Document ID: chunk:federal_register_of_legislation:F2024C00356:reg:21:p27
Version: federal_register_of_legislation:F2024C00356
Segment Type: reg
Provision Reference: reg 21 (pt 27/35)
Character Range: 362112–365129

constant level at the point at which PNC flow rate is controlled, the pressure and/or temperature at inlet to the PNC must be measured and reported for the purposes of correcting particle concentration measurements to standard conditions.
              1.3.6. The sum of the residence time of the PTS, VPR and OT plus the T90 response time of the PNC shall be no greater than 20 s.
              1.4. Recommended System Description
               The following section contains the recommended practice for measurement of particle number. However, any system meeting the performance specifications in paragraphs 1.2. and 1.3. is acceptable.
               Figure 14 is a schematic drawing of the recommended particle sampling system.

Figure 14
Schematic of Recommended Particle Sampling System

              1.4.1. Sampling System Description
               The particle sampling system shall consist of a sampling probe tip in the dilution tunnel (PSP), a particle transfer tube (PTT), a particle pre-classifier (PCF) and a volatile particle remover (VPR) upstream of the particle number concentration measurement (PNC) unit. The VPR shall include devices for sample dilution (particle number diluters: PND1 and PND2) and particle evaporation (Evaporation tube, ET). The sampling probe for the test gas flow shall be so arranged within the dilution tract that a representative sample gas flow is taken from a homogeneous air/exhaust mixture. The sum of the residence time of the system plus the T90 response time of the PNC shall be no greater than 20 s.
              1.4.2. Particle Transfer System
               The sampling probe tip (PSP) and particle transfer tube (PTT) together comprise the particle transfer system (PTS). The PTS conducts the sample from the dilution tunnel to the entrance to the first particle number diluter. The PTS shall meet the following conditions:
               It shall be installed near the tunnel centre line, 10 to 20 tunnel diameters downstream of the gas inlet, facing upstream into the tunnel gas flow with its axis at the tip parallel to that of the dilution tunnel.
               It shall have an internal diameter of ≥ 8 mm.
               Sample gas drawn through the PTS shall meet the following conditions:
               It shall have a flow Reynolds number (Re) of < 1.700;
               It shall have a residence time in the PTS of ≤ 3 seconds.
               Any other sampling configuration for the PTS for which equivalent particle penetration for particles of 30 nm electrical mobility diameter can be demonstrated will be considered acceptable.
               The outlet tube (OT) conducting the diluted sample from the VPR to the inlet of the PNC shall have the following properties:
               It shall have an internal diameter of ≥ 4 mm;
               Sample Gas flow through the POT shall have a residence time of ≤ 0.8 seconds.
               Any other sampling configuration for the OT for which equivalent particle penetration for particles