Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p45
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 45/108)
Character Range: 1010645–1013693

Any leaks between the flow-measuring device and the UFM will seriously affect the accuracy of the calibration.
Figure A5/8
UFM calibration configuration

              3.4.5.7.2. The suction device shall be started. Its speed and/or the position of the flow valve shall be adjusted to provide the set flow for the validation and the system stabilised. Data from all instruments shall be collected.
              3.4.5.7.3. For UFM systems without a heat exchanger, the heater shall be operated to increase the temperature of the calibration air, allowed to stabilise and data from all the instruments recorded. The temperature shall be increased in reasonable steps until the maximum diluted exhaust temperature expected during the emissions test is reached.
              3.4.5.7.4. The heater shall be subsequently turned off and the suction device speed and/or flow valve shall be adjusted to the next flow setting that will be used for vehicle emissions testing after which the calibration sequence shall be repeated.
              3.4.5.8. The data recorded during the calibration shall be used in the following calculations. The air flow rate Qs at each test point shall be calculated from the flow meter data using the manufacturer's prescribed method.
              where:
                     Qs  is the air flow rate at standard conditions (101.325 kPa, 273.15 K (0 °C)), m3/s;
                     Qreference is the air flow rate of the calibration flow meter at standard conditions (101.325 kPa, 273.15 K (0 °C)), m3/s;
                     Kv is the calibration coefficient.
              For UFM systems without a heat exchanger, Kv shall be plotted as a function of Tact.
              The maximum variation in Kv shall not exceed 0.3 per cent of the arithmetic average Kv value of all the measurements taken at the different temperatures.
              3.5. System verification procedure
              3.5.1. General requirements
              3.5.1.1. The total accuracy of the CVS sampling system and analytical system shall be determined by introducing a known mass of an emissions gas compound into the system whilst it is being operated under normal test conditions and subsequently analysing and calculating the emission gas compounds according to the equations of Annex B7. The CFO method described in paragraph 3.5.1.1.1. of this annex and the gravimetric method described in paragraph 3.5.1.1.2. of this annex are both known to give sufficient accuracy.
              The maximum permissible deviation between the quantity of gas introduced and the quantity of gas measured is ±2 per cent.
3.5.1.1.1. Critical flow orifice (CFO) method
              The CFO method meters a constant flow of pure gas (CO, CO2, or C3H8) using a critical flow orifice device.
              A known mass of pure carbon monoxide, carbon dioxide or propane gas shall be introduced into the CVS system through the calibrated critical orifice. If the inlet pressure is high enough, the flow rate  which is restricted by means of the critical flow