Diesel Exhaust Fluid (DEF) is a liquid that is injected into the exhaust system of engines equipped with Selective Catalytic Reduction (SCR) systems. SCR reduces emissions of nitrogen oxides (NOx) in diesel engine exhaust.
Diesel Exhaust Fluid (DEF) is available in many brands, including those brands that carry the AdBlue or API certification. DEF is also generically referred to as urea.
In engines equipped with SCR emissions reduction system, DEF is injected in controlled amounts into the engine exhaust stream. At the elevated exhaust temperature, urea in DEF is converted to ammonia. The ammonia chemically reacts with NOx in diesel exhaust in the presence of the SCR catalyst. The reaction converts NOx into harmless nitrogen (N2) and water (H2O).
Note: Follow all applicable industry standards and all applicable governmental, environmental, safety guidelines, practices, regulations, and mandates.
Note: These general recommendations and guidelines concerning maintenance and care of DEF and DEF storage systems are not intended to be all inclusive. Discuss proper DEF safety, health, handling, and maintenance practices with your DEF supplier. Use of these general recommendations and guidelines does not lessen the responsibility of the engine owner and/or DEF supplier to follow all industry standard practices for DEF storage and for DEF handling.
Characteristics of DEF and Urea Fluids
DEF solutions are typically of 32.5 percent concentration urea. However, some marine engines may use DEF (32.5 percent urea concentration) or urea solutions of 40 percent concentration. All DEF solutions that are of 32.5 percent urea must meet all the requirements defined by the "ISO 22241-1" standard.
The caps of DEF tanks are blue, as required by emissions regulations. Fill DEF only in clearly marked DEF tanks that have the blue cap.
Caterpillar recommends the use of DEF available through the Cat parts ordering system for use in Cat engines equipped with SCR systems. Refer to Table 1 for part number information:
Cat Part Number (32.5% Urea) | Container Size |
---|---|
350-8733 | 2.5 gal bottle |
350-8734 | 1000-L tote |
In North America, commercial DEF of 32.5 percent urea concentration that is API approved and meets all the requirements defined in "ISO 22241-1" may be used in Cat engines that are equipped with SCR systems.
Outside of North America, commercial DEF of 32.5 percent urea concentration that meets all requirements defined in "ISO 22241-1" may be used in Cat engines that are equipped with SCR systems.
The supplier should provide documentation to prove the DEF is compliant with the requirements of "ISO 22241-1".
NOTICE |
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Cat does not warrant the quality or performance of non-Cat fluids. |
NOTICE |
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Do not use agriculture grade urea solutions. Do not use any DEF 32.5 percent fluid that does not meet "ISO 22241-1" Requirements in SCR emissions reduction systems. Use of these fluids can result in numerous problems including damage to SCR equipment and a reduction in NOx conversion efficiency. |
DEF is a solution of solid urea that is dissolved in demineralized water to produce a final concentration of 32.5 percent urea. Most SCR systems are designed to operate only on DEF concentration of 32.5 percent. DEF solution of 32.5% urea has the lowest attainable freeze point of
Marine engines and other specific applications may use urea solutions of 32.5 percent or 40 percent concentrations in engines equipped with SCR systems. Refer to the information given specifically for marine engines in this DEF article and to your engine Operation and Maintenance Manual.
Cat offers refractometers that can be used to measure DEF concentration. Refer to Table 2 for the part numbers. Follow the instructions provided with the instruments.
Cat DEF Refractometers | ||
Refractometer Part Numbers | 360-0774 | Digital display, easy to use, and multifunctional
(DEF, coolant, battery fluid, and more) |
431-7087 | Analog, specific to DEF, and requires a multi-step test procedure |
Urea Solution Recommendations for Marine Engines
US waters are an International Maritime Organization (IMO) NOx Emissions Control Area (NECA). Low NOx engines are required in these areas. These engines may require the use of Diesel Exhaust Fluid (DEF) and other urea solutions for engines equipped with Selective Catalytic Reduction (SCR) systems. If required, Cat marine engines are designed to operate on DEF of urea concentrations of 32.5 percent (by weight) or 40 percent (by weight). The crystallization temperature of 40 percent urea solution is
Vessels that are traveling internationally and that have on/off NOx controls must enable these controls prior to entering a NECA. For US flagged vessels, on/off controls are not allowed without an exemption during international travel. The controls must always be on. Foreign destinations should be reviewed for supply of ULSD fuel and DEF prior to departure. Exemptions for ULSD or DEF use by US flagged vessels may be requested from the US Environmental Protection Agency (EPA). The EPA can be contacted at the following address:
complianceinfo@epa.govWhen used in marine engines, DEF of 32.5 percent urea concentration must meet all the guidelines and quality recommendations given in this Chapter.
When used in marine engines, urea solutions of 40 percent concentration must follow all the DEF guidelines and quality recommendations given in this chapter and must meet the characteristics listed in Table 4 for 40 percent concentration. The supplier should provide documentation to prove that the urea solution is compliant with the characteristics published in Table 4.
Refer to your engine Operation and Maintenance Manual to determine the concentration of urea solution allowed in your engine.
NOTICE |
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Cat does not warrant the quality or performance of non-Cat fluids and greases. |
DEF solution is typically colorless and clear. Changes to color or clarity are indicators of quality issues. Quality of DEF can degrade when stored and handled inappropriately or if DEF is not protected from contamination. Details are provided below.
If quality issues are suspected, testing of DEF should focus on urea percentage, alkalinity as NH3 and biuret content. DEF that does not pass all these tests or that is no longer clear should not be used.
Note: Caterpillar strongly recommends that customers purchase the pre-mixed DEF urea solution from a reputable supplier. The DEF must satisfy all the specifications of quality given in this chapter of this Special Publication. Urea solutions that are not made of urea and water of the appropriate quality and cleanliness may damage the SCR system. Poor or questionable quality DEF can lead to additional repair and maintenance costs to the customer. Cat warranties do not cover failures caused by or related to use of out of specification urea solutions in Tier 4 Stage IIIB MLIT Step 4 products equipped with SCR systems.
DEF is corrosive. Due to the corrosion caused, DEF must be stored in tanks constructed of approved materials. Recommended storage materials:
Stainless Steels:
- 304 (S30400)
- 304L (S30403)
- 316 (S31600)
- 316L (S31603)
Alloys and metals:
- Chromium Nickel (CrNi)
- Chromium Nickel Molybdenum (CrNiMo)
- Titanium
Non-metallic materials:
- Polyethylene
- Polypropylene
- Polyisobutylene
- Teflon (PFA)
- Polyfluoroethylene (PFE)
- Polyvinylidene fluoride (PVDF)
- Polytetrafluoroethylene (PTFE)
Materials NOT compatible with DEF solutions include aluminum, copper, copper alloys, magnesium, zinc, nickel coatings, silver and carbon steel and solders containing any of the above. Unexpected reactions may occur if DEF solutions come in contact with any non-compatible material or unknown materials.
Follow all local regulations covering bulk storage tanks. Follow proper tank construction guidelines. Tank volume typically should be 110% of planned capacity. Appropriately vent indoor tanks. Plan for control of overflow of the tank. Heat tanks that dispense DEF in cold climates.
Bulk tank breathers should be fitted with filtration to keep airborne debris from entering the tank. Desiccant breathers should not be used because water will be absorbed, which potentially can alter DEF concentration.
Follow all local regulations covering transport and handling. DEF transport temperature is recommended to be
- Nitrile Rubber (NBR)
- Fluoroelastomer (FKM)
- Ethylene Propylene Diane Ionomer (EPDM)
The condition of hoses and other nonmetallic items that are used with DEF should be monitored for signs of degradation. DEF leaks are easily recognizable by white urea crystals that accumulate at the site of the leak. Solid urea can be corrosive to galvanized or unalloyed steel, aluminum, copper, and brass. Leaks should be repaired immediately to avoid damage to surrounding hardware.
Contaminants can degrade the quality and life of DEF. Filtering DEF is recommended when dispensed into the DEF tank. Filters should be compatible with DEF and should be used exclusively with DEF. Check with the filter supplier to confirm compatibility with DEF before using. Mesh-type filters using compatible metals, such as stainless steel, are recommended. Paper (cellulose) media and some synthetic filter media are not recommended because of degradation during use.
Care should be taken when dispensing DEF. Spills should be cleaned immediately. Machine or engine surfaces should be wiped clean and rinsed with water. Caution should be used when dispensing DEF near an engine that has recently been running.
Note: Spilling DEF onto hot components may cause the release of ammonia vapors. Do not breathe ammonia vapors. Do not clean up any spills with bleach.
DEF fluid is stable when stored and handled properly. The quality of DEF rapidly degrades when stored at high temperatures. The ideal storage temperature for DEF is between
The length of storage of DEF is listed in the following table:
Storage Temperature | Expected DEF Life |
---|---|
Below |
18 months |
|
12 months |
|
6 months |
Above |
test quality before use |
Refer to "ISO 22241" document series for more information about DEF quality control.
Note: Dispose of all fluids according to applicable regulations and mandates.
General Characteristics of DEF
For detailed information on the requirements and characteristics of DEF, refer "ISO 22241". For a quick reference, typical characteristics of DEF are given in Table 4.
Characteristics for Urea Solutions | |||
---|---|---|---|
Property | Unit | DEF 32.5 percent | Urea Solution 40 percent |
Urea content | 32.5 percent (1) | 40 percent (2) | |
Alkalinity as NH3 | Percent | 0.2 | 0.2 |
Density at |
g/L | 1.087 - 1.093 (3) | 1.108 - 1.114 (4) |
Refractive Index at |
1.381 - 1.384 (5) | 1.394-1.397 (6) | |
Biuret | Percent | 0.3 max | |
Aldehydes | mg/kg | 5 max | |
Insoluble Matter | mg/kg | 20 max | |
Aluminum | mg/kg | 0.5 max | |
Calcium | mg/kg | 0.5 max | |
Chromium | mg/kg | 0.2 max | |
Copper | mg/kg | 0.2 max | |
Iron | mg/kg | 0.5 max | |
Magnesium | mg/kg | 0.5 max | |
Nickel | mg/kg | 0.2 max | |
Phosphate (PO4) | mg/kg | 0.5 max | |
Potassium | mg/kg | 0.5 max | |
Sodium | mg/kg | 0.5 max | |
Zinc | mg/kg | 0.2 max |
(1) | Acceptable range is 31.8 - 33.2 percent |
(2) | Acceptable range is 39-41 percent |
(3) | Target value is 1.090 g/L |
(4) | Target value is 1.112 |
(5) | Target value is 1.382 |
(6) | Target value is 1.3956 |