Document ID: chunk:federal_register_of_legislation:F2012C00283:reg:21:p5
Version: federal_register_of_legislation:F2012C00283
Segment Type: reg
Provision Reference: reg 21 (pt 5/39)
Character Range: 270076–273145

air and exhaust gases shall be homogeneous at the point where the sampling probe is located (see paragraph 1.3.3. below). The sampling probe shall extract a representative sample of the diluted exhaust gas.

       1.2.3.  The system shall enable the total volume of the diluted exhaust gases to be measured.

       1.2.4.  The sampling system shall be gas-tight. The design of the variable-dilution sampling system and the materials that go to make it up shall be such that they do not affect the pollutant concentration in the diluted exhaust gases. Should any component in the system (heat exchanger, cyclone separator, blower, etc.) change the concentration of any of the pollutants in the diluted exhaust gases and the fault cannot be corrected, then sampling for that pollutant shall be carried out upstream from that component.

              1.2.5.  All parts of the dilution system that are in contact with raw and diluted exhaust gas, shall be designed to minimise deposition or alteration of the particulates or particles. All parts shall be made of electrically conductive materials that do not react with exhaust gas components, and shall be electrically grounded to prevent electrostatic effects.
              1.2.6.  If the vehicle being tested is equipped with an exhaust pipe comprising several branches, the connecting tubes shall be connected as near as possible to the vehicle without adversely affecting its operation.
              1.2.7.  The variable-dilution system shall be so designed as to enable the exhaust gases to be sampled without appreciably changing the back-pressure at the exhaust pipe outlet.
              1.2.8.  The connecting tube between the vehicle and dilution system shall be designed so as to minimize heat loss.
              1.3.  Specific Requirements
              1.3.1.  Connection to Vehicle Exhaust
                The connecting tube between the vehicle exhaust outlets and the dilution system shall be as short as possible; and satisfy the following requirements:

                (a) Be less than 3.6 m long, or less than 6.1 m long if heat insulated.                Its internal diameter may not exceed 105 mm;

               (b) Shall not cause the static pressure at the exhaust outlets on the vehicle being tested to; differ by more than 0.75 kPa at 50 km/h,               or more than 1.25 kPa for the whole duration of the test from the               static pressures recorded when nothing is connected to the vehicle               exhaust outlets. The pressure shall be measured in the exhaust               outlet or in an extension having the same diameter, as near as               possible to the end of the pipe. Sampling systems capable of               maintaining the static pressure to within 0.25 kPa may be used if               a written request from a manufacturer to the Technical Service               substantiates the need for the closer tolerance;

                 (c) Shall not change the nature of the exhaust gas;

                 (d) Any elastomer connectors employed shall