Clearing the Air on Global Emissions Standards for Non-Road and Marine Diesel Engines
Global emissions standards for non-road and marine diesel engines continue to tighten and fuel filtration will continue to play an important role in meeting these new challenges. To gain a clearer picture of emissions standards, individual regions and vehicle categories need to be analysed.
In Europe, stage IV emissions requirements closely mirror those in the US. Stage IV came into force in 2014, a standard that necessitates emissions to be measured on-engine during both a steady state and transient test cycle
Among many noteworthy points, for the main power sector (130 to 560 kW), the NOx standard is the same between Europe and the US. However, the PM (particulate matter) standard in the US is 20% lower than Europe. What’s more, unlike the US, Europe currently has no limitation for engines over 560 kW in this category.
Switching focus to non-road legislation for diesel engines in the US, criteria emissions limits reduced steadily from 1996 to 2011. As a consequence, this sector has seen the most significant changes in the shortest time, a development that has driven a total shift in applied technology. The non-road legislation is staggered in four stages (Tiers 1-4), with Tier 4 being the current legislation.
Due to the difference in engine cost at different power levels, the emissions targets are staggered by power band. For instance, it would clearly be cost prohibitive to apply a full heavy duty style exhaust after-treatment system to a light duty engine. Useful emission equipment life requirements also apply depending on engine duty cycle.
Away from land-based vehicles, the IMO (International Maritime Organization) regulates emissions from ship exhausts through standards known as Tier I, II and III of MARPOL 73/78.
Tier I was introduced in May 2005 and covers engines greater than 130 kW installed on vessels on or after 1 January 2000 or which undergo major conversions after that date. Tiers II and III were adopted in 2008 and cover new fuel quality specifications, improved NOx standards for existing pre-2000 engines, and globally-based ocean regions and ‘Emission Control Areas’ with specified emission reduction requirements. Actual emission levels are defined by engine rated speed and the area of operation.
Although there are no limits on soot, generally no visible smoke is acceptable. Avoiding smoke requires higher injection pressures, especially at partial load, and therefore high pressure common rail injection systems are increasingly being deployed.
While it’s easy to focus on the requirements for regions that have adopted enhanced criteria emissions standards, lesser regulated markets should not be overlooked when it comes to fuel system demands.
In the industrial engine market it is becoming standard practice to sell the engines/ vehicles/ machines into lesser regulated countries after several years of operation in the original market. Often ‘de-tier’ kits are applied to the engines to remove systems that are not required in the new market. However, the fuel system is at the heart of the engine and this will normally remain on the vehicle as it enters service in a new market. It should also be noted that fuel quality in these markets can be significantly worse than the original market, therefore the filtration requirements can be different.
In conclusion, all engine sectors from small passenger engines to large marine vessels, have witnessed a focused effort to reduce harmful exhaust emissions. For on-road applications the emissions levels have dropped to the point where further reductions will have smaller environmental impact. As a result, future changes in legislation for harmful emissions will focus on refinements to address specific issues rather than major order of magnitude reductions that have been seen in the past. Fuel systems will continue to play an important role in the package of technologies being applied to meet the challenge.
This article is a small edited portion of a study conducted by AVL that was commissioned by Parker Hannifin Racor Divis