Diesel Exhaust Fluid (DEF)

DEF LabelsCummins Tier 4 Final engines with >751 hp use Selective Catalytic Reduction (SCR) to reduce NOx in the exhaust.  A key ingredient in the exhaust aftertreatment is Diesel Exhaust Fluid (DEF).

DEF is a non-toxic solution of 67.5% water and 32.5% automotive grade urea and is one of the key elements of the SCR system. It has high purity requirements - defined by the International Organization for Standardization specification ISO 22241-1, and the American Petroleum Institute.

The 32.5% DEF solution is preferred for use with most SCR systems worldwide due to optimum cold weather performance.  At this specific 32.5% concentration the solution has the lowest freezing point of all possible concentrations and allows the urea and water to freeze and thaw at the same rate allowing the proper concentration for the SCR exhaust system. 

DEF Consumption

DEF consumption will vary depending upon the environment, operation and duty cycle of equipment. On average, DEF consumption is 3% to 5% of fuel consumption. As fuel consumption increases, DEF consumption also increases, so it is important to consider the highest consumption rates of the equipment when planning DEF delivery and storage.

Storage and Handling

DEF poses no serious risk to humans, animals or the environment, but it is not compatible with all materials. DEF is safe to handle and store, non-toxic, non-polluting and non-flammable. While it does freeze at 12°F, it is important to note that frozen DEF does not impact the start-up or operation of the vehicle. When stored or exposed to extreme temperatures, DEF does not become toxic.

SCR systemThe SCR system, tank and distribution system on the equipment are all designed to be fully compatible with DEF properties to avoid corrosion, evaporation and contamination. Each system includes sensors that monitor DEF quality and level as well as heated lines from the tank to the SCR unit to maximize system performance. However, additional care must also be taken when selecting bulk DEF storage and delivery systems. All hoses, fittings, and storage tanks must be made of DEF-approved materials such as stainless steel, certain plastics, titanium or EPDM rubber in order to avoid chemical contamination of the DEF and expensive damage to the SCR system.

It is recommended that DEF be stored between 12°F and 86°F. When stored within this range, shelf life will be greater than one year, and when stored below 65°F, shelf life is extended to 2 years.

DEF Availability

DEF Storage
The on-highway market has driven massive DEF infrastructure growth in the last few years with over 1,000 DEF pump locations across North America. Increased off-highway demand will drive increased non-road availability over the next few years through various fuel and chemical service providers.

DEF is available in a variety of sizes:

  • Bulk (>5,000 gal.)
  • Plastic & Disposable Totes (275 and 330 gal.)
  • Drum (55 gal.)
  • Small Packages (1 and 2.5 gal.)

DEF does require special dispensing equipment. This DEF handling equipment is available at many of the same locations that provide fuel and other fluid handling equipment throughout North America.

More information on DEF can be found on cumminsfiltration.com.