Temperature Considerations for Diesel Exhaust Fluid Storage Tanks

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Diesel Exhaust Fluid (DEF) plays a crucial role in controlling emissions from diesel engines. This colorless, non-hazardous fluid may look simple. But storing it in a proper diesel exhaust fluid tank is crucial. 

Temperature, in particular, can significantly influence DEF’s shelf life, quality, and performance. Ignoring temperature guidelines may lead to costly maintenance issues and environmental setbacks. Understanding how temperature affects DEF is crucial for ensuring stable performance and supporting emission goals year-round.

Ideal Storage Temperatures for DEF

According to ISO22241, DEF must be stored in a cool, dry place with temperatures between 12°F (-11°C) and 86°F (30°C). This specific range helps protect the fluid’s chemical composition and safeguards its emission-reducing properties.

DEF stored above 86°F for extended periods begins to degrade. The urea inside the solution breaks down, making the DEF less effective in reducing nitrogen oxide emissions. Long-term exposure to excessive heat also reduces the fluid’s shelf life.

Why Proper DEF Storage Matters

DEF contains:

• 32.5% high-purity urea
• 67.5% deionized water

This exact mix enables the proper functioning of the Selective Catalytic Reduction (SCR) system. However, both components react sensitively to environmental changes.

Some of the effects of poor storage are as follows:

1. Urea Breaks Down Under Prolonged Heat Exposure

When stored above 86°F (30°C) for extended periods, the urea in DEF begins to degrade. Heat accelerates chemical reactions that weaken the urea, reducing its ability to convert harmful nitrogen oxides into harmless nitrogen and water vapor. As urea concentration drops, so does the fluid’s ability to support emissions control systems.

2. Cold Temperatures Cause Freezing and Expansion

In environments with temperatures below 12°F (-11°C), DEF begins to freeze. As the fluid turns solid, it expands by up to 7%. If the tank design does not account for this expansion, it may crack or warp under pressure. Frozen DEF also slows or stops system flow, delaying start-up times or triggering system errors.

3. Poor Storage Conditions Shorten Shelf Life

DEF typically has a shelf life of up to two years when stored between 12°F and 86°F. Outside this range, chemical stability decreases. High temperatures speed up urea breakdown, while repeated freeze-thaw cycles can introduce contamination or air pockets. DEF stored in fluctuating or extreme conditions will lose its potency much faster.

4. Emission Systems Suffer From Fluid Degradation

When DEF quality drops, emission systems like the Selective Catalytic Reduction (SCR) system cannot function properly. Sensors may detect off-spec fluid and trigger alerts or reduce engine power. Over time, poor-quality DEF can damage injectors and clog lines. It may also increase the risk of unplanned maintenance or costly repairs.

Effects of Higher Temperatures on DEF

DEF resists quick evaporation due to its composition. However, extended exposure to temperatures above 86°F may cause:

• Gradual breakdown of urea
• Reduced overall effectiveness
• Shorter shelf life

Although the fluid remains chemically safe, its performance suffers when stored improperly. The water content may start to evaporate slightly, but this only becomes a concern under direct sunlight or in poorly shaded storage.

Some of the methods to prevent overheating include:

• Store the diesel exhaust fluid tank under a canopy or shelter.
• Use UV-resistant tank materials.
• Avoid placing storage tanks in open, sunlit areas.

Simple precautions make a big difference in preserving DEF integrity.

Why DEF Freezes

Even though freezing does not harm DEF’s quality, it can disrupt system performance temporarily and place stress on storage equipment. Several conditions increase the risk of freezing, especially during winter.

Some of the key reasons include the following:

• Cold Weather

Sub-freezing temperatures in winter can easily cause DEF to freeze, particularly at night or early morning. Even if daytime temperatures rise, stored DEF may remain frozen if containers or lines stay exposed to cold weather.

• Long Idle Times

Extended downtime for vehicles, such as overnight parking or weekends off, allows DEF systems to reach ambient temperatures. When idle periods coincide with cold weather, DEF in tanks and lines can freeze, delaying operation.

• Low DEF Levels

A diesel DEF tank with a higher fluid volume maintains a more consistent temperature. Low DEF levels freeze more easily because smaller volumes have less thermal mass and lose heat faster. Tanks that remain less than half full in winter are more likely to experience freezing or slush formation.

How to Prevent DEF Freezing

While freezing does not damage DEF, frozen fluid can delay vehicle starts or cause pressure issues in the system. Preventing freezing involves utilizing smart storage and system design to maintain stable internal temperatures, even in extreme weather conditions.

1. Heating Solutions for Cold Climates

Heating systems provide consistent internal warmth and ensure DEF stays above freezing.

• Band heaters: Wrap around tanks to distribute heat evenly.
• Immersion heaters: Heat fluid from the inside.
• Heated cabinets or enclosures: Protect tanks from extreme freezing conditions.
• Thermostatic controls: Automatically activate heating as needed.

Heating solutions are most effective in areas where winter temperatures frequently drop below freezing.

2. Material Durability in Extreme Temperature 

Tanks built for DEF storage must withstand both high heat and sub-zero cold. The most effective storage systems use:

• Fiberglass-reinforced plastic (FRP): Chemically resistant, durable, and ideal for thermal shifts.
• High-density polyethylene (HDPE): Resilient and flexible for moderate climates.
• UV-protected materials: Prevent sun damage and maintain stable internal temperatures.

Strong materials reduce the risk of cracking, warping, or leaking due to temperature expansion and contraction.

3. Insulation Vs. Active Heating Systems

Insulation slows heat transfer and keeps DEF from freezing too quickly. However, insulation alone does not provide active temperature control.

The benefits of insulation systems include the following:

• Foam-jacketed tanks reduce external influence.
• Insulated wraps or covers help maintain the existing fluid temperature.

Active heating systems offer:

• Controlled warming in sub-freezing temperatures.
• Consistent temperature maintenance regardless of weather.
• Prevention of freeze-thaw cycles that can degrade tank structures.

A combination of insulation and active heating works well for DEF protection in cold environments.

Protecting DEF Quality Starts with Smarter Storage

Temperature-sensitive fluids, such as DEF, require storage solutions that provide consistency and protection. The ideal temperature range preserves urea quality and prevents harmful breakdown. 

Belding Tank Technologies supplies diesel storage tanks that handle harsh conditions without compromising safety or performance. Contact us for trusted solutions tailored to various seasons.

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