Cause 1: High temperature failure
Long term high temperature conditions of SCR catalyst will cause high temperature deactivation, which will reduce the metal working capacity in SCR catalyst, thus greatly reducing the catalyst activity. Even when the engine is in good condition and is properly debugged, different road conditions will cause excessive SCR catalyst temperature for its improper use.
Cause 2: chemical poisoning
Precious metal catalyst on SCR catalyst carrier has strong adsorption on sulfur, phosphorus, carbon monoxide, incomplete combustibles, lead, manganese, etc. At the same time, noble metal catalyst has strong oxidation catalysis, which makes the adsorbed incomplete combustibles of diesel oil easier to be oxidized, condensed and polymerized to form colloidal carbon deposit, causing blockage of SCR catalyst.
Cause 3: carbon deposit blockage deactivation
The blockage of SCR catalyst carbon deposit is gradually formed, which is reversible. The blockage can be reduced by chemical processes such as oxidation and gasification, or by physical processes such as desorption and evaporation of volatile components and gaseous components.
Reason 4: Road congestion
The SCR catalyst is likely to be blocked when driving on congested roads due to the maximum amount of incomplete combustibles produced by vehicles during acceleration and deceleration.
Cause 5: No dismantling, cleaning and maintenance
As a large amount of colloid carbon will be washed down during the cleaning process, it is easy to cause the SCR catalyst to be blocked, which is also the reason for the increased fuel consumption of some vehicles after the maintenance without disassembly.
Reason 6: Severe bump or bottom dragging
The catalytic carrier of the catalyst is a ceramic or metal device. After the vehicle with SCR catalyst ceramic catalyst carrier is towed, severe collision may break the ceramic core of the catalyst and scrap it.
Cause 7: Fuel supply system failure
The oil circuit is a place with many failures. Although many advanced engine control systems now have self-protection functions, once a cylinder fails, the computer will automatically cut off the fuel injector of the cylinder and prevent it from supplying fuel in order to protect the engine and the catalyst, few machines have such advanced functions after all, and many machines do not have such functions at present.
Cause 8: After treatment system failure
When the urea pump in the post-treatment has problems; The nozzle on the urea system is blocked or has quality problems; The urea itself is unqualified; Leakage of tail gas pipe; It will lead to the poor atomization effect of urea injection. The urea solution is directly sprayed onto the exhaust pipe wall. At the same time, because the tail pipe is always at high temperature, the water is easy to evaporate, which leads to crystallization.
Post time: Dec-09-2022