[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: 40CFR86.331-79]

[Page 603-604]
 
                   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 D_Emission Regulations for New Gasoline-Fueled and Diesel-Fueled 
           Heavy-Duty Engines; Gaseous Exhaust Test Procedures
 
Sec. 86.331-79  Hydrocarbon analyzer calibration.

    The following steps are followed in sequence to calibrate the 
hydrocarbon analyzer. It is suggested, but not required, that efforts be 
made to minimize relative response variations.
    (a) If necessary, follow manufacturer's instructions for instrument 
start-up and basic operating adjustments.
    (b) Set the oven temperature 5 [deg]C hotter than the required 
sample-line temperature. Allow at least one-half hour after the oven has 
reached temperature for the system to equilibrate.
    (c) Initial fuel flow adjustment. With the fuel and air-flow rates 
set at the manufacturer's recommendations, introduce a 350 ppmC75 ppmC span gas to the detector. Determine the response 
at a given fuel flow from the difference between the span-gas response 
and the zero-gas response. Incrementally adjust the fuel flow above and 
below the manufacturer's specification. Record the span and zero 
response at these fuel flows. A plot of the difference between the span 
and zero response versus fuel flow will be similar to the one shown in 
Fig. D79-3.
[GRAPHIC] [TIFF OMITTED] TR06OC93.170


Adjust the fuel-flow rate to the rich side of the curve, as shown. This 
is initial flow-rate setting and may not be the final optimized flow 
rate.
    (d) Oxygen interference optimization. Choose a range where the 
oxygen interference check gases (see Sec. 86.308) will fall in the 
upper 50 percent. Conduct this test with the oven temperature set as 
required. Oxygen interference check gas specifications are found in 
Sec. 86.308.
    (1) Zero the analyzer.
    (2) Span the analyzer with the zero-percent oxygen blend for 
gasoline-fueled engines. Diesel engine instruments shall be spanned with 
the 21-percent oxygen blend.
    (3) Recheck zero response. If it has changed more than 0.5 percent 
of full scale repeat paragraphs (d) (1) and (2) of this section.
    (4) Introduce the 5 percent and 10 percent oxygen interference check 
gases.
    (5) Recheck the zero response. If it has changed more 1 percent of full scale, repeat the test.
    (6) Calculate the percent of oxygen interference (%O2I) 
for each mixture in step (4).

[[Page 604]]

[GRAPHIC] [TIFF OMITTED] TR06OC93.081

A = hydrocarbon concentration (ppmC) of the span gas used in step (2).
B = hydrocarbon concentration (ppmC) of the oxygen interference check 
gases used in step (4).

    (7) The percent of oxygen interference (%O2I) must be 
less than 3.0 percent for all required oxygen 
interference check gases prior to testing.
    (8) If the oxygen interference is greater than the specifications, 
incrementally adjust the air flow above and below the manufacturer's 
specifications, repeating paragraphs (d) (1) through (7) of this section 
for each flow.
    (9) If the oxygen interference is greater than the specification 
after adjusting the air flow, vary the fuel flow and thereafter the 
sample flow, repeating paragraphs (d) (1) through (7) of this section 
for each new setting.
    (10) If the oxygen interference is still greater than the 
specifications, repair or replace the analyzer, FID fuel, or burner air 
prior to testing. Repeat this section with the repaired or replaced 
equipment or gases.
    (e) Linearity check. For each range used, check linearity as 
follows:
    (1) With the fuel flow, air flow and sample flow adjust to meet the 
oxygen interference specification, zero the analyzer.
    (2) Span the analyzer using a calibration gas that will provide a 
response of approximately 90 percent of full-scale concentration.
    (3) Recheck the zero response. If it has changed more than 0.5 
percent of full scale, repeat steps (1) and (2).
    (4) Record the response of calibration gases having nominal 
concentrations of 30, 60, and 90 percent of full-scale concentration. It 
is permitted to use additional concentrations.
    (5) Perform a linear least square regression on the data generated. 
Use an equation of the form y = mx, where x is the actual chart 
deflection and y is the concentration.
    (6) Use the equation z = y/m to find the linear chart deflection (z) 
for each calibration gas concentration (y).
    (7) Determine the linearity (%L) for each calibration gas by:
    [GRAPHIC] [TIFF OMITTED] TR06OC93.082
    
    (8) The linearity criterion is met if the %L is less than 2 percent for each data point generated. Below 40 ppmC 
the linearity criterion may be expanded to 4 
percent. For each emission test, a calibration curve of the form y = mx 
is to be used. The slope (m) is defined for each range by the spanning 
process.
    (9) If the %L for any point exceeds the specifications in step (8), 
the air, fuel, and sample-flow rates may be varied within the boundaries 
of the oxygen interference specifications.
    (10) If the %L for any data point still exceeds the specifications, 
repair or replace the analyzer, FID fuel, burner air, or calibration 
bottles prior to testing. Repeat the procedures of this section with the 
repaired or replaced equipment or gases.
    (f) Optimized flow rates. The fuel-flow rate, air-flow rate and 
sample-flow rate are defined as ``optimized'' at this point.

[[Page 605]]