Cat® Tier 4 Final engines for inland waterway vessels reduce NOx emissions through the use of an aftertreatment system. That system uses Diesel Exhaust Fluid, or DEF, to break down NOx into harmless nitrogen and water. Other industries have used DEF — often referred to as “urea” — for years, but it’s relatively new to the inland waterway market. That’s led to lots of questions and misconceptions. Here’s what you need to know about DEF storage:

How much space should I allot on board for DEF storage?

A good rule of thumb is to install a DEF tank that’s 10% the size of your fuel tank. Your Cat dealer can help you figure out the space you need based on refueling practices and schedules. One benefit of using higher concentration DEF (60% de-ionized water and 40% urea versus 67.5% de-ionized water and 32.5% urea) is that it requires less storage space — but make sure to weigh the availability of one product versus the other, as well as freeze/crystallization protection requirements, to make a decision.

Does DEF have special storage requirements?

DEF simply needs to be kept in a cool, dry, well-ventilated area. The ideal storage temperature is 15°F to 77°F (-9°C to 25°C). According to ISO 22241-1 standards, DEF should last for at least a year when stored below 86°F (30°C) and approximately 18 months when stored below 77°F (25°C).

What types of tanks should I store DEF in?

Storage tanks made of stainless steel (304, 304L, 316) and some polyethylene/polypropylene materials (which are free of additives) are fine. Avoid tanks with carbon steel, zinc-coated metals, nonferrous metals, soldered joints or metals containing aluminum or magnesium.

Doesn’t DEF degrade easily?

DEF only degrades if it’s exposed to extreme temperatures or direct sunlight, and naval architects have addressed this issue. The size of the tanks in conjunction with the consumption and location outside of extreme temperature zones should eliminate nearly any degradation effect on the product.

Do you have additional questions about Tier 4 Final engines for inland waterways, DEF supply and safety or the differences between the Caterpillar solution and other options on the market? You’ll find more details here, and you can always turn to your local Cat dealer for answers.