A Sensible Introduction to Tier 4 from Volvo Construction Equipment
Volvo outlines the various technologies being used to meet Tier 4 requirements
What is Tier 4? How does it work? Why do we need it? When must we have it in our construction equipment? How will Tier 4 affect you, an off-road equipment owner? This is a complex subject, one full of technology and engineering detail that we probably do not need - nor understand -but must bear the burden of trying to comprehend.
The information on Tier 4 provided in this document will ease that burden and answer specific questions you have raised. And the source is quite reputable. Volvo built its first internal combustion engine in 1893, and since then the company has become the world's second largest manufacturer of heavy-duty diesel engines in the 9 to 18 liter category. The new generation of Volvo diesel engines, featuring Volvo Advanced Combustion Technology - V-ACT - has been engineered for off-road applications and to meet the specific needs of each Volvo machine. They are solid proof of the company's high level of engine technology and experience in successfully applying innovative solutions for performance and productivity - and to meet the requirements of Tier 4.
How and when will the tighter emissions standards impact off-road customers?
Engines 25 to 75 hp (19 to 56 kW):
Tier 4 started in 2008 for engines less than 75 hp (56 kW). In this power range Volvo has achieved 2008 Tier 4 emissions levels without the need for exhaust aftertreatment. 2013 will see another significant reduction in emissions.
For Engines 75 hp (56 kW) and greater Tier 4 is comprised of two significant stages. First is Tier 4a - sometimes referred to as interim Tier 4 or Tier 4i and second is Tier 4b - sometimes referred to as Tier 4 final. The Tier 4 standards require significant emission reductions of both particulate matter (PM) and Nitrogen Oxides (NOx).
Tier 4a - is a significant PM or black smoke/soot reduction along with a significant NOx reduction. NOx is defined as nitrogen monoxide (NO) and nitrogen dioxide (NO2).
Implementation:
Tier 4b - a further but substantial NOx only reduction
Implementation:
The Emissions Box: In general what is done within the engine to reduce NOx creates PM. What is done to reduce PM creates NOx. As high temperatures burn off the black soot or PM, it creates NOx. Conversely, cooler temperatures reduce NOx but increase soot (PM). This creates the problem of "getting in the box" that the engine developers fret about. Below is a graph of the different "boxes" showing how the levels of PM and NOx emissions have been drastically reduced over the years. The smallest red box shows the levels in 2014.
Moving forward we will see "in-cylinder" solutions and "external" solutions to emissions reductions. In cylinder solutions take care of emissions (either all or part) within the cylinder or combustion chamber. These solutions may have external help, like cooled exhaust gas recirculation (EGR) but ultimately what leaves the cylinder through the exhaust port meets the specific goal of the manufacturer. If only part of the emissions equation is solved in cylinder, what is left must be treated externally. In the case of particulate matter treated externally, the use of a particulate filter may be used. NOx can be addressed through the use of an SCR catalyst. There are arguments about which solutions provide the best efficiency, convenience and performance.
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