AdBlue / DEF - Fact and Fiction
Sunday, January 1, 2012
The latest European emissions legislation has meant that of the 440,000 commercial vehicles on the Britain’s roads, about 180,000 are now equipped with Selective Catalytic Reduction (SCR) and use AdBlue® diesel emission fluid - or DEF as it is known in North America. Thanks to the changes in legislation there has been a dramatic reduction in noxious nitrogen oxides and particulate matter in recent years.
However, the SCR/AdBlue® system is still relatively new and elements of it are widely misunderstood. So, to clarify, there are two different innovations: Selective Catalytic Reduction (SCR) and Exhaust Gas Recirculation (EGR). Both of these require an exhaust gas after-treatment. At present, EGR cannot meet the requirements of Euro VI legislation, whereas SCR can.
What is AdBlue®?
AdBlue® is a clear liquid made up of 32.5% urea (which comprises carbon, nitrogen, oxygen and hydrogen) and 67.5% demineralised water. In the SCR process this solution reacts with and neutralises nitrogen oxides (NOx).
Is it added to diesel?
No it is a completely separate system and doesn’t come into contact with the diesel.
Is there a separate tank?
Yes and it usually has a blue filler cap or stickers.
How do you top up?
With an ordinary nozzle; vehicles use so little AdBlue® that this only has to be done periodically.
Is it hazardous?
As it is made up of water and an organic compound, it is completely safe, and less corrosive than brine to metal or concrete. It is clean, harmless and environmentally friendly. It is indeed the least hazardous of all of all the fluids used in a truck.
How do I find it?
Go to www.vda.de or www.AdBlue®4you.com for stockists.
What happens if I put diesel into the AdBlue® tank accidentally?
In some vehicles, the neck of the AdBlue® tank has been designed with a circular magnet to prevent a diesel nozzle fitting into it. Others have stickers. In the rare cases where somebody has accidentally filled the AdBlue® tank with diesel, the entire SCR system has to be changed which is expensive.
I’ve heard AdBlue® is expensive.
No, it’s not. Surveys of the market by the trade press have reported a wide diversity of prices – from less than 30p per litre for bulk buys, up to 85p per litre for one can. For an idea of how long it will last, a 75 litre tank would be enough for a two axle tractor to travel from London to Istanbul and back; the actual amounts used however depend on the nature of the work. Also, SCR used with AdBlue®, improves fuel economy which more than compensates for the cost of AdBlue®.
What if it freezes?
It won’t freeze completely until it reaches -11°C. It starts freezing at -10°C.
Freezing does not affect its performance once thawed. Also, AdBlue® tanks tend to be next to exhausts, which keep the temperature of the contents above freezing when the engine is running. Where the AdBlue® tank is situated elsewhere, it is heated using engine coolant which is circulated through the tank.
Will I damage the engine if the AdBlue® tank becomes contaminated?
The purity of AdBlue® needs to be protected throughout production and handling. Should it be contaminated by inadequate storage or handling, then the SCR system will cease to work correctly and this could result in a vehicle operating illegally. Depending on the extent of the impurity, degradation leading to the clogging of the catalyst can happen gradually or quickly. Also, because contaminated AdBlue® damages the SCR System this will affect any related insurance claims.
Funnels or containers that have been previously used for lubricants or fuel must not be used for AdBlue dispensing or storage as this will contaminate the AdBlue®. Do not store AdBlue in direct sunlight.
Running out of AdBlue® shuts down the engine.
No it doesn’t. Firstly there is an AdBlue® gauge which will give you plenty of warning. If you did run out, the vehicle would go into 60% of original torque, enabling you to drive to a supplier. Keeping a few litres of AdBlue® with you in the vehicle will enable the necessary mileage to find a top up.
If I drive a vehicle without AdBlue® am I breaking the law?
Yes. Exceeding maximum emissions runs the same risk whether the system is SCR or EGR.