Incorporation of a Test for Exhaust Sulfate Emissions into the Federal Emission Testing Procedure


                    Incorporation of a Test for Exhaust

        Sulfate Emissions into the Federal Emission Testing Procedure
                                   by
                           Michael W. Leiferman
                              December 1975
                                 Notice

     Technical support reports for regulatory action do not necessarily
represent the final EPA decision on regulatory issues.  They are intended
to present a technical analysis of an issue and recommendations resulting
from the assumptions and constraints of that analysis.  Agency policy
constraints or data received subsequent to the date of release of this
report may alter the recommendations reached.  Readers are cautioned to
seek the latest analysis from EPA before using the information contained
herein.
                Standards Development and Support Branch
                  Emission Control Technology Division
              Office of Mobile Source Air Pollution Control
                   Office of Air and Waste Management
                 U.S. Environmental Protection Agency

-------
        Incorporation of a Test for Exhaust Sulfate Emissions
             into the Federal Emission Testing Procedure
Abstract
     There are many possible sequences in which a test procedure for
gaseous exhaust emissions, evaporative emissions, and exhaust sulfate
emissions could be conducted.  This report identifies a few of these
sequences which appear to be appropriate for the measurement of these
emissions.  These candidate test procedures are then compared on the
basis of test result accuracy and consistency, and the laboratory
requirements of test time and manpower.
Introduction
     The EPA is developing test procedures for the measurement of
exhaust sulfuric acid emission.  At present, vehicles are certified
for certain gaseous exhaust emissions and evaporative hydrocarbon
emissions.  Unfortunately, it is not appropriate to measure both the
gaseous and sulfate emissions during the same type of vehicle opera-
tion.  Therefore, a vehicle driving cycle has been developed for the
measurement of exhaust sulfate levels.

     It is desirable to perform the sulfate emission testing in such
a way that it will not affect the measured values of either the gas-
eous exhaust or evaporative emissions.  Since the levels of these
emissions may be affected by the vehicle's history for some period of
time prior to testing, it is desirable to minimize any changes to the
current test procedure.  Other considerations in the addition of a
sulfate test to the established procedures are increases in test time
and manpower requirements, and the test accuracy and repeatability.
The purpose of this report is to identify the possible test sequences
which would be most appropriate.  The advantages and disadvantages of
these procedures are then discussed.

-------
                                 -2-
     A major change in the evaporative emission test procedure is cur-
rently being proposed.  This report assumes that this newly proposed
procedure (SHED technique) will be in effect prior to the publication
of the sulfuric acid test procedure.
Discussion

     In choosing candidate test procedures, it was desirable to iden-
tify sequences in which the sulfate test would have a minimum effect
on the gaseous and evaporative tests.  With this consideration, it was
decided that certain sequences in the current procedure could not be
changed.  These were as follows:

     1)  The gaseous exhaust emission test (from initial key-on
         to the end of the hot transient test) could not be
         changed.  That is, bag 3 could not be collected at
         some different time.

     2)  The gaseous exhaust emission test (hereafter re-
         ferred to as the FTP) must be preceded by at least
         12 hours of key-off condition.

     3)  The diurnal evaporative test must be preceded by
         at least 11 hours of key-off condition.

     4)  The hot-soak evaporative test must be preceded by
         an FTP driving cycle.

     In addition, it was assumed that only one sulfate emission test
(SET) cycle will be conducted, and that this SET can only follow an
FTP, a hot start bag 3 portion of an FTP cycle, another SET or, pos-
sibly, a highway fuel economy test (HFET).  The reasons for the lat-
ter restriction are that (1) sulfate baseline tests are being con-
ducted using either an FTP, HFET, or another SET to precede the SET;
(2) these three test cycles provide good representations of the dif-
ferent types of "immediate" preconditioning which should be consid-
ered; and (3) the addition of a different SET preconditioning cycle
would significantly increase the time and manpower required to con-
duct the test.

-------
1 * Test:
>ceJigre
n
$oa.k
STAHT
— ^LA-4
II .ht-
$0'"gv/a'e>
-------
-4-
ConsIdarable concern has been expressed regarding the influence
of vehicle preconditioning on sulfate emissions. The sulfate emission
baseline study now being conducted provides a comparison of FTP versus
HFET preconditioning. Approximately one-half of the data from this
program has now been received. The clearest message from this data is
that measured sulfate values for individual vehicles have more vari-
ability than gaseous exhaust emissions. For some vehicles, the mea-
sured sulfate levels were higher after the FTP than after the HFET.
Other vehicles showed the opposite trend. As a result, the data
showed no statistically significant difference between FTP and HFET
immediate preconditioning in regards to the level of sulfate emis-
sions. Available baseline data also indicate that the type of pre-
conditioning does not affect the repeatability of sulfate emission
measurements. Consequently, no one of the candidate cycles appears
preferable to the others on the basis of sulfate emission level or
test repeatability.

Although sulfate baseline testing is not showing a difference in
sulfate levels between immediate preconditioning with an FTP or HFET,
other tests have shown that catalysts can store sulfates during some
types of operation and release them during other types of operation. •••
Sulfate tests conducted under EPA contract at Southwest Research In-
stitute on four vehicles have shown this quite clearly. Results of
these tests are contained in Appendix A. As shown, three of the four
vehicles stored sulfates during the 30 mph cruise mode and then re-
leased sulfates on the acceleration mode from 30 to 60 mph. Because
of such occurrences, it is desirable to operate all vehicles in a
similar manner for some period of time prior to testing for sulfate
emissions. The type of operation the vehicles has undergone prior to
their arrival at the Ann Arbor laboratory cannot be closely controlled.
Because of this, there is an advantage in conducting the sulfate test
near the end of the emission certification procedure* as done in se-
quence A.

Other concerns associated with a sulfate emission test are time
and manpower needs. Table I is a comparison of test time and manpower
requirements among the current test procedure and the various test
procedures shown in Figure 1 (including evaporative testing and sul-
fate testing, where applicable). This analysis is based on 0PM1s
"Technician Man-hours Required per Full 1975-type FTP", and "Techni-
cian Man-hours Required per HFET" as of April, 1975. These documents
are attached as pages B-l through B-3 of Appendix B of this report.
The estimated time requirements of the proposed procedures are based
1. "Sulfate Control Technology, Appendix II", ECTD report.
-------
TABLE I
COMPARISON OF TIME AND MAN-POWER REQUIREMENTS
FOR VARIOUS EMISSION TEST PROCEDURES
Test
Procedure
Current
SHED
A
BI
BII
C
Technician
time, hr
11.2
9.4
10.3
10.2
9.6
10.2
Total
time, hr
20.7
18.9
19.4
19.2
18.9
18.2
Working
time, hr
9.7
7.9
8.4
8.2
7.9
8.2
2nd Day
working time, hr
6.5
6.0
6.5
5.3
5.3
4.6
2nd Day Working +
peripheral* time, hr
7.8
7.2
7.8
6.4
6.4
5.5
*A prorated time for peripheral tasks as defined in Appendix B, page B-2
-------
-6-
on modifications of the current test procedure. A detailed break-
down of the estimated time for each procedure is contained in
Appendix B, Figures B-l and B-2.

As shown in Table I, the current test procedure requires more
time than the proposed SHED test. This is mainly because the SHED
procedure does not include AMA preconditioning or fuel system pres-
sure check. The candidate sulfate cycles require up to about one
hour more technician time and one-half hour more working time than
the proposed SHED procedure. In this analysis it was assumed that
if the HFET follows the FTP or the SET driving cycle, then a pre-
conditioning HFET cycle is not required. With this assumption,
Table I shows the amount of working time required on the second day
of the sulfate sequences is no longer than the working time required
with the current procedure. It should be mentioned that the first
four columns of Table I do not include time for peripheral tasks as
defined in the time study in Appendix B. The fifth column does
include this additional time requirement.

The major advantage of procedure A is that the sulfate test does
not interfere with the exhaust and evaporative tests, and the esti^
mated time requirement for procedure A is not much greater than that
for the other procedures. However, this sequence requires the vehi-
cle to be moved on and off the dynamometer twice on the second day
instead of once as in the other candidate procedures. In the time
estimate, it was assumed that the time required to move a vehicle on
or off the dynamometer was always constant. Since there would be an
additional vehicle move using procedure A, this might result in more
congestion and a somewhat longer time per vehicle move (amounting to
perhaps 0.1 or 0.2 additional hour per test).

Although procedures BI, BII, and C require less test time than
procedure A, they do include changes in the present testing sequence.
In procedure BI, the HFET precedes the diurnal test. A five-vehicle
test conducted at the EPA Ann Arbor laboratory showed that there was
a significant difference in diurnal losses between LA4 and HFET pre-
conditioning cycles.^ These tests were conducted by the SHED proce-
dure, and the results are presented in Appendix C. As shown, the
measured diurnal losses from each vehicle were lower when precondi-
tioning was done with the HFET cycle. This was due to increased
canister purging which resulted from the higher speed operation.
The mean of all vehicles using LA4 preconditioning was 2.29 g/test,
2. "Vehicle Preconditioning: LA-4 vs. HFET", In-House Test
Program, Report No. 2.
-------
-7-

and the mean of all vehicles using HFET preconditioning was 1.73
g/test. The statistical analysis on page C-2 shows that this
difference was significant at a 95% level of confidence.

In procedure BII, the SET cycle serves as preconditioning for
the diurnal test. Tests have not been conducted to determine if pre-
conditioning with this cycle will give different diurnal losses than
preconditioning with the LA4 (FTP) cycle. The average speed is 15 mph
higher on the SET than on the LA4. Therefore, it is expected that
canister purging during the SET would be greater than during the LA4,
but not as great as during the HFET (29 mph higher average speed than
LA4).

In sequence C, it is also possible that evaporative emission
levels will be different than as measured in the current sequence.
During the hot-soak test, the temperature inside the SHED is signif-
icantly higher than in the current soak area. This difference is
about 8°C (15°F). Therefore, more vapors are generated during a hot-
soak SHED test than during a hot-soak in the soak area. Consequently,
the canister is loaded more during the SHED test, and the vapors
generated during the following diurnal test will probably be more
difficult to control. Also, in sequence C, the hot-soak portion of
the evaporative test is quite near the beginning of the test sequence.
Because of this, it could be possible that the condition of the can-
ister prior to the start of the test procedure may affect the result
of the hot-soak test. A comparison of the advantages and disadvan-
tages of the candidate test procedures is summarized in Table II.

Conclusions

1. All candidate test cycles which have been presented require
less technician time, less working time, and less total time than the
current testing procedure (with the evaporative test and HFET included).

2. Candidate test procedure A is the only one in which the
current emission test procedure is not altered by the sulfate test.

3. Changes in the present emission test sequence (as required
in procedures BI, BII, and C) could affect evaporative and/or exhaust
emissions. Due to higher vehicle speed prior to parts of the evapor-
ative test, it is estimated that any effect would be to decrease the
severity of the evaporative test.

4. The shortest of the proposed sequences (procedure BII) is
estimated to save 0.7 hour of technician time, and 0.5 hour of test
time as compared to procedure A.

Recommendation

Proposed sequence A should be adopted as the official testing
procedure when sulfate emission testing is conducted.
-------
-8-
TABLE II
COMPARISON OF THE ADVANTAGES AND DISADVANTAGES
OF THE CANDIDATE EMISSION TEST PROCEDURES
Test
Procedura
Advantages
Disadvantages
Comments
Sulfate testing does
not affect current
exhaust or evapora-
tive procedure.

All tests con-
ducted on the same
day so ambient and
vehicle changes
are minimal.

Has the greatest
amount of con-
trolled pre-
conditioning.
Takes most manpower
and working time.
Takes most time on
2nd day so more
chance of running
out of time.
Might require more
than estimated time
or need additional
test coordination
because vehicle
must go on and off
dynamometer twice
during the 2nd day.
BI Takes less time
and substantially
shorter 2nd day
than sequence A.
Diurnal preceded by
HFET which purges
canister more than
FTP.

Hot-soak might be
affected by HFET
before the cold-
soak.
HFET is incorporatec
into the testing
procedure.
BII Takes least time
and substantially
shorter 2nd day
than sequence A.
Diurnal preceded by
SET which probably
purges canister more
than FTP.

Hot-soak might be
affected by SET be-
fore cold-soak.
HFET is incorporatec
into the testing
procedure.
Takes less time
and substantially
shorter 2nd day
than sequence A.
Hot-soak might
be affected by
vehicle opera-
tion prior to
start of test-
ing sequence.
-------
APPENDIX A
Effect of Vehicle Operation
on Sulfate Storage and Release
-------
Tost No.
Test Type
ATTACHMENT 1 ' ?ART -.1
Cold'LA-4
Hot LA-4
SET-7
SET-7
IIWFET
HWFET
Accel to 30
30 mph
Accel to 60
60 .mph

r^SM^^0^/--^^
^m\m\^±;^^^^:^
7J-h±rn—T Sv—:^J57-~/r£!--|'---.'- \~,
^ry\—.:'c~::\-.;-^
o
Cumulative Fuel Sulfur, grams
FIGURE *. CUMULATIVE SULFUR RECOVERED IN EXHAUST AS A
FUNCTION OF SULFUR CONSUMED WITH FUEL FOR A 1975
49 STATE FLY MOUTH GRAN FURY
(Swr.I Car EM-1)
-------
TEST

1
2
3 and 4
5 and 6
7
8
9
10
TEST
Cold LA-4
Hot LA-4
SET-7
HWFET
Accel to 30 mph
30 mph Steady
Accel to 60 mph
60 mph Steady
ATTACHMENT 2 PART 2
10 r
CO
g
rt
M
hO

X
W
o
d
r-\
|
o
8
6
4 -^
0
24 6
Cumulative Fuel Sulfui', grams
8
10
FIGURE 2. CUMULATIVE SULFUR RECOVERED IN EXHAUST
AS A FUNCTION OF SULFUR CONSUMED WITH FUEL
IN A 1975 CALIFORNIA PLYMOUTH GRAN FURY
(SwRI CAR EM-3) >^jjCj.JTH_CATALYST WITH AIR INJECTION
-------
w
a
rt
M
W)
•t
JH
J3
X
W
-
c!
u
1
2
3 and 4
5 and 6
7
8
9
10
TEST TYPE
Cold LA-4
Hot LA-4
SET-7
HWFET
Accel to 30 mph
30 mph Steady
Accel to 60 mph
60 mph Steady
ATTACHMENT 3 PART 3
2 -r^ii
o L/p
o
2468
Cuniulative Fuel Sxilfur, grams
10
FIGURE 1. CUMULATIVE SULFUR RECOVERED IN EXHAUST AS A
FUNCTION OF SULFUR CONSUMED WITH FUEL IN A 1975 49-STATE
CHEVROLET IMPALA (SwRI CAR EM-2)
T A LJCS;^
-------
TE$1_NO.
1
2
3 and 4
5 and 6
7
8
9
10
TEST TYPE
Cold L.A-4
Hot LA-4
SET-7
HVVFET
Accel to 30 mph
30 mpli Steady-
Accel to 60 rnph
60 rnph Steady
ATTACHMENT 4 1'AIM A
10
CO
6
p)
»H
bO
CO
4->
M
3
&
X
w
CJ
• rl
4-»
d
»—i
.1
^1
o
8
0
2 JZL
46s
Cumulative Fuel Sulfur, grams
>-]C.U.HV: 3. CUMIT.1,ATIVK SU.LFD.U RECOVERlv.D IN KXIIAUST
A.S A FUNCTION OF SULFUR CONSUMED WITH .FUEL
IN A 197ii CALIFORNIA CHEVROLET 1MPALA
(SwRl CAR EM--4) PEI.Ll'y.L'l'.-T) CATALYST V/1TH AIR INJECTION
-------
APPENDIX B
Technician Man-hour and Working Time Requirements
for the Various Test Sequences
-------
6-
TECHNICIAN MAN-HOURS REQUIRED
PER FULL 1975~TYP~lf FT~P
Average Minutes
Segment of Technician Time
1. Vehicle Inspection and AMA
a. Locate and inspect vehicle, paper work 12
b. Weigh vehicle 12
lie. Add fuel 2
* d. Precondition vehicle (AMA) 60
e. Measure idle CO and speed, and timing 10
.1/f. Measure axle ratio 20
Subtotal 116
2. Preconditioning
a. Drain fuel 15
b. Pressure check 12
JL/c. Add fuel 16
_l/d. Install vehicle on dynamometer 12
e. Inertia and HP setting 5
f. LA-4 30
g. Remove vehicle from dynamometer 8
h. Soak
Subtotal 98
3. j)iurnal and Evaporative Emission Measurement
a. Drain fuel 12
* b. Canister preparation 7
* c. Installation of plumbing 18
* d. Installation of heat blanket, thermo- 10
couple, check recorder
* e. Weigh and ins (.all canisters 12
l/f. Add fuel (to 40% cap.) 20
* g. Heat build 80
* h. Seal and remove canisters, plumbing, blanket 8
Subtotal 167
-------
0 -2-
A. Exhaust Emission Running Loss Measurement
a. Set dynamometer HP and inertia 15
JjYb. Install vehicle on dynamometer 25
JL/c. Manufacturer Kep check 5
^./d. Exhaust emission test 110
e. Remove vehicle 6
Subtotal 161
5. Evaporative Emission Test
* a. Reinstall plumbing 6
* b. Hot soak
* c. Remove plumbing 12
* d. Weigh canisters 6
e. Complete and dispose of documentation 6
f. Park vehicle and return keys 10
Subtotal 40

Subtotal Total 582
21
Time prorated per test for peripheral tasks — 78
Total Minutes 660
Technician Man-Hours/Test 11.0
NOTES
* Deleted for non-evap test
JL/ Includes more than 1 technician.
2j Time prorated to FTP for peripheral tasks is to cover the
following:
Average Hours
Per Day
1. Trouble shooting .5.5
2. Test coordination 5.5
3. Making.sample bags .8
4. Changing gas bottles .25
5. Locating manufacturer's special equipment 1.0
6. Completing job orders, void reports, etc. 1.25
7. Filling fuel carts 1.0
8. .Emptying dump fuel .75
9. Replacing paper and scale in recorders .75
10. Locating equipment for test 2.25
11. Delay for idle set by manufacturer 1.0
TOTAL 20.05
Prorated tinWtest (20.05 •:- 15 average tests per day) 1.3 hrs
(70 mmutes.)
-------
u-
B-3-

TECHNICIAN MAN-HOURS REQUIRED
PER HIGHWAY FUEL ECONOMY TEST
>,
Average Minutes
After 24 Hours After FTP of Technician Time
1. Obtain keys and paper work 8
I/ 2. Locate vehicle, check and add fuel 15
3. Run AMA 60
JL/ 4. Re-enter building, install vehicle on dyno 16
5. Set HP and inertia 10
6. Run LA-4 23
i/ 7. Warm-up and sample FET 50
8. Remove vehicle 6
9. Park vehicle and return keys 10
10. Complete and dispose of documentation 6
204 (3.4 hrs)
3-24 Hours After FTP
Replace LA-4 + AMA with 5 min. warm-up 126 (2.1 hrs)
Within 3 Hours After FTP
No 5 min. warm-up, no LA-4 121 (2 hrs)
Immediately After Emission Test
Check paper, pen, dyno 5
Wait for manufacturer, CSD Rep 5
Warm up and sample FET 50
60 (1 hr)

NOTE: I/ Includes more than 1 technician.
-------
6-4-
se d
SHED
8'

Sin R Tj — 9—\

I A-/*\
\ TC/

LA -4-

• x*
11 hr ^

' i)* I*
O l \J K tv f\ L

1 /!_^

^lOrt™ Cvfl ^

!/--,! ^,
\ .
•• (v ^
,„ >_,
/^^

v^
7
10
10

HFF"rl *fc fsropl
1 1 • 1 1 j ^ j^j-1 ^- ^j

MI LI | ^ ~ -"—]'.> i o *•'

ew4.jp
., I ii W I 1
18
| FTP,
•/r __
i> ^
**
7
2.
rSET
4-6

x~
/O
Ljc t*r
Mr t i
26
i
0 •> -*.
t* fc- <^l
.6 hr
-------
SHED
8-5-
u
vk'rtq TJVVK-
i—IIS
8.4-Kc
9.1. hr.
7.9 hr.

ST/lftT
i
-9-
1 ^\

Lf\-<*r

!O miM

Q15
1 '
j
e
,
->-|H. SOAK

^ IP h.y i Diuf WAL
. LJ L 5CU.1S 1 ;
ncn' s 'if h' 1
•^o~f '
-1 "— -:
So^K j

->-

'
FTP

•^1
1
'SET]
O -9
- I
-^
•
r
•ThFETH^ [SroPJ
-H / !23|5
HFET
/5 j 22—H
8-2 hr.
-------
APPENDIX C
Effect of Pre-conditioning Cycles
(LA4 and HFET) on Diurnal Evaporative Losses
-------
W
e
n
(0
o
u
•H

Q
3 -
2 .
1 .

• —

\
\
V

—

'sj
\
\
\
\
\
\
\
\
*\
\
\

1 1 LAA Prep
f\X^l HFET Prep

•^
\
\
\
\
\
\
>
\
\
\

m ra

^
\
\
\
\
\
\

Caraaro Matador New Vega Volks- 5 Vehicle

Yorker wagon Mean
Figure C-l Diurnal HC Losses for LA4 and HFET Preps
C-l
-------
of Variance for Oi
Loss Results
Vehicle
Test

LA-4 Prep

HFET Prep
TC

Canaro
0.47
0.80
1.48
0.61
1.01
0.54
'4.91 '

Mntador
4.19
4.37
5.07
2.91
4.05
3.99
24:58

New Yorker
6.49
3.94
3.10
2.51
3.68
2.68
22.40

Vej;a
0.69
0.45
0.48
0.52
0.52
0.45
3.11

Volkswagen
1.08
0.93
0.84
0.78
0.82
0.91
5.36

34.38

25.98
,\
T= 60.36
No. of columns, c - 5
No., of rows, r - 2

I 2/N - 121.44

.E.xr- 208.66

Tjc7 - 1168.45

Z Tr2 - 1856.94

£ Tcr2 -598.91

SSC • ETc 2/n'T - T2/N - 73.30

SSr - ETr 2/n'c - T2/N - 2.35

SScr - ETcr 2/n - T2/N - SSC - SSr

SSC - EX2 - T 2/N - 87.22
2.54
No. of replicates, n " 3
Total. Mo. of tests, N » 30
SS
res
. SSt - SSC - SSr - SS(
cr
9.03
Source of
Variation
Vehicles
Test: Type
Vehicle-Test
Interaction
Ronidual
Total
SS
73.30
2.35
2.54
9.02
87.22
DF
5-1 - 4
2-1 - 1
(4) (1) - 4
29-9-20
30-1-29
M S,
(SS/DF)
18.33
2.35
0.64
0.45

HSR,
(MS/MS res)
40.73
5.22
1.42

<
>
>
>
<

F
(a- 0.05.)
2.87
4.35
2.87

Hoa: Rejected a 95Z.C.L.
Hob: Rejecteda 95% C.L.
Hoc: Accepted
• C-2
-------