You Need To Know About SCR -The 3 most important details
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The Back Door Is Blocked And TheTruck Is Boring. You Need To Know About Scr

  • SCR (selective catalytic reduction) after-treatment technology allows the urea solution to be sprayed into the after-treatment unit can reduce NOx emissions. However, even with such after-treatment equipment, sometimes there are some problems.
  • A truck driver has just put over 60,000 miles on his truck. Recently, there was a sharp drop in power and an increase in fuel consumption. After checking that there was no problem with the engine, he realized that an SCR selective reduction after-treatment unit had been added to the after-treatment, so he suspected that the series of problems were caused by a clogged after-treatment unit.
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Add urea saving screw of SCR

  • Due to the high sulfur content of domestic diesel, in order to adapt to this situation, the domestic SCR post-treatment system mostly adopts vanadium based which is insensitive to sulfur. However, this vanadium-based post-treatment carrier has a disadvantage. The catalytic effect is not ideal when the temperature is low, so the system does not inject urea when the exhaust temperature does not reach 200 ℃.
  • The principle of SCR this screw is that after the sensor is raised, it will cause the sensor to be inaccurate. During normal driving, let the sensor think that the exhaust temperature does not meet the standard, so as to achieve the effect of less or no urea injection. Because the sensor is out of alignment, the system does not spray when it should be sprayed, but it becomes normal to spray hard when it should not be sprayed. In this way, it is easy to cause crystals of urea solution to block the post-treatment device.
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Deliberately driving with SCR low throttle for a long time

  • We have learned that catalysts need to be at the proper operating temperature. Many truck drivers purposely run at low speed and low throttle when cruising on flat roads to save fuel. At this time, the exhaust temperature and the carrier will not reach the working temperature.
    In addition, the mist spray caused by the urea screw will not be able to continuously decompose the catalytic urea solution and cannot fully participate in the products of the catalytic reaction, i.e., crystallization, attached to the urea solution. The catalyst surface, results in the blockage of the catalyst channel.
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SCR system failure

  • In addition to the above two cases, the SCR system itself has design defects or faults, such as the front section of the exhaust pipe is too long and the thermal insulation measures are not in place; The urea injection pressure is abnormal, the atomization is not good, or the nozzle is not tightly closed; The emptying pipeline of urea pump after flameout is not complete; The damage of urea filter element leads to impurities blocking the nozzle and so on, which may lead to the crystallization blockage of the post-treatment system.
  • To sum up, the blockage of the SCR system is not just the problem of urea. If it is not used properly, even if you buy the best urea, it will cause the failure of crystallization blocking the catalyst. If only the urea crystal is blocked, the catalyst can be regenerated and reduced by cleaning。
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