Document ID: chunk:federal_register_of_legislation:F2008C00323:reg:20:p17
Version: federal_register_of_legislation:F2008C00323
Segment Type: reg
Provision Reference: reg 20 (pt 17/23)
Character Range: 192829–195695

dilution tract that a representative sample gas flow can be taken from the homogeneous air/exhaust mixture and an air/exhaust gas mixture temperature of 325 K (52 C) is not exceeded immediately before the particulate filter. The temperature of the gas flow in the flow metre may not fluctuate by more than  3 K, nor may the mass flow rate fluctuate by more than  5 per cent. Should the volume of flow change unacceptably as a result of excessive filter loading, the test shall be stopped. When it is repeated, the rate of flow shall be decreased and/or a larger filter used. The filters shall be removed from the chamber no earlier than an hour before the test begins.

           The necessary particle filters shall be conditioned (as regards temperature and humidity) in an open dish which has been protected against dust ingress for at least 8 and for not more than 56 hours before the test in an air-conditioned chamber. After this conditioning the uncontaminated filters will be weighed and stored until they are used. If the filters are not used within one hour of their removal from the weighing chamber they shall be re-weighed.

           The one-hour limit may be replaced by an eight-hour limit if one or both of the following conditions are met;

           a stabilised filter is placed and kept in a sealed filter holder assembly with the ends plugged, or;

           a stabilised filter is placed in a sealed filter holder assembly which is then immediately placed in a sample line through which there is no flow.

           4.3.3.  Calibration

           Each analyser shall be calibrated as often as necessary and in any case in the month before type approval testing and at least once every six months for verifying conformity of production.

           The calibration method to be used is described in Appendix 6 to this Annex for the analysers referred to in paragraph 4.3.1. above.

           4.4.  Volume measurement

           4.4.1.  The method of measuring total dilute exhaust volume incorporated in the constant volume sampler shall be such that measurement is accurate to  2 per cent.

           4.4.2.  Constant volume sampler calibration

           The constant volume sampler system volume measurement device shall be calibrated by a method sufficient to ensure the prescribed accuracy and at a frequency sufficient to maintain such accuracy.

           An example of a calibration procedure which will give the required accuracy is given in Appendix 6 to this Annex. The method shall utilise a flow metering device which is dynamic and suitable for the high flow-rate encountered in constant volume sampler testing. The device shall be of certified accuracy traceable to an approved national or international standard.

           4.5.  Gases

           4.5.1. Pure gases

           The following pure gases shall be