[Code of Federal Regulations]

[Title 40, Volume 31]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR1065.307]



[Page 713-716]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents

 

                Subpart D_Calibrations and Verifications

 

Sec.  1065.307  Linearity verification.



    (a) Scope and frequency. Perform a linearity verification on each 

measurement system listed in Table 1 of this section at least as 

frequently as indicated in the table, consistent with measurement system 

manufacturer recommendations and good engineering judgment. Note that 

this linearity verification may replace requirements we previously 

referred to as ``calibrations''. The intent of a linearity verification 

is to determine that a measurement system responds proportionally over 

the measurement range of interest. A linearity verification generally 

consists of introducing a series of at least 10 reference values to a 

measurement system. The measurement system quantifies each reference 

value. The measured values are then collectively compared to the 

reference values by using a least squares linear regression and the 

linearity criteria specified in Table 1 of this section.

    (b) Performance requirements. If a measurement system does not meet 

the applicable linearity criteria in Table 1 of this section, correct 

the deficiency by re-calibrating, servicing, or replacing components as 

needed. Before you may use a measurement system that does not meet 

linearity criteria, you must demonstrate to us that the deficiency does 

not adversely affect your ability to demonstrate compliance with the 

applicable standards.

    (c) Procedure. Use the following linearity verification protocol, or 

use good engineering judgment to develop a different protocol that 

satisfies the intent of this section, as described in paragraph (a) of 

this section:

    (1) In this paragraph (c), we use the letter ``y'' to denote a 

generic measured quantity, the superscript over-bar



[[Page 714]]



to denote an arithmetic mean (such as y), and the subscript ``ref'' to 

denote the known or reference quantity being measured.

    (2) Operate a measurement system at its specified temperatures, 

pressures, and flows. This may include any specified adjustment or 

periodic calibration of the measurement system.

    (3) Zero the instrument as you would before an emission test by 

introducing a zero signal. Depending on the instrument, this may be a 

zero-concentration gas, a reference signal, a set of reference 

thermodynamic conditions, or some combination of these. For gas 

analyzers, use a zero gas that meets the specifications of Sec.  

1065.750 and introduce it directly at the analyzer port.

    (4) Span the instrument as you would before an emission test by 

introducing a span signal. Depending on the instrument, this may be a 

span-concentration gas, a reference signal, a set of reference 

thermodynamic conditions, or some combination of these. For gas 

analyzers, use a span gas that meets the specifications of Sec.  

1065.750 and introduce it directly at the analyzer port.

    (5) After spanning the instrument, check zero with the same signal 

you used in paragraph (c)(3) of this section. Based on the zero reading, 

use good engineering judgment to determine whether or not to rezero and 

or re-span the instrument before proceeding to the next step.

    (6) Use instrument manufacturer recommendations and good engineering 

judgment to select at least 10 reference values, yrefi, that are within 

the range from zero to the highest values expected during emission 

testing. We recommend selecting a zero reference signal as one of the 

reference values of the linearity verification.

    (7) Use instrument manufacturer recommendations and good engineering 

judgment to select the order in which you will introduce the series of 

reference values. For example you may select the reference values 

randomly to avoid correlation with previous measurements, you may select 

reference values in ascending or descending order to avoid long settling 

times of reference signals, or as another example you may select values 

to ascend and then descend which might incorporate the effects of any 

instrument hysteresis into the linearity verification.

    (8) Generate reference quantities as described in paragraph (d) of 

this section. For gas analyzers, use gas concentrations known to be 

within the specifications of Sec.  1065.750 and introduce them directly 

at the analyzer port.

    (9) Introduce a reference signal to the measurement instrument.

    (10) Allow time for the instrument to stabilize while it measures 

the reference value. Stabilization time may include time to purge an 

instrument and time to account for its response.

    (11) At a recording frequency of at least f Hz, specified in Table 1 

of Sec.  1065.205, measure the reference value for 30 seconds and record 

the arithmetic mean of the recorded values, yi. Refer to Sec.  1065.602 

for an example of calculating an arithmetic mean.

    (12) Repeat steps in paragraphs (c)(9) through (11) of this section 

until all reference quantities are measured.

    (13) Use the arithmetic means yi, and reference values, yrefi , to 

calculate least-squares linear regression parameters and statistical 

values to compare to the minimum performance criteria specified in Table 

1 of this section. Use the calculations described in Sec.  1065.602.

    (d) Reference signals. This paragraph (d) describes recommended 

methods for generating reference values for the linearity-verification 

protocol in paragraph (c) of this section. Use reference values that 

simulate actual values, or introduce an actual value and measure it with 

a reference-measurement system. In the latter case, the reference value 

is the value reported by the reference-measurement system. Reference 

values and reference-measurement systems must be NIST-traceable. We 

recommend using calibration reference quantities that are NIST-traceable 

within 0.5% uncertainty, if not specified otherwise in other sections of 

this part 1065. Use the following recommended methods to generate 

reference values or use good engineering judgment to select a different 

reference:



[[Page 715]]



    (1) Engine speed. Run the engine or dynamometer at a series of 

steady-state speeds and use a strobe, a photo tachometer, or a laser 

tachometer to record reference speeds.

    (2) Engine torque. Use a series of calibration weights and a 

calibration lever arm to simulate engine torque. You may instead use the 

engine or dynamometer itself to generate a nominal torque that is 

measured by a reference load cell or proving ring in series with the 

torque-measurement system. In this case use the reference load cell 

measurement as the reference value. Refer to Sec.  1065.310 for a 

torque-calibration procedure similar to the linearity verification in 

this section.

    (3) Electrical work. Use a controlled source of current and a watt-

hour standard reference meter. Complete calibration systems that contain 

a current source and a reference watt-hour meter are commonly used in 

the electrical power distribution industry and are therefore 

commercially available.

    (4) Fuel rate. Operate the engine at a series of constant fuel-flow 

rates or re-circulate fuel back to a tank through the fuel flow meter at 

different flow rates. Use a gravimetric reference measurement (such as a 

scale, balance, or mass comparator) at the inlet to the fuel-measurement 

system. Use a stopwatch or timer to measure the time intervals over 

which reference masses of fuel are introduced to the fuel measurement 

system. The reference fuel mass divided by the time interval is the 

reference fuel flow rate.

    (5) Flow rates--inlet air, dilution air, diluted exhaust, raw 

exhaust, or sample flow. Use a reference flow meter with a blower or 

pump to simulate flow rates. Use a restrictor, diverter valve, a 

variable-speed blower or a variable-speed pump to control the range of 

flow rates. Use the reference meter's response as the reference values.

    (i) Reference flow meters. Because the flow range requirements for 

these various flows are large, we allow a variety of reference meters. 

For example, for diluted exhaust flow for a full-flow dilution system, 

we recommend a reference subsonic venturi flow meter with a restrictor 

valve and a blower to simulate flow rates. For inlet air, dilution air, 

diluted exhaust for partial-flow dilution, raw exhaust, or sample flow, 

we allow reference meters such as critical flow orifices, critical flow 

venturis, laminar flow elements, master mass flow standards, or Roots 

meters. Make sure the reference meter is calibrated by the flow-meter 

manufacturer and its calibration is NIST-traceable. If you use the 

difference of two flow measurements to determine a net flow rate, you 

may use one of the measurements as a reference for the other.

    (ii) Reference flow values. Because the reference flow is not 

absolutely constant, sample and record values of nrefi for 30 seconds 

and use the arithmetic mean of the values, nref, as the reference value. 

Refer to Sec.  1065.602 for an example of calculating arithmetic mean.

    (6) Gas division. Use one of the two reference signals: (i) At the 

outlet of the gas-division system, connect a gas analyzer that meets the 

linearity verification described in this section and has not been 

linearized with the gas divider being verified. For example, verify the 

linearity of an analyzer using a series of reference analytical gases 

directly from compressed gas cylinders that meet the specifications of 

Sec.  1065.750. We recommend using a FID analyzer or a PMD/MPD 

O2 analyzer because of their inherent linearity. Operate this 

analyzer consistent with how you would operate it during an emission 

test. Connect a span gas to the gas-divider inlet. Use the gas-division 

system to divide the span gas with purified air or nitrogen. Select gas 

divisions that you typically use. Use a selected gas division as the 

measured value. Use the analyzer response divided by the span gas 

concentration as the reference gas-division value. Because the 

instrument response is not absolutely constant, sample and record values 

of xrefi for 30 seconds and use the arithmetic mean of the values xref, 

as the reference value. Refer to Sec.  1065.602 for an example of 

calculating arithmetic mean.

    (ii) Using good engineering judgment and gas divider manufacturer 

recommendations, use one or more reference flow meters to verify the 

measured flow rates of the gas divider.



[[Page 716]]



    (7) Continuous constituent concentration. For reference values, use 

a series of gas cylinders of known gas concentration or use a gas-

division system that is known to be linear with a span gas. Gas 

cylinders, gas-division systems, and span gases that you use for 

reference values must meet the specifications of Sec.  1065.750.

[GRAPHIC] [TIFF OMITTED] TR13JY05.021