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DEF (Diesel Exhaust Fluid), also known as AUS 32, is a high purity chemical solution, comprised of 32.5% urea and 67.5% de-ionized water. Urea is produced by the synthesis of ammonia and CO2 (carbon dioxide). DEF is produced from Automotive grade Urea, a particularly pure grade of Urea, with low levels of metals, minerals, and other substances potentially harmful for the SCR system and catalyst. It is important to only buy products named DEF, manufactured according to the ISO 22241 standard. DEF production is regulated by the American Petroleum Institute (API). API offers further information on its website www.apidef.org under the theme “DEF” with an actual list of certified producers. Only buy DEF from a company that appears in the API DEF directory, or from a distributor of those brands.
Diesel Exhaust Fluid can be purchased by the haulier on the road at a truckstop, service station or manufacturer dealership. It is also possible to arrange for a supply of DEF direct to the haulier’s base of operations. Chemical producers and distributors, Oil companies, and other renown players of the automotive market offer their own brand of DEF.
“SCR” stands for Selective Catalytic Reduction. It’s the name of a post-combustion technology treatment for diesel engines, which allows them to reduce their harmful emissions of NOx (nitrogen oxides). This technology was first introduced in the 80’s; power plants, cement , waste incinerators, glass factories and refineries have been utilizing an ammonia based reagent in a stationary SCR system to reduce NOx emissions in the atmosphere. During the years the size of the SCR system has been reduced and adapted to diesel vehicles. Moreover, instead of ammonia (dangerous and not easy to handle), the system now utilize Urea, ammonia safe carrier, diluted in de-ionized water. Almost all of the main engine manufacturers use this technology to meet the requirements of new legislation on NOx (Nitrogen oxides) emissions.
In the USA, emissions from vehicles are regulated by the Clean Air Act. The use of urea SCR NOx control is coming to the US with the implementation of the so-called EPA2010 emission standard, which is effective as of January 1st 2010 and sets the NOx emission limits at 0,3 g/kWh. Diesel Exhaust Fluid (DEF) is regulated by the American Petroleum Institute (API).
There are different emission standards around the world, setting specific NOx and other polluting agents emission limits:
In Europe, current legislation Euro VI has brought the limits to an outstanding reduction of 80% for NoX (Nitrogen Oxides) and 66% for PM (Particulate Matter) compared with previous limits. The new Standard has become effective on January 1st 2014.
DEF (Diesel Exhaust Fluid) is a simple and non-hazardous product. As an example it’s much less dangerous than windshield washer fluid or antifreeze. However, SCR system is extremely sensitive to impurities; for this reason it is essential to prevent DEF contamination to ensure SCR system functions correctly, and also to avoid expensive repair costs. Below some clear rules to follow when using the solution