DEF Date Codes
A date code, or date of manufacture, can be found on just about any package of DEF. This is called out in the specification for DEF: ISO 22241. How to read the date of manufacture on BlueDEF also k...
Forum Discussion
aruba5er:
Thanks for your question.
DEF is an unsaturated solution of pure water and pure urea. The percentage of urea is (nominally) 32.5%. This concentration was selected so that as it melts after freezing, the concentration of urea remains at about 32.5%. This allows vehicle DEF dosing controllers (which operate on a volumetric basis) to reliably reduce NOx to the required level when a mixture of liquid and frozen DEF is present in the tank. Of course urea solubility in water is dependent upon temperature, but at the freezing point of the solution (-11 C or 12 F) the solubility of urea in water is about 32.5%.
Repeated freeze-thaw cycles have no effect on DEF. The specification for storage and handling of DEF (ISO22241-3) does not limit the number of freeze-thaw cycles. Heat applied to thaw DEF must be limited to assure that the resulting liquid DEF at the heater interface does not significantly decompose into ammonia. A poorly designed DEF thaw system that exposes DEF to high temperatures may result in production of ammonia and a slight reduction in urea concentration.
Urea that precipitates during a freeze-thaw cycle should re-dissolve readily or be captured in the vehicle's DEF filter (that is integral to the system) where it will eventually dissolve. I've dissolved a lot of "technically pure urea" and "pure water" and experimentally determined that freeze-thaw does not affect the concentration of urea after thawing. I use a laboratory grade refractometer to measure urea concentration.
The primary issue with freezing of DEF is expansion - a container full of DEF that freezes can easily burst if frozen. Most vehicle tanks accommodate this by incorporating ullage space that allows expansion and use pump-back systems that drain supply lines and other trapped volumes.
Most "urea crystals" observed by DEF users result from evaporation and are not an issue unless they cling to poorly designed level sensors or other DEF system components.
Note: The storage temperature limits for DEF apply only to original packaging and tanks prior to dispensing in your vehicle and are intended to limit the amount of ammonia in the solution to .2% when handled by users and in underground tanks. Your vehicle DEF tank is vented, and can easily accommodate the ammonia liquid and vapor that result from storage in the vehicle tank in a hot climate. The decomposition of DEF to ammonia is relatively slow at temperatures under 250F and the vehicle controller can easily accommodate the small reduction in urea percentage that results from decomposition to ammonia.
buta4: I agree with your observation about date codes. That is why I asked for the information from Peak. I have no idea why their date code is so arcane. Most other DEF uses MM/DD/YY as you suggest.:)
Thanks for your question.
DEF is an unsaturated solution of pure water and pure urea. The percentage of urea is (nominally) 32.5%. This concentration was selected so that as it melts after freezing, the concentration of urea remains at about 32.5%. This allows vehicle DEF dosing controllers (which operate on a volumetric basis) to reliably reduce NOx to the required level when a mixture of liquid and frozen DEF is present in the tank. Of course urea solubility in water is dependent upon temperature, but at the freezing point of the solution (-11 C or 12 F) the solubility of urea in water is about 32.5%.
Repeated freeze-thaw cycles have no effect on DEF. The specification for storage and handling of DEF (ISO22241-3) does not limit the number of freeze-thaw cycles. Heat applied to thaw DEF must be limited to assure that the resulting liquid DEF at the heater interface does not significantly decompose into ammonia. A poorly designed DEF thaw system that exposes DEF to high temperatures may result in production of ammonia and a slight reduction in urea concentration.
Urea that precipitates during a freeze-thaw cycle should re-dissolve readily or be captured in the vehicle's DEF filter (that is integral to the system) where it will eventually dissolve. I've dissolved a lot of "technically pure urea" and "pure water" and experimentally determined that freeze-thaw does not affect the concentration of urea after thawing. I use a laboratory grade refractometer to measure urea concentration.
The primary issue with freezing of DEF is expansion - a container full of DEF that freezes can easily burst if frozen. Most vehicle tanks accommodate this by incorporating ullage space that allows expansion and use pump-back systems that drain supply lines and other trapped volumes.
Most "urea crystals" observed by DEF users result from evaporation and are not an issue unless they cling to poorly designed level sensors or other DEF system components.
Note: The storage temperature limits for DEF apply only to original packaging and tanks prior to dispensing in your vehicle and are intended to limit the amount of ammonia in the solution to .2% when handled by users and in underground tanks. Your vehicle DEF tank is vented, and can easily accommodate the ammonia liquid and vapor that result from storage in the vehicle tank in a hot climate. The decomposition of DEF to ammonia is relatively slow at temperatures under 250F and the vehicle controller can easily accommodate the small reduction in urea percentage that results from decomposition to ammonia.
buta4: I agree with your observation about date codes. That is why I asked for the information from Peak. I have no idea why their date code is so arcane. Most other DEF uses MM/DD/YY as you suggest.:)
