How to protect your SCR and secure your DEF in cold weather
Key Highlights
- Implement active heating methods such as engine-integrated heaters, electric block heaters, and insulated blankets to prevent DEF freezing during cold weather.
- Use passive insulation like wraps and protective shields on DEF tanks and lines to reduce heat loss and prolong operational temperatures.
- Conduct thorough pre-winter SCR system checks, including verifying heating elements, sensors, and software updates to ensure system readiness.
- Maintain high-quality DEF storage by avoiding exposure to sunlight and high temperatures, and perform regular inspections for system integrity.
- Invest in insulation solutions and routine maintenance to minimize downtime, prevent costly repairs, and ensure compliance with emission standards during winter.
Winter is around the corner, and when temperatures drop, your selective catalytic reduction (SCR) system faces threats involving its diesel exhaust fluid (DEF).
DEF is crucial for ensuring your truck engine remains compliant with emission standards. While it’s a straightforward product, winter’s harsh temperatures can impact its behavior. According to the National Highway Safety Administration, DEF begins to freeze when exposed to temperatures of 12 degrees F and below. When it freezes, DEF expands and thickens, increasing the risk of damage to storage tanks, especially if they are filled to capacity. If a DEF tank is overfilled without allowance for expansion, cracks can form and internal seals in the injector and pump can be damaged. Plus, as DEF cools or evaporates, urea can crystallize and deposit in the SCR system. Prolonged idling and frequent short trips can trigger this, too.
Meanwhile, SCR systems require periodic DEF replenishment to ensure optimal performance of the emission system. However, SCR catalysts require temperatures above approximately 392 degrees Fahrenheit to be effective. When a truck starts after sitting overnight in cold temperatures, the entire exhaust system is at ambient temperature, requiring time for the SCR to warm up. During this entire warmup period, the SCR system may not function properly. The engine will produce nitrogen oxides and might pass straight through the inactive catalyst and out the tailpipe, and it can also cause electronic and diagnostic problems. Ice forming on the surface of a level sensor can result in incorrect system readings.
A successful SCR system for cold weather can prevent this kind of system damage, reduce emissions, and ensure your trucks perform well despite the cold. To encourage this, here are actionable thermal strategies to prevent DEF freezing.
How to prevent DEF freezing in commercial fleets
Protecting your fleet’s DEF tanks is crucial to ensure a seamless operation during the winter months. A couple options to do so include active heating, component insulation, and regular maintenance.
Active heating
One way to avoid issues related to frozen DEF is to avoid the problem in the first place, primarily by keeping your truck warm. If possible, keep your fleet in a heated garage whenever possible to minimize the chances of DEF freezing.
But for fleets operating in extreme climates or trucks with SCR-exposed components, aftermarket retrofits provide an added layer of protection from “flash freezing” during short stops, where the engine is turned off for an extended period. Many modern commercial trucks also often have engine-integrated heaters, but you can add one if your vehicle doesn’t. These heaters also have diesel engines, which require a higher cylinder temperature compared to gasoline vehicles. For another option, an electric block heater is an excellent solution to ensure smoother startups when freezing temperatures arrive.
Insulated heating blankets specifically engineered for DEF tanks also help ensure optimal temperatures.
Component insulation
Additionally, there are several low-cost, passive strategies for improving the efficiency of your active heating solutions.
Adding insulated wraps to pumps and lines can slow down the rate of heat loss, keeping the DEF warmer for longer periods after the engine is shut off. This reduces the need for a full thaw cycle upon restart, saving time and energy.
But even if a fleet uses these tactics, it can be worth having back-up solutions. For example, even if a fleet uses insulated wraps to keep their system at a good temperature, they could also benefit from protective shields made of composite or metal to also protect their truck components from ice chunks and road spray.
Regular maintenance and software adjustments
Beyond having the right tools on hand to help out your truck’s SCR system, extensive SCR system checks are crucial before winter sets in, too.
To start, technicians should verify that heating elements and insulation are functioning correctly to maintain proper diesel emissions control. To do so, make sure the system’s electrical connections are functioning and free of corrosion, and check that the sensor is working correctly. Diagnostic software can also help command the DEF heaters to activate and view the live data stream of DEF level, temperature, and quality sensor.
Beyond making sure the SCR system is working well before winter, it also helps to make sure your fleet is using quality DEF. Using DEF that is licensed by the American Petroleum Institute ensures it meets the rigorous standards required by manufacturers, and keeping it away from direct sunlight and high temperatures while it’s in storage helps make sure its ready to go when needed.
Additionally, technicians should make sure that a truck's electronic control unit (ECU) is properly updated in preparation for winter. The ECU is the brain of the entire SCR system, controlling the injection of DEF to reduce harmful emissions. It monitors engine conditions and utilizes sensors to determine the amount of DEF to inject, ensuring the system efficiently converts nitrogen oxides into harmless water and gas. Many engine manufacturers periodically release software updates or cold-weather calibrations that can enhance the engine’s warmup strategy and prevent winter-related issues down the line.
Every strategy discussed is an investment that protects you from costly downtime, financial losses, penalty fees and operational inefficiencies. To avoid DEF freezing, conduct quarterly inspections and functionality checks, verify warmup strategies with your dealer or maintenance team, and invest in insulation solutions to future-proof your fleet against cold weather.
About the Author
Rose Morrison
Rose Morrison is the managing editor of Renovated. She is a skilled researcher and contributing writer for various industry publications. She specializes in fleet management, related software and sustainability. When not writing, Rose is keenly interested in environmental practices and better building.