EPA Compliance Instructions
An SCR management strategy must include the following, per the EPA:
- Low DEF reservoir alerts are sent by the driver warning system.
- Measures to entice drivers: a cap on restarts, a fuel lockout mechanism, or engine deceleration until the reducing agent is refilled
- Aqueous urea quality monitoring system to prevent dilution or replacements
- Supply infrastructure: Ensures the availability of aqueous urea
- System dependability and durability: For heavy-duty highway diesels, a minimum service interval of at least 150,000 miles (240,000 km) and a warranty requirement of 435,000 miles (700,000 km) are required.
- Deactivation protection and tamper-resistant security
Since SCR became a prerequisite for aftertreatment A supply system has developed that makes DEF accessible at truck stops, OEM dealerships, fuelling stations, and repair/service operations in all engines produced in 2010 with the exception of Navistar and Caterpillar. Regardless of branding, every DEF marketed in North America has the same chemical composition. Between DEF and the AdBlue that one OEM brands their product, there is no distinction.
Due to an accumulation of emissions credits gained on their engine families over the previous ten years, Navistar is now offering engines that do not comply with 2010 EPA NOx emissions standards. However, Navistar claims that employing EGR on every engine in their family, they will be able to fulfill both the 2013 and 2016 EPA criteria. In order to reduce the likelihood that an SCR system may be used without DEF, the EPA mandates the inclusion of last-resort persuasive operator notifications. For compliance, the system must be able to recognize erroneous or overly diluted DEF right away.
In 2011, the price of DEF, a 32% aqueous urea solution, in the US was little under $3 a gallon. This indicates that there is some adverse operational cost effect. However, because it is domestically manufactured, the price of aqueous urea should be considerably more constant than that of fuel.
VENTILATION FOR CLOSED CRANKCASES
Highway diesel engines were needed to have a closed crankcase ventilation (CCV) system, which is a diesel engine version of the automobile positive crankcase ventilation (PCV) system, in order to comply with 2007 emissions requirements. Some 2010 engines use static electricity to stop crankcase gas emissions. The electrostatic oil separator (EOS) now used in DD-Series engines charges and separates liquid droplets in crankcase gas. Preventing crankcase gases from venting to the atmosphere is the goal of a CCV system. Crankcase gases are made up of:
- Cylinder blow-by gas from engines
- Gases that lubricant boils off
Composition of Crankcase Gas
The mixture of raw diesel, partially burned fuel, combustion byproducts, and boil-off engine lubricant residues really makes up the makeup of the gases in a diesel engine crankcase. Although it is widely acknowledged that it is hazardous, little of it is made. The presence of wet air, heat, and a lot of sloshing and churning activity in the crankcase adds to the complexity of the chemical reaction. As technicians, we categorize crankcase gas as a simple HC emission.
Operation of CCV and EOS
The PCV circuits used in autos may be directly compared to CCV and EOS systems diesel. To apply some pull on the crankcase, the CCV system is routed upstream from the turbocharger impeller housing. The 2007 Cummins ISC engine shown in Figure has a filter assembly that is situated on top of the rocker housing cover and through which the CCV piping is passed. It is important to follow OEM guidelines for CCV service intervals.
EOS works by giving suspended oil droplets in crankcase gas an electrical charge before electrostatically separating them so they may be reabsorbed into the sump oil. EOS cleans the crankcase gas and lowers internal engine fouling.