Understanding Diesel Exhaust Fluid (DEF)

Diesel exhaust fluid (DEF) is a non-hazardous solution which breaks down dangerous NOx emissions into nitrogen and water when sprayed into the exhaust stream of diesel vehicles. Stored in a separate tank, it is not a fuel additive and does not come into contact with diesel fuel. With the increasing use of DEF in Tier 4 Final machines, contractors must understand how to properly use and store it. 

But what happens when this important solution “goes bad?” If bad DEF is used in a piece of equipment, a number of possible issues can occur such as:

-    Increased consumption by equipment

-    Engine de-rating or shutdown

-    Damage to components, including DEF dosing pump and diesel particulate filter 

-    Loss of DEF effectiveness

-    Malfunctions with a machine’s SCR system 

Thankfully, understanding the characteristics of DEF can help keep it in working condition for equipment. Seven key areas should be noted:

1.    Shelf Life

DEF doesn’t have any preservatives, meaning it has a shelf life. Thankfully, it’s fairly long – it can usually be stored up to one year. 

2.    Correct Containers

DEF must be stored in ISO-approved containers made from durable composite materials. DEF is corrosive to aluminum, so containers made from stainless steel, polypropylene, and high-density polyethylene are preferable options. It is not recommended to reuse DEF containers, due to potential fluid contamination. 

Also, DEF and all other fluid storage containers should be labeled. This can prevent mistaking DEF for regular fuel or another fluid which could cause serious damage if put in the wrong tank of a machine. 

3.    Cold Temperatures

Freezing temperatures won’t harm DEF. While it will begin turning slushy at 12 degrees Fahrenheit and eventually freeze solid, it can be thawed and used without any problems. It will, however, expand when frozen, so it’s best not to fill containers completely. 

4.    Hot Temperatures

While the cold won’t harm DEF, prolonged exposure to heat and sun can cause the solution to degrade. Storing DEF at 50 degrees Fahrenheit is ideal. It should be noted however, that even if it is stored in a cool area with approved containers, direct sunlight is still armful to DEF, meaning it should be stored indoors or in the shade. 

5.    Proper Dispensing

Keeping container nozzles and equipment fill points clean can help avoid contamination when dispensing DEF. It should only be dispensed directly into machines via the nozzle of the storage container. It should not be dispensed via a funnel or transferred to another container, even if they are clean, as it may be contaminated by dirt or other contaminates. 

It should also be noted that DEF should never be used in a machine’s diesel fuel tank. DEF has a designated tank which has a smaller opening and a blue cap, making it easy to identify. 

6.    Safe Handling

While DEF is not toxic, flammable, or explosive, it should still be handled with care to avoid spills, contact with eyes, or accidental ingestion. 

If spilled on the floor, cover with an absorbent, non-combustible material like sand. Collect and dispose of the material in an appropriate container. If spilled in a sink, on a vehicle or clothing, or gets in contact with eyes, flush immediately and completely with water. 

7.    Teamwork

All company team members should know how to properly store and use DEF. It’s recommended to put one person in charge of DEF care, who can then inform others about best practices. 

If DEF becomes contaminated or degraded, do not use it. The best way to determine if DEF is contaminated or degraded is to look for a cloudy or colored appearance. DEF is naturally clean, so any discoloration or cloudiness is an indicator that it has gone bad. Small particles, larger rocks, and dirt are also contaminates that are easy to see.

Bad DEF should be disposed of immediately and ethically. Do not pour down a drain or dump it outside. Check with your local government and environmental agency to learn how to properly dispose of DEF.  

Understanding how to properly store and care for DEF is crucial. By educating your team on how to store and use DEF, you can avoid the cost of wasted DEF and damage to your equipment.