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Find Answers to Your Questions about DEF and SCR

Answers to Questions About What is DEF

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  • How does EGR work and why is this technology essentially being replaced by SCR?

    EGR stands for Exhaust Gas Recirculation. EGR was the technology that most manufacturers used to meet the first rounds of emissions regulations in 2004 and 2007. In an EGR system, exhaust gas is cooled and recycled back through the engine. The combustion temperature in the cylinder is reduced, thus lowering NOx production. However, the cooler combustion produces more particulate matter due to the less efficient operating temperature. Also, the engine is not operating at its optimal combustion temperature, consequently reducing fuel efficiency and engine power.The advantages of an SCR system is that it allows the engine to operate at higher temperatures in order to optimize performance, meanwhile reducing NOx levels.

  • What happens to DEF if it exposed to high temperatures?

    DEF’s shelf life begins to degrade at high temperatures. If it is maintained at or above 120 degrees Fahrenheit it will slowly begin to form small amounts of ammonia. Check with your supplier of DEF to for more information on proper handling of DEF in extreme temperatures.

  • What is DEF?

    DEF stands for Diesel Exhaust Fluid. It is a 32.5% solution of chemically pure Urea and 67.5% demineralized or deionized water. It is a non-regulated non hazardous solution. You may also see it referred to as NOx reduction agent AUS32 or AdBlue, both terms are common in Europe.

  • What is DEF used for?

    Most diesel engine manufacturers have adopted SCR (Selective Catalytic Reduction) technology to meet 2010 EPA emissions standards. “SCR is the aftertreatment technology that treats exhaust gas downstream of the engine. Small quantities of DEF are injected into the exhaust upstream of a catalyst, then converts to ammonia in the exhaust stream and reacts with NOx over the catalyst to form harmless nitrogen gas and water.” Source: www.cumminsfiltration.com.

  • Is DEF a fuel additive?

    No, DEF is injected into the diesel engine's exhaust stream. It is stored in its on stand-alone tank, usually located right beside the diesel tank. It commonly has a blue cap or other blue indicator to identify it as DEF (whereas diesel is often associated with the color green).

  • Is DEF a hazardous substance?

    No, DEF is a stable, non-toxic solution that can be transported without the use of a DOT approved hazardous substance placard.

  • What does DEF look like?

    DEF is a clear, colorless liquid.

  • How much does DEF weigh?

    DEF weighs approximately 9 lbs per gallon. Compared to diesel fuel at approx 7.05 lbs and gasoline at an average of 6.19 lbs, DEF is a relatively heavy product.

  • Does DEF go bad?

    As long as DEF is stored between 10 and 90 degrees Fahrenheit it should last at minimum of 1 year.

  • Does DEF freeze?

    Yes, DEF has a freezing point of +12 degrees Fahrenheit but the DEF can be used after it thaws from its frozen state.

  • I keep hearing about how important DEF purity is. How do I know if my DEF is pure and up to spec?

    The only true way to know would be to pull a sample and send it off to a laboratory for testing. However, many manufacturers have become API (American Petroleum Institute) certified, a voluntary program that monitors the quality of DEF. Remember, DEF is a clear, colorless liquid. If you see any color, haze, phase separation, or sediment in your DEF container, this should be an immediate red flag.

  • Is SCR new technology?

    SCR has been used in Europe since 2006 and has a proven track record. There are more than 600,000 SCR trucks operating in Europe with more entering the market each day.

  • Can I use agricultural grade UREA in my SCR vehicle?

    No, DEF is a very pure solution of high grade Urea and demineralized or deionized water. Agricultural grade Urea often has additives such as formaldehyde to prevent the product from clumping when in a dry form.

  • Is DEF and SCR just for cars and trucks?

    No, In order to meet EPA emissions requirements in 2013 and 2014 and beyond, off-road diesel engine manufacturers are beginning to adopt this same technology early. This is leading to use in locomotives, tractors mining and boats and seagoing vessels.

  • What is Urea?

    Urea is a compound of nitrogen that turns to ammonia when heated. It is commonly used in agriculture as fertilizer.

  • Will DEF harm my aluminum tank?

    Although DEF will not “harm” many materials, it is actually the metal of many storage containers (such as aluminum) that will leach into the DEF and contaminate it.

  • What materials are compatible with DEF?

    There are far more materials that are not compatible with DEF than are. Stainless steel and DEF approved poly are commonly used materials in the construction of DEF equipment. ISO 22241 defines what are acceptable materials for use in the storage and handling of DEF. Specially formulated DEF hose must be used in the transfer and dispensing of the Diesel Exhaust Fluid.

  • Does DEF have an MSDS sheet? If so, where can I obtain this document?

    Yes, Contact your supplier of DEF for an MSDS sheet.