The Role of DEF in Emission Control and Compliance
Diesel Exhaust Fluid (DEF) is the reactant necessary for the Selective Catalyst Reduction System (SCR system) function. DEF is required for the proper after-treatment operation of your emissions system. It is a carefully blended aqueous urea solution of 30% high-purity urea and 70% deionized water (Specifications vary by manufacturer).
DEF used in Cat SCR Systems must meet the requirements outlined in the International Organization for Standardization (ISO) standard 22241-1.
Diesel Exhaust Fluid (DEF)?
The engine needs two things to run – Diesel fuel and DEF.
So if you fill-up the DEF tank every time you fuel up your fuel tank, you’ll always be ready to go. The fuel tank and the DEF tank are sized proportionately. This means that if you start with full tanks, you’ll empty them both at about the same rate.
There are level gauges in the cab to indicate the DEF level.
If you run out of diesel exhaust fluid (DEF), your engine will lose power, and then it will shut down. If you run out of diesel fuel or DEF, your engine will shut down.
The shelf life of DEF is a function of ambient storage temperature. DEF will degrade over time depending on temperature and exposure to sunlight. Expectations for shelf life as defined by ISO Spec are the minimum expectations for shelf life when stored at constant temperatures. If stored between 10 and 90 deg F, shelf life will easily be one year. If the maximum temperature does not exceed approximately 75 deg F for an extended period of time, the shelf life will be two years.
Always refer to the manufacturer’s recommendations for storage and shelf life.
DEF exposure to constant, high storage temperature may impact shelf life. Extensive testing in very hot climates has confirmed that DEF stored at high temperatures will degrade.
Your machine’s operation and maintenance manual contains information on DEF, including contamination control and proper storage.
Remember that poor DEF quality can result in performance, aftertreatment, and operational concerns.
Contaminated DEF can lead to Costly Repairs, Operator Inducements and result in engine derate or system lockout.
For more information on the effects of DEF and the after treatment system refer to the previous article: “E1389 – AFTERTREATMENT #1 SCR OPERATOR INDUCEMENT”
Overview
Overview of the Cat® Tier 4 Final Delayed Engine Shutdown (DEF) process. Always remember to refer to your specific machine’s Operation & Maintenance Manual for more information.
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