[ANNEX VI U.K. TYPE IV TEST THE DETERMINATION OF EVAPORATIVE EMISSIONS FROM VEHICLES WITH SPARK-IGNITION ENGINES
Appendix 1 CALIBRATION OF EQUIPMENT FOR EVAPORATIVE EMISSION TESTING
[2. CALIBRATION OF THE ENCLOSURE U.K.
2.3. Calibration and hydrocarbon retention test of the chamber U.K.
The calibration and hydrocarbon retention test in the chamber provides a check on the calculated volume in 2.1 and also measures any leak rate. The enclosure leak rate must be determined at the enclosure's introduction to service, after any operations in the enclosure which may affect the integrity of the enclosure, and at least monthly thereafter. If six consecutive monthly retention checks are successfully completed without corrective action, the enclosure leak rate may be determined quarterly thereafter as long as no corrective action is required.
2.3.1. The enclosure must be purged until a stable hydrocarbon concentration is reached. The mixing fan is turned on, if not already switched on. The hydrocarbon analyser is zeroed, calibrated if required, and spanned. U.K.
2.3.2. On variable-volume enclosures the enclosure must be latched to the nominal volume position. On fixed-volume enclosures the outlet and inlet flow streams must be closed. U.K.
2.3.3. The ambient temperature control system is then turned on (if not already on) and adjusted for an initial temperature of 308 °K (35 °C) [309 °K (36 °C)]. U.K.
2.3.4. When the enclosure stabilizes at 308 °K ± 2 °K (35° ± 2 °C) [309 °K ± 2 °K (36° ± 2 °C)], the enclosure is sealed and the background concentration, temperature and barometric pressure measured. These are the initial readings C HC,i , P i and T i used in the enclosure calibration. U.K.
2.3.5. A quantity of approximately 4 grams of propane is injected into the enclosure. The mass of propane must be measured to an accuracy and precision of ± 02, % of the measured value. U.K.
2.3.6. The contents of the chamber must be allowed to mix for five minutes and then the hydrocarbon concentration, temperature and barometric pressure are measured. These are the final readings C HC,f , P f and T f for the calibration of the enclosure as well as the initial readings C HC,i , P i and T i for the retention check. U.K.
2.3.7. On the basis of the readings taken in 2.3.4 and 2.3.6 and the formula in 2.4, the mass of propane in the enclosure is calculated. This must be within ± 2 % of the mass of propane measured in 2.3.5.. U.K.
2.3.8. For variable-volume enclosures the enclosure must be unlatched from the nominal volume configuration. For fixed-volume enclosures, the outlet and inlet flow streams must be opened. U.K.
2.3.9. The process is then begun of cycling the ambient temperature from 308 °K (35 °C) to 293 °K (20 °C) and back to 308 °K (35 °C) [308,6 °K (35,6 °C) to 295,2 °K (22,2 °C) and back to 308,6 °K (35,6 °C)] over a 24-hour period according to the profile [alternative profile] specified in Appendix 2 within 15 minutes of sealing the enclosure. (Tolerances as specified in section 5.7.1 of Annex VI). U.K.
2.3.10. At the completion of the 24-hour cycling period, the final hydrocarbon concentration, temperature and barometric pressure are measured and recorded. These are the final readings C HC,f , T f and P f for the hydrocarbon retention check. U.K.
2.3.11. Using the formula in 2.4, the hydrocarbon mass is then calculated from the readings taken in 2.3.10 and 2.3.6. The mass may not differ by more than 3 % from the hydrocarbon mass given by 2.3.7.] ] U.K.