The Silencer Is Blocked- 1 Most Important Reason
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The Silencer Is Blocked. What Does It Have To Do With Inferior Urea Solution

Since the launch of the national four heavy truck, some Truck drivers were surprised to find that the muffler of their car would be blocked after a period of use.

Theblockage of the muffler and the silencer is actually the blockage of the catalyst carrier

Some truck drivers will ask, how can the silencer be blocked when we arrive at the fourth national day? There was no problem with the third car. That’s because, at the Fourth National Congress, most domestic heavy trucks are equipped with an SCR post-treatment system, and there are more catalyst carriers for catalytic reaction in the muffler.

The Silencer
  • Working principle of SCR: the SCR system injects urea solution into the tail gas pipe of diesel. The ammonia produced by the decomposition of urea solution is mixed with the tail gas and reacts with the catalyst on the carrier in the muffler the silencer to react the nitrogen oxides in the tail gas to produce nitrogen and water, so as to finally achieve the purpose of purifying the tail gas.
  • If the muffler is blocked, it will lead to poor engine exhaust. The consequence of poor exhaust is that the the silencer power decreases and the fuel consumption increases.
The Silencer
  • Some truck drivers find that their vehicles have weak power and high fuel consumption. They will disassemble the muffler and remove the blocked catalyst carrier, so that the vehicle power can be restored. Of course, without the catalyst, the vehicle’s exhaust emission will not reach the standard.
    Strictly speaking, the blockage of the silencers of the fourth and fifth national trucks is actually the blockage of the catalyst carrier.

why is there a catalyst carrier in the silencer?

In order to make the tail gas better contact with the silencer catalyst for better catalytic reaction, the catalyst carrier is designed with many small round holes.

The Silencer
  • Through the small round holes on the the silencer carrier, the tail gas can fully contact with the catalyst to change the nitrogen oxides in the tail gas into nitrogen and water.
The Silencer
  • In order to facilitate the layout of the whole vehicle, generally, the catalyst carrier for post-treatment will be encapsulated in the muffler.
  • There are two main reasons for catalyst carrier blockage
    The catalyst carrier in the muffler is blocked for two main reasons: 1. The fuel injector is damaged; 2. Crystallization of urea solution.
  • The fuel injector is damaged, causing black smoke due to large fuel injection
    The blockage of muffler is also related to the damage of fuel injector?
  • Because the fuel injector is damaged, there is the possibility of excessive fuel injection. Too much diesel enters the cylinder and the diesel fails to burn completely. Incomplete combustion of diesel fuel will be discharged into the the silencer muffler in the form of black smoke (soot).
The Silencer
  • These black smoke are actually fine particles. These fine particles will be adsorbed on the pores of the catalyst carrier in the muffler. When the particles reach a certain amount, the pores of the carrier will be blocked, resulting in the blockage of the muffler.
  • Poor quality urea has many impurities, and the crystallization blocks the silencer
    In addition to injector failure, urea crystallization can also lead to blockage of muffler.
    There are many reasons for urea crystallization, including the position of urea nozzle; Injection angle of urea nozzle; The temperature of exhaust gas and the quality of urea solution will cause crystallization and block the muffler.
The Silencer
  • So why does inferior urea cause urea crystallization? It’s because of poor quality urea and many impurities! Not pure enough. Impurities in inferior urea solution will cause sticking and wear of urea nozzle, resulting in abnormal operation.
  • The abnormal injection angle and amount of urea nozzle will lead to urea crystallization. The urea nozzle is damaged seriously, and even the urea solution drips into the silencer.
The Silencer
  • The urea solution enters the pores of the catalyst carrier to form crystals. The more crystals accumulate, the pores of the catalyst carrier will be blocked, and the muffler will be blocked.
  • Urea crystallization: urea solution that fails to carry out reduction reaction forms crystalline objects under the action of high temperature the silencer of tail gas.
  • In recent years, with the improvement of the car concept of truck drivers, truck post-treatment technology has become more and more mature. Now there are fewer silencers blocked due to urea crystallization.
  • From the two major causes of muffler blockage, adding high-quality diesel, regularly replacing diesel filter elements for maintenance, and adding high-quality urea can avoid the fault of muffler blockage to a certain extent.
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