The aftertreatment system also needs to be maintained

What is an SCR aftertreatment system? 

Under the action of catalyst, SCR injects reducing agent ammonia or urea to reduce NOx in exhaust gas into N2 and H2O, so as to achieve the purpose of energy saving and emission reduction.

The SCR technical structure is also relatively simple, as long as a set of urea reductant system is added on the basis of the engine, and then the urea aqueous solution is added regularly. Not only does this technology improve vehicle fuel economy, it also helps extend service intervals.

After the exhaust gas comes out of the turbine, it enters the exhaust mixing pipe. A urea metering injection device is installed on the mixing pipe, and the urea aqueous solution is injected. The urea undergoes hydrolysis and pyrolysis at high temperature to generate NH3, and NH3 is used on the surface of the SCR system catalyst to reduce NOX , discharge N2.

The system mainly includes urea pump, urea nozzle, urea tank, etc., so the maintenance of the SCR system usually focuses on these three aspects.

● SCR aftertreatment system maintenance tips

1. Maintenance of urea pump 

Since there is residual liquid in the urea dosing pump and pipeline after the vehicle stops working, it is necessary to perform emptying work after the vehicle is turned off to prevent crystallization or freezing.

All urea dosing pumps have filters or filter elements, which must be cleaned or replaced regularly according to technical requirements, otherwise it will lead to blockage or damage over time, resulting in loss of filtering effect, which will inevitably lead to system malfunction.

2. Maintenance of urea nozzle

If the quality of the vehicle urea solution is not good enough, some insoluble impurities and substances contained in the inferior vehicle urea solution may accumulate and may block and destroy the urea nozzle.

In addition, the cause of the blockage of the urea nozzle may also be caused by the residual sediment in the urea reaction of the vehicle, so we usually need to maintain the urea nozzle and clean the urea nozzle frequently. Hot water soaking can be used.

And the injectors are made of 304 stainless steel with a ceramic core. Do not drop the nozzle when servicing, as this may damage the ceramic coating.

3. Maintenance of urea tank

The highest level of the urea tank should be filled with urea solution to 100% (90% in winter when the temperature is low), and when the urea solution is consumed to 20%, the urea solution needs to be added; and the urea level needs to be checked every day; and whether the urea solution is leaking.

When the engine is maintained every year, open the bottom of the urea tank for cleaning, and release the sediment in the tank. It is also necessary to check from time to time if white crystals are found at the vent valve or the liquid filling port, which can be rinsed with clean water or wiped with a damp cloth. If the vent valve is found to be blocked, it can also be cleaned or replaced with clean water. In addition, replace the filter screen in the box every 2 to 3 years, and check whether the plug-in and pipe joints are in good condition from time to time.

 Under normal circumstances, there are many cases of SCR post-processor replacement assembly. In order to save driving costs, it is necessary to regularly clean and maintain the SCR system and select reliable vehicle urea. It should be noted that the SCR post-processing system has strict requirements on the relative positional relationship of each assembly, and the manufacturer has arranged it in a modular manner, so everyone should pay attention when cleaning and maintaining it, do not arbitrarily change its position.