73-17-AW
Evaluation of the IPM RS-5 Flame lonization Detector
February 1973
Office of Air and Water Programs
Emission Control Technology Division
Environmental Protection Agency
-------
Background
On January 23, 1973, a demonstrator model of the IPM RS-5 flame
ionization detector was delivered to the Ann Arbor EPA facility
by sales representative Phillip Thomas. The unit was to be used
to measure hydrocarbons in the exhaust of both gasoline and diesel
engines as part of an evaluation program. Results were compared
with similar tests run with a Beckman 402 FID.
There are two important features which set the IPM FID apart from
others on the market. First, the fuel is pure hydrogen rather than
a hydrogen-helium mixture. The manufacturer claims that this results
in a higher flame temperature (about 2000°F as compared to about
1400°F in the Beckman 402) which is said to result in a better break-
down of heavier hydrocarbons. The second important feature is an
adjustment for oxygen interference. Essentially this involves op-
timizing the flame to avoid interference from oxygen brought in with
the sample.
Instrument Description
The IPM is a compact unit with dimensions 270 X 420 X330 (10.6 X
16.5 X 13 inches) mm, and a weight of 17 kg (37.5 Ibs). Maximum
range is 0-10,000 ppm carbon and minimum range is 0-10 ppm carbon.
>ven temperature is adjustable from ambient to 200°C (392°F). A
auge on the front panel indicates sample flow in millimeters of
water, and a porous ceramic filter is removable through the front of
the unit. Claimed detector response time is 0.5 seconds. There is
no indicator for flame out.
The instrument comes with either a three or six meter (10 or 20 ft.)
stainless steel heated sample line. Provision is made for measuring
sample temperature entering the burner but no means is provided for
measuring temperature in the sample line. The unit can be obtained
for operating on 115 volt AC power supplies.
Test Program :
Tests were run on the Mercedes-Benz Diesel, the Opel Diesel, and on
two 197- prototype Mazdas with rotary engines. Tests were run accord-
ing to the 1975 Federal Test Procedure. One test was run on the Opel
Diesel with the Beckman 402 and the IPM sampling in parallel. In
addition, bag samples were made containing ethyl alcohol, methyl
alcohol and formaldehyde (37% formaldehyde, 12% methyl alcohol, re-
mainder water), and analyzed with both the Beckman 402 and IPM. The
evaluation did not include a measure of the relative response of the
IPM (compared to the Beckman 402) to different hydrocarbon compounds.
-------
-2-
t ample point for the FID was immediately downstream of the.dilution
ox. The sample was drawn through a transverse probe mounted in the
CVS duct. Initially the sample line supplied with the IPM unit was
used. After several tests, the electrical power supply line to the
heating element broke off flush with the FID and was not repairable
without disassembling the FID. In the interests of time, it was de-
cided to use another sample line. An attempt was made to use the
Beckman Teflon sample line, but we were unable to heat the line to a
sufficient temperature. The third and final sample line which was used
successfully for the remainder of the tests was the stainless steel
line built in-house by our laboratory personnel. This line included
-an in-line filter located a short distance after the probe to prevent
soot build-up in the sample line and FID.
Sample line temperature was 375°F with the stainless steel line and
approximately 177°F with the Beckman Teflon line. Oven temperature
of the IPM was 170-175°C (338-347°F). Oven temperature of the Beckman
402 was 375°F.
Results
Testing the Mazdas gave an opportunity to use the IPM on a vehicle
which required the use of two ranges on the FID. Approximately the
first 40 seconds of bags 1 and 3 required the use of the 0-1000 ppm
range. The remainder of the bags were run on a range of 0-100 ppm.
hen switching down from the higher range to the lower range, it took
rom two to four seconds for the instrument to recover from being pegged
below zero. According to the manufacturer's representative this is
due to a loaded capacitor's having to bleed-off before the instrument
responds accurately to conditions in the flame. The same effect occurs
when changing from the 0-100 ppm range to the 0-10 ppm range. The
The recovery time in this case is somewhat longer, about ten seconds.
The instrument has good retention of its calibration when switching
from one range to another, provided that it is calibrated in the
higher of the two ranges. There is little zero shift when changing
ranges.
Results obtained from testing the Mercedes Diesel were consistent with
previous results (see Table I). IPM FID data gave approximately twice
the grams per mile obtained from the cold bags. When running the
Beckman 402 and IPM FIDs in parallel, approximately the same concen-
trations of hydrocarbons were obtained from both instruments (see
Table II).
When testing the bag samples of aldehydes and alcohols, we were looking
for a comparison with the Beckman 402 to see if the IPM gave substant-
ially higher readings. This was not the case as both the Beckman and
IPM gave approximately the same readings on the bags.
-------
-3-
'onclusions
In general, the IPM unit gave satisfactory performance throughout
the evaluation period. It showed somewhat faster response than the
Beckman 402, and was much less sensitive to physical disturbances than
the Beckman. The IPM would probably be a better unit for operation on
a routine basis than our Beckman 402 because of its greater stability.
The substitution of knobs in place of adjusting screws for control of
fuel and air flows would improve the ease of operation and also quicken
the procedure for optimizing the flame.
We did not consistently see the higher peak hydrocarbon concentrations
in Diesel exhaust that the manufacturer claims we should see. The
probable reason for this is that we sample dilute rather than raw
exhaust.
-------
TABLE I
IPM RS-5 FID
Mercedes-Benz 220 Diesel
Gaseous Emissions (grams/mile)
Test No.
1
2
3
4
HC
Hot FID
-
0
0
0
.30
.40
.37
HC
Cold Bag
0
0
0
0
.19
.18
.16
.16
CO
1
1
1
1
.58
.51
.34
.46
CO?
434
416
409
411
NOx
.97
.80
.82
.76
1
1
1
1
.55
.17
.45
.38
average of
tests 2-4 0.36 0.17 1.44 412.79 1.33
average of six
tests using
Beckman 402 " .
FID 0.35 0.19 1.38 454.24 1.55
-------
TABLE II
OPEL REKORD DIESEL
Beckman 402 FID and IPM FID
Hydrocarbon Concentrations (ppm)
Beckman 402 IPM
Bag 1 35.36 . 31.84
Bag 2 19.08 18.56
Bag 3 31.08 30.11
-------
TABLE III
Operating Characteristics of the IPM RS-5 FID
IPM RS-5
Operating features:
span and zero insensitive to scale changes
span and zero have negligible drift during testing ('75 FTP)
(less than .5 ppm) and minimal from day to day
stable readings, steady signals
stabilizes near final nominal values within a few hours from
cold start
fast response
fast approach to nominal values
easy correction for 02 interference
calibration relatively easy
provision for sample line heating automatically controllable
provision for sample heating
sample § sample line heating adjustable
flexible stainless steel heated sample line
sample temperature monitoring (in sample block)
low gas consumption
flame easily ignited
no problem with flame outs
compact
simplified
Some possible desired features (all easily incorporated):
provision to monitor gas temperature in sample line
readily adjustable sample temperature set point
------- |