1 General
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - International Codes - NOx Technical Code (2008) - Technical Code on Control of Emission of Nitrogen Oxides from Marine Diesel Engines - Appendix 3 - Specifications for analysers to be used in the determination of gaseous components of marine diesel engine emissions - 1 General

1 General

  1.1 The components included in an exhaust gas analysis system for the determination of the concentrations of CO, CO2, NOx, HC and O2 are shown in figure 1. All components in the sampling gas path must be maintained at the temperatures specified for the respective systems.

Figure 1 Arrangement of exhaust gas analysis system

  1.2 An exhaust gas analysis system shall include the following components. In accordance with chapter 5 of this Code equivalent arrangements and components may, subject to approval by the Administration, be accepted.

  • .1 SP – Raw exhaust gas sampling probe

  • A stainless steel, straight, closed-end, multi-hole probe. The inside diameter shall not be greater than the inside diameter of the sampling line. The wall thickness of the probe should not be greater than 1 mm. There should be a minimum of three holes in three different radial planes sized to sample approximately the same flow.

  • For the raw exhaust gas, the sample for all components may be taken with one sampling probe or with two sampling probes located in close proximity and internally split to the different analysers.

  • Note: If exhaust pulsations or engine vibrations are likely to affect the sampling probe, the wall thickness of the probe may be enlarged subject to the approval of the Administration.

  • .2 HSL1 – Heated sampling line

  • The sampling line provides a gas sample from a single probe to the split point(s) and the HC analyser. The sampling line shall be made of stainless steel or polytetrafluoroethylene (PTFE) and have a 4 mm minimum and a 13.5 mm maximum inside diameter.

  • The exhaust gas temperature at the sampling probe shall not be less than 190oC. The temperature of the exhaust gas from the sampling point to the analyser shall be maintained by using a heated filter and a heated transfer line with a wall temperature of 190oC ± 10oC.

  • If the temperature of the exhaust gas at the sampling probe is above 190oC, a wall temperature greater than 180oC shall be maintained.

  • Immediately before the heated filter and the HC analyser a gas temperature of 190oC ± 10oC shall be maintained.

  • .3 HSL2 – Heated NOx sampling line

  • The sampling line shall be made of stainless steel or PTFE and maintain a wall temperature of 55oC to 200oC, up to the converter C when using a cooling unit B, and up to the analyser when a cooling unit B is not used.

  • .4 HF1 – Heated pre-filter (optional)

  • The required temperature shall be the same as for HSL1.

  • .5 HF2 – Heated filter

  • The filter shall extract any solid particles from the gas sample before the analyser. The temperature shall be the same as for HSL1. The filter shall be changed as necessary.

  • .6 HP – Heated sampling pump (optional)

  • The pump shall be heated to the temperature of HSL1

  • .7 SL – Sampling line for CO, CO2 and O2

  • The line shall be made of PTFE or stainless steel. It may be heated or unheated.

  • .8 CO2/CO – Carbon dioxide and carbon monoxide analysers

  • Non-dispersive infrared (NDIR) absorption. Either separate analysers or two functions incorporated into a single analyser unit.

  • .9 HC – Hydrocarbon analyser

  • Heated flame ionization detector (HFID). The temperature shall be kept at 180oC to 200oC.

  • .10 NOx – Nitrogen oxides analyser

  • Chemiluminescent detector (CLD) or heated chemiluminescent detector (HCLD). If a HCLD is used, it shall be kept at a temperature of 55oC to 200oC.

    • Note: In the arrangement shown NOx is measured on a dry basis. NOx may also be measured on a wet basis in which case the analyser shall be of the HCLD type.

  • .11 C – converter

  • A converter shall be used for the catalytic reduction of NO2 to NO prior to analysis in the CLD or HCLD.

  • .12 O2 – Oxygen analyser

  • Paramagnetic detector (PMD), zirconium dioxide (ZRDO) or electrochemical sensor (ECS). ZRDO shall not be used for dual fuel or gas-fuelled engines.

  • Note: In the arrangement shown O2 is measured on a dry basis. O2 may also be measured on a wet basis in which case the analyser shall be of the ZRDO type.

  • .13 B – cooling unit

  • To cool and condense water from the exhaust sample. The cooler shall be maintained at a temperature of 0oC to 4oC by ice or refrigerator. If water is removed by condensation, the sample gas temperature or dew point shall be monitored either within the water trap or downstream. The sample gas temperature or dew point shall not exceed 7oC.

  1.3 The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (see 1.6) and 5.9.7.1 of this Code. It is recommended that the analysers be operated such that the measured concentration falls between 15% and 100% of full scale, where full scale refers to the measurement range used.

  1.4 If the full-scale value is 155 ppm (or ppmC) or less, or if read-out systems (computers, data loggers) that provide sufficient accuracy and resolution below 15% of full scale are used, concentrations below 15% of full scale are also acceptable. In this case, additional calibrations are to be made to ensure the accuracy of the calibration curves.

  1.5 The electromagnetic compatibility (EMC) of the equipment shall be such as to minimize additional errors.

1.6 Accuracy

1.6.1 Definitions

ISO 5725-1: 1994/Cor 1: 1998, Accuracy (trueness and precision) of measurement methods and results – Part 1: General principles and definitions, Technical Corrigendum 1.

ISO 5725-2: 1994, Accuracy (trueness and precision) of measurement methods and results – Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method.

1.6.2 An analyser shall not deviate from the nominal calibration point by more than ± 2% of the reading over the whole measurement range except zero, or ± 0.3% of full scale, whichever is larger. The accuracy shall be determined according to the calibration requirements laid down in section 5 of appendix 4 of this Code.

1.7 Precision

The precision, defined as 2.5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, shall be not greater than ± 1% of full-scale concentration for each range used above 100 ppm (or ppmC) or ± 2% of each range used below 100 ppm (or ppmC).

1.8 Noise

The analyser peak-to-peak response to zero and calibration or span gases over any 10–second period shall not exceed 2% of full scale on all ranges used.

1.9 Zero drift

Zero response is defined as the mean response, including noise, to a zero gas during a 30–second time interval. The drift of the zero response during a one-hour period shall be less than 2% of full scale on the lowest range used.

1.10 Span drift

Span response is defined as the mean response, including noise, to a span gas during a 30-second time interval. The drift of the span response during a one-hour period shall be less than 2% of full scale on the lowest range used.

Parent topic: Appendix 3 - Specifications for analysers to be used in the determination of gaseous components of marine diesel engine emissions
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