Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:1800:p5
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 1800 (pt 5/12)
Character Range: 516512–519064

sampling probe SP and the transfer tube TT. The total flow through the tunnel is adjusted with the flow controller FC1 connected either to the diluent flow or to the suction blower for the total tunnel flow. The flow controller FC1 may use qmew or qmaw and qmf as command signals for the desired exhaust split. The sample flow into DT is the difference of the total flow and the diluent flow. The diluent flow rate is measured with the flow measurement device FM1, the total flow rate with the flow measurement device FM2. The dilution ratio is calculated from these two flow rates. From DT, a particulate sample is taken with the particulate sampling system (see Figure 16).
       Figure 13
       Scheme of partial flow dilution system (fractional sampling type)
       a = exhaust  b = to PB or SB  c = details see Figure 16  d = to particulate sampling system  e = vent

A.2.2.2. Components of Figures 12 and 13
 EP Exhaust pipe
 The exhaust pipe may be insulated. To reduce the thermal inertia of the exhaust pipe a thickness to diameter ratio of 0.015 or less is recommended. The use of flexible sections shall be limited to a length to diameter ratio of 12 or less. Bends shall be minimized to reduce inertial deposition. If the system includes a test bed silencer the silencer may also be insulated. It is recommended to have a straight pipe of six pipe diameters upstream and three pipe diameters downstream of the tip of the probe.
 SP Sampling probe
 The type of probe shall be either of the following:
(a) Open tube facing upstream on the exhaust pipe centreline;
(b) Open tube facing downstream on the exhaust pipe centreline;
(c) Multiple hole probe as described under SP in paragraph A.2.1.3.;
(d) Hatted probe facing upstream on the exhaust pipe centreline as shown in Figure 14.
 The minimum inside diameter of the probe tip shall be 4 mm. The minimum diameter ratio between exhaust pipe and probe shall be four.
 When using probe type (a), an inertial pre-classifier (cyclone or impactor) with at 50 per cent cut point between 2.5 and 10 µm shall be installed immediately upstream of the filter holder.
           Figure 14
           Scheme of hatted probe

 TT Exhaust transfer tube
 The transfer tube shall be as short as possible, but:
(a) Not more than 0.26 m in length, if insulated for 80 per cent of the total length, as measured between the end of the probe and the dilution stage;
 or
(b) Not more than 1 m in length, if heated above 150 °C for 90 per cent of the total length, as measured between the end of the probe and