Contractor Power

With great power comes great responsibility. It may be Stan Lee comic book wisdom, but it’s actually not a bad metaphor for the evolving tale of engines and emissions regulations. For hundreds of years, man has yearned for more powerful engines. But over the past three decades, governments around the world have sought to balance those power needs with equally important considerations of eco-cleanliness, sustainability and public health.

In the U.S. construction industry (specifically diesel engines for compact equipment), these regulations are called Tier emissions standards — created by the Environmental Protection Agency (EPA) to push the diesel engine manufacturing industry to create cleaner burning engines. Today’s regulations have their roots in the Clean Air Act of 1970, one of the most significant environmental laws in U.S. history, which created sweeping laws to reduce and control air pollution. Among other air pollutants, the Clean Air Act addresses particulate matter (PM, known as soot) and nitrogen oxides (NOx).

Nitrogen oxides react with sunlight and other substances in the atmosphere to create ground-level ozone, otherwise known as smog. Particulate matter and NOx come from many sources, including diesel engines. In an effort to reduce and control PM and NOx emissions, the Clean Air Act required the EPA to, among other things, establish and enforce progressively more stringent emissions requirements for all new off-road diesel engines starting in 1996, known as the Tier emissions standards.

For the construction industry today, off-highway diesel engine Tiers are coming to a head as the final and most stringent set of regulations (called Tier 4) are already here for small diesel engines. The initial standards (PM compliance) are referred to as “Interim Tier 4,” while the next standards (NOx/hydrocarbons compliance) are referred to as “Tier 4 Final.” The 25- to 74-hp power band hit Interim Tier 4 in 2008 and the Final Tier 4 standards for all horsepower ranges are fast approaching from 2013 through 2015. Tier 4 Interim in North America demands a moderate reduction in the levels of NOx of between 15 and 50 percent, depending on rating. The reduction in the levels of particulate matter of up to 95 percent is truly the significant move. It is intended to drive the use of exhaust after-treatment devices to achieve this — these will be new systems and technologies (like diesel particulate filters or diesel oxidation catalysts) that will not only change the way your diesel engine works, but also its size, envelope and maintenance procedures.

Interim Tier 4 will take effect in January 2011 for engines greater than 175 hp and one year later for engines from 75 to 175 hp. Three years on, in 2014 and 2015, Tier 4 Final/Stage IV will demand a further 80 to 90 percent reduction in NOx, which will also drive additional new technology. With this new Tier 4 deadline being phased in 2011, we decided to ask major engine manufacturers like Perkins, Kohler, John Deere Power Systems and Cummins how these new diesel engines work and what will change for the contractor? Over the next five pages, they tell us their stories, detailing the evolving balance of power and responsibility in the off-highway diesel engine market.

Keith Gribbins is managing editor of Compact Equipment, based in Peninsula, Ohio.

For Interim Tier 4 there are two primary technology paths engine manufacturers will use to reduce nitrogen oxides (NOx) and particulate matter (PM). The first is with cooled exhaust gas recirculation (EGR) and an exhaust filter. EGR lowers NOx and the exhaust filter reduces PM. The second way to reduce emissions is with selective catalytic reduction (SCR) and a diesel oxidation catalyst (DOC). The SCR system lowers NOx while the DOC reduces PM.

Cooled EGR is essentially the opposite of SCR. Cooled EGR cools and mixes measured amounts of exhaust gas with incoming fresh air to lower the engine’s peak combustion temperature, thereby reducing NOx to an acceptable level. Because of the lower combustion temperatures used to reduce NOx with the cooled EGR approach, there is an increase in PM. To reduce PM to acceptable levels, exhaust gases are routed through an exhaust filter, located downstream of the engine, containing a DOC and diesel particulate filter (DPF). PM is trapped in the filter and — through a process called passive regeneration which utilizes normal engine exhaust temperatures — the PM is oxidized into nitrogen gas and carbon dioxide, then expelled through the exhaust pipe.

With the SCR approach, the technology increases the peak combustion temperature in the engine and the result is less particulate matter but NOx levels are increased. If mandated PM levels cannot be achieved, any further reduction in PM is accomplished by a chemical reaction in a DOC. To reduce the higher levels of NOx, a diesel exhaust fluid (DEF) is injected into the exhaust stream downstream of the engine. When the exhaust gases combine with the DEF in the SCR catalyst, NOx is broken down into nitrogen gas and water vapor and expelled through the exhaust pipe.

John Deere is going to continue with cooled EGR technology to meet Interim Tier 4 regulations. We’re taking our proven Tier 3 PowerTech Plus engine platform with cooled EGR and adding an exhaust filter. Throughout Tier 3, we have gained experience with cooled EGR technology over a wide range of applications and have established a proven record of increased performance, fuel economy and durability. We believe the cooled EGR technology is a simple solution that will provide the best total fluid economy — without the need for a second fluid to meet IT4 emissions regulations.

The proven single-fluid approach of our cooled EGR technology means owners and operators won’t have to incur the cost of diesel fuel plus the additional cost for a second fluid (DEF) required by SCR systems. While SCR is an effective technology for reducing NOx, it also requires that the vehicle or machine be fitted with a separate DEF tank, a sophisticated DEF injection system and a tamper-proof diagnostic system. Because DEF freezes, heating systems for the vehicle tank and delivery lines are required. The SCR solution also increases annual maintenance costs.

We’ve researched the different technologies, and from a global perspective believe that cooled EGR with the addition of an exhaust filter is the best approach for meeting IT4 emission regulations. Cooled EGR is a simple approach, has a proven track record throughout Tier 3 and is already supported by our global network of dealers and engine distributors.

Doug Laudick is the manager of product planning for John Deere Power Systems, based in Waterloo, Iowa.

Recently, new engine emission standards have been applied to the smaller end of the power spectrum. This was certainly the case with Tier 4 Final standards taking effect for engines developing less than 25 hp in 2008, the same year engines in the 25- to 74-hp range had to meet the Tier 4 Interim standards. Everything larger than 74 hp comes onboard in 2011 and 2012 for Tier 4 Interim. Since the Perkins industrial range includes diesels as small as 12 hp and as large as 300 hp, our engineers have been dealing with Tier 4 compliance issues much longer than many competitive engine builders. This experience has provided insights into the application of appropriate emission-reduction technologies that may not be intuitively obvious.

For example, controlling oxides of nitrogen (NOx) in small engines is accomplished most efficiently with a simple valve timing change that leaves a measured amount of exhaust gas in the cylinder. This has the effect of reducing the total amount of oxygen in the cylinder during combustion so that less NOx is produced.

The same result can be achieved with exhaust gas recirculation (EGR), but that requires the addition of controls and external pipe work. Simply closing the exhaust valves while there is a specified amount of exhaust gas left in the cylinder requires neither. This approach provides a dependable solution that also eliminates the maintenance issues associated with EGR systems, and the cost of the additional components they require. While this approach works for small engines, it is not as effective on larger ones. These engines use a suite of technologies including Perkins’ NOx reduction system (NRS), a sophisticated form of EGR, combined with electronic controls, high pressure common rail fuel injection, diesel particulate filter (DPF) and a diesel oxidation catalyst (DOC).

The inclusion of the DPF in the emission control suite is another example of the value of the insights that can be gained over time in dealing with these issues. In this case, Perkins worked closely with customers during the development cycle to understand the requirements of literally thousands of different applications. To do this we hosted customers in our Technology Integration Workshops which addressed the full range of Tier 4 compliance issues ranging from determining the best location for after-treatment technology, to finding ways to increase power density so the new engines would fit in the same footprint as those they replaced.

Perkins engineers determined that the larger engine lines could technically meet the emission standards using only a DOC and a muffler, but we felt adding the DPF technology reduced the full life-cycle cost of ownership while improving the ability to integrate the new engines into many existing customer applications. Although DPFs are perceived to have their own set of challenges — they were challenges that we were able to overcome.

All DPFs accumulate soot over time that has to be burned off with hot exhaust gasses. Within the Perkins range there are differing regeneration strategies to ensure that all Perkins powered applications are able to operate productively, with no interruption to the machine work cycle. In the mid-range models Perkins has adopted a unique low temperature regeneration system. In the 1200 Series models up to 174 hp, the system has a precious metal catalyst that can regenerate soot at low temperatures up to 250 degrees C. This system minimizes the precious metal used and saves fuel by not using diesel to regenerate.

In other areas of the range — for instance above 174 hp — the range uses a high temperature strategy. Here, the objective is to minimize precious metal content and maximize fuel economy. While this system uses diesel to regenerate, it actually improves fuel economy by regenerating in a controlled way, before soot accumulation impacts engine performance. Whilst this appears complex, it allows Perkins to optimize fuel economy and transient performance throughout the range by having a DPF and then allows us to maximize engine powers to give best productivity for the machine.

In addition to performance, Perkins looked at service elements of life-cycle cost with extensive DPF service intervals (up to 5,000 hours) and entirely service free DPF technologies. At the small end of the product spectrum, customer input from the Technology Integration Workshops also influenced Perkins’ decision to continue using mechanical fuel injection for Tier 4 Interim compliant engines producing less than 75 hp. Mechanical injection is less expensive than electronic systems and more tolerant of contaminated fuels. This makes mechanically injected diesels more suitable for use with biodiesel or jet fuels, both increasingly common in small engine applications like compressors and generators.

In most of Perkins’ new Tier 4 Interim compliant engine range, the engines are actually smaller than the predecessor engines they will replace. For example, Perkins’ new 850 Series mid-size engine produces 40 percent more power than its predecessor. Among other things, that means packaging issues for next generation after-treatment equipment needed to meet Tier 4 Final regulations for the over 75-hp engines should be minimal. Indeed, over the past three years of collaboration with Perkins customers, Perkins has yet to find an installation that cannot be powered by Perkins for both Tier 4 Interim and Tier 4 Final throughout the 12- to 300-hp range.

These are certainly exciting times within the industry. Keep an eye on the small engine part of the industry, because if history is any guide, that’s where any future changes will happen first.

Allister Dennis is a product marketing manager for Perkins Engines Co. Ltd., based in Peterborough, England.

Speaking from an industry perspective, most engine manufacturers will rely on a mix of existing technology to meet Tier 4 Final standards in 2013 for diesel engines rated 25 to 74 hp. Technologies will include electronic fuel injection (EFI)/common rail systems (CRS) for more efficient combustion, cooled exhaust gas recirculation technologies (EGR) to reduce NOx, diesel particulate filters to capture and control particulate matter (PM) and turbochargers to overcome any power loss inherent in EGR and to create turbulence for a better fuel mixture. And finally, you will see perhaps a catalyst on the exhaust to burn off unspent fuel, further depressing NOx output.

When discussing EPA Tier 4 Interim and Tier 4 Final specific to Kohler Engines, it’s important to keep in mind Kohler’s range of power offerings, which fits within the 74 hp and below category established by the U.S. Environmental Protection Agency. As a result, our engines rated below 25 hp have been subject to and compliant with Tier 4 Final emission levels since 2008. For Kohler Engines, the “Tier 4 Final event” occurs in 2013 when interim standards (0.30 particulate matter) give way in favor of the final standard of 0.03 PM for diesel engines rated 25 to 74 hp. The much discussed Tier 4 Interim standards set to take effect in 2011 for diesel engines rated 174 hp and above do not apply to Kohler Engines base on our current power range offering.

Kohler diesel engines — especially those 19 kW and above — in a post-Tier 4 Final world will boast significantly reduced NOx and PM emissions. They will both comply with Tier 4 Final and still achieve the same level of power and performance. OEMs and contractors can look forward to certain other benefits as a result of EPA Tier 4 and its attendant technology. With Tier 4 driving engine manufacturers to deploy better engine technology, enhancements such as CRS and turbochargers will become more commonplace. And with CRS and turbochargers come increased fuel efficiency and possibly improved power levels and performance.

Engines using a particulate filter to achieve Tier 4 emission standards may accelerate maintenance cycles, but added maintenance requirements will likely be limited to servicing of the particulate filter. As far as Tier 4 Interim and Final price impact to end customers, “incremental” is the key word. For Kohler and for its competitors, attaining cleaner exhaust standards currently necessitates additional components be added to a diesel engine. These additional components and emissions technologies will likely lead to an industry-wide incremental increase in purchase costs. On the other hand, fuel savings enhancements such as CRS can lower total cost of ownership over time. It’s important to underscore any cost increase associated with Tier 4 solutions as being incremental. The amount of cost increase will heavily depend on the Tier 4 solution deployed by a particular engine manufacturer.

At Kohler Engines, unique technologies relevant to Tier 4 thus far have been Kohler engineers. While the commonplace industry technology known as EGR has played a role in Kohler achieving applicable Tier 4 Interim and Final emission standards, the uniqueness of Kohler’s solution has been wrapped up in concepts by Kohler engineers that yielded improvements to fuel injectors and controls in the combustion chamber. “New systems” thus far have been limited to EGR.

In our opinion, when an engine’s specifications include both EGR and SCR (selective catalytic reduction), the resulting engine delivers emissions reduction capabilities beyond that of an engine featuring EGR alone. Due to the more stringent nature of EPA emissions standards for on-highway engines vs. off-highway engines, SCR becomes necessary to achieve EPA emissions compliance for on-highway. Rather than framing the issue as EGR vs. SCR or on-highway vs. off-highway engines, the key factor for consideration is the requisite EPA emissions standard for any given engine. While EGR has become a standard component on most diesel engines in an effort to meet Tier 4 Final, SCR will be specified as needed in accordance with more rigorous emission regulations placed upon larger power outputs. One technology builds upon another; a diesel engine with SCR likely has EGR as well.

Jeff Wilke is a product manager for Kohler Diesel, based in Kohler, Wis.

In mid-December, before the holidays, the California Air Resources Board (CARB) took further steps to tweak its controversial emission standards for off-highway diesel engine fleets, aimed at contractors who use all types of construction equipment. The state announced it was making its regulations more flexible for businesses, fighting air pollution and protecting public health by offering a variety of options to comply with regulations to reduce soot from diesel engines.

“No other state and no other nation has such an extensive set of rules to slash pollution from diesel engines,” said CARB chairman Mary D. Nichols. “The diesel rules for vehicles cover almost everything that moves on or off the road, from trucks and buses to off-road construction equipment, and over the next 12 years they will prevent 3,900 premature deaths by removing thousands of tons of diesel soot from the air we breathe. The changes we set in place today will continue those public health benefits while reducing the cost of compliance by more than 60 percent.”

The amendments complement earlier emission control measures that aggressively target diesel pollution, which is associated with a host of health ailments including cancer. With the amended regulations in place, diesel particulate matter emissions will be reduced from today’s levels by 50 percent by 2014 and 70 percent by 2020. Over the past year, CARB staff held 20 public workshops throughout the state to solicit stakeholder input and discuss options for revising diesel control measures affecting commercially owned trucks, buses, port trucks, tractor trailers and off-road vehicles, including construction and large-spark ignition equipment.

Off-Road Regulation (Construction Equipment):

First approved in July 2007, this pioneering regulation — the first of its kind in the nation — is aimed at reducing diesel emissions from the state’s estimated 150,000 off-road vehicles used in construction, mining, airport ground support and other industries. The state’s economic downturn, which began after this regulation was adopted, heavily impacted this sector, causing emissions to decline primarily due to fewer pieces of equipment in use, along with reduced activity of the remaining equipment. As amended, the regulation will:

1. Delay implementation for all fleets by four years;
2. Reduce costs by 97 percent in next five years;
3. Expand or extend credits for businesses that comply before their deadline or have downsized;
4. And ease annual requirements to clean up engines (e.g., small fleets can extend the phase-out period for oldest equipment over 10 years, from 2019 to 2029).

For more details on the Off-Road Regulation, please see: www.arb.ca.gov/ordiesel