P. 1


# OAR Box 1830 Prepped by Ollie Stewart



## Document

Number: 

# 235 ) IV-B-2 8 Docket Number: 

# A-87-1 1

Printed 11/13/20089:00:23 AM

Sheet 235of 236P. 2 V 

## J"**% 

# w JA N 

## 1 4 199

4 \ UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y I NARB©RTrTilTDHXG5RI«1 4810 5

MEMORANDU M OFFIC E O F AI R AN D RADIATIO N

SUBJECT :
FROM :
THRU : Determinatio n o f Flo wRat e fo r Vapo r Ven t Lin e

Lea k i n Onboar d Vapo r Recover ySyste m B r Sp e ya n J . Manning , Mechanica l Enginee r 0. (V /V L \ ecia l Regulator yProject s Branc h^V^ f j' {AfMl

^^<U

TO : Glen n W . Passavant , Branc hChie f

Specia l Regulator yProject s Branc h Docke t No . A-87-1 1 Th e purpos e o f thi s mem o i s t o discus s th e methodolog yuse d t o determin e th e maximu mleakag e rat e i n th e onboar d vapo r recover y ven t lin e tha t coul d occu r befor e th e onboar d diagnosti c (OBD ) syste mindicate d a problem . Ahol e large r tha n 0.0 4 inche s woul d b e detecte d a s a failur e b yth e OB D syste man d woul d requir e repair ; therefore , w e determine d th e amoun t o f vapo r tha t coul d lea k ou t o f th e ven t lin e durin g a refuelin g withou t OB D detection . Fo r thi s analysis , th e leak-hol e wa s assume d t o b e a n orific e wit h a pressur e differenc e acros s it . W e assume d tha t th e 0. 5 inc h diameter-ven t lin e ha d a constan t vapo r flo wrat e o f 12. 5 gallon s pe r minut e throug hi t an d a pressur e insid e i t o f 1 0 inche s o f wate r (o r 5 2 lb/ft 2 ) greate r tha n th e ambien t ai r (atmospheri c pressure ) . A s mentione d above , th e orific e wa s assume d t o hav e a diamete r o f 0.0 4 inches . Th e flui d i n th e vapo r ven t lin e wa s assume d t o b e a 4 0 percen t gasolin e vapo r an d 6 0 percen t ai r mixture . Th e densit y o f th e mixtur e wa s determine d t o b e 0.11 5 lb/ft 3 a t a temperatur e o f 8 0 degree s Fahrenheit . Th e lea k rat e wa s determine d usin g a n equatio n fo r th e flo wo f fluid s wit hconstan t densit ythroug ha n orifice :
v 0 = C 0 *[2g( P i " P 0 )l/P ] 1/2 , wher e
v 0 ••

= velocit ythroug hth e orifice , C 0 = orific e coefficient , g = gravitationa l acceleration , p L = pressur e insid e ven t line , p 0 = atmospheri c pressure , p = density .P. 3

Sinc e th e Reynold s numbe r a t th e orific e wa s greate r tha n 20,000 , w e use d a constan t orific e coefficien t o f 0.61 . Th e lea k rat e i s show n below .

v 0 - 0.6 1 * [ ( 2 * (32. 2 ft/s 2 ) * ( 5 2 lb/ft 2 ) ) / 0.11 5 lb/ft 3 ] 1/ 2

v 0 = 10 4 ft/sec . Th e correspondin g volumetri c flo wrat e i s 0.4 1 gal/mi n(flo wrat e
= v 0 * Orific e area) . Furthermore , fou r gram s o f gasolin e vapo r i s equivalen t t o on e gallo n o f vapor . Thus , fo r a two-minut e refuelin g (abou t 2 0 gallons) , 3 gram s o f gasolin e vapo r i s projecte d t o lea k throug h a 0.0 4 inc hdiamete r vent-lin e hol e int o th e atmosphere . Thi s calculate d valu e i s supporte d b ytestin g performe d b y th e America n Petroleu mInstitute . I n tha t testin g the ymeasure d th e mas s o f vapo r pushe d throug ha 0.0 5 inc horific e fro mth e fue l tan k durin g a refuelin g event . Th e attache d lette r fro m Exxo n indicate s tha t i n al l bu t on e case , th e emission s fro mth e tan k wer e 3 gram s o r les s regardles s o f th e RV P o f th e fuel . Thus , th e vapo r flo wrat e fro ma lea k undetecte d b ya n OB D syste mwoul d b e 3 gram s o r les s pe r refueling , dependin g o n th e amoun t o f fue l dispensed . Attachmen tP. 4 

### SENT.BY:LINDEN , N J ;12-14-9 3 ;10:21A M; EXXO NRE S & ENG-PRD- + 31 3 74 1 7816; #II 3 

# E^p N RiStlARG H AN D iNOINEIRIN G COMPAN Y
P.O . BO X51 , LINDEN , NE WJERSE Y07036-O05 1 PRODUCTS RESEARC H DIVISIO N CH . Martine

z Dlrwto r Fuel s RsMans h Uboratm y 

### Decembe r 13 , 199 3 Mr
. G
. Passavan

t EPAMotor

Vehicle Emission s Laborator y 2S6 S Plymout

hRd
. An nArbor , M I 48190 5 Dea r Glenn , I was able t o retriev e th e followin g dat ao nth e weigh

t gai no f th e productionevaporativ e canister during arefuelin

g even t (se e attachedsheet)
. Thefou r vehicle s ar

e the four vehicle s describedinm

y SA Epapers . Th e refuelin

g condition s are thos e describedi nm y SA Epaper s (i.e. , not th e sam e condition s fo

r th e dispensedandtank

temperatures)
. The onl

y modification s t o th e vehicle s wa s th e installationo f thermocouple s t o measur

e tan k vapor an dliqui dtemperatures . Otherwis e th e vehicle s were productionvehicles
. The events ar e not necessaril y i norder bu t are a s I retrievedthemfro

mth e boxes
. The dat aindicate s t o me that th e weigh t gaino f th e productionevaporative canister for thes e fou r vehicle s during arefijelin

g even t are between0 an

d3 gram s an

dver y muc hvehicle dependent
. I f there ar e an

y questions , pleas e call Sincerely ,

Georg e Musse

r

R = 93 % 90 8 47 4 233 5 12-14-9 3 11:30A M P00 2 #4 6P. 5

:LINDEN , N J

Dat e Vehicl e
Dec . 198 7 Buic k Apr. 198 8 Ford Apr . 198 5 Pontia c

Apr- 198 5 Dodg e ;12-14-9 3 ;10:22A M

Te^ tFuel RV P 

### ps i 9 9 9 9 9 9 1 2 

### 9 9 10. 5 

### 12 10. 5 

### 12 

### 9 9 10. 5 

### 1 2 1 2 

### 9 10. 5 

### 1 2 

### 9 1 2 10. 5 

### 1 2 

### 9 10. 5 

### 1 2 

### 9 10. 5 10. 5 

### 9 1 2 

### 9 1 2 

### 9 1 2 10. 5 ; EXXO N RE S & ENG-PRL

V - 2 - 

## Evaporativ eCaniste r Weigh tGai n gram s 

### 2. 3 2. 2 2. 0 0. 0 1.0 1.0 3 2 2 1 0 2 3 2 2 1 2 2 1 1 3 1 J 1 1 1 0 I 1 1 1 1 1 0 1 1 1 1 2 31 3 74 1 7816; # 3 / 3

R= 97 % 90 8 47 4 233 5 12-14-9 3 11:30A M P00 3 tt46