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Common Diesel Exhaust Fluid Issues & How to Avoid Them

Common Diesel Exhaust Fluid Issues & How to Avoid Them

Common Diesel Exhaust Fluid Issues & How to Avoid Them

Problem: Mixing DEF with diesel fuel


One common issue stemming from diesel exhaust fluid (DEF) is intermixing the fluid with diesel fuel. DEF and fuel tanks are sometimes located near each other on machines, so this is a common issue with very expensive consequences.

DEF is a selective catalytic reduction (SCR) which is used as an emissions control solution for diesel engines. DEF is incorporated in engine systems via the DEF tank and mixing the fluid with diesel fuel can potentially create thousands of dollars in damage.

To avoid this issue, operators should become familiar with the difference between the two tanks before use. Usually the DEF filling port is smaller in diameter than that of the diesel tank and the cap for the DEF tank is typically blue.

It’s important to train operators on the difference between the two tanks and the exigency of never intermixing DEF and fuel. If/when this issue does arise, do not start the engine and call a technician, immediately. If ever in doubt whether the right tank was filled with DEF, drain and flush the tank(s).

Problem: DEF contamination


DEF is very prone to contamination if exposed to other materials or fluids, even minimally. If contaminated, DEF will not perform efficiently. Contamination around the fuel cap or in-and-around the storage area can create issues like an uptick in consumption, a malfunctioning system or an engine which starts to intermittently shut down.

If these issues arise, monitoring the concentration of urea-based DEF may be necessary. Ideal concentration is between 32.5 and 37 percent.

The best way to avoid issues related to DEF contamination (and downtime) is to train all operators and maintenance staff to clean the area around the tank before the fuel cap is removed and to make sure that DEF is stored properly in designated containers and to never store in containers used for other fluids.

Problem: Improper handling of DEF


Another common problem that people can encounter with DEF stems from mishandling the substance. It’s important to properly store the fluid to avoid complications like premature degradation. Here are the pertinent pointers to remember when storing DEF:

  • Store out of direct sunlight.
  • Store in stainless steel or plastic totes or as directed by the manufacturer.
  • Store indoors in a cool, dry location.
  • It’s best to store in an area between 12 and 86 degrees Fahrenheit.
  • DEF expands in very cold temperatures so if storing in a cold area, use an expandable container.

For more information, check out this helpful Diesel Exhaust Fluid checklist from Volvo Construction Equipment or contact us today!

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