Truck Maintenance 101: Guide To Emission And Exhaust Treatment Systems
For a long time, diesel-powered trucks emitted greenhouse gasses into the environment. As a result, most trucks come with an aftertreatment system (ATS) to minimize harmful exhaust emissions. When combusted diesel leaves the engine, the ATS treats it to reduce its environmental effects while maintaining the optimum function of the truck’s engine.
However, many truck owners have had difficulties maintaining and repairing exhaust treatment systems. A well-maintained exhaust treatment system maximizes uptime and guarantees that emissions are consistently below the government’s threshold. This article will guide you on how exhaust treatment systems work and how to maintain them.
The main parts of a truck’s exhaust treatment system are the selective catalytic reduction (SCR) and the diesel particulate filter system (DPF). Selective catalytic reduction lowers the nitrogen oxide levels, while the diesel particulate filter system decreases the number of particles released by diesel combustion.
The SCR system comprises the following:
- Diesel Exhaust Fluid (DEF): This is a solvent composed of deionized water and urea. It’s usually injected into the exhaust stream to decrease nitrogen oxide emissions.
- SCR: This is a chemical reaction catalyst that converts decomposed diesel exhaust fluid and exhaust stream into a substance that adheres to government regulations on greenhouse gas
- Decomposition Chamber: This is a chamber that helps combine the exhaust stream with the diesel exhaust fluid and the SCR.
- Diesel Exhaust Fluid Pump: This is a component of the DEF delivery system that pumps the fluid through filters and maintains pressure between the dozer and the pump.
- Diesel Exhaust Fluid Dozer: This introduces the DEF into the exhaust treatment system.
The DPF system is composed of the following:
- DPF: This is a percolator that filters and removes more than 85% of the particles from the exhaust.
- Diesel Oxidation Catalyst (DOC): This oxidizes hydrocarbons and carbon monoxide and reduces the particulates.
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How It Works
The toxic gasses in the exhaust stream leave the turbo for the exhaust treatment system. The DPF system contains DOC—a combination that collects the accumulated carbon and oxidizes it to remove the particulate matter.
Meanwhile, the diesel exhaust fluid is introduced in the decomposition reactor’s exhaust gas to remove nitrogen oxide and nitrogen dioxide. Next, the product leaves the decomposition reactor into the SCR system.
This process turns the poisonous nitrogen oxide and nitrogen dioxide into water vapor and harmless nitrogen gas. Also, this procedure efficiently removes toxic emissions, leading to an almost zero-toxic emission from the exhaust pipe.
There are various parts you should consider when maintaining the exhaust treatment system of your truck. These include the injector, dosing module, temperature sensors, nitrogen oxide inlet and outlet, diesel particulate filter, and catalyst section. Checking them at once may be difficult; therefore, you can categorize them into three for efficient maintenance.
Diesel Particulate Filter Section
The diesel particulate filter system collects particulates in the truck’s exhaust, and continuous accumulation can lead to clogging. Clogging can affect the performance of the exhaust system.
Hence, you should frequently service it at intervals recommended by your truck’s manufacturer to guarantee its effectiveness. You can also confirm from your service manual when to replace it.
Most truck manufacturers recommend you clean your DPF system when your dash lamp notifies you or after every 10,000 hours or 400,000 miles. Ignoring the dash lamp notification can impair your truck’s torque capacity and general function.
Some manufacturing companies offer cleaning services and may exchange your dirty DPF for a clean one. It’s essential to check if your manufacturer provides such services since it can save you a great deal of time and money.
Diesel Exhaust Fluid Section
Modern heavy-duty trucks have fluid quality sensors in the diesel exhaust fluid section. The sensor measures the concentration and quality of the DEF in the tank to validate its purity.
If your truck doesn’t have a sensor, you can use a refractometer to test the quality of the fluid. Its purest form should measure 32.5 percent. This percentage reduces as you continue using the truck until it drops below a particular threshold.
When this happens, you’ll get an illuminating alert on your dashboard. Consider replacing the fluid once you get an alert since some trucks may lose their accelerator function.
Automated And Parked Regeneration
Automatic and parked regeneration is a technique that cleans the ash, oil, and soot trapped in the DPF’s filter.
Automatic regeneration happens in long-distance journeys and at intervals commanded by the engine control system in most automatic trucks. When the exhaust’s temperature is favorable, the soot is oxidized and removed, cleaning the filter system.
On the other hand, parked regeneration or manual regeneration happens at the driver’s will. Short-distance operations don’t provide the exhaust with the required temperature to oxidize the soot.
So, for long-distance highway operations, you may have to do manual regeneration. Otherwise, your exhaust emissions can become poisonous, thus attracting a penalty for neglecting government regulations.
Exhaust treatment systems are often neglected during overall truck maintenance. However, these systems are necessary for the optimum performance of heavy-duty trucks. An impure DEF and an unclean DPF filter can block or impair your truck’s emission system.
Failure to adhere to the recommended cleaning and replacement intervals can damage the emission control system, reduce acceleration capacity, and cause other engine performance issues. Moreover, you can incur high repair costs when all you could have done is simple routine maintenance.