(viii)

Section 3 is replaced by the following: ‘3. CALIBRATION OF THE PARTICULATE MEASURING SYSTEM 3.1. Introduction The calibration of the particulate measurement is limited to the flow meters used to determine sample flow and dilution ratio. Each flow meter shall be calibrated as often as necessary to fulfil the accuracy requirements of this Directive. The calibration method that shall be used is described in section 3.2. 3.2. Flow measurement 3.2.1. Periodical calibration 3.2.2. Carbon flow check 3.2.3. Pre-test check 3.3. Determination of transformation time (for partial flow dilution systems on ETC only) 3.4. Checking the partial flow conditions The range of the exhaust gas velocity and the pressure oscillations shall be checked and adjusted according to the requirements of section 2.2.1 of Annex V (EP), if applicable. 3.5. Calibration intervals The flow measurement instrumentation shall be calibrated at least every 3 months or whenever a system repair or change is made that could influence calibration.’ To fulfil the absolute accuracy of the flow measurements as specified in section 2.2 of Appendix 4 to this Annex, the flow meter or the flow measurement instrumentation shall be calibrated with an accurate flow meter traceable to international and/or national standards. If the sample gas flow is determined by differential flow measurement the flow meter or the flow measurement instrumentation shall be calibrated in one of the following procedures, such that the probe flow q mp into the tunnel shall fulfil the accuracy requirements of section 4.2.5.2 of Appendix 4 to this Annex: The flow meter for q mdw shall be connected in series to the flow meter for q mdew, the difference between the two flow meters shall be calibrated for at least 5 set points with flow values equally spaced between the lowest q mdw value used during the test and the value of q mdew used during the test. The dilution tunnel may be bypassed. A calibrated mass flow device shall be connected in series to the flowmeter for q mdew and the accuracy shall be checked for the value used for the test. Then the calibrated mass flow device shall be connected in series to the flow meter for q mdw, and the accuracy shall be checked for at least 5 settings corresponding to dilution ratio between 3 and 50, relative to q mdew used during the test. The transfer tube TT shall be disconnected from the exhaust, and a calibrated flow measuring device with a suitable range to measure q mp shall be connected to the transfer tube. Then q mdew shall be set to the value used during the test, and q mdw shall be sequentially set to at least 5 values corresponding to dilution ratios q between 3 and 50. Alternatively, a special calibration flow path, may be provided, in which the tunnel is bypassed, but the total and dilution air flow through the corresponding meters as in the actual test. A tracer gas, shall be fed into the exhaust transfer tube TT. This tracer gas may be a component of the exhaust gas, like CO2 or NOx. After dilution in the tunnel the tracer gas component shall be measured. This shall be carried out for 5 dilution ratios between 3 and 50. The accuracy of the sample flow shall be determined from the dilution ration r d: Text of image qmp = qmdew rd The accuracies of the gas analysers shall be taken into account to guarantee the accuracy of q mp. A carbon flow check using actual exhaust is recommended for detecting measurement and control problems and verifying the proper operation of the partial flow system. The carbon flow check should be run at least each time a new engine is installed, or something significant is changed in the test cell configuration. The engine shall be operated at peak torque load and speed or any other steady state mode that produces 5 % or more of CO2. The partial flow sampling system shall be operated with a dilution factor of about 15 to 1. If a carbon flow check is conducted, the procedure given in Appendix 6 to this Annex shall be applied. The carbon flow rates shall be calculated according to sections 2.1 to 2.3 of Appendix 6 to this Annex. All carbon flow rates should agree to within 6 % of each other. A pre-test check shall be performed within 2 hours before the test run in the following way: The accuracy of the flow meters shall be checked by the same method as used for calibration (see section 3.2.1) for at least two points, including flow values of q mdw that correspond to dilution ratios between 5 and 15 for the q mdew value used during the test. If it can be demonstrated by records of the calibration procedure under section 3.2.1 that the flow meter calibration is stable over a longer period of time, the pre-test check may be omitted. The system settings for the transformation time evaluation shall be exactly the same as during measurement of the test run. The transformation time shall be determined by the following method: An independent reference flowmeter with a measurement range appropriate for the probe flow shall be put in series with and closely coupled to the probe. This flowmeter shall have a transformation time of less than 100 ms for the flow step size used in the response time measurement, with flow restriction sufficiently low as to not affect the dynamic performance of the partial flow dilution system, and consistent with good engineering practice. A step change shall be introduced to the exhaust flow (or air flow if exhaust flow is calculated) input of the partial flow dilution system, from a low flow to at least 90 % of full scale. The trigger for the step change should be the same one used to start the look-ahead control in actual testing. The exhaust flow step stimulus and the flowmeter response shall be recorded at a sample rate of at least 10 Hz. From this data, the transformation time shall be determined for the partial flow dilution system, which is the time from the initiation of the step stimulus to the 50 % point of the flowmeter response. In a similar manner, the transformation times of the qmp signal of the partial flow dilution system and of the q mew,i signal of the exhaust flow meter shall be determined. These signals are used in the regression checks performed after each test (see section 3.8.3.2 of Appendix 2 to this Annex). The calculation shall be repeated for at least 5 rise and fall stimuli, and the results shall be averaged. The internal transformation time (< 100 msec) of the reference flowmeter shall be subtracted from this value. This is the “look-ahead” value of the partial flow dilution system, which shall be applied in accordance with section 3.8.3.2 of Appendix 2 to this Annex.

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Source: EUR-Lex (Cellar) · retrieved 2026-11-10 · Text as adopted (Official Journal); later amendments are not incorporated in this text.