Since January 1, 2010, on-highway vehicles sold by any truck OEM other than Navistar have been equipped with a selective catalytic reduction (SCR) system using diesel exhaust fluid (DEF). “Therefore, it is highly likely that many [contractors] either have or soon will have one of these engines on their lot/site,” says Brad Williamson, Engine and Component Marketing, Daimler Trucks North America.
“DEF has been mostly used on on-road vehicles. However, there have been a number of DEF users in stationary applications,” adds Thierry Leprince, R&D manager at Nett Technologies, a manufacturer of SCR systems for construction equipment. He adds that some OEMs are in the process of certifying SCR-equipped non-road engines for Tier 4 Interim emissions standards.
Already this year, Case and Kobelco have introduced Tier 4 Interim-certified earthmovers incorporating SCR, and Cummins announced that SCR will be a primary element in its Tier 4 Final products extending from 75 to 675 hp starting in 2014. Other OEMs and engine suppliers are likely to follow suit.
With SCR on its way to becoming more common in construction fleets, it’s important to have a grasp on how to properly manage and maintain the system. This includes proper handling of the fluid that makes up one of its primary components.
Treat with respect
Diesel exhaust fluid is a solution of 67.5% deionized water and 32.5% high-purity urea, a compound of nitrogen that turns to ammonia when heated.
“DEF is the reactant necessary for the functionality of the SCR system,” says Clint Schroer, off-highway communications, Cummins Inc. “Small quantities… are sprayed into the exhaust upstream of the SCR catalyst. This then converts the NOx [oxides of nitrogen] to harmless nitrogen and vapor.”
“Its primary function in controlling emissions,” Williamson elaborates, “is to act as an ammonia-carrying agent to create a chemical reaction between the exhaust gases and ammonia to break down NOx into nitrogen and water.” These byproducts are then released into the atmosphere via the exhaust stack/pipe.
As far as fluids go, DEF is fairly innocuous — it’s nontoxic, non-polluting, non-hazardous and nonflammable. But that doesn’t mean it shouldn’t be treated with the same respect as other fluids found in your fleet.
“Similar to any fluid used with equipment and vehicles, DEF and tanks should be kept free from debris,” says Schroer. “To minimize the risk of contamination, you should treat DEFs like any other fluid you use with your machines — such as lubricants, coolants and fuels — by ensuring that they are always stored in containers and remain clean.”
Avoid temperature extremes
DEF comes in a variety of container sizes, from 1-gal. bottles up to 330-gal. IBCs (totes). It’s recommended that it be stored in its original packaging, or placed in containers made of approved materials.
“The material used for storing and/or transferring DEF should be compatible with DEF,” says Leprince. “High-density polyethylene can be used in bottle packages, but larger containers should be stainless steel or other ISO 22241-approved materials.”
Under ideal conditions (not exceeding 75° F), DEF can be stored for up to two years. But it can degrade over time.
“We don’t recommend storing DEF for more than one year,” says Gary Simons, director, Technology Development - Exhaust/Emissions, Donaldson Company, Inc. “The amount of DEF purchased should match the usage rate... DEF containers should be stored between temperatures of 15° F and 90° F, and not in direct sunlight.”
Schroer adds, “DEF should be stored in a cool, dry, well-ventilated area out of direct sunlight. The shelf life of DEF is a function of ambient storage temperature... DEF will degrade over time, depending on the temperature and exposure to sunlight.”