AdBlue Systems

Anti-pollution standards are becoming more demanding. Commercial vehicles must meet such standards and for that reason, they shall install the well-known “Anti-pollution Systems”. 

This article describes one of the most famous systems, the SCR (Selected Catalytic Reduction), which was first used in commercial vehicles to meet Euro 4 standards, coming into effect on October 1 2006. This is the system that is still being used by most manufacturers in order to meet Euro 6 anti-pollution standards, in force since 2014.

This system is based on the addition of AdBlue to the exhaust gases. AdBlue is a fluid, made up of water and urea, which is injected, in small amounts, in the exhaust gases, before they enter the catalytic converter, in order to reduce the NOx particles (nitrogen oxides) released into the atmosphere.  

It is very important to keep these systems in perfect conditions, since they can be easily damaged if a preventive maintenance is not performed, particularly in the winter and with extremely low temperatures.

The reason why the extreme cold may affect the correct operation of these systems is the high content of water in the AdBlue, since it can be easily frozen in pipes and injectors when the circuit is not kept clean and when the product is not able to circulate correctly.

AdBlue, features and composition

• Freezing point -11ºC
• Boiling point 40ºC
• 68% Water
• 32% Urea

To ensure the proper operation of such systems, it is necessary to use an AdBlue quality meeting the ISO standard 22241-1 and to carry out a preventive maintenance once a year at the very least. This maintenance service includes the replacement of the main filter and the cleaning of the pre-filter and the injector.

Main components

The exhaust gases treatment according to the SCR technique consists of a simple system with not many components: AdBlue Tank (1), Pump Unit (2), Dosing Unit (3), Muffler (4) and SCR catalytic converter (5).

Image of the main filter and the pre-filter in a Denox 2

Pre-filter at the AdBlue supply intake in the module

Main filter in the AdBlue module

After performing the preventive maintenance, it is necessary to check whether the anti-pollution system works correctly. To do so, we need the JALTEST diagnostics tool. This device facilitates different actuations to check the proper operation of the system, besides enabling the necessary calibrations when one or more components are replaced.

These actuations are:

• Diagnostics
• AdBlue pressure build-up/reduction test, to check the correct operation of the pump.
• AdBlue circuit purge
• Maximum pump delivery/measurement of the metered quantity, to check whether the system injects the correct amount of AdBlue.
• Calibration of the AdBlue module. It is necessary to perform this calibration when the dosing module is replaced.

Dosing module from a Denox 2

Damián Muñoz

Technical Assistance Department