CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER C—AIR PROGRAMS (Parts 50–99) > PART 86—CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES > SUBPART D—Emission Regulations for New Gasoline-Fueled and Diesel-Fueled Heavy-Duty Engines; Gaseous Exhaust Test Procedures (§86.301-79 to §86.348-79) > 86.329-79—System response time; check procedure.

86.329-79—System response time; check procedure.

(a) Check the system response time by the following procedure:
(1) Stabilize the operating temperature of the sample line, sample pump, and heated filters.
(2) Introduce an HC span gas into the sampling system at the sample probe or valve V2 at atmospheric pressure. Simultaneously, start the time measurement.
(3) When the HC instrument response is 95 percent of the span gas concentration used, stop the time measurement.
(4) If the elapsed time is more than 20.0 seconds, make necessary adjustments.
(5) Repeat with the CO, CO2, and NOX instruments and span gases.
(b) Option. If the following parameters are determined, the initial system response time may be generally applied to future checks.
(1) Analyzer and bypass flow rates. (i) Determine by experimentation the minimum analyzer and bypass flow rates individually and in combination that will produce a response time as close as possible to 20.0 seconds per paragraph (a) of this section.
(ii) Record the highest minimum flow rate for each flow meter as determined in step (i).
(2) Capillary flow analyzers. This procedure is applicable only to analyzers that have sample capillaries such as the HFID and CL analyzers. It is also assumed that the system has sample/span valves that perform the function of valves V9 and V13 in Figure D79-1.
(i) Operate the analyzer(s) at the in-use capillary pressure.
(ii) Adjust the bypass flow rate to the flow rate recorded in paragraph (b)(1)(ii) of this section.
(iii) Measure and record the response time from the sample/span valve(s) per paragraph (a) of this section.
(iv) The response time (step (iii)) can be determined by switching from the “sample” position to the “span” position of the sample/span valve and observing the analyzer response on a chart recorder. Normally, the “sample” position would select a “room air” sample and the “span” position would select a span gas.
(v) Adjust the bypass flow rate to the normal in-use value.
(vi) Measure and record the response time from the sample/span valve(s) per paragraph (a) of this section.
(vii) Determine the slowest response time (step (iii) or step (iv)) and add 2 seconds to it.