Abstract
This paper presents an experience in utilizing Thermal Spray Coating Technology on top of weld build-up of CS Pressure Vessel eroded shell. The column is under rich amine service and had severe erosion on some of its internal surface of the shell. Column trays collapse had directed the flow of hot rich amine into the internal service of the shell causing sever erosion. Wall thickness of eroded area decreased below the minimum thickness Tmin. Minimum required wall thickness was restored by weld build-up in accordance with ASME PCC-2 (Repair of Pressure Equipment and Piping). Moreover, PWHT was required by the standard after retention of nominal wall thickness in order to relieve the residual stresses introduced to the melt after weld build-up in order to avoid any Stress Corrosion Cracking. However, heat treatment of this column was infeasible due to stability analysis results that show instability of the column during heat treatment. Moreover, laying down the column to perform PWHT is highly costly and would significantly impact shutdown schedule of the unit. Therefore, thermal spray metal coating has been utilized as a cladding layer on top of weld build-up surface in order to isolate the welded surface from corrosive environment and hence avoid stress corrosion cracking.
