Document ID: chunk:federal_register_of_legislation:F2012C00283:reg:21:p21
Version: federal_register_of_legislation:F2012C00283
Segment Type: reg
Provision Reference: reg 21 (pt 21/39)
Character Range: 314649–317504

sampling particulate mass emissions. However, a sampling probe, acting as an appropriate size-classification device, such as that shown in Figure 13, is acceptable as an alternative to a separate pre-classifier.
              1.3.2. Sample Pump and Flow Meter
              1.3.2.1. The sample gas flow measurement unit shall consist of pumps, gas flow regulators and flow measuring units.
              1.3.2.2. The temperature of the gas flow in the flow meter may not fluctuate by more than ±3 K, except during regeneration tests on vehicles equipped with periodically regenerating after treatment devices. In addition, the sample mass flow rate must remain proportional to the total flow of diluted exhaust gas to within a tolerance of ±5 per cent of the particulate sample mass flow rate. Should the volume of flow change unacceptably as a result of excessive filter loading, the test shall be stopped. When it is repeated, the rate of flow shall be decreased.
              1.3.3. Filter and Filter Holder
              1.3.3.1. A valve shall be located downstream of the filter in the direction of flow. The valve shall be quick enough acting to open and close within 1 s of the start and end of test.
              1.3.3.2. It is recommended that the mass collected on the 47 mm diameter filter (Pe) is ≥ 20 µg and that the filter loading should be maximized consistent with the requirements of paragraphs 1.2.3. and 1.3.3.
              1.3.3.3. For a given test the gas filter face velocity shall be set to a single value within the range 20 cm/s to 80 cm/s unless the dilution system is being operated with sampling flow proportional to CVS flow rate.
              1.3.3.4. Fluorocarbon coated glass fibre filters or fluorocarbon membrane filters are required. All filter types shall have a 0.3 µm DOP (di-octylphthalate) collection efficiency of at least 99 per cent at a gas filter face velocity of at least 35 cm/s.
              1.3.3.5. The filter holder assembly shall be of a design that provides an even flow distribution across the filter stain area. The filter stain area shall be at least 1,075 mm2.
              1.3.4. Filter Weighing Chamber and Balance
              1.3.4.1. The microgram balance used to determine the weight of a filter shall have a precision (standard deviation) of 2 µg and resolution of 1 µg or better.
               It is recommended that the microbalance be checked at the start of each weighing session by weighing one reference weight of 50 mg. This weight shall be weighed three times and the average result recorded. If the average result of the weighings is ±5 µg of the result from the previous weighing session then the weighing session and balance are considered valid.
               The weighing chamber (or room) shall meet the following conditions during all filter conditioning and weighing