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