[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: 40CFR1065.308]



[Page 716-718]

 

                   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.  1065.308  Continuous gas analyzer system-response and 

updating-recording verification.



    (a) Scope and frequency. Perform this verification after installing 

or replacing a gas analyzer that you use for continuous sampling. Also 

perform this verification if you reconfigure your system in a way that 

would change system response. For example, perform



[[Page 717]]



this verification if you add a significant volume to the transfer lines 

by increasing their length or adding a filter; or if you change the 

frequency at which you sample and record gas-analyzer concentrations.

    (b) Measurement principles. This test verifies that the updating and 

recording frequencies match the overall system response to a rapid 

change in the value of concentrations at the sample probe. Gas analyzer 

systems must be optimized such that their overall response to a rapid 

change in concentration is updated and recorded at an appropriate 

frequency to prevent loss of information.

    (c) System requirements. To demonstrate acceptable updating and 

recording with respect to the system's overall response, use good 

engineering judgment to select one of the following criteria that your 

system must meet:

    (1) The product of the mean rise time and the frequency at which the 

system records an updated concentration must be at least 5, and the 

product of the mean fall time and the frequency at which the system 

records an updated concentration must be at least 5. This criteria makes 

no assumption regarding the frequency content of changes in emission 

concentrations during emission testing; therefore, it is valid for any 

testing.

    (2) The frequency at which the system records an updated 

concentration must be at least 5 Hz. This criteria assumes that the 

frequency content of significant changes in emission concentrations 

during emission testing do not exceed 1 Hz.

    (3) You may use other criteria if we approve the criteria in 

advance.

    (4) For PEMS, you do not have to meet this criteria if your PEMS 

meets the overall PEMS check in Sec.  1065.920.

    (d) Procedure. Use the following procedure to verify the response of 

a continuous gas analyzer system:

    (1) Instrument setup. Follow the analyzer system manufacturer's 

start-up and operating instructions. Adjust the system as needed to 

optimize performance.

    (2) Equipment setup. Using minimal gas transfer line lengths between 

all connections, connect a zero-air source to one inlet of a fast-acting 

3-way valve (2 inlets, 1 outlet). Using a gas divider, equally blend an 

NO-CO-CO2-C3H8-CH4 (balance 

N2) span gas with a span gas of NO2. Connect the 

gas divider outlet to the other inlet of the 3-way valve. Connect the 

valve outlet to an overflow at the gas analyzer system's probe or to an 

overflow fitting between the probe and transfer line to all the 

analyzers being verified.

    (3) Data collection. (i) Switch the valve to flow zero gas.

    (ii) Allow for stabilization, accounting for transport delays and 

the slowest instrument's full response.

    (iii) Start recording data at the frequency used during emission 

testing. Each recorded value must be a unique updated concentration 

measured by the analyzer; you may not use interpolation to increase the 

number of recorded values.

    (iv) Switch the valve to flow the blended span gases.

    (v) Allow for transport delays and the slowest instrument's full 

response.

    (vi) Repeat the steps in paragraphs (d)(3)(i) through (v) of this 

section to record seven full cycles, ending with zero gas flowing to the 

analyzers.

    (vii) Stop recording.

    (e) Performance evaluation. (1) If you chose to demonstrate 

compliance with paragraph (c)(1) of this section, use the data from 

paragraph (d)(3) of this section to calculate the mean rise time, 

T10-90, and mean fall time, T90-10, for each of 

the analyzers. Multiply these times (in seconds) by their respective 

recording frequencies in Hertz (1/second). The value for each result 

must be at least 5. If the value is less than 5, increase the recording 

frequency or adjust the flows or design of the sampling system to 

increase the rise time and fall time as needed. You may also configure 

digital filters to increase rise and fall times.

    (2) If a measurement system fails the criterion in paragraph (e)(1) 

of this section, ensure that signals from the system are updated and 

recorded at a frequency of at least 5 Hz.

    (3) If a measurement system fails the criteria in paragraphs (e)(1) 

and (2) of this section, you may use the continuous analyzer system only 

if the deficiency does not adversely affect your



[[Page 718]]



ability to show compliance with the applicable standards.