On an SCR NOx reduction system, the driver or maintenance manager must monitor and ensure that the DEF tank (shown in inset) is topped off.
selling point. (This marks the first time engine manufacturers have had the opportunity to improve fuel economy while complying with EPA standards rather than suffering a loss.) In fact, engine manufacturers using SCR are touting a three to five per cent net fuel mileage improvement even after the added expense of the DEF urea/water mixture, which is expected to cost about the same as diesel and will be burned at about a one per cent ratio. (To put that in real-world terms, a highway truck with a 13-gallon DEF tank will be able to travel the equivalent of New York to Los Angeles and then back to Denver before running out of DEF, according to Dave McKenna, powertrain products marketing manager with Mack.)
Initial concerns about DEF availability seem to be unfounded. A distribution network is already taking form at North American truck stop fuel islands and the urea/water mix should be available in tote jugs of various sizes at truck stops as well as truck and engine dealers. That being said, the fluid does freeze at 12 degrees Fahrenheit, which is no doubt unsettling for truckers operating in the Canadian oilpatch. Fortunately, the DEF tank is heated and will almost instantly thaw enough of the fluid upon engine start-up to allow the driver to be on his or her way unhindered. EPA 2010 engines will be equipped with sophisticated on-board diagnostics that will read the truck’s tailpipe emissions and detect whether or not the system
is functioning and DEF is being used as required. If the truck runs out of DEF on the road, engine power will be downgraded and eventually the driver will be unable to start the engine until the DEF is topped off. While SCR is new to North America, it has been widely used around the world and extensive field testing has been conducted here as well. Detroit Diesel recently announced it has completed more than 25 million miles of real-world testing for its BlueTec SCR system in North America. “The 2010 BlueTec technology will be one of most extensively tested emissions technology systems in our company’s history,” says David Siler, director of marketing with Detroit Diesel. OIL & GAS INQUIRER • DECEMBER 2009
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