Care and feeding of Tier 4 Final-complaint engines
Fuel and diesel exhaust fluid quality are critical to success
In newer equipment that uses selective catalytic reduction (SCR) systems to meet EPA Tier 4 emission requirements, what goes into the fuel and diesel exhaust fluid (DEF) tanks must meet much stricter quality requirements.
Contaminated fuel or DEF will spell trouble and lead to downtime and expensive repairs.
Fuel considerations
“This technology drastically reduces diesel engine emissions—great news for the environment—but requires a much higher level of fuel quality for reliable engine operation. To assure new Tier 4 EPA engines perform effectively, reliably and without damage requires the use of ultra-low sulfur diesel (ULSD) fuel and that you properly filter fuel,” says Greg Rappa, Western Global global marketing manager an international manufacturer of innovative fuel and fluid storage solutions.
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Tips for DEF use in off-road equipment
Source: Thunder Creek |
“ULSD fuels contain 15 ppm or less of sulfur content. Failure to use ULSD fuel can result in severe damage or failure to the engine, fuel system, diesel particulate filtration systems and exhaust aftertreatment systems of your equipment,” Rappa says.
Older engines may have been able to perform effectively using fuels that did not meet engine specifications, or that were contaminated with water or other particles without negative long-term consequence. “In the new engines, using this same fuel can result in reduced efficiency, increased maintenance costs, and potentially cause permanent damage to the engine — which will ultimately cost time and money to repair or replace. Because high pressure fuel rails and other internal engine components can be damaged by particles as small as 5 microns, high quality fuel filtration should be a key priority on any worksite.
“Excessive water in fuel will cause permanent engine damage. Tier 4 engine systems include fuel/water separation filters to assure water-free fuel; these separation filters must be properly maintained to be effective,” Rappa says.
To assure high ultra-low sulfur diesel fuel quality, Rappa suggests purchasing fuel only from reputable providers. “Inspect bulk fuel tanks once a month for contamination by water or other particulates. Periodic testing of fuel by an independent lab is recommended. Also, clean the tanks regularly.”
Follow all guidelines in the vehicle maintenance manual and the engine manufacturer’s service information for regular servicing instructions of fuel and filtration systems. Never ignore warning information or fault codes given by the engine control module (ECM).
DEF considerations
DEF is a solution made up of 32.5 percent urea and 67.5 percent deionized water. It is metered into the exhaust system and completes a chemical reaction in the exhaust stream to break down up to 90 percent of the nitrous oxide into harmless hydrogen and water. It’s the secret sauce to the success of these systems, and requires extreme diligence from
anyone who comes in contact with the DEF or storage systems.
“DEF is not a fuel additive and never comes into contact with diesel fuel. Instead, it is stored in a separate tank, typically identified by a blue filler cap,” says Rappa. It is automatically injected into the exhaust stream by a metering system at a rate that depends on the aftertreatment system, but is typically 2 to 6 percent of the diesel consumption volume. “This low dosing rate ensures long DEF refill intervals and minimizes the DEF tank size,” he says.
It’s extremely important to keep DEF contaminant-free, reports Steve Ile, owner and territory sales manager of Thunder Creek Equipment, which makes systems to protect the quality of DEF. “DEF is contaminated by direct or airborne contact with many common elements. As little as a tenth of a teaspoon of many contaminants is enough to bring a 5,000 gallon tank of DEF off-spec.
“On-highway equipment goes to the DEF refill location, but in off-highway applications, DEF must be delivered to the machine. This distinction is significant because DEF is easily contaminated and off-road environments are, quite frankly, dirty.”
Contaminants affect the catalyst in the SCR system. “The inside of a catalyst is structured like a honeycomb and over time, contaminants get trapped in that honeycomb structure. Some will cause corrosion as they react with DEF, which is 32.5 percent urea. Others form gummy deposits that will eventually plug the catalyst.
“Damage to the catalyst is not immediate, but once contaminants have been introduced, damage is irreversible and can’t be repaired – only replaced. SCR systems are expensive and are usually not covered by warranty,” adds Ile.
A system using contaminated DEF becomes less effective at removing emissions, so it will begin to consume more DEF. Eventually, the damage will cause the SCR system to shut down. “Depending on the machine, this may either initiate a fault code or shut the machine down entirely. Once signs of contamination are present, it’s usually too late,” Ile says.
Ile adds that common sources of DEF contamination are dirt, dust, fuel, oil and debris; earth metals found in tap water; and copper-, chromium-, zinc- or nickel-plated metal found in fittings, couplers and other fluid handling equipment. “The greatest risk of contamination occurs when DEF is transferred to the machine. If DEF is handled the same way fuel and other fluids are handled, it’s likely DEF will be contaminated,” Ile says.
The ISO 22241 standard identifies proper practices for making and handling DEF. When considering DEF transfer and storage equipment, make sure the manufacturer uses materials approved in the standard. At Thunder Creek, for example, DEF hoses are manufactured in an isolated area to assure there is no cross-contamination from other areas of the facility and each system is sterilized and sealed in accordance with the standard.
Prevent contamination
DEF purity is irrelevant without proper handling practices, says Ile. “Best practice is to handle DEF like a hospital handles surgical equipment. If the scalpel is manufactured in a sterile environment but the janitor punctured the package when it’s put it in the supply closet, it’s no longer clean.”
Thunder Creek offers a DEF handling solution that prevents contamination. “This is a closed system that dispenses DEF without exposing it to contamination,” Ile says.
Prolonged exposure to direct sunlight and higher temperatures will cause DEF to degrade faster. Generally, this is how temperature affects DEF quality and life:
DEF freezes at 12 F; freezing and thawing do not affect the chemical properties of DEF, Ile says, but the fluid needs to be fully thawed before use. “DEF expands by approximately 7 percent when frozen. This can cause damage to pumping components and fully filled, closed containers,” says Ile.
Temperature and humidity may also impact DEF consumption. When the engine intake air is warmer and more humid, more nitrogen oxides are created so more DEF is required to remove it.
Ile offers one final piece of advice: “DEF filtration systems do not
remove contaminants; they only remove particulates that may be
present in the DEF.”
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