With temperatures now dropping into the teens, many questions come up regarding frozen Diesel Exhaust Fluid (DEF). It is no question that solid or slushy DEF can lead to error codes and equipment malfunctions. Whether in storage tanks or in equipment, DEF can freeze and possibly cause issues.

As temperatures drop below 12 F, DEF will begin to solidify and not work as intended. But when temperatures rise again and the DEF thaws, it regains its effectiveness as a catalyst to convert harmful NOx emissions into safe nitrogen, water and trace amounts of carbon dioxide.

DEF is a mixture of automotive grade urea and deionized water. The specific ratio used allows the whole mixture to freeze and thaw together like water and ice. The individual components do not separate or negatively impact the effectiveness of the solution.

Cycles of freezing and thawing have no effect on DEF quality, regardless of how many times the cycle is repeated. This is especially important for vehicles equipped with Selective Catalytic Reduction (SCR) systems regularly subjected to harsh winter conditions.

Most equipment manufacturers have designed their SCR systems to operate under a grace period with a means to thaw frozen DEF tanks and supply lines before the grace period expires. Heaters or coolant lines are often run through the solution to quickly restore the performance of the SCR system.

Error codes and system malfunctions can happen when these systems fail and do not operate as designed. While system failures can be frustrating, antifreeze or other additives should never be added to the DEF tank as purity will be compromised and cause different problems.

If crystalized DEF is around the mouth of a container or on your SCR system, it is a sign of evaporation, not product damage from freezing.

Essentially, crystallization is a sign that water has evaporated from the solution and the urea has simply “salted out.” The crystals can be flushed away with water as DEF is not harmful to the environment.

To maintain operability in all weather conditions, stored DEF should be kept in storage well above freezing temperatures.

Heated blankets and other storage solutions are available. If not, tanks and containers must be able to endure product expansion as the product can become 7% larger in volume as it becomes solid.

An appropriate grade of stainless steel or high-density polyethylene plastic that resists corrosion is required as corrosion can negatively impact the product’s purity.

Contact your local FS Energy Specialist for trouble-free DEF solutions.

Curt Dunafin serves as GROWMARK’s FS Energy Services manager. He can be reached at cdunafin@growmark.com.