Appendix IV to Part 92 - Guidelines for Determining Equivalency Between Emission Measurement Systems
40:22.0.1.1.6.12.1.9.22 : Appendix IV
Appendix IV to Part 92 - Guidelines for Determining Equivalency
Between Emission Measurement Systems
This appendix describes a series of correlation criteria that
EPA considers to be reasonable for the purpose of demonstrating
equivalency between two test systems designed to measure the same
emissions during FTP locomotive testing. These criteria are
presented here only as guidelines. When requested to make a finding
of equivalency, EPA could base its decision on criteria other than
those listed here, where EPA has reason to believe that these
criteria are not appropriate.
(a) General approach. (1) Multiple tests should be
conducted in pairs on the same locomotive or engine using each of
the measurement systems.
(2) Variations for other parameters, such as test fuel, should
be minimized to the maximum extent possible.
(3) Locomotive and/or locomotive engine tests conducted in
accordance with the provisions of Subpart B of this part are
preferred. Where appropriate, engine tests conducted in accordance
with 40 CFR part 89 may also be used.
(4) Equivalency of the systems should be determined by comparing
individual modal data, individual cycle-weighted data, and the
average cycle-weighted results from each system.
(b) Correlation criteria for particulate measurements.
(1) The correlation coefficient (R 2) for individual modal data
should be 0.90, or higher.
(2) The maximum deviation between any pair of cycle-weighted
data should be 15 percent, or less.
(3) The ratio of average cycle-weighted results using the
alternate system to the average cycle-weighted results using the
specified Part 92 system (i.e., avgalt/avgspc) should be between
0.97 and 1.05.
(c) Correlation criteria for other measurements.
Correlation parameters for gaseous pollutants should be better than
those specified in paragraph (b) of this appendix for particulate
measurements.
(d) Minimum number of tests. The recommended minimum
number of tests with each system necessary to determine equivalency
is:
(1) Four locomotive or locomotive engine tests, conducted in
accordance with the provisions of subpart B of this part; or
(2) Seven 8-mode nonroad engine tests, conducted in accordance
with the provisions of 40 CFR part 89.
(e) Statistical outliers. Statistical outliers may be
excluded consistent with good engineering judgement. Outliers
should be replaced by rerunning each excluded test point. Where
more than one outlier is excluded, is recommended to perform one
additional pair of tests (in addition to the minimum number
specified in paragraph (d) of this appendix) for each two outliers
excluded.
[63 FR 18998, Apr. 16, 1998, as amended at 70 FR 40457, July 13,
2005]