Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:1800:p8
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 1800 (pt 8/12)
Character Range: 523801–526559

in length, then all tubing in excess of 4 m shall be insulated, except for an in-line smoke meter, if used. The radial thickness of the insulation shall be at least 25 mm. The thermal conductivity of the insulating material shall have a value no greater than 0.1 W/mK measured at 673 K. 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.
 PDP Positive displacement pump
 The PDP meters total diluted exhaust flow from the number of the pump revolutions and the pump displacement. The exhaust system backpressure shall not be artificially lowered by the PDP or diluent inlet system. Static exhaust backpressure measured with the PDP system operating shall remain within 1.5 kPa of the static pressure measured without connection to the PDP at identical engine speed and load. The gas mixture temperature immediately ahead of the PDP shall be within 6 K of the average operating temperature observed during the test, when no flow compensation (EFC) is used. Flow compensation is only permitted, if the temperature at the inlet to the PDP does not exceed 323 K (50 °C).
 CFV Critical flow venturi
 CFV measures total diluted exhaust flow by maintaining the flow at chocked conditions (critical flow). Static exhaust backpressure measured with the CFV system operating shall remain within 1.5 kPa of the static pressure measured without connection to the CFV at identical engine speed and load. The gas mixture temperature immediately ahead of the CFV shall be within 11 K of the average operating temperature observed during the test, when no flow compensation (EFC) is used.
 SSV Subsonic venturi
 SSV measures total diluted exhaust flow by using the gas flow function of a subsonic venturi in dependence of inlet pressure and temperature and pressure drop between venturi inlet and throat. Static exhaust backpressure measured with the SSV system operating shall remain within 1.5 kPa of the static pressure measured without connection to the SSV at identical engine speed and load. The gas mixture temperature immediately ahead of the SSV shall be within 11 K of the average operating temperature observed during the test, when no flow compensation (EFC) is used.
 HE Heat exchanger (optional)
 The heat exchanger shall be of sufficient capacity to maintain the temperature within the limits required above. If EFC is used, the heat exchanger is not required.
 EFC Electronic flow compensation (optional)
 If the temperature at the inlet to the PDP, CFV or SSV is not kept within the limits stated above, a flow compensation system is required for continuous measurement of the flow rate and control