With growing public awareness of environmental protection, national emission standards for vehicles are becoming increasingly stringent. Since the implementation of China’s National IV emission standards, most diesel vehicles have been required to install SCR aftertreatment systems to effectively reduce pollutant emissions.
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In the SCR aftertreatment system, urea solution (hereinafter referred to as urea) plays a critical role. However, due to urea’s tendency to crystallize, the SCR system requires regular inspection and maintenance. What aspects should we pay attention to?
Regular Cleaning of the Urea Nozzle
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The urea nozzle is a component of the SCR aftertreatment system and can be categorized into two types: air-assisted nozzles and airless nozzles. Both types are prone to clogging and crystallization. If the urea nozzle becomes blocked, it will lose its spraying capability. When the ECU computer control system detects such an abnormality, it will restrict the engine’s torque output. Therefore, it is advisable to use genuine urea. Although inferior urea may be cheaper, it is more likely to form crystals, leading to frequent clogging of the urea nozzle and making cleanup more troublesome in the long run.
Regular Inspection of the Temperature Sensor
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If the temperature sensor malfunctions, it cannot accurately monitor the exhaust pipe temperature. In such cases, the temperature value reported by the sensor to the computer may not match the actual exhaust temperature, potentially causing the urea nozzle to activate prematurely or not at all. If urea is injected into a low-temperature catalyst, it will not undergo the necessary chemical reaction and will instead form crystals. Thus, it is important to regularly check whether the temperature sensor is functioning properly. If urea crystals are found on the sensor surface, clean it promptly.
Avoid Using Inferior Diesel
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The catalyst is the core component of the SCR aftertreatment system. It reacts chemically with urea to efficiently eliminate exhaust pollutants. However, the catalyst has high technical requirements regarding the sulfur content in diesel engine emissions. If inferior diesel is used, excessive sulfur dioxide may enter the catalyst. Once the catalyst fails, the engine’s power output will be restricted due to excessive emissions. Therefore, inferior diesel not only damages the engine but also causes various issues for the SCR aftertreatment system.
Regular Cleaning of the Filter and Urea Tank
In the SCR aftertreatment system, special attention should be paid to the filter submerged in urea for extended periods. These filters can accumulate urea crystals and filtered impurities. Once the filter becomes clogged, the vehicle will trigger a fault alarm, and in severe cases, it may affect normal operation.
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As for the urea tank, during annual vehicle maintenance, the bottom of the tank should be opened to remove sediment. When the vehicle is operating normally and the urea level drops to around 20%, it is necessary to refill the tank. Ensure the filter remains submerged in urea to prevent crystallization on exposed parts, which could eventually lead to clogging.
In summary, fellow truck drivers should perform regular maintenance on the SCR aftertreatment system to keep it in good working condition. This not only ensures optimal engine performance but also reduces vehicle emissions, contributing to cleaner air.