Initial NVFEL Evaporative Emission Test Results from Marine Fuel Tanks
Test Procedures Baseline Emissions Pressure Relief Valves Limited Flow Orifices Volume Compensating Bag Insulation Permeation Future Testing Examples of Certification
Meeting Between Industry and EPA
August 7, 2001
Test Procedures 72-96 F (22-36 C) diurnal highest of 3 days (1 day used here to save time when testing pressure strategies)
measured in SHED certification fuel soaking required to stabilize permeation
Sealed Housing for Emission Determination
40% fill 9 RVP gasoline
20
22
24
26
28
30
32
34
36
38
0 12 24 36 48 60 72
Test Time [hours]
SH
ED
Te
mp
era
ture
[C
elc
ius
]
Test Tanks and Baseline Emissions
Moeller, blow molded, portable tank, 6 gallon
2.3 g/gal/day* *adjusted from 50% to 40% fill
Ezell, aluminum, installed tank, 17 gallon
2.2 g/gal/day
Inca, rotationally molded, installed tank, 23 gallon
2.5 g/gal/day
Inca, rotationally molded, installed tank, 31 gallon
have not tested yet
Wade-Reddy Model
2.3 g/gal/day
Pressure Relief Valves We modified an automotive cap with to allow us to
vary the spring tension Tests performed on aluminum fuel tank to remove the
variable of permeation
Pressure Relief Evaporative Emission Test DataAluminum Marine Fuel Tank
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5
Pressure Relief Setting [psi]
HC
[g
ram
s/g
all
on
/da
y]
Limited Flow Orifices Looked at three orifice sizes
– orifice limits rate of vapor leaving tank– this increases the pressure in the tank
25 micron– peak delta P of 3.1 psi (did not start test at zero psi, so will retest)
– 0.24 g/gal/day (probably good--appears sonic flow maintained)
75 micron– peak pressure of 1.6 psi– 1.2 g/gal/day
Pressure, Temperature, and HC Traces
1.4 PSI Cap
-5
0
5
10
15
20
25
30
35
40
0 240 480 720 960 1200 1440
seconds
de
g C
, gra
ms
, ps
i
75 Micron LFO
-5
0
5
10
15
20
25
30
35
40
0 240 480 720 960 1200 1440
seconds
de
g C
, gra
ms
, ps
i
Temperature
Emissions
Pressure (1.4 psi peak)
Temperature
Emissions
Pressure (1.6 psi peak)
Volume Compensating Bag
Purpose of bag is to expand and contract to minimize pressure build-up
We tested a 1.5 gallon bag in 6 gallon tank Peak pressure 0.8 psi 0.4 g/gal/day
(likely permeation) 3 day test Tedlar bag
Vacuum Relief
Fill CapOpen to
Atmosphere
Air Bladder
Liquid Fuel
FuelVapor
Pressure Relief
We are looking into other bag materials
Insulation The purpose of the insulation is to minimize the change in
temperature the fuel sees through the day We insulated the flat plastic tank with 3 inches construction
foam (R-15) and saw about a 50% reduction in emissions We are looking into insulation that may be more appropriate for
this application Initial testing on a PWC suggests fuel temperature follows
ambient temperature
Evaporative Emission Results for Insulated Flat, Plastic Tank
Test Day SHED Temperature Fuel Temperature Evaporative HC
Day #1Day #2Day #3
72-96F72-96F72-96F
72-82F78-86F80-86F
1.2 g/gal/day1.0 g/gal/day0.8 g/gal/day
Permeation EPA testing
– new blow molded tank showed low permeation– new rotationally molded tank showed higher permeation– currently soaking 3 plastic tanks to stabilize permeation rates– looking into impermeable materials/treatments
Other data– 1992 data on high-density polyethylene automotive tank
• 3.0 g/day on a 22 gallon tank (0.14 g/gal/day)
– 1986 USCG data on 3 rotationally molded tanks at 104 F• 18 g/day on a 12 gallon tank (1.5 g/gal/day)• 25 g/day on an 18 gallon tank (1.4 g/gal/day)• 20 g/day on an 18 gallon tank (1.1 g/gal/day)
Suggests permeation may be significant contributor to evaporative emissions
Future Testing
Collecting more data to better define a correlation between technology combinations and emissions for the purposes of design-based certification
Permeation testing (and materials investigation) Investigate insulation further Diurnal and LFO tests on the plastic tanks Open to other technology options
– bladder, floating vapor barrier, others?
Example of Design-Based Certification
NOTE: we are still refining our design criteria and will continue to do so as we collect more data
EXAMPLE– Baseline = 2.2 g/gal/day aluminum tank– If targeting a 50% reduction
COULD USE:– R-15 insulation with LFO to prevent convection– 1.5 psi pressure relief valve– possibly R-10 insulation with 1.0 psi pressure relief valve– (with a plastic tank, may need to use non-permeable material or target lower
diurnal emissions to offset permeation)
Example of Credits Calculation for ABT
Consider averaging to a 50% reduction from 2.2– product of ten 100 gallon tanks and five 50 gallon tanks
– want to avoid new technology on 50 gallon tanks
Calculating Debits– 5 tanks X 60 gallons X (2.2-1.1 g/gal/day) = 330
Need to make up with credits– 330 / (10 tanks X 100 gallons) = 0.33 g/gal/day
– 1.1 - 0.33 = 0.77 g/gal/day
If certified 100 gallon tanks to 0.7 g/gal/day– 10 tanks X 100 gallons X (1.1-0.7 g/gal/day) = 400
– would be able to bank or trade 400 - 330 = 70 credits
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