United States
           Environmental Protection
           Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
January 1981
           Air
v>EPA     Guideline Series

          Control of Volatile
          Organic Emissions from
          Volatile Organic Liquid
          Storage in Floating and
          Fixed Roof Tanks
          Preliminary Draft

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                                                       453D81001

                              NOTICE

This document has not been formally released by EPA and should not now be construed to represent
Agency policy. It is being circulated for comment on its technical accuracy and policy implications.
             Control of Volatile Organic
         Emissions from Volatile Organic
           Liquid Storage in  Floating  and
                    Fixed Roof Tanks
                   Emission Standards and Engineering Division
                         Contract No. 68-02-3168
                             Prepared for

                   U.S. ENVIRONMENTAL PROTECTION AGENCY
                      Office of Air, Noise, and Radiation
                   Office of Air Quality Planning and Standards
                   Research Triangle Park, North Carolina 27711

                            January 1981

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                         GUIDELINE SERIES
The guideline series of reports is issued by the Office of Air Quality
Planning and Standards (OAQPS) to provide information to state and local
air pollution control agencies; for example, to provide guidance on the
acquisition and processing of air quality data and on the planning and
analysis requisite for the maintenance of air quality.  Reports published
in this series will be available - as supplies permit - from the Library
Services Office (MD-35), U. S. Environmental Protection Agency, Research
Triangle Park, North Carolina  27711, or for a nominal fee, from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia  22161.

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                             Table of Contents
                                                                     Page
Li st of Tabl es	      vi
Li st of Fi gures	      V1 n 1
Chapter 1.0  Introduction and Summary	      1-1
        1.1  Introduction	      1-1
        1.2  Summary of Model Regulation	      1-2
Chapter 2.0  Emissions from VOL Storage	      2-1
        2.1  Industry Description	      2-1
        2.2  Storage Tanks	      2-1
             2.2.1  Types of Storage Tanks	      2-1
             2.2.2  Types of Seals	      2-3
             2.2.3  Storage Tank Emissions and Emission
                    Equations	      2-8
        2.3  Model Tanks and Uncontrolled Emissions	      2-12
             2.3.1  Fixed Roof Tank	      2-12
             2.3.2  Floating Roof Tank	      2-16
             2.3.3  Small Tank	      2-16
        2.4  References for Chapter 2	      2-17
Chapter 3.0  Emissions Control  Techniques	      3-1
        3.1  Introduction	      3-1
        3.2  Emissions Control  Techniques	      3-1
             3.2.1  Internal Floating Roofs in Fixed Roof
                    Tanks	      3-2
             3.2.2  Rim-Mounted Secondary Seals on External
                    Fl oati ng Roofs	      3-3
                                  iii

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                        Table of Contents (continued)

                                                                     Page
             3.2.3  Fixed Roofs on External  Floating Roof
                    Tanks	      3-3
             3.2.4  Contact Internal  Floatinq Roofs in
                    Non-Contact Internal  Floating Roof Tanks...      3-5
             3.2.5  Liquid-Mounted Primary Seals on
                    Contact Internal  Floating Roofs	      3-5
             3.2.6  Rim-Mounted Secondary Seals on Contact
                    Internal  Floating Roofs	      3-5
        3.3  Retrofit Considerations	      3-7
             3.3.1  Fixed Roof Tanks  with Internal Floating
                    Roofs	      3-7
             3.3.2  Rim-Mounted Secondary Seals on External
                    Fl oati ng  Roofs	      3-7
             3.3.3  Fixed Roofs on External  Floating Roof
                    Tanks..	      3-7
             3.3.4  Secondary Seals on non-contact Internal
                    Fl oati ng  Roofs	      3-8
        3.4  References for Chapter 3	      3-9
Chapter 4.0  Environmental  Analysis of RACT	      4-1
        4.1  Air Pollution	      4-1
        4.2  Water Pollution	      4-3
        4.3  Solid Waste Disposal..	      4-3
        4.4  Energy	      4-3
        4.5  References for Chapter 4	      4-4
Chapter 5.0  Control  Cost Analysis of RACT	      5-1
        5.1  Bases for Installed Capital  Costs	      5-1
             5.1.1  Cost of Installing a Contact Internal
                    Floating  Roof	      5-1
                                   iv

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                       Table of Contents  (continued)
                                                                     Page
             5.1.2  Cost of  Installing a Fixed Roof	       5-4
             5.1.3  Cost of  Installing Secondary Seals	       5-4
             5.1.4  Cost of  Cleaning, Degassing, and
                   Certification	       5-4
        5.2   Bases  for Annualized Costs	       5-4
             5.2.1  Annual Capi tal Charges	       5-10
             5.2.2  Direct Operating Costs	       5-10
             5.2.3  Recovery Credits	       5-11
        5.3   Emission Control Costs	       5-11
             5.3.1  Small Model Storage Tank	       5-11
             5.3.2  Average  Fixed Roof Model Storage Tank	       5-11
             5.3.3  Average  Floating Roof Model Storage Tank...       5-15
        5.4   Cost Effectiveness	       5-15
        5.5   References for  Chapter  5	       5-18
Chapter 6.0  Model  Regulation and Discussion	       6-1
        6.1   Model  Regulation	       6-1
        6.2   Discussion	       6-6
             6.2.1  Introduction	       6-6
             6.2.2  Review of the Records	       6-6
             6.2.3  Inspections	       6-7
             6.2.4. Equivalency	       6-7
             6.2.5  Compliance Schedule	       6-9
        6.3   References for  Chapter  6	       6-10
 Appendix A   Emission Source Test Data VOL Storage Tanks
 Appendix B   Example Calculations for Determining Reduction  in
             Emissions from  Implementation of RACT

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LIST OF TABLES

Table 2-1

Table 2-2

Table 2-3
Table 2-4
Table 4-1
Table 5-1

Table 5-2

Table 5-3

Table 5-4

Table 5-5
Table 5-6
Table 5-7
Table 5-8
Table 5-9

Table A-l

Table A-2

Table A-3


Emission factors K and n 	
s
Summary of emission factors K. and m for floating
roofs 	
Fitting multipliers 	
Model tank parameters and emissions 	
Impact of RACT on VOC emissions from storage tanks.
Cost of installing a contact internal floating roof
in an existing fixed roof tank 	
Cost of installing a fixed roof on an existing
external floating roof tank 	
Cost of installing a secondary seal on an existing
internal or external floating roof 	
Cost of cleaning, degassing, and certification
of a storage tank 	
Bases for annual i zed cost estimates 	
Recovery credi ts 	
Installed capital costs 	 	
Annual i zed control costs for model storage tanks 	
Cost effectiveness for model storage tanks under
RACT 	
Summary of test conditions, for phase I,
contact- type internal floating roof 	
Summary of test conditions for phase II,
non-contact-type internal floating roof 	
Summary of test conditions for phase III, double
deck external floating roof 	
Page
2-13


2-13
2-14
2-15
4-2

5-2

5-2

5-6

5-6
5-9
5-12
5-13
5-14

5-16

A-7

A-12

A-14
    VI

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LIST OF TABLES (continued)
Table A-4
Table A-5
Table A-6
Table A-7
Table A-8
Measured benzene emissions from EPA phase I
testing, contact-type internal floating roof 	
Measured benzene emissions from EPA phase III
testing double deck external floating roof 	
Seal loss factors for average seal gaps and the
basis of estimation 	
Measured and estimated breathing losses from
fixed-roof tanks 	
Comparison of measured losses with those calculated
usina API 2518 	
Page
A-16
A-17
A-19
A-22
A-25
             Vll

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                               LIST OF FIGURES

                                                                    Page
Figure 2-1  Typical  fixed-roof tank	     2-2
Figure 2-2  External  floating roof tank (pontoon type)	     2-4
Figure 2-3  Internal  floating roof tanks	     2-5
Figure 2-4  Primary seals	     2-6
Figure 2-5  Typical  flotation devices and perimeter seals
            for internal  f 1 oating roofs	     2-9
Figure 3-1  Metallic shoe seal with shoe-mounted secondary seal.     3-4
Figure 3-2  Rim mounting  of a secondary seal  on an internal
            floating roof	      3-6
Figure 5-1  Cost of installing a contact internal  floating roof
            in an  existing fixed roof tank	      5-3
Figure 5-2  Cost of installing a fixed roof on an  existing
            external  floating roof tank	      5-5
Figure 5-3  Cost of installing a secondary seal on an existing
            internal  or external floating roof	      5-7
Figure 5-4  Cost of cleaning, degassing, and certification	      5-8
Figure A-l  Simplified process and instrumentation schematic...      A-2
Figure A-2  Position of the contact-type internal  floating roof
            within the emissions test tank	      A-5
Figure A-3  Rim mounting  of the flapper secondary  seal	      A-6
Figure A-4  Installed shingle-type seal	      A-8
Figure A-5  Position of the non-contact-type internal floating
            roof within the emissions test tank	      A-9
Figure A-6  Cross-sectional  view of the shingle-type seal
            installation	      A-10
Figure A-7  Position of the double deck external floating roof
            within the emissions test tank	      A-13
                                   vm

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                        1.0  INTRODUCTION AND SUMMARY
1.1  INTRODUCTION
     The Clean Air Act Amendments of 1977 require each State in which there
are areas in which the national  ambient air quality standards (NAAQS) are
exceeded to adopt and submit revised State implementation plans (SIP) to
EPA.  Revised SIP's were required to be submitted to EPA by January 1, 1979.
States which were unable to demonstrate attainment with the NAAQS for ozone
by the statutory deadline of December 31, 1982, could request extensions for
attainment with the standard.  Such extensions could not go beyond
December 31, 1987.  States granted such an extension are required to submit
a further revised SIP by July 1, 1982.
     Section 172(a)(2) and (b)(3) of the Clean Air Act require that
nonattainment area SIP's include reasonably available control technology
(RACT) requirements for stationary sources.  As explained in the "General
Preamble for Proposed Rulemaking on Approval of State Implementation Plan
Revisions for Nonattainment Areas," (44 FR 20372, April 4, 1979) for ozone
SIP's, EPA permitted states to defer the adoption of RACT regulations on a
category of stationary sources of volatile organic compounds (VOC) until
after EPA published a control techniques guideline (CTG) for that VOC source
category.  See also 44 FR 53761 (September 17, 1979).  This delay allowed
the states to make more technically sound decisions regarding the application
of RACT.
     The CTG documents provide State and local air pollution control agencies
with an information base for proceeding with development and adoption of
regulations which reflect RACT for specific stationary sources.  Consequently,
CTG documents review existing information and data concerning the technology
and cost of various control techniques to reduce emissions.  CTG documents
also identify control techniques and suggest emission limitations which EPA
considers the "presumptive norm" broadly representative of RACT for the
entire stationary source category covered by a CTG document.

                                   1-1

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     The CTG documents are, of necessity, general  in nature and do not fully
account for variations within a stationary source category.  RACT, however,
is defined as the lowest emission limitation that a particular source is
capable of meeting by the application of emission control  technology that is
reasonably available considering technical and economic feasibility.  Thus,
reasons may exist for regulations developed by States to deviate from the
"presumptive norm" included in a CTG document.  The CTG document, however,
is a part of the rulemaking record which EPA considers in reviewing revised
SIP's, and the information and data contained in the document is highly
relevant to EPA's decision to approve or disapprove a SIP revision.  Where a
State adopts emission limitations that are consistent with the information
in the CTG, it may be able to rely solely on the information in the CTG to
support its determination of RACT.  Where this is not the case, the State
must include documentation with its SIP revision to support and justify its
RACT determination.
     This draft CTG document includes a model regulation based upon the
"presumptive norm" considered broadly representative of RACT for the
stationary source category covered by this document.  The sole purpose of
this model regulation is to assist State and local agencies in development
and adoption of regulations for specific stationary sources.  This model
regulation is not to be construed as rulemaking by EPA.
     This CTG document is being released in working draft form to achieve
two objectives.  First, to provide an opportunity for public review and
comment on the information and regulatory guidance contained in the document;
and second, to provide as much assistance and lead time as possible to State
and local agencies preparing RACT regulations for specific stationary
sources covered by this document.
1.2  SUMMARY OF MODEL REGULATION
     The model regulation applies to storage tanks with a capacity larger
than 151,416 liters (40,000 gallons) storing a volatile organic liquid (VOL)
with an actual vapor pressure greater than 10.5 kPa (1.5 psia).  Storage
tanks which are used to store petroleum liquids are excluded from the model
regulation.

                                    1-2

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     This model regulation requires that affected VOL storage tanks be
retrofitted with RACT.  The RACT required by the model  regulation is a
contact internal floating roof with primary and secondary seals.   Tanks that
are currently equipped with an internal floating roof are exempt.  Affected
fixed roof tanks must install a contact internal floating roof with a liquid-mounted
or metallic shoe primary seal and a continuous secondary seal.  Affected
external floating roof tanks must install a fixed roof over the tank.  The
model regulation does not require that existing primary seals which are not
RACT be removed and replaced by a liquid-mounted or metallic shoe primary
seal, or that existing secondary seals which are not RACT be removed and
replaced with a continuous secondary seal.  However, when a primary seal is
replaced it must be replaced with a liquid-mounted or metallic shoe primary
seal and when a secondary seal is replaced, it must be replaced with a
continuous secondary seal.
     The owner or operator of each storage tank is required to visually
inspect the internal floating roof, the primary seal, and the secondary seal
prior to initial fill and whenever the tank is emptied and degassed but at
least once every five years.  If the owner or operator of the storage tank
finds any defects in the internal floating roof, or any holes, tears, or
other openings in the seals or seal fabric, the control equipment must be
repaired before filling the tank.  More frequent inspections are not
required; however the tanks must be maintained in good repair as outlined in
the model regulation.
     The recordkeeping requirements of the model regulation require that
each owner or operator of a storage tank storing a VOL with an actual vapor
pressure greater than 1.0 psia keep a record of the VOL being stored, the
average monthly storage temperature of the VOL, and the actual vapor
pressure of the liquid at the average monthly storage temperature.
     No periodic reports are required in the model regulation.  However, the
Director is to be notified in writing at least 30 days prior to the
refilling of the storage tank in order to afford the State air pollution
agency an opportunity to inspect the control equipment.
                                   1-3

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     Provisions are made in the model  regulation for an owner or operator  of
a storage tank to apply for an alternative control  device.   Alternative
control devices must reduce emissions  by at least 90 percent.  The emission
reduction efficiency of the alternative control  device would be determined
by comparing emissions resulting from  its use with  emissions resulting from
use of a fixed-roof storage tank.   The owner or  operator must provide any
calculations, data, or other evidence  which is necessary for determination
of control efficiency.
                                    1-4

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                    2.0  EMISSIONS FROM VOL STORAGE

2.1  INDUSTRY DESCRIPTION
     VOL storage tanks are primarily located at chemical  manufacturing
facilities and bulk terminals.  A terminal is a non-manufacturing site that
stores commodities in bulk quantity.
     Tanks are used for storing a variety of materials:   raw materials,
final products or usable by-products, as well as waste tars, residues, and
nonusable by-products.  The vapor pressure of the material  stored is a major
factor in the choice of tank type used.  Other factors,  such as material
stability, safety hazards, and multiple use, can also affect the choice of
tank type for a particular organic chemical.
2.2  STORAGE TANKS
2.2.1  Types of Storage Tanks
     2.2.1.1  Fixed Roof Tanks.  A typical fixed roof tank is shown in
Figure 2-1.  This type of tank generally consists of a cylindrical steel
shell with a permanently affixed roof that varies from a cone-shaped to a
dome-shaped design.
     Of presently employed tank designs, the fixed roof tank is the least
expensive to construct and is generally considered the minimum accepted
standard for storage of VOL.  The tank is designed to operate at a slight
internal pressure above or below atmospheric pressure, and as a result,
emissions from breathing, filling, and emptying can be appreciable.
     Breather valves (pressure-vacuum valves) are commonly installed on
many fixed roof tanks to prevent vapors from escaping due to temperature
and barometric pressure changes or very small liquid level  fluctuations.
However, these valves vent vapors to the air during normal  filling and
allow air into the tank during emptying.
                                    2-1

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PRESSURE-VACUUM
     VALVE
GAUGE HATCH
  MANHOLE
                                                        MANHOLE
                                                           NOZZLE
                                                           (FOR SUBMERGED FILL
                                                           OR DRAINAGE)
               Figure 2-1.   Typical  fixed-roof tank.
                                2-2

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     2.2.1.2  External Floating Roof Tanks.   A typical  external  floating
roof tank is shown in Figure 2-2.  This type of tank consists of a steel
cylindrical shell equipped with a deck or roof that floats on the surface of
the stored liquid, rising and falling with the liquid level.   The liquid
surface is completely covered by the floating roof except in  the small
annular space between the roof and the shell.  A seal attached to the roof
contacts the tank wall (except for small  gaps in some cases)  and covers the
remaining area.  The seal slides against the tank wall  as the roof is raised
or lowered.
     2.2.1.3  Internal Floating Roof Tanks.   An internal floating roof tank
is essentially a fixed roof tank with a cover floating  on or  several  inches
above the liquid surface inside the tank.  Internal floating  roofs that
float on the liquid surface are contact roofs, as shown in Figure 2-3a.
Contact roofs include (1) aluminum sandwich panel roofs with  a honeycombed
aluminum core floating in contact with the liquid, and  (2) pan-type steel
roofs floating in contact with the liquid.  Internal floating roofs that
float above the liquid surface are non-contact roofs, as shown in Figure 2-3b.
Non-contact type roofs typically consist of an aluminum deck  on an aluminum
grid framework supported above the liquid surface by tubular  aluminum pontoons.
The roof rises and falls with the liquid level.  In addition, circulation
vents and an open vent at the top of the fixed roof are often provided to
minimize the possibility of hydrocarbon vapors accumulating in concentrations
approaching the explosive range.
2.2.2  Types of Seals
     2.2.2.1  External Floating Roof Tank Seals.  Regardless  of tank design,
a floating roof requires a closure device to seal the gap between the tank
wall and the roof perimeter.  Primary seals, the lower seal of a two seal
system, can be made from a variety of materials suitable for  organic liquids.
The basic designs available are: (1) mechanical shoe seals, (2) liquid-filled
seals, and (3) resilient foam log seals.   One major difference in seal
design is how the seal is mounted with respect to the liquid.  Figure 2-4c exhibits
a vapor space between the liquid and seal, whereas in Figures 2-4b and
2-4d, the seals are resting on the liquid surface.
                                    2-3

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ro
-P.
                                                                               ROOF LEG SUPPORT

                                                                                   PRIMARY  SHOE  SEAL
  AUTOMATIC
BLEEDER VENT
                            Figure 2-2.  External floating roof tank  (pontoon  type).

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                      ANTI-ROTATION
                      ROOF FITTING
CENTER
 VENT
    PERIPHERAL
    ROOF VENT/
 INSPECTION HATCH
   i INCH DIAMETER
  SS GROUND CABLES
ANTI-ROTATION CABLE
                 GROUND  CABLE  ROOF
                    ATTACHMENT
                                                                        OVERFLOW VENT
             MANHOLE
                           a.  Contact internal floating roof.
                                        CENTER
                                         VENT
      GROUND CABLE
     ROOF ATTACHMENT
    PERIPHERAL ROOF VENT/
       INSPECTION HATCH
    i INCH DIAMETER
   SS GROUND CABLES
      PRIMARY SEAL-
         RIM PLATE
          MANHOLE
                      TANK SUPPORT COLUMN
                       WITH COLUMN WALL
                      ANTI-ROTATION
                       ROOF  FITTING

                         OVERFLOW
                            VENT
                       ANTI-ROTATION CABLE
                          PASSES  THROUGH
                          FITTING BOLTED
                           TO RIM PLATE

                        RIM  PONTOONS
                       VAPOR SPACE

                   ANTI-ROTATION LUG
                    WELDED TO FLOOR
                                                           TANK SUPPORT COLUMN
                                                            WITH COLUMN WELL
                        b.  Non-contact internal floating roof.

                      Figure 2-3.  Internal floating roof tanks.

                                           2-5

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 a.  Metallic shoe seal
b.   Liquid-filled seal  with
    weather shield.
                 Floating Roof

               Vapor Space
Tank
Wall
^
Scuff
Band —
^
Metallic Weather
« Shield
i
„ 	 \
Floating roof
Liquid filled
^tube
	 _ 	 >
— 	 	
' .. ..



 c.  Resilient foam-filled seal
     with weather shield.
d.  Resilient foam-filled seal
    with weather shield.
Tank
Wall
           Metallic Weather
         ^/Shield
                Floating roof


                Seal  fabric


                Resilient foam
                 log


                Vapor space
          Metallic Weather
              Shield
                                                          Floating  roof
                    fabric
               Resilient foam
                log
                    Figure 2-4.   Primary seals.

                                2-6

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     2.2.2.1.1  Mechanical shoe seal.  The mechanical  shoe seal, which is
shown in Figure 2-4a, is characterized by a 75 to 130 cm (30" to 51") high
metal sheet called the shoe which is held against the vertical  tank wall.
The shoe is connected by braces to the floating roof and is held tightly
against the wall by springs or weighted levers.  A flexible coated fabric
called the envelope is suspended from the shoe seal to the floating roof to
form a gastight cover over the annular space between the roof and the primary
seal.
     2.2.2.1.2  Liquid-filled seal.   A liquid-filled seal (Figure 2-4b)  may
be a tough fabric band or envelope filled with a liquid, or it may be a  20
to 25 cm (8-10") diameter flexible polymeric tube filled with a liquid and
sheathed with a tough fabric scuff band.  The liquid is commonly a petroleum
distillate or other liquid which would not contaminate the stored product if
the tube is ruptured.  Liquid-filled seals are mounted on the product liquid
surface with no vapor space below the seal.
     2.2.2.1.3  Resilient foam-filled seal.  A resilient foam-filled seal is
similar to a liquid-filled seal except that a resilient foam log is used in
place of the liquid.  The resiliency of the foam log permits the seal to
adapt itself to some imperfections in tank dimensions and to even partially
or completely fill some protrusions.  The foam log may be mounted above  the
liquid surface (vapor-mounted) or on the liquid surface (liquid-mounted).
Typical vapor-mounted and liquid-mounted seals are presented in Figures  2-4c
and 2-4d, respectively.
     2.2.2.1.4  Weather shield.  A weather shield (Figures 2-4b, 2-4c, and
2-4d) may be installed over the primary seal to protect it from deterioration
caused by debris and exposure to the elements.  Typically, a weather shield
is an arrangement of overlapping thin metal sheets pivoted from the floating
roof to ride against the tank wall.   This type of seal is also known as  a
shingle seal.
     2.2.2.2  Internal Floating Roof Tank Seals.  Internal floating roofs
typically incorporate two types of flexible, product-resistant primary
seals:  resilient foam-filled seals and wiper seals.  Similar to those
employed on external floating roofs, these seals close the annular vapor

                                   2-7

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space between the edge of the floating roof and the tank shell.   They
compensate for tank shell irregularities, thus allowing the roof to move
freely up and down in the tank without binding.
     2.2.2.2.1  Resilient foam-filled seal.  A resilient foam-filled seal
used on an internal floating roof is similar in design to that described in
section 2.2.2.1.3.  Two types of resilient foam-filled seals for internal
floating roofs are shown in Figures 2-5a and 2-5b.   These seals can either
be several inches above the liquid surface (vapor-mounted) or mounted in
contact with the liquid surface (liquid-mounted).
     2.2.2.2.2  Wiper seal.  A closed-cell, or other type of elastomeric
wiper (Figure 2-5c) can also be used to close the  annular vapor space.
This type of seal, which is generally vapor-mounted can fit continuously
around the circumference of the floating roof.  One design consists of
overlapping segments of seal material (shingle-type seal).
2.2.3  Storage Tank Emissions and Emission Equations
     2.2.3.1  Fixed Roof Tank Emissions.  The two  major types of emissions
from fixed roof tanks are breathing losses and working losses.  Breathing
loss is the expulsion of vapor from a tank due to  expansion and contraction
resulting from diurnal temperature and barometric  pressure changes.  The
emissions occur in the absence of any liquid level  change in the tank.
     Working losses consist of filling and emptying losses.  Filling losses
are associated with an increase of the liquid level in the tank.  The vapors
are expelled from the tank when the pressure inside the tank exceeds the
relief pressure as a result of filling.  Emptying  losses occur when air
drawn into the tank during liquid removal becomes  saturated with hydrocarbon
vapor and expands, thus exceeding the capacity of  the vapor space.
     2.2.3.2  Fixed Roof Emission Equations.  The  EPA Report, Publication
No. AP-42, emission equations for breathing and working losses were used to
estimate VOL emissions from fixed roof tanks.   However, breathing losses
calculated using these equations were discounted by a factor of four in
light of test results reported by EPA,  the Western Oil and Gas Association
       Q
(WOGA),  and the German Society for Petroleum Science and Carbon Chemistry
(DGMK).9
                                2-8

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a.  Resilient foam-filled seal (vapor-mounted).
    Tank wall
  \\v          L
    Resilient foam-filled seal
                              Contact  internal  floating  roof
                              (aluminum  sandwich  papel roof)
b.  Resilient foam-filled seal (liquid-mounted),
        Resilient foam-filled seal
                        Contact internal floating roof
                        (pan-type steel roof)        /
   Tank wall
c.   Elastomeric wioer seal.
      Elastomeric wiper seal
 (.-'' V
                                  /
                            Non-contact internal floating roof
       Pontoon
   "Metal seal ring

Tank wall
                                                  (J
                                    Pontoon
                                                   Note:   v - vapor
                                                          L - liquid
  Figure 2-5.   Typical  flotation devices and perimeter seals
                      for internal  floating roofs.
                              2-9

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The equations used in determining the emission estimates for  fixed  roof
tanks, reflecting this change, follow:
       LT = LB + L,                                         (2-1)
       LB = 9.15 x 10"6 M f(P) D1'73^.51!0-^            (2-2)
       Lw = 1.09 x 10~8NPKnVN                               (2-3)
where, Ly = total loss (Mg/yr)
       LB = breathing loss (Mg/yr)
       L, = working loss (Mg/yr)
       M  = molecular weight of product vapor (Ib/lb mole);  (avg. mol . wt.  is  80)
       P  = true vapor pressure of product (psia)
           /    P    xO.68
           \         ;
             14.7-P
        D = tank diameter (ft)
        H = average vapor space; assumed tank height/2 (ft)
        T = average diurnal  temperature change in  °F(avg. temp,  change is  20°F)
       F  = paint factor; 1.0 for clean white paint
        C = tank diameter factor;
            for diameter >_ 30 feet, C = 1
            for diameter < 30 feet,
               C = 0.0771 D - 0.0013 (D2) - 0.1334
          =. turnover factor
                                                                                 10
       K
            for turnovers > 36, k  =
            for turnovers < 36 k  = 1
                          —     n
                                       6N
       N  = number of turnovers per year
       V  = tank capacity (gal)
     2.2.3.3. External Floating Roof Tank Emissions.   Standing-storage
losses, which result from causes other than breathing or change in the
liquid level, constitute the major source of emissions from floating roof
tanks.  The largest potential source of these losses  is an improper fit
between the seal and the tank shell (seal losses).   As a result some liquid
surface is exposed to the atmosphere.   When air flow across the tank creates
pressure differences around the floating roof, air flows into the annular
vapor space on the leeward side and an air-vapor mixture flows out on the
windward side.
                                   2-10

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     Withdrawal loss is another source of emissions from floating-roof
tanks.  When liquid is withdrawn from a tank, the floating roof is lowered
and a wet portion of the tank wall is exposed.   Withdrawal loss is the
vaporization of liquid from the wet tank wall.
     2.2.3.4  Internal Floating Roof Tank Emissions.  Internal  floating
roof tanks generally give the same sources of emissions as external  floating
roof tanks.  Consequently, standing storage and withdrawal constitute two
sources of emissions from these tanks.  Fitting loss, which is  a result of
penetrations in the roof for deck fittings, roof column supports, or other
openings, can also account for significant emissions from internal floating
roof tanks.
     2.2.3.5  Floating Roof Tank Emission Equations.  VOL emissions from
external floating roofs and internal floating roofs, were estimated using
equations based on an EPA study of emissions from benzene storage tanks.
     From the equations presented below, it was possible to estimate the
Total Evaporation Loss, Ly, which is the sum of the Withdrawal  Loss, LW,
the Seal Loss, L<., and the Fitting Loss, Lp.
       LT = Lw + LF * Ls                                   (2-4)
       Lw = 0.943 QCWL/2205D                               (2-5)
       LS = KS VnMvD f(P)/2205                             (2-6)
       LF = NKF V^ f(P)/2205                             (2-7)
where LT = total loss (Mg/yr)
       LW = withdrawal loss (Mg/yr)
       LS = seal loss (Hg/yr)
       Lp = fitting loss (Mg/yr)
     f(P) = 0.068P/((1 + (1 - 0.068P)0-5)2)
       MV = molecular weight of product vapor (Ib/lb mole)
       P  = true vapor pressure of product (psia)
       D  = tank diameter (ft)
      WL  = density of product (Ib/gal); 8 Ibs/gal12
       V  = average wind speed for the tank site (mph);
                                     12
            10 mph average wind speed
       Q  = product average throughput (bbl/yr);
            tank capacity (bbl/turnover) x Turnovers/yr

                                    2-11

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       KS  = seal factor; see Table 2-1
       KF  = fitting factor; see Table 2-2
       n   = seal wind speed exponent, See Table 2-1
       m   = fitting wind speed exponent; See Table 2-2
       c   = product withdrawal shell clingage factor bbl/(ft2 x 103);
             use 0.0015 bbl/(ft2 x 103) for VOL in a welded steel tank with
             light rust
       N   = fitting multiplier; See Table 2-3
2.3  MODEL TANKS AND UNCONTROLLED EMISSIONS
     This section describes the model tanks and presents the uncontrolled
emission rate from each model tank.  There are three model tanks used in
subsequent analyses:  a fixed roof tank, a floating roof tank, and a small
tank.  The parameters for the fixed roof and floating roof tanks were deter-
mined from data obtained during an industry survey conducted for the U.S.
Environmental Protection Agency.    These data show that floating roof tanks
are normally much larger than fixed roof tanks and frequently store liquids
of higher vapor pressure.  A small tank was included in the model tanks to
illustrate the environmental and economic impact on a small tank.
    The uncontrolled emission rate of a storage tank is largely dependent
upon the tank's turnover rate.  The turnover rate is determined by dividing
the annual throughput of the tank by the capacity of the tank.   A storage
tank at a chemical manufacturing plant usually has a higher annual turnover
rate than a tank at a storage terminal.  In general the annual turnover rate
of a storage tank decreases as the tank capacity increases.  The small fixed
roof tank and the average fixed roof tank have a turnover rate of 50 turnovers
per year.  The average floating roof tank has a turnover rate of 10 turnovers
per year.
2.3.1.  Fixed Roof Tank
     The model fixed roof tank is not equipped with emission control
technology.  The model tank representing average conditions has a capacity
of 480,747 liters (127,000 gallons) and stores a liquid with a vapor pressure
of 10.5 kPa (1.5 psia).  This tank has a diameter of 8 meters (26 feet) and
a height of 10 meters (32 feet).  Using equation 2-1 for fixed roof tanks,
the emissions for the model tank are 7.22 Mg/yr for 50 turnovers per year.
(See Table 2-4).
                                   2-12

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                    Table 2-1.  EMISSION FACTORS K, AND n
       Type of roof                                K<.
Contact internal floating roof
  Primary seal only                               26.7               0.1
  Primary and secondary seals                      8.3               0.3
Non-contact internal floating roofs
  (Primary and secondary seals)                    7.3               1.2
External floating roof
  Primary seal only                               50.5               0.7
  Primary and secondary seals                     77.0               0.1
     Table 2-2.  SUMMARY OF EMISSION FACTORS Kp AND m FOR FLOATING ROOFS
Case
number
1
2
3


Pan roof
Roof
description
type internal floating roof
Bolted cover type internal floating roof
External
floating roof

KF
132
309
0

m
0
0.3
0
                                    2-13

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                 TABLE  2-3.   FITTING MULTIPLIERS
       D                                                     N
tank diameter,                                             fitting
      ft                                                multiplier
       D <  20                                               0.5
  20 £ D <  75                                               1
  75 £ D < 100                                               2
 100 £ D < 120                                               3
 125 < D < 150                                               4
 150 £ D < 175                                               5
 175 < D < 200                                               6
                              2-14

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                                TABLE 2-4.  MODEL TANK PARAMETERS AND EMISSIONS
ro

K-»
in
Model tank
Small tank3
Average fixed roof
Average floating roof0
Vapor
pressure
kPa (psia)
10.5
10.5
15.2
(1.5)
(1.5)
(2.2)
Capacity
liters (gal)
151,416 (40,000)
480,747 (127,000)
3,482,579 (920,000)
Emissions
Mg/yr
2.29
7.22
23.08
      a5 m  (17  ft) diameter;  7 m  (24  ft)  height;  50  turnovers/year.

      b8 m  (26  ft) diameter;  10 m (32  ft) height; 50 turnovers/.year."

      C19 m (62 ft) diameter; 12  m (40 ft)  height; 10  turnovers/year.

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2.3.2  Floating Roof Tank
     The model floating roof tank is an external  floating roof tank with
primary seals.  This model tank has a capacity  of 3,482,579 liters
(920,000 gallons) and stores a liquid with a vapor pressure of 15.2 kPa
(2.2 psia).  It has a diameter of 19 meters (62 feet) and a height of 12 meters
(40 feet).  Using equation 2-4 for floating roof tanks the emissions are
23.08 Mg/yr for 10 turnovers per year.  (See Table 2-4).
2.3.3  Small Tank
     The model tank representing small tanks is a fixed roof tank.  The
majority of existing tanks in this size range are fixed roof tanks with no
control technology.  The capacity of this tank is 151,416 liters
(40,000 gallons) and the liquid it stores has a vapor pressure of 10.5 kPa
(1.5 psia).  This tank has a diameter of 5 meters (17 feet) and a height of
7 meters (24 feet).  The emissions from this uncontrolled tank are 2.29 Mg/yr
for 50 turnovers per year.  (See Table 2-4).
                                   2-16

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2.4  REFERENCES FOR CHAPTER 2
1.   Erickson, D.G., Emission Control  Options for the Synthetic Organic
     Manufacturing Industry, Hydroscience, Inc.   Knoxville,  Tennessee.
     (Unpublished draft submitted in fulfillment of EPA contract no.  68-02-2577.)

2.   Radian, Inc.  The Revised Organic Chemical  Producers Data Base System,
     Final Interim Report.  Austin, Texas, (submitted in fulfillment of EPA
     contract no. 68-03-2623) March 1979.

3.   Booz, Allen, and Hamilton, Foster D.  Snell  Division, Cost of Hydrocarbon
     Emissions Control to the U.S.  Chemical  Industry (SIC 28), Manufacturing
     Chemists Association.  Florham Park,  New Jersey.  December 1977.

4.   Letter from Rockstroh, M.A., TRW to Moody,  W.T., TRW, February 1,  1980.

5.   International Liquid Terminals Association.  Bulk Liquid Terminals and
     Storage Facilities, 1979 Directory.  Washington, D.C.  1979, 85 p.

6.   U.S. Environmental Protection Agency.  Compilation of Air Pollution
     Emission Factors.  Research Triangle  Park,  North Carolina.  Report No.
     AP-42, August 1977.

7.   Western Oil and Gas Association.   Hydrocarbon Emissions from Fixed
     Roof Petroleum Tanks, prepared by Engineering Science,  Inc.  Los
     Angeles, California.  July 1977.

8.   U.S. Environmental Protection Agency.  Emission Test Report-Breathing
     Loss Emissions from Fixed Roof Petrochemical Storage Tanks.  EMB
     Report 78-OCM-5.  Research Triangle Park, North Carolina.  February 1979.

9.   German Society for Petroleum Science  and Carbon Chemistry (DGMK) and
     the Federal Ministry of the Interior  (BMI).  Measurement and Determina-
     tion of Hydrocarbon Emissions in the  Course of Storage and Transfer in
     Above-Ground Fixed Cover Tanks With and Without Floating Covers,
     BMI-DGMK Joint Projects 4590-10 and 4590-11, Translated for EPA by
     Literature Research Company, Annandale, Virginia.

10.  Hydroscience, Inc.  Emissions Control Options for the Synthetic Organic
     Chemicals Manufacturing Industry:  Storage and Handling Report, Draft
     Report.  Knoxville, Tennessee.  October  1978.

11.  U.S. Environmental Protection Agency.  Measurement of Benzene Emissions
     from a Floating Roof Test Tank.  Publication No. EPA-450/3-79-020,
     Research Triangle Park, North Carolina.  June 1979.

12.  See reference 10.

13.  See reference 10.

                                     2-17

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                     3.0  EMISSIONS CONTROL TECHNIQUES
3.1  INTRODUCTION
     This chapter describes techniques for controlling emissions from VOL
storage tanks and discusses the relative emission reduction capabilities for
these control techniques.
     As discussed in Chapter 2, there are three types of tanks which are
used to store volatile organic liquids:  fixed roof tanks, external  floating
roof tanks, and internal floating roof tanks.  The various techniques
discussed in this chapter for controlling VOC emissions from these types of
storage tanks were chosen on the basis of tests conducted for EPA on a
6 meter (20 foot) diameter pilot test tank fitted with several different
floating roof and seal combinations (See Appendix A).   The tests were
conducted on a storage tank containing benzene.  It is believed that the
benzene test results can be applied to any tank storing VOL.  The roof and
seal combinations tested and discussed in this chapter are:  (1) an external
floating roof with a metallic shoe primary seal (EFRps); (2) an external
floating roof with a metallic shoe primary seal and a rim-mounted secondary
seal (EFRss); (3) a non-contact internal floating roof with shingled,
vapor-mounted primary and secondary seals (ncIFRss); (4) a contact internal
floating roof with a liquid-mounted primary seal (cIFRps); and (5) a contact
internal floating roof with a liquid-mounted primary seal and a continuous
secondary seal (cIFRss).  Several roof and seal combinations which have not
been tested are also discussed.
3.2   EMISSIONS CONTROL TECHNIQUES
     As discussed in Chapter 2, emissions from storage tanks are primarily a
function of tank capacity, vapor pressure of the liquid stored, and the
annual turnover rate.  The VOC emissions from storage tanks increase with
increasing tank capacity, vapor pressure, and turnover rate.  The emissions
reduction obtained through the use of various control techniques depends upon

                                   3-1

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the type of tank and the roof and seal combination employed.  A contact
internal floating roof with primary and secondary seals provides the greatest
emission reduction over all other roof and seal combinations.  Emissions from
an external floating roof tank can be reduced by building a fixed roof over
the tank, which converts it to a contact internal floating roof tank.  A
contact internal floating roof provides a greater emission reduction than a
non-contact internal floating roof.  Installation of a secondary seal on a
floating roof with only a primary seal will also reduce the emissions.
3.2.1  Internal Floating Roofs in Fixed Roof Tanks
     Fixed roof tank emissions can be reduced by installing internal floating
roofs and seals in the tanks to minimize evaporation of the product being
stored.  Floating roof and seal combinations which have been tested for use
in fixed roof tanks, are (1) a non-contact internal floating roof with
shingled, vapor-mounted primary and secondary seals; (2) a contact internal
floating roof with a liquid-mounted primary seal; (3) a contact internal
floating roof with a liquid-mounted primary seal and a continuous secondary
seal.  Based on these test results, a non-contact internal floating roof
with shingled, vapor-mounted primary and secondary seals is not as effective
in reducing emissions as a contact internal floating roof with a liquid-
mounted primary seal.   Consequently, a larger emissions reduction can be
achieved by fitting a fixed roof tank with a contact internal floating roof
and a liquid-mounted primary seal rather than a non-contact internal floating
roof and shingled, vapor-mounted primary and secondary seals.  Installation
of a continuous secondary seal on a contact internal floating roof showed
the best emissions reduction.
     Several other roof and seal combinations, which have not been tested,
are also available for controlling the emissions from fixed roof tanks.  Some
of these include: (1) a non-contact internal floating roof with a vapor-mounted
primary seal; (2) a contact internal floating roof with a vapor-mounted
primary seal; and (3) a contact internal floating roof with vapor-mounted
primary seal and a continuous secondary seal.  Based on engineering judgment,
a non-contact roof with a vapor-mounted primary seal would be less effective
at reducing emissions than the non-contact roof tested, which was equipped
with both primary and secondary seals.  In addition, information presented in

                                     3-2

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                                                2
American Petroleum Institute (API) Bulletin 2517  regarding the effectiveness
of liquid-mounted and vapor-mounted primary seals on external  floating roofs
indicates that the contact internal floating with a liquid-mounted primary
seal which was tested would be more effective at reducing emissions than a
contact internal floating roof with a vapor-mounted primary seal.  As was
also indicated in the testing of a contact internal floating roof, a secondary
seal over a vapor-mounted primary seal may be expected to result in even
larger emissions reduction.
3.2.2  Rim-Mounted Secondary Seals on External Floating Roofs
     A rim-mounted secondary seal on an external floating roof is a continuous
seal which extends from the floating roof to the tank wall, covering the
entire primary seal.  Installed over a mechanical shoe seal, this secondary
seal has been demonstrated to effectively control VOC emissions which escape
from the small vapor space between the shoe and the wall, and  through any
openings or tears in the seal envelope (see Figure 2-4a).  Rim-mounted
secondary seals should also be effective in controlling emissions from the
liquid- and vapor-mounted primary seals shown in Figures 2-4b, 2-4c, and
2-4d.  However, their effectiveness has not been tested on external floating
roof tanks.
     Another type of secondary seal, which has not been tested, is a
shoe-mounted secondary seal.  A shoe-mounted seal extends from the top of the
shoe to the tank wall (see Figure 3-1).  These seals do not provide protection
against VOC leakage through the envelope.  Holes, gaps, tears, or other
defects in the envelope can allow direct interchange between the saturated
vapor under the envelope and the atmosphere; the wind can enter this space
through envelope defects, flow around the circumference, and exit with
saturated or near saturated VOC vapors.  For these reasons a shoe mounted
secondary seal is not as effective as a rim-mounted secondary  seal.
3.2.3  Fixed Roofs on External Floating Roof Tanks
     Installing a fixed roof on an existing external floating  roof tank would
reduce emissions by reducing the effect of wind sweeping vapors out of the
vapor space and into the atmosphere.
                                    3-3

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                    Secondary Seal
                     (Wiper Type)
                            Floating Roof

                           Vapor Space
Figure 3-1.   Metallic shoe seal  with shoe-mounted
                      secondary  seal.
                       3-4

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3.2.4  Contact Internal Floating Roofs in Non-Contact Internal  Floating
       Roof Tanks
     The EPA tests on floating roofs have demonstrated that non-contact
internal floating roofs with shingled, vapor-mounted primary and secondary
seals may not be as effective in reducing emissions as contact internal
floating roofs with liquid-mounted primary seals.   Based on these studies,
one emissions control technique for internal floating roof tanks is to use
contact internal floating roofs with liquid-mounted primary seals instead of
non-contact internal floating roofs with shingled, vapor-mounted primary and
secondary seals.  The use of a continuous secondary seal on the contact
internal floating roof has been demonstrated to result in a"larger emissions
reduction.
     Two roof and seal combinations, which have not been tested, are (1) a
contact internal floating roof with a vapor-mounted primary seal; and (2) a
contact internal floating roof with vapor-mounted primary and secondary
seals.  Engineering judgement indicates that the use of either of these roof
and seal combinations would result in lower emissions than those associated
with the use of a non-contact roof with a vapor-mounted primary seal or
vapor-mounted primary and secondary seals.
3.2.5  Liquid-Mounted Primary Seals on Contact Internal Floating Roofs
                                                       p
     Based on information reported in API Bulletin 2517  and engineering
judgement, vapor-mounted primary seals are not as effective in reducing
emissions as liquid-mounted primary seals.  As a result, one technique to
reduce the emissions from tanks having contact internal floating roofs is to
use liquid-mounted rather than vapor-mounted primary seals.
3.2.6  Rim-Mounted Secondary Seals on Contact Internal Floating Roofs
     Contact internal floating roofs, like other types of floating roofs, can
have not only a primary seal to cover the annular vapor space, but also a
rim-mounted secondary seal (Figure 3-2).  This secondary seal, which is
typically a wiper seal or a resilient foam-filled seal, minimizes the effects
of the air currents inside the tank sweeping vapors out of the annular vapor
space.  This type of seal is continuous and extends from the floating roof to
the tank wall, covering the entire primary seal.

                                    3-5

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               Secondary Seal
                           Primary Seal
                            Immersed In  Liquid
                                   Contact  Type
                                  Internal  Floating Roof
Figure 3-2.   Rim mounting of a  secondary seal  on  an
                   internal  floating roof.
                        3-6

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3,3  RETROFIT CONSIDERATIONS
     This section will discuss possible considerations that fixed roof tank
owners and operators may have in retrofitting their tanks with internal
floating roofs.  In addition, considerations associated with the retrofitting
of rim-mounted secondary seals on external floating roofs, and the conversion
of external floating roof tanks to internal floating roof tanks will be
discussed.  Prior to retrofit construction, tank owners will have to schedule
time for the tank to be out of service.  The tank and roof must then be
cleaned and degassed before workers may enter the tank to begin retrofitting.
3.3.1  Fixed Roof Tanks With Internal Floating Roofs
     Several modifications may be necessary on a fixed roof tank before it
can be equipped with an internal floating roof.  Tank shell deformations and
obstructions may require correction, and special structural modifications
such as bracing, reinforcing, and plumbing vertical columns may be necessary.
Anti-rotational guides should be installed to keep cover openings in alignment
with roof openings.  Special vents must be installed on the fixed roof or on
the walls at the top. of the shell to minimize the possibility of VOL vapors
approaching the explosive range in the vapor space.
3.3.2  Rim-Mounted Secondary Seals on External Floating Roofs
     Retrofitting problems may be encountered when a secondary seal is installed
above a primary seal.  Some primary seals are designed to accommodate a large
amount of gap between the primary seal and the tank wall.  Some secondary
seals may not be able to span as large a gap and, consequently, excessive
gaps may result between the secondary seal and the tank shell.
3.3.3  Fixed Roofs on External Floating Roof Tanks
     In order to install a fixed roof on an existing external floating roof
tank, several tank modifications may be required.  For example, special
structural modifications such as bracing and reinforcing may be necessary to
permit the external floating roof tank to accommodate the added weight of a
fixed roof.
                                    3-7

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3.3.4  Secondary Seals on Non-Contact Internal  Floating Roofs
     Retrofitting problems may be encountered when installing a secondary
seal on a non-contact internal floating roof.  Unlike the contact internal
floating roof, the non-contact internal floating roof does not have an outer
rim on which to attach a secondary seal.  Extensive modifications to the
roof may be required in order to install a secondary seal on a non-contact
internal floating roof.
                                    3-8

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3.4  REFERENCES FOR CHAPTER 3
1.   U.S. Environmental Protection Agency.  Measurement of Benzene Emissions
     from a Floating Roof Test Tank.  Publication No. EPA-450/3-79-020,
     Research Triangle Park, North Carolina.  June 1979.

2.   American Petroleum Institute.  Evaporation Loss from External Floating
     Roof Tanks.  API Bulletin 2517.  February 1980.
                                    3-9

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                    4.0  ENVIRONMENTAL ANALYSIS OF RACT

     The environmental impacts that would result from implementing reasonably
available control technology (RACT) are examined in this chapter.  Included
in this chapter are estimates of VOC emissions from storage tanks before and
after implementation of RACT.  These emission estimates were calculated
                                                   12345
using the emission equations outlined in Chapter 2.           The percent
reduction of VOC emissions that could be achieved with RACT is also presented.
The beneficial and adverse environmental impacts of RACT on air pollution,
water pollution, solid waste generation, and energy consumption are also
discussed.
4.1  AIR POLLUTION
     Reasonably available control technology will affect fixed roof tanks
and external floating roof tanks.  Fixed roof tanks that are equipped with
internal floating roofs are not affected.  For a fixed roof tank RACT is a
contact internal floating roof with secondary seals.  For an external
floating roof tank RACT is secondary seals and a fixed roof.  An external
floating roof tank that has secondary seals will be retrofitted with a fixed
roof.  An external floating roof with primary seals will be retrofitted with
secondary seals and a fixed roof.
     Implementation of RACT will have a significant beneficial impact on air
pollution emissions from VOL storage tanks.  The annual emissions from each
model tank outlined in Chapter 2 before and after control by RACT are
presented in Table 4-1.  Implementation of RACT will reduce VOC emissions
from the small tank, which is a fixed roof tank, 85 percent from 2.29 Mg/yr
to 0.35 Mg/yr.  Implementation of RACT will reduce emissions from the
average model fixed roof tank 92 percent from 7.22 Mg/yr to 0.58 Mg/yr.
For the average external floating roof tank with primary seals, RACT will
reduce emissions 93 percent from 23.08 Mg/yr to 1.57 Mg/yr.  There are no
adverse air pollution impacts associated with RACT.
                                     4-1

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       TABLE 4-1.  IMPACT OF RACT ON VOC EMISSIONS FROM STORAGE TANKS
Model tank
Small tank3
Average fixed roof
Average floating roofc
Emissions
before
RACT
(Mg/yr)
2.29
7.22
23.08
Emissions
after
RACT
(Mg/yr)
0.35
0.58
1.57
Emissions
reduction
(Mg/yr)
1.94
6.64
21.51
Percent
reduction
(*)
85
92
93
 The capacity of this tank is 151,416 liters (40,000 gallons);  the vapor
 pressure is 10.5 kPa (1.5 psia);  the diameter is 5 meters (17  feet);  the
 height is 7 meters (24 feet);  the annual  turnover rate is 50.
     capacity of this tank is 480,747 liters (127,000 gallons);  the vapor
 pressure is 10.5 kPa (1.5 psia);  the diameter is 8 meters (26 feet);  the
 height is 10 meters (32 feet);  the annual  turnover rate is 50.
CVOC emissions for a floating roof tank are based on an external  floating
 roof with primary seals.   The capacity of this tank is 3,482,579 liters
 (920,000 gallons); the vapor pressure is 15.2 kPa (2.2 psia); the diameter.
 is 19 meters (62 feet); the height is 12 meters (40 feet); the annual
 turnover rate is 10.
                                      4-2

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4.2  WATER POLLUTION
     Implementation of RACT would result in no adverse water pollution
impacts.  Wastewater is not generated during the storage of VOL.  Retrofitting
a tank with RACT will not generate wastewater.
4.3  SOLID WASTE DISPOSAL
     Implementation of RACT would result in an insignificant amount of solid
waste.  Normal operation of a floating roof results in wear on the roof and
especially on the seals.  Solid waste in the form of worn out roofs and
seals is generated when the roof or seals of a tank are replaced.
4.4  ENERGY
     The implementation of RACT calls for an emission control technique that
requires no additional energy consumption.  A beneficial impact would be
experienced by saving VOL that has already been manufactured and transported
to fixed roof and external floating roof tanks.
                                     4-3

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4.5  REFERENCES FOR CHAPTER 4
1.   U.S. Environmental  Protection Agency.   Compilation of Air Pollution
     Emission Factors.  Research Triangle Park, North Carolina.  Report
     No.  AP-42.   August 1977.

2.   Engineering Science, Inc.   Hydrocarbon Emissions from Fixed-Roof
     Petroleum Tanks.  Western  Oil and Gas Association.  Los Angeles,
     California.  July 1977.

3.   U.S. Environmental  Protection Agency.   Emission Test Report—Breathing
     Loss Emissions from Fixed-Roof Petrochemical Storage Tanks.  Research
     Triangle Park, North Carolina.  EMB Report 78-OCM-5,  February 1979.

4.   German Society for Petroleum Science and Carbon Chemistry (DGMK) and
     the Federal Ministry of the Interior (BMI).  Measurement and Deter-
     mination of Hydrocarbon Emissions in the Course of Storage and Transfer
     in Above-Ground Fixed Cover Tanks With and Without Floating Covers.
     BMI-DGMK Joint Projects 4590-10 and 4590-11.  (Translated for EPA by
     Literature Research Company, Annandale, Virginia.)

5.   U.S. Environmental  Protection Agency.   Measurements of Benzene Emissions
     from a Floating-Roof Test  Tank.  Research Triangle Park, North Carolina.
     Report No.  EPA-450/3-79-020.  June 1979.
                                    4-4

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                    5.0  CONTROL COST ANALYSIS OF RACT

     The cost of implementing RACT for volatile organic compound (VOC)
emissions from volatile organic liquid (VOL) storage tanks is presented in
this chapter.  The bases for the installed capital cost estimates presented
in this chapter will be identified and discussed.  This chapter will  discuss
the bases for the annualized costs, including product recovery credits.  The
estimated emission control costs associated with control by RACT will be
presented for each of the model tanks discussed in Chapter 2.  This Chapter
will also present the cost effectiveness of RACT for each of the model
tanks.
5.1  BASES FOR INSTALLED CAPITAL COSTS
     Installed capital costs represent the total investment required for
installing retrofit VOC control equipment on existing VOL storage tanks.
This includes the cost of the equipment, materials, labor for installation,
and other associated costs.  The capital costs presented in this chapter
                                                    123
were obtained through vendor quotes and EPA reports. ' '   The capital  costs
of implementing RACT affect two types of tanks: fixed roof tanks and external
floating roof tanks.  This section describes the installed capital costs
associated with each type of tank.  These costs have been updated to
                            4
second-quarter 1980 dollars.
5.1.1  Cost of Installing a Contact Internal Floating Roof
     The installed capital costs of retrofitting a fixed roof tank with a
                                                      5
contact internal floating roof are shown in Table 5-1.   These costs represent
the total cost of installing a contact internal floating roof including the
purchased equipment, equipment installation, and design engineering.  These
costs do not include cleaning, degassing, and certification of the tank or
the cost-of taking the tank out of service.  The installed capital cost of
the contact internal floating roof is a function of the diameter of the tank
as shown in Figure 5-1.

                                    5-1

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       TABLE 5-1.  COST OF INSTALLING A CONTACT INTERNAL FLOATING ROOF
                            IN AN EXISTING FIXED ROOF TANKa
Tank u
dimensions
(meters)
8 x 12
13 x 15
14 x 17
21 x 12
27 x 15
Installed capital
cost of a
contact internal
floating roofc
$10,700
$17,600
$20,200
$37,300
$56,300
aCosts are in second-quarter 1980 dollars and do not include cleaning,
 degassing, and certification.
 Diameter x height.
cBased on cost of an aluminum contact internal floating roof (Ref.  5).

         TABLE 5-2.  COST OF INSTALLING A FIXED ROOF ON AN EXISTING
                             EXTERNAL FLOATING ROOF TANK9
Tank .
dimensions
(meters)
8 x 12
13 x 15
14 x 17
21 x 12
27 x 15
Installed capital
cost of
fixed roof
$ 8,700
$15,900
$18,200
$37,500
$57,600
aCosts are in second-quarter 1980 dollars and do not include cleaning.
 degassing, and certification.
 Diameter x height.
cBased on cost of an aluminum dome (Ref.  6),
                                    5-2

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en


CJ
                       o


                     u-§
                     o  »
                       o
                       i o
                     Q O

                     UJ __l
                      t/1
                            60
                            50
                            40
30
                            20
                            10
                                                10       15       20



                                                     TANK  DIAMETER (m)
                                               25
30
35
                  Figure 5-1.  Cost of installing  a  contact  internal  floating roof in an existing

                                        fixed  roof tank  (second-quarter 1980 dollars).5

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5.1.2  Cost of Installing a Fixed Roof
     The installed capital costs of retrofitting an external  floating roof
tank with a fixed roof are shown in Table 5-2.    These costs  represent the
total cost of installing the fixed roof including the purchased equipment,
equipment installation, and design engineering.   These costs  do not include
cleaning, degassing, and certification of the tank or the cost for taking
the tank out of service.  The installed capital  cost of the fixed roof is a
function of tank diameter as shown in Figure 5-2.
5.1.3  Cost of Installing Secondary Seals
     The installed capital costs of retrofitting an internal  or external
floating roof with secondary seals are shown in  Table 5-3 .  These costs
represent the total cost of installing the secondary seal including
purchased equipment, equipment installation, and design engineering.  These
costs do not include cleaning, degassing, and certification of the tank or
the cost for taking the tank out of service.  The installed capital cost  of
the secondary seal is a function of tank diameter as shown in Figure 5-3.
5.1.4  Cost of Cleaning, Degassing, and Certification of a Tank
     The capital costs of cleaning, degassing,  and certification of a
                                    Q
storage tank are shown in Table 5-4.   The storage tank must be emptied,
cleaned, and degassed before workers can begin  to retrofit the tank with
RACT.  This cost does not include the cost of taking the tank out of service.
The cost of cleaning, degassing, and certifying  the tank is a function of
tank capacity as shown in Figure 5-4.
5.2  BASES FOR ANNUALIZED COSTS
     The annualized cost of an air pollution control system is the total
annual expenditure required to build, operate,  and maintain the system
minus the value of the recovered product.  The annualized cost consists
of the annual capital charges, the direct operating costs, and the recovery
credits.  The bases used to estimate annualized  costs in this section are
presented in Table 5-5.
                                    5-4

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                       60 I
                  O

                  CD

                  O
                        50
                  o

                  s

                  Q
                  UJ
                  X
     40
                        30
CJl
I

en
O
o
                  U    20
                  D-


                  O


                  Q
                        10
                                           10       15       20


                                                 TANK DIAMETER (m)
                                                    25
30
35
                   .Figure  5-2.
              Cost of installing a fixed roof on an  existing external

                floating roof tank (second-quarter 1980 dollars)I6

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    TABLE 5-3.   COST OF INSTALLING A SECONDARY  SEAL  ON  AN  EXISTING INTERNAL
                               OR EXTERNAL  FLOATING  ROOF3
Tank L
dimensions
(meters)
8 x 12
13 x 15
14 x 17
21 x 12
27 x 15
Installed
capital cost
of secondary
seal 7
$ 4,380
$ 6,350
$ 7,360
$ 9,990
$12,100
aCosts are in second quarter 1980 dollars  and  do  not  include  cleaning,
 degassing and certification.
 Diameter x height.
          TABLE  5-4.   COST OF CLEANING, DEGASSING, AND CERTIFICATION
                                  OF A STORAGE TANK3
Tank ,
dimensions
(meters)
8 x 12
13 x 15
14 x 17
21 x 12
27 x 15
Tank
capacity
(liters)
602,000
2,000,000
2,610,000
4,160,000
8,590,000
Cost of cleaning,
degassing, and
certification®
$1,495
$2,300
$2,875
$3,910
$7,070
 aCosts  are  in  second-quarter 1980 dollars,

  Diameter x height.
                                     5-6

-------
                           o
                           o
                           o
                           LU

                           CO
                           
-------
               o
               o
               o
on

oo
8
                               I
                         I
  I
              1000     2000
                                               3000     4000     5000     6000


                                                CAPACITY OF TANK (TO3 LITERS)
I
7000     8000     9000
                            Figure  5->4.   Cost  of Cleaning,  Degassing,' and Certification

                                                     (second-quarter 1980 dollars)'.8

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                TABLE 5-5.   BASES FOR ANNUALIZED COST ESTIMATES
              Item
                                                   Cost basis
 1.
 2.
    Annual capital charges
    a.  Capital recovery
        Contact internal floating
          roof
        Fixed roof
        Secondary seals
        Cleaning, degassing, and
          certification

    b.  Annual charges for taxes,
          insurance, and administration
    Direct operating costs
    a.  Annual maintenance charges
    b.  Annual inspection charges

3.  Annual recovery credit
0.1175* x installed capital cost
0.1175.  x installed capital cost
0.1628  x installed capital cost

0.1628  x installed capital cost

0.04 x total installed capital cost0


0.05 x total installed capital cost0
0.01 x total installed capital cost0

$330/Megagram
 Capital  recovery factor based on 20 year life and 10 percent interest rate.

DCapital  recovery factor based on 10 year life and 10 percent interest rate.
fS
"Reference 9.
4
 Reference 10.
                                        5-9

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5.2.1  Annual  Capital  Charges
     Annual capital charges consist of capital  recovery and annual-charges
for taxes, insurance,  and administration.
     The capital  recovery is obtained from annualizing the installed capital
cost for control  equipment.  The installed capital  cost is annualized by
using a capital  recovery factor (CRF).  The CRF is  a function of the .
interest rate and useful equipment lifetime.  The capital  recovery for each
component is determined by multiplying the CRF for  that component by the
installed capital cost for that component.  The total  capital recovery is
determined by summing  the capital  recoveries of all  the components of the
installed capital costs.  The equation for the capital recovery factor is:
                                1(1 + i)"
                      CRF  =
                              (1 + i)" -1
where i = interest rate, expressed as a decimal
      n = economic life of the equipment in years.
The capital recovery factors used to annualize the intalled capital  costs of
the control equipment are summarized in Table 5-5.   The interest rate is
assumed to be ten percent.    The useful lifetime of the installed contact
                                                                12
internal floating roof and the installed fixed roof is 20 years.    The
useful lifetime of the secondary seals is 10 years.    The cost of cleaning,
degassing and certification of the tank is annualized over 10 years because
that is the minimum lifetime of the secondary seals.  The installed equip-
ment has no salvage value.
     The annual costs for taxes, insurance, and administration are assumed
                                              14
to be 4 percent of the installed capital cost.
5.2.2  Direct Operating Costs
     The annual direct operating costs for the control equipment include the
cost of maintaining the equipment and periodic inspection of the equipment.
                                                                   15
The maintenance cost is five percent of the installed capital cost.     The
inspection cost is one percent of the installed capital cost.
                                     5-10

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5.2.3  Recovery Credits
     Implementation of RACT decreases the amount of VOL lost through
evaporation.  The value of the VOL saved is a product recovery credit.   This
product recovery credit is used in determining the net annualized cost  of
the control equipment.  The credit is based on a VOL value of $330/Mg.
The recovery credits for each model tank are presented in Table 5-6.
5.3  EMISSION CONTROL COSTS
     This section will present and discuss the estimated emission control
costs of RACT for each of the model storage tanks developed in Chapter  2.
The installed capital costs for each model storage tank are summarized  in
Table 5-7.  The annualized costs for each model  tank are summarized in
Table 5-8.
5.3.1  Small Model Storage Tank
     The installed capital cost of RACT for the small model storage tank is
based on a fixed roof tank.  This tank has a capacity of 151,416 liters
(40,000 gallons).  The diameter of the tank is 5 meters (17 feet) and the
height is 7 meters (24 feet).  Most tanks of this size are fixed roof tanks.
As can be seen in Table 5-7 the installed capital cost of $12,540 consists
of the installed costs for the contact internal  floating roof, the secondary
seal, and the cost of cleaning, degassing, and certifying the tank.  The net
annualized cost, including the product recovery credit, is $2,288 as  shown
in Table 5-8.
5.3.2  Average Fixed Roof Model Storage Tank
     The installed capital cost of RACT for the average fixed roof model
storage tank is $16,670.  The capacity of this tank is 480,747 liters
(127,000 gallons).  The diameter of the tank is 8 meters (26 feet) and  the
height is 10 meters (32 feet).  The installed capital cost consists of  the
installed costs for the contact internal floating roof, the secondary seal,
and the cost of cleaning, degassing, and certifying the tank.   The net
annualized cost, including the product recovery credit, is $1703 as shown in
Table 5-8.
                                     5-11

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                            TABLE 5-6.   RECOVERY CREDITS

Model
storage
tanks
Emissions3
before
RACT
(Mg/yr)
Emissions
after
RACT
(Mg/yr)

Emission
reduction
(Mg/yr)

Emission
reduction
(*)
Recovered
product
value,
($/yr)
 Small tank

 Average      .
   fixed roof

 Average
   floating roof
 2.29


 7.22


23.08
0.35


0.58


1.57
 1.94


 6.64


21.51
85


92


93
  640


2,191


7,098
 Emissions were calculated using the emissions equations outlined in Chapter 2
 (Ref. 18, 19, 20, 21, 22).
 Based on an average price of $330/Mg (Ref.  17).
CVOC emissions for a small tank are based on a fixed roof tank.   The capacity
 of this tank is 151,416 liters (40,000 gallons);  the vapor pressure is 10.5 kPa
 (1.5 psia); the diameter is 5 meters (17 feet);  the height is 7 meters (24 feet);
 the annual turnover rate is 50.

 The capacity of this tank is 480,747 liters (127,000 gallons);  the vapor pressure
 is 10.5 kPa (1.5 psia); the diameter is 8 meters  (26 feet); the height is 10 meters
 (32 feet); the annual turnover rate is 50.

eVOC emissions for a floating roof tank are based  on an external floating roof
 with primary seals.  The capacity of this tank is 3,482,579 liters (920,000 gallons);
 the vapor pressure is 15.2 kPa (2.2 psia);  the diameter is 19 meters (62 feet);
 the height is 12 meters (40 feet); the annual turnover rate is  10.
                                        5-12

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                     TABLE 5-7.   INSTALLED CAPITAL COSTS'
Cost item
Installed floating roof ($)
Installed fixed roof ($)
Installed secondary seals ($)
Cleaning, degassing, and
certification ($)
Total ($)

Small
tankb
8,120

3,310
1,110
12,540
Model storage tank
Average
f i xed
roofc
10,800

4,530
1,340
16,670

Average
floating
roof"

30,660
9,020
3,450
43,130
 Costs  are in second-quarter 1980 dollars.
3Instaned capital  costs  for a  small  tank  are  based  on  retrofitting  a  fixed
 roof tank with a capacity of 151,416 liters  (40,000 gallons)  and  a  diameter
 of 5 meters  (17 feet).
"Installed capital  costs  are based on retrofitting a tank with a capacity  of
 480,747  liters (127,000  gallons) and a  diameter of  8 meters  (26 feet).
 Installed capital  costs  for a  floating  roof tank are based on retrofitting
 a  tank with  a capacity of 3,482,579  liters  (920,000 gallons)  and  a  diameter
 of 19  meters (62 feet).
                                    5-13

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         TABLE 5-8.  ANNUALIZED CONTROL COSTS FOR MODEL STORAGE TANKS'
Model storage tank
Small
Cost parameter tank"
Average
f i xed
roofc
Average
floating
roofd
 Installed capital costs

 Annualized costs
   Annual capital charges
12,540
16,670
43,130
Capital recovery
Taxes, insurance and
administration
Subtotal
Direct operating costs
Maintenance
Inspection
Subtotal
Total annual i zed cost
Annual recovery credit
Net annual i zed cost
1,674
502
2,176

627
125
752
2,928
(640)
2,288
2,226
667
2,893

834
167
1,001
3,894
(2,191)
1,703
5,633
1,725
7,358

2,156
431
2,587
9,945
(7,098)
2,847
 Costs are in second-quarter 1980 dollars.

 Annualized control costs for a small tank are based on retrofitting a fixed
 roof tank with a capacity of 151,416 liters (40,000 gallons) and a diameter
 of 5 meters (17 feet).

GAnnualized control costs are based on retrofitting a tank with a capacity
 of 480,747 liters (127,000 gallons) and a diameter of 8 meters (26 feet).

 Annualized control costs for a floating roof tank are based on retrofitting
 a tank with a capacity of 3,482,579 liters (920,000 gallons) and a diameter
 of 19 meters (62 feet).

eCosts in parentheses are cost credits.
                                     5-14

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5.3.3  Average Floating Roof Model  Storage Tank
     The installed capital  cost of RACT for the average floating  roof  model
storage tank is $43,130.  The capacity of this tank is  3,482,579  liters
(920,000 gallons).  The diameter of the tank is 19 meters (62 feet)  and  the
height is 12 meters (40 feet).   The installed capital  cost consists  of the
installed costs for the fixed roof, the secondary seal, and the cost of
cleaning, degassing, and certifying the tank.  The net  annualized cost,
including the product recovery credit, is $2847 as shown in Table 5-8.
5.4  COST EFFECTIVENESS
     Cost effectiveness is the net annual ized cost per  megagram of VOC
controlled annually.  The cost effectiveness of RACT for each model  storage
tank is the net annualized cost for implementing RACT divided by  the
emission reduction gained under RACT.   The cost effectiveness of  RACT  is
summarized in Table 5-9.
     The implementation of RACT on the small model storage tank which  is a
fixed roof tank results in a net annual cost of $2,288  and an emission
reduction of 1.94 Mg/yr.  This results in a net cost effectiveness of
$l,179/Mg.
     The implementation of RACT in the case of the average fixed  roof  model
storage tank results in a net annual cost of $1,703 and an emission  reduction
of 6.64 Mg/yr.  This results in a net cost effectiveness of $256/Mg.
     The implementation of RACT in the case of the average floating  roof
model storage tank results in a net annual cost of $2847 and an emission
reduction of 21.51 Mg/yr.  This results in a net cost effectiveness  of
$132/Mg.
     A comparison of the cost effectiveness of RACT for each model storage
tank reveals that cost effectiveness improves as the model tank size,
turnover rate, and the vapor pressure of the liquid being stored  increases.
As the tank size, turnover rate, and vapor pressure of  the liquid being
stored increase the emissions and the emission reduction increase
                                   5-15

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        TABLE  5-9.   COST EFFECTIVENESS  FOR MODEL  STORAGE TANKS  UNDER RACT
                                Small
                                tankb
                                           Model  storage tank
                 Average
                  fixed
                  roofc
                   Average
                  floating
                    roofd
 Total  annualized
   cost ($)

 Total  annual  recovery
   credit ($)a

 Net annualized  cost ($)

 Total  VOL reduction
2,928


 (640)

2,288
 3,894


(2,191)

 1,703
 9,945


(7,098)

 2,847
(Mg/yr)
Cost effectiveness
(annual $/Mg VOL)
1.94

1,179
6.64

256
21.51

132
 Values  in  parentheses  indicate  cost  credits.

n"he cost effectiveness for a small  tank is based on a fixed roof tank with a
 capacity of 151,416 liters (40,000  gallons) and a diameter of 5 meters (17 feet),

cThe cost effectiveness of this  tank  is based on a capacity of 480,747 liters
 (127,000 gallons) and  a diameter of  8 meters (26 feet).
 The cost effectiveness of this  tank  is based on a capacity of 3,482,579 liters
 (920,000 gallons) and  a diameter of  19 meters (62 feet).
                                       5-16

-------
which affects the cost effectiveness.   As the tank diameter increases the
annual costs for the control equipment increases.  However, the increase in
annual emission reduction is greater relative to the increase in annual
cost so that there is an overall improvement in cost effectiveness.   The
cost effectiveness is also sensitive to the value of the product being
stored.  The cost effectiveness of the control equipment improves as the
value of the product being stored increases.
                                   5-17

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5.5  REFERENCES FOR CHAPTER 5


 1.  Letter and attachments from Roney,  E.W.,  PETREX,  Inc.,  (Warren,  Pennsylvania),
     to D.C. Ailor, TRW, Inc., (Research Triangle Park,  North Carolina).
     February 28, 1979.   Features of PETREX Internal  Floating Roofs.

 2.  Telecon.  G.N. Houser, TRW, Inc., (Research Triangle Park,  North Carolina),
     to Ken Wilson, Pittsburgh Des-Moines Steel  Company, (Des-Moines, Iowa).
     January 25, 1979.   Cost of installing an  aluminum dome  roof over an
     external floating  roof.

 3.  U.S. Environmental  Protection Agency.  Control  of Volatile  Organic
     Emissions from Petroleum Liquid Storage in  External Floating Roof Tanks.
     Report No. EPA-560/2-78-047.  Research Triangle Park, North Carolina.
     December 1978.

 4.  Chemical Engineering/Economic Indicators.   87J21):7. October 20, 1980.
     87(8):7.  April 21, 1980.  85(0):7

 5.  See reference 1.

 6.  See reference 2.

 7.  See reference 3.

 8.  See reference 3.

 9.  U.S. Environmental  Protection Agency.  Draft Report - Volatile Organic
     Compound Emissions  From Volatile Organic  Liquid Storage Vessels  -
     Background Information for Proposed Standards.   EPA Contract No. 68-02-2063.
     September 1980.

10.  Telecon.  R.E. Sommer, GCA/Technology Division,  (Chapel  Hill, North
     Carolina), to W.T.  Moody, TRW, Inc., (Research  Triangle Park, North
     Carolina).  November 6, 1980.  Value of VOL to  be used  in calculation  of
     recovery credits.

11.  See reference 9.

12.  See reference 9.

13.  See reference 9.

14.  See reference 9.

15.  See reference 9.

16.  See reference 9.
                                     5-18

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17.  See reference 10.

18.  U.S. Environmental  Protection Agency.   Compilation of Air Pollution
     Emission Factors.   Research Triangle Park,  North Carolina.   Report
     No. AP-42.   August 1977.

19.  Engineering Science, Inc.   Hydrocarbon Emissions from Fixed-Roof
     Petroleum Tanks.   Western  Oil and Gas  Association.  Los  Angeles,
     California.  July 1977.

20.  U.S. Environmental  Protection Agency.   Emission Test Report—Breathing
     Loss Emissions from Fixed-Roof Petrochemical  Storage Tanks.   Research
     Triangle Park, North Carolina.   EMB Report  78-OCM-5, February 1979.

21.  German Society for Petroleum Science and Carbon Chemistry (DGMK)  and the
     Federal Ministry of the  Interior (BMI).  Measurement and Determination
     of Hydrocarbon Emissions  in the Course of Storage and Transfer in
     Above-Ground Fixed Cover Tanks With and Without Floating Covers.
     BMI-DGMK Joint Projects  4590-10 and 4590-11.   (Translated for EPA by
     Literature Research Company, Anhadale, Virginia.)

22.  U.S. Environmental  Protection Agency.   Measurements of Benzene Emissions
     from a Floating-Roof Test  Tank.  Research Triangle Park, North Carolina.
     Report No.  EPA-450/3-79-020.  June 1979.
                                     5-19

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                     6.0  MODEL REGULATION AND DISCUSSION

6.1  MODEL REGULATION
     This chapter includes a model  regulation based on the "presumptive norm"
which is considered broadly representative of RACT for storage of volatile
organic liquids (VOL).  The model  regulation is included solely as guidance
to assist state and local agencies  in drafting their own specific RACT.
Consequently, the model regulation  is illustrative in nature and is not to be
construed as rulemaking by EPA.
§XX.010  Applicability
     (A)  This regulation applies  to all  volatile organic liquid storage
          tanks having capacities  greater than 151,416 liters (40,000 gallons)
          and storing volatile organic liquids with an actual vapor pressure
          greater than 10.5 kilo Pascals (1.5 psia).
     (B)  This regulation exempts  storage tanks which are used to store
          petroleum liquids, or which are equipped with an internal floating
          roof.
     (C)  This regulation is applicable to all volatile organic liquid
          storage tanks in the following areas:
§XX.020  Definitions
          Except as otherwise required by the context, terms used in this
          Regulation are defined in the General Statutes, the General Provisions,
          or in this section as follows:
               "Actual vapor pressure" means the pressure exerted by a
          volatile organic liquid  when it is in equilibrium with its own
          vapor at the temperature of the volatile organic liquid in the
          storage tank.

                                    6-1

-------
     "Alternative control technology" means any device or procedure
which reduces volatile organic compound emissions from storage
tanks other than floating roof control equipment.
     "External floating roof" means a storage tank cover in an open
top tank consisting of a double deck or pontoon single deck which
rests upon and is supported by the liquid being contained and is
equipped with a closure seal or seals to close the space between
the roof edge and tank wall.
     "Internal floating roof" means a storage tank cover that
rests partially or completely upon the liquid surface inside a
storage tank with a permanently affixed roof.
     "Liquid-mounted seal" means a foam-filled or liquid-filled
primary seal mounted in contact with the liquid between the tank
wall and the floating roof continuously around the circumference
of the tank.
     "Metallic shoe seal" includes, but is not limited to, a metal
sheet held vertically against the wall of the storage tank by
springs or weighted levers which is connected by braces to the
floating roof.  A flexible, coated fabric (envelope) spans the
annular space between the metal sheet and the floating roof.
     "Petroleum liquids" mean crude oil, condensate, and any
finished or intermediate products manufactured or extracted in a
petroleum refinery.
     "Primary seal" means the lower seal forming a closure between
the wall of the storage tank and the internal floating roof.
     "Secondary seal" means the upper seal forming a closure that
completely covers the space between the wall of the storage tank
and the internal floating roof.
     "Storage tank" means each tank used for the storage of volatile
organic liquid, but does not include pressure vessels designed to
operate without emission to the atmosphere except under emergency
conditions.
                          6-2

-------
               "Volatile organic compound"  means any organic  compound which
          participates in atmospheric photochemical  reactions or  is measured
          by the applicable test method or  equivalent State methods.
               "Volatile organic liquid" means  any organic liquid that
          produces volatile organic compounds as vapors.
§XX.030  Standards
     (A)  The owner or operator of each storage tank to which this regulation
          applies shall  equip each storage  tank with the  following:
          (1)  A fixed roof in combination  with an internal floating roof
               with a primary seal  and a continuous  secondary seal, meeting
               the following specifications:
               (a)  The internal floating roof  shall be of the type that
                    rests completely on the surface of the volatile organic
                    liquid inside the storage tank at all times except
                    during initial  filling  and  during those intervals when
                    the storage tank is completely emptied and subsequently
                    refi11ed.
               (b)  The primary seal shall  be a liquid-mounted primary  seal
                    or a metallic shoe primary  seal  except where  the floating
                    roof is already equipped with a primary seal. When a
                    primary seal is replaced the primary  seal shall be
                    replaced with a liquid-mounted primary seal or metallic
                    shoe primary seal.
               (c)  Each opening in the internal floating roof, except  for
                    automatic bleeder vents and leg sleeves,  shall be equipped
                    with a cover, seal, or  lid  which is in a  closed position
                    at all times (i.e., no  visible gap),  except when the
                    device is in actual use.  Automatic bleeder vents are to
                    be closed at all times  when the roof  is floating, except
                    when the roof is being  floated off or is  being landed on
                    the roof leg supports.
                                      6-3

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          (2)   An  alternative  control  technology which  achieves an overall
               emission reduction  efficiency  of at  least  90  percent by
               weight.   The overall  emission  reduction  efficiency will be
               determined by comparing volatile organic compound emissions
               to  the atmosphere resulting  from use of  the alternative
               control  technology  with volatile organic compound emissions
               to  the atmosphere resulting  from storage of the volatile
               organic  liquid(s) in  question  in a fixed roof storage  tank
               fitted with a conservation vent.  The owner or operator shall
               provide  any calculations, data, or other evidence which is
               necessary for determination  of overall emission reduction
               efficiency.
     (B)   The  owner or  operator shall  maintain each storage  tank so that the
          following conditions are met:
          (1)   No  visible holes, tears, or  other openings in the secondary
               seal or  seal  fabric;
          (2)   No  volatile organic liquid accumulated on  or  defects in the
               internal floating roof; and
          (3)   No  visible gaps between the  secondary seal and the wall of
               the storage tank.
§XX.040  Inspection
     (A)   After installing the control equipment specified in §XX.030(A)
          and  prior to  filling the storage  tank, the owner or operator of
          each affected storage tank shall  visually inspect  the internal
          floating roof, primary seal, and  secondary seal.   If the owner or
          operator finds holes, tears, or other openings  in  the primary
          seal, the secondary  seal,  or the  seal fabric, or defects in the
          internal floating roof,  or both,  the owner or operator shall
          repair the items before  filling the storage tank.
     (B)   The  owner or  operator of each affected storage  tank shall visually
          inspect  the internal floating roof, the primary seal, and the
          secondary seal whenever  the storage tank  is emptied and degassed,
          but  at least  once every  5  years after installing the control

                                    6-4

-------
          equipment.   In the case of the periodic  5 year  inspection,  the
          owner or operator shall  notify the Director  in  writing  at least
          30 days prior to the refilling of each storage  tank  to  afford the
          Director the opportunity to have an observer present for inspecting
          the floating roof and seals.   If the owner or operator  finds that
          the internal floating roof has defects,  the  primary  seal or the
          secondary seal has holes, tears, or other openings in the seal or
          the seal fabric, the owner or operator shall  repair  the items so
          that they meet the requirements of §XX.030(B) before refilling the
          storage tank.
§XX.050   Recordkeeping
     (A)  The owner or operator of each storage tank storing a volatile
          organic liquid with an actual vapor pressure greater than 7.0 kilo
          Pascals (1.0 psia) shall  maintain a record of the volatile  organic
          liquid being stored, the average monthly storage temperature of
          the volatile organic liquid,  and the average monthly actual vapor
          pressure of that liquid.
          (1)  For a single-component volatile organic liquid  the actual
               vapor pressure may be obtained from standard reference texts
               or determined by ASTM (American Society of Testing and Materials)
               Method D-2879-75 (1980).
          (2)  For a volatile organic liquid mixture,  the actual  vapor
               pressure shall be taken as the lesser of the following:

               (a)  The sum of the actual vapor pressures of each component
                    weighted by its mole fraction, or
               (b)  The sum of the actual vapor pressures of each organic
                    component weighted by its mole fraction.
               (c)  Or as obtained from standard reference texts  or as
                    measured by an appropriate method  approved by the Director.
          These records shall be kept for two years.
                                    6-5

-------
§XX.060   Compliance Schedule
          The owner or operator of a volatile organic liquid storage tank
          subject to this regulation shall  meet the applicable increments  of
          progress contained in the following schedule for installation of a
          VOC control device:
     (A)  Submit final plans for the emission control equipment 	
          [four months after implementation of regulation].
     (B)  Award contracts for the emission  control  equipment 	
          [three months after submittal  of final  control  plan].
     (C)  Initiate on-site construction  or installation of the emission
          control equipment	[four months after the contract for
          the emission control  equipment is awarded].
     (D)  Complete on-site construction  or installation of the emission
          control equipment	[two months after the on-site
          construction begins].
     (E)  Achieve final compliance with  the regulation	[one month
          after installing the control  equipment].

6.2  DISCUSSION
6.2.1  Introduction
     Adequate enforcement of the regulation consists of determining that all
tanks affected by the regulation are retrofitted  to RACT and that RACT is
adequately maintained to reduce VOC emissions.  Review of the records will
ensure that tanks larger than 151,416 liters (40,000 gallons) storing a
liquid with a vapor pressure greater than 10.5 kPa  (1.5 psia) are equipped
with RACT.  Inspection of the tanks will ensure that the internal floating
roofs and seals are being inspected and  maintained  as required by the
regulation.
6.2.2  Review of the Records
     During an inspection by a State representative a review of the records
kept by the owner or operator of the storage tank should be made.  These
records should have data on the VOL stored, the average monthly storage
                                   6-6

-------
temperature of the liquid, and the average monthly actual  vapor pressure of
the liquid at that temperature for all tanks storing a VOL with an actual
vapor pressure greater than 7.0 kPa (1.0 psia).
     During a review of the records the State representative should determine
if all applicable storage tanks are in compliance.  The actual  vapor pressure
of the stored liquid should be calculated and recorded at the average monthly
temperature of the stored liquid.  The inspector may wish to review the
method the owner or operator used to determine the actual  vapor pressure.
Several methods are available for determination of the actual vapor pressure.
If the actual vapor pressure were calculated, the inspector may check that
the procedure used in the calculations is correct.  In the previous CTG
documents the term "true vapor pressure" was used instead of "actual vapor
pressure."  The term "actual vapor pressure" is used in this document to
explicitly describe the vapor pressure of the VOL stored as the vapor pressure
at the actual conditions at which the VOL is stored.
6.2.3  Inspections
     Inspections should be made as frequently as required for adequate
enforcement of the regulation.  An inspection of the facility should include
a thorough review of the records and a visual inspection of as many tanks as
the Director or inspector deems necessary.  Once every five years all
affected storage tanks are required to be emptied, cleaned, and degassed and
an inspection of the control equipment made.  The tank owner or operator
must notify the Director at least 30 days prior to refilling the tank.  This
opportunity should be taken by the Director to inspect, from within the
tank, the internal floating roof, the primary seal, and the secondary seal.
To conduct a visual inspection of the control equipment the inspector should
be equipped with an explosion proof flashlight and other appropriate safety
equipment.
6.2.4  Equivalency
     The purpose of the equivalency provision in the model regulation is to
allow a tank owner or operator to develop an equally effective alternative
volatile organic compound control technology for a specific tank or group of
tanks.  An alternative control technology is any means of VOC emission
                                      6-7

-------
reduction other than floating roof control  equipment.   If a floating roof is
to be installed as RACT then the model  regulation requires that it be a
contact internal floating roof with a liquid-mounted or metallic-shoe primary
seal and a continuous secondary seal.
     A tank owner or operator may be able to design an alternative technology
to control VOC's from storage tanks which will result in less cost to the
tank owner or operator.  For equivalency, the tank owner or operator must
demonstrate that emissions from an alternative control technology are less
than or equal to the emissions from a storage tank which meet the requirements
of the State regulation.  Equivalent vapor control technologies must be
approved by the Director.
     Typical add-on alternative controls which may be demonstrated as equivalent
to RACT are carbon adsorbers, thermal and catalytic incinerators, and
refrigerated condensers.  In a typical  add-on control  system, vapors remain
in the tank until the internal pressure reaches a preset level.  A pressure
switch then activates blowers to collect and transfer the vapors.  Both
carbon adsorbers and condensers allow the VOC to be recovered.  Thermal and
catalytic incinerators destroy the VOC vapors.
     The model regulation requires that alternative control devices reduce
emissions of VOC's by at least 90 percent.  The emission reduction performance
of alternative control devices is determined by comparing the estimated VOC
emissions from the alternative control  device with the uncontrolled VOC
emissions from a fixed roof storage tank with a conservation vent.  The
uncontrolled emissions can be calculated from the emission equations for
                i
fixed roof tanks presented in Chapter 2 and Appendix B.  The uncontrolled VOC
emissions from the fixed roof storage tank are calculated based on the
actual vapor pressure of the volatile organic liquid(s) that are stored at
the anticipated highest average monthly temperature.  The controlled emission
rates from the alternative control device will normally be determined from
engineering calculations or emission test data.
                i
                1
                                   6-8

-------
     Two typical control procedures which reduce the formation of VOC's  are
pressurized tanks and refrigerated tanks.  When filling a storage tank with
VOL the liquid normally displaces vapor in the tank.  A pressurized tank is
designed to operate without venting the displaced vapor.  The vapor remains
in the tank and the internal pressure builds up.  Pressurized storage tanks
designed to operate without emissions to the atmosphere except under emergency
conditions are exempt in the model regulation.  A refrigerated tank can  also
be used to prevent VOC vapor formation.  The vapor pressure of a VOL is
temperature dependent.  If the VOL is sufficiently refrigerated the maximum
temperature of the stored VOL will be low enough to ensure that the actual
vapor pressure of the VOL is less than 10.5 kPa (1.5 psia).  A storage tank
storing a VOL with an actual vapor pressure of less than 10.5 kPa (1.5 psia)
at the stored temperature is exempt in the model regulation.
6.2.5  Compliance Schedule
     The compliance schedule in the model regulation is based on estimates
from equipment vendors and construction contractors on the length of time
                                      1-12
required to retrofit a tank with RACT.      This compliance schedule reflects
the time required to retrofit a single tank with RACT considering the demand
for RACT equipment as of December, 1980.  The compliance schedule in the
model regulation may have to be modified for a particular area or situation
depending upon the availability of RACT equipment and the number of tanks
which must be retrofitted at any given location or plant.  For example,  when
the State regulations become effective there may be an immediate increase in
the demand for RACT equipment resulting in a backlog of orders.  Additionally,
there may be a limited number of local construction contractors capable  of
retrofitting VOL storage tanks with RACT which would also impact on the  time
required to retrofit tanks with RACT.  Another consideration when determining
the compliance schedule is the number of tanks at a particular site which
must be retrofitted with RACT.  A tank owner or operator with a large number
of tanks may not be able to have all tanks to which RACT is applicable
install RACT concurrently.  Therefore, an extended compliance schedule may
be necessary for these tank owners or operators.
                                      6-9

-------
6.3  References for Chapter 6

 1.  Telecon.  R.E. Sommer, GCA/Technology Division,  (Chapel  Hill,  North
     Carolina), to Mike Curtis,  Conservatek,  (Conroe,  Texas).   November 14,  1980.
     Time required to purchase and install an aluminum dome for an  external
     floating roof tank.

 2.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North Caroline),
     to Bill Wagner, Petrex, (Warren,  Pennsylvania).   December 5, 1980.
     Internal floating roof compliance schedule.

 3.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North Carolina),
     to Thomas Smith, Mayflower Vapor Seal Corporation, (Little Ferry,  New Jersey).
     December 5, 1980.  Internal  floating roof compliance schedule.

 4.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North Carolina),
     to Mike Curtis, Conservatek, (Conroe, Texas).   December 5, 1980.   Internal
     floating roof compliance schedule.

 5.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North Carolina),
     to Fred Coon, Brown Minneapolis Tank Manufacturing Company, (St.  Paul,
     Minnesota).  December  9, 1980.   Internal floating roof compliance  schedule.

 6.  Telecon. T. Epstein, GCA/Technology Division.  (Chapel  Hill, North  Carolina),
     to Ron Brown, GATX Tank Erection Corporation,  (Chicago,  Illinois).
     December 9, 1980.  Internal  floating roof compliance schedule.

 7.  Telecon.  T.  Epstein,  GCA/Technology Division   (Chapel Hill, North Carolina)-
     to Dick Reimers, Pittsburgh Des-Moines Steel Company,  (Pittsburgh,
     Pennsylvania).  December 9, 1980.  Internal  floating roof compliance
     schedule.

 8.  Telecon.  T.  Epstein.  GCA/Technology Division,  (Chapel Hill, Ncrth Carolina),
     to Doyle West, Tank Service, Incorporated, (Tulsa, Oklahoma),  December 9,  1980.
     Internal floating roof compliance schedule.

 9.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North
     Carolina), to Jim Hart, Ultrafloat Corporation,  (Houston, Texas).
     December 9, 1980.  Internal  floating roof compliance schedule.

10.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North
     Carolina), to LC.Creith, Altech Industries,  (Allentown, Pennsylvania).
     December 9, 1980.  Internal  floating roof compliance schedule.

11.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North Carolina),
     to William Cook, Sandford Floating Roof, (Gushing, Oklahoma).   December 9,  1980.
     Internal floating roof compliance schedule.

12.  Telecon.  T.  Epstein,  GCA/Technology Division,  (Chapel Hill, North Carolina),
     to Victor Gazgi, Stoplos Company, (East Orange,  New Jersey).   December 9,  1980.
     Internal floating roof compliance schedule.


                                      6-10

-------
APPENDIX A - EMISSION SOURCE TEST DATA

-------
                APPENDIX A - EMISSION SOURCE TEST DATA

A.I  INTRODUCTION
     This appendix describes the emissions source test data obtained by a
U.S. Environmental Protection Agency test program and used in the development
of this control techniques guideline (CTG) document.  The facilities tested
are described, the test methods used are identified, and the data obtained
presented.
A.2  ESTIMATING EMISSIONS FROM FLOATING ROOF TANKS
     The emissions from external and internal floating roof tanks storing
VOL were estimated using equations developed for EPA by the Chicago Bridge
and Iron Company (CBI).  This section summarizes the test methods, test
results, and conclusions from this study.
A.2.1  Description of Test Facility
     The VOL emissions test program was performed in a test tank which
contained benzene at CBI's research facility in Plainfield, Illinois.  The
test tank was 20 feet in diameter and had a 9 foot shell height (see
Figure A-l).  The lower 5'-3" of the tank shell was provided with a
heating/cooling jacket through which a heated or cooled water/ethylene
glycol mixture was continuously circulated to control the product temperature.
     The effect of wind blowing across the open top of a floating roof tank
was simulated by means of a blower connected to the tank by either a 30-inch
or 12-inch diameter duct.  An inlet plenum with rectangular openings was
used to distribute the air entering the test tank shell.  This air exited
from the tank through a similar plenum into a 30-inch diameter exit duct.
The 12-inch diameter air inlet duct was used for the internal floating roof
simulation tests, and the 30-inch diameter inlet duct was used for the
external floating roof simulation tests (which required larger air flow
rates).  While one size of inlet duct was in use, the other size was always
closed.

                                     A-l

-------
                    INLET
               CONCENTRATION
                 BLOWER
                 OUTLET
                   TEMP
                                                                      OUTLET
                                                                    CONCENTRATION
                                                                         I
                                                   AIR FLOW
                                                   'CONTROL
                                                    VALVE
          FLOW RATE
i
IN3
                                                                                                               RIM HEATING
                                                                                                               SUPPLY TEMP
                                            PRODUCT
                                          TEMPERATURE
                                                                                                 __js"/     ^r    ,k     ir
 BLOWER
DISCHARGE
 PRESSURE
      \
          VON
          /OFF
        AIR BLOWER
                                                 FLOATING ROOF TANK
                                                   20'dia. x 5' high
                                             SHELL HEATING SUPPLY
                                                                                       SHELL HEATING
                                                                                        SUPPLY TEMP
                                             SHELL HEATING RETURN
                            Figure A-l.   Simplified  process  and instrumentation schematic.

-------
     A.2.1.1  Principal  Instrumentation.   The principal  instrumentation
consisted of the following equipment:
     1.    The air speed in the inlet duct was measured with a Flow Technology,
          Inc., air velometer, Model No.  FTP-16H2000-GJS-12.
     2.    The total hydrocarbon concentrations were measured with Beckman
          Instruments, Inc., Model  400, total hydrocarbon analyzers.   Two
          instruments were used, one for the inlet and one for the outlet.
     3.    The airborne benzene concentration at the test facility was
          measured with an HNU Systems, Inc., portable analyzer,  Model
          PI 101.
     4.    The local barometric pressure was measured with a Fortin, Model  453,
          mercury barometer.
     5.    During unmanned periods (nights and weekends), the barometric
          pressure was measured with a Taylor Instruments, aneroid baro-
          meter, Weather-Hawk Stormoscope Barometex No.  6450.
     6.    The temperatures were measured with copper/constantan thermo-
          couples and recorded with a multipoint potentiometer, Doric
          Scientific Corp., Digitrend, Model 210.
     A.2.1.1.1  Analyzer calibration.   Calibration gas mixtures were provided
by Matheson Gas Products Company for the purpose of calibrating both the
total hydrocarbon analyzers and the portable analyzer.  Gas mixtures of
three different benzene concentrations in ultra zero air were used:
                              0.894     ppmv
                              8.98      ppmv
                             88.6       ppmv
     The inlet air analyzer and the portable analyzer were routinely calibrated
with the 0.894 ppmv benzene calibration gas.  The outlet air analyzer was
calibrated with the gas mixture closest to the concentration currently being
measured by the analyzer.  Both total  hydrocarbon analyzers were calibrated
at the beginning of each 8-hour shift, and the portable analyzer was calibrated
at least twice a week.
     A.2.1.2  Product Description.   The benzene used during the testing
program was nitration grade benzene, as defined in ASTM-D-835-77.
                                    A-3

-------
A.2.2  Test Method
     The testing was done in three phases, each using a different type of
floating roof.  Phase I used a contact-type internal  floating roof.   Phase II
used a noncontact-type internal floating roof.  Phase III used a double-deck
external floating roof.
     A total of 29 tests were conducted during the three phases.  Conditions
were varied to determine the following:
     o    Emissions from a tight primary seal.
     o    Emissions from a tight primary seal and secondary seal.
     o    Effect of gaps in the primary and/or the secondary seal.
     o    Contribution of deck fittings (penetrations) to emissions.
     o    Effect of vapor pressure (temperature) on emissions.
     A.2.2.1  Description of Floating Roof and Seals.
     A.2.2.1.1  Phase I. contact-type internal floating roof.  A cross-
sectional view of the position of the floating roof within the test tank is
shown in Figure A-2.
     A flapper secondary seal was used during some of the tests.  This seal
was 15 inches wide, with internal stainless steel reinforcing fingers.  A
sketch of its installation on the rim of the contact-type internal floating
roof is shown in Figure A-3.
     Description of test conditions--The test conditions for Phase I  are
summarized in Table A-l.  This table presents a brief overview of the various
temperatures, seal configurations, and deck fitting sealing conditions for
the Phase I emissions tests.
     A.2.2.1.2  Phase II, noncontact-type internal floating roof.  The
internal floating roof for the Phase II tests was fitted with shingled,
flapper type primary and secondary seals.  A plan view sketch of a portion
of the shingle-type seal is shown in Figure A-4.  Also, the dimensions of a
single piece, or shingle, of the seal is shown.  Figures A-5 and A-6
illustrate the details of the shingled, flapper type seal that was installed
in lieu of the single continuous flapper seal used during the propane/octane
tests.  Figure A-5 shows a cross-sectional view of the position of the
noncontact-type internal roof within the emissions test tank.
                                    A-4

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30" Diameter
 \Air Duct
   Removable External
      Cone Roof

Air Plenum
      Rim Space Heating
       & Cooling
               Shell
             Heating  £
              Cooling'
              Jacket
                        N
                             SR-8 Resilient
                               Foam Seal
               Product level
                                               \Contact-type
                                              internal  floating
                                                    roof
    Figure A-2.   Position of the contact-type  internal  floating  roof
                          within the emissions test  tank.
                              A-5

-------
  Bottom of Air Opening
   Flapper-Type
  Secondary Seal
                       Clips  on  3"  Centers  Fastening
                       'Secondary Seal  to Rim of  Roof
                      ,Primary Seal  Immersed  in  Benzene
                      •Contact-type
                       Internal  Floating  Roof
Figure A-3.   Rim mounting of the flapper secondary  seal
                            A-6

-------
Table A-1.   SUMMARY OF TEST CONDITIONS FOR PHASE I,
        CONTACT-TYPE INTERNAL FLOATING ROOF
Test
No.
EPA-1
EPA-2
EPA- 3
EPA-4
EPA- 5
EPA-6
EPA -7
EPA-8
EPA- 9
EPA-10
EPA- 11
EPA-12
EPA-13
EPA-1 4
EPA-1 5
EPA-16
Prod.
Temp.
«F)
80
80
100
100
100
100
100
80
60
75
80
75
75
75
75
75
Primary
Seal
Gaps
None
None
None
None
None
4-l«i"x72"
None
None
None
None
l-lJj"x72"
None
4-lJj"x72"
1-1TX72"
None
S-Vx24"
Sec.
Seal
None
None
None
None
None
None
None
None
None
Yes
None
Yes
Yes
Yes
None
None
Sec.
Seal
Gaps
None
None
None
None
None
None
None
None
None
None
None
None
None
4-lJjBx72'
None
None
Gage
Hatch
Unsealed
Sealed
Sealed
Sealed
Sealed
Sealed
Unsealed
Sealed
Sealed
: Sealed
Sealed
i
Sealed
Sealed
Scaled
Sealed
Sealed
Deck
Fittings
Unsealed
Unsealed
Unsealed
Sealed
Sealed
Sealed
Unsealed
Sealed
Sealed
Sealed
Sealed
Sealed
Sealed
Sealed
Sealed
Sealed
Notes
Partial Test
Partial Test
Partial Test
Partial Test





Void Test







-------
                                                      m
                                       12
                     INDIVIDUAL PIECE OF SHINGLE-TYPE  SEAL
             Tank Shell
Rim Plate
                                                     Steel  Clamp  Bar
                                   PLAN  VIEW
                      (the same detail  was  used  for  both
                         primary and  secondary seals)
                   Figure  A-4.   Installed  shingle-type  seal.
                                      A-8

-------
30" Diameter
  Air Duct
                     Removable External
                       Cone Roof
               Air Plenum
      S
Space Heating^
ooling Coils^.^
'

"n
ID
*>
Shell
Heating &
Cooling
Jacket' — '

                         \
                               Air Opening
                                 Non-Contact-Type
                                    Internal
                                  Floating Roof
(O
                                                               CO
                                                               0)
LL
    Figure A-5.  Position of the non-contact-type internal floating
                    roof within the emissions test tank.
                               A-9

-------
C71
C
QJ
Q.
o

S-
•r-
<
                            SecondaryvSeal
                            Foam Tape
                                                    Steel  Clamp  Bar

                                                        olted Joint
                          Primary Seal
                                Foam Tape
                                Rim Plate
                        Fabric Seal for Mounting  Bracket
                            Mounting Bracket for
                             Secondary Seal
                                                          Deck  Skin
                              Deck Skin Clamp Beam Assembly

                                                       Deck Skin

                                                 \
    Figure A-6.   Cross-sectional  view of the shingle-type
                          seal  installation.
                             A-10

-------
     Description of test conditions—A description of test conditions for
Phase II are summarized in Table A-2.  This table presents a brief overview
of the various temperatures, seal configurations, and deck fitting sealing
condition for the Phase II emissions tests.
     A.2.2.1.3  Phase III, external double deck floating roof.   A cross-
sectional view of the position of the double deck roof within the test tank
is shown in Figure A-7.  This figure also illustrates a metallic shoe seal
mounted on a double deck external floating roof.  When a secondary seal  was
required, the flapper type secondary seal from Phase I was reused.  However,
in order to fit it to the double deck roof, the length of the secondary seal
had to be shortened, because of the slightly smaller diameter of the double
deck roof.
     Description of test conditions—The test conditions for Phase III are
summarized in Table A-3.  This table presents a brief overview of the various
temperatures, seal configurations, and deck fitting sealing condition for
the Phase III emissions tests.
A.2.3  Emissions Test Data
     A.2.3.1  The Effect of Vapor Pressure on Emissions.  Several emissions
tests (EPA-5, EPA-9, and EPA-15) were initially conducted to determine the
effect of the product vapor pressure, P, on the emissions rate.   This relationship
was evaluated during these tests by varying the product temperature in the
pilot test tank which had been fitted with a contact-type internal floating
roof and a liquid-mounted primary seal.  The product temperatures maintained
during the three respective tests were 100°F (EPA-5), 60°F (EPA-9), and 75°F
(EPA-15).  Based on these tests, the emissions are directly related to the
vapor pressure function, f(P):
                     f(P) =           14'7
                                        P \°.5  2
     A. 2. 3. 2  The Effect of Seal Gap Area on Emissions.   Several  tests were
performed to determine the rates of emission as a function of seal  gap area.
                                    A-ll

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                                Table A-2.  SUMMARY OF TEST CONDITIONS FOR PHASE II,


                                      NON-CONTACT-TYPE INTERNAL FLOATING ROOF
>

>—>
ro
Test
No.
EPA- 17
EPA-18
EPA-19
EPA-20
EPA-21
EPA-22
Product
Temp.
(°F)
75
75
75
75
75
75
Primary
Seal
Gaps
None
2-1/2 "x24"
None
None
None
None
Sec.
Seal
Yes
Yes
Yes
Yes
Yes
Yes
Sec.
Seal
Gaps
None
2-1/2 "x24"
None
None
None
None
Deck
Fittings
Sealed
Sealed
Sealed
Sealed
Sealed
Unsealed
Notes


Rim space temporarily sealed
with plastic film.
Rim space temporarily sealed
with plastic film, and deck
seams also sealed.
Same conditions as EPA-20, but
with additional sealing of deck
seams.
Same conditions as EPA-21, but
with all the temporary seals
removed from the deck fitting*.

-------
                       Removable  External
                          Cone Roof
              Air Plenum
30" Diameter
  Air Duct
                                   Double Deck  External
                                       Floatinq Roof
       Rim  Space Heating
       & Cooling Coils
                Shell
              Heating &
               Cooling
               Jacket
      LL
   Figure A-7.  Position of the double deck external floating roof
                      within the emissions test tank.
                               A-13

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Table A-3.  SUMMARY OF TEST CONDITIONS FOR PHASE III,
           DOUBLE DECK EXTERNAL FLOATING ROOF
Test
No.
EPA-23
EPA-24
EPA-25P
EPA-25
EPA-26
EPA-27
EPA-28
EPA-29
Product
Temp.
(°F)
75
75
75
75
75
75
75
75
Primary
Seal
Gaps
None
2-l"x24"
2-l"x24"
2-l"x24"
2-l"x24"
None
4-1 1/2 "x7 2"
4-1 1/2 "x72"
Sea.
Seal
None
None
Yes
Yes
Yes
Yes
Yes
None
Sec.
Seal
Gaps
None
None
1-1 l/4"x
377"
None
2-1/2 "x24"
None
2-1/2 "x24«
None
Notes
Deck fittings sealed for all
tests.








-------
     Table A-4 presents the seal gap areas tested and the measured emissions
for the Phase I testing of a contact-type internal floating roof.  Several
conclusions are apparent from these tests:
     1.   A comparison of the emissions measured during tests EPA-5, EPA-9,
          and EPA-15 with the emissions measured during tests EPA-11 and
          EPA-16 clearly demonstrates that increasing gap areas in the
          primary seal increases emissions.
     2.   A comparison of the emissions measured during tests EPA-5, EPA-9,
          and EPA-15 with the emissions measured during test EPA-12, in
          addition to a comparison of the emissions measured during tests
          EPA-11 and EPA-13, demonstrates that the addition of a secondary
          seal reduces emissions.
     3.   A comparison of the emissions measured during tests EPA-12 and
          EPA-13 shows that, as long as the secondary seal has no gaps, the
          emissions rate is generally independent of the amount of gap in
          the primary seal.
     No relationship between seal gap area and emissions could be established
from the Phase II testing of a noncontact-type internal floating roof.  This
was probably a result of the shingle-type primary and secondary seals used
during the tests.
     Table A-5 presents the seal gap areas and the measured emissions for
the Phase III testing of a double deck external floating roof.  Several
conclusions are apparent from these tests:
     1.   A comparison of the emissions measured during tests EPA-23 and
          EPA-24 demonstrates that small gap areas in the primary shoe seal
          do not increase emissions.
     2.   A comparison of the emissions measured during tests EPA-23 and
          EPA-27, in addition to a comparison of the emissions measured
          during tests EPA-24 and EPA-25, demonstrates that the addition of
          a secondary seal reduces emissions.
     3.   A comparison between similar cases in Tables A-4 and A-5 demon-
          strates that the emissions from an external floating roof tank are
          higher than the emissions from a contact-type internal floating
          roof tank similarly equipped.
                                    A-15

-------
                       Table A-4.   MEASURED BENZENE EMISSIONS FROM EPA PHASE I TESTING
                                     CONTACT-TYPE INTERNAL FLOATING ROOF
Test
Primary seal
number
of gaps
total gap
size
(inVft)
Secondary seal
number
of gaps
total gap
size
(1nz/ft)
Emissions
Mhs/dav^
5 mph 10 mph 15 mph
I
t—>
cr>
EPA- 5,
EPA- 9,
EPA-153
EPA- 11
EPA-16
EPA-12
EPA-13
0
4
2
0
4
— •
21
1.3
~ •
21
b
b
b
0
0
2.7
5.8
4.8
0 1.0
0 1.0
3.3
10.1
5.8
1.7
Y-7
3.7
14.0
7.2
2.3
2.3
         Calculated  as  benzene at 1.75 psia TVP from the 20 foot diameter test tank.


          No  secondary seal.

-------
             Table A-5.  MEASURED BENZENE EMISSIONS FROM EPA PHASE III TESTING,
                           DOUBLE DECK EXTERNAL FLOATING ROOF
Test
Primary seal
number
of gaps
total
qap9size
(inVft)
Secondary seal
number
of gaps
total
qap9size
(inVft)
Emissions
Mbs/day^
5 mph 10 mph 15 mph
EPA-23
EPA-27
EPA-24
EPA-25
EPA-26
0
0
2
2
2
—
—
3.4
3.4
3.4
a
0
a
0
2
20
9.3
20
9.3
1.3 17.4
32
10.0
32
10.0
23
43
10.4
43
10.4
27
No secondary seal.

-------
     A.2.3.3  The Development of Seal Factors (K ) and Hind Speed Exponents (n).
                                        " "       j                 ' """
     The emission factors (K  and n) for internal and external floating
roofs with primary seals and primary and secondary seals were developed from
the emissions test data previously discussed.  The emissions factors for
contact internal floating roofs and external floating roofs having primary
seals and primary and secondary seals are average seal factors developed
from the emission test data and field tank gap measurement data.  Using a
methodology similar to one discussed in American Petroleum Institute (API)
Publication 2517,  the test data from selected EPA Phase I and Phase III
tests were weighted to represent gap measurement data collected by the
California Air Resources Board (CARB) during seal gap area surveys on
external floating roof tanks.  Based on engineering judgment, it is reasonable
to assume that they are also representative of the seal gaps on internal
floating roof tanks.
     Consequently, the emission factors for a contact-type internal floating
roof with a primary seal (cIFRps) were estimated based on the weighted
average of tests EPA-15 and EPA-16, which have no measurable seal gap and
1.3 square inches of seal gap per foot of tank diameter, respectively.
Because 65 percent of the tanks surveyed by CARB had no measurable gaps, the
emissions measured during test EPA-15, the test with no measurable gap, was
weighted at 65 percent.  The remaining 35 percent was assigned to the emissions
measured during test EPA-16.
     The General Linear Models (GLM) procedure of the Statistical Analysis
System (SAS) was employed for the analysis.  Each data set was assigned a
weight value corresponding to the seal gap occurrence frequency found in the
CARB measurements.  The K  and n values were then determined by a linear
                         o
regression of the common logarithm of the emissions versus the common logarithm
of the windspeed.
     Similarly, the emission factors for a contact-type internal floating
roof with primary and secondary seals (cIFRss), an external floating roof
with a primary seal (EFRps), and an external floating roof with primary and
secondary seals (EFRss) were estimated by applying appropriate weighting
factors to the EPA test data to represent the CARB tank survey data.
Table A-6 summarizes the emission factors for internal and external floating
roofs.
                                    A-18

-------
          Table A-6.  SEAL  LOSS FACTORS  FOR AVERAGE SEAL GAPS
                     AND THE BASIS OF  ESTIMATION^

Roof and
seal3
cIFRps

cIFRss

ncIFRss
EFRps


EFRss

EPA i
test
EPA-15
EPA-16
EPA-13
EPA-14
EPA- 17, 18
EPA-23
EPA-24
EPA- 29
EPA-25
EPA-26
Primary Secondary
seal gap, seal gap, Weighting
n2/ft tank in2/ft tank factors
diameter diameter (%)
0 no seal
1.3 no seal
21 0
21 21
0, 1.3 0, 1.3
0 no seal
3.4 no seal
14.4 no seal
3.4 0
3.4 1.3
65
35
95
5
NAb
10
85
5
75
25
Emission
Factors
Ks
26.7 0.1

8.3 0.2

7.3 1.2
50.5 0.7


77.0 0.1

 cIFRps  = contact  internal  floating roof with  a  primary seal;  cIFRss  =
 contact internal  floating  roof with primary and secondary seals;
 ncIFRss = noncontact internal  floating roof with primary and  secondary
 seals;  EFRps  = external  floating  roof with  a  primary seal;  EFRss  =
 external floating roof with primary and secondary seals.

3Not applicable.   Tests weighted equally.
                                A-19

-------
     Some of the data collected during the Phase I and Phase III  tests were
not used to develop emission factors.   Data collected during Phase I tests
EPA-1 through EPA-4 were not used because these tests were performed primarily
to evaluate the performance of the test facility.   Data collected during
test EPA-10 were voided because the secondary seal was incompatible with
benzene.  Data collected during test EPA-11 were not used because the seal
gap area was unrealistically large.
     Data collected during Phase III test EPA-25P were not used because of a
failure of the secondary seal.  Data collected during test EPA-28 were not
used because the seal gap area was unrealistically large.
     Additionally, while the testing did not specifically address the
control effectiveness of placing a fixed roof over an external floating
roof, it is reasonable to assume that the emissions from a tank so modified
would be equivalent to the emissions from a contact internal floating roof
tank similarly equipped.
A.3  ESTIMATING EMISSIONS FROM FIXED-ROOF TANKS
     As discussed in Chapter 2, the working and breathing loss equations
from AP-42 were used to estimate benzene emissions from fixed-roof tanks
storing benzene.  However, breathing losses estimated using these equations
were discounted by a factor of 4, based on recent fixed-roof tank tests
conducted for the Western Oil and Gas Association (WOGA), EPA, and the
German Society for Petroleum Science and Carbon Chemistry (DGMK).
A.3.1  WOGA and EPA Studies
      During 1977 and 1978, 56 fixed-roof tanks were tested for WOGA and
EPA.  Fifty of these tanks, which were tested for WOGA, were located in
Southern California and contained mostly California crudes, fuel  oils, and
diesel and jet fuel.  These tanks were in typical refinery, pipeline, and
production services.  The remaining six tanks, which were tested for EPA,
contained isopropanol, ethanol, acetic acid, ethyl benzene, cyclohexane, and
formaldehyde, respectively.
     A.3.1.1  Test Methods For The HOGA and EPA Studies.  The test methods
for the WOGA and EPA studies followed the methods described in the American
Petroleum Institute (API) Bulletin 2512, "Tentative Methods of Measuring
                                    A-20

-------
Evaporative Loss from Petroleum Tanks and Transportation Equipment," Part II,
Sections E and F.  This document recommends that the emissions from a fixed-
roof tank be estimated by measuring the hydrocarbon concentrations and flow
rates leaving the tank.
     In the WOGA study, the volume of vapors expelled from a tank was measured
using a large and a small positive displacement diaphragm meter and a turbine
meter connected in parallel.  Three meters were used to cover the potential
range of flow rates.  These meters were connected to the tank with flexible
tubing.  Vapor samples, which were taken from the tank using a heated sample
line, were analyzed continuously with a total hydrocarbon analyzer.  With
continuous monitoring, fluctuations in the hydrocarbon concentration could
be noted.  Periodically, grab samples were taken and analyzed with a gas
chromatograph, providing details on hydrocarbon speciation.
     In the EPA study, the volume of vapor emitted from a tank was measured
by positive displacement meters of either the bellows or rotary-type, depending
on flow rate.  Both meters were mounted so they could be manually switched
for positive and negative flow through a one-way valve which was weighted,
when applicable, to simulate the action of a pressure-vacuum valve.  Vapors
from the tank were sampled using a heated sample line (to reduce condensation
in these lines), and then monitored with a total hydrocarbon analyzer calibrated
specifically for the chemical in the tank.  For the formaldehyde tank, a
thermal conductivity gas chromatograph was used instead of a flame ionization
detection gas chromatograph.
     A.3.1.2  Test Data and Conclusions from the WOGA and EPA Studies.  In
these studies, 33 tank tests were available for correlation with the API 2518
breathing loss equation which is the basis for the breathing loss equation
in AP-42.  Table A-7 lists the emissions measured during each of these tests
and the emissions calculated using the API equation.  Measured versus calculated
emissions for each of these tanks are also presented in Table A-7.  Of the
33 tanks tested, only two had measured emissions larger than those calculated
using the API breathing loss equation.  In general, the API equation overestimated
breathing losses by approximately a factor of four.
     An additional 13 tank tests from the WOGA study were available for
evaluating the emissions from a fixed-roof tank in continuous working operation.
However, because of limited and scattered data, and the fact that breathing

                                    A-2:1

-------
Table A-7.   MEASURED AND ESTIMATED BREATHING
        LOSSES FROM FIXED-ROOF TANKS

Test
No. Type of product
Measured
Breathing Calculated
loss, breathing loss,
(kg/day) (kg/day)
Measured/loss
calculated loss
EPA Study:
1
2
3
4
5
6
7
8
9
10
11
12
WOGA
1
2
3
4
5
6
7
8
9


Isopropanol
Isopropanol
Ethanol
Ethanol
Ethanol
Acetic acid,
glacial
Acetic acid,
glacial
Ethyl benzene
Ethyl benzene
Cyclohexane
Cyclohexane
Cyclohexane
Study:
Crude
Crude
Fuel oil
Crude
Fuel oil
Deisel
Crude
Crude
Crude


6.8
7.7
2.7
1.5
2.6
10.9
20.4
5.0
6.8
9.1
7.7
6.3

0
0
0
0
4.5
0
60.3
43.5
54.0
(continued)
A-22
16.3
15.0
18.2
20.4
17.2
34.5
42.7
14.5
16.8
70.1
56.3
61.7

3.6
8.6
10.0
1.4
30.4
14.5
175.2
72.2
187


0.42
0.52
0.15
0.08
0.15
0.32
0.48
0.34
0.41
0.13
0.14
0.10

0.00
0.00
0.00
0.00
0.01
0.00
0.34
0.60
0.29



-------
Table A-7.   Concluded

Test
No.
10
11
12
13
14
15
16
17
18
19
20
21
Average
Type of product
Jet component
Crude
Crude
Crude
Fuel oil
Crude
Crude
Crude
Crude
Crude
Crude
Diesel

Measured
Breathing Calculated
loss, breathing loss,
(kg/day) (kg/day)
0
0
2.3
62.6
0.9
20
102
261
0
2.7
0
5.4

13.2
3.2
15.4
49.0
10.4
30.0
134.3
172.5
6.4
64.5
0.5
14.1

Measured/loss
calculated loss
0.00
0.00
0.15
1.28
0.09
0.67
0.76
1.51
0.00
0.04
0.00
0.39
0728
       A-23

-------
losses could not be separated out of the emissions, no suggestions were made
for developing a new correlation for working losses from fixed-roof tanks.
A.3.2  DGMK Study
     During 1974 and 1975, emissions tests were conducted by the German
Society for Petroleum Science and Carbon Chemistry (DGMK) on a 3,000 cubic
meter fixed-roof tank storing gasoline.  The tests were designed to evaluate
the effects of both climate and method of operation on the emissions from
the tank over a long period of time.
     A.3.2.1  Test Methods for the DGMK Study.  A large number of parameters
were measured and recorded during the tests, including the volume of vapor
leaving the tank, concentration of hydrocarbons in the emitted vapor, gas
pressure and temperature in the tank, liquid temperature, liquid level,
ambient temperature, air pressure, and solar radiation.  In addition, using
discontinuous measurements, vapor samples were analyzed in a laboratory for
speciation and total hydrocarbons.
     The flow rates from the tank were measured using three bellows gas
counters connected to the breathing valves on the tank.  Three gas counters
were used so that extremely high and extremely low volume flows could be
determined.  The three bellows gas counters were installed on the roof of
the tank.  The pressure drop across the counters was 20 mm water on the
column at full load.  The additional pressure drop caused by the counters
was compensated for by installing a new set of breathing valves.
     An electrically heated sampling line was connected from the outlet of
each of the bellows gas counters to the measurement room.  The vapors were
analyzed with a flame ionization detector (FID) for total hydrocarbon content.
Grab samples were also analyzed using two different gas chromatographic
techniques to determine total hydrocarbons and individual components.
     A.3.2.2  Test Data and Conclusions from the DGMK Study.  Table A-8
presents the measured breathing and working losses and the losses calculated
using the API 2518 breathing and working loss equations.  A comparison of
the measured and calculated losses indicates that the measured breathing
losses are only 24 percent of the estimated breathing losses.  In addition,
measured working losses are approximately 96 percent of the working losses
estimated using API 2518.
                                    A-24

-------
       Table A-8.   COMPARISON OF MEASURED LOSSES WITH
               THOSE CALCULATED USING API 2518

Time
period
(days)
Breathing
69
46
45
160
Measured
(Mg)
lossb
2.0
0.6
0.7
3.3
Calculated3
(Mg)

6.6
3.9
3.2
13.7
Measured/cal cul ated

0.30
0.15
0.22
0.24
Working loss
69
46
45
160
12.2
11.3
5.9
29.4
12.2
12.9
5.6
30.7
1.0
0.88
1.05
0.96
aAPI Bulletin 2518, "Evaporation Loss from Fixed-Roof
 Tanks."
 Includes withdrawal loss.
                          A-25

-------
A.4  REFERENCES FOR APPENDIX A

1.   American Petroleum Institute.  Evaporation Loss from External
     Floating-Roof Tanks.   API Publication 2517.  February 1980.

2.   Letter from Tedone, M., TRW, Incorporated, to VOL Docket.
     August 12, 1980.  Emission Factors for VOL and Benzene.
                                    A-26

-------
   APPENDIX B - EXAMPLE CALCULATIONS
FOR DETERMINING REDUCTION IN EMISSIONS
      FROM IMPLEMENTATION OF RACT

-------
                                 APPENDIX B
             EXAMPLE CALCULATIONS FOR DETERMINING REDUCTION IN
                    EMISSIONS FROM IMPLEMENTATION OF RACT

     The purpose of this appendix is to provide example calculations and
procedures for computing the emissions before and after the implementation
of reasonably available control technology (RACT) for volatile organic
liquid storage tanks.  The equations used to calculate emissions from
storage tanks were presented in Chapter 2.  They are presented again in this
appendix with an example calculation to illustrate the calculation of
emissions from storage tanks.  To calculate an emission reduction one first
calculates the emissions before implementation of RACT.  The emissions after
the installation of RACT are then calculated.  The emission reduction is
computed by subtracting the emissions before implementation of RACT from the
emissions after the implementation of RACT.  The emissions from the imple-
mentation of RACT are from a contact internal floating roof tank with
primary and secondary seals.  The emissions before the implementation of
RACT are typically from a fixed roof tank or an external floating roof tank.
     The parameters needed to calculate the emissions from a fixed roof tank
are the molecular weight, the average monthly vapor pressure of the liquid
being stored, the tank diameter, height, and capacity, the average diurnal
temperature change, the color of the paint on the tank, and the annual
turnover rate for the tank.  The parameters needed to calculate the emissions
from a floating roof tank (internal or external) are the molecular weight,
the vapor pressure, the density of the liquid being stored at the average
monthly temperature of the liquid, the diameter and capacity of the tank,
the average windspeed at the tank site, and the annual turnover rate for the
tank.  The average diurnal temperature change and the average windspeed in
the area where a tank is located can be obtained from historical meteorological
data.  The tank parameters such as diameter, height, capacity, average
                                    B-l

-------
turnover rate, and color of external  paint on the tank can  be obtained from
the tank owner or operator.  The properties of the liquid being  stored such
as average monthly vapor pressure,  density, and molecular weight at  the
average monthly temperature of the  liquid can be obtained from standard
reference texts.
Example Calculation
     An example calculation is presented assuming the storage tank before
implementation of RACT is a fixed roof tank and implementation of PACT
changes this tank to an internal floating roof tank with primary and
secondary seals.
     For this illustration a storage tank with a capacity of 6,427,376 liters
(1,697,933 gallons), a diameter of  25.9 meters (85 feet), and a  height of
12.2 meters (40 feet) is used.  The tank is storing methyl  ethyl ketone
(2 butanone) having an average monthly liquid temperature of 25°C (77°F).
At this temperature the liquid has  an actual vapor pressure of 13.4  kPa
(1.9 psia), a density of 0.805 kg/ml  (6.72 Ib/gal), and a molecular  weight
of 98.96 kg/kg mole (Ib/lb mole).  This tank has an average annual turnover
rate of 15 and is located in an area where the average diurnal temperature
change is 11°C (20°F).
Calculation of Emissions Before Implementation of RACT
     The equations used in determining the example emission estimates before
implementation of RACT are for fixed roof tanks as follow:

l-        LT=LB+LW   6
2.        LB = 9.15 x 10" M f(P) D1-7^0-51!0-^
3.        Lw = 1.09 x 10" MPKnVN
where,    Lj = total loss (Mg/yr)
          Ln = breathing loss (Mg/yr)
          LW = working loss (Mg/yr)
          M  = molecular weight of  product vapor (Ib/lb mole); 98.96 Ib/lb mole
          P  = true vapor pressure  of product (psia); 1.9 psia

        f(P) =  (i/TTlp- >°'68      ; °'2733
          D  = tank diameter (ft);  85 feet
          H  = average vapor space; assumed tank height/2  (ft);  20 feet
          T  = average diurnal temperature change in °F; 20°F
                                     B-2

-------
         F   = paint factor; 1.0 for clean white paint
          C  = tank diameter factor;
               for diameter >_ 30 feet, C = 1
               for diameter < 30 feet,
                    C = 0.0771 D - 0.0013 (D2)  - 0.1334
         K   = turnover factor
               for turnovers > 36, kn =  18°6*  N
               for turnovers <_ 36 k  = 1
          N  = number of turnovers per year ;  15
          V  = tank capacity (gal) ; 1,697,933  gallons
     Substituting the numbers into the equations yields:
         LB = (9.15 x 10"6)(98.96)(.2733)(85)1.73(20)°.51(20)°.5(1.0)(1.0)
         LB  =9.72 Mg/yr
         Lw  = (1.09 x 10"8)(98.96)(1.9)(1.0)(1,697,933)(15)
         Lw  =52.20 Mg/yr
         LT  = LB + Lw = 61.92 Mg/yr
     If the storage tank before the implementation of RACT is  an  external
floating roof tank, then the emission estimates are calculated using  the
equations presented in Chapter 2 for floating roof tanks.   The equations for
calculating emissions from an external roof tank are the  same  as  the  equations
presented in the next section for calculating emissions from an internal
floating roof tank except that different values for certain parameters
(i.e., KS Kp, m, n) are used in the equations.                  :
Calculation of Emissions After Implementation of RACT
     The equations used in determining the example emission estimates from
implementation of RACT are for a contact internal floating roof with  primary
and secondary seals and are given by the following equations for  emissions
from floating roof tanks:
i.       LT  =LW + LS + LF
2.       Lw  = 0.943 QCWL/2205D
3.       Ls  = Ks VnMvD f(P)/2205
4'       LF  = NKVmM  f(P)/2205
                                    B-3

-------
where    LT  = total  loss (Mg/yr)
         LW  = withdrawal!oss (Mg/yr)
         LS  = seal  loss (Mg/yr)
         Lp  = fitting loss  (Mg/yr)
       f(P)  = 0.068P/((1 +  (1 -  0.068P)0-5)2);  0.0346
         MV  = molecular weight of product vapor (Ib/lb mole);  98.96 Ib/lb
               mole
          P  = true vapor pressure of product (psia);  1.9 psia
          D  = tank diameter (ft); 85 feet
         WL  = density of product (Ib/gal); 6.72 Ib/gal
          V  = average wind  speed for the tank site (mph); 10 mph
          Q  = product average throughput (bbl/yr); 606,400 bbl/yr
               (tank capacity (bbl/turnover) x Turnovers/yr)
         KS  = seal  factor;  8.3 (see Table 2-1)
         KF  = fitting factor; 132 (ses Table 2-2)
          n  = seal  wind speed exponent; 0.3 (see Table 2-1)
          m  = fitting wind  speed exponent; 0.0 (see Table 2-2)
          c  = product withdrawal  shell clingage factor bbl/(ft2 x 103);
               use 0.0015 bbl/(ft2 x 103) for VOL in a welded steel  tank
               with light rust
          N  = fitting multiplier; 2 (see Table 2-3)
     Substituting the numbers into the equations yields:
         Lw  = (0.943)(606,400)(.0015)(6.72)/(2205)(85)
         Lw  =0.03 Mg/yr
         Ls  = (8.3)(10)°-3(98.96)(85)(0.0346)/(2205)
         Ls  =2.19 Mg/yr
         LF  = (2)(132)(10)°'°(98.96)(0.0346)/(2205)
         LF  =0.41 Mg/yr
         LT  = Lw + Ls + LF  = 2.63 Mg/yr
Emission Reduction from Implementation of RACT
     The errission reduction  is computed by subtracting the emissions after
implementation of RACT from the emissions before implementation of RACT.
                                     B-4

-------
          ER = 61.92 - 2.63 = 59.29 Mg/yr

          ED(«) = ^-^ (100) = 96%
           K      61.92
     The total VOC emission reduction from all  affected storage tanks  in  a
State is the sum of the emission reductions from each storage tank to  which
RACT applies which is in the areas of nonattainment with the national  ambient
air quality standard for ozone.
                                     B-5

-------