[Code of Federal Regulations]
[Title 40, Volume 17]
[Revised as of July 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR86.123-78]
[Page 489-491]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 86_CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND
ENGINES--Table of Contents
Subpart B_Emission Regulations for 1977 and Later Model Year New Light-
Sec. 86.123-78 Oxides of nitrogen analyzer calibration.
The chemiluminescent oxides of nitrogen analyzer shall receive the
following initial and periodic calibration.
(a) Prior to introduction into service and at least monthly
thereafter the chemiluminescent oxides of nitrogen analyzer must be
checked for NO2 to NO converter efficiency. Figure B78-9 is a
reference for paragraphs (a) (1) through (11) of this section.
[[Page 490]]
(1) Follow the manufacturer's instructions for instrument startup
and operation. Adjust the analyzer to optimize performance.
(2) Zero the oxides of nitrogen analyzer with zero-grade air or
zero-grade nitrogen.
(3) Connect the outlet of the NOX generator to the sample
inlet of the oxides of nitrogen analyzer which has been set to the most
common operating range.
(4) Introduce into the NOX generator analyzer-system an
NO in nitrogen (N2) mixture with an NO concentration equal to
approximately 80 percent of the most common operating range. The
NO2 content of the gas mixture shall be less than 5 percent
of the NO concentration.
(5) With the oxides of nitrogen analyzer in the NO mode, record the
concentration of NO indicated by the analyzer.
[GRAPHIC] [TIFF OMITTED] TR06OC93.160
[[Page 491]]
(6) Turn on the NOX generator O2 (or air)
supply and adjust the O2 (or air) flow rate so that the NO
indicated by the analyzer is about 10 percent less than indicated in
step (5). Record the concentration of NO in this NO + O2
mixture.
(7) Switch the NOX generator to the generation mode and
adjust the generation rate so that the NO measured on the analyzer is 20
percent of that measured in step (5). There must be at least 10 percent
unreacted NO at this point. Record the concentration of residual NO.
(8) Switch the oxides of nitrogen analyzer to the NOX
mode and measure total NOX. Record this value.
(9) Switch off the NOX generation but maintain gas flow
through the system. The oxides of nitrogen analyzer will indicate the
NOX in the NO + O2 mixture. Record this value.
(10) Turn off the NOX generator O2 (or air)
supply. The analyzer will now indicate the NOX in the
original NO in N2 mixture. This value should be no more than
5 percent above the value indicated in step (4).
(11) Calculate the efficiency of the NOX converted by
substituting the concentrations obtained into the following equation:
Percent Efficiency = [1 + (a-b)/(c-d)] x 100
where:
a = concentration obtained in step (8).
b = concentration obtained in step (9).
c = concentration obtained in step (6).
d = concentration obtained in step (7).
If converter efficiency is not greater than 90 percent corrective action
will be required.
(b) Initial and periodic calibration. Prior to its introduction into
service and monthly thereafter the chemiluminescent oxides of nitrogen
analyzer shall be calibrated on all normally used instrument ranges. Use
the same flow rate as when analyzing samples. Proceed as follows:
(1) Adjust analyzer to optimize performance.
(2) Zero the oxides of nitrogen analyzer with zero-grade air or
zero-grade nitrogen.
(3) Calibrate on each normally used operating range with NO in N2
calibration gases having nominal concentrations of 15, 30, 45, 60, 75,
and 90 percent of that range. For each range calibrated, if the
deviation from a least-squares best-fit straight line is 2 percent or
less of the value at each data point, concentration values may be
calculated by use of a single calibration factor for that range. If the
deviation exceeds 2 percent at any point, the best-fit non-linear
equation which represents the data to within 2 percent of each test
point shall be used to determine concentration.
(c) When testing methanol-fueled vehicles, it may be necessary to
clean the analyzer frequently to prevent interference with
NOX measurements (see EPA/600/S3-88/040).
[42 FR 32954, June 28, 1977, as amended at 42 FR 45652, Sept. 12, 1977;
52 FR 47869, Dec. 16, 1987; 58 FR 58422, Nov. 1, 1993; 60 FR 34347, June
30, 1995]