Precautions for SCR maintenance and urea use

Maintenance of SCR system

The selective catalytic reduction (SCR) after-treatment system in heavy-duty trucks can be divided into two types: electrically driven and pneumatically driven. The vehicle's urea tank, made of plastic material, is used in the electrically driven system, while the pneumatically driven system utilizes an aluminum alloy urea tank. Currently, the majority of SCR systems in use are electrically driven, with the pneumatically driven SCR system being less common.

In the case of an electrically driven urea tank, there is no need to release any pressure while refilling the urea solution. Simply opening the urea cap allows for the addition of the solution. However, for a pneumatically driven urea tank, which contains pressurized air, it is important to release the air before refilling. This process is quite convenient as well. To release the pressure, the urea cap should be loosened a few turns to allow the air to escape. Once the compressed air is completely released, the cap can be fully opened to add the urea.

In order to save money, it is necessary to regularly clean and maintain the SCR system and use a reliable automotive urea. When performing annual engine maintenance, open the bottom of the urea tank to clean it and release the deposits in the tank.

If you find white crystals at the ventilation valve or liquid filling port, flush with water or wipe with a damp cloth. If the ventilation valve is found to be clogged, it can also be cleaned with water or replaced. In addition, 2 years to 3 years to replace the box filter, and from time to time to check the plug-in and piping joints.

Precautions for refilling urea solution

There are two ways to add urea solution: one is to fill it with a urea filler, and the other is to add urea directly from a bucket.

Once the sealed lid of the bucket of urea solution has been opened, try to fill the entire amount of urea solution at once.

Because the used urea tube will have residual urea liquid, and it will quickly crystallize and bond to the tube wall, when used again, this crystallized urea will enter the urea tank, resulting in SCR aftertreatment failure.

It is also important to regularly clean the inside of the urea tank, which tends to accumulate impurity deposits and crystals, as well as the outside of the urea tank, especially around the tank lid, and don't let the spoils fall into the tank when you fill it up with urea.

After parking, do not immediately disconnect the power supply of the entire vehicle, SCR processing system after parking have a blowing process, the purpose is to exclude the urea in the pipeline, to avoid crystallization clogging, the entire blowing process is carried out after the engine is turned off, lasts about 30-120 seconds.

So you will still hear a slight rattle from the SCR when you stop the car, and if there isn't a little bit of sound, you'll want to have your SCR aftertreatment system serviced. Therefore it is recommended to disconnect the power to the entire vehicle only when the vehicle key switch has been turned off for two minutes.