F2ANNEX VITYPE IV TEST

THE DETERMINATION OF EVAPORATIVE EMISSIONS FROM VEHICLES WITH SPARK-IGNITION ENGINES

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Appendix 1CALIBRATION OF EQUIPMENT FOR EVAPORATIVE EMISSION TESTING

F11.CALIBRATION FREQUENCY AND METHODS

1.1.

All equipment must be calibrated before its initial use and then calibrated as often as necessary and in any case in the month before type-approval testing. The calibration methods to besued are described in this Appendix.

1.2.

Normally the series of temperatures which are mentioned firstly must be used. The series of temperatures within square brackets may alternatively be used.

2.CALIBRATION OF THE ENCLOSURE

2.1.Initial determination of enclosure internal volume

2.1.1.

Before its initial use, the internal volume of the chamber must be determined as follows. The internal dimensions of the chamber are carefully measured, allowing for any irregularities such as bracing struts. The internal volume of the chamber is determined from these measurements.

For variable-volume enclosures, the enclosure must be latched to a fixed volume when the enclosure is held at an ambient temperature of 303 °K (30 °C) [(302 °K (29 °C)]. This nominal volume must be repeatable within ± 0,5 % of the reported value.

2.1.2.

The net internal volume is determined by subtracting 1,42 m3 from the internal volume of the chamber. Alternatively the volume of the test vehicle with the luggage compartment and windows open may be used instead of the 1,42 m3.

2.1.3.

The chamber must be checked as in 2.3. If the propane mass does not agree with the injected mass to within ± 2 % then corrective action is required.

2.2.Determination of chamber background emissions

This operation determines that the chamber does not contain any materials that emit significant amounts of hydrocarbons. The check must be carried out at the enclosure's introduction to service, after any operations in the enclosure which may affect background emissions and at a frequency of at least once per year.

2.2.1.

Variable-volume enclosures may be operated in either latched or unlatched volume configuration, as described in 2.1.1 Ambient temperatures must be maintained at 308 °K ± 2 °K (35° ± 2 °C) [309 °K ± 2 °K (36° ± 2 °C)], throughout the 4-hour period mentioned below.

2.2.2.

Fixed volume enclosures must be operated with inlet and outlet flow streams closed. Ambient temperatures must be maintained at 308 °K ± 2 °K (35° ± 2 °C) [309 °K ± 2 °K (36° ± 2 °C)] throughout the four-hour period mentioned below.

2.2.3.

The enclosure may be sealed and the mixing fan operated for a period of up to 12 hours before the four-hour background sampling period begins.

2.2.4.

The analyser (if required) must be calibrated, then zeroed and spanned.

2.2.5.

The enclosure must be purged until a stable hydrocarbon reading is obtained, and the mixing fan turned on if not already on.

2.2.6.

The chamber is then sealed and the background hydrocarbon concentration, temperature and barometric pressure are measured. These are the initial readings CHC,i, Pi and Ti used in the enclosure background calculation.

2.2.7.

The enclosure is allowed to stand undisturbed with the mixing fan on for a period of four hours.

2.2.8.

At the end of this time the same analyser is used to measure the hydrocarbon concentration in the chamber. The temperature and the barometric pressure are also measured. These are the final readings CHC,f, Pf and Tf.

2.2.9.

The change in mass of hydrocarbons in the enclosure must be calculated over the time of the test in accordance with 2.4 and must not exceed 0,05 g.

2.3.Calibration and hydrocarbon retention test of the chamber

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.

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.

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)].

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 CHC,i, Pi and Ti used in the enclosure calibration.

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.

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 CHC,f, Pf and Tf for the calibration of the enclosure as well as the initial readings CHC,i, Pi and Ti for the retention check.

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..

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.

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).

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 CHC,f, Tf and Pf for the hydrocarbon retention check.

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.

2.4.Calculations

The calculation of net hydrocarbon mass change within the enclosure is used to determine the chamber's hydrocarbon background and leak rate. Initial and final readings of hydrocarbon concentration, temperature and barometric pressure are used in the following formula to calculate the mass change.

MHC = k · V · 10-4 · CHC, f · PfTf - CHC, i · PiTi + MHC, out - MHC, imath

where:

MHC

hydrocarbon mass in grams

MHC,out

mass of hydrocarbon exiting the enclosure, in the case of fixed-volume enclosures for diurnal emission testing (grams)

MHC,i

mass of hydrocarbon entering the enclosure, in the case of fixed volume enclosures for diurnal emission testing (grams)

CHC

hydrocarbon concentration in the enclosure (ppm carbon (NB: ppm carbon = ppm propane × 3))

V

enclosure volume in cubic metres as measured in section 2.1.1.

T

ambient temperature in the enclosure in K,

P

barometric pressure in kPa,

k

17,6;

where:

i

is the initial reading.

f

is the final reading

3.CHECKING OF FID HYDROCARBON ANALYZER

3.1.Detector response optimization

The FID must be adjusted as specified by the instrument manufacturer. Propane in air should be used to optimize the response on the most common operating range.

3.2.Calibration of the HC analyzer

The analyzer should be calibrated using propane in air and purified synthetic air. See section 4.5.2 of Annex III (Calibration and span gases).

Establish a calibration curve as described in sections 4.1 to 4.5 of this Appendix.

3.3.Oxygen interference check and recommended limits

The response factor (Rf) for a particular hydrocarbon species is the ratio of the FID C1 reading to the gas cylinder concentration, expressed as ppm C1.

The concentration of the test gas must be at a level to give a response of approximately 80 % of full scale deflection, for the operating range. The concentration must be known, to an accuracy of ± 2 % in reference to a gravimetric standard expressed in volume. In addition the gas cylinder must be preconditioned for 24 hours at a temperature between 293 K and 303 K (20 ° and 30 °C).

Response factors should be determined when introducing an analyzer into service and thereafter at major service intervals. The reference gas to be used is propane with balance purified air which is taken to give a response factor of 1,00.

The test gas to be used for oxygen interference and the recommended response factor range are given below:

Propane and nitrogen 0,95 ≤ Rf ≤ 1,05.

4.CALIBRATION OF THE HYDROCARBON ANALYZER

Each of the normally used operating ranges are calibrated by the following procedure:

4.1.

Establish the calibration curve by at least five calibration points spaced as evenly as possible over the operating range. The nominal concentration of the calibration gas with the highest concentrations to be at least 80 % of the full scale.

4.2.

Calculate the calibration curve by the method of least squares. If the resulting polynominal degree is greater than 3, then the number of calibration points must be at least the number of the polynominal degree plus 2.

4.3.

The calibration curve must not differ by more than 2 % from the nominal value of each calibration gas.

4.4.

Using the coefficients of the polynominal derived from 3.2, a table of indicated reading against true concentration shall be drawn up in steps of no greater than 1 % of full scale. This is to be carried out for each analyzer range calibrated. The table shall also contain other relevant data such as:

  • date of calibration,

  • span and zero potentiometer readings (where applicable),

  • nominal scale,

  • reference data of each calibration gas used,

  • the actual and indicated value of each calibration gas used together with the percentage differences,

  • FID fuel and type,

  • FID air pressure.

4.5.

If it can be shown to the satisfaction of the Regulatory Agency that alternative technology (e.g. computer, electronically controlled range switch) can give equivalent accuracy, then those alternatives may be used.