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API Publ 1673:2009 pdf download

API Publ 1673:2009 pdf download.Compilation of Air Emission Estimating Methods for
Petroleum Distribution and Dispensing Facilities. Filling a UST
When a UST is filled, the incoming liquid displaces vapors in the tank. In balanced filling, the vapors are routed to the tank truck, and the only emissions are from any collection losses as the vapors go to the tank truck. Thus, for balanced submerged fill, the AP-42 emission rate is relatively low (40 mgIL). Although the emission rate might be expected to be a function of the leak tightness of the tank truck, AP-42 does not provide factors to make this distinction.
For filling operations that do not use vapor balancing, the vapors in the UST are vented to the atmosphere. Breathing
Breathing losses from USTs are caused by vapor expansion due to diurnal heating, just as for aboveground storage tanks. However, underground tanks experience less daily temperature variation than aboveground tanks. UST breathing losses may be further reduced by equipping the vent pipe with a pressure/vacuum valve (vent valve). EPA does not distinguish between controlled and uncontrolled breathing losses for USTs, but emission factors for controlled scenarios are available from CARB.
Some dispensing facilities use aboveground storage tanks, for which breathing losses can be estimated using the same method as for aboveground storage tanks at distribution facilities [see standing storage loss for fixed-roof tanks in 3.1.2.la)].
3.2.3 Vehicle Refueling
Vehicle refueling emissions include vapor displacement and spillage. EPA’s EIIP Volume Ill, Chapter 11, “Gasoline
Marketing [26],” Section 3.1.1, recommends that the MOBILE model be used to estimate vehicle refueling emissions.
Onboard refueling vapor recovery (ORVR) is increasingly used to reduce emissions and ORVR use is accounted for
in the MOBILE model.
Information on estimating emissions that occur during vehicle refueling at dispensing facilities can be found in the following.
a) EPA’s MOBILE software. EPA’s EIIP Volume Ill, Chapter 11, Section 3.1.1 states:
“… MOBILE makes use of improved predictive equations to calculate refueling emission factors, including sensitivity to temperature and Reid vapor pressure (RVP), and these have not yet been incorporated into published AP-42 factors for refueling. Additionally, the user may provide information on local Stage II emission controls to develop an emission factor for controlled emissions.”
c)CARB Emission lnventory Factors,Section 4.10,”Gasoline Dispensing Facilities,” May 1999, provides loading,
breathing, vehicle refueling, and spillage emission factors for uncontrolled and controlled scenarios at gasolinedispensing facilities.
d)AP-42,Section provides emission factors for controlled and uncontrolled vehicle refueling and for spillage.Refueling emissions may be controlled by a balance system or a vacuum-assist system. The balance system relieson the pressure created by the fuel entering the vehicle’s tank to force the vapors through the hose and into thedispensing facility’s storage tank. A vacuum-assist system uses a vacuum to pull the vapors from the vehicle’s tankand move them to the storage tank.
Spillage includes the following.
a) Spitback, which occurs when the vehicle’s tank is filled at a faster rate than vapors can escape from the tank.Federal rules limit spitback to 1 gm per vehicle refueling,which is equivalent to 26 mg/L assuming 10 gal pervehicle refueling.
b)Overfills, which can occur when the nozzle shut-off mechanism fails or the operator overrides it.c) Post-fill drips from nozzles.
Spillage was estimated in several studies noted in the EPA Technical Guidance document, including APl 4498 (28)These studies measured spills for both uncontrolled and controlled vehicle refueling.
A summary of emission factors for vehicle refueling and spillage is presented in Table 11.A more reliable estimate ofemissions would be obtained by using EPA’s MOBILE software, which does account for ORVR controls.


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