Document ID: chunk:federal_register_of_legislation:F2023C00229:reg:9:p44
Version: federal_register_of_legislation:F2023C00229
Segment Type: reg
Provision Reference: reg 9 (pt 44/71)
Character Range: 335958–338896

through a detector which gives an electrical signal that depends on their concentration. Since it is not a continuous analysis technique, it can only be used in conjunction with the bag sampling method as described in Annex III, Appendix 4, Section 3.4.2.

              For NMHC an automated GC with a FID shall be used. The exhaust gas shall be sampled into a sampling bag from which a part shall be taken and injected into the GC. The sample is separated into two parts (CH4/Air/CO and NMHC/CO2/H2O) on the Porapak column. The molecular sieve column separates CH4 from the air and CO before passing it to the FID where its concentration is measured. A complete cycle from injection of one sample to injection of a second can be made in 30 s. To determine NMHC, the CH4 concentration shall be subtracted from the total HC concentration (see Annex III, Appendix 2, Section 4.3.1).

              Figure 9 shows a typical GC assembled to routinely determine CH4. Other GC methods can also be used based on good engineering judgement.

        Figure 9

        Flow diagram for methane analysis (GC method)

              Components of Figure 9

              PC Porapak column

              Porapak N, 180/300 μm (50/80 mesh), 610 mm length × 2,16 mm ID shall be used and conditioned at least 12 h at 423 K (150 °C) with carrier gas prior to initial use.

              MSC Molecular sieve column

              Type 13X, 250/350 μm (45/60 mesh), 1 220 mm length × 2,16 mm ID shall be used and conditioned at least 12 h at 423 K (150 °C) with carrier gas prior to initial use.
              OV Oven

              To maintain columns and valves at stable temperature for analyser operation, and to condition the columns at 423 K (150 °C).
              SLP Sample loop

              A sufficient length of stainless steel tubing to obtain approximately 1 cm3 volume.

              P Pump

              To bring the sample to the gas chromatograph.

              D Dryer

              A dryer containing a molecular sieve shall be used to remove water and other contaminants which might be present in the carrier gas.

              HC

              Flame ionisation detector (FID) to measure the concentration of methane.

              V1 Sample injection valve

              To inject the sample taken from the sampling bag via SL of Figure 8. It shall be low dead volume, gas     tight, and heatable to 423 K (150 C).

              V3 Selector valve

              To select span gas, sample, or no flow.

              V2, V4, V5, V6, V7, V8 Needle valve

              To set the flows in the system.

              R1, R2, R3 Pressure regulator

              To control the flows of the fuel (= carrier gas), the sample, and the air, respectively.

              FC Flow capillary

              To control the rate of air flow to the FID.

              G1, G2, G3 Pressure gauge

              To control the flows