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Emission Standards

EU: Nonroad Engines: In-Service Monitoring


In-service monitoring (ISM) of nonroad engines was introduced for select categories of Stage V engines in 2017 via Commission Delegated Regulation (EU) 2017/655 of 19 December 2016 [5168]. The regulation requires in-service monitoring of gaseous emissions from variable speed Stage V engines from 56 to 560 kW (categories NRE-v-5 and NRE-v-6).

This is a reporting requirement and in-service emissions limits have not yet been established. The intent is to prepare for an in-service conformity requirement.

Nonroad mobile machinery (NRMM) is available in a wide variety of machines used in a wide variety of duty cycles. Therefore, defining general parameters for describing a testing duty cycle would be difficult. Instead, the regulation requires that for the machinery being tested, ISM be performed with duty cycles representative of their real operation by the usual professional operator while avoiding disproportionate amounts of idling.

General Requirements

Engines subject to in-service monitoring shall be installed in one of the most representative categories of non-road mobile machinery for the selected engine type or, where applicable, engine family.

Engines are tested using portable emissions measurement systems (PEMS). Two testing scheme options are available:

  1. Test 9 engines near the start of the emissions durability period (EDP) before 2023 and 9 engines near the end of the EDP before 2025 (Table 1)
  2. Test 9 engines per year for 4 consecutive years

Testing is to be done in a single operating sequence unless the test conditions do not enable reaching the minimum test duration, Table 1, or when the machinery selected for testing is employed in multiple working activities with different duty cycles. In the latter cases, data from several operating sequences can be combined.

Table 1
Summary of parameters for ISM testing
Temperature, min.-7°C
Temperature, max.-0.4514·(101.3-pb) + 311 K
where pb is the ambient pressure, kPa
Altitude max.Ambient pressure ≥ 82.5 kPa
Start of evaluationCoolant > 70°C or
Coolant stable ±2 K for 5 minutes.
No later than 20 minutes after engine start
DPF regeneration correctionNot mentioned
When testing is carried out56≤P<130 kW: before 20% of EDP and after 55% of EDP
130≤P<560 kW: before 30% of EDP and after 70% of EDP
PollutantsCO, CO2, NOx, THC
GPS dataOptional
Duration of test5 to 7 times NRTC cycle work or
5 to 7 times NRTC CO2 mass
Data consistency: correlation between measured and calculated fuel flow rateR2 ≥ 0.90
from 15% to max fuel flow rate
MAWWork windows and CO2 windows
Valid work-based windowsAverage power > 20% Pmax
Valid CO2 mass-based windowsDuration < 3600·Wref/(0.2·Pmax)
Proportion of valid windows≥50%
Power threshold for valid windows20%
Conformity factorMonitoring only

Data Validity

Data validity is based on the concept of working and non-working events. Only working events are used for calculating work or CO2 mass to define averaging windows and the pollutant emissions over these averaging windows. Non-working events can be short (≤ 10 minutes) or long (> 10 minutes) and for which one of the following conditions are met:

  1. The engine power is less than 10% of the engine’s maximum net power
  2. During cold start (see Table 1)
  3. Ambient conditions not met (see Table 1)
  4. While periodic checks or the measurement instruments are occurring
  5. A period up to 4 minutes after a long non-working event during which exhaust temperature < 523 K (250°C)

Non-working events < 2 minutes are considered working events and merged with the surrounding working events. Working events < 2 minutes are merged into surrounding non-working events longer than 2 minutes. The first 2 minutes of all non-working events are considered as working events. These criteria are applied in several steps which are outlined in the example of Figure 1

Figure 1. Steps to define a data set for analysis

Step 1: Detect and split into working events and non-working events.
Step 2: Merge short working events (≤ 2 minutes) into non-working events.
Step 3: Exclude working events after long non-working events.
Step 4: Include non-working events after working events.

Data Analysis

The moving average window (MAW) method is used to calculate emissions with the window length equal to the engine CO2 mass (reference CO2 mass, mCO2ref) or work (reference work, Wref) measured over the NRTC, Figure 2.

[SVG image]
Figure 2. MAW: Moving averaging window method

Valid work-based windows (WBW) are those for which the average power exceeds 20% of the maximum engine power (Pmax). Valid CO2 mass-based windows are those shorter than 3600·Wref/(0.2·Pmax). The percentage of valid averaging windows shall be ≥ 50 % for both methods. Averaging window conformity factor distributions are reported as minimum, maximum and 90th percentile values.

Acknowledgements: Karsten Mathies of TÜV Hessen has graciously provided valuable guidance and background information for this article.