo is calculated by:

Hvo = Hs - Hl + Hr0	(1-I64£)

where:

Hs = tank shell height, 12 ft (given)

Hl = stock liquid height, 8 ft (given)

Hro = roof outage, 1/3 HR = 1/3(Sr)(Rs)	(1 -_17+6)

Sr = tank cone roof slope, 0.0625 ft/ft (given) (see Note 1 to Equation 1 -1644-)

Rs = tank shell radius = 1/2 D = 1/2 (6) = 3

Substituting values in Equation 1-174-6 yields,

Hro = 1/3 (0.0625)(3) = 0.0625 ft

Then use Equation 1 -1644 to calculate Hvo,

Hvo = 12 - 8 + 0.0625 = 4.0625 ft

4406/^J_8

Liquid Storage Tanks

7.1-161


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Therefore,

Vv = — (6)2 (4.0625) = 114.86 ft3
4

b. Vapor density, Wv:

= ^	(I-

222+)
where:

psici ¦ ft'

R = ideal gas constant = 10.731 -

lb - mole ¦ R

Mv = stock vapor molecular weight, lb/lb-mole

Pva = stock vapor pressure at the daily average daily liquid surface temperature Tt.a. psia
Tt-A——daily Ty =	average liquid surfacevapor temperature, E°R

First, calculate Tla using Equation 1-2826.

TLA = 0.444 Taa+ 0.^6 TB +0.00^005 aI	(1-

2826)
where:

Taa = daily average daily ambient temperature, E°R
Tb = liquid bulk temperature, E°R

I = average daily total solar insolation. Btu/ft2=»d = 1.56&458 (see Table 7.1-7)
a = tank pakrtsurface solar absorptance = 0.4225 (see Table 7.1-6. for white paint in average
condition)

Taa and Tb must be calculated from Equations 1-3022 and 1-312&.

_ Tax + Tan	n

Iaa	^	*.1_

2

3027)

from Table 7.1-7, for Denver, ColoradpT (use Boulder as the nearest location listed):

Tax = average daily maximum ambient temperature = 64.3E2^F
Tan = average daily minimum ambient temperature = 36.2EJ/T

Converting to E°R:

Tax = 64.3 + 160 ~ 521.3E2 + 459.7 = 523.9°R
Tan = 36.2 + 160 ~ 196.2E1 + 459.7 = 495.8°R

Therefore,

7.1-162

Liquid Storage TanksEMISSION FACTORS

44-06/07-18


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Taa= (5213 + 196.523.9 + 495.8V2V2 ~ 510.25 E = 509.85 °R

Tb = liquid bulk temperature = Taa + 0.003 a 6et—I	[1

	

31)

Taa = 510.25 E509.85 °R from previous calculation

a ——paint = surface solar absorptance = 0.4^25 (see Table 7.1-6)

I = average daily total solar insolation on a horizontal surface = 1.568 158 Btu/ft2=»d (see
Table 7.1-7)

Substituting values in Equation 1 -3 13#

Tb = 509.85 + 0.003 (0.25) 1.458 = 510.25 + 6 (0.17) 1 - 510.27 E9 °R

Using Equation 1-2826.

Tla = (0.11) (510.25E1) (509.85°R) + 0.566 (510.27E92R) + 0.0079005 (0.4725) (1.568458) =
512.36E3^R

Second, calculate Pva using Raoult's Law.

According to Raoult's Law, the partial pressure of a component is the product of its pure vapor
pressure and its liquid mole fraction. The sum of the partial pressures is equal to the The total vapor
pressure of the component mixture stock is equal to the sum of the partial pressures of its components.

The pure vapor pressures for benzene, toluene, and cyclohexane can be calculated from Antoine's
equation. Table 7.1 -35 provides the Antoine's coefficients for benzene, which are A = 6.905906.
B = 1,211.0330, and C = 220.79. For toluene, A = 6^54-7.017. B = 1.344^377.6. and C = 219.18222.64.
For cyclohexane, A = 6.844-845. B = 1.201.53203.5. and C = 222.6586. Therefore:

log P = A	—

T + C

Tla, average liquid surface temperature fE£^C) = (512.36—492-3 - 491.7)/!.8 = 114
For benzene,

log P = 6.906 — 1,2110

6	(11.4+220.79)

P = 17.9019.03 mmHg = 0.926948 psia

Similarly for toluene and cyclohexane,

P = 0.255261 psia for toluene
P = 0.966986 psia for cyclohexane

In order to calculate the mixture vapor pressure, the partial pressures need to be calculated for
each component. The partial pressure is the product of the pure vapor pressures of each component
(calculated above) and the mole fractions of each component in the liquid.

44-06/0718

Liquid Storage Tanks

7.1-163


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The mole fractions of each component are calculated as follows:

Component

Amount, lb

)-Mi

Moles

Xi

Benzene

2,812

78.411

36.0

0.90

Toluene

258

92.414

2.80

0.07

Cyclohexane

101

84.216

1.20

0.03

Total





40.0

1.00

where:

Mi = molecular weight of component
Xi = liquid mole fraction

The partial pressures of the components can then be calculated by multiplying the pure vapor
pressure by the liquid mole fraction as follows:

Component

P at 52EJ£F

Xi

Ppartial

Benzene

0.926948

0.90

0.^853

Toluene

0.255261

0.07

0.018

Cyclohexane

0.966986

0.03

0.029030

Total



1.0

0.&M901

The vapor pressure of the mixture is then 0.&8Q901 psia.

Third, calculate the molecular weight of the vapor, Mv. Molecular weight of the vapor depends
upon the mole fractions of the components in the vapor.

Mv =

where:

Mi = molecular weight of the component
yi = vapor mole fraction

The vapor mole fractions, yi, are equal to the partial pressure of the component divided by the
total vapor pressure of the mixture.

Therefore,

ybenzene = Ppartial/Ptotal = 0.S33853/0.88Q901 = 0.947
Similarly, for toluene and cyclohexane,

7.1-164

Liquid Storage TanksEMISSION FACTORS

4406/0718


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Ytoluene Ppartial/Ptotal 0.020
Ycyclohexane Ppartial/Ptotal 0.033

The mole fractions of the vapor components sum to 1.0.
The molecular weight of the vapor can be calculated as follows:

Component

Mi

y>

Mv

Benzene

78.4-11

0.947

74.0

Toluene

92.414

0.020

1.84

Cyclohexane

84.216

0.033

2.78

Total



1.0

78.6

Now calculate Ty using Equation 1-33.

	Tv = 0.7Taa + 0.3Tr + 0.009 « I	(1-33)

Tv = 0.7 (509.85) + 0.3 (510.9) + 0.009 (0.25) (1.458)

Tv = 513.4 °R

Since all variables have now been solved, the stock density, Wv, can be calculated:

W MvPva
v RTV

(7S.6K0.901) =L29xl0_2lb

(10.731)(513.4) '	ft3

c. Vapor space expansion factor, Ke:

Ke . atv + apv-apb	(|J?a

TLA Pa - PVA

where:

A Tv = average daily vapor temperature range, E°R
A Pv = average daily vapor pressure range, E°R
A Pb = breather vent pressure setting range, psia
Pa = atmospheric pressure, 44^12.12 psia fevenfor Denver. Colorado (use Boulder as the
nearest location listed)

Pva = vapor pressure at average daily average liquid surface temperature, psia = 0.&8Q901 psia
(from
Step 4b)

Tla = daily average daily liquid surface temperature, E°R = 512.36E3^R (from Step 4b)

44-06/^18

Liquid Storage Tanks

7.1-165


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First, calculate the average daily vapor temperature range from Equation 1-7X:

Atv = 0.7 A Ta + 0.02a I	(1-7&)

where:

A Tv = average daily vapor temperature range, E°R
A Ta = average daily ambient temperature range = Tax - Tan
a = tank paintsurface solar absorptance, 0.4225 (given)

I = average daily total solar insolation. 1.568158 Btu/ft2=»d (given)

from Table 7.1-7, for Denver (Boulder). Colorado:

Tax = 64.3E2^F
Tan = 36.3EPF

Converting to E°R,

Tax = 64.3 + 160 - 521.3E2 + 459.7 = 523.9°R
Tan = 36.2 + 160 - 196.2E1 + 459.7 = 495.8°R

From Equation 1-1112 and: A Ta = Tax - Tan

ATa = 521.3 196.2523.9 -495.8 = 28.1E°R

Therefore,

ATV = 0.727 (28.1) + (0.0^02)(0.17)( 156825) (1458) = 27.2E(TR
Second, calculate the average daily vapor pressure range using Equation 1-9:

APv = Pvx-Pvn	(1-9)

Pvx, Pvn = vapor pressures at the average daily maximum, minimum liquid temperatures can be
calculated in a manner similar to the Pva calculation shown earlier.

Tlx = maximum liquid temperature, Tla + 0.25 A Tv (from Figure 7.1-17)

Tln = minimum liquid temperature, Tla - 0.25 A Tv (from Figure 7.1-17)

Tla = 512.363 (from Step 4b)

ATV = 27.2E(TR
Tlx = 512.363 + (0.25) (27.20) = 519.3E05°R or 59E.35°F
Tln = 512.363 - (0.25) (27.20) = 505.4E55°R or 45E.85°F

Using Antoine's equation, the pure vapor pressures of each component at the minimum liquid
surface temperature are:

Pbenzene = 0.2#&780 psia

Ptoluene = 0.203210 psia

P cyclohexane 0.294815 psia

The partial pressures for each component at Tln can then be calculated as follows:

7.1-166

Liquid Storage TanksEMISSION FACTORS

+4-06/0218


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Component

P at 45E.85°F

X

Ppartial

Benzene

0.75X780

0.90

0.-6X702

Toluene

0.303210

0.07

0.04015

Cyclohexane

0.794815

0.03

0.03024

Total



1.0

0.74741

Using Antoine's equation, the pure vapor pressures of each component at the maximum liquid
surface temperature are:

Pbenzene = 1.44150 psia
Ptoluene = 0.33-324 psia
P cyclohexane 1.4X191 psia

The partial pressures for each component at Tlx can then be calculated as follows:

Component

P at 59.35°F

X

Ppartial

Benzene

1.44150

0.90

1.Q3035

Toluene

0.33324

0.07

0.03023

Cyclohexane

1.4X191

0.03

0.04036

Total



1.0

1.09094

Therefore, the vapor pressure range, A Pv = Plx - Pln = 1.09—094 - 0.744)741 = 0.3X353 psia.
Next, calculate the breather vent pressure, A Pb, from Equation 1-1044:

APb = Pbp-Pbv	(1-1044)

where:

Pbp = breather vent pressure setting = 0.03 psia (given) (see Note 3 to Equation 1 -75)
Pbv = breather vent vacuum setting = -0.03 psig (given) (see Note 3 to Equation 1^5)
A Pb = 0.03 - (-0.03) = 0.06 psig

	Pa = 12.12 psia from Table 7.1-7. for Denver. Colorado (use Boulder as the nearest location

listed)

Finally, Ke, can be calculated by substituting values into Equation \-3~.—5+

K + 0.079

b 512.3 (12.12-0.901)

4406/0718

Liquid Storage Tanks

7.1-167


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d. Vented vapor space saturation factor, Ks:

KS =				(1-2130)

1 + 0.053 PVA Hvo	_

where:

Pva = 0.880 psia (from Step 4b)

Hvo = 4.0625 ft (from Step 4a)

Ks =		—-——		 = 0.838

^ 1+0.053 (0.901) (4.0625)

5.	Calculate standing storage losses.

Ls = 365 W^vKbKsVvWvKeKs

Using the values calculated above:

lb_

fi3

Vv = 114.86 ft3 (from Step 4a)

Ke= 0.0^079 (from Step 4c)

Ks= 0.844-838 (from Step 4d)

Ls = 365 (1.26-29_x 1Q-2)(114.86)(0.Q33079)(0.Si1) - 31.2838) = 36 lb/vr

6.	Calculate working losses.

The amount of VOCs emitted as a result of filling operations can be calculated from the following
equation:

Lw = (0.0010) (M^mKQXY^KN ¥Kp>WvKb	(1 -3529)

Wv= 1.2629 x 10 2 —— (from step 4b)

From Stop 1:

	Mv-—78.6 (from Stop 1b)

	Piii——0.880 psia (from Step 1b)

where:

	Vn = 5.614 O (when IHm is unknown; equation 1-39)

Q = 8,450 gal/yr x 2.381/ 42 bbl/100 gal = 2012 bbl/yr (given)

	Vo = 5.614 (201.2) = 1.130 ft3/vr

Kp = product factor, dimensionless = 1 for volatile organic liquids, 0.75 for crude oils. 1.0 for

all other stocks
Kn = 1 for turnovers N <36 (given)

N = turnovers per year =-$¦

	N = £HnT/(HTy-HTN)	(1-36)

7.1-168	Liquid Storage TanksEMISSION FACTORS	4406/^Jl


-------
	SHot = (5.614 O) / (fa/4) D2)	(1-37)

	SHm =(5.614) (201.2) / (fa/4) 62) = 39.9 ft

	Ht.x =11.5 ft (given)

	Htn =4.5 ft (given)

	N =39.9 / (11.5 - 4.5) = 5.7

	Wv= 1.29 x 10 2 lb/ft3 (from Step 4b)

	Kr = 1 for vent settings of +/- 0.03 psig (from Equation 1-35)

Lw= (0.0010)(78.61.130)(1)(1)(0.880)(20!)(!)(!) - 13.9 0129) (1) = 15 lb/vr

7.	Calculate total losses. Lt.

Lt = Ls + Lw

where:

Ls= 34^36 lb/yr
Lw= 43^15 lb/yr

Lx= 317 + 13.9-18.136 + 15 = 51 lb/vr

8.	Calculate the amount of each component emitted from the tank.

The amount of each component emitted is equal to the weight fraction of the component in the
vapor times the amount of total VOC emitted. Assuming 100 moles of vapor are present, the number of
moles of each component will be equal to the mole fraction multiplied by 100. This assumption is valid
regardless of the actual number of moles present. The vapor mole fractions were determined in Step 4b.
The weight of a component present in a mixture is equal to the product of the number of moles and
molecular weight, Mi, of the component. The weight fraction of each component is calculated as follows:

... , ,	. pounds.

Weight fraction =	

total pounds

Therefore,

Component

No. of moles x

M;

Poundsi

Weight fraction

Benzene

(0.947 x 100) = 94.7

78.4-11

7,396397

0.94

Toluene

(0.02x 100) = 2.0

92.4-14

184

0.02

Cyclohexane

(0.033 x 100) = 3.3

84.3-16

278

0.04

Total

100



7.&5&859

1.0

The amount of each component emitted is then calculated as:

Emissions of component = (weight fraction1)(Li)

+4-06/0^18

Liquid Storage Tanks

7.1-169


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Component

Weight fraction x

Total VOC emitted, lb/yr =

Emissions, lb/yr

Benzene

0.94

4&A-51

4^248

Toluene

0.02

4St451

\J)S6

Cyclohexane

0.04

4St451

4^32.0

Total





4&4-51

7.1-170

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


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Example 2 - Chemical Mixture in a Horizontal Tank - Assuming that the tank mentioned in Example 1 is
now horizontal, calculate emissions. (Tank diameter is 6 ft and length is 12 ft.)

Solution:

Emissions from horizontal tanks can be calculated by adjusting parameters in the fixed roof
equations. Specifically, an effective diameter, De, is used in place of the tank diameter, D. The vapor
space height, Hvo, is assumed to be half the actual tank diameter.

1. Horizontal tank adjustments. Make adjustments to horizontal tank values so that fixed roof tank
equations can be used. The effective diameter, De, is calculated as follows:

The vapor space height, Hvo is calculated as follows:

Hvo = j- vapor space outage, ft; use He/2 from Equation 1-15 for horizontal tanks

q-i5)

Hyp

fa/4) D =¥2 (6) ~ 3 ft

2.36 ft

2. Given the above adjustments the standing storage loss. Ls. can be calculated.

Calculate values for each effected variable in the standing loss equation.

Ls =365 VvWvKeKs

Vv and Ks depend on the effective tank diameter, De, and vapor space height, Hvo.

These variables can be calculated using the values derived in Step 1:

_ 71 ,

Vv (De ) Hvo

Vv = | (9.57)2 (2.36) = 170 ft3

+±06/0? 18

Liquid Storage Tanks

7.1-171


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=	1	

Ks 1 + (0.053) (PvA) (Hvo)

Ks =	, 1 w		 = 0.899

^ 1+0.053 (0.901) (2.36)

3.	Calculate standing storage loss using the values calculated in Step 2.

Ls = 365 VvWvKeKs

Vv = 216.10170 ft3 (from Step 2)

Wv = 1.2629 x 10 2 lb/ft3 (from Step 4b, example 1)

Ke = 0.077079 (from Step 4c, example 1)

Ks = 0.877399 (from Step 2)

Ls = (365)( 1.2629 x lQ-2)(216.10170)(0.07?079)(0.g7?899)

Ls = 67-457 lb/yr

4.	Calculate working loss. Since the parameters for working loss do not depend on diameter or vapor
space height, the working loss for a horizontal tank of the same capacity as the tank in Example 1 will be
the same.

Lw = 4^915 lb/yr

5.	Calculate total emissions.

Lt = Ls + Lw

Lx = 67.1 + 13.9- 8157 + 15 = 72 lb/yr

7.1-172

Liquid Storage TanksEMISSION FACTORS

44-06/07-18


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Example 3 - 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 tank
has 10 turnovers per year. 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 the inside surface of the
shell. The tank shell is painted white, and the tank is located in Newark, New Jersey. The floating deck 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 ports 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. Because 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 = kwft + Lr. + Lp + LpLs + Lw	(2-1)

LwpLs = Lk + Lf + Lp	(2-2)

	Lw = (0.943) QCsWl/D	(2-194)

LR = (KRa + KRbVn)P*DMvKc	(2-23)

Lf = FfP*MvKc	(2-J_35-)

Ld = KdSdD2P*MvKc	(2-189)

where:

Lt = total loss, lb/yr

—Lw = working (withdrawal) loss, lb/yr
Lr = rim seal loss from external floating roof tanks, lb/yr
Lf = deck fitting loss, lb/yr

Ld = deck seam loss, lb/yr = 0 for external floating roof tanks
Q = product average throughput, bbl/yr

Cs = product withdrawal shell clingage factor, bbl/1,000 ft2; see Table 7.1-10
Wl = density of liquid, lb/gal

D = tank diameter, ft
KRa = zero wind speed rim seal loss factor, lb-mole/ft=»yr; see Table 7.1.8
KRb = wind speed dependent rim seal loss factor, lb-mole/(mph)nft=»yr; see Table 7.1-8
v = average ambient wind speed for the tank site, mph

4406/0^18

Liquid Storage Tanks

7.1-173


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n = seal wind speed exponent, dimensionless
P* = the vapor pressure function, dimensionless

PVA

where:

Pva=	the true vapor pressure of the materials stored, psia

Pa =	atmospheric pressure, psia = 14.274 psia from Table 7.1-7 for Newark. New Jersey

Mv =	molecular weight of product vapor, lb/lb-mole

Kc =	product factor, dimensionless

Ff =	the total deck fitting loss factor, lb-mole/yr

'i(NFtKFt) = [(JVFl^l)+(JV„X„) + ... + (JVF„/Xr„/)j

;=1

where:

Nf; = number of fittings of a particular type, dimensionless. N|.-. is determined for the specific

tank or estimated from Tables 7.1-12, 7.1-13, or 7.1-14
Kf; = deck fitting loss factor for a particular type of fitting, lb-mole/yr. Kf; is determined for

each fitting type from Equation 2-152 and the loss factors in Table 7.1-12
nt- = number of different types of fittings, dimensionless; nt- = 3 (given)

Kd = deck seam loss per unit seam length factor, lb-mole/ft/yr
Sd = deck seam length factor, ft/ft2

4. Identify parameters to be calculated/determined from tables. In this example, the following parameters
are not specified: Wl, Ff, C, Kr3, KRb, v, n, Pva, P*, Mv, and Kc. The following values are obtained from
tables or assumptions:

Kc = 1.0 for volatile organic liquidsall stocks other than crude oil (given in Section 7.1.3.2)
C = 0.0015 bbl/1,000 ft2 fortanks with light rust (from Table 7.1-10)

KRa= 1.6 (from Table 7.1-8)

K^ = 0.3 (from Table 7.1-8)
n = 1.6 (from Table 7.1-8)

Since the wind speed for the actual tank site is not specified, the wind speed for Newark, New Jersey is
used:

v = 10.23 mph (see Table 7.1-9-7)

Ff, Wl, Pva, P*, and Mv still need to be calculated.

Ff is estimated by calculating the individual Kf; and N|.-. for each of the three types of deck fittings used in

this example. For the ungasketed access hatches with unbolted covers, the Kf value can be calculated
using information from Table 7.1-12. For this fitting, Kh, = 36, Km, = 5.9, and m = 1.2. The value for Kv

7.1-174

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


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for external floating roof tanks is 0.7 (see Section 7.1.3, Equation 2-15D. There is normally one access
hatch. So,

Kpaccess hatch KFa + KFb(Kvv)m

= 36 + 5.9 [(0.7)( 10.3-3.)]12

Kpaccess hatch

98.199.2 lb-mole/yr

N I'acccss hatch	1

The number of vacuum breakers can be taken from Table 7.1-13. For a tank with a diameter of 20 feet
and a pontoon roof, the typical number of vacuum breakers is one. Table 7.1-12 provides fitting factors
for weighted mechanical actuation, ungasketed vacuum breakers when the average wind speed is 10.3-3
mph.

Based on this table, Kf3 = 7.8, Ka = 0.01, and m = 4. So,

KFvacuum breaker KFa + Kpb (Kvv)m
KFvacuum breaker 7.8 "I" 0. 01 [(0.7)(10.23)]4
KFvacuum breaker ^3-34.8 lb-mole/yr

N I'vaciium breaker 1

For the ungasketed gauge hatch/sample ports with weighted mechanical actuation, Table 7.1-12 indicates
that floating roof tanks normally have only one. This table also indicates that Kh, = 2.3, Ka = 0, and
m = 0. Therefore,

KFgauge hatch/sample port	— KFa + Kpb (Kvv)m

KFgauge hatch/sample port	2.3 "I" 0

KFgauge hatch/sample port	2.3 lb-lTlolc/yT

NFgauge hatch/sample port	1

Ff can be calculated from Equation 2-146:
ff = £(KFl)(NFl)

7=1

=(9&A99.2)( 1 )+(33-34.8)( 1 )+(2.3)( 1)

=131.5 136.3 lb-mole/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 lb of liquid mixture. Using
this assumption, the mole fractions calculated will be valid no matter how many pounds of liquid actually
are present. The corresponding amount (pounds) of each component is equal to the product of the weight
fraction and the assumed total pounds of mixture of 1,000. The number of moles of each component is
calculated by dividing the weight of each component by the molecular weight of the component. The
mole fraction of each component is equal to the number of moles of each component divided by the total
number of moles. For this example the following values are calculated:

Component

Weight
fraction

Weight, lb

Moles

Mole
fraction

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Liquid Storage Tanks

7.1-175


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Molecular
weight, Mi,
lb/lb-mole





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

Total

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.

6. Determine the dai-k-avcragc daily liquid surface temperature. The daily-average daily liquid surface
temperature is equal to:

Tla = 0.744 Taa + 0.3S6 TB + 0.0080.0079 a I
Taa = (Tax + Tan)/2
Tb = Taa + 0.007 a 6 II

For Newark, New Jersey (see Table 7.1-7):

Tax = 62^E63.3°F = 522.2E523.0°R
Tan = 15.9E16.0°F = 505.6E7°R
1= 146».236 Btu/ft2^d

From Table 7.1-6, a = 0.+725

Therefore;

Taa = (522t2523.0 + 505.67V2 = 513.9E514.35°R
Tb= 513.9ER+ 6 (0.17) 1 ~513.92E514.35 + 0.007 (0.25X1236) = 516.5TR
Tla = 0.711 (513.9) + 0.56 (513.92) + 0.0079 ((514.35) + 0.317)(1.165 (516.51) + 0.008
(0.25)(1236)

= 517.5515.5E°R = 57.855t&E°F - 56EF

7. Calculate partial pressures and total vapor pressure of the liquid. The vapor pressure of each component
at 57.85&E°F can be determined using Antoine's equation. 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).

7.1-176

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4406/07-18


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Component

P at 57.8S6E°F

X

Ppartial

Benzene

1.1004

0.773

0.850SQ

Toluene

0.3139

0.131

0.041Q3S

Cyclohexane

1.140&

0.096

0.109404

Totals



1.00

1.0000943

The total vapor pressure of the mixture is estimated to be J_.

8. Calculate mole fractions in the vapor. The mole fractions of the components in the vapor phase are
based upon the partial pressure that each component exerts (calculated in Step 7).

So for benzene:

Ybenzene

where:

= P

i/Ptotal = 0.850/1. (

partial/ -r total

= 0.850

ybenzene = mole fraction of benzene in the vapor
Ppartial partial pressure of benzene in the vapor, psia
Ptotal = total vapor pressure of the mixture, psia

Similarly,

Ytoluene
Ycyclohexane

The vapor phase mole fractions sum to 1.0.

9. Calculate molecular weight of the vapor. The molecular weight of the vapor depends upon the mole
fractions of the components in the vapor.

Mv = 3Mty+IM|Vi

where:

Mv = molecular weight of the vapor, lb/lb-mole
Mi = molecular weight of component i, lb/lb-mole
yi = mole fraction of component i in the vapor, lb-mole/lb-mole

0.041/1.C

¦	= 0.0410

¦	= 0.10940

Component

Mi



Mv = ^I£MI)(yI)

Benzene

78.1

0.850

66.39

Toluene

92.1

0.0410

3.786S

Cyclohexane

84.2

0.10940

9.1826

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Liquid Storage Tanks

7.1-177


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Total

1.00

79.43

The molecular weight of the vapor is 79.43- lb/lb-mole.

10. 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 and total molecular weight calculated in Step 9:

7 =ZiM

ZiV:

Mv

= (0-85)(78.1) = Q M836 for benzene
v' 79.3

(0.040)(92.1) _ o Q4048 for toluene
79.3

= (Q11Q)(84.2) =() +2| |6for cyciohexane

79.3

11. 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 = Lwb + Lr + LpLw + Ls
	Ls = Lk + Lf

a. Calculate working (withdrawal) losses:

LwpLw =	0.943 QCWl/D
where:

Q =	100,000 gal x 10 turnovers/yr (given)

=	1,000,000 gal x 2.381 bbl/100 gal = 23,810 bbl/yr

C =	0.0015 bbl/103 ft2 (from Table 7.1-10)

Wl =	143/11 (wt fraction in liquid)/(liquid component density from Table 7.1-3)]

Weight fractions
Benzene = 0.75 (given)
Toluene = 0.15 (given)
Cyciohexane = 0.10 (given)

Liquid densities

Benzene = 7.432 (see Table 7.1-3)
Toluene = 7.324 (see Table 7.1-3)
Cyciohexane = 6.546 (see Table 7.1-3)

WL =	l/[(0.75/7.432) + (0.15/7.324) + (0.10/6.546)]

=	1/(0.4041025 + 0.0205-0207 + 0.Q4540155)

=	1/0.43691387

=	7.32 lb/gal

D =	20 ft (given)

7.1-178

Liquid Storage TanksEMISSION FACTORS

+4-06/03J1


-------
LwpLw — 0.943 QCWl/D

= [0.943(23,810)(0.0015)(7.3-2)/20]
= 12 lb of VOC/yr from withdrawal losses

b. Calculate rim seal losses:

Lr= (KRa + KRbVn)DP*MvKc

where:

Kr3 =	1.6 (from Step 4)

KRb =	0.3 (from Step 4)

v =	10.23 mph (from Step 4)

n=	1.6 (from Step 4)

Kc =	1 (from Step 4)

Pva =	1.0000.912 psia (from Step 7) (formula from Step 3)

D =	20 ft

P

4406/0718

Liquid Storage Tanks

7.1-179


-------
	p*	

= a.oooQ^/i4.?74yg+ri-a.oooQ^/i4.?74)i05')2 = 0.01&7

Mv =	79.43- lb/lb-mole (from Step 9)

Lr =	[(1.6 + (0.3X10.23)16)](0.018?)(20)(79.43)(1.0)

=	m(14.1)(0.018)(20)(79.4)(1.0)

=	403 lb of VOC/yr from rim seal losses

c.	Calculate deck fitting losses:

Lf=	FfP*MvKc

where:

Ff =	131.5136.3 lb-mole/yr (from Step 4)

P*=	0.018?

Mv=	79.43- lb/lb-mole

Kc =	1.0 (from Step 4)

Lf=	<4-34t5- (136.3X0.0182X79.43-X1.0)

=	1954X4- lb/yr of VOC emitted from deck fitting losses

d.	Calculate total losses:

Lt =	LwbLw + Lr + Lf

=	12 + 376 + 181103 + 195

=	610569 lb/yr of VOC emitted from tank

12. Calculate amount of each component emitted from the tank. For an external floating roof tank, the
individual component losses are determined by Equation 40-2:

Therefore,

L-rbenzene
L-rtoluene
LTcyclohexane

Lt- — (Zv^Lr + Lf) + (Z^XLwpLw)

= (0.81)(557836)(598)
= (0.010X557048X598!
= (0.12)(557116)(598)

(0.75)(12) = 51047? lb/yr benzene

(0.15)(12) = 3124 lb/vr toluene
(0.10X12) = 716& lb/yr cyclohexane

7.1-180

Liquid Storage TanksEMISSION FACTORS

44-06/07-18


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Example 4 - Gasoline in an Internal Floating Roof Tank - Determine emissions of product from a
1 million gallon, internal floating roof tank containing gasoline (RVP 13). The tank is painted white and
is located in Tulsa, Oklahoma. The annual number of turnovers for the tank is 50.Product is pumped into
and out of the tank simultaneously. The sum of decreases in the liquid level is 1.735 feet. 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 has a column-supported fixed roof. The tank's deck is welded and equipped with the following:
(1) two access hatches with unbolted, ungasketed covers; (2) an automatic gauge float well with an
unbolted, ungasketed cover; (3) a pipe column well with a flexible fabric sleeve seal; (4) a sliding cover,
gasketed ladder well; (5) adjustable deck legs; (6) a slotted guidepole/sample pipe well with a gasketed
sliding cover; and (7) a weighted, gasketed vacuum breaker. The following data are available on the
concentrations of air toxics in the liquid phase, by weight:

Component

Weight Percent In Liquid

Benzene

0.55

Toluene

1A

Ethvlbenzene

M

Xylenes

6$

Solution:

1.	Determine tank type. The following information must be known about the tank in order to use the
floating roof equations:

-- the number of columns
-- the effective column diameter

-- the rim seal description (vapor- or 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 Reid vapor pressure data have already been compiledis available.
Raoult's Law will not be used-: to determine the true vapor pressure of the liquid (as it was in the prior
example), but it will be used to estimate vapor phase fractions of the air toxic components. 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 SPECIATE data base.

3.	Select equations to be used.

Lt =Lwp-^ Ls + Lw	(2-1)

+4-06/0^18

Liquid Storage Tanks

7.1-181


-------
(2-42)
(2-194)

Lk = (Kkil + Kkhvn)DP'!MvK.	(2-23)

Lf =FfP*MvKc	(2-_I3a)

Ld =KdSdD2P*MvKc	(2-\m)

where:

Lt =	total loss, lb/yr

—Ls = standing loss, lb/vr

	Lw =	working (withdrawal) loss, lb/yr

Lr =	rim seal loss, lb/yr

Lf =	deck fitting loss, lb/yr

Ld =	deck seam loss, lb/yr

Q =	product avoragoannual net throughput (tank capacity [bbl] times turnovers per year),.
bbl/yr

Cs =	product withdrawal shell clingage factor, bbl/1,000 ft2

Wl =	density of liquid, lb/gal

D =	tank diameter, ft

Nc =	number of fixed roof support columns, dimensionless

Fc =	effective column diameter, ft

KRa =	zero wind speed rim seal loss factor, lb-mole/ft=»yr

KRb =	wind speed dependent rim seal loss factor, lb-mole/(mph)nft=»yr

v =	average ambient site wind speed (zero for internal floating roof tanks), mph

Mv =	the average molecular weight of the product vapor, lb/lb-mole

Kc =	the product factor, dimensionless

P* =	the vapor pressure function, dimensionless

p* =

1+1

PVA

Pa )\



0.5

	=	 Pva = the vapor pressure of the material stored, psia

Pa = average atmospheric pressure at tank location, psia
Ff = the total deck fitting loss factor, lb-mole/yr

X! (KFi) (NF,) - [(NfjKfj) + (Nf2Kf2) + ... + (Nfd Kpnf)]

;=1

and:

7.1-182

Liquid Storage TanksEMISSION FACTORS

4406/07-18


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Nf; = number of deck fittings of a particular type, dimensionless. N|.-. is
determined for the specific tank or estimated from Table 7.1-12

Kf; = deck fitting loss factor for a particular type of deck fitting, lb-
mole/yr. Kfis determined for each fitting type using Table 7.1-12 and.
for an internal floating roof tank. Equation 2-16

nf = number of different types of fittings, dimensionless

Kd = the deck seam loss factor, lb-mole/ft=^yr

= 0.14 for nonwelded decks

= 0 for welded decks

Sd = deck seam length factor, ft/ft2

Lseam/A deck

where:

Lseam total length of deck seams, ft

Adeck = area of deck, ft2 = 7rD2/4

4. Identify parameters to be calculated or determined from tables. In this example, the following
parameters are not specified: Wt,. Nc. Fc, PC. Pva. Mv, Kr3, Kj^-v, P*, Kc, Ff, Kd, Sp, and fe. The
density of the liquid (Wt,) 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 air toxic components in the vapor can be obtained from
speciation manuals. Therefore, several steps required in preceding examples will not be required in this
example. In each case, if a step is not required, the reason is presented.^

The wind speed, v. is assumed to be zero for an internal floating roof tank, and thus values are not needed
for K^b and n for the rim seal. Similarly, the deck fitting loss factor Ki- is equal to KFai. from Equation 2-
16.

The following parameters can be obtained from tables or assumptions:

Kc = 1.0 for volatile organic liquidsall stocks other than crude oil
Nc = 1 (from Table 7.1-11)

Fc = 1.0 (assumed)

4406/0^18

Liquid Storage Tanks

7.1-183


-------
KRa=	0.3 (from Table 7.1-8)

	0.6 (from Table 7.1 8)

v =	0 for internal floating roof tanks

Mv =	62 lb/lb-mole (from Table 7.1-2)

Wl =	5.6 lb/gal (from Table 7.1-2)

C =	0.0015 bbl/1,000 ft2 (from Table 7.1-10)

Kd =	0 for welded decks so Sd is not needed

Ff =	3-1 (Kf; ;Nf;4). where values for KFai. are from Table 7.1-12

5. Calculate mole fractions in the liquid. This step is not required because liquid Mole fractions are only
used to calculateof the air toxic components in the liquid can be calculated using Raoult's Law. Assume
that the properties of m-xvlene will suitably represent the component identified as Xylenes. The
molecular weight of the liquid vapor pressure, whichstock is given as 92 lb/lb-mole, and thus liquid mole
fractions of individual components can be calculated using Equation 40-4.

_ZLiMl

	Xi -

M,

(00055X92) = Q 0065 for benzene

78.1

_ (0.076X92) =Q(

r,		 u. 075 9 for toluene

92.1

= (0.014)(92) = o o 121 for ethvlbenzene
106.2 		

.Xj - °69'>P2') in this example. = 0.0598 for xylenes

106.2

6. Calculate the da+k-avcragc daily liquid surface temperature. The daily average daily liquid surface
temperature is equal to:

	T^a——OA'] Taa + 0.56 Tb + 0.0079 cl I

[2.86 (Hs/D) + 1.43] TAA + [3.52 (Hs/D) + 3.79] TB + 0.027 ocR I + 0.017(Hs/D) oc5 I
Tla ~	6.38 (Hs/D) + 5.22

Taa = (Tax + Tan)/2

7.1-184

Liquid Storage TanksEMISSION FACTORS

44-06/Q748


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Tb = Taa + 0.003 a 6et—1-1
For Tulsa, Oklahoma (see Table 7.1-7):

Tax = 71.3£PF = 530.97E81R
Tan = 49.2E6°F = 508.87E509.3°R
1= 1.333427 Btu/ffe'd
From Table 7.1-6, a = 0.4725
Therefore.

	Taa= (530.8 + 509.3V2 = 520.05°R

	Tr = 520.05 + 0.003 (0.25) 1.427 = 521.12°R

	Tt a = 0.34 (520.05) + 0.66 (521.12) + 0.0032 (0.25)(1.427) + 0.0010 (0.25)(1.427)

	Tta= 176.82 + 343.94+ 1.14 + 0.36

	Tt a= 522.26°R or 62.6°F

7. Calculate partial pressures and total vapor pressure of the liquid. The total vapor pressure of gasoline
RVP 13 can be calculated from Equation 1-25. using values for the vapor pressure constants A and B
from Table 7.1-2..

B

PVA = exp A - —
5043^6

PVA = exp 11.644 —

62.6 + 459.7,

Pva = 7.30 psia at 62.6°F

From Table 7.1-7. Pa = 14.39 psi

Therefore,

P

T^aa- (530.97 + 508.87)72-519.92ER

1 +

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Liquid Storage Tanks

7.1-185


-------
	TB~ 519.92 + 6(0.17) 1~519.91ER

	TbA- 0.11 (519.92)+ 0.56 (519.91) + 0.0079(0.17)(1,373)

	TbA- 228.76 + 291.17+ 1.81

	521.77ER or 62E

	P* = (7.30/14.39)/ri + (l-(7.30/14.39))" 512

	P*= 0.175

The vapor pressure of each component at 62.6°F

7. Calculate- can be determined using Antoine's equation. Since Raoult's Law is assumed to apply in this
example, the partial pressures and total vapor pressure of each component is the liquid- mole fraction (xi)
times the vapor pressure of gasoline RVP 13 can bo intorpolatodthe component (P). from Table 7.1 2. The
interpolated vapor pressure at 62EF is equal to 7.18 psia. Therefore.Equation 40-3.

^ ~ (7.18/1 l.7)/| 1 + (1 (7.18/1 1.7))^|3
0.166

Component

P at 62.6°F

Xi

Ppartial

Benzene

1.2579

0.0065

0.0082

Toluene

0.3587

0.0759

0.0272

Ethvlbenzene

0.1135

0.0121

0.0014

Xvlenes

0.0989

0.0598

0.0059

8. Calculate mole fractions of components in the vapor. This step is not required because vapor The mole
fractions are needed to calculatefraction of each component in the weight fractions and vapor phase is the
molecular weightpartial pressure of the component (Partial) divided by the total vapor, which are already
specified, pressure of the mixture (Pva). from Equation 40-3.

Vi P nartial/PvA

Vi = 0.0082 / 7.30 = 0.0011 for benzene
Vi = 0.0272 / 7.30 = 0.0037 for toluene

7.1-186

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


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Vi = 0.0014 / 7.30 = 0.0002 for ethvlbenzene

	Vi = 0.0059 / 7.30 = 0.0008 for xylenes

9.	Calculate molecular weight of the vapor. This step is not required because the molecular weight of
gasoline vapor is already specified.

10.	Calculate weight fractions of components of the vapor. The weight fractionsfraction of
componentseach component in gasolinethe vapor phase can be obtained from a VOC speciation
manual.calculated using Equation 40-6.

7 =21Ml

A Vi

Mv

Zvi = (0 0°11)(78 1) =0.0014 for benzene
62

(0.0037)(92.1)	+1

	Zvi =	 = 0.00^3 for toluene

62

	zri=(0 0002)(106'2) = 0.0003 for ethvlbenzene

62

	Zvi = (0 0008)(106 2) =0.oo14 for xylenes

62

11.	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.

Lt = Lwp + Lr. + Lp + LpLw + Ls

	Ls = Lk + Lf + Lp

a. Calculate working (withdrawal) losses:

kwekv = [(0.943)QCWl]/D [1 + (NCFC)/D]
where:

Q = (rc/4) D2 (IHnn/5.614)

	= fa/4) (70)2 (1.000.000 gal)(50 turnovors/yr)

		 (50.000.000 gal)(2.381 bbl/100 ga!735/5.614) = 1.190.500189.359 bbl/vr

+4-06/0^18

Liquid Storage Tanks

7.1-187


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C =	0.0015 bbl/1,000 ft2

WL=	5.6 lb/gal

D =	70 ft

Nc=	1

Fc=	1

Lw©Lw=	[(0.943)(l,49G^OG)(189a3591X0.0015)(5.6)]/70[l +(l)(l)/70]

=	1404^7 lb/yr VOC for withdrawal losses

b.	Calculate rim seal losses:

Lr = (KRa + KRbVn)DP*MvKc
Since v = 0 for IFRT's:

Lr= KRaDP*MvKc

where:

KRa = 0.3 lb-mole/ft=«vr
D = 70 ft
P* = 0.446175
Mv = 62 lb/lb-mole
Kc= 1.0

Lr = (0.3)(0.466)Q751i70)(62)(1.0) = 344230 lb/yr VOC from rim seals

c.	Calculate deck fitting losses:

Lf= FfP*MvKc

where:

Ff= 3E(KFiNFi)

KF[ = K| ;, for internal floating roof tanks since the wind speed is zero (see Equation 2-168-).

7.1-188

Liquid Storage TanksEMISSION FACTORS

4406/07-18


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The number of deck legs is determined from Table 7.1-15 as follows:

	Ntvn = (5 + D/10 + D2/600)

	Nfd! = (5 + 70/10 + (70)2/600)

Nfdi = 20

Substituting values for K|.;i taken from Tables 7.1-12 and 7.1 15 for access hatches, gauge float well, pipe
column well, ladder well, deck legs, sample pipe well, and vacuum breaker, respectively, yields:

Ff = (36)(2) + (14)(1) + (10)(1) + (56)(1) + (7.9r5 + (70/10) + (703/60Qffl(20) + (43^J-)(1) +
(6.2)(1)

= 361 359 lb-molc/vr

P* = 0.446175

Mv = 62 lb/lb-mole

Kc= 1

Lf = (364359)(0.466175)(62)( 1.0) = 3.345-900 lb/vr VOC from deck fittings

d.	Calculate deck seam losses:

Ld= KdSdD2P*MvKc
Since Kd = 0 for IFRT's with welded decks,

Ld = 0 lb/yr VOC from deck seams

e.	Calculate total losses:

Lt = Lw© + Lr + Lf + Ld

= 140433 + 34-6230 + 3.745900 + 0 = 4.06X300 lb/yr of VOC emitted from the tank

12. Calculate amount of each component emitted from the tank. The individual component losses are
equal to:

Lt. = (Zv^Lr + Lf + Ld) + (Zl^Lwb)

Therefore.

	LTbenzene (0.0014)(4.130) + (0.0055)(140) = 6.6 lb/vr benzene

4406/0318

Liquid Storage Tanks

7.1-189


-------
	LTtoluene (0.0055)(4.130)

LTethvl benzene (0.0003)(4.130)
	LTxvlenes (0.0014)(4.130)

(0.076H 140) = 33 lb/vr toluene
(0.014)f 140) = 3.2 lb/vr ethvlbenzene
(0.069)(T40) = 15 lb/vr xylenes

Since the liquid weight fractions are unknown, the individual component losses are calculated based on
the vapor weight fraction and the total losses. This procedure should yield approximately the same values
the above equation because withdrawal losses are typically low for floating roof tanks. The amount of

as-

each component emitted is the weight fraction of that component in the vapor (obtained from a VOC
species data manual and shown below) times the total amount of VOC emitted from the tank. The table
below shows the amount emitted for each component in this example.

Constituent

Weight Percent In Vapor

Air toxics
Benzene
Toluene
Ethylbonzono
O xylene

Nontoxics
Isomers of pentane
N butane
Iso butane
N pentane
Isomers of hexane

3 methyl pentane

Hexane

Others

Total

q 66

223$

9 g3

2M
4t&4
2h4Q

| QQ

Source: SPECIATE Data Base Management System. Emission Factor and Inventory Group. U-£t
Environmental Protection Agency. Research Triangle Park. NC. 1993.

7.1-190

Liquid Storage TanksEMISSION FACTORS

4-+06/02J_8


-------
Example 5 - Floating Roof Landing Loss for an External Floating Roof Tank - Determine emissions of
product from the landing of a floating roof in an external floating roof tank containing gasoline during the
month of April. The tank is painted white and is located in Port Arthur. Texas. The tank is 120 ft in
diameter and 40 ft high, and has a nominally flat bottom. The floating roof is landed while the tank
contains gasoline having an RVP of 12. and is refloated with gasoline having an RVP of 7.0. For both
gasolines, the benzene concentration is known to be 0.5 percent by weight in the liquid. The deck support
legs are set at a height of 3 feet, and the liquid is lowered to a level of one foot. The tank is refilled three
days after the landing of the floating roof.

Solution:

1.	Determine tank type. The tank is an external floating roof storage tank.

2.	Determine estimating methodology. Gasoline consists of many organic compounds, all of which are
miscible in each other, which form a homogenous mixture. The molecular weight of gasoline will be
taken from a table and the true vapor pressure will be calculated from the Reid vapor pressure of the
mixture. Weight fractions of components of interest in the vapor phase will be calculated from
concentrations in the liquid phase, using Raoult's Law.

3.	Select equations to be used.

	Ltt. = Lst. + Lft	(3-1)

^SLwincL

= 0.57 nd DP* Mv<5.9D2hiPWi	(3-4. 3-10)

-Lfl ~

fPi A Vy^

V RTv J

Mv (rv/ ,S') <(5.9D2 hie Wi - LST) + (0.15 PVA Vv Mv/ RTv) (3-16. 3-18)

where:

Ltt =	total losses during roof landing, lb

Lst =	standing idle loss during roof landing, lb (= Lst wind for external floating-roof tanks)

LsLwind	standing idle loss due to wind, lb

0.57 =	daily rim seal factor; (K^a + K^b v")/365. where K^a = 6.7. K^b = 0.2. v = 10. and n = 3.0

nd =	number of days that the tank is standing idle, days

D =	tank diameter, ft

P* =	a vapor pressure function, dimensionless

My =	stock vapor molecular weight, lb/lb-mole

5.9 =	combination of constants (re/4) and 7.48 gal/ft3

hie =	effective height of the stock liquid, feet

Wi =	density of the liquid inside the tank, lb/gal

Lft =	filling loss during roof landing, lb

+4-06/0^18

Liquid Storage Tanks

7.1-191


-------
	Pva = true vapor pressure of the liquid inside the tank, psia

	Vv = volume of the vapor space, ft3

	R = ideal gas constant. 10.731 psia ft3 /lb-mole °R

	Tv = average temperature of the vapor and liquid below the floating roof. °R (= Taa)

	Cf = filling saturation correction factor for wind, dimensionless

	S = filling saturation factor, dimensionless (0.60 for a full liquid heel; 0.50 for a partial liquid

heel).

4. Identify parameters to be calculated/determined from tables. In this example, the following parameters
are not specified: P*. Mv. Wi. Pva. Vv. Tv. Cr and S.

The following values are obtained from tables or assumptions:

	My = 66 lb/lb-mole, from Table 7.1-2 as a default value for the vapor phase molecular weight

of all gasolines.

	Wi = 5.6 lb/gal, from Table 7.1-2 for gasoline.

	Ty = 68.9 °F (528.6 °R) from Table 7.1-7. the average ambient temperature (Taa) for April in

Port Arthur. TX.

	S = 0.60 for a full liquid heel.

Values for the following parameters still need to be calculated:

	P* = a vapor pressure function, dimensionless. P* is needed to calculate the standing idle loss.

which occurs with a heel of gasoline (RVP 12) in the tank.

PVA

p* =	Za	

The true vapor pressure. Pva. in the equation for P* is the same as the true vapor
pressure. Pva. in the calculation of the landing loss. Typical atmospheric pressure. Pa. for
Port Arthur. TX is obtained from Table 7.1-7. as 14.75 psi.

	Pva = true vapor pressure of the liquid inside the tank, psia

	Determine Pva using Equation 1-25. with values for the constants A and B determined

from the equations in Figure 7.1-15 using the given Reid vapor pressure and the default
value of 3.0 given for the distillation slope S in Table 7.1-2.

A = 15.64 - 1.854 S05 - (0.8742-0.3280 S05)ln(RVP)

7.1-192

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


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B = 8.742 - 1.042 S0 5 - (1.049-179.4 S05)ln(RVP)

For gasoline RVP 12. the calculated values of A. B. P and P* are:

	A = 11.668

	B =5102.7

Pva = 7.50 psia at 68.9 °F
P* = 0.176

For gasoline RVP 7.0. the calculated values of A. B and Pva are:
A= 11.833
B = 5500.6

	Pva = 4.16 psia at 68.9 °F

Vv = volume of the vapor space, ft3

Determine the vapor space volume Vv using Equation 3-22. where the height of the vapor
space under the floating roof is the difference between the floating roof leg height and the
depth of the liquid heel, which are given as 3 feet and 1 foot respectively. Thus the height
of the vapor space under the floating roof is 2 feet, and the vapor space volume is:

Vv= (2) (k 1202/4)

Vv = 22620 ft3

CSf = filling saturation correction factor for wind, dimensionless

Cs) 1 ! ,3_21l

Solve for Kf.:



ke — ./V' >0
Tla I' • I'::,



where:

	ATv = 0.7 ATa + 0.02 a I	[K7}

	For Port Arthur. TX in April. Tax equals 78.3°F. Tan equals 59.5°F. and I equals 1.649

Btu/ft2 d per Table 7.1-7.

	ATy = 0.7 (78.3 - 59.5) + 0.02 (0.25 for a white tank in average condition) (1.649) = 21.4°R

	A Pv = Pvx - Pvn

	Pvx and Pvn are the true vapor pressures at Tt x and Tt.n. respectively.

+4-06/0^18

Liquid Storage Tanks

7.1-193


-------
From Figure 7.1-17:

Tix= Tta + 0.25 ATy = 68.9+ 0.25 (21.4) = 74.3°F

Tttm = Tt a - 0.25 ATv = 68.9-0.25 (21.4) = 63.5°F

Pvx= 8.27 psia

Pvn = 6.79 psia

APv = (8.27-6.79)= 1.48 psi

	 b 528.6 (14.75-7.50)

Solve for Ks:

Ks 1 + 0.053 PvaHvo	£Mil

where:

	Pva = 7.50 psia

	Hyp = 2 feet

	Kg =	\	= 0.557

1+0.053 (7.50)(2)

then:

( (0.57-1-120-0.176-66)—f1-0.245 f 7'50'22'620 )-66-0.557)

Csf = 1-1 -r	V	x Vl/°ll1;5l8-6l.	^ I = 0.64

(l-0.245< 7 50 22'62° )-66-0.557)+(r 7 50 22'62° >66-0.6o)

V	VlO.731-528.6/	J \\10.731-528.6/	j /

5. Calculate mole fractions in the liquid. The mole fraction of benzene in the liquid can be calculated
using Raoult's Law. The molecular weight of the liquid stock is given as 92 lb/lb-mole, and thus liquid
mole fractions of individual components can be calculated using Equation 40-4.

_ZLiMl

- Xi	

M,

r, = (0 0°5)(92) =0.0059 for benzene
78.1

6. Calculate partial pressures and total vapor pressure of the liquid. The total vapor pressure of gasoline
RVP 12 and of gasoline RVP 7 is given in Step 4.

For gasoline RVP 12. the calculated value of Pva is:

	Pva = 7.50 psia at 68.9 °F

For gasoline RVP 7.0. the calculated value of Pva is:

	Pva = 4.16 psia at 68.9 °F

From Table 7.1-7. Pa = 14.75 psi

7.1-194

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


-------
The vapor pressure of benzene at 68.9°F can be determined using Antoine's equation. Since Raoult's Law
is assumed to apply in this example, the partial pressure of benzene is the liquid mole fraction (x,) times
the vapor pressure of benzene (P). from Equation 40-3.

Component

P at 68.9°F

Xi

Ppartial

Benzene

1.4912

0.0059

0.0088

7.	Calculate mole fractions of components in the vapor. The mole fraction of benzene in the vapor phase
is the partial pressure of the component (Partial) divided by the total vapor pressure of the mixture (Pva).
from Equation 40-5. The total pressure depends upon the RVP. and thus the mole fraction of benzene
must be calculated separately for gasoline RVP 12 and for gasoline RVP 7.0.

	Vi P nartial/PvA

RVP 12

	Vi = 0.0088 / 7.50 = 0.0012 for benzene

RVP 7

	Vi = 0.0088 / 4.16 = 0.0021 for benzene

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 components of the vapor. The weight fraction of each component in the
vapor phase can be calculated using Equation 40-6.

7 =21Ml

	Z Vi

Mv

RVP 12

	Zri= (°'0012)(78'1) =0.0014 for benzene

66

RVP 7

	Zri = (0 0021)(78 1) = 0.0025 for benzene

66

10. Calculate standing idle loss,
a. Check the limit on standing idle loss:

+4-06/0^18

Liquid Storage Tanks

7.1-195


-------
	L/SLmax ^ 5.9 D2 heW,

	LsLmax ^ 5.9 (120)2(1) (5.6) = 480.000 lb

b.	Check the calculated standing idle loss:

	LsT.wind = 0.57 na D P* My

	LsLwind 0.57 (3) (120) (0.176) (66) = 2.400 lb < 480.000 lb

	LsT.wind = 2.400 lb

c.	Calculate the benzene standing idle loss:

Lst iien7ene = 2.400(0.0014) lb benzene

Lst henzen,. = 3.4 lb benzene

11. Calculate the filling loss.

a.	Check the limit on filling loss:

	L[.| ^ (5.9 D2 hie Wi)- Lst + 0.15 (Pva Vv / RTv) My

Lft^. < 5.9 (120)2 (1) (5.6) - 2.400 + 0.15 r(4.16)(22.620)l/r(10.731)(528.6)l (66) = 470.000 lb

b.	Check the calculated filling loss:

The prior stock was gasoline having an RVP of 12. and the roof was refloated with gasoline having an
RVP of 7.0. It may be reasonably assumed that the arrival vapors were remaining from the prior stock,
and the generated vapors were from the incoming stock. The vapor saturation factor for incoming vapors
is 0.15 per the discussion on drain-dry tanks in section 7.1.3.3.2.

Check the total wind-corrected saturation factor for refilling of a landed external floating roof, using the
value for CSf calculated in Step 4:

CfS= (0.64) (0.60) = 0.38

Given the saturation factor of 0.15 for the generated vapors, the saturation factor for the arrival vapors is
therefore (0.38 - 0.15) = 0.23.

Calculate the arrival loss:

(P V ^

_ 1 VA ' V

'FL ~ ,, ...

Mr (c„

Lfl (arrival) = (¦

10.731-528.6.

7.5-22,620

¦ 66 ¦ 0.23 = 4501b

7.1-196

Liquid Storage TanksEMISSION FACTORS

-H-06/Q218


-------
Calculate the generated loss:

/ 4.16- 22,620 \

Lfl (generated) = I — ¦ 66 ¦ 0.15 = 160 lb
tLK&	J VlO.731 ¦ 528.6J

Calculate the total filling loss:

	Lft = 450+ 160 = 610 lb <480.000 lb

	Lft = 6101b

c. Calculate the benzene filling loss: Apply the vapor weight fraction of RVP 12 gasoline to the arrival
loss and the vapor weight fraction of RVP 7 gasoline to the generated loss.

	LpLbenzene 450(0.0014) + 160(0.0025) lb benzene

Lft hpn7pne = 1.0 lb benzene

12. Calculate total losses for the floating roof landing event. The total loss is the sum of the standing loss
and the filling loss.

	Ltt. = Lst. + Lft

	Ltt = 2.400 + 610 = 3.000 lb

	LTLbenzene 3.4 + 1.0 = 4.4 lb benzene

4406/07.18

Liquid Storage Tanks

7.1-197


-------
Example 6 - Cleaning Loss for an External Floating Roof Tank - Calculate emissions for cleaning the
tank mentioned in Example 5. assuming that tank cleaning operations began on the third day after the
floating roof was landed, rather than the tank having been refilled as described in Example 5.

Assume that on the third day of the floating roof landing, forced ventilation was started up to vent
the vapor space to a control device which had a vapor reduction efficiency of 95%. Commencement of
forced ventilation marked the end of the floating roof landing and the beginning of the tank cleaning
event. The one-foot heel of remaining gasoline described in Example 5 was removed by means of vacuum
trucks. The amount of gasoline then remaining in puddles in the bottom of the tank was judged to be the
equivalent of about one-eighth of an inch deep if it were spread evenly over the bottom of the tank, and
about three inches of gasoline remained in the bottom of a 24-inch diameter sump. The equivalent of six
inches of diesel was then added to the tank. The forced ventilation continued to be operated at 3.000 cubic
feet per minute (cfm) throughout the day and night of the first day of tank cleaning.

The next morning, the beginning of the second day of tank cleaning, the vapor concentration was
found to be less than 10.000 ppmv. At this time the mixture of diesel and gasoline in the bottom of the
tank was vacuumed out, leaving an average of about one-half inch of wet sludge remaining on the tank
bottom. The control device was disconnected and forced ventilation continued through the second day of
tank cleaning, venting directly to atmosphere, as workers cleaned out the sludge. At the end of the second
day of tank cleaning, the vapor concentration was measured at 3.800 ppmv and the forced ventilation was
turned off over night. The equivalent of about one-eighth inch of wet sludge remained in the bottom of
the tank.

The forced ventilation was restarted on the morning of the third day of tank cleaning, venting to
atmosphere. Workers rinsed the tank bottom and removed all remaining volatile material, leaving the tank
clean and gas free by the end of the day. At this point, the tank cleaning operation was deemed to be
complete from an emissions estimating viewpoint, and the tank was deemed to be out of service. While
forced ventilation was continued on subsequent days for the safety of workers inspecting the tank,
emissions had ceased due to the removal of all volatile material.

The tank cleaning events and hourly readings of vapor concentration are listed below:
Day Time Concentration	Activity

	(ppmv)	

1 10:00	380.000	Start up forced ventilation to control device.

Vacuum out gasoline heel.

Begin pumping in diesel.

First hour is considered vapor space purge.
11:00	190.000	Continued forced ventilation, routed to control device.

12:00	130.000

13:00	101.000

14:00	85.000

15:00	73.000

16:00	63.000

17:00	53.500

18:00	46.000

7.1-198

Liquid Storage TanksEMISSION FACTORS

+4-06/07-18


-------
Day Time Concentration	Activity

	(ppmv)	

19:00	40.000

20:00	35.000

21:00	31.000

22:00	27.700

23:00	24.700

0:00	22.000

1:00	19.700

2:00	17.700

3:00	16.000

4:00	14.400

5:00	12.900

6:00	11.500

7:00	10.200

8:00	9.100

9:00	8.200 45.300 ppmv. average for first day of continued forced ventilation.

Disconnect control device.

Vacuum out all free flowing liquid.
7.400	Continued forced ventilation, vented to atmosphere.

6.700
6.100
5.550
5.100
4.700
4.350
4.050

3.800 5.300 ppmv. average for second day of continued forced ventilation.
Forced ventilation turned off.

2 10:00
11:00
12:00
13:00
14:00
15:00
16:00
17:00
18:00

6:00	19.000	Re-start of forced ventilation (to atmosphere).

First hour is considered vapor space purge.
Continued forced ventilation, vented to atmosphere.

7:00

10.100

8:00

5.500

9:00

3.800

10:00

2.200

11:00

1.500

12:00

1.050

13:00

700

14:00

400

15:00

150

16:00

0

+4-06/0^18

Liquid Storage Tanks

7.1-199


-------
Day Time Concentration

(ppmv)

Activity

17:00
18:00

0
0

2.100 ppmv. average for third day of continued forced ventilation.

Tank cleaning is complete; forced ventilation may continue for
worker safety during inspections, but all volatile material has
been removed and the tank is deemed out of service.

Solution:

1. Select equations to be used.

Jj'V = LP + LCV

Mill



14^1

-Lev — 60 Qv ncv tv Cv ( ^T^G) — 5-9 ^)2 h

leWu

(4-10. 4-12)

_Lsr = 60 Qv ncv tv Cv (^f) < 0-49 Fe D2 ds Wu

(4-10. 4-13)

where:

Lfv = total emissions due to forced ventilation during a tank cleaning event, lb

Lp = vapor space purge emissions associated with the first air change following
commencement of forced ventilation, lb

_LCV = emissions from continued forced ventilation following the first air change, lb
Pva = the true vapor pressure of the exposed volatile material in the tank (psia)

3

Vy = volume (ft ) of the vapor space
R = the ideal gas constant (psia fP per lb-mole °R)

	= 10.731 psia ft^ per lb-mole °R

Ty =	the average temperature of the vapor space ( R)

	=	the average ambient temperature (°R).

My =	the stock vapor molecular weight (lb/lb-mole)

S =	the vapor space saturation factor during the initial vapor space purge (dimensionless)

7.1-200

Liquid Storage TanksEMISSION FACTORS

44-06/Q748


-------
60 is the conversion of hours to minutes, min/hr

3

	Oy = average ventilation rate during continued forced ventilation, ft /min

	yinrr = the duration of continued forced ventilation, days

	ty = the daily period of forced ventilation, hr/dav

	Cy = average vapor concentration by volume during continued forced ventilation.

dimensionless

	P_a = atmospheric pressure at the tank location, psia

MCG = calibration gas molecular weight, lb/lb-mole
	D = the tank diameter, feet

	hje = the effective height of the stock liquid and sludge for the given stage of continued forced

ventilation, ft

	Wj_= the density of the stock liquid, pounds per gallon

	5.9 = combination of constants (re/4) and 7.48 gal/ft3

	He = the fraction of the sludge that evaporates (= 0.20 if unknown)

	ds = the average depth of sludge, inches

2.	Identify parameters to be calculated/determined from tables. In this example, the following parameters
are not specified: Pva. Vv. Tv. My. S. Mra. and Wi.

The following values are obtained from tables or assumptions:

	Pva =	7.50 psia for the RVP 12 gasoline, from Example 5.

	Vv =	22.620 ft3 for the initial condition of one foot of stock remaining, from Example 5.

	Tv =	68.9 °F (528.6 °R). from Example 5.

	My =	66 lb/lb-mole for gasoline, from Table 7.1-2.

	S=	0.38 from Example 5.

	Men =	16 lb/lb-mole for methane, from Table 7.1-3.

	Wi =	5.6 lb/gal for gasoline and 7.1 lb/gal for diesel. from Table 7.1-2.

3.	Calculate the initial vapor space purge emissions.

+4-06/0^18

Liquid Storage Tanks

7.1-201


-------
-L"=aw)Mvs

TV

= ( 7-5-22,620 \ 66	= y50
	 y V10.731-528.6/

The vapor space purge emissions were routed to a control device having an efficiency of 95%. and thus
the net vapor space purge emissions are calculated as follows:

	Lpi = 750 (1 -0.95) = 38 lb

4. Calculate first day of continued ventilation emissions (routed to control device),
a. Check the limit on continued ventilation emissions for the first day:

Calculate the mass of liquid remaining in the tank after vacuuming out the one foot of remaining gasoline
and flooding the tank bottom with diesel.

The remaining gasoline is the equivalent of one-eighth of an inch across the entire bottom of the tank,
plus 3 inches in a 24-inch diameter sump.

	Equivalent depth of the liquid in the sump, if spread across the entire tank bottom:

	(3 inches)*(7t (2/12)2/4) / (n 1202/4) = 0.0008 inches

	Total effective depth of gasoline remaining in the bottom of the tank:

	(0.125 inches) + (0.0008 inches) = 0.1258 inches = 0.010 feet

The depth of diesel in the bottom of the tank is:

6 inches = 0.5 feet

V max_

5.9 D2 hie Wi

	LcVmax < 5.9 (120)2 (0.010»5.6 + 0.5»7.1) = 310.000 lb

b. Check the calculated continued ventilation emissions for the first day:


-------
5. Calculate the second day vapor space purge emissions.

The forced ventilation ran throughout the night on the first day of tank cleaning, and thus there was no
standing idle period during which vapors could build up in the vapor space, and there were no vapor
space purge emissions on the morning of the second day of tank cleaning.

	Lpq= 01b

6. Calculate second day of continued ventilation emissions (routed directly to atmosphere),
a. Check the limit on continued ventilation emissions for the second day:

Calculate the mass of liquid remaining in the tank after vacuuming out all free flowing liquid and leaving
one-half inch of wet sludge in the bottom of the tank.

	LCV < 0-49 Fp J) 2 c/< Wl.

where:

	tie = the fraction of the sludge that evaporates (= 0.20 if unknown)

	D = the tank diameter, feet

_= the average depth of sludge, inches

Wl = the density of the stock liquid, pounds per gallon

9

the constant. 0.49. has units of gal/(in. ft ). and the other terms are defined as shown above.

In the liquid phase, the density of diesel is greater than the density of gasoline and, as shown in the
calculations above for the first day, most of the remaining liquid is diesel. It would, then, be both
reasonable and conservative to use the density of diesel in calculating the mass of remaining liquid.

LCV < 0-49 (0.20) (120)2 (0.5) (7.1) = 5.000 pounds
b. Check the calculated continued ventilation emissions for the second day:

(Pa Mcg'

LCv — 60 Qv ncv tv Cvy

( 5,300 \ ( 14.75-16

Lrv = 60 ¦ 3,000 ¦ 1 - 9 ¦ 	 ¦ 	 = 3601b < 5,0001b

VI,000,000/ V10.731 ¦ 528.6/

Lev? = 360 lb

The second day of continued ventilation emissions were routed directly to atmosphere, and thus the net
vapor space purge emissions are calculated as follows:

Lrv>.= 360 (1 -0.0) = 360 lb

+4-06/0^18

Liquid Storage Tanks

7.1-203


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7. Calculate the third (last) day vapor space purge emissions.

The forced ventilation was discontinued overnight between the second and third days of tank
cleaning, and thus there was an overnight standing idle period. There would, then, be a vapor space purge
on the morning of the third day of tank cleaning. The vapors originated from a mixture of diesel and
gasoline. While most of the liquid was pumped out during the second day, the relative volumes of diesel
and gasoline would have been as described above for the limit on continued ventilation emissions for the
first day. The effective depths were 0.01 feet for gasoline and 0.5 feet for diesel. for a total initial depth of
0.51 feet. The volumes are then calculated from the liquid depths and the diameter of the tank:

Gasoline: 0.01 (;t)(120)2 / 4 = 113 ft3

Diesel:	0.50 (;t)(120)2 / 4 = 5.655 ft3

Multiply the volumes of each liquid by its liquid density to calculate the mass of each. Values of 5.6
lb/gal for gasoline and 7.1 lb/gal for diesel are obtained from Table 7.1-2.

Gasoline: 113 (5.6) (7.48) = 4.733 1b

Diesel:	5.655 (7.1) (7.48) = 300.3261b

The conversion factor of 7.48 has units of gallons per cubic foot.

The total weight is 4.733 + 300.326 = 305.059 lb. The weight of each liquid may then be divided by the
liquid phase molecular weight to calculate the number of moles of that liquid. Molecular weights are
obtained from Table 7.1-2.

Gasoline: 4.733 /92 = 51

Diesel:	300,326/188 = 1,597

The total number of moles is (51 + 1.597) = 1.648. and the mole (volume) fractions in the liquid phase
may be calculated:

Gasoline: 51 / 1,648 = 0.031

Diesel:	1,597/1,648 =0.969

From Example 5. the temperature at the bottom of the tank is 68.9 F. and the true vapor pressure of the
gasoline at that temperature is 7.50 psia. Calculate the true vapor pressure of the diesel at 68.9 F. using
Equation 1-25 with values for the A and B constants from Table 7.1-2.

P = exp

B

A--

A = 12.101

B = 8907°R

P= 0.0087 psia

The partial pressure of each component is the liquid mole (volume) fraction times the true vapor pressure:

7.1-204	Liquid Storage TanksEMISSION FACTORS	4406/^Jl


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Gasoline:

0.031*7.50 = 0.233 psia

Diesel:

0.969*0.0087 = 0.0084 psia

The vapor space purge emissions for the third day can then be computed separately for each component:

Pva = the partial pressure of the given component, psia

Vv = the volume under the landed floating roof, cubic feet

Determine the vapor space volume Vv using Equation 3-22. where the height of the vapor
space under the floating roof is the floating roof leg height (neglecting the one-eighth
inch height of sludge remaining in the tank). In that this example is a continuation of the
floating roof landing in Example 5. the leg height is given as 3 feet. However, it is more
common for the legs to be set in the high leg position when cleaning the tank.

7V = temperature °R = 68.9 + 459.7 = 528.6

My = vapor phase molecular weight of the given component, from Table 7.1-2

	Gasoline: 66

	Diesel; 130

S = saturation factor = 0.50 from 7.1.3.4.1

	Lp3 = 46+ 3 = 49 lb

8. Calculate third (last) day of continued ventilation emissions (routed directly to atmosphere),
a. Check the limit on continued ventilation emissions for the last stage:

After a day of removing sludge, about one-eighth inch of sludge remained in the bottom of the tank.
	Lcvmax < 0.49 Fe D2 ds Wl

	LcVmax < 0.49 (0.20) (120)2 (0.125) (7.1) = 1.300 lb

where:

Vv= (3) (jt 1202/4) = 33930 ft3
R = 10.731 psia ft^ per lb-mole °R

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b. Check the calculated continued ventilation emissions for the last day:

(Pa Mcg

LCv — 60 Qv ncv tv Cv

RT,

v

2,100 \ ( 14.75-16
Lcv = 60 ¦ 3,000 ¦ 1 ¦ 12 ¦ 77---—- ¦ ,nr7n, rnnJ = 190 lb < 1-300 lb

<1,000,000; V10.731 ¦ 528.6

Lcv^ = 190 lb

The last day of continued ventilation emissions were routed directly to atmosphere, and thus the net vapor
space purge emissions are calculated as follows:

Lev, = 190(1 -0.0)= 1901b

6. Calculate total losses for the tank cleaning event. The total loss is the sum of the vapor space purge
emissions and the continued ventilation emissions for each day of forced ventilation while volatile
material remained in the tank. These emissions are summarized as follows:

Lp	Lev

Day 1

38

410

Dav 2

0

360

Dav 3

49

190

Total

87

960

The total emissions during tank cleaning (forced ventilation) are then:

	Lfv = Lp + Lev

	Lfv = 87 + 960 = 1.000 lb

Note that emissions from this example were significantly mitigated by the flushing of the tank bottom
with diesel to reduce the vapor concentration relatively quickly, and by the routing of vapors to a control
device until the vapor concentration was reduced substantially (comparing the start of day 2 to the start of
day 1 shows that the vapor concentration when the control device was disconnected was about two
percent of the initial reading). It's evident from step 4.b above that emissions would have been several
tons per day if these mitigation steps had not been taken.

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7.1.6 Historical Equations

Equations in this section were historically used to obtain approximate values, but have been
replaced with more accurate equations.

7.1.6.1 Average Daily Vapor Pressure Range

The following method was historically available for approximating APy. with some loss of
accuracy, however it is no longer recommended.

An 0.50BPvaATv

AIV =	—2		(60-1)

LA

where:

	APy = average daily vapor pressure range, psia

	B = constant in the vapor pressure equation. °R; the value used here must be the B constant

for the two-constant expression in Equation 1-25

	Pva = vapor pressure at the average daily liquid surface temperature, psia; see Notes 1 and 2 to

Equation 1-22

	Tt a = average daily liquid surface temperature. °R; see Note 3 to Equation 1-22

	ATy = average daily vapor temperature range. °R; see Note 1 to Equation 1-5

7.1.6.2 Fixed Roof Tank Working Loss

Working loss for fixed roof tanks had historically been estimated using Equation 60-2. The
temperature for purposes of determining the vapor density was assumed to be 63°F (523°R) in Equation
60-2. and thus the vapor density was represented as (My 10.731 «523). The coefficient of 0.0010
was based on this simplification of the vapor density, combined with the 5.614 term for converting barrels
to cubic feet, resulting in (5.614)/(10.731*523) = 0.0010.

	Lw 0.0010 M Pj:4 OK~N KP	(60-2)

where:

	Lw = working loss, lb/vr

My = vapor molecular weight, lb/lb-mole; see Note 1 to Equation 1-22
Pva = vapor pressure at average daily liquid surface temperature, psia; see Notes 1 and 2 to
Equation 1-22

Q = annual net throughput (tank capacity Ibbl I times annual turnover rate), bbl/vr
Kn = working loss turnover (saturation) factor, dimensionless
	for turnovers >36. Kn = (180 + N)/6N

for turnovers <36. Kn = 1

N = number of turnovers per year, dimensionless
5.614 0

N	M=31

y LX

where:

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Vt.x = tank maximum liquid volume, fit3

Vlx=jD2Hly	(60-4)

where:

	D = diameter, ft

	Ht x = maximum liquid height, ft

	Kp = working loss product factor, dimensionless

	for crude oils Kp = 0.75

	for all other organic liquids. Kp = 1

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REFERENCES FOR SECTION 7.1

1.	Lave rm an. R.J.. Emission Reduction Options For Floating Roof Tanks, Chicago Bridge and Iron
Technical Services Company, Presented at the Energy Week 1996, Conference on Pipelines,
Terminals and Storage, George R. Brown Convention Center Houston, TX, January 29 - February 2,
1996.

2.	VOC Emissions From Volatile Organic Liquid Storage Tanks-Background Information For Proposed
Standards, EPA-450/3-81-003a, U. S. Environmental Protection Agency, Research Triangle Park,
NC. July 1984.

3.	Alternative Control Techniques Document: Volatile Organic Liquid Storage in Floating and Fixed
Roof Tanks, EPA-453/R-94-001, U. S. Environmental Protection Agency, Research Triangle Park,
NC, January 1994.

4.	Evaporation Loss From Internal Floating Roof Tanks, Third Edition, Publication 2519, American
Petroleum Institute, Washington, DC, June 1983.

5.	Evaporative Loss from Floating-Roof Tanks, Manual of Petroleum Measurement Standards, Chapter
19.2, Third Edition, American Petroleum Institute, Washington, D.C., October 2012.

6.	[Reserved]

7.	Benzene Emissions From Benzene Storage Tanks-Background Information For Proposed Standards,
EPA-450/3-80-034a. U. S. Environmental Protection Agency, Research Triangle Park. NC.

December 1980.

8.	Evaporative Loss from Fixed-Roof Tanks. Manual of Petroleum Measurement Standards. Chapter
19.1. Fifth Edition. American Petroleum Institute. Washington. D.C.. June 2017.

9.	Estimating Air Toxics Emissions From Organic Liquid Storage Tanks. EPA-450/4-88-004. U. S.
Environmental Protection Agency. Research Triangle Park. NC. October 1988.

10.	Barnett. H.C.. et al.. Properties Of Aircraft Fuels. NACA-TN 3276. Lewis Flight Propulsion
Laboratory. Cleveland. OH. August 1956.

11.	Petrochemical Evaporation Loss From Storage Tanks. First Edition. Bulletin No. 2523. American
Petroleum Institute. Washington. D.C.. 1969.

12.	SIMS Data Base Management System, Version 2.0, U. S. Environmental Protection Agency,

Research Triangle Park, NC, 1990.

13.	Comparative Climatic Data Through 1990. National Oceanic and Atmospheric Administration.
Asheville. NC. 1990.

14.	National Solar Radiation Data Base, 1961-1990, prepared by National Renewable Energy
Laboratory, Golden, CO, distributed by National Climatic Data Center, Asheville, NC, September
1992.

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15.	Ferry. R.L.. Documentation Of Rim Seal Loss Factors For The Manual Of Petroleum Measurement
Standards: Chapter 19—Evaporative Loss Measurement: Section 2—Evaporative Loss From Floating
Roof Tanks, preliminary draft. American Petroleum Institute. April 5. 1995.

16.	Written communication from R. Jones, et al.. Midwest Research Institute, to D. Beauregard. U. S.
Environmental Protection Agency. Final Fitting Loss Factors For Internal And External Floating
Roof Tanks. May 24. 1995.

17.	Written communication from A. Parker and R. Neulicht. Midwest Research Institute, to

D. Beauregard. U. S. Environmental Protection Agency. Fitting Wind Speed Correction Factor For
External Floating Roof Tanks. September 22. 1995.

18.	Use Of Variable Vapor Space Systems To Reduce Evaporation Loss. Bulletin No. 2520. American
Petroleum Institute, New York, NY, 1964.

19.	Written communication from A. Parker, Midwest Research Institute, to D. Beauregard, U. S.
Environmental Protection Agency, Final Deck Fitting Loss Factors for AP-42 Section 7.1, February
23, 1996.

20.	Courtesy of R. Ferry, TGB Partnership, Hurdle Mills, NC.

21.	Evaporative Loss from Storage Tank Floating Roof Landings, Manual of Petroleum Measurement
Standards, Chapter 19.6, Part 1, First Edition, American Petroleum Institute, Washington, D.C.,
February 2017.

22.	Evaporative Loss Reference Information and Speciation Methodology. Manual of Petroleum
Measurement Standards. Chapter 19.4. Third Edition. Addendum 2. American Petroleum Institute-
Washington. D.C.. June 2017.

23.	Evaporative Loss from the Cleaning of Storage Tanks. Technical Report 2568. American Petroleum
Institute. Washington. D.C.. November 2007.

24.	Ferry. R.L.. Distillate Flushing Study - Bench and Field Testing - Final Report, prepared for the
American Petroleum Institute. December 2013.

25.	2016 Emissions Inventory Guidelines. RG-360/16. Appendix A. Technical Supplement 6. Texas
Commission on Environmental Quality. Austin. TX. January 2017.

26.	Short-term Evaporative Loss Estimation from Atmospheric Storage Tanks. Technical Report 2576.
First Edition. American Petroleum Institute. Washington. D.C.. July 2016.

27.	Evaporative Loss from Closed-vent Internal Floating-roof Storage Tanks. Technical Report 2569.
American Petroleum Institute. Washington. D.C.. August 2008.

28.	Guide to Fire Hazard Properties of Flammable Liquids. Gases, and Volatile Solids, NFPA 325. 1994
edition. National Fire Protection Institute. Ouincv. MA. 1994.

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