Valves for Urea Solution (Carbamide / DEF / AdBlue) Service
Urea solution is encountered in three main industrial contexts: (1) 32.5% aqueous urea (DEF/AdBlue) for SCR diesel exhaust aftertreatment; (2) high-concentration urea solution (70–85%) in urea fertiliser plants (Stamicarbon/Snamprogetti processes) at high temperature and pressure; and (3) urea prilling/granulation where molten urea at 140°C is handled. High-concentration urea is highly corrosive to carbon steel at elevated temperature, requiring SS 316L or duplex materials.
Pressure Range
1 barg (DEF/dilute) to 150 barg (urea synthesis loop)
Temperature
Ambient (DEF) to 200°C (synthesis loop)
Industries
Fertiliser plants (urea), Diesel aftertreatment (DEF/AdBlue), Chemical synthesis
Key Properties — Urea Solution (Carbamide / DEF / AdBlue)
- 32.5% aqueous urea (DEF/AdBlue): mild corrosion at ambient — SS 316L or HDPE preferred
- Concentrated urea (>70%) at elevated temperature: highly corrosive to carbon steel
- Molten urea at 140°C: moderate corrosion, SS 316L required
- Decomposes to ammonia and CO₂ above 135°C if not kept moving
- Crystallises on cooling — heat tracing and jacketed valves often required
Material Compatibility — Urea Solution (Carbamide / DEF / AdBlue)
Ratings are indicative. Actual compatibility depends on concentration, temperature, velocity, and presence of contaminants. Always consult corrosion tables or a materials engineer.
| Material | Rating | Notes |
|---|---|---|
| SS 316L | Excellent | Standard material for all urea concentrations. Passive film stable in urea. |
| Duplex 2205 | Excellent | Used in high-pressure urea synthesis loops at elevated temperature. |
| Carbon Steel | Poor | Not recommended for concentrated or hot urea — severe corrosion. |
| Hastelloy C-276 | Excellent | Used in the most aggressive urea carbamate conditions in synthesis loops. |
| PTFE-lined | Good | Acceptable for dilute urea (DEF/AdBlue) service. |
Recommended Valves
Ball Valve (SS 316L, PTFE seats)
Standard isolation for urea solution pipelines; fire-safe where required
Globe Valve (SS 316L or Duplex)
Control service in urea synthesis loops — precise flow regulation
Diaphragm Valve (SS 316L, PTFE diaphragm)
Concentration control in DEF/AdBlue blending and dosing systems
Gate Valve (SS 316L)
Isolation on urea storage tanks and main transfer headers
Safety Relief Valve
Pressure relief on synthesis loop and vessel overpressure protection
Valves to Avoid
Carbon steel valves for any concentrated urea
Cast iron valves
Bronze in high-concentration urea at elevated temperature
Special Considerations
Applicable Standards
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