Erosion of Austenitic Stainless Steel 90° Elbows of Charge Heater Tubes in Atmospheric Residue De-Sulphurization Unit (ARDS) of Mina Abdulla Refinery

Erosion of Austenitic Stainless Steel 90° Elbows of Charge Heater Tubes in Atmospheric Residue De-Sulphurization Unit (ARDS) of Mina Abdulla Refinery
Kuwait National Petroleum Company
By:  Muased Al Arada, Mutlaq M. AL-Enezi , Sunil V.  Vipat , Anil Kumar Ray
Kuwait National Petroleum Company, Mina Abdulla Refinery
P.O.Box-69, SAFAT, KUWAIT-13001
Abstract:
Charge heater radiation and convection coils (tubes, U-bends & 90° radiation outlet elbows) in Atmospheric Desulphurization Unit (ARDS) of Mina Abdulla Refinery  are made up of TP 347SS material. Charge heater is used for heating of atmospheric residue prior to entering into ARDS  reactors for further desulphurization / de-metallization.  Severe erosion and thinning was observed in the 90° radiation elbows (Material ASTM A-403 WPS 347) during Year 2002 shutdown after a service life of about 12 Years. Erosion was noticed in charge heaters H-12-101 & H-12-201in both the ARDS Trains. These radiation 90° elbows are outside the charge heater firebox up stream of the heater outlet header.

Metallurgical analysis of the 90° radiation outlet elbows did not find any abnormality or metallurgical issues that would have contributed to the localized thinning. This particular erosion phenomenon was restricted to a small area of the 90° elbows at outer radius and it resembled like a sharp knife like attack at the point of maximum damage. Severe erosion occurred probably due to the impingement of coke particles at the outer radius during steam-air decoking operation, when velocities of steam/air may reach very high magnitude. The high velocity steam/air stream carrying coke particles might have caused a bullet like impact at the point of incidence and the metal thereof was removed causing erosion.

Keywords
Erosion, Austenitic Stainless Steel, ARDS, Coke deposition, Steam Air Decoking, High Pressure, High Temperature.