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# 75 ) ll-A-1 2 Docket Number: 

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### f\-tf-\l IT-A- i 2 . EPA-AA-SDSB-86- 3 -Technica l Repor t

Evaluatio n o f the Feasibilit y o f Liqui d Fillnec k Seal s

Decembe r 198 6

NOTIC E Technica l report s d o no t necessaril yrepresen t fina l EPA decision s o r positions . The yar e intende d t o presen t technica l analysi s o f issue s using dat a whic har e currentl yavailable . Th e purpos e i n th e releas e o f suc hreport s i s t o facilitat e th e exchang e o f technica l informatio n an d t o infor

m th e publi c o f technica l development s whic hmayfor mth e basi s fo r a fina l EPA decision , positio n o r regulatoryaction .

Standard s Developmen t an d Suppor t Branc h Emissio n Contro l TechnologyDivisio n Offic e o f Mobil e Source s Offic e o f Ai r an

d Radiatio n U.S . Environmenta l Protectio n Agenc yP. 3

i Tabl e o f Content s

Sectio n Pag e I . Introduction/Overvie w2 II . Evaluatio n o f Liqui d Sea l Concept s 5 A . PreliminaryAnalysi s an d Experimenta l Desig n 5 B . In-Tub e Liqui d Trap 1 3 C . .J-Tub

e Liqui d Sea l 1 7 D . Submerge d Fil l 2 0 E . Technique s fo r Reducing Require d Fil l Heigh t 2 3 F . Discussion/Conclusion s 2 8 III . Benc hTesting o f a Liqui d Sea l Onboar d System3 5 A . Descriptio n o f the Prototyp e System3 5 B . Evaluatio n o f SystemEfficienc y4 1 IV . Conclusion s 4 9 Reference s 5 3 Appendi x5 4P. 4 -2

- I . Introduction/Overvie w Th e onl ysignifican t uncontrolle d sourc e o f hydrocarbo n emission s frommoto r vehicle s i s the gasolin e vapo r whic h escape s during vehicl e refueling . I n a n uncontrolle d refueling , th e vapor s tha t ar e displace d during th e refueling even t pas s throughthe fillnec k an d escap e t o th e atmosphere . System s designe d t o contro l thes e emission s ar e calle d refueling vapo r contro l systems . Whe n the control s ar e vehicl e based , theyar e generall yreferre d t o a s onboar d vapo r recovery systems . Th e essentia l ingredient s o f an onboar d vapo r recover ysystemare : 1 ) a fillnec k sea l t o preven t vapor s fro mescaping t o th e atmospher e vi a the fillneck , 2 ) a fue l tank ven t an

d vapo r lin e fro m the fue l tank t o allo wfo r displacemen t o f refueling vapors , an d 3 ) a metho d o f removing hydrocarbon s fro

mthe vapor s displace d fromthe fue l tank an d storin g them fo r purging a t a late r time . Normall ythi s i s accomplishe d throughthe us e o f a carbo n canister . Thi s repor t i s primaril yconcerne d wit hfillnec k sea l portio n o f the onboar d vapo r recoverysystem . Historically , th e fillnec k seal s mos t ofte n discusse d a s part , o f onboar d system s ar e mechanica l seals . I n a mechanica l sea l system , a temporaryphysica l barrie r i s create d betwee n th e sea l an d th e nozzl e whe n the fue l nozzl e i s properl yinserte d int o th e fillnec k (se e Figur e 1) . Thi s barrie r (usuall yreferre d t o a s a seal ) prevent s the vapor s fro mescaping ou t th e fillnec k whe n the fue l i s dispensed . I n a n extensiv e developmen t an d testing programconducte d i n 1978 , AP I demonstrate d tha t mechanica l seal s ca n effectivel y preven t vapor s fro mescaping throughth e fillnec k ove r th e usefu l lif e o f a light-dut yvehicl e whe n use d unde r norma l conditions.[1 ] However , some concer n ha s bee n expresse d abou t the safety , durability , an d integrit yo f th e mechanica l sea l approach . Concern s abou t th e mechanica l sea l fal l i n thre e areas :

• Fillnec k seal s ma yrequir e a pressur e relie f valv e t o dea l wit hpotentia l fue l tank overpressure s whic h coul d occu r a s a resul t o f failur e o f th e fue l nozzl e automati c shut-of f mechanis mo r a blockag e i n th e vapo r lin e betwee n th e fue l tank an d th e carbo n canister . Withou t a pressur e relie f valve , tank overpressure s coul d resul t in a fue l spitbac k wit h potentia l fue l tank overpressures .Figur e 1 P. 5



### FIL L PIP E MODIFICATION S ROTAR YSEA L ROTAR YSEALTRA P DOO R

LEA D RESTRICTO R



### RL LPIP E MODIRCATION S ROTAR YSEA L ROTAP YSEA L TRA P DOO R SPOUT

LEA D RESTRICTO RP. 6 -4

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• Unde r some advers e in-us e conditions , a mechanica l sea l mayrequir e maintenanc e o r replacemen t t o retai n a highin-us e efficiency . Thi s depend s i n larg e par t o n th e materia l use d t o mak e th e sea l an d th e degre e t o whic hth e mechanica l sea l mountin g withi n the fillnec k protect s i t fromunusua l wea r o r abuse .

• I f no t properl ydesigned , th e mechanica l sea l ma yb e susceptibl e t o tampering b yth e consumer . Instead o f using a mechanica l sea l i n th e fillneck , on e alternativ e i s th e us e o f a liqui d seal . Th e ide a o f using a liqui d sea l i n th e fillnec k wa s introduce d earl yi n th e developmen t o f onboar d vapo r recoverysystems . Arepor t publishe d i n 197 3 b yth e America n Petroleu mInstitut e identifie d an

d briefl yevaluate d severa l differen t liqui d sea l concepts.[2 ] Aliqui d sea l systemuse s a fillnec k desig n whic h route s th e incoming fue l i n suc ha wa ytha t th e fue l itsel f prevent s the vapor s fro m escaping vi a th e fillneck . Th e us e o f a liqui d sea l desig n woul d hel p t o eliminat e the potentia l problem s associate d wit ha mechanica l seal . Sinc e a ne wsea l i s forme d a t eac hrefueling , i n us e durabilit y an d maintenanc e ar e no t i n question . Also , sinc e th e liqui d sea l fillnec k i s no differen t i n appearanc e than curren t fillneck s an

d th e fue l itsel f form s th e seal , liqui d seal s ar e essentiall ytamper-proof . Th e proble mo f overpressur e during refueling woul d b e eliminated , becaus e fue l woul d bac k u p i n the fillnec k a s soo n a s an ypressur e buil t up . Th e fue l nozzl e woul d the n eithe r shu t of f automaticall yo r coul d b e shu t of f manually , sinc e th e nozzl e operato r coul d se e the overfil l condition . I n addition , liqui d sea l system s ma yb e somewha t les s costl ytha n mechanica l seal s sinc e a pressur e relie f devic e mayno t b e required . Th e purpos e o f thi s repor t i s t o evaluat e th e liqui d sea l approac ht o fillnec k vapo r containmen t a s a practica l alternativ e t o the mor e widel yrecognize d mechanica l seal . Afte r evaluatin g severa l differen t liqui d sea l approaches , th e performanc e o f on e o f th e liqui d sea l design s i s the n evaluate d i n a simpl e prototyp e onboar d contro l system . Th e firs t portio n o f th e repor t cover s evaluatio n o f th e liqui d sea l concepts . I t start s wit ha conceptua l analysi s o f th e liqui d sea l an d provide s a

n overvie wo f th e experimenta l an d analytica l methodologyuse d i n th e testing . The n i t examine s eac ho f thre e basi c liqui d sea l design s individually : th e "in-tube " liqui d trap , the "J-tube, " an d th e submerge d fill . Th e testing don e o n eac hdesig n i s outline d an d th e strength s an

d weaknesse s o f eac har e noted . Next , a proble mP. 7 -5

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comrno n t o eac hdesign , ai r entrainmen t an d bubbl e proliferatio n i n the fillneck , i s discusse d an d variou s method s o f controlling thes e problem s ar e evaluated . Th e firs t portio n o f the repor t close s wit hconclusion s abou t the adaptabilit yo f thes e liqui d sea l design s t o curren t fue l tank fillnec k configurations . Th e second portio n o f th e repor t discusse s th e performanc e o f a crude , firs t generatio n liqui d sea l fillnec k (J-tube ) o n a simpl e prototyp e onboar d system . I t begin s wit ha descriptio n o f the keycomponent s neede d fo r a n onboar d contro l syste man d the n describe s the component s use d in EPA' s systeman d ho w thes e me t th e performanc e criteri a neede d fo r the liqui d seal . Th e tes t procedur e use d t o evaluat e the performanc e o f thi s systemi n a serie s o f benc htest s i s describe d an d thi s i s followe d b

ya discussio n o f the tes t result s including system efficienc yan

d source s o f emissions . Th e repor t the n close s wit hsome conclusion s abou t th e performanc e o f liqui d seal s an d compare s themt o result s achieve d fo r mechanica l seals . II . Evaluatio n o f Liqui d Sea l Concept s A . PreliminaryAnalysi s an d Experimenta l Desig n 1 . Introductio n . Th e ter

m"liqui d seal " i n the contex t o f a n onboar d vapo r recoverysystemrefer s t o an ysystemo f fue l tank an d fillnec k i n whic ha colum n o f liqui d separate s in-tank vapo r from atmospheri c air . On e keyparamete r i n evaluatin g th e feasibilit yan

d performanc e o f liqui d seal s i s th e fil l heigh t require d t o maintai n a liqui d sea l during a refueling event . I f the fil l heigh t availabl e i s les s tha n tha t needed , th e fue l risin g i n th e nec k wil l caus e a prematur e shut-of f o f th e nozzle . On e o f th e majo r goal s i n thes e evaluation s wa s t o determin e th e minimu mfil l height s necessaryt o completel y refil l th e tank using liqui d seal s i n the fillneck . Thi s sectio n develop s some model s whic hhel p t o predic t th e manne r i n whic hthes e liqui d seal s woul d perform an d wha t fil l heigh t migh t b e necessaryt o mak e us e o f a liqui d sea l a s a n alternativ e t o a mechanica l seal . First , th e stati c situatio n i s discusse d an

d a mathematica l mode l relating fillnec k heigh t t o tan k backpressur e i n th e stati c situatio n i s presented . The n th e dynami c effect s tha t ar e par t o f a typica l refueling even t an

d tha t complicat e th e mathematica l mode l ar e introduced . Third , a n experimenta l desig n fo r testing th e variou s fillnec k configuration s i s outlined . Fourth , th e genera l tes t procedur e fo r testing the liqui d sea l concept s i s developed .P. 8

• 6

- 2 . Stati c Situatio n Anyliqui d tra

p system

ca n b e modele d b yth e simpl e 'U ' tube systemshow

n i n Figur e 2 . I n the stati c situation , the vertica l fil l height , h f , require d t o suppor t an yinduce d tan k backpressure , P B , ca n b e foun d using th e basi c equatio n o f flui d statics . I n thi s case :

P B = Po + pgh f , wher e P B = tank backpressure , gaug e P o = referenc e gaug e pressur e a t referenc e height , h= 0 p = densit yo f flui d i n tank g = acceleratio n o f gravit ya t tes t altitud e h f = require d fil l heigh t abov e referenc e heigh t Fo r example , t o suppor t a backpressur e o f 5 inche s H 2 0 unde r stati c conditions , a gasolin e colum n (specifi c gravit y= 0.72 ) woul d hav e t o ris e approximatel y7 inche s abov e the referenc e height . S o vertica l fil l heigh t woul d hav e t o b e a t leas t 7 inches . During testing ^ a wate r manomete r wa s use d t o gaug e pressur e s o tha t pressur e coul d b e read .directl yin inche s o f H 2 0 . I f fuel s wer e dispense d veryslowly , thi s mode l coul d be use d t o analyz e the system . I t i s not , however , an d th e nex t sectio n look s a t th e dynami c effect s o f a refueling . 3 . Dynami c Effect s Anumbe r o f factor s complicat e thi s mode l fo r a typica l refueling event . Thes e include :

• Dynamics : A t a typica l gasolin e pum p fue l i s dispense d a t a rat e o f 7-1 0 gallons/minut e (gal/min) ; thu s th e systemi s no t static .

• Injectio n effect : Th e kineti c energyo f th e gasolin e a s i t flow s ou t o f th e dispensing nozzl e tend s t o ai d th e flowo f gasolin e int o th e tank an d t o reduc e the require d fil l height .

• Turbulenc e an d ai r entrainment : Th e interactio n betwee n liqui d an d ai r i n th e fillnec k i s quit e turbulent . Thi s interactio n tend s t o greatl y increas e th e require d fil l height .Figur e 2 - 'U ' Tub e

P b = tank backpressure , guag e P o = o = referenc e guag e pressur e h f = require d fillnec k heigh t P. 9P.1 0 -8

- Observation s during informa l testing o f the 'U ' tub e se t u p o f Figur e 2 , suppor t the intuitiv e hypothesi s tha t require d fil l heigh t i s directl yrelate d t o tan k backpressur e fo r an y give n fue l flowrat e an d fillnec k configuration . I n the stati c situation , P B an

d h r ar e relate d b ya constan t conversio n factor , the liqui d density . I n the dynami c situation , th e relationshi p i s muc hmor e complex , wit hflui d density , viscosity , surfac e tension , an d othe r factor s al l interacting i n a highl yturbulen t flow . I n thi s dynamic , turbulen t situation , i t wa s expecte d tha t P B an d h r woul d vary directl yan

d tha t a

n increas e i n tan k backpressur e woul d increas e the fil l heigh t necessaryt o suppor t tha t pressure . A mathematica l analysi s o f suc ha turbulent , dynami c flowwa s outsid e th e scop e o f thi s investigation , s o a mathematica l mode l wa s no t developed . Instead , th e relationshi p betwee n tan k backpressur e an d fillnec k heigh t wa s determine d experimentall yfo r th e thre e liqui d seal s evaluated . 4 . Experimenta l Desig n Th e ultimat e goa l o f th e test s conducte d b yEPAwa s t o compar e th e performanc e o f a numbe r o f liqui d sea l fillnec k configuration s unde r uniformtes t condition s an d procedures . Becaus e th e optima l experimenta l desig n wa s no t intuitivel y obviou s whe n testing began , a serie s o f developmenta l test s wer e performe d wit hwate r a s th e tes t fluid . Thes e test s wer e don e t o evaluat e a numbe r o f experimenta l design s withou t th e safet yconcern s an

d expens e involve d wit hgasolin e testing . Thes e preliminarytest s wer e performe d using standar d ta p water , an

d fillnec k system s wer e constructe d using metal , tygon , an

d plexiglass . Thes e system s wer e the n attache d t o a standar d automotiv e fue l tank having a nomina l capacit yo f abou t 1 8 gallons . Al l gasolin e test s wer e performe d wit h indolen e clea r a s th e tes t fluid , an d sinc e plexiglas s i s incompatibl e wit hgasoline , system s wer e buil t o f meta l an d tygon . Th e temperatur e during thi s testing wa s th e prevailin g ambien t temperatur e (nominall y80°F) . Th e developmenta l wate r test s wer e carrie d ou t i n a 'U ' tub e systemsuc ha s the on e describe d abov e an d diagramme d i n Figur e 2 . Dat a wa s take n relating fil l heigh t t o tank backpressur e fo r differen t fillnec k configuration s during thes e developmenta l wate r tests . Th e numerica l result s o f thes e test s prove d t o be o f littl e us e i n predicting th e result s o f th e gasolin e testing , however , becaus e o f th e grea t difference s i n th e propertie s o f wate r an d gasolin e (se e Tabl e 1) . However , th e test s wer e veryhelpfu l i n isolating th e parameter s tha t woul d prov e critica l i n determinin g require dP.1 1 -9

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Tabl e 1

i Propertie s o f Wate r an d Gasolin e a t 20° C Propert yWate r Gasolin e (n-Octane ) Densit y(lb/gal ) 8.3 0 5.8 3 Viscosit y(Centipoise ) 1. 0 0.5 4 Surfac e Tensio n (Dynes/cm ) 72. 8 21. 8 Source : CR C - Chemistryan d Physic s Handboo k an d Perry' s Chemica l Engineering Handbook , 5t hEd .-10

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fillnec k height . Th e qualitativ e result s o f thi s preliminary testing whic har e importan t t o the experimenta l desig n ar e outline d below :

• Th e systemperforme d a s predicte d b yth e 'U ' tub e mode l - require d fil l heigh t varie d directl ywit h tan k backpressure .

• Increasing fue l inflowrat e increase d require d fil l height . Bubbling cause d b yth e mixing o f flui d entering th e fillnec k wit hai r i n th e fillnec k wa s observe d t o increas e a s dispensing rat e increased .

• Change s i n fillnec k diamete r (or volum e pe r uni t length ) affecte d require d fil l heights . Generally , require d fil l height s increase d wit hdecreasin g fillnec k diameters .

• Th e orientatio n o f th e dispensing nozzl e i n th e fillnec k affecte d fil l height . I f th e nozzl e wa s oriente d appropriately , the liqui d tende d t o adher e t o th e fillnec k wall . I f thi s was . done , ai r entrainmen t an

d bubbling wer e reduce d leading t o a decreas e i n require d fil l height . Th e result s o f thes e test s confirme d tha t thes e factor s woul d hav e t o be controlle d t o ensur e consisten t tes t results . Base d o n observation s during the wate r testing , th e U-tub e systemappeare d t o creat e a veryadequat e seal . T o furthe r evaluat e th e feasibilit yo f thi s approach , a "u " wa s buil t int o a 2-inc hplexiglas s pip e an d teste d using water . A s wil l be discusse d below , th e testing showe d tha t the smalle r cros s sectiona l are a fo r flowwithi n th e tra p require d to o higha fil l heigh t t o b e practical . However , thi s experimen t reveale d usefu l informatio n o n flowan d turbulenc e characteristics . Base d o n th e experienc e gaine d fromthi s preliminar y testing an

d supplemente d b

yinformatio n containe d i n th e SAE Recommende d Practic e regarding refueling emissions , standar d tes t condition s wer e chose n t o tes t th e liqui d sea l fue l tank system s using gasolin e unde r condition s likel yt o occu r during a typica l refueling event.[3 ] Thes e condition s wer e use d i n th e test s whic hevaluate d the fil l heigh t requirement s an d othe r performanc e aspect s o f th e liqui d seal s system . Th e backpressur e wa s se t a t five inche s H 2 0 . I t i s expecte d tha t carbo n canister s an d thei r accompanying tubing an d valve s ca n b e designe d t o accommodat e norma l refueling rate s wit htank backpressure s o f 5 inche s H 2 0 o r less . Thi s i s supporte d b

yexperimenta l evidenc e presente d i n an AP I-11

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repor t date d October , 1978.[1 ] Th e repor t quote s backpressure s a s lo wa s 2 inche s H 2 0 , a t a refueling rat e o f eigh t gal/min . Al l thre e o f the fillnec k sea l approache s evaluate d b yEPAwer e teste d a t 5 inche s H 2 0 backpressur e an d mos t wer e teste d a t some lesse r backpressures . Fue l dispensin g rat e wa s als o standardized . Typica l fue l dispensing rate s averag e fro m7 t o 1 0 gal/min , bu t th e fue l car t availabl e fo r us e in thi s testing had a maximu mfue l dispensing . rat e o f 7. 5 gal/min . Therefore , thi s wa s th e designate d fue l flowrat e fo r gasolin e testing . A s wa s mentione d above , fillnec k cros s sectiona l are a als o affect s require d fillnec k heigh t an d had t o b e standardized . Becaus e mos t stoc k fillneck s hav e a n oute r diamete r o f approximatel ytwo inches , thi s wa s chose n a s the bas e fillnec k diamete r an

d tygo n o r meta l tubing o f thi s diamete r wa s used . Als o mentione d above , fue l nozzl e orientatio n ca n als o affec t require d fil l height , bu t the optima l orientatio n i s differen t fo r eac hfillnec k configuration . Also , nozzl e orientatio n i s on e o f the keyhuma n factor s . in vehicl e refueling , an

d mayvarysignificantl yfro moperato r t o operato r an d vehicl e t o vehicle . Fo r thes e reasons , fue l nozzl e orientatio n wa s no t standardize d t o minimiz e fil l height . Instead , fo r eac hfillnec k configuratio n th e nozzl e wa s oriente d i hth e manne r that; , woul d normall yoccu r in-us e i f the nozzl e wer e t o res t verticall yi n the fillnec k perpendicula r t o th e surface . Th e standar d tes t condition s describe d abov e wer e the n incorporate d int o the standar d tes t procedur e develope d fo r the gasolin e testing . Th e standar d setu p fo r testing th e liqui d sea l design s i s show n i n Figur e 3 . Th e gat e valv e mounte d o n top o f th e tank wa s use d t o regulat e th e siz e o f th e orific e throughwhic han

yvapo r leaving th e tank mus t pass . Th e backpressur e induce d i n the fue l tank wa s controlle d fo r an y fue l inflo wrat e b ychanging th e positio n o f th e gat e valve . Prio r t o th e star t o f eac htest , th e manomete r wa s zeroed , th e fue l tank wa s leveled , an d th e gat e valv e opene d t o abou t on e fourt ho f wid e open . Th e fue l car t wa s turne d o n an d fue l dispense d a t th e highes t availabl e rate . Th e gat e valv e wa s the n close d unti l backpressur e wa s stabilize d a t th e desire d valu e (initially , 5 inche s H 2 0 ) . Th e heigh t o f th e fluid/bubbl e colum n i n the fillnec k wa s the n measure d whe n backpressur e stabilized . Thi s valu e wa s recorde d a s th e require d fil l height . Th e tank wa s draine d an d th e operatio n repeated .P.1 4

Figur e 3 Standar d Experimenta l Setu p h= require d fillnec k heigh t

Bo xRepresent s Liqui d Sea l Syste m / Fil l Nozzl e

T Gat e Valv e



## ~ l 

## H L 

# £. " 1 h 0 rt c T-13

- A t thi s point , fue l RV P an d dispense d an

d tank temperatur e wer e no t important . Neithe r th e RVP o f th e fue l o r th e fue l temperature s mentione d abov e wer e controlled . Th e testing o f eac hsystemgenerall yadhere d t o th e tes t procedur e outline d above , althoughsome detail s wer e specifi c t o th e individua l system s being tested . Th e mos t significan t differenc e betwee n individua l test s wa s th e measuremen t o f fil l height . Fil l heigh t ca n b e generall ydefine d a s follows : Th e valu e o f th e vertica l componen t o f a vecto r froma poin t o n th e plan e o f ful l tank fue l leve l t o th e poin t wher e th e ti p o f th e dispensing nozzl e rest s i n th e fillnec k (the vertica l distanc e fromth e tank ful l leve l t o th e nozzl e tip) . Th e peculiaritie s o f th e measuremen t o f fil l heigh t fo r eac hindividua l systemwil l b e discusse d i n th e section s o f thi s repor t whic hdea l wit hth e specifi c designs . I t shoul d als o b e note d her e tha t fil l height , a s use d i n thi s report , doe s no t includ e th e distanc e from the inserte d nozzl e ti p t o location . th e ga s cap location . Thi s distanc e b e include d i n an

yfillnec k design . B . In-Tub e Liqui d Tra p 1 . Introductio n (2- 3 inches ) wpul d hav e t o

Th e firs t liqui d sea l approac hteste d wa s th e "in-tube " liqui d trap . Th e in-tub e trap wa s chose n fo r stud ybecaus e th e preliminar ywate r testing showe d tha t th e syste mcoul d provid e a positiv e sea l an d coul d b e installe d b ymodifyin g onl yth e fillneck , leaving th e tank essentiall yunchanged . I f thi s wer e possible , an

d th e fillnec k heigh t requirement s permitted , th e desig n coul d b e adapte d t o fi t a numbe r o f vehicles . Thi s sectio n look s a t th e in-tub e trap an d it s performanc e unde r th e standar d tes t conditions . A n in-tub e trap i n th e fillnec k operate s b ycreatin g a liqui d barrie r betwee n th e gasolin e vapo r i n th e tank an d th e atmosphere . It s operatio n i s simila r t o tha t o f th e hom e sink drai n pipe , bu t th e 'U ' shape d trap i s buil t int o th e fillpip e rathe r tha n bending th e fillpip e int o a 'U ' shape . Adiagramo f th e in-tub e liqui d trap an d illustration s o f th e parameter s describin g it s constructio n ar e shown i n Figur e 4 . Th e trap wa s designe d t o divid e th e tub e int o thre e channel s o f equa l cross-sectiona l area . Liqui d i s trappe d i n th e upwar d opening 'U ' , an d i f tank backpressur e increase sP.1 6

Side Vie w Figur e 4 In-Tub e Tra p

3otto m View Dimension s Plexiglas s a = c = 0.73 " b= 0.54 " D = 2.0 "

Meta l a = c = 1.1 " b= 0.8 " D = 3.0 "

d = Tra

p Depth

A= B = CP.1 7 -15

- during refueling , a liqui d colum n wil l ris e abov e tha t 'U ' unti l th e pressur e i s offset . "Tra p security " describe s th e susceptibilit yo f th e tra p systemt o allowing vapo r t o pas s throughi t during th e refueling event . Trap securit yca n b e increase d b

yincreasing th e dept ho f the liqui d seal , bu t increasing thi s dept hmigh t als o increas e th e require d fillnec k height . Normally , wit ha n in-tub e liqui d trap , th e dept hwoul d jus t nee d t o be adequat e t o accommodat e refueling o n slope d terrain . So , t o refue l o n a 30 ° incline , a tra p dept ho f one-hal f inc hwoul d b e sufficien t (fo r th e larg e tra p show n i n Figur e 4) . Tw o trap s wer e buil t fo r testing . Th e smalle r tra p wa s se t i n a two inchdiamete r plexiglas s tube . Thi s tra p wa s buil t s o tha t flowthroughthe tra p coul d b e visuall ymonitore d during th e preliminarywate r testing . Alarge r 3 inc hdiamete r tra p wa s buil t entirel yo f meta l s o tha t gasolin e coul d b e use d a s th e primarytes t fluid . 2 . Tes t Procedure s Figur e 5 i s a schemati c o f the experimenta l setu p use d t o tes t th e in-tub e liqui d traps . I t i s importan t t o not e th e locatio n o f th e tra p i n relatio n t o th e tank ful l level . I f spatia l efficienc ywer e optimize d i n a productio n configuration , the tra p woul d actuall yb e a t the roo f o f fue l tank insid e th e vapo r space , and, , th e upwar d opening 'U ' woul d ope n a t th e tan k ful l level . However , fo r the sak e o f convenience , thes e trap s wer e buil t o n to p o f the tank , an d henc e require d fil l heigh t wa s measure d from th e top o f th e upwar d openin g 'U ' t o th e nozzl e tip . 3 . Results/Discussio n A s wa s mentione d previously , some o f the developmenta l testing discusse d earlie r i n thi s repor t wa s don e o n a n in-tub e liqui d trap . Th e dimension s o f tha t tra p ar e thos e liste d unde r "Plexiglass " i n Figur e 4 . Th e developmenta l testing showe d tha t a tra p buil t insid e a 2 inc hdiamete r tub e woul d no t be larg e enought o suppor t a backpressur e o f 5 inche s H 2 0 . Th e channel s throughwhic hliqui d wa s suppose d t o flo w (approximatel y1 squar e inch ) simpl ywer e no t larg e enought o allo wliqui d t o pas s throughquickly . I n orde r t o accommodat e gasolin e an d highe r flowrate s an d t o reduc e require d fillnec k height , a large r in-tub e tra p wa s se t i n a 3 inc hdiamete r tube . Th e dimension s o f th e tra p ar e show n i n Figur e 4 unde r "Metal" . Using th e standar d tes tFigur e 5 Experimenta l Setu p Fo r In-Tub eTrap P.1 8

Fil l Nozzl e

Require d Fillnec k Heigh t

Ful l Tan k Leve lP.1 9 -17

- procedure , th e tank wa s fille d wit ha require d fil l heigh t o f onl y1 1 inches . Thi s i s a verygoo d result , considering tha t i n th e stati c "situation a nec k heigh t o f 7 inche s woul d b e neede d t o suppor t a 5 inc hH 2 0 backpressur e ( 5 inches/0.7 2 = 6.9 4 inches) . Th e implication s o f thi s resul t ar e discusse d late r i n th e report . 4 . Conclusion s Afil l heigh t o f approximatel y1 1 inche s fo r the in-tub e liqui d tra

p i s quit e acceptabl e fo r man yvehicl e applications . However , th e in-tub e liqui d tra p approac hha s some drawbacks . First , th e in-tub e tra p coul d be relativel ycomple xt o construc t o n a productio n basis . Also , sinc e the tra p require d a 3 inc hdiamete r fillnec k t o performadequatel yunde r th e standar d tes t conditions , curren t fillpip e design s migh t hav e t o be modifie d t o accommodat e it s use. * A3 inc hdiamete r expansio n i n some fillneck s maycreat e vehicl e packaging problems . Howeve r no fue l tan k change s woul d b e necessaryan d th e in-tub e liqui d trap ha s al l th e advantage s o f liqui d sea l system s tha t wer e describe d above . Packaging problem s coul d be eliminate d i f the in-tub e tra p wer e buil t int o th e insid e to p o f the fue l tank . Th e advantage s an d disadvantage s o f th e in-tub e trap ar e discusse d furthe r following th e examinatio n o f th e othe r liqui d sea l approaches . C . "J " Tub e Liqui d Sea l 1 . Introductio n Th e secon

d liqui d sea l approac ht o refueling vapo r containmen t examine d wa s th e 'J ' tub e liqui d seal . Th e 'J ' tub e wa s chose n fo r stud ybecaus e i t wa s a logica l extensio n fromth e in-tub e tra p approac han

d woul d tak e onl ymino r change s i n fue l tank an d fillnec k t o instal l an d ha s al l th e advantage s o f liqui d seals . Thi s sectio n look s a t th e fil l heigh t necessaryfo r th e 'J ' tub e systemwhe n evaluate d unde r th e standar d tes t conditions . Th e 'J ' tub e systemi s show n i n Figur e 6 . Th e 'J ' tub e i s simpl ya modifie d 'U* tub e (lik e t-ha t show n i n Figur e 2) . Th e differenc e i s tha t i n th e 'J ' systemth e fue l tank itsel f replace s th e downstream , vertica l portio n o f the drainpipe . Th e ultimat e siz e o f th e tra p an d fillpip e diamete r neede d depend i n par t o n th e systembackpressure . Syste m backpressur e les s tha n th e 5-inchH 2 0 use d her e ar e achievable, * an

d woul d reduc e th e diamete r o f th e in-tub e trap .Figur e6 - *J ' Tube



### ^niLf

« • HEIGH T



### nr,r~z:. —

* T 

### * ^ F



### ^«-< - «-F^ LP.2 1

-19

- Th e dimension s o f the 'J ' systemalong wit hillustration s o f some o f the descriptiv e term s use d in the discussio n ar e give n in Figur e 6 . I t shoul d be note d tha t the liqui d tra p i s locate d insid e th e fue l tank , an

d the to

p o f th

e tra p i s locate d o n o r nea r the ful l tan k plane . Thi s promote s spatia l efficienc yan

d make s maximu

m us e o f availabl e fillnec k height . 2 . Tes t Procedur e Becaus e the 'J'-tube tra p i s locate d insid e o f the fue l tan k an d fil l heigh t i s measure d fro m ful l tan

k leve l t o the nozzl e insertio n point , the standar d tes t metho d wa s followe d exactl yin thi s case . 3 . Results/Discussio n The 'J ' tub e tes t result s ar e liste d below :

Fue l dispensing rat e = 7. 5 gal/min . Backpressur e (inche s H-0 ) 

### Require d p 

## UAc8§i? h t 16. 0 13. 5 11. 0 5. 0 4. 0 3. 0 Th e 1 6 inche s o f fil l heigh t require d t o fil l the tan k a t five inche s H2 O backpressur e wa s mor e than expecte d base d on extrapolatio n o f th e result s o f th

e developmenta l wate r test s discusse d earlier . Althoughbubbling , du e t o the mixing o f wate r wit hai r in the fillneck , wa s observe d during developmenta l tests , the violenc e o f the bubbling during gasolin e testing wa s no t full yexpected . Th e extensiv e bubbling in the fillnec k wa s the caus e o f the larg e require d fil l heights . i t wa s clea r fro mthi s testing tha t i f bubbling coul d be controlled , require d fillnec k height s coul d b e reduced . Thi s coul d be manage d b yreducing the backpressur e or controlling the proliferatio n o f bubble s in the fillnec k during refueling . 4 . Conclusio n Th e 'J ' tube , a simpl e modificatio n o f the 'U ' tube , wa s teste d using the standar d tes t method . Excessiv e turbulenc e an d bubblin g in the fillnec k mad e a fil l heigh t o f 1 6 inche s necessaryfor refueling unde r the standar d tes t conditions . Th e contro l o f th

e bubbl e problem , an d some method s o f fillnec k heigh t reductio n ar e discusse d in sectio n E . I t i s importan t t o not e tha t the *J ' tube tra p appeare d t o be doing it s jobo f controllin g emissions . Aroug hmeasuremen t-20

-

o f the hydrocarbo n concentratio n a t th e fillnec k mout hwa s take n wit ha lowe r explosiv e limi t (LEL ) meter . Th e mete r showe d no differenc e betwee n the reading s take n a t th e fillnec k mout han

d reading s take n aroun d th e tes t chamber . D . Submerge d Fil l 1 . Introductio n Th e thir d an

d fina l liqui d sea l systeminvestigate d wa s the submerge d fill . I n a submerge d fil l system , the fillnec k open s int o th e fue l tank belo wth e liqui d surface . B yfilling th e tank fro

mbelo wthe surface , a liqui d sea l i s naturall y forme d betwee n in-tank vapo r an d atmospheri c air . Adrawing o f a submerge d fil l systemi s show n i n Figur e 7 . Th e significan t feature s o f the submerge d fil l systemar e liste d below :

• Th e securit yo f th e liqui d tra p i s goo d an

d i t improve s a s the tan k fills .

• Apressur e relie f valv e woul d hav e t o b e incorporate d int o an ysubmerge d fil l system . I f th e line s fro

mfue l tank t o carbo n caniste r becam e blocked , tank pressurizatio n during refueling coul d becom e a problem . I f th e backpressur e i n th e tank ros e betwee n refuelings , whe n th e ga s cap wa s remove d fro

mth e fillneck , th e overpressur e coul d caus e gasolin e t o spi t ou t o f th e neck . Th e pressur e relie f valv e i s neede d t o eliminat e thi s problem .

• Th e fillnec k heigh t i s no t critica l during th e earl y stage s o f refueling . Onl yi n th e las t 1 0 percen t o f th e fil l i s th e ful l fil l heigh t used , a s th e bac k pressur e cause d b yth e fue l leve l i n th e tank increases . 2 . Tes t Procedur e I n a submerge d fil l system , th e locatio n o f th e to p o f th e liqui d tra

p rise s a s the tank fills . On e majo r chang e wa s mad e i n the standar d tes t procedur e t o accommodat e thi s uniqu e featur e o f th e submerge d fill . Sinc e th e top o f the liqui d tra p rise s during refueling , th e entir e fillnec k heigh t i s onl y neede d during th e fina l stag e o f refueling ; whe n th e top o f th e tra p approache s th e ful l tank liqui d level . Therefor e require dP.2 3

Figur e7 - Submerge dFil l

rJOZZLi

Fun .-22

-

fil l heigh t mus t b e measure d jus t prio r t o the en d o f th e refueling event . Fo r thes e tests , fil l heigh t wa s measure d whe n abou t 1 8 gallon s o f fue l ha d bee n dispense d (int o a nomina l 1 8 gallo n tank) . 3 . Results/Discussio n Th e result s o f the testing o f the submerge d fil l system , ar e presente d below : Flowrate : 7. 5 gal/mi n

Backpressur e (Inche s H 2 0 ) Require d Fil l Heigh t (inches ) 5. 0 4. 5 1 6 1 3 Thes e result s ar e simila r t o the result s for an d the bubbl e proble m wa s eviden t onc e again . th e • 'J 1 tube , Ther e ha s bee n some previou s effectivenes s o f the submerge d refueling vapors . Preliminaryla b foun d the submerge d fil l t o b e a n wor k don e t o fil l sea l in wor k don e b

y effectiv e metho d evaluat e the controlling EP Ai n 197 9 o f refueling vapo r control.[4 ] Crud e sampling don e wit han LE L mete r support s thi s finding . Sample s take n during refueling fro m nea r the mout ho f the fillnec k showe d no highe r hydrocarbo n concentration s than di d background samples . 4 . Conclusion s Th e submerge d fil l approac hwa s evaluate d using the standar d tes t procedure , an d require d fil l heigh t wa s measure d jus t prio r t o completio n o f the refueling . A t a backpressur e o f 5 inche s H2 O a fil l heigh t o f abou t 1 6 inche s wa s neede d t o accommodat e the larg e liquid/bubbl e colum n in the fillnec k cause d b

yexcessiv e turbulenc e an d ai r entrainmen t during refueling . Ther e ar e fue l tan k fillnec k configuration s currentl yi n us e tha t coul d no t b e easil yadapte d t o accommodat e fillnec k height s o f 1 6 inches . Sinc e bubblin g i n the fillnec k i s the reaso n for the large r fil l heights , a reductio n i n the bubblin g shoul d lead t o a lowe r require d fil l height . Th e nex t sectio n o f th e repor t addresse s th e bubbling proble man d possibl e contro l techniques .-23

-

E . Technique s Fo r Reducing Require d Fil l Heigh t 1 . Introductio n Al l th e liqui d sea l system s buil t wit h2 inc hdiamete r tubing neede d extende d fillneck s t o accommodat e th e larg e gasoline/bubbl e colum n tha t ros e abov e th e liquid/ai r interfac e i n th e fillnec k during refueling . Thi s sectio n o f th e repor t examine s bubbling an d ai r entrainmen t during refueling an d evaluate s som e possibl e method s o f fil l heigh t reduction . Bubbling i s cause d by : 1 ) th e violen t mixing o f th e gasolin e leaving th e dispensin g nozzl e wit htha t alread yi n th e fillneck , an

d 2 ) ai r entraine d i n th e flui d flowb yth e ventur i systemi n th e dispensin g nozzle . Ther e ar e thre e basi c mean s o f controlling bubbling i n th e fillnec k throughmodificatio n o f th e fillneck . Th e firs t i s t o reduc e th e violenc e o f th e mixing o f dispense d fue l wit htha t alread yi n th e fillneck . Anothe r i s t o physicall yobstruc t o r direc t th e backu

p o f bubble s i n th e neck . Th e thir d i s t o creat e a systemt o dissipat e th e kineti c energ yo f th e dispense d fuel . Also , part ' o f th e bubbl e proble mcoul d b e eliminate d b y reducing th e amoun t o f ai r being entraine d i n th e fue l during refueling . Thi s ai r entrainmen t i s cause d b ytwo phenomena . First , th e automati c shutof f . ventur i system i n standar d fue l dispensin g equipmen t add s ai r t o th e fue l being dispensed . Second , ai r i s entraine d i n th e fue l a s a by-produc t o f th e turbulenc e i n th e fillneck . Th e second o f thes e two phenomen a ca n b e affecte d b

yfillnec k modification s whil e th e firs t coul d onl yb e change d b

ymodifyin g th e nozzle . Thi s sectio n look s a t th e problem s o f ai r entrainmen t an d bubbling , an

d examine s some fillnec k modification s designe d t o contro l bubblin g an d reduc e fil l heights . 2 . Ai r Entrainmen t Th e entrainmen t o f ai r i n th e flui d flo waffect s fil l heigh t in.tw o ways . First , a s fue l i s dispense d an d mixe s wit h fue l i n th e fillneck , ai r i s drawn int o th e mixtur e an d bubble s ar e forme d increasing require d fil l height . Second , i f ai r make s it s .wa

yint o th e fue l tank wit hth e fuel , th e amoun t o f vapo r force d ou t o f th e tank during refueling an d th e tank backpressur e (fo r a give n flowrate ) ar e increased . Th e bubbling proble mi s discusse d i n th e nex t sectio n o f th e report . Thi s sectio n look s a t th e entraine d ai r tha t make s it s wa yint o th e fue l tank .-24

-

Ates t wa s performe d o n the 'J ' tube system t o determin e i f ai r wa s entering the tank alon g wit hgasoline . Th e tank wa s fille d wit h2 0 gallon s o f gasolin e an d the vapor s displace d b y the gasolin e wer e collecte d an d the volume o f thos e vapor s measure d b

ypulling the vapor s througha dryga s meter. * Bot h th e dispense d an

d tank fue l wer e a t th e prevailing temperature , s o vapo r expansio n o r shrinkag e shoul d hav e bee n nea r zero . Th e result s o f the test s ar e show n below : Gasolin e Dispense d Vapo r Collecte d Tria l No . (gallons ) (gallons ) 1 2 0 22. 2 2 2 0 22. 4 3 2 0 22. 8 No attempt s wer e mad e t o identif ythe source s o f th e entraine d air , bu t i t wa s fairl yeviden t tha t i t wa s cause d b y ai r bubble s being trappe d in the fue l entering th e tank . Thi s i n tur n wa s cause d b yth e turbulen t mixing i n the fillneck . Althoughthi s testing wa s conducte d o n th e J-tub e system , i t i s als o likel yt o occu r t o simila r degree s i n bot hthe submerge d fil l an d in-tub e trap . Th e phenomeno n o f entraine d ai r entering th e fue l tank i s significant . Whe n th e carbo n caniste r an d tubing ar e designe d fo r a give n liqui d sea l configuration , th e amoun t o f ai r entraine d mus t b e determine d an d figure d i n th e design . System s tha t allo wmor e ai r t o ente r th e fue l tank wil l nee d t o transpor t mor e vapo r a t a give n fue l inflowrate . Thi s may als o increas e th e hydrocarbo n load t o b e capture d b yth e canister , sinc e th e entraine d ai r mayenhanc e evaporatio n o f th e dispense d fuel . Some o f the entrainmen t mayb e avoide d throughth e contro l o f th e mixing o f gasolin e an d ai r i n th e fillneck . Thi s i s examine d next . 3 . Bubbling an

d Turbulenc e Th e mos t obviou s sourc e o f bubbling i n th e fillnec k i s th e violen t mixing o f th e gasolin e being dispense d wit hth e gasolin e alread

yi n th e fillneck . T o examin e bubbl e formation , a tygo n fillnec k wa s mounte d o n th e 'J ' tub e system , an d th e patter n o f bubbl e flowi n th e nec k wa s observed . Althoug hth e patter n o f flo wdepend s o n th e orientatio n o f th e fue l

I t wa s possibl e t o pu t 2 0 gallon s o f liqui d i n a tank having a nomina l capacit yo f 1 8 gallon s becaus e th e tank wa s modifie d wit ha liqui d sea l an d vent , bu t di d no t hav e a fil l limiter . Thu s th e vapo r spac e o f th e tank als o containe d fuel , whic hwoul d no t normall yb e th e case .-25

-

dispensing nozzl e in the fillnec k an d o n the configuratio n an d cross-sectiona l shap e an d are a o f the fillneck , a typica l bubbl e patter n i s show n i n Figur e 8 . Th e patter n show n wa s generate d in a tw o inchdiamete r tube wit ha roun d cross-section . Th e sketc hi s helpfu l in tha t i t highlight s th e poin t o f bubbl e generatio n an d show s th

e rout e tha t th

e bubble s tak e in climbing toward the automati c shutof f por t on the nozzle . Sinc e gasolin e bubble s in th e fillnec k coul d contribut e t o prematur e nozzl e shut-offs , severa l differen t technique s t o reduc e bubbl e generatio n wer e examined . Thes e include d approache s t o eliminating bubble s befor e the yreache d the fue l nozzl e an d approache s t o reducing bubbl e formatio n b y decreasing the amoun t o f turbulen t mixing in the fillneck . Whil e the approache s examine d her e wer e b yno mean s comprehensive , (i.e. , man yothe r option s exist ) on e approac h identifie d wa s quit e successful . Thi s approac hinvolve d replacing a sectio n o f th e standar d 2 inchdiamete r tubing wit ha sectio n o f 4 inch , diamete r tubing . Th e resulting 'reservoir ' adde d volume t o the fillnec k an d serve d a s a settling chambe r in whic hthe bubble s forme d an d burs t withou t rising in th e fillneck . Th e us e o f suc ha reservoir , the dimension s o f whic hwer e chose n rathe r arbitrarily , had a significant , impac t on require d fillnec k height . Th e reservoi r ide a wa s teste d a s an additio n t o the J-tub e setu p discusse d in Sectio n c . The reservoi r i s diagramme d i n Figur e 9 . Th e procedur e use d t o gaug e require d fillnec k heigh t wa s the same a s tha t use d for th e J-tub e withou t the reservoir . Th e result s o f testing thi s systemar e show n below : Fue l inflowrat e = 7. 5 gal/mi n Backpressur e Require d Fillnec k (inche s H2O ) Heigh t (inches ) 5 1 1 4 9. 5 3 6. 5 Simila r result s wer e obtaine d whe n the in-tub e tra p an d submerge d fil l system s wer e teste d wit hreservoi r typ e fillnecks . Th e in-tub e tra p se t in 3 inchdiamete r tubing ha s a "buil t in " reservoi r - the tubing i s large r than the stock , systemalready . Thi s sea l systemneede d a fil l heigh t o f onl y 1 1 inches . Th e submerge d fil l system , wit hthe reservoi r use d for the 'J ' tube attached , achieve d simila r result s (1 1 inche s require d fil l height) . Th e result s o f thi s tes t showtha t a 

# f roperl ydesigne d reservoi r systemcan greatl yreduc e require d illnec k height .P.2 8

Figur e 8 Bubbl e Flo w Patter n

Stati c Cas e

Liqui d Leve lP.2 9

Figur e 9 Resevoi r

To p Vie w

Sid e Vie w T o Nozzl e

< — 2. lo.- *

4 in . Stoc k Fillnec k

Reservio r

T o TankP.3 0 -28

- Anothe r approac ht o bubbl e contro l involve s the us e o f a simpl e baffl e t o contro l flowin the fillnec k a s i s nowuse d i n some vehicl e designs . Mor e specificall ythe inflowo f fue l an d th e backflo wo f bubble s ca n b e separate d wit hth e us e o f a baffling system . Th e simpl e baffling systemshow n i n Figur e 1 0 direct s an

d smooth s the inflowo f fue l an d als o direct s an d restrain s the backflo wo f bubbles . Th e baffl e restrict s inflo w t o on e portio n o f th e fillnec k an d encourage s muc ho f th e bubbl e backflo wt o ris e i n the other . Th e vent s nea r th e top o f th e baffl e allo wcirculating ai r an d vapo r t o pas s through th e baffle , bu t an yremaining bubble s ar e poppe d b yth e edge s o f the vent s befor e theycan reachthe nozzl e ventur i tube . Test s wer e conducte d t o determin e the fillnec k heigh t requiremen t fo r the submerge d fil l tan k wit ha baffle d fillneck . Th e procedur e describe d i n Sectio n D.3 . fo r th e submerge d fil l withou t baffling wa s followed . A t a fue l inflow rat e o f 7. 5 gal/mi n an d tan k backpressur e o f 5 inche s H 2 0 , require d fillnec k heigh t wa s reduce d t o 11. 5 inches , a decreas e o f 5. 5 inches . Th e baffl e approac hwa s no t evaluate d wit h.the in-tub e tra p o r J-tube , bu t coul d b e use d i f th e baffl e extende d fo r enoughint o th e liqui d t o separat e the liquid/bubbl e flow . 4 . Discussio n Th e reservoi r an

d baffl e approache s discusse d abov e wer e successfu l i n reducing fillnec k heigh t requirement s b yabou t 3 0 percent . O f the portio n o f th e fillnec k heigh t tha t ca n b e attribute d t o th e dynami c affect s o f refueling , th e reductio n i s approximatel y5 5 percent . Thi s reductio n i s quit e significan t give n th e limite d time an d resource s committe d t o thi s effort , an

d suggest s furthe r improvemen t i s possible . F . Discussion/Conclusion s 1 . Summary On e o f th e ke ycomponent s o f a n onboar d refueling vapo r recoverysystemi s a fillnec k sea l t o preven t the escap e o f vapor s during refueling . Whil e mechanica l sea l approache s hav e bee n demonstrate d successfully , ther e ar e concern s abou t th e safety , durability , an d integrit yo f the mechanica l sea l approach. ' A s a

n alternativ e t o a mechanica l seal , EPAha s evaluate d th e practicalit yo f implementing a liqui d sea l approach . Th e practicalit yaspec t o f the liqui d sea l approac h involve s thre e factors : fil l heigh t requirements , safety , an d syste mefficiency . Syste mefficienc yi s discusse d i n th e nex tP.3 1

Figur e 1 0 Baffle d Fillnec k

Nozzl e

Inflo w



# ____ _

# _J U

Sid e Vie w Fron t Vie w-30

-

portio n o f thi s report . Fil l heigh t requirement s ar e importan t becaus e o f concern s regarding prematur e nozzl e shut-off . I n orde r t o evaluat e th e potentia l suitabilit yo f variou s liqui d seal s wit hrespec t t o fil l heigh t requirements , system s wer e teste d unde r standar d tes t conditions : a fue l dispensing rat e o f 7. 5 gal/mi n an

d a tan

k backpressur e o f 5 inche s H 2 0 . Th e vertica l fillnec k heigh t require d fo r norma l refueling o n eac h a t th e thre e liqui d sea l approache s wa s measure d an d recorde d fo r eac hsystem . Du e t o the excessiv e amoun t o f bubbling generate d during refueling , fillnec k height s o f a t leas t 1 6 inche s wer e neede d t o refue l the tan k fo r the J-tube an d submerge d fil l approaches . Becaus e o f fillnec k heigh t limitation s impose d b y some curren t vehicl e models , effort s wer e mad e t o reduc e th e fil l heigh t requirement s o f the liqui d sea l systems . Thi s involve d fillnec k modification s aime d a t controlling ai r entrainmen t an

d bubbling i n the fillneck . Throughthe us e o f reservoir s an

d baffles , fil l height s wer e reduce d t o 1 1 inches . Th e reductio n o f 5 inche s i s significant , considering tha t seve n inche s o f fillnec k heigh t woul d be necessaryt o suppor t a backpressur e o f 5 inche s H 2 0 unde r stati c conditions . Th e effec t o f dynamic s wa s reduce d t o 4 inches . Th e result s o f th e fil l heigh t evaluation s ar e summarize d i n Tabl e 2 . Th e safet yo f liqui d . sea l approache s mus t als o b e considered . Mos t notably , liqui d sea l system s canno t pressuriz e during refueling suc ha s coul d occu r fo r mechanica l sea l systems . An

yincreas e i n pressur e during refueling woul d caus e fue l t o ris e i n th e fillnec k an d automati c shutof f t o occur . Th e on e safet yproblemtha t mus t b e addresse d fo r th e liqui d sea l systemi s the possibl e spitbac k o f fue l whe n the ga s cap i s remove d prio r t o refueling . Spi t bac k coul d occu r i f the line s t o the carbo n caniste r becam e blocke d an d pressur e buil t i n th e tank prio r t o refueling . Whe n th e ga s cap wa s removed , some o f th e fue l forming th e liqui d sea l coul d b e force d ou t o f the fillnec k a s pressur e equalized . Spi t bac k ca n b e avoide d b yeithe r 1 ) removing the liqui d sea l afte r refueling o r 2 ) including a pressur e relie f system t o ven t tank pressur e befor e spi t bac k ca n occur . Th e in-tub e tra p an d 'J ' tub e us e th e firs t alternative . B

ydrilling a smal l hol e a t th e bottomo f th e upwar d opening 'U ' i n thes e designs , th e liqui d tra p ca n operat e during refueling , an d the n drai n soo n afte r th e even t ha s bee n completed .-31

- Tabl e 2 Benc hTes t Fil l Heigh t Requiremen t

System In-Tub e Trap J-Tube Submerge d Fil l Stati c 7 " 7 " 7 " Bas e

System

- 16 " 16 " 11 "

11 " 11 " Modifie d System (3 " pip e (reservo (baffle ) 5 " H 2 0 backpressure , 7. 5 gp m dispensing rate , 2" fillpip e diameter .-32

- Th e submerge d fil l system , o n the othe r hand , mus t includ e a mor e comple xpressur e relie f system . Ther e ar e a numbe r o f way s t o incorporat e the pressur e relie f systemint o th e submerge d fill . On e o f the simple r pressur e relie f system s i s show n i n Figur e 11 . Th e smal l tube enter s the tan k abov e the ful l tank liqui d level , s o i t i s neve r submerged . A s refueling take s place , the *U ' portio n o f th e smal l tub e i s fille d wit h fluid . Whe n th e ga s ca p i s remove d prio r t o refueling , th e pressur e i s vente d throughthe smal l tub e befor e spitbac k ca n occur . The . amoun t o f pressur e neede d t o ven t the system ca n b e change d b

ychanging th e dept ho f th e 'U ' portio n o f th e smal l tube . Althoughth e spi t bac k problemca n be easil ysolve d fo r an yo f th e systems , the alteratio n o f the submerge d fil l i s clearl ymor e comple x than tha t require d fo r the in-tub e tra p o r 'J ' tub e liqui d seals . 2 . Conclusion s Ther e ar e two mai n question s t o b e addresse d in concluding th e firs t portio n o f thi s report . First , i s th e liqui d sea l approac ht o fillnec k vapo r containmen t a practica l alternativ e t o the mechanica l sea l a s par t o f a n onboar d refueling vapo r recoverysystem ? Second , whic hsystem s teste d i n the stud yar e th e mos t promising fo r furthe r development ? Th e answe r t o the firs t o f thes e question s i s generall y yes . Th e liqui d sea l could , b e adapte d t o fi t mos t light-dut y vehicle s an

d truck s a s currentl yproduced , bu t ther e ar e some vehicle s tha t do no t provid e adequat e fil l heigh t t o emplo ythe liqui d seal . Ther e ar e two majo r classe s o f fillnec k configurations , th e sid e fil l an d th e rea r fill . Th e sid e fil l configuration s wil l be discusse d first . Th e liqui d sea l design i s adaptabl e t o mos t sid e fil l vehicles . I n fact , mos t vehicle s coul d probabl ybe equippe d wit ha n unmodifie d fillnec k (n o baffl e o r reservoir ) . Fo r othe r vehicl e models , the lengt ho f th e fillnec k i s sufficien t t o permi t th e us e o f a liqui d sea l wit ha modified , bubbl e reducing fillneck . Further , i t appear s tha t change s coul d b e mad e i n mos t sid e fil l vehicle s t o increas e th e fillnec k heigh t i f needed , b

ychanging th e locatio n o f th e ga s cap o n th e vehicl e body . Rea r fil l configuration s ar e muc hles s receptiv e t o th e liqui d sea l approac hthan ar e sid e fills . Th e fillnec k heigh t o f some rea r fil l vehicle s i s a s littl e a s 5 inches . Afil l heigh t o f 5 inche s coul d accommodat e a backpressur e o f onl y 3.1 5 inche s H 2 0 unde r stati c conditions . Th e limite d testing conducte d b

yEP Asuggest s tha t wit ha carefull ydesigne dP.3 5

Figur e 1 1 Submerge d Fil l wit hPressur e Relie f

^an k Overpressur e Relie f Valv eP.3 6 -34

- reservoir , a fillnec k heigh t coul d probabl yb e reduce d t o approximatel y6. 0 inche s (3. 0 inc hH 2 0 backpressur e an d a 7. 5 gal/mi n fil l rate) . I f a manufacture r wer e convince d o f th e superiorit yo f the rea r fil l configuration , an d wante d t o us e a liqui d sea l system , change s i n fue l tan k an d ga s ca

p location s woul d hav e t o be made . However , thes e change s migh t b e relativel yinvolved . Anothe r approac hwoul d b e t o creat e a horizonta l reservoi r b yextending the fillpip e horizontall y acros s the to

p o f th e fue l tank , (eithe r outsid e o r inside ) . Th e fue l woul d the n ente r the tan k a t the opposit e end . Anothe r optio n ope n t o manufacturer s o f rea r fil l vehicle s woul d b e the us e o f a mechanica l seal . Th e accompanying safet y concern s woul d have t o b e addressed . Nevertheless , i t i s importan t t o not e tha t mos t curren t rea r fil l vehicl e model s ar e being phase d ou t an d no newmodel s o f thi s desig n hav e bee n introduce d recently . I n the pos t 199 0 time frame few , i f any , ne wmodel s wit hrea r fil l tank s ar e expecte d i n th e ne w car/ligh t truc k fleet . Th e secon

d questio n t o b e addresse d i s whic hsystem examine d i s promising fo r furthe r development . Ther e ar e four characteristic s tha t ar e importan t i n comparing thes e liqui d seals . Th e firs t i s the spatia l efficienc yo f the syste ma s measure d b

yrequire d fil l height . Th e tes t result s sugges t tha t al l o f the system s ca n be modifie d t o ge t nearl yequa l results . Eac hsystem evaluate d neede d a fillnec k heigh t o f approximatel y1 1 inche s t o .suppor t a backpressur e o f 5 inche s H 2 0 a t a fue l dispensing rat e o f 7. 5 gal/min . Th e submerge d fil l systemdoe s hav e a n advantag e i n thi s area , however , sinc e th e ful l fil l heigh t i s neede d onl ya s th e tank approache s the ful l level . Refueling safet yi s the second majo r characteristi c fo r compariso n o f th e liqui d sea l systems . Bot hth e in-tub e tra p an d 'J ' tub e nee d onl yon e mino r modificatio n t o avoi d an y spitbac k problem . However , th e submerge d fil l syste mneed s a pressur e relie f systemlik e tha t describe d earlier . Th e submerge d fil l systemi s a t a disadvantag e i n thi s respect . Th e thir d characteristi c o f compariso n fo r thes e system s i s th e complexit yo f th e liqui d sea l itself . Th e in-tub e tra p i s th e mos t comple xo f th e three . Th e submerge d fil l an d 'J ' tub e design s woul d b e muc hles s difficul t t o buil d an d ar e probabl ymor e practica l fo r thi s reason . Th e fina l basi s o f compariso n i s th e securit yo f th e liqui d sea l define d i n term s o f the probabilit yo f vapo r escapin g t o th e atmospher e during refueling . Th e bigges t concer n abou t t.a p securit yarise s whe n a vehicl e sit s o n slope d terrai n during refueling . Th e in-tub e trap an d 'J ' tub eP.3 7 -35

- trap s ca n be designe d t o ensur e securit yu p t o an

yreasonabl e angl e chosen . Th e submerge d fil l system work s differentl ytha n thes e systems , however . Fo r th e submerge d fil l t o functio n properly , th e fue l mus t ente r the tan k belowthe liqui d surface , bu t whe n the tan k i s nearl yempty , the mout ho f the fillnec k wil l be onl yslightl ybelo wthe liqui d level . I f the vehicl e wer e o n a n incline , th e fillnec k mayno t b e submerge d a t al l o r maybe onl ypartiall ysubmerged , an d some vapo r coul d escap e during th e earl ystage s o f refueling . I t i s clea r fro

mthe discussio n tha t eac hsystemha s bot h strong an

d wea k points , bu t mos t o f the problem s wit han yo f the system s ca n be resolve d wit ha . moderat e amoun t o f effort . Th e relativ e complexit yo f th e in-tub e tra p suggest s tha t thi s desig n maybe the mos t costl yt o produce , bu t i f installe d in the insid e to

p o f the tank i t coul d b e implemente d wit hno othe r fillpip e modifications . Th e othe r tw o system s ar e als o clearl ywort hfurthe r investigatio n i f the liqui d sea l concep t i s being developed . Base d o n the safet yadvantage , the J-tub e i s somewha t preferabl e t o the submerge d fill , an d EPAha s selecte d tha t approac hfo r inclusio n in the prototyp e liqui d sea l onboar d system develope d fo r benc htesting . . Th e J-tub e wa s als o selecte d becaus e o f EPA' s previou s experienc e wit hthe submerge d fil l whic hshowe d veryhighefficiencie s i n a benc h test.[4 ] Th e nex t portio n o f thi s repor t cover s EPA' s programt o evaluat e the efficienc yo f a J-tub e liqui d seal . Th e discussion s cove r th e remainde r o f the component s neede d fo r a benc hevaluatio n o f the systeman d the efficienc ytesting conducte d b

yEPA . Ill . Benc hTesting o f a Liqui d Sea l Onboar d System A . Descriptio n o f th e Prototyp e System 1 . Introductio n Onc e th e evaluatio n o f the thre e liqui d sea l concept s wa s complete , EPAdesire d t o evaluat e th e efficienc yo f a liqui d sea l i n a simpl e prototyp e onboar d refueling contro l system . A s wil l b e describe d below , th e prototyp e systemconstructe d fo r thi s evaluatio n wa s relativel ycrude , an d incorporate d onl y th e essentia l components . No attempt s wer e mad e t o ad d component s o r incorporat e modification s t o reduc e th e refueling emissio n rat e o r optimiz e systemefficiency . Thi s sectio n o f th e repor t briefl yexamine s th e thre e component s adde d downstream

o f th e fue l tank t o complet e the prototyp e system .P.3 8 -36

- T o complet e the prototyp e systemthre e additiona l component s wer e needed . Thes e includ e a fil l limiter , a properl ysized ' vapo r line , an d a n activate d carbo n canister . Eac ho f thes e component s i s discusse d below , in th e contex t o f th e flowrat e an

d backpressur e design characteristic s mentione d abov e an

d the overal l efficienc yo f the prototyp e system . 2 . Fil l Limite r While.i t doe s no t directl yaffec t systembackpressur e o r efficiency , a fil l limite r i s neede d in onboar d systemdesign s wher e the vapo r ven t outle t i s locate d in the fue l tank vapo r drive . O n presen t fue l tanks , the automati c shut-of f featur e o f th e fue l nozzl e i s activate d whe n tan k bac k pressur e increase s a t th e en d o f the refueling even t an d cause s th e fue l i n the tan

k t o bac k u

p int o the fillnec k an d cove r th e nozzl e spou t wit hliquid . However , wit ha properl ydesigne d onboar d systemfue l tank backpressure s ar e minima l sinc e vapo r i s vente d during refueling . Th e smal l amoun t o f syste m backpressur e whic hdoe s exis t i s no t adequat e t o bac k th e fue l u p int o the fillnec k an d allowoperatio n o f the automati c shut-of f featur e o f the fue l nozzle . Therefore , a .fil l limite r i s neede d t o clos e the vapo r ven t whe n the tank i s ful l an d thu s increas e th e backpressure . Withou t a fil l limite r i t i s quit e possibl e tha t the tan k coul d b e fille d wel l beyond it s nomina l capacity . Fo r onboar d equippe d vehicle s using sid e fil l tank s wit hexterna l .ven t line s (a s in Figur e 12) , th e onboar d systemha s littl e effec t o n the refueling process . Th e refueling even t terminate s the wayi t doe s o n presen t vehicles , an d thu s a fil l limite r i s no t needed . Th e EPAprototyp e onboar d systemuse d a rea r fil l fue l tank withou t a

n externa l ven t line , s o a simpl e floa t valv e wa s neede d a s a fil l limiter . Th e floa t wa s constructe d o f th e same materia l use d fo r th e tank' s fue l leve l indicator . I t wa s suspende d fromth e roo f o f the tank o n a simpl e wir e i n suc ha wa ytha t i t woul d floa t o n th e fue l a s the tank approache d full , an

d woul d nes t int o the vapo r ven t whe n th e tank wa s full . Thi s woul d stop th e venting o f vapo r whic hwoul d immediatel yincreas e systembackpressur e an d thu s woul d quickl y lea d t o activatio n o f the nozzl e automati c shut-off . Befor e discussing th e vapo r line , two point s abou t th e fil l limite r an

d it s operatio n shoul d b e noted . First , EPA' s simpl e prototyp e di d no t includ e a liquid/vapo r separator , rollove r valv e o r a ven t closur e valve . Thes e wer e no t necessaryfo r a simpl e benc hset-u p intende d onl yfo r evaluatio n o f refueling emission s control . Second , EPAdi d no t experienc e significan t problem s wit hfue l spillag e du e t o operatio n o f th e fil l limiter , a s ha s bee n suggeste d b yFigur e 1 2 

## Typical Current

Evaporativ eSyste m

PRESSURE/VACUU M RELIE FCA P EXTERNA LVEN TLIN E

FLOAT/ROLLOVE R VALV E 

# • 3/8 " DIA . 8 ' LON G ^ .05 " DIA . LIMITIN G ORIFIC E

1 4 GALLO NFUE LTAN K PURG EVALV E

1 LITE R CARBO N CANISTE R T O PURG E INDUCTIO N POIN TP.4 0 -38

- some.[5 ] Thi s perhap s wa s du e t o the fac t tha t th e syste m evaluate d b

yEPAinclude d a reservoi r i n th e fillneck . 3 . Vapo r Lin e Th e purpos e o f the vapo r lin e i s t o conve ygasolin e vapo r fro mthe fue l tan

k t o the carbo n canister . I t mus t be size d an d constructe d o f materia l suc htha t i t doe s no t unnecessaril y increas e th e systembackpressur e (whic haffect s the fil l heigh t requirement) , an

d mus t be impermeabl e t o gasolin e vapors . T o mee t thes e requirements , thre e characteristic s o f the vapo r line an

d it s us e mus t be considere d an d evaluate d concurrently . Thes e includ e the vapo r lin e diameter , th e vapo r line configuratio n o r layout , an d th e vapo r line material . Th e affec t o f thes e thre e characteristic s o n system backpressur e an d permeabilit yo f vapor s i s discusse d below . A s gasolin e vapor s flowthroughth e lines , bot hmajo r an d mino r pressur e losse s occu r whic hinhibi t vapo r flowan d directl yaffec t systembackpressure . Th e vapo r line diamete r make s a majo r contributio n t o the pressur e losses , sinc e i t represent s a majo r contractio n i n th e flow . Th e . othe r majo r pressur e losse s ar e cause d b yfunctiona l resistanc e t o th e vapo r flow . Thi s i s a functio n o f th e vapo r lin e diameter , lengt ho f vapo r lin e used , an d t o some degre e the vapo r lin e material . Mino r pressur e losse s ar e mainl ycause d b ythe vapo r lin e layou t o r configuration . Thi s include s an ybends , elbows , expansion s o r contraction s i n the line , a s wel l a s an yothe r deviation s fromth e straigh t flowi n a vapo r lin e o f a constan t cros s sectiona l area . A s wa s discusse d earlie r i n relatio n t o fillnec k seals , th e contro l systemwa s designe d s o tha t th e vapo r lin e an d caniste r resul t i n a fue l tank backpressur e o f n o mor e tha n 5 inche s o f H 2 0 . Aserie s o f test s wa s designe d t o empiricall y determin e wha t siz e vapo r lin e woul d b e appropriat e fo r a typica l ligh t dut yvehicl e application . Thes e test s wer e performe d o n complet e contro l system s (J-tub e equippe d fue l tank , vapo r line , carbo n canister ) subjecte d t o actua l refuelings . Th e tes t condition s wer e constan t excep t fo r th e cross-sectiona l are a o f the tubing whic hwa s varie d fromtes t t o test . Althoug honl yon e tubing materia l wa s tested , th e test s (summarize d i n Tabl e 3 ) showe d tha t vapo r lin e wit ha n inne r diamete r o f a t leas t 1/ 2 inc hwoul d hav e t o b e use d t o keep bac k pressur e belo w5 inche s H 2 0 fo r th e entir e system . T o b e safe , vapo r lin e o f 5/ 8 inchinne r diamete r wa s use d fo rP.4 1 -39

- Tabl e 3 Vapo r Lin e Pressur e Drop Contribution s P , Inche s H 2 0 Tub e ID , Inc h 3/ 8 1/ 2 5/ 8 1/ 2 5/ 8 Tub e

1 5 1 5 1 5 8 1 2 Conf : ft. , ft. , ft. , ft. , ft. , iguratio n 6 bend s 6 6 4 4 bend s bend s bend s bend s Benc h Tes t 5 2. 2 1. 2 1. 5

. 9P.4 2 -40

- contro l system

testing , although1/ 2 inc hvapo r woul d clearl y b e reasonabl e for man yvehicl e applications. * Th e tubin

g materia l i s als o veryimportan t t o th e functioning o f the contro l system . Th e mos t importan t characteristi c o f appropriat e tubing material s i s impermeabilit yt o gasolin e an d gasolin e vapors . I f a vapo r lin e whic hwa s permeabl e t o gasolin e vapor s wa s use d a s par t o f th e contro l system , hydrocarbon s coul d escap e fro mthe tubing , defeating the purpos e o f th e contro l system . Ther e ar e a numbe r o f tubin

g material s whic hwoul d be appropriat e fo r thi s application . Flexibility , densit yan d cos t characteristic s ar e al l factor s t o be weighe d i n deciding betwee n hard rubber , softer , mor e flexibl e rubbe r an d stee l materials . Adoubl e walled , flexibl e rubbe r fue l lin e wa s use d i n EPA' a prototyp e onboar d contro l systemsinc e 5/ 8 inchimpermeabl e vapo r lin e wa s no t commerciall yavailable . 4 . Carbo n Caniste r Activate d carbo n fo r captur e an d storag e o f gasolin e vapor s ha s bee n use d successfull yi n automotiv e application s fo r mor e than ten years . T o appl ythi s technologyt o contro l o f refueling emission s i n EPA' s benc hevaluation , th e caniste r mus t no t increas e systembackpressur e mor e than i s necessary , an d i t mus t b e size d an d loade d wit henoughactivate d carbo n t o efficientl ycaptur e essentiall yal l refueling emissions . Thes e tw o factor s ar e closel ylinke d sinc e caniste r siz e an d desig n bot himpac t backpressure . Rathe r than designing a n optimu

mcanister , i t wa s EPA' s goa l t o construc t o r obtai n a caniste r whic hwa s adequatel y size d t o captur e al l refueling emission s froma n 1 8 gallo n fue l tank an

d ye t woul d no t increas e tota l systembackpressur e t o mor e than 5 inche s H 2 0 . First , t o assis t i n meeting th e backpressur e reguirement , EP Ahel d discussion s wit hsevera l manufacturer s o f activate d carbon . Base d o n thes e discussions , EPAselecte d Westvac o extrude d woo d bas e activate d carbo n fo r us e i n th e canister . Informatio n presente d b ythe vendo r indicate d tha t th e extrude d activate d carbo n migh t hav e a highe r workin g butan e workin g capacit yan

d bette r pressur e drop characteristic s tha n th e mor e conventiona l activate d carbon s nowuse d i n evaporativ e emissio n applications . However , i t appear s tha t an yo f th e activate d carbo n type s sol d b yth e differen t companie s woul d als o wor k successfull yi n capturin g refueling vapors , bu t thes e woul d Thi s discussio n briefl yaddresse s ho wvapo r lin e diamete r affect s backpressure . An ysystemdesig n woul d hav e t o conside r vapo r lin e length , configuration , caniste r effects , etc. , i n additio n t o vapo r lin e diameter .-41

-

hav e differen t performanc e characteristic s differen t amoun t o f activate d carbon . an d woul d requir e a I n sizing the canister , the nex t step woul d b e t o estimat e th e tota l amoun t o f activate d carbo n needed , base d o n gasolin e vs . butan e working capacity , apparen t density , othe r factors . A s i s show n o n Tabl e 4 , EP

A carbo n be d o f 105 0 gram s woul d be require d refueling emission s fro ma n 1 8 gallo n tank , densit yo f 3 0 gm/10 0 ml , a caniste r o f abou t woul d b e needed . carbo n agin g an d estimate s tha t a t o captur e al l A t a n apparen t 350 0 milliliter s Alternatively , however , EP Aturne d t o wor k previousl y conducte d b

yMobi l Researc han d Developmen t i n thei r 197 8 onboar d demonstratio n program . I n tha t progra m Mobi l use d a 435 0 m l caniste r t o contro l refueling an d evaporativ e emission s froma carburette d 197 8 Pontia c Sunbir d whic hhad a n 18. 5 gallo n fue l tank.[l ] A n inquiryt o Mobi l reveale d tha t th e caniste r shel l whic hi s show n i n Figur e 1 3 wa s stil l o n han d an d availabl e fo r loan , s o thi s caniste r shel l wa s use d b yEP A i n the prototyp e system . Thi s caniste r wa s loade d wit h approximatel y140 0 gram s o f activate d carbon , somewha t mor e tha n neede d base d o n Tabl e 4 . 5 . Conclusio n W e hav e no wdescribe d al l portion s o f th e prototyp e onboar d systemuse d t o evaluat e th e efficienc yo f the J-tub e liqui d seal . Th e prototyp e onboar d systeminclude d th e following components :

J-tub e liqui d fillnec k sea l wit hreservoi r 1 8 gallo n fue l tank fil l limite r 5/ 8 inc hvapo r lin e 435 0 m l activate d carbo n caniste r Th e result s o f EPA' s evaluatio n testing o n thi s systemar e describe d i n th e nex t portio n o f thi s report . B . Evaluatio n o f SystemEfficienc y 1 . Introductio n Onc e the prototyp e onboar d systemhad bee n constructe d i n a benc hconfiguration , a serie s o f refueling emission s test s wer e conducte d t o evaluat e the efficienc yo f th e systeman d t oP.4 4
-42

- Tabl e 4 Tota l Require d Carbo n Bed

Refueling Emission s 14 4 g (a t 8 g/ga l fo r 1 8 gallons ) Activate d Carbo n Needed : 70 0 g 5 0 Percen t Carbo n Aging Allowanc e an d Safet yFacto r 35 0 g Tota l 105 0 g Base d o n a gasolin e working capacit yo f 6. 3 g mgasolin e vapor/10 0 m l carbon , an d a n apparen t densit y• o f 3 0 g m carbon/10 0 m l carbon .- ^ 

# ———

# ^~ < m 

# I FIGUR E 1 3



## REFUELINGSYSTE M

CARBON CANISTE R

Carbo n 

# r^r^ r



# r^r r [ m/m/l/M / / / / i/V 

# ri^T^T^ Foam

-ZZZZZZZZZZZZZZZZZ



# zzzzzz__rH Foa m

Wir e Mes h Fiberglass Ai rFilte r

Su n bird Carbureto r Bow l Fittin g Chevrolet Carbureto r Bow l Valves 0.047 " Blee

d to Fue l Tan k Sid e Vie wo fTo p Disc n n—i - 1/8 " Plexiglass

1 " Dia . x l 3/4 " Long Plexiglas s Tub

e Wir e Mes h Glued t o Botto m o fTub e o fTub e

Chevrolet Purg e Valve , Drille d to 0.180 " Caniste rDimension s 6 " Hig h 8 " Diamete r Carbon : BPL-F 3 1550 Gram s 435 0 M L-44

-

drawsome conclusion s a s t o whethe r liqui d sea l system s coul d hav e a s higha

n efficienc ya s mechanica l seals . Thi s portio n o f th e repor t describe s howthes e test s wer e done , the result s o f th e testing , an d draw s some conclusion s abou t th e efficienc y o f liqui d sea l systems . 2 . Descriptio n o f Tes t Procedur e Th e refueling test s wer e conducte d i n a standar d evaporative , emission s SHE D whic hhad bee n modifie d t o allo wth e entryo f a fue l hos e fitting int o th e sid e wall . Fue l wa s dispense d froma standar d fue l deliverycart . Th e genera l tes t procedur e followe d i s outline d i n Tabl e 5 , an

d i s discusse d below . Th e refueling contro l system benc hsystemwa s place d i n th e SHE D an d fille d t o 1 0 percen t o f nomina l tank capacity . Th e fue l tan k wa s the n heate d t o th e desire d temperatur e insid e th e ope n SHE D wit hthe fue l cap on. * Th e purg e fan wa s operating i n the SHE D during thi s time . Th e dispense d fue l had bee n heate d t o it s desire d temperatur e previously . A t th e en

d o f th e heating , the heating blanket s wer e unplugged , the fue l nozzl e wa s inserte d int o the fillneck , th e mixing fan s wer e restarted , an d the SHE D wa s sealed . A background reading wa s take n i n th e seale d SHE D befor e refueling began . Th e refueling wa s the n performe d b yturning o n the fue l car t fro mth e outsid e th e SHED . Th e refueling wa s terminate d whe n automati c shu t of f occurred . Afina l FI D reading wa s the n take n in th e SHED , an d the SHE D floo r an d fillnec k are a wer e checke d fo r fue l spills . Th e refueling emission s t o th e SHE D wer e evaluate d a s th e differenc e betwee n th e initia l an

d fina l FI D readings , wit happropriat e adjustment s fo r th e smal l portio n o f th e SHE D volum e occupie d b yth e benc happaratus . Followin g th e terminatio n o f th e testing , th e carbo n caniste r wa s weighe d an d the n purge d wit ha tota l o f 30 0 cf mo f ambien t ai r t o remov e refueling vapor s fro mth e canister . Base d o n reductio n i n caniste r weights , thi s amoun t o f ai r wa s mor e tha n sufficient . Followin g completio n o f th e purge , th e canister'wa s weighe d again . Finally , befor e describin g th e result s o f th e testing , i t i s importan t t o discus s th e temperatur e an d RVP characteristic s A s wil l b e discusse d later , a coupl e o f test s wer e conducte d wit hth e fue l cap loos e during th e hea t buil d t o estimat e th e effect s o f hea t buil d emissions .P.4 7 -45

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Tabl e 5 Tes t Sequenc e 1 . Drai n an

d refue l tank t o 1 0 percen t o f nomina l capacity , 2 . Connec t hea t blanket s an d thermocouples , fue l ca p on . 3 . Hea t tan

k t o desire d temperatur e an d stabilize . 4 . Inser t fue l nozzle , se t latcha t highlevel . 5 . Clos e SHE D an d star t mixing fans . 6 . Tak e initia l sampl e reading (usin g FID) . 7 . Remov e cap , refue l tank t o automati c shut-off . 8 . Chec k fo r spill s an d nozzl e shut-off . 9 . Tak e fina l sampl e reading (usin g FID) . 10 . Disconnect , hea t blanket s an d thermocouples .-46

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o f the tes t fuel s used . Th e dispense d an d fue l tan

k temperature s wer e se t a t 92° F +

_2° F t o be consisten t wit h previou s testing conducte d b yEP Aan d t o b e representativ e o f th e temperatur e propose d b yEP Ain it s recommende d practic e for testing o f refueling emission s levels.[6,7 ] Fuel s o f 11. 8 an d 9. 0 ps i RV

P wer e used i

n the program . Howeve r mos t test s wer e conducte d using the 11. 8 RV P fue l sinc e i t woul d be expecte d t o creat e highe r refueling emission s an d thu s woul d be a mor e stringen t evaluatio n o f systemefficiency . 3 . Refuelin g Emissio n Tes t Result s Th e result s o f the refueling emissio n test s ar e summarize d in Tabl e 6 ; mor e detaile d informatio n on eac htes t i s provide d in Appendi x A . Th e emissio n result s show n includ e 7 test s a t 11. 8 RV P an d 3 test s a t 9. 0 RVP . Th e efficienc yo f th e contro l systemca n b e evaluate d b

y comparing the refueling losse s t o the SHE D t o the tota l refueling emission s base d on the su mo f refueling losse s t o th e SHE D an

d caniste r weigh t gain . Unde r thi s approac hthe efficienc ycan be calculate d a s show n below : PF P = i
_

losses.t o SHE D x100 % 

### caniste r wt . gai n + losse s t o SHE D Using thi s approach , the averag e efficienc yi s 9 8 percen t for the 11. 8 ps i fue l an d 96. 6 percen t for th e 9. 0 ps i fuel . Value s range d fro m 95. 8 t o 99. 4 percen t wit ha n averag e o f abou t 9 7 percent . However , thes e result s clearl yindicat e tha t theoretica l efficiencie s o f 9 8 percen t or mor e ar e availabl e for liqui d sea l systems . Thi s compare s t o efficiencie s o f 96-9 9 percen t for a mechanica l sea l system.[1,8 ] A s wa s note d previously , tw o test s wer e conducte d wit hth e fue l ca

p loos e during the hea t buil d t o asses s howmuc hhea t buil d emission s wer e affecting th e tota l caniste r vapo r load . Referring t o Tabl e 6 , test s 1- 5 wer e conducte d wit hthe fue l ca p on and

- full yseale d during the hea t build , whil e test s 6 an d 7 wer e conducte d wit hthe ca p onl yloosel yin place . A compariso n o f th

e test s show s tha t the caniste r weigh t gai n an d th e apparen t refueling emissio n rat e wer e greate r whe n the ca p wa s on an

d sealed . T o some degre e the caniste r wa s accepting vapo r fro

mthe tan

k during the hea t buil d simila r t o wha t now occur s in a diurna l evaporativ e emission s test . However , a s can be see n fro

m Tabl e 6 , thi s ha s littl e effec t on th e system efficienc yevaluatio n for the program . Al l value s fal l withi n the 96-9 9 percen t efficienc yrange .P.4 9

RV P 11. 8 ps i

9. 0 ps i -47 -

Tes t 1 2 3 4 5 6 7 Liqui d Cond i I T 91. 0 90. 8 92. 0 91. 0 91. 9 92. 0 91. 0 Tab l Sea l Contro l tion s I D 92. 0 90. 3 90. 5 91. 7 91. 9 92. 0 92. 5 Ga l 12. 5 15. 5 15. 0 15. 1 14. 0 15. 5 12. 5 e 6 Syste mEfficiencie s Los s t o SHED(q ) 2. 3 3. 6 6. 1 4. 9 2. 5 2. 0 1. 5 Caniste r

W t Gain(q ) 153. 3 168. 1 164. 1 129. 3 123. 9 170. 5 163. 0 Percen t

Efficienc y 99. 4 97. 9 96. 4 . 96. 3 98. 0 98. 8 99. 1 Avg . EF F98. 0 0 8 0 9 1 0 . 92. 0 93. 0 92. 0 93. 0

92. 2 92. 5 18. 5 15. 0 15. 0 6. 0

3. 6 4. 0 135. 5

121. 1 120. 8 95. 8

97. 1 96. 8 Avg . EF F96. 6-48

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Th e turbulen t mixing i n th e fillpip e discusse d previousl y an d th e subsequen t entrainmen t o f bubble s i n the liqui d entering th e tank suggest s tha t the liqui d sea l mayb e generating additiona l refueling emission s relativ e t o th e uncontrolle d fue l tank . Uncontrolle d refueling emission s wer e no t evaluate d o n th e benc hsystem , bu t a simila r fue l tank wa s evaluate d o n th e 198 3 Oldsmobil e Cutlas s evaluate d i n a previou s EPAtes t program.[7 ] Th e result s o f tha t testing indicat e tha t uncontrolle d refueling emission s fo r thi s vehicl e ca n b e predicte d using th e equatio n Losse s (g/gal ) = -5.58 4 - 0.114[AT(°F) ] + 0.085 7 [T D (°F) ] + 0.52 0 [RVP(psi)] , wher e A T = T T - T D . Substituting th e temperatur e an d RVP condition s o f Tabl e 6 int o thi s equatio n (T D = 92°F , A T = 0F° , RVP = 11. 8 psi ) yield s an emissio n rat e o f 8. 4 g/gal . Fo r comparison , two test s wer e conducte d o n the prototyp e onboar d systemwithou t th e caniste r i n place . Th e refueling emissio n rat e average d 9. 9 g/ga l fo r the two test s (Test s 85-1363 , 136 4 i n Appendi x A) . Th e compariso n o f th e actuall yoccurring an d predicte d emission s discusse d above , lead s t o th e conclusio n tha t i n thi s cas e th e liqui d sea l increase d the emissio n rate . However , using thi s dat a i t i s no t .possibl e t o precisel yquantif yth e effect ; th e us e o f an averag e coul d b e misleadin g du e t o th e relativel ysmal l numbe r o f test s an d the rang e i n value s seen . Ideally , comparison s shoul d b e mad e betwee n identica l tank s wit han

d withou t a liqui d sea l wit ha s man yothe r variable s a s possibl e controlled . Aclos e revie wo f th e detaile d result s i n Appendi xA reveal s tha t 14-15. 5 gallon s wa s dispense d i n mos t tests , bu t ove r 1 8 gallon s wa s dispense d i n on e test . Thi s late r tes t wa s th e firs t conducte d i n th e serie s an d led t o th e conclusio n tha t th e fil l limite r installe d i n th e tank di d no t wor k properl yan

d an overfil l occurred . However , whe n th e fil l limite r wa s modifie d an d reinstalle d i t droppe d to o lowint o th e tank an

d abou t a gallo n o f nomina l tank capacit ywa s lost . Thi s account s fo r th e differenc e i n th e dispense d gallon s among th e tests , an

d explain s wh

ythe amoun t o f fue l dispense d in mos t test s wa s somewha t les s than 9 0 percen t o f nomina l tank capacity . 4 . Sourc e o f Emission s I n additio n t o assessing th e contro l efficienc yo f th e system , test s wer e als o conducte d t o locat e th e sourc e o f refueling emission s fromth e contro l system . Th e firs t ste p i n thi s proces s involve d checking the fue l tank an d vapo r lin e fo rP.5 1 -49

- leaks . Thi s wa s don e b yremoving th e caniste r fro mthe system , plugging the vapo r lin e (a t th e caniste r end ) an d pressurizin g the tank . Aliqui d wa s the n applie d t o the tank an d vapo r lin e s o tha t leak s coul d b e seen . Th e systemwa s fre e fro mleak s s o the onl ypossibl e source s o f emission s wer e the fillnec k an d th e caniste r (i f breakthroughwer e occurring) . I n orde r t o isolat e th e emission s fromth e fillneck , th e caniste r wa s lef t of f o f the systeman d wa s replace d wit ha plasti c vapo r bag . Refueling operation s wer e performe d wit hthe vapo r ba g i n plac e an d th e refueling los s wa s measured . I n thi s way , onl yth e emission s fro

mthe fillnec k wer e measured . Th e result s from thi s se t o f test s ar e show n i n Tabl e 7 . Th e refueling losse s fromth e contro l systemwit hth e vapo r bag ar e verysimila r t o thos e emitte d fromth e contro l systemwit hthe caniste r i n place . Th e projecte d efficiencie s show n i n Tabl e 7 wer e develope d b ydividing the refueling losse s b

yth e predicte d emissio n leve l foun d using th e equatio n cite d previously . Sinc e the refueling los s an d efficienc ynumber s o f Tabl e 7 ar e verysimila r t o thos e i n Tabl e 6 , i t appear s tha t mos t o f th e refueling los s come s fro mth e fillneck . IV . Conclusion s Th e purpos e o f the developmen t an d tes t program s conducte d wa s t o evaluat e th e practicalit yan d feasibilit yo f liqui d fillnec k seal s a s a n alternativ e t o th e mor e widel y demonstrate d mechanica l seals . Th e EPAprogramcovere d a laboratoryevaluatio n o f thre e differen t liqui d sea l concept s an d benc htesting o f a simpl e prototyp e onboar d systemusin g a liqui d seal . Th e evaluatio n o f th e liqui d sea l concep t led t o severa l conclusions .

• Th e availabl e fil l heigh t o n mos t sid e fil l passenge r car s an d ligh t truck s i s sufficien t t o permi t th e us e o f liqui d seal s withou t prematur e nozzl e shut-off .

• Fo r some sid e fil l vehicles , reduction s i n fil l heigh t woul d nee d t o b e achieve d throughinterna l fillpip e modification s t o contro l th e bubble s cause d b yth e strong turbulen t mixing i n th e fillpipe .

• Rea r fil l vehicle s woul d requir e mor e substantia l fillpipe , tank , o r othe r modification s t o us e liqui d seal s an

d thu s mayb e bette r suite d t o mechanica l seals .

# r -50

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Tabl e 7 Source s o f Refueling Emission s o n a Controlle d System *

Condition s Los s t o Predicte d Percen t Tes t T T T DGal . SHED(q ) Emissions(q ) Efficienc y 1 1 91. 0 - 92. 5 13. 3 2. 4 115. 0 97. 9 1 2 91. 0 92. 5 13. 5 2. 8 116. 8 97. 6 Vapo r ba g use d t o replac e canister ; RVP = 11.8 .-51

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• Liqui d sea l system s (especiall yth e J-tub e an d in-tub e trap ) appea r t o hav e safet yadvantage s ove r the mechanica l sea l an d submerge d fill .

• Th e strong turbulen t mixing i n the fillpip e entrain s ai r int o th e fue l entering the tank , an d increase s th e volum e o f vapo r whic hi s displace d from th e tank a s i t i s refilled . Severa l keyconclusion s ca n als o be draw n fromthe benc h testing o f a prototyp e onboar d systemusing a liqui d seal .

• Th e efficienc yo f the liqui d sea l system s i s comparabl e t o tha t achieve d b ymechanica l seals . Th e mechanica l sea l system s evaluate d b yAP I showe d efficiencie s o f 9 6 t o 9 9 percent . Th e liqui d sea l system s evaluate d i n thi s projec t showe d efficiencie s i n tha t range .

• Wit himprovement s i n th e contro l system , consistentl yhighcontro l efficiencie s (9 8 percen t an d greater ) ar e easil ywithi n reac hfor . liqui d sea l systems .

• Fo r a liqui d sea l systemwit ha n adequatel ysize d carbo n canister , mos t refueling losse s appea r t o aris e fromthe fillneck .

• Th e ai r entrainmen t cause d b ythe turbulen t mixing i n th e fillnec k appear s t o increas e the tota l refueling emission s loa d t o th e carbo n canister . Dat a generate d i n thi s tes t programi s insufficien t t o precisel yquantif ythi s effect . Th e primarypurpos e o f thi s progra mwa s t o demonstrat e th e feasibilit yo f liqui d fillnec k sea l concepts . Th e benc h prototyp e develope d her e wa s clearl ya firs t generatio n system ; n o attempt s wer e mad e t o optimiz e th e desig n t o reduc e th e effect s o f entrainmen t o r t o maximiz e contro l efficiencies . Improvement s i n bot harea s ar e possible , a s demonstrate d i n late r wor k conducte d b yAPI . [8 ] Thi s wor k show s tha t onboar d system s using liqui d fillnec k seal s cahconsistentl ycontro l refueling emission s wit hefficiencie s o f 9 8 t o 9 9 percent . Th e ' developmen t an d tes t program s conducte d b yEPA demonstrat e tha t liqui d sea l system s ar e indee d practica l alternative s t o mechanica l sea l systems . Analysi s suggest s tha t liqui d seal s ar e superio r t o mechanica l seal s in th e area s o f durability , tampering , an d safety , an

d hav e equa l efficiencie s fo r controllin g refueling emissions . However , th eP.5 4 -52

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wor k conducte d b

yEPAindicate s tha t liqui d seal s mayb e mor e attractiv e fo r sid e fil l than rear fil l vehicles , an d th e ai r entrainmen t cause d b yturbulen t mixing i n th e fillpip e may actuall yincreas e refueling emission s an d creat e th e nee d fo r a large r caniste r than tha t require d fo r mechanica l seals . Thu s some trade-off s mayexis t betwee n mechanica l an d liqui d fillnec k seals . Eithe r liqui d o r mechanica l fillnec k seal s coul d b e use d a s par t o f - a

n onboar d system . Eac happroac hha s it s strength s an d weaknesses , bu t bot hhav e bee n demonstrate d t o hav e high efficiencie s o n prototyp e systems . Whethe r a liqui d o r mechanica l sea l system i s preferabl e woul d hav e t o be evaluate d separatel yfo r eac hvehicl e model .-53

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Reference s 1 . "On-Boar d Contro l o f Refueling Emissions , Demonstratio n o f Feasibility, " Mobil e Researc han d Developmen t Corp. , fo r America n Petroleu mInstitute , Washington , D.C , Octobe r 2 1978 . 2 . "Contro l o f Refueling Emission s wit ha n Activate d Carbo n Caniste r o n the Vehicl e - Performanc e an d Cos t Effectivenes s Analysis, " Olso n Laboratories , Inc. , fo r America n Petroleu

mInstitute , Washington , D.C , October , 1973 . 3 . "SA

E Recommende d Practic e ( J 1045 ) - Instrumentatio n an d Technique s fo r Vehicl e Refueling Emission s Measurement. " 4 . "Statu s o f In-Hous e Refueling Los s Measurements, " Memorandu

mfro m Marti n Reinemann t o Rober t Maxwell , U.S . EPA , SDSB , Marc h6 , 1979 . 5 . "Ford Moto r Compan yComment s o n the Evaluatio n o f Ai r Pollutio n RegulatoryStrategie s fo r th e Gasolin e Marketin g Industry, " Nov . 1984 . 6 . "Draf t Recommende d Tes t Procedur e fo r th e Measuremen t o f Refueling Emissions, " Lis a Snapp , EPATechnica l Report , EPA-AA-SDSB-85-5 , July , 1985 . 7 . "Refueling Emission s fromUncontrolle d Vehicles, " D . Rothma n an

d R . Johnson , EPARepor t EPA-AA-SDSB-85-6 , 1985 . 8 . "Vehicl e Onboar d Refueling Control, " AP I Publicatio n 4424 , Marc h1986 .P.5 6 -54

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APPENDI X A Detaile d Tes t Result sFue l Tan k Benc hTest s FUEL-COMMERCIA

L UNLEADED , SUMMER , 92° F DISPENSED * ^ 1

Temperature s ° F

Tes t No . 85-069 4 85-012 0 85-012 1 85-012 3 85-069 8 85-069 9 85-135 8 85-136 2 85-136 8 84-563 3 84-563 4 84-563 5 85-136 3 85-136 4 Dat e

10-31-8 4 11-05-8 4 11-06-8 4 11-07-8 4 11-08-8 4 11-09-8 4 12-19-8 4 01-04-8 5 01-11-8 5 08-23-8 4 08-24-8 4 08-24-8 4 01-04-8 5 01-03-8 5 Ini

tia l 66. 8 68." 2 68. 3 69. 5 67.5 5 67. 0 61. 0 67. 7 60. 5 69. 0 67. 0 67. 9 70. 7 67. 7 Fina l 91.0 . 91. 0 90. 8 91. 0 92. 0 91. 0 92. 0 91. 0 91. 9 92. 0 93. 0 92. 0 92. 0 92. 5 Fina l Va p 89. 0 88. 8 89. 0 89. 0 90. 0 89. 5 88. 5 89. 5 91. 0 90. 2 89. 0 90. 3 89. 0 90. 8 Ma x T 3. 0 3. 0 3. 0 3. 5 3. 0 3. 0 3. 5 3. 0 5. 3 2. 0 2. 0 2. 0 4. 0 3. 0 Dis

pense d 92. 0 92. 5 90. 3 91. 0 92. 0 92. 5 90. 5 91. 7 91. 9 93. 0 92. 2 92. 5 89. 8 90. 0 Dis

pense d Gal

lon s 12. 5 13. 3 15. 5 13. 5 15. 5 12. 5 15. 0 15. 1 14. 0 18. 5 15. 0 15. 0 14. 3 14. 5 Refuel

in g Loss , gms . 2. 3 2. 4 3. 6 2. 8 2. 0 1. 5 6. 1 4. 9 2. 5 6. 0 3. 6 4. 0 134. 8 151. 5 Caniste r

W t Gai n 153. 3 N A 168. 1 N A 170. 5 163. 0 164. 1 129. 3 123. 9 135. 5 121. 1 120. 8 N A N A Dis

pensing Time Min,Se c 1'46 " 2'04 " 2'11 " 1'57 " 2'19 " 1'49 " 2'16 " 2'08 " 2'50 " 3'41 " 2'56 " 2'55 " 2'00 " 2'09 " Hea t

Tim e Mr,Mi n 57 " 52 " 56 " 45 " 51 " 55 " 58 " 40 " 45 " 46 " 48 " 48 " 56 " 42 " Spillage/Comment s Non e None , vapo r ba g None , manua l shutof f None , vapo r ba g None , can i n bo x multi-fueling None , mult i fueling None , Benzen e 13 A Controlle d None , caniste r onl y during refueling Non e None , manua l shutof f None , manua l shutof f Controlle d w/ o caniste r Controlle d w/ o caniste r Al l test s wer e a t 11. 8 RV P excep t 84-5633 , 5634 , and 5635 .