GASKET 4H9026 - Caterpillar

Ammonia is required to reduce NOx to nitrogen and water. Urea (Diesel Exhaust Fluid) is a nontoxic source of ammonia. The DEF is slightly alkaline with a pH of 9.0 - 9.5. A 32.5 percent solution is used to ensure that the SCR system receives the proper concentration of urea. This concentration is needed for the chemical reactions that reduce emissions.Diesel Exhaust Fluid (DEF) Recommendations
For use in Cat engines, DEF concentration must be 32.5 percent, meeting all requirements defined by "ISO 22241-1".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:
Table 1
Cat Part Number    Container Size    
350-8733     2.5 gal bottle    
350-8734     1000 L tote    In North America, commercial DEF 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 that meets all requirements defined in "ISO 22241-1" may be used in Cat engines that are equipped with SCR systems.The owner/operator should provide documentation to prove the DEF is compliant with the requirements of "ISO 22241-1".To obtain locations of DEF suppliers, call (888)-598-8186 or (309)-494-7532.
Cat does not warrant the quality or performance of non-Cat fluids.
Do not use agriculture grade urea solutions. Do not use any fluids that do 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. DEF concentration of 32.5 percent is optimal for use in SCR systems. DEF solution of 32.5 percent urea has the lowest attainable freeze point of −11.5° C (11.3° F). DEF dosing systems and "ISO 22241-1" specifications are designed for a solution that is 32.5 percent.Caterpillar offers a refractometer, Cat part number 360-0774, that can be used to measure DEF concentration. Follow the instructions provided with the instrument. Appropriate commercial portable refractometers can be used to determine urea concentration. Follow the instructions from the manufacturer.DEF Guidelines
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 or a DEF quality fault is active, testing of DEF should focus on urea concentration, alkalinity as NH3 and Biuret content. DEF that does not pass all these tests should not be used.Materials compatibility
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)
409 (S40900)
439 (S43035)Alloys and metals:
Chromium Nickel (CrNi)
Chromium Nickel Molybdenum (CrNiMo)
TitaniumNon-metallic materials:
Polyethylene
Polypropylene
Polyisobutylene
Teflon (PFA)
Polyfluoroethylene (PFE)
Polyvinylidene fluoride (PVDF)
Polytetrafluoroethylene (PTFE)Materials NOT compatible with DEF solutions include Aluminum, Magnesium, Zinc, Nickel coatings, Silver and Carbon steel and Solders containing any of the above. Unexpected reactions may occur if DEF solutions