[Code of Federal Regulations]
[Title 40, Volume 31]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR1065.307]
[Page 714-717]
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 715]]
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 716]]
(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 717]]
(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