When the diesel-driven vehicle industry was pushed into much more stringent emissions standards, engineers went to work on a number of technologies to make it happen. Today's modern diesel engine is nothing like what was in use just a decade ago. The rise of common-rail diesel engines with superefficient combustion cycles that burn more of the fuel injected is the start, but emissions from the machines still needed attention.
That led to the rise in the use of tools including the diesel particulate filter, the diesel oxidation catalyst and selective catalytic reduction. That last tool, SCR, relies on a component that's becoming very familiar to truck and farm equipment owners — diesel exhaust fluid.
This fluid, which is urea-based but specially formulated for engine use, has another issue farmers and other users should know about — it freezes.
Recently, the American Petroleum Institute issued a release looking at key factors for managing DEF. Targeted to the truck market, the information offers valuable tips for off-highway equipment as well.
DEF is a mixture of what API calls technically pure urea and purified water, and it freezes at 11 degrees F. While that sounds pretty cold, temperatures already hitting the upper Midwest in November show that it can get pretty cold out there.
Anyone who's taken a middle school chemistry class will tell you one other fact. Unlike most compounds, when water freezes, it expands. In fact, DEF can expand up to 7% when frozen. Having a block of DEF in the tank is one thing, but damaging that same tank due to expanded frozen fluid can cause longer-term trouble.
Running and frozen DEF
The key is to make sure the tank isn't too full when temperatures drop. That gives you some expansion headroom in the tank. The next advice is not to use additives to thaw the DEF, because you want to keep that product pure.
DEF is a key component in SCR, which significantly reduces nitrogen oxide from diesel emissions as part of a chemical process. API advises that DEF needs to remain pure for it to work properly.
Most truck, tractor and combine DEF tanks have heating elements. You can start the vehicle and let that element thaw the DEF for proper equipment operation. But Jeffrey Harmening, manager, API, notes that beyond cold weather, there are other issues about DEF to consider.
"Drivers accustomed to purchasing DEF in containers should look at the expiration date on the bottle and be sure to use it before this date, as the product has a limited shelf life," he warns.
If the date isn't present on the bottle he advises asking the retailer for the most recently delivered containers.
If you're buying DEF in bulk for the shop, make sure you understand the shelf-life of the product from your supplier. Harmening also notes that an API certification mark on the container is valuable as well. Many diesel engine makers are recommending API-licensed DEF for their vehicles.
Storage conditions matter with DEF, and the product can last up to 12 months in storage — or longer in optimum conditions. The label will have recommended storage temperatures. API recommends that you not store it for too long in your truck once purchased, especially in a storage area of your vehicle which can be exposed to heat or sunlight.
DEF in the shop
Harmening points out that API has found one big misconception: Fleet managers believe that if the urea concentration of their DEF is on spec, then the fluid meets the required quality. "While it is true that the concentration is very important, there are many other important characteristics built into the ISO 22241 specification regarding DEF," Harmening says.
If you're buying DEF in bulk, check to see that your supplier is providing product that conforms to the entire ISO quality standard. Harmening says one way to do that is to ensure that the supplier has a certificate of analysis (or quality) with every shipment that addresses all quality characteristics the specification requires.
you can see a directory of licensees at the API website.
In the shop, be sure to handle, store and dispense DEF so off-spec product isn't getting into your tank. Consider rotating stock to use the oldest product first, and maintain proper storage temperatures in the shop. Heat can be a problem, too, if you store DEF at temperatures above 86 degrees.
Other factors to consider include storage tanks dedicated to DEF; a closed-loop system for transferring DEF to keep dirt out; dedicated equipment for dispensing DEF; and that anything used to dispense DEF should be cleaned with distilled or deionized water, followed by a DEF rinse.
Adds Harmening: "The quality of the DEF going into your vehicle is as important as the quality of the engine oils or fuels used."