[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR92.129]
[Page 460-462]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 92--CONTROL OF AIR POLLUTION FROM LOCOMOTIVES AND LOCOMOTIVE ENGINES--
Table of Contents
Subpart B--Test Procedures
Sec. 92.129 Exhaust sample analysis.
(a) The analyzer response may be read by automatic data collection
(ADC) equipment such as computers, data loggers, etc. If ADC equipment
is used the following is required:
[[Page 461]]
(1) The response complies with Sec. 92.130.
(2) The response required in paragraph (a)(1) of this section may be
stored on long-term computer storage devices such as computer tapes,
storage discs, or they may be printed in a listing for storage. In
either case a chart recorder is not required and records from a chart
recorder, if they exist, need not be stored.
(3) If the data from ADC equipment is used as permanent records, the
ADC equipment and the analyzer values as interpreted by the ADC
equipment are subject to the calibration specifications in Secs. 92.118
through 92.122, as if the ADC equipment were part of the analyzer.
(b) Data records from any one or a combination of analyzers may be
stored as chart recorder records.
(c) Software zero and span.
(1) The use of ``software'' zero and span is permitted. The process
of software zero and span refers to the technique of initially adjusting
the analyzer zero and span responses to the calibration curve values,
but for subsequent zero and span checks the analyzer response is simply
recorded without adjusting the analyzer gain. The observed analyzer
response recorded from the subsequent check is mathematically corrected
back to the calibration curve values for zero and span. The same
mathematical correction is then applied to the analyzer's response to a
sample of exhaust gas in order to compute the true sample concentration.
(2) The maximum amount of software zero and span mathematical
correction is 10 percent of full scale chart deflection.
(3) Software zero and span may be used to switch between ranges
without adjusting the gain of the analyzer.
(4) The software zero and span technique may not be used to mask
analyzer drift. The observed chart deflection before and after a given
time period or event shall be used for computing the drift. Software
zero and span may be used after the drift has been computed to
mathematically adjust any span drift so that the ``after'' span check
may be transformed into the ``before'' span check for the next mode.
(d) For sample analysis perform the following sequence:
(1) Warm-up and stabilize the analyzers; clean and/or replace filter
elements, conditioning columns (if used), etc., as necessary.
(2) Leak check portions of the sampling system that operate at
negative gauge pressures when sampling, and allow heated sample lines,
filters, pumps, etc., to stabilize at operating temperature.
(3) Optional: Perform a hang-up check for the HFID sampling system:
(i) Zero the analyzer using zero air introduced at the analyzer
port.
(ii) Flow zero air through the overflow sampling system, where an
overflow system is used. Check the analyzer response.
(iii) If the overflow zero response exceeds the analyzer zero
response by 2 percent or more of the HFID full-scale deflection, hang-up
is indicated and corrective action must be taken.
(iv) The complete system hang-up check specified in paragraph (f) of
this section is recommended as a periodic check.
(4) Obtain a stable zero reading.
(5) Zero and span each range to be used on each analyzer used prior
to the beginning of the test sequence. The span gases shall have a
concentration between 75 and 100 percent of full scale chart deflection.
The flow rates and system pressures shall be approximately the same as
those encountered during sampling. The HFID analyzer shall be zeroed and
spanned through the overflow sampling system, where an overflow system
is used.
(6) Re-check zero response. If this zero response differs from the
zero response recorded in paragraph (d)(5) of this section by more than
1 percent of full scale, then paragraphs (d) (4), (5), and (6) of this
section should be repeated.
(7) If a chart recorder is used, identify and record the most recent
zero and span response as the pre-analysis values.
(8) If ADC equipment is used, electronically record the most recent
zero and span response as the pre-analysis values.
[[Page 462]]
(9) Measure (or collect a sample of) the emissions continuously
during each mode of the test cycle. Indicate the start of the test, the
range(s) used, and the end of the test on the recording medium (chart
paper or ADC equipment). Maintain approximately the same flow rates and
system pressures used in paragraph (d)(5) of this section.
(10)(i) Collect background HC, CO, CO2, and
NOX in a sample bag (optional).
(ii) Measure the concentration of CO2 in the dilution air
and the diluted exhaust for particulate measurements.
(11) Perform a post-analysis zero and span check for each range used
at the conditions specified in paragraph (d)(5) of this section. Record
these responses as the post-analysis values.
(12) Neither the zero drift nor the span drift between the pre-
analysis and post-analysis checks on any range used may exceed 3 percent
for HC, or 2 percent for NOX, CO, and CO2, of full
scale chart deflection, or the test is void. (If the HC drift is greater
than 3 percent of full-scale chart deflection, hydrocarbon hang-up is
likely.)
(13) Determine HC background levels (if necessary) by introducing
the background sample into the overflow sample system.
(14) Determine background levels of NOX, CO, or
CO2 (if necessary).
(e) HC hang-up. If HC hang-up is indicated, the following sequence
may be performed:
(1) Fill a clean sample bag with background air.
(2) Zero and span the HFID at the analyzer ports.
(3) Analyze the background air sample bag through the analyzer
ports.
(4) Analyze the background air through the entire sample probe
system.
(5) If the difference between the readings obtained is 2 percent or
more of the HFID full scale deflection:
(i) Clean the sample probe and the sample line;
(ii) Reassemble the sample system;
(iii) Heat to specified temperature; and
(iv) Repeat the procedure in this paragraph (e).