Robert Marringa is a product marketing manager for Case Construction Equipment.
With U.S. Environmental Protection Agency (EPA) Tier 4 interim emissions standards for off-highway equipment scheduled to take effect in 2011, construction business owners are trying to determine the new regulation's expected impact on their operations and finances. The interim standards, to be followed in 2014 by final Tier 4 standards, aim to virtually eliminate nitrogen oxides (NOx) and particulate matter (PM) emissions.
Tier 4 emissions standards represent the EPA’s biggest step so far toward reaching near-zero emissions from heavy equipment.
Case Construction Equipment has joined other manufacturers in describing compliance plans to address Tier 4 interim standards across its product line, which includes more than ninety equipment models, ranging from 11.3 kW (15.15 hp) to 397 kW (532 ho).
As the interim standards apply only to manufacturers and new equipment, construction business owners don’t face any immediate federal compliance issues regarding their current off-highway fleets.
Contractors will eventually have to purchase compliant machines, and the new technology will come with at least an incremental increase in cost. Some manufacturers already have warned of price increases due to Tier 4 compliance.
Before contractors feel any direct effect from the evolution to Tier 4, they may face regulations and enforcement procedures at the state government level. For the past few years, for example, manufacturers and equipment owners have been tracking the California Air Resource Board’s (CARB) in-use rule that imposes emissions standards and strict reporting regulations for off-highway equipment.
Requirements and solutions for upgrading existing equipment have yet to be defined by the EPA.
Reducing the Main Pollutants to Meet Tier 4 Emission Standards
Key to meeting Tier 4 is reducing the main pollutants in emissions: carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC) and particulate matter (PM). Emissions limits are particularly focused on curbing airborne NOx and PM.
When Tier 4 final standards are met, construction equipment will emit 90 percent less particulate matter and nitrogen oxides, compared to what was allowed under Tier 3.
Nitrogen oxides are produced during combustion when the engine is at its hottest. Particulate matter includes tiny carbon particles and other poisonous substances that are created when not all fuel is burned during combustion.
In February, Case described solutions that use two distinct technologies, cooled exhaust gas recirculation (CEGR) and selective catalytic reduction (SCR), to meet Tier 4 emission requirements. Most other manufacturers are implementing one solution over the other exclusively.
Case sees advantages to both technologies, depending on engine size and load and also application demands. Case has a long-term preference for SCR, especially in equipment with heavier loads. However, Case believes the dual technology strategy provides the most cost-effective and efficient way to manage the technology adoption.
How Selective Catalytic Reduction Works
The engine is tuned for maximum efficiency, and the high combustion temperatures reduce PM levels but increase NOx levels. SCR is an after-treatment system that creates a chemical reaction by adding diesel exhaust fluid (DEF). This transforms the NOx into nitrogen and water, substances that occur naturally in the atmosphere. No particulate filter is required.
How CEGR Works
In a CEGR system, exhaust gases are cooled, blended with fresh air and then returned to the cylinder, lowering combustion temperatures and dramatically reducing nitrogen oxides. PM levels are then reduced through use of an after-treatment exhaust filter system.
At Case, Tier 4 technology solutions are integral to the machine design, so there will be no after-market add-ons or awkward constructions.
For ease of serviceability, with models that use CEGR technology, there is a regular maintenance interval for the diesel particulate filter. To accommodate the technology in Case models, the design allows for easy customer access to change that filter. And, with Case models that incorporate SCR technology, the DEF additive fill point is positioned for customer convenience.
Benefits of CEGR and SCR Solutions
Both CEGR and SCR technologies offer a variety of benefits. For example, the SCR approach offers reduced fuel consumption resulting from a very efficient combustion process, reduced long-term maintenance because of the inherently simple design, and high performance made possible by the after-treatment.
The CEGR solution employs familiar technology. The basic engine technology does not change dramatically from Tier 3, so service and maintenance measures remain familiar to contractors. CEGR does not require you to change the way you operate your equipment.
Regardless of the technology employed, contractors’ Tier 4-compliant equipment will contribute to maintaining a cleaner environment for generations to come.
Construction Business Owner, May 2010