SCR, also known as selective catalytic reduction, is a type of active emission control system in the diesel powered car. Automotive-grade urea (AdBlue) is often served as reductant source. Reductant agent will be injected into the exhaust stream of the engine, then convert nitrogen oxide into nitrogen, water vapor, and carbon dioxide after the chemical reaction, thus discharged through vehicle tailpipe. Basing on the EPA emissions standards, all heavy-duty diesel truck engines must reduce particulate matter and nitrogen oxides to near zero level.

AdBlue has already became consumables of SCR system nowadays. AdBlue are comprised of urea (32.5%) and demineralized water (67.5%). The concentration of urea has a considerable influence on the reduction rate of nitrogen oxide and crystallization point of the urea solution. The improper concentration will affect the transformation efficiency and cause residual ammonia which will lead to the secondary pollution. The in-built warning sensor will alert the driver when the AdBlue level is low, and AdBlue should be poured in tank by professional filler nozzle, and how to avoid the miss-filling of AdBlue must take into consideration during the early design stage of the whole SCR System.

ISO 22241-4 detailed describes the working principle of magnetic design. Magnetic switch on the nozzle will be opened only under the magnetic field of magnetic adaptor, and AdBlue will be allowed into the tank. Therefore, miss-milling into the diesel tank is made impossible.

About AdBlue Resistance Magnet

AdBlue is alkaline, thus steel, cast iron, cast aluminum, and solder will be corroded by it, then normal operation of SCR system will be affected by the relevant corrosion material. This is exactly why designers apply magnetic design in SRC system. Sintered Neodymium magnets also have risks to be corroded under the alkaline conditions, and magnet manufacturers developed AdBlue resistance magnet for filling system under this background.