What is a SCR system?
The SCR system generally consists of a catalyst that reacts with engine exhaust to break down the environmentally harmful exhaust components. Catalysts are typically ceramic with reactive metals embedded in the ceramic surface. Between the reactive metal nodes are pore spaces where exhaust enters the catalyst. Injector nozzles spray controlled dose of DEF into the exhaust before entering the catalyst. The DEF vaporizes and decomposes into ammonia and carbon dioxide, which then reacts with the nitrogen oxide in the exhaust to form the harmless by products of nitrogen and water. DEF and diesel should never be mixed.
DEF system components include a fill port, DEF tank, lines from the tank to the SCR and injection nozzles. DEF dispensers should be clearly marked. The fill port for the DEF tank is designed to be a smaller diameter than the diesel tank’s fill port. This insures the diesel nozzle cannot be inserted into the DEF tank’s fill port.
In addition, the DEF tank fill port should have a blue cap so it can be readily identified. SCR systems have built in warnings to detect non-DEF substances. The SCR catalyst will signal the driver with a warning and code of impending SCR interruption if non-DEF enters the SCR catalyst.
What will happen if I put diesel into a DEF tank?
Diesel is less dense than DEF, at 7 pounds per gallon compared to over 9 pounds per gallon for DEF, and will therefore float on the DEF. If diesel enters the SCR catalyst, significant damage can occur that may require servicing or the far more costly replacement of the catalyst. The DEF tank should be drained and thoroughly cleaned with deionized water before refilling. DEF is very easily contaminated. For example, one teaspoon of aluminum will contaminate an entire tanker load (5,000 gallons.) of DEF.
What will happen if I put DEF into a diesel tank?
An initial consequence of putting DEF into the diesel tank of a truck is the diesel fuel is contaminated because DEF is composed of urea and water. If the engine started and introduces the diesel and DEF mixture into the engine longer term consequences will occur.
If the DEF is introduced into a diesel storage tank the DEF it will not only contaminate the diesel it will also, if not removed, cause damage to the fuel system. DEF is corrosive and harmful to several metals including carbon steel, brass, aluminum, copper magnesium nickel and zinc.
The following steps are recommended if DEF accidentally pumped into a truck’s diesel tank. If DEF in accidentally added to a diesel storage tank follow steps #2, 4, and 5.
- Do not start the engine and contact your engine service provider
- Drain the diesel tank and dispose the fuel following your local regulations
- Drain the diesel fuel conditioning module
- Flush the fuel system
- Replace all filters
Where can I learn more about Diesel Exhaust Fluid?
Innovative Fueling Solutions provides fueling tanks and dispenser equipment to the fueling industry, with a focus on DEF dispensing systems. Feel free to contact us today for more information about diesel exhaust fluid or for any other fueling needs you may have.