Q. Corrosion Assessment of Flare and VRU System?
The worst case scenario shall be considered during material selection of Flare KO Drums. Depending on the fluid composition entering the flare header and the liquid composition collected in the Flare KO Drum, it may be corrosive to CS material.
Corrosion shall be studied on a case by case basis and normal prevention method is to increasing the CA of Flare KO Drum (normally up to 4.8mm or 6.4mm for severe cases) or applying internal coating. Operating temperature shall be considered when specifying internal coating.
As there is always a liquid water phase present in the system, there is risk for wet H2S corrosion up to the Flare KO Drum. It is highly recommended to consider NACE requirement for the Headers and Flare KO Drums. HP KO Drum is recommended to receive PWHT to minimize risk of SSC and SOHIC. Clean steel shall also be used to reduce the risk of HIC. There is no need to use HIC resistant materials.
Dew point corrosion shall be considered by relevant vendor. Flare Tip shall be upgraded to 310SS to prevent high temperature oxidation and cold end corrosion.
The condensing phase prior to compression in VRU package is primarily water. Depending on the gas composition (CO2/H2S ratio), upgrading the metallurgy to 316L SS may be necessary. The entire VRU package shall be in full compliance with NACE requirements.