Diesel Particulate Filter (DPF), Exhaust Gas Recirculation (EGR), and, Sintered Catalytic Reduction (SCR)

Much publicity has surrounded diesel vehicles recently, for example #Dieselgate.
Consequently, vehicle manufacturers have attempted to reduce diesel exhaust emissions by various means to meet exhaust particulate (soot) emissions standards such as Euro 5 and now Euro 6.
Exhaust gas recirculation (EGR) recirculates engine exhaust gases back in to the engine combustion chambers to re-attempt burn and reduce soot output from the vehicle exhaust.

Sintered Catalytic Reduction (SCR)or alternatively named Selective Catalytic Reduction (SCR) is a system where diesel exhaust fumes pass through a catalyst filter structure built in to the exhaust system to lessen pollutants.

A urea based Diesel Exhaust Fluid (DEF) aftertreatment solution is sprayed at high pressure in to the exhaust gas stream produced from a diesel engine (exhaust gas aftertreatment), prior to exhaust gases entering a hot catalyst chamber to reduce emissions by breaking down Nitrogen Oxides (NOx) from the engine combustion process in to Nitrogen and Water.

What is Adblue® ?

Adblue® is the commercial trade name for a (VDA German approved) high purity 32.5% Urea based purified aqueous (water based) solution used as a diesel exhaust aftertreatment fluid (DEF) to reduce pollutant exhaust emissions. Despite its tradename implying a blue colour, Adblue® is a colourless liquid.

Vehicles likely to use Urea based Exhaust Aftertreatment Systems

Exhaust aftertreatment systems are commonly fitted to vehicles fitted with medium to large diesel engines including

Exhaust Aftertreatment System Components

Diagnostic equipment may be required to read scr fault codes and clear error history after a repair has been completed.

Typical DPF system fault codes:
P13E400 The remaining driving distance is limited due to diesel emissions fluid dosing system defect
P13F600 The engine cannot be started because the exhaust after treatment system is affected.
DPF differential pressure sensor fault codes.
Fault codes relating to diesel particulate filter soot accumulation.
P1498 excessive soot accumulation / loading of diesel particulate filter, partial blockage.

Diesel Particulate Filter (DPF) Regeneration

If the electronic control unit (ecu) has detected a high carbon soot build up percentage loading of the diesel particulate filter, then a dpf regeneration may be required.
The Ecu may automatically start dpf regeneration during a driving cycle if sufficient conditions are met such as engine and exhaust temperature and gas flow calculated from engine rpm and load.
Forced Dpf regeneration may be activated using special funcions of vehicle diagnostic equipment.

Dpf regeneration attempts to burn off carbon soot deposits by increasing temperature and may result in the exhaust dpf getting very hot which can introduce fire risks if flammable materials are in close proximity.

Diesel particulate filters may be refurbished by specialist companies requiring removal of the filter and off site dedicated cleaning process.

Vehicles fitted with dpf systems often specify low ash engine oil usage.

Legal Implications of Exhaust Aftertreatment Systems

Strict legislation enforces vehicle manufacturers to fit exhaust aftertreatment systems to reduce smog.
HGV and PSV Commercial vehicle operators in the road transport industry may be subject to compliance checks by DVSA to make sure that the adblue system fitted is operational.
Warning: Heavy fines and loss of the vehicle operators licence can result where the manufacturers adblue system has been bypassed by fitting of an adblue emulator which could fool the diesel engine computer in to thinking a faulty or missing adblue system is still operational. see link to Eu regs OJ L171

Remapping

Powertrain control parameters are stored in vehicle computer software as a map. It is possible to rewrite the control software map to remove dpf and scr functions to render the system inactive however this may contravene legislation and also jeopardise any vehicle warranty and introduce potential manufacturers liability claims affecting vehicle insurance. Vehicles used for special purposes may be remapped to suit at operator's risk. Testing the vehicle with an engine dynamometer (dyno) or rolling road is recommended following remapping.

Exhaust Aftertreatment Fluid Storage and Contamination

Adblue® requires clean storage to prevent contamination which may block filters and exhaust catalyser injector system. Filling from multi use containers and drums should be avoided to prevent cross contamination. Site and field refuelling of construction, quarry, and agricultural machines can expose adblue systems to dirt and particle contaminants which could cause future reakdown.

PPE and Risk Assessment

Although urea based exhaust treatment fluid is described as non hazardous there are some risks assosciated with eye contact, spillage, slight ammonia gas release, and ingestion which may cause nausea. COSHH data sheets are found readily on chemical manufacturers websites.

Safety glasses and gloves are recommended when handling treatment fluids.

Adblue® may be contained in a pressurised system.

Adblue® Standards for Aqueous Urea Solution AUS32

Adblue® is a registered trademark of VDA used on this webpage for reference purposes only, no further link is expressed or implied.

DIN 70070

ISO 22241 International Standards Organisation (link opens in new tab)

GB29518-13 this is a Chinese standard despite the GB prefix.