Problem No. 61: Carbamate safety valve problems

The heart of any urea plant is the high-pressure urea synthesis section. Properly functioning safety valves are vital to protect the high-pressure section against ruptures due to pressures that are too high in case of upset conditions. However, the very corrosive intermediate ammonium carbamate makes the reliable and proper functioning of safety valves more challenging.

Traditional safety valves suffer from crevice corrosion problems causing small leakages which often go undetected. These small leakages can lead to the risk of crystallisation of ammonium carbamate in the outlet line of the safety valve even when heat tracing is applied (see picture).