Truck Parts and Service | Heavy Duty Trucking, Aftermarket, Service Info
Issue link: http://read.dmtmag.com/i/700851
22 Service Bay W hen it was fi rst introduced in 2010, diesel exhaust fl uid was touted as a miracle cure. A se- cret ingredient. The answer to trucking's multi-billion dollar emission question. In the aftermarket it went from an unknown product to a must-stock item, and today the solution known as DEF can be found at distribution facilities, big box retailers and fueling stations nationwide. Everyone carries it, nearly all after- treatment systems require it and diesel particulate fi lters don't stay clean for long without it. But ask a driver or counterperson how it works and you'll be surprised at some of the responses. Diesel exhaust fl uid might be universal, but it's hardly universally understood. For aftermarket businesses who'd like to know more about the fl uid they're selling, the story of DEF begins with SCR. What is DEF, and why is it needed? Diesel exhaust fl uid is a simple solution of 67.5 percent deionized water and 32.5 percent high-purity urea, and works with selective catalytic reduction (SCR) systems to reduce Nitrous Oxide (NO x ) emissions from diesel engines. The mixture was fi rst introduced in the commercial trucking industry late last decade by engine manufacturers as a means to achieve — with SCR — the then-proposed U.S. Environmental Pro- tection Agency (EPA) 2010 medium- and heavy-duty emission standards. In a Q&A bulletin from that time, Cummins Filtration described the partnership between SCR and DEF as follows: "SCR is the aftertreatment technology that treats exhaust gas down- stream of the engine. Small quantities of diesel exhaust fl uid are injected into the exhaust upstream of a catalyst, where it vaporizes and decomposes to form am- monia and carbon dioxide. The ammo- nia [NH 3 ] is the desired product which in conjunction to the SCR catalyst, converts the NO x to harmless nitrogen [N 2 ] and water [H 2 O]." "What you're trying to do with DEF is alter the chemistry" within an aftertreat- ment system, says Allen Schaeffer, execu- tive director at the Diesel Technology Forum. By inserting properly formulated DEF into a closed SCR system at an optimal temperature, Shaeffer says NOx is quickly transformed, and results in emissions that are "as clean as or cleaner than the air going in" to an engine. DEF is formulated at 32.5 percent urea to provide the fl uid the lowest possible freeze point, and SCR systems are calibrated to 32.5 percent "so that optimum NO x will be reduced during operation," Cummins says. Similar to oil, DEF formulation and quality is monitored by the American Petroleum Institute (API). Using a purity standard published by the International Organization for Standardization (ISO), API's Diesel Ex- haust Fluid (DEF) Certifi cation Program is "intended to ensure that the diesel exhaust fl uid used in SCR-equipped cars and trucks provides the purity required by diesel engine manufacturers and the quality to preserve the emissions control system and the environment." Every factory fi ll DEF in North America has been certifi ed by API. T R U C K P A R T S & S E R V I C E | J u l y 2 0 1 6 Cummins' selective catalytic reduction (SCR) system works with DEF and a diesel particulate fi lter (DPF) to reduce emissions. It's all about maintaining a closed system. You don't know you have a problem until something shows up in the engine. – Allen Schaeffer, executive director at the Diesel Technology Forum