The Non-Road Mobile Machinery (Emission of Gaseous and Particulate Pollutants) Regulations 1999

Appendix 1

MEASUREMENT AND SAMPLING PROCEDURES

1.  Gaseous and particulate components emitted by the engine submitted for testing shall be measured by the methods described in Annex V. The methods of Annex V describe the recommended analytical systems for the gaseous emissions (section 1.1) and the recommended particulate dilution and sampling systems (section 1.2).

Dynamometer specification

1.1  An engine dynamometer with adequate characteristics to perform the test cycle described in Annex III, section 3.6.1 shall be used. The instrumentation for torque and speed measurement shall allow the measurement of the shaft power within the given limits. Additional calculations may be necessary.

The accuracy of the measuring equipment must be such that the maximum tolerances of the figures given in section 1.3 are not exceeded.

Exhaust gas flow

1.2  The exhaust gas flow shall be determined by one of the methods mentioned in sections 1.2.1 to 1.2.4.

Direct measurement method

1.2.1  Direct measurement of the exhaust flow by flow nozzle or equivalent metering system (for detail see ISO 5167).

Note: Direct gaseous flow measurement is a difficult task. Precautions must be taken to avoid measurement errors which will impact emission value errors.

Air and fuel measurement method

1.2.2  Measurement of the air flow and the fuel flow.

• Air flow-meters and fuel flow-meters with an accuracy defined in section 1.3 shall be used.

• The calculation of the exhaust gas flow is as follows:

• 

• or

• 

• or

• 

Carbon balance method

1.2.3  Exhaust mass calculation from fuel consumption and exhaust gas concentrations using the carbon balance method (see Annex III, Appendix 3).

Total dilute exhaust gas flow

1.2.4  When using a full flow dilution system, the total flow of the dilute exhaust (G_TOTW, V_TOTW) shall be measured with a PDP or CFV—Annex V, section 1.2.1.2. The accuracy shall conform to the provisions of Annex III, Appendix 2, section 2.2.

Accuracy

1.3  The calibration of all measurement instruments shall be traceable to national (international) standards and comply with the following requirements:

Number	Item	Permissible deviation (±values based on engines maximum values)	Permissible deviation (±values according to ISO 3046)	Calibration intervals (months)
(1) The calculations of the exhaust emissions as described in this Directive are, in some cases, based on different measurement and/or calculation methods. Because of limited total tolerances for the exhaust emission calculation, the allowable values for some items, used in the appropriate equations, must be smaller than the allowed tolerances given in ISO 3046-3.
(2) Full flow systems—the CVS positive displacement pump or critical flow Venturi shall be calibrated following initial installation, major maintenance or as necessary when indicated by the CVS system verification described in Annex V.
1	Engine speed	2%	2%	3
2	Torque	2%	2%	3
3	Power	2%(1)	3%	not applicable
4	Fuel consumption	2%(1)	3%	6
5	Specific fuel consumption	not applicable	3%	not applicable
6	Air consumption	2%(1)	5%	6
7	Exhaust gas flow	4%(1)	not applicable	6
8	Coolant temperature	2K	2K	3
9	Lubricant temperature	2K	2K	3
10	Exhaust gas pressure	5% of maximum	5%	3
11	Inlet manifold depressions	5% of maximum	5%	3
12	Exhaust gas temperature	15K	15K	3
13	Air inlet temperature (Combustion Air)	2K	2K	3
14	Atmospheric pressure	0.5% of reading	0.5%	3
15	Intake air humidity (relative)	3%	not applicable	1
16	Fuel temperature	2K	5K	3
17	Dilution tunnel temperatures	1.5K	not applicable	3
18	Dilution air humidity	3%	not applicable	1
19	Diluted exhaust gas flow	2% of reading	not applicable	24 (partial flow) (full flow)(2)

1.4  Determination of the gaseous components

General analyser specifications

1.4.1  The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (section 1.4.1.1). It is recommended that the analysers be operated such that the measured concentration falls between 15% and 100% of full scale.

• If the full scale value is 155 ppm (or ppm C) 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—Annex III, Appendix 2, section 1.5.5.2.

• The electromagnetic compatibility (EMC) of the equipment shall be on a level as to minimise additional errors.

Measurement error

1.4.1.1  The total measurement error, including the cross sensitivity to other gases—see Annex III, Appendix 2, section 1.9 shall not exceed ± 5% of the reading or 3.5% of full scale, whichever is smaller. For concentrations of less than 100 ppm the measurement error shall not exceed ± 4ppm.

Repeatability

1.4.1.2.  The repeatability, defined as 2.5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than ± 1% of full scale concentration for each range used above 155 ppm (or ppm C) or ± 2% of each range used below 155 ppm (or ppm C).

Noise

1.4.1.3.  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.

Zero drift

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

Span drift

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

Gas drying

1.4.2.  The optional gas drying device must have a minimum effect on the concentration of the measured gases. Chemical dryers are not an acceptable method of removing water from the sample.

Analysers

1.4.3.  Sections 1.4.3.1 to 1.4.3.5 of this Appendix describe the measurement principles to be used. A detailed description of the measurement systems is given in Annex V.

The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearizing circuits is permitted.

Carbon monoxide (CO) analysis

1.4.3.1.  The carbon monoxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type.

Carbon dioxide (CO₂) analysis

1.4.3.2.  The carbon dioxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type.

Hydrocarbon (HC) analysis

1.4.3.3.  The hydrocarbon analyser shall be of the heated flame ionization detector (HFID) type with detector, valves, pipework, etc, heated so as to maintain a gas temperature of 463 K (190°C) ± 10 K.

Oxides of nitrogen (NO_X) analysis

1.4.3.4.  The oxides of nitrogen analyser shall be of the chemiluminescent detector (CLD) or heated chemiluminescent detector (HCLD) type with a NO₂/NO converter, if measured on a dry basis. If measured on a wet basis, a HCLD with a converter maintained above 333 K (60°C) shall be used, provided the water quench check (Annex III, Appendix 2, section 1.9.2.2) is satisfied.

Sampling for gaseous emissions

1.4.4.  The gaseous emissions sampling probes must be fitted at least 0.5m or three times the diameter of the exhaust pipe—whichever is the larger—upstream of the exit of the exhaust gas system as far as applicable and sufficiently close to the engine as to ensure an exhaust gas temperature of at least 343 K (70°C) at the probe.

• In the case of a multicylinder engine with a branched exhaust manifold, the inlet of the probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions from all cylinders. In multicylinder engines having distinct groups of manifolds, such as in a ‘V’-engine configuration, it is permissible to acquire a sample from each group individually and calculate an average exhaust emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emissions calculation the total exhaust mass flow of the engine must be used.

• If the composition of the exhaust gas is influenced by any exhaust after-treatment system, the exhaust sample must be taken upstream of this device in the tests of stage I and downstream of the device in the tests of stage II. When a full flow dilution system is used for the determination of the particulates, the gaseous emissions may also be determined in the diluted exhaust gas. The sampling probes shall be close to the particulate sampling probe in the dilution tunnel (Annex V, section 1.2.1.2, DT and section 1.2.2, PSP). CO and CO₂ may optionally be determined by sampling into a bag and subsequent measurement of the concentration in the sampling bag.

Determination of the particulates

1.5.  The determination of the particulates requires a dilution system. Dilution may be accomplished by a partial flow dilution system or a full flow dilution system. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems, and maintain the temperature of the diluted exhaust gas at or below 325 K (52°C) immediately upstream of the filter holders. De-humidifying the dilution air before entering the dilution system is permitted, if the air humidity is high. Dilution air pre-heating above the temperature limit of 303 K (30°C) is recommended, if the ambient temperature is below 293 K (20°C). However, the diluted air temperature must not exceed 325 K (52°C) prior to the introduction of the exhaust in the dilution tunnel.

• For a partial flow dilution system, the particulate sampling probe must be fitted close to and upstream of the gaseous probe as defined in section 4.4 and in accordance with Annex V, section 1.2.1.1, figures 4-12 EP and SP.

• The partial flow dilution system has to be designed to split the exhaust stream into two fractions, the smaller one being diluted with air and subsequently used for particulate measurement. From that it is essential that the dilution ratio be determined very accurately. Different splitting methods can be applied, whereby the type of splitting used dictates to a significant degree the sampling hardware and procedures to be used (Annex V, section 1.2.1.1).

• To determine the mass of the particulates, a particulate sampling system, particulate sampling filters, a microgram balance and a temperature and humidity controlled weighing chamber are required.

• For particulate sampling, two methods may be applied:

  • the single filter method uses one pair of filters (see section 1.5.1.3 of this Appendix) for all modes of the test cycle. Considerable attention must be paid to sampling times and flows during the sampling phase of the test. However, only one pair of filters will be required for the test cycle.

  • the multiple filter method dictates that one pair of filters (see section 1.5.1.3 of this Appendix) is used for each of the individual modes of the test cycle. This method allows more lenient sample procedures but uses more filters.

1.5.1.  Particulate sampling filters

Filter specification

1.5.1.1.  Fluorocarbon coated glass fibre filters or fluorocarbon based membrane filters are required for certification tests. For special applications different filter materials may be used. All filter types shall have a 0.3μm DOP (di-octylphthalate) collection efficiency of at least 95% at a gas face velocity between 35 and 80 cm/s. When performing correlation tests between laboratories or between a manufacturer and an approval authority, filters of identical quality must be used.

Filter size

1.5.1.2.  Particulate filters must have a minimum diameter of 47 mm (37 mm stain diameter). Larger diameter filters are acceptable (section 1.5.1.5).

Primary and back-up filters

1.5.1.3.  The diluted exhaust shall be sampled by a pair of filters placed in series (one primary and one back-up filter) during the test sequence. The back-up filter shall be located no more than 100 mm downstream of, and shall not be in contact with the primary filter. The filters may be weighed separately or as a pair with the filters placed stain side to stain side.

Filter face velocity

1.5.1.4.  A gas filter velocity through the filter of 35 to 80 cm/s shall be achieved. The pressure drop increase between the beginning and the end of the test shall be no more than 25 kPa.

Filter loading

1.5.1.5.  The recomended minimum filter loading shall be 0.5 mg/1 075 mm² stain area for the single filter method. For the most common filter size the values are as follows:

Filter diameter	Recommended stain diameter	Recommended minimum loading
(mm)	(mm)	(mg)
47	37	0.5
70	60	1.3
90	80	2.3
110	100	3.6

For the multiple filter method, the recommended minimum filter loading for the sum of all filters shall be the product of the appropriate value above and the square root of the total number of modes.

1.5.2.  Weighing chamber and analytical balance specifications

Weighing chamber conditions

1.5.2.1.  The temperature of the chamber (or room) in which the particulate filters are conditioned and weighed shall be maintained to within 295 K (22°C) ± 3 K during all filter conditioning and weighing. The humidity shall be maintained to a dewpoint of 282.5 (9.5°C) ± 3 K and a relative humidity of 45 ± 8%.

Reference filter weighing

1.5.2.2.  The chamber (or room) environment shall be free of any ambient contaminants (such as dust) that would settle on the particulate filters during their stabilisation. Disturbances to weighing room specifications as outlined in section 1.5.2.1 will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personnel entrance into the weighing room. At least two unused reference filters or reference filter pairs shall be weighed within four hours of, but preferably at the same time as the sample filter (pair) weighing. They shall be the same size and material as the sample filters.

• If the average weight of the reference filters (reference filter pairs) changes between sample filter weighing by more than ± 5% (± 7.5% for the filter pair) of the recommended minimum filter loading (section 1.5.1.5), then all sample filters shall be discarded and the emissions test repeated.

• If the weighing room stability criteria outlined in section 1.5.2.1 is not met, but the reference filter (pair) weighing meet the above criteria, the engine manufacturer has the option of accepting the sample filter weights or voiding the tests, fixing the weighing room control system and re-running the test.

Analytical balance

1.5.2.3.  The analytical balance used to determine the weights of all filters shall have a precision (standard deviation) of 20 μg and a resolution of 10 μg (1 digit = 10 μg). For filters less than 70 mm diameter, the precision and resolution shall be 2 μg and 1μg respectively.

Elimination of static electricity effects

1.5.2.4.  To eliminate the effects of static electricity, the filters shall be neutralized prior to weighing, for example, by a Polonium neutralizer or a device of similar effect.

Additional specifications for particulate measurement

1.5.3.  All parts of the dilution system and the sampling system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, must be designed to minimise deposition or alteration of the particulates. All parts must be made of electrically conductive materials that do not react with exhaust gas components, and must be electrically grounded to prevent electrostatic effects.