The guidelines to be developed by IMO should be in accordance with the provisions of paragraph 2.4.5 of the NOx Technical Code. As stated there a NOx monitoring and recording device approved by the Administration based on these guidelines is specified as an on-board NOx verification procedure.

　

According to the provisions of paragraph 6.1 of the NOx Technical Code, after installation of a pre-certificated engine on board a ship, every marine diesel engine shall have on-board verification surveys conducted as specified in 2.1.1.2 to 2.1 .1.4 (of the NOx Technical Code) to verify that the engines continue to comply with the NOx emission limits contained in regulation 13 of Annex VI (and paragraph 3.1 of the NOx Technical Code).

　

Chapter 3 of the NOx Technical Code specifies the Nitrogen Oxides Emission Standards including limits as weighted NOx emissions as well as test cycles and weighting factors to be applied. However, in paragraph 6.3.9 of the NOx Technical Code provisions are made for onboard verification using the simplified measurement method for the case that engine operation on board under a test cycle specified in 3.2 may not be possible. Similar provisions are necessary for on-board verification using direct measurement and monitoring.

　

Although the verification of compliance with the NOx emission limits is to be done for steady-state operation using the test cycles specified in paragraph 3.2 of the NOx Technical Code the guidelines are to include a definition of continuous NOx monitoring taking into account both steady-state and transient operation of the engine, according to paragraph 2.4.5 of the NOx Technical Code. Drawing data continuously, i.e. in practice frequently dependent on both the ability of the device and the load profile of the engine, allows the differentiation of suitable and unsuitable operation modes of the engine for the aimed verification purpose. Continuous monitoring also may be used to indicate changes in NOx influencing engine parameters, i.e. components and adjustments.

　

Nevertheless, it is not necessary to draw all data needed for an exact determination of the actual NOx emission value if the engine operation mode proves to be unsuitable. The determination of the NOx emission value requires calculation of the gaseous emissions as specified in paragraph 5.12 of the NOx Technical Code including a correction to reference conditions, i.e. ambient conditions etc.

　

In developing guidelines for NOx monitoring and recording devices priority should be given to the development of a definition of continuous NOx monitoring and the specification for the equipment to ensure the reliability of the equipment, and possibly data recording, processing, and retention.

　

　

2.1　Continuous means that the device is connected to the engine and active all the time the engine is running provided that no maintenance or calibration is necessary.

　

2.2　Continuous monitoring means that the necessary sensors are installed and active all the time the engine is running provided that no maintenance or calibration is necessary.

　

2.3　Continuous NOx monitoring means that the sensors for all operating values necessary for determination of the NOx emission value are installed and active all the time the engine is running provided that no maintenance or calibration is necessary. These sensors may be suitable for direct NOx monitoring or for indirect NOx monitoring. It is not necessary to draw all sensor signals if the engine operation mode proves to be unsuitable for verification of compliance with the NOx emission limits.

　

2.4　Direct NOx monitoring (measurement of NOx) means that the NOx concentration in the exhaust gas is measured as one of the necessary operating values. However, as the Nitrogen Oxide (NOx) Emission is defined according to the NOx Technical Code as the total emission of nitrogen oxides, calculated as the total weighted emission of NO2 and determined using the relevant test cycles further operating values are necessary for determination of the emission value.

　

2.5　Indirect NOx monitoring (measurement of engine combustion performance) means that the NOx concentration in the exhaust gas is not used for determination of the emission value but other operating values which are related to the NOx emission performance. Subject to the approval of the Administration, the engine manufacturer specifies the necessary operating values and demonstrates their influence on NOx.

　

2.6　Relevant emission limit means the applicable value from the maximum allowable NOx emission limits for marine Diesel engines as specified in both regulation 13 of Annex VI and the NOx Technical Code.

　

2.7　Emission value means the actual NOx emission value as defined in the NOx Technical Code, i.e. the total emission of nitrogen oxides, calculated as the total weighted emission of NO2 and determined using the relevant test cycles and measurement methods.