Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p37
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 37/108)
Character Range: 988379–991390

is designed to inhibit condensation by such techniques, or combination of techniques, as:
                  (a) Reducing water content in the dilution air (dilution air dehumidification);
                  (b) Heating of the CVS dilution air and of all components up to the diluted exhaust flow measurement device and, optionally, the bag sampling system including the sample bags and also the system for the measurement of the bag concentrations.
              In such cases, the selection of the CVS flow rate for the test shall be justified by showing that condensation of water cannot occur at any point within the CVS, bag sampling or analytical system.
              3.3.5. Volume measurement in the primary dilution system
              3.3.5.1. The method of measuring total dilute exhaust volume incorporated in the constant volume sampler shall be such that measurement is accurate to ±2 per cent under all operating conditions. If the device cannot compensate for variations in the temperature of the mixture of exhaust gases and dilution air at the measuring point, a heat exchanger shall be used to maintain the temperature to within ±6 °C of the specified operating temperature for a PDP CVS, ±11 °C for a CFV CVS, ±6 °C for a UFM CVS, and ±11 °C for an SSV CVS.
              3.3.5.2. If necessary, some form of protection for the volume measuring device may be used e.g. a cyclone separator, bulk stream filter, etc.
              3.3.5.3. A temperature sensor shall be installed immediately before the volume measuring device. This temperature sensor shall have an accuracy of ±1 °C and a response time of 1 second or less at 62 per cent of a given temperature variation (value measured in water or silicone oil).
              3.3.5.4. Measurement of the pressure difference from atmospheric pressure shall be taken upstream from and, if necessary, downstream from the volume measuring device.
              3.3.5.5. The pressure measurements shall have a precision and an accuracy of ±0.4 kPa during the test. See Table A5/5.
              3.3.6. Recommended system description
              Figure A5/3 is a schematic drawing of exhaust dilution systems that meet the requirements of this annex.
              The following components are recommended:
                  (a) A dilution air filter, which may be pre-heated if necessary. This filter shall consist of the following filters in sequence: an optional activated charcoal filter (inlet side), and a HEPA filter (outlet side). It is recommended that an additional coarse particle filter be situated before the HEPA filter and after the charcoal filter, if used. The purpose of the charcoal filter is to reduce and stabilize the hydrocarbon concentrations of ambient emissions in the dilution air;
                  (b) A connecting tube by which vehicle exhaust is admitted into a dilution tunnel;
                  (c) An optional heat exchanger as described in paragraph 3.3.5.1. of this annex;
                  (d) A mixing device