## EPA-450/2-78-047 OAQPS NO.. 

## 1.2-116 

# Controlof Volatile Organic Emissionsfrom Petroleum Liquid Storage in 

# External Floating RoofTanks

EmissionStandardsand Engineering Division

. .

U.S.'ENVIRONMENTALPROTECTION AGENCY Officeof Air, Noise,and Radiation OfficeofAir Quality Planningand Standards Research Triangle Park, North Carolina27711 December 1978OAQPS GUIDELINESERIES

Y Theguidelineseries of reportsisbeingissuedbythe OfficeofAir Quality Planningand Standards (OAQPS)to provide informationtostate and localair pollution controlagencies; forexample.to provide guidanceonthe acquisitionand processingofair qualitydataandonthe planningandanalysisrequisiteforthemaintenanceof airquality. Reportspublishedinthisserieswillbeavailable-assuppliespermit-fromthe LibraryServicesOff~ce (MD35).U.S. Environmental ProtectionAgency, ResearchTriangle Park,NorthCarolina2771I;or,foranomrnal fee, fromthe National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161.

Publication No. EPA-45012-78-047 OAQPS NO.1.2-1 16Chapter 7.0 1.1 Chapter 2.0 2.1 2.2

2.3 Chapter 3.0

. 3.1 3.2

3.3 Chapter 4.0 4.1 TABLE OF CONTENTS Page Introduction 

# ............ 1-1 Need toRegulate

# ........... 1-1 Sources and Types of Emissions 

# ..... 2-1 External Floating Roof Tanks 

# . 2-1 Primary Seals 

# . ? 

# . 2-3 2.2.1 Mechanical Shoe Seal 

# . 2-4 2.2.2 Resilient Foam Seal 

# ....... 2-4 2.2.3 Liqufd-FilledSeal 

# . 2-6 

### References 

# ............ 2-7 Control Techno1ogy 

# .......... 3-1

w Rim-Mounted Secondary Seal 

# . 3-1 Wind Induced Emissions 

# ....... i 3-3 3.2.1 Shoe Seals on Welded Tanks 

# ..... 3-3 3.2.2 Liqufd-Mounted Resilient Foam and LiquSd-Filled Seals on Welded Tanks 

# . . 3-5 3.2.3 Vapor-Mounted Resilient Foam Seal on Welded Tank 

# .......... 3-5 3.2.4 Riveted Tanks 

# ......... 3-7 References 

# ............. 3-10 Cost Analysis 

# ............ 4-1 Introduction 

# ............ 4-1 4.1.1 Purpose 

# ........... 4-1 4.1.2 Scope 

# ............ 4. 1 4.1.3 

### Use o f Model StorageTanks 

# . 4-1
iiiChapter 4.2

4.3 4.4 4.5 Chapter 5.0
5.1 5.2 5.3 Appendix A

Appendix B Page 4.1.4 Bases for Capital and Annualized 

# . . . 4-5 Page Control of Emissions from External Floating Roof Tanks 

# . . 

# . . 

# . . 

# . 

# . . 

# . . . 

# . 4-6 4.2.1 Model Cost Parameters 

# . . . . . . 

# . 4-6 4.2.2 Control Costs 

# . . . 

# . . . 

# . . . 4-6 Cost Effectiveness 

# . . . 

# . . . . . 

# . 4-8 Economics of Scale 

# . . . . 

# . . . 

# . . . 4-13 References 

# . . . 

# . . . 

# . . . . . 4-15

.- Recommended Regulations, Compliance Test Method and Record Keeping 

# . 

# . . . . 

# . . . 5-1 Recommended Regulations 

# . 

# . . . . . . 

# . 5- 1 Compliance Test Method 

# . . . 

# . . . . . . 5-3 Monitoring and Record Keeping 

# . . 

# . . . . . 5-3 Selection of Experimental Tests forWind Induced Emission Calculations 

# . . 

# . . . . .A-1 A. Methodology of Selection 

# . 

# . . . . 

# . . A-1 B. Selection of Welded Tank with Shoe Seal and Rim-Mounted Secondary Seal 

# . . . 

# . . A-2 C. Welded ,Tankwith Shoe Seal and ShoeMounted Secondary Seal 

# . . . 

# . . . . A-3 D. Riveted Tank with a Shoe Seal and RimMounted Secondary 

# . . 

# . . . 

# . . . 

# . A-3 E. Resilient ~oam ~eai Mounted in RimVapor Space of Welded Tank 

# . . . 

# . . 

# . . 

# . A-6 References 

# . . 

# . . . . . 

# . . . . . 

# . A-8 * Calculation of Wind Induced Emissions from Experimental Tests 

# . 

# . . . 

# . . . . 

# . B-1 YI A. Equation forWind Induced Emissions 

# . 

# . . B-1 B. EpforTestTank 

# . 

# . . 

# . . . . . 

# . B-1

### Page Appendix C. Emission Calculations 

# . B-3 C.l Primary Seal With and Without RimMounted Secondary 

# ........ B-3 C.2 Shoe Seal with Shoe-Mounted Secondary 

# . 8-3 References 

# .............. B-6

# 0 LIST OF TABLES Page Table4-1 Technical Parameters Used in Developing Gasoline Storage Tank Control Costs 

# .... Table 4-2 Cost Parameters Used in Computing Control Costs. 

# ............. Table 4-3 Control Cost Estimates forModel Existing Gasoline Storage Tank 

# ........ Table 4-4 Cost Effectiveness of Control1ing Floating Roof StorageTanks 

# ..........4-10 Table 4-5 Factor forEstimating the Cost Effectiveness of Controlling Crude Oil StorageTanks 

# ... 4-12 ~p~eidix 

### A Table A-1 Seal Gap Area in Inspected Welded Tanks with Shoe Seal Compared toCBI Experimental Tests 

# . A-4 A-2 Seal Gap Area in Inspected Riveted Tanks with 

# a Shoe Seals Compared toCBI Experimental Tests 

# . A-5 A-3 Seal Gap Area in Inspected Welded Tank with Non-Metallic Seals Compared toCBI Experimental Tests 

# .......... A-7 Appendix B Table B-7 Ep versus Wind Speed 

# ........8-2 B-2 Emissions from 100ftpl Gasoline Tank 

# .... 8-4 8-3 Emissions from 100 ft

### fl Welded Gasoline Tank with Shoe Mounted Secondary Seal 

# ..... B-5LIST 

### OF FIGURES Page Figure 

### 2-1 External Floating Roof Tank (pontoon type) 

# . 

# - 2-2 Figure 2-2 Primary Seals 

# . . . . 

# - . 

# . , 

# . . 

# - 2-5 Figure 3-1 Rim-Mounted Secondary Seals 

# . 

# . . . . . 

# . Figure 

### 3-2 Emissions from 100 ftDiameter Welded Gasoline Tank with Primary Shoe Seal at 16.1 kph (10 mph) Average Wind Speed 

# . . 

# . 

# - . . . 

# . . Figure 

### 3-3 Emissions from 100 ft~iametek Welded Gasoline Tank 

### with Primary Foam Seal 

### atl6.1 kph (10mph) Average Wind Speed 

# . 

# - . . 

# - . . . . Figure 3-4 Emissions from 100 ftDiameter Riveted Gasoline Tank with Primary Shoe Seal at 16.1 kph (10 mph) Average Wind Speed 

# . . . 

# . 

# - . . . . 

# .EPA policy isto express a11 measurements inAgency documents inmetric units. Dual units are sometimes given inthe text for clarity. Listed below are abbreviations and canversion factors for English equivalents ofmetric units. Frequently used measurements are also presented indual units below for the reader's convenience. METRIC UNIT ALTERNATE UNIT CONVERSION.

.

, . .. ki 1

ogram (kg) pound (Ib)

, ,, kgx2.205= ton kg x 1.1 x 10- 

# YS = tons metric ton (m ton) or pound (Ib) Mg x 2205 = Ibs megagram (Mg) ton Mg 

### x 1.102 = tons k i1 ometer (km) mile (mi) km 

### x 0.621 = mi 

### ki1ometers per hour '(kph) miles per hour (mph) kph x 0.621 = mph meter (m) foot (ft) m x 3.281 = ft centimeter (cm) inch (in) 

### cm x 0.394 = in liter (1) gallon (gal) 1 x 0.264 = barrel (bbl) 1 x 6.3 x bbl : Pascal (Pa) atmospheres (aim) Pa x 9.9 x = atm pounds per square Pa x 6.7 x = psi inch (psi) atmospheres (atm) kPa x 9.9 x 10'~ = atm pounds per square kPa x 0.145 = psi inch (psi) FREQUENTLYUSED MEASUREMENTS 1,600,000 1 422,000 gal 10,000 bbl 150,0001 40,000gal % 950 bbl

10.5kPa c 1.52psi 13.8 kPa 2.0 psi 27.6kPa 4psi 9.7 kph 6 mph 41.4kPa 

# , 6psi 16.1 kph % 10 mph 69.0 kPa 10 psi 22.5 kph % 14 mph
viii

### Liquidmounted -. 

### means a primary seal mounted so the bottom cf the seal 

# 0

covers the liquid surface between the tank shell and the floating roof. Vapormounted means a primary seal mounted so there is an annular vapor space underneath the seal. The annular vapor space isbounded by the

L. 

### bottom of the primary seal, the tank shell, the liquid surface, and the floating roof. J 

### Petroleum liquids means crude oil, condensate, and any finished or intermediate products manufactured or extracted in

### a petroleum refinery. True vapor pressure means the equilibrium partial pressure exerted
' I 

### by a petroleum liquid 

### as determined in

### accordance with

### methods described in

### American'Petroleum Institute (API) Bulletin 2517, Evaporation Loss from Floating Roof Tanks, 1962. The API procedure may not be applicable to some high 

### viscosity or high pour crudes. 

# d Available estimates of truevapor pressure may be used in

### special
cases such as'these. Volati1 e Organic Compounds (VOC) means compounds which under favorable conditions may participate in

### photochemical reactions to form oxidants.

### This document is relat$edto the control of volatile organic compounds (VOC) 

### from the storage of petroleum liquids in external floating roof tanks.

- 

### Methodology described in this document represents the presumptive norm or reasonably available control technology (RACT) that can be applied to

. , 

### existing external floating roof storage tanks. RACT is defined as the lowest emission limit that a particular source is capable of meeting by 

### the application 

### - . of control technology that is reasonably available considering technological and economic feasibility. It may require technology that has been applied 

### to similar,but not necessarily identical, source categories. It is not intended that extensive research and development be conducted before a 

### given control technology can be applied to the source. This does not, however, preclude requiring a short-termevaluation program to permit the application of a given technology to a particular source. The latter effort is
an appropriate technology-forcing aspect of RACT.
1.1 

### NEED TO REGULATE Control techniques guidelines concerning RACT are being prepared for those industries that emit significant quantities of air pollutants in areas of the country where National Ambient Air Qua1i

### ty Standards 

### (NAAQS) are not beingattained. Storage tanks for petroleum liquids are a significant source of VOC. A control techniques guideline (CTG) for storage of petroleum 1 iquids infixed roof tanks (EPA-450/2-77-036) was published in December 1977, RACT forfixed roof tanks was defined asthe retrofitwith internal floating roofs


### or equivalent

# . The following recommended control measures apply toexternal floating roof tanks (EFRT) larger than 150,000 liters (950 bbls) storing petroleum liquids. They do not'apply tofixed roof ortanks with orwithout internal floating roofs, nor do they apply tosmall production tanks. In general, RACT for external floating roof tanks (EFRT) is defined as follows: (I) A welded EFRT equipped with primary metallic shoe or liquidmounted seals is required toretrofitwith a rim-mounted secondary seal if theTVP ofthe stored'liquid exceeds 27.6 kPa (4 psi). (2) A welded orriveted EFRT equipped with primary vapor-mounted 

### seals is required toretrofitwith a rim-mounted secondary if theTVP of the stored liquid exceeds 10.5 kPa (1.5 psi). (3) A riveted EFRT equipped with primary metallic shoe or 1iquidmounted seals 

### is alsorequired toretrofitwith a rim-mounted secondary if' theTVP of the stored 1 iquid exceeds 10.5 kPa (1.5 psi).,: Specificreconunendations,for regulations, including'exemptions, arepresented in Chapter 5.0. Estimated emissions from the affected EFRT's during 1978

### were 65,000 megagrams/year (71,630 tons/yr)

# . The proposed recommendations would reduce these emissions to30,000 megagrams/year (33,060 tons/yr)

# . The emission estimates used inthis document 

### were calculated from data obtained by Chicago Bridge and Iron Company (CBI) on a 6.1 

### m (20 ft)

### diameter test tank. Data obtained by Pi 

### ttsburgh-Des Moines Steel Company (PDM)
on a 10.7 

### m (35 ft)diameter testtank were used toverify RACT 

### for liquidmounted sealswhich are liquid or foam filled. An 

### American Petroleum Institute (API) emission test program, scheduled forcompletion in 

### 1979, 

### is expected to provide verification of the validity of the scale-up techniques used herein. Cost effectiveness of retrofitting rim-mounted secondary seals to EFRT's is 

### dependent on tank size, product type, product value, average wind speed and other factors. For example, the installed capital cost 

### for retrofitting
a rim-mounted secondary seal to a 30.5 

### m (100 ft)

### diameter welded tank equipped with 

### a primary shoe seal isabout $77,000. The net annual cost aftercredit forrecovered product 

### is $3,140 

### when storing gasoline ata TVP 

### of 41.4 kPa (6 

### psi) and an average wind 

### speed of 16.1 kph (10 mph). A 

### welded tank having a vapor-mounted primary seal and a riveted tank having a primary metal 1 ic shoe seal can be retrofitted with

### a rim-mounted secondary seal for the same capital cost. However, in

### these two cases under the same storage conditions the emission reductions are larger and the net annual cost is$1930 forthewelded tank with 

### the vapor-mounted seal and $1750 for the riveted tank with

### the shoe seal. The cost effectiveness for the above th&e cases is$373, $117, and $99 per megagram of emissions controlled, resbectively. At

### lower wind 

### speeds and vapor pressures, the cost effectiveI 

### nesb would be higher. At

### higher wind 

### speeds and vapor pressures, the cost
I 

### effbctiveness would be 1 ower. I

### SOURCES AND 

### TYPES OF EMISSIONS
There arean estimated 13,800 internal and external floatingroof tanks

' 

### storing petroleum liquids atrefineries, terminals, tank farms and along pipelines.

# ' Of 

### these, 10,700 arestoring liquidswhose vapor pressures equai
or exceed 10.5 kPa. Data arenot available toestablish how many of these are

. 

### external floating roof tanks. 2.1 EXTERNAL FLOATING ROOF 

### TANKS An external floating roof tank consists of a steel cylindrical shell equipped with a deck 

### lor roof which floats on the surfaceof the stored liquid, rising and falling with the 

### liquid level (Figure 2-1). 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 tothe 

### roof contacts the 

### tank wall and covers the

### remaining area. The 

### seal slidesagainst the 

### tank wall as the roof is 

### raised or lowered. The primary route of VOC 

### emissions 

### is by this seal. When a conmercial fitbetween the seal and thetank wall 

### is maintained, most losses by the seal areattributable tothewind.293,4,5y6 

### Wind induced losses occur when airflow across the tank creates pressure differences around 

## * the floatingroof, causing airtoflow intothe annular vapor space on the 

### leeward side and airplus VOC 

### toflow out on thewindward side. Improper or loose fit

,.. . 

## * Unless the primary seal is 

### liquid-mounted, the

### vapor spacebounded by the 

### sliding seal, wall, roof, and liquid surfacedefines an annular vapor space.- - - .-- Figure2-1. External floating rooftank(pontoontype).

### of the seal creates gaps or openings between the seal and the tank wall. These gaps expose the liquid surface directly to the wind 

### and sun, which combine to increase emissions. The wind flows across the tank, scouring the vapor space and sweeping away VOC. 

### In addition, leakage through holes

, . in

### the envelope (the fabric cover that is used to bridge the space between
+ 

### the 

### seal and the floating roof) 

### or around the envelope attachment bolts can

a 

### be a significant source of loss from shoe seals. Other causes of emissions are: (1) 

### release of dissolved air saturated with VOC 

### because of barometric pressure changes; (2) 

### solar heating of liquid in the rim space which increases liquid vapor pressure and VOC 

### migration; (3)

### evaporation of the liquid which clings to the tank wall when the tank is being emptied (wetting 10sses)~; (4) 

### breathing of the vapor space due tochanges in the ambient temperature or barometric pressure; or (5) 

### changes in

### the bulk liquid temperature. Wind-induced losses are larger than all of these. 2.2 PRIMARY SEALS 

### There are basically three types of primary seals; mechanical shoe seals, resilient foam seals, and liquid-filled seals. Although there are other designs, these three comprise the vast majority of primary seals in

### use today. A 

### weather guard isoften installed over primary seals to protect the seals from deterioration caused by dust, rain or sunlight. Typically, a weather guard is an arrangement of overlapping thin

### metal sheets pivoted from the floating roof to ride against the tank wall. This helps protect the product from contamination, but 

### its effect on gaps and hence wind-induced emissions isvariable. Some weather guard designs could do littleto curb emissions where other tighter designs may be reasonably effective over certain types of primary or secondary seals. Because of the uncertainties associated 2-3------- - - I with emissions contt~ol, the weather guard isnot usually considered as 

# Q effective an emission control device as a secondary seal.



### -

## --- 

# __ -

. 2.2.1 Mechanical Shoe Seal The mechanical shoe seal is characterized by a 75 to 130 cm (30" to 51") high metal sheet (the "shoe") held against the vertical tank wall (Figure 2-2a). The shoe is connected by braces to the floating roof and isheld tightagainst thewall by springs or weighted levers. A flexible coated fabric (the "envelope") is suspended from the shoe seal to the floating roof to close the annular space between the roof and the primary seal. Emissions from the mechanical shoe seal occur from the exposed liquid surface inthe gap spaces between the shoe and the tank wall, and through openings in the envelope or shoe. Close fitting primary shoe seals effectively reduce emissions from the liquid surface inthe gap space, as do shoe-mounted secondary seals (Figure 2-2a).8 Shoe-mounted secondary seals are discussed inChapter 3.0. Emissions are also affected by the envelope and shoe conditions. Holes, tears, or other openings in the envelope or shoe allow direct communication between the annular vapor space and the atmosphere. Through these openings, the wind can scour the vapor space, exiting with VOC laden vapors.

- 2.2.2 Resilient Foam Seal As illustrated inFigure 2-2c,d, resilient foam primary seals fill the annular space between the floating roof and tank wall with a continuous compressible foam log encased ina protective tube. The resiliency of the foam log allows the seal to adapt itself to some imperfections in tank dimensions and even tofill or partially fill some protrusions. The foam log may be vapor-mounted (Figure 2-2c) or 1 iquid-mounted (Figure 2-2d).

# --- TANKi

METALLICWEATHER GUARD,

, 

# ~21 

# y

LIQUIDFILLEDTUBE

a. Metallicshoesealwith shoe-mounted secondary.



# - , 

## , METALLICWEATHER GUARD. 

## / 

## / TANK, TANK WALLs WALL

RESILIENT FOAMLOG'

c. Resilientfoamsealwith weatherguard (vapor-mounted).

## , Figure2-2PrimarySeals 2-5

## (D When a foam seal is vapor-mounted emissions can be much higher than when liquid-mounted. 

### A gap between a vapor-mounted foam seal and the wall allows direct comnunicationbetween the atmosphereand the vapor spacebounded by the seal, the roof, the tank wall, and the product 1

### iquid. When 

### a foam seal is liquid-mounted,the vapor space is eliminated and losses are comparable in magnitude to those for the shoe seal. 2.2.3 

### Liquid-Filled Seal 

### A liquid-filled seal may be 

### a tough fabric band or envelope filled with
a liquid, or itmay be a 20-25 cm (8-10") 

### diameter flexiblepolymeric tube filledwith a liquid and sheathed with a tough fabric scuff band (Figure 2-2b). The liquid is comnonly a petroleum distillate or other liquid thatwould not contaminate the stored product 

### if the tube ruptured. Liquid-fi

### 1 1ed seals are mounted on the product liquid surfacewith no vapor space. They are usually 

## (0 protected by a weatherguard. Losses from tanks equipped with 

### 1iquid-mounted 1

### iquid-fi

### 1led primary 9 

### seals are comparable in magnitude to shoe seals and liquid-mounted foam seals.2.3 REFERENCES 1. Eva1iration ofHydrocarbon Emissions 

### fryPetrol.eum'ti.quid Storage, EPA-450/3-78-012, March, 1978. 2. SOHIO/CBI Floating Roof Emission Program, Interim Report, October 7, 1976. 3. SOH,IO/CBI,Floating Roof Tank Emission-Program, Final Report, November, 1976. 4. Western Oi1 and GasAssociation, Metal1icSealing.Ring. Emission TestProgram, Interim Report, Chicago Bridge & Iron Company, January, 1977. 5. Western Oi1 and Gas Assqciation, Metallic SealingR,ing-Emission Test Program, Final Report, Chicago Bridge & Iron Company, March, 1977. 6. Western Oil and 

### Gas Association, Metal1icSea,lingRing Emission 

# a Test Program, Supplemental Report, Chicago Bridge & Iron Company, June, 1977.

' 7. SOHIO/CBI Floating Roof Tank Ernissi0.n'Test Prog,ram, Supplemental ~eport, Chicago Bridge & Iron Company, February 15, 1977. 8. Floating Roof Seal Development

# - Emission Test Measurement on Proposed CBI Wiper-Type Secondary Seal for SR-1 ,Seals, Chicago Bridge & Iron Company, February 23, 1977. R 9. Measurement of Emissions froma Tube Seal Equip-pedFloating Roof Tank, Pittsburgh-Des Moines Steel Company, October 9, 1978.3.0 CONTROL TECHNOLOGY
Recomended control technology for existing external floating roof tanks with primary foam, liquid-filled, and metallic shoe seals 

### is retrofitting with a rim-mounted secondary seal. A rim-mounted secondary seal 

### is defined
as a continuous device extending from the floating roof to the tank wall, and installed over the primary seal. 3.1 RIM-MOUNTED SECONDARY SEAL A rim-mounted secondary seal is continuous and extends from the floating roof to the tank wall, covering the entireprimary seal. Installed over a mechanical shoe seal, this secondary seal can effectively control VOC that escape from the small vapor space between the shoe and 

### the wall, and through any openings or tears inthe seal envelope which would permit direct communication of the seal system vapor space with the atmosphere (see Figure 3.1.a). Rim-mounted secondary seals are effective in controlling emissions from the liquid and vapor-mounted primary seals shown inFigure 3.1. 1,2,3,4,5 The secondary seals can often be rendered inoperative by cooling and hardening of waxy, heavy pour crude oils. These crudes cause a deposit on the tank wall which is scraped onto the roof when the tank isworked, damaging the secondary seal. Another type of secondary seal that iscommonly installed on external floating roof tanks is a shoe-mounted secondary seal. A shoe-mountedTANK! -~'--WALLI

RIM-MOUNTED SECONDARYSEAL


# - 

# IL /

VAPORSPACE-

.



# - a. Shoesealwithrim-mountedsecondary secondaryseal. r RlMMOUNTED SEAL ,SECONDARY SEAL 

# 1 L/,sryARy

TANK' 

## WALL^

SEAL FABRIC,
RESILIENT FOAMLOG'

VAPORSPACE:

Resilientfoamseal~va~ormounted).~ withrim-mounted secondary Figure3-1 Rim-MountedSecondarySealsseal extends from the top of the shoe to the tank wall (see Figure 2-2a). Shoe-mounted seals do not provide protection against VOC leakage through theenvelope. Holes, gaps, tears, or other defects inthe envelope can allow direct communication between the saturated vapor under the envelope and the atmosphere and the wind can enter this space through envelope defects, flow around the circumference and exit with saturated or near saturated vapors.

Three 30.5 

### m (100 ft)diameter tanks were chosen as base cases for emission calculations; a welded tank with a primary shoe seal

## ,a welded tank with 

### a vapor-mounted resilient foam seal, and a riveted tank witha primary shoe seal. The emission reduction that would occur from installing a secondary seal over each of these base cases isdiscussed below. 3.2.1 Shoe Seals on Welded Tanks When storing a 27.6 kPa (4 psi) vapor pressure product, a rim-mounted secondary seal installed over a primary shoe seal reduces emissions from 11.2 megagrams per year (Figure 3-2a) to 2.8 megagrams per year (Figure 3-2d)- A shoe-mounted seal installed on a primary shoe seal reduces emissions from 11.2 megagrams per year to 5.3 megagrams per year (Figure 3.2~) for the
same product. Emission reductions for various seal configurations arebest illustrated over a range of product vapor pressures by Figure 3-2. The amount of emissions curbed for each progressively stricter control option increases as the TVP of the stored liquid increases. For example, by subtracting (d) from (a) inFigure 3-2, the emission reduction for installing 

## * The emission rates throughout this chapter are calculated for a 30.5 

### m (100 ft)diameter tank storing 41.4 kPa (6 psi) vapor pressure gas01ine with an average wind speed of 16.1 kph (10 mph). The average vapor molecular

. weight was assumed tobe 65, typical for gasoline- Emission rates may be scaled according to'Appendix 

### B,24 a 

# - Primary shoe seal, 

### no secondary seal 

# I 

# Ib 

## - Primary shoe seal with gapped shoe-mounted secondary seal c 

# - Primary 

### shoe seal with tight shoe-mounted secondary seal d 

## - Primary shoe seal with tightrim-mounted secondary seal 2 2

VOC 

### Emi

### s si 0-ns (megagrams/yr)

psi kPa
True Vapor Pressure of Stored Product Figure 3-2. EMISSIONS FROM 30.5 

### rn (100 ft)DIAMETER WELDED GASOLINE TANK WITH PRIMARY SHOE SEAL AT 16.1 kph (10 mph) AVERAGE WIND SPEED 

# 8

# a a rim-mounted secondary seal over a primary shoe seal is only about 5.1 meyagrams per year for s-toring a 27.6 kPa (4 psi) product, but the reduction increases to 18 megagrams per year if the stored 1 iquid has a TVP

-- - -- - -- . - of 69 kPa 110 psi). Emissions from 

### a tank equipped with a shoe seal and shoe-mounted secondary seal storing 41.4 kPa (6 psi) vapor pressure product are 5.3 megagrams per year. Retrofitting this tank with a rim-mounted secondary seal would reduce emissions by only 2.5 megagrams per year. Thus, tanks
now equipped with a primary shoe seal and a shoe-mounted seal are controlled reasonably well and need not be retrofitted with a rim-mounted secondary seal. Nevertheless, the susceptibilityof this system to envelope leaks and gaps make good inspection and maintenance practices imperative. A shoe 

# e seal without any secondary seal should not be retrofitted with a shoemounted secondary. 3.2.2 Liquid-Mounted Resilient Foam and Liquid-Filled Seals on Welded Tanks Liquid-mounted resilient foam and liquid-filled primary seals have approximately the same emission rates as primary shoe seals and exhibit the

same emission reduction trends with control (see ~igure 

### 3-2,c); 

# ow ever in some cases the stored liquid may be harmful tothe seal, making liquidmountina im~ractical. 3.2.3 Vapor-Mounted Resilient Foam Seal on Welded Tank As discussed in Section 2.2.2, this primary seal has the potential for high emissions when vapor-mounted. These emissions can be effectively controlled by retrofitting with a rim-mounted secondary seal provided the gap between the secondary seal and tank wall iscarefully controlled. This is 

## @ illustrated in Figure 3.3 C

### - 500 

# -

400 

# -

-



# - 300 

### -

-



# - 200 

## - 

# -

-

V

h 45 

### - a 

## - Foam seal mounted 

### inthe vapor space, gapped, no secondary seal 40 

# - b

# - Gapped foam seal with gapped rim-mounted secondary seal VOC Emissions (megagrams/yr) 35 

## - d no secondary seal



## - Gapped foam seal mounted inthe vapor 30 

## - space with tight rim-mounted secondary seal e 

## - Tight foam seal mounted inthe 25 

### - vapor space with a tight rimmounted secondary seal 20 

## -
15 

### -

2 3 4 5 6 7 8 9 10 11 psi
I I I I I I I 10 20 3 0 40 50 60 70 True Vapor Pressure of Stored Product Figure 3.3. EMISSIONS FROM 100 FT DIAMETER WELDED GASOLINE TANK WITH PRIMARY FOAM SEAL, 16.1 kph (10 mph) AVERAGE WIND SPEED 3-6Emissions from a tank storing a 41.4 kPa (6 psi) vapor pressure product equipped with a vapor-mounted resilientfoam seal are 18.6 megagrams per year,if the primary seal has a tight commercial fit(Figure 3-3c) and 212 megagrams per year if the primary seal 

### is slightlygapped (Figure 3-3a). With a tight rim-mounted secondary seal, emissions from a gapped primary seal arereduced from 212 megagrams peryear to4.3 megagrams per year (Figure 3-3d). When installed over a tight primary seal, emissions are reduced from 18.6 megagrams per year to2.2 megagrams peryear (Figure 3-3e). With a gapped primary seal and a gapped secondary seal, emissions are 95.3 megagrams per year (Figure 3-3b). 3.2.4 Riveted Tanks ~iveted 'tanks present special problems regardless of primary seal design. The primary seal 

### must ride over 

### the protruding rivet heads when 

### the tank 

### is being worked, creating gaps. If the primary seal stops or is riding on a
row of rivet heads,the gaps can be nearly continuous and the wind-induced emissions extremely high. The portion of 

### the seal riding on the rivets (and the riveted members) depends on design, and varies with location in the tank. Emissions based on experimental tests conducted to evaluate a shoe seal incontact with a "worst case" simulated rivet row are shown in

. . Figure 3-4a. '6 Installation of a rim-mounted secondary seal over this primary shoe seal reduces emissions from 39.9 to22.3 megagrams peryear based on one 

### test and to7.1 megagrams per year based on another (the only difference being the rivet row design withwhich the,secondary seal was in contact), 

### Atmore

. , favorable roof locations ina riveted tank, emissions will be lower. Emissions from a welded tank with a rim-mounted secondary

### were 2.8 megagrams per year.loo " a 

## - Shoe seal, no secondary seal b

# - Shoe seal with rim-mounted secondary 90 

## - seal, Position I



## - c 

## - Shoe seal with rim-mounted secondary 80 seal, Position I1 d 

## - Welded tank with shoe seal and 

### rimVOC Emissions 70 mounted secondary (megagrams/yr) 60 

### - 50 

### - 40 

# - 30 

# - 20 

## - 10
,

I I I I I I I I 1 1,2 3 I 4 I 5 6 I 

### 7 I 8 9 I 101 11psi 10 20 3 0 40 50 60 7 0 kPa True Vapor Pressure of Stored Product Figure 3-4. EMISSIONS FROM 30.5 

### m (100 ft)DIAMETER RIVETED GASOLINE TANK WITH PRIMARY SHOE SEAL AT 16.1 kph (10mph) 

### AVERAGE WIND SPEED

### Rivet heads are particularly harsh on primary seals, and seal condition may deterioratemore rapidly. Frequent i

### nspections and good maintenance practices must be followed tocontrol emissions from riveted tanks.3.3 REFERENCES 1. SOHIO/CBI Floating Roof Emission Program, Interim Report, October 7, 1976. 2. SOHIO/CBI. Floating Roof Tank Emission Program, Final Report, November, 1976. 3. Western,Oil and Gas Association, Meta,lic ,SealingRing Emission Test Program, Interim Report, Chicago Bridge & Iron Company, January, 1977. 4. Western Oi1 and Gas Association, ~eta1,ic 'Sealfng-' Ring. 

### EyJssion Test Program, Final Report, Chicago Bridge & Iron Company, March, 1977. 

### R 5. Measurement of Emissions,froma Tube.Seal Equipped Floating Roof Tank Pittsburgh-Des Moines Steel Company, October 9, 1978. -3 6. 

### Western Oi1 and Gas Associ,ation, Metallic Sealing Ring Emission Test Program, Supplemental Report, June, 1977.4.0 COST ANALYSIS

4.1.1 Purpose The purpose of this chapter 

### is topresent estimated costs for control of volati1 e organic compound (VOC) emissions from existing external floating roof petroleum liquid storage tanks. 4.1.2 Scope Estimates of capital and annualized costs arepresented forcontrolling emissions from existing external floating roof storagetanks. The estimates pertain towelded and riveted steel tanks used for storing gasoline. 

### Current standards forfloating roof tanks require the

### use of singleclosure (primary) seals, so thecost of control is limited totheadditional cost of installing (retrofitting) a secondary seal on existing tanks. Control costs are

. , developed fora model existing external floating roof tank with a diameter of 30.5 

### m (100 ft)

### ,a height of 12.2 

### m (40 ft)and a storagecapacity of 8,910,000 liters, A range of cost effectiveness ratios arepresented for storinggasoline that allow for varying operating conditions, locations, and control costs of tanks, 4.1.3 Use of Mode1 Storage Tanks Gasoline storagetanks vary in sizewith typical diameters ranging from less than 9.1 

### m (30 ft)tomore than 91.5 

### m (300 ft). Since itwould be impractical todetermine costs forall tank sizes, a middle sizemodel
was selected for this cost analysis. Table 4-1 presents the cases evaluated
4-1Tab1e 4-1. +TECHNICAL PAMETERS USED INDEVELOPING GASOLINE STORAGE TANK CONTROL COSTS

I. StorageTank Size: Diameter: 30.5 m (100 ft) Height: 12.2 m (40 ft) Capacity: 8,910,000 liters 8,910 m3 (55,000 bbls) 11. Wind Speed and Vapor Pressure 9.7 kph (6 mph) 13.8 kPa (1.52 psi) 16.1 kph (10 mph) 27.6 kPa (2.0 psi) 

### f N 22.5 kph (14mph) 41.4 kPa (6.0 psi) 69.0 kPa (10.0 psi) 

### III. VOC Control Efficiencies: (see Table B-2, Appendix B) Rimmounted secondar-yseals on floating roof tanks:
a. Case I

# - Welded tank withthe following primary seals

## - shoe seal, liquid-mounted foam seal, or 1iquid-mounted 1iquid-fi1ledseal 

## - (75%) b. Case I1

# - Welded tank withthe following primary seal

# - a vapor-mounted foam seal

# - (84

# - 88%)
C. Case 111

# - Riveted tank withthe following primary seal

# - a metallic shoe seal 

# - (45%)w a I 4 

# 0 

# a Table 4-1 (Continued) TECHNICAL PARAMETERS USED INDEVELOPING SASOLINE STORAGE TANK CONTROL

a IV. Emissions Before Control (Mg/yr) :, CASE Wind Velocity True 

### Vapor

Pressure 13.8 kPa



### f CJ NOTE: All cases

# - primary seals

# - no secondary V. .EmissionAfter Control (Mg/yr) : a CASE Wind Velocity True 

### Vapor

Pressure

NOTE: A11 cases

# - A rim-mounted 

### 1secondary was used over the specified primary seal.Table 4-1 (Continued) TECHNICAL PARAMETERS USED INDEVELOPING GASOLINE STORAGE TANK CONTROL COSTS

VI

# . Emissions Controlled (Mg/yr) :

### a
CASE Wind Velocity True 

### Vapor

Pressure

- aReference Appendi#

### -Aand 

### B

# .

### and the technical parameters used in

### the analysis. The parameters were selected as being representative sf average annual wind 

### speed on the United States Gulf Coast, East Coast and West Coast, respectively, and expected ranges of product true vapor pressure at stored temperatures. Emissions and emission reductions arebased on extrapolations from a 6.1 

### m (20 

### ft) diameter test tank to the full sizemodel tank (see Appendix A 

### and B).

# ' Itwill 

### be noted from Table B-2, Appendix B, 

### that Cases I1 and I11 do not represent predictions of maximum achievable emission reductions. .Accordingly, cost effectiveness for these cases (see Section 4.3)


### are conservatively high. 

### 4.1.4 Bases for Capital and Annualized 

### Cost Estimates Capital cost estimates represent the total investment required to purchase and retrofit the control systems on existing storage tanks including the cost of cleaning and degassing tanks. Costs for research and development, lost time during 

### installation and start-up, and other highly variable costs are not included in

### the estimates, These costs vary
sowidely from case tocase and from situation to situation that itis 

### virtual1y impossible torealistical ly quantify these costs. A11capital costs reflect second quarter 1978dollars. Annualized control cost estimates include operating labor, maintenance, credits for petroleum savings, and annualized capital charges. Cost estimates were obtained from an EPA 

### contractor, equipment vendors, tank service companies, local airpollution control reports, and an API contractor. Credits for gasoline savings due to emission control have been calculated from the emission reductions projected from the experimental tests.

### The annualized capital charges are sub-divided intocapital recovery costs (depreciation and interest costs) and costs for property taxes, insurance, and administration. Depreciation and'interest costs have been computed using a capital recovery factor based on a 10year secondary seal lifeand an interest rate of 10 percent per annum. Costs for property taxes, insurance and administration are computed at4 percent of the capital costs. All 

### annualized costs arefor one year periods commencing with

### the second quarter of 1978. 4.2 CONTROL OF 

### EMISSIONS FROM EXTERNAL 

### FLOATING ROOF STORAGE TANKS 

### 4.2.1 Mode1 Cost Parameters Cost parameters used in

### computing secondary seal control costs are presented in

### Table 4-2. These parameters arebased on actual cost data from 

### an oil industryjournal

# ,* a National Energy Information Center monthly publication,3 

### an EPA

### c~ntractor,~ seal vendors,5y6

### tank service cmpanies,7y8 

### 1 ocal airpol1 uti 

### on control reports,9y10

### an API contractoP,11 and EPA 

### estimates, 4.2.2 Control Costs Table 4-3 shows the estimated costs of controlling VOC 

### emissions from themodel floating roof storage tank. The estimates pertain to existing welded and riveted floating roof petroleum liquids tanks that are equipped with

### primary closure seals. The installed capital costs are average industry costs of retrofitting a secondary seal on the model storage tank. The annual operating and maintenance costs areestimated based on normal maintenance and inspection programs. The annualized capital charges consist of the capital recovery costs using 

### capital recovery factorwith 

### 10percent annual interest rate and 10year secondary seal lifeplus 4 percent of 

# 0 4-6

### Table 4-2. 

### COST PARAMETERSUSED IN COMPUTING CONTROL COSTS



### I. Gasoline valuea



### II. SecondarySeal Value: 

### A. Installed (Retrofit)Capital Costs:b Tank with primary seal : 

### $176 per 1

### inear m. B. 

### Annual Maintenance cost:' 5% of installed capital cost plus annual inspection charge of $200. C. Replacement ~ife:'~ 10

### years

b~verage installed cost of retrofitting secondary seal per References 4,5, 6,7,8,9 

### and 10. 

### '~nnual maintenance cost per EPA estimate and annual inspectioncharge per Reference 12. 

### d~xpected replacement life per References 

### 4and 8.installed capital cost for property taxes, insurance and administration. The total annual control system costs are the sum of the annual operating and maintenance costs and annualized capital charges. Annual petroleum credits from control1 ing (reducing) emissions are not included i

### n these costs. From Tab1e 4-3, itcan be seen that the average instal1 ed capital cost of a secondary seal on a 30.5 

### m (100 ft)diameter tank is $16,900 and the total annual control system cost average is $4,400. 4.3 COST EFFECTIVENESS Table 4-4 presents the cost effectiveness ratios of controlling gasoline emissions from themodel existing floating roof tank. The $100.64/m3 price ' for gasoline was established by averaging the per barrel prices of regular, premium and no-lead gasoline from three different areas. The per barrel price was then converted to a $/m3



# . The cost effectiveness ratios for crude oil may be approximated by mu1tiplying the cost effectiveness ratios in Table 4-4 by 1.38. For the development of this factor see Table 4-5. This factor reflects the different average values and emission rates of the two liquids. The amount of emissions controlled (reduced) varies with wind velocity, absolute vapor pressure and control efficiency. Higher wind velocity, greater vapor pressure and higher control efficiency will result 

### ina greater quantity of controlled emissions and larger petroleum credits; opposite (low) values will result 

### ina smaller quantity of emissions controlled and lesser petroleum savings. Since a range of the above controlling factors is needed to cover the typical range 0.f tank operating conditions and locations, cost effectiveness ratios have been determined using various vapor pressure and wind velocity values for the factors and control system costs. 4-8~ Table 4-3. CONTROL COST ESTIMATES FOR

.. MODEL EXISTING GASOLINE STORAGE TANK

- Facility Size: 30.5 mdiameter (100 ft) 12.2 m height (40 ft)

8,910,000 1 iteG-sii%i-ty (55,000

- .--- bbl)

--. - - Faci1i tyType: External Floating Roof Tank
Control Device: RimMounted Secondary Seal
Type of

### Primwy 

### Closure Sea! : CASE- I CASE 'II CASE 111

. - InstalledCapital Cost ($000):a 16.9

, Annual Operati g and Maintenance 1 .I Cost ($000):

# 6

'

### f aAnnualized Capital Charges ($000): 3.3 Total Annual Control System Cost 4.4 (Not including petroleum

credits)($000):d + a~verage installedcost ofretrofitting secondary seal on existing floating rooftank per References 4,5,6,7,8, and 9. 

### I b~nnual operating and maintenance cost per EPA estimate and annual inspection charge per Reference 12. 'capital recovery costs (using capital recovery factor with 10%annual interest rate, 10year secondary seal life)

plus 4%of installed capital cost for propertytaxes, insurance, and administration. d~um ofannual operating and maintenance cost plus annualized capital charges; but, does not include petroleum credits (savings).0 Table 4-4. COST EFFECTIVEMESS OF COlNTROLLIF(GFLOATINGROlOFGASOLIJE-STORAGZNKS 5 SEAL. LIQUID-MOUNTEDkoAM StALs LIQUIbMOUNTED LIQUID-FILLED SEAL Wind Velocity 

## ! 9.' kph 16. koh True Vapor Pressure


## -- 11.4 kPa 59.0 kPa 

# - It,) kPa 159.0 kP 13.8 kPa. 27.6 kPa 

# - 13.8 kPa 27.6 kPa
VOC EmissionsControlled (Reduced) (Mg/yr)a 

# 1 1.I6 

# ( 2.53 4.15 8.84 2.36 5.12 Annual Petroleum ~avi (Credits) ($00,0/yr) 

# 1 (1.33) (.35) (-77) Total Annual Control system

Cost ($000/yr) 

### I 4.4 4.4 4.4 4.4 4.4 4.4 Net Annual Cost (credit)
.. 

# 1 1 )c 

# 1 4.24

# 1 4i2 3.77 3.O7 4.05 3.68 (bO~0Olyr Cost (credit)per Mg of

Control ed Emissions 3655 1589 908 347 1716 709 

# a (BIMg)
I I I1

## - WELI D TANK

# - RIMARY F iM SEALJ

_ - .- -- . . ! d Wind Velocity <ph True Vapor Pressure $1.4 kPa 13.8 kPa
VOC Emissions Controlled (Reduced) (Mgl~r)~ Annual Petroleum ~a;i gs (Credits) ($000/yr)

## 1 Total Annual Control

System Cost ($000/yr Net Annual gost (credit) ($000/yr Cost (credit)per Mg

of Contr lled Emissions ($lW~ . QR-MOUNTED.-- -- Tab1.e4-4 (continued). COST EFFECTIVENESS OF CONTROLLING FLOATING ROOF GASOLINE STORAGE TANKS

..... - ...... 

### - CASE 111

# - RIVETED

### 2% 

### WXITPRIMARY-SHOE-SEAL

- I Wind Velocity 

### I 9.7 kph kph I I I True Vapor Pressure 

# 1 13.8 k~al 27.6 k~al 41.4 kPa (6 11.4 kPa
VOC Emissions Contr;l led (Reduced) (Mg/yr) Annual Petroleum Savi gs (Credits) ($000/yr)

### ! Total Annual Control System

Cost ($000/yr) Net Annual gost (credit) ($000/~r) Cost (credit) per Mg of

Controlled Emissions ($/~g Id
"per Table 4-1. b(~missionsBefore Control) x (VOC Control Efficiency) x (Recovered Petroleum Liquid Value) t (AverageLiquid Density) 'sum ofAnnual Petroleum savings (Credits) and Total Annual Control System Cost. d(#et Annual Cost (credit) ) t (VOCEmissions Controlled (~educed) ).

### For the model existing gasoline floating roof tank, it should be noted from Table 4-6that the cost effectiveness ranges from a cost of $3,665 to a credit of $66 per Mg of controlled emissions. The corresponding cost effectiveness ratios of crude oil emission controlled using the 1.38 factor, vary from 

### a cost of $5,044 to a cost of $25 per Mg. Thus, due to the higher value and emission rate of gasoline, the cost effectiveness for crude oil ranges from $66 to $1389 higher per Mg of controlled emissions than for gas01ine. 

### 4.4 ECONOMICS OF SCALE The preliminary cost of retrofitting a secondary seal to existing floating roof tanks were also developed for a 10.7 m (35 ft) diameter tank and a 53.3 

### m (175 ft) diameter tank. These were developed to check the 1

### inearity of the scaling effect on cost effectiveness developed for our model tank. 

### As could be expected there were some dis-economies of scale in the cost effectiveness of the smaller tank. This resulted in the smaller tank cost effectiveness ($/Mg of emissions control

### 1ed) being approximately 105 percent of the cost effectiveness of the 30.5 m (100 

### ft) diametermodel tank. Also, as expected, the larger tank had some economies of scale. This resulted in the 

### 1arger tank cost effectiveness ($/Mg of emissions control led) being approximately 85percent of the cost effectiveness of the 30.5 m (100 

### ft) diametermodel tank. IC O m L n N mm*- a m -4.5 REFERENCES 1, "Meghods for Extrapolating Chicago-Bridge and Iron 6.1 M 

### (20.Ft,J. Test

..- -- Tank Results to Full SivzeTank,!' EPA--0APQS Draft Report,
.- April, 1978. 2. "Refined-products prices", Oil and Gas Journal, March 27, 1978. 3. Monthly Energy Review, June 1978, office of ~nercj~ Information and Analysis, National Energy Information Center, 4. R. Bakshi, Pacific Environmental Services, Inc.; Santa Monica, Cal. Petroleum storage tank and seal cost data memo to fileby P..A. Quaney, U.S. Environmental Protection Agency, dated November 2, 1977. 5. J. Hunter, \iestsrn Petro-Chemical Co., Los Anyeles, Cal

# . Petroletini

~ storage tank seal cost. data memo to file by R.A. Quaney, U.S. Environniental Frotection Agency, dated November 2, 1977. 

# - 6. K. J. Kolkmeier, Pittsburgh-Des Moines Steel Co., Pittsburgh, 

### Pa. Petrolcim storage tank seal cost data memo to fileby R.A. Quaney,U.S. Environri;mtal Protection Agency, dated November 2, 1977. 

### 7. H.R. Wiggs, Tank Service, Inc., Tulsa, Oklahoma. Letter toR. 

### tl. Schippers,' U. S. Environrzentai Protection Agency, dated May 18, 1977. 8. J. Mulkey, Tank Service, Inc., blilniington, Del. seal cost data memo to fileby R.A. Quaney,U.S. Agency, dated November 2, 1977. 9. California Air Resources Board. Public hearing Rule 463 of SCAQHD, June 25, 1976. 10. Califoriiia Air Resources Board. Pub1ichearing Rule 463 of SCAQMD,March 25, 1976. Petroleum storage tank Environmental Protection



# - Proposed Ammendnents to.



## - Proposed A~nnendicents to
11. Dr. W. Sheppard, Battelle Columbus Laboratories

### ,Col ulnbiis

### ,Ohio. Petroleun liquids transportation cost,datamemo to fileby R.A. Q~laney, U.S. Environmental Protection Agency, dated EIovei~lber 2, 1977. 12. R. H. Schippers, U.S. Environmental Protee tion Agency. Me1i10on Sscondar-y S2als on New Petroleum Product Storage Tanks, dated I4ay 25, 1977.5.0 RECOMMENDED REGULATIONS, COMPLIANCE TEST METHOD, AND RECORD KEEPING
The affected faci1 ities are external floating roof storage tanks with aciti es greater than 150,000 1 iters (950 bbls) containing petroleum liquids with a true vapor pressure greater than 10.5 kPa (1.5 psi)

# . 5.1 RECOMMENDED REGULATIONS Recommended regulations for 

### the storage of petroleum liquids in external floating roof tanks are: 1

# . Except where specifically exempted (See 5.1.4), a11 external floating roof tanks with capacities greater than 150,000 liters shall be retrofitted with a continuous secondary seal extending from 

### the floating roof to

### the tank wall (a rim-mounted secondary) if: (a) the tank isa welded tank, the true vapor pressure of the contained liquid is 27.6 kPa (4.0 psi) 

### or greater,and the primary seal is one of the following:(i) ametalli c-type shoe seal, a liquid-mounted foam seal,
or a liquid-mounted liquid-filled type seal, 

### or (ii) any other closure device which can 

### be demonstrated equivalent to the above primary seals. (b) the tank isa riveted tank, the true vapor pressure of the

. -- - - - - - - contained 1 iquid is 10.5 kPa (1.5 psi) or greater,and the closure device is as described in 5.1.1 (a).(c) the tank isa welded or riveted tank, the true vapor pressure of the contained liquid is5 10.5 kPa (1.5 psi) and the primary seal is vapor-mounted. When such primary seal closure device can be demonstrated equivalent to the primary seals described in5.1.9 (a), the provisions of 5.1.1 (a) apply. 2. The seal closure devices shall meet the following requirements: (a) there shall be no visible holes, tears, or other openings in the seal(s)or seal

### (s)fabric. (b) the seal(s)must be intact and uniformly in place around the circumference of the floating roof between the floating roof and the tank wall. (c) the gap area of gaps exceeding 0.32 cm (1/8 inch) in width tiaween the secondary seal installed pursuafit to 5.1.1 (c)and the tank wall shall not exceed 6.5 cm2 per 0.3 

### m of tank diameter (1.0 i n2 per foot of tank diameter). 3. All openings in the external floating roof, except for automatic bleeder vents, 

### rim space vents,and leg sleeves, are to provide a projection below the liquid surface. The openings are to be equipped with a cover, seal
or lid. The cover, seal or lid isto be in a closed position at all times except when the device 

### is in actual use. Automatic bleeder vents are to be closed at all times except when the roof isfloated off or landed on the roof leg supports and 

### rim vents are to be setto open when the roof isbeing floated off the roof leg supports or at the manufacturer's recommended setting. Any emergency roof drain isto be provided with a slotted membrane fabric
cover or equivalent cover that covers at least 90 percent of the area of the opening. 4. The following are specifically exempted from the requirements of 5.1.1:

### (a) external floating roof tanks having capacities less than 1,600,000 liters (10,000 bbls) used to storeproduced crude oil and condensate prior to custody transfer. 

### (b) ametallic-type shoe seal in

### a welded tank which has a secondary seal from the top of the shoe seal to the tank wall (a shoe-mounted secondary). (c) external floating roof tanks storingwaxy, heavy pour crudes. 5. 

### External floating roof tanks with 

### a closure orother devices installed which will control VOC 

### emissions with an effectiveness equal to or greater than the seals requi red in

### 5.1.1 (a). L 

### 5.2 COMPLIANCE TEST METHOD 

### 1. Compliance for external floating roof tanks does not require measurement of the primary or secondary seal gap area, except as required tomeet 5.1.2 (c)

## ,and can be determined by visual inspection. 2. For compliance with 

### 5.1.2 (c), the secondary seal gap area can be determined by measuring the length and width of the gaps around the entire circumference of the secondary seal. Only gaps' greater than or equal to 0.32 cm (1/8 inch) shall be used in

### computing the gap area. The area,ofthe gaps can be accumulated to determine compliance.
5.3 MONITORING AND RECORD 

### KEEPING Itis 

### recommended that the routine visual inspections be conducted annually
or at shorter intervals, and that the secondary seal gap measurements be made annually. Evidence of any type of malfunction (asnoted above) is

### to be recorded. When a liquid having a true vapor pressure greater than 7.0 kPa (1.0 psi) is 

### stored in

### an external floating roof tank not equipped with a secondary seal01- 

### a~proved a1ternative control technology (see 

### 5.1.5), 

### a reco~d should be 

### maintained for no more than twoyears of the averagemonthly storage temperature,the type of liquid,and the Reid vapor pressure of the liquid. The true vapor pressuremay be determined by using the averagemonthly storage temperature and typical Reid vapor pressure of the contained liquid
or from typical availabledata on the contained liquid. Supporting analytical data can be requested if there is a question on the values reported.APPENDIX A SELECT IONOF EXPERIMENTAL TESTSFOR WIND INDUCED EMISSION CALCULATIONS


### An experimental 20' P) test tank atthe Plainfield, Illinois, Research Center of Chicago Bridge and Iron Company (CBI) has been extensively used by industry to investigate the mechanisms causing hydrocarbon emissions from f 1 oating roof tanks. s233y495y6 A large number of tests were conducted on various types of seals to study the effect of parameters such as wind speed, gap between the seal and tank wall, and the leak rate of the shoe seal vapor space system on hydrocarbon emissions. Secondary seal efficiency was evaluated. Methods for extrapolating specific test results from the 20' P) test tank to full size tanks have been developed. This appendix describes the methodology used inselecting specific tests for extrapolation which
are considered representative of average field tank conditions. A. METHODOLOGY OF SELECTION The selection of CBI tests on primary seals which represent the "average" primary seal gap in the fieldwas based on EPA's analysis of

r tank inspections made in 1976 by regulatory agencies in California. A total w of 398 tanks were included in this analysis; 163welded tanks with primary shoe seals, 141 welded tanks with non-metallic seals of either the foam or liquid type, and 94 riveted tanks with shoe seals. Tanks equipped with a weather guard over the primary seal were included. Excluded were 47 tanks Lwhich were reported tohave either a "double" or "wiper" secondary seal. In the inspections, gaps between the primary seal and tank wall were measured with probes or rods of varying dimensions. The width and length of each gap was recorded. Itwas not possible to derive from the inspection data an average gap width inthe field that was comparable to a specific CBI test, nor a range of gap width patterns which could be compared to one 

### or several CBI tests. The final selection was made by comparing the gap areas inthe tanks 2 tnspected tothe gap area inthe CBI tests expressed as in /ft of tank diameter. 

### B. SELECTION OF WELDED TANK WITH SHOE SEAL AND RIM-MOUNTEDSECONDARY SEAL A number of tests were made with single shoe seals having gaps up to 1 112 inches simulated by forcing the primary seal away from the tank wall with spacer bar arrangements. 73899 In all of these tests the leakage rate for the seal system (the space bounded by the shoes, the envelope, the rim space and liquid) averaged about 0.032 SCFM per foot of tank diameter at 1 112 inches of H20 pressure drop. A leakage rate of 0.50 SCFM 

### at 1.5 inches of H20 is considered commercia1ly achievable. Further research was conducted by CBI to establish the relationship between shoe seal emissions and leak rate. The leak rate of seals inspected inCalifornia isunknown. The final determination of thebase case forcalculating wind induced emissions for a primary shoe seal
was made by; (1) using themethodology described in (A), and (2) using a 

### test that simulated a leak rate of 0.8 SCFM/ft of tank diameter at 1.5 inches of H20 pressure drop. This leak rate appears reasonable based on field test data and the California inspections which revealed relatively few tanks with openings
or tears 

### inthe envelope. A-2- -- A comparison of the gap area in the inspected tanks with specific CBI tests is shown in Table A-1. Selected tests on envelope leak rate simulations
are also shown inthis table, Itwill be noted from Table A-1 that 89 percent of the tanks had gap
areas (inZ/fttank diameter) equivalent to tests whgre emissions remained relatively unchanged from a shoe seal with a tightcommercial fitto one having a gap(s) up to one inch.

. - Test W-12 has a comnercial fitand simulates a seal system vapor space leak rate of 0.8 SCFM per ftof tank diameter at 1.5" H20 W-12 was selected as the base case forwind induced emission calculations. A rim-mounted sec0ndar.y over the W-12 primary seal was then judged tohave at least a 75 percent efficiency based on numerous.secondary seal single seal combinations tested with var.ying gaps inthe primary, secondary, or both, &ring the same test. ' C. 

### WELDED TANK WITH SHOE SEAL AND SHOE-MOUNTED SECONDARY SEAL A secondary wiper seal mounted on the shoe was tested with a tight comnercial fitand with gaps.''' The efficiency of the wiper ineach of these tests was used to estimate the base case (testW-12) emission reductions. D. RIVETED TANK WITH A SHOE SEAL AND RIM-MOUNTED SECONDARY Test W-28 was made with a single shoe seal incontact with simulated

. - .- - -- :.. . .. - .- horizontal and vertical rivet rows.!] Table A-2 gives a comparison of the gap
area in the inspected tanks and the gap area inthis test configuration, The gap area ina riveted tank will vary withthe position of the roof in the tank and the rivet patterns in W-28 represent a condition where gaps may be expected tobe atmaximum. This isjudged to be the reason why the inspectedTAB'LEA-1. SEAL GAP AREA IN INSPECTED WELDED TANKS WITH SHOE-SEAL COMPARED TO CBI EXPERIMENTAL TESTS

20 Ft. Diameter Experimental Test Tank Tanks Inspected Envelope Gaps inSeal Leakage Width T'otal ~rea~ [nch' per Ft. Number Percent at 1

### .5" Hz0 (inch) (inch 2, Tank Dia. 0 2 2 (%tank

circ.)

4
0 0 0 0

a~apor pressure

# - 5 psia, wind speed

# - 10mph. 

### ? b~ncludes area of tapers P 0 

### 7 1.75 in2/ft tank dimeter d> 1.75 4.3 i n2/ft tank diameter e> 4.3 79.35 in2/ft tank diameter f> 9.35 

### 714.7 i n2/ft tank diameter Includes only one tank > 14.7 Continuous gaps thismagnitude not recorded ininspections; these tanks are included inW-26 (%).gap areas, taken atrandom roof positions, are considerably lower than W-28. The inspected gap areas inthe riveted tanks are substantially greater than in the welded tanks inTab1e A-1

# . Also, the numbers of gaps in the riveted tanks
were farmore numerous than inthe welded tanks and gaps inriveted tanks may exhibit the characteristics of the continuous gap intestW-6. A rim-mounted secondary over W-28 was tested incontact with two rivet patterns, tests W-29 and W-31. Emissions were calculated for both these tests and reductions obtained by subtraction from W-28. E. RESILIENT FOAM SEAL MOUNTED IN RIM VAPOR SPACE OF WELDED TANK Two tests were selected for the single seal. A single seal test with a "tight commercial fit" (Test 13, 16, 20, 21) and the same seal with gaps (Test 23). 12,13 A rim-mounted secondary with a "tight commercial fit"was installed ineach of the above tests. Emissions were then calculated for each (Test 32 and 34A) and mission reduction obtained by difference. Inspection data for "non-metallic" seals are presented inTable A-3. The seals were not identified by type (liquid filled or foam) or location (rim vapor space or inthe liquid surface). For comparative purposes emissions were developed for a secondary seal with gaps (Test 34B) installed over a primary seal with gaps (Test 23).ra, a, L 0 3 .r cn V) 0 a, C, L n w 

# - L n o an s (d 3 > (d nREFERENCES 1. SOHIO/CBI Fl.oat.ingRoof Etyission Program, Interim Report, October 7, 1976. 2. SOHIO/CBI Floating Roof Tank Emission Program, Final Report, November, 1976. 3. 

### Western Oil and Gas.Association, Metallic Sealing Ring Emission Test Program, Interim Report, Chicago Bridge & Iron Company, January, 1977. 4. Western Oi1 and Gas Asspciation,Metal1ic Sea1.i.n-g Ring,,Emission Test Program, Supplemental Report, Chicago Bridge & Iron Company, June, 1977. 5. SOHIO/CBI Floating Roof Tank Emission Test Program, Supplemental Report, Chicago Bridge and Iron Company, February 15, 1977. 6. Floating Roof Seal Development 

## - Emissio~n Test Measurement on Proposed CBI Wiper-Type Secondary Seal for SR-1 Seals, Chicago Bridge & Iron Company, February 23, 1977. 7. Mestern Oil and. Gas Association, Metallic Sealing Ring Emission Test Program, Final Report, Chicago Bridge & Iron Company, March, 1977. Reference 4, Op. C3t. Reference 2, Op. Cit. Reference 6, OP. Cit. Reference 4, Op. Cit, Reference 1

## ,Op. Cit. Reference 2, Op. Cit.APPENDIX B CALCULATION OF WIND INDUCED EMISSIONS FROM EXPERIMENTAL TESTS
A. EQUATIONFOR WIND INDUCED EMISSIONS 4 Emissions were extrapolated from the 20' 

### fl test tank selected tests to

u the 100' 

### 0 model gas01ine storage tank using the following equation:' y293

Where: 

### EF = Emissi'ons from full sizetank, megagramslyr Ep = Emissions from testtank at5.0 psi, lbs/day PF = Vapor pressure of stored product in full size tank, psi DF = Diameter of full size tank, feet = 100 MHC = Molecular weight of full size tank hydrocarbon emissions (hydrocarbonvapor molecular weight), 1 bs/lb mole = 65

B. Ep FOR THE TEST TANK In each specific test emissions were measured atvarying simulated wind speeds. These results were then plotted to yield a smooth "Epvs Windspeed"
curve for each test.4 Ep values for the selected tests and various wind speeds read from these plots are given in Table B-1.

i_ In the 100' !ilmodel tank analysis wind speeds of 6 mph, 10mph, and 14 mph
were used. These represent mean average annual wind speeds on the West Coast, Gulf Coast and East Coast, respectively. B-1-- TABLE B-1 

## - Ep (lbslday) 

### vs Wind Speed (mph) (20' Test Tank 

## - 5.0 psi)

Sel ected Tests

Welded Tank 

## - Shoe Seal Single Seal (W-1 ,W-2 W-1R) Single Seal (W-12) ~im-~ounted Secondary (25% W-12) ShoeSvlounted Secondarj Tight Fit (6-2) Shoe-Mounted Secondarj Gaps (C-1) Riveted Tank 

## - Shoe Seal Single Seal (W-28) ~im41ounted Secondary (W-29) Rim-Mounted Secondary (W-31) Welded Tank

# - 'Foam Seal In Rim Vapor Space Single Seal (13,16,20, 21

### 1 Single Seal (23) Rim

### -MOM ted Secondary (34A) Rim-Mounted Secondary (32) Rim-Mounted Secondary (34B)C. 

### EMISSION CALCULATIONS 1 Primary Seal With andWitbut Rim-Mounted Secondary

, Using 

### the equation in 

### (A) emissions were calculated for each of the C 

### selected tests atwind 

### speeds of 6 mph, 

### 10mph 

### and 14mph, 

### and stored gas01ine

c 

### .vaporpressures of 2 

### psi, 4 psi, 6 

### psi and 10,psi. Emissions reductions are the differencebetween the single seal case (base case) and secondary seal case (control case). The results for a model 100' tank storing gasoline whose hydrocarbon emissions have a molecular weight of 65.0 1 bs/lb 

### mole are given in

### Table 8-2. C.2 

### Shoe Seal With 

### Shoe-Mounted Secondary The shoe mounted secondary was tested on-aprimary shoe'seal with a vapor space leak rate of < 

### 0.1 SCFM per ftof tank diameter,

### (Tests-C-1 

## ,C-2, 

### and W-1R). Emissions controlled in

### Test C-1 and C-2 were calculated atvarious wind 

### speed and vapor pressure parameters. The emissions controlled were then subtracted from the emissions in the base case, Test W-12, to determine emissions from a shoe

### mounted secondary. The results are given in Table 8-3.TABLE 8-2

## - WISSIDNS FM 1010' $ GASOLINETANK (MEGAGWSIYR)

Experimental Test IeldedTank-Shoe Seal

Shoe Mounted Secondary Adj.C-2 0.81 1.77 2.91 AEmissions (SeeTab1e3) 0.74 1.59 2.62 Shoe Mounted Secondarv AEmissions " Ad.1.C-1 (see 3, 

### 1 

# 1 1.07

0.48 

### 1 

# 1 2.33 1.03 

### 1 

### j 3.84 1.69 :ivetedTank-Shoe Seal

Rim Mounted Secondary AEmissions Rim Mounted Secondary AEmissions 5.78 12.33 

### 1 20.28 eldedTank-Resilient Foam eal inRim Vapor Space

Single Seal (with no gaps) i3,16,20,21 3.02 6.54 10.76 Secondary Seal (no gaps) 32 0.35 0.76 1.25 ~~missions~ 2.67 5.78 9.51 Single Seal (with gaps) 23 26.72 57.91 95.27 Secondary Seal (no gaps) AEmissions 34A 0.47 25.25 1.03 56.88 

### 1 1.69 93.58 econdary Seal with Gaps ver Primary Seal with Gaps 34B 1.81 3.92 6.46 Emission Reduction used inChapter 4.0 Extrapolated-- TABLE B-3 

## - EMISSIONS FROM 100' 0 WELDED GASOLINE TANK WITH 

### - SHOE MOUNTED SECONDARY SEAL (MEGAGRAMSIYR) Wind Speed

## - MPH tored Product Vapor Pressure-PSIA

Experimental Test Test Number hoe Mounted secondaryight Fit Base Case: Shoe Seal with W1, WlR, Leak Tight W2 Envelope Base Case with Shoe C-2 Mounted Secondary

Controiied by Secondary Shoe Seal with Envelope W-12 Leak Rate 0.8 SCFMIft Tank 0

## - 1 112" H20

Control1ed by Secondary Shoe Seal with Shoe Adjusted Mounted Secondary C-2 hoe Mounted SecondaryithGaps Base Case: Shoe Seal with Leak Tight W1, W1R Envelope W2 Base Case with Shoe C-1 Mounted Secondary

Control1ed by Secondary Shoe Seal with Envelope Leak Rate 0.8 SCFMIft W-12 Tank $

### - 1 112" H20

Control1ed by Secondary Shoe Seal with Shoe Adjusted Mounted Secondary ' C-1REFERENCES 1. Su~ary of 20 foot Diameter PilotFloating Rpof Hydrocarbo-n Emission Test 

### Results, Chicago Bridge & Iron Company, December 28, 1977. 2. Hydrocarbon Emission Lpss MeasuremeMs ona 2Q'- @. Floating Roof Tank with 

### a Type SR-1 Seal for a Product atVarious Vapor Pressures, Chicago Bridge & Iron Company, October 25, 1977. 3. Methods for Extrapolating Chicago Bridge & Iron Company 20,' TestTank 

### Results to.Full SizeTanks, EPA, OAQPSDraft Report, April, 1978. 4. Reference 1,Op Cit.TECHNICAL REPORTDATA (Please readZnshuctlonsonthereversebefore completing) REPORTNO. 2. 3. RECIPIENT'S ACCESSION NO.



## - - - - TITLEANDSUBTITLE 5. REPORT DATE Control of Volatile Organic: Emissions from December 1978

- ORGANIZATIONCODE Petroleum Liquid Storage in External Floating Roof T Richard 

## K.Burr, ESED Jack G. Wright, SASD 8. PERFORMINGORGANIZATIONREPORT hlO. AUTHORE) 

### Kerri C. Brothers, ESED OAQPSNO. 1.2-116
PERFORMINGORGANIZATION NAMEANDADDRESS 10. PROGRAM ELEMENT NO. U.S. Environmental Protection Agency Office of 

### Air Qua1 ityPlanning.and Standards 11.CONTRACT/GRANT NO. Emission Standards and Engineering Division Research Triangle Park, North Carolina 27711 2. SPONSORlNG AGENCY NAMEANDADDRESS
14. SPONSORING AGENCY CODE

I 5. SUPPLEMENTARY NOTES

6. ABSTRACT This report provides the necessary guidance for development of regulations 1 imiting emissions of volatile organiccompounds (VOC) from storage of petroleum 1 iquids inexternal floating roof tanks. Reasonably available control technology (RACT) is defined inthis document; cost analysis forRACT is included for evaluating the cost effectiveness of controlling external floating roof tank sources.

7. KEYWORDS ANDDOCUMENTANALYSIS DESCRIPTORS >. IDENTIFIEFWOPEN ENDEDTERMS Air Pollution Air Pollution Control StorageTanks Regulatory Guidance StationarySources Organic Vapors

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