Document ID: chunk:federal_register_of_legislation:F2023C00229:reg:9:p63
Version: federal_register_of_legislation:F2023C00229
Segment Type: reg
Provision Reference: reg 9 (pt 63/71)
Character Range: 385683–388678

least 5 mm. The probe diameter shall ensure a representative sampling and a sufficient flow through the opacimeter.

              TT Transfer tube

              The transfer tube shall:
                —    Be as short as possible and ensure an exhaust gas temperature of 373 ± 30 K (100 °C ± 30 °C) at the entrance to the measuring chamber.

                —    Have a wall temperature sufficiently above the dew point of the exhaust gas to prevent condensation.

                —    Be equal to the diameter of the sampling probe over the entire length.

                —    Have a response time of less than 0,05 s at minimum instrument flow, as determined according to Annex III, Appendix 4, Section 5.2.4.

                —    Have no significant effect on the smoke peak.

              FM Flow measurement device

              Flow instrumentation to detect the correct flow into the measuring chamber. The minimum and maximum flow rates shall be specified by the instrument manufacturer, and shall be such that the response time requirement of TT and the optical path length specifications are met. The flow measurement device may be close to the sampling pump, P, if used.

              MC Measuring chamber

              The measuring chamber shall have a non-reflective internal surface, or equivalent optical environment. The impingement of stray light on the detector due to internal reflections of diffusion effects shall be reduced to a minimum.

              The pressure of the gas in the measuring chamber shall not differ from the atmospheric pressure by more than 0,75 kPa. Where this is not possible by design, the opacimeter reading shall be converted to atmospheric pressure.

              The wall temperature of the measuring chamber shall be set to within ± 5 K between 343 K (70 °C) and
              373 K (100 °C), but in any case sufficiently above the dew point of the exhaust gas to prevent condensation. The measuring chamber shall be equipped with appropriate devices for measuring the temperature.

              OPL Optical path length

              The length of the smoke obscured optical path between the opacimeter light source and the receiver, corrected as necessary for non-uniformity due to density gradients and fringe effect. The optical path length shall be submitted by the instrument manufacturer taking into account any measures against sooting (e.g. purge air). If the optical path length is not available, it shall be determined in accordance with ISO IDS 11614, Section 11.6.5.

              LS Light source

              The light source shall be an incandescent lamp with a colour temperature in the range of 2 800 to 3 250 K or a green light emitting diode (LED) with a spectral peak between 550 and 570 nm. The light source shall be protected against sooting by means that do not influence the optical path length beyond the manufacturers specifications.

              LD Light detector

              The detector shall be