Charge heater radiant and convection coils (tubes, U-bends & 90° radiant outlet elbows)
in Atmospheric Desulfurization 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 desulfurization / de-metallization. Severe erosion and
thinning was observed in the 90° radiation elbows during Year 2002 shutdown after a
service life of about 12 Years. Erosion was noticed in charge heaters H-12-101 & H-12-201
in both ARDS Trains. These radiation 90° elbows are outside the charge heater firebox
upstream of the heater outlet header.
This particular erosion phenomenon was restricted to a small area of the 90° elbows and
resembled a sharp knife-like attack at the point of maximum damage. The most probable
reasons for such severe erosion was the impingement of coke particles at the outer
radius during online spalling and steam/air decoking operation during which velocities of
steam/air may reach a very high magnitude. The high velocity steam/air stream carrying
coke particles causes a bullet like impact on the point of incidence and the metal thereof
is removed causing erosion.
Keywords: erosion, austenitic stainless steel, ARDS, online spalling, steam/air decoking,
high pressure, high temperature