Maintenance: Exhaust detox

The U.S. Environmental Protection Agency, California and New Jersey have already enacted mandatory diesel emission reductions standards, and other states, including Texas, New York, Ohio, Arizona and Massachusetts are not far behind. This puts affected contractors in a tough situation: should you repower (replace older engines with newer engines), retrofit your fleet with exhaust control technologies or buy new equipment?

You may not be in a position to buy an all-new fleet or repower your machines, so exhaust retrofits can present a cost-effective solution. What’s best for your fleet, however, hinges on emissions regulations in your area, the type of machines you need to retrofit, their engine sizes and applications.

Clean air will cost you
Currently, retrofit manufacturers – including Donaldson, Cleaire, Cummins and OEMs such as John Deere – are working to develop a wider array of emissions control devices in hopes of verification from the EPA and the California Air Resources Board. Regulations will not be limited to states with approved emissions rules, but also apply to non-attainment areas, or areas with air pollution levels that exceed the EPA’s air quality standards.

“Our strategy is to use our Tier 4 development experience to bring products to the off-road market that will satisfy the (EPA’s/California’s) Best Available Control Technologies requirement and will encompass various aftertreatment technologies,” says Clint Schroer, off-highway communications manager, Cummins.

While retrofitting can be less expensive than buying new equipment, it’s still not cheap. “Retrofit cost is not so much based on the equipment, but rather the size of the engine,” says Joe Mastanduno, product marketing manager, engine and driveline, John Deere Construction and Forestry. “It’s much cheaper to retrofit if you’re below 170 horsepower.” The cost of diesel particulate filters ranges from $15,000 for 150 to 300 horsepower engines all the way to $40,000+ for engines up to 500 horsepower. Installation fees depend on the machine and available installation space.

Visit for a list of verified emissions control devices.

DOCs vs. DPFs
Early on in the emissions battle, Ironman Parts and Services, a Corona, California-based provider of industrial filtration systems for heavy on- and off-road equipment, primarily sold diesel oxidation catalysts for off-road port applications and saw more interest in repowering engines than diesel particulate filters.

A DOC consists of a honeycombed canister coated with catalytic materials that converts carbon monoxide, hydrocarbons and particulate matter into harmless gases. DOCs require little to no maintenance, and according to Ironman many people found these effective in meeting on-road emissions regulations. “As gas blows through a DOC, it’s chemically treated at every moment so the device never accumulates anything, unlike a DPF,” Mastanduno says.

But from an off-road standpoint, Best Available Control Technologies requires the use of DPFs (or flow-through filters) instead of DOCs to maximize particulate matter reduction. As a result, suppliers like Ironman have seen a spike in DPF demand and fewer requests for repowering and DOCs.

“Across the board, full-trap diesel particulate filters catch about 95 percent of emissions and get more efficient at trapping particulate matter the longer they are in service,” says Charlie Cox, emissions technology consultant, Ironman.

When used with selective catalytic reduction catalysts, DPFs speed the break down of particulate matter and nitrogen oxide emissions. “Wall-flow DPF designs provide the most effective filtration. With wall-flows, gas flows in through an open channel and gets pushed through a series of channels before exiting,” says Fred Schmidt, director of retrofit emissions, Donaldson.

Since DPFs require more installation space than DOCs and can limit an operator’s visibility, Schmidt says some manufacturers could begin installations inside the engine compartment or the cab.

Active or passive retrofits: When choosing a retrofit, fleet owners must decide whether they want an active or passive retrofit system. “In the past, you’d just break the exhaust pipe and put something in,” Mastanduno says. “Now there are more components and it all has to be installed correctly.”

Active systems can employ a computer and/or other components – such as sensors that monitor temperature – to control the filter. Unlike a passive system, which uses a catalyst and engine heat to continuously burn off soot (known as regenerating), an active system runs without a catalyst and uses a heat source to regenerate once the filter begins to fill up.

“Active systems use an external force to clean the filter, like an electric heater or a burner system,” says Tom Swenson, director of distribution development and support, Cleaire. They also may be better for dirtier or older engines.

With a relatively clean engine, a passive device will work as long as the engine maintains its heat. But, a passive filter can only hold X amount of soot since it has to keep burning the soot off.

Back pressure concerns: One major factor that continues to affect retrofit performance is back pressure sensitivity. According to Schmidt, DPFs increase back pressure, which can affect fuel economy.

California requires back pressure monitoring so the user constantly is aware of filter performance. “Depending on the filter location, if there is too much back pressure against other parts it could melt them or set the filter on fire,” Mastanduno explains. To be safe, install a monitor in the operator’s compartment. The monitor will display a yellow or green light when working correctly, and an orange light as pressure builds and the filter begins to plug. If you ever see a red light, the filter has plugged and the engine will lose power. In the same token, a red light on the monitor can also indicate catastrophic engine failure.

“Back pressure monitors have software on board so they’re constantly monitoring,” Cox says. “Technicians can pull the data off the system and see how the filter has been performing. When something becomes a problem, we just pull the data off and check it to see when the issue began. This is most important for troubleshooting, but it’s available all the time in case a fleet operator wants to know about performance before a problem occurs.”

Cleansing process
Unfortunately, companies providing retrofit installation and services are few and far between at the moment. Ironman primarily serves customers in California, and contractors with heavy equipment fleets in other states affected by tightening emissions regulations typically turn to their equipment dealers for installation once they’ve purchased a retrofit.

To locate cost-effective and verified emissions control devices (or VDECs), Ironman provides retrofit consultations, where they develop fleet-specific compliance strategies and perform in-field, piece-by-piece machine assessments. “Companies that are more familiar with emissions regulations may only require retrofit installations, while others need a little more hands-on assistance,” Cox says.

If you need guidance following a consultation, Ironman offers a mobile emission service, where a technician provides equipment assessments, retrofit installations, data logging (for example, temperature testing), emergency services and preventive maintenance. Individual services, such as consultations, can be purchased alone or combined with other services for additional comprehensive packages. If you’re unsure of your compliance efforts after retrofitting, Ironman will do an on site compliance audit, much like an ARB inspection, to check fleet records.

When necessary, Ironman technicians can clean and de-ash DPFs in the field, but you can also do this with the proper equipment or take it to a distributor, if applicable. Filter service life differs according to a machine’s engine maintenance, application and load factor. Unlike DOCs, DPFs require regular maintenance and monitoring to ensure proper performance. Typically, you only need to clean your filter to remove ash or if the filter does not burn particulate matter quickly enough. Depending on the machine application and downtime considerations, Cummins’ Schroer says you may want a spare filter on hand when removing ash on your primary filter.

Cox says several device manufacturers recommend de-ashing full-trap DPFs when the device has been in service for a maximum of 500 hours on a dirty engine or 1,000 hours on a clean engine – but that’s only with correct engine performance. But Schmidt advises cleaning filters once every 60,000 miles (or 2,000 hours) or once a year – whichever comes first. “But keep in mind off-road engines are much dirtier so they may plug up more,” Schmidt says.

For three-piece DPF designs, cleaning takes about two hours with a cleaning machine and then up to three hours for re-installation. “You can also ship it to a retrofit installer like Ironman for cleaning,” Cox says. De-ashing through Ironman costs around $250 and up.

Two cleaning systems are available: a thermal regenerator (much like an industrial oven) or a pulse cleaning unit. Both are expensive, ranging from $10,000 to $15,000. The oven heats the filter up slowly to burn off built-up ash, while the pulse cleaning unit blows ash out of the substrate into a collection basin. Once the material has been burned or blown off, it must be disposed of at an oil recycling or hazardous material site.

It may be best to request training with cleaning and installation, since mistakes are expensive. For example, Cox says he’s seen a new technician hose out a substrate with water and ruin a $7,000 filter. “One guy put a filter in backwards (to the exhaust stream) to blow out the ash and it melted down the substrate,” he says.

Although durable, the filters also don’t handle shock treatment well. Cox once saw a customer remove a filter and shake all the ash of it. “He was covered in gray and had just spent $10,000 to blow concentrated ash all over himself,” Cox says. “When used correctly, retrofits work – but people have to make sure they know what they’re doing.”

California’s proposed rule becomes law
The state of California has approved the California Air Resources Board’s In-Use Off-Road Diesel Vehicle Regulation, effective June 15. As a member of California ARB’s Off-Road Implementation Advisory Group, filtration systems provider Ironman Parts and Services is attempting to educate its customers about the rule – scheduled to take effect in 2009. The regulation will require California fleets with 25-horsepower engines or greater to either meet fleet average targets for specific emissions, or apply exhaust retrofits to a percentage of the fleets’ horsepower per year. (See chart on pg. 52).

“We’re seeing an interest in retrofitting earlier than the March 2009 cut off date,” says Charlie Cox, emissions technology consultant for Ironman. Fleet owners who retrofit before the rule takes effect can obtain early implementation credits to spread out compliance costs. For example, if you are required to retrofit 1,000 horsepower in your first compliance year and you retrofit 500 horsepower now, ARB will give you credit for 1,000 horsepower. Any horsepower you take care of early on will earn double credit.

Whether you have a small, medium or large fleet, Cox says it’s better to retrofit older equipment and keep it running, instead of waiting until the implementation deadlines – when the demand and cost for exhaust retrofits may have ballooned. “Everyone (in California) is going to have to eventually comply anyway,” he notes. “It’s up to fleet owners whether they want to spend a little over a few years or a lot in one year. Grant money or not, people should take advantage of these early credits.”

For now, paper forms indicating you retrofitted your fleet prior to the compliance date are all ARB requires. Soon, ARB will have its Diesel Online Off-Road Reporting System operational.

Funding for retrofit projects varies by state, but the EPA’s National Clean Diesel Campaign has almost $50 million available in grant funding for retrofits. For more information, visit

At press time
Some OEMs have partnered with retrofit manufacturers. Caterpillar, for instance, just announced it plans to work with CleanAir Systems of Sante Fe, New Mexico, to begin offering retrofits.