Document ID: chunk:federal_register_of_legislation:F2023C00229:reg:9:p59
Version: federal_register_of_legislation:F2023C00229
Segment Type: reg
Provision Reference: reg 9 (pt 59/71)
Character Range: 375039–378017

sampling filters. The dilution air flow rate is usually constant whereas the sample flow rate is controlled by the flow controller FC3. If electronic flow compensation EFC (see Figure 20) is used, the total diluted exhaust gas flow is used as command signal for FC3.

       2.4.1. Components of Figures 21 and 22

              PTT Particulate transfer tube (Figures 21, 22)

              The particulate transfer tube must not exceed 1 020 mm in length, and must be minimised in length whenever possible. Where applicable (i.e. for partial flow dilution fractional sampling systems and for full flow dilution systems), the length of the sampling probes (SP, ISP, PSP, respectively, see Sections 2.2 and 2.3) shall be included.

              The dimensions are valid for:

                —    the partial flow dilution fractional sampling type and the full flow single dilution system from the tip of the probe (SP, ISP, PSP, respectively) to the filter holder;

                —    the partial flow dilution total sampling type from the end of the dilution tunnel to the filter holder;

                —    the full flow double dilution system from the tip of the probe (PSP) to the secondary dilution tunnel.

              The transfer tube:

                —    may be heated to no greater than 325 K (52 °C) wall temperature by direct heating or by dilution air pre-heating, provided the air temperature does not exceed 325 K (52 °C) prior to the introduction of the exhaust in the dilution tunnel;

                —    may be insulated.

              SDT Secondary dilution tunnel (Figure 22)

              The secondary dilution tunnel should have a minimum diameter of 75 mm, and should be of sufficient length so as to provide a residence time of at least 0,25 seconds for the doubly-diluted sample. The primary filter holder FH shall be located within 300 mm of the exit of the SDT.

              The secondary dilution tunnel:

                —    may be heated to no greater than 325 K (52 °C) wall temperature by direct heating or by dilution air pre-heating, provided the air temperature does not exceed 325 K (52 °C) prior to the introduction of the exhaust in the dilution tunnel;

                —    may be insulated.

              FH Filter holder(s) (Figures 21, 22)

              For primary and back-up filters one filter housing or separate filter housings may be used. The requirements of Annex III, Appendix 4, Section 4.1.3 shall be met.

              The filter holder(s):

                —    may be heated to no greater than 325 K (52 °C) wall temperature by direct heating or by dilution air pre-heating, provided the air temperature does not exceed 325 K (52 °C) prior to the introduction of the exhaust in the dilution tunnel;

                —    may be insulated.

              P Sampling pump (Figures 21, 22)

              The particulate sampling pump shall be located sufficiently distant from the tunnel so that the