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Emission Standards - Category 1 And 2

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Tier 1-2 Standards

Emission standards for engines Category 1 and 2 are based on the land-based standard for nonroad and locomotive engines. The emission standards, referred to as Tier 2 Standards by the EPA, and their implementation dates are listed in the following table. The Tier 1 NOx standard, equivalent to MARPOL Annex VI, was voluntary under the 1999 rule, but was made mandatory by the 2003 (Category 3) rule for Category 2 and Category 1 engines of above 2.5 liter displacement per cylinder, effective 2004.

The regulated emissions include NOx+THC, PM, and CO. There are no smoke requirements for marine diesel engines. The regulators believed that the new PM standards will have a sufficient effect on limiting smoke emissions.

In the earlier proposal, the EPA also listed a more stringent Tier 3 standard to be introduced between 2008 and 2010. The Tier 3 standard was not adopted in the final 1999 rule.




Blue Sky Series Program.

The 1999 regulation sets a voluntary “Blue Sky Series” program which permits manufacturers to certify their engines to more stringent emission standards. The qualifying emission limits are listed in Table 3. The Blue Sky program begins upon the publication of the rule and extends through the year 2010.

Recreational Vessels (2002 Rule).

Recreational vessels standards are phased-in beginning in 2006, depending on the size of the engine as listed in Table 4. These standards are similar to the Tier 2 standards for Category 1 commercial vessels.

Recreational engines are also subject to NTE limits. There are no smoke requirements for recreational marine diesel engines. Similarly to commercial vessels, a voluntary “Blue Sky Series” limits exist for recreational vessels, which are based on a 45% emission reduction beyond the mandatory standards.

Tier 3-4 Standards

The standards and implementation schedules are shown in Table 5 through Table 8. The engine-based Tier 3 standards are phasing in over 2009-2014. The aftertreatment-based Tier 4 standards for commercial marine engines at or above 600 kW are phasing in over 2014-2017. For engines of power levels not included in the Tier 3 and Tier 4 tables, the previous tier of standards—Tier 2 or Tier 3, respectively—continues to apply.

A differentiation is made between high power density engines typically used in planing vessels and standard power density engines, with a cut point between them at 35 kW/dm3 (47 hp/dm3).

In addition to the above NOx+HC and PM standards, the following CO emission standards apply for all Category 1/2 engines starting with the applicable Tier 3 model year:
  •   .    8.0 g/kWh for engines < 8 kW,
  •   i.   6.6 g/kWh for engines ≥ 8 kW and < 19 kW,
  •   ii.  5.5 g/kWh for engines ≥ 19 kW and < 37 kW,
  •   iii. 5.0 g/kWh for engines ≥ 37 kW.


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